scholarly journals A Numerical Analysis of Selected Elastic-Plastic Fracture Parameters for DEN(T) Plates under Plane Strain Conditions

2017 ◽  
Vol 22 (1) ◽  
pp. 49-80 ◽  
Author(s):  
M. Graba
Keyword(s):  
Numerical Analysis ◽  
Fracture Mechanics ◽  
Plane Strain ◽  
Plastic Material ◽  
Crack Tip ◽  
Limit Load ◽  
Material Model ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Elastic Plastic

Abstract This paper provides a numerical analysis of selected parameters of fracture mechanics for double-edge notched specimens in tension, DEN(T), under plane strain conditions. The analysis was performed using the elastic-plastic material model. The study involved determining the stress distribution near the crack tip for both small and large deformations. The limit load solution was verified. The J-integral, the crack tip opening displacement, and the load line displacement were determined using the numerical method to propose the new hybrid solutions for calculating these parameters. The investigations also aimed to identify the influence of the plate geometry and the material characteristics on the parameters under consideration. This paper is a continuation of the author’s previous studies and simulations in the field of elastic-plastic fracture mechanics [4, 6, 16, 17, 31].

A Path Independent Integral and the Approximate Analysis of Strain Concentration by Notches and Cracks

1968 ◽  
Vol 35 (2) ◽  
pp. 379-386 ◽  
Author(s):  
J. R. Rice
Keyword(s):  
Plastic Material ◽  
Crack Tip ◽  
Plastic Zone Size ◽  
Crack Model ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Direct Evaluation ◽  
Strain Concentration ◽  
Hydrostatic Tension ◽  
Elastic Plastic

A line integral is exhibited which has the same value for all paths surrounding the tip of a notch in the two-dimensional strain field of an elastic or deformation-type elastic-plastic material. Appropriate integration path choices serve both to relate the integral to the near tip deformations and, in many cases, to permit its direct evaluation. This averaged measure of the near tip field leads to approximate solutions for several strain-concentration problems. Contained perfectly plastic deformation near a crack tip is analyzed for the plane-strain case with the aid of the slip-line theory. Near tip stresses are shown to be significantly elevated by hydrostatic tension, and a strain singularity results varying inversely with distance from the tip in centered fan regions above and below the tip. Approximate estimates are given for the strain intensity, plastic zone size, and crack tip opening displacement, and the important role of large geometry changes in crack blunting is noted. Another application leads to a general solution for crack tip separations in the Barenblatt-Dugdale crack model. A proof follows on the equivalence of the Griffith energy balance and cohesive force theories of elastic brittle fracture, and hardening behavior is included in a model for plane-stress yielding. A final application leads to approximate estimates of strain concentrations at smooth-ended notch tips in elastic and elastic-plastic materials.

The Inelastic Line-Spring: Estimates of Elastic-Plastic Fracture Mechanics Parameters for Surface-Cracked Plates and Shells

1981 ◽  
Vol 103 (3) ◽  
pp. 246-254 ◽  
Author(s):  
D. M. Parks
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Computing Time ◽  
Crack Tip ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Elastic Plastic ◽  
Plates And Shells ◽  
Crack Tip Opening

Recent studies of the mechanics of elastic-plastic and fully plastic crack growth suggest that such parameters as the J-integral and the crack tip opening displacement can, under certain conditions, be used to correlate the initiation and early increments of the ductile tearing mode of crack growth. To date, elastic-plastic fracture mechanics has been applied mainly to test specimen geometries, but there is a clear need for developing practical analysis capabilities in structures. In principle, three-dimensional elastic-plastic finite element analysis could be performed, but, in fact, such analyses would be prohibitively expensive for routine application. In the present work, the line-spring model of Rice and Levy [1-3] is extended to estimate the J-integral and crack tip opening displacement for some surface crack geometries in plates and shells. Good agreement with related solutions is obtained while using orders of magnitude less computing time.

scholarly journals Numerical Analysis of the Influence of In-Plane Constraints on the Crack Tip Opening Displacement for SEN(B) Specimens Under Predominantly Plane Strain Conditions

2016 ◽  
Vol 21 (4) ◽  
pp. 849-866 ◽  
Author(s):  
M. Graba
Keyword(s):  
Numerical Analysis ◽  
Plane Strain ◽  
Crack Tip ◽  
Strain Hardening Exponent ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
New Formula ◽  
Crack Tip Opening ◽  
The Relationship

Abstract This paper presents a numerical analysis of the relationship between in-plane constraints and the crack tip opening displacement (CTOD) for single-edge notched bend (SEN(B)) specimens under predominantly plane strain conditions. It provides details of the numerical model and discusses the influence of external load and in-plane constraints on the CTOD. The work also reviews methods for determining the CTOD. The new formula proposed in this paper can be used to estimate the value of the coefficient dn as a function of the relative crack length, the strain hardening exponent and the yield strength - dn(n, σ0/E, a/W), with these parameters affecting the level of in-plane constraints. Some of the numerical results were approximated using simple mathematical formulae.

Validation on the Relationship Between J Integral and CTOD for Offshore Structural Steel Weldments by Experimental and Numerical Analyses

2014 ◽  
Author(s):  
Dong Hyun Moon ◽  
Jeong Soo Lee ◽  
Jae Myung Lee ◽  
Myung Hyun Kim
Keyword(s):  
Plastic Deformation ◽  
Crack Tip ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Constraint Factor ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Plastic Constraint ◽  
The Relationship

Elastic plastic fracture mechanics (EPFM) is the domain of fracture analysis which considers extensive plastic deformation at crack tip prior to fracture. J integral and crack tip opening displacement (CTOD) have been commonly used as parameters for EPFM analysis. The relationship between these parameters has been extensively studied by industry and academia. The plastic constraint factor can serve as a parameter to characterize constraint effects in fracture involving plastic deformation. Therefore, the characteristics of plastic constraint factor are important in EPFM analysis. In this study, the relationship between J Integral and CTOD was investigated by conducting fracture toughness tests using single edge notched bend (SENB) specimens. Also, plastic constraint factor was investigated by using finite element analysis. Numerical analysis was carried out using ABAQUS elastic-plastic analysis mode.

Elastic-Plastic Finite Element Analysis of the Effect of the Compressive Loading on Fatigue Crack Tip Parameters

2008 ◽  
Vol 392-394 ◽  
pp. 980-984 ◽  
Author(s):  
Y. Sha ◽  
Hui Tang ◽  
Jia Zhen Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compressive Stress ◽  
Kinematic Hardening ◽  
Compressive Loading ◽  
Crack Tip ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Element Analysis ◽  
Elastic Plastic

In this paper, a detailed elastic-plastic finite element analysis of the effect of the compressive loading on crack tip plasticity is studied based on the material’s kinematic hardening model. Five centre-cracked panel specimens with different crack lengths are analyzed. The analysis shows that in a tension-compression loading the maximum spread of the crack tip reverse plastic zone increases with the increase of the compressive stress and the near crack tip opening displacement decreases with the increase of the compressive stress at the same nominal stress intensity factor. The applied compressive stress is the main factor controlling the near crack tip parameters.

Investigation on Constraint Effect of a Reactor Pressure Vessel Subjected to Pressurized Thermal Shocks

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Guian Qian ◽  
Markus Niffenegger
Keyword(s):  
Fracture Mechanics ◽  
Pressure Vessel ◽  
Plastic Material ◽  
Crack Tip ◽  
Constraint Effect ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Crack Tip Constraint ◽  
Reactor Pressure ◽  
Thermal Shocks

The integrity of a reactor pressure vessel (RPV) related to pressurized thermal shocks (PTSs) has been extensively studied. This paper introduces the method of using fracture mechanics for the integrity analysis of a RPV subjected to PTS transients. A 3-D finite element (FE) model is used to perform thermal and fracture mechanics analyses by considering both elastic and elastic–plastic material models. The results show that the linear elastic analysis leads to a more conservative result than the elastic–plastic analysis. The variation of the T-stress and Q-stress (crack tip constraint loss) of a surface crack in a RPV subjected to PTSs is studied. A shallow crack is assumed in the RPV and the corresponding constraint effect on fracture toughness of the material is quantified by the K–T method. The safety margin of the RPV is larger based on the K–T approach than based only on the K approach. The J–Q method with the modified boundary layer formulation (MBL) is used for the crack tip constraint analysis by considering elastic–plastic material properties. For all transient times, the real stress is lower than that calculated from small scale yielding (SSY) due to the loss of crack tip constraint.

scholarly journals Fracture mechanics by three-dimensional crack-tip synchrotron X-ray microscopy

2015 ◽  
Vol 373 (2036) ◽  
pp. 20130157 ◽  
Author(s):  
P. J. Withers
Keyword(s):  
Fracture Mechanics ◽  
Three Dimensional ◽  
Crack Tip ◽  
Quantitative Measure ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Face ◽  
X Ray

To better understand the relationship between the nucleation and growth of defects and the local stresses and phase changes that cause them, we need both imaging and stress mapping. Here, we explore how this can be achieved by bringing together synchrotron X-ray diffraction and tomographic imaging. Conventionally, these are undertaken on separate synchrotron beamlines; however, instruments capable of both imaging and diffraction are beginning to emerge, such as ID15 at the European Synchrotron Radiation Facility and JEEP at the Diamond Light Source. This review explores the concept of three-dimensional crack-tip X-ray microscopy, bringing them together to probe the crack-tip behaviour under realistic environmental and loading conditions and to extract quantitative fracture mechanics information about the local crack-tip environment. X-ray diffraction provides information about the crack-tip stress field, phase transformations, plastic zone and crack-face tractions and forces. Time-lapse CT, besides providing information about the three-dimensional nature of the crack and its local growth rate, can also provide information as to the activation of extrinsic toughening mechanisms such as crack deflection, crack-tip zone shielding, crack bridging and crack closure. It is shown how crack-tip microscopy allows a quantitative measure of the crack-tip driving force via the stress intensity factor or the crack-tip opening displacement. Finally, further opportunities for synchrotron X-ray microscopy are explored.

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