Stress Analysis In 2-D Indentation-induced Delamination Test

In the present paper, stress analysis is conducted to investigate the indentation stress in delamination test of a film/substrate system by using a microwedge indenter. The Finite Element Method (FEM) is employed in the stress analysis with different geometrical and mechanical parameters of wedge angle, penetration depth, film thickness, delamination size, Young's modulus and yield strength of the indented film. Based on the analysis results Loading Indentation Stress and the Unloading Indentation Stress are defined. The main achievements are as follows:1) The film is an elastic-perfectly plastic material. Based on the FEM results, the empirical formulae for these two indentation stresses are obtained by fitting the curve of indentation stress and penetration depth. There is a critical indentation depth. When the penetration depth is smaller than the critical value, the indentation stress is parabolic function of the indentation depth. However, the indentation stress becomes constant when penetration depth is larger than the critical value. The energy release rate is calculated for the indentation-induced interfacial crack.2) The film is bi-linearity strength material. Based on the elastic-perfectly plastic material, considering the strengthening factor, the empirical formulae for loading and unloading indentation stress with and without the residual stress are obtained.3) The film is a bilayer one with the same thickness and different elastic-perfectly plastic material properties. The indentation stresses in the uplayer and downlayer are calculated when the Dundurs elastic mismatch parameter a is respectively-0.5 and 0.5. The empirical formula for the loading indentation stress is presented.