3D-FE-Analysis of CT-specimens including viscoplastic material behavior and nonlocal damage

2009 ◽  
Vol 46 (2) ◽  
pp. 352-357 ◽  
Author(s):  
Jana Velde ◽  
Ursula Kowalsky ◽  
Tim Zümendorf ◽  
Dieter Dinkler
Keyword(s):  
Fe Analysis ◽  
Material Behavior ◽  
Viscoplastic Material ◽  
Nonlocal Damage

Computer Aided Design of an Effective Fixture for FSW Processes of Titanium Alloys

2011 ◽  
Vol 473 ◽  
pp. 304-309
Author(s):  
Gianluca Buffa ◽  
Livan Fratini
Keyword(s):  
Titanium Alloys ◽  
Computer Aided Design ◽  
Welding Process ◽  
Optimal Solution ◽  
Fusion Welding ◽  
Material Behavior ◽  
Viscoplastic Material ◽  
3D Fem ◽  
Friction Stir ◽  
Aluminum And Magnesium Alloys

During the last years welded titanium components have been extensively applied in aeronautical and aerospace industries because of their high specific strength and corrosion resistance properties. Friction Stir Welding (FSW) is a solid state welding process, currently industrially utilized for difficult to be welded or “unweldable” aluminum and magnesium alloys, able to overcome the drawbacks of traditional fusion welding techniques. When titanium alloys are concerned, additional problems arise as the need for very high strength and high temperature resistant tools, gas shield protection and high stiffness machines. Additionally, the process is characterized by an elevated sensitivity to temperature variations, which, in turn, depends on the main operative parameters. Numerical simulation represents the optimal solution in order to perform an effective process optimization with affordable costs. In this paper, a fully 3D FEM model for the FSW process is proposed, that is thermo-mechanically coupled and with rigid-viscoplastic material behavior. Experimental clamping parts are modeled and the thermal loads are calculated at the varying of the cooling strategy. Finally, the effectiveness of the cooling systems is evaluated through experimental tests.

Computational Aspects in the Elasto/Viscoplastic Material Behavior of Solids

2012 ◽  
Vol 567 ◽  
pp. 192-199 ◽  
Author(s):  
Fabio de Angelis
Keyword(s):  
Constitutive Model ◽  
Material Behavior ◽  
Inelastic Behavior ◽  
Viscoplastic Material ◽  
Solid Materials ◽  
Numerical Examples ◽  
Computational Aspects ◽  
Computational Procedures ◽  
Consistent Tangent Operator ◽  
Algorithmic Procedure

In the present paper a computational algorithmic procedure is presented for modeling the elasto/viscoplastic behavior of solid materials. The effects of different loading programs on the inelastic behavior of rate-sensitive materials are analyzed with specific numerical examples. An appropriate solution scheme and a consistent tangent operator are applied which are capable to be adopted for general computational procedures. Numerical computations and results are reported which illustrate the rate-dependence of the constitutive model in use.

Development of LSTM networks for predicting viscoplasticity with effects of deformation, strain rate and temperature history

2021 ◽  
pp. 1-30
Author(s):  
Lahouari Benabou
Keyword(s):  
Strain Rate ◽  
Short Term Memory ◽  
Internal State ◽  
Material Behavior ◽  
Temperature History ◽  
Loading Conditions ◽  
Viscoplastic Material ◽  
Temperature Changes ◽  
History Effects ◽  
Deformation Strain Rate

Abstract In this paper, long short-term memory (LSTM) networks are used in an original way to model the behavior of a viscoplastic material solicited under changing loading conditions. The material behavior is dependent on history effects of plasticity which can be visible during strain rate jumps or temperature changes. Due to their architecture and internal state (memory), the LSTM networks have the ability to remember past data to update their current state, unlike the traditional artificial neural networks (ANNs) which fail to capture history effects. Specific LSTM networks are designed and trained to reproduce the complex behavior of a viscoplastic solder alloy subjected to strain rate jumps, temperature changes or loading-unloading cycles. The training datasets are numerically generated using the constitutive viscoplastic law of Anand which is very popular for describing solder alloys. The Anand model serves also as a reference to evaluate the performances of the LSTM networks on new data. It is demonstrated that this class of networks is remarkably well suited for replicating the history plastic effects under all the tested loading conditions.

Finite-element modeling of partially prestressed concrete beams with unbonded tendon under monotonic loadings

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Pandimani ◽  
Markandeya Raju Ponnada ◽  
Yesuratnam Geddada
Keyword(s):  
Finite Element ◽  
Prestressed Concrete ◽  
Nonlinear Response ◽  
Concrete Beams ◽  
Fe Analysis ◽  
Material Behavior ◽  
Fe Model ◽  
Ansys Software ◽  
Content Type ◽  
Prestressing Tendon

Purpose The partially prestressed concrete beam with unbonded tendon is still an active field of research because of the difficulty in analyzing and understanding its behavior. The finite-element (FE) simulation of such beams using numerical software is very scarce in the literature and therefore this study is taken to demonstrate the modeling aspects of unbonded partially prestressed concrete (UPPSC) beams. This study aims to present the three-dimensional (3-D) nonlinear FE simulations of UPPSC beams subjected to monotonic static loadings using the numerical analysis package ANSYS. Design/methodology/approach The sensitivity study is carried out with three different mesh densities to obtain the optimum elements that reflect on the load–deflection behavior of numerical models, and the model with optimum element density is used further to model all the UPPSC beams in this study. Three half-symmetry FE model is constructed in ANSYS parametric design language domain with proper boundary conditions at the symmetry plane and support to achieve the same response as that of the full-scale experimental beam available in the literature. The linear and nonlinear material behavior of prestressing tendon and conventional steel reinforcements, concrete and anchorage and loading plates are modeled using link180, solid65 and solid185 elements, respectively. The Newton–Raphson iteration method is used to solve the nonlinear solution of the FE models. Findings The evolution of concrete cracking at critical loadings, yielding of nonprestressed steel reinforcements, stress increment in the prestressing tendon, stresses in concrete elements and the complete load–deflection behavior of the UPPSC beams are well predicted by the proposed FE model. The maximum discrepancy of ultimate moments and deflections of the validated FE models exhibit 13% and −5%, respectively, in comparison with the experimental results. Practical implications The FE analysis of UPPSC beams is done using ANSYS software, which is a versatile tool in contrast to the experimental testing to study the stress increments in the unbonded tendons and assess the complete nonlinear response of partially prestressed concrete beams. The validated numerical model and the techniques presented in this study can be readily used to explore the parametric analysis of UPPSC beams. Originality/value The developed model is capable of predicting the strength and nonlinear behavior of UPPSC beams with reasonable accuracy. The load–deflection plot captured by the FE model is corroborated with the experimental data existing in the literature and the FE results exhibit good agreement against the experimentally tested beams, which expresses the practicability of using FE analysis for the nonlinear response of UPPSC beams using ANSYS software.

Deformable Image Registration Between Cardiac PET Images Encompassing a Range of Physical Heart Sizes

2011 ◽  
Author(s):  
Benjamin R. Coleman ◽  
Alexander I. Veress
Keyword(s):  
Mechanical Performance ◽  
Fe Analysis ◽  
Material Behavior ◽  
Patient Specific ◽  
Stress And Strain ◽  
Myocardial Tissue ◽  
Cardiac Pet ◽  
Considerable Research ◽  
Deformation Stress

Cardiac mechanical performance depends upon myocardial tissue elongation and contraction. Deformation, stress and strain within the myofibers provide valuable information about potential tissue adaptation [1]. Specifically, the stress state of the tissue is believed to drive remodeling of the myocardium. Because it is not possible to measure in-vivo stress in the human heart, considerable research has gone into developing patient specific, mathematical models of the heart based on finite element (FE) analysis and cardiac imaging [2, 3]. Stress estimates from these models could yield valuable information about of the material behavior of the myocardium that would provide valuable information for research into cardiac pathologies.

FE Analysis of Size Effect on Deformation Behavior of Metal Microtube Considering Surface Roughness in Flaring Test

2009 ◽  
Vol 623 ◽  
pp. 79-87 ◽  
Author(s):  
Mohammad Ali Mirzai ◽  
Kenichi Manabe
Keyword(s):  
Surface Roughness ◽  
Size Effect ◽  
Wall Thickness ◽  
Size Effects ◽  
Fe Analysis ◽  
Material Behavior ◽  
Test Results ◽  
Feature Size ◽  
Analysis And Design ◽  
Smoothing Process

Reliable test results that show the material characteristics of a micromaterial are necessary for the accurate analysis and design of microforming processes. The size effects in the microforming are predicted to have a significant impact on the material behavior. Two size effects are explored in metallic materials. One is the grain size effect, and the other is the feature/specimen size effect. In this study, the feature size effect on the smoothing process with the consideration of tool surface roughness is investigated numerically for metal microtubes by the flaring test. Stainless-steel (SUS 316L) microtubes with the same outer diameter of 500 μm and different wall thicknesses of 50, 25 and 10 μm were used in the FE analysis to study the feature size effect on the microscale by the flaring test. The surface roughnesses of the inner and outer surfaces of the microtube, as well as the surface asperity of the conical tool, were modeled in the cyclic concave-convex configuration. It is found, in the flaring test with using rough and fine tools, that the smoothing process on the inner surface of the microtube (ISM), as well as the plastic strain in the wall thickness of microtube, is affected owing to the rigidity of the microtube, which decreases as the wall thickness of the microtube decreases. These results suggest that the feature size affects the flaring test results for the metal microtube.

A new loading history for identification of viscoplastic properties by spherical indentation

2004 ◽  
Vol 19 (1) ◽  
pp. 101-113 ◽  
Author(s):  
N. Huber ◽  
E. Tyulyukovskiy
Keyword(s):  
Strain Curve ◽  
Material Behavior ◽  
Creep Process ◽  
Spherical Indentation ◽  
Loading History ◽  
Viscoplastic Material ◽  
Stress Strain Curve ◽  
Material Parameters ◽  
Depth Data ◽  
Variable Combination

In this paper a new loading history for extracting the stress–strain curve as well as the viscosity and creep behavior from indentation experiments is developed. It is based on a simple model describing the viscoplastic spherical indentation with a power-law hardening rule and a velocity-dependent overstress. Using this model, patterns were generated consisting of load-depth data and corresponding material parameters. The loading history for the simulation of the patterns was considered as a variable combination of loading and creep processes. To compare the identification potential of different loading histories, the inverse problem of determining the viscoplastic material parameters was solved by using neural networks. The emerging loading history uses a multiple-creep process with equidistant load steps and allows an identification of material parameters with much higher accuracy than with single creep. It will be used for further work, where the identification method is generalized using more realistic finite element simulations for a finite deformation elastic–viscoplastic material behavior.

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