| For the sake of protecting the environment and saving resouces, a big trend of automobile manufactures is to reduce fuel consumption with a high security level. The most effective way to reduce fuel consumption is to reduce vehicle weight. To reduce weight and ensure the safety performance of vehicles, more and more researches focus on high strength steel. The basic mechanical properties of high strength steel include strength, hardness, microstructure and so on. However, traditional testing methords either cause irreversible damage or coet long time. In order to solve the problems above and satisfy the requirement of rapid non-destructive testing on site, this paper aims at non-destructive test of high strength steel using Magnetic Barkhausen Noise(MBN).When ferromagnetic material is under the alternating magnetic field, the domain wall will revolve. MBN is the electromagnetic signals generated by domain wall revolving. The stress and microstructure such as grain size, martensite fraction and carbon content of the material act as the main factors influence the signal strength. Since these microstructure are strongly associated with material mechanical properties, MBN can be used to represent material mechanical properties.This work studies the MBN signal under elastic-plastic deformation of two typical high-strength steel, dual-phase steel(DP steel) and transformation induced plasticity steel(TRIP steel), and finds that MBN change trends can clearly manifest the continuous yield effect of DP steel, and TRIP effect of TRIP steel. Demonstrated that MBN signal can be used as a new method to observe structure transformation of high-strength steel.The MBN detecting instrument is used to test the machenical properties of high strength steel parts. In this parer, the hardness and strength of hot stamping B pillar and the residual stress of cold stamping parts are tested. The results show that MBN can test the machenical properties of the parts quickly and accurately. |
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