In practical design, the question of existence or non-existence of fatigue limit seems little more than an irrelevant academic discussion. Nevertheless, the answer affects many aspects of the fracture mechanics, such as, the calculation of damage accumulation; recognition of the multiplicity of fatigue mechanisms (and consequently, the multiplicity of S–N fields); interpretation of non-propagating cracks; and repercussion on the Kitagawa-Takahashi diagram. Various prestigious scientists deny the existence of a fatigue limit based on the results of failures in very high cycle fatigue (VHCF) regime, far below the high cycle fatigue (HCF) limit. However, the asymptotic extrapolation of the experimental results beyond the scope of testing with S–N models, cannot confirm or deny this hypothesis if those models do not fulfil indispensable physical and statistical requirements. Some phenomenological models based on solid statistical conditions (stability, limit conditions and compatibility), ensure the necessary existence of an asymptotic fatigue limit for each of the possible failure mechanisms. This may or may not be zero according to the experimental results but only the presence of an asymptotic fatigue limit can avoid the absurdity of fatigue failure under zero load value.

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关于疲劳极限存在与否的考虑：对实际设计的影响

在实际设计中，疲劳极限存在与否的问题似乎只是一个无关紧要的学术讨论。然而，答案会影响断裂力学的许多方面，例如损伤累积的计算；认识到疲劳机制的多样性（因此，S-N 场的多样性）；非扩展裂纹的解释；以及对北川-高桥图的影响。根据远低于高周疲劳 (HCF) 极限的甚高周疲劳 (VHCF) 状态下的失效结果，许多著名科学家否认存在疲劳极限。然而，实验结果的渐近外推超出了 S-N 模型的测试范围，如果这些模型不满足必不可少的物理和统计要求，则无法证实或否认这一假设。一些基于固体统计条件（稳定性、极限条件和兼容性）的现象学模型确保每个可能的失效机制都必须存在渐近疲劳极限。根据实验结果，这可能为零也可能不为零，但只有渐近疲劳极限的存在才能避免零载荷值下疲劳失效的荒谬性。