Mechanics Problems In Indentation Delamination Test Method

Based on Von Karman nonlinear plate theory, the fracture mechanics model of delaminated film in indentation-induced delamination test of thin film/ substrate systems is re-studied. The substrate deformation is modeled by three coupled springs and the compliances are determined by dimension analysis and finite element method. By use of the finite element method and based on the theory of fracture mechanics, a method is proposed to calculate the stress intensity factors of interfacial cracks. Empirical formulae of stress intensity factors at the edge of the delaminated film are given.The shooting method is used to solve the non-linear post- buckling problem. The critical stress for buckling is calculated. The stress intensity factors, the energy release rate and the phase angle are obtained for various values of elastic mismatch between the film and the substrate. The results show that the substrate deformation must be taken into account in buckling analysis of delaminated film.Based on the above results, a new model is developed for indentation-induced delamination test. Numerical solutions are given for the critical dimension of the plastic zone, the stress intensity factors, the energy release rate and the phase angle. Comparing the results with those based on the widely used model, it is found that the difference is obvious and sometimes is several times larger. The plastic zone and the indention induced stress have great influences on the buckling behavior of the delaminated film.