scholarly journals Identification and validation of an extended Stewart-Cazacu micromechanics damage model applied to Ti–6Al–4V specimens exhibiting positive stress triaxialities

2021 ◽  
pp. 146442072110099
Author(s):  
Carlos Rojas-Ulloa ◽  
Marian Valenzuela ◽  
Víctor Tuninetti ◽  
Anne-Marie Habraken
Keyword(s):  
Damage Model ◽  
Tensile Tests ◽  
Experimental Results ◽  
Ductile Material ◽  
Large Strains ◽  
State Variables ◽  
Material Parameter Identification ◽  
Microscopy Imaging ◽  
Research Software ◽  
Numerical Predictions

In this research, the Stewart-Cazacu micromechanics coupled damage model is extended and validated adding nucleation and coalescence models as new damage mechanisms. The Ti–6Al–4V titanium alloy is chosen as a suitable hcp ductile material to be modeled using this extended damage law. The characterization of the damage evolution in this alloy is addressed throughout a quasi-static experimental campaign. Damage characterization relies on in situ X-ray tomography data and scanning electron microscopy imaging technique. The validation procedure consists in the implementation into the finite element research software Lagamine of ULiège and in the comparison of numerical predictions and experimental results. Load–displacement curves and damage-related state variables at fracture configuration from smooth and notched bar specimens submitted to tensile tests are analyzed. The nucleation and coalescence model extensions as well as an accurate elastoplastic and damage material parameter identification for Ti–6Al–4V samples are essential features to reach a validated model. The prediction capabilities exhibited for large strains are in good agreement with experimental results, while the near-fracture strains can still be improved.

A Nonlinear Damage Model of Hardening-Softening Materials

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
M. Ganjiani
Keyword(s):  
Damage Mechanics ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Tensile Tests ◽  
Internal Variable ◽  
Integration Algorithm ◽  
Finite Element Program ◽  
Variable Theory ◽  
Numerical Predictions ◽  
Type Variable

In this paper, an elastoplastic-damage constitutive model is presented. The formulation is cast within the framework of continuum damage mechanics (CDM) by means of the internal variable theory of thermodynamics. The damage is assumed as a tensor type variable and its evolution is developed based on the energy equivalence hypothesis. In order to discriminate the plastic and damage deformation, two surfaces named as plastic and damage are introduced. The damage surface has been developed so that it can model the nonlinear variation of damage. The details of the model besides its implicit integration algorithm are presented. The model is implemented as a user-defined subroutine user-defined material (UMAT) in the abaqus/standard finite element program for numerical simulation purposes. In the regard of investigating the capability of model, the shear and tensile tests are experimentally conducted, and corresponding results are compared with those predicted numerically. These comparisons are also accomplished for several experiments available in the literature. Satisfactory agreement between experiments and numerical predictions provided by the model implies the capability of the model to predict the plastic deformation as well as damage evolution in the materials.

scholarly journals A generalized mechanical model using stress–strain duality at large strain for amorphous polymers

2020 ◽  
pp. 108128652095846
Author(s):  
CA Bernard ◽  
D George ◽  
S Ahzi ◽  
Y Rémond
Keyword(s):  
Mechanical Model ◽  
Mechanical Response ◽  
Amorphous Polymer ◽  
Large Strain ◽  
Amorphous Polymers ◽  
3D Models ◽  
Experimental Results ◽  
Large Strains ◽  
Stress Strain ◽  
Numerical Predictions

Numerous models have been developed in the literature to simulate the thermomechanical behavior of amorphous polymers at large strain. These models generally show a good agreement with experimental results when the material is submitted to uniaxial loadings (tension or compression) or in the case of shear loadings. However, this agreement is highly degraded when they are used in the case of combined load cases. A generalization of these models to more complex loads is scarce. In particular, models that are identified in tension or compression often overestimate the response in shear. One difficulty lies in the fact that 3D models must aggregate different physical modeling, described with different kinematics. This requires the use of transport operators complex to manipulate. In this paper, we propose a mechanical model for large strains, generalized in 3D, and precisely introducing the adequate transport operators in order to obtain an exact kinematic. The stress–strain duality is validated in the writing of the power of internal forces. This generalized model is applied in the case of a polycarbonate amorphous polymer. The simulation results in tension/compression and shear are compared with the classical modeling and experimental results from the literature. The results greatly improve the numerical predictions of the mechanical response of amorphous polymers submitted to any load case.

Progressive damage characteristics of screwed single-lap CFRPI-metal joint subjected to tensile loading at RT and 350°C

2021 ◽  
pp. 002199832098559
Author(s):  
Yun-Tao Zhu ◽  
Jun-Jiang Xiong ◽  
Chu-Yang Luo ◽  
Yi-Sen Du
Keyword(s):  
Damage Model ◽  
Tensile Loading ◽  
Tensile Tests ◽  
Displacement Curve ◽  
Progressive Damage ◽  
Damage Characteristics ◽  
Metal Joint ◽  
Static Tensile ◽  
Strength And Stiffness ◽  
Progressive Damage Model

This paper outlines progressive damage characteristics of screwed single-lap CFRPI-metal joints subjected to tensile loading at RT (room temperature) and 350°C. Quasi-static tensile tests were performed on screwed single-lap CCF300/AC721-30CrMnSiA joint at RT and 350°C, and the load versus displacement curve, strength and stiffness of joint were gauged and discussed. With due consideration of thermal-mechanical interaction and complex failure mechanism, a modified progressive damage model (PDM) based on the mixed failure criterion was devised to simulate progressive damage characteristics of screwed single-lap CCF300/AC721-30CrMnSiA joint, and simulations correlate well with experiments. By using the PDM, the effects of geometry dimensions on mechanical characteristics of screwed single-lap CCF300/AC721-30CrMnSiA joint were analyzed and discussed.

scholarly journals A New No Equilibrium Fractional Order Chaotic System, Dynamical Investigation, Synchronization, and Its Digital Implementation

Inventions ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 49
Author(s):  
Zain-Aldeen S. A. Rahman ◽  
Basil H. Jasim ◽  
Yasir I. A. Al-Yasir ◽  
Raed A. Abd-Alhameed ◽  
Bilal Naji Alhasnawi
Keyword(s):  
Adaptive Control ◽  
Fractional Order ◽  
Chaotic System ◽  
Real World ◽  
Experimental Results ◽  
Chaotic Attractors ◽  
State Variables ◽  
Digital Implementation ◽  
Dynamical Behaviors ◽  
Real World Applications

In this paper, a new fractional order chaotic system without equilibrium is proposed, analytically and numerically investigated, and numerically and experimentally tested. The analytical and numerical investigations were used to describe the system’s dynamical behaviors including the system equilibria, the chaotic attractors, the bifurcation diagrams, and the Lyapunov exponents. Based on the obtained dynamical behaviors, the system can excite hidden chaotic attractors since it has no equilibrium. Then, a synchronization mechanism based on the adaptive control theory was developed between two identical new systems (master and slave). The adaptive control laws are derived based on synchronization error dynamics of the state variables for the master and slave. Consequently, the update laws of the slave parameters are obtained, where the slave parameters are assumed to be uncertain and are estimated corresponding to the master parameters by the synchronization process. Furthermore, Arduino Due boards were used to implement the proposed system in order to demonstrate its practicality in real-world applications. The simulation experimental results were obtained by MATLAB and the Arduino Due boards, respectively, with a good consistency between the simulation results and the experimental results, indicating that the new fractional order chaotic system is capable of being employed in real-world applications.

Numerical investigation of the propagation of shock waves in rigid porous materials: development of the computer code and comparison with experimental results

1996 ◽  
Vol 324 ◽  
pp. 163-179 ◽  
Author(s):  
A. Levy ◽  
G. Ben-Dor ◽  
S. Sorek
Keyword(s):  
Porous Materials ◽  
Initial Conditions ◽  
Computer Code ◽  
Experimental Results ◽  
Numerical Code ◽  
Materials Development ◽  
Numerical Predictions ◽  
Wide Range ◽  
Dimensional Version ◽  
The One

The governing equations of the flow field which is obtained when a thermoelastic rigid porous medium is struck head-one by a shock wave are developed using the multiphase approach. The one-dimensional version of these equations is solved numerically using a TVD-based numerical code. The numerical predictions are compared to experimental results and good to excellent agreements are obtained for different porous materials and a wide range of initial conditions.

Transferability of the Gurson Damage Model Parameters with Charpy and Tensile Tests with Different Constrain Level

2009 ◽  
Vol 65 ◽  
pp. 19-31
Author(s):  
Ruben Cuamatzi-Melendez ◽  
J.R. Yates
Keyword(s):  
Strain Rate ◽  
Damage Model ◽  
Rolling Direction ◽  
Fracture Initiation ◽  
Tensile Tests ◽  
Model Parameters ◽  
Gurson Model ◽  
Finite Element Program ◽  
Element Program ◽  
Gurson's Model

Little work has been published concerning the transferability of Gurson’s ductile damage model parameters in specimens tested at different strain rates and in the rolling direction of a Grade A ship plate steel. In order to investigate the transferability of the damage model parameters of Gurson’s model, tensile specimens with different constraint level and impact Charpy specimens were simulated to investigate the effect of the strain rate on the damage model parameters of Gurson model. The simulations were performed with the finite element program ABAQUS Explicit [1]. ABAQUS Explicit is ideally suited for the solution of complex nonlinear dynamic and quasi–static problems [2], especially those involving impact and other highly discontinuous events. ABAQUS Explicit supports not only stress–displacement analyses but also fully coupled transient dynamic temperature, displacement, acoustic and coupled acoustic–structural analyses. This makes the program very suitable for modelling fracture initiation and propagation. In ABAQUS Explicit, the element deletion technique is provided, so the damaged or dead elements are removed from the analysis once the failure criterion is locally reached. This simulates crack growth through the microstructure. It was found that the variation of the strain rate affects slightly the value of the damage model parameters of Gurson model.

scholarly journals Forming limit diagram prediction of 6061 aluminum by GTN damage model

2018 ◽  
Vol 19 (2) ◽  
pp. 202 ◽  
Author(s):  
Rasoul Safdarian
Keyword(s):  
Damage Model ◽  
Forming Limit Diagram ◽  
Numerical Results ◽  
Experimental Results ◽  
Correct Selection ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Gtn Model ◽  
Gtn Damage Model

Forming limit diagram (FLD) is one of the formability criteria which is a plot of major strain versus minor strain. In the present study, Gurson-Tvergaard-Needleman (GTN) model is used for FLD prediction of aluminum alloy 6061. Whereas correct selection of GTN parameters’ is effective in the accuracy of this model, anti-inference method and numerical simulation of the uniaxial tensile test is used for identification of GTN parameters. Proper parameters of GTN model is imported to the finite element analysis of Nakazima test for FLD prediction. Whereas FLD is dependent on forming history and strain path, forming limit stress diagram (FLSD) based on the GTN damage model is also used for forming limit prediction in the numerical method. Numerical results for FLD, FLSD and punch’s load-displacement are compared with experimental results. Results show that there is a good agreement between the numerical and experimental results. The main drawback of numerical results for prediction of the right-hand side of FLD which was concluded in other researchers’ studies was solved in the present study by using GTN damage model.

scholarly journals Determination of Forming Limits Based on Finite Element Simulations

2021 ◽  
Author(s):  
Fuhui Shen ◽  
Kai Chen ◽  
Junhe Lian ◽  
Sebastian Münstermann
Keyword(s):  
Finite Element ◽  
Damage Mechanics ◽  
Tensile Tests ◽  
Finite Element Simulations ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
Anisotropic Plasticity ◽  
Forming Limits ◽  
Dog Bone ◽  
Spatio Temporal

Two categories of experiments have been performed to obtain the experimental forming limits of a ferritic stainless steel from uniaxial to equibiaxial tension, including Nakajima tests and tensile tests of flat specimens with different geometries of the central hole as well as the notched dog bone. The plasticity behavior of the investigated material is described using an evolving non-associated anisotropic plasticity model, which is calibrated based on experimental results of uniaxial tensile tests along different loading directions. A damage mechanics model is calibrated and validated based on the global force and displacement response of tensile tests. Finite element simulations of the Nakajima tests and the tensile tests of various geometries have been performed using the anisotropic material model. A novel spatio-temporal method is developed to evaluate the forming limits under different stress states by quantitatively characterizing the plastic strain distribution on the specimen surface. The forming limits have been independently determined from finite element simulation results of tensile specimens and Nakajima specimens using the spatio-temporal evaluation method. The forming limits obtained from numerical simulations of these two types of experiments are in good agreement with experimental results.

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