Research On Stress Detection Based On Magnetic Measurement

With the rapid progress of the world industry, more and more ferro-magnetic material is used in everywhere. Therefore, the safety testing for the ferro-magnetic material is becoming more and more important. There are two methods for the testing of the ferro-magnetic material, destructive testing and nondestructive testing. The method of stress concentration detection based on magnetic measurement can not only detect the defect which has already exist, but also for the stress concentration region, which produce the defect as the precursor region can be detected. For the early warning of this detection method, and the equipment operability and low cost, it absorbs more people'attention.The theory of the stress detection based on magnetic measurement is ferro-magnetic material's magnetostrictive effect. Under outside force, the magnetoresistance of the ferro-magnetic material will change. Using the magnetic sensor can convert the change of the magnetoresistance into the change of the voltage on the test coil, so as to achieve the purpose of testing.This paper introduces the principle of magnetization and the ferro-magnetic material's macro and micro magnetic properties, describes the hardware resources and software environment of the stress detection based on magnetic measurement experiment, the system of stress detection based on magnetic measurement include magnetic measurement sensor, hardware measure, data acquisition and fitting systems.. At last, detecting the stress concentration region of the measured plate. The experiment is carried on the hydraulic tensile machine to detect the stress concentration of the plate and the force is loading step by step, through different excitation current and excitation frequency to detect the plate with different defect depths. So that, the characteristics of the signal in the stress concentration region can be found. Experiments confirmed the feasibility of the method that detecting the stress concentration region using magnetic measurement. In the elastic deformation region, the magnetic measure output signal of stress concentration region decreases with the increase of stress linearly, in the region of plastic it appears nonlinear, fracture in steel moment, the output signal decreases rapidly, and the experiment achieved satisfactory results.