Explanation

fracture of materials under alternating stress is called fatigue, and fatigue strength M refers to the ability of materials to resist fatigue damage. It is one of the most important mechanical performance indicators to be considered in the design of components subjected to dynamic loads. fatigue limit or endurance limit is often used to characterize the fatigue strength of materials. fatigue limit refers to the maximum stress of materials without failure after infinite cycles under the action of alternating stress. It represents the fatigue strength of materials under infinite life. Some materials have low stress level. However, fatigue fracture will still occur, that is, there is no fatigue limit of infinite life. This often requires a predetermined number of cycles. The determination of the maximum alternating stress that reaches this cycle number without fracture is called the endurance limit or conditional fatigue limit of materials. There are many factors that affect the fatigue strength of materials, such as the composition of materials, inclusions, microstructure, white stress condition, sample size, machining accuracy and test methods, etc., which will have a significant impact on fatigue performance. Therefore, the experimental measured values are relatively scattered, and often take a variety of average. According to the stress state, loading mode, environmental medium, etc. of components, fatigue phenomenon can be roughly divided into high cycle fatigue, low cycle fatigue, thermal fatigue, corrosion fatigue, contact fatigue, etc. They have different fatigue behaviors and characteristics.

Classification