Fatigue crack propagation modes: plastic deformation mode and damage accumulation mode

2020 ◽  
Vol 222 (1-2) ◽  
pp. 111-122
Author(s):  
Shigeru Hamada ◽  
Kejin Zhang ◽  
Motomichi Koyama ◽  
Masaharu Ueda ◽  
Hiroshi Noguchi
Keyword(s):  
Plastic Deformation ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Damage Accumulation ◽  
Deformation Mode ◽  
Accumulation Mode

Pre-Strain Effects on Mixed-Mode Fatigue Crack Propagation Behaviour of the P355NL1 Pressure Vessels Steel

2018 ◽  
Author(s):  
João Ferreira ◽  
José A. F. O. Correia ◽  
Grzegorz Lesiuk ◽  
Sergio Blasón González ◽  
Maria Cristina R. Gonzalez ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Mixed Mode ◽  
Pressure Vessels ◽  
Mode I ◽  
Pure Mode

Pressure vessels and piping are commonly subjected to plastic deformation during manufacturing or installation. This pre-deformation history, usually called pre-strain, may have a significant influence on the resistance against fatigue crack growth of the material. Several studies have been performed to investigate the pre-strain effects on the pure mode I fatigue crack propagation, but less on mixed-mode (I+II) fatigue crack propagation conditions. The present study aims at investigating the effect of tensile plastic pre-strain on fatigue crack growth behavior (da/dN vs. ΔK) of the P355NL1 pressure vessel steel. For that purpose, fatigue crack propagation tests were conducted on specimens with two distinct degrees of pre-strain: 0% and 6%, under mixed mode (I+II) conditions using CTS specimens. Moreover, for comparison purposes, CT specimens were tested under pure mode I conditions for pre-strains of 0% and 3%. Contrary to the majority of previous studies, that applied plastic deformation directly on the machined specimen, in this work the pre-straining operation was carried out prior to the machining of the specimens with the objective to minimize residual stress effects and distortions. Results revealed that, for the P355NL1 steel, the tensile pre-strain increased fatigue crack initiation angle and reduced fatigue crack growth rates in the Paris region for mixed mode conditions. The pre-straining procedure had a clear impact on the Paris law constants, increasing the coefficient and decreasing the exponent. In the low ΔK region, results indicate that pre-strain causes a decrease in ΔKth.

Fractals and Catastrophe Analysis of Fatigue Crack Propagation for Sample by Plastic Deformation

2011 ◽  
Vol 399-401 ◽  
pp. 2169-2172
Author(s):  
Yu Xin Yao
Keyword(s):  
Plastic Deformation ◽  
Fractal Dimension ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Cycle ◽  
Fractal Characteristics ◽  
Stress Cycles ◽  
The Law

Fractals and catastrophe analysis are applied to analyze photos of the law of crack of three sets of fatigue samples under different stress cycles. The results indicate that the law of crack has fractal characteristics. For undestroyed samples, the law of crack appears and develops, and the fractal dimension tends to be constant eventually. For destroyed samples, fractal dimension development is divided into four stages, that is, increasing gradually, increasing stably, decreasing stably and decreasing rapidly to the approximate value of one. When rupture occurs, the catastrophe point is the corresponding number of stress cycle.

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