ISO 12108旨在提供产生疲劳裂纹扩展速率数据的规范。试验结果用疲劳裂纹扩展速率表示，作为线弹性断裂力学理论定义的裂纹尖端应力强度因子范围的函数。 本国际标准描述了对预裂纹缺口试样施加循环力的方法。裂纹长度是根据经过的力循环次数测量的。根据收集的裂纹长度和相应的力循环关系，确定疲劳裂纹扩展速率，并将其表示为应力强度因子范围的函数。 ISO 12018描述了当最大应力强度因子接近受控不稳定性时，确定从阈值应力强度因子范围到不稳定裂纹扩展开始的疲劳裂纹扩展速率的试验。它主要用于评估以线弹性应力为主的各向同性金属材料，且仅在垂直于裂纹平面（模式I应力条件）的情况下施加力，且应力比恒定。

ISO 12108 is intended to provide specifications for generation of fatigue crack growth rate data. Test results are expressed in terms of the fatigue crack growth rate as a function of crack-tip stress intensity factor range as defined by the theory of linear elastic fracture mechanics. This International Standard describes a method of subjecting a precracked notched specimen to a cyclic force. The crack length is measured as a function of the number of elapsed force cycles. From the collected crack length and corresponding force cycles relationship the fatigue crack growth rate is determined and is expressed as a function of stress intensity factor range. ISO 12018 describes tests for determining the fatigue crack growth rate from the threshold stress-intensity factor range to the onset of unstable crack extension as the maximum stress intensity factor approaches controlled instability. It is primarily intended for use in evaluating isotropic metallic materials under predominantly linear-elastic stress conditions and with force applied only perpendicular to the crack plane (mode I stress condition), and with a constant stress ratio.