| Bone milling is one of the most important links in bone surgery.Since the machining parameters during milling affect the changes of milling force and surface roughness,excessive milling force can easily lead to bone cracks.Bone cracks and surface roughness affect the quality of the bone surface.The poor quality of the bone surface results in the inability of human bone and implants to cooperate well.In order to reduce the milling force of the bone milling process and reduce the bone surface roughness,the bone surface quality after bone surgery is better.In this paper,ultrasonic vibration-assisted bone milling technology is introduced,and the motion and mechanism of ultrasonic vibration-assisted milling of cortical bone are theoretically analyzed,and the milling force and bone chip shape of ordinary milling and ultrasonic vibration-assisted milling of cortical bone are compared through experiments.,bone cracks and surface roughness.The influence trend of ultrasonic vibration milling parameters on milling force and surface roughness was obtained through experiments.Finally,the genetic algorithm was used to optimize the milling force and surface roughness of ultrasonic vibration-assisted milling of cortical bone.The specific research contents are as follows:(1)The ordinary milling and ultrasonic vibration-assisted milling processes were analyzed,and the kinematic model of the trajectory of the selected point of the cutting edge was obtained,and the separation characteristics of ultrasonic vibration-assisted milling were analyzed;then the velocity characteristics of axial ultrasonic milling were analyzed,The conditions and critical milling speed for the generation of tool-chip separation characteristics of ultrasonic vibration-assisted milling are obtained.(2)The milling component force of ultrasonic vibration-assisted milling is theoretically analyzed,and then an ultrasonic vibration-assisted bone milling test platform is built to conduct milling experiments.Firstly,the single factor test was used to compare the milling force,chip shape and bone crack of ordinary milling and ultrasonic vibration milling,and it was verified that the intermittent cutting characteristics of ultrasonic vibration assisted milling can reduce the milling force.Then,the ultrasonic vibration milling parameters were studied in the same cortical bone thickness The effect of the following on the milling force.The processed bone surface was observed by scanning electron microscope(SEM),and the influence law between milling force and bone crack was obtained.(3)The removal mechanism of ultrasonic vibration-assisted milling of bone material was analyzed,and an empirical model of surface roughness of ultrasonic vibration-assisted milling was established.A measurement platform was built to measure the bone surface roughness,and the bone surface roughness of the two processing methods was compared.The influence of ultrasonic vibration milling parameters on the surface roughness under the same cortical bone thickness was studied and analyzed.(4)The Box-Behnken test plan was designed by Minitab software,and the milling force and surface roughness were measured by ultrasonic vibration-assisted bone milling test platform and surface roughness measurement platform to obtain test data.Based on the experimental data,a quadratic regression prediction model of ultrasonic vibration milling parameters,milling force and surface roughness was established,and the response surface analysis was carried out to obtain the influence law between the factors.The parameter’s influence weight on the milling force and surface roughness.Based on the quadratic regression prediction model,the genetic algorithm is used for multi-objective optimization,and the parameters of ultrasonic vibration milling are optimized with the minimum milling force and minimum surface roughness as the objectives. |
