The Quantitative Research Of Q235 Samples Between Different Stress Concentration And Magnetic Memory

Stress concentration is one of the important reasons for mechanical components or equipment failure and even the accident.The local stress analysis is the important basis to evaluate the structural stability, security, and life, especially in the critical stress that lead to injury. It is important to prevent accidents. When put the stress to ferromagnetic material, ferromagnetic not only can produce elastic strain, also can produce magnetostrictive proper strain. When the ferromagnetic components both in the stress field and the earth’s magnetic field, the intensity of residual magnetic induction and the magnetization growth. After removaling the load, magnetic field remains unchanged. That is called the magnetic memory phenomenon. Therefore using the phenomenon can effectively prognosis the stress concentration, and quantitatively evaluate the local stress.In this paper, based on the theory of force-magnetic effect, center circular holes specimens of Q235 material, center semicircle ends long straight hole specimens, both ends notched semicircular specimens, both ends V-notch specimens are taken as the research object.According to the generating magnetic effect phenomenon after loaded, the force magnetic quantitative relationship is researched. Four specimens were respectively tested tensile test, using dynamic stress analysis system and magnetic memory detector to record local maximum stress value of the specimens and the relative leakage magnetic field normal component values. Experiments show that ferromagnetic material under geomagnetic field environment bearing loading can produce different degree of leakage magnetic field, with different specimens because of the cross section shape will produce different extent of stress concentration, the leakage magnetic field will be larger along with the larger local stress, and the rate of change is different. According to the rules, the local maximum stress value on the stress concentration location and relative leakage magnetic field normal component value are extracted, a quantitative relationship is established.In order to establish an accurate magnetic quantitative evaluation formula, select ANSYS finite element analysis software to simulate the magnetic field distribution of specimen in the stress field and geomagnetic field. According to the change rule of the magnetic properties of materials by external forces, simulate stress concentration area of the specimen after attribute assignment. Extract the simulation results of local maximum stress value and relative leakage magnetic field normal component.Compared with the experimental values and analyzed error, draw magnetoelastic effect of irreversible component values. Eventually determine and fix quantify evaluation formula in order to determine whether local maximum stress beyond the yield limit.