發泡材料在變速率衝擊下材料壓縮性質分析與緩衝效應評估

EVA Foam Compressive Mechanical Property Analysis and Buffering Effects at Different Impact Velocities

游愷迪(Kai-Ti Yu)

指導教授 ： 劉德騏

國立中正大學/工學院/機械工程學系/碩士(2013年)

摘要

發泡材料普遍地應用在現今人類生活中各個領域包含車輛載具、建築工程、運輸包裝等，其功能主要為吸震與緩衝，並用以保護物體結構或人體免於受損傷害，而本研究則探討用於運動鞋中底的材料乙烯/醋酸乙烯酯共聚物(Ethylene Vinyl Acetate，簡稱EVA)，由於人體運動或衝撞產生不同的衝擊速度，單一掉落高度撞擊試驗並無法模擬出試片不同速率下衝擊與回彈特性，因此本研究建立一套評估發泡材料在不同速率衝擊下緩衝性質的方法，並應用有限元素法搭配類神經網路訓練，評估發泡材料的吸能性質。
本研究分為實驗與模擬兩大部分，實驗的部分內容包括靜態拉伸壓縮實驗、衝擊實驗以及高速攝影方法，從實驗結果結合有限元素分析及類神經網路方法進行逆算，取得不同速率衝擊下材料曲線並與實驗驗證。另一方面建立有限元素分析模型，模擬發泡材料受到衝擊過程之狀態並且觀察過程中材料負載及卸載狀況。最後依照模擬結果比對衝擊實驗材料變形的情形來驗證材料曲線參數，由此提供將來在工程應用的模擬方法。

關鍵字

速率效應 ； 掉落衝擊試驗 ； 有限元素法 ； 發泡材料

並列摘要

Nowadays, foam materials are widely used in various fields of mankind life like vehicle engineering, construction engineering, packaging materials and so on. The main functions of this type of material is shock absorbing and impact cushioning, so it could be used to protect the structure or human body from injury. This study focus on the material which shoe midsoles are usually made of called Ethylene Vinyl Acetate or EVA. Because of human motions with different speeds, a single height drop test cannot respond the foam specimen loading and unloading in different velocities. Therefore, this study developed a method for estimating cushioning effect of material specimen, and use finite element method with neural network to evaluate foam material energy absorbing property.
This study consists of two major parts. The first part is experiment including quasi-static compression test, tensile test and drop impact tests with high speed camera. In experiment process, using foam molding process makes proper specimens and observing deformation of foam. Applied to the deformation data and neural network method, the process could inversely calculate stress-strain curves in medium strain rate. In the second part, this study applied finite element method with material parameters which are calculated before to simulate drop test process, and verify the result with experiment data. The results from the study could be used in the engineering application to evaluate EVA foam energy absorbing effect.

並列關鍵字

Stain Rate Effect ； Drop Test ； Finite Element Method ； Foam Material

參考文獻

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