The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Stelios Kyriakides - One of the best experts on this subject based on the ideXlab platform.
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Material Response localization and failure of an aluminum alloy under combined shear and tension part ii analysis
International Journal of Plasticity, 2019Co-Authors: Kelin Chen, Martin Scales, Stelios KyriakidesAbstract:Abstract The Responses of the tubular specimens loaded under combined tension and torsion in Part I exhibited limit load instabilities followed by extensive localized deformation prior to failure. The present manuscript outlines an analytical framework that aims to establish the extent to which plasticity can reproduce the measured Responses up to the onset of failure without the introduction of damage-induced softening effects. The analysis incorporates a suitably calibrated non-quadratic anisotropic yield function, a Material hardening Response extracted to large strains from a simple shear test, and a finite element model with refined 3-D elements. The analysis successfully reproduces the shear and axial stress levels during the homogeneous deformation parts of the Response, the stresses and deformations at the load maxima, and the parts with decreasing stress associated with localized deformation. Furthermore, the geometry of the necked zones and the rapid growth of strain inside them are reproduced to levels that correspond to the recorded failure strains. Critical aspects of this successful effort are the non-quadratic anisotropic yield function and the Material hardening adopted. It is concluded that the framework developed, combined with a suitable failure criterion based on results like those in Part I, constitute a viable tool for establishing the end of life of structures in engineering practice.
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effects of anisotropy on Material hardening and burst in the bulge test
International Journal of Solids and Structures, 2016Co-Authors: Kelin Chen, Martin Scales, Stelios Kyriakides, Edmundo CoronaAbstract:Abstract The hydraulic bulge test provides a means for testing sheet metal under a nearly equibiaxial stress state. Failure is delayed, allowing measurement of the Material Response at significantly larger strains than in the traditional uniaxial test. This study uses experiment and analysis to develop a methodology for incorporating anisotropy in the extraction of the Material stress–strain Response from a bulge test. A custom six-inch bulge testing facility is used to test aluminum alloy discs to failure. The curvature and strains at the apex of the bulge are monitored via stereo digital image correlation (DIC). Anisotropy is modeled via the 18-parameter non-quadratic yield function of Barlat et al. (2005), which is calibrated through independent tests on specimens from the same sheet as the bulge test specimens. The extraction of the Material Response uses the measured deformation at the apex and a flow rule based on the calibrated yield function. An equibiaxial state of stress or strain at the apex is not assumed. The extracted Material Response and the anisotropic yield function are subsequently used to simulate numerically the bulge test using solid elements. The results illustrate the effect of anisotropy on the extracted Material stress–strain Response and on the onset of localization that precedes failure.
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underlying Material Response for luders like instabilities
International Journal of Plasticity, 2013Co-Authors: Julian F Hallai, Stelios KyriakidesAbstract:Abstract The initial yielding of some low carbon steels exhibits a Material instability known as Luders banding. This is a dislocation driven phenomenon that macroscopically manifests as inhomogeneous deformation. For example, in a displacement controlled uniaxial test Luders banding leads to coexistence of two deformation regimes while the stress remains relatively unchanged. Shape memory alloys whose behavior is governed by solid–solid phase transformations, in some temperature regimes exhibit similar localizations albeit reversible. Such localizations have undesirable consequences in structural applications such as stretch marks and structural instabilities. Modeling of this behavior in order to assess its consequences in structures is hampered because the true Material Response over the stress plateau is unknown. This work used an experimental technique, outlined in Shioya and Shiroiri (1976) that extracts the underlying Material Response of such Materials from a tensile test. Laminates consisting of face-strips of a hardening Material and an unstable core, if properly designed, can suppress the inhomogeneous deformation of the core resulting in a monotonically increasing Response. This method revealed that both steel and NiTi strips have up-down-up Responses. The extracted Responses incorporated in finite element models are shown to reproduce both the laminate experiments and the behavior of strips made of unstable Materials alone.
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determination of anisotropy and Material hardening for aluminum sheet metal
International Journal of Solids and Structures, 2012Co-Authors: Nicolas Tardif, Stelios KyriakidesAbstract:Abstract Sheet metal forming, crushing simulations of thin-walled structures, and other large deformation processes require knowledge of the Material stress–strain behavior to large strains. The Material Response of sheets measured in the traditional uniaxial tension test usually terminates at strains of a few percent due to necking. It can be extrapolated to some degree using results from biaxial tests (e.g., equibiaxial tension) but not to sufficiently large strains. This work shows a systematic methodology that uses a combination of experiment and analysis to extract the Material Response at much larger strains. This is achieved by accurately following the deformation in the necked region of a custom tensile test specimen. The test is simulated numerically using a 3D FE model and the Material Response is iteratively extrapolated until the calculated and measured force-elongation match. For the Al-6061-T6 sheet metal of interest, the process is complicated by inherent anisotropies introduced during the rolling of the sheets. The anisotropy is characterized by a set of uniaxial and biaxial tests conducted in parallel. The results are used to calibrate the 18-parameter non-quadratic Yld2004-3D yield function. The calibrated yield function is then used to simulate the tensile test. The Material hardening is iteratively adjusted by comparing the measured and calculated force–displacement Response and validated by the corresponding measured strains and shape of the neck.
Brian Falzon - One of the best experts on this subject based on the ideXlab platform.
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modelling matrix damage and fibre matrix interfacial decohesion in composite laminates via a multi fibre multi layer representative volume element m2rve
International Journal of Solids and Structures, 2014Co-Authors: Ganesh Soni, Ramesh Singh, Mira Mitra, Brian FalzonAbstract:A three-dimensional multi-fibre multi-layer micromechanical finite element model was developed for the prediction of mechanical behaviour and damage Response of composite laminates. Material Response and micro-scale damage mechanism of cross-ply, [0/90]ns, and angle-ply, [±45]ns, glass-fibre/epoxy laminates were captured using multi-scale modelling via computational micromechanics. The framework of the homogenization theory for periodic media was used for the analysis of the proposed ‘multi-fibre multi-layer representative volume element’ (M2RVE). Each layer in M2RVE was represented by a unit cube with multiple randomly distributed, but longitudinally aligned, fibres of equal diameter and with a volume fraction corresponding to that of each lamina (equal in the present case). Periodic boundary conditions were applied to all the faces of the M2RVE. The non-homogeneous stress–strain fields within the M2RVE were related to the average stresses and strains by using Gauss’ theorem in conjunction with the Hill–Mandal strain energy equivalence principle. The global Material Response predicted by the M2RVE was found to be in good agreement with experimental results for both laminates. The model was used to study effect of matrix friction angle and cohesive strength of the fibre–matrix interface on the global Material Response. In addition, the M2RVE was also used to predict initiation and propagation of fibre–matrix interfacial decohesion and propagation at every point in the laminae.
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A multifibre multilayer representative volume element (M2RVE) for prediction of matrix and interfacial damage in composite laminates
2012Co-Authors: Ganesh G Soni, Ramesh Singh, Mira Mitra, Brian FalzonAbstract:Multiscale micro-mechanics theory is extensively used for the prediction of the Material Response and damage analysis of unidirectional lamina using a representative volume element (RVE). This paper presents a RVE-based approach to characterize the Material Response of a multi-fibre cross-ply laminate considering the effect of matrix damage and fibre-matrix interfacial strength. The framework of the homogenization theory for periodic media has been used for the analysis of a 'multi-fibre multi-layer representative volume element' (M 2 RVE) representing cross-ply laminate. The non-homogeneous stress-strain fields within the M 2 RVE are related to the average stresses and strains by using Gauss theorem and the Hill-Mandal strain energy equivalence principle. The interfacial bonding strength affects the in-plane shear stress-strain Response significantly. The Material Response predicted by M 2 RVE is in good agreement with the experimental results available in the literature. The maximum difference between the shear stress predicted using M 2 RVE and the experimental results is ~15% for the bonding strength of 30MPa at the strain value of 1.1%.
Daniel Krajcarz - One of the best experts on this subject based on the ideXlab platform.
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influence of Material structure on forces measured during abrasive waterjet awj machining
Materials, 2020Co-Authors: Libor M Hlavac, Adam Stefek, Daniel KrajcarzAbstract:Material structure is one of the important factors influencing abrasive waterjet (AWJ) machining efficiency and quality. The force measurements were performed on samples prepared from two very similar steels with different thicknesses and heat treatment. The samples were austenitized at 850 °C, quenched in polymer and tempered at various temperatures between 20 °C and 640 °C. The resulting states of Material substantially differed in strength and hardness. Therefore, samples prepared from these Material states are ideal for testing of Material Response to AWJ. The force measurements were chosen to test the possible influence of Material structure on the Material Response to the AWJ impact. The results show that differences in Material structure and respective Material properties influence the limit traverse speed. The cutting to deformation force ratio seems to be a function of relative traverse speed independently on Material structure.
Vadim V Silberschmidt - One of the best experts on this subject based on the ideXlab platform.
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analysis of Material Response to ultrasonic vibration loading in turning inconel 718
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Naseer Ahmed, A V Mitrofanov, V I Babitsky, Vadim V SilberschmidtAbstract:The paper is focused on the analysis of the surface layer formed on a workpiece treated with ultrasonically assisted turning (UAT) in comparison to conventional turning (CT). Various experimental methods are used to study the difference between the two machining techniques: nanoindentation, light microscopy and scanning electron microscopy (SEM). The experimental part of the paper studies the Material Response to CT and UAT in terms of Material's hardness, residual stresses, and changes in the microstructure. The difference in the distribution of residual stresses in the machined surface layer is further studied by means of numerical (finite element) simulations. A three-dimensional thermomechanically coupled finite element (FE) model of both UAT and CT is used to study temperature distributions in the process zone and thermally induced stresses. Numerical results are compared with the obtained experimental data.
Thierry Magin - One of the best experts on this subject based on the ideXlab platform.
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Two-way coupled simulations of stagnation-point ablation with transient Material Response
International Journal of Thermal Sciences, 2018Co-Authors: Pierre Schrooyen, Alessandro Turchi, Koen Hillewaert, Philippe Chatelain, Thierry MaginAbstract:Abstract Ablative Materials are extensively used in aerospace applications to protect the integrity of the spacecraft during atmospheric entry. Both thermal and mechanical stresses have to be withstood in the severe operating conditions typical of space missions. An accurate modeling of the phenomena taking place when these Materials are exposed to such a harsh environment is crucial to ensure the success of future, more demanding, missions. This study aims to couple two tools able to handle two different aspects of the ablative Material modeling: a stagnation-line flow solver featuring an integrated ablative boundary condition, and a Material Response code. The coupling algorithm allows for time accurate solutions of the ablative Material thermal Response accounting for detailed surface chemistry, in-depth Material behavior, and surface recession. Two different coupling strategies have been implemented, based either on a direct or an iterative procedure. The developed tool is used to rebuild plasma wind tunnel experiments performed in the von Karman Institute Plasmatron facility. The outcomes of the two strategies are compared, showing a satisfactory agreement with the experimental data. Among the two analyzed coupling procedures, the direct coupling proved to be computationally less expensive, while conserving the same accuracy of the more complex iterative procedure for the analyzed cases. A sensitivity analysis is also conducted to understand the discrepancy with experimental data and show the effects of four uncertain Material parameters: thermal conductivity, density, emissivity, and catalytic efficiency.
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discontinuous galerkin discretization for one dimensional in depth thermal Response of ablative Material
Gordon Research Conference Atmospheric reentry physics, 2013Co-Authors: Pierre Schrooyen, Koen Hillewaert, Thierry Magin, Philippe ChatelainAbstract:This poster shows the development of a one dimensional Material Response code to a high enthalpy flux using a discontinuous Galerkin formulation. Results are compared with other state-of-the-art code.
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a short review of ablative Material Response models and simulation tools
2011Co-Authors: Jean Lachaud, Thierry Magin, Ioana Cozmuta, Nagi N MansourAbstract:A review of the governing equations and boundary conditions used to model the Response of ablative Materials submitted to a high-enthalpy flow is proposed. The heritage of model-development efforts undertaken in the 1960s is extremely clear: the bases of the models used in the community are mathematically equivalent. Most of the Material-Response codes implement a single model in which the equation parameters may be modified to model different Materials or conditions. The level of fidelity of the models implemented in design tools only slightly varies. Research and development codes are generally more advanced but often not as robust. The capabilities of each of these codes are summarized in a color-coded table along with research and development efforts currently in progress.