Effect of the enhanced assumed strain technique on the wrinkling prediction of thin aluminum film coated sheets

Conference (2010, September)

Modeling of Crack Propagation in Weld Beam-to-Column Connection Submitted to Cyclic Loading with Cohesive Zone Model

in Journal of ASTM International (2010), 7(5),

During the earthquakes in Japan and California in the 1990s, cracks appeared in some weld beam-to-column connections of heavy rigid frame steel buildings. This prompted the necessary assessment of the ... [more ▼]

During the earthquakes in Japan and California in the 1990s, cracks appeared in some weld beam-to-column connections of heavy rigid frame steel buildings. This prompted the necessary assessment of the performance of weld connections in terms of rotation capacity and crack propagation. In the present study, experimental tests were performed where weld connections were submitted to cyclic loadings with increasing amplitude until a macro crack event was reached. However the crack phenomenon depends on many parameters: the geometry, the material, the welding process…. For this reason, it was interesting to develop a finite element modeling of these connections in order to complete these experiments and perform a parametric study. This paper describes the finite element model development, its material parameter identification and its comparison with experimental results. The weld connections were modeled by using three-dimensional mixed solid elements. The constitutive laws applied were elastoplastic with isotropic hardening identified for the base metal and the weld metal. Crack propagation was modeled by a cohesive zone model. The parameters of this cohesive zone model were identified by an inverse method with the modeling of three point bending tests of precracked samples performed on the base and weld metals. The fatigue damage generated by the cyclic loading was computed by the fatigue continuum damage model of Lemaitre and Chaboche, which was coupled with the cohesive zone model. [less ▲]

Temperature wrinkling prediction in metal/polymer multilayer coatings

in International Journal of Material Forming (2010, April), 3(supplement 1), 559-562

Two modeling approaches, analytical and numerical ones were carried out to simulate the mechanical behaviour of a coated metal steel sheet under thermo-mechanical loads. As the metallic film and the ... [more ▼]

Two modeling approaches, analytical and numerical ones were carried out to simulate the mechanical behaviour of a coated metal steel sheet under thermo-mechanical loads. As the metallic film and the polymer layer have different dilatation coefficients, temperature increase and/or humidity variation can result in a compressive state in the metallic film, and yield to bucking. This phenomenon is called wrinkling. It can be prevented by a stiff polymer layer or a stable film due to adapted thickness and mechanical properties. Wrinkling phenomenon has received increasing attention because of important uses of polymeric coating in many industrial applications. To better understand and predict this phenomenon, analytical and numerical models have been developed and compared. [less ▲]

Simulation of bending process of hardening metallic sheets using damage model. Part I: Theoretical development and numerical implementation.

in Materials Science & Engineering : A (2010), 528(1), 434-441

This paper deals with the pure bending of thin and thick metallic sheets under plane strain condition. Its main objective is to construct an efficient, robust, incremental numerical tool that can be used ... [more ▼]

This paper deals with the pure bending of thin and thick metallic sheets under plane strain condition. Its main objective is to construct an efficient, robust, incremental numerical tool that can be used to simulate the bending process and predict the sheets’ bendability. In this investigation, the material constitutive law describing the mechanical behavior of the sheet is defined by an extended Gurson model. This model generalizes Gurson's original one to account for both plastic anisotropy and mixed (isotropic and kinematic) hardening of the matrix. In this model, only the growth phase of voids was considered (without taking into account nucleation). Here, the extended model was coupled with the kinematics of the pure bending process and with the equilibrium equations, and then implemented in an incremental numerical tool in order to predict the bendability of the sheets studied. This bendability was then verified using two different criteria. Part I of this paper focuses on the constitutive law, fulfillment of the force equilibrium, the thickness evolution and the shift of the neutral fiber, together with a comparison and discussion of the choices made by other authors regarding these parameters. The validation of the model developed in this paper will be carried out in Part II through simulations of the pure bending process. [less ▲]

Accurate stress computation in plane strain tensile tests for sheet metal using experimental data

in Journal of Materials Processing Technology (2010), 210

Miniaturization induced size effects: Experimental and numerical investigation of size effects linked to the miniaturization of metallic components

in Scale transition for plastic crystalline and microstructured materials: from experiment to numerical modeling (2010)

The manufacturing of small metallic components for MEMS is a great challenge for industries. However, the lack of knowledge about the mechanical behavior of metals when they are employed in small ... [more ▼]

The manufacturing of small metallic components for MEMS is a great challenge for industries. However, the lack of knowledge about the mechanical behavior of metals when they are employed in small components can reduce the economical development of MEMS due to manufacturing and reliability issues. The objective of this work is to provide new scientific results to improve the understanding of the mechanical properties of micro-components. Experimental and numerical (strain gradient plasticity model) tensile tests are performed on thin nickel single crystals and polycrystals (thickness larger than 10 m) showing different size effects depending on the dimensions of the samples. These effects are then taken into account in new simplified numerical models for the prediction of micro-forming processes. [less ▲]

Study of the effects of α-grain proportion, shape and orientation on the mechanical behavior of Ti-5553 by FE simulations

Conference (2010)

Twinning in pure titanium subjected to monotonic simple shear deformation

in Acta Materialia (2010)

Two different textures of pure Ti were subjected to monotonic simple shear and this for three different orientations of the texture versus the shear direction. EBSD and TEM observations reveal the ... [more ▼]

Two different textures of pure Ti were subjected to monotonic simple shear and this for three different orientations of the texture versus the shear direction. EBSD and TEM observations reveal the presence of {10-12} and {11-22} twins. A statistical relevant analysis of the morphology of these twins combined with a resolved shear stress (RSS) analysis was performed. This analysis reveals that {10-12} and {11-22} twins have a similar average thickness, but the {10-12} twins show a far larger spread on their thickness compared to {11- 22} twins and can grow to almost the size of the original parent grain. Correlation of the twin fractions with the RSS analysis shows that this RSS technique is an acceptable method explaining the difference in twin fractions for different textures and orientations. A detailed analysis shows that {11-22} twins occur in average with a smaller volume fraction but with a higher RSS, indicating they are more difficult to nucleate or grow compared to {10-12} twinning. In general a higher RSS value on the twin plane is not connected with a higher twin thickness; only in case of {10-12} twins the highest RSS values show clearly thicker twins. [less ▲]

Material parameter identification of Cazacu's model for Ti6Al4V using the simulated annealing algorithm

in Materials Science Forum (2010), 636-637

Phenomenological yield criteria are generally described by many material parameters. A technique to identify these parameters is required to find the best fit to the results of the mechanical tests. The ... [more ▼]

Phenomenological yield criteria are generally described by many material parameters. A technique to identify these parameters is required to find the best fit to the results of the mechanical tests. The parameter identification by the classical simulated annealing technique is presented in this paper. This algorithm, based on Metropolis’ works [1,2], is a global optimization method that distinguishes between different local optima to reach the global optimum. The anisotropic model used in this study is the one proposed by [3]. To prove the efficiency of the proposed algorithm, the material parameters of Ti6Al4V titanium alloy are identified and compared with those obtained using different identification procedures and the same experimental data. [less ▲]

Critical resolved shear stresses and hardening parameter optimisation using crystal plasticity model for Ti6AL4V sheet based on simple tension tests & texture evolution

Conference (2010)