Chemie und Prozesstechnik
Filtern
Erscheinungsjahr
- 2019 (34) (entfernen)
Dokumenttyp
Referierte Publikation
- ja (34) (entfernen)
Schlagworte
- Thermography (3)
- Composite (2)
- Cracks (2)
- NDT (2)
- Nondestructive testing (2)
- Reinforced concrete (2)
- Zerstörungsfreie Prüfung (2)
- 2D model (1)
- 3D particle analysis (1)
- 3D printing (1)
- 3D visualization (1)
- AET (1)
- ASIC (1)
- Acoustic sensors (1)
- Active thermography (1)
- Additive manufacturing (1)
- Ageing (1)
- Anisotropic fiber orientation (1)
- Artificial neural networks (1)
- Artificial weathering (1)
- Atomic and molecular mapping (1)
- Backlighting (1)
- Bauwesen (1)
- Beton (1)
- Blind structured illumination (1)
- Brücken (1)
- CFRP (1)
- Cement (1)
- Cement-based materials (1)
- Chemometrics (1)
- Chloride (1)
- Civil engineering (1)
- Coda wave interferometry (1)
- Computed tomography (1)
- Concrete (1)
- Cone Shaped Phased Array (1)
- Corresponding relative humidity (1)
- Corrosion (1)
- DVC (1)
- Damage detection (1)
- Data Processing (1)
- Data reconstruction (1)
- Deconvolution (1)
- Digital detector array (1)
- Distributed fiber optic sensors (1)
- Dual Energy Imaging (1)
- Eddy current (1)
- Eddy current testing (1)
- Electrochemical deposition (ECD) (1)
- Embedded sensors (1)
- Enriched finite element method (1)
- Evaporative drying (1)
- FEM (1)
- Ferroelectret (1)
- Fiber Bragg grating (FBG) (1)
- Fiber-reinforced concrete (1)
- Finite-element analysis (1)
- Flat bottom holes (1)
- Flow Chemistry (1)
- Heat diffusion (1)
- High Speed Testing (1)
- High resolution (1)
- Hollow Axle Inspection (1)
- Image processing (1)
- In-situ testing (1)
- Inline NMR Spectroscopy (1)
- Integrated Processes (1)
- Inverse analysis (1)
- Irradiation (1)
- LIBS (1)
- Lamb waves (1)
- Laser Thermography (1)
- Laser thermography (1)
- Laser-induced breakdown spectroscopy (LIBS) (1)
- Lehrplan (1)
- MOF (1)
- Magnetoresistive sensor (1)
- Messunsicherheit (1)
- Modular Production (1)
- Multivariate calibration (1)
- Nachrechnung (1)
- Neutron imaging (1)
- Non-invasive glucose sensing (1)
- Notches (1)
- Numerical Modelling (1)
- Numerical modelling (1)
- Opaque materials (1)
- Optical fibers (1)
- Paper watermark (1)
- Photon Counting Detectors (1)
- Photoplethysmography (1)
- Pile testing (1)
- Polymer (1)
- Polymers (1)
- Porous building materials (1)
- Pressure Vessels (1)
- Process Analytical Technology (1)
- Pulsed thermography (1)
- Quantification (1)
- Quantitative moisture measurement (1)
- RFID based sensors (1)
- Radiation shielding (1)
- Radiology (1)
- Reaction Monitoring (1)
- Sandstones (1)
- Saturation (1)
- Scaled boundary finite element method (1)
- Shaker (1)
- Singular stress (1)
- Spectral induced polarization (1)
- Spectroscopy (1)
- Static Mixing (1)
- Stress intensity factors (1)
- Stress strain relations (1)
- Structural health monitoring (1)
- Structured heating (1)
- Subsurface defects (1)
- Super-resolution imaging (1)
- Synchrotron Radiation (1)
- TRISO (1)
- Thermal wave (1)
- Three-dimensional measurement (1)
- UV/VIS spectroscopy (1)
- Ultrasonic Testing (1)
- Ultrasonic imaging (1)
- Ultrasonic transducers (1)
- VCSEL (1)
- VCSEL array (1)
- Validation studies (1)
- Vibrational spectroscopy (1)
- Water transport (1)
- Wavelet transformation (1)
- X-ray (1)
- X-ray Radiography (1)
- X-ray caustics (1)
- X-ray computed tomography (CT) (1)
- X-ray computed tomography (XCT) (1)
- X-ray imaging (1)
- X-ray reflectivity (1)
- X-ray refraction (1)
- agricultural economy (1)
- embedded sensor (1)
- environment (1)
- fluorescence (1)
- gas analysis (1)
- spectroscopy (1)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (34) (entfernen)
This paper presents an approach to the automatic enrichment of finite elements in the vicinity of a stress singularity. The enrichment consists of semi-analytical singular modes constructed using the Scaled Boundary Finite Element Method (SBFEM).
In contrast to analytical methods, the SBFEM provides modes for inhomogeneous and anisotropic materials without additional effort. The finite element basis can be of arbitrary order and remains unaltered by the enrichment. The approach requires enrichment in only one layer of elements around a node. Due to the compatibility of SBFEM with FEM, there is no Need for transitional elements, and there are no parasitic terms. The approach is tested for several benchmark problems. The stress intensity factors are computed based on techniques inspired by the SBFEM. The proposed procedure is compared to a Standard finite element implementation and shows a significant improvement in the error of the displacement field for problems involving singular stresses.
We demonstrate the use of a 3D printed radial collimator in X-ray powder diffraction and surface sensitive grazing incidence X-ray diffraction. We find a significant improvement in the overall Signal to background ratio of up to 100 and a suppression of more than a factor 3⋅10⁵ for undesirable Bragg reflections generated by the X-ray “transparent” windows of the sample environment.
The background reduction and the removal of the high intensity signals from the windows, which limit the detector’s dynamic range, enable significantly higher sensitivity in experiments within sample environments such as vacuum chambers and gas- or liquid-cells. Details of the additively manufactured steel collimator geometry, alignment strategies using X-ray fluorescence, and data analysis are also briefly discussed. The flexibility and affordability of 3D prints enable designs optimized for specific detectors and sample environments, without compromising the degrees of freedom of the diffractometer.
Additively manufactured test specimens made of polyamide 12 (PA 12) by Laser Sintering as well as of acrylonitrile butadiene styrene (ABS) by Fused Layer Modelling, were characterised with active thermography directly after manufacturing and after artificial weathering. For this, two different excitation methods (flash and pulse heating) were used and compared, regarding their suitability for the detection of constructed and imprinted defects inside the test specimens. To increase the quality of the thermograms, data processing methods like thermal signal reconstruction (TSR) and Fourier Transformation after TSR were applied. To further investigate the long-term stability of the additively manufactured test specimens towards environmental stress, like UV radiation, heat, humidity, water contact and frost with active thermography, an artificial weathering test over 2000 hours (~3 months) was applied to the specimens. The monitoring of the changes in the optical properties of the weathered plastics was supplemented by spectral reflectance and UV/VIS spectroscopy.
High sensitivity is an important requirement for air-coupled ultrasonic sensors applied to materials testing. With a lower acoustic impedance than any piezoelectric material, charged cellular polypropylene (PP) offers better matching to air with a similar piezoelectric coefficient. The piezoelectric properties of charged cellular PP originate from their polarization, creating permanent internal voltage. The sensitivity of the sensor can be increased by applying additional dc bias voltage, as it has been done already for transmitters. This work presents the first ultrasonic sensor based on charged cellular PP including a high-voltage module providing dc bias voltage up to 2 kV. This bias voltage led to an increase in the signal-to-noise ratio of up to 15 ± 1 dB. The measurement of the received signal depending on the applied bias voltage is proposed as a new method of determining the internal voltage of ferroelectrets. The sensor combined with a cellular PP transmitter was applied to nondestructive testing of a rotor blade segment and glued-laminated timber, enabling imaging of the internal structure of these specimens with a thickness around 4 cm.
Guided waves (GW) are of great interest for non-destructive testing (NDT) and structural health monitoring (SHM) of engineering structures such as for oil and gas pipelines, rails, aircraft components, adhesive bonds and possibly much more. Development of a technique based on GWs requires careful understanding obtained through modelling and analysis of wave propagation and mode-damage interaction due to the dispersion and multimodal character of GWs. The Scaled Boundary Finite Element Method (SBFEM) is a suitable numerical approach for this purpose allowing calculation of dispersion curves, mode shapes and GW propagation analysis. In this article, the SBFEM is used to analyse wave propagation in a plate consisting of an isotropic aluminium layer bonded as a hybrid to an anisotropic carbon fibre reinforced plastics layer. This hybrid Composite corresponds to one of those considered in a Type III composite pressure vessel used for storing gases, e.g., hydrogen in automotive and aerospace applications. The results show that most of the wave energy can be concentrated in a certain layer depending on the mode used, and by that damage present in this layer can be detected. The results obtained help to understand the wave propagation in multi-layered structures and are important for further development of NDT and SHM for Engineering structures consisting of multiple layers.
Gegenüber dem Neubauentwurf können bei der Bewertung von bestehender Bausubstanz Sicherheitsreserven genutzt werden, da Unsicherheiten, die beim Bau auftreten können, besser bekannt oder nicht mehr vorhanden sind. Können solche Unsicherheiten genauer bewertet werden, z. B. durch die Feststellung der genauen Lage der Spannglieder bei einer Spannbetonbrücke, so können Sicherheitsbeiwerte reduziert werden, ohne dass es dabei zu Auswirkungen auf das normativ festgelegte Zuverlässigkeitsniveau kommt. Mittlerweile sind Prüfmethoden an Bauwerken wirtschaftlich einsetzbar und auch so leistungsfähig, dass die für die Tragfähigkeit und Gebrauchstauglichkeit wesentlichen Parameter identifiziert werden können. Ein wesentlicher Punkt ist hierbei die Integration derartiger Messergebnisse in Rechenmodelle, die für die Nachrechnung des Bauwerks verwendet werden. Dies können sowohl semiprobabilistische Rechenmodelle als auch vollprobabilistische Modelle sein. Bei semiprobabilistischen Methoden können aus den Messergebnissen Teilsicherheitsbeiwerte berechnet und abgeleitet werden, die dann in den bekannten Nachweisformaten gemäß den Eurocodes und der Nachrechnungsrichtlinie berücksichtigt werden. Bei vollprobabilistischen Nachweisen können die Messdaten in Form von Verteilungsdichtefunktionen mit gemessenen Variationskoeffizienten direkt in das Rechenmodell eingehen. In einer dreiteiligen Aufsatzreihe werden die Messverfahren und die Nutzung der Ergebnisse bei der Nachrechnung vorgestellt. Der vorliegende Teil 1 zeigt die Möglichkeiten des Einsatzes von zerstörungsfreien Prüfverfahren und bewertet deren Leistungsfähigkeit. Messen heißt wissen. Dieses Wissen spiegelt die Realität wider und soll den Tragwerksplaner bei der Entscheidungsfindung über die Sicherheit und Zuverlässigkeit von Bestandsbauwerken unterstützen.
Photothermal radiometry with an infrared camera allows the contactless temperature measurement of multiple surface pixels simultaneously. A short light pulse heats the sample. The heat propagates through the sample by diffusion and the corresponding temperature evolution is measured at the sample’s surface by an infrared camera. The main drawback in radiometric imaging is the loss of the spatial resolution with increasing depth due to heat diffusion, which results in blurred images for deeper lying structures. We circumvent this information loss due to the diffusion process by using blind structured illumination, combined with a non-linear joint sparsity reconstruction algorithm. The structured illumination is realized by parallel laser lines from a vertical-cavity surface-emitting laser (VCSEL) array controlled by a random binary pattern generator. By using 150 different patterns of structured illumination and our iterative joint sparsity algorithm, it was possible to resolve 1 mm thick lines at a distance down to 0.5 mm, which results in a resolution enhancement of approximately a factor of four compared to the resolution of 5.9 mm for homogenous illuminated thermographic reconstruction.
Due to the penetration of harmful chlorides into concrete, e.g. from de-icing salt, damage processes such as chloride-related pitting corrosion can occur if critical values are exceeded. In this study, multiphase materials such as chloride-contaminated concrete are examined in detail. A direct comparison is made by analyzing the spectroscopic information of simultaneously measured atomic and molecular emissions with laser-induced breakdown spectroscopy (LIBS). In addition, the influence on the calibration is examined on the basis of the combined spectral information of both reaction paths of the penetrated chlorides. The calibration models of univariate and multivariate methods were validated using reference samples with wet chemical analysis. The results are applied to a concrete sample of a parking deck, which was also analyzed by potentiometric wet chemistry. In order to account for the heterogeneity of concrete, spatially (200 μm) and spectroscopically (0.1 nm) resolved LIBS measurements were performed using a fully automated laboratory system. Simultaneous measurements with three spectrometers allow the analysis of the emission processes of several elements such as Cl, Ca, O, Si and Mg as well as the newly formed molecules CaO and CaCl. The evaluation of the molecular emission in combination with atomic lines extends the analytical performance, since different concrete phases such as aggregates and cement matrix can be better represented. The measurements were carried out in ambient air and with helium purge gas. The limit of detection (LOD) achieved for a combined evaluation of atomic and molecular emission was determined to be 0.028 wt%.
In various kinds of radiography, deficient transmission imaging may occur due to backlighting inside the detector itself arising from light or radiation scattering. The related intensity mismatches barely disturb the high resolution contrast, but its long range nature results in reduced attenuation levels which are often disregarded. Based on X-ray observations and an empirical formalism, a procedure is developed for a first order correction of detector backlighting. A backlighting factor is modeled as a function of the relative detector coverage by the sample projection. Different cases of sample transmission are regarded at different backlight factors and detector coverage. The additional intensity of backlighting may strongly affect the values of materials’ attenuation up to a few 10%. The presented scenario provides a comfortable procedure for corrections of X-ray or neutron transmission imaging data.
There have been an increasing number of publications on flow chemistry applications of compact NMR. Despite this, there is so far no comprehensive workflow for the technical design of flow cells. Here, we present an approach that is suitable for the design of an NMR flow cell with an integrated static mixing unit. This design moves the mixing of reactants to the active NMR detection region within the NMR instrument, presenting a feature that analyses chemical reactions faster (5–120 s region) than other common setups. During the design phase, the targeted mixing homogeneity of the components was evaluated for different types of mixing units based on CFD simulation. Subsequently, the flow cell was additively manufactured from ceramic material and metal tubing. Within the targeted working mass flow range, excellent mixing properties as well as narrow line widths were confirmed in validation experiments, comparable to common glass tubes.