The Analysis Of Material Plastic Properties Based On Nanoindentation And Finite Element Simulation

With the booming of Nanotechnology, the applications of nano-scale materials are mainly in the industry of Electronic Engineering, Biologic Engineering, Medicine Science and Aerospace. Therefore, people pay more and more attentions to the nano-scale materials. However, the traditional method of testing materials is not applicable to these materials. A novel method-nanoindentation was proposed, which is a new technology to measure material properties. The displacement of the indenter (0.1-100nm) is monitored and recorded during the experiment Therefore, a relationship between load and displacement is obtained after the experiment, which can be used to analyze the elastic properties of the material. The method is extremely suitable to measure the properties of thin films, coating, materials in MEMS and other materials of small volume.Because the theory of nanoindentation lies in the elastic solution of indentation, the current technique only allows measuring limited material properties from nanoindentation tests, such as Young's modulus, hardness and stiffness. Plastic properties of materials are also of great importance in industrial applications. This thesis proposes a new method to find the stress-strain relations of material in the plastic range based on finite element simulation of the nanoindentation process. The process of nanoindentation is a quasi-static process. ANSYS and ABAQUS were used to analyze the simulation of cylindrical and conic indenter respectively. By varying input material properties, different load-displacement curves can be obtained from finite element simulation. Comparing FE load-displacement curves with the experimental one, the best match should indicate the correct input of material properties.The stress-strain relations obtained by this approach were compared with the actual stress-strain relations of the tested material. A good correlation was obtained. Thus, the validity of this approach was proved The proposed approach to find the plastic properties by the combination of nanoindentation and finite element simulation can be optimized in the future, which will be the solid base of the material applications.