Ballistic impact is one of the major causes for traumatic brain injury (TBI) and ballistic helmets are designed to provide protection from TBI. In real life, it is impossible to use real human subjects for experiments. Therefore, simulation based-methods are convenient to assess the rear effect to ballistic helmet impact and can provide crucial insights to injury. Rear effect happens when the interior of helmet is deformed and contacts with the human head. This paper proposes a simulation-based method to study the rear effect by using Head Injury Criterion (HIC) when the ballistic helmeted headform is impacted by a bullet with different impact angles and at various impact positions. Commercial software package LS-DYNA is employed to simulate the impact. A high fidelity headform model including detailed skull and brain has been used for the simulation purpose. Helmet and bullet are modeled according to the real shapes. The results show that, with a larger impact angle, the HIC score is smaller and therefore there is less damage to the brain. Based on the HIC scores obtained from the impact simulations at various impact positions, the bullet from back is the most dangerous position to the wearer.
Respirator use is an integral part of occupational safety and health practice. The challenge is to design respirators with the best fit and highest comfort level for all workers of diverse anthropometry. This paper presents a method to simulate the interaction between a respirator and a headform, and solutions for the universal design of respirators. Three-dimensional digital headforms and respirators are obtained using reverse engineering techniques. The commercial software, LS-DYNA, is used to model and simulate the interaction between a respirator and headform to determine the key factors that affect respirator fit and comfort. Both the respirator and headform are modeled as shell elements and are deformable. The results show that strap forces play an important role in pressure distribution on the face.
Human head is the most important but fragile part of human body. In order to design the head-gear and study the sophisticated capabilities of human head, the head models have been developing for decades. There are two types of human head models: digital headform and finite element model (biomechanical head model). The complexity of head structure makes these attempts very difficult until the invention of the high-speed computers and the modern medical devices like computed tomography (CT) or magnetic resonance imaging (MRI). Head modeling also has widely potential use in the design process of personal head and face protective equipment (PHFPE). Hazards of processes or environment, chemical hazards, radiological hazards, or mechanical irritants are encountered daily for workers. Those hazards are capable of causing injury or illness through absorption, inhalation, or physical contact. PHFPE includes helmets, masks, eye protection and hearing protection. This study attempts to review different kinds of head models and PHFPE, such as respirators, helmets and goggles. It mainly focuses on the historical developments.
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