TY - CONF A1 - Zerbst, Uwe T1 - Damage development and damage tolerance of structures manufactured by selective laser melting N2 - The additive manufacturing technology of Selective Laser Melting (SLM) experiences a rapid development within an increasing marked of quite different application fields. The properties of SLM materials and structures are influenced by a number of tech-nological parameters such as the metal powder (particle size, homogeneity, cleanliness), the laser tool (power, beam diameter, pulse lengths), the scanning operation (speed, sequence and orientation of melting paths), parameters of the over-all equipment (design and preheating of the base plate, currents and turbulence in the protective gas atmosphere) and, last not least, the hatching strategy including the build-up direction of the structure with respect to the loading direction of the component. For the perspective use of SLM structures as load carrying, safety-relevant components the knowledge of their mechanical properties is necessary. It is essential to understand these in the context of the manufacturing-related features and at the back-ground of the basic characteristics of metallic materials: crystal lattice, microstructure and material defects. The paper provides an overview on factors which affect the mechanical parameters stiffness, strength, ductility, toughness, fatigue crack propagation and fatigue strength in the context of selective laser melting. T2 - 3rd International Symposium on Fatigue Design an Material Defects, FDMD 2017 CY - Lecco, Italy DA - 19.09.2017 KW - Fatigue strength KW - Fracture mechanics KW - Initial crack size KW - Short crack propagation KW - Multiple crack propagation PY - 2017 AN - OPUS4-43853 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Analytical flaw assessment N2 - The paper provides a review on analytical flaw assessment methods with the focus on fracture under monotonic loading and fatigue crack propagation. The first topic comprises linear elastic as well as elastic-plastic fracture mechanics approaches. It essentially follows their historical development. Topics which are separately discussed are reference/Limit loads, the treatment of secondary stresses, strength mismatch, constraint, unstable crack propagation (monotonic R-curve analyses) and statistical aspects. With respect to fatigue crack propagation the analytical treatment of crack closure and constraint and the Determination of the cyclic elastic-plastic crack driving force is discussed. Finally, cyclic Rcurve analyses are briefly addressed. KW - Monotonic and cyclic crack driving force KW - Secondary stresses KW - Strength mismatch KW - Constraint KW - Crack closure KW - R-curve analysis PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.12.002 SN - 0013-7944 SN - 1873-7315 VL - 187 SP - 316 EP - 367 PB - Elsevier AN - OPUS4-44234 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Hensel, J. A1 - Nitschke-Pagel, T. A1 - Tchoffo Ngoula, D. A1 - Beier, T. T1 - Welding residual stresses as needed for the prediction of fatigue crack propagation and fatigue strength N2 - Welding residual stresses have an impact on the performance of welded structures, on their fracture resistance, their resistance against fatigue crack propagation and, most important, their fatigue strength and fatigue lifetime. The present paper provides an overview on the issue mainly from the point of view of the application of fracture mechanics to the determination of the fatigue strength as the topic of this Special issue. Besides own experimental and theoretical data a comprehensive discussion is provided in that context which includes the definition and interaction of short- and long-range (or reaction) residual stresses, the effect of cyclic mechanical loading and its treatment in fracture and fatigue analyses. KW - Welding residual stresses KW - Fracture KW - Fatigue crack propagation KW - Elastic follow-up PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.10.024 SN - 0013-7944 VL - 198 SP - 123 EP - 141 PB - Elsevier AN - OPUS4-46860 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Vormwald, M. A1 - Beier, T. T1 - Fatigue strength and fracture mechanics - A general perspective N2 - Common fracture mechanics based fatigue considerations are usually limited to the residual lifetime determination of so-called long cracks. The extension of this concept to the total lifetime, as in the S-N curve approach, requires an adequate description of short crack propagation which cannot be based on the Delta K concept, and it must consider the crack closure phenomenon as well as its gradual build-up at the short crack stage. Further, it has to provide a meaningful definition of initial crack dimensions and a solution for the multiple crack problem at stress levels higher than the fatigue limit as it is specific for some configurations such as weldments. This paper aims at a discussion of all these points and offers possible solutions which are illustrated by examples taken from the German IBESS project on fracture mechanics based determination of the fatigue strength of weldments, the results of which will be discussed in more detail in this Special issue. KW - Fatigue strength KW - Endurance limit KW - Fracture mechanics KW - Short crack propagation KW - Multiple cracking KW - Weldments PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.04.030 SN - 0013-7944 SN - 1873-7315 VL - 198 SP - 2 EP - 23 PB - Elsevier AN - OPUS4-46862 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Fatigue strength and fracture mechanics of mechanical components N2 - The present paper provides a discussion on all these topics and it offers solutions for it. The authors present an analytical solution of a Delta J based crack driving force based on an R6 type approach but modified for cyclic loading. The gradual build-up of the crack closure effect is modelled by the so-called cyclic R curve which describes the crack size dependency of the fatigue crack propagation threshold in the short crack regime. It is explained how the cyclic R curve is experimentally determined and how it can be estimated by a modified Kitagawa-Takahashi approach. T2 - Proceedings of the 7th International Conference on Mechanics and Materials in Design T2 - 7th International Conference on Mechanics and Materials in Design CY - Albufeira, Portugal DA - 11.07.2017 KW - Fatigue strength KW - S-N curve KW - Crack propagation KW - J-integral KW - Residual lifetime PY - 2017 SN - 978-989-98832-7-7 SP - 507 EP - 508 AN - OPUS4-46863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Die zyklische R-Kurve als Kenngröße des Kurzrisswachstums N2 - Unter der zyklischen R-Kurve versteht man die Abhängigkeit des Schwellenwertes gegen Ermüdungsrissausbreitung von der Risstiefe im Kurzrissbereich. Bei Spannungsverhältnissen R = omin/omax < ca. 0,7 erhöht sich der Schwellenwert AKltl ausgehend von einer intrinsischen, werkstoffspezifischen Untergrenze mit zunehmender Risstiefe, bis er einen risslängenunabhängigen Wert erreicht. Ursache ist der graduelle Aufbau unterschiedlicher Rissschließeffekte. Die besondere Bedeutung des Kurzrisswachtums allgemein und der zyklischen R-Kurve speziell besteht darin, dass sie ein physikalisches Bindeglied zwischen der konventionellen Schwingfestigkeit (Wöhlerkurve) und der Bruchmechanik repräsentieren. Der Beitrag befasst sich sowohl mit der experimentellen Ermittlung der zyklischen R-Kurve als auch mit ihrer Anwendung auf Rissarrest im Zusammenhang mit Schwingfestigkeitsbetrachtungen. Die experimentelle Ermittlung der zyklischen R-Kurve erfordert einen experimentellen Aufwand, der deutlich über den der Langrissbruchmechanik hinausgeht. Insbesondere im Anfangsbereich ist eine sehr genaue Messung der Risstiefe erforderlich, was eine Verbesserung etwa der konventionellen Potentialmethode erforderlich macht. Von wesentlicher Bedeutung ist auch, dass der Ausgangsriss vor Beginn des eigentlichen Versuchs keine Rissschließeffekte gesehen haben darf. Realisiert wird das durch eine vorgeschaltete Phase von sog. „Compression Pre-cracking“, d.h. durch Anschwingen komplett im Druckbereich. T2 - DVM Tagung der Werkstoffprüfung 2018 CY - Bad Neuenahr, Germany DA - 06.12.2018 KW - Kurzrissbruchmechanik KW - Zyklische R-Kurve KW - Rissschließphenomen KW - Rissarrest PY - 2018 AN - OPUS4-46874 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Defects as a root cause for fatigue failure of metallic components N2 - The Topic of the presentationis a discussion on defects which can cause failure in cyclically loaded metallic components. Although also touching Features such as material defects such as pores or micro-shrinkages, etc. and geometric defects such as surface roughness and secondary notches (which are not considered in the design process) which origin in manufacturing, and others the presentation concentrates on non-metallic inclusions. It is prefaced by an introduction to the life cycle of a fatigue crack from initiation up to fracture. Special emphasis is put on the fact that only cracks which are not arrested during one of their distinct Propagation stages can grow to a critical size. T2 - VIII. International Conference on Engineering Failure Analysis CY - Budapest, Ungarn DA - 08.06.2018 KW - Metallic components KW - Material defects KW - Micro-shrinkages PY - 2018 AN - OPUS4-46875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Bruch, Schwingfestigkeit und Ermüdungsrissfortschritt von Schweißverbindungen N2 - Die Präsentation diskutiert Besonderheiten von Schweißnähten bei der Bestimmung der Zähigkeit bei monotoner Belastung, bei der Ermittlung des zyklischen Rissfortschritts und bei der Ermittlung der Gesamtlebensdauer/Schwingfestigkeit mittels moderner bruchmechanischer Methoden. Besonderes Augenmerk liegt auf der Inhomogenität des Werkstoffs in den einzelnen Nahtbereichen, die sich statistisch (stochastische Verteilung von Gefügeschwachstellen) und systematisch (Effekte von Festigkeits-Mismatch) auswirkt. Als weiterer Faktor kommen Schweißeigenspannungen hinzu, bei denen für die bruchmechanische Analyse eine Fallunterscheidung in primäre und sekundäre Eigenspannungen vorgenommen werden muss. Diskstiert werden die Konsequenzen für die Zähigkeitsermittlung und die Bauteilbewertung. T2 - Sitzung AK "Prüfungs- und Prüfstandkonzepte für die NUtzfahrzeugbranche CY - Alpen/Niederrhein, Germany DA - 25.10.2018 KW - Schwingfestigkeit KW - Ermüdungsrissfortschritt KW - Schweißverbindungen PY - 2018 AN - OPUS4-46877 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Beier, T. A1 - Schork, B. T1 - The IBESS model – Elements, realisation and validation N2 - The work presents the procedure developed within the German research project IBESS, which allows for the fracture mechanics-based prediction of the fatigue strength of welded joints under constant amplitude loading. Based on the experimental observations of the crucial failure mechanisms, the approach focuses on the short crack propagation, where elastic-plastic fracture mechanics and the build-up of closure effects must be considered as well as the variability of the local geometry at the weld toe and the modelling of multiple crack interaction. Analytical solutions are provided for the approximation of the through-thickness stress profiles at the weld toe and for the determination of the crack driving force in the form of a plasticity-corrected stress intensity factor range ∆K_p. Proposals for the determination of the initial crack size and the crack closure factor are also included. The approach is validated against a large number of experimental data, which comprises fatigue tests on individual cracks monitored by heat tinting and beach-marking techniques, as well as stress life curves. Three kinds of welded joints, two steels of significant different strengths and three stress ratios are considered. The results show that the procedure provides good estimations of the statistical distribution of the fatigue strength of welded joints both for the finite and infinite life regime. Furthermore, the predictions are compared with available benchmark data for structural steels. KW - Welded joints KW - Life prediction KW - Fatigue crack growth KW - Short cracks KW - Crack closure PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.08.033 SN - 0013-7944 SN - 1873-7315 VL - 198 SP - 171 EP - 208 PB - Elsevier AN - OPUS4-46852 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Gerwien, Peter A1 - Kucharczyk, P. A1 - Münstermann, S. A1 - Schork, B. T1 - Fracture-mechanics-based prediction of the fatigue strength of weldments. Material aspects N2 - Any fracture mechanics based determination of the fatigue strength of weldments requires different input information such as the local weld geometry and material data of the areas the crack is passing through during its propagation. The latter is so far not a trivial task as the fatigue crack is usually initiated at the weld toe at the transition from the weld metal to the heat affected zone and it subsequently propagates through the different microstructures of the latter to eventually grow into the base material and to cause final fracture. This paper describes how the material input information has gained particularly for heat affected zone material by thermo-mechanically simulated material specimens for two steels of quite different static strength. The data comprise the cyclic stress-strain curve, the crack closure effect-corrected crack growth characteristics, long crack fatigue crack propagation thresholds, the dependency of the parameter on the crack length and monotonic fracture resistance. The substantial experimental effort was necessary for the validation exercises of the IBESS approach, however, within the scope of practical application more easily applicable estimating methods are required. For that purpose the paper provides a number of appropriate proposals in line with its check against the reference data from the elaborate analyses. KW - Heat affected zone KW - Cyclic stress-strain curve KW - Fatigue crack propagation KW - Fatigue crack propagation threshold KW - Fracture resistance PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.09.010 SN - 0013-7944 SN - 1873-7315 VL - 198 SP - 79 EP - 102 PB - Elsevier AN - OPUS4-46854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Maierhofer, J. A1 - Kolitsch, S. A1 - Gänser, H.-P. A1 - Pippan, R. T1 - The cyclic R-curve – Determination, problems, limitations and application N2 - The so-called cyclic R curve, i.e. the crack size dependence of the fatigue crack propagation threshold in the physically short crack regime, is a key parameter for bringing together fatigue strength and fracture mechanics concepts. Its adequate determination is of paramount importance. However, notwithstanding this relevance, no test guideline is available by now and only very few institutions have spent research effort on cyclic R curves so far. The aim of the present paper is to give an overview on the state-of-the-art. Besides an introduction into the basic principles, the discussion will concentrate on the experimental determination on the one hand and questions of its application on the other hand. KW - Cyclic R-curve KW - Fatigue crack propagation threshold KW - Crack closure mechanisms KW - Cyclic R-curve analysis KW - Kitagawa-Takahashi diagram PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.09.032 SN - 0013-7944 SN - 1873-7315 VL - 198 SP - 45 EP - 64 PB - Elsevier AN - OPUS4-46855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Tchoffo Ngoula, D. A1 - Beier, T. A1 - Vormwald, M. T1 - Cyclic J-integral: Numerical and analytical investigations for surface cracks in weldments N2 - The cyclic J-integral (∆J-integral) is a crack tip parameter of elastic-plastic fracture mechanics which can be used as governing parameter for the description of fatigue crack growth (FCG) in metallic structures. In this contribution, it is applied for modelling FCG in weldments. The ∆J-integral is determined by means of analytical approximation formulas as well as numerical methods. An analytical solution, which takes into account effects of the local ligament plasticity, was derived. This solution is based on well established methods such as R6, BS7910 and SINTAP which were modified for cyclic loading. It incorporates methods for the description of short crack closure behaviour as well as the well known analytical (long) crack closure function of Newman. A specific code was written to evaluate the ∆J-integral numerically in the course of finite element based crack growth simulations. The code was first validated for an infinite plate with centre crack by applying elastic and elastic-plastic material behaviour. Next, the ∆J-integral was calculated for cracks in various butt and cruciform welded joints. The results were compared with the results of the derived analytical approximation formula. A good accordance was achieved between the results. KW - Cyclic J-integral KW - Elastic-plastic fracture mechanics KW - Fatigue crack growth KW - Short cracks KW - Weldments PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.06.023 SN - 0013-7944 VL - 198 SP - 22 EP - 44 PB - Elsevier AN - OPUS4-46857 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Schork, B. A1 - Kaffenberger, M. A1 - Oechsner, M. A1 - Kucharzcyk, P. A1 - Hensel, J. A1 - Bernhard, J. A1 - Tchuindjang, D. T1 - The effect of the local and global weld geometry as well as material defects on crack initiation and fatigue strength N2 - The paper provides an application of the IBESS approach to the investigation of the influence of various parameters of the global and local weld geometry as well as material defects on the fatigue strength of weldments. For this purpose, the global weld parameters, such as the weld toe radius, the flank angle, the excess weld metal, local secondary notches (in the present study as a measure of surface imperfections) and inclusions sizes have been determined as statistical distributions for different joint types and geometries and two steels of different strengths. The results are in line with literature data and reveal the potential of the theoretical approach to predict the correct trends. The combination with an advanced weld quality system has been demonstrated to be possible. KW - Weldments KW - Fatigue strength KW - Fracture mechanics KW - Weld geometry KW - Inclusions KW - Multiple crack initiation PY - 2018 DO - https://doi.org/10.1016/j.engfracmech.2017.07.001 SN - 0013-7944 SN - 1873-7315 VL - 198 SP - 103 EP - 122 PB - Elsevier AN - OPUS4-46858 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Defekte als Ursache für das Versagen metallischer Komponenten N2 - Ein Defekt ist „eine Imperfektion …, für die in einer quantitativen Analyse gezeigt werden kann, dass sie Versagen verursacht hat, welches ohne die Imperfektion nicht aufgetreten wäre“. Defekte in diesem Sinn können einerseits Werkstoffimperfektionen wie nichtmetallische Einschlüsse, Poren und Porennester, Nichtdurchschweißungen oder Bereiche defekter Mikrostruktur, andererseits unbeabsichtige geometrische Imperfektionen wie Kratzer, Eindrücke, Korrosionsgrübchen, Einbrandkerben, zu große Oberflächenrauheit u.a. sein. Sie können in der Fertigung, im Betrieb oder auch bei der Wartung entstehen. Nicht jede Imperfektion ist ein Defekt im oben genannten Sinn. Entscheidend ist zumeist nicht, dass an ihr ein oder mehrere Risse initiiert werden, sondern dass wenigstens ein Riss wachstumsfähig bleibt und so innerhalb der projektierten Lebensdauer zum Bruch oder anderweitigem Versagen führt. Aufgrund des begrenzten Umfangs bleibt die vorliegen-de Übersicht beschränkt. T2 - Sitzung des DVK AK Betriebsfestigkeit CY - Stuttgart/Renningen, Germany DA - 26.09.2018 KW - Werstoff- und geometrische Imperfektion KW - Rissausbreitungsstadien KW - Rissarrest KW - Einschlüsse KW - Poren KW - Oberflächenschädigung KW - Rauheit PY - 2018 AN - OPUS4-46883 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Vormwald, M. T1 - Fatigue strength and fracture mechanics N2 - If fracture mechanics shall be applied to the total lifetime respectively the fatigue limit of components (within the meaning of the S-N curve approach) it has to address four challenges: (a) It has to adequately describe so-called short crack propagation, which cannot be based on the common long crack concepts for principle reasons. Since the crack size is in the order of the plastic zone size, the modelling of short crack propagation cannot be based on the common linear elastic Delta K concept. Instead, an elastic-plastic parameter such as the cyclic J integral has to be applied. A second point is that the crack closure concept has to be modified in that the crack opening stress is not a constant, crack size- independent parameter but shows a transient behaviour with increasing short crack size. (b) It has to provide a meaningful definition of the initial crack dimensions as the starting point for an S-N curve relevant (residual) lifetime analysis. This can be based either on the (statistical) size of material defects which can be treated as cracks or by the size of the crack which would arrest subsequent to early crack propagation, whatever is larger. (c) It has to cope with the problem of multiple cracks for load levels higher than the fatigue limit such as it occurs in many applications in the absence of very large initial defects. (d) This requires consequent statistical treatment taking into account variations in the local geometry of the area where crack initiation has to be expected as well as the scatter in the initial crack size and in the material data used for the analyses. T2 - 2nd International Conference on Structural Integrity CY - Funchal, Madeira, Portugal DA - 04.09.2017 KW - Fatigue strength KW - Fracture mechanics KW - Initial crack size KW - Short crack propagation KW - Multiple crack propagation PY - 2017 DO - https://doi.org/10.1016/j.prostr.2017.07.065 SN - 2452-3216 VL - 5 SP - 745 EP - 752 AN - OPUS4-42545 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Vormwald, M. T1 - Fatigue strength and fracture mechanics N2 - If fracture mechanics shall be applied to the total lifetime respectively the fatigue limit of components (within the meaning of the S-N curve approach) it has to address four challenges: (a) It has to adequately describe so-called short crack propagation, which cannot be based on the common long crack concepts for principle reasons. Since the crack size is in the order of the plastic zone size, the modelling of short crack propagation cannot be based on the common linear elastic Delta K concept. Instead, an elastic-plastic parameter such as the cyclic J integral has to be applied. A second point is that the crack closure concept has to be modified in that the crack opening stress is not a constant, crack size- independent parameter but shows a transient behaviour with increasing short crack size. (b) It has to provide a meaningful definition of the initial crack dimensions as the starting point for an S-N curve relevant (residual) lifetime analysis. This can be based either on the (statistical) size of material defects which can be treated as cracks or by the size of the crack which would arrest subsequent to early crack propagation, whatever is larger. (c) It has to cope with the problem of multiple cracks for load levels higher than the fatigue limit such as it occurs in many applications in the absence of very large initial defects. (d) This requires consequent statistical treatment taking into account variations in the local geometry of the area where crack initiation has to be expected as well as the scatter in the initial crack size and in the material data used for the analyses. T2 - 2nd International Conference on Structural Integrity CY - Funchal, Madeira, Portugal DA - 04.09.2017 KW - Fatigue strength KW - Fracture mechanics KW - Initial crack size KW - Short crack propagation KW - Multiple crack propagation PY - 2017 AN - OPUS4-42546 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Beier, T. A1 - Tchoffo Ngoula, D. T1 - Approximation of the crack driving force for cracks at notches under static and cyclic loading N2 - The work deals with the efficient calculation of the elastic-plastic crack driving force (J-integral for monotonic loading andΔJ-integral under cyclic loading) for short cracks at notches as essential parameter for the reliable static and fatigue assessment of notched structures. The J- or ΔJ-integral is calculated based on analytical solutions for stress intensity factors, estimated by means of well-known weight function solutions in the case of cracks under power-law stress distributions. A plasticity-correction function is applied to the stress intensity factors to obtain the final expression of the crack driving force. The comparison between analytical solutions and finite element calculations in case of cracks at the weld toe in welded joints shows good agreement. T2 - 2nd International Conference on Structural Integrity CY - Funchal, Madeira, Portugal DA - 04.09.2017 KW - Structural integrity KW - Fracture mechanics KW - Crack driving force KW - Notches PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-425577 DO - https://doi.org/10.1016/j.prostr.2017.07.111 SN - 2452-3216 VL - 5 SP - 875 EP - 882 PB - Elsevier B.V. AN - OPUS4-42557 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Lessons learned on FFS particulary of (short) fatigue crack propagation N2 - The presentation provides a brief overview on results obtained in the context of fracture mechanics based flaw assessment particularly in the context of short crack propagation. Background is the planned updating of international fitness-for-service procedures such as BS 7910. Specific topics addressed are the determination of the cyclic elastic-plastic crack driving force, the description of the gradual build-up of the crack closure phenomenon at the short crack stage, cyclic R curve analysis and residual stresses. T2 - 2nd "Mind the Gap" in FFS assessment procedures workshop CY - Bristol, United Kingdom DA - 19.10.2017 KW - Reference yield load KW - Cyclic J-integral KW - Crack closure phenomenon PY - 2017 AN - OPUS4-42559 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - IBESS - Ergebnisse und Ausblick N2 - Der Vortrag bietet eine Übersicht über die im Rahmen des IBESS-Projektes entwickelte Methodik zur bruchmechanischen Ermittlung der Schwingfestigkeit von Schweißverbindungen. Schwerpunkte sind die Beschreibung des Wachstums kurzer Risse, die mit den klassischen linear-elastischen Bruchmechanik-Konzepten nicht möglich ist, die Ermittlung einer physikalisch sinnvollen Ausgangsrissgröße für das Bruchmechanik-Modell, die Ermittlung der Bauteildauerfestigkeit und des Zeitfestigkeitsastes diverser Schweißnahtgeometrien und eine Diskussion der Eigenspannungsproblematik. Die Ergebnisse werden mittels Validierungsbespielen illustriert. T2 - Sitzung des DVS FA 9 (Konstruktion und Festigkeit) CY - Braunschweig, Germany DA - 03.05.2017 KW - Bruchmechanik KW - IBESS KW - Schwingfestigkeit PY - 2017 AN - OPUS4-42563 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - IBESS - an integral method for fracture mechanics-based determination of the fatigue strength of weldments N2 - The paper provides an overview on the results of a German cluster project on the use of fracture mechanics to the determination of the fatigue strength of weldments with fatigue cracks originating at the weld toes. The approach includes (a) a concept for short crack propagation for which the common K concept is not applicable and the crack closure effects are still being gradually build-up, (b) a method for determining fatigue life relevant initial crack sizes as they are needed in any fracture mechanics analysis and (c) multiple cracking and crack coalescence at load levels higher than the endurance limit. The analyses are stochastically performed. Both, the endurance limit as defined for 107 loading cycles and the finite life branch of the S-N curve are determined. Besides a brief introduction into the approach, a wide range of validation examples is presented. These comprise different weldment types (butt welds, cross joints and longitudinal stiffened plates), two steels of quite different strengths, different weld geometries due to different welding techniques (TIG, MAG), as-welded and stress relieved welds and different stress ratios varying from R = -1 to R = 0.5. T2 - Vortrag beim TWI (Welding Institute) CY - Great Abington, Cambridge, UK DA - 06.06.2017 KW - Fracture mechanics KW - S-N curve KW - Weldments PY - 2017 AN - OPUS4-43771 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Hellmann, C. T1 - An analytical fracture mechanics model for estimation of S-N curves of metallic alloys containing large second phase particles N2 - An analytical fracture mechanics model for predicting the finite life fatigue strength of components is presented which combines a number of well established and newly developed approaches such as Murakami's and McEvily's approach for describing the transient behaviour of crack closure of short cracks, the analytical (long) crack closure function of Newman which became part of the widely used NASGRO approach, the R6 procedure, a method for improving the ligament yielding correction f(Lr ) of R6 proposed by the authors of the present paper and other elements. Basic assumption is the preexistence of initial flaws such that the crack initiation or nucleation stage is small and can be neglected. The application of the model is demonstrated for small tension plates of aluminium Al 5380 H321 with artificial initial defects generated by FIB technology, the size of which was fixed on the basis of fractographic investigations on broken, smooth specimens. KW - S-N curve KW - Fatigue life prediction KW - R6 KW - Short fatigue-cracks KW - Crack closure PY - 2012 DO - https://doi.org/10.1016/j.engfracmech.2011.12.001 SN - 0013-7944 SN - 1873-7315 VL - 82 SP - 115 EP - 134 PB - Elsevier Science CY - Kidlington AN - OPUS4-25456 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Ainsworth, R. A. A1 - Madia, Mauro T1 - Reference load versus limit load in engineering flaw assessment: A proposal for a hybrid analysis option N2 - The net section limit load FY necessary for assessment at static loading is a key input for the accuracy of any elastic–plastic flaw assessment procedure of the R6 type. Unfortunately available limit load solutions are of variable quality since they have been obtained over decades by different methods. As a consequence the results of the fracture analyses such as the critical load or crack size are limited in their accuracy and are often significantly conservative. Further, common limit load solutions based on ligament yielding are inadequate in a number of cases even for through crack configurations and should be replaced by some kind of local yielding solutions. In the present paper a simple and straightforward reference load definition is proposed instead of the limit load which strictly corresponds to a ligament yielding parameter Lr = 1 in the R6 Routine and similar approaches such as the European SINTAP and FITNET methods. This can be determined by finite element simulation for any geometry. In addition to a previous study on thin wall notched plates the method is applied to plates containing shallow semi-elliptical surface cracks. The results demonstrate that the approach provides a suitable extension and improvement of the existing methods. KW - Flaw assessment KW - Reference stress method KW - R6 procedure KW - SINTAP KW - FITNET KW - Limit load KW - Reference load PY - 2012 DO - https://doi.org/10.1016/j.engfracmech.2011.10.018 SN - 0013-7944 SN - 1873-7315 VL - 91 SP - 62 EP - 72 PB - Elsevier Science CY - Kidlington AN - OPUS4-27279 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Hellmann, D. T1 - Fracture mechanics model for predicting fatigue strength of metallic alloys containing large second phase particles N2 - An analytical fracture mechanics model for predicting finite life fatigue strength of components is presented which combines a number of well established and newly developed approaches such as Murakami's and McEvily's approach for describing the transient behaviour of crack closure of short cracks, the analytical (long) crack closure function of Newman, the R6 procedure modified by a method for improving the ligament yielding correction proposed by the authors and other elements. Basic assumption is the pre-existence of initial flaws such that the crack initiation or nucleation stage is small and can be neglected. The application of the model is demonstrated for small tension plates of aluminium Al 5380 H321 with artificial initial defects generated by FIB technology, the size of which was fixed on the basis of fractographic investigations on broken, smooth specimens. T2 - ECF 19 - 19th European conference on fracture - Fracture mechanics for durability, reliability and safety CY - Kazan, Russia DA - 26.08.2012 KW - Fatigue strength KW - S-N curve KW - Fracture mechanics KW - Crack propagation KW - Short cracks KW - Bruchmechanik KW - Schwingfestigkeit KW - Bauteilbewertung PY - 2012 SN - 978-5-905576-18-8 IS - Proceeding-ID 116 SP - 1 EP - 14 AN - OPUS4-27278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scacco, F. A1 - Zerbst, Uwe A1 - Meneghetti, G. A1 - Madia, Mauro T1 - Comparison between PSM and IBESS approaches for the fatigue life estimation of weldments N2 - In the framework of the fatigue assessment of welded components, several methods are available in design standards such as the nominal stress, hot-spot stress, notch stress and linear elastic fracture mechanics approaches. The present paper aims at comparing two advanced local approaches for the fatigue strength assessment of different welded joints made of steel. The first one is IBESS which is based on short crack fracture mechanics. The second one is the PSM which instead involves the strain energy density approach. Both methods will be briefly presented, and the fatigue life prediction results discussed. The results obtained for the joint geometries considered in this work show advantages and drawbacks of the approaches, which are thoroughly analysed as well. KW - Fatigue KW - Welded joints KW - FAT class KW - IBESS KW - Peak stress method (PSM) KW - Finite element (FE) PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545139 DO - https://doi.org/10.1007/s40194-022-01284-7 SP - 1 EP - 23 PB - Springer AN - OPUS4-54513 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Werner, Tiago T1 - Estimation of the Kitagawa-Takahashi diagram by cyclic R curve analysis N2 - The Kitagawa-Takahashi (KT) diagram is a proven concept for describing the fatigue limit in presence of a defect or crack. It can be determined empirically with great experimental effort. It can also be estimated by means of the El Haddad relationship if the endurance limit and the long fatigue crack propagation threshold are available in reasonable accuracy. A third option is the determination using the cyclic R-curve, which describes the dependency of the fatigue crack propagation threshold on the crack growth at the short crack propagation stage. This can be experimentally determined using a closure-free initial pre-crack. It can then be applied to the determination of crack arrest for a given applied load and a given defect or crack size. Compared to the other two methods mentioned above, this option has considerable advantages: It can be applied to any component and any stress ratio. It allows the treatment of multiple cracks and provides estimations of the S-N curve in the finite life regime as well as at the endurance limit. Compared to the empirical determination of the KT diagram, the experimental effort is significantly lower and compared to the El Haddad approach it avoids problems such as the use of non-conservative long fatigue crack propagation thresholds (when the conventional load reduction method is applied to materials prone to corrosion) and the mathematical predetermination of the curve shape. The work introduces the method and provides a critical discussion as well as quantitative comparison between the different methods. T2 - FATIGUE DESIGN 2021 CY - Online meeting DA - 17.11.2021 KW - Fatigue life KW - Endurance limit KW - Kitagawa-Takahashi diagram KW - Cyclic R-curve PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-544931 DO - https://doi.org/10.1016/j.prostr.2022.03.032 SN - 2452-3216 VL - 38 SP - 309 EP - 316 PB - Elsevier B.V. AN - OPUS4-54493 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönherr, J. A. A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Geilen, M. B. A1 - Klein, M. A1 - Oechsner, M. T1 - Robust determination of fatigue crack propagation thresholds from crack growth data N2 - The robust determination of the threshold against fatigue crack propagation DKth is of paramount importance in fracture mechanics based fatigue assessment procedures. The standards ASTM E647 and ISO 12108 introduce operational definitions of DKth based on the crack propagation rate da/dN and suggest linear fits of logarithmic DK– da/dN test data to calculate DKth. Since these fits typically suffer from a poor representation of the actual curvature of the crack propagation curve, a method for evaluating DKth using a nonlinear function is proposed. It is shown that the proposed method reduces the artificial conservativeness induced by the evaluation method as well as the susceptibility to scatter in test data and the influence of test data density. KW - Fatigue crack propagation threshold KW - ISO 12108 KW - ASTM E647 KW - Data evaluation methods KW - Experimental determination PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552153 DO - https://doi.org/10.3390/ma15144737 SN - 1996-1944 VL - 15 IS - 14 SP - 1 EP - 21 PB - MDPI CY - Basel AN - OPUS4-55215 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe T1 - The effect of the environmental conditions on the threshold against fatigue crack propagation N2 - The threshold against fatigue crack propagation (ΔKth) is a crucial parameter for the damage tolerance assessment of engineering components subjected to cyclic loading and it is composed by two distinct components, one intrinsic, dependent on the elastic material properties and the lattice type, and one extrinsic, related to the occurrence of crack closure effects. An important issue is that several factors can influence ΔKth and, in general, the fatigue crack propagation behavior. In this work, the influence of the experimental procedure, air humidity, stress ratio and test frequency on da/dN-ΔK data has been investigated. Results are discussed with their potential causes and consequences on the calculations of the residual lifetime. KW - Fatigue crack propagation threshold KW - Crack closure effect KW - Experimental procedure KW - Environmental conditions PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-544905 DO - https://doi.org/10.1016/j.prostr.2022.03.030 VL - 38 SP - 292 EP - 299 PB - Elsevier B.V. AN - OPUS4-54490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Vergleichende Untersuchungen zum intrinsischen Schwellenwert der da/dN-ΔK-Kurve N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung, Δ𝐾𝑡ℎ, und dem sich anschließenden Schwellenwertbereich der 𝑑𝑎𝑑𝑁⁄−Δ𝐾-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - 53. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Online meeting DA - 18.02.2021 KW - Schadenstolerante Bauteilauslegung, Restlebensdauer, intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung PY - 2021 SN - 2366-4797 SP - 211 EP - 220 PB - Deutscher Verband für Materialforschung und -prüfung e.V. (DVM) CY - Berlin AN - OPUS4-52704 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Der Schwellenwert der da/dN-∆K-Kurve als Auslegungskriterium für die Bauteilbewertung N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung ∆Kth und dem sich anschließenden Schwellenwertbereich der da/dN-∆K-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - Tagung Werkstoffprüfung 2020 CY - Online meeting DA - 03.12.2020 KW - Schadenstolerante Bauteilauslegung, KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung KW - Restlebensdauer PY - 2020 DO - https://doi.org/10.48447/WP-2020-025 SP - 1 EP - 8 AN - OPUS4-52788 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhu, Jiangchao A1 - Madia, Mauro A1 - Schurig, Michael A1 - Kruse, Julius A1 - Conrad, Fabian A1 - Schlums, Hartmut A1 - Kontermann, Christian A1 - Zerbst, Uwe T1 - On the use of representative specimens for the structural integrity assessment of safety-relevant rotating components N2 - Safety-relevant components, for which a failure in service could have catastrophic consequences, are usually designed for extremely low probability of failure and they are subjected to stringent part qualification procedures according to guidelines set by regulatory agencies. Manufacturers are often forced to perform tests on full scale or scaled components to ensure the structural integrity under defined loading conditions, which usually implies a huge experimental and financial effort. Therefore, companies try to develop new strategies such as digital twins, which allow to massively reduce costs, without compromising safety. This work presents a new quasi-static testing and assessment concept, the main idea of which is to replace, or at least reduce, the experimental testing on components by testing specimens representative of the component. Fracture mechanics specimens have been designed iteratively by numerical simulations to match the stress state at the crack-tip of the maximum permissible defect defined by regulatory agencies for the component. Potentially, the major benefit of the proposed approach is that the tests can be performed on conventional laboratory testing machines. The effectiveness of the methodology is demonstrated in case of the structural integrity assessment of a Ni-base superalloy aero-engine turbine disk at overspeed conditions. KW - Structural integrity KW - Turbine disk KW - Burst KW - Fracture mechanics KW - Representative specimens KW - Quasi-static testing PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624208 DO - https://doi.org/10.1016/j.engfracmech.2024.110710 SN - 0013-7944 VL - 314 SP - 1 EP - 23 PB - Elsevier Ltd. AN - OPUS4-62420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Ainsworth, R. A. A1 - Beier, H.T. A1 - Pisarski, H. A1 - Zhang, Z. L. A1 - Nikbin, K. A1 - Nitschke-Pagel, T. A1 - Münstermann, S. A1 - Kucharczyk, P. A1 - Klingbeil, Dietmar T1 - Review on fracture and crack propagation in weldments - A fracture mechanics perspective N2 - Welding is one of the most common methods in industrial practice for joining components. Its main advantages are high speed in manufacturing combined with low costs and, usually, a high degree of flexibility, integrity and reliability. Nevertheless, welding is a highly complex metallurgical process and, therefore, weldments are susceptible to material discontinuities, flaws and residual stresses which may lead to structural failure and life time reduction. As a consequence weldments are an important field of fracture mechanics methods although its application is more complex than for homogeneous or non-welded structures. The aim of the paper is to provide an overview on the current state of fracture mechanics application to weldments. It starts by discussing the specific features which any fracture mechanics analysis of weldments has to take into account. Then, the experimental determination of fracture toughness, fatigue crack propagation and tensile properties of weldments is addressed. Finally, the analytical determination of the crack driving force in components and structural integrity assessment approaches for weldments are presented. KW - Weldments KW - Fracture mechanics KW - Fracture toughness KW - Fatigue crack propagation KW - Residual stresses KW - Strength mismatch PY - 2014 DO - https://doi.org/10.1016/j.engfracmech.2014.05.012 SN - 0013-7944 SN - 1873-7315 VL - 132 SP - 200 EP - 276 PB - Elsevier Science CY - Kidlington AN - OPUS4-32819 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Arafah, D. A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Beretta, S. A1 - Cristea, M.E. T1 - Instability analysis of pressurized pipes with longitudinal surface cracks N2 - Recently three of the authors of this paper presented analytical solutions for reference loads of plate geometries with semi-elliptical surface cracks subjected to tension, bending, combined tension-bending and biaxial tension. These solutions were shown to provide more accurate crack driving force estimates than the conventional limit load solutions available in the literature, and the method behind them allowed for a wider application range. Within the present paper a methodology for the fracture analysis of thick-wall pressurized pipes using the R6 assessment method and considering both, biaxial and combined tension-bending loading is developed and validated. The analyses are carried out analytically, and the comparison between the predicted critical loads and experimental burst test failure loads shows satisfying agreement, this way demonstrating the potential of the proposed method. KW - Burst test KW - Pipes KW - R6 KW - Reference load KW - Biaxial loading KW - Tearing instability KW - Plastic collapse KW - Limit load PY - 2015 DO - https://doi.org/10.1016/j.ijpvp.2015.01.001 SN - 0308-0161 VL - 126-127 SP - 48 EP - 57 PB - Applied Science Publ. Ltd. CY - Barking AN - OPUS4-32820 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Model for fracture mechanics based prediction of the fatigue strength of engineering alloys containing microscopical initial defects T2 - 2nd International Conference on Fatigue Design and Materials Defects (FDMD II) CY - Paris (Frankreich) DA - 2014-06-11 PY - 2014 AN - OPUS4-33237 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Assessment of welded joints by fracture mechanics. IBESS - Delevopment of a procedure N2 - The idea to determine the fatigue strength of weldments by means fractuie mechanics was originally based on the empirical observation that the major portion of the fatigue life in weldments is frequently spent in crack propagation. The present paper gives a brief OverView on the basic principles of fracture mechanics-based determination of fatigue strength and on special features which have to be considered for weldments. Based on this Information, the ongoing research project IBESS is introduced and briefly reviewed. T2 - 4th Symposium on Structural Durability CY - Darmstadt DA - 14.05.2014 PY - 2014 AN - OPUS4-33239 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schöne, Dieter A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Experimentelle Ermittlung des Schwellenwertes DeltaKth mittels unterschiedlicher Methoden und für verschiedene Spannungsverhältnisse N2 - ln den letzten Jahren hat sich gezeigt, dass die Ermittlung des Schwellenwertes DeltaKth nach den bestehenden Standardvorschriften für verschiedene Materialien zu nichtkonservativen Werten führt. Das ergibt sich im Vergleich mit Schwellenwerten, die man mit Anrissen erhält, die hinsichtlich der Ober- und der Unterlast komplett im Druckbereich erzeugt wurden. Dort, wo die Diskrepanz auftritt, verstärkt sie sich mit abnehmendem Spannungsverhältnis. ln der vorliegenden Studie wurden an einem mittel- und einem hochfesten Stahl bei unterschiedlichen Spannungsverhältnissen Schwellenwerte bestimmt. Anwendung fanden die konventionelle Lastabsenkungsmethode nach ASTM-Standard und ein Verfahren, bei dem der Langrissscbwellenwert als Endpunkt der sogenannten Zyklischen R-Kurve erhalten wird. Dieses folgt im Wesentlichen der von Pippan et al. entwickelten Methode, ergänzt diese jedoch durch eine eigene Verfahrensvariante. T2 - 47. Tagung des DVM-Arbeitskreises Bruchvorgänge und Bauteilsicherheit - Bruchmechanische Werkstoff- und Bauteilbewertung: Beanspruchungsanalyse, Prüfmethoden und Anwendungen CY - Freiberg, Germany DA - 10.02.2015 KW - Ermüdungsrissausbreitung KW - Schwellenwert KW - Lastabsenkung KW - Druckanschwingen KW - Zyklische R-Kurve KW - Fatigue crack propagation KW - Threshold KW - Load decreasing KW - Compression pre-cracking KW - Cyclic R curve PY - 2015 SN - 1616-4687 SP - 269 EP - 283 AN - OPUS4-32569 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - The Fatigue Crack Propagation threshold as a design criterion - actual developments and open issues T2 - ESIS TC1/TC3 workshop on "The fatigue crack propagation threshold as a design criterion" CY - Poitiers, France DA - 2014-11-04 PY - 2014 AN - OPUS4-31686 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scolavino, L. A1 - Beretta, S. A1 - Madia, Mauro A1 - Zerbst, Uwe T1 - Critical speed of flawed rotors: global vs local approach N2 - The burst of a disc in rotating machinery can cause catastrophic damage of the equipment and, more importantly, it can represent a mortal threat to anyone in the sphere of influence of the event. In order to minimize the danger associated to a rotating component failure, burst testing is required by the authorities in order to set safety margins to the normal operating speeds. Moreover more accurate predicting tools are required for designing the components. This paper presents the results of a numerical and analytical study on the assessment of the crack driving force for discs containing surface flaws. The aim is to provide a simple, though reliable, tool in order to be able to calculate the possible dangerous in-service speed for a rotating component and, therefore, to set burst margins above the normal operating conditions of the equipment. An R6-like flaw assessment procedure is adopted considering different assumptions in the definition of the critical speed and the analytical predictions are compared with the results of elastic-plastic finite element analysis of disc. In particular, the validity and potentiality of the method is proved for surface flaws in different positions in the disc. T2 - ASME Turbo Expo 2014 - GT2014 CY - Düsseldorf, Germany DA - 16.06.2014 KW - Critical speed KW - Flawed rotors KW - Flaw assessment PY - 2014 SN - 978-0-7918-4576-9 DO - https://doi.org/10.1115/GT2014-26881 VL - 7A SP - 26881, 1 EP - 8 AN - OPUS4-32382 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Der Schwellenwert DKth als Auslegekriterium. Aktuelle Entwicklungen und Fragestellungen. T2 - 47. Tagung des DVM-Arbeitskreises Bruchvorgänge CY - Freiberg DA - 2015-02-10 PY - 2015 AN - OPUS4-32351 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Bauteilbewertung gegen Bruch. Demonstrationsbeispiele Druckbehälter T2 - 47. Tagung des DVM-Arbeitskreises Bruchvorgänge; Weiterbildungsseminar CY - Freiberg, Germany DA - 2015-02-09 PY - 2015 AN - OPUS4-32843 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Primär- und Sekundärspannungen in der Bruchmechanik-Analyse T2 - 47. Tagung des DVM-Arbeitskreises Bruchvorgänge; Weiterbildungsseminar CY - Freiberg, Germany DA - 2015-02-09 PY - 2015 AN - OPUS4-32844 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Statistische Aspekte der Bauteilbewertung T2 - 47. Tagung des DVM-Arbeitskreises Bruchvorgänge; Weiterbildungsseminar CY - Freiberg, Germany DA - 2015-02-09 PY - 2015 AN - OPUS4-32845 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Werkstoffverhalten unter zyklischer Belastung T2 - DVM-Fortbildungsseminar "Bruchmechanische Prüfverfahren" CY - Freiburg, Germany DA - 2015-03-17 PY - 2015 AN - OPUS4-32836 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Anwendungsphilosophien der Bruchmechanik in der Bauteilbewertung T2 - 47. Tagung des DVM-Arbeitskreises Bruchvorgänge; Weiterbildungsseminar CY - Freiberg, Germany DA - 2015-02-09 PY - 2015 AN - OPUS4-32840 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Rissspitzenbeanspruchung bei linear elastischem und elastisch-plastischem Deformationsverhalten. Praktische Ermittlung T2 - 47. Tagung des DVM-Arbeitskreises Bruchvorgänge; Weiterbildungsseminar CY - Freiberg, Germany DA - 2015-02-09 PY - 2015 AN - OPUS4-32842 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Klinger, Christian T1 - Anmerkungen zur Auslegung und zum sicheren Betrieb von Radsatzwellen aus der Sicht von Betriebsfestigkeit und Bruchmechanik N2 - Die Sicherheit von Radsatzwellen beruht gegenwärtig auf zwei Säulen: der Schwingfestigkeitsauslegung und periodischen Inspektionen. Ausgehend von einem Schadensfall, der gebrochenen ICE 3-Welle von Köln, 2008, werden ausgewählte Aspekte dieser beiden Säulen diskutiert und Vorschläge zur weiteren Verbesserung gemacht. Diese betreffen u. a. Fragen einer Betriebszeitbegrenzung, Veränderungen der Schwingfestigkeit während des Betriebs infolge von Korrosion und Steinschlag, den Einfluss von Korrosion auf Schwingrissinitiierung und -fortschritt, den potenziellen Einfluss nichtmetallischer Einschlüsse auf die Schwingfestigkeit, die Möglichkeiten, sie im Rahmen der Qualitätssicherung zu detektieren, sowie Fragen der Bruchmechanik und der Zuverlässigkeit zerstörungsfreier Schwingriss-Prüfverfahren im Rahmen eines Konzepts regelmäßiger Inspektionen. KW - Radsatzwellen KW - Schwingfestigkeit KW - Sichere Lebensdauer KW - Schadenstoleranz KW - Zerstörungsfreie Inspektion KW - Korrosion KW - Steinschlag KW - Nichtmetallische Einschlüsse PY - 2014 DO - https://doi.org/10.3139/120.110593 SN - 0025-5300 VL - 56 IS - 7-8 SP - 528 EP - 534 PB - Hanser CY - München AN - OPUS4-31355 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe ED - Baumgartner, J. ED - Melz, T. T1 - Assessment of welded joints by fracture mechanics IBESS - the development of a procedure N2 - The idea to determine the fatigue strength of weldments by means fracture mechanics was originally based on the empirical observation that the major portion of the fatigue life in weldments is frequently spent in crack propagation. The present paper gives a brief overview on the basic principles of fracture mechanics-based determination of fatigue strength and on special features which have to be considered for weldments. Based on this information, the ongoing research project IBESS is introduced and briefly reviewed. T2 - SoSDiD - 4th Symposium on structural durability in Darmstadt CY - Darmstadt, Germany DA - 2014-05-14 KW - Fracture mechanics KW - Fatigue strength KW - (Residual) lifetime KW - Weldments PY - 2014 SP - 49 EP - 66 PB - Fraunhofer Verlag AN - OPUS4-31321 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Referenzlastlösungen für die Ermittlung der elastisch-plastischen Rissspritzenbeanspruchung in Platten-Strukturen unter Zug-, Biege-, kombinierter Zug-Biege- und zweiaxialer Zugbelastung T2 - 46. Tagung des DVM-Arbeitskreises Bruchvorgänge CY - Kassel, Germany DA - 2014-02-11 PY - 2014 AN - OPUS4-29738 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Fracture mechanics as a tool in failure analysis T2 - ICEFA IV CY - Lisbon, Portugal DA - 2014-07-06 PY - 2014 AN - OPUS4-31122 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zerbst, Uwe T1 - Reference load solutions for plates with semi-elliptical surface cracks T2 - ECF 20 - European Conference on Fracture CY - Trondheim, Norway DA - 2014-06-30 PY - 2014 AN - OPUS4-31123 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Arafah, D. A1 - Zerbst, Uwe T1 - Reference load solutions for plates with semi-elliptical surface cracks subjected to biaxial tensile loading N2 - The yield or limit load is a key parameter with respect to the accuracy of flaw assessment based on R6 type procedures such as the R6 routine, the SINTAP and FITNET method, the standard BS 7910 and others. In a number of previous papers two of the present authors proposed the use of a reference load instead of the common limit load, which not only provided more exact fracture mechanics predictions, but showed also a wider and more general application range than the conventional parameter. Here the method has been extended to biaxial tensile loading and it has been successfully validated by a thorough comparison with finite element results and alternative solutions available in the literature. KW - Flaw assessment KW - R6 procedure KW - Limit load KW - Reference load KW - Biaxial tensile loading PY - 2014 DO - https://doi.org/10.1016/j.ijpvp.2014.02.004 SN - 0308-0161 VL - 119 SP - 19 EP - 28 PB - Applied Science Publ. Ltd. CY - Barking AN - OPUS4-31429 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -