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<p>This study investigates the surface effects on the operation of double-ended dislocation sources in single-crystal micropillars under compression. A comprehensive theoretical framework is formulated to derive the stress field of the source segment and the corresponding Peach-Koehler (PK) forces acting on this segment near the free surfaces. An analytical formulation is then developed to compare the source strength with and without the influence of the surface stress. The results reveal that the surface effects on the dislocation source strength are highly sensitive to the interplay between the source length and its distance from the free surface. These surface effects can either enhance or reduce the critical stress required for the source operation by up to 50%, leading to significant fluctuations in yield strength, as commonly observed in discrete dislocation dynamics simulations and experimental studies. These findings provide different interpretations for the size-dependent and stochastic yield stress behavior in face-centered cubic (FCC) micropillars.</p>

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Surface effects on double-ended dislocation sources in single-crystal micropillars: implications for size-dependent and stochastic yield strength

  • 期刊论文

  • 发表日期：

    2025年6月2日

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  • Xu Zhang,
  • Dayang Deng,
  • M. Ye,
  • T. Sumigawa,
  • H. R. Ma,
  • Xuewei Huang

摘要

This study investigates the surface effects on the operation of double-ended dislocation sources in single-crystal micropillars under compression. A comprehensive theoretical framework is formulated to derive the stress field of the source segment and the corresponding Peach-Koehler (PK) forces acting on this segment near the free surfaces. An analytical formulation is then developed to compare the source strength with and without the influence of the surface stress. The results reveal that the surface effects on the dislocation source strength are highly sensitive to the interplay between the source length and its distance from the free surface. These surface effects can either enhance or reduce the critical stress required for the source operation by up to 50%, leading to significant fluctuations in yield strength, as commonly observed in discrete dislocation dynamics simulations and experimental studies. These findings provide different interpretations for the size-dependent and stochastic yield stress behavior in face-centered cubic (FCC) micropillars.