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Schlagworte
- Fracture mechanics (25)
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- Ermüdungsrissausbreitung (1)
- Ermüdungsrissfortschritt (1)
- FAT class (1)
- FAT class approach (1)
- FAT class concept (1)
- FEM (1)
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- Failure Assessment Diagram (1)
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- Fatigue S-N curve (1)
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- Fatigue crack propagation stages (1)
- Fatigue crack propagation stagesdefects (1)
- Fatigue life prediction (1)
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- Finite element (FE) (1)
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- Fracture assessment (1)
- Fracture of weldments (1)
- Global stability criterion (1)
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- HAZ (1)
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- Heat affected zone (1)
- IBESS-Prozedur (1)
- ISO 12108 (1)
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- In-situ Process Monitoring (1)
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- Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung (1)
- J-Integral (1)
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- Kritische Last (1)
- Kurz- und Langriss-Ermüdungsbruchmechanik (1)
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- Kurzrisswachstum (1)
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- Monotonic and cyclic crack driving force (1)
- Multiple crack initiation (1)
- Multiple cracking (1)
- Non-destructive Materials (1)
- Non-destructive inspection (1)
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- Non-propagating cracks (1)
- Non-sharp defects (1)
- Notch fatigue (1)
- Notch sensitivity (1)
- Notches (1)
- Nuclear reactor systems (1)
- Numerische Analyse (1)
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- Peak stress method (PSM) (1)
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- Rissspitzenbelastung (1)
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- Root cause (1)
- Safety (1)
- Safety assessment (1)
- Schadenstolerante Bauteilauslegung (1)
- Schadenstolerante Bauteilauslegung, (1)
- Schadenstolerante Bauteilauslegung, Restlebensdauer, intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung (1)
- Schweißeigenspannungen (1)
- Schweißeigenspannungs-Tiefen-Profile (1)
- Schwellenwert (1)
- Schwellenwert gegen Ermüdungsrissausbreitung (1)
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- Stabilität von Eigenspannungen (1)
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- Steel (1)
- Steel 316L (1)
- Stiffness (1)
- Strength mis-match (1)
- Stress analysis (1)
- Stress intensity factor (1)
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- Structures (1)
- Struktur Integrität (1)
- Surface roughness (1)
- SN curve (1)
- Tearing instability (1)
- Testing parameters (1)
- Threshold (1)
- Transferability to components (1)
- Turbinenscheibe (1)
- Weld fatigue (1)
- Weld geometry (1)
- Weld toes (1)
- Werstoff- und geometrische Imperfektion (1)
- Zerstörungsfreie Prüfung (1)
- Zuverlässigkeit (1)
- damage tolerance (1)
- fatigue crack propagation (1)
- fatigue strength (1)
- fracture mechanics (1)
- inspection (1)
- probability (1)
- railway axles (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (52)
- 9.4 Integrität von Schweißverbindungen (49)
- 9.0 Abteilungsleitung und andere (7)
- 5 Werkstofftechnik (6)
- 5.1 Mikrostruktur Design und Degradation (5)
- 9.6 Additive Fertigung metallischer Komponenten (5)
- 8 Zerstörungsfreie Prüfung (3)
- 8.5 Röntgenbildgebung (3)
- 4 Material und Umwelt (2)
- 9.3 Schweißtechnische Fertigungsverfahren (2)
Paper des Monats
- ja (1)
Eingeladener Vortrag
- nein (40)
The two-part paper provides an overview on the state-of-the-art in the application of engineering fracture mechanics to weldments. This, of course, cannot be exhaustive but is limited to butt and fillet welds with crack initiation at weld toes. In the present first pari, the authors briefly focus on the susceptibility of welds to cracks and other defects. Following this, they discuss in more detail the consequences of material inhomogeneity across the weld for fracture mechanics. Inhomogeneity causes scatter in fracture toughness and strength mis-match effects which both have to be considered in fracture toughness testing, crack driving force determination and fracture assessment of welded components. Part 2 of the paper series will add a discussion of welding residual stresses and questions of applying fracture mechanics to residual as well as total lifetime estimation of welds under cyclic loading.
The presentation provides a discussion and damage tolerant assessment of metallic AM components. In the focus are problems of the determination of representative material data, the effect of material defects and residual stresses. Starting with the actual state-of-the-art in the field, options and possibilities of a damage tolerant design for AM are discussed.
A discussion is provided on demands that must be met in order to apply fracture mechanics to the determination of overall fatigue lifetime and strength, i.e., S-N curves and fatigue limits. These comprise the determination of the cyclic crack driving force for all stages of fatigue crack propagation, in particular for the short crack stage where the crack driving force has to be determined for elastic-plastic deformation and the gradual build-up of the crack closure phenomenon. Special emphasis is put on a fatigue damage relevant specification of the initial crack size. Different approaches in the literature are discussed. Another important aspect is the adequate treatment of multiple crack propagation. Finally, the discussion is illustrated by an example of a butt weld made of a medium strength steel.
Der Vortrag thematisiert die Behandlung von Schweißeigenspannungen bei der Auslegung geschweißter Bauteile. Ausgehend von Fragen der Klassifizierung unterschiedlicher Typen von Eigenspannungen wird auf Fragen der Behandlung von Primär- und Sekundärspannungen, der Ermittlung und Aussagefähigkeit von Eigenspannungs-Tiefen-Profilen und der Stabilität der Eigenspannungen bei zyklischer Beanspruchung eingegangen. Neben der Auslegung auf Bruch wird die Beschreibung der Ermüdungsrissausbreitung bei Vorhandensein von Eigenspannungen diskutiert, wobei neben der klassischen Langrissbruchmechanik auch Besonderheiten der Kurzrissbruchmechanik angesprochen werden.
The acronym IBESS stands for "Integrale Bruchmechanische Ermittlung der Schwingfestigkeit von Schweißverbindungen" which, translated from German, means "integral fracture mechanics determination of the fatigue strength of welds". the method introduced in this study is the outcome of a German Research cluster in which eight partners were involved. A list of them is found at the end this study. The IBESS method is characterized by a number of partially novel aspects and elements of fracture mechanics applied to the evaluation of fatigue stength of welds. The most important ones are: (a) Determination of fatigue crack propagation for mechanically/physically short and long cracks. (b) Determination of an elastic-plastic crack driving force for the treatment of mechanically short cracks. To that purpose an analytical expression for the cyclic J-integral was developed and validated against finite element results. (c) The gradual build-up of the crack closure phenomenon is determined by using cyclic R-curves which describe the crack size dependency of the fatigue crack propagation threshold in the physically short crack growth regime. (d) A physically meaningful initial crack size is defined for total life consideration. It is based on a two-criteria approach. Based on a cyclic R-curve analysis, the crack size at crack arrest is determined as a lower bound. If, however, a pre-existing crack-like defect is larger than this, its dimensions define the initial crack size. (e) Multiple crack propagation at the weld toe is considered. (f) In conjunction with this, the variation of the weld toe geometry is considered in a stochastic model. (g) As a result, both the fatigue limit (defined for 107 loading cycles) and the finite life (high cycle) fatigue S-N curve are obtained statistically. (h) At various analysis steps, parametric equations have been developed which allow for analytical calculations instead of complete stochastic analyses based on finite elements which are unrealistic even at present. (i) The method has been validated with a large number of S-N curves including two materials, three weldment types with two geometries, each referring to differnt manufacturing technologies and the as-welded and stressrelieved state. (j) Althrough not finally solved, an extended discussion is provided on the issue of welding residual stresses including their redistribution under cyclic loading. (k) A number of simplifications is proposed at lower analyses levels which, however, partly lack complete validation by now.
This book provides a comprehensive and thorough guide to those readers who are lost in the often-confusing context of weld fatigue. It presents straightforward information on the fracture mechanics and material background of weld fatigue, starting with fatigue crack initiation and short cracks, before moving on to long cracks, crack closure, crack growth and threshold, residual stress, stress concentration, the stress intensity factor, J-integral, multiple cracks, weld geometries and defects, microstructural parameters including HAZ, and cyclic stress-strain behavior. The book treats all of these essential and mutually interacting parameters using a unique form of analysis.
This third part of the review on defects as root cause of fatigue failure addresses cavities (pores, micro-shrinkages, unmelted regions), defective microstructures and microcracks as material defects and defects due to local damage during manufacturing, service and maintenance such as dents, scratches and localized corrosion. In addition, damage due to contact fatigue and the effect of surface roughness are discussed in the context of fatigue failure. Also addressed is the competition between different kinds of defects in controlling the initiation and early growth of fatigue cracks.
According to the definition of the ASM handbook [1,3], a defect is "an imperfection. that can be shown to cause failure by a quantitative analysis and that would not have occurred in the absence of the imperfection". The topic of the present three-part review is a discussion of defects which can cause failure in cyclically loaded structures. The features discussed comprise material defects such as non-metallic inclusions, pores or micro-shrinkages, etc. and geometric defects such as surface roughness and secondary notches which have their origin in manufacturing, and defects such as surface damage due to scratches, impact events or contact fatigue as well as corrosion pits which arise in service. In this first part, the discussion is prefaced by an introduction to basic aspects which are essential for a deeper understanding of the characteristics and mechanisms how the defects influence fatigue crack initiation and propagation. These include the life cycle of a fatigue crack from initiation up to fracture, crack arrest, multiple crack initiation and coalescence, and the material and geometrical properties affecting these.
Defects as a root cause of fatigue failure of metallic components. II: Non-metallic inclusions
(2019)
This second part of the review on defects as root cause of fatigue failure comprises the origin, the nature and the effects of non-metallic inclusions. Topics addressed are the different kinds of inclusions formed during the manufacturing process, various types of mis-match causing local stresses and, as a consequence, fatigue crack initiation, and effects of characteristics such as size, morphology, localization, spatial distribution and orientation of the defects on the fatigue behavior. Methods for inclusion counting and sizing are discussed along with statistical aspects necessary to be considered when evaluating structural components.