Applicability of damage models for failure analysis of threaded bolts

Damage models have been applied in engineering applications. In the present work both Gurson-Tvergaard-Needleman (GTN) model and the progressive damage model have been employed to describe plastic deformation and damage behaviour in the tensile bars and threaded bolts. The predictive capabilities of the models are critically assessed. The parameters in the damage models are identified from uniaxial tensile tests. The models are applied to predict failure of the threaded bolts. Numerical results reveal both models agree with experimental data in uniaxial tension and in threaded bolts. The overall results do not show substantial differences. However, damage evolutions from both damage models display very different developments. Whereas the GTN model confirms damage nucleation in the specimen center of the uniaxial tensile bars, as observed in experiments, the progressive damage model predicts damage starts from the specimen surface where the plastic strain reaches its maximum. In threaded bolts both models do not show significant deviations in predicting the ultimate loading. The progressive damage model without stress triaxiality consideration predicts an unrealistic ductile fracture process and cannot be applied to metallic materials.