Study On Surface Characteristics Of Cortical Bone Cut By Sodium Chloride Abrasive Water Jet

Biomedicine is closely combined with mechanical engineering,which promotes the development of biomedicine.Traditional cutting methods such as milling and grinding are widely used in bone surgery.They produce a large cutting force in the cutting process,making the cutting section prone to cracks.The cracks,surface damage,and micron and submicron damage of the bone section all affect the regeneration and healing of bone.Abrasive water jet technology as a cold processing method,the cutting process has the advantage of no thermal effect,reducing the risk of thermal necrosis to the bone tissue.At the same time,the small particle size of the abrasive grains produces smaller cutting forces making the cutting section have fewer cracks.With material removal at the micron scale,the removal effect is good.The removal effect is good when removing materials on a micron scale.Cutting of biological bone material using soluble abrasive jets,the cutting section has no abrasive residue and can ensure the integrity of the cutting section structure.It is of great significance to the research and development of orthopedic surgery and medical devices.In this paper,the abrasive water jet is used to cut cortical bone,focusing on the surface characteristics of the cutting section.Through the theoretical analysis and Experimental Research on the cutting mechanism of an abrasive water jet,combined with the micromorphology of the cutting section,the removal mechanism of the abrasive water jet on cortical bone is obtained.To investigate the microscopic characteristics of the machined surface of cortical bone.Using the univariate method to investigate the influence of traverse speed and target distance on the roughness of the bone cutting section.Orthogonal experiments were also designed to analyze the primary and secondary effects of jet pressure,traverse speed,and target distance on the roughness of the bone surface and the optimal combination of parameters.And the morphological structure of the microscopic texture of the cutting section was also characterized.This paper mainly obtains the following research results:(1)With the increase of cutting depth,the roughness of the cutting section in different directions shows the trend of first decreasing,then stabilizing,and then increasing.After cutting,a unique section shape is formed.According to its characteristic differences and roughness distribution law,the increase along the cutting depth can be divided into "initial area,"smooth area," and "rough area." There are some differences in the surface roughness values of different areas along the same cutting direction and the comparison relationship:rough area > initial area > smooth area.When the traverse speed is 10 mm / min,the roughness of the bone-cutting section is the smallest.With the increase of traverse speed,the roughness of the bone-cutting section increases;With the rise of target distance,the section roughness first decreases and then increases.The target distance is 3mm,and the roughness of the cutting section is the smallest.Under the same experimental parameters,the section roughness is different in different cutting directions.The roughness of the machined surface cut along the vertical direction is more significant than that cut in the parallel order.(2)The effect of transverse velocity on the surface roughness of cortical bone was most apparent,followed by jet pressure and target distance.The impact of jet pressure on surface roughness was more significant than that of target distance in the vertical direction.In contrast,the effect of target distance was greater than that of jet pressure in the parallel order.When the jet pressure is from 240 MPa to 320 MPa,the roughness of the section decreases gradually.A better cutting section can be obtained by appropriately increasing the target distance and jet pressure.In this experiment,the best experimental parameters are transverse velocity 10 mm /min,pressure 320 MPa,and target distance of 3 mm.(3)In the vertical direction,the scratch length of the initial area is 100-300 ?m,width8-18 ?m,depth 6-10 ?m.The scratch length in the initial site is the same as that in the smooth area.The scratch length in the rough area increases compared with the first two areas.With the rise of cutting depth,the scratch width first decreases and then increases,and the depth gradually decreases.The scratch length of the initial area in the parallel direction is 100-170?m,width 8-13 ?m,and depth 3-7 ?m.The scratch distribution law is similar to that in the vertical direction.Compared with the vertical direction,the scratch depth in the initial and smooth areas is reduced by 2-3 ?m.Increase the scratch length in the rough area by 100-200?m.(4)When abrasive jet cutting cortical bone,the material removal mainly depends on the impact damage of abrasive particles on collagen fibers.The generation and propagation of cracks accelerate the material removal process.In the cut in and cut out areas,there is the phenomenon of bone fiber pulling out in the amount in and cut out areas.Multiple abrasive particles cut the bone fiber once or numerous times in the cutting process.The fracture of bone fiber is flat,the bone cutting section forms microcracks,and the crack propagation causes the rupture of bridging collagen fibers.