Local magnetic domaions generate the dislocation and release a physics effect-
magneto-elasticity noise when the ferromagnetic
material is locally magnetized.It has been found by a German physiscist,H.Barkarsen in 1919 and is called Magnetic Barkhausen Noise or
Magneto-elasticity Noise,briefly written as MBN.It has been found in experiment that this noise is strongly dependent on elements of material and stress state.Changes of physical parameter of a few the ten-thousandth would cause changes of Magneto-elasticity Noise.The instrument for testing residual stress using magneto-elasticity noise technology is developed by means of stress states and releasing noises of materials under and altemating magnetic field.This paper adopts zero-point rating curve technology to make a rating curve of MNB-σ by means of magneto-elasticity noise increasing with the decrease of stretching force and decreasing with the decrease of pressure force.It can measure stress of ferrimagnetic frame member through correspondence MBN size of MBN-σ rating curve.The distribution and characterization of
residual stresses on the welding assembly are tested.In order to apply in engineering,a nondestructive testing technology is propsed.