Application of HyperWorks in Developing Human Body Models for Vehicle Crash Assessment

The University of Michigan Transportation Research Institute (UMTRI) is a leading research center dedicated to achieving safe and sustainable transportation for a global society. UMTRI is committed to interdisciplinary research that focuses on increasing driver safety. Since its inception in 1965, UMTRI has earned a significant national and international reputation for its motor vehicle safety research related to injury biomechanics. This research, largely focused in UMTRI’s Biosciences Group, involves research on the biomechanics of motor vehicle occupants, as it relates to occupant injury assessment, crash protection, and occupant accommodation.

The University of Michigan Transportation Research Institute (UMTRI) was faced with the challenge of developing finite-element human body models that account for the effects of age, gender, and obesity on injury risk in vehicle crashes. The existing injury assessment tools, including finite-element human models, did not account for different body shape and composition variations among the population. This was a significant issue as analysis of crash injury databases by UMTRI showed that occupant characteristics, such as age, sex, and body mass index (BMI) significantly affect the risks for thoracic and lower extremity injuries in vehicle crashes. The challenge was to broaden vehicle crash protection to encompass all vehicle occupants by developing detailed, parametric-based finite element human body models that represent a wide range of human attributes.

UMTRI developed a computational framework to build parametric finite element whole-body human models for crash simulation. The framework consisted of three modeling steps: statistical model development of human anthropometry, mesh morphing based on body landmarks, and stochastic material model assignment. The statistical model development of human anthropometry involved the establishment of sub-models: the sitting posture model, the body surface contour model, and the bone geometry model. The mesh morphing technique developed by UMTRI was based upon the assumption that the finite element model mesh from a human model can be changed smoothly into other geometries without developing new finite element meshes. Altair HyperMesh and its morphing module (HyperMorph) were used throughout the whole process of developing the parametric whole-body human models. Once the finite element mesh based on these morphing procedures was generated, material properties for occupants with different characteristics (age, gender, BMI) were assigned to different body components.

• The application of HyperWorks in developing human body models for vehicle crash assessment has led to significant operational results. The parametric finite element human-body models developed were used to investigate the obesity effects of occupant responses during frontal crashes. The simulation results showed that obese occupants tend to undergo larger excursions than non-obese occupants and are at significantly higher risk of sustaining injuries to the thorax and lower extremities in frontal crashes compared to non-obese occupants. This is mainly due to increased body mass and relatively poor fit of the belt restraints caused by obese occupant soft tissues around the abdomen. The study successfully demonstrated the feasibility of applying parametric finite element human-body models to investigate the obesity effects of occupant responses during frontal crashes.

• Development of parametric finite element whole-body human models for crash simulation
• Establishment of sub-models: the sitting posture model, the body surface contour model, and the bone geometry model
• Application of mesh morphing techniques to change the finite element model mesh from a human model into other geometries without developing new finite element meshes