New Hybrid Approach in Obtaining Plastic properties by Nanoindentation, Finite Element Method and Modified Dimensional Analysis

One of the main challenges in nanoindentation tests is to work-out a method in order to obtain the material properties through the test results. Using a hybrid method which combines the experimental results of nanoindentation tests with FEM analysis is considered as one of the main solutions for this problem. In order to calculate the mechanical properties, an explicit method was developed on the basis of modified dimensional analysis method. The main advantage of this method is to provide unique answers without any need for iteration so that it would minimize the calculations significantly. In this paper, the mechanical properties of Titanium in plastic phase (yield stress and strain hardening Module) are calculated by utilizing this method. For the first time, the dimensional analysis was used for the bilinear constitutive equation (with two dimensionless parameters), and in the finite element analysis, the general form of the Johnson-Cook equation was utilized. The most important property of plastic state, namely, the yield stress, was extracted in proper agreement with reference values. In the process of solving, a new method for error analysis based on calculating the resultant errors and determining the extremum error in the entire range of parameters was successfully developed and applied. Finally, in order to calibrate the solution, it was also proposed to set up the critical conditions of the problem, such as the indenter tip radius. It was concluded that the use of a radius more than 200 nm leads to a more consistent response to the experiment.