Experimental And Simulation Study Of Mechanical Properties Of Porous Ti-15Mo Alloy Formed By Selective Laser Melting

In the biomedical field,the stress shielding effect caused by the mismatch of mechanical properties between metal implants and implanted bone is an urgent problem to be solved.On the one hand,in the selection of materials,materials with low elastic modulus,corrosion resistance and good biocompatibility should be selected as much as possible;on the other hand,in the selection of structures,porous structures are chosen to simulate the characteristics of loose implant bone.In addition,there is a lack of precision in the preparation of porous structures by traditional methods,and the processing difficulties cannot meet the requirements of personalization.To address these problems,this paper selects Ti-15Mo alloy material to form porous structures by using selective laser melting technology,and the main research contents and conclusions of this paper are as follows:(1)Homogeneous structure BCC,BCCZ,FCC,FCCZ and FBCCZ models,as well as gradient structure GBCC and GFCC models of lattice structure were designed to derive the relationship equation between its branch diameter and porosity for homogeneous structure.For the problem of sensitivity of cell size and branched diameter to porosity,models with different cell sizes and branched diameters are designed,and it is concluded that the porosity of FBCCZ structure is most sensitive to the change of cell size and cell diameter,while BCC is least sensitive to it.(2)Simulation of the forming process of the lattice structure was carried out by the software Simufact Additive,and it was confirmed that the designed structures could be formed well.Different lattice structures designed for Ti-15Mo alloy were successfully prepared by selective laser melting technique.The specimens were tested in compression and it was found that the specimens did not fracture significantly and had good plasticity.The uniform structure and the gradient structure have different failure modes;the uniform structure generally fails diagonally,while the gradient structure fails in the form of layer-by-layer collapse.The elastic modulus of the different structures ranges from 0.4 to 3GPa,which is in accordance with the elastic modulus of trabecular bone in the range of 0.02 to 3GPa,meeting the mechanical property requirements of human bone implants.Comparing the energy absorption performance of the homogeneous structure and its gradient structure,it was concluded that the gradient structure has a larger total amount of energy absorption.(3)The effects of single-cell and stacked models of BCC structure on mechanical properties were investigated,and it was found that the elastic modulus and yield strength of single-cell model were higher than those of its stacked model.The mechanical properties of this structure can be studied with 27 stacking models to improve the computational efficiency.The elastic film modulus and yield strength of the same structure with different relative densities were analyzed,and it was found that the elastic modulus and yield strength increased with the increase of relative density.The stress cloud diagram reveals the existence of stress concentration in the lattice structure.The stresses at the nodes of the BCC model were reduced by topology optimization and re-modeled,and the highest stress at the nodes was reduced from 1118 MPa to 755MPa after optimization.