Fatigue Failure in Mechanical Engineering

Study Notes

Fatigue failure is a common cause of mechanical engineering failures worldwide, occurring in components subjected to time-varying loads.
Fatigue failure is a three-stage process involving crack formation, crack growth, and final fracture.
To predict fatigue failure, fatigue tests are conducted by subjecting components to stress cycles and plotting the results on an S-N curve.
Endurance limit is an important parameter in fatigue design, representing the stress range below which a component will not fail due to fatigue.
Differentiate between high cycle fatigue (more than 10,000 cycles) and low cycle fatigue (fewer cycles with elastic and plastic deformation).
S-N curves published in engineering codes are adjusted downwards to reduce the probability of failure.
Mean stress in fatigue testing can affect fatigue life, with tensile mean stress typically resulting in a shorter fatigue life.
Goodman diagram is used to adjust the endurance limit for mean stress effects to determine if a component will have an infinite life.
Rainflow counting method simplifies complex stress spectra into constant amplitude cycles, and Miner's rule calculates cumulative damage to assess fatigue failure.
Linear Elastic Fracture Mechanics approach is used to determine fatigue life in structures with existing cracks by calculating critical crack size and growth time.

Description

Learn about the three-stage process of fatigue failure involving crack formation, growth, and final fracture. Understand how fatigue tests and S-N curves help in predicting failure, and differentiate between high cycle and low cycle fatigue. Explore the impact of mean stress, Endurance limit, Goodman diagram, Rainflow counting, Miner's rule, and Linear Elastic Fracture Mechanics on fatigue life assessment.