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Computational Methods of the Identification of Chaboche Isotropic-Kinematic Hardening Model Parameters Derived from the Cyclic Loading Tests

Wójcik Marta, Gontarz Andrzej, Skrzat Andrzej, Winiarski Grzegorz

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 1

61--75

EN

The Chaboche-Lemaitre combined isotropic-kinematic hardening model (CKIH) gives an overall information about the material behaviour under cyclic loading. The identification of hardening parameters is a difficult and time-consuming problem. The procedure of the parameters identification using the experimental hysteresis curve obtained in a cyclic loading test under strain control is presented in details here for a S235JR construction steel. The last stabilized cycle extracted from the hysteresis curve is required for the identification of hardening parameters. The model with three backstresses is tested here. The optimization algorithm is also used for the improvement of the agreement between experimental and numerical data. In order to include some uncertainty of experiment and the identification procedure, the authorial algorithm written on the basis of the fuzzy logic soft-computing method is applied here. The results obtained show that the identification procedure presented in this paper ensures the good agreement between the experimental tests and numerical calculations. The correct selection of parameters associated with the hardening is essential for the right description of material behaviour subject to loading in different engineering problems, including in metal forming processes.

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Mandrel-Free Bending of Tubes with Small Radii – A Theoretical and Experimental Study

Michalczyk Jacek, Gontarz Andrzej, Wiewiórska Sylwia, Winiarski Grzegorz

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 4

189--205

EN

This paper presents the theoretical and experimental results of a study investigating a new method for tube bending. The method involves three-point bending of a tube without using a mandrel. The bending process was conducted with a small bending radius of Rg = 1.5Dz (where Dz is the outside diameter of the bent tube) and a large bending angle of 1800. The novelty of the proposed solution is the use of new shapes of bending roll impression. Instead of the standard circular-shaped impression, an elliptical-shaped impression was used. The aim of the study on the proposed small radius tube bending technique was to optimize the shape of roll impression in terms of minimizing ovalization and flattening of the tube cross section in the bending zone. Previous studies only showed that circular impressions were inefficient. The tube bending process conducted with a circular impression roll, without the use of a mandrel or other type of filling to achieve an angle ranging 900 ÷ 1800 , led to the flattening of the cross section. The tube wall in the upper zone would crack or its cross section would become deformed and oval. This theoretical and experimental study was conducted on tubes with an outside diameter of Dz=20 mm and a wall thickness of g=2 mm, made of 16Mo3 boiler steel and EN-AW 6060 aluminum alloy. Obtained results were then used to determine the ranges of bending roll impression parameters that ensured that the product would meet the standardized conditions of cross-sectional ovalization in the bending zone. The tool developed for this study can be applied in industrial practice.

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Evaluation of the impact of electron beam welding parameters on the mechanical properties and microstructure of the resulting joint for 39CrMoV13 and M50NiL steel grades

Wencel Zbigniew, Wiewiórowska Sylwia, Wieczorek Paweł, Michalczyk Jacek, Gontarz Andrzej

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e200, 2022

EN

The paper covers a study consisting on the implementation of the electron beam welding process of two steel grades: 39CrMoV13 and M50NiL. The welding process was carried out for two values of electron beam debunching, obtaining a joint having different widths. Then, for the samples, after each welding variant, heat treatment was carried out consisting of double tempering at 520 °C for 3 h, and single freezing at − 84 °C for 3 h, combined with single tempering at 520 °C for 3 h. The impact of the parameters of the electron beam welding process and the subsequent heat treatment process on the mechanical properties and microstructure of the resulting joint was analysed. The conducted tests allowed to select the optimum welding technology combined with the heat treatment process for the tested steel grades ensuring that a weld is obtained in which the level of mechanical properties was close to the level of values obtained for the base material.

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Research of the Tool Velocity and Product Shape Aspects of the Hot Radial Rolling of C45 Steel Rings

Surdacki Piotr, Gontarz Andrzej, Winiarski Grzegorz, Samołyk Grzegorz

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 4

352--363

EN

The control of product shape and dimensions poses some problems in hot ring rolling. In the rolling process, material flows both circumferentially and axially, which leads to increased ring height. Changes in shape and dimensions of ring cross section depend on several process parameters, which makes it difficult to predict ring diameter. This paper presents the results of a study investigating the hot radial rolling process for C45 steel rings in terms of the effect of main roll feed speed on product geometry. It was found that the application of a higher feed speed of the main roll and thus of a greater ratio between this speed and circumferential speed of the main roll led to increased axial material flow and reduced cross-sectional defect known as ”fishtail”. Machining losses generated due to cross-sectional defects were also determined. Results were used to determine the feed speed to circumferential speed ratio ensuring the lowest possible cross-sectional defect and material consumption.

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Flange formation in aluminium alloy EN AW 6060 tubes by radial extrusion with the use of a limit ring

Winiarski Grzegorz, Gontarz Andrzej, Samolyk Grzegorz

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1020--1028

EN

The paper presents the results of tube flange forming by radial extrusion. The process was carried out according to two variants: with and without the use of a limit ring. The objective of the study reported in this paper was to determine the effect of the die corner radius and the gap height on the course of the radial extrusion process, determine the limit diameter of the flange and effect of limit ring dimensions on the radial extrusion process performed with the use of this ring. The research was performed in cold working conditions with the use of tubular billet made of 6060 aluminium alloy. The analyses were based on experimental tests using a testing machine and numerical calculations based on FEM. Obtained results dem-onstrate that the use of a limit ring has a positive effect on the state of stress in the extruded flange, which – in turn – allows to produce flanges with relatively big diameters. Such flanges are also characterised by lower thickening than those produced by radial extrusion process without ring.