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題 名 | 圍壓與幾何形狀對絕熱過程剪力帶之影響研究=A Study of the Adiabatic Shear Band Influenced by the Confined Pressure and the Geometric Configuration |
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作 者 | 李有豐; | 書刊名 | 臺北科技大學學報 |
卷 期 | 33:1 2000.03[民89.03] |
頁 次 | 頁25-49 |
分類號 | 440.35 |
關鍵詞 | 高應變率; 絕熱過程剪力帶; 圍壓; 幾何形狀; High strain rate; Adiabatic shear band; Confined pressure; |
語 文 | 中文(Chinese) |
中文摘要 | 本文介紹利用哈金生桿(Hopkinson Bar)實驗的技巧來描述延展性金屬在高應率 荷載下,溫度、應變率及應變與塑性應力流(Plastic Flow Stress)之間的關係,並且使用 了鉭-10%鎢合金材料來進行試驗;同時也採用Taylor等人所發展的PRONTO-2D[1,2]有限元素 程式來進行絕熱過程剪力帶之分析。其中程式所使用的材料組成律運算法則是由 Nemat-Nasser與李有豐[3,4]所發展出來的,這個方法之結果是無條件穩定而且精度相當 高,另外其計算之精度與時間增量(或應變增量)大小無關,因此此一材料組成律運算法應 用在分析延展性金屬之絕熱過程剪力帶是相當適合的。本文將透過上述之技巧來了解絕熱過 程之剪力帶發生原因與發生的機制,另外藉由改變試體的幾何形狀與控制邊界之圍壓來避免 在機械製造過程中或其它高應變率荷載下絕熱過程剪力帶之發生。 |
英文摘要 | Experimental techniques are described and illustrated for direct measurement of temperature, strain-rate, and strain effects on the flow stress of metals over a broad range of strains and strain rates. The tantalum-10% tungsten alloy is used in the experiment. The finite-element simulations are performed using PRONTO-2D [1, 2], in which an explicit constitutive algorithm is used. This algorithm, developed by Nemat-Nasser and Li [3, 4[, is always stable and accurate, independent of the time or strain increments. The constitutive model and the constitutive algorithm are used to simulate adiabatic shear bands produced in a hat-shaped specimen under controlled conditions. The simulation shows good correlation with experiments. Then, this work try to change the specimen configuration and confined pressure of the specimen to prevent the initiation of adiabatic shear bands under high strain rate loading or high speed machining. The main purpose of this paper is to establish the mechanisms of the initiation of adiabatic shear banding and to change the configurations of the specimen and the confined pressure so as to prevent the initiation of shear banding in mechanical processes. |
本系統中英文摘要資訊取自各篇刊載內容。