Micromechanical Modeling of Two-Phase Steels

2000 ◽  
Vol 653 ◽  
Author(s):  
Mikael Nygårds ◽  
Dilip Chandrasekaran ◽  
Peter Gudmundson
Keyword(s):  
Micromechanical Model ◽  
Tensile Tests ◽  
Micromechanical Modeling ◽  
Uniaxial Tensile ◽  
The Finite Element Method ◽  
Stress Strain ◽  
Two Phase ◽  
Representative Cell ◽  
Strain Data ◽  
Good Agreement

AbstractA two-dimensional micromechanical model based on the finite element method is presented to model two-phase ferritic/pearlitic steels, by aid of generalised plane strain elements. A periodic representative cell containing 100 ferrite grains, and the desired fraction pearlite is used. By applying periodic boundary conditions, loading by an average stress or strain state is possible.Uniaxial tensile tests were performed on specimens containing the ferrite and pearlite microstructures, and on two-phase materials containing 25% and 58% pearlite respectively. The stress-strain data of the pearlite material is used to fit a laminar dependent Taylor relation to represent the pearlite workhardening. Thereafter, laminar spacings in the two-phase materials are measured, and the total stress-strain response of the materials is modelled. Comparisons between generated data and experiments show good agreement up to a strain of 2%.

A Micromechanical Model of the Tensile Behavior of Woven Fabric

1997 ◽  
Vol 67 (6) ◽  
pp. 445-459 ◽  
Author(s):  
M. L. Realff ◽  
M. C. Boyce ◽  
S. Backer
Keyword(s):  
Micromechanical Model ◽  
Tensile Behavior ◽  
Woven Fabric ◽  
Uniaxial Tensile ◽  
Stress Strain ◽  
Strain Behavior ◽  
Yarn Properties ◽  
Micromechanical Approach ◽  
Uniaxial Tensile Stress ◽  
Good Agreement

This work takes a micromechanical approach to fabric tensile modeling. The entire uniaxial tensile stress-strain behavior of the fabric is modeled from the constitutive yarn properties (tensile, bending, flattening, and consolidation behavior) and the original fabric geometry. Techniques for measuring these yarn properties are described. In most cases, there is good agreement between the theoretical and experimental results for several fabrics of differing weave and yarn construction. Modified approaches are suggested for those cases where prediction of fabric stress-strain behavior deviates from the experimental data.

An Experimentally Validated Micromechanical Model for Elasticity and Strength of Hydroxyapatite Biomaterials

2008 ◽  
Vol 1132 ◽  
Author(s):  
Andreas Fritsch ◽  
Luc Dormieux ◽  
Christian Hellmich ◽  
Julien Sanahuja
Keyword(s):  
Micromechanical Model ◽  
Strength Properties ◽  
Micromechanical Modeling ◽  
Uniaxial Tensile ◽  
Structure Property ◽  
Mechanical Stiffness ◽  
Statistical Correlations ◽  
Continuum Micromechanics ◽  
Structure Property Relationships ◽  
Good Agreement

ABSTRACTHydroxyapatite biomaterials production has been a major field in biomaterials science and biomechanical engineering. As concerns prediction of their stiffness and strength, we propose to go beyond statistical correlations with porosity or empirical structure-property relationships, as to resolve the material-immanent microstructures governing the overall mechanical behavior. The macroscopic mechanical properties are estimated from the microstructures of the materials and their composition, in a homogenization process based on continuum micromechanics. Thereby, biomaterials are envisioned as porous polycrystals consisting of hydroxyapatite needles and spherical pores. Validation of respective micromechanical models relies on two independent experimental sets: Biomaterial-specific macroscopic (homogenized) stiffness and uniaxial (tensile and compressive) strength predicted from biomaterial-specific porosities, on the basis of biomaterial-independent (‘universal') elastic and strength properties of hydroxyapatite, are compared to corresponding biomaterial-specific experimentally determined (acoustic and mechanical) stiffness and strength values. The good agreement between model predictions and the corresponding experiments underlines the potential of micromechanical modeling in improving biomaterial design, through optimization of key parameters such as porosities or geometries of microstructures, in order to reach desired values for biomaterial stiffness or strength.

A New Look at Measurements of Network Density

1986 ◽  
Vol 59 (1) ◽  
pp. 138-141 ◽  
Author(s):  
Robert A. Hayes
Keyword(s):  
Hysteresis Loop ◽  
Interaction Parameters ◽  
Network Density ◽  
Stress Strain ◽  
Solvent Interaction ◽  
Solvent Method ◽  
Strain Data ◽  
Good Agreement ◽  
Polymer Solvent ◽  
New Look

Abstract A two-solvent method for determining the polymer-solvent interaction parameters independently of stress-strain data is described. The values obtained are much lower than those reported previously. Network densities calculated from swelling data and these interaction parameters are in good agreement with those calculated from the return portion of a hysteresis loop at high elongations.

Collagen; ultrastructure and its relation to mechanical properties as a function of ageing

1972 ◽  
Vol 180 (1060) ◽  
pp. 293-315 ◽  
Keyword(s):  
Deformation Behaviour ◽  
Life Time ◽  
Periodic Pattern ◽  
Albino Rats ◽  
Structure And Properties ◽  
Stress Strain ◽  
Good Correspondence ◽  
Bearing Unit ◽  
Strain Data ◽  
Good Agreement

Tail tendons from Fischer and Sprague-Dawly albino rats of ages from 2 weeks to 3 years were investigated under the polarizing microscope as regards structure and deformation behaviour. Periodically extinguishing bands were observed along the otherwise featureless tendons. By analysing the behaviour of this extinction pattern under appropriate rotations of the tendon, it could be deduced that the orientation of the basic birefringent units varies periodically along the tendon and that this periodic pattern corresponds to a planar arrangement of the anisotropic entities. All the relevant parameters of this periodic structure could be determined in a representative manner from polarizing optics alone. Subdivision of the tendons revealed regularly undulating or rather crimped subunits in good correspondence to what has been deduced from the extinction bands in the intact tendons. The crimp angle was found to decrease while the periodicity increased - in approximate proportion to the length of the tail - with the age of the rat implying constancy of crimp number during the life time of the animal. On elongation the periodicity was gradually removed. The calculated fibre elongation necessary to eliminate the crimp was in good agreement with observation for mature rats but was larger for young rats implying the simultaneous stretching of the fibre itself. Stress-strain properties of tendons were measured and models for crimp straightening were tested. It was found that a model containing inflexible hinges, corresponding to the ‘elastica’ problem in mechanics gave reasonable fit with experiment. Analysis of stress-strain data on this basis leads to a basic load bearing unit, the diameter of which increases from 100 to 500 nm with the age of the animal. Implications of these findings for the structure and properties of the tendons, also in relation to ageing are pointed out.

Methods for the Experimental Evaluation of True Stress-Strain Curves After Necking of Conventional Tensile Specimens: Exploratory Investigation and Proposals

2012 ◽  
Author(s):  
Grace Kelly Q. Ganharul ◽  
Nick de Brangança Azevedo ◽  
Gustavo Henrique B. Donato
Keyword(s):  
Real Time ◽  
Weighted Average ◽  
Tensile Tests ◽  
Plastic Instability ◽  
True Stress ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
High Definition ◽  
Stress Strain

Numerical elastic-plastic simulations have undergone significant expansion during the last decades (e.g. refined fracture mechanics finite element models including ductile tearing). However, one limitation to increase the accuracy of such models is the reliable experimental characterization of true stress-strain curves from conventional uniaxial tensile tests after necking (plastic instability), which complicates the direct assessment of the true stress-strain curves until failure. As a step in this direction, this work presents four key activities: i) first, existing correction methods are presented, including Bridgman, power law, weighted average and others; ii) second, selected metals are tested to experimentally characterize loads and the geometric evolution of necking. High-definition images are used to obtain real-time measurements following a proposed methodology; iii) third, refined non-linear FEM models are developed to reproduce necking and assess stresses as a function of normalized neck geometry; iv) finally, existing correction methods are critically compared to experimental results and FEM predictions in terms of potential and accuracy. The experimental results evaluated using high-definition images presented an excellent geometrical characterization of instability. FEM models were able to describe stress-strain-displacement fields after necking, supporting the exploratory validations and proposals of this work. Classical methodologies could be adapted based on experiments to provide accurate stress-strain curves up to failure with less need for real-time measurements, thus giving further support to the determination of true material properties considering severe plasticity.

CAD/CAE for stress–strain properties of multifilament twisted yarns

2016 ◽  
Vol 87 (6) ◽  
pp. 657-668 ◽  
Author(s):  
Keartisak Sriprateep ◽  
Erik LJ Bohez
Keyword(s):  
Computer Aided Design ◽  
Maximum Stress ◽  
Tensile Behavior ◽  
Assembly Model ◽  
The Finite Element Method ◽  
Stress Strain ◽  
Filament Assembly ◽  
Computer Aided ◽  
Aided Design ◽  
Good Agreement

A method is presented for modeling the tensile behavior of multifilament twisted yarns. A filament assembly model and a computer-aided design/computer-aided engineering (CAD/CAE) approach are proposed for the tensile analysis. The geometry of the twisted yarn and the nonlinear filament properties were considered. The finite element method (FEM) and large deformation effects were applied for computation of the stress–extension curves. Ideal yarn structures of five layers with different twist angles were simulated to predict the tensile behavior of each filament and each layer. The stress acting on the filaments after yarn extension could be directly analyzed by the FEM. The stress distribution in the filaments showed that the highest stress regions were located at the filament in the center of the yarn and decreased slightly to the yarn surface. The stress–extensions of the filaments were converted to yarn tensile behavior that is shown in terms of the maximum and average stress–extension curves. The results of this prediction model were compared with the stress–strain curves of high-tenacity rayon yarn and the energy method. The maximum stress–extension curves showed very good agreement with experimental results and are more accurate than those obtained by previous methods.

A Simple Discrete Method for the Simulation of the Preforming of Woven Fabric Reinforcement

2012 ◽  
Vol 504-506 ◽  
pp. 213-218 ◽  
Author(s):  
Walid Najjar ◽  
Xavier Legrand ◽  
Cedric Pupin ◽  
Philippe Dal Santo ◽  
Serge Boude
Keyword(s):  
Inverse Method ◽  
Shear Stiffness ◽  
Tensile Tests ◽  
Woven Fabric ◽  
Uniaxial Tensile ◽  
Plane Shear ◽  
Discrete Method ◽  
Shell Elements ◽  
Woven Reinforcement ◽  
Good Agreement

In this paper, a discrete approach for the simulation of the preforming of dry woven reinforcement is proposed. A “unit cell” is built using elastic isotropic shells and axial connectors instead of bars and beams used in previous studies. Shell elements are used to take into account the in-plane shear stiffness and to manage contact phenomenon with the punch and die. Connectors reinforce the structure in the yarn directions and naturally capture the specific behavior of the fabric. To identify the material parameters, uniaxial tensile tests and bias tests have been employed. A numerical algorithm, coupling Matlab and Abaqus/Explicit, is used to determine the shear parameters by an inverse method. The model has been implemented in Abaqus to simulate hemispherical stamping. Experimental results are compared to numerical simulations, good agreement between both results is shown.

Deformation Plasticity Failure Assessment Diagram (DPFAD) for Materials With Non-Ramberg-Osgood Stress-Strain Curves

1995 ◽  
Vol 117 (4) ◽  
pp. 346-356 ◽  
Author(s):  
J. M. Bloom
Keyword(s):  
Tensile Stress ◽  
Manganese Steel ◽  
Uniaxial Tensile ◽  
J Integral ◽  
Stress Strain ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Strain Data ◽  
Deformation Plasticity ◽  
Uniaxial Tensile Stress

This paper presents a brief history of the evolution of the Central Electricity Generating Board’s (CEGB) R-6 failure assessment diagram (FAD) procedure used in assessing defects in structural components. The reader is taken from the original CEGB R-6 FAD strip yield model to the deformation plastic failure assessment diagram (DPFAD), which is dependent on Ramberg-Osgood (R-O) materials to general stress-strain curves. An extension of the DPFAD approach is given which allows the use of material stress-strain data which do not follow the R-O equation such as stainless steel or carbon manganese steel. The validity of the new approach coined piecewise failure assessment diagram (PWFAD) is demonstrated through comparisons with the J-integral responses (expressed in terms of failure assessment diagram curves) for several cracked configurations of non-R-O materials. The examples were taken from both finite element and experimental results. The comparisons with these test cases demonstrate the accuracy of PWFAD. The use of PWFAD requires the availability of deformation plasticity J-integral solutions for several values of the strain-hardening exponent as well as uniaxial tensile stress-strain data at the temperature of interest. Lacking this information, the original R-O DPFAD approach using known engineering yield and ultimate strengths would give the best available approximation. However, it is strongly recommended that actual uniaxial tensile stress-strain data be used when available.

Mechanical Behavior of Internally Pressurized Copper Tube for New HVACR Applications

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Frank F. Kraft ◽  
Tommy L. Jamison
Keyword(s):  
Strain Range ◽  
Type Equation ◽  
Tensile Tests ◽  
Copper Tube ◽  
Instability Criterion ◽  
Burst Pressure ◽  
Stress Strain ◽  
Property Variation ◽  
Axial Tension ◽  
Strain Data

This paper reviews and simplifies basic theory to predict plastic strain and burst pressure of internally pressurized, thin-walled copper tube for (heating, ventilation, air conditioning, and refrigeration applications. Predictions are based upon material stress–strain data obtained from basic tensile tests. A series of pressure tests was performed at 635 to 1500 psi (4.38–10.34 MPa), and until burst, on tubes ranging from 0.625 in. (15.87 mm) to 2.125 in. (53.97 mm) in diameter. A Voce type equation is shown to provide superior correlation to tensile and instability data, such that accurate projections can be made. An assessment of the classical power-law (Ludwik–Hollomon) equation is also presented, and it did not simultaneously correlate well with stress–strain data and satisfy the Considère instability criterion in uni-axial tension. Nevertheless, its use still led to reasonably accurate burst pressure predictions due to the strain range over which it was applied. Property variation (with respect to tube size) and anisotropy were observed in the transverse and axial tube directions for 1.125 in. (28.6 mm) and 2.125 in. (54.0 mm) diameter tube. Thus, the importance of representative and accurate material data in the transverse (hoop) direction is emphasized.

High Strain Rate Tensile Behavior of Carbon Fiber Reinforced Aluminum Laminates

2005 ◽  
Author(s):  
Yuanxin Zhou ◽  
Pingwen Mao ◽  
Mohammad F. Uddin ◽  
Shaikh Jeelani
Keyword(s):  
Carbon Fiber ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Strain Rate Range ◽  
Fiber Reinforced ◽  
Stress Strain ◽  
Static Tensile ◽  
Carbon Fiber Reinforced ◽  
Good Agreement

In this paper, loading and loading-unloading tests of carbon fiber reinforced aluminum laminates (CRALL) have been carried out in a tensile impact apparatus, and quasi-static tensile tests have been performed on a MTS-810 machine. Complete stress-strain curves of composite in the strain rate range from 0.001–1200 1/s have been obtained. Experimental results show that CRALL composite is a strain rate sensitivity material, the tensile strength and failure strain both increased with increasing strain rate. A linear strain hardening model has been combined with Weibull distribution function to establish a constitutive equation for CRALL. The simulated stress-strain curves from model are in good agreement with the test data. The analysis of the model shows that the Weibull scale parameter, σ0, increased with increasing strain rate, but Weibull shape parameter, β, can be regarded as a constant.

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