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Eingeladener Vortrag
- nein (73)
The stress vs. strain curve of materials is affected the rate of imposed straining. Among the methods for dynamic testing the technique known as 'split Hopkinson pressure bar' (SHPB) has evolved into the most widely used one to exert high-speed straining. The theory behind it comprises simple equations to compute stress and strain. The reliability of the strain analysis can be assessed by digital image correlation (DIC). The present results indicate that the visually observed strain is smaller than predicted by theory.
The integration of finite element method (FEM) into the least-squares adjustment presented in is further extended for a joint evaluation of an elastostatic model and displacement field measurement. For linear solids which obey the Hooke's law, the material parameters determination from measurements is being examined.
Aktueller Stand der Normung
(2015)
Schnelle Lastwechsel führen v.a. in dickwandigen Kraftwerksbauteilen zu starken thermischen und mechanischen Beanspruchungen, da sich hohe Temperaturgradienten über der Wand des Bauteils einstellen. Es ergeben sich komplexe Lastkollektive aus zeitlich veränderlichen Spannungen/Dehnungen und Temperaturen, die formal einer Kombination aus Kriechbeanspruchung, Kriechermüdung und thermomechanischer Ermüdung (TMF) entsprechen.
The use of supplementary cementing materials (SCMs) added to concrete mixtures can avoid the alkali-silica reaction. Such materials have a wide range of composition and therefore the inhibition mechanisms can be very differently.
The effectiveness of SCMs which provide silica and alumina into the alkaline solution cannot only be explained by reducing the OH--concentration of the pore solution. From dissolution experiments in potassium hydroxide solutions, an interaction was noted between the aggregate and five SCMs via the alkaline solution. Under specific conditions, no silica is released from the aggregate grains.
Mineralogical investigations (XRD, SEM+EDX) of the grain surfaces confirm that quartz is the main source of silica. In the presence of alumina providing SCMs, the quartz dissolution is strongly reduced or even sometimes stopped. On surfaces of grains a very thin layer can be observed which is probably responsible for reduction or stopping of the silica dissolution and therefore for the inhibition of ASR.
The knowledge of dissolution processes of aggregates and supplementary cementing materials (SCMs) in alkaline solutions can help to describe the expansion of concretes caused by alkali-silica reaction (ASR) and the effects to avoid ASR by using SCMs in more details. Therefore, dissolution experiments in alkaline solutions under different pH values and different temperatures were performed using aggregates in the original grain size and SCMs in different ratios. The concentrations of soluble silica and additionally alumina were determined by ICP-OES. The investigations showed that up to now the “best” conditions to explain the damage behavior of concrete structures are a pH value of 13 (e.g. 0.1 M KOH solution) and a temperature of 80 °C. The evaluation bases on the parameter “excess silica” which is calculated from the dissolved silica and alumina of the aggregates and the SCMs. It was demonstrated that SCMs reduce and sometimes stop the dissolution of aggregates. The efficiency of the SCMs depends on their amount and chemical composition.
The reliable characterization of subsurface contamination of spatially extended contaminated sites is a challenging task, especially with an unknown history of land use. Conventional technologies often fail due to temporal and financial constraints and thus hinder the redevelopment of abandoned areas in particular. Here we compare two site screening techniques that can be applied quickly at relatively low cost, namely Direct Push (DP)-based groundwater sampling and tree core sampling. The effectiveness of both methods is compared for a rural megasite contaminated with chlorinated hydrocarbons. Unexpected pollution hot spots could be identified using both of these methods, while tree coring even enabled the delineation of the contaminant plume flowing into an adjacent wetland inaccessible for DP units. Both methods showed a good agreement in revealing the spatial pattern of the contamination. The correlation between groundwater concentrations and equivalent concentrations in wood was linear and highly significant for trichloroethene. Correlation was less obvious for its metabolite cis-dichloroethene, but still significant. As outcome of our study we recommend tree coring and for initial screening in combination with a DP sampling to retrieve quantitative data on groundwater pollutants in order to assess the contamination situation of a non- or only partly investigated site. The subsequent placement of monitoring wells for long-term monitoring of contamination levels is recommended. A combination of methods would achieve more relevant information at comparable or possibly even lower efforts in comparison to a conventional site investigation.
Improving resource efficiency at the end-of-life stage is illustrated in this paper by the example of materials recovery from waste, here from residues out of municipal solid waste incineration (MSWI). With mechanical treatment valuable materials like ferrous and non-ferrous metals and secondary construction material can be extracted from MSWI bottom ash. The potential contribution on the resource efficiency will be discussed.
In November 2007, OECD’s Working Party on Manufactured Nanomaterials (WPMN) launched the Sponsorship Programme for the Testing of Manufactured Nanomaterials (hereafter the Testing Programme). The objective was to conduct specific tests, relevant to human health and environmental safety endpoints, on a variety of manufactured nanomaterials (MN). The outcomes of the Testing Programme were intended to assess the applicability of the existing test guidelines1 to nanomaterials, as well as to provide useful information on any intrinsic properties of MNs, which are different from the same bulk material with greater external dimensions. Understanding the properties of NMs is crucial to choose appropriate strategies for hazard identification, risk assessment or risk management measures. The Testing Programme involved delegations from OECD member countries, some non-member economies and other stakeholders. The broad international representation, from a range of delegations enabled the programme to pool expertise and resources without which this programme would not have been possible.
Increasing performance and energy efficiency of Gas Metal Arc Welding by a high power tandem process
(2015)
Standard Gas Metal Arc Welding (Standard GMAW) and a high power Tandem GMAW (TGMAW) process are evaluated with respect to energy efficiency. Current, voltage and overall equipment power are measured and energy consumption is determined. The new key performance indicator Electrical Deposition Efficiency is introduced to reflect the energy efficiency of GMAW processes. Additionally, wallplug efficiency of the equipment is determined in order to identify the overall energy consumption. Results show that energy efficiency as well as economic process performance can be significantly increased by application of the TGMAW process. Furthermore findings indicate that wall-plug efficiency of the equipment is independent of power Level and material transfer mode. A metal plate of 30 mm thick structural steel is joined by Standard GMAW and TGMAW to demonstrate the total energy savings for a real weld. Electricity consumption is reduced by more than 20 % using the high power TGMAW process.
Structuring of LTCC Substrates by a Combination of Pressure-Assisted Sintering and Hot Embossing
(2015)
A novel technology for the structuring of low temperature co-fired ceramic (LTCC) surfaces is introduced. The commercial LTCC Ceramtape GC is shaped in a zero-shrinkage process by embossing a glass-like carbon mold into the softened LTCC during pressure-assisted sintering. Diverse raised and lowered structures including rings, grids, and characters were fabricated. It was found that de-airing of mold cavities is crucial for the molding of embossments. De-airing is possible through pore channels in the LTCC if embossing is performed at intermediate temperatures. The influence of LTCC viscosity on the mold filling behavior during the formation of raised structures is discussed. For accurate molding and proper densification of the LTCC, hot embossing with 0.41 MPa at 775 °C and subsequent heating under load to 850 °C is proposed. Embossing of precise, 40 µm deep circular cavities and 50 µm high raised bars and characters is demonstrated. Thereby, the high potential of the hot-embossing process for micro-patterning of LTCC is illustrated.
In this paper we present the results of imaging studies of ancient Egyptian metallic artifacts using micro-Computed Tomography (micro-CT). Micro-CT is a non-destructive imaging method with high spatial resolution, which enables the examination of the internal structure of objects. It is thus especially suitable for the investigation of cultural heritage and archaeological findings, when it is not possible to sample or difficult to manipulate the object. Using specialized software for 3D visualization and segmentation, data sets of two objects were analyzed. We gained a clear view of the inner structure of a metallic archaeological artifact from the necropolis of Abusir el-Meleq, which is believed to be very ancient in the Egyptian archaeological context (from the Predynastic Era), and were able to distinguish its different omponents under the thick layers of external concretions. These components give hints about the production technology of the object. We also investigated the contents of a closed metal box found near Abusir dated to the Late/Greco-Roman Period. The identified Content corresponds either to sediments or to mineral remains of the original content of the box. Both artifacts are from excavations conducted in Egypt and are part of the archeological collection of the Ägyptisches Museum und Papyrussammlung in Berlin.
In order to estimating the amount and kind of emissions from polymeric sporting tracks a laboratory test was developed in BAM that combines artificial weathering and subsequent batch and column tests [1, 2, 3]. The goal consisted in nvestigating a possible change of emissions into soil and groundwater of a new sporting ground as a function of ageing and egradation of the system. At various stages of the weathering, the samples were removed and subjected to especially designed column extraction tests for the solid samples. Both these extracts and the accumulated rainwater run-off of the weathering device were subjected to analytical tests of their ingredients. The overall aim of the test consisted in developing ontrollable, reproducible, and standardisable conditions and methods of investigation that would allow an estimation of the emissions in the course of outdoor application of about five years.
Die meisten organischen Biozide gehören zu der Gruppe der schwerflüchtigen organischen Verbindungen (SVOC – semi volatile organic compounds). Zu den klassischen Bioziden zählen u.a. Lindan, Pentachlorphenol PCP) und Dichlordiphenyltrichlorethan (DDT) und zu den neueren u.a. Dichlofluanid, Tebuconazol und Permethrin. Biozide kamen in Museen vor allem in den 50er und 60er Jahren zum Schutz der Exponate zum Einsatz,1 wo sie hauptsächlich in Depoträumen zu finden sind, in welchen sie zum akuten und zum präventiven Schutz vor Schadorganismen eingesetzt wurden.2 Im Laufe der Zeit wurde jedoch festgestellt, dass sich der Einsatz von Bioziden negativ auf die menschliche Gesundheit auswirkt und auch zu Schäden an den behandelten Exponaten führen kann. 3 Verschiedene Möglichkeiten der Biozidanalytik und der Einfluss von Senkeneffekten auf die Analytik werden in diesem Beitrag vorgestellt.
The syntheses, crystal structures, and physical properties of [HFe19O14(OEt)30] and {Fe11(OEt)24}1 are reported. [HFe19O14(OEt)30] has an octahedral shape. Its core with a central Fe metal ion surrounded by six m6-oxo ligands is arranged in the rock salt structure. {Fe11(OEt)24}1 is a mixedvalence coordination polymer in which FeIII metal ions form three 3D interpenetrating (10,3)-b nets. The arrangement of the FeIII ions can also be compared to that of Si ions in a-ThSi2. Thus, the described structures are at the interface between molecular and solid-state chemistry.
High resolution in situ monitoring of the initial cement hydration influenced by organic admixtures
(2015)
Numerous admixtures are used in the building practice to customize the properties of the cement paste during application. The influences of admixtures on the course of cement hydration and formation of hydrate phases have to be considered. Polycarboxylate ether (PCE) based polymeric superplasticizers (SPs) are known to retard the setting of the cement paste. The extent of the retardation differs depending on the molecular structure of the SP. Additionally, the presence of a stabilizing agent (SA) in the cement paste has a retarding side effect on the setting. The initial cement hydration processes and the detailed mechanisms of the retardation influenced by PCEs, as well as their interactions with particular SAs, are insufficiently understood. Up to now, only the results of phenomenological studies were taken into account to describe this retardation process. A detailed structure analysis monitoring the change of the phase composition during the hydration was never applied. Both SP and SA affect the adsorption of the sulphate ions on the clinker particles, causing changes in the formation of ettringite during the initial hydration, and are therefore a crucial part of the setting process itself. Here, the initial hydration of cement influenced by the interaction of SP and SA was monitored in situ by synchrotron X-ray diffraction. The high time resolution of the measurements allowed a continuous detection of the hydrates formed. The hydration was followed from the starting point of water addition and for couple of hours afterwards. The hydration of the levitated cement pellets containing starch as SA was initialized by adding aqueous solutions of different commercial SPs. Changes in the ettringite formation were detected in comparison to the reference hydration of pure cement.
A pilot study for the quantitative surface analysis of multi-element alloy films has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study is to ensure the equivalency in the measurement capability of national metrology institutes for the quantification of multi-element alloy films. A Cu(In,Ga)Se2 (CIGS) film with non-uniform depth distribution was chosen as a representative multi-element alloy film. The atomic fractions of the reference and the test CIGS films were certified by isotope dilution - inductively coupled plasma/mass spectrometry. A total number counting (TNC) method was used as a method to determine the signal intensities of the constituent elements, which are compared with their certified atomic fractions. The atomic fractions of the CIGS films were measured by various methods, such as Secondary Ion Mass Spectrometry (SIMS), Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-Ray Fluorescence (XRF) analysis and Electron Probe Micro Analysis (EPMA) with Energy Dispersive X-ray Spectrometry (EDX). Fifteen laboratories from eight National Metrology Institutes (NMIs), one Designated Institute (DI) and six non-NMIs participated in this pilot study. Although the average atomic fractions of 18 data sets showed rather poor relative standard deviations of about 5.5 % to 6.8 %, they were greatly improved to about 1.5 % to 2.2 % by excluding 5 strongly deviating data sets from the average atomic fractions. In this pilot study, the average expanded uncertainties of SIMS, XPS, AES, XRF and EPMA were 3.84%, 3.68%, 3.81%, 2.88% and 2.90%, respectively. These values are much better than those in the key comparison K-67 for composition of a Fe-Ni alloy film. As a result, the quantification of CIGS films using the TNC method was found to be a good candidate as a subject for a CCQM key comparison.
Endosulfan – an agricultural insecticide and banned by Stockholm Convention – is produced as a 2:1 to 7:3 mixture of isomers endosulfan I (ESI) and endosulfan II (ESII). Endosulfan is transformed under aerobic conditions into endosulfan sulfate (ESS). The study shows for 76 sampling locations in German forests that endosulfan is abundant in all samples with an opposite ratio between the ESI and ESII than the technical product, where the main metabolite ESS is found with even higher abundance. The ratio between ESI/ESII and ESS show clear dependence on the type of stands (coniferous vs. deciduous) and humus type and increases from deciduous via mixed to coniferous forest stands. The study argues for a systematic monitoring of ESI, ESII, and ESS and underlines the need for further research, specifically on the fate of endosulfan including biomagnifications and bioaccumulation in soil.
Molecular imaging of inflammatory lung diseases, such as asthma, has been limited to date. The recruitment of innate immune cells to the airways is central to the inflammation process. This study exploits these cells for imaging purposes within the lung, using inhaled polystyrene nanoparticles loaded with the near-infrared fluorescence dye Itrybe (Itrybe-NPs). By means of in vivo and ex vivo fluorescence reflectance imaging of an ovalbumin-based allergic airway inflammation (AAI) model in hairless SKH-1 mice, we show that subsequent to intranasal application of Itrybe-NPs, AAI lungs display fluorescence intensities significantly higher than those in lungs of control mice for at least 24 h. Ex vivo immunofluorescence analysis of lung tissue demonstrates the uptake of Itrybe-NPs predominantly by CD68+CD11c+ECF-L+MHCIIlow cells, identifying them as alveolar M2 macrophages in the peribronchial and alveolar areas. The in vivo results were validated by confocal microscopy, overlapping tile analysis, and flow cytometry, showing an amount of Itrybe-NP-containing macrophages in lungs of AAI mice significantly larger than that in controls. A small percentage of NP-containing cells were identified as dendritic cells. Flow cytometry of tracheobronchial lymph nodes showed that Itrybe-NPs were negligible in lung draining lymph nodes 24 h after inhalation. This imaging approach may advance preclinical monitoring of AAI in vivo over time and aid the investigation of the role that macrophages play during lung inflammation. Furthermore, it allows for tracking of inhaled nanoparticles and can hence be utilized for studies of the fate of potential new nanotherapeutics.
Konventionell wird in der Bauteilauslegung zwischen Konzepten der Schwing- und Betriebsfestigkeit auf der einen und der Bruchmechanik auf der anderen Seite unterschieden. Werden in der Schwingfestigkeitsbewertung Gesamtlebensdauern ermittelt, so sind es in der Bruchmechanik Restlebensdauern bei Vorhandensein eines größeren, d.h., bereits zerstörungsfrei auffindbaren Risses. Daneben gibt es seit längerem Bestrebungen, bruchmechanische Ansätze auch für die Ermittlung der Gesamtlebensdauer fruchtbar zu machen. Der besondere Wert einer solchen Kombination besteht darin, dass die Bruchmechanik die explizite theoretische Behandlung von Eingangsparametern (Kerben, Oberflächenrauhigkeit, Mittelspannung, etc.) erlaubt, die in den konventionellen Ansätzen mit vergleichsweise hoher Ungenauigkeit halbempirisch einbezogen werden. Der Beitrag stellt einen von den Autoren entwickelten bruchmechanischen Ansatz zur Ermittlung von Wöhlerkurven vor, der eine Reihe innovativer Merkmale wie die Anwendung der elastischplastischen Bruchmechanik auf kurze Risse, die Ermittlung der Ausgangsrissgröße aus Rissarrestbetrachtungen, die Beschreibung der transienten Entwicklung des Rissschließeffekts mit Hilfe zyklischer R-Kurven (Risslängenabhängigkeit des Schwellenwertes von der Risstiefe), die theoretische Erfassung von Mehrfachrisswachstum bei Lastniveaus oberhalb der Dauerfestigkeit und statistische Aspekte umfasst. Das diskutierte Beispiel ist eine Schweißverbindung (Stumpfnaht) und wurde im Rahmen des laufenden Cluster-Projektes IBESS (Integrale bruchmechanische Ermittlung der Schwingfestigkeit von Schweißverbindungen) generiert.
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been suggested as a promising tool for the investigation of pollen, but the usefulness of this approach for classification and identification of pollen species has to be proven by an application to samples of varying taxonomic relations.
Gamma radiation induced effects in perfluorinated polymer optical fibers for sensing applications
(2015)
Radiation induced attenuation in perfluorinated polymer optical fiber was investigated as a potential mean for online. in situ gamma radiation monitoring. Spectral dependence of radiation induced attenuation was measured in the visible and near infrared range. Attenuation spectrum exhibits sharp increase both towards the ultraviolet and infrared side of the spectrum with 3 distinct peaks around 1400 nm. The fiber sensitivity to gamma radiation was further evaluated at two commonly used IR wavelengths (1310nm and l550nm} by pre- and post-irradiation optical time-domain reflectometry measurements. The examined fiber is sensitive up to lOO kGy of total absorbed dose with only minor saturation towards the large dose values. The influence of gamma radiation on the fiber mechanical properties was studied as well. Up to the maximal dose of 100 kGy, no significant deterioration of fiber strength and elasticity was observed.
The analytical utility of a new and simple to use ionization method, matrix-assisted ionization (MAI), coupled with ion mobility spectrometry (IMS) and mass spectrometry (MS) is used to characterize a 2-armed europium(III)-containing poly(ethylene glycol) (Eu-PEG) complex directly from a crude sample. MAI was used with the matrix 1,2-dicyanobenzene, which affords low chemical background relative to matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI). MAI provides high ion abundance of desired products in comparison to ESI and MALDI. Inductively coupled plasma-MS measurements were used to estimate a maximum of 10% of the crude sample by mass was the 2-arm Eu-PEG complex, supporting evidence of selective ionization of Eu-PEG complexes using the new MAI matrix, 1,2-dicyanobenzene. Multiply charged ions formed in MAI enhance the IMS gas-phase separation, especially relative to the singly charged ions observed with MALDI. Individual components are cleanly separated and readily identified, allowing characterization of the 2-arm Eu-PEG conjugate from a mixture of the 1-arm Eu-PEG complex and unreacted starting materials. Size-exclusion chromatography, liquid chromatography at critical conditions, MALDI-MS, ESI-MS, and ESI-IMS-MS had difficulties with this analysis, or failed.
Trimesoyl chloride is polycondensed with various alpha,omega'-alkanediols in dichloromethane at different concentrations using equifunctional feed ratios. As evidenced by MALDI-TOF (matrix assisted laser desorption/ionization-time of flight) mass spectrometry the soluble reaction products mainly consist of perfect multicyclic oligomers and polymers. The solphase extracted from the gels also consists of perfect multicycles. SEC (size exclusion chromatography) measurements show that both soluble reaction products and extracted solphases also contain a high molar mass fraction of perfect and nonperfect multicycles extending up to masses beyond 10 5 g mol-1. When the polycondensation is stopped after a few minutes perfect multicycles are already detectable in the reaction mixture along with functional (multi)cyclic oligomers. These results prove that at initial monomer concentrations < 0.2 mol L-1 networks and large multicyclic polymers are synthesized from functional cyclic oligomers formed in early stages of the polycondensation and not from hyperbranched polymers. This interpretation is presented as 'egg-first theory' and compared with the 'hen-first theory' of Stockmayer and Flory.
Coatings deposited by magnetron co-sputtering from a single RF magnetron with a ceramic SnO2 target with iron inset in argon plasma were studied. The mass spectra of the process identified Sn+ and SnO+ species as the dominant species sputtered from the target, but no SnO2+ species were detected. The dominant positive ions in argon plasma are Ar+ species. The only detected negative ions were O-. Sputtered neutral tin related species were not detected. Iron related species were also not detected because their concentration is below the detection limit.
The concentration of iron dopant in the tin oxide coatings was controlled by the RF bias applied on the substrate holder while the discharge pressure also has some influence. The iron concentration was in the range from 0.9 at.% up to 19 at.% increasing with the substrate bias while the sheet resistivity decreases. The stoichiometry ratio of O/(Sn + Fe) in the coatings increased from 1.7 up to 2 in dependence on the substrate bias from floating bias (- 5 V) up to - 120 V of RF self-bias, respectively. The tin in the coatings was mainly bonded in Sn4 + state and iron was mainly in Fe2 + state when other tin bonding states were detected only in a small amounts. Iron bonding states in contrary to elemental compositions of the coatings were not influenced by the RF bias applied on the substrate.
The coatings showed high transparency in the visible spectral range. However, an increased metallic behavior could be detected by using a higher RF bias for the deposition. The X-ray diffraction patterns and electron microscopy pictures made on the coatings confirmed the presence of an amorphous phase.
High-temperature-high pressure stress-strain testing of materials in CO2-containing saline solutions
(2015)
In-situ stress-strain testing under corrosive environment, such as corrosive gasses (e.g. CO2) and highly saline water, is a challenge in testing corrosion fatigue of materials, e.g. for geothermal application or CCS (carbon capture and storage). The first corrosion chamber system was designed for performance at ambient pressure up to 100 °C. The second allows for corrosion fatigue testing at high pressure up to 200 bar and 400 °C. The highly flexible corrosion chambers allow for fast changing and easy alignment of test samples, visual monitoring, CAD-camera monitoring electrochemical measurements, O2-partial pressure or gas partial pressure measurement. Novelty is the fixing of the corrosion chamber directly onto the specimen, that guarantees best fitting and enables the test system to be modified easily suiting a variety of fatigue test machines. All parts of the test system are conforming to the technical rules.
Continuously tuneable liquid crystal based stripline phase shifter realised in LTCC technology
(2015)
This work presents the design, fabrication and measurements of a low temperature cofired ceramic (LTCC) integrated liquid crystal (LC) phase shifter. The effective permittivity of the phase shifter and therefore its differential phase shift can be tuned continuously by orienting the LC directors with electric fields. The phase-shift demonstrator is designed for Ka-band frequencies around 30 GHz and represents a stripline filled with LC, embedded inside an LTCC multilayer structure, which provides a space-qualified and hermetically-sealed LC cavity within an RF-capable material system. The total length of the device is 37 mm while the phase shifting LC section has a length of 14.6 mm. At 30 GHz it exhibits a differential phase shift of 60° with an insertion loss around 6 dB, resulting in a figure of merit around 10°/dB. An advantage is that the insertion loss is nearly independent of the tuning state of the LC. The response time of the phase shifter, depending on the desired LC orientation, is between 62 ms and 37 s.
As polypeptoids become increasingly popular, they present a more soluble and processable alternative to natural and synthetic polypeptides; the breadth of their potential functionality slowly comes into focus. This report analyzes the ability of an alkyne-functionalized polypeptoid, poly(N-propargyl glycine), to crosslink upon heating. The crosslinking process is analyzed by thermal analysis (differential scanning calorimetry and thermogravimetric analysis), Fourier-transform infrared, electron paramagnetic resonance, and solid-state NMR spectroscopy. While a precise mechanism cannot be confidently assigned, it is clear that the reaction proceeds by a radical mechanism that exclusively involves the alkyne functionality, which, upon crosslinking, yields alkene and aromatic products.
In diesem Artikel wird ein 3D FE-Modell für den Brückenübergangsbereich vorgestellt, das eine Bewertung hinsichtlich des Langzeitverhaltens ermöglicht und an dem Optimierungsmaßnahmen diskutiert werden können. Bestandteile des numerischen Modells sind das Fahrzeug-Fahrwegmodell mit Brückenstruktur und eine Randformulierung mit der SBFEM. Die hier diskutierten Optimierungsmaßnahmen fokussieren sich auf eine reine Anpassung der Fahrwegsteifigkeit durch elastische Elemente auf der Brückenstruktur.
Zusammen mit der Genauigkeit von Messungen ist die ihnen zugeordnete Messunsicherheit Ausdruck und Maß von Vergleichbarkeit und Richtigkeit. Die Messunsicherheit spielt ebenso die Schlüsselrolle im Aufbau einer Rückführbarkeitskette, wie in diesem Beitrag beschrieben. Es ist der vierte und letzte Teil einer Artikelserie (siehe Infokasten), die Einblicke gibt in die Arbeit des DIN-Normenausschusses „Gasanalyse und Gasbeschaffenheit“ (DIN NA 062-05-73 AA) sowie der international tätigen Technical Committees 158 und 193 der ISO.
In this work, the effect of the pressure-assisted sintering process on buried thick film resistors integrated in LTCC multilayer has been studied. Four commercial resistor pastes with sheet resistivities between 10 kΩ and 10 MΩ/cm were analyzed. First they were characterized by SEM/EDX, XRD and Laser diffraction to determine composition and particle distribution. The pastes consist of isolating particles and of Ruthenium based particles that are supposed to build the conductive phase. The pastes were screen printed on LTCC green tape (DP 951) and buried in four layer laminates. Sintering was done in two ways, pressureless (PLS) and also pressure-assisted (PAS). The pressureless sintered resistors showed electrical resistance values roughly in the range of the nominal sheet resistivity and only relatively small fluctuation within one sample. The PAS samples on the other hand showed significantly higher resistances and larger deviations. The microstructure of the sintered resistors was again investigated by SEM and XRD. It seems that the resistivity is determined by the ratio of the two Ruthenium phases RuO2 and Pb2Ru2O6.5, where RuO2 has the higher conductivity. Buried resistors cannot be trimmed by a laser to adjust the resistance. But we discovered that a refiring step will reduce and normalize the resistivity of the PAS resistors significantly.
Sintering and foaming of barium and calcium silicate glass powder compacts have been studied for different powder milling. Sintering was measured by means of heating microscopy backed up by XRD, DTA, Vacuum Hot Extraction (VHE) and electron microscopy. Foaming intensity strongly increased with decreasing glass partiefe size. Although powder compacts were uniaxially pressed and sintered in ambient air, foaming was affected by the milling atmosphere and most intensive for milfing in C02. Conformingly, VHE studies revealed that foaming of fully sintered samples was mainly driven by C02, even for powders milled in technical air, Ar and N2. Prolonged storage of air milled barium silicate glass powders in ambient air before pressing and sintering caused further increase of foaming intensity. These findings indicate that carbonaceous species are preferentially trapped to or close beneath the powder surface during milling and later storage. The temperature range of C02 degassing from fully sintered barium and calcium silicate g/ass powder compacts fits the temperature ranges of decomposition of BaC03 and CaC03 mix-milled with the respective barium and calcium silicate glass powders.
Components in the Aerospace, Power and Automotive engineering sectors are frequently subjected to cyclic stresses induced by thermal fluctuations and mechanical loads. For the design of such components, reliable material property data are required which need to be acquired using well accepted and reproducible test procedures for thermo-mechanical fatigue (TMF) loading. Available materials TMF property data are limited so that there is a need for further TMF data generated by TMF testing. The TMF behaviour of materials is often desired to be simulated in models which describe the cyclic stress-strain behaviour, the fatigue life and the cyclic crack growth behaviour. There is a continuous need for the development and amendment of such models. Models can be validated by using materials in industrial applications which are subjected to TMF loading.
Two Photon Microscopy (2PM) generates microscopic images out of depth of biological samples. Up to now the method is restricted by narrow limitations of the field of view, the imaging depth and the orientation of the image field. A new approach overcomes these boundaries and delivers high resolution images revealing very specific information on clinically and biologically relevant tissue and cell structures. The status of the 2PM technology is critically reviewed and the options are discussed. The advantages of the new approach demonstrated by excellent tissue images.
Diclofenac (DCF) wird als nicht-steroidales, antientzündliches Arzneimittel gegen Fieber, Entzündungen, rheumatische Erkrankungen und Schmerzen eingesetzt. 70 % werden nach Einnahme wieder ausgeschieden. Aufgrund unvollständiger Elimination in den Kläranlagen lassen sich Rückstände im Trinkwasser und im Oberflächengewässer nachweisen. Diclofenac wird in der Umweltanalytik v.a. mittels GC-MS oder LCMS nachgewiesen. Bioanalytische Methoden machen sich die spezifische Antigen-Antikörper-Wechselwirkung zunutze, so z.B. Immunoassays. Die hierfür erforderlichen Antikörper werden durch Immunisierung mit einem Konjugat aus dem Analyten und einem Trägerprotein gewonnen. Die Kopplung kann direkt über die Carboxylfunktion von Diclofenac erfolgen. Um Abschirmungseffekte zu vermeiden, kann zwischen Protein und Analy1 ein Spacer sinnvoll sein.
In contact with aqueous media glass tends to corrode leading to different surface properties. For the precision application this alteration might cause product failure. Hence precise knowledge of the surface interactions is essential. We performed an extensive investigation on the behavior of borosilicate glass under corrosive attack in order to identify critical processes. We identified appropriate investigation methods including sequential chemical analysis, ATR-IR, ellipsometry and SNMS. These techniques allow to identify the influence of specific production processes.
Mit Hilfe des KorroPad-Prüfverfahrens konnten verschiedene umgebungs- sowie prozessbedingte Einflüsse in Parameterstudien gezielt untersucht werden. So konnte der negative Einfluss von korundbasierten Schleifmitteln auf die Passivschichtausbildung nachgewiesen werden. Weiterhin konnte mittels KorroPad die Wirksamkeit verschiedener Oberflächenbearbeitungsverfahren bei der Schweißnahtnachbearbeitung untersucht und daraus Erkenntnisse für die Prozessoptimierung gewonnen werden. In den hier gezeigten Untersuchungen hat sich das KorroPad-Prüfverfahren für die Beschreibung der Passivschichtstabilität als hervorragend geeignet erwiesen.
The expression of cell surface glycans terminating with sialic acid (SA) residues has been found to correlate with various disease states there among cancer. We here report a novel strategy for specific fluorescence labeling of such motifs. This is based on sialic acid-imprinted core–shell nanoparticles equipped with nitrobenzoxadiazole (NBD) fluorescent reporter groups allowing environmentally sensitive fluorescence detection at convenient excitation and emission wavelengths. Imprinting was achieved exploiting a hybrid approach combining reversible boronate ester formation between p-vinylphenylboronic acid and SA, the introduction of cationic amine functionalities, and the use of an NBD-appended urea-monomer as a binary hydrogen-bond donor targeting the SA carboxylic acid and OH functionalities. The monomers were grafted from 200 nm RAFT-modified silica core particles using ethylene glycol dimethacrylate (EGDMA) as cross-linker resulting in a shell thickness of ca. 10 nm. The particles displayed strong affinity for SA in methanol/water mixtures (K = 6.6 × 105 M-1 in 2% water, 5.9 × 103 M-1 in 98% water, Bmax ≈ 10 µmol g-1), whereas binding of the competitor glucuronic acid (GA) and other monosaccharides was considerably weaker (K (GA) = 1.8 × 103 M-1 in 98% water). In cell imaging experiments, the particles selectively stained different cell lines in correlation with the SA expression level. This was further verified by enzymatic cleavage of SA and by staining using a FITC labeled SA selective lectin.
Recently, the detection of molecular species in laser-induced breakdown spectroscopy (LIBS) has gained increasing interest, particularly for isotopic analysis. In LIBS of organic materials, it is predominantly CN and C2 species that are formed, and multiple mechanisms may contribute to their formation. To gain deeper insight into the formation of these species, laser-induced plasma of 13C and 15N labeled organic materials was investigated in a temporally and spatially resolved manner. LIBS on fumaric acid with a 13C labeled double bond allowed the formation mechanism of C2 to be investigated by analyzing relative signal intensities of 12C2, 12C13C, and 13C2 molecules. In the early plasma (<5 µs), the majority of C2 originates from association of completely atomized target molecules, whereas in the late plasma, the increased concentration of 13C2 is due to incomplete dissociation of the carbon double bond. The degree of this fragmentation was found to be up to 80% and to depend on the type of the atmospheric gas. Spatial distributions of C2 revealed distinct differences for plasma generated in nitrogen and argon. A study of the interaction of ablated organics with ambient nitrogen showed that the ambient nitrogen contributed mainly to CN formation. The pronounced anisotropy of the C15N to C14N ratio across the diameter of the plasma was observed in the early plasma, indicating poor initial mixing of the plasma with the ambient gas. Overall, for accurate isotope analysis of organics, LIBS in argon with relatively short integration times (<10 µs) provides the most robust results. On the other hand, if information about the original molecular structure is of interest, then experiments in nitrogen (or air) with long integration times appear to be the most promising.
Under the assumption of local thermal equilibrium, a numerical algorithm is proposed to find the equation of state for laser-induced plasmas (LIPs) in which chemical reactions are permitted in addition to ionization processes. The Coulomb interaction in plasma is accounted for by the DebyeHückel method. The algorithm is used to calculate the equation of state for LIPs containing carbon, silicon, nitrogen, and argon. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules N2 ,C2 ,Si2 ,CN,SiN,SiC and their ions. The algorithm is incorporated into a fluid dynamic numerical model based on the NavierStokes equations describing an expansion of LIP plumes into an ambient gas. The dynamics of LIP plumes obtained by the ablation of SiC, solid silicon, or solid carbon in an ambient gas containing N2 and Ar is simulated to study formation of molecules and molecular ions.
Raman microspectroscopy provides the means to obtain local orientations on polycrystalline materials at the submicrometer level. The present work demonstrates how orientation-distribution maps composed of Raman intensity distributions can be acquired on large areas of several hundreds of square micrometers. A polycrystalline CuInSe2 thin film was used as a model system. The orientation distributions are evidenced by corresponding measurements using electron backscatter diffraction (EBSD) on the same identical specimen positions. The quantitative, local orientation information obtained by means of EBSD was used to calculate the theoretical Raman intensities for specific grain orientations, which agree well with the experimental values. The presented approach establishes new horizons for Raman microspectroscopy as a tool for quantitative, microstructural analysis at submicrometer resolution.
New V-shaped non-centrosymmetric dyes, possessing a strongly electron-deficient azacyanine core, have been synthesized based on a straightforward two-step approach. The key step in this synthesis involves palladium-catalysed cross-coupling of dibromo-N,N'-methylene-2,2'-azapyridinocyanines with arylacetylenes. The resulting strongly polarized π-expanded heterocycles exhibit green to orange fluorescence and they strongly respond to changes in solvent polarity. We demonstrate that differently electron-donating peripheral groups have a significant influence on the internal charge transfer, hence on the solvent effect and fluorescence quantum yield. TD-DFT calculations confirm that, in contrast to the previously studied bis(styryl)azacyanines, the proximity of S1 and T2 states calculated for compounds bearing two 4-N,N-dimethylaminophenylethynyl moieties establishes good conditions for efficient intersystem crossing and is responsible for its low fluorescence quantum yield. Non-linear properties have also been determined for new azacyanines and the results show that depending on peripheral groups, the synthesized dyes exhibit small to large two-photon absorption cross sections reaching 4000 GM.
Dieser Bericht beschreibt ein Systemmodell für eine integrale Ermittlung und Prognose der Schadens- und Zustandsentwicklung der Elemente eines Brückensystems unter Berücksichtigung von Ergebnissen aus Inspektionen und Überwachung. Das Systemmodell wurde anhand eines ausgesuchten Spannbetonüberbaus in einzelliger Kastenbauweise entwickelt. Es besteht aus zwei integralen Teilmodellen: ein Modell zur Beschreibung des Systemschädigungszustandes und ein Modell zur Beschreibung der Standsicherheit. Für die Modellierung des stochastischen Systemschädigungszustandes eines Brückensystems werden dynamische Bayes'sche Netze (DBN) vorgeschlagen. Dieser Ansatz ermöglicht es, alle relevanten Schädigungsprozesse und deren stochastische Abhängigkeiten zu berücksichtigen. Ein wesentlicher Vorteil dieses Ansatzes ist es, dass DBN ideal dafür geeignet sind, Bayes'sche Aktualisierungen auf Grundlage von Informationen aus Inspektionen und Überwachungsmaßnahme auf eine effiziente und robuste Art und Weise durchzuführen. Der DBN-Ansatz ist deshalb für die Entwicklung von Software für das Erhaltungsmanagement von alternden Brückenbauwerken, die vom Benutzer keine vertieften Kenntnisse der Zuverlässigkeitstheorie verlangt, ideal geeignet. Für die Modellierung der Standsicherheit eines alternden Kastenträgers wird vereinfachend Biegeversagen des globalen Längssystems betrachtet. Zur Berechnung der maximalen Traglast eines Kastenträgers infolge des Systemschädigungszustandes wird ein plastisch-plastisches Verfahren eingesetzt, wobei die Beanspruchungen mittels der Fließgelenktheorie unter Ausnutzung der plastischen Beanspruchbarkeit der Querschnitte des Kastenträgers ermittelt werden. Ein Kastenträger versagt, wenn sich durch die Ausbildung einer ausreichend großen Anzahl von Fließgelenken eine kinematische Kette ausbildet. Dieser Modellierungsansatz berücksichtigt Redundanzen, die sich aus der plastischen Beanspruchbarkeit der Querschnitte und der statischen Unbestimmtheit eines Kastenträgers ergeben. Zum Nachweis der praktischen Einsetzbarkeit des entwickelten Systemmodells wurde ein Software-Prototyp entwickelt, der eine intuitiv benutzbare graphische Benutzeroberfläche (Front-End) mit einem Berechnungskern (Back-End) koppelt. Die aktuelle Version des Software-Prototyps implementiert ein Modell der chloridinduzierten Bewehrungskorrosion und ein Tragwerksmodell, welches das Verfahrens der stetigen Laststeigerung zur Bestimmung der maximalen Traglast des Kastenträgers auf der Grundlage eines Finite-Elemente-Modells umsetzt. Zur Durchführung von Bayes'schen Aktualisierungen des Systemschädigungszustandes auf der Grundlage des DBN-Modells implementiert der Prototyp den Likelihood-Weighting-Algorithmus. Die entwickelte Architektur des Prototyps ermöglicht eine Erweiterung der Software um weitere Schädigungsprozesse. Der entwickelte Software-Prototyp ermöglicht Benutzern ohne vertiefte Kenntnisse der Zuverlässigkeitstheorie eine Berechnung des Einflusses von Bauwerksinformationen auf den Systemschädigungszustand und die Tragsicherheit eines Kastenträgers. Auf dieser Grundlage können effiziente Inspektions- und Überwachungsmaßnahmen identifiziert und das Erhaltungsmanagement optimiert werden.
For the assessmentand for monitoring of timber structures there are numerous promising methods that enable the quantitative description of the current condition of construction elements or parts of a structure. This concerns material properties like modulus of elasticity, moisture content and density as well as structural properties like dynamic characteristics, localization of inhomogeneities, cracks, and biological attack. During the work in COST Action FP 1101, since 2012 the capability of experimental methods are discussed and compared. This covers electrical and electromagnetic wave methods (resistivity, microwave, Radar, X-Ray), elastic waves (ultrasound, pile testing) and mechanical testing (static and dynamic). Describing and collecting the use of the experimental methods for monitoring purposes was the objective of working group 3 "Monitoring of Timber Structures" of the COST Action. Monitoring capabilities will extend the use of timber structures to further applications in civil engineering. So far, no standard exists but collections of application examples and review papers representing the state of the art. From there needs for further developments regarding monitoring and NDT methods for timber structures can be identified and these are described in this paper.
Gradient porous silicon nitride (Si3N4) was fabricated by a novel vacuum foaming and freeze drying process. Aqueous Si3N4 slurries were foamed at vacuum pressure of 50–90 kPa, the green body was obtained by the freeze drying process, a gradient pore structure with porosities of 72–90% was achieved after pressureless sintering at 1680 °C. The porosity was increased with decreasing vacuum pressure. The pore structure consists of large pores (~100 μm) on top, medium pores (~45 μm) on the wall of the large pores, and small pores (~0.7 μm) in the matrix. Such gradient porous Si3N4 with macro- and micro-pores has potential application as high temperature filters.
DIN 50100 definiert die Bedingungen für den Schwingfestigkeitsversuch, der zur Ermittlung von Kennwerten dient, die das Verhalten metallischer Werkstoffe und Bauteile bei zyklischer Beanspruchung mit einer konstanten Lastamplitude beschreiben (Wöhlerversuch). Die Norm umfasst die Versuchsdurchführung, die Versuchsauswertung sowie die Dokumentation von lastgeregelten Wöhlerversuchen im Zeit- und Langzeitfestigkeitsbereich. Mit DIN 50100 soll erreicht werden, dass die Wöhlerlinien verschiedener Prüfstellen miteinander vergleichbar und die wesentlichen Randbedingungen der Versuchsdurchführung dokumentiert werden. Da die Ergebnisse von Schwingfestigkeitsversuchen streuen, ist die Treffsicherheit für die Schätzung der Kennwerte von der Anzahl der Versuche einer Versuchsreihe abhängig. In Abhängigkeit von einer geforderten Treffsicherheit wird durch die DIN 50100 der erforderliche Stichprobenumfang vorgegeben.
Room temperature mechanical behavior of extruded Mg–Y–Zn alloys with varying fractions of LPSO phase was studied in tension and compression along the extrusion direction. The microstructure is characterised by elongated LPSO fibers along the extrusion direction within the magnesium matrix. Moreover, the magnesium matrix presents a bimodal grain structure with dynamically-recrystallized grains and deformed, elongated grains with the basal plane parallel to the extrusion direction. The beginning of plasticity depends on the volume fraction of deformed and DRX grains. Alloys with low volume fraction of LPSO phase (<10 vol%), with a high volume fraction of deformed grains, show the typical behavior of extruded magnesium alloys where yield stress in tension is higher than in compression. This effect is, however, reversed as the volume fraction of the LPSO phase increases since DRX grains are majority.
Different electronic sensor systems coupled with multivariate data analysis were applied to characterize and classify seven saffron samples and to verify their declared geographical origin. The proposed electronic sensing consists of a low-cost electronic nose (E-nose) based on metal oxide semiconductor sensors and a voltammetric electronic tongue (VE-tongue) based on voltammetric sensors. The ability of multivariable analysis methods such as Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and Support Vector Machines (SVMs) to classify the saffron samples according to their geographical origin have been investigated. Both PCA and HCA have shown an overlapping of E-nose responses. Moreover, the SVM analysis of the E-nose database reached a 66.07% success rate in the recognition of the saffron sample odour. On the other hand, good discrimination has been reached using PCA and HCA in the VE-tongue characterization case, besides a 100% accuracy in the saffron flavour recognition was attained. To validate the proposed electronic sensing systems, analytical chemical methods such as SPME-GC-MS and UV-Vis spectrophotometry were used. These analytical methods could be helpful tools to identify the composition of volatile compounds of the analysed saffron samples. Moreover, UV-Vis spectrophotometry was also used to determine the non-volatile profile of the samples from different geographic origins. It is demonstrated that the electronic sensing systems' findings are in a satisfactory correlation with the analytical methods. In the light of these results, we might say that the electronic systems offer a fast, simple and efficient tool to recognize the declared geographical origin of the saffron samples.
Fiber optic sensors have gained increasing importance in recent years and are well established in many areas of industrial applications. In this paper, we introduce a concept of a self-diagnostic fiber optic sensor. The presented sensor is to resolve the problems of embedded fiber optic sensors in complex structures and to enable the validation under operational conditions. For this purpose, different magnetostrictive coated fiber optic sensors were developed and various experiments were performed to verify their mode of operation and to determine the respective reproducibility. The measuring principle is illustrated by obtained experimental results, which showed a change in wavelength from 1 pm at a magnetic field strength change of 0.25 mT. In addition, the temperature characteristics of the implemented magnetostrictive sensor were analyzed and an experimental factor of 1.5 compared to a reference fiber optic sensor was determined.
Porous polymer membranes made via electrostatic complexation are fabricated from a water-soluble poly(ionic liquid) (PIL) for the first time. The porous structure is formed as a consequence of simultaneous phase separation of the PIL and ionic complexation with an acid, which occurred in a basic solution of a nonsolvent for the PIL. These membranes have a stimuli-responsive porosity, with open and closed pores in isopropanol and in water, respectively. This property is quantitatively demonstrated in filtration experiments, where water is passing much slower through the membranes than isopropanol.
An ionization scheme for fast online mass spectrometric interrogation of levitated droplets is presented. That renewed method comprises the output of an a Er:YAG laser at λ = 2.94 µm which is in resonance with the OH stretch vibration band of solvents like water and alcohols. A temporal pulse width larger than the time needed for pressure redistribution and also above the temperature redistribution time constant was found to lead to soft evaporation/ionization. Despite these mild desorption conditions, no additional postionization is found to be needed. Accordingly, the ionization is found to be very soft resulting in entirely intact analyte ions and concentration dependent cluster ions. Resulting mass spectra of small amino acids and large antibiotics are presented showing the versatility of the introduced technique. Above a critical mass of m ≈ 1 kDa, the formed ions carry multiple charges as it is typical for thermospray or electrospray ionization. The detection technique enables fast contactless analysis of the chemical composition of levitated microreactors and, thus, paves the way for future contactless reaction monitoring.
For many sealing applications rubbers are applied due to their special material properties and easy use. In many applications as e.g. in aviation, traffic or process technology the material can be exposed to low temperatures during operation. Therefore it is important to know the material behaviour at those low temperatures to determine the temperature range that allows a safe operation of the seal. As rubbers are used as main sealing materials for containers for low and intermediate level radioactive waste and as additional component to metal seals in spent fuel and high acitve waste containers, a comprehensive elastomer investigation program is run at BAM. This program comprises investigations of elastomer overall performance, durability, influence of gamma irradiation and low temperature behaviour.
In this paper we focus on the behaviour of elastomer seals below ambient temperatures after a fast partial release. Despite the primarily static application conditions of many seals their behaviour after partial compression release is of interest with regard to potential decrease of leak-tightness.
For this investigation a special setup was designed which allows the partial release of compressed seal systems at different temperatures accompanied by leakage rate measurements.
The results for FKM seals are presented and discussed.
Metal organic vapor phase epitaxy (MOVPE) of Mn-rich (Mn,Ga)As on (001) oriented GaAs wafers resulted in atomically ordered (Mn,Ga)As crystallites of two morphological kinds, partially embedded on the wafer surface and fully embedded within the single crystalline matrix. While the former were apparently free of defects (other than unavoidable point defects), the latter contained two domains separated by a grain boundary. Since atomic ordering can be modeled by space group symmetry descent considerations (Bärnighausen trees) that start with the space group of the known crystallographic phases of random (Mn,Ga)As alloys with specified chemical compositions, reasonable structure hypotheses have been derived for two atomically ordered Mn0.75Ga0.25As phases that we call the trigonal α' and the monoclinic β' phases. The implications of these structure hypotheses are in agreement with the results of a range of scanning transmission electron microscopy (STEM) and parallel illumination electron diffraction (ED) studies that include quantitative energy dispersive X-ray spectroscopy, X-ray spectroscopic imaging, as well nanobeam diffraction and high angle precession ED. The coexistence of two domains within the fully embedded crystallites is predicted by the corresponding Bärnighausen tree and observed experimentally for the fully embedded crystallites.
This paper presents the continuous dynamic measurements of an aging prestressed box-beam bridge during the period from 2000 to 2013, which consists of dynamic properties and environmental/operational factors, as well as the Variation of the extracted health features after removing the environmental/operational effects. Firstly, the variations of frequency estimates, temperatures and traffic loads from 2000 to 2013 are described. Subsequently, correlation analysis between them indicates the nonlinear influences of the temperature on the frequency estimates. The Multiple Linear Regression (MLR) method is used to remove the environmental/operational effects and the health index is proposed by performing the Novelty Detection analysis of the residual errors. Finally, the variations of the health index may indicate clear structural modifications that can be also characterized by the long term monitoring of the dynamic strain in the prestressed cable.
Ein statistischer Bewertungsansatz für Technologien oder Produkte erfordert die Festlegung definierter Grenzwerte für die Mindestzuverlässigkeit, um die Wahrscheinlichkeit eines kritischen Versagens auf einem akzeptablen Niveau bewerten zu können. Dabei gestaltet sich sowohl die Definition akzeptierter Technologierisiken als auch die Ermittlung der tatsächlichen Risiken auf der Basis von Eintrittswahrscheinlichkeit und der Konsequenz eines Versagens stets komplex. Am Beispiel des statistischen Ansatzes der BAM zur Sicherheitsbeurteilung von Composite-Druckgefäßen wird das definierte Sicherheitsniveau und die zu erwartenden Konsequenzen ermittelt und bestehenden Akzeptanzgrenzen gegenübergestellt.
Partial penetration welding with a fiber laser at a 9-kW laser power was carried out on 20-mm-thick plates at different positions and analyzed by both experimental and numerical methods. Experiments were carried out for four different angular positions at 1.5 m/min welding speed. All four cases showed a tail-like structure of molten pool on the top surface. The in-depth mechanisms of the energy input characteristics in fiber laser position welding for eight different positions were studied by numerical simulation using the volume-of-fluid (VOF) method. Experimental and numerical results were compared for four cases and showed fair agreement. Observation of flow pattern and bead shape revealed that gravity had little influence on bead shape and flow structure, but changed the pore structure considerably. Flow structure showed a periodic behavior which probably nullified the effect of gravity in position welding. Most of the laser rays reached the bottom of the keyhole without interruption and then multiple reflections started within the keyhole. The first five reflections inside the keyhole delivered around 70 % of the total energy.
The fire behaviour of light-weight material used in structural applications is regarded as the main challenge to be solved for mass transportation. The task is to perform realistic experiments, including a mechanical test scenario under fully developed fires, to improve the material's reliability in structural applications. Our approach utilises an intermediate-scale test set-up (specimen size 500 × 500 mm) to apply realistic compressive loads and fully developed fires directly to one side of a carbon-fibre-reinforced sandwich composite. Three different intumescent coatings were applied to sandwich structures and compared to a bench-scale study. The results emphasise intumescent coatings as a promising method to sustain fire resistance, multiplying the time to failure. Nevertheless, the realistic intermediate-scale test using severe direct flame application underlines the extremely short failure times when the actual composite components are tested without any additional insulation.
Location estimation and navigation, especially on smartphones has shown great progress in the past decade due to its low cost and ability to work without additional infrastructure. However, a challenge is the positioning, both in terms of step detection, step length approximation as well as heading estimation, which must be accurate and robust, even when the use of the device is varied in terms of placement or orientation. In this paper, we propose a scheme for retrieving relevant information to detect steps and to estimate the correct step length from raw inertial measurement unit (IMU) data. This approach uses Bidirectional Long Short-Term Memory Recurrent Neural Networks (BLSTM-RNNs). Designed to take contextual information into account, the network can process data gathered from different positions, resulting in a system, which is invariant with respect to transformation and distortions of the input patterns. An experimental evaluation on a dataset produced from 10 individuals demonstrates that this new approach achieves significant improvements over previous attempts and increase the current state-of-the-art results even in the presence of variations and degradations. We achieved a mean classification rate of 98.5% and a standard deviation of 0.70 for 10000 different test sequences and an average error of 1.45% regarding the step length. Thus is the best result on the task gathered in the experiments compared with competing techniques.
In den letzten Jahren ist die Bestimmung der Position eines sich bewegenden Objektes eine immer interessanter werdende Information geworden. Die aktuelle Position oder der zurückgelegte Weg wird mittels miniaturisierter integrierter 3D-Sensoren bestimmt. Durch die Integration dieser Sensoren in moderne Smartphones oder in spezielle robuste Hardware sind die Anwendungsgebiete vielseitig. Die ermittelte Position innerhalb von Gebäuden ist dabei für den Kaufmann innerhalb eines Shoppingcenters aber auch für den Feuerwehrmann im Einsatz wichtig. Für den Kaufmann bedeutet es durch gezielte Angebote potenzielle Kunden anzusprechen und damit seinen Umsatz zu steigern. Für den Einsatzleiter der Feuerwehr ist die genaue Position seiner Feuerwehrmänner im Einsatz lebensrettend und bietet damit eine zusätzliche Sicherheit für die Einsatzkraft. Das hier vorgestellte Multisensorsystem, allgemein als Inertialsystem bezeichnet, und das darauf angewendete Verfahren zur Positionsbestimmung wird in diesem Bericht vorgestellt und näher beschrieben. Die systematischen und zufälligen Messunsicherheitsbeiträge des Inertialsystems und deren Auswirkungen auf die Bestimmung der aktuellen Position und somit auf den resultierenden zurückgelegten Weg werden erörtert.
Glas ist ein sehr verbreiteter Werkstoff und eines der ältesten Produkte neben Keramik, Eisen und Bronze, die der Mensch schon frühzeitig herzustellen in der Lage war. Es dauerte jedoch Jahrrausende bis zur ersten wissenschaftliche Beschreibung der Glasstruktur. Sie erfolgte erstmals 1903 von TAMMANN als eine stark unterkühlte Flüssigkeit. VOGEL (1992) gibt einen Überblick über die klassischen Glasstrukturtheorien. Ganz allgernein kann Glas als ein anorganisches Schmelzprodukt definiert werden, das abgekühlt und erstarrt ist, ohne zu kristallisieren, weshalb Glas auch durchsichtig ist. Es kann aus einfachen und nahezu überall und unbegrenzt vorhandenen Rohstoffen hergestellt werden. Die Hauptbestandteile sind Sand, Soda, Pottasche und Kalk. Wesentliche Eigenschaften des Glases sind seine gute Verarbeitbarkeit mir verschiedenartigen Techniken wie Gießen, Blasen, Ziehen und die Möglichkeit, durch die Zugabe von unterschiedlichen Oxiden auch farbige Gläser herzustellen.
Nitrogen- and oxygen-based plasma polymer films are materials with a complex and partially elusive surface chemistry. We present an overview of innovative and established X-ray photoelectron spectroscopy (XPS)-based analysis strategies developed to elucidate the surface chemistry of such films. We focus on both experimental methods and data analysis strategies and include the following topics: high-resolution spectra curve fitting, aging, chemical derivatization, and depth profiling by angle- and energy-resolved XPS.
In this contribution, the development and application of optical and thermographic methods for the nondestructive evaluation of delaminations, cracks and further substructures in Connection with bulging is presented.
Since delaminated fagade elements show geometric as well as thermal anomalies, surface geometry and defects beneath the surface were investigated. As methods, Stereo photogrammetry, a tracking based method for tactile recording of geometric 3D data and active thermography were used. Two case studies were assessed with a combination of these methods: the plaster scratches at the Magdeburg Cathedral and a mural painting in Cobbelsdorf, both located in Germany. While the plaster scratches have been investigated by artificial heating with an infrared radiator, the rural painting was tested by analysing the temperature increase due to solar heating.
Die Bundesanstalt für Materialforschung und –prüfung (BAM) wurde von der AG 3 der Kommission Lagerung hoch radioaktiver Abfallstoffe gebeten, Anforderungen an Behälter für die Endlagerung hoch radioaktiver Abfallstoffe im Hinblick auf ih-re Rückholbarkeit während des Endlagerbetriebes und ihre Bergbarkeit nach Ver-schluss des Endlagers über einen Zeitraum von 500 (bis 1.000 ?) Jahren darzu-stellen. Die BAM kommt diesem Wunsch auf der Grundlage ihrer langjährigen Er-fahrungen und Fachkenntnisse auf den Gebieten der Bauartprüfung und der si-cherheitstechnischen Begutachtung von Transport- und Lagerbehältern für radio-aktive Stoffe nach.
The safety of components or constructions is of great importance in the manufacturing and processing of metallic materials. Solidification cracking as well as the weldability of materials remain still for many years a highly contentious issues, particularly with regard to the causes of the hot crack formation. Many of studies have been conducted to determine the critical condition of occurrence of the solidification cracking. In this study different digital image correlation measuring techniques in conjunction with laser diodes as the illuminating source have been employed to measure the arising strain field during the laser welding process at the surface of the workpiece directed to the laser beam in the close vicinity of the weld pool. The Controlled Tensile Weldability test (CTW) was used to apply an external tensile load during the laser beam welding in order to generate the solidification cracks. The results showed that by means of those techniques it is possible to measure the strain field without any disturbances from the intense welding light or the smoke. Additionally, the strain and the strain rate as a critical factor determining solidification crack formation can be measured and analyzed.
Probing local pH-based precipitation processes in self-assembled silica-carbonate hybrid materials
(2015)
Crystallisation of barium carbonate in the presence of silica can lead to the spontaneous assembly of highly complex superstructures, consisting of uniform and largely co-oriented BaCO3 nanocrystals that are interspersed by a matrix of amorphous silica. The formation of these biomimetic architectures (so-called silica biomorphs) is thought to be driven by a dynamic interplay between the components, in which subtle changes of conditions trigger ordered mineralisation at the nanoscale. In particular, it has been proposed that local pH gradients at growing fronts play a crucial role in the process of morphogenesis. In the present work, we have used a special pH-sensitive fluorescent dye to directly trace these presumed local fluctuations by means of confocal laser scanning microscopy. Our data demonstrate the existence of an active region near the growth front, where the pH is locally decreased with respect to the alkaline bulk solution on a length scale of few microns. This observation provides fundamental and, for the first time, direct experimental support for the current picture of the mechanism underlying the formation of these peculiar materials. On the other hand, the absence of any temporal oscillations in the local pH another key feature of the envisaged mechanism challenges the notion of autocatalytic phenomena in such systems and raises new questions about the actual role of silica as an additive in the crystallisation process.
The legend continued: The International Symposium NonDestructive Testing in Civil Engineering (NDT-CE) had returned to Berlin. The Bundesanstalt für Materialforschung und -prüfung (BAM) and the Technical University of Berlin (TUB) hosted this prestigious event in the industrial landmark building Peter-Behrens-Halle and the Test Site Technical Safety (TTS) in Horstwalde in September 2015. Almost 300 participants from more than 35 countries gathered to present recent research, exchange knowledge and to lest the newest equipment in NDT-CE. This symposium, held regularly in various locations all over the world, was organized for the third time in Berlin and is by far the largest of its kind.
The use of flames as part of shows is state of the art. Besides pyrotechnic flame projectors, the use of projectors that produce flames by burning various gases, liquids and dusts is significantly increasing. In this study infrared radiation in the wavelength range from 7.5 to 14 microns was measured for several systems (flame projectors) and set in relation to known human pain threshold levels. From this relation safety distances been determined for a static scenario (audience watching show) and compared with those of approved pyrotechnic articles.
The development of the vapour plume during the laser beam welding of metals with propagation directions along the laser beam axis leads to a reduction of the absorbed laser power in the keyhole. These unfavourable effects can be significantly mitigated by the application of a reduced ambient pressure thus decreasing the interaction between the laser beam and evaporation products, which leads to more stable welding process and results in increased penetration depth. A conventional technique use a vacuum chamber principle, similar to that, used for electron beam welding. Application of this technique is restricted by the camera size and reduces thus the advantages of this approach especially for large components. We demonstrate a possibility of mobile local vacuum application, which allows to generate a reduced pressure only in small region around the keyhole. By using of specially designed mobile pressure lock which can be moved along the welding direction absolute pressure of around 200 mbar could be obtained. This is sufficient to increase the welding depth by around 50%. Coupons from S355 were welded with an incremental laser power from 5 kW to 12 kW at atmospheric pressure and compared to those welded at ambient pressure of 200 mbar. The evaluation of the longitudinal section revealed an increase of the welding depth by about 35%. Furthermore, the welding trials in butt joint configuration on 15 mm thick plates at various laser beam power performed for atmospheric and reduced ambient pressure of around 200 mbar. The increase in welding depth up to 40% was established for reduced pressure. Particularly, low welding speeds under reduced pressure were especially advantageous in terms of increasing the welding depth.
Among the large number of new ambient ionization schemes in the last few years, dielectric barrier discharge (DBD) has witnessed special attention. In this contribution a versatile dual mode DBD is introduced and characterized by means of optical emission spectroscopy and time-of-flight mass spectrometry. A direct comparison of the individual results from spectroscopy, spectrometry and transient current/voltage consumption gives evidence for the existence of two individual operational mechanisms. The first is driven by rapid transient changes in the potential difference between the two electrodes over time (usually denoted as the homogeneous mode), while the second is caused at high static potential differences (leading to filamentary discharges). The transient versus steady-state characteristics of the individual discharge origin suggest the driving force for the current flow to be inductive and capacitive, respectively. In most cases of dielectric barrier plasmas both discharge types coexist as competitive ion formation channels, however, detailed plasma characteristics of DBDs operated under different conditions allow for a clear distinction of the individual contributions. In this way, two characteristic product channels for the ionization of ambient water could be observed resulting in the generation of either preferentially protonated water clusters or ammonium water clusters. Careful tuning of the operation parameters of the discharge device allows an operation predominated by either of the two modes. As a consequence, facile switching into the desired operational mode results in either protonated molecules or ammoniated molecules of the analyte. Plasma characteristics for both moieties were evaluated and cross-correlated on the basis of several factors including: the production of reagent ions, the individual appearance of current/voltage profiles, UV/Vis spectroscopy, voltage and flux dependence and the individual response to test compounds. Although the filamentary mode has been already discussed in the literature to induce fragmentation processes, no experimental evidence for analyte dissociation could be found in the case of the test compounds used
Bright, long-lived emission from first-row transition-metal complexes is very challenging to achieve. Herein, we present a new strategy relying on the rational tuning of energy levels. With the aid of the large N-Cr-N bite angle of the tridentate ligand ddpd (N,N′-dimethyl-N,N′-dipyridine-2-ylpyridine-2,6-diamine) and its strong σ-donating capabilities, a very large ligand-field splitting could be introduced in the chromium(III) complex [Cr(ddpd)2]3+, that shifts the deactivating and photoreactive 4T2 state well above the emitting 2E state. Prevention of back-intersystem crossing from the 2E to the 4T2 state enables exceptionally high near-infrared phosphorescence quantum yields and lifetimes for this 3d metal complex. The complex [Cr(ddpd)2](BF4)3 is highly water-soluble and very stable towards thermal and photo-induced substitution reactions and can be used for fluorescence intensity- and lifetime-based oxygen sensing in the NIR.
The German Federal Police approached the Federal Institute for Materials Research and Testing (Bundesanstalt für Materialforschung und -prüfung, BAM) with the question whether different machines, which are available in public areas, provide a certain amount of protection against the effects of explosions/detonation. The devices of interest were ticket vending machines, found on train Station platforms, as well as x-ray Scanners used for examining luggage or mail at airports and Offices, respectively. A series of experiments was carried out using a number of different explosives, e.g. plastic explosives, improvised explosive devices (IEDs) and pyrotechnic articles. Documentation was done applying video and highspeed video recordings, pressure measurements etc. The results of these experiments are currently under discussion among the different authorities. The final report shall then be used as a basis for further discussions about possible changes in guidelines and legislation in order to further increase the level of public safety.
Der Kerbschlagbiegeversuch ist als Prüfverfahren seit langem international genormt. Zu garantierende Kerbschlagarbeitswerte sind in Produktnormen weltweit festgelegt. Gleichwohl enthalten ganze Normenreihen für Stähle falsche Festlegungen zur Verwendung von Untermaßprobenergebnissen. Im Mittelpunkt der vorliegenden Studie stehen die Auswertung von KV-T-Daten und die Skalierung von Untermaßprobenergebnissen. Hierzu wurden an ISO-V-Proben der Breiten 2,5; 5; 7,5 und 10 mm aus vier Baustählen im Streckgrenzenbereich von 235 bis 960 MPa dicht belegte KV-T-Kurven ermittelt. Es wurden unterschiedliche Vorgehensweisen zur Kurvenanpassung und Festlegung von Übergangstemperaturen wie auch der Hoch- bzw. Tieflagenarbeit untersucht. Die Ergebnisse unterstreichen unter anderem, dass die in festgelegte Vorgehensweise, nach der Untermaßprobenergebnisse proportional auf Normprobenmaße zu skalieren sind, nicht nur zu falschen, sondern auch nicht-konservativen Kerbschlagarbeitswerten führen kann. Das Ausmaß dieses Probenbreiteneffektes ist Werkstoff- und temperaturabhängig. Da die Kerbschlagarbeit als Abnahmekriterium verwendet wird, ergeben sich unmittelbare wirtschaftliche und sicherheitstechnische Konsequenzen. Es ist zu schlussfolgern, dass die entsprechenden Produktnormenreihen dringend zu überarbeiten sind.
The objective of the FATWELDHSS project was to study post-weld treatment techniques and their effect on the fatigue life of MAG welded attachments in High Strength Steel (HSS). Fatigue cracks in steel structures often occur at welded joints, where stress concentrations due to the joint geometry and tensile residual stresses are relatively high. Fatigue life improvement techniques, which rely on improving the stress field and/or the surface geometry around the welded joints, are generally known to be beneficial. Therefore, within the framework of this project, the following were examined: diode laser weld toe re-melting; High Frequency Mechanical Impact (HFMI) treatment; Low Transformation Temperature (LTT) filler wires Laser diode re-melting was used to improve the surface profile at the weld toe and thus reduce stress concentrations. HFMI treatment involving high frequency hammering of the weld toe is another technique that can produce a smooth weld toe profile but, more significantly, which also can introduce compressive residual stresses. Lastly, two new LTT filler wires were developed within the project as these can decrease or even remove tensile residual stresses resulting from weld zone shrinkage. An extensive fatigue testing programme was set up to establish the levels of improvement in the fatigue lives of the welded attachments achieved by application of the selected improvement techniques. Furthermore, two industrial demonstrators were selected that could show the project achievements in terms of facilitating the introduction of high strength steels by overcoming the limitations posed by the fatigue properties of the welded joints. In addition, modelling tools were developed to predict the residual stresses at the welded joint. Finally, practical guidelines were developed for enhancing the fatigue strength of HSS welded structures
The European laser safety standards EN 207, EN 208, and EN 12254 each contain an annex B, which serves as a guidance for the selection of products. These annexes are informative only and are therefore not binding. As there are a variety of hazard scenarios, it is not recommended to change these annexes to a normative status, through which they would become mandatory. Instead, it is recommended to allow users to apply their own skills and know-how in selecting appropriate products, justifying where and why they deviate from the guidance in the standards. This paper explains the background on which the guidance for selection in the annexes of the standards is based and shows physically meaningful leeway.
A novel method for the determination of phomopsin A (1) in lupin flour, pea flour, and bean flour as well as whole lupin plants was established based on stable isotope dilution assay (SIDA) LC-MS/MS using 15N6-1 as an isotopically labeled internal standard. Artificially infected samples were used to develop an optimized extraction procedure and sample pretreatment. The limits of detection were 0.5–1 µg/kg for all matrices. The limits of quantitation were 2–4 µg/kg. The method was used to analyze flour samples generated from selected legume seeds and lupin plant samples that had been inoculated with Diaporthe toxica and two further fungal strains. Finally, growing lupin plants infected with D. toxica were investigated to simulate a naturally in-field mycotoxicosis. Toxin levels of up to 10.1 µg/kg of 1 were found in the pods and 7.2 µg/kg in the stems and leaves.
Unsere Aufgabe im Fachbereich 3.4 der Bundesanstalt für Materialforschung und prüfung (BAM) ist die sicherheitstechnische Begutachtung von Transport- und Lagerbehältern für radioaktiven Abfall, die für langfristige Zwischenlagerung ausgelegt sind. Ein Arbeitsschwerpunkt ist die Bewertung der Lebensdauer von Metall- und Elastomerdichtungen in den Behältern im Hinblick auf die Anforderungen für langfristige Behältersicherheit (min. 40 Jahre in Deutschland). Um die Eigenschaftsänderungen der Elastomerdichtungen während einer beschleunigten Alterung über lange Zeiträume (bis zu fünf Jahre) untersuchen zu können, wurde ein Alterungsprogramm an ausgewählten Elastomeren (HNBR, EPDM, FKM) begonnen.
Im Gegensatz zu Normalterungsverfahren altern wir keine Normteile, sondern O-Ringe im unverpressten sowie verpressten Zustand. Diese Vorgehensweise ermöglicht die Bewertung des Einflusses der Verpressung auf die Alterung sowie die Untersuchung des Bauteilversagens mittels Leckageratenmessungen unter anwendungsnahen Bedingungen. Weitere Charakterisierungsmethoden sind Härtemessung, dynamisch-mechanische Analyse (DMA), Thermogravimetrie (TGA), Druckspannungsrelaxation, Druckverformungsrest (DVR), Dichtebestimmung und Zugversuch. Das Ziel ist, die Leckagerate mit anderen Eigenschaften bzw. Methoden zu korrelieren, um so ein aussagekräftiges und leichter zu bestimmendes Lebensdauerkriterium für elastomere O-Ringe abzuleiten.
Während der Alterung können in Abhängigkeit von Material sowie Alterungsdauer und –temperatur Inhomogenitäten aufgrund von diffusionsbegrenzter Oxidation auftreten, durch die sich unterschiedliche Eigenschaften an der Oberfläche und im Volumen der Dichtung ergeben, was zu falschen Lebensdauerabschätzungen führen kann. Mittels Mikrohärtemessung über den Querschnitt werden diese Effekte charakterisiert und bei der Extrapolation mittels Zeit-Temperatur-Verschiebung und Arrheniusgraph berücksichtigt. Bisher liegen Daten von bis zu einem Jahr bei vier verschiedenen Temperaturen (75 °C, 100 °C, 125 °C und 150 °C) gealterten Proben vor. Nach 100 Tagen bei 150 °C weisen HNBR und EPDM schon einen DVR von über 80 % auf, aber noch keinen signifikanten Anstieg der Leckagerate. Diese sinkt zunächst während der Alterung, da die Permeabilität aufgrund von Vernetzungsreaktionen sinkt. Bei HNBR ist dies aufgrund der dominanteren Vernetzungsreaktionen während der Alterung noch stärker ausgeprägt als bei EPDM.
Untersucht wurden Verschleißpartikel als elektronentransparente Proben auf dünnen Trägerfolien mit einem hochauflösendem Rasterelektronenmikroskop und energiedispersiver Röntgenspektrometrie im Transmissionsmodus.
Die hohe laterale Auflösung dieser modernen Methoden ermöglicht eine morphologische Charakterisierung der Verschleißpartikel bis in den nm-Bereich. Die hochauflösende Elementanalyse erlaubt eine Interpretation der Zusammensetzung und damit Rückschlüsse auf die Verschleißpartikelbildung. Die tribologischen Untersuchungen sind an einem Modell-Verschleißtribometer nach DIN 51834-2 geschmiert, aber ohne Ölkreislauf, durchgeführt worden. Die Präparation der Verschleißpartikel über eine Entnahme und Übertragung einer geringen Schmierstoffmenge mit einer Mikropipette auf eine TEM-Trägerfolie ist mit einem geringen Aufwand möglich. Der präparative Aufwand ist relativ gering. Das benötigte Schmierstoffvolumen beträgt wenige Mikroliter (0,001 ml).
Die Untersuchung zeigt die geringe geometrische Größe der Verschleißpartikel und bestätigt indirekt die These der Reaktionsschichtbildung mit einer geringen Schichtdicke, die ständig verschleißt und sich stetig neu bildet. Die beschriebenen Verschleißprozesse sind in der Modell-Verschleiß-Prüfung mit sehr hohen Pressungen am Versuchsbeginn nachweisbar.
Wenn etwas nicht funktioniert, fehlschlägt oder in einem Unfall endet, dann beschränkt sich die Fehlersuche in den meisten Fällen auf die direkt Betroffenen, also auf die Personengruppe, die unmittelbar mit der Führung oder Bedienung eines Produkts betraut ist. Zunächst werden Fehlbedienungen vermutet, Unterlassungshandlungen, Überforderungen oder nicht bemerkte Fehler usw. Kann die Unfallursachenermittlung kein menschliches Fehlverhalten nachweisen, Gerät die Technik ins Visier. Hin und wieder kommt es jedoch vor, dass die direkt Betroffenen alles richtig gemacht haben und die Technik nicht versagt hat, aber trotzdem ein Unfallereignis oder eine Zielabweichung auftrat. Eine Unfalluntersuchung kann dann u. U. auch in die Managementetage führen, in Verantwortungsbereiche die sich hinter geschlossenen Türen befinden und die Untersuchung einer Fehlerkette nicht unbedingt erleichtern. Im folgenden Beitrag werden einige interessante Fälle in Erinnerung gerufen.
Kohlendioxid (C02), das z.B. aus dem Abgas von fossilgefeuerten Kraftwerken, Stahlwerken oder Zementwerken abgetrennt wird, enthält Verunreinigungen. Dies sind beispielsweise Wasserdampf, 02, S0X, NOx und H2S. Derartige Gasmischungen sind instabil und ihre Komponenten können zu weiteren Produkten reagieren. Wenn Wassermoleküle zur Verfügung stehen, können saure Lösungen kondensieren. Die Korrosion von Werkstoffen und Bauteilen in Kontakt mit den transportierten Gasmischungen wird an der BAM in Laborversuchen untersucht, Das wichtigste Ziel ist, sichere und bezahlbare Kombinationen von zugelassenen Konstruktionswerkstoffen und Grenzwerten für Verunreinigungen im C02-Strom vorzuschlagen. In den bisherigen Arbeiten hat sich herausgestellt, dass für eine verlässliche Aussage die Experimente möglichst realitätsnah durchgeführt werden sollten. Hierfür müssen die Parameter: hoher Druck (um 100 bar), Temperatur (um 60 °C), Strömungsverhältnisse (laminar oder turbulent) sowie mechanische Spannung kombiniert werden. Für diese Anforderungen wurden Prüfstände entwickelt und Experimente durchgeführt.
Specific drug formulation additives: Revealing the impact of architecture and block length ratio
(2015)
Combining poly(ethylene glycol) (PEG) with sequence-defined peptides in PEG–peptide conjugates offers opportunities to realize next-generation drug formulation additives for overcoming undesired pharmacological profiles of difficult small molecule drugs. The tailored peptide segments provide sequence-specific, noncovalent drug binding, and the hydrophilic PEG block renders the complexes water soluble. On the basis of a peptide sequence known to bind the photosensitizer m-tetra(hydroxyphenyl)chlorin (m-THPC) for photodynamic cancer therapy, a set of different conjugate architectures is synthesized and studied. Variations in PEG block length and amplification of the peptidic binding domain of PEG–peptide conjugates are used to fine tune critical parameters for hosting m-THPC, such as drug payload capacities, aggregation sizes, and drug release and activation kinetics.
An electromagnetic weld pool support system for 20 mm thick duplex stainless steel AISI 2205 was investigated numerically and compared to experiments. In our former publications, it was shown how an AC magnetic field below the process zone directed perpendicular to the welding direction can induce vertically directed Lorentz forces. These can counteract the gravitational forces and allow for a suppression of material drop-out for austenitic stainless steels and aluminum alloys. In this investigation, we additionally adopted a steady-state complex magnetic permeability model for the consideration of the magnetic hysteresis behavior due to the ferritic characteristics of the material. The model was calibrated against the Jiles-Atherton model. The material model was also successfully tested against an experimental configuration before welding with a 30 mm diameter cylinder of austenitic stainless steel surrounded by duplex stainless steel. Thereby, the effects of the Curie temperature on the magnetic characteristics in the vicinity of the later welding zone were simulated. The welding process was modelled with a 3D turbulent steady-state model including heat transfer and fluid dynamics as well as the electromagnetic field equations. Main physical effects, the thermo-capillary (Marangoni) convection at the weld pool boundaries, the natural convection due to gravity as well as latent heat of solid–liquid phase transitions at the phase boundaries were accounted for in the model. The feedback of the electromagnetic forces on the weld pool was described in terms of the electromagneticinduced pressure. The FE software COMSOL Multiphysics 4.2 was used in this investigation. It is shown that the gravity drop-out associated with the welding of 20 mm thick duplex stainless steel plates due to the hydrostatic pressure can be prevented by the application of AC magnetic fields between around 70 mT and 90 mT. The corresponding oscillation frequencies were between 1 kHz and 10 kHz and the electromagnetic AC powers were between 1 kW and 2.3 kW. In the experiments, values of the electromagnetic AC power between 1.6 kW and 2.4 kW at oscillation frequencies between 1.2 kHz and 2.5 kHz were found to be optimal to avoid melt sagging or drop-out of melt in single pass fullpenetration laser beam welding of 15 mm and 20 mm thick AISI 2205.
Full penetration high power bead-on-plate laser beam welding tests of up to 20 mm thick 2205 duplex steel plates were performed in PA position. A contactless inductive electromagnetic (EM) weld pool support system was used to prevent gravity drop-out of the melt. Welding experiments with 15 mm thick plates were carried out using IPG fiber laser YLR 20000 and Yb:YAG thin disk laser TruDisk 16002. The laser power needed to achieve a full penetration was found to be 10.9 and 8.56kW for welding velocity of 1.0 and 0.5 m min(-1), respectively. Reference welds without weld pool support demonstrate excessive root sag. The optimal value of the alternating current (AC) power needed to completely compensate the sagging on the root side was found to be approximate to 1.6 kW for both values of the welding velocity. The same EM weld pool support system was used in welding tests with 20 mm thick plates. The laser beam power (TRUMPF Yb:YAG thin disk laser TruDisk 16002) needed to reach a full penetration for 0.5 m min(-1) was found to be 13.9 kW. Full penetration welding without EM weld pool support is not possible-the surface tension cannot stop the gravity drop-out of the melt. The AC power needed to completely compensate the gravity was found to be 2 kW. (C) 2016 Laser Institute of America
The inhalation of radon (222Rn) decay products is the leading cause of lung cancer apart from tobacco smoking. Besides the permeation of radon from the subsoil through the basement as main source of radon in indoor air, also building materials have to be taken into consideration, especially at low air change rates in buildings. The Construction Products Regulation (EC, 2010) gives essential requirements for construction works regarding the release of dangerous substances such as toxic gases and radiation to which radon can be assigned. The recently adopted Basic Safety Standards Directive (EC, 2013), which has to be ratified by each European member state in between the next three years sets reference levels for indoor radon concentrations for the first time. In research project financed by the German Ministry for the Environment, Nature Conservation, Building and Nuclear Safety a practical, reliable and easily applicable test procedure for the determination of radon exhalation from building materials – based on ISO 16000-9 (ISO, 2006) and CEN/TS 16516 (CEN, 2013) – should be developed. In contrast to the static test procedure published by Richter et al. (2013), dynamically operated test chambers shall be foregrounded. First results of this study are presented, focused on the reliable measurement of radon background concentration and the selection of suitable radon test devices, representing the basic elements of the subsequent work.
Thermal decomposition of AIBN Part A: Decomposition in real scale packages and SADT determination
(2015)
In this paper the thermal decomposition of 2,2′-azobisisobutyronitrile (AIBN) was investigated in real scale packages of different sizes and in 500 mL Dewar vessels. Packages containing 5 kg, 20 kg and 50 kg of AIBN have been investigated according to the UN test H.1 method and the 500 mL Dewar experiments were performed according to the UN test H.4 method. The self-accelerating decomposition temperature (SADT) was determined for the different masses and for the 500 mL Dewar vessel. Additionally, DSC curves have been recorded in closed crucibles. All these experimental data are the basis of a series of forthcoming papers dealing with the simulation of the SADT for different masses using reliable kinetic data.
Proben unterschiedlich wärmebehandelter, hochlegierter, rostfreier Stahlqualitäten, die potenziell als Injektionsrohr-Stähle eingesetzt werden können - AISI 420 X46Cr13, AISI 420J X20Cr13 und AISI 630 X5CrNICuNb16-4 - wurden bei 60 °C sowohl bei Normaldruck als auch bei 100 bar für 700 bis 8.000 Stunden in einem C02-gesättigtem, synthetisch hergestellten Laboraquiferwasser ausgelagert. Dieses Laboraquiferwasser entspricht der erwarteten Zusammensetzung des Aquiferwassers des norddeutschen Beckens, in das im CCS- Versuchsfeld von Ketzin (CCS Carbon Capture and Storage) über zwei Jahre hinweg technisch reines C02 injiziert wurde. Die Korrosionsraten und Schichtwachstumsraten auf den Stählen sind am niedrigsten für Stähle, die vor der Langzeitauslagerung gehärtet und anschließend zwischen 600 °C und 670 °C angelassen wurden. Lokale Korrosion (Lochfraß) zeigt sich in Form von kleinsten Löchern auf der Stahloberfläche. Der Durchmesser dieser Löcher nimmt mit steigendem Kohlenstoffgehalt des Stahls ab. Gleichzeitig nimmt die Anzahl der gezählten Löcher auf der Oberfläche zu. Insgesamt wird festgestellt, dass Stähle mit einer martensitischen Gefügestruktur in dieser nachempfundenen CCS-Atmosphäre die beste Korrosionsbeständigkeit gegenüber dem C02-gesättigten, salinen Aquifer bietet.
The key objective of this work is to create a comprehensive comparison between experimental analysis methods for detecting crosslinking reaction in EVA encapsulant material during PV module fabrication process. Several analytical methods, spanning from classical gel content extraction measurements over different thermo-analytic and mechanical approaches to spectroscopic analysis as Thermally Stimulated Current (TSC), have been investigated as to their ability to reveal the crosslinking state of ethylene vinyl acetate (EVA). The basic results show that TSC complements perfectly other thermal analysis methods like as Differential Scanning Calorimetry (DSC), Dynamic Mechanical Thermal Analysis (DMTA) to determine fundamental properties of EVA such as molecular mobility characteristics and also to monitor the crosslinking reaction. Exothermic peak as revealed by DSC analysis can be used to estimate the crosslinking rate of EVA during PV module encapsulation process as fast quality control test. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
L'objectif principal de ce travail est de permettre une meilleure compréhension entre les différentes techniques analyses expérimentales pour détecter la réaction de réticulation au niveau de lencapsulant Ethylène-Vinyle Acétate (EVA), durant le process de fabrication d'un module PV. Plusieurs méthodes d'analyse, allant du test classique d'extraction du taux de gel aux différentes techniques d'analyses thermomécaniques ainsi que les techniques d'analyse de spectroscopie comme le courant stimulé thermiquement (TSC), ont été étudiés pour permettre de révéler le phénomène de la réaction de réticulation de l'encapsulant l'EVA. Les résultats de base montrent que la TSC complète parfaitement d'autres méthodes d'analyses thermiques comme la calorimétrie différentielle à balayage (DSC), l'analyse mécanique dynamique (DMTA) pour déterminer les propriétés fondamentales de l'EVA. Ces techniques permettent de déterminer les caractéristiques relatives à la mobilité moléculaire et aussi pour mieux mettre en évidence la réaction de réticulation. Le pic exothermique comme révélé par l'analyse par DSC, peut être utilisé pour estimer le taux de réticulation de l'EVA au cours du process d'encapsulation du module PV comme un test rapide de contrôle de qualité.
The maintenance of the transport infrastructures and their further development are going to remain focal points for investment and research in Germany in future. According to the latest development forecasts made by both the federal government and Deutsche Bahn, even if rail´s percentage share of the market were to remain unchanged, growth of around 50% would be expected in the next ten years, especially in freight traffic. This growth is necessitating considerable development both in the technical design of the tracks and in the abatement of the noise and vibration caused by railway traffic.
Three strategies to sample volatile organic compounds (VOC) from lung cancer cell lines cultured in vitro were compared. Headspace solid phase microextraction was applied in situ to culture flasks and alternatively to subsamples of headspace gas or to nutrient solution subsamples followed by gas chromatography–mass spectrometry. The direct quantification of 55 VOC in the headspace of cell cultures was validated and is discussed with respect to reproducibility and system-related interferences. The role of the VOC background from culture media and usually employed polystyrene culture vessels is examined and was seen to invoke potentially misleading conclusions. The commercial A549 and two further adenocarcinoma cell lines displayed largely similar VOC profiles with distinct differences regarding certain individual substances. There is evidence for the inappropriateness of the standard cell culturing methods in the search for volatile cancer markers.
The application of high-strength fine-grained structural steels with yield stress ≥ 690 MPa permits significant weight reductions and cost savings. Since welding is the major joining technology, e.g. in mobile crane industry, the sustainable and economical application of these grades depends on the load-bearing capacity and safety of the welds. An economical processing of high-strength steels is determined above all by the avoidance of cold cracking, apart from achieving demand-oriented mechanical properlies in the weid area. High tensile residual stresses are disadvantageaus regarding the cold cracking resistance and strength of welded components. Furthermore, high restraints commonly appearing in component welds increase residual stresses. Hence, in this research the influences of heat control on residual stresses and the overall structural Ioad of welded structures were quantified. The relationship between the weid thermal cycle and the resulting residual stress under additional shrinkage restraint was analysed by a successive augmentation of the restraint intensity. This was achieved by systematic low Ioad and component weid tests. lt was observed that the heat control significantly affects the local residual stresses and the overall structural Ioad of welded structures. A high interpass temperature increases the global and local welding stresses in particular. Moreover, the transferability of experimental welding results obtained from small specimens according to applicable codes to real component geometries was investigated. With the help of these findings it is possible to improve existing heat control concepts for high-strength steel welding.
Aktuelle Bestrebungen zum Leichtbau sowie zur Erhöhung der Energie- und Ressourceneffizienz führen zum steigenden Einsatz hochfester Feinkornbaustähle in einer deutlich wachsenden Anzahl von Branchen. Mit zunehmender Festigkeit steigt die Herausforderung an die schweißtechnische Verarbeitung und Bemessung der Konstruktion infolge engerer Verfahrensgrenzen und hoher Streckgrenzenverhältnisse [1]. Moderne modifizierte Sprühlichtbogenprozesse gestatten neben den bekannten wirtschaftlichen Vorteilen gerade im Zusammenhang mit der veränderten Nahtgeometrie, dem reduzierten Schweißnahtvolumen sowie Gesamtwärmeeintrag deutlich geringere schweißbedingte Beanspruchungen. Dadurch erhöht sich die Beanspruchbarkeit hochfester Schweißkonstruktionen. in den Untersuchungen wurde der Einfluss von Schweißprozess und damit verbundener Nahtgeometrie auf die Eigenspannungsausbildung und Gesamtbeanspruchung in hochfesten Schweißverbindungen ermittelt. Mit einer speziellen Prüfanlage (CTW-Test) wurden Proben unter definiertem, bauteilrelevantem Einspanngrad in Nahtquerrichtung mehrlagig geschweißt. Dabei zeigte sich insbesondere für das Nahtvolumen ein signifikanter Einfluss auf die globalen Reaktionsspannungen. Ferner sind die lokalen Zugeigenspannungen im Bereich des Schweißgutes durch den Einsatz modifizierter Sprühlichtbogenprozesse geringer.
Bei Schweißkonstruktionen aus modernen Feinkornbaustählen, wie sie beispielsweise im Hochbau, im Anlagenbau und im Kranbau vorkommen, sind aus folgenden Gründen enge Verfahrensgrenzen für die Wärmeführung zu beachten: das spezielle Gefüge und das vergleichsweise hohe Streckgrenzenverhältnis bzw. die geringen plastischen Verformungsreserven. Zum Einstellen der Gefügeeigenschaften sind mit Hilfe von Vorwärm- bzw. Zwischenlagentemperaturen und Streckenenergien die Abkühlzeiten Δt8/5 möglichst exakt einzuhalten Wie beispielsweise in DIN 1011-2 und SEW 088 nachzulesen ist, basieren Prüfverfahren und empirische Ansätze zum Abschätzen von Schweißwärmezyklen auf dem Kohlenstoffäquivalent. Über die bisherigen Laboruntersuchungen zur Entstehung von Eigenspannungen im unmittelbaren Schweißbereich hinaus muss der Einfluss der Wärmeführung im Zusammenhang mit den Steifigkeitsverhältnissen umgebender Montageteile analysiert werden. Numerische und experimentelle Untersuchungen haben z.B. ergeben, dass eine äußere Schrumpfbehinderung in Nahtquerrichtung durch den Einspanngrad RFy bemessen werden kann. Im Rahmen des Fosta-Forschungsprojekts P 922 wurden Versuchsschweißungen im Stumpfstoß mit V-Naht an den Werkstoffen S690QL, S960QL, S700MC und S960MC mit 8 mm und 20 mm Blechdicke und typischen Schweißparametern aus dem Kranbau durchgeführt. Für S690QL mit 20 mm Blechdicke sind die Ergebnisse wie folgt dargestellt: a) Abkühlzeit in Abhängigkeit von Zwischenlagentemperatur und Streckenenergie, b) mikroskopische Aufnahme des Schweißguts und der Wärmeeinflusszone und c) des Schweißgutgefüges (Abkühlzeit Δt8/5=13 s). Mit einer hydraulischen 2-MN-Prüfanlage wurden Schrumpfbehinderung und gleichzeitig Reaktionskräfte gemessen, während des Vorwärmens, des Schweißens und des Abkühlens. Das Ergebnis zeigt, dass die resultierenden mechanischen Beanspruchungen der gesamten Schweißverbindung erheblich von der Höhe der Schrumpfbehinderung und der Wärmeabführung während des Schweißens abhängig sind.