Influences Of Residual Stress On Load-Depth Curve In Indentation Test

The residual stress research can be traced back to 1841 when Neumann F E issued the first quantitative research paper of the residual stress. However, the residual stress causes extremely complicated and has not been found mature and reliable theoretical analysis and calculation method. The technology of measuring residual stress hasn't had remarkable development until center of the 20th century, because of the advancement of microelectronics-photonics and widely applying of computer. To this day, the methods of measuring residual stress have had more than ten, and separated into two kinds summarily. One is the method of automatically mechanical releasing; the other is the method of nondestructive physics testing. The first method is to make residual stress release by mechanical processing or other mechanical method, and then calculating residual stress is based on strain. Its precision is high, but it is destructive largely for material. Nondestructive physics testing measures residual stress utilizing change of physical properties of material or structural parameters of crystal.Among the nondestructive physics testing, indentation test is a new nondestructive measurement of residual stress, widely used to extract the mechanical properties of materials for its fast, simple, precise and non-destructive merits. Its advantage is nondestructive or harm small for material. Residual stress can make material canker, craze and reduce fag intension of material, still affect property of physics and mechanics. Because it destroys structural intension, many accidents have occurred in history. So study and estimating of residual stress is significance for production and scientific test.This paper is based on micron indentation test, finite element simulation to analyze the effect of the material residual stress on the load-depth curve. Load-depth curve was gained by the indentation test and finite element simulation. The two curves are fitting very well, which proves that using finite element simulation of indentation test result is reliable. Then, finite element simulates and analyzes the low carbon steel specimen of different residual stress state on material surface, contrast with the load-displacement curve of different residual stress state. Finally, the design of the one-way loading device, influences of residual stress on the load-depth curve is analyzed combining with finite element simulation.Indentation test and Finite element analysis show that the estimating residual stress based on micron indentation is feasible, the error of which is less than 16%. It can satisfy actual demand completely. The methods of indentation can show material mechanical properties from several nanometers to hundreds of microns, and then it is economical, convenient and rapid, so it will primly promote technology of estimating surface residual stress on micro-volume material.