| Porous structures have been widely used in high-tech fields such as automobiles,aerospace,and biomedicine due to their excellent properties such as light weight,high specific strength,energy absorption,and biocompatibility.With the rapid development of additive manufacturing technology,people have higher requirements for the innovation and complexity of porous structure design,hoping to explore diversified,flexible and controllable porous structures with excellent performance,especially non-uniform functionally graded porous structures.In this paper,under the background of selective laser melting technology,the parametric design of porous structures is carried out based on implicit surfaces,and the mechanical properties of porous structures are systematically explored through numerical simulation and mechanical experiments.First,to address the low efficiency of porous structure modeling,an efficient software application was developed that integrates functions such as implicit surface visualization,porosity calculation,and CAD file export;A corresponding optimization strategy was proposed for the pillar pinch-off behavior of the classical Primitive surface and the I-WP surface,which increased the forming porosity from 79% and 98% to more than 99%,and improved the uniformity of the pillar channel;An implicit surface hybrid design method is proposed to generate SCBCC-IS and BCCZ-IS structures with continuously varying curvatures.Secondly,the relationship between the mechanical properties of porous structures with different topological geometries and the number of cell array layers was explored through numerical simulation,and it was found that the elastic modulus and yield strength decreased gradually and tended to be stable with the increase of the number of cell array layers;Comparing and analyzing the stress distribution of the same topological geometry porous structure generated by implicit surface and CAD design method,the latter has more obvious stress concentration effect;Using fe-safe software to study the fatigue characteristics of the implicit surface porous structure,the fatigue life is BCCZ-IS>SCBCC-IS>BCC-IS,and the smaller the porosity,the stronger the resistance to fatigue failure.Thirdly,the mechanical properties parameters of the printed 316 L substrate are established,the elastic modulus is 196 Gpa,the nominal yield strength is 469 Mpa,and the density is 99.3%;SLM formed the implicit curved porous compression specimen and tensile specimen,obtained accurate mechanical properties parameters by combining quasi-static compression and tensile experiments,and established the Gibson-Ashby model of mechanical properties and porosity.The results show that BCCZ-IS has the highest yield strength and elastic modulus,while SCBCC-IS is slightly higher than BCC-IS;The energy absorption characteristics of the porous structure are studied,and it is found that the effective absorbed energy strain of BCC-IS is positively correlated with the porosity,while BCCZ-IS and SCBCC-IS have no obvious regularity,and the effective absorbed energy value is BCCZ-IS >SCBCC-IS > BCC-IS.Finally,in order to deploy the redundant materials of the components to the high loadbearing area,a stress-sensing-based variable density porous structure design method is proposed,and the cantilever beam is filled with a gradient porous structure.The simulation results show that,compared with the uniform porous cantilever,the The stress distribution of the functionally graded porous cantilever beam is more uniform,and the bending deformation is also lower;Aiming at the mismatch between the stiffness of the femoral stem prosthesis and the human femur in hip replacement surgery,a variable-density porous structure design method based on regional classification was proposed,and a functionally graded porous femoral stem of the proximal AGS type was constructed,which can effectively reduce stress shielding impact. |
