The Biomechanical Response Research Of Pelvis Under Different Working Conditions

The pelvic bone is one of the most important structures within the human body,which transferthe weight of the upper body to the hip joint.The pelvicis composed of sacrum,coccyx,iliums and articular joint between bones.The pelvic is prone to fracture with serious injury,due to its complicated and irregular shape.In this paper,on the basis of perfecting the human finite element(FE)model,the pelvic damage threshold under axial impact loading was established.Refined human pelvis FE model was constructed,the load transfer path and the influence of muscle force in a walking circle was analyzed.The human pelvic model was development based on the CT images.Several software,such as Mimics,ICEM,Hypermesh and Abaqus were used to build the FE model,which includes the bony structure,cartilage,endplate and ligaments.The bony structure was meshed into hexagonal structured grids and the soft tissues were meshed into tetrahedral unstructured grids.The present studies dealt with the stress distribution and load transfer across the pelvic during a walking circle,and the influence of muscle force was also evaluated.The pelvic,as a sandwich structure,the major part of hip joint force was predominantly transferred by cortical bone.The transfer path of hip joint force was loaded through femur then to the superior side of acetabulum cartilage,then to the posterior side of the acetabular and the posterior column of the acetabulum,additionally some force was also transfer to contralateral pelvic through the pubic ramus.The muscle severed a positive function in reducing stress concentration and producing a more even stress distribution over the pelvic bone,while it did a little influence on the load transfer path.The stress distribution in some key position(i.e,acetabulum,pelvic double-wall,sacroiliac joints,arcuate line and the pubic ramus)show a larger value without muscle forces.The WSUHM(The Wayne State University Human Model)was further improved by building a detailed lumbar spine and pelvis model with high biofidelity.The acceleration response characteristics of the lumbar and pelvic were got and its fracture model was constructed.Based on the theoretical analysis,the criterion of pelvic injury and its tolerance limit were put forward.A comprehensive parametric study was performed to establish the relationship of injury patterns/threshold and impact parameters.Additionally,the relationship between the impact pulse and human injury pattern was constructed.The data on the material properties,constitutive relation and damage mechanism of cortical bone was still limited.The workflow of the parameter studies and corresponding experimental analysis was constructed.The experiment under quasi-static and dynamic compression were conducted to explore the strain effect of cortical bone with different fiber direction.The fracture mechanism of cortical bone were investigated with SEM,and fracture crack propagation in the longitude specimen was along the haversian canal,while the fractureof transverse specimen was due to the shear failure of haversian canal.The parameters of cortical bone were optimized by optimizing software modeFRONTIER and computational simulation software ls-dyna,additionally,the evaluation procedures,which was write by python were used to evaluate the parameters.It provides a powerful to analysis the macroscopic mechanical properties and microscopic damage of cortical bone.