The Development Of A MBN Instrument For Testing The Stresses And Hardness Of Ferromagnetic Materials

With the development of modern industry, science and technology, the Nondestructive detection technology (NDT) has become an important means to ensure the quality of products as well as the safety of the equipments and has formed a new, independent and comprehensively applied sciense and technology. The NDT technology tests the various defects and some physical properties of the material by way of physical or/and chemical means without destroying the material being tested. Generally speaking, the quantitative analysis of the defects of the material, such as the shape, the size, the location, the orientation, the distribution of the defects and the inclusions, and the estimation of the quality of the material and products that may have defects by means of modern NDT technology, such as ultrasonic, X-ray, magnetic powder, osmosis, vortex, etc, have been quite successful. But the test of some physical or mechanical properties, such as residual stress, fatigue, microstructure, hardness, thickness of the coating, etc, of ferromagnetic materials and products is still a little demanding for modern NDT technology.Magnetic Barkhausen Noise (MBN) technology has been developed in the past twenty years also. It is a new and still developing NDT technology and the MBN test can be carried out simultaneously, online and at appointed location. The instrument is portable and very convenient. Many properties of the ferromagnetic material, such as residual stress, fatigue life, hardness, microstructure, surface state, etc, can be tested and monitered by MBN technology and it can also be used to analysis and evaluate the state of a whole product or equipment. It is a very promising NDT technology.Ferromagnetic material has very good elasticity and plasticity and many other good qualities, such as unyielding and enduring, etc. It is a widely used industry material now and in the future and can't be replaced. But breakdown of the products made from ferromagnetic materials sometimes may occur which can cause serious problems and may endanger people's life sometimes. Therefore, the test of various properties of ferromagnetic materials, such as stress, hardess and fatigue, etc, is very important. In this paper, the mechanism of the generation of MBN signal and its relation to the various properties of ferromagnetic materials, such as stress, hardness, microstructure and fatigue, etc, are discussed thorougthly and carefully. The relationships between MBN and the stress and hardness of various ferromagnetic materials under different magnetic-field intensity have been mastered on the whole and on the foundation of which an instrument for testing the stresses and hardness of ferromagnetic materials using MBN technology has been developed. This instrument consists of three parts: the sensor, the signal alignment circuit and the singalchip. The details of the circuit structure of the three parts are introduced in this paper and the whole source program code of the assembly language is given out. Because of the limitation of my capability, there must be some shortcomings and errors in this paper, which I'd like you to point out and not to hesitate to tell me so that they can be corrected.