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Posterior translation of the tibia with respect to the femur can stretch the posterior cruciate ligament (PCL). Fifteen millimeters of relative displacement between the femur and tibia is known as the Injury Assessment Reference Value (IARV) for the PCL injury. Since the anterior protuberance of the tibial plateau can be the first site of contact when the knee is flexed, the knee bolster is generally designed with an inclined surface so as not to directly load the projection in frontal crashes. It should be noted, however, that the initial flexion angle of the occupant knee can vary among individuals and the knee flexion angle can change due to the occupant motion. The behavior of the tibial protuberance related to the knee flexion angle has not been described yet. The instantaneous angle of the knee joint at the timing of restraining the knee should be known to manage the geometry and functions of knee restraint devices.

The most severe ankle skeletal injury called pilon fractures can cause long term disability and impairment. Based on previous experimental studies, the pilon fractures are regarded as caused by a high-energy compressive force in the ankle joint and affected by a muscular tension force generated by emergency braking. However, quantitative injury criteria for the pilon fractures are still unknown. More accurate prediction of bone fractures in the distal tibia using a FE model of human lower leg can help us know the quantitative injury criteria. Therefore we newly proposed an anisotropic inelastic constitutive model of cortical bone including damage evolution and then implemented it to a FE code, LS-DYNA. The proposed model successfully reproduced most of anisotropy, strain rate dependency, and asymmetry of tension and compression on material and failure properties of human femoral cortical bone.

A reduction in brain disorders owing to traumatic brain injury (TBI) caused by head impacts in traffic accidents is needed. However, the details of the injury mechanism still remain unclear. In past analyses, brain parenchyma of a head finite element (FE) model has generally been modeled using simple isotropic viscoelastic materials. For further understanding of TBI mechanism, in this study we developed a new constitutive model that describes most of the mechanical properties in brain parenchyma such as anisotropy, strain rate dependency, and the characteristic features of the unloading process. Validation of the model was performed against several material test data from the literature with a simple one-element model. The model was also introduced into the human head FE model of THUMS v4.02 and validated against post-mortem human subject (PMHS) test data about brain displacements and intracranial pressures during head impacts.

Accurate prediction of occupant head kinematics is critical for better understanding of head/face injury mechanisms in side impacts, especially far-side occupants. In light of the fact that researchers have demonstrated that muscle activations, especially in neck muscles, can affect occupant head kinematics, a human body finite element (FE) model that considers muscle activation is useful for predicting occupant head kinematics in real-world automotive accidents. In this study, we developed a human body FE model called the THUMS (Total HUman Model for Safety) Version 5 that contains 262 one-dimensional (1D) Hill-type muscle models over the entire body. The THUMS was validated against 36 series of PMHS (Post Mortem Human Surrogate) and volunteer test data in this study, and 16 series of PMHS and volunteer test data on side impacts are presented. Validation results with force-time curves were also evaluated quantitatively using the CORA (CORrelation and Analysis) method.

A finite element model of the human lower extremity has been developed to predict lower extremity injuries in full frontal and offset frontal impact. The model included 30bones from femur to toes. Each bone was modeled using crushable solid elements for the orbicular bone and damageable shell elements for the cortical bone. The models of the long bones for the lower extremities were validated against data obtained from quasi-static 3-pointbending tests by Yamada (1970). The ankle, knee and hip joints were modeled as bone-to-bone contacts and included major ligaments and tendons. The ankle model was validated against data obtained from quasi-staticdorsiflexion, inversion and eversion tests by Petit et al. (1996) and against data obtained from dynamic impactcadaveric tests by Kitagawa et al. (1998). The possibility of using this model to predict injuries was discussed.

Previous studies have hypothesized that the shoulder may be used to absorb some impact energy and reduce chest injury due to side impacts. Before this hypothesis can be tested, a good understanding of the injury mechanisms and the kinematics of the shoulder is critical for occupant protection in side impact. However, existing crash dummies and numerical models are not designed to reproduce the kinematics and kinetics of the human shoulder. The purpose of this study was to develop a finite element model of the human shoulder in order to achieve a deeper understanding of the injury mechanisms and the kinematics of the shoulder in side impact. Basic anthropometric data of the human shoulder used to develop the skeletal and muscular portions of this model were taken from commercial data packages. The shoulder model included three bones (the humerus, scapula and clavicle) and major ligaments and muscles around the shoulder.

A few reports suggest differences in injury outcomes between cadaver tests and real-world accidents under almost similar conditions. This study hypothesized that muscle activity could primarily cause the differences, and then developed a human body finite element (FE) model with individual muscles. Each muscle was modeled as a hybrid model of bar elements with active properties and solid elements with passive properties. The model without muscle activation was firstly validated against five series of cadaver test data on impact responses in the anterior-posterior direction. The model with muscle activation levels estimated based on electromyography (EMG) data was secondly validated against four series of volunteer test data on bracing effects for stiffness and thickness of an upper arm muscle, and braced driver's responses under a static environment and a brake deceleration.

To investigate the effect of muscle activity in pre-impact on injury outcome, we developed a human arm finite element model with muscles which consisted of solid elements and truss elements that could be used for simulating muscle stiffness change for the inputted activity and 3-D geometry of each muscle. Two series of experimental tests on muscle stiffness change and arm flexion were conducted for validation of the model. Comparisons between the simulation results and test data indicated the model validity. Lateral impact simulations for a left arm demonstrated that the muscle activity in pre-impact had significant effects on the motion and stress distribution of the arm bones.

Several three-dimensional (3D) finite element (FE) models of the human body have been developed to elucidate injury mechanisms due to automotive crashes. However, these models are mainly focused on 50th percentile male. As a first step towards a better understanding of injury biomechanics in the small female, a 3D FE model of a 5th percentile female human chest (FEM-5F) has been developed and validated against experimental data obtained from two sets of frontal impact, one set of lateral impact, two sets of oblique impact and a series of ballistic impacts. Two previous FE models, a small female Total HUman Model for Safety (THUMS-AF05) occupant version 1.0ϐ (Kimpara et al., 2002) and the Wayne State University Human Thoracic Model (WSUHTM, Wang 1995 and Shah et al., 2001) were integrated and modified for this model development.

Injuries of the human brain and spinal cord associated with the central nervous system (CNS) are seen in automotive accidents. CNS injuries are generally categorized into severe injuries (AIS 3+). However, it is not clear how the restraint conditions affect the CNS injuries. This paper presents a newly developed three-dimensional (3D) finite element head-neck model in order to investigate the biomechanical responses of the brain-spinal cord complex. The head model consists of the scalp, skull, and a detailed description of the brain including the cerebrum, cerebellum, brainstem with distinct white and gray matter, cerebral spinal fluid (CSF), sagittal sinus, dura, pia, arachnoid, meninx, falx cerebri, and tentorium. Additionally, the neck model consists of the cervical vertebral bodies, intervertebral discs, muscles, ligaments, spinal cord with white and gray matter, cervical pia, and CSF.