ISO 12135, which provides a fracture toughness test procedure, requires crack front straightness. In order to meet this requirement in weld specimens, Annex C to ISO 15653 provides a local compression (LC) technique. Although this technique has been used widely, some interested parties have reported that it often results in excessive underestimation of the critical CTOD. Following these previous studies, the authors reviewed the appropriate LC conditions and presented the typical effects of LC on fracture toughness and crack front straightness in this paper. In this regard, we conducted numerical analysis, sacrificial test, and fracture toughness test and investigated the LC effect on the crack front straightness and fracture toughness. In conclusion, a typical LC with an appropriate platen results in a straight crack front, but also has a large influence on fracture toughness, and it is difficult to solve this problem only by adjusting the amount of LC strain.

提供断裂韧性测试程序的ISO 12135要求裂纹的正面平直度。为了满足焊接试样中的这一要求，ISO 15653的附录C提供了局部压缩（LC）技术。尽管此技术已被广泛使用，但一些有关方面报告说，它经常导致对关键CTOD的过低估计。在进行了这些先前的研究之后，作者回顾了适当的液相色谱条件，并在本文中介绍了液相色谱对断裂韧性和裂纹前沿平直度的典型影响。在这方面，我们进行了数值分析，牺牲试验和断裂韧性试验，并研究了LC对裂纹前沿平直度和断裂韧性的影响。总而言之，典型的LC和合适的压板会导致笔直的裂纹前沿，