Interpretation of Crack Arrest Fracture Toughnesses Measured with Various Steels

In this work, the effect of steel grade on the fatigue resistance of deep-rolled crankshafts is analysed. In the first part of this paper, the mechanisms leading to the increase of the fatigue resistance brought by the deep rolling treatment, is presented. This reinforcement is mainly linked to crack arrest due both to a decrease of the in-depth stress concentration factor and to remaining compressive residual stresses induced by the deep rolling. In a second part, an analytical model of residual stresses generation by deep-rolling and fatigue is presented. In this model the low cyclic fatigue behaviour of the steel is taken into account, and the residual stress stability with bending fatigue cycling can be predicted. After a presentation of the experimental validation on two different microstructures (baintic and ferrito- perlitic), this model is used for analysing the main parameters of the deep-rolling process and fatigue resistance.

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French RPV PTS Assessment: An Overview of EDF Research and Development in Progress on Thermalhydraulic, Materials and Mechanical Aspects

Aging Management and Component Analysis ◽

10.1115/pvp2003-2151 ◽

2003 ◽

Author(s):

Dominique Moinereau ◽

Jean-Michel Frund ◽

Henriette Churier-Bossennec ◽

Georges Bezdikian ◽

Alain Martin

Keyword(s):

Structural Integrity ◽

Three Dimensional ◽

Crack Arrest ◽

Pressure Vessels ◽

Short Description ◽

Constraint Effect ◽

Materials Properties ◽

Integrity Assessment ◽

Pressurized Thermal Shock ◽

Reactor Pressure

A significant extensive Research & Development work is conducted by Electricite´ de France (EDF) related to the structural integrity re-assessment of the French 900 and 1300 MWe reactor pressure vessels in order to increase their lifetime. Within the framework of this programme, numerous developments have been implemented or are in progress related to the methodology to assess flaws during a pressurized thermal shock (PTS) event. The paper contains three aspects: a short description of the specific French approach for RPV PTS assessment, a presentation of recent improvements on thermalhydraulic, materials and mechanical aspects, and finally an overview of the present R&D programme on thermalhydraulic, materials and mechanical aspects. Regarding the last aspect on present R&D programme, several projects in progress will be shortly described. This overview includes the redefinition of some significant thermalhydraulic transients based on some new three-dimensional CFD computations (focused at the present time on small break LOCA transient), the assessment of vessel materials properties, and the improvement of the RPV PTS structural integrity assessment including several themes such as warm pre-stress (WPS), crack arrest, constraint effect ....

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Acoustic Emission Analysis of Nanoindentation-Induced Fracture Events

MRS Proceedings ◽

10.1557/proc-841-r8.10 ◽

2004 ◽

Vol 841 ◽

Author(s):

Pawel Dyjak ◽

Raman P. Singh

Keyword(s):

Acoustic Emission ◽

Brittle Materials ◽

Signal Amplitude ◽

Crack Arrest ◽

Quantitative Information ◽

Local Failure ◽

Emission Analysis ◽

Specimen Holder ◽

Cube Corner ◽

Ae Signal

ABSTRACTMonitoring of acoustic emission (AE) activity was employed to characterize the initiation and progression of local failure processes during nanoindentation-induced fracture. Specimens of various brittle materials were loaded with a cube-corner indenter and AE activity was monitored during the entire loading and unloading event using an AE transducer mounted inside the specimen holder. As observed from the nanoindentation and AE response, there were fundamental differences in the fracture behavior of the various materials. Post-failure observations were used to identify particular features in the AE signal (amplitude, frequency, rise-time) that correspond to specific types of fracture events. Furthermore, analysis of the parametric and transient AE data was used to establish the crack-initiation threshold, crack-arrest threshold, and energy dissipation during failure. It was demonstrated that the monitoring of AE signals yields both qualitative and quantitative information regarding highly local failure events in brittle materials.

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