A prior study [1] benchmarks a relatively new axisymmetric Flat Bottom Hole (FBH) specimen concept for use in crack growth threshold testing, with reduced crack initiation loads achieved by applying by an electrical pulse around the notch tip prior to testing.

In this study, an improved electrothermal pulsing technology is used with higher current capability, and more precisely timed pulses. Electrical pulses were applied at high amplitude to initiate the crack at further reduced loads, and also at a lower amplitude to locally heat tint the crack tip during the test to leave visible marks on the fracture surface for post-test evaluation. For specimen, one of the marks was applied at near-threshold conditions before the completion of the threshold test to evaluate whether the marking method introduces artifact into the results. A small, but quantifiable artifact was observed immediately following marking at near threshold conditions, vanishing after 0.001-0.003 in. of crack growth. Test results include data for Ti 6-4 forging and Inconel 718 forging.

先前的研究[1]对用于裂纹扩展阈值测试的相对较新的轴对称平底孔（FBH）试样概念进行了基准测试，通过在测试之前在缺口尖端周围施加电脉冲来实现降低的裂纹萌生载荷。

在这项研究中，使用了一种改进的电热脉冲技术，该技术具有更高的电流容量和更精确的定时脉冲。在测试过程中，以高振幅施加电脉冲以在进一步减小的载荷下引发裂纹，并以较低振幅施加电脉冲以局部加热着色尖端，从而在断裂表面上留下可见的痕迹，以进行测试后评估。对于标本，在完成阈值测试之前，在接近阈值的条件下施加一个标记，以评估标记方法是否将假象引入结果中。在接近阈值条件下进行标记后立即观察到一个小的但可量化的伪影，在0.001-0.003英寸的裂纹扩展后消失。测试结果包括Ti 6-4锻件和Inconel 718锻件的数据。