Elastic-Plastic Analysis for Cracked Members

1976 ◽  
Vol 98 (1) ◽  
pp. 47-55 ◽  
Author(s):  
P. D. Hilton
Keyword(s):  
Finite Element ◽  
Small Strain ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Crack Face ◽  
Exterior Surface ◽  
Elastic Plastic ◽  
Finite Element Procedure ◽  
Hollow Cylindrical Specimen ◽  
Cracked Specimens

Elastic-plastic finite element analyses are performed for cracked specimens of various geometries and material properties. The calculations are based on the small strain, J2-deformation theory of plasticity; employing a power hardening model for the material behavior under uniaxial tensile loading. The finite element procedure includes the use of a specialized plastic, crack tip singularity element; and, it is applicable to the geometric idealizations of plane stress, plane strain, and axial symmetry. Results are presented for tensile and bending specimens containing exterior cracks and for a hollow cylindrical specimen with a circumferential crack subjected to tensile and pressure loading. Numerical values are reported for the plastic intensity factor, the crack face separation at the exterior surface, and the J-integral. Both the implications of these results to fracture prediction and the limitations on their applicability as a consequence of geometric and material modeling idealizations are discussed.

Bodner-Partom Constitutive Model and Nonlinear Finite Element Analysis

1990 ◽  
Vol 112 (3) ◽  
pp. 287-291 ◽  
Author(s):  
F. A. Kolkailah ◽  
A. J. McPhate
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Plastic Strain ◽  
Constitutive Model ◽  
Finite Element Model ◽  
Numerical Technique ◽  
Element Model ◽  
Material Behavior ◽  
Model Parameters ◽  
Elastic Plastic

In this paper, results from an elastic-plastic finite-element model incorporating the Bodner-Partom model of nonlinear time-dependent material behavior are presented. The parameters in the constitutive model are computed from a leastsquare fit to experimental data obtained from uniaxial stress-strain and creep tests at 650°C. The finite element model of a double-notched specimen is employed to determine the value of the elastic-plastic strain and is compared to experimental data. The constitutive model parameters evaluated in this paper are found to be in good agreement with those obtained by the other investigators. However, the parameters determined by the numerical technique tend to give response that agree with the data better than do graphically determined parameters previously used. The calculated elastic-plastic strain from the model agreed well with the experimental strain.

Finite Element Analysis on Nitinol Medical Applications

2002 ◽  
Author(s):  
Xiao-Yan Gong ◽  
Alan R. Pelton
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Element Analysis ◽  
Highly Nonlinear ◽  
Device Applications ◽  
Specific Material

Nitinol, an alloy of about 50% Ni and 50% Ti, is a very unique material. At constant temperature above its Austenite finish (Af) temperature, under uniaxial tensile test, the material is highly nonlinear and capable of large deformation to the ultimate strain on the order of 15%. This material behavior, known as superelasticity, along with its excellent biocompatibility and corrosion resistance, makes Nitinol a perfect material candidate for many medical device applications. However, the nonlinear material response also requires a specific material description to perform the stress analysis. The user developed material subroutine from HKS/West makes the simulation of the Nitinol devices possible. This article presents two case studies of the nonlinear finite element analysis using ABAQUS/Standard and the Nitinol UMAT.

Finite Element Modeling of Hydraulic Excavator in Soil Cutting Process

2011 ◽  
Vol 145 ◽  
pp. 240-244
Author(s):  
Wei Yang ◽  
Pan Ke Wei ◽  
Ji Ming Sun
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Large Scale ◽  
Element Model ◽  
Material Behavior ◽  
Von Mises Stress ◽  
Hydraulic Excavator ◽  
Arbitrary Lagrangian Eulerian ◽  
Elastic Plastic ◽  
Soil Cutting

A three-dimensional finite element model of hydraulic excavator is proposed to simulate soil cutting. To consider nonlinear soil behaviors, we apply the theory of Arbitrary Lagrangian-Eulerian (ALE) and explicit dynamic method to analyze a large scale fluid-solid structure interaction problem. The elastic-plastic assumption theory is introduced to simulate soil material behavior during the process of soil cutting because the nonlinear elastic-plastic model has advantages of simultaneously accounting for dynamic effects of strain hardening, strain rate, automatic mesh contact with friction capability, soil mechanical behavior and soil-bucket interaction. Soil-bucket interaction is modeled as friction with adhesion depending upon different influencing factors. This paper also investigates the parameters that may cause computational instability in soil cutting analysis. The difficulties in the numerical simulation of soil cutting are overcome by adopting suitable parameters to meet the requirement of proper mesh separation criterion. The proposed modeling can also be used to predict soil stress distribution, soil deformation and Von Mises stress distribution of component in hydraulic excavator.

An Efficient Multi-Scale Modeling Method that Reveals Coupled Effects Between Surface Roughness and Roll-Stack Deformation in Cold Sheet Rolling

2021 ◽  
pp. 1-53
Author(s):  
Feng Zhang ◽  
Arif S Malik
Keyword(s):  
Surface Roughness ◽  
Finite Element ◽  
Rough Surface ◽  
Material Behavior ◽  
Sheet Rolling ◽  
Elastic Plastic ◽  
Multi Scale ◽  
Macro Scale ◽  
Surface Contact ◽  
Rough Surface Contact

Abstract In thin-gauge cold rolling of metal sheet, the surface roughness of work-rolls is known to affect the rolled sheet surface morphology, the required rolling load, and the roll wear. While modeling of rough surfaces using statistical asperity theory has been widely applied to problems involving semi-infinite solids, the application of asperity distributions and their elastic-plastic behavior has not been considered in roll-stack models for cold sheet rolling. In this work, a simplified-mixed finite element method (SM-FEM) is combined with statistical elastic-plastic asperity theory to study contact interference and coupling effects between a rough work-roll surface and the roll-stack mechanics in cold sheet rolling. By mixing equivalent rough-surface contact foundations, Hertz foundations, and Timoshenko beam stiffness, an approach is created to efficiently model interactions between the micro-scale asperities and the macro-scale roll-stack deformation. Nonlinearities from elastic-plastic material behavior of the asperities and the sheet, as well as changing contact conditions along the roll length, are also accommodated. Performance of the multi-scale SM-FEM approach is made by comparison to a continuum finite element virtual material model. 3D studies for a 4-high mill reveal new multi-scale coupling behaviors, including non-uniform roughness transfer, and perturbations to the sheet thickness ‘crown’ and contact force profiles. The described multi-scale SM-FEM approach is general and applies to rough surface contact problems involving plates and shear-deformable beams having multiple contact interfaces and arbitrary surface profiles.

Finite Element Analysis of Complex Corrosion Defects

2002 ◽  
Author(s):  
Duane S. Cronin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Burst Pressure ◽  
Uniaxial Tensile ◽  
Element Analysis ◽  
Internal Corrosion ◽  
Corrosion Defect ◽  
Elastic Plastic ◽  
Defect Assessment ◽  
Corrosion Defects

Aging gas and oil transmission pipeline infrastructure has led to the need for improved integrity assessment. Presently, external and internal corrosion defects are the leading cause of pipeline failure in Canada, and in many other countries around the world. The currently accepted defect assessment procedures have been shown to be conservative, with the degree of conservatism varying with the defect dimensions. To address this issue, a multi-level corrosion defect assessment procedure has been proposed. The assessment levels are organized in terms of increasing complexity; with three-dimensional elastic-plastic Finite Element Analysis (FEA) proposed as the highest level of assessment. This method requires the true stress-strain curve of the material, as determined from uniaxial tensile tests, and the corrosion defect geometry to assess the burst pressure of corrosion defects. The use of non-linear FEA to predict the failure pressure of real corrosion defects has been investigated using the results from 25 burst tests on pipe sections removed from service due to the presence of corrosion defects. It has been found that elastic-plastic FEA provides an accurate prediction of the burst pressure and failure location of complex-shaped corrosion defects. Although this approach requires detailed information regarding the corrosion geometry, it is appropriate for cases where an accurate burst pressure prediction is necessary.

Three-Dimensional Finite Element Elastic–Plastic Model for Subsurface Initiated Spalling in Rolling Contacts

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
John A. R. Bomidi ◽  
Farshid Sadeghi
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Fatigue Damage ◽  
Three Dimensional ◽  
Rolling Contact ◽  
Material Behavior ◽  
Lower Percentage ◽  
Fe Model ◽  
Plastic Model ◽  
Elastic Plastic

In this investigation, a three-dimensional (3D) finite element (FE) model was developed to study subsurface initiated spalling observed in rolling line contact of tribo components such as bearings. An elastic–kinematic hardening–plastic material model is employed to capture the material behavior of bearing steel and is coupled with the continuum damage mechanics (CDM) approach to capture the material degradation due to fatigue. The fatigue damage model employs both stress and accumulated plastic strain based damage evolution laws for fatigue failure initiation and propagation. Failure is modeled by mesh partitioning along unstructured, nonplanar, intergranular paths of the microstructure topology represented by randomly generated Voronoi tessellations. The elastic–plastic model coupled with CDM was used to predict both ratcheting behavior and fatigue damage in heavily loaded contacts. Fatigue damage induced due to the accumulated plastic strains around broken intergranular joints drive the majority of the crack propagation stage, resulting in a lower percentage of life spent in propagation. The 3D FE model was used to determine fatigue life at different contact pressures ranging from 2 to 4.5 GPa for 33 different randomly generated microstructure topology models. The effect of change in contact pressure due to subsurface damage and plastic strain accumulation was also captured by explicitly modeling the rolling contact geometry and the results were compared to those generated assuming a Hertzian pressure profile. The spall shape, fatigue lives, and their dispersion characterized by Weibull slopes obtained from the model correlate well with the previously published experimental results.

scholarly journals A Simple and Efficient Method for Obtaining the Whole-Range Uniaxial Tensile Properties of Pipeline Steel

Metals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 555
Author(s):  
Lingzhen Kong ◽  
Lingbo Su ◽  
Xiayi Zhou ◽  
Liqiong Chen ◽  
Jie Chen ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Pipeline Steel ◽  
True Strain ◽  
Strain Curve ◽  
Element Model ◽  
True Stress ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Output Data

To obtain the whole-range true stress-true strain curves of API X65, a method is proposed based on the equal proportion principle and digital images. The tensile elongation was obtained by tracing the gauge points on the specimen surface, and the true strain and true stress of API X65 were calculated according to the formulae. The obtained true stress-true strain curves were validated by a 3-D finite element model. The true stress-true strain curve was set as the input data, while the engineering stress-engineering strain curve was set as the output data. The output data of the finite element model was the same as that of the experiment test. The findings imply that the proposed method could acquire reliable, whole-range true stress-true stain curves. These curves, which depict the material behavior of pipeline steel from initial elongation to fracture, could provide basic data for pipeline defect tolerance limit analysis and fracture assessment.

An innovation in finite element simulation via crystal plasticity assessment of grain morphology effect on sheet metal formability

2021 ◽  
pp. 146442072110246
Author(s):  
Mostafa Habibi ◽  
Roya Darabi ◽  
Jose C de Sa ◽  
Ana Reis
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Crystal Plasticity ◽  
Forming Limit Diagram ◽  
Material Behavior ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Polycrystal Plasticity ◽  
Grain Distribution

Experimental and numerical study regarding the uniaxial tensile test and the forming limit diagram are addressed in this paper for AL2024 with the face-centered cube structure. First, representation of a grain structure can be obtained directly by mapping metallographic observations via scanning electron microscopy approach. Artificial grain microstructures produced by Voronoi Tessellation method are employed in the model using VGRAIN software. By resorting to the finite element software (ABAQUS) capabilities, the constitutive equations of the crystal plasticity were utilized and implemented as a user subroutine material UMAT code. The hardening parameters were calibrated by a trial and error approach in order to fit experimental tensile results with the simulation. Then the effect of the changing grain size, the heterogeneity factor, and the grain aspect ratio were studied for a uniaxial tensile test to emphasize the importance of the microstudy behavior of grains in material behavior. Furthermore, the polycrystal plasticity grain distribution was employed in the Nakazima test in order to obtain the forming limit diagram. The crystal plasticity-driven forming limit diagram reveals more accurate strains, taking into account the involving the micromechanical features of the grains. An innovative approach is pursued in this study to discover the necking angle, both in tensile test or Nakazima samples, showing a good agreement with the experiment results.

Advances in COD Equations — Circumferential Through-Wall Cracks

2012 ◽  
Author(s):  
Bruce A. Young ◽  
Rick J. Olson ◽  
Matthew Kerr
Keyword(s):  
Finite Element ◽  
Crack Opening ◽  
Full Range ◽  
Independent Solution ◽  
Loading Conditions ◽  
Finite Element Analyses ◽  
Crack Face ◽  
Elastic Plastic ◽  
Piping Systems ◽  
Bending Loads

Non-linear fracture mechanics equations for through-wall cracks in a pipe are used to analyze piping systems for either critical flaw size or critical loading conditions as part of probabilistic Leak-Before-Break (LBB) failure analyses under the eXtremely Low Probability of Rupture (xLPR) program co-sponsored by the U.S. Nuclear Regulatory Commission (US NRC) and the Electric Power Research Institute (EPRI). The xLPR analysis techniques use a large number of independent analysis solutions to determine an overall assessment of system failure probability. As part of the assessment, each independent solution requires the solution of the crack opening displacement (COD) for a through-wall crack (TWC) in a pipe under the prescribed loading conditions. The COD evaluations are then used to determine a leak rate for the given load conditions and crack sizes. The purpose of this paper is to present results which advance the start-of-the-art for determining the elastic-plastic functions for crack opening displacements (COD) for a TWC in a pipe system under combined tension and bending loads. The current method used to determine COD in xLPR, a blending of tension and bending solution from the GE-EPRI Handbook, determined the continuum equations using structural finite element analyses with shell type elements. Since that body of work was undertaken, there have been significant advancements in computing capability such that structural finite element analyses with three-dimension continuum elements are currently feasible. The use of continuum elements provides several advantages over shell elements; such as, the ability to elicit details of variation in the COD through the thickness of the pipe wall and to apply pressure to the crack face due to the internal pipe pressure. Furthermore, the original GE-EPRI solutions were limited for the case of combined tension and bending loads. The existing GE-EPRI solutions for combined loading conditions are limited to pipe radius-to-wall thickness (R/t) ratios of 10 or greater, typical of those piping systems found in the boiling water reactor (BWR) fleet. For the PWR piping systems of concern today, which are subject to primary water stress corrosion cracking (PWSCC), the R/t ratios are typically 5 or less. As a result of the limitations with the existing GE-EPRI method for predicting COD, Battelle and US NRC staff set out to develop a comprehensive COD prediction tool for combined loadings which would be applicable to both PWR as well as BWR piping. This effort involved a matrix of over 1,200 finite element analyses for a full range of pipe sizes, R/t ratios, through-wall crack (TWC) lengths, and internal pipe pressures. It is anticipated that there will be several parts to this effort. Part I, discussed in this paper, focuses on the development of the model and the initial investigation into the elastic- and elastic-plastic fitting functions for the prediction of COD (i.e., the V and h functions). Future parts of this effort will focus on such issues as the effect of restraint of pressure induced bending on COD, the effect of weld residual stresses on COD, J-Integral estimation schemes, and development of variable crack-face pressure.

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