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Influence of the variability of the elastics properties on plastic zone and fatigue crack growth

Kebir T., Benguediab M., Imad A.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 4

919--934

EN

Several theoretical models have been proposed to predict the fatigue crack growth range (FCGR) process using solid mechanics, based theoretical tools and basic or fundamental mechanical properties. Moreover crack growth is linked to the existence of a plastic zone at the crack tip when the formation and intensification are accompanied by dissipation of energy. The overall objective of the present research is to develop, verify, and extend the computational efficiency of the model for fatigue crack growth range (FCGR) function by elastic properties, cyclic hardening and celebrated Paris law. The influence of the variability to elastic properties (Young’s modulus E, tensile strength e and cyclic hardening exponent n’) is a necessary analysis in this work. The predictions of the proposed model were compared with experimental data obtained by [1].

2

A Model for Fatigue Crack Growth in the Paris Regime under the Variability of Cyclic Hardening and Elastic Properties

Kebir T., Benguediab M., Imad A.

Fatigue of Aircraft Structures

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2017

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Iss. 9

117--135

EN

Over the last 60 years, several models have been developed governing different zones of fatigue crack growth from the threshold zone to final failure. The best known model is the Paris law and a number of its based on mechanical, metallurgical and loading parameters governing the propagation of cracks. This paper presents an analytical model developed to predict the fatigue crack propagation rate in the Paris regime, for different material properties, yield strength (σy), Young’s modulus (E) and cyclic hardening parameters (K’, n’) and their influence by variability. The cyclic plastic deformation at a crack tip or any other cyclic hardening rule may be used to reach this objective, for to investigate this influence, these properties of the model are calibrated using available experimental data in the literature. This FCGR model was validated on Al-alloys specimens under constant amplitude load and shows good agreement with the experimental results.

3

Ductile Tearing Analysis in Overmatched Welded Joints

Imad A.

Machine Dynamics Problems

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2006

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Vol. 30, No. 2

40-53

EN

Numerical analysis has been carried out to evaluate the ductile fracture in an overmatched welded joints case using a standard CT specimen. These investigations have been performed by analysing the monometallic, bimetallic and trimetallic configurations in order to compare global approaches (i.e. the J integral and CTOD) with a local approach (Rice and Tracey model). The different cases lead to a globally similar evolution of CTOD and of the J integral. These two parameters are not really affected when changing the configuration while the void growth ratio (R/Ro) is very sensitive to the strain and strain fields around the crack tip. Furthermore, according to the parameter (R/Ro) distribution at the crack tip, it seems possible to predict the crack propagation direction in the overmatched welded joints case.