Estimating Surface Residual Stress Based On Indentation And Finite Element Simulation

The technology of measuring residual stress began in the thirties of 20th century. It have had remarkable development,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. One is the method of automatically mechanical releasing; the other is the method of nondestructive testing. The first method is to make the part release residual stress, and then calculating residual stress is based on strain. Its precision is high, but it is destructive for material. The second method is composed of X ray method, neutron diffraction method, magnetism method, ultrasonic method, electron spot intervening method, metal magnetism memory method. These methods are expensive, but nondestructive 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. So study and estimating of residual stress is signality for production and scientific test.With development of the technology of surface project and micro electro mechanical systems, conventional method can't measure mechanical property of micron and nanometer material. A new method for estimating residual stress based on indentation technology is proposed in this paper, in which how to estimate material surface residual stress by instrumented sharp indentation and finite element simulation are studied. First, load versus depth curve is gained by indentation test, and then is compared with result of finite element simulation. They are very accordant. This proves result of finite element simulation is credible; Secondly, load versus depth curve of several residual stress states is gained by finite element simulation on samples of low carbon steel. The average residual stress is estimated by the shifts in the indentation loads for several stressed states from that of the unstressed state and elastic-plastic contact theory; If stress ratio is known, the ponderance of residual stress in different directions will be gained.The results show that the estimating residual stress based on indentation test...