Nopporn Khaewpong

Chestband Analysis of Human Tolerance to Side Impact

A series of 26 human cadaver tests with chestband instrumentation and accelerometers were completed to assess side impact injury tolerance. A Heidelberg-type sled test system was used with thorax, abdomen, and pelvic load plates. Tests were conducted at two different velocities: 24 kph and 32 kph. Test conditions included rigid wall, padded wall, and pelvic offset. Accelerations were recorded at rib 4, rib 8, and T12. Up to three chestbands were placed on each surrogate. Injury criteria including the Average Spine Acceleration (ASA) 15N, Thoracic Trauma Index (TTI), normalized chest deflection, and Viscous Criterion (VC) were computed. Resulting injuries ranged from Abbreviated Injury Scale (AIS) 0 to AIS 5. Rib fractures were the most common injury. In general, measured parameters were higher for high velocity tests compared to low velocity tests. The padded wall condition produced lower peak forces, accelerations, and chest deflections compared to the rigid wall condition. A new injury criterion combining TTI and the maximum normalized chest deformation parameter (Max%C) was derived. This criterion yielded the best statistical outcomes compared to any of the other injury criteria. The present test protocol including extensive measurements of cadaver specimens provides a means to develop a most efficacious injury criterion for side impact. (A) For the covering abstract of the conference see IRRD E201172.

The Axial Injury Tolerance of the Human Foot/Ankle Complex and the Effect of Achilles Tension

Axial loading of the foot/ankle complex is an important injury mechanism in vehicular trauma that is responsible for severe injuries such as calcaneal and tibial pilon fractures. Axial loading may be applied to the leg externally, by the toepan and/or pedals, as well as internally, by active muscle tension applied through the Achilles tendon during pre-impact bracing. The objectives of this study were to investigate the effect of Achilles tension on fracture mode and to empirically model the axial loading tolerance of the foot/ankle complex. Blunt axial impact tests were performed on forty-three (43) isolated lower extremities with and without experimentally simulated Achilles tension. The primary fracture mode was calcaneal fracture in both groups. However, fracture initiated at the distal tibia more frequently with the addition of Achilles tension (p < 0.05). Acoustic sensors mounted to the bone demonstrated that fracture initiated at the time of peak local axial force. A survival analysis was performed on the injury data set using a Weibull regression model with specimen age, gender, body mass, and peak Achilles tension as predictor variables (R2 = 0.90). A closed-form survivor function was developed to predict the risk of fracture to the foot/ankle complex in terms of axial tibial force. The axial tibial force associated with a 50% risk of injury ranged from 3.7 kN for a 65 year-old 5th percentile female to 8.3 kN for a 45 year-old 50th percentile male, assuming no Achilles tension. The survivor function presented here may be used to estimate the risk of foot/ankle fracture that a blunt axial impact would pose to a human based on the peak tibial axial force measured by an anthropomorphic test device.

Injury Severity in Restrained Children in Motor Vehicle Crashes

This paper attempts to assess the real-world crashworthiness performance of the various child restraint systems covered by FMVSS 213 and motor-vehicle safety belts. The analysis is based on a sample of 103 cases of children who sustained injuries in motor vehicle crashes and were admitted to Childrens National Medical Center in Washington D.C., a level 1 trauma center. Although the study is still under way, the preliminary findings, which are presented here, suggest a number of important directions for future study and analysis.

Deployment of Air Bags into the Thorax of an Out-of-Position Dummy

The air bag has proven effective in reducing fatalities in frontal crashes with estimated decreases ranging from 11% to 30% depending on the size of the vehicle. At the same time, some air bag designs have caused fatalities when front-seat passengers have been in close proximity to the deploying air bag. The objective of this study was to develop an accurate and repeatable out-of-position test fixture to study the deployment of air bags into out-of-position occupants. Tests were performed with a fifth percentile female Hybrid III dummy and studied air bag loading on the thorax using draft ISO-2 out-of-position occupant positioning. All tests were performed in one of four nominal positions with respect to the steering wheel plane using a production depowered air bag from the current automobile fleet. Dummy positioning on the test fixture was found to be repeatable to within 0.3 cm on all axes. This variation was within the dimensional similarity of the two available fifth percentile female Hybrid III dummies. A large variation in occupant response was found with a very small change in effective distance from the sternum to the air bag module. Nearly 50% variation in peak chest center-of-gravity resultant acceleration was found when moving from the sternum pressed on the air bag module to the sternum effectively being 2 cm from the module. In addition, large variations in occupant response were found with vertical and horizontal displacements of the occupant with respect to the air bag module center. Also, a qualitative change in air bag deployment was found on changing the horizontal position by 4 cm to the left. These variations have significant implications for expected response from in-vehicle out-of-position dummy tests.

Comparison of upper extremity test devices for the evaluation of frontal air bags

Abstract This study examines the response of two upper extremity test devices under driver-side air bag deployment to contribute to the development of dummy surrogates for the investigation of primary contact forearm injuries during air bag deployments. The first of these test devices, the SAE 5th Percentile Female Arm (SAE arm), is an anthropomorphic representation of a small female forearm and upper arm that is instrumented with load cells, accelerometers and potentiometers to enable the determination of upper extremity kinematics and dynamics. The second, the Research Arm Injury Device (RAID), is a simple beam test device designed for detailed investigation of moments and accelerations resulting from close contact in the initial stages of air bag deployment. It includes strain gauges distributed along its length to measure the distribution of moment applied by the air bag deployment. The study used four air bags representing a wide range of aggressivities in the current automobile fleet. Logistic risk functions for forearm fracture were developed using existing cadaver studies and the moment response of each test device. These risk functions indicate that, for 50 per cent risk of ulna or ulna/radius fractures, the SAE arm peak forearm moment is 67 N m while the RAID peak forearm moment is 373 N m.