Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Dokumenttyp
- Zeitschriftenartikel (29)
- Beitrag zu einem Tagungsband (7)
- Vortrag (7)
- Monografie (2)
- Buchkapitel (1)
- Forschungsbericht (1)
Schlagworte
- Fracture mechanics (9)
- Fatigue crack propagation threshold (6)
- Fatigue (4)
- Fatigue strength (4)
- Additive manufacturing (3)
- Component assessment (3)
- Constraint (3)
- Crack closure (3)
- Cyclic R-curve (3)
- Defects (3)
- Fatigue crack propagation (3)
- Kitagawa-Takahashi diagram (3)
- Rissarrest (3)
- Turbine disk (3)
- Weldments (3)
- Bruchmechanik (2)
- Burst (2)
- Cyclic J-integral (2)
- Cyclic R-curve analysis (2)
- Endurance limit (2)
- Experimental procedure (2)
- Fatigue crack growth (2)
- Fatigue life (2)
- Fracture (2)
- Fracture resistance (2)
- Material defects (2)
- Micro-shrinkages (2)
- Non-metallic inclusions (2)
- Pores (2)
- Residual stresses (2)
- Schwingfestigkeit (2)
- Short cracks (2)
- Welded joints (2)
- Welding residual stresses (2)
- 316L (1)
- AM 316L stainless steel (1)
- ASTM E647 (1)
- Additive Manufacturing (1)
- Analytisches Modell (1)
- Bauteilauslegung (1)
- Bauteilbewertung (1)
- Bruch (1)
- Bruchmechanische Kennwerte (1)
- Bruchmechanische Konzepte (1)
- Chapetti’s and IBESS model (1)
- Characterisation (1)
- Codes and standards (1)
- Constraint faktor (1)
- Contact fatigue (1)
- Corrosion pits (1)
- Crack Tip Opening Displacement (CTOD) (1)
- Crack arrest (1)
- Crack closure effect (1)
- Crack closure mechanisms (1)
- Crack-closure (1)
- Cyclic stress-strain curve (1)
- Damage tolerance (1)
- Damage tolerant component design (1)
- Data evaluation methods (1)
- Defekte Eigenspannung (1)
- Effective crack propagation data (1)
- Einflussfaktoren auf Rissfortschrittsdaten (1)
- Einschlüsse (1)
- Elastic follow-up (1)
- Elastic-plastic fracture mechanics (1)
- Environment (1)
- Environmental conditions (1)
- Environmental effect (1)
- Environmental effects (1)
- Ermüdungsrissfortschritt (1)
- Experimental determination (1)
- FAT class (1)
- FAT class approach (1)
- FEM (1)
- Fail-safe (1)
- Fail-safe design (1)
- Failure Assessment Diagram (1)
- Fatigue S-N curve (1)
- Fatigue crack initiation (1)
- Fatigue crack propagation stages (1)
- Fatigue crack propagation stagesdefects (1)
- Fatigue loading (1)
- Fatigue strength and life (1)
- Finite element (FE) (1)
- Flaw assessment procedures (1)
- Flaw interaction (1)
- Fracture Mechanics (1)
- Fracture assessment (1)
- Global stability criterion (1)
- Graphite modules (1)
- HAZ (1)
- HCF (1)
- Heat affected zone (1)
- IBESS (1)
- IBESS-Prozedur (1)
- ISO 12108 (1)
- Impact damage (1)
- In-situ Process Monitoring (1)
- Inclusion cluster (1)
- Inclusion size (1)
- Inclusions (1)
- Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung (1)
- J-Integral (1)
- Kritische Last (1)
- Kurzrissbruchmechanik (1)
- Kurzrisswachstum (1)
- L-PBF (1)
- LCF (1)
- Life prediction (1)
- Ligamentplastifizierung (1)
- L‐PBF (1)
- Metallic components (1)
- Mis-match (1)
- Mismatch (1)
- Monotonic and cyclic crack driving force (1)
- Multiple crack initiation (1)
- Multiple crack propagation (1)
- Multiple cracking (1)
- Multiple cracks (1)
- Non-destructive Materials (1)
- Non-sharp defects (1)
- Nuclear reactor systems (1)
- Oberflächenschädigung (1)
- Overspeed (1)
- Oxide-induced crack closure (1)
- Peak stress method (PSM) (1)
- Poren (1)
- Process development (1)
- R-curve analysis (1)
- Rauheit (1)
- Representative material properties (1)
- Repräsentative Werkstoffeigenschaften (1)
- Restlebensdauer (1)
- Rissausbreitung (1)
- Rissausbreitungsstadien (1)
- Rissschließeffekte (1)
- Rissschließfunktion (1)
- Rissschließphenomen (1)
- Rissspitzenbelastung (1)
- Risswiderstand (1)
- S-N curve (1)
- Safety (1)
- Schadenstolerante Bauteilauslegung (1)
- Schadenstolerante Bauteilauslegung, (1)
- Schadenstolerante Bauteilauslegung, Restlebensdauer, intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung (1)
- Schweißverbindungen (1)
- Schwellenwert gegen Ermüdungsrissausbreitung (1)
- Scratches (1)
- Secondary stresses (1)
- Short crack propagation (1)
- Shrinkages (1)
- Standardisation (1)
- Statistics (1)
- Steel (1)
- Steel 316L (1)
- Stiffness (1)
- Strength mismatch (1)
- Stretch-Zone (1)
- Structural integrity (1)
- Struktur Integrität (1)
- Surface roughness (1)
- Testing parameters (1)
- Turbinenscheibe (1)
- Weld geometry (1)
- Weld toe geometry (1)
- Werstoff- und geometrische Imperfektion (1)
- Zyklische R-Kurve (1)
Organisationseinheit der BAM
- 9.4 Integrität von Schweißverbindungen (47) (entfernen)
Paper des Monats
- ja (1)
Eingeladener Vortrag
- nein (7)
Die Anwendung bruchmechanischer Methoden zur schadenstoleranten Bauteilauslegung ist für zyklische Lasten im Bereich der Paris-Geraden Stand der Technik. Technisch relevant sind jedoch häufig geringere Lasten im Schwellenwertbereich der d𝑎/d𝑁-Δ𝐾-Kurve. Aufgrund des großen Einflusses von Rissschließeffekten ist dessen Bestimmung jedoch nicht nur aufwändig, sondern auch potenziell fehlerbehaftet. Die Bauteilauslegung erfolgt zweckmäßigerweise auf der Basis effektiver, d. h. rissschließkorrigierter Rissfortschrittsdaten. Von großer Bedeutung ist auch der intrinsische Schwellenwert, unterhalb dessen keine Risserweiterung mehr eintritt. In diesem Forschungsprojekt erfolgte eine Untersuchung des Einflusses verschiedener Prüfverfahren und Umgebungsbedingungen auf die Ermittlung des Schwellenwerts gegen Ermüdungsrissausbreitung Δ𝐾th. Es wurden statistisch abgesicherte Empfehlungen zur experimentellen Ermittlung des intrinsischen Schwellenwerts Δ𝐾th,eff abgeleitet. Dieser dient auch als Eingangsparameter einer weiterentwickelten Prozedur zur Bauteilauslegung auf der Basis bei einem Lastverhältnis von 𝑅 ≈ 0,8 ermittelter, effektiver, Rissfortschrittsdaten. Es zeigte sich, dass die bei einem Lastverhältnis von 𝑅 ≈ 0,8 in Laborluft bei höherer Prüffrequenzen (≥90 Hz) ermittelten Schwellenwerte eine konservative Abschätzung des intrinsischen Schwellenwerts erlaubten. Bei Lastverhältnissen 𝑅 ≪ 0,8 wurde ein teilweise stark ausgeprägter Einfluss extrinsischer Effekte auf das Rissfortschrittsverhalten festgestellt. Eine Untersuchung der Bruchflächen ergab Oxidschichtdicken in der Größenordnung mehrerer hundert Nanometer. Bei Reduktion der Prüffrequenz auf ≈55 Hz und Prüfung in feuchter Luft (60 % r.F. und 80 % r.F.) konnte auch bei 𝑅 = 0,8 Rissschließen beobachtet werden. Die weiterentwickelte Prozedur zur Bauteilauslegung auf Basis effektiver Rissfortschrittsdaten lieferte aber stets konservative Ergebnisse in einem tolerierbaren Fehlerbereich und ist deshalb zur Anwendung geeignet. Die im Projekt gewonnenen Erkenntnisse tragen zu einer robusten Bauteilauslegung auf bruchmechanischer Basis bei. Der stark reduzierte Versuchsumfang bei Nutzung effektiver Rissfortschrittsdaten gegenüber der Ermittlung von spannungsverhältnisabhängigen Rissfortschrittskurven beschleunigt und vereinfacht die Bauteilauslegung auf Basis bruchmechanischer Methoden.
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of 𝐽-integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest 𝐽 -integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. In addition, probabilistic aspects are also considered in the calculations.
The knowledge of fatigue crack propagation data in terms of their effective values is important for a conservative and safe life assessment of components subjected to cyclic loading. To overcome issues related to the precise consideration of the crack-closure effects on experimental data obtained at small R ratios, closure-free data have been obtained at R ≈ 0.8 by different experimental procedures. The statistical analysis of the intrinsic fatigue crack propagation threshold obtained experimentally has shown a small data scatter and good agreement between procedures. When compared with effective values obtained from analytical corrections of closure-affected data, the data obtained at R ≈ 0.8 should lead to a conservative life estimation.
In 2015, the University of Manchester hosted a workshop (‘Mind the Gap’) aimed at identifying gaps in a number of structural integrity fitness-for-service procedures, including R5, R6, BS 7910 and API/ASME. The findings were subsequently summarised in a journal paper and shared with the relevant stakeholders. A second workshop, this time hosted by the University of Bristol in 2017, was intended to build on the findings of the earlier event, identifying which gaps had been filled, which remain and whether new ones have been identified in the meantime. ‘Mind the Gap 2’ was wide-ranging, including consideration of failure by fracture, fatigue crack growth, hightemperature creep and environmentally assisted crack growth, along with the use of innovative techniques to follow the progress of crack growth from the atomic to the macroscopic scale. A summary of the whole event is thus outside the scope of a single paper, so here we concentrate mainly on advances in fracture assessment, on the interface between inspection and ECA, and on how developments are being incorporated into structural integrity procedures. There is a particular emphasis on the energy transition in the UK, where the planned energy mix will include both nuclear power and offshore wind.
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present two alternative burst speed assessment methods under development based on the Failure Assessment Diagram (FAD) and a global stability criterion, respectively. In the scope of the fracture mechanics assessment, the failure modes hoop-burst and rim-peeling are investigated with semicircular surface cracks modelled at the critical regions on the turbine disk. The comparison of the predicted critical rotational speed shows good agreement between the assessment methods.
Die sichere Auslegung von Bauteilen kommt an der Anwendung bruchmechanischer Methoden heute nicht mehr vorbei. Das vorliegende Buch bietet eine Einführung in diese Methoden mit besonderen Schwerpunkten auf dem aktuellen Stand der bruchmechanischen Kennwertermittlung und den Methoden der analytischen bruchmechanischen Bauteilbewertung. Es beschreibt die Mechanismen von Risswachstum und Bruch, die grundlegenden Konzepte der Bruchmechanik, die analytische Ermittlung der Rissspitzenbelastung in Bauteilen sowie die Anwendung der Bruchmechanik in unterschiedlichen Kontexten. Der Schwerpunkt liegt dabei auf der praktischen Anwendung u. a. anhand von Demonstrationsbeispielen, die im Detail nachvollzogen werden können.
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on productionsimilar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. In particular, the rimpeeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk, with the crack plane perpendicular to the radial direction. The crack is therefore subjected to a biaxial stress state and grows under increasing rotational speed until it triggers the rim-peeling failure. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of -integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest -integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. Probabilistic aspects are also considered in the calculations.
Using the case study of a fail-safe design criterion for a steering knuckle of a commercial vehicle, the effect of stiffness/constraint on the crack driving force in the component is discussed. The problem arises when assessment procedures such as R6, BS 7910 or SINTAP/FITNET are applied in conjunction with substitute geometries for determining the model parameters K-factor and limit load (or a substitute for the latter), as it is common practice. In the example, the conservatism was so pronounced that this procedure was in fact unusable. A way out could be the finite element-based determination of the model parameters and their use in the analytical framework. This procedure is useful and effective if the finite element-based calculations are used in parameter sensitivity analyses.
The impact of crack closure and environmental effects on the experimental determination of the fatigue crack propagation threshold is a major problem for the assessment of cyclically loaded components, especially at low stress ratios 𝑅. In this work, the influence of the experimental procedure and air humidity on d𝑎∕d𝑁 − 𝛥𝐾 data at different 𝑅 is discussed. Unlike the results at 𝑅 = −1, the threshold values obtained at 𝑅 ≈ 0.8, i.e. under negligible crack closure levels, show a very small scatter band regardless of the variation of the test parameters and environmental conditions.
Design methodology of vessel produced by L PBF stainless steel using representative specimens
(2022)
This work presents the preliminary results of an ongoing project with a double objective: on the one hand, the characterisation of the mechanical properties against fatigue damage of an additively manufactured 316 stainless steel produced by laser powder bed-based (L-PBF) technology; on the other hand, the implementation of numerical simulation techniques able to predict the mechanical behaviour of the material in order to optimise and reduce the design costs of vessels used in the chemical sector. The current state of the work developed in this research framework allows showing the first batch of experimental results of crack propagation rate (FCGR) and high cycle fatigue (HCF) tests. The geometry of the vessels studied presents three clearly differentiated regions, either in terms of thickness (11-15 mm) or concerning the inclination of the walls to the direction of manufacturing (0º - 45º). The experimental campaign carried out so far allows identifying the differences in behaviour when comparing different extraction locations around the vessel. This is due to the variations in thermal cycles that the deposited material undergoes during the manufacturing process. Therefore, this causes variations in the microstructure which lead to changes in the response of the material. In this work, these differences are analysed qualitatively and quantitatively from the results of FCGR and HCF, thus allowing to locate the regions with the highest risk in terms of structural integrity against fatigue. This preliminary phase together with the numerical simulation of the additive manufacturing process are key to achieving a reliable description and modelling of the material. The latter will make it possible to address the priority aim of this project, involving the manufacture of independent samples whose properties are representative of the original material extracted from the reference vessels. It is, therefore, a comprehensive methodology for the design of additively manufactured components based on the localised fatigue mechanical properties of representative specimens.