Inverse Identification of CDM Model Parameters for DP1000 Steel Sheets Using a Hybrid Experimental-Numerical Methodology Spanning Various Stress Triaxiality Ratios

2013 ◽  
Vol 554-557 ◽  
pp. 2103-2110 ◽  
Author(s):  
Zhen Ming Yue ◽  
Celal Soyarslan ◽  
Houssem Badreddine ◽  
Khemais Saanouni ◽  
A. Erman Tekkaya
Keyword(s):  
Constitutive Model ◽  
Pure Shear ◽  
Stress Triaxiality ◽  
Experimental Tests ◽  
Image Correlation ◽  
Material Surface ◽  
Model Parameters ◽  
Mixed Hardening ◽  
Steel Sheets ◽  
Strain Paths

A hybrid experimental-numerical methodology is presented for the identification of the model parameters regarding a mixed hardening anisotropic finite plasticity fully coupled with isotropic ductile damage in which the micro-crack closure effect is given account for, for steel sheets made of DP1000. The experimental tests involve tensile tests with smooth and pre-notched specimens and shear tests with specimen morphologies recently proposed by D.R. Shouler, J.M. Allwood (Design and use of a novel sample design for formability testing in pure shear, Journal of Materials Processing Technology, Volume 210, Issue 10, 1 July 2010, Pages 1304-1313). These tests cover stress triaxiality ratios lying between 0 (pure shear) and 1/√3 (plane strain). To neutralize machine stiffness effects displacements of the chosen material surface pixels are kept track of using the digital image correlation system ARAMIS, where recorded inputs are synchronized with force measurements. On the numerical part, developed constitutive model is implemented as user defined material subroutine, VUMAT, for ABAQUS/Explicit. FE models for the test cases are built using 3D brick elements (rather than thin shells) and devising developed VUMAT for the constitutive model, model parameters are identified using an inverse parameter identification procedure where the objective function relies on the difference of experimentally observed-numerically predicted forces for the selected pixel displacements. The validity of the material model and transferability of its parameters are tested using tests involving complex strain paths.

State of the Art of Constitutive Model of Concrete Materials Based on Damage Mechanics

2011 ◽  
Vol 194-196 ◽  
pp. 848-852
Author(s):  
Duo Xin Zhang ◽  
Qing Yun Wang
Keyword(s):  
Constitutive Model ◽  
Damage Mechanics ◽  
State Of The Art ◽  
Constitutive Models ◽  
Experimental Tests ◽  
Constitutive Relationship ◽  
Model Parameters ◽  
Softening Effect ◽  
Volumetric Expansion ◽  
Concrete Materials

This study centered on the development of constitutive model of the material based on damage mechanics. Volumetric expansion, unilateral behavior and softening effect have been pointed out as three difficulties during setting constitutive model of concrete, the applicable and deficiency of the existed constitutive relationship been reviewed, and the methods used to deal above difficulties were overviewed, Meanwhile, the background of existed model has been summarized and listed systematically. The development of a thermodynamic approach to constitutive model of concrete, with emphasis on the rigorous and consistency both in the formulation of constitutive models and in the identification of model parameters based on experimental tests has been potential direction of the future study, and hoped furnished basement for the elastic to plastic coupled damage mechanics constitutive model of concrete.

Experimental and Numerical Characterization of the Stress-Strain Behavior of Weak Sandstone Formations for Sanding Assessment

2018 ◽  
Author(s):  
Nubia Aurora González Molano ◽  
Jacobo Canal Vila ◽  
Héctor González Pérez ◽  
José Alvarellos Iglesias ◽  
M. R. Lakshmikantha
Keyword(s):  
Constitutive Model ◽  
Equivalent Plastic Strain ◽  
Experimental Tests ◽  
Thick Wall ◽  
Triaxial Tests ◽  
Experimental Program ◽  
Model Parameters ◽  
Sand Production ◽  
Strain Behavior ◽  
Weak Sandstone

In this study an extensive experimental program has been carried out in order to characterize the mechanical behavior of two weak sandstone formations of an offshore field for application to sand production modeling. The experimental tests included Scratch tests, Triaxial tests and Advanced thick wall cylinder tests (ATWC) where the sand production initiation and the cumulative sand produced were registered. Numerical simulations of experimental tests were then performed using an advanced elasto-plastic constitutive model. Triaxial tests simulations allowed calibrating the constitutive model parameters. These parameters were employed for the numerical simulation of the ATWC in order to determine the equivalent plastic strain threshold required to the onset of sand production observed in laboratory for sanding assessment. Results obtained highlight the importance to use a realistic representation of the rock behavior focusing on post-yield behavior in order to build confidence in model predictions.

Revisiting the ring hoop test in additively manufactured metal tubes

2021 ◽  
pp. 030932472110452
Author(s):  
João PM Pragana ◽  
Ivo MF Bragança ◽  
Carlos MA Silva ◽  
Paulo AF Martins
Keyword(s):  
Stainless Steel ◽  
Pure Shear ◽  
Image Correlation ◽  
Steel Tubes ◽  
Tension Tests ◽  
316 L Stainless Steel ◽  
Strain Paths ◽  
Aisi 316 ◽  
Aisi 316 L ◽  
Thickness Measurements

This paper is focussed on the mechanical and formability characterisation of wire-arc additive manufactured (WAAM) AISI 316-L stainless-steel tubes. The methodology to be presented involved carrying out tension and ring hoop tension tests on specimens extracted from the tube longitudinal, transverse and inclined directions. The force evolutions, acquired from the load cells, and the strain measurements, retrieved from digital image correlation and from thickness measurements along the cracks, allowed obtaining the stress-strain curves, the strain paths and the onset of failure by fracture for the three different tube directions. Special attention was paid to the ring hoop test, which was revisited to determine the appropriateness of using ring specimens with one or two dumbbell geometries. The originality of using the ring hoop tension test in WAAM tubes with strong anisotropic behaviour allowed obtaining strain loading paths that range from plane strain to pure shear deformation conditions. Resort to commercial AISI 316-L stainless-steel tubes during the presentation is included for reference purposes.

New methodology for the characterization of failure by fracture in bulk forming

2018 ◽  
Vol 53 (4) ◽  
pp. 242-247 ◽  
Author(s):  
Joao P Magrinho ◽  
Maria Beatriz Silva ◽  
Luis M Alves ◽  
AG Atkins ◽  
Paulo AF Martins
Keyword(s):  
Metal Forming ◽  
Stress Triaxiality ◽  
Image Correlation ◽  
Principal Strain ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Aisi 1045 ◽  
Steel Aisi ◽  
Strain Paths ◽  
Strain Space

This article is focused on the formability limits by fracture obtained from standard bulk metal forming tests performed with cylindrical, tapered and flanged specimens. A total of two novel features are presented: the use of digital image correlation to determine strain paths and immersion of steel specimens in liquid nitrogen after the onset of crack formation to reveal the mode of fracture. A new methodology to determine the fracture loci in principal strain space is proposed based on the combination of experimental force–displacement evolutions with in-plane strain measurements. The experimental work is performed in cold-drawn steel AISI 1045 and two new formability tests with different values of stress triaxiality are proposed for obtaining strains at fracture in regions of principal strain space that are not sufficiently well covered by standard bulk metal forming tests.

On the Extraction of Elastic–Plastic Constitutive Properties From Three-Dimensional Deformation Measurements

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
A. J. Gross ◽  
K. Ravi-Chandar
Keyword(s):  
Constitutive Model ◽  
Tensile Test ◽  
Three Dimensional ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Model Parameters ◽  
Material Models ◽  
Elastic Plastic ◽  
Constitutive Properties ◽  
Deformation Measurements

In this article, a coupled experimental and numerical method is utilized for characterizing the elastic–plastic constitutive properties of ductile materials. Three-dimensional digital image correlation (DIC) is used to measure the full field deformation on two mutually orthogonal surfaces of a uniaxial tensile test specimen. The material’s constitutive model, whose parameters are unknown a priori, is determined through an optimization process that compares these experimental measurements with finite element simulations in which the constitutive model is implemented. The optimization procedure utilizes the robust dataset of locally observed deformation measurements from DIC in addition to the standard measurements of boundary load and displacement data. When the difference between the experiment and simulations is reduced sufficiently, a set of parameters is found for the material model that is suitable to large strain levels. This method of material characterization is applied to a tensile specimen fabricated from a sheet of 15-5 PH stainless steel. This method proves to be a powerful tool for calibration of material models. The final parameters produce a simulation that tracks the local experimental displacement field to within a couple percent of error. Simultaneously, the percent error in the simulation for the load carried by the specimen throughout the test is less than 1%. Additionally, half of the parameters for Hill’s yield criterion, describing anisotropy of the normal stresses, are found from a single tensile test. This method will find even greater utility in calibrating more complex material models by greatly reducing the experimental effort required to identify the appropriate model parameters.

Dynamic Constitutive Relation and Fracture Model of Q235A Steel

2013 ◽  
Vol 274 ◽  
pp. 463-466 ◽  
Author(s):  
Li Lin ◽  
Feng Fan ◽  
Xu Dong Zhi
Keyword(s):  
Fracture Strain ◽  
Stress Triaxiality ◽  
Rate Sensitivity ◽  
Experimental Tests ◽  
Model Parameters ◽  
Element Calculation ◽  
Tension Tests ◽  
Split Hopkinson ◽  
Strength And Ductility ◽  
Split Hopkinson Tension Bar

Strength and ductility data for Q235A steel from 20 oC to 950 oC was obtained from a series of experimental tests. The stress rate sensitivity was studied by conducting Split-Hopkinson Tension Bar (SHTB) test and uniaxial tension test on smooth cylindrical specimens while the influence of stress triaxiality on ductility was revealed by conducting upsetting tests, tension tests on pre-notched cylinder specimens and torsion tests on SASs. Slightly modified versions of the two Johnson–Cook (J–C) models describing flow stress and fracture strain are presented to characterize the properties of Q235A steel as function of strain rate, temperature and stress triaxiality. Corresponding model parameters were calibrated based on the test data and with the help of finite element calculation. It was found that the modified Johnson–Cook (MJC) models give more close predictive results compared with the original J–C models.

scholarly journals A Constitutive Model Incorporating Mixed Soil Slurry for Interface

2021 ◽  
Vol 276 ◽  
pp. 01021
Author(s):  
Kai Peng ◽  
Guohui Wang ◽  
Yaolai Liu ◽  
Xiaoliang Wang ◽  
Dong Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Strain Softening ◽  
Cement Content ◽  
Experimental Tests ◽  
Coarse Grained ◽  
Model Parameters ◽  
Soil Slurry ◽  
Shear Tests ◽  
Generalized Potential Theory ◽  
Coarse Grained Soil

In projects, mixed soil slurry between cut-off wall and coarse-grained soil always exists. It may influence on or change mechanical properties of interface between coarse-grained soil and structure. The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under mixed soil slurry. The significant dilatancy and stress-strain softening can be achieved through the results, which also indicate that the cement content play an important role in the shear strength of the interface. The peak strength and the position when the dilatancy occurs are related to both normal stress and cement content. An elasto-plastic constitutive model for interface considering mixed soil slurry was formulated in the framework of generalized potential theory. The entire model parameters can be identified by experimental tests. Finally, the predictions of the model have been compared with experimental results, and results show the model is reasonable and practical.

scholarly journals Effect of the Triaxiality in Plane Stress Conditions. Triaxiality Effect in a PVC Material

2013 ◽  
Vol 3 (1) ◽  
pp. 373-380
Author(s):  
N. Selini ◽  
M. Elmeguenni ◽  
M. Benguediab
Keyword(s):  
Pure Shear ◽  
Stress Triaxiality ◽  
Volumetric Strain ◽  
Experimental Tests ◽  
Plastic Instability ◽  
Pressure Vessels ◽  
Polymer Materials ◽  
Plastic Behavior ◽  
Anisotropic Plastic ◽  
Plastic Volumetric Strain

Polymer materials are gaining more and more importance in engineering applications. A new methodology of analysis is required in order to assess the capability of such material in withstanding complex loads. Therefore, the behavior of these materials currently arouses a great research interest. The use of PVC plastic pipes in pressure vessels and pipelines has increased rapidly in the last decade. In order to determine the plastic behavior of PVC, an experimental method is presented. Through the results obtained from experimental tests, in the first part of this paper, we investigate the use of a phenomenological model proposed by G’Sell and Jonas. The true stress-strain response under large plastic deformation was investigated in different stress triaxiality frameworks. Particular attention was given to volumetric strain evolution, separation resulting from elastic volumetric strain, plastic volumetric strain and pure shear. The effect of stress triaxiality on plastic instability and fracture strain was also examined. The deformation process should be considered as explained, and the anisotropic plastic response induced by the deformation could be introduced in constitutive equations of G’Sell.

scholarly journals Experimental and Numerical Studies of Low-Profile, Triangular Grid-Stiffened Plates Subjected to Shear Load in the Post-Critical States of Deformation

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3699 ◽  
Author(s):  
Łukasz Święch
Keyword(s):  
Pure Shear ◽  
Experimental Tests ◽  
Production Costs ◽  
Image Correlation ◽  
Experimental Investigations ◽  
Triangular Grid ◽  
Reference Structure ◽  
Shear Load ◽  
Low Profile ◽  
Thin Walled

Constant developments in manufacturing technology have made it possible to introduce integrally stiffened elements into load-bearing, thin-walled structures. The application of thin-walled elements with integral stiffeners potentially increases buckling and critical loads to maintain the mass of the structure and lower production costs. This paper presents the results of experimental investigations and numerical Finite Element Modelling (FEM) analyses of low-profile, isosceles grid stiffened, aluminium alloy plates subjected to pure shear load. Conducted research included analysing buckling and post-buckling states of deformation, taking into account both geometrical and physical nonlinear effects. Use of the Digital Image Correlation (DIC) system during the experimental tests created representative equilibrium pathways and recorded displacement field distributions over the plate surface. The model was initially validated against the experimental results. The results for the stiffened plate were compared to the reference structure in the form of a smooth plate with equivalent mass. Comparative analyses included examining the displacement fields and stress efforts over the plates. The stiffening configuration under examination increased the critical buckling load by 300% in comparison to the unstiffened structure with the same mass. Obtained results also indicate potential problems with areas of concentrated stress in the case of an incorrect geometry design near to the boundary conditions.

scholarly journals Finite element modelling of the Taylor impact test in 3D with the Coupled Eulerian-Lagrangian method

2021 ◽  
Author(s):  
François Ducobu ◽  
Anthonin Demarbaix ◽  
Olivier Pantalé
Keyword(s):  
Constitutive Model ◽  
Impact Test ◽  
Reference Model ◽  
Constitutive Models ◽  
Experimental Tests ◽  
Model Parameters ◽  
Cutting Operation ◽  
Taylor Impact ◽  
Taylor Impact Test ◽  
Future Work

When modelling a cutting operation, the constitutive model of the machined material is one of the key parameters to obtain accurate and realistic results. Up to now, the Johnson-Cook model is still the most used, even if an increasing number of models, such as the Hyperbolic TANgent (TANH) model, were introduced last years to overcome its limitations and come closer to the actual material behaviour. Experimental tests on dedicated equipment are usually required to identify the parameters of the constitutive models. This paper introduces the Coupled Eulerian-Lagrangian (CEL) formalism to model in 3D the Taylor impact test, one of the common tests to perform that parameters identification. Indeed, one identification way involves modelling the test to determine the constitutive model parameters by comparing the experimental and the numerical samples geometries. The developed CEL model is validated against a Lagrangian reference model for a steel alloy and the Johnson-Cook constitutive model. The main goal of using the CEL method is to get rid of the elements distortion due to the high strains and strain rates during the test. Mesh dependence of the results is highlighted and a recommendation is provided on the mesh to adopt for future work. The CEL model of the 3D Taylor impact test is then extended to the use of the TANH model. The results are finally compared with that of the Johnson-Cook constitutive model.

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