The Configurational Force Concept in Elastic-Plastic Fracture Mechanics−Instructive Examples

2009 ◽  
Vol 417-418 ◽  
pp. 297-300 ◽  
Author(s):  
R. Schöngrundner ◽  
Otmar Kolednik ◽  
Franz Dieter Fischer
Keyword(s):  
Driving Force ◽  
Plastic Material ◽  
Shielding Effect ◽  
Integral Approach ◽  
J Integral ◽  
Configurational Force ◽  
Crack Driving Force ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Elastic Plastic Materials

This paper deals with the determination of the crack driving force in elastic-plastic materials and its correlation with the J-Integral approach. In a real elastic-plastic material, the conventional J-integral cannot describe the crack driving force. This problem has been solved in Simha et al. [1], where the configurational force approach was used to evaluate in a new way the J-integral under incremental plasticity conditions. The crack driving force in a homogeneous elastic-plastic material, Jtip, is given by the sum of the nominally applied far-field crack driving force, Jfar, and the plasticity influence term, Cp, which accounts for the shielding or anti-shielding effect of plasticity. In this study, the incremental plasticity J-integral and the crack driving force are considered for a stationary and a growing crack.

J-integral and crack driving force in elastic–plastic materials

2008 ◽  
Vol 56 (9) ◽  
pp. 2876-2895 ◽  
Author(s):  
N SIMHA ◽  
F FISCHER ◽  
G SHAN ◽  
C CHEN ◽  
O KOLEDNIK
Keyword(s):  
Driving Force ◽  
J Integral ◽  
Crack Driving Force ◽  
Elastic Plastic ◽  
Plastic Materials ◽  
Elastic Plastic Materials

On Determining Elastic Modulus from Instrumented Indentation

2013 ◽  
Vol 668 ◽  
pp. 616-620
Author(s):  
Shuai Huang ◽  
Huang Yuan
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Plastic Material ◽  
Instrumented Indentation ◽  
Computational Simulations ◽  
Elastic Plastic ◽  
Modified Method ◽  
Plastic Materials ◽  
Elastic Plastic Material ◽  
Elastic Plastic Materials

Computational simulations of indentations in elastic-plastic materials showed overestimate in determining elastic modulus using the Oliver & Pharr’s method. Deviations significantly increase with decreasing material hardening. Based on extensive finite element computations the correlation between elastic-plastic material property and indentation has been carried out. A modified method was introduced for estimating elastic modulus from dimensional analysis associated with indentation data. Experimental verifications confirm that the new method produces more accurate prediction of elastic modulus than the Oliver & Pharr’s method.

A Note on the Path-Dependence of the J-Integral Near a Stationary Crack in an Elastic-Plastic Material With Finite Deformation

2012 ◽  
Vol 79 (4) ◽  
Author(s):  
Dorinamaria Carka ◽  
Robert M. McMeeking ◽  
Chad M. Landis
Keyword(s):  
Finite Deformation ◽  
Path Dependence ◽  
Plastic Material ◽  
Crack Tip ◽  
J Integral ◽  
Stationary Crack ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Elastic Plastic Material ◽  
Elastic Perfectly Plastic

In this technical brief, we compute the J-integral near a crack-tip in an elastic-perfectly-plastic material. Finite deformation is accounted for, and the apparent discrepancies between the prior results of the authors are resolved.

Assessment of Fully Plastic J and C*-Integral Solutions for Application to Elastic-Plastic Fracture and Creep Crack Growth

1993 ◽  
Vol 115 (3) ◽  
pp. 228-234 ◽  
Author(s):  
D. R. Lee ◽  
J. M. Bloom
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Driving Force ◽  
Creep Crack Growth ◽  
J Integral ◽  
Finite Element Program ◽  
Hardening Material ◽  
Crack Driving Force ◽  
Elastic Plastic ◽  
Creep Crack

A critical part of the assessment of defects in power plant components, both fossil and nuclear, is the knowledge of the crack driving force (K1, J, or C*). While the determination of the crack driving force is possible using finite element analyses, crack growth analyses using finite element methods can be expensive. Based on work by Il’yushin, it has been shown that for a power law hardening material, the fully plastic portion of the J-integral (or the C*-integral) is directly related to an h1 calibration function. The value of h1 is a function of the geometry and hardening exponent. The finite element program ABAQUS was used to evaluate the fully plastic J-integral and determine the h1 functions for various geometries. The Ramberg-Osgood deformation theory plasticity model, which may be used with the J-integral evaluation capability, allows the evaluation of fully plastic J solutions. Once it was established that the grid used to generate the h1 functions was adequate (based on the more recent work of Shih and Goan), additional runs were made of other configurations given in the EPRI Elastic-Plastic Fracture Handbook. Differences as great as 55 percent were found when compared to results given in the Handbook (single-edge crack plate under tension and plane stress with a/b = 0.5). Effects of errors in h1 on predicted failure load and creep crack growth are discussed.

Kinetics of Diffusional Phase Transformation in Multicomponent Elastic-Plastic Materials

2003 ◽  
Vol 125 (3) ◽  
pp. 266-276 ◽  
Author(s):  
F. D. Fischer ◽  
N. K. Simha ◽  
J. Svoboda
Keyword(s):  
Driving Force ◽  
Chemical Potential ◽  
Volume Fraction ◽  
Plastic Material ◽  
Atomic Diffusion ◽  
Elastic Plastic ◽  
Plastic Materials ◽  
Elastic Plastic Materials ◽  
Kinetics Of ◽  
Diffusional Transformation

The goal of this paper is to derive a micromechanics framework to study the kinetics of transformation due to interface migration in elastic-plastic materials. Both coherent and incoherent interfaces as well as interstitial and substitutional atomic diffusion are considered, and diffusional transformations are contrasted with martensitic ones. Assuming the same dissipation for the rearrangement of all substitutional components and no dissipation due to diffusion in an interface in the case of a multicomponent diffusional transformation, we show that the chemical driving force of the interface motion is represented by the jump in the chemical potential of the lattice forming constituent. Next, the mechanical driving force is shown to have the same form for both coherent and frictionless (sliding) interfaces in an elastic-plastic material. Using micromechanics arguments we show that the dissipation and consequently the average mechanical driving force at the interface due to transformation in a microregion can be estimated in terms of the bulk fields. By combining the chemical and mechanical parts, we obtain the kinetic equation for the volume fraction of the transformed phase due to a multicomponent diffusional transformation. Finally, the communication between individual microregions and the macroscale is expressed by proper parameters and initial as well as boundary conditions. This concept can be implemented into standard frameworks of computational mechanics.

A Unified Fatigue Life Calculation Model for Notched Components Based on Elastic-Plastic Fracture Mechanics

2007 ◽  
Vol 348-349 ◽  
pp. 525-528 ◽  
Author(s):  
G. Savaidis ◽  
A. Savaidis ◽  
O. Hertel ◽  
M. Vormwald
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Driving Force ◽  
Calculation Model ◽  
J Integral ◽  
Initial Model ◽  
Crack Driving Force ◽  
Elastic Plastic ◽  
Notched Specimens ◽  
Notched Components

Based on Dankert’s et al. [1] initial model for the elastic-plastic evaluation of fatigue crack growth in sheets providing elliptical notches, a generalized procedure enabling an improved evaluation of the effective ranges of the crack driving force (i.e. the J-Integral) as well as the application to arbitrary notched components has been developed [2]. The present paper presents the basic topics of the calculation model as well as its verification using experimental results from notched specimens with various notch shapes subjected to cyclic loading with various load ratios.

scholarly journals Configurational forces in cyclic metal plasticity

2019 ◽  
Vol 300 ◽  
pp. 08009
Author(s):  
Aris Tsakmakis ◽  
Michael Vormwald
Keyword(s):  
Driving Force ◽  
Plastic Material ◽  
Kinematic Hardening ◽  
Yield Function ◽  
Configurational Forces ◽  
Isotropic Hardening ◽  
Crack Driving Force ◽  
Metal Plasticity ◽  
Elastic Plastic ◽  
Von Mises

The configurational force concept is known to describe adequately the crack driving force in linear fracture mechanics. It seems to represent the crack driving force also for the case of elastic-plastic material properties. The latter has been recognized on the basis of thermodynamical considerations. In metal plasticity, real materials exhibit hardening effects when sufficiently large loads are applied. Von Mises yield function with isotropic and kinematic hardening is a common assumption in many models. Kinematic and isotropic hardening turn out to be very important whenever cyclic loading histories are applied. This holds equally regardless of whether the induced deformations are homogeneous or non-homogeneous. The aim of the present paper is to discuss the effect of nonlinear isotropic and kinematic hardening on the response of the configurational forces and related parameters in elastic-plastic fracture problems.

Evaluation of Cracks Embedded in Zones With Large Scale Plasticity in Subsea HPHT Equipment – Comparing FAD and Driving Force Approaches

2021 ◽  
Author(s):  
Mandar Kulkarni ◽  
Carlos Lopez ◽  
Daniel Kluk ◽  
John Chappell
Keyword(s):  
Fracture Mechanics ◽  
Plastic Strain ◽  
Driving Force ◽  
Large Scale ◽  
Plastic Region ◽  
Assessment Method ◽  
Pressure Vessels ◽  
Integral Approach ◽  
J Integral ◽  
Elastic Plastic

Abstract Fracture mechanics assessments for pressure vessels are performed to determine critical flaw sizes and/or estimate the fatigue life of a growing crack as a means of establishing inspection intervals for the equipment. In most cases the evaluation is performed based on methods described in API 579-1/ASME FFS-1 and BS7910. The approaches described in these standards are mostly based on a linear elastic fracture mechanics approach. Even though plasticity can be accounted for by using a failure assessment diagram (FAD); however, even with this approach the effect of plastic strain around the crack is not explicitly considered. This paper presents an approach as per API 579, Annex 9G.5 which recommends utilizing a driving force method whereby the J-integral is directly evaluated from an elastic-plastic finite element model. The main goal is to study differences between the FAD approach against the elastic-plastic J-integral approach wherein the crack is modeled explicitly. Simplified representative geometries are considered for this study. Two scenarios for the plastic zone are considered a) crack present during initial loading with no residual plastic strain and b) crack in a residual stress zone. Different crack sizes are considered for this comparison study ranging from small cracks completely embedded within the plastic region and larger cracks with partial embedment. The paper presents comparison studies which highlight the key differences between different analysis approaches with the aim of identifying the most conservative assessment method for different crack geometries.

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