Assembly by Means of Local Magnetization Method

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.