Crack opening and closing behaviors under cyclic loadings in annealed copper

Cyclic loading tests were performed for the through-thickness center cracked specimen of annealed copper under load - and displacement-controlled conditions. The crack opening/closing behaviors were experimentally examined, and then calculated by means of elastic-plastic finite element method, employing the constitutive equation, which was proposed by the authors in their earlier papers. The calculated load-displacement responses were in quite good agreement with the measured ones under both the test conditions. The large crack opening generated on the first tensile load excursion decreases on the following unloading and compressive loading excursions under the load-controlled condition at the load ratio R-L = - 1.0. The crack opening displacement reaches the smaller value at the second maximum tensile load point than at the first one. Meanwhile, the greatly opened crack on the first tensile load excursion reduces its opening displacement at the successive unloaded point, and the crack opening displacements at the tensile peak load and the unloaded point tend to reach the corresponding stable states under the displacement-controlled cyclic loading at the displacement ratio R-D=0. The calculation describes quite well such crack opening/closing behaviors under both the cyclic loading conditions.