BACKGROUND:The use of helmets was considered to be one of the important prevention strategies employed on construction sites. The shock absorption performance of a construction (or industrial) helmet is its most important performance parameter. Industrial helmets will experience cumulative structural damage when being impacted repeatedly with impact magnitudes greater than its endurance limit. OBJECTIVE:The current study is to test if the shock absorption performance of Type I construction helmets subjected to repeated impacts can be improved by applying polyethylene air-bubble cushions to the helmet suspension system. METHODS:Drop impact tests were performed using a commercial drop tower test machine following the ANSI Z89.1 Type I drop impact protocol. Typical off-the-shelf Type I construction helmets were evaluated in the study. A 5 mm thick air-bubble cushioning liner was placed between the headform and the helmet to be tested. Helmets were impacted ten times at different drop heights from 0.61 to 1.73 m. The effects of the air-bubble cushioning liner on the helmets’ shock absorption performance were evaluated by comparing the peak transmitted forces collected from the original off-the-shelf helmet samples to the helmets equipped with air-bubble cushioning liners. RESULTS:Our results showed that a typical Type I construction helmet can be subjected to repeated impacts with a magnitude less than 22 J (corresponding to a drop height 0.61 m) without compromising its shock absorption performance. In comparison, the same construction helmet, when equipped with an air-bubble cushioning liner, can be subjected to repeated impacts of a magnitude of 54 J (corresponding to a drop height 1.52 m) without compromising its shock absorption performance. CONCLUSIONS:The results indicate that the helmet’s shock absorbing endurance limit has been increased by 145% with addition of an air-bubble cushioning liner.

中文翻译：

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聚乙烯气泡垫提高I型施工头盔反复冲击减震性能的应用

背景：头盔的使用被认为是建筑工地采取的重要预防策略之一。建筑（或工业）头盔的减震性能是其最重要的性能参数。工业头盔在受到大于其耐力极限的反复冲击时，会经历累积性结构损坏。【摘要】：目的:研究在头盔悬挂系统中应用聚乙烯气泡缓冲垫能否提高I型施工头盔在反复冲击下的减震性能。方法：根据 ANSI Z89.1 Type I 跌落冲击协议，使用商用跌落塔试验机进行跌落冲击测试。在研究中评估了典型的现成 I 型建筑头盔。5 毫米厚的气泡缓冲衬垫放置在头型和要测试的头盔之间。头盔在 0.61 到 1.73 m 的不同跌落高度下受到了 10 次冲击。通过比较从原始现成头盔样品收集到的峰值传递力与配备气泡缓冲衬垫的头盔，评估气泡缓冲衬垫对头盔减震性能的影响。结果：我们的研究结果表明，典型的 I 型施工头盔可以承受小于 22 J（对应跌落高度 0.61 m）的重复冲击，而不会影响其减震性能。相比之下，同样的施工头盔，当配备气泡缓冲衬垫时，可承受 54 J（对应跌落高度 1.52 m）的重复冲击，而不会影响其减震性能。结论：结果表明，添加气泡缓冲衬垫后，头盔的减震耐久性极限提高了145%。