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Yehia, N. A. B.

Publications and source records attributed to Yehia, N. A. B..

3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

On the effect of quarter-point element size on fracture criteria

The effect of the quarter-point element size on the solution parameters of fracture criteria is investigated in view of its effect on the computed stress intensity factors. An analytical relationship between the error in calculating crack propagation increment and stress intensity for single mode problems is obtained while, for mixed mode problems, the investigation is based on numerical experimentation. The singular element size is found to have a substantial effect on both crack propagation angle and increment for the geometries considered.

Yehia, N. A. B.↗
NASA NTRS1985

Automatic crack propagation tracking

A finite element based approach to fully automatic crack propagation tracking is presented. The procedure presented combines fully automatic mesh generation with linear fracture mechanics techniques in a geometrically based finite element code capable of automatically tracking cracks in two-dimensional domains. The automatic mesh generator employs the modified-quadtree technique. Crack propagation increment and direction are predicted using a modified maximum dilatational strain energy density criterion employing the numerical results obtained by meshes of quadratic displacement and singular crack tip finite elements. Example problems are included to demonstrate the procedure.

Shephard, M. S.↗
NASA NTRS1985

On the use of the T-criterion in fracture mechanics

The applicability of the maximum dilatational strain energy density criterion, T-criterion, as proposed by Theocaris and Andrianopoulos, is investigated for use in a crack propagation study. It is found that the T-criterion has to be modified to correctly determine the fracture load. A detailed comparison between the minimum strain energy density criterion, S-criterion, and the new modified T-criterion is given for generalized plane stress and plane strain conditions.

Yehia, N. A. B.↗