Magnetic Memory Detection Of The Distribition Of Residual Stress On Hardened Layer

Gear and shaft parts are the transmission components of aero-engine, the existence of the unfavorable residual stress can make parts fatigue failure. This paper attempts to analyze the distribution law of the gear residual stress from the MMM(metal magnetic memory, MMM) detection, so that it can provide a basis for testing the surface integrity of critical aero-engine transmission components and ultimately achieve the purpose of improving anti-fatigue manufacturing technology.This paper is based on the principle of magnetic memory testing, designing a set of suitable magnetic memory device to detect the residual stress of gear components.There are two samples of tablets which are made of 20 CrMnTi. The first one is used to measure mechanical properties of the plate material and the stress concentration area, the other group do the same test after carburizing and quenching, and then compared with the first results of the first group.Find out what influenced on the rules of the residual stress distribution and material mechanics performance through analysising the stress distribution rule of the material and carburizing and quenching.The numerical simulation of the residual stress for analyzing the relationship between the force of the gear material which is caused by different loading and the magnetic memory signal by using the ANSYS software to test the model of the tablets which are made of 20 CrMnTi.The research results show that the plates which are made of 20 CrMnTi gear material with the hole sample don’t have the stress concentration phenomenon without loading, while under different loading, the stress concentration area near the tablet sample hole, and residual stress near the hole becomes big when it is perpendicular to the pull direction, but when the residual stress is parallel to the pull direction,it becomes small.When the loading reaches the begnning of the inhomogeneous plastic deformation stage and the uneven plastic deformation stage, the magnetic memory signal becomes remarkable.During the inhomogeneous plastic deformation stage, with the increase of the loading, the magnetic memory signal and the residual stress near the hole is sharply mutation; When the loading is located in the uneven plastic deformation stage, with the increase of loading, residual stress and the magnetic memory signal variation gradient is relatively stable.Under the same loading,the sample tablets with holes present the distrubution of the magnetic field component of the normal vector is relatively chaos, but the trend of the stress concentration area is consistent, after carburizing and quenching stress concentration area in sample hole area is smaller, but the stress concentration distribution is very uneven in the samples.In this paper, the use of magnetic memory signal analysis to test the residual stress of the gear in service for some time on its hardened layer, the residual stress concentration on the vicinity of the gear surface and the gear root fillet. if the gear surface once have wear,it would focus a lot of residual stress at the boundary of wear.The research results provide a reference of integrity indicator for the rapid detection of gear parts residual stress concentration area and key component surface of aero-engine.