ABSTRACT A local fracture criterion based on strain energy density components E. Vitale, .L. Bertini Ill.partilœnto di c.ostruziarl M;iccanicœ e Nucleari Via Diotisalvi, 2 - PISA (Italy) The present work proposes a local _ fracture model applicable to bath brittle and ductile fracture, which is based on the strain energy density distribution around the crack-tip. The observation that the deviatoric energy component is at a relative maximum at an angle of approximately 70 degrees from the crack plane, while the hydrostatic component is at a maximum at O degrees, is related to the ductile (tearuw and brittle (cleavage) fracture mechanisms which respectively act along these planes; then the fracture conditions are associatedwil:h~e attainment of critical values of the energy· components all over a fracture process zone of finite dimensions. The nr:xiel is applied, via an elastic-plastic Finite Element 2-dimensional analysis of a Colll)act Tension specimen, to the prediction of the brittle-ductile transition and of Warm Pre-Stress effects in the A533-B steel. Results are compared with experimental data and found to be in good qualitative and quantitative agreement. Finally a discussion is reported in which bath the theoretical assumptions and the application procedures are critici.zed in order to outline the limJtations of the model and the areas of possible development. 1. INTRODUCTION Fractographie observatioos in many low-strength steels, which exhibit the typ:ica.l brittle- ductile transition behaviour, have shown that low temperature (low toughness)fractures are mainly due to cleavage mechanisms which act along low energy cleavage pl.aœs, whereas high toughness fracture is dominated by microvoid coalescence along planes of naximum shear strain. In the last years several models have been proposed in the attempt to relate these microscopie observations to local mechanical criteria govenrlng the fracture process,/1-11( 'Ile development of local fracture criteria has proved to be of great importance for a deeper understanding of macroscopic fracture behaviour and has contributed to the explanatiœ of many experimental evidences. In the present work a local fracture criterion, based on the distribution of strain energy density around the crack~tip/12/, is applied to predict the brittle-ductile transition behaviour as well as some Warm -Pre-Stress (WPS) effects in A533-B steel. The application is 153
A local fracture criterion based on strain energy density components
Jun 24, 2023
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