English  |  正體中文  |  简体中文  |  全文筆數/總筆數 : 60879/93651 (65%)
造訪人次 : 1187467      線上人數 : 34
RC Version 7.0 © Powered By DSPACE, MIT. Enhanced by NTU Library & TKU Library IR team.
搜尋範圍 查詢小技巧:
  • 您可在西文檢索詞彙前後加上"雙引號",以獲取較精準的檢索結果
  • 若欲以作者姓名搜尋,建議至進階搜尋限定作者欄位,可獲得較完整資料
  • 進階搜尋
    請使用永久網址來引用或連結此文件: https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/45976

    題名: Transient dislocation emission from a crack tip
    作者: Yang, Wei;Tang, Jia-cai;Ing, Yi-shyong;Ma, Chien-ching
    貢獻者: 淡江大學航空太空工程學系
    關鍵詞: A. Dislocations;A. Crack tip;Dynamic fracture;Brittle-to-ductile transition;Rate effect
    日期: 2001-10
    上傳時間: 2013-03-20 16:23:18 (UTC+8)
    出版者: Kidlington: Pergamon
    摘要: Transient nature of dislocation emission from a crack tip gives a new twist to the study of brittle-to-ductile transition. In a class of materials, only the dislocations traveling at high speed may escape from the crack tip. The nucleation of a fast moving dislocation, however, requires a higher level of activation energy, as supported by many experimental data. The present paper explores this scenario under the restriction that the dislocation moves along the crack extension plane. Fundamental solutions of moving dislocations are derived, and which provide the drag forces on the dislocations and the shielding to the crack tip. Nucleation of a fast moving dislocation is examined under the Peierls–Nabarro theory. Incremental dislocation flux is created continuously from the crack tip, and moves away at a constant speed. At a judgmental time of dislocation emission, the displacement jump relates to the holding force along the crack extension plane by a periodic inter-planar potential, and the singular stress induced by the transient and rate-dependent displacement jump negates the original crack tip singularity. A dynamic overshoot calculation under quasi-steady assumption provides an escape velocity of dislocations. To achieve it, extra activation energy is required for the transient dislocation nucleation and that reduces the dislocation nucleation rate along the crack front. When compared with the rate-insensitive process of cleavage, the transient dislocation emission process allows us to predict the rate dependency of the brittle versus ductile behavior of materials.
    關聯: Journal of the Mechanics and Physics of Solids 49(10), pp.2431-2453
    DOI: 10.1016/S0022-5096(01)00046-1
    顯示於類別:[航空太空工程學系暨研究所] 期刊論文


    檔案 大小格式瀏覽次數



    DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library & TKU Library IR teams. Copyright ©   - 回饋