Study On TIG Additive Of Bionic Primary Structure With Typical Proportional Features And Shell Structure

Natural shell materials have attracted people's attention because of their unique "soft and hard" interwoven structure,which shows high strength and toughness.At present,the bionics of the microstructure of the shell is mainly imitating the pearl layer,ignoring the overall effect of the prism layer and the pearl layer.The bionic study of the peral layer and the whole structure,composed of peral layer and prism layer,is mainly carried out in this paper.In this paper,taking Hyriopsis cumingii shell as the research object,the microstructure and mechanical properties of pearl layer and the whole structure were studied respectively,and the relationship between the whole structure and mechanical properties of shell were discussed.The results of shell experiments show that the polygonal edges on the surface of the prism layer vary in size and are randomly distributed,with a surface edge length of 1.8 ?m-15.3 ?m and a thickness of 37 ?m-595.3 ?m,accounting for 1%-35% of the total thickness of the prism layer and pearl layer,and the surface edge length of the nacreous layer aragonite wafer is 1.4 ?m-6.5?m,and the thickness is 360 nm-975 nm.The average tensile strength and average tensile elastic modulus of Hyriopsis cumingii pearl layer are 32.4 MPa and 3 GPa,and the average tensile strength and average tensile elastic modulus of the whole structure are 28.9 MPa and 2.7 GPa.The average bending strength and average bending elastic modulus of Hyriopsis cumingii pearl layer are 166.1 MPa and 36.2 GPa,and the average bending strength and average bending elastic modulus of the whole structure are 182.7 MPa and 35.8 GPa.The measured bending strength of the whole structure is about 10% higher than that of pearl layer,and the failure strain rate is about 12.2% higher.When the force is parallel to the shell direction,the toughening mechanism of the aragonite wafer plays an important role,and the performance of the pearl layer is better than that of the the whole structure;when the force is perpendicular to the shell direction,the prism layer plays the role of bearing force,and the pearl layer deforms and absorbs energy.This new toughening mechanism improves properties of the whole structure..In the nano-indentation experiment,when the indentation depth is 2000 nm,the average indentation load,hardness and elastic modulus of the prism layer are 37%,52.4% and 31.4% higher than those of the pearl layer,respectively.Based on the study of shells,the structural features of shells are extracted and the primary structures of pearl layer,prism layer and pearl layer of bionic shells are designed according to typical proportional features.The bionic proportional characteristic structures are prepared by TIG wire arc additive manufacturing technology,and the microstructure and mechanical properties of bionic features structures with different proportions are studied.The main results show that the average yield strength and average bending strength of the structure imitating pearl layer are measured by strain rate 1700 /S Hopkinson bar test and three-point bending test are between pure stainless steel and pure high strength steel,but lower than bionic prism layer and pearl layer proportional characteristic structures.The strength of the the proportional characteristic structure with imitating prism layer and pearl layer shows an upward trend with the increase of the proportion of prism layer.The yield strength and bending strength of the proportional characteristic structure with prismatic layer and pearl layer accounting for 40% of prismatic layer reach the strength level of pure high-strength steel.The average impact toughness of bionic proportional characteristic structure is between pure stainless steel and pure high strength steel,and the impact toughness of primary structure of imitation pearl layer is better than that of prism layer and pearl layer proportional characteristic structure.The impact toughness of the proportional characteristic structure of imitating prism layer and pearl layer decreases gradually with the increase of the proportion of prism layer.The prism layer accounts for 40% of the proportion of the prism layer and pearl layer,the strength of the structure has reached the level of pure high strength steel,and the impact toughness is 15.9% higher than that of pure high strength steel.