Mixed mode I/II crack propagation in stainless steel 316L sheets by large plastic deformations: Prediction of critical load by combining LEFM with fictitious material concept

2021 ◽  
Vol 247 ◽  
pp. 107657
Author(s):  
A.R. Torabi ◽  
H. Sadeghian ◽  
M.R. Ayatollahi
Keyword(s):  
Stainless Steel ◽  
Crack Propagation ◽  
Critical Load ◽  
Mixed Mode ◽  
Mode I ◽  
Stainless Steel 316L ◽  
Plastic Deformations ◽  
Large Plastic Deformations ◽  
Material Concept

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.

Elastic–plastic damage prediction in notched epoxy resin specimens under mixed mode I/II loading using two virtual linear elastic failure criteria

2020 ◽  
Vol 29 (7) ◽  
pp. 1100-1116
Author(s):  
AS Rahimi ◽  
MR Ayatollahi ◽  
AR Torabi
Keyword(s):  
Mixed Mode ◽  
Mode I ◽  
Equivalent Material ◽  
Mean Stress ◽  
Stress Criterion ◽  
Elastic Plastic ◽  
Notched Specimens ◽  
Plastic Damage ◽  
Equivalent Material Concept ◽  
Material Concept

Elastic–plastic damage of a ductile epoxy resin is investigated for the first time in the configuration of semicircular bend specimen weakened by U-shaped notches under mixed mode I/II loading conditions. U-notched specimens are prepared from the characterized epoxy material with different notch rotation angles and notch tip radii. Load-carrying capacities of the U-notched specimens are experimentally obtained by performing fracture tests under various combinations of mode I and mode II loading. The reformulated Equivalent Material Concept is employed for the polymeric material in conjunction with the maximum tangential stress and mean stress criteria to provide the theoretical predictions without any necessity for elastic–plastic analyses of their damage. Scanning electron microscopy micrographs are also taken from the fracture surfaces and utilized for realizing the micromechanical processes of damage in the tested specimens. A very good consistency is found between the experimental results and the predictions of the combined Equivalent Material Concept-maximum tangential stress criterion, as well as those of the Equivalent Material Concept-mean stress criterion.

Numerical Investigation on Mixed Mode (I-II) Fracture Propagation of CCBD Specimens Under Confining Pressure

2021 ◽  
pp. 2050111
Author(s):  
Jiuzhou Huang ◽  
Jianxiong Li ◽  
Xin Pan ◽  
Tianzhou Xie ◽  
Wen Hua ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Numerical Method ◽  
Mixed Mode ◽  
Early Stage ◽  
Relative Length ◽  
Confining Pressure ◽  
Secondary Development ◽  
Weight Functions ◽  
Mode I ◽  
Initiation And Propagation

A new numerical method, verified by the analytical solution of the weight functions and experimental paths, is developed to evaluate the crack initiation and propagation generally in mixed mode (I-II). This numerical method combining the interaction integral method and the maximum tangential stress (MTS) criterion is based on the finite element method of secondary development. The influence of combined confining pressure and diametric forces on crack propagation trajectories for CCBD specimens are studied. It is indicated that the crack propagation direction independent of the confining pressure keeps the same with the line of original crack as the loading angle is equal to [Formula: see text]. But when the loading angle is greater than [Formula: see text], the curvature of the curve trajectory in the early stage of crack propagation increases with a larger confining pressure. Further, it is found that larger values of the loading angle and relative length will make the effect of confining pressure more significant at the early stage of crack growth.

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