What is amplitude fatigue?
A constant amplitude fatigue loading (or constant amplitude loading) is a fatigue loading in which all the load cycles are identical. A load cycle is usually called either just a cycle or a fatigue cycle. The notation used is shown in Figure 3.1. A cycle is the smallest unit of the stress history which repeats exactly.
What is variable amplitude?
Variable amplitude fatigue analysis is based on the same concepts as constant amplitude fatigue analysis with the addition of cycle counting and damage summation. In a variable amplitude loading history, equivalent constant amplitude cycles must be identified.
How does stress amplitude affect fatigue?
With a variation in stress amplitude the fatigue life reduces as maximum stress increases, for a constant minimum stress of zero, as shown in Fig. 7. When the maximum stress is increased whilst constant stress amplitude is maintained, the service life increases despite an increase in maximum stress.
What is stress amplitude fatigue?
The stress amplitude at which failure occurs for a given number of cycles is the fatigue strength. N is the number of cycles required for a material to fail at a certain stress range in fatigue life. The stress range, ΔS = Smax–Smin, and number of cyclic loading are defined in Figure 12.2.
What is constant amplitude fatigue limit?
Constant-amplitude (CA) fatigue loading is defined as fatigue under cyclic loading with a constant amplitude and a constant mean load. The fatigue limit is a threshold value of the stress amplitude.
What is variable loading?
A variable load is a load that is applied over an area; that is, a surface. A variable load can be applied in any direction specified by a vector or can be applied normal to the surface. A function can be defined to control the magnitude of the load at different locations on the surface.
What is fatigue strength material?
Fatigue strength is the highest stress that a material can withstand for a given number of cycles without breaking. Fatigue strength is affected by environmental factors, such as corrosion. The maximum stress that can be applied for a certain number of cycles without fracture is the fatigue strength.
What is fatigue engineering?
Fatigue is defined as a process of progressive localized plastic deformation occurring in a material subjected to cyclic stresses and strains at high stress concentration locations that may culminate in cracks or complete fracture after a sufficient number of fluctuations.
What is variable stress?
The stresses which vary from a minimum value to a maximum value of the same nature (i.e. tensile or compressive) are called fluctuating stresses. When a material is subjected to repeated stresses, it fails at stresses below the yield point stresses. Such type of failure of a material is known as fatigue.
What is the effect of variable load?
The variable load on the plant increases the cost of the production of electrical energy. An alternator operates at maximum efficiency near its rated capacity. If a single alternator is used, it will have poor efficiency during periods of light loads on the plant.