Anaylisis Of Microstructure And Residual Stress Using Electromagnetic Heating Effect

The crack prevention using electric heat effect is a newly sprung up method in recent years. A transient powerful current is loaded to a piece of component conductive plate with a crack resulting in crack arrest. Owing to its applications and effectiveness, much attention is paid to it. However, there is a lack of systematic research on crack arrest in metal dies, both domestically and abroad.Theoretical analysis, numerical simulation, experimental surveys and ultrasonic detecting have been used for proposed research on crack prevention in metal dies using electromagnetic heating. The results obtained can provide the theoretical basis for solving practical problems. The main work can be outlined as follows:(1)The complex function method is used as a basis for the theoretical model of the crack prevention in metal dies using electromagnetic heating. The heat source power, temperature field are studied around the crack tip in metal dies when the pulse current is switched on.(2)The experiment has been conducted on a pulse current generator (model ZL-2) developed by the authors. Metal dies with crack are studied. The results of structural microscopic and electrical microscopic observation show that: a white-bright layer is formed around the crack tip. The hardness, density and toughness durability are higher than the base. The microscopic principle of crack prevention by a pulse current discharge is clarified. The mechanical performance of the structure around the crack tip is tested after crack prevention by WDW3100 microcomputer control of electronic universal testing machines.(3)Ultrasonic testing technology is applied to the crack prevention using electric heat effect for the first time. The change of residual stress around the crack tip before and after pulse discharge is checked using this method.(4)The electrical, thermal and mechanical fields are coupled in the process of the calculations. The evolutive process of current-temperature-stress is by numerical analysis. The temperature and residual stress field of both unilateral and spatial cracks in metal dies are calculated, and the numerical simulation results correspond to the experimental analysis.So, the realistic practicability of the technique has been validated through theoretical analysis, experimental analysis and numerical simulation. Especially the study of 2A12 aluminum alloy, it provides exploratory study for this technology using in the aviation field. The state of residual stress after pulse discharge which this article discussed can provide viable foundation for production. This technique could forge ahead from experimental stage to practical application.