APPLICATION OF MAGNETIC BARKHAUSEN NOISE METHOD FOR CHARACTERISATION OF RESIDUAL STRESSES

摘要

Magnetic methods are used for the non-destructive testing in engineering industries widely because of its simple and reliable operation, The magnetic techniques are applicable only to materials which can be magnetised upon electrification. The techniques include Magnetic particle testing, Magnetic coercive method and Magnetic Barkhausen Noise. Magnetic Barkhausen Noise reveals the stress, hardness and surface condition of materials. Also Magnetic Barkhausen Noise varies with microstructure of the material. In this research work, the application of the Magnetic Barkhausen Noise technique is investigated in checking the residual stresses and surface damages produced on the ferrite grade materials, provided proper calibration is carried out for the process and material. The calibration was carried out for SA106 Grade B material, extracted from 25 mm thick pipe and SMAW welding process was employed for the welding. The Bi-axial calibration differentiates the residual stress state in base metal, HAZ and weld metal regions. The method of calibration for residual stress and sensitivity of Barkhausen technique with respect to longitudinal and transverse direction is discussed.