Joel Stitzel

Computational model of the pregnant occupant: predicting the risk of injury in automobile crashes

OBJECTIVEnThe goal of this study was to create a computational model of the pregnant occupant of a motor vehicle to predict fetal outcome in crashes.nnnSTUDY DESIGNnA finite element uterine model of a 7-month pregnant woman was created and integrated into a multibody human model. Unrestrained, three-point belt, and three-point belt plus airbag tests were simulated at speeds that ranged from 13 to 55 km per hour.nnnRESULTSnPeak uterine strain, as determined by the model, correlated well with the risk of fetal death, as determined by investigations of car crashes. The strain in the uterine wall exceeded the limits of the tissue in simulations of no restraint at 35 km per hour and three-point belt tests at 45 and 55 km per hour. The safest restraint for the pregnant driver is the combination three-point belt and airbag.nnnCONCLUSIONnThe model is a good first step toward the prediction of the risk of fetal death and verified experimental findings that note the importance of proper restraint use for the pregnant occupant.

A new methodology for investigating airbag-induced skin abrasions

Although airbags have been shown to reduce the incidence of life-threatening injuries, they have increased the risk of minor injuries such as those to the skin. Based on the distribution of injuries that can be directly attributed to the airbag itself, it is believed that shear loading exists as a mechanism for these skin injuries. The purpose of this study was to develop a new methodology designed to assess the injury potential from different types of airbag with respect to shear loading. This new methodology utilized a high-speed impactor to accelerate the airbag fabric past a sample of skin. Contact normal forces were monitored by the use of pressure sensors, and fabric velocity was determined from a high-speed video. The abraded skin samples were analysed using light microscopic analysis and ultraviolet light source photography. A new abrasion rating method was developed called the total abrasion score, which allows for quantifiable differentiation between the abrasions caused by different airbag fabric and seam types.

Experimental Analysis of Airbag Seam Design: High-Rate Shear Testing for Skin Abrasions

Approximately 66u2009peru2009cent of all airbag deployments in the USA result in at least one skin injury, with 47u2009peru2009cent of these skin injuries attributed directly to the airbag deployment. The purpose of the present study was to evaluate the risk of skin abrasions from the airbag fabric seam design by using a new shear testing methodology. High-rate shear loading was performed with a pneumatic impactor that propelled a section of airbag fabric across porcine skin at 85u2009m/s. Twenty-seven tests (three control and 24 with fabric) were performed using eight different seam designs. A 40u2009cmu2009×u200910u2009cm section of airbag fabric with each seam was forced across a 5u2009cmu2009×u20095u2009cm section of fresh porcine skin that was acquired within 2u2009h post-mortem. No abrasions were observed in the three control tests, but abrasions were observed in all 24 of the tests conducted using airbag fabric. The unturned, sewn seam orientation resulted in significantly more severe abrasions than the woven, unturned seam orientation (Pu2009=u20090.01). This new system and results illustrate that different seam designs can result in different skin abrasion risk. Moreover, the data show that severe abrasions can be caused by normal pressures well below the 1.75u2009MPa injury threshold previously published.