Research And Prediction Of Multi-scale Mechanical Properties For Am Parts

The improvement of the mechanical properties of additive-manufactured parts and the optimization of manufacturing processes are the inherent requirements for the development of additive manufacturing industries.Establishing the analysis method of mechanical properties for the technology of additive manufacturing is the key to developing the technology of additive manufacturing.Based on the micro scale,meso scale and macro scale,the key factors that affect the mechanical properties of the parts are studied on the fused deposition molding technology.The relationship between the technological parameters and the microstructure,the meso structure and the mechanical properties is established,and the mechanical constitutive model of the FDM parts is explored and the mechanical properties of the parts are predicted under the various process parameters.The orthogonal experiment scheme is established to obtain the optimum parameter combination and the mechanical properties of the parts is improved The specific research contents are as follows:(1)Research on the relationship between temperature and mechanical performance of parts at microscopic scale.Different nozzle temperatures result in different microstructures of the material,which in turn leads to different mechanical properties at the macroscopic scale.Through the study of the influence of temperature on the microstructure of materials,the mapping relationship between temperature microstructures and mechanical properties is established,and the influence of temperature on the mechanical properties of materials is studied.A single factor experimental scheme is established to obtain better nozzle temperature and improve the mechanical properties of FDM parts.(2)Study on the relationship between packing density and mechanical properties at mesoscale.Through the establishment of the mapping model between the filling density and microstructure and mechanical response,the influence of the filling density on the mechanical properties is studied.Based on the homogenization theory,the mechanical average response of the material in all directions is studied.And the prediction model of the mechanical properties of the equivalent unit is established,three groups of single factor experimental schemes are established to verify the mechanical model.The mechanical properties of the equivalent element under each filling density are obtained.(3)Research on prediction of mechanical properties of multilayer FDM parts at macro scale.For the mechanical properties of FDM parts in the thickness direction of layered features,the stress-strain relationship of the monolayer equivalent unit is studied based on the meso structure mechanical response model and the classical laminating theory.The influence of inter laminar tensile and bending coupling on mechanical properties is analyzed,a prediction model of the equivalent unit mechanical properties on multi-layer FDM parts is established.The stiffness matrix of the equivalent element of multi-layer FDM parts is obtained,the relationship between the modulus of elasticity and the stiffness matrix is studied,the mechanical energy of the equivalent unit is characterized.The three-factor mixed-level experimental scheme was established to analyze the influence of various factors on the mechanical properties and verify the correctness and applicability of the theoretical model.(4)Study on the relationship between process parameters and mechanical properties of parts.Based on the range analysis,the key parameters,such as packing density and filling angle,which significantly affect the mechanical properties are obtained.Based on the theoretical prediction model,the elastic modulus of the equivalent units at each angle and density were obtained,and the influence of filling angle and packing density on the mechanical properties was analyzed.The optimal combination of process parameters is selected to meet the functional requirements of FDM parts.