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Failure behavior of spot welds is investigated under impact loading conditions. Three different impact speeds were selected to test both HSLA steel and mild steel specimens under combined opening and shear loading conditions. A test fixture was designed and used to obtain the failure loads of spot weld specimens of different thicknesses under a range of combined opening and shear loads with different impact speeds. Accelerometers were installed on the fixtures and the specimens for investigation of the inertia effects. Optical micrographs of the cross sections of failed spot welds were obtained to understand the failure processes in both HSLA steel and mild steel specimens under different combined impact loads. The experimental results indicate that the failure mechanisms of spot welds are very similar for both HSLA steel and mild steel specimens with the same sheet thickness. These micrographs show that the sheet thickness can affect the failure mechanisms.

An age-dependent, serious-to-fatal (AIS3+), thoracic risk curve was derived and evaluated for frontal impacts. The study consisted of four parts. In Part 1, two datasets of post mortem human subjects (PMHS) were generated for statistical and sensitivity analyses. In Part 2, logistic regression analyses were conducted. For each dataset, two statistical methods were applied: (1) a conventional maximum likelihood method, and (2) a modified maximum likelihood method. Therefore, four statistical models were derived — one for each dataset/statistical method combination. For all of the resulting statistical models (risk curves), the linear combination of maximum normalized sternum deflection and age of the PMHS was identified as a feasible predictor of AIS3+ thoracic injury probability. In Part 3, the PMHS-based risk curves were transformed into test-dummy-based risk curves. In Part 4, validation studies were conducted for each risk curve.

Lower-body injury data for adults in real-world frontal impacts in the National Automotive Sampling System (NASS) were collected, analyzed, and modeled via statistical methods. Two levels of lower-body injury were considered: maximum serious-to-fatal (MAIS3+) and moderate-to-fatal (MAIS2+). In the analysis, we observed that a substantial fraction of all lower-body injured occupants had no recorded floor/toe pan intrusion: 47% of all MAIS3+ injured occupants; 69% of all MAIS2+ injured occupants. In the statistical modeling, we developed binary logistic regression models to fit the MAIS3+ and MAIS 2+ injury data. The statistically significant variables (p ≤ 0.05) were the speed change of the crash, postcrash floor/toe pan intrusion, level of restraint, occupant age, and occupant gender.