Development of Noninteraction Material Models With Cyclic Hardening

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Thomas Bouchenot ◽  
Bassem Felemban ◽  
Cristian Mejia ◽  
Ali P. Gordon
Keyword(s):  
Elevated Temperatures ◽  
Kinematic Hardening ◽  
Critical Role ◽  
Constitutive Models ◽  
Cyclic Hardening ◽  
Material Model ◽  
General Purpose ◽  
Pressure Vessels ◽  
Single Element ◽  
Critical Components

Simulation plays a critical role in the development and evaluation of critical components that are regularly subjected to mechanical loads at elevated temperatures. The cost, applicability, and accuracy of either numerical or analytical simulations are largely dependent on the material model chosen for the application. A noninteraction (NI) model derived from individual elastic, plastic, and creep components is developed in this study. The candidate material under examination for this application is 2.25Cr–1Mo, a low-alloy ferritic steel commonly used in chemical processing, nuclear reactors, pressure vessels, and power generation. Data acquired from prior research over a range of temperatures up to 650 °C are used to calibrate the creep and plastic components described using constitutive models generally native to general-purpose fea. Traditional methods invoked to generate constitutive modeling coefficients employ numerical fittings of hysteresis data, which result in values that are neither repeatable nor display reasonable temperature dependence. By extrapolating simplifications commonly used for reduced-order model approximations, an extension utilizing only the cyclic Ramberg–Osgood (RO) coefficients has been developed. This method is used to identify the nonlinear kinematic hardening (NLKH) constants needed at each temperature. Single-element simulations are conducted to verify the accuracy of the approach. Results are compared with isothermal and nonisothermal literature data.

Application of Ramberg-Osgood Plasticity to Determine Cyclic Hardening Parameters

2016 ◽  
Author(s):  
Thomas Bouchenot ◽  
Bassem Felemban ◽  
Cristian Mejia ◽  
Ali P. Gordon
Keyword(s):  
Elevated Temperatures ◽  
Kinematic Hardening ◽  
Constitutive Models ◽  
Cyclic Hardening ◽  
Material Model ◽  
General Purpose ◽  
Pressure Vessels ◽  
Component Level ◽  
Critical Components ◽  
Plastic Components

Critical components of modern turbomachinery are frequently subjected to a myriad of service conditions that include diverse mechanical loads at elevated temperatures. The cost, applicability, and accuracy of either numerical or analytical component-level simulations are largely dependent on the material model chosen for the application. A non-interaction (NI) model derived from individual elastic, plastic, and creep components is developed in this study. The candidate material under examination for this application is 2.25Cr-1Mo, a low-alloy ferritic steel commonly used in chemical processing, nuclear reactors, pressure vessels, and power generation. Data acquired from literature over a range of temperatures up to 650°C are used to calibrate the creep and plastic components described using constitutive models generally native to general-purpose FEA. Traditional methods invoked to generate coefficients for advanced constitutive models such as non-linear kinematic hardening employ numerical fittings of hysteresis data, which result in values that are neither repeatable nor display reasonable temperature-dependence. By extrapolating simplifications commonly used for reduced-order model approximations, an extension utilizing only the cyclic Ramberg-Osgood coefficients has been developed to identify these parameters. Unit cell simulations are conducted to verify the accuracy of the approach. Results are compared with isothermal and non-isothermal literature data.

Modelling of grey cast iron for application to brake discs for heavy vehicles

2016 ◽  
Vol 231 (1) ◽  
pp. 35-49 ◽  
Author(s):  
Gaël Le Gigan ◽  
Magnus Ekh ◽  
Tore Vernersson ◽  
Roger Lundén
Keyword(s):  
Cast Iron ◽  
Elevated Temperatures ◽  
Kinematic Hardening ◽  
Frictional Heating ◽  
Material Model ◽  
Tensile Tests ◽  
Brake Disc ◽  
Brake Discs ◽  
Different Temperatures ◽  
Tension And Compression

Cast iron brake discs are commonly used in the automotive industry, and efforts are being made to gain a better understanding of the thermal and mechanical phenomena occurring at braking. The high thermomechanical loading at braking arises from interaction between the brake disc and the brake pads. Frictional heating generates elevated temperatures with a non-uniform spatial distribution often in the form of banding or hot spotting. These phenomena contribute to material fatigue and wear and possibly also to cracking. The use of advanced calibrated material models is one important step towards a reliable analysis of the mechanical behaviour and the life of brake discs. In the present study, a material model of the Gurson–Tvergaard–Needleman type is adopted, which accounts for asymmetric yielding in tension and compression, kinematic hardening effects, viscoplastic response and temperature dependence. The material model is calibrated using specimens tested in uniaxial cyclic loading for six different temperatures ranging from room temperature to 650 °C. A special testing protocol is followed which is intended to activate the different features of the material model. Validation of the model is performed by using tensile tests and thermomechanical experiments. An application example is given where a 10° sector of a brake disc is analysed using the commercial finitie element code Abaqus under a uniformly applied heat flux on the two friction surfaces. The results indicate that the friction surface of the hat side and the neck can be critical areas with respect to fatigue for the uniform heating studied.

scholarly journals Finite Element Analysis of RC Beams by the Discrete Model and CBIS Model Using LS-DYNA

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Seung H. Yang ◽  
Kwang S. Woo ◽  
Jeong J. Kim ◽  
Jae S. Ahn
Keyword(s):  
Finite Element ◽  
Discrete Model ◽  
Kinematic Hardening ◽  
Material Model ◽  
General Purpose ◽  
Solid Model ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Finite Element Software ◽  
Concrete Elements

There are several techniques to simulate rebar reinforced concrete, such as smeared model, discrete model, embedded model, CLIS (constrained Lagrange in solid) model, and CBIS (constrained beam in solid) model. In this study, however, the interaction between the concrete elements and the reinforcement beam elements is only simulated by the discrete model and CBIS (constrained beam in solid) model. The efficiency and accuracy comparisons are investigated with reference to the analysis results by both models provided by LS-DYNA explicit finite element software. The geometric models are created using LS-PrePost, general purpose preprocessing software for meshing. The meshed models are imported to LS-DYNA where the input files are then analyzed. Winfrith and CSCM concrete material options are employed to describe the concrete damage behavior. The reinforcement material model is capable of isotropic and kinematic hardening plasticity. The load versus midspan deflection curves of the finite element models correlate with those of the experiment. Under the conditions of the same level of accuracy, the CBIS model is evaluated to have the following advantages over the discrete model. First, it has the advantage of reducing the time required for FE modeling; second, saving computer CPU time due to a reduction in total number of nodes; and third, securing a good aspect ratio of concrete elements.

scholarly journals On Stress-Strain Relations Suitable for Cyclic and Other Loading

1981 ◽  
Vol 48 (3) ◽  
pp. 479-485 ◽  
Author(s):  
D. C. Drucker ◽  
L. Palgen
Keyword(s):  
Kinematic Hardening ◽  
Cyclic Hardening ◽  
Pressure Vessels ◽  
Mean Stress ◽  
Proportional Loading ◽  
Stress Strain ◽  
Analysis And Design ◽  
First Approximation ◽  
Cyclic Straining ◽  
Independent Domain

The analysis and design of pressure vessels and other structures subjected to cyclic loading and occasional large overloads requires stress-strain relations sufficiently simple to be usable with computer programs and yet adequate to describe the essential aspects of the response of the material. One such form with two quite different options is proposed for the time-independent domain which avoids the difficulties of earlier approaches. It has the kinematic hardening attributes needed for reversal of loading, allows for cyclic hardening or softening, gives zero mean stress as the asymptotic response to cyclic straining between fixed limits of strain, and reduces to a J2 stress-hardening form for radial or proportional loading so that it can model both cyclic and other loading to a good first approximation.

Using the Nonlinear Kinematic Hardening Material Model of Chaboche for Elastic–Plastic Ratcheting Analysis

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Arturs Kalnins ◽  
Jürgen Rudolph ◽  
Adrian Willuweit
Keyword(s):  
Kinematic Hardening ◽  
Strain Curve ◽  
Material Model ◽  
Pressure Vessels ◽  
Temperature Fields ◽  
Maximum Temperature ◽  
Hardening Material ◽  
Finite Element Software ◽  
Accumulated Strain ◽  
Constant Maximum

Commonly used design codes for power plant components and pressure vessels include rules for ratcheting analysis that specify limits on accumulated strain. No guidance is provided on the use of the material model. The objective of the paper is to provide guidance that may be helpful to analysts. The Chaboche nonlinear kinematic (NLK) hardening material model is chosen as an appropriate model. Two methods are selected for its calibration that can determine the parameters for stainless steels. One is manual that requires no outside software and the other uses finite element software. Both are based on the monotonic stress–strain curve obtained from a tension specimen. The use of the Chaboche parameters for cases when ratcheting is caused by cyclic temperature fields is selected as the example of an application. The conclusion is that the number of allowable design cycles is far higher when using the parameters with temperature dependency than those at the constant maximum temperature that is being cycled.

A Nonlinear Rubber Material Model Combining Fractional Order Viscoelasticity and Amplitude Dependent Effects

2008 ◽  
Vol 76 (1) ◽  
Author(s):  
N. Gil-Negrete ◽  
J. Vinolas ◽  
L. Kari
Keyword(s):  
Fractional Derivative ◽  
Dynamic Behavior ◽  
Fractional Order ◽  
Constitutive Models ◽  
Material Model ◽  
General Purpose ◽  
Fe Model ◽  
Rubber Material ◽  
Rubber Compounds ◽  
Von Mises

A nonlinear rubber material model is presented, where influences of frequency and dynamic amplitude are taken into account through fractional order viscoelasticity and plasticity, respectively. The problem of simultaneously modeling elastic, viscoelastic, and friction contributions is removed by additively splitting them. Due to the fractional order representation mainly, the number of parameters of the model remains low, rendering an easy fitting of the values from tests on material samples. The proposed model is implemented in a general-purpose finite element (FE) code. Since commercial FE codes do not contain any suitable constitutive model that represents the full dynamic behavior of rubber compounds (including frequency and amplitude dependent effects), a simple approach is used based on the idea of adding stress contributions from simple constitutive models: a mesh overlay technique, whose basic idea is to create a different FE model for each material definition (fractional derivative viscoelastic and elastoplastic), all with identical meshes but with different material definition, and sharing the same nodes. Fractional-derivative viscoelasticity is implemented through user routines and the algorithm for that purpose is described, while available von Mises’ elastoplastic models are adopted to take rate-independent effects into account. Satisfactory results are obtained when comparing the model results with tests carried out in two rubber bushings at a frequency range up to 500 Hz, showing the ability of the material model to accurately describe the complex dynamic behavior of carbon-black filled rubber compounds.

scholarly journals Viscoplastic Parametric Analysis of Cylindrical Specimen Under Cyclic Behaviour

2021 ◽  
pp. 75-82
Author(s):  
Panagiotis J. Charitidis
Keyword(s):  
Cyclic Loading ◽  
Numerical Study ◽  
Kinematic Hardening ◽  
Cyclic Hardening ◽  
Material Model ◽  
Cyclic Plasticity ◽  
Axial Deformation ◽  
Cyclic Behaviour ◽  
Von Mises ◽  
Cyclic Plasticity Model

The present study tries to present a cyclic hardening model with the aim to simulate quantitatively the material response under strain controlled cyclic loading in tension-compression, of specified axial deformation. A numerical study was carried out to investigate the cyclic constitutive behaviour of alloy Indium under viscoplastic deformation. The analysis was performed under prescribed symmetric strain-controlled cyclic loading. The model contains both isotropic and kinematic hardening components, while the analysis were performed using Comsol Multiphysics for only 60 seconds duration. The kinematic hardening was described by using multiple back stresses. Multiple back stresses can provide a smoother transition between the elastic and plastic deformation, and it improves the general shape of the hysteresis loop. Two cases (geometries) have been examined in this study. From the material model and finite element cyclic plasticity model results, it is found that for the same parameters, but different dimensions there is difference on the stress-strain curves as well as on the von Mises stresses.

Numerical Models of Hysteretic Steel Damper with a Hollow Diamond Shape for Energy Dissipation

2015 ◽  
Vol 802 ◽  
pp. 243-248
Author(s):  
Daniel R. Teruna ◽  
Taksiah A. Majid ◽  
Bambang Budiono
Keyword(s):  
Energy Dissipation ◽  
Numerical Models ◽  
Kinematic Hardening ◽  
Cyclic Hardening ◽  
Material Model ◽  
Isotropic Hardening ◽  
Simplified Models ◽  
Hardening Material ◽  
Hardening Rule ◽  
Steel Damper

Numerical studies were conducted to evaluate the behaviour of a hollow diamond shaped hysteretic steel plate damper under in-plane cyclic loading. The combine hardening material model based on Chaboche kinematic hardening rule and exponential isotropic hardening rule was proposed to trace the cyclic hardening behaviour of the steel damper. For engineering design purposes, simplified models based on bilinear and trilinear models were also presented. Numerical results showed that hysteretic curve obtained from Chaboche model and the simplified models correlate well with experimental results. Furthermore, the validity of the simplified models is verified through a comparison of its hysteretic energy dissipation with the actual test data.

Using the Nonlinear Kinematic Hardening Material Model of Chaboche for Elastic-Plastic Ratcheting Analysis

2013 ◽  
Author(s):  
Arturs Kalnins ◽  
Jürgen Rudolph ◽  
Adrian Willuweit
Keyword(s):  
Kinematic Hardening ◽  
Strain Curve ◽  
Material Model ◽  
Pressure Vessels ◽  
Stress Strain Curve ◽  
Hardening Material ◽  
Elastic Plastic ◽  
Finite Element Software ◽  
Chaboche Model

Two calibration processes are selected for determining the parameters of the Chaboche nonlinear kinematic hardening (NLK) material model for stainless steel. One process is manual that requires no outside software and the other follows a finite element software. The basis of the calibration is the monotonic stress-strain curve obtained from a tension specimen subjected to unidirectional loading. The Chaboche model is meant for elastic-plastic ratcheting analysis that is included in commonly used design codes. It is chosen because it is known that it can represent realistically the materials that are used for power plant components and pressure vessels. To test the calibration results, a pressurized cylindrical shell subjected to thermal cycling is selected as an example. It was found that, for the example, no more than four Chaboche components should be used in the determination of its parameters.

The Role of the SLP in Autism Spectrum Disorder Screening and Assessment

2008 ◽  
Vol 15 (2) ◽  
pp. 50-59 ◽  
Author(s):  
Amy Philofsky
Keyword(s):  
Language Development ◽  
Critical Role ◽  
Children With Autism ◽  
Autism Spectrum ◽  
Children With Asd ◽  
Prevalence Estimates ◽  
Notable Increase ◽  
Screening Assessment ◽  
Critical Components

AbstractRecent prevalence estimates for autism have been alarming as a function of the notable increase. Speech-language pathologists play a critical role in screening, assessment and intervention for children with autism. This article reviews signs that may be indicative of autism at different stages of language development, and discusses the importance of several psychometric properties—sensitivity and specificity—in utilizing screening measures for children with autism. Critical components of assessment for children with autism are reviewed. This article concludes with examples of intervention targets for children with ASD at various levels of language development.

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