Effect Of Internal Defects On The Tensile And Shear Strength In Additively-Manufactured Aluminum Alloys By Simulation Investigation

The special forming method of additive manufacturing（3D printing）technology makes it have unique advantages in many fields,especially in the field of weight reduction design of civil aircraft,and the performance and weight of structural parts are optimized simultaneously.In the civil aircraft structural materials are more commonly used aluminum alloy,and laser selective melting（SLM-Selective Laser Melting）is the most common process for printing aluminum alloys.However,due to the particularity of the metal additive manufacturing process,some defects will inevitably appear inside it that cannot be ignored.The appearance of defects causes the strength properties of the print to change.Metal additive manufacturing processes are costly and internal defects complex.The effect of internal defects on tensile and shear strength is studied experimentally,which requires higher funds and a long test period.Therefore,it is a reasonable and efficient research method to carry out quantitative research on the influence of defects on static strength in combination with elastoplastic finite element simulation technology.In this paper,SLM additive manufacturing aluminum alloy material is used as the research object,and the influence of internal defects on tensile and shear strength is studied by finite element simulation method.First of all,due to the differences in manufacturing processes,the finite element modeling method of additive manufacturing test pieces is different from that of traditional machined test pieces.To ensure the reliability of this elastoplastic finite element simulation.This article starts with geometric models,material parameters,damage models,and meshing.Through the comparative analysis of finite element results,the parameters required for finite element analysis are reasonably adjusted to establish a finite element modeling method suitable for SLM metal additive manufacturing prints.Secondly,the tensile and shear strength test of SLM additive fabricated aluminum alloy standard materials with and without prefabrication defects is planned and carried out,and the finite element analysis model is established and verified by the test data.First,a room temperature tensile model without preset defects is preliminarily established,and then based on this model,the room temperature tensile model with preset defects is established again,that is,the internal defect analysis model,and finally the shear model is established.Through verification,the error of the experimental and finite element results of the three models does not exceed 8%.This modeling approach is justified.Finally,through this model,the relationship between defects and tensile and shear strength is explored.In addition,a quantitative estimation formula for tensile strength weakening with net cross-sectional area as the main influencing factor and a shear strength estimation formula with defect location as the main influencing factor were established.According to the formula,in the case of A_d/A₀≤15%.Combined with a small amount of experimental data,the values of the comprehensive impact factors K_Z and K_Jwere reasonably adjusted.The weakening formula of the influence of defects on tensile and shear strength under the process parameters of SLM aluminum alloy can be established.The research results can guide the selection of SLM aluminum alloy additive manufacturing process parameters,and promote and improve the application of metal additive manufacturing in civil aircraft structural design.