Bilateral Crack Growth Behavior Of Q345Steel Under Uniaxial Tensile Load

Frequently, the destruction of engineering material is the result of the interaction of multiple cracks, multiple crack interaction and its extension mechanism is a difficult problem to be solved in fracture mechanics. This paper studies the mechanical response of Q345steel specimens containing bilateral crack under uniaxial tensile loading using experimental and finite element method, the main works are summarized as follows:1) Through uniaxial tensile test of parallel bilateral crack of different vertical spacing specimens, results showed vertical spacing has important influence on the extended model of bilateral crack. When vertical spacing of bilateral crack was10mm, crack along horizontal extended first, then along deflected angle of about45degrees, finally crack series. When vertical spacing of bilateral crack was20mm, two cracks horizontal expanded and not connected in series. For the sample size of this paper, crack critical vertical spacing of series and not was between15-16mm.2) Experimental studied crack propagation with different initial crack length and angle. Results showed initial crack angle has no significant effect on crack extended direction and tensile load-displacement curve; initial crack length has no effect on crack propagation paths. The longer initial cracks, the smaller maximum-load.3) Five kinds of failure criteria are used to simulate the test process. All of those failure criteria can simulate crack developed path, load-displacement curve coincides with test. For specimen2010x, crack extended length and crack developed oblique angle’slightly deviate with test.4) Studied influence factors of crack expanded direction. Stress at crack tip had small influence on crack expanded direction, but when some large stress value of the two cracks front intersected at developed process, crack would change the direction. Equivalent plastic strain and damage threshold near crack tip elements were much larger than others. Crack always extended along the direction equivalent plastic strain and damage threshold were maximum.5) Fracture modes were analyzed. Damage was divided into tension and shear. Based on these factors, proposed a new failure criterion, some specimens were simulated with the criterion. Results showed new criterion could describe crack extended model well, and load-displacement curves were also similar with test.