Acquirement Of Johnson-Cook Parameters And Research On The Law Of Drilling Force About Human Cortical Bone

Bone drilling operation in fracture operation is one of the more common operations in surgery.The outermost layer of biological bones is composed of a dense cortical bone structure with high strength and hardness,which carries most of the loads received by the organism.However,the bone material itself has the characteristics of poor thermal conductivity,honeycomb structure,and brittleness,making it susceptible to damage due to drilling force or drilling temperature during the drilling process,which in turn affects the patient’s postoperative recovery.At present,most of the researches on bone drilling are based on animal bones using experimental and simulation methods to study the influence of drilling parameters,drill bit structure,etc.on the force or temperature generated during the drilling process.However,animal bones may not truly reflect the unique drilling properties of human bones in the drilling process.Therefore,this paper studies the Johnson-Cook parameters of human cortical bone to establish a more realistic finite element model of human cortical bone drilling,which has extraordinary medical value for future fracture operations.In this paper,by combining simulation and experiment,the constitutive model parameters of bone material in the process of drilling bone are deeply studied.Firstly,based on the commonly used bone constitutive model parameters,Advant Edge simulation software was used to establish a drilling finite element model.Then,according to the existing experimental data of human cortical bone drilling force,the downhill simplex method of multivariate function is used to continuously carry out finite element iterative simulation,and finally the important Johnson-Cook constitutive model parameters of human cortical bone are obtained.By selecting the top angle,helix angle,and fillet radius of the drill bit for orthogonal simulation experiments and data analysis,the minimum drilling force blade structure of the human cortical bone and the regression model between each factor and the drilling force are obtained.Finally,a drilling experiment of pig femur was carried out.It was found that the drilling rules of pig femur and human cortical bone were consistent,and the relative error between the two was 13%～21%.When the experimental drilling force of pig femur was reduced by 15%,it can be used to roughly reflect the drilling characteristics of human bones.At the same time,the variation law of the drilling force of the pig femur with the rotation speed and the progress speed is consistent with the established human cortical bone simulation model,indicating the two have certain commonalities.