Research On Electromagnetic Thermal Arrest Sthengthening And Fatigue Properties Of The High Strength

Engineering structures often bear alternating load in the process of serving, causing the fatigue cracks. Cracks will cause serious harm, or even catastrophic consequences in the actual production and life. Using the electromagnetic heat effect to improve the safety and reliability of engineering structures with cracks or defects is a non-equilibrium electromagnetic refining technology gradually developed in recent years. The effect of crack arrest and strengthening by electromagnetic heat and fatigue properties of high-strength steel specimens with a single-edge crack after the discharge are researched through using theoretical analysis, numerical simulation and experimental methods, and the research contents are as follows:The stress intensity factor at the time of pulse current discharge in metal structure with a single-edge crack bearing the three-point bending load is theoretically calculated. The theoretical formula of phase transformation stress around crack tip after the discharge is deduced by using transient heat conduction equations contained a heat source, phase transformation kinetics and the theory of Eshelby equivalent inclusion.This article analyzed the effect of electromagnetic heat crack arrest for high-strength steel 30 Cr Mn Si Ni2 A with different crack lengths by finite element numerical simulation. The results of temperature field and stress field indicate that efficiency of electromagnetic heat crack arresting is associated with the length of crack. Heat compression stress instantly generated by electromagnetic heat effect can curb the crack propagation effectively.30Cr Mn Si Ni2 A and 35 Cr Mo high-strength steel with a single-edge crack were used to perform electromagnetic heating crack arrest experiment using the self-made ZL-2 super pulse current generation equipment and fatigue life comparison test by fatigue testing machine. The reason of the electromagnetic enhancement technology to improve the fatigue life of high-strength steel specimen under alternating cyclic loads was analyzed by comparative study on the crack tip morphology, the microstructure, the microhardness and mechanical properties before and after the discharge.Theoretical analysis, numerical simulation study and experimental results show that the thermal heat effect can be using for strengthening and preventing high-strength steel crack propagation, improving the fatigue life. The conclusions can provide reference and guidance for the practical engineering problems.