Research On The Crack Arrest Strengthening In Casting Aluminium Alloy Pistou Material By Electromagnetic Heating

Using the electromagnetic heat effect to prevent crack growth of metal components isvery promising non-equilibrium crack arrest technology, having the role of improvingstructure safety, reliability and curb the role of crack propagation. This paper in orderto make this technology with distinct advantages to apply in the actual production,selecting broader application casting Al alloy piston material in internal-combustionengine, Research on influence of electromagnetic heating arrest technology to this specialmaterial of casting Al alloy from the theoretical analysis, the value simulation, theexperimental study and the ultrasonic testing four aspects. For technology popularizationto the non-ferrous metal component crack arrest laing the foundations.(1)The theoretical formula of stress intensity factorK1and strain energy densityfactor S around crack tip before and after electromagnetic heating crack arrest is deducedusing the heat source power calculation formulas and complex function theory knowledge,further deduced the distortion energy density factorS dand volumetric energy densityfactorS vusing near crack tip asymptotic solution. The comparative analysisofK1, S,S dandS vnear the crack tip before and after the discharge. Simultaneouslyanalysised the above various quantities along with current density change situation, Andcan be verified using electromagnetic heating effect crack arrest feasibility by the criterionof fracture mechanics.(2)Research on crack arrest effect to casting Al alloy metal components with crackusing electromagnetic heating application of finite element software ANSYS. Solving nearthe crack tip of current density field, temperature field and thermal stress field after thedischarge using thermal-electricity-structure coupling numerical analysis method, At thesame time, the comparative analysis ofK1and S under external loads near the crack tipbefore and after the crack arrest using APDL Parametric languages based on ANSYS. Andthe comparative and error analysis ofK1and S between theoretical analysis solutionand the numerical simulation results.(3)Research on arrest arrest-strengthening effect to casting Al alloy metal components with crack from the angle of the experiment. Carries on precise marking tothe three-dimensional configuration defects of casting Al alloy metal using ultrasonic andCT equipment, cutting into rectangular tensile specimens containing crack using the wirecutting machine, designing the supporting fixture device according to the selectedspecimen shape, Simultaneously completing the scheme design and process design ofelectromagnetic heating crack-arrest. Followed completing electromagnetic heatingcrack-arrest experiments using the existing equipment zl-2super pulse current generatingdevice. And with the method of comparative experimental study, The comparativeanalysis of macro-morphology and microstructure of the crack tip before and afterelectromagnetic heating crack-arrest.(4)Discussed the possibility, judgment method and the characteristics of ultrasonicdetection to casting flaw detection. Measured change situation of the amplitude and echosound of casting Al alloy components with crack before and after the pulse dischargeusing ultrasonic NDT. The comparison its residual stresses and grain size...