Materials Science Forum
Vol. 508
Vol. 508
Materials Science Forum
Vols. 505-507
Vols. 505-507
Materials Science Forum
Vols. 503-504
Vols. 503-504
Materials Science Forum
Vol. 502
Vol. 502
Materials Science Forum
Vols. 500-501
Vols. 500-501
Materials Science Forum
Vols. 498-499
Vols. 498-499
Materials Science Forum
Vols. 495-497
Vols. 495-497
Materials Science Forum
Vol. 494
Vol. 494
Materials Science Forum
Vols. 492-493
Vols. 492-493
Materials Science Forum
Vols. 490-491
Vols. 490-491
Materials Science Forum
Vols. 488-489
Vols. 488-489
Materials Science Forum
Vols. 486-487
Vols. 486-487
Materials Science Forum
Vols. 483-485
Vols. 483-485
Materials Science Forum Vols. 495-497
Paper Title Page
Abstract: A model based on Marciniak-Kuczynski (M-K) theory [1] for the prediction of forming limit diagrams (FLDs) for anisotropic sheet metals is presented. The plastic anisotropy is taken into account by the shape of the yield locus generated on the basis of measured crystallographic texture. As a result, not only the material behavior during the monotonic loading can be well described and predicted, but also the complex strain-path changes during the forming process can be taken into account. Examples of predicted FLDs for two aluminum alloys are given. Comparisons with experimental results are presented.
1573
Abstract: Polycrystalline materials develop texture as a result of various manufacturing processes. In this paper the effect of texture of material on wear resistance and friction coefficient of AISI304 stainless steel samples was studied. Three different types of surface textures were produced from the same stainless steel raw material. Texture measurements were performed to obtain information from the specimen surface. Friction tests were performed using a Micro Scratch tester with the capability of monitoring acoustic emission and frictional force during scratch tests.
1579
Abstract: The texture influence on the mechanical behavior during uniaxial tension was studied in AZ31 (Mg – 3 Al – 1 Zn in wt.%), one of the common wrought Mg alloys. Since three tensile samples were cut in 0°, 45°, 90° to the extrusion direction, the initial bar texture influences on the mechanical behavior differently. In-situ texture measurements were carried out using hard X-rays under loading condition. According to the initial texture loading results in a variation of the mechanical behavior (yield strength, ultimate tensile strength and strain hardening rate) and in different final textures. The different texture development in each sample relates directly to the activation of different deformation systems, which is strongly influenced by the initial texture
1585
Abstract: Low carbon steel (usually in sheet form) has found a wide range of applications in
industry due to its high formability. The inner and outer panels of a car body are good examples of such an implementation. While low carbon steel has been used in this application for many decades, a reliable predictive capability of the forming process and “springback” has still not been achieved. NIST has been involved in addressing this and other formability problems for several years. In this paper, texture produced by the in-plane straining and its relationship to springback is reported.
Low carbon steel sheet was examined in the as-received condition and after balanced biaxial straining to 25%. This was performed using the Marciniak in-plane stretching test. Both experimental measurements and numerical calculations have been utilized to evaluate anisotropy and evolution of the elastic properties during forming.
We employ several techniques for elastic property measurements (dynamic mechanical analysis, static four point bending, mechanical resonance frequency measurements), and several calculation schemes (orientation distribution function averaging, finite element analysis) which are based on texture measurements (neutron diffraction, electron back scattering diffraction). The following objectives are pursued: a) To test a range of different experimental techniques for elastic property measurements in sheet metals; b) To validate numerical calculation methods of the elastic properties by experiments; c) To evaluate elastic property changes (and texture development) during biaxial straining. On the basis of the investigation, recommendations are made for the evaluation of elastic properties in textured sheet metal.
1591
Abstract: An analysis of the hardening process in grains and its effect on texture development of hcp materials is performed. It corresponds to the cases of Zr and Zn, which present different c/a relationship and, consequently, their deformation modes and the associated activities are different. The self consistent viscoplastic model is used for the prediction of texture evolution Results show the importance of the self and latent hardening introduced by the prismatic slip in Zr and the latent hardening effects introduced by pyramidal slip on compressive twinning in Zn.
1597
Abstract: Using a simple analytical flow function, an analysis of the deformation field in symmetrical rolling has been carried out. The so-obtained varying velocity gradient is incorporated into the Taylor polycrystal plasticity model to simulate the development of the deformation texture. The initial discontinuity in the deformation field of the entering material element on the flow lines is also taken into account. Multiple passes of the material is simulated. A strong texture gradient is obtained in good agreement with experiments carried out for rolling of plane carbon steel. It is shown that the shear component of the texture is strongly related to the nature of multiple passes of the rolling operation.
1603
Abstract: The Swift effect, i.e. the length changes during torsion of solid bars with axial freedom of deformation is analysed theoretically for polycrystalline copper. In the simulations, the bar is divided into 5 tubes and in each tube the texture development is simulated with the help of the Taylor viscoplastic polycrystal model. The distribution of the hydrostatic stress is obtained from the equilibrium equation and the zero axial force requirement is satisfied with the help of an iterative scheme. The simulations reproduce faithfully the observed axial deformation and texture development. A second technique, based on the minimum plastic power is also applied to predict the length changes and textures. This technique leads to results which are nearly equivalent to the results obtained from the technique based on the equilibrium equation.
1609
Abstract: The plastic anisotropy was measured for a commercial AZ31 magnesium sheet and compared with results from a model calculation using a self consistent viscoplastic model. The anisotropy of plastic flow stresses can be explained by the off-basal character of the texture and the activation of the prismatic slip in addition to the basal, pyramidal slip and the > < 1 1 01 } 2 1 01 { twinning system. The strain anisotropy r ( r = ew/et ; ew, et – strains in width and thickness directions of a sheet material ), as obtained from model calculations, fits qualitatively with in-situ measured values. Results from these model calculations are compared with texture simulations and discussed in further consideration of the microstructure of the sheet material.
1615
Abstract: The plastic and elastic deformation of PM two-phase Iron-Copper polycrystals was
studied experimentally and modelled by a FEM model calculation, taking into account anisotropic elasticity and crystal plasticity. Following quantities were experimentally measured and calculated by a FEM model calculation: A local strain distribution and rolling textures. For a judgement of model predictions the orientation densities of the bcc a-fibres of Iron and of the fcc b-fibres of Copper were considered. Good predictions of the texture evolution were found in cases only, where local micromechanical interactions are not too much influenced by the heterogeneity of the microstructure. The implications of these results for the development and use of FEM schemes for modelling heterogeneous polycrystal plasticity are discussed.
1621
Abstract: This work investigates the micro-mechanics of a multiphase steel sheet during a uniaxial tensile test. Based on crystal plasticity theory, one assesses how the distribution of strain and stress is influenced by the presence of a soft b.c.c. phase and a strong f.c.c. phase. The two phases have been characterized by neutron diffraction. Initial textures are used as input in crystal plasticity simulations. Lattice strains measured in the tensile direction serve to fit hardening parameters. Three modeling hypotheses are tested: the Taylor model assumes uniform strain, the ALAMEL model considers the interaction of pairs of adjacent grains, and a finite element mesh is used to distribute strain and stress over the complete aggregate. The accuracy of each modeling is evaluated based on experimental measurements of the macroscopic stress, the heterogeneity of plastic strain, and the texture development in the two phases.
1627