| The upper limb of human body is very vulnerable in the traffic accidents.Although the research on the injury mechanism of upper limb can avoid injuries,there is a lack of research on the impact biomechanics of upper limb in China.The injury probability of upper limb in the car crash is 13.5%,and a minor fracture or ligament contusion can affect its function with a long period of recovery,which brings heavy burdens to the injured and society.The research on injury biomechanics for Chinese human body is the scientific basis for the enactment of Chinese automobile safety regulations.Therefore,it is necessary to study the injury mechanism and protection of the upper limb of the occupants.In order to study the impact biomechanics response and injury mechanism of Chinese human body,a high precision finite element model for 50 percentile Chinese male adult upper limb was established based on anatomical structure and CT scan image data of a Chinese upper limb.The model includes the clavicle,scapula,humerus,ulna,radius and bones of hand,as well as joints,ligaments and muscles and skins of upper limb.In order to improve the biofidelity of the model,and specially to express the nonuniformity of the section of cortical bone and discontinuity of inner and outer surface of backbone,fitting was processed for the geometric surface.The finite element model was established with the thickness and shape of the cortical bone section varied continuously based on the geometrical surface of long bones.The model was validated in quasi-static and dynamic loading conditions after screening and summarizing the experimental data of foreign post mortem human subjects.The reliability of model was simulated for long bones and forearm model,as well as the shoulder joint in side impact and forearm under the loading of airbag impact.The results showed that the model can accurately reproduce the response and injury of the upper limb of human body.The model has a high biofidelity in simulation and obtains the injury thresholds of the 50 percentile Chinese adult male upper limb at the same time.The impact response and injury analysis of upper limb were studied both in side impact and airbag impact by using the validated upper limb finite element model.Based on the simulation of the side impact of car door and the upper limb,the kinematics and dynamics response of the upper limb and the maximum stress distribution of bone and the position of the fracture of the shoulder were obtained by the analysis of the collision process and the contact force and stress distribution.We analyzed the influence between the injury of upper limb and the airbag mass flow rate as well as the driver's position under different groups of simulations.The results showed that the risk of forearm fractures was increased with the increase of the forearm radial velocity.When the mass flow rate of airbag reduced to half of the former,the forearm distal average velocity decreased 19.1%,and the peak velocity decreased by 9.0% accordingly.When the distance of forearm and the airbag changed from 0 to 15,25 and 35 mm respectively,the forearm distal average velocity decreased 23.8,45.1 and 56.7% accordingly,and the peak velocity decreased by 1.6,28.4 and 42.0% respectively.The study shows that the clavicle is easy to fracture in side impact,and both the scapula and humerus are less injured.The fracture location of clavicle usually occurs at the 1/3 of the acromial extremity of clavicle.The injury risk of the upper limb of passenger is related to the radial velocity of the forearm.Reducing the mass flow rate of airbag or increasing the distance between forearm and airbag can decrease the fracture risk of upper limb.The upper limb finite element model can accurately analyze the impact biomechanics response of upper limb,and analyse of the upper limb response in vehicle collision accidents qualitatively and quantitatively.The model can provide support for the evaluation of automotive safety restraint system and for the development of vehicle safety. |
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