In the present paper, the very‐high‐cycle fatigue (VHCF) response of a structural adhesive used for automotive applications, Betaforce 4600G modified with microspheres, has been experimentally assessed. Ultrasonic fully reversed tension–compression tests up to 10⁹ cycles have been carried out with the testing machine developed by the authors on adhesives without macroscopic defects and on adhesives with artificial defects, inserted during the butt‐joint preparation. Fracture surfaces have been observed with the optical microscope and the P‐S‐N curves estimated. Experimental results have shown that defect location significantly affects the VHCF strength and fracture surfaces exhibit a peculiar morphology with three distinct characteristic regions.

中文翻译：

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结构环氧胶粘剂的疲劳响应高达109个循环

在本文中，已经通过实验评估了用于汽车应用的结构胶（用微球改性的Betaforce 4600G）的超高周疲劳（VHCF）响应。作者开发的测试机对对接准备过程中插入的无宏观缺陷的胶粘剂和具有人为缺陷的胶粘剂进行了超声波完全反向拉伸-压缩测试，最多进行了10 ⁹个循环。用光学显微镜观察了断裂表面并估计了P-S-N曲线。实验结果表明，缺陷位置会显着影响VHCF强度，并且断裂表面表现出具有三个不同特征区域的特殊形态。