Study On Mechanical Properties Of Vibration Assisted Micro Milling Of Bone Materials

Due to the continuous occurrence of orthopedic diseases,and a serious threat to the safety and health of human beings.in order to reduce cutting force and improve surface quality to improve surgical safety and facilitate the recovery of patient,studies the vibration assisted micro milling technology used for bone material removal,using mathematical modeling,finite element simulation analysis and experiments,the method of combining The cutting force and surface quality of the bone material are analyzed,the main content is as follows:Analyzing the mechanical properties and milling characteristics of bone materials,and dividing the milling of bone materials into three cutting directions: parallel,across and transverse.According to the characteristics of the shear area and ploughing area,based on the oblique cutting microelement model,considering the structural characteristics of the anisotropy of the bone material,the ploughing phenomenon caused by the scale effect and combined with the two-dimensional vibration assisted micro milling kinematics characteristics of the tool,the cutting force prediction model of vibration assisted micro milling for bone material was established by mechanical analysis.According to the mechanical properties of bone materials,the two-dimensional vibration assisted micro milling process of heterogeneous bone materials was simulated by using finite element software.The analysis of the failure form of the osteon and the surface defects of bone materials shows that in the conventional milling,the extrusion effect of the tool easily strips the osteon from the bone matrix along the cement line and leaves the surface defect in the same direction as its distribution.However,after the applied vibration,the mode of action of the tool and the bone material workpiece changes,the vibration effect leads to an increased strain rate of bone material,and the osteon are more prone to fracture.The maximum defect depth on the surface of bone material decreased first and then increased slowly with the increase of amplitude.The maximum defect depth decreases with increasing frequency.In the same conditions,the surface depression depth of the osteon was the largest when milling along the transverse direction,indicating that the cutting performance of the bone material along this direction was the worst.The vibration assisted micro milling system is used to carry out two-dimensional vibration assisted micro milling experiments under different processing conditions,verify the milling force model and finite element simulation analysis of bone materials,and study the influence of processing parameters such as cutting direction,amplitude and frequency on the cutting force and surface quality of bone materials respectively.The experimental results show that the cutting force is the greatest in the transverse cutting direction,and the cutting force is close in the parallel and across cutting directions.With the increase of amplitude,the cutting force first decreases and then increases.With the increase of frequency,the cutting force shows a decreasing trend.The vibration effect is beneficial to improve the surface quality of bone material when the amplitude is small,while the surface quality is negative when the amplitude is large.With the increase of frequency,the surface defect degree of bone material showed a trend of decreasing gradually.Suitable machining parameters can reduce the cutting force and improve the surface quality in the process of vibration assisted micro milling of bone material,which provides guidance for the selection of cutting parameters in the process of vibration assisted micro milling of bone material.