Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (20068)
- Zeitschriftenartikel (18091)
- Posterpräsentation (6239)
- Beitrag zu einem Tagungsband (6053)
- Beitrag zu einem Sammelband (2318)
- Forschungsbericht (780)
- Sonstiges (377)
- Buchkapitel (360)
- Dissertation (299)
- Zeitschriftenheft (Herausgeberschaft für das komplette Heft) (262)
Sprache
- Deutsch (30599)
- Englisch (24458)
- Mehrsprachig (196)
- Französisch (41)
- Russisch (31)
- Spanisch (21)
- Ungarisch (11)
- Tschechisch (7)
- Italienisch (7)
- Japanisch (5)
Schlagworte
- Korrosion (432)
- Corrosion (415)
- Concrete (395)
- Fluorescence (350)
- Nanoparticles (336)
- Additive manufacturing (312)
- Simulation (267)
- Zerstörungsfreie Prüfung (252)
- LIBS (250)
- Hydrogen (232)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (2381)
- 6 Materialchemie (2309)
- 7 Bauwerkssicherheit (1865)
- 1 Analytische Chemie; Referenzmaterialien (1844)
- 9 Komponentensicherheit (1538)
- 5 Werkstofftechnik (1172)
- 4 Material und Umwelt (1131)
- 3 Gefahrgutumschließungen; Energiespeicher (857)
- 6.3 Strukturanalytik (643)
- 6.1 Oberflächen- und Dünnschichtanalyse (628)
- 9.4 Integrität von Schweißverbindungen (597)
- 2 Prozess- und Anlagensicherheit (590)
- 7.6 Korrosion und Korrosionsschutz (578)
- 8.5 Röntgenbildgebung (575)
- 6.6 Physik und chemische Analytik der Polymere (515)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (488)
- 9.3 Schweißtechnische Fertigungsverfahren (483)
- 2.1 Sicherheit von Energieträgern (369)
- 8.4 Akustische und elektromagnetische Verfahren (364)
- 1.2 Biophotonik (351)
- 1.4 Prozessanalytik (347)
- 7.2 Ingenieurbau (346)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (341)
- 5.1 Mikrostruktur Design und Degradation (338)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (334)
- 1.1 Anorganische Spurenanalytik (330)
- 8.0 Abteilungsleitung und andere (291)
- 8.3 Thermografische Verfahren (286)
- 5.2 Metallische Hochtemperaturwerkstoffe (285)
- 4.1 Biologische Materialschädigung und Referenzorganismen (272)
- 7.4 Baustofftechnologie (258)
- 1.8 Umweltanalytik (248)
- 4.3 Schadstofftransfer und Umwelttechnologien (247)
- 6.2 Material- und Oberflächentechnologien (246)
- 8.6 Faseroptische Sensorik (244)
- 1.9 Chemische und optische Sensorik (237)
- 9.2 Versuchsanlagen und Prüftechnik (236)
- S Qualitätsinfrastruktur (236)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (229)
- 9.0 Abteilungsleitung und andere (229)
- 5.4 Multimateriale Fertigungsprozesse (222)
- 7.1 Baustoffe (221)
- 6.0 Abteilungsleitung und andere (213)
- 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung (189)
- 3.3 Sicherheit von Transportbehältern (184)
- 3.1 Sicherheit von Gefahrgutverpackungen und Batterien (178)
- 4.2 Material-Mikrobiom Wechselwirkungen (174)
- 1.7 Organische Spuren- und Lebensmittelanalytik (170)
- 3.2 Gefahrguttanks und Unfallmechanik (169)
- 9.5 Tribologie und Verschleißschutz (169)
- 9.6 Additive Fertigung metallischer Komponenten (165)
- 4.5 Kunst- und Kulturgutanalyse (163)
- 3.4 Sicherheit von Lagerbehältern (157)
- 5.6 Glas (156)
- 5.3 Polymere Verbundwerkstoffe (133)
- 1.5 Proteinanalytik (131)
- 4.0 Abteilungsleitung und andere (131)
- S.2 Digitalisierung der Qualitätsinfrastruktur (129)
- 1.6 Anorganische Referenzmaterialien (119)
- 5.5 Materialmodellierung (119)
- 6.7 Materialsynthese und Design (111)
- 7.7 Modellierung und Simulation (98)
- 3.0 Abteilungsleitung und andere (95)
- 3.5 Sicherheit von Gasspeichern (91)
- 5.0 Abteilungsleitung und andere (85)
- S.3 Ökodesign und Energieverbrauchskennzeichnung (83)
- VP Vizepräsident (82)
- VP.1 eScience (80)
- 1.3 Instrumentelle Analytik (79)
- 7.0 Abteilungsleitung und andere (74)
- 7.3 Brandingenieurwesen (70)
- 2.0 Abteilungsleitung und andere (66)
- 2.5 Konformitätsbewertung Explosivstoffe/Pyrotechnik (58)
- 2.2 Prozesssimulation (56)
- P Präsident (56)
- 1.0 Abteilungsleitung und andere (49)
- P.0 Präsident und andere (43)
- 2.3 Einstufung von Gefahrstoffen und -gütern (38)
- 2.4 Prüfung und Bewertung von Explosivstoffen/Pyrotechnik (37)
- 6.4 Materialinformatik (31)
- S.1 Qualität im Prüfwesen (20)
- 3.6 Elektrochemische Energiematerialien (16)
- 4.6 Molekulare und angewandte Entomologie (15)
- PST Präsidiale Stabsstelle (15)
- 9.1 Komponenten für Energieträger (9)
- Z Zentrale Dienstleistungen (6)
- Z.1 Organisation, Controlling (6)
- S.0 Abteilungsleitung und andere (5)
- VP.2 Informationstechnik (5)
- KM Kommunikation, Marketing (1)
- MP Mitglied des Präsidiums (1)
- MP.0 Mitglied des Präsidiums und andere (1)
Paper des Monats
- ja (103)
Nickel-based alloys have been widely used for gas turbine blades owing to their excellent mechanical properties and corrosion resistance at high temperatures. The operating temperatures of modern gas turbines have been increased in pursuit of increased thermal efficiency. Turbine blades are exposed to these high temperatures combined with mechanical stresses, resulting in material damage through creep, fatigue, and other mechanisms. These turbine blades must be regularly inspected and replaced as needed, to prevent the loss of efficiency, breakdown, and catastrophic failure. Repair of the damaged turbine blades is often a more practical and cost-effective option than replacement, as replacement is associated with high costs and loss of material resources. To this end, state-of-the-art repair technologies including different additive manufacturing and brazing processes are considered to ensure efficient repair and optimum properties of repaired components.
In any repaired part, materials property-mismatches and/or inner defects may facilitate the crack initiation and propagation and thus reduce the number of load cycles to failure. Therefore, a fundamental understanding of the fatigue crack growth and fracture mechanisms in joining zones is required to enable the prediction of the remaining life of repaired components and to further improve and adapt the repair technologies.
Fatigue crack growth experiments have been conducted on SEN (Single Edge Notch) specimens joined via brazing, and pre-sintered Preform (PSP) and multi-materials (casted/printed) specimens layered via additive manufacturing (AM). The experiments were performed at 950 °C and various stress ratios. The crack growth was measured using DCPD (Direct Current Potential Drop) method. The stress intensity factors for joined SEN specimens were calculated using the finite element method and then used to derive the fatigue crack growth curves. Metallographic and fractographic analyses were conducted to get insight into the fracture mechanism.
Results show that the experimental technique for fatigue crack growth was successfully adapted and applied for testing joined specimens. Furthermore, the initial tests indicate that the investigated braze filler material provides a lower resistance to crack growth, and bonding defects cause a crack to deviate to the interface of the base material and joining zone. In AM-sandwich specimens, the crack growth rates are significantly reduced when the crack reaches the interface of printed material and casted material. The obtained crack growth data can be used to calibrate a crack growth model, which will further be utilized to predict the remaining life of repaired components.
High Temperature Fatigue Crack Growth in Nickel-Based Alloys Refurbished by Additive Manufacturing
(2024)
Hybrid additive manufacturing plays a crucial role in the restoration of gas turbine blades, where, e.g., the damaged blade tip is reconstructed by the additive manufacturing process on the existing blade made of a parent nickel-based alloy. However, inherent process-related defects in additively manufactured material, along with the interface created between the additively manufactured and the cast base material, impact the fatigue crack growth behavior in bi-material components. This study investigates the fatigue crack growth behavior in bi-material specimens of nickel-based alloys, specifically, additively manufactured STAL15 and cast alloy 247DS. The tests were conducted at 950 °C with stress ratios of 0.1 and −1. Metallographic and fractographic investigations were carried out to understand crack growth mechanisms. The results revealed significant retardation in crack growth at the interface. This study highlights the potential contributions of residual stresses and microstructural differences to the observed crack growth retardation phenomenon, along with the conclusion from an earlier study on the effect of yield strength mismatch on crack growth behavior at a perpendicular interface in bi-material specimens.
Nickelbasierte Superlegierungen werden in großem Umfang für Gasturbinenschaufeln verwendet, da sie einer Kombination aus hoher Belastung und hohen Temperaturen widerstehen können. Um die Effizienz moderner Gasturbinen zu verbessern, werden hohe Betriebstemperaturen angestrebt. Diese hohen Temperaturen verbunden mit mechanischen Belastungen führen zu Materialschäden aufgrund von Kriechen, Ermüdung und anderen Schadensmechanismen. Aus diesem Grund werden Turbinenschaufeln regelmäßig im Rahmen von Wartungs- und Instandsetzungsmaßnahmen geprüft und falls erforderlich ausgetauscht, um ein katastrophales Versagen im Betrieb zu vermeiden. Ein kompletter Austausch ist mit sehr hohen Kosten verbunden, weshalb geeignete Reparaturverfahren entwickelt wurden und werden. Neue Reparaturtechnologien wie die Additive Fertigung, Lötverfahren und der Einsatz von vorgesinterten Vorformen (Presintered Preform PSP) sollen eine effiziente Reparatur und optimale Eigenschaften der reparierten Bauteile sichterstellen.
Im Allgemeinen stellen die Fügezonen typische Schwachstellen dar, da sie die Anrissbildung und Rissausbreitung erleichtern und die Anzahl der Lastzyklen bis zum Bruch reduzieren können. Aus diesem Grund ist eine umfassende Untersuchung des Rissfortschrittsverhaltens in diesen, durch neue Reparaturtechnologien entstandenen Bereichen erforderlich, um die Restlebensdauer der Turbinenschaufeln vorherzusagen.
Als ein erster Beitrag zu dieser Fragestellung werden Ergebnisse von Rissfortschrittsversuchen (Fig. 1) an SENT-Proben vorgestellt, die durch Engspaltlöten gefügt wurden. Die Versuche wurden bei einer Temperatur von 950 °C und einem Spannungsverhältnis R = 0,1 durchgeführt. Die Erfassung des Rissfortschritts erfolgte mit dem Gleichstrom-Potentialsonden-Verfahren. Mit der Finite-Element-Methode konnte der Spannungsintensitätsfaktor für gefügte SENT-Proben berechnet werden, der dann zur Berechnung der Risswachstumskurven verwendet wurde. Eine abschließende licht- und rasterelektronenmikroskopische Untersuchung der Bruchflächen soll einen Beitrag zum Verständnis der Bruchmechanismen liefern und klären, ob der Riss sich im Lotwerkstoff, im Grundwerkstoff oder in der Grenzfläche ausbreitet. Die Ergebnisse werden zur Kalibrierung des Rissfortschrittsmodells und der Auslegung zukünftiger Komponenten verwendet.
Photon-based additive manufacturing technologies such as SLA, DLP, LCM, moreover volumetric two-photon-polymerization, Xolography and holographic technologies promise the highest accuracy and dimensional freedom. But to transfer the light through the feedstock it needs sufficient transparency at the used light wavelength. Ceramic particles used for powder processing routes act as scattering sites and therefore hinder the light transmission, unless…
The particle size and particle size distribution are chosen small and narrow enough. Particles which are smaller than roughly 1/10th of the light wavelength, mostly nanoparticles around 5nm size, decrease scattering vastly. This turns resins even with homogeneously distributed ceramic weight fraction of up to 80% transparent again. Feedstocks could be prepared for the highly accurate two-photon-polymerization gaining the smallest yttria stabilized zirconia structures with a resolution of 500nm and unique mechanical properties. The same feedstocks could be applied to DLP and LCM as layer-by-layer AM-technologies for bigger parts. Hybridizing both technologies lead to ceramic parts with microscopic accuracy at macroscopic dimensions. The feedstock was even applied to the volumetric Xolography with the highest transparency requirement so far and to versatile and flexible holographic AM.
Highly filled nano-particle containing transparent ceramic feedstocks open the way for technical ceramics in high precision manufacturing where the performance and durability and accessibility are increased and created by the unique ceramic properties such as mechanical strength, chemical and thermal resistance and biocompatibility
In order to be able to manipulate ceramic powder compacts and ceramic suspensions (slurries) in their volume with light, a minimum transparency of the materials is required. Compared to polymers and metals, ceramic materials are characterized by the fact that they have a wide electronic band gap and therefore a wide optical window of transparency. The optical window generally ranges from less than 0.3 µm to 5 µm wavelength. Therefore, to focus light into the volume of a ceramic powder compact, its light scattering properties need to be tailored. In this study, we present the physical background and material development strategies for the application of two-photon polymerization (2PP), Xolography and selective volumetric sintering for the additive manufacturing of structures in the volume of ceramic slips and green compacts.
Nickel-based alloys have been widely used for gas turbine blades owing to their excellent mechanical properties and corrosion resistance at high temperatures. The operating temperatures of modern gas turbines have been increased in pursuit of increased thermal efficiency. Turbine blades are exposed to these high temperatures combined with mechanical stresses, resulting in material damage through creep, fatigue, and other mechanisms. These turbine blades must be regularly inspected and replaced as needed, to prevent the loss of efficiency, breakdown, and catastrophic failure. Repair of the damaged turbine blades is often a more practical and cost-effective option than replacement, as replacement is associated with high costs and loss of material resources. To this end, state-of-the-art repair technologies including different additive manufacturing and brazing processes are considered to ensure efficient repair and optimum properties of repaired components.
In any repaired part, materials property-mismatches and/or inner defects may facilitate the crack initiation and propagation and thus reduce the number of load cycles to failure. Therefore, a fundamental understanding of the fatigue crack growth and fracture mechanisms in joining zones is required to enable the prediction of the remaining life of repaired components and to further improve and adapt the repair technologies.
Fatigue crack growth experiments have been conducted on SEN (Single Edge Notch) specimens joined via brazing, and pre-sintered Preform (PSP) and multi-materials (casted/printed) specimens layered via additive manufacturing (AM). The experiments were performed at 950 °C and various stress ratios. The crack growth was measured using DCPD (Direct Current Potential Drop) method. The stress intensity factors for joined SEN specimens were calculated using the finite element method and then used to derive the fatigue crack growth curves. Metallographic and fractographic analyses were conducted to get insight into the fracture mechanism.
Results show that the experimental technique for fatigue crack growth was successfully adapted and applied for testing joined specimens. Furthermore, the initial tests indicate that the investigated braze filler material provides a lower resistance to crack growth, and bonding defects cause a crack to deviate to the interface of the base material and joining zone. In AM-sandwich specimens, the crack growth rates are significantly reduced when the crack reaches the interface of printed material and casted material. The obtained crack growth data can be used to calibrate a crack growth model, which will further be utilized to predict the remaining life of repaired components.
Advanced ceramics printed with photon-based additive manufacturing deals with anisotropic mechanical properties from the layer-by-layer manufacturing. Motivated by the success in using highly filled transparent slurries containing nanoparticles for powder-based two-photon-polymerization (2PP) for advanced ceramic printing, this works approach is the transfer to Xolography, a volumetric additive manufacturing technology based on linear two-photon excitation and without recoating steps. This paper reports the results of a preliminary investigation optimizing the photocurable slurry to the requirements of Xolography in terms of transparency, over a significantly larger mean free path, compared to 2PP. A feedstock filled with 70 % weight fraction of ceramic particles (∼30 vol%) exhibiting an exceptionally high degree of transparency in the relevant wavelength range of 400–800 nm was prepared from 5 nm zirconia nanoparticles. The high transparency of the photocurable slurry is attributed to the near-monomodal particle size distribution of the zirconia nanoparticles used.
AbstractTwo‐photon polymerization (2PP) additive manufacturing (AM) utilizes feedstocks of ceramic nanoparticles of a few nanometers in diameter, enabling the fabrication of highly accurate technical ceramic design with structural details as small as 500 nm. The performance of these materials is expected to differ from conventional AM ceramics, as nanoparticles and three‐dimensional printing at high resolution introduce new microstructural aspects. This study applies 2PP‐AM of yttria‐stabilized zirconia to investigate the mechanical response behavior under compressive load, probing the influence of smallest structural units induced by the line packing during the printing process, design of sintered microblocks, and sintering temperature and thereby microstructure. We find a dissipative mechanical response enhanced by sintering at lower temperatures than conventional. The pursued 2PP‐AM approach yields a microstructured material with an increased number of grain boundaries that proposedly play a major role in facilitating energy dissipation within the here printed ceramic material. This microplastic response is further triggered by the filigree structures induced by hollow line packing at the order of the critical defect size of ceramics. Together, these unique aspects made accessible by the 2PP‐AM approach contribute to a heterogeneous nano‐ and microstructure, and hint toward opportunities for tailoring the mechanical response in future ceramic applications.
Photoresponsive molecular crystals have sparked interest owing to their potential application prospects. In this study, we achieved dual mechanical responses of a cyanostilbene-based crystal BN. The crystal exhibited both stress-induced mechanical flexibility and light-induced photomechanical bending. Two distinct mechanical responses are related to different underlying phenomena and were not interlinked. While elasticity is attributed to criss-cross packing arrangement in the isotropic structure, photomechanical bending is attributed to the formation of heterogeneous phase distribution due to monomer to dimer cycloaddition product formation. The crystal did not demonstrate photoswitching activity. However, it exhibited thermal reversibility, highlighting reversible dimer to monomer conversion.
A long-term study was conducted on double-lap spruce wood-concrete joints to investigate their shear strength and stiffness over a 12-month period. These joints were manufactured using both wet and dry processes, each incorporating two adhesive types for bonding the wood to the concrete: a brittle epoxy and a ductile polyurethane (PUR). The experimental design exposed the joints to three specific long-term environments: (1) outdoor exposure, (2) indoor conditions with applied load, and (3) outdoor conditions with applied load. The wood concrete joints exposed to outdoor conditions were subjected to destructive shear testing at intervals of 0 (serving as the reference sample), 2, 4, 6, and 12 months, respectively. For joints subjected to both indoor and outdoor conditions with shear loading, the shear deformation of joints was monitored continuously over the 12 months before performing the destructive tests. A gradual reduction in the shear stiffness and strength of dry joints (produced using the dry bond method) exposed to outdoor conditions was observed over a 12-month period, primarily due to bond failure at the concrete-adhesive interface. The wet joints exhibited no degradation in shear stiffness and strength across long-term conditions over the same period. The bond failure observed in dry joints was predominantly associated with stresses arising from dimensional changes in the wood. No degradation was found in the cross-linking density of the adhesive or in the concrete’s compressive stiffness and strength.