The Effect Of Compressive Stress On Magnetic Memory Signal Of Q235Steel

Non-destructive testing techniques are of significant influence on guaranteeing the reliability of structures or members. The elastic residual stresses, the early plastic defects or the macro-cracks can reduce the bearing capacity of these engineering materials and structures, even cause the sudden accident. However, the traditional non-destructive testing methods are not valid to detect the hidden damage before the macro-cracks or defects. The metal magnetic memory technology proposed firstly by Doubov, a Russian scientist, is a new technology of non-destructive testing. Compared with the traditional electromagnetic non-destructive detection methods, this new technology is of many advantages, for instance, it has the faster detection speed and it is not required for an external excitation. In addition, it is easy to be carried and it has the higher sensitivity to test the stress concentrated area. Therefore, this method is deemed to have potentials in detecting early damage.Although there are some experimental-researches on the metal magnetic memory technology, they are all aiming at the signal characteristics under the tensile conditions during the elastic-plastic stages, it is lack of systematic research on magnetic memory testing mechanism against the compressive loading. Based on the research of the metal magnetic memory technology, the magnetic flux leakage signals of the normal vector of the compacted specimen are tested and the relationship between the normal leakage signals and the earth’s magnetic field is studied. Under the tested conditions, the corresponding relations between the slopes of leakage signals and the applied compressive loadings are established, which provide the experimental basis for the future theoretical modeling.The detection method of the metal magnetic memory technology is improved, making it possible to measure the small signals with a high accuracy. This method is beneficial to the design of the sample sizes in the future experiment for the metal magnetic memory technology.