Dynamic Mechanical Properties Study Of Selective Laser Melting(SLM) On 3D Printed Shaped Parts Under Different Loading Condition

The 3D print technology has developed rapidly,and has a more and more application field in military,aerospace,biomedical and other fields.Selective Laser Melting method(SLM)has similar properties to traditional technical,and it is the most widely used 3D metal printing technology in industry.Because the specimens printed by SLM technology exist crystal orientation,which makes their properties asymmetric.Therefore,the study on the dynamic properties of SLM 3D printing materials is of great significance for military and aerospace analysis applications.In this paper,we carried on the research of the d ynamic properties of stainless(GP1)SLM 3D printing under different loading conditions,adopt the Split Hopkinson Pressure Bar(SHPB),and digital image correlation method(DIC)to study the dynamic mechanical property of material under compression,tensile stress,and sheer loading.The results show:(1)As the research requirement of small specimen under quasi-static and dynamic tensile stress,we used closed M-shaped tensile stress specimen,it can improve the influence of global rotational distortion of the specimen on the additional bending moment of the stretch section,and ensure uniform deformation of stretch section.The M-shaped tensile stress specimen can be loaded dynamically by traditional Split Hopkinson Pressure Bar(SHPB),and avoid the connection problem between specimen and tensile stress bars when using Split Hopkinson Tensile Bar.It has the advantages of easy loading,high precision,and can realize the dynamic tensile test with 5900s^-1and even higher strain rate to obtain dynamic stress-strain curve.(2)We used the SLM method to print the cylinder compression specimen,M-shaped specimen,and hat-shaped shear specimen of stainless steel(GP1),and used Split Hopkinson pressure bar(SHPB)technology to carry out research of dynamic property test under a serial of compression,tensile stress,and sheer tests.We also analyze the dynamic mechanical property of the stainless steel(GP1)printed by 3D SLM method,the results show:(a)The tensile and compression properties of stainless steel(GP1)printed by 3D SLM are basically the same under quasi-static loading,and in the strain strengthening period,the stress-strain curve shows warped phenomenon which is different from ductile metal materials.(b)The dynamic properties of SLM 3D printed stainless steel(GP1)is significantly different under different loading conditions,with the largest compression yield strength,followed by tensile yield strength and smallest shear yield strength or fracture strain;(c)The SLM 3D printed stainless steel(GP1)has strain strengthening effect,and its dynamic tensile yield strength is higher than that of quasi-static,and its yield strength strain rate effect is linear with the logarithmic strain rate,and t he strain rate effect is also related to the loading state.The sensitivity coefficient under tensile stress state is186,which is same as shear state,and higher than the sensitivity of the logarithmic strain rate under compression state,which is 62.598.