Abstract:In this paper, an elastoplastic-anisotropic damage constitutive model is proposed for the identification of damage parameters of Al2024-T3 by micro-hardness measurements. For this purpose, micro-hardness experiments are conducted on the surface of the specimens after the standard tensile tests. A procedure for the identification of the damage as a tensor variable is followed and then, the parameters of the model are calibrated. Also, the constitutive equations are implemented in a finite element explicit code … Show more
“…Based on this data, we can conclude that the Al2024-T3 alloy has low sensitivity to the strain rate. The damage–strain data extracted by the micro hardness measurement (Ganjiani, 2013) are shown in Figure 2(b). Figure 1.Dimensions of the tensile specimen (mm) used for characterization of the material at different strain rates.Figure 2.The data of tensile test conducted on Al2024-T3 at different strain rates: (a) stress–strain and (b) damage–strain.…”
In this article, a rate-dependent elastoplastic-damage constitutive model considering the effect of strain rate has been developed. The derivation of this model has been established based on the irreversible thermodynamics with internal variables within the fundamentals of Continuum damage mechanics (CDM). For investigating the rate effect, an additional power function dependent on the effective strain rate has been involved in the plastic dissipation function (dynamic plastic yield surface). The damage has been assumed as a tensor-type variable and based on the energy equivalence hypothesis, the damage evolution has been developed. The proposed constitutive model has been implemented into user-defined subroutines UMAT and VUMAT in the finite-element program ABAQUS/(Standard and Explicit). For this purpose, the implicit and explicit stress integration algorithms of the model have been explained. The model has been validated by comparing the predicted results with experimental data conducted on Al2024-T3. These experiments are including the tensile and double-notched tests. Furthermore, the numerical results have been compared with some data available in the literature. The numerical examples show the excellent correlation between experiments and simulations for stress (or force) and damage results.
“…Based on this data, we can conclude that the Al2024-T3 alloy has low sensitivity to the strain rate. The damage–strain data extracted by the micro hardness measurement (Ganjiani, 2013) are shown in Figure 2(b). Figure 1.Dimensions of the tensile specimen (mm) used for characterization of the material at different strain rates.Figure 2.The data of tensile test conducted on Al2024-T3 at different strain rates: (a) stress–strain and (b) damage–strain.…”
In this article, a rate-dependent elastoplastic-damage constitutive model considering the effect of strain rate has been developed. The derivation of this model has been established based on the irreversible thermodynamics with internal variables within the fundamentals of Continuum damage mechanics (CDM). For investigating the rate effect, an additional power function dependent on the effective strain rate has been involved in the plastic dissipation function (dynamic plastic yield surface). The damage has been assumed as a tensor-type variable and based on the energy equivalence hypothesis, the damage evolution has been developed. The proposed constitutive model has been implemented into user-defined subroutines UMAT and VUMAT in the finite-element program ABAQUS/(Standard and Explicit). For this purpose, the implicit and explicit stress integration algorithms of the model have been explained. The model has been validated by comparing the predicted results with experimental data conducted on Al2024-T3. These experiments are including the tensile and double-notched tests. Furthermore, the numerical results have been compared with some data available in the literature. The numerical examples show the excellent correlation between experiments and simulations for stress (or force) and damage results.
“…To obtain a credible result of strain measurement, we have to use a technique enabling measurement on big enough volume of a uniformly stressed material (Representative Volume Element). In most cases, such kind of a specimen is used also for damage investigations (Niazi et al, 2013;Ganjiani, 2013;Shen et al, 2014). To investigate the effect of permanent deformation (plastic strain) on the structure of the material, such kind of the specimen is usually deformed to reach a particular level of plastic strain in the entire gage part and then unloaded to perform structural analysis.…”
An innovative method for investigation of deformation-induced damage of elastic-plastic materials is proposed. A static tension test, performed on a specimen with a variable cross--section gage part enabled analysis of degradation of the material structure for all stages of permanent deformation. Modified Johnson model has been used to quantify damage. Analysis of the damage of the specimen surface as well as observations of the damage induced inside the gage part of the specimen has been performed using SEM observations. Debonding at the interface between a hard inclusion and a ductile matrix has been found to be responsible for initiation of cracks on the specimen surface as well as inside the gage part of the specimen. Analysis of the subsequent void growth has been performed. Surface cracks are associated with plastic deformation resulting in an increase of the surface roughness. Variations of the specimen surface roughness have been found to be in good correlation with the damage parameter. This correlation enables the use of surface roughness as the relative damage indicator for the investigated material and deformation mode.
“…Nevertheless, extensions of the model have been proposed, for example including damage anisotropy (e.g. [15] and [16]) or Lode angle (e.g. [1] and [17]) for low stress-triaxiality applications.…”
Section: Introductionmentioning
confidence: 99%
“…Experimental identification of Lemaitre damage variable is typically performed through observation of variation in modulus of elasticity [11] and [12] or microhardness [15] and [18] by the uniaxial tensile experiment. The out-of-plane damage value is then estimated through the in-plane measurements [10].…”
The mechanical characteristics of sheet metals are typically identified in the in-plane direction, although the sheet-metal forming processes (e.g., blanking, deep-drawing) are normally applied in the out-of-plane direction. As the mechanical characteristics are not necessarily constant, their direct experimental evaluation through the forming process would enable material monitoring and process optimization, and, additionally, material characterization in the out-of-plane direction. Full, partial (to a certain depth) and sequential (consecutive partial steps to full penetration) blanking experiments are performed on a laboratory blanking apparatus to correlate the out-of-plane material characteristics with the in-plane ones. The well-established in-plane approach to damage is introduced for the out-of-plane direction to determine the isotropic Lemaitre damage variable. Furthermore, yield and ultimate shear stresses are determined and correlated to their respective in-plane counterparts, offering a new insight in the sheet-metal blanking process. Keywords: cutting and forming, constitutive behavior, elastic-plastic material, mechanical testing, ductile damage, out-of-plane experiment Highlights • Experimental out-of-plane sheet-metal material characterization. • Use of in-plane approach for out-of-plane characterization. • Direct material characterization and correlation to in-plane parameters. • Experimental Lemaitre damage characterization in the out-of-plane direction. • Full, partial and sequential blanking experiments on laboratory blanking apparatus.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
