Browsing by Author "Sasaki, S"

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    Residual thermal stress analysis in cylindrical steel bars using finite element method and artificial neural networks
    Toparli, M; Sahin, S; Ozkaya, E; Sasaki, S
    In this study, it was proposed that the residual stresses within steel bars after quenching in water from 600 degreesC could be calculated by using the finite element method (FEM) and an artificial neural network (ANN) algorithm. Three modelled cylindrical specimens of AISI 1020 steel were heated and then quenched in water. Using FEM, temperature distribution with time and thermal residual stress values in the samples were calculated after cooling. The analysis was extended to elastic-plastic deformation during the quenching of steel cylinders of various diameters. The calculated temperature and thermal residual stress values were used in training a multi-layer, feed forward, back propagation ANN algorithm. The results obtained via the ANN algorithm method have been compared with the FEM results. Comparison showed good agreement. (C) 2002 Elsevier Science Ltd. All rights reserved.
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    Modelled and measured residual stresses in a bimaterial joint
    Sahin, S; Toparli, M; Ozdemir, I; Sasaki, S
    A finite element technique has been used to predict residual and thermal stresses due to welding. For this purpose, a steel-brass material couple was chosen and thin plates of the materials were hard brazed. The finite element study was carried out using two-dimensional models. After the temperature distributions as a result of welding were calculated, thermal and residual stress values obtained. Thermo-elasto-plastic formulations using a von-Mises yield criterion with linear isotropic-hardening were employed. For this deformation, the initial stress method was used and the kinematical Bauschinger effect was considered. The authors prepared all calculation programs using FORTRAN 77. To obtain residual stresses that occur during the welding, the hole-drilling strain-gage method was chosen and conducted in accordance with the ASTM Standard E 837-99. The agreement between the calculated results and the experimental data shows that the finite element analysis method is reliable. (C) 2002 Elsevier Science B.V. All rights reserved.