Influence of residual stress on instrumented spherical indentation
                                                                            CHENG Wenqiang
                  (College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014, China)

Abstract: Aiming at the instrumented spherical indentation response were affected by residual stress, the mechanical parameters of two commonly used engineering materials were tested, namely aluminum alloy LY12 and titanium alloy TC4. Then a spherical finite element simulation model was established and its reliability had verified by instrumented spherical indentation test. Based on these preliminary work, the indetation force, pileupsinkin and radius of the contact plastic zone were systematically studied under different residual stress. The results indicate that, with the increase of residual compressive stress, the indentation load becomes larger, the pileup tends to occur, and the radius of the plastic area increases; with the increase of residual tensile stress, the influence of indentation response is opposite. These phenomena can provide a basis for judging the internal residual stress and placement of sensitive elements in the indentation test.

Key words: residual stress; spherical indentation; finite element simulation; plastic deformation