Regularities of fatigue crack initiation and growth in two-phases titanium alloy after beach mark formation under VHCF regime

Procedia Structural Integrity Pub Date : 2025-01-01 DOI:10.1016/j.prostr.2025.06.081

Shanyavskiy A. , Nikitin A. , Nikitin I.

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Abstract

The paper introduces the results of fatigue crack growth (FCG) tests under high-frequency loading (20 kHz). The FCG tests are performed in stepwise decreasing of stress intensity factor (SIF) value. The morphology of the obtained fracture surfaces is investigated by scanning electron microscopy (SEM). The study is focused on the analysis of local areas located just ahead from crack tip (beach marks). These marks are reflecting the forced stop of the cyclic loading during the FCG test for correction the stress intensity factor value. Results of SEM observations shows the fatigue crack ‘re-initiation’ just ahead of these beach marks in the bulk of material after the start of new cyclic loading. This new crack nucleation takes place from the boundary junction of neighboring alpha-phase or cleaved single alpha-phase. The discovered mechanism of fatigue crack growth was implemented in the mathematical model. The numerical simulation of crack front shape under high-frequency loading shows a suitable agreement between the prediction and experimental results.

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VHCF条件下两相钛合金滩痕形成后疲劳裂纹萌生与扩展规律

本文介绍了高频载荷（20khz）下疲劳裂纹扩展（FCG）试验结果。FCG试验采用应力强度因子（SIF）值逐步减小的方法进行。用扫描电子显微镜（SEM）研究了所得断口的形貌。这项研究的重点是对裂缝尖端（海滩痕迹）前方的局部区域进行分析。这些标记反映了在FCG试验期间循环加载的强制停止，以校正应力强度因子值。扫描电镜观察结果表明，在新循环加载开始后，在这些海滩标记之前的大块材料中，疲劳裂纹“重新开始”。这种新的裂纹形核发生在相邻α相或被劈裂的单个α相的边界交界处。将发现的疲劳裂纹扩展机理用数学模型实现。对高频载荷作用下裂纹前缘形状的数值模拟表明，预测结果与实验结果吻合较好。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Procedia Structural Integrity

CiteScore

1.70

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0.00%

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