# Fatigue (Miner’s Rule)

## Description

In materials science fatigue occurs when a material is subjected to repeated loading and unloading. The failure of the material occurs when there are k groups of different stress magnitudes in a spectrum, Si (1 ≤n ≤ k), each of them contributing ni(Si) cycles, if Ni(Si) is the number of cycles to failure of a constant stress reversal Si. C is experimentally found to be between 0.7 and 2.2. Usually for design purposes, C is assumed to be 1.

Related formulas## Variables

k | Number of different stress groups (dimensionless) |

n | Spectrum of stress levels in each group (dimensionless) |

f_{n} | Number of cycles accumulated at stress Si (dimensionless) |

N_{n} | Number of cycles to failure of a constant stress reversal Si (dimensionless) |

C | Fraction of life consumed by exposure to the cycles at the different stress levels (dimensionless) |