NUMERICAL-EXPERIMENTAL INVESTIGATION OF SINGULARITY AT A CRACK IN NONLINEAR RUBBER ELASTICITY

The purpose of this research is to study experimentally and numerically the nature of the singularity at the tip of a double crack emanating from a central circular hole in a tensile rubber sheet. The rubber exhibits both kinematic (geometric) and material nonlinearities. The Moony-Rivlin constitutive relation was assumed and the material coefficients were evaluated experimentally. After preparation of the rubber, the sheets were subjected to uniaxial tension such that the cracks were under large deformations Mode-I. Displacements in the vicinity of the crack tip were measured using the moire method (4.8,4.9). The linear case was first studied using the finite elements programs LEARN (5.20) and NONSAP (5.21). The strain singularity (n) in {dollar}{lcub}rm sb{lcub}r{rcub}sp{lcub}-n{rcub}{rcub}{dollar} was calculated and values of n = 0.5 were obtained in both cases at the tip of the crack without using singularity elements, thereby providing computational confidence. The nonlinear case was then analyzed numerically using NONSAP. Experimental and numerical results were then compared with the theoretical values obtained by Knowles (1.39) and Stephenson (1.24).; The numerical results agreed with theoretical predictions more closely than the experimental measurements where a lower value of the singularity was obtained. All results indicate the singularity decreases with increased deformation. The Moony-Rivlin material model predicts the nonlinear elastic response reasonably well.