激光定向能量沉积不锈钢件加工性能及表面质量研究OA

In the hybrid additive-subtractive manufacturing of 316L stainless steel,only dry machining can be adopted.The residual heat generated by additive manufacturing affects the surface quality during subsequent subtractive machining,which in turn deteriorates the service life and performance of hybrid-manufactured components.Investigating the effects of residual heat from additive processes on cutting performance and surface quality helps reduce tool wear,improve machined surface quality,and ultimately enhance the service life and operational performance of parts produced via hybrid additive-subtractive manufacturing. This study adopts a combined simulation and experimental approach for analysis.A modified Johnson-Cook(JC)constitutive equation is applied in the cutting simulation model,which is integrated into the finite element model via secondary development.Combined with experimental results,the effects of rising workpiece temperature on tool surface temperature and tool wear during machining are analyzed,along with the post-machining surface flow stress.Based on variations in workpiece temperature,the evolution laws of cutting force and specific cutting energy after single-pass and multi-pass machining are investigated.Experimental results reveal that for 316L stainless steel fabricated via laser directed energy deposition(LDED),the stress-strain curves obtained from Split Hopkinson Pressure Bar tests under dynamic compression gradually decline with the increase of temperature.The modified Johnson-Cook(JC)constitutive equation established based on the material's stress-strain responses at elevated temperatures and high strain rates can accurately predict the evolution of mechanical properties during dynamic compression.The reliability of the cutting simulation model is further verified by the variation of cutting forces.Both simulation and experimental results indicate that within the workpiece temperature range of 20-400℃,the rising temperature softens the workpiece and reduces its yield stress.Meanwhile,temperature elevation facilitates dislocation slip during the cutting of LDED-316L.Consequently,the cutting force and machined surface flow stress decrease progressively along with the rising workpiece temperature,and the specific cutting energy also presents a downward trend.At 220℃,the surface roughness is reduced by 68.93%compared with that at 20℃.When the temperature rises to 260-400℃,excessive heat drastically aggravates adhesive wear and diffusion wear of the cutting tool,leading to increased tool loss and risen surface roughness.Specifically,the surface roughness at 400℃increases by 26.65%relative to the value at 220℃.It is demonstrated that the relationship between workpiece temperature and surface quality is not simply linear,and tool wear exerts a more prominent effect on the machined surface quality during cutting. In hybrid additive-subtractive manufacturing,selecting an appropriate residual temperature from the additive process for subtractive machining under dry cutting conditions can not only reduce the cutting force and specific cutting energy,but also mitigate tool wear and improve machined surface quality.