Research On The Stress-constrained Topology Optimization Method Of Thermoelastic Structures And Its Application In Automobile Structure Desig

With the rapid development of China’s automobile industry,energy shortage and environmental pollution problems are becoming more and more serious.Therefore,reducing the overall vehicle mass to improve fuel economy is still the overall research direction and development trend of automobiles.Under the premise of meeting the structural strength and safety,the lightweight design of automotive structures or components has important engineering value.As a structural optimization method applied in the conceptual design stage,topology optimization can give full play to the performance of materials and achieve optimal structural design while meeting the requirements of stiffness and strength.In view of this,this paper develops a topology optimization method for thermoelastic structures considering stress constraints and applies it to the lightweight design of automotive components.Around the above,the main research results of this paper are as follows:(1)Stress-constrained topology optimization design method for steady-state thermoelastic structures based on uniform temperature difference.The finite element equations of the steadystate thermoelastic structure are derived,and the global stress constraint method is used and solved with sensitivity.The structural volume fraction is considered as the target and the maximum equivalent force of the unit is considered as the constraint.The design variables are optimized by the moving asymptote method and density filters are used to avoid the tessellation of the optimization results.Comparing the optimization results of stress constraint with those of flexibility as the target shows that the use of global stress constraint can effectively control the maximum stress of the structure and avoid the stress concentration phenomenon to meet the strength requirements of the material.Meanwhile,the increase in temperature difference increases the target volume fraction of the structure simultaneously,indicating that higher stresses require more materials to carry,reflecting the effectiveness of the proposed method.(2)The optimal design of the stress-constrained topology of a steady-state thermoelastic structure subjected to a non-uniform temperature field is carried out.The effect of temperature field is considered so that the structure is subjected to both mechanical and thermal load coupling,and the global temperature constraint method is used to limit the maximum temperature value of the structure.The effects of stress and temperature constraints on the topology are discussed through three different mathematical models for topology optimization.Numerical calculations show that a single stress or temperature constraint leads to a surge in the maximum temperature or maximum stress of the structure,respectively,while the simultaneous constraint can effectively control the maximum stress and maximum temperature of the structure and achieve the volume minimization of the optimized structure.(3)Research on the optimal design of temperature and stress-constrained topology of thermoelastic structures for transient temperature fields.The steady-state temperature field is an ideal state,while the heat transfer phenomena in practical engineering applications are transient in nature.Considering the effect of transient temperature field,the maximum temperature value and maximum stress value are aggregated into a global time-domain temperature or stress value using aggregation function for the discontinuity in time and space dimensions,and the constraint function is established.Numerical examples show that the optimal topology results in a significant transient effect and the proposed method can effectively control the maximum temperature or maximum stress of the structure in a given operating time.(4)A stress-constrained topology optimization method is used for the lightweight design of the swan-neck tail bracket and engine piston.Firstly,a suitable design space is selected,and then boundary conditions such as load and displacement are applied and topology optimization is performed.The results show that the masses of the optimized tail bracket and piston are reduced to a certain extent compared with the initial model,and the displacement and equivalent force of the topology also meet the design requirements,which verifies the feasibility of the proposed method and provides theoretical guidance for the lightweight design of the tail bracket and piston as well as other key parts of the vehicle.