Research On Thermal-mechanical Coupling Fatigue Model Of Cast Aluminum Alloy

Casting aluminum alloy has an irreplaceable role in the application and status of the industry.For the performance requirements of aluminum alloys,there are higher standards and requirements in various industries.The fatigue failure of aluminum alloy is one of the important failure modes.In the past,a lot of researches have been done on the composition,structure and properties of aluminum alloy,which are based on material science and focus on the study of low temperature and low cycle fatigue.Aiming at the fatigue problem of aluminum alloy under high temperature and high temperature thermal-mechanical coupling,this paper combines mechanics and material science based on discrete medium mechanics theory and applied discrete element numerical simulation method to provide theoretical preparation for the study of new alloy materials from the mechanical point of view.The development of materials points out practical directions and ways to shorten the development cycle of new aluminum alloy materials resistant to high temperature and high cycle fatigue.In this paper,the discrete element software UDEC is used to simulate the high temperature and high cycle fatigue of two-phase aluminum alloy Al-30%Cu with different metallographic phases.Firstly,through the FISH language that comes with UDEC,the numerical simulation test is carried out for the normal temperature tensile test of the two-phase Al-30%Cu alloy,which shows the feasibility of numerical simulation.Furthermore,the mechanical properties of the two-phase Al-30%Cu alloy under the thermal-mechanical coupling of high temperature andhigh temperature were studied by the contact stiffness of the contact surfaces of different phases and the shape of the second phase alloy.The numerical simulation mainly obtained the following.in conclusion:(1)Regarding the influence of metal interface stiffness on the fatigue resistance of aluminum alloy,the research indicates that the stiffness of the contact surface between the two phases of the two-phase Al-30%Cu alloy has a great influence on the fatigue properties of the alloy,and the contact surface stiffness is too large or too small is not conducive to improve the fatigue resistance of the two-phase Al-30%Cu alloy,only the appropriate contact surface stiffness value,that is,when the normal stiffness of the discontinuous surface is 200e4 GPa,and the tangential stiffness is 200e4 GPa,the Al-30%Cu alloy can exert good fatigue resistance under complex mechanical conditions.(2)For the shape of the second phase of the alloy,the anti-fatigue properties of the "ball" shape and the "L" shape were mainly studied.The research shows that the two-phase Al-30%Cu alloy undergoes thermal expansion under the thermal-mechanical coupling of high temperature and high temperature.The volume of the alloy increases,and the maximum deformation occurs at the centroid of the alloy.When the shape of the second phase alloy is different,The two-phase Al-30%Cu alloy with the spherical shape can better absorb the crack growth energy and effectively prevent the thermal-mechanical coupling fatigue.In this paper,the finite element software ANSYS is used to calculate the fatigue numerical simulation of the aluminum alloy truss footbridge.The fatigue simulation calculation of aluminum alloy footbridge under four load combinations is simulated.The stiffness,strength and stability of aluminum alloy footbridge are calculated respectively.Fatigue damage at the most unfavorable position of aluminum alloy bridge under the most unfavorable combined load is simulated.Numerical simulation mainly got the following conclusions:(1)In the stiffness check of the finite element model of aluminum alloy truss footbridge,the maximum deflection under the four load combinations is 21.49 mm,which is less than the allowable deflection allowable value L/800(28.75 mm).In the strength check of the aluminum alloy truss footbridge,the maximum stress value of the truss member under the most unfavorable load combination is 18.9 MPa,which is less than the yield strength of the material is 260 MPa.The natural frequency of the flyover under pedestrian load meets the requirements for comfort.(2)The research shows that the aluminum alloy footbridge generates deflection deformation under the action of the most unfavorable load combination,and the most unfavorable position occurs in the span of the footbridge.The fatigue damage at the most unfavorable position of the aluminum alloy bridge under the most unfavorable loadcombination is simulated.The results show that the fatigue bridge will not be damaged during the service life,indicating that the aluminum alloy bridge has better performance in fatigue strength.Studying the fatigue model of alloy materials under high temperature and high cycle load,it has certain guiding significance for both the fatigue relief under complex stress load and the shortening of the development cycle of new alloy materials.