TY - CONF A1 - Avila Calderon, Luis Alexander A1 - Rehmer, Birgit A1 - Ulbricht, Alexander A1 - Mohr, Gunther A1 - Evans, Alexander A1 - Skrotzki, Birgit T1 - Low-cycle-fatigue behavior of stainless steel 316L manufactured by laser powder bed fusion N2 - This contribution presents the results of an experimental study on the LCF behavior of an austenitic 316L stainless steel produced by laser powder bed fusion featuring a low defect population, which allows for an improved understanding of the role of other typical aspects of a PBF‑LB microstructure. The LCF tests were performed between room temperature and 600 °C. A hot‑rolled 316L variant was tested as a reference. The mechanical response is characterized by strain-life curves, a Coffin‑Manson‑Basquin fitting, and cyclic deformation curves. The damage and deformation mechanisms are studied with X-ray computed tomography, optical and electron microscopy. The PBF‑LB/M/316L exhibits lower fatigue lives at lower strain amplitudes. The crack propagation is mainly transgranular. The solidification cellular structure seems to be the most relevant underlying microstructural feature determining the cyclic deformation behavior. T2 - TMS 2024 Annual Meeting & Exhibition CY - Orlando, Florida, US DA - 03.03.2024 KW - AGIL KW - Additive Fertigung KW - Mikrostruktur KW - LCF KW - 316L PY - 2024 AN - OPUS4-59782 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Jürgens, Maria T1 - Verhalten des hochwarmfesten Stahles P92 unter zyklischen thermo-mechanischen Bedingungen in lastflexiblen Dampfkraftwerken N2 - Die Erzeugung von Erneuerbaren Energien unterliegt starken Schwankungen, die von konventionellen Kraftwerken ausgeglichen werden müssen, um das Stromnetz stabil zu halten. Für die konventionellen Kraftwerke bedeutet dies eine zunehmend zyklische Fahrweise, die zu häufigeren Last- und Temperaturwechseln führt. Von den eingesetzten Werkstoffen fehlen Daten zum Verhalten unter zyklischer Fahrweise. Ziel dieser Arbeit ist es daher, für P92, einen als Rohrleitungswerkstoff eingesetzten hochwarmfesten Stahl, zu untersuchen, welche Auswirkungen zyklische Fahrweisen auf die Schädigungsprozesse und Lebensdauern haben. Da durch den zyklischen Betrieb eine verstärkte Schädigung durch Ermüdungsprozesse zu erwarten ist, wurden dehnungskontrollierte isotherme (LCF) und nicht-isotherme (TMF) Ermüdungsversuche mit und ohne Haltezeit bei verschiedenen Temperaturen bzw. Temperaturintervallen durchgeführt. Mit den Haltezeitversuchen soll dabei das Kriech-Ermüdungs-Verhalten untersucht werden. Bei den TMF-Versuchen wurde zusätzlich die Temperaturrate variiert, um näher an den realen Lastwechselgeschwindigkeiten zu prüfen. Schließlich wurden auf Basis der durchgeführten LCF- und TMF-Versuche betriebsnahe Versuchsprozeduren entwickelt, um unterschiedliche Betriebsmodi in einem Versuch abzubilden. Die durchgeführten mechanischen Versuche stellen eine umfangreiche Basis zu Ermüdungsdaten an P92 dar. Neben der Abhängigkeit der Lebensdauer von Temperatur, Temperaturintervall und –rate, sowie Dehnung und Haltezeit, konnte auch das Entfestigungsverhalten genauer charakterisiert werden. Sowohl Haltezeiten als auch das Reduzieren der Temperaturrate können die Lebensdauer erheblich verringern. Dabei kommt es gerade bei vermeintlich kleinen Dehnungen, bei denen die Streckgrenze nur leicht überschritten wird, zu einer Lebensdauerreduzierung. Haltezeiten verstärken zudem die zyklische Entfestigung. Die fraktographische Analyse der Proben hat ergeben, dass es keinen direkten Zusammenhang zwischen der Entfestigung und der Bildung von Nebenrissen gibt. Stattdessen zeigen EBSD- und TEM-Untersuchungen, dass es zur Bildung einer Subkornstruktur kommt und die Entfestigung auf dem Verschwinden von Kleinwinkelkorngrenzen beruht. Während bei den LCF-Proben eine reine Ermüdungsschädigung vorliegt, konnte bei einigen TMF-Proben eine kriechdominierende Schädigung nachgewiesen werden. Die betriebsnahen Zyklen zeigen, dass sich mit den durchgeführten Versuchen das reale Betriebsverhalten gut abschätzen lässt. Da es jedoch auch Parameterkombinationen gibt, bei denen keine Änderung des Entfestigungs- und Lebensdauerverhaltens auftritt, sollte genau bekannt sein, welche Belastungen in einem Bauteil auftreten. KW - P92 KW - LCF KW - TMF KW - Energiewende KW - Kriechermüdung KW - Energy transition KW - Creep-fatigue PY - 2020 DO - https://doi.org/10.14279/depositonce-10538 SP - 1 EP - 144 CY - Berlin AN - OPUS4-51571 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonntag, Nadja A1 - Jürgens, Maria A1 - Skrotzki, Birgit A1 - Olbricht, Jürgen T1 - Creep-fatigue of P92 in service-like tests with combined stress- and strain-controlled dwell times N2 - Complex service-like relaxation- and creep-fatigue tests with strain- and stress-controlled dwells and fatigue cycle durations of approx. 2200 s were performed exemplarily on a grade P92 steel at 620 ◦C in this study. The results indicate deviations in the prevailing creep mechanisms of long-term relaxation and creep dwells, affecting subsequent dwells, load shifts, and the macroscopic softening behavior quite differently. In addition, fracture surfaces and longitudinal metallographic sections reveal intergranular crack growth for complex loading with stress-controlled dwells, whereas complex strain-controlled tests enhance oxidation and transgranular crack propagation. These findings substantiate the limited transferability of relaxation-fatigue to creep-fatigue conditions. KW - Tempered martensite-ferritic steel KW - P92 KW - Dwell periods KW - Creep-fatigue interaction KW - Stress relaxation PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564239 DO - https://doi.org/10.1016/j.ijfatigue.2022.107381 SN - 0142-1123 VL - 168 SP - 1 EP - 12 PB - Elsevier Ltd. AN - OPUS4-56423 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo A1 - Jürgens, Maria A1 - Sonntag, Nadja A1 - Olbricht, Jürgen A1 - Skrotzki, Birgit T1 - Cyclic operation performance of 9 -12% cr ferritic martensitic steels part 1: cyclic mechanical behavior under fatigue and creep fatigue loading N2 - 9-12% Cr ferritic-martensitic stainless steels are widely used as high temperature construction materials in fossil fueled power plants due to their excellent creep and oxidation resistance, but changes in electricity markets during the last two decades have considerably changed the typical working conditions of these facilities. The growing share of renewable energy sources in power generation forces most of these plants into flexible operation with frequent load shifts or shutdowns. These cyclic operation profiles constitute a major lifetime issue, raising the question which fundamental processes govern the reaction of ferritic-martensitic steels to cyclic load and temperature variations. The present contribution reports on current findings obtained in a multidisciplinary project funded by German Ministry of Education and Research (BMBF) which combines cyclic mechanical and cyclic oxidation testing of different 9-12% Cr grades with detailed microstructural analyses and related micromechanical modeling. In the present first part of our contribution, an overview will be given on the results obtained in the mechanical testing programme of the project. Mechanical analyses were carried out on P91 and (mainly) P92 steel grades, particularly looking at softening phenomena and lifetimes obtained in isothermal cyclic loading (low cycle fatigue, LCF), non-isothermal cyclic loading (thermo-mechanical fatigue, TMF), and service-like combinations of creep and fatigue periods. For this purpose, cylindrical specimens were extracted from thick-walled steam pipes, orthogonal to the pipe axis, and subjected to strain controlled cyclic loading (± 0.2 to ±0.5 % mechanical strain) to different degrees of softening at temperatures up to 620 °C. The test results will be presented and discussed with a focus on the impact of hold periods (i.e. combined creep-fatigue conditions) on mechanical softening, lifetime and crack formation. Details on the microstructural evolution and their representation in a micromechanical model will be given in a second, complementary contribution to this conference. T2 - 45. MPA-Seminar CY - Stuttgart, Germany DA - 01.10.2019 KW - Tempered Martensite Ferritic Steels KW - Low Cycle Fatigue KW - Creep-Fatigue KW - Thermo-Mechanical Fatigue KW - P92 PY - 2019 AN - OPUS4-50050 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Sonntag, Nadja T1 - Untersuchung magnetischer Streufelder in einem inhomogen verformten Baustahl mittels passiv-magnetischer Prüfverfahren N2 - Die Metal Magnetic Memory (MMM) Methode ist ein standardisiertes, zerstörungsfreies Prüfverfahren, das für die Detektion von lokal geschädigten Materialbereichen in ferromagnetischen Bauteilen oder Proben verwendet wird. Es basiert auf der Annahme lokaler magnetoelastischer Wechselwirkungen an Spannungskonzentrationsstellen, die schwache magnetische Streufelder an den geschädigten Prüfkörperoberflächen hervorrufen. Die MMM-Methode überträgt dabei die für einachsige und elastische Verformungen entwickelten magnetoelastischen Modellvorstellungen ohne weitere Anpassungen in den Schädigungskontext, der jedoch mehrachsige Beanspruchungen und elastisch-plastische Deformationsprozesse erwarten lässt. Das Ziel der Arbeit ist es daher, die gängigen MMM-Hypothesen zur Signalentstehung fach- und skalenübergreifend und unter stärkerer Berücksichtigung mechanischer und mikrostruktureller Aspekte zu überprüfen. Zu diesem Zweck wurden zum einen gekerbte Flachzugproben aus einem unlegierten Baustahl inhomogen elastisch-plastisch verformt und die entstehenden magnetischen Streufelder an deren Oberflächen mit einem Drei-Achsen-GMR-Magnetometer detektiert. Die so ermittelten Magnetfeld-verteilungen wurden für unterschiedliche Verformungszustände ortsaufgelöst und richtungsabhängig mit gemessenen Dehnungsverteilungen (digitale Bildkorrelation) und mit simulierten Lastspannungs-verteilungen korreliert. Die eingeschnürten Probenbereiche wurden zusätzlich topographisch mittels Streifenlichtprojektion und Weißlichtinterferenzmikroskopie vermessen, um den Magnetisierungs-prozess ebenfalls vor dem Hintergrund geometrischer Effekte diskutieren zu können. Um systematische, verformungsinduzierte Veränderungen der magnetischen Mikrostruktur (magnetischer Domänen) im polykristallinen, quasi-isotropen Material nachzuweisen, wurde zum anderen ein in dieser Arbeit entwickelter statistischer Ansatz der Domänenanalyse angewandt. Hierfür wurde das Material zunächst durch Härteeindrücke mehrachsig elastisch-plastisch verformt, und die verformten Probenbereiche wurden anschließend mit Hilfe der Bitterstreifentechnik hauptsächlich bei niedriger Vergrößerung lichtmikroskopisch untersucht. Die beobachteten makroskopischen Domänen-kontraste wurden über ein analytisches, kontaktmechanisches (ECM-) Modell und über Makro-Eigen-spannungsmessungen (energiedispersive Synchrotron-Beugungsuntersuchungen) charakteristischen Verformungszonen unter den Härteeindrücken zugeordnet. Die Ergebnisse dieser Untersuchungen belegen, dass die Entstehung der Streufelder – entgegen bisheriger Annahmen – nicht allein auf mechanische Spannungs- und Verformungsgradienten im Material zurückzuführen, sondern auch topographisch bedingt ist. Die Vernachlässigung überlagerter geometrischer Effekte kann zu sicherheitsrelevanten Fehlinterpretationen der magnetischen Signale führen. Einachsige magnetoelastische Modellvorstellungen sollten zudem nicht ohne Anpassungen auf komplexe Beanspruchungen übertragen werden, da u. a. sowohl mechanische Größen (wie Spannungen oder Dehnungen) als auch mikrostrukturelle Parameter (wie z. B. Versetzungsdichten) bei komplexen Belastungen als ortsabhängige Variablen behandelt werden müssen. Die in dieser Arbeit beobachteten Domänenkontraste lassen sich zweifelsfrei charakteristischen Verformungszonen zuordnen, mikro-strukturell jedoch nicht allein mit anzunehmenden Gradienten der Versetzungsdichte erklären. Statt-dessen entstehen beispielsweise lokale Verformungstexturen, die zusätzliche magnetische Anisotropien bewirken könnten. Da bisher weder die makroskopischen noch die mikrostrukturellen Ursachen der Streufeldentstehung hinreichend verstanden sind, scheint die MMM-Methode für die quantitative Bewertung des Schädigungszustands derzeit ungeeignet. N2 - The Metal Magnetic Memory (MMM) method is a standardized, nondestructive testing method used for the detection of locally damaged material areas in ferromagnetic components or samples. It assumes local magnetoelastic interactions in stress concentration zones, causing weak magnetic stray fields on the damaged specimen surfaces. The MMM method transfers magnetoelastic model conceptions developed for uniaxial and elastic deformations without further adjustments into the damage context, which is, however, associated with multiaxial stresses and elastic-plastic deformations. The objective of this thesis is therefore to verify prevalent MMM hypotheses concerning the signal generation, putting emphasis on complex mechanical and microstructural aspects of damage while using interdisciplinary and multi-scale approaches. To this end, on the one hand, notched tensile specimens made of an unalloyed structural steel were inhomogeneously (elastically and plastically) deformed and deformation-induced magnetic stray fields were then detected by a three-axis GMR magnetometer. The obtained surface magnetic field distributions were correlated with measured strain distributions (digital image correlation) and with numerically simulated mechanical stress distributions (finite element analysis). To enable discussions on the magnetization process against the background of geometrical effects, the necked specimen regions were additionally investigated using optical profilometry methods (fringe projection and white light interference microscopy). On the other hand, a newly developed meso-scale approach to magnetic domain analysis was applied to prove systematic, deformation-induced changes of the magnetic microstructure within the polycrystalline, quasi-isotropic material: After multiaxial elastic-plastic deformation of coupon specimens by hardness indentation, the deformed sample regions were studied by Bitter technique in optical microscopy, preferably at low magnification. The observed macroscopic domain contrasts were related to characteristic deformation zones below the indents by using an analytical model from the field of contact mechanics (ECM) and macro-residual stress measurements (obtained from energy-dispersive synchrotron diffraction experiments). It is demonstrated that the formation of magnetic stray fields, quite contrary to previous assumptions, results not only from mechanical (e.g. stress) gradients within the material, but is also topographically induced. The neglect of such superimposed geometric effects may also lead to safety-relevant misinterpretations of the magnetic signals. Furthermore, uniaxial magnetoelastic model concepts should not be applied to complex stress/strain conditions without adaptation since both mechanical quantities (such as stresses or strains) and microstructural parameters (such as dislocation densities) must be treated as location-dependent variables. The observed magnetic domain contrasts could clearly be assigned to characteristic deformation zones but cannot be explained solely by hypothesized gradients of the dislocation density. Instead, for example, local deformation textures emerge, which may cause additional magnetic anisotropies. The MMM method currently seems unsuitable for quantitative damage assessments of components or specimens since neither the macroscopic nor the microstructural origins of the stray field formation have yet been sufficiently understood. KW - Magnetoelastischer Effekt KW - Magnetische Domänen KW - Mehrachsige Verformung KW - Schädigung KW - Unlegierter Baustahl KW - Magnetoelastic effect KW - Magnetic domains KW - Multiaxial deformation KW - Damage KW - Structural steel PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484302 DO - https://doi.org/10.14279/depositonce-8524 SP - 1 EP - 117 CY - Berlin AN - OPUS4-48430 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Sonntag, Nadja A1 - Jürgens, M. A1 - Uhlemann, Patrick A1 - Skrotzki, Birgit A1 - Olbricht, Jürgen T1 - Datasets for Service-Like Creep-Fatigue Experiments on Grade P92 Steel N2 - The dataset contains experimental mechanical data from complex service-like creep-fatigue experiments performed isothermally at 620 °C and a low strain amplitude of 0.2 % on tempered martensite-ferritic grade P92 steel. The data sets in text file format provide cyclic deformation (min. and max. stresses) and the total (hysteresis) data of all recorded fatigue cycles for three different creep-fatigue experiments: 1) a standard relaxation fatigue (RF) test with symmetrical dwell times of three minutes introduced at minimum and maximum strain, 2) a fully strain-controlled service-like relaxation (SLR) test combining these three-minute peak strain dwells with a 30-minute dwell in between at zero strain, and 3) a partly stress-controlled service-like creep (SLC) test combining the three-minute peak strain dwells with 30-minute dwells at constant stress. Further information on data and data acquisition, analysis, and experimental details are given in “Experimental Data from Service-Like Creep-Fatigue Experiments on Grade P92 Steel”, submitted to Data in Brief. Additional analyses of these datasets, as well as experimental findings and discussions are presented in “Creep-Fatigue of P92 in Service-Like Tests with Combined Stress- and Strain-Controlled Dwell Times”, submitted to International Journal of Fatigue. KW - Creep-fatigue KW - Stress relaxation KW - Dwell-Fatigue KW - Tempered martensite-ferritic steel PY - 2022 DO - https://doi.org/10.5281/zenodo.7198218 PB - Zenodo CY - Geneva AN - OPUS4-55995 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mohr, Gunther A1 - Sommer, Konstantin A1 - Knobloch, Tim A1 - Altenburg, Simon A1 - Recknagel, Sebastian A1 - Bettge, Dirk A1 - Hilgenberg, Kai T1 - Process Induced Preheating in Laser Powder Bed Fusion Monitored by Thermography and Its Influence on the Microstructure of 316L Stainless Steel Parts N2 - Undetected and undesired microstructural variations in components produced by laser powder bed fusion are a major challenge, especially for safety-critical components. In this study, an in-depth analysis of the microstructural features of 316L specimens produced by laser powder bed fusion at different levels of volumetric energy density and different levels of inter layer time is reported. The study has been conducted on specimens with an application relevant build height (>100 mm). Furthermore, the evolution of the intrinsic preheating temperature during the build-up of specimens was monitored using a thermographic in-situ monitoring set-up. By applying recently determined emissivity values of 316L powder layers, real temperatures could be quantified. Heat accumulation led to preheating temperatures of up to about 600 °C. Significant differences in the preheating temperatures were discussed with respect to the individual process parameter combinations, including the build height. A strong effect of the inter layer time on the heat accumulation was observed. A shorter inter layer time resulted in an increase of the preheating temperature by more than a factor of 2 in the upper part of the specimens compared to longer inter layer times. This, in turn, resulted in heterogeneity of the microstructure and differences in material properties within individual specimens. The resulting differences in the microstructure were analyzed using electron back scatter diffraction and scanning electron microscopy. Results from chemical analysis as well as electron back scatter diffraction measurements indicated stable conditions in terms of chemical alloy composition and austenite phase content for the used set of parameter combinations. However, an increase of the average grain size by more than a factor of 2.5 could be revealed within individual specimens. Additionally, differences in feature size of the solidification cellular substructure were examined and a trend of increasing cell sizes was observed. This trend was attributed to differences in solidification rate and thermal gradients induced by differences in scanning velocity and preheating temperature. A change of the thermal history due to intrinsic preheating could be identified as the main cause of this heterogeneity. It was induced by critical combinations of the energy input and differences in heat transfer conditions by variations of the inter layer time. The microstructural variations were directly correlated to differences in hardness. KW - Additive manufacturing KW - Laser powder bed fusion KW - In-situ process monitoring KW - Thermography KW - Heat accumulation KW - Inter layer time KW - Cellular substructure PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-529240 DO - https://doi.org/10.3390/met11071063 VL - 11 IS - 7 SP - 1063 PB - MDPI CY - Basel, Schweiz AN - OPUS4-52924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zocca, Andrea A1 - Lüchtenborg, Jörg A1 - Mühler, T. A1 - Wilbig, Janka A1 - Mohr, Gunther A1 - Villatte, T. A1 - Léonard, Fabien A1 - Nolze, Gert A1 - Sparenberg, M. A1 - Melcher, J. A1 - Hilgenberg, Kai A1 - Günster, Jens T1 - Enabling the 3D Printing of Metal Components in μ-Gravity N2 - As humanity contemplates manned missions to Mars, strategies need to be developed for the design and operation of hospitable environments to safely work in space for years. The supply of spare parts for repair and replacement of lost equipment will be one key need, but in-space manufacturing remains the only option for a timely supply. With high flexibility in design and the ability to manufacture ready-to-use components directly from a computeraided model, additive manufacturing (AM) technologies appear extremely attractive. For the manufacturing of metal parts, laser-beam melting is the most widely used AM process. However, the handling of metal powders in the absence of gravity is one prerequisite for its successful application in space. A gas flow throughout the powder bed is successfully applied to compensate for missing gravitational forces in microgravity experiments. This so-called gas-flow-assisted powder deposition is based on a porous Building platform acting as a filter for the fixation of metal particles in a gas flow driven by a pressure difference maintained by a vacuum pump. KW - Additive manufacturing KW - µ-gravity KW - Laser beam melting KW - Parabolic flight KW - 3D printing PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-492190 DO - https://doi.org/10.1002/admt.201900506 SP - 1900506 PB - WILEY-VCH Verlag GmbH AN - OPUS4-49219 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schneider, M. A1 - Bettge, Dirk A1 - Hilgenberg, Kai A1 - Binder, M. A1 - Dollmeier, K. A1 - Dreyer, M. A1 - Klöden, B. A1 - Schlingmann, T. A1 - Schmidt, J. T1 - Reproducibility and Scattering in Additive Manufacturing: Results from a Round Robin on PBF-LB/M AlSi10Mg Alloy T1 - Reproduzierbarkeit und Streuung bei der additiven Fertigung: Ergebnisse eines Ringversuchs mit einer PBF-LB/M AlSi10Mg-Legierung N2 - The round robin test investigated the reliability users can expect for AlSi10Mg additive manufactured specimens by laser powder bed fusion through examining powder quality, process parameter, microstructure defects, strength and fatigue. Besides for one outlier, expected static material properties could be found. Optical microstructure inspection was beneficial to determine true porosity and porosity types to explain the occurring scatter in properties. Fractographic analyses reveal that the fatigue crack propagation starts at the rough as-built surface for all specimens. Statistical analysis of the scatter in fatigue using statistical derived safety factors concludes that at a stress of 36.87 MPa the fatigue limit of 107 cycles could be reached for all specimen with a survival probability of 99.999 %. N2 - Im Rahmen eines Ringversuchs wurde durch die Untersuchung der Pulverqualität, der Prozessparameter, der Gefügefehler, der Festigkeit und der Ermüdung die Zuverlässigkeit bestimmt, die Nutzer von AlSi10Mg-Proben erwarten können, die mit pulverbettbasiertes Schmelzen mittels Laser (engl. Laser Powder Bed Fusion) gefertigt worden sind. Abgesehen von einem Ausreißer wurden die erwarteten statischen Materialeigenschaften erreicht. Eine optische Gefügeprüfung diente dazu, die tatsächliche Porosität und Arten von Porosität zu ermitteln, um die bei den Eigenschaften auftretende Streuung zu erklären. Fraktographische Unterschungen zeigen eine bei allen Proben von der rauen Oberfläche im As-built-Zustand ausgehende Ermüdungsrissausbreitung. Aus der statistischen Analyse der Streuung bezüglich der Ermüdung unter Anwendung von statistischen abgeleiteten Sicherheitsfaktoren geht hervor, dass alle Proben die Dauerfestigkeit von 107 Zyklen bei einer Spannung von 36,87 MPa mit einer Überlebenswahrscheinlichkeit von 99,999 % erreichten. KW - Additive manufacturing KW - Reproducibility KW - Reliability PY - 2022 DO - https://doi.org/10.1515/pm-2022-1018 SN - 2195-8599 VL - 59 IS - 10 SP - 580 EP - 614 PB - De Gruyter AN - OPUS4-55935 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Portella, Pedro Dolabella A1 - Ulbricht, Alexander A1 - Evans, Alexander A1 - Altenburg, Simon A1 - Ehlers, Henrik A1 - Hilgenberg, Kai A1 - Mohr, Gunther T1 - Monitoring additive manufacturing processes by using NDT methods N2 - In this presentation we discuss the online monitoring of metallic AM parts produced by the Laser Powder Bed Fusion (LPBF) process by using optical, thermographic and electromagnetic methods. In a first approach we present the detection of defects generated during the process and discuss how to improve these methods for the optimization of design and production of metallic AM parts. T2 - ABENDI - Workshop CY - Online meeting DA - 19.11.2020 KW - Additive Fertigung PY - 2020 AN - OPUS4-52042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonntag, Nadja A1 - Piesker, Benjamin A1 - Ávila Calderón, Luis Alexander A1 - Mohr, Gunther A1 - Rehmer, Birgit A1 - Agudo Jácome, Leonardo A1 - Hilgenberg, Kai A1 - Evans, Alexander A1 - Skrotzki, Birgit T1 - Tensile and Low‐Cycle Fatigue Behavior of Laser Powder Bed Fused Inconel 718 at Room and High Temperature N2 - This study investigates the room‐ and high‐temperature (650 °C) tensile and low‐cycle‐fatigue behavior of Inconel 718 produced by laser powder bed fusion (PBF‐LB/M) with a four‐step heat treatment and compares the results to the conventional wrought material. The microstructure after heat treatment is characterized on different length scales. Compared to the wrought variant, the elastic and yield properties are comparable at both test temperatures while tensile strength, ductility, and strain hardening capacity are lower. The fatigue life of the PBF‐LB/M variant at room temperature is slightly lower than that of the wrought material, while at 650 °C, it is vice versa. The cyclic stress response for both material variants is characterized by cyclic softening, which is more pronounced at the higher test temperature. High strain amplitudes (≥0.7%) at room temperature and especially a high testing temperature result in the formation of multiple secondary cracks at the transitions of regions comprising predominantly elongated grain morphology and columns of stacked grains with ripple patterns in the PBF‐LB/M material. This observation and pronounced crack branching and deflection indicate that the cracks are controlled by sharp micromechanical gradients and local crystallite clusters. KW - Additive manufacturing KW - Fatigue damage KW - Heat treatment KW - Inconel 718 KW - Laser powder bed fusion KW - Low-cycle fatigue KW - Tensile strength PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-599316 DO - https://doi.org/10.1002/adem.202302122 SN - 1527-2648 SP - 1 EP - 17 PB - Wiley AN - OPUS4-59931 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ávila Calderón, Luis Alexander A1 - Rehmer, Birgit A1 - Schriever, Sina A1 - Ulbricht, Alexander A1 - Agudo Jácome, Leonardo A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Skrotzki, Birgit T1 - Kriech- und Bruchverhalten von additiv hergestelltem austenitischem Stahl 316L. Vergleich zum konventionellen Werkstoff. N2 - Eine kritische Aufgabe im Rahmen der Etablierung von Prozess-Struktur-Eigenschafts-Performance-Beziehungen bei der additiven Fertigung (AM) von Metallen ist die Ermittlung von zuverlässigen und gut dokumentierten Kennwerten zum Materialverhalten sowie das Schaffen von Wissen über die Struktur-Eigenschafts-Korrelation. Schließlich ist dies die Grundlage für die Entwicklung gezielterer Prozessoptimierungen und zuverlässigerer Lebensdauer-Vorhersagen. In diesem Zusammenhang zielt dieser Beitrag darauf ab, Daten und Erkenntnisse über das Kriechverhalten des austenitischen Edelstahls 316L zu liefern, der mittels Laser-Powder-Bed-Fusion (L-PBF) hergestellt wird. Um dieses Ziel zu erreichen, wurden Proben aus konventionellem warmgewalztem sowie AM-Material gemäß den bestehenden Normen für konventionelles Material geprüft und vor und nach dem Versagen mikrostrukturell charakterisiert. Die Probekörper wurden aus einzelnen Blöcken des AM-Materials gefertigt. Die Blöcke wurden mit einer Standard-Scan- und Aufbaustrategie hergestellt und anschließend wärmebehandelt. Das Kriechverhalten wird anhand der Kriechlebensdauer und ausgewählter Kriechkurven und Kennwerte beschrieben und vergleichend bewertet. Der Einfluss von Defekten und Mikrostruktur auf das Materialverhalten wird anhand von zerstörenden und zerstörungsfreien Auswertungen an ausgewählten Proben analysiert. Der AM-Werkstoff zeigt kürzere Kriechlebensdauern, erreicht das sekundäre Kriechstadium deutlich schneller und bei geringerer Dehnung und weist eine geringere Kriechduktilität im Vergleich zu seinem konventionellen Gegenstück auf. Das Kriechschädigungsverhalten des AM-Werkstoffs ist eher mikrostruktur- als defektgesteuert und ist durch die Bildung intergranularer Kriechrisse gekennzeichnet. Als kritische Merkmale werden die Versetzungsdichte sowie die Versprödung der Korngrenzen identifiziert. Die Mikro-Computertomographie (µCT) erweist sich als Alternative zur Metallographie, um die Kriechschädigung zu analysieren. T2 - Sitzung des DGM-Arbeitskreises Mechanisches Werkstoffverhalten bei hoher Temperatur CY - Online meeting DA - 07.10.2020 KW - 316L KW - Kriechen KW - Additive Fertigung KW - Mikrostruktur KW - Mikro-Computertomographie PY - 2020 AN - OPUS4-51824 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Altenburg, Simon A1 - Mohr, Gunther A1 - Baesso, Ilaria A1 - Straße, Anne A1 - Pittner, Andreas A1 - Pignatelli, Giuseppe A1 - Seeger, Stefan A1 - Nazarzadehmoafi, Maryam A1 - Ehlers, Henrik A1 - Gohlke, Dirk A1 - Homann, Tobias A1 - Scheuschner, Nils A1 - Ulbricht, Alexander A1 - Heinrich, P. A1 - Maierhofer, Christiane T1 - Process monitoring of additive manufacturing of metals - an overview of the project ProMoAM N2 - The project ProMoAM is presented. The goal of the project is to evaluate which NDT techniques or combination of techniques is suited for in-situ quality assurance in additive manufacturing of metals. To this end, also 3d-data fusion and visualization techniques are applied. Additional ex-situ NDT-techniques are used as references for defect detection and quantification. Feasability studies for NDT-techniques that are presently not applicable for in-situ use are performed as well. The presentation gives a brief overview of the whole project and the different involved NDT-techniques. T2 - Workshop od Additive Manufacturing: Process, materials, simulation & implants CY - Berlin, Germany DA - 13.05.2019 KW - Additive manufacturing KW - Process monitoring KW - NDT PY - 2019 AN - OPUS4-48087 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Ávila, Luis A1 - Werner, Tiago A1 - Sommer, Konstantin A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Charmi, Amir A1 - Mohr, Gunther A1 - Rehmer, Birgit A1 - Skrotzki, Birgit A1 - Falkenberg, Rainer A1 - Bettge, Dirk A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Kromm, Arne A1 - Hilgenberg, Kai A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Ageing behaviour of laser powder bed fused 316L: a powder to failure approach N2 - Laser powder bed fusion (LPBF) is an additive manufacturing process for materials which inherently tends to yield various degrees of metastable hierarchical microstructures, defects and high residual stresses in the as-built condition depending on the process parameters. The understanding of the evolution of these typical features during heat treatment and subsequent thermal and mechanical ageing is crucial for the wider acceptance for safety critical structures. A multi-disciplinary research project at BAM studying the development of the microstructure, defects, residual stresses typical of LPBF 316L and their evolution during thermal and mechanical ageing has led to insights into the stability of these inherent features. This presentation aims to give a broad overview of the project with a few specific cases of investigation. Firstly, the formation of residual stresses, the nature of the initial microstructure, the tensile properties and a modelling approach to understand the anisotropy will be presented. This will be followed by examples of studies of their evolution during heat treatment, long term thermal exposure, and room temperature and high temperature mechanical testing compared to a baseline of conventional wrought variant of the same alloy. T2 - International Conference on Additive Manufacturing 2021 (ICAM 2021) CY - Online meeting DA - 01.11.2021 KW - Ageing KW - Additive manufacturing KW - Laser powder bed fusion KW - AGIL PY - 2021 AN - OPUS4-54106 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Ávila, Luis A1 - Werner, Tiago A1 - Sommer, Konstantin A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Charmi, Amir A1 - Mohr, Gunther A1 - Altenburg, Simon A1 - Rehmer, Birgit A1 - Skrotzki, Birgit A1 - Falkenberg, Rainer A1 - Bettge, Dirk A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Kromm, Arne A1 - Hilgenberg, Kai A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Entwicklung der Mikrostruktur der mechanischen Eigenschaften und der Eigenspannungen in L-PBF 316L N2 - Die additive Fertigung (AM) metallischer Werkstoffe mittels Laser Powder Bed Fusion (L-PBF) ermöglicht einzigartige hierarchische Mikrostrukturen, die zu Verbesserungen bestimmter mechanischer Eigenschaften gegenüber konventionell hergestellten Varianten derselben Legierung führen können. Allerdings ist das L-PBF-Verfahren häufig durch das Vorhandensein hoher Eigenspannungen gekennzeichnet, die es zu verstehen und zu mindern gilt. Daher ist das Verständnis der Mikrostrukturen, der Eigenspannungen und der daraus resultierenden mechanischen Eigenschaften entscheidend für eine breite Akzeptanz bei sicherheitskritischen Anwendungen. Die BAM hat ein multidisziplinäres Forschungsprogramm gestartet, um diese Aspekte bei LPBF 316L zu untersuchen. Der vorliegende Beitrag stellt einige der wichtigsten Ergebnisse vor: der Einfluss von Prozessparametern auf die Mikrostruktur, der Einfluss von Mikrostruktur und Textur auf die Festigkeit, Kriechverhalten und Schädigung und die Stabilität von Eigenspannungen und Mikrostruktur unter Wärmebehandlungsbedingungen. T2 - DGM 3. Fachtagung Werkstoffe und Additive Fertigung CY - Dresden, Germany DA - 11.05.2022 KW - Mechanische Eigenschaften KW - Additive Fertigung KW - L-PBF 316L KW - Entwicklung KW - Mikrostruktur KW - Eigenspannung PY - 2022 AN - OPUS4-55786 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonntag, Nadja A1 - Skrotzki, Birgit A1 - Stegemann, Robert A1 - Löwe, Peter A1 - Kreutzbruck, M. T1 - The role of surface topography on deformation-induced magnetization under inhomogeneous elastic-plastic deformation N2 - It is widely accepted that the magnetic state of a ferromagnetic material may be irreversibly altered by mechanical loading due to magnetoelastic effects. A novel standardized nondestructive testing (NDT) technique uses weak magnetic stray fields, which are assumed to arise from inhomogeneous deformation, for structural health monitoring (i.e., for detection and assessment of damage). However, the mechanical and microstructural complexity of damage has hitherto only been insufficiently considered. The aim of this study is to discuss the phenomenon of inhomogeneous “self-magnetization” of a polycrystalline ferromagnetic material under inhomogeneous deformation experimentally and with stronger material-mechanical focus. To this end, notched specimens were elastically and plastically deformed. Surface magnetic states were measured by a three-axis giant magnetoresistant (GMR) sensor and were compared with strain field (digital image correlation) and optical topography measurements. It is demonstrated that the stray fields do not solely form due to magnetoelastic effects. Instead, inhomogeneous plastic deformation causes topography, which is one of the main origins for the magnetic stray field formation. Additionally, if not considered, topography may falsify the magnetic signals due to variable lift-off values. The correlation of magnetic vector components with mechanical tensors, particularly for multiaxial stress/strain states and inhomogeneous elastic-plastic deformations remains an issue. KW - Magnetic stray fields KW - Magnetomechanical effect KW - Damage KW - Topography KW - Multiaxial deformation KW - Notch KW - Plastic deformation KW - Metal magnetic memory KW - Digital image correlation KW - Structural steel PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-457878 DO - https://doi.org/10.3390/ma11091518 SN - 1996-1944 VL - 11 IS - 9 SP - 1518, 1 EP - 26 PB - MDPI CY - Basel, Switzerland AN - OPUS4-45787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander A1 - Avila Calderon, Luis A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Evans, Alexander A1 - Skrotzki, Birgit A1 - Bruno, Giovanni T1 - Evolution of Creep Damage of 316L Produced by Laser Powder Bed Fusion N2 - The damage mechanisms of metallic components produced by process laser powder bed fusion differ significantly from those typically observed in conventionally manufactured variants of the same alloy. This is due to the unique microstructures of additively manufactured materials. Herein, the focus is on the study of the evolution of creep damage in stainless steel 316L specimens produced by laser powder bed fusion. X-ray computed tomography is used to unravel the influence of the process-specific microstructure from the influence of the initial void distribution on creep damage mechanisms. The void distribution of two specimens tested at 600 °C and 650 °C is analyzed before a creep test, after an interruption, and after fracture. The results indicate that the formation of damage is not connected to the initial void distribution. Instead, damage accumulation at grain boundaries resulting from intergranular cracking is observed. T2 - Annual International Solid Freeform Fabrication Symposium CY - Austin, TX, USA DA - 14.08.2023 KW - AISI 316L KW - Additive Manufacturing KW - Computed Tomography KW - Creep KW - Laser Powder Bed Fusion KW - Microstructure KW - PBF-LB/M/316L PY - 2023 AN - OPUS4-58285 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Beygi Nasrabadi, Hossein A1 - Skrotzki, Birgit A1 - Hanke, Thomas A1 - Eisenbart, Miriam T1 - Mechanical testing ontology (MTO) N2 - The materials mechanical testing ontology (MTO) was developed by collecting the mechanical testing vocabulary from ISO 23718 standard, as well as the standardized testing processes described for various mechanical testing of materials like tensile testing, Brinell hardness test, Vickers hardness test, stress relaxation test, and fatigue testing. Versions info: V2 developed using BFO+CCO top-level ontologies. V3 developed using PROVO+PMDco top-level ontologies. V4 developed using BFO+IOF top-level ontologies. Repositories: GitLab: https://gitlab.com/kupferdigital/ontologies/mechanical-testing-ontology GitHub: https://github.com/HosseinBeygiNasrabadi/Mechanical-Testing-Ontology MatPortal: https://matportal.org/ontologies/MTO IndustryPortal: https://industryportal.enit.fr/ontologies/MTO KW - Ontology KW - Mechanical testing KW - FAIR data PY - 2023 UR - https://gitlab.com/kupferdigital/ontologies/mechanical-testing-ontology/ PB - GitLab CY - San Francisco, CA, USA AN - OPUS4-58271 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Beygi Nasrabadi, Hossein A1 - Hanke, Thomas A1 - Skrotzki, Birgit T1 - Semantic Representation of Low‐Cycle‐Fatigue Testing Data Using a Fatigue Test Ontology and ckan.kupferdigital Data Management System N2 - Addressing a strategy for publishing open and digital research data, this article presents the approach for streamlining and automating the process of storage and conversion of research data to those of semantically queryable data on the web. As the use case for demonstrating and evaluating the digitalization process, the primary datasets from low‐cycle‐fatigue testing of several copper alloys are prepared. The fatigue test ontology (FTO) and ckan.kupferdigital data management system are developed as two main prerequisites of the data digitalization process. FTO has been modeled according to the content of the fatigue testing standard and by reusing the basic formal ontology, industrial ontology foundry core ontology, and material science and engineering ontology. The ckan.kupferdigital data management system is also constructed in such a way that enables the users to prepare the protocols for mapping the datasets into the knowledge graph and automatically convert all the primary datasets to those machine‐readable data which are represented by the web ontology language. The retrievability of the converted digital data is also evaluated by querying the example competency questions, confirming that ckan.kupferdigital enables publishing open data that can be highly reused in the semantic web. KW - Accessible KW - CKAN KW - Interoperable KW - Digitalizations KW - Ontologies KW - Reusable data KW - Fatigue testing PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-604991 UR - https://onlinelibrary.wiley.com/doi/10.1002/adem.202400675 DO - https://doi.org/10.1002/adem.202400675 SN - 1527-2648 SP - 1 EP - 11 PB - Wiley AN - OPUS4-60499 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sänger, Johanna C. A1 - Riechers, Birte A1 - Pauw, Brian R. A1 - Maaß, Robert A1 - Günster, Jens T1 - Microplastic response of 2PP‐printed ceramics N2 - 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. KW - Manufacturing KW - Mechanical properties KW - Microstructure KW - Plasticity KW - Zirconia: yttria stabilized PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-605176 DO - https://doi.org/10.1111/jace.19849 SN - 1551-2916 SP - 1 EP - 10 PB - Wiley CY - Oxford [u.a.] AN - OPUS4-60517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -