Advanced Structural Analysis/Part I - Theory/Failure Modes/Fatigue/Crack Initiation/Loading/Load Spectra/Miner-Palmgren rule

From Wikibooks, open books for an open world
Jump to: navigation, search

Introduction[edit]

Load histories in real applications are often complex and irregular. The total fatigue effect of such loads can be estimated by the Miner-Palmgren rule, see the equation below. Fatigue failure is assumed to occur when the Miner-Palmgren equation is true.

D = \sum{\frac{n_i}{N_i}}

Where:
D= a constant, often ranging between 0.33 and 3
n_i= the number of occurrences of a specific load cycle progression, i
N_i= the fatigue life of a specific load cycle progression, i


Shortcomings of Miner's rule[edit]

The Miner-Palmgren rule is rather rough and neglects several important qualities of a general load history. Among these properties are the order and shape of the individual cycles.