Effect of Surface Stress on Indentation Response of Elastic-Plastic Materials

In this study, nanoindentation technology is applied to evaluate the elastic-plastic law of mechanical properties of small-sized in-situ packaging materials. As one of the most appealing advantage, the proposed method requires only a single nanoindentation, which means the nanoindentation experiments can be performed at minor effort. Combined with nanoindentation technology, the mechanical behavior of packaging materials in single-point nanoindentation loading process was simulated by the finite element method. The effect of surface stress on nanoindentation was studied numerically. In the finite element simulations, after applying prestress to the substrate material, the single-point nanoindentation was numerically analyzed up to the same indentation depth. Based on the finite element predictions, the mechanical properties of materials subjected to prestressing in different directions are studied. By comparing the applied load-penetration depth curves, stress contour, plastic zone and pile-up behavior, the influence of surface stress on the elastic-plastic material is elucidated.