How does fatigue failure occur?

What causes fatigue failure? Most fatigue failures are caused by cyclic loads significantly below the loads that would result in yielding of the material. The failure occurs due to the cyclic nature of the load which causes microscopic material imperfections (flaws) to grow into a macroscopic crack (initiation phase).

What is fatigue failure theory?

Fatigue failure is defined as the tendency of a material to fracture by means of progressive brittle cracking under repeated alternating or cyclic stresses of an intensity considerably below the normal strength.

What is cyclic loading in fatigue?

Cyclic loading is defined as the continuous and repeated application of a load (fluctuating stresses, strains, forces, tensions, etc.) on a material or on a structural component that causes degradation of the material and ultimately leads to fatigue.

What is low cycle fatigue and high cycle fatigue?

High cycle fatigue require more than 104 cycles to failure where stress is low and primarily elastic. Low cycle fatigue is characterized by repeated plastic deformation (i.e. in each cycle) and therefore, the number of cycles to failure is low.

What are the main types of cyclic loading that lead to fatigue?

The process of fatigue consists of three (3) stages: a) Initial fatigue damage loading to crack nucleation and crack initiation. b) Progressive cyclic growth of a crack (crack propagation) until the remaining uncracked cross-section of the part becomes too weak to sustain the loads imposed.

How can cyclic fatigue be prevented?

Premature fatigue failure is prevented by careful attention to detail at the design stage to ensure that cyclic stresses are sufficiently low to achieve the required endurance. Stress concentrations should be avoided where possible; a design with smooth ‘flowing’ lines is usually the optimum.

What is high cycle fatigue and low cycle fatigue?

What is the difference between high cycle fatigue and low cycle fatigue?

The difference between low cycle fatigue (LCF) and high cycle fatigue (HCF) has to do with the deformations. LCF is characterized by repeated plastic deformation (i.e. in each cycle), whereas HCF is characterized by elastic deformation.

When fatigue occurs above cycle it is called high cycle fatigue?

When the fatigue occurs above 103 cycles (usually 104 or more), it is usually called High-cycle fatigue. The material is subject to lower loads, usually less than 2/3 of the yield stress. The deformation is in elastic range.

What are the parameters of fatigue cycle?

The fatigue cycle has several important stress parameters that can affect the fatigue properties of materials, and these are: Maximum fatigue stress σmax. Mean (or steady-state) fatigue stress σm, which is the average of the maximum and minimum stress in the cycle: σm = ( σmax + σmin )/2.

What is fatigue and how does it occur?

Fatigue is the condition whereby a material cracks or fails because of repeated (cyclic) stresses applied below the ultimate strength of the material. Fatigue failure often occurs quite suddenly with catastrophic result.

What is meant by fully reversed fatigue loading?

Fully-reversed fatigue loading involves the material being loaded in tension (which is considered positive stress) and compression (negative stress) within a single cycle. The magnitude of the alternating stress σa is the same in tension and compression.

Can fatfatigue modeling predict the failure location of welded structures?

Fatigue modeling of the welded structure was performed using the parameters obtained from the fatigue modeling of the specimens. Finally, the fatigue life and the failure location predicted by the fatigue modeling showed a good agreement with those obtained from fatigue testing of the structure.