An optimized V-notched specimen is proposed for the determination of mode III, or torsional, critical distance. Numerical procedures are provided for the inverse determination of this length, and then for a statistical analysis of the resulting skew-normal distribution, as obtained from (symmetric) normal distributions of the plain and notched specimen strengths. An experimental example is shown on steel 42CrMo4 + QT, with clear evidence of a significantly larger mode III critical distance than mode I. A parametric analysis is then presented to evaluate the effects of size of the specimen on the standard deviation of the inverse search critical distance probability distribution.

建议使用优化的 V 型缺口试样来确定模式 III 或扭转临界距离。提供了用于反向确定该长度的数值程序，然后用于对产生的偏斜正态分布进行统计分析，如从平面和缺口试样强度的（对称）正态分布中获得的。在钢 42CrMo4 + QT 上显示了一个实验示例，有明显证据表明模式 III 临界距离比模式 I 大得多。然后提出参数分析以评估试样尺寸对逆搜索临界值标准偏差的影响距离概率分布。