YEAR OLD Research Articles

Development and Validation of an Older Occupant Finite Element Model of a Mid-Sized Male for Investigation of Age-related Injury Risk.

The aging population is a growing concern as the increased fragility and frailty of the elderly results in an elevated incidence of injury as well as an increased risk of mortality and morbidity. To assess elderly injury risk, age-specific computational models can be developed to directly calculate biomechanical metrics for injury. The first objective was to develop an older occupant Global Human Body Models Consortium (GHBMC) average male model (M50) representative of a 65 year old (YO) and to perform regional validation tests to investigate predicted fractures and injury severity with age. Development of the GHBMC M50 65 YO model involved implementing geometric, cortical thickness, and material property changes with age. Regional validation tests included a chest impact, a lateral impact, a shoulder impact, a thoracoabdominal impact, an abdominal bar impact, a pelvic impact, and a lateral sled test. The second objective was to investigate age-related injury risks by performing a frontal US NCAP simulation test with the GHBMC M50 65 YO and the GHBMC M50 v4.2 models. Simulation results were compared to the GHBMC M50 v4.2 to evaluate the effect of age on occupant response and risk for head injury, neck injury, thoracic injury, and lower extremity injury. Overall, the GHBMC M50 65 YO model predicted higher probabilities of AIS 3+ injury for the head and thorax.

Application of an anatomically-detailed finite element thorax model to investigate pediatric cardiopulmonary resuscitation techniques on hard bed

ObjectivesImproved Cardiopulmonary Resuscitation (CPR) approaches will largely benefit the children in need. The constant peak displacement and constant peak force loading methods were analyzed on hard bed for pediatric CPR by an anatomically-detailed 10 year-old (YO) child thorax finite element (FE) model. The chest compression and rib injury risk were studied for children with various levels of thorax stiffness. MethodsWe created three thorax models with different chest stiffness. Simulated CPR׳s in the above two conditions were performed. Three different compression rates were considered under the constant peak displacement condition. The model-calculated deflections and forces were analyzed. The rib maximum principle strains (MPS׳s) were used to predict the potential risk of rib injury. ResultsUnder the constant peak force condition, the chest deflection ranged from 34.2 to 42.2mm. The highest rib MPS was 0.75%, predicted by the compliant thorax model. Under the normal constant peak displacement condition, the highest rib MPS was 0.52%, predicted by the compliant thorax model. The compression rate did not affect the highest rib MPS. ConclusionsResults revealed that the thoracic stiffness had great effects on the quality of CPR. To maintain CPR quality for various children, the constant peak displacement technique is recommended when the CPR is performed on the hard bed. Furthermore, the outcome of CPR in terms of rib strains and total work are not sensitive to the compression rate. The FE model-predicted high strains were in the ribs, which have been found to be vulnerable to CPR in the literature.

Development and validation of a parametric child anthropomorphic test device model representing 6–12-year-old children

Children from 6 to 12 year-old (YO) restrained in motor vehicles by seatbelts designed for adults often experience poor belt fit that results in adverse outcomes in crashes. Computer modelling provides a means to investigate the effects of body size on the injury risks in crashes beyond the few sizes of anthropomorphic test devices (ATDs) that are available. In this study, a parametric ATD model capable of representing 6–12 YO children was developed using MADYMO. A more realistic representation of pelvis and abdomen geometry, modified joint stiffness and improved contact characteristics were added to a MADYMO model of the Hybrid-III 6 YO ATD. The new parametric ATD model was validated against results from 12 sled tests using real second-row vehicle seats with Hybrid III 6 YO and 10 YO ATDs under different restraint configurations using a multi-objective optimisation method. The model validity was evaluated by statistical assessments of output measurements between the tests and simulations. Results showed that the model-predicted ATD head, chest and pelvis accelerations, as well as the seatbelt forces were in good agreement with those from the tests. This validated parametric child ATD model provides a useful tool to investigate the body size effects and to develop restraint system design guidelines for 6–12 YO child occupants.