A Counting Method for Fatigue Monitoring Based on Extreme Value Window

Abstract

The invention discloses a fatigue monitoring counting method based on an extreme value window, and relates to the field of the multiaxial fatigue strength theory. The counting object of a traditionalrain flow counting method is extended from the equivalent stress extreme point of a single time point to the extreme value window containing several time points. The traditional rain flow counting process considering the equivalent stress is changed into a three-dimensional rain flow counting process that simultaneously considers the six-direction stress data of the multiaxial variable amplitude load history. The invention proposes a new cycle amplitude determining method, a stress extreme point eliminating method, and a stress history rearrangement inspection method for the extreme value window and a formula thereof. The extreme value window is introduced to fully consider the phase difference between the stresses in a multiaxial stress state when calculating each cycle amplitude, so thatthe traditional rainflow counting method using equivalent stress synthesis is changed into a three-dimensional rainflow counting method that considers six-direction stress at the same time. Accordingto the fatigue monitoring counting method based on the extreme value window, the extreme value window is introduced, and the six-direction stress can be considered at the same time, so that the cyclecounting result of the multiaxial load history is more accurate and reliable.

Description

technical field [0001] The invention relates to the technical field of pressure pipeline multi-axis cycle counting, in particular to a fatigue monitoring and counting method based on an extreme value window. Background technique [0002] Multiaxial fatigue failure is a main failure mode of pressure pipelines. Because it bears complex multiaxial variable amplitude loads such as complex internal pressure and thermal stress, the classic uniaxial fatigue counting method does not take into account the potential relationship between multiaxial stresses. The phase difference cannot meet the counting requirements under multi-axis loads. In order to realize the accurate counting of fatigue cycles under multi-axial loads, and to be applicable to engineering practice conveniently and effectively, it is imperative to propose a new multi-axial counting method. [0003] Compared with uniaxial fatigue, although some progress has been made in the research of multiaxial fatigue, there are s...

AI Technical Summary

Problems solved by technology

Most of the existing multi-axis counting methods are relatively complicated and cannot be directly applied to actual engineering

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