A Shape Memory Alloy Energy Absorber for Backpack Design

Abstract

Individuals employed in specific recreational, occupational, and military pursuits often carry heavy loads, using variety of pack systems. Recreational hikers and backpackers commonly carry subsistence and comfort items in backpacks. Firefighters, foot soldiers, and other emergency personnel carry extremely heavy backpack loads and walk longer distances than most of their civilian counterparts. It is shown that the physiological strain in terms of heart rates increases considerably when a user carries a load of more than 10.4 kg. Besides, additional stains are induced due to improper ergonomic design of backpacks' structures, which generate unbalanced loads to the user. Since shape memory alloys (SMAs) possess superior form-setting capability and pseudo-elastic properties, which in turn are perfect materials as a damper at the temperature above their austenite finish temperature (A f ), embedding an ergonomically-designed SMA energy absorber based on the users' motion, physiological, and ergonomic information into backpacks' structures is able to alleviate these excess strains for sporty and military applications. In this regard, this article presents the feasibility of using a specially designed SMA energy absorber for imbedding into shoulder belts of backpacks to alleviate the dynamic stress imposed onto shoulder of the backpackers. Our experimental results revealed that a certain amount of energy generated from the weight of the backpack can be absorbed by the absorber, which eventually can reduce the risk of fatigue and pain imposed on the backpackers.