scholarly journals Measurement of J-integral using stress and strain fields near a crack tip - An application of the computer picture processing.

1988 ◽  
Vol 37 (419) ◽  
pp. 957-963
Author(s):  
Naoki SONEDA ◽  
Shinobu YOSHIMURA ◽  
Genki YAGAWA
Keyword(s):  
Crack Tip ◽  
Stress And Strain ◽  
J Integral ◽  
Picture Processing ◽  
Strain Fields ◽  
Computer Picture

Effect of Welded Mechanical Heterogeneity on Local Stress and Strain Ahead of Growing Crack Tips in the Piping Welds

2011 ◽  
Author(s):  
Lingyan Zhao ◽  
He Xue ◽  
Wei Tang ◽  
Xiurong Fang
Keyword(s):  
Crack Tip ◽  
Local Stress ◽  
Stress And Strain ◽  
Strain Fields ◽  
Mechanical Heterogeneity ◽  
Constant Loading ◽  
Primary Loop ◽  
Weld Joints ◽  
Growing Crack ◽  
Crack Tips

Primary loop recirculation (PLR) piping weld joints are more susceptible to stress corrosion cracking (SCC). But it is difficult to accurately predict SCC growth rate in PLR piping weld joints because the material and mechanical properties in weld joints are quite complicated. Especially, it is provided that hardening in the weld heat-affected zone (HAZ) might play an important role in promoting SCC growth. Considering welded mechanical heterogeneity, the local stress and plastic strain fields ahead of growing crack tip in 316L PLR piping weld joints are analyzed, the effect of constant stress intensity factor (KI) and constant loading on SCC behaviors of PLR piping weld joints is investigated in this study. The results show that the mechanical fields of SCC tips behave quite differently under constant KI and constant loading because of welded mechanical heterogeneity and advanced crack length, which demonstrate that the effect of constant loading on the stress and strain ahead of the growing crack tip is bigger than that of constant KI.

Analysis on Anti-Crack Mechanism of High Elastic Asphalt Stress Absorption Interlayer

2011 ◽  
Vol 287-290 ◽  
pp. 3-8
Author(s):  
Bin Yang ◽  
Qin Shou Huang ◽  
Ding Ming Yuan ◽  
Jin Hua Huang
Keyword(s):  
Strain Field ◽  
Thermal Load ◽  
Crack Tip ◽  
Element Model ◽  
Stress And Strain ◽  
J Integral ◽  
Comparison Analysis ◽  
Wheel Load ◽  
Asphalt Overlay ◽  
The Impact

Based on the fracture mechanics, a finite element model of plane strain is employed to make a comparison analysis on the stress and strain field of reflective crack tip under the impacts of wheel load and thermal load of two different kinds of asphalt overlay—one overlay is set with stress absorption interlayer and the other is not. Results show that, under the impact of wheel load, the most unfavorable load position of reflective crack tip is 15cm of load center line away from the crack tip level. Under the effect of wheel load and thermal load, the stress and strain field of reflective crack tip has been greatly improved after setting the stress absorption interlayer and the stress intensity factor K and J-integral decrease obviously, which show that stress absorption interlayer plays a good role in anti-crack.

An Analysis of the Roles of J and Q in the Assessment of Fracture for Quasi-Statically Extending Cracks in Residual Stress Fields

2009 ◽  
Author(s):  
David W. Beardsmore ◽  
J. K. Sharples ◽  
C. J. Madew ◽  
M. Jackson
Keyword(s):  
Residual Stress ◽  
Fracture Mechanics ◽  
Stress Field ◽  
Crack Tip ◽  
Stress And Strain ◽  
Stationary Crack ◽  
Proportional Loading ◽  
Strain Fields ◽  
Elastic Plastic ◽  
Crack Tip Fields

It is well known that the crack tip stress and strain fields for a crack in an elastic-plastic body depend on the crack tip contour integral J, the Q-stress, and the elastic-plastic properties of the material. This dependence is the fundamental basis of conventional two-parameter J-Q fracture mechanics assessments. It is normally assumed that the crack is created in an unstressed body, or else is inserted concurrently into an existing non-zero stress and strain field such that the crack tip fields build up monotonically and dominate at the crack tip. In such cases, the crack may be regarded as stationary and the J-Q procedure is valid provided that care is taken to calculate J and Q properly when initial stress and/or strains exist. When a crack is introduced progressively and quasi-statically into a component, the location of the crack tip will move along a distinct path. If the component contains residual stress and this is of a significant size along the crack tip path, a re-distribution of the residual stress will occur as the crack tip moves. Specifically, the stress field ahead of the crack tip will unload as the crack tip advances so that non-proportional loading will occur behind the advancing crack tip. In elastic-plastic materials, a wake of plasticity will usually be deposited in the material behind the moving or growing crack tip. Similar effects will also occur when a stationary crack extends due to critical or sub-critical processes. The presence of a plastic wake alters the stress and strain fields at the crack tip so that they do not generally match the fields of a stationary crack. Moreover, J and Q may not describe the stress and strain fields, invalidating the use of the fracture mechanics procedure for such cases. In this paper, a Finite Element analysis of J and Q is carried out for a quasi-statically extending crack inserted in a strip of elastic-plastic material containing an initial residual stress field. Care is taken to model the crack tip conditions appropriately as the crack extends and J is determined using the JEDI post-processing program which can allow for the effects of initial plastic strains and non-proportional loading. An assessment is made of the crack tip field and the likelihood of further extension or fracture is made using local approach models. The analysis considers both cleavage and ductile fracture. The extent of the relationship between J and Q and the crack tip fields is established and the validity of the J-Q procedure to such cases is discussed. The paper considers whether the procedure is conservative when J and Q are determined from an analysis of a stationary crack of the same size inserted into the same initial field.

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