Analyzing the Response of the Pelvis During Vertical Loading

Underbody blasts (UBB) have become the most prevalent threats to soldiers in theater. These events typically occur from a bomb, mine, or improvised explosive device (IED), and are characterized by very high accelerations and short durations. During UBBs, life threatening injuries can occur when the pelvis is loaded from blast energy that is transmitted through the floor and into the seat of the vehicle. To better protect soldiers, a better understanding of how the pelvis is injured during UBBs is needed. Finite element models are commonly used to study injuries and can be used to test countermeasures to injury; however, modern pelvis finite element models lack high-rate material properties and are not suitable for simulating UBBs. The goal of this research is to find high-rate material properties of gluteal tissue and investigate the load path through the pelvis during vertical loading. To achieve this, the load response of eleven gluteal tissue specimens at high rates were captured through indentation of gluteal tissue specimens. A material model was created using an inverse finite element technique in which the tissue indentation of each specimen was simulated using specimen specific finite element models. The material properties were optimized through subsequent simulations until the error between the force response of the finite element models and the experimental tests was minimized. Then, a component pelvis finite element model was created to simulate previous pelvis UBB experimental tests. Boundary and input conditions were recreated, and the new tissue model was used for the gluteal tissue. Tools were then created to analyze the load path through the pelvis while being loaded vertically. It was found that in the loading rates tested, the rate of the impact did not affect the amount of load carried by the tissue or the load path through the pelvis. However, it was found that tissue thickness, tissue stiffness, and sacroiliac joint material properties all had significant effects on the effective load path through the pelvis. The insight from this thesis will assist ongoing research in understanding how the pelvis is injured during UBBs so that effective countermeasures can be created to protect soldiers in the battlefield.