| Applied pulse current is developed the non-equilibrium electromagnetic refiningtechnology in metal solidification process in recent years, having the role of the refininggrain and improving metal organizations. Using the electromagnetic heat effect to preventcrack growth of metal components is another very promising non-equilibrium crack arresttechnology, having the role of improving structure safety, reliability and curb the role ofcrack propagation. This paper is based on above two technologies, by the appropriatepulse current from ZL-2equipment to contain crack or defect of metals material, this notonly reduce stress concentration factor of the crack or defect, also can make the crack tippassivation and reached the purpose of the crack arrest. At the same time, the molten metalof the crack tip will occur recrystallization and phase transition, grain are refined,achieving the purpose of strengthening toughening. The research content mainly includesfollowing several aspects:(1) Research on arrest-strengthening effect to40CrNiMo gear steel with containingunilateral crack. Experimentally, The comparative analysis of chemical composition, themicrostructures, the microhardness, tensile properties and impact properties near thecrack tip before and after the discharge. The theoretical formula of phasetransformation stress around crack tip is deduced using transient heat conductionequations, phase transformation kinetics and Eshelby equivalent inclusion. Numericalsimulation, Considering that effect of the volume change and yield strength change on thephase transformation stresses, and carries on the numerical simulation to it.(2) Research on crack arrest effect to45steel metal components with half-embeddingcrack using electromagnetic heating effect. Experimentally, study on process parametersof pulse discharge (discharge voltage) to arrest-strengthening effect, and the comparativeanalysis of the crack tip morphology, the microstructures and the microhardness near thecrack tip before and after the discharge. Theoretically, Solving phase transformationstresses of phase transition region around crack tip After crack arrest strengthening, anddiscuss the influence of various parameters on it. Numerical simulation, Analysis of electromagnetic heating crack arrest strengthening to45#steel metal components withhalf-embedding crack.(3) Research on the phase transformation stresses of20CrMnTi steel metalcomponents with embedding crack after electromagnetic heating effect. Experimentally,The comparative analysis of the crack tip morphology, the microhardness, tensileproperties and impact properties near the crack tip before and after the discharge.Theoretically, more complete mechanical model of the phase transformation stress isdeduced, and discussed that the influence law of the amount of martensite transformationand process parameters of pulse discharge on the phase transformation stresses. Numericalsimulation, carries on the numerical simulation to the phase transformation stresses aroundcrack tip after electromagnetic heating crack-arrest.This paper from experimental research, theoretical analysis and numerical simulationthree aspects, research on crack arrest-strengthening effect to different forms crack anddifferent material of metal components using electromagnetic heating effect. The resultsshowed that: electromagnetic heating crack-arrest technology has theoretical feasibilityand practical application prospect. |
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