Fatigue is defined as the effect of repeated application of stress to the material. Testing for fatigue is important because its development on the material is more insidious. Before a material actually breaks, it may have less obvious signs of damage such as deformations or cracks. While usually not visible to the naked eye, these localized effects of stress and fatigue can grow larger with time, which can lead to the eventual destruction of the material. Fatigue can be influenced by multiple factors, such as the size, shape, and design of the component, and the level of stress it experiences regularly.