27th International Technical Conference on the Enhanced Safety of Vehicles (ESV): Enhanced and Equitable Vehicle Safety for All: Toward the Next 50 Years
This paper describes the development of THUMS Version 7 which is a virtual human body model (HBM) to be used for simulating impact kinematics and injuries of occupants assuming a reclined seating posture in vehicle frontal collisions. In highly automated vehicles, it is expected that occupants wish to take various sitting positions including a reclined posture. Prior research has found that there is a relatively high possibility of injury to the occupant for a reclined posture in vehicle collisions. If the lap belt engagement with the pelvis is lost in a frontal collision, there is the possibility that the internal organs are highly loaded. The latest released Version 6 does not have precise representation of the small intestine but has a generic soft solid. It was decided to upgrade THUMS for accurate prediction of internal organ injury. The geometry and mechanical properties of the small intestine and the other relevant body parts were fundamentally revised in Version 7. The interaction between the pelvis and lap belt was most important in simulating occupant kinematics leading to the abdominal loading. The pelvis dimensions and soft tissue thickness of the anterior pelvis were carefully reviewed to represent the belt-pelvis interaction in the average body-size occupant. Three anthropometry models were generated: 5th-percentile adult female (AF05), 50th-percentile adult male (AM50), and 95th-percentile adult male (AM95). The geometry and material properties of the abdominal soft tissue, small intestine and mesentery were carefully defined to realistically reproduce the mechanical responses during the abdominal loading by referring to the loading test data on actual human tissues reported in the literature. The lumbar spine was also revised. Prior research has found that the lumbar spine receives a high load when the pelvis is firmly restrained to prevent disengagement of the lap belt in a reclined posture. The material properties of the intervertebral discs and spinal ligaments were carefully reviewed. The validity of the updated models was examined by comparing the mechanical responses with the test data from Post Mortem Human Subjects (PMHS). It was confirmed that the Version 7 responses generally matched the test data or fell within the test data variability. The validations were performed at both component and whole-body level by referring to the available test data.