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首页> 外文会议>NATO Advanced Research Workshop on Surface Waves in Anisotropic and Laminated Bodies and Defects Detection; 20011030-1102; Moscow(RU) >THE NON-UNIQUENESS OF CONSTANT VELOCITY CRACK PROPAGATION
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THE NON-UNIQUENESS OF CONSTANT VELOCITY CRACK PROPAGATION

机译：恒定速度裂纹扩展的非唯一性

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摘要

Experiments have shown that constant velocity appears in small scale yielding cases of approximate self-similar crack expansion. This fact contradicts theoretical evidence if the specific energy dissipation is assumed to be a velocity independent material constant. Moreover, the constant velocity obtained is not a material constant, but it depends on the remote load. Theoretical analyses of constant velocity propagation under steady state or self-similarity fail to produce a unique solution, because the introductory phase is not taken into account. Consideration of this phase can only be done with full knowledge of the material behaviour, in particular that of the process region. A material model like the cell model strongly indicates a non-continuum behaviour for low velocities, gradually developing into a continuum behaviour. For crack propagation in simple atomic lattices, atomistic molecular dynamics appears to work well, but so far only for extremely small crack lengths. A history dependence on the development of the process region during the introductory phase leading to constant velocity crack propagation is suggested by the cell model, but it is difficult to estimate how strong it is. It might be less strong in some materials than in others, and it might be less strong in the shearing modes than in the opening mode.
机译：实验表明，在近似自相似裂纹扩展的小规模屈服情况下，会出现恒定速度。如果假定比能量耗散是与速度无关的材料常数，则该事实与理论证据相矛盾。此外，获得的恒定速度不是材料常数，而是取决于远程负载。在稳态或自相似下恒速传播的理论分析无法产生唯一的解决方案，因为未考虑入门阶段。仅在充分了解材料性能（尤其是过程区域的性能）的情况下才能考虑此阶段。像细胞模型这样的材料模型强烈表明了低速的非连续性行为，逐渐发展为连续性行为。对于简单原子晶格中的裂纹扩展，原子分子动力学似乎工作良好，但到目前为止仅适用于极短的裂纹长度。单元模型提出了在引入阶段导致等速裂纹扩展的历史过程依赖于过程区域的发展，但是很难估计它的强度。它在某些材料中可能不如在其他材料中强，并且在剪切模式下可能不如在打开模式下强。

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