Simulation Of Spinning Process Of Cast Spinning Aluminum Alloy Wheel And Study On Fatigue Properties Of The Inner Rim

The wheel,as an important bearing structure in the process of vehicle static and driving,its performance directly affects the safety,braking and reliability of the vehicle.The fundamental purpose of using aluminum alloy wheels is to reduce the weight of wheels as much as possible under the premise of ensuring safety.The inner rim fatigue cracking of cast spinning aluminum alloy wheel affects the driving safety significantly.Therefore,through finite element simulation,composition testing,metallography test,hardness test,room temperature tensile test,room temperature high cycle fatigue test(R=-1)and the corresponding fracture analysis,this paper explores the reason why the inner rim of cast spinning A356 aluminum alloy wheel is easier to crack.The method to solve the problem is proposed according to the cracking mechanism.The specific research is as follows:(1)By simulating the spinning process of a wheel,It is discovered that the deformation of the middle and lower parts of the rim is large.Near the hump,the forming effect becomes worse due to material accumulation.The upper part of the spinning zone and the inner rim of the wheel are basically cast structure,without obvious deformation traces.But the connection between the hump and the inner rim has a good deformation effect because of the repeated spinning and the thin thickness.With the increase of the spinning pass,the forming effect of the inner rim becomes better.T6 heat treatment(Solution treatment and artificial aging)has a certain degree of separation effect on the matrix.Mg and Si are further diffused and dissolved into the matrix,and the form becomes round and fine ball or granular.(2)The hardness of the wheel increases by about 100% after T6 heat treatment.The area with higher hardness is mainly the zone with large spinning deformation or the inner rim(the area that solidifies first in casting and has the fine organization),but there is little difference in the hardness of each part.After T6 heat treatment,the yield strength of each position is increased by about 140%,the tensile strength of each position is increased by about 100%,and the elongation is slightly increased;Spinning slightly increases the strength of the material,and greatly increases the elongation of the material.The results and tensile fracture were analyzed.The room temperature tensile damage mechanism of A356 aluminum alloy was investigated.Shrinkage porosity,shrinkage cavity and other casting defects will greatly reduce the tensile properties of the material.If the defect is small or no defect.The cracking mainly started from the second phase.(3)In the high-cycle fatigue experiment of A356 aluminum by tensile and compressive loading,the rim fatigue limit(91.67MPa)is greater than the inner rim fatigue limit(75MPa).According to the S-N curve,the high cycle fatigue performance of the rim is obviously better than that of the inner rim.The smaller the stress,the more obvious the fatigue performance advantage of the rim.In the case of repeated loading,shrinkage porosity and other casting defects,will greatly reduce the fatigue life of the material.If there is no significant casting defect,the microstructure fineness affects the cracking to some extent,but the aggregation of brittle phase is more likely to expose its defects under repeated loading.Therefore,although the rim microstructure is slightly thicker than the inner rim,the distribution of brittle phase is more dispersed,and it is not easy to form stress aggregation under repeated loading.If there is no obvious weak point,it can be considered that most positions bear the load,and there will not be a large number of cleavage planes near the source area caused by the premature cracking of a point.If there is no eutectic Si rich zone near the crack source,transgranular fracture will occur;if the eutectic Si rich zones exist,most of them follow the intergranular fracture.It is found by measuring the area proportion of each area that the larger the source area is,the longer the fatigue life will be.A model of the influence of defects,eutectic Si distribution and microstructure density on mechanical properties during tensile and fatigue failure was established.