Study On The Factors Influencing The Machining Quality Of Biological Bone Materials In Soluble Grain Jet Cutting

Drilling,sawing,milling and other methods commonly used in bone tissue surgery generate heat during processing,and the accumulation of heat increases the local temperature of the processed material,which is easy to cause tissue thermal damage.Abrasive water jet has the unique advantages of greatly reducing the osteotomy temperature and tissue thermal damage,which has become a new technical means in bone cutting surgery.The traditional abrasive water jet commonly uses garnet,corundum and other mineral abrasses.Although it has strong cutting ability,the abrasive particles are easy to be embedded in bone tissue during the cutting process of biological bone materials,which is difficult to remove and is not conducive to the healing of bone tissue or even toxic.Therefore,soluble crystals with biocompatibility should be used as abrasives to cut bone tissue in bone cutting surgery to prevent side effects to patients.In this paper,three kinds of soluble crystal particles with biocompatible sodium chloride,sucrose and xylitol were used as abrasives to carry out cutting experiments on bovine dense bone,focusing on the influence of the density,hardness,solubility,crystal morphology and other physical and chemical properties of soluble abrasives on the roughness and cutting depth of bovine dense bone cutting,and analyzing the scratch distribution characteristics of the cutting section.At the same time,mechanical properties of bone tissue and sodium chloride crystal were measured and analyzed,and the research conclusions were as follows:(1)Bone tissue is greatly affected by loading rate.With the increase of loading rate,the yield strength of bone sample increases,and longitudinal bone sample(the axial direction of bone unit is parallel to the loading direction)is more affected by loading speed than transverse bone sample(the axial direction of bone unit is perpendicular to the loading direction).At the low loading rate of 0.05 mm/min and 0.5 mm/min,sodium chloride crystal is less affected by the loading rate and the yield strength difference is only 0.6%;at the high loading rate of 5 mm/min,the yield strength difference is 10.18% due to the loading rate.(2)According to the mechanical properties and fracture state shown during bone-like compression,the dense bone of bovine femur has obvious anisotropic mechanical properties.With the continuous action of load,the dense bone changes from plastic to brittle,and finally presents the characteristics of brittle material.Sodium chloride single crystals exhibit brittleness at fast compression and ductility at slow compression,and sodium chloride shows a transition from ductility to brittleness when the loading rate increases to a critical level of about 5mm/min.(3)The density,hardness,solubility and crystal structure of soluble crystals all have effects on the cutting quality.In the case of penetrating cutting,the difference of density has the most obvious effect on the cutting quality,and the surface roughness of bone samples processed by soluble crystals with low density is smaller.When it is impossible to cut through the bone,the difference in solubility has the most obvious effect on the cutting quality,and the cutting depth of the bone is greater when the crystal with slow dissolution rate is processed.Under the experimental design parameters,the three kinds of soluble crystal jets can fully realize the stable cutting of biological bone materials.When the xylitol particles with the lowest density were used as abrasive cutting,the minimum surface roughness was obtained when the pressure was 280 MPa,the transverse velocity was 10 mm/min,and the target distance was 1 mm.The Ra value was 3.19 μm.The maximum cutting depth of 47.15 mm was obtained when the pressure was 280 MPa,the transverse velocity was 10 mm/min and the target distance was 1 mm.(4)With the increase of transverse velocity,the length,width and depth of the three grain jet cutting bone sections are increased,so the cutting surface quality can be improved by properly reducing the transverse velocity;With the increase of target distance,there is a certain difference in the length,width and depth of the three grain jet cutting bone section scratch performance,which is caused by the difference in the nature of abrasive,small density,small mass of xylitol particles need a relatively short acceleration time,select a smaller target distance scratch depth is shallower,better cutting surface quality,The density and mass of sodium chloride and sucrose particles require relatively long acceleration time,and the larger target distance is selected to make the scratch depth shallower and the cutting ability stronger.(5)The scratches obtained by the jet cutting of sodium chloride grains are basically wide and deep,the scratches obtained by the jet cutting of sucrose grains are long and narrow,and the scratches obtained by the jet cutting of xylitol grains are short and narrow.The morphological characteristics of abrasive are the main factors that lead to the differences in the length,width and depth of the scratches on the three kinds of jet cutting surfaces.The morphology of sodium chloride particles is square with rounded edges and corners,and the cutting ability is poor.The scratches produced by cutting are relatively wide,and the scratches produced by the cutting of large crystal particles are longer.