An Analysis of Wrinkling in the Swift Cup Test

1980 ◽  
Vol 102 (3) ◽  
pp. 241-248 ◽  
Author(s):  
N. Triantafyllidis ◽  
A. Needleman
Keyword(s):  
Deformation Theory ◽  
Annular Plate ◽  
Plastic Material ◽  
Beam Model ◽  
Linear Elastic ◽  
Theory Of Plasticity ◽  
Flange Wrinkling ◽  
Elastic Plastic Material ◽  
Elastic Spring ◽  
Flow Theory Of Plasticity

The onset of flange wrinkling in the Swift cup test is analyzed as a plastic bifurcation problem. The flange is modelled as an annular plate made of an orthotropic elastic-plastic material that is isotropic in the plane of the plate. The critical drawing stress and displacement obtained employing a deformation theory of plasticity and a flow theory of plasticity are compared. The effects of flange geometry and material properties on wrinkling are investigated. Employing a simple linear elastic spring model of the blankholder, the effect of blankholder stiffness on wrinkling is studied. The present results for the critical stress at the onset of wrinkling and for the number of wrinkles are compared with those obtained previously employing a beam model of the flange.

Elasto-Plastic Analysis of Thick Cylinders Subjected to Internal Electro-Magnetic Loading

2012 ◽  
Vol 28 (3) ◽  
pp. 423-430 ◽  
Author(s):  
H. Rajabi ◽  
A. Darvizeh
Keyword(s):  
Differential Equations ◽  
Shear Deformation ◽  
Deformation Theory ◽  
Plastic Material ◽  
Displacement Vector ◽  
Time Integration ◽  
Shear Deformation Theory ◽  
Elastic Plastic Material ◽  
Electro Magnetic ◽  
Von Mises

AbstractA study of elasto-plastic deformation of circular cylindrical shells subjected to internal electromagnetic forces is presented in this paper. The five governing equations in terms of resultant forces and resultant moments with respect to basic displacement vector components u, v and w are used. Theoretical formulations, based on the first-order shear deformation theory (FSDT), take into consideration transverse shear deformation and rotary inertia. The deformation theory of plasticity is employed for constitutive equations. The cylinders are composed of an elastic-plastic material with the von Mises yield criteria and non-linear plastic behaviour. Galerkin method is employed to convert the partial differential equations (PDEs) to ordinary differential equations (ODEs). The Newmark family of methods is used to numerically time integration of system of coupled second order ODEs. In order to prove the validity of the presented method and the solving process, the results obtained with the present analysis are compared with a set of available data. Good agreement observed between the results of the two approaches. Certainly, the aim of this paper is to create a more reliable and precise mathematical model of hollow-cylinders to avoid performing several experiments.

Observation of Micro-Tensile Behavior of Thin Film TiN and Au using ESPI Technique

2005 ◽  
Vol 875 ◽  
Author(s):  
Yong-Hak Huh ◽  
Dong-Iel Kim ◽  
Jun-Hee Hahn ◽  
Gwang-Seok Kim ◽  
Chang-Doo Kee ◽  
...  
Keyword(s):  
Thin Film ◽  
Tensile Strain ◽  
Plastic Material ◽  
Speckle Pattern ◽  
Electronic Speckle Pattern Interferometry ◽  
Linear Elastic ◽  
Specimen Width ◽  
Measurement Algorithm ◽  
Elastic Plastic Material

AbstractMicro-tensile properties of hard and soft thin films, TiN and Au, were evaluated by directly measuring tensile strain in film tension using the micro-ESPI(electronic Speckle Pattern Interferometry) technique. Micro-tensile stress-strain curves for these films were obtained and the properties were determined. TiN thin film 1 μm thick and Au films with two different thicknesses (t=0.5 μm and 1 μm) were deposited onto the silicon wafers, respectively, and micro-tensile specimens wide 50, 100 and 200 μm were fabricated using micromachining. In-situ measurement of the micro-tensile strain during tensile loading was carried out using the subsequent strain measurement algorithm and the ESPI system developed in this study. The micro-tensile curves showed that TiN thin film was a linear-elastic material showing no plastic deformation and Au thin film was an elastic-plastic material showing significant plastic flow. Effect of the specimen dimensions on mechanical properties was examined. It was revealed that tensile strengths for both films were slightly increased with increasing specimen width. Furthermore, variations of yielding strengths for the thin film Au with change of the dimension were investigated.

A finite-element method applied to predicting fatigue-crack growth

1973 ◽  
Vol 8 (4) ◽  
pp. 294-304 ◽  
Author(s):  
D Walton ◽  
N J Woodman ◽  
E G Ellison
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Plastic Material ◽  
Crack Opening ◽  
Plastic Zone Size ◽  
Yield Model ◽  
Opening Displacement ◽  
Element Analysis ◽  
Linear Elastic ◽  
Elastic Plastic Material

A finite-element analysis is presented to determine the stress and strain fields at and near the tip of a crack in an elastic-plastic material. These results, together with estimates of the crack opening displacement and plastic-zone size, are compared with equivalent values obtained from linear elastic fracture mechanics and the strip-yield model. Finally the finite-element-strain field data are used in a model which predicts the rates of fatigue-crack propagation; these correlate well with experimental results.

Structural Integrity Evaluation for the Analysis of Corroded Pipelines With Multiple Corrosion Defects

2006 ◽  
Author(s):  
Alejandro Andueza ◽  
Thiago Pontual
Keyword(s):  
Structural Integrity ◽  
Plastic Material ◽  
Material Model ◽  
Model Generation ◽  
The Finite Element Method ◽  
Failure Pressure ◽  
Linear Elastic ◽  
Asme Code ◽  
Corrosion Defects ◽  
Elastic Plastic Material

The structural integrity evaluation of corroded pipelines is very important for the management of systems that are in operation in order to help managers in the important decision of repairing the line. The required models for the analysis of corroded pipelines with multiple corrosion defects are in many cases a hard task to be generated. This paper presents a new methodology for the generation of full 3D hex meshes for the analysis using the Finite Element Method. The algorithm, developed specifically for the analysis of corroded pipelines, makes the task of model generation with multiple corrosion defects easier and faster. Examples with one and two corrosion defects are presented using a linear-elastic material model and the corresponding results compared to the criteria established by ASME code sec. VIII div. 2. The same models are analyzed using ideal elastic-plastic material model in order to determine the minimum failure pressure for the corroded pipes. The numerical failure pressures obtained are also compared to the values obtained from DNV RP-F101 method for single defects and experimental results. Finally, a new repairing methodology that allows the continuous operation of the pipeline in a safer way is presented. This methodology can help managers in the undertaking of scheduling a full repair of the pipeline in a much more flexible way.

Novel Plasticity Integration Algorithm in Improved Inverse Analysis Method and its Verification in Clover-Shaped Cup Drawing

2011 ◽  
Vol 366 ◽  
pp. 121-126
Author(s):  
Xiao Yang Lu ◽  
Xiao Li Lu ◽  
Bing Tao Tang ◽  
Li Li Huang
Keyword(s):  
Inverse Analysis ◽  
Deformation Theory ◽  
Flow Theory ◽  
Loading History ◽  
Analysis Method ◽  
Integration Algorithm ◽  
Theory Of Plasticity ◽  
Inverse Analysis Method ◽  
Cup Drawing ◽  
Flow Theory Of Plasticity

An improved inverse analysis method is developed based on the final workpiece in Euler coordinate system. The drawbeads and the radius of the die introduce a complex bending-unbending loading history as the material passes through these regions. Unlike the widespread inverse analysis using deformation theory of plasticity, in order to consider loading history, the improved inverse analysis method uses the constitutive equation based on flow theory of plasticity. In order to avoid numerous iterations to ensure the numerical stability in Newton-Raphson scheme to obtain plastic multiplier , a novel plastic integration algorithm is proposed to consider bending–unbending effects. A clover-shaped cup drawing example is numerically simulated with the inverse analysis method based on deformation theory of plasticity and the improved one based on flow theory of plasticity. These simulated results are compared with those of the incremental forward finite element solver LS-DYNA simultaneously. The comparisons of blank configurations and the effective strain distribution show that the proposed plasticity integration algorithm is effective and reliable.

On the Effect of Scattering of Bolt Forces on Gasket Stress

2006 ◽  
Author(s):  
Manfred Schaaf ◽  
Friedrich Schoeckle ◽  
Jaroslav Bartonicek
Keyword(s):  
Plastic Material ◽  
Analytical Calculation ◽  
Large Degree ◽  
Outer Diameter ◽  
Elastic Plastic ◽  
Linear Elastic ◽  
Non Linear ◽  
Realistic Description ◽  
Lift Off ◽  
Elastic Plastic Material

To guarantee integrity and tightness of bolted flanged connections a set of gasket characteristics (for tightness e.g. QMIN(L), QSMIN(L), tightness class L) has to be known. These characteristics are determined in simplified standardized tests with uniform gasket stress levels, in which the effect of the scattering of the bolt force is neglected. In this paper, results of Finite Element studies with real flange models are presented in which the local distribution of the gasket stress was determined in dependence of the scatter of the bolt forces. In the calculations, different models of the material characteristics are evaluated. A linear elastic approach, a nonlinear elastic approach and a non-linear elastic-plastic approach of the gasket behaviour is analysed. The results of the FEM studies demonstrated that elastic-plastic material laws are necessary for a realistic description of the material behaviour. The calculations in which the elastic-plastic gasket behaviour is considered give a nearly uniform gasket stress distribution along the gasket circumference despite a large scatter in the bolt force. This means that a non-uniform load transmission into the BFC is “damped” through the flange rings to a large degree and the gasket is compressed almost uniformly along the circumference. In radial direction an increase of the gasket stress from the inner to the outer diameter can be observed. Depending on the material law used, a lift-off of the flange ring from the gasket at the inner diameter (caused by the flange rotation) is obtained (linear elastic approach). Using a non-linear elastic or elastic-plastic approach for the gasket material the gasket stays in contact with the flange surfaces over the entire width of the gasket. These experiences can only partly be considered in analytical calculation codes such as EN 1591-1 (1). This is one reason why there are often discussions about the tightening factors of different mounting procedures and therefore difficulties in stress and tightness analysis can occur.

Technical Basis for Characterization of Multiple Closely Separated Flaws Located in Different Planes

2017 ◽  
Author(s):  
Sébastien Blasset ◽  
Tomas Nicak ◽  
Elisabeth Keim ◽  
Ralf Tiete ◽  
Florian Obermeier
Keyword(s):  
Plastic Material ◽  
Material Behavior ◽  
Specific Work ◽  
3D Numerical Modeling ◽  
Elastic Plastic ◽  
Linear Elastic ◽  
Current Interaction ◽  
Elastic Plastic Material ◽  
Technical Basis ◽  
Non Destructive

Non-destructive inspection records have to be characterized before evaluation of acceptance if they are evaluated as material or fabrication flaws. When multiple flaws are detected by volumetric examination, the question of interacting flaws arises if they are close to each other: can the conventional approach based on individual flaw be applied? Alternative flaw characterization requirements may be applied in lieu of using current codes by considering recent fracture mechanics research. In order to relax the conservatism of current interaction criteria, specific work was performed to describe interaction rules for flaws located in different planes. The proximity criteria are valid for linear elastic or limited elastic plastic material behavior : this is generally the case in large components. This paper presents the technical basis including validation of the proximity criteria based on a specific component with several flaws and considering 3D numerical modeling using elastic-plastic material behavior in order to check if the plastic material behavior affects the selected proximity criteria. The component is submitted to uniform (pressure) and non-uniform loading (like thermal shock).

Numerical Evaluation of Plastic Buckling of Short Cylinders Under Combined Loading

2018 ◽  
Vol 18 (06) ◽  
pp. 1850081 ◽  
Author(s):  
Federico Guarracino ◽  
Maria Grazia Simonelli
Keyword(s):  
Deformation Theory ◽  
Numerical Evaluation ◽  
Initial Imperfection ◽  
Flow Theory ◽  
Material Behavior ◽  
Combined Loading ◽  
Plastic Buckling ◽  
Theory Of Plasticity ◽  
Plates And Shells ◽  
Flow Theory Of Plasticity

The so-called “plastic buckling paradox” originates from the fact that the Prandtl–Reuss’ flow theory of plasticity overestimates the plastic buckling load of plates and shells, whereas Hencky’s deformation theory of plasticity provides results that are more accurate. However, it has been shown that this problem can be overcome by introducing certain initial imperfection in accurate finite element (FE) simulations based on the flow theory of plasticity. 1 – 4 The present study goes deeper into the problem and reveals that in the case of short cylinders under combined loading, which have long been the object of extensive research in the elastic range, 5 a different modeling of the material behavior can also trigger a mode jumping from the initial imperfection, which may even reverse the reported predictions by the flow and deformation theories of plasticity. This fact must be taken in maximum consideration when performing nonlinear FE analyses for estimating the plastic buckling of thin and moderately thin short cylindrical shells.

scholarly journals A simplified numerical approach to the evaluation of residual shaft friction induced by concrete curing in drilled shafts on granular soils

2020 ◽  
Vol 13 (5) ◽  
Author(s):  
Augusto Bopsin Borges ◽  
Renato Vaz Linn ◽  
Fernando Schnaid ◽  
Samir Maghous
Keyword(s):  
Bearing Capacity ◽  
Plastic Material ◽  
Numerical Approach ◽  
Drilled Shafts ◽  
Load Test ◽  
Curing Process ◽  
Linear Elastic ◽  
Load Tests ◽  
Elastic Plastic Material ◽  
Shaft Friction

ABSTRACT: Conventional interpretation procedures of load tests on instrumented piles rely upon measurements of strains that assume as zero for strains measured at the instant immediately before starting the test as reference configuration. However, some experimental evidence shows that concrete in drilled shafts undergoes strains induced by the curing process comparable in magnitude to the strains measured during the load tests. It is therefore expected that mobilization of shaft friction takes place before the load test. Several authors have performed experimental and numerical analyses aiming to quantify the influence of those pre-load test concrete volumetric strains on the measured bearing capacity using different approaches. The present work aimed to establish a reference framework for the existing and future works on this topic. In order to assess the influence of concrete strains induced by curing process on the shaft friction before the start of the load tests in drilled shafts, several finite element numerical simulations are performed, considering the thermal, autogenous and drying strains. The analyses consider concrete as an isotropic linear-elastic material and the soil as an elastic-plastic material using the Mohr-Coulomb constitutive model natively implemented in the software ABAQUS. The results are interpreted focusing on the relevancy on the bearing capacity and load distribution along drilled shafts considering or not the strains induced by concrete curing.

Asymptotic Analysis of a Mode I Crack Propagating Steadily in a Deformation Theory Material

1987 ◽  
Vol 54 (1) ◽  
pp. 79-86 ◽  
Author(s):  
P. Ponte Castan˜eda
Keyword(s):  
Strain Hardening ◽  
Deformation Theory ◽  
Plastic Material ◽  
Mode I ◽  
Algebraic Equations ◽  
Nonlinear Algebraic Equations ◽  
Stress Functions ◽  
Elastic Plastic Material ◽  
Stress And Deformation ◽  
Distribution Of Stress

The near-tip asymptotic stress and deformation fields of a crack propagating steadily and quasi-statically into an elastic-plastic material are presented. The material is characterised by J2-deformation theory, suitably modified to account for unloading and reloading, together with linear strain-hardening. The cases of plane strain and plane stress Mode I are considered. The governing equations are integrated analytically with the assistance of Muskhelishvili’s complex variable formulation. The boundary and continuity conditions then lead to a set of nonlinear algebraic equations in the coefficients of the stress functions to be solved numerically. Explicit results are given for the strength of the singularity, and for the distribution of stress in the plastic loading, elastic unloading, and plastic reloading regions, as functions of the strain-hardening parameter.

Sign in / Sign up

Export Citation Format

Share Document