| In recent years, with the increase in vehicle ownership, vehicle dynamic performancegradually improved, a large number of highway construction, and highly energetic,trauma-like traffic accidents result in a higher rate of morbidity and mortality. Every yearabout15-60million people who were injured, about5-12million deaths causing hugeeconomic losses and made the family heavy spiritual harm. Traffic accidents resulted insevere injuries to the head and thorax more frequently than injury to other body regions. Inparticular, thorax injuries are common in vehicular accidents and is second only to headinjuries, thorax injuries account for13%of minor to moderate injuries and29%of all seriousto fatal injuries. Rib fractures are the most frequent lesions in traumatic thorax injury. Whilerespiratory diseases such as pneumonia, flail chest, and pneumo/hemothorax are regarded asthe leading complications associated with sternum and multiple rib fractures. Therefore, it isvery practical significance and value in engineering to increase understanding thoraxbiomechanical response and the factors influencing thoracic trauma may lead to improvedsafety features and a decrease in fatalities and injuries. Improving safety to minimize or avoidfatalities and injuries is a primary field of research for automotive designers and legislators.The present study focuses on the dynamic response and injuries of the thorax by usingthe simulation analysis method. Elaboration and derives the basic theories and formulas usedin the simulation process. Especially for a non-linear calculation process using the explicitalgorithm basic principle, the contact algorithm, time step control, contact problems iterativemethod derivation of formulas. Comparing the advantages and disadvantages of thetetrahedral and hexahedral elements in the simulation, proposed the hexahedral elements formodeling the main tissue of the human body and method of establishing the human-bodybiomechanical model. An integrative medical Anatomical structure, a human bodybiomechanical model was developed. The model featured in great detail the main anatomicalcharacteristics of skeletal tissues, soft tissues, and internal organs, including the head, neck,shoulder, thoracic cage, abdomen, spine, pelvis, pleurae and lungs, heart, aorta, arms, legs,and other muscle tissues and skeletons. The material properties of all tissues in the humanbody model were obtained from literature. Material model can accurately simulate the rib fracture and soft tissue injury. Validations of the human body model have been made againstCadavers responses for frontal and side impact and for the mathematical lumped massmodel.The accuracy of the model response was investigated through experimental testing on(PMHS) during front thoracic and side pendulum impacts. The model well agreed with thefront thoracic and side pendulum impact tests and had a reasonable correlation during thefrontal thoracic pendulum impact test. The thorax response was excellent when theforce–time, compression–time, and force–compression were considered. The human bodymodel was validated for frontal and lateral impacts to the thorax. The responses well agreedwith those of human bodies sustaining impact loads. The model can also predict skeletalinjuries such as bone fractures and ligament ruptures. Overall, the predicted model responsereasonably well agreed with the experimental data and highlighted areas for futuredevelopments. The model can be used to further evaluate thoracic injury in real-worldcrashes.Through the in-depth analysis of material properties of the ribs, this paper uses theestablished and verified finite element (FE) model of the human thorax to investigate thesensitivity of structural responses and rib fractures to age-related rib material properties toprovide guidelines for the development of FE thorax models used in impact for biomechanicsand injury assessment. Age-related rib material properties were determined based on previousexperimental test results, research and age-related cortical bone material parameters (such ascortical bone thickness, elastic modulus, ultimate stress, failure strain rate), the cortical bonematerial parameters of young and elderly individuals, analysis of Sternal deformation underlow-speed frontal impact, and the number of fractured ribs. The results show that elasticmodulus changes under low-speed frontal impact, with less Sternal deformation resulting inless affected rib fractures. Lower ultimate stress corresponds with greater Sternal deformation,and more fractured ribs correspond with less failure strain. The degree of sternal deformationcorresponded with more fractured ribs. The older the patient, the greater was the sternaldeformation, the number of sternal fractures, and the number of fractured ribs.The simulationresults show that sternal deformation is a highly favorable index for assessing rib fractures. Incar crash safety regulations, the thorax deformation index for frontal crashes is76mm. Thisindex more accurately reflects rib fracture injury, and it can be adopted for different age groups. The evaluation criteria in this index should be changed to reduce rib fractures,thereby reducing the number of thorax injuries among the elderly in automobile collisions.This paper uses the established and verified finite element (FE) model of the humanthorax to investigate the sensitivity of different impact speeds and different impact directionto provide guidelines for the development of FE thorax models used in impact forbiomechanics and injury assessment. The results showed that the greater the impact velocity,the contact force of the chest, the deformation of the sternum, chest internal organizationpressure, the acceleration of the vertebrae, chest viscosity index VC greater. By comparingthe various types of damage, the same speed impacts the different position of the internaltissue damage different, frontal impact chest pressure greater than in side impacts. Ribfractures in the side impact more serious than Frontal Impact, whether front or side impact,the maximum pressure on the heart. Excessive heart pressures likely to cause increased aorticpressure and aortic rupture. Through parameters compared with indices of damageassessment on the front and side impact of thorax, thorax pressure is effective for the damageassessment of the internal organs in the thorax, can be used in automobile collisionregulations for the internal organs damage assessment.Finally, this paper uses the established and verified finite element (FE) model of thehuman thorax to investigate the sensitivity of different angles and different steering wheelheight in impact for biomechanics and injury assessment. The results showed that the higherthe steering wheel position, rib fractures, pulmonary contusion, heart and other internalorgans of the chest injury is more serious. When the steering wheel position in the middle ofthe chest and abdomen, the liver, stomach, diaphragm injury is more serious and ribs andinternal organs of the chest with less damage. When the steering wheel position in theabdomen, intestines, stomach produces large compressive deformation, while the Sternal ribsand the chest visceral injury are small. Steering column mounting angle, the contact force issmaller, the greater the deformation, the greater the pressure chest, Therefore, from the pointof view to meet regulations should increase the mounting angle of the steering columnreduces the contact force. But from the viewpoint of visceral injury shall meet the regulationsof the mounting angle of the steering column reducing the pleural pressure decrease,increasing the collision contact area between the chest and the steering wheel, reducing damage to the internal organs.The results from this study suggested that the numerical finite element model developedhere in could be used as a powerful tool for improving front and side impact automotivesafety. The model can be used to evaluate thoracic injury in real world crashes andautomotive safety regulations and dummy design and development. |
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