Verification of Linear Dependence of Plastic Zone Size on J-Integral for Mixed-Mode Loading

2015 ◽  
Vol 751 ◽  
pp. 15-20 ◽  
Author(s):  
Stanislav Žák ◽  
Jana Horníková ◽  
Pavel Šandera ◽  
Jaroslav Pokluda
Keyword(s):  
Plastic Zone ◽  
Crack Growth ◽  
Mixed Mode ◽  
Plastic Zone Size ◽  
Small Scale ◽  
Shear Mode ◽  
Mode Ii ◽  
Zone Size ◽  
Shear Cracks ◽  
Loading Modes

Determination of fatigue crack growth characteristics under shear-mode loading is a rather complicated problem. To increase an efficiency and precision of such testing, special specimens enabling simultaneous propagation of shear cracks under II, III and II+III loading modes started to be used rather recently. However, a description of crack growth rate in terms of appropriate fracture mechanics quantities demands a precise assessment of plastic zone size under various shear-mode loading levels. This contribution is focused on the numerical elasto-plastic analysis of stress-strain field at the crack tip in specimens made of a pure polycrystalline (ARMCO) iron loaded by mixed mode II+III. The dependence of plastic zone size on theJ-integral value described the wide region of loading. The results reveal that formixed mode II+III the small scale yielding conditions are fulfilled in the region where plastic zone size is smaller than 1/10 of the total crack length.

Specimens for Simultaneous Mode II, III and II+III Fatigue Crack Propagation: Elasto-Plastic Solution of Crack Tip Stress-Strain Field

2014 ◽  
Vol 891-892 ◽  
pp. 1585-1590 ◽  
Author(s):  
Jana Horníková ◽  
Pavel Šandera ◽  
Stanislav Žák ◽  
Jaroslav Pokluda
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Strain Field ◽  
Simple Procedure ◽  
Crack Tip ◽  
Small Scale ◽  
Shear Mode ◽  
Mode Ii ◽  
Threshold Region ◽  
Stress Strain

Determination of fatigue crack growth characteristics under shear-mode loading is a rather complicated problem. To increase an efficiency and precision of such testing, special specimens enabling simultaneous propagation of shear cracks under II, III and II+III loading modes started to be used rather recently. K-calibration of these specimens was performed and, after unique pre-crack and heat-treatment procedures, effective thresholds in several metallic materials could be measured. However, a description of crack growth rate in terms of appropriate fracture mechanics quantities demands a precise assessment of plastic zone size under various shear-mode loading levels. This contribution is focused on the numerical elasto-plastic analysis of stress-strain field at the crack tip in specimens made of a pure polycrystalline (ARMCO) iron. The results reveal that the small scale yielding conditions are fulfilled in the near-threshold region. Starting from ΔK values approximately two times higher than the threshold, however, the ΔKJ or ΔJ approach should already be utilized. Probably the most interesting result of the analysis lies in a simple procedure that enables us to separate individual loading components ΔKJ,II and ΔKJ,III, applied in the mixed-mode II+III part of the specimen, by comparing elasto-plastic and elastic solutions.

A Better Estimation of Plastic Zone Size at the Crack Tip Beyond Irwin's Model

2013 ◽  
Vol 80 (5) ◽  
Author(s):  
Y. J. Jia ◽  
M. X. Shi ◽  
Y. Zhao ◽  
B. Liu
Keyword(s):  
Plastic Zone ◽  
Crack Tip ◽  
Plastic Zone Size ◽  
Quantitative Relation ◽  
Small Scale ◽  
Crack Plane ◽  
Zone Size ◽  
Small Scale Yielding ◽  
Scale Yielding ◽  
Remote Stress

Irwin's model on plastic zone at the crack tip is discussed in many fracture mechanics textbooks. However, we found in Irwin's model that the internal resultant force on the crack plane and the one applied in remote field are not strictly balanced. This imbalance leads to the error in the scenario of small scale yielding, and an improper finite plastic zone size (PZS) is predicted when the remote stress approaches the yielding strength. In this paper, an improved model is developed through surrendering some main assumptions used in Irwin's model and an infinite PZS is then predicted as the remote stress goes up close to yielding strength, which implies that this estimation can be applied to situations with large scale yielding. In small scale yielding cases, the new estimation of PZS agrees well with finite element simulation results. In addition, a more accurate quantitative relation between the PZS and the effective stress intensity factor is derived, which might help characterize fracture behaviors in engineering applications.

scholarly journals A Methodology to Determine the Effective Plastic Zone Size Around Blunt V-Notches under Mixed Mode I/II Loading and Plane-Stress Conditions

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1042
Author(s):  
Ali Reza Torabi ◽  
Behnam Shahbazian ◽  
Mirmilad Mirsayar ◽  
Sergio Cicero
Keyword(s):  
Plastic Zone ◽  
Plane Stress ◽  
Mixed Mode ◽  
Ductile Failure ◽  
Plastic Zone Size ◽  
Stress Conditions ◽  
Mode I ◽  
Zone Size ◽  
Elastic Plastic

The determination of the ductile failure behavior in engineering components weakened by cracks and notches is greatly dependent on the estimation of the plastic zone size (PZS) and, particularly, the effective plastic zone size (EPZS). Usually, time-consuming complex elastic–plastic analyses are required for the determination of the EPZS. Such demanding procedures can be avoided by employing analytical methods and by taking advantage of linear elastic analyses. In this sense, this work proposed a methodology for determining the PZS around the tip of blunt V-notches subjected to mixed mode I/II loading and plane-stress conditions. With this aim, firstly, existing approximate mathematical expressions for the elastic stress field near round-tip V-notches reported in the literature are presented. Next, Irwin’s approach (fundamentally proposed for sharp cracks) and a yield criterion (von Mises or Tresca) were applied and are presented. With the aim of verifying the proposed methodology, elastic–plastic finite element analyses were performed on virtual AISI 304 steel V-notched specimens. It was shown that the analytical formulations presented cannot estimate the complete shape of the plastic zone. However, the EPZS, which is crucial for predicting the type of ductile failure in notched members, can be successfully estimated.

Effect of Microcrack on Plastic Zone Size ahead of Main Crack in Small-scale Plasticity

2010 ◽  
pp. 237-244
Author(s):  
B. Bachir Bouiadjra ◽  
M. Benguediab ◽  
M. El Meguenni ◽  
M. Belhouari ◽  
B. Serier ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Main Crack ◽  
Plastic Zone Size ◽  
Small Scale ◽  
Zone Size
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