Wyniki wyszukiwania - BazTech

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Assessment of the influence of the bending form shape on the stress and plastic strain values in a cold bending pipe

Nozdrzykowski Krzysztof, Stępień Mateusz, Grządziel Zenon

Zeszyty Naukowe Politechniki Morskiej w Szczecinie

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2024

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nr 78 (150)

35--48

EN

Abstract This paper presents the results of modelling research concerned with the technological process of the cold bending of a pipe. Stress and plastic strain studies are carried out using the finite element method (FEM) on a thick-walled pipe and various shapes of bending form. The results of the research are benchmarked in terms of the correctness of the implementation of the bending process, including the change in the pipe outside diameter and wall thickness. The level of ovalisation of the cross-section in the bending pipe is used as the primary criterion for assessing the correctness of the bending process. The results show that the most favourable properties in terms of minimising the ovalisation of the pipe cross-section are provided by the use of a bending form with a trapezoidal shape.

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Straight and Bent Bars Buckling Considered as the Axial Displacement of One Bar End

Berczyński Stefan, Dunaj Paweł, Grządziel Zenon

Multidisciplinary Aspects of Production Engineering

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2020

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Vol. 3, Iss. 1

57--70

EN

A new approach has been taken to the problem of straight and bent bar buckling, where bar buckling is considered as a function of axial displacement of one end. It was assumed that the length of a bar being buckled at any instant of buckling is the same as that of a straight bar, regardless of the size of axial displacement of one end of the bar. Based on energy equations, a formula was derived for the value of axial displacement of one bar end or buckling amplitude in the middle of bar length as a function of compressive force. The established relationships were confirmed by simulation tests using the finite element software Midas NFX and by experimental tests.

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Modelling and Simulation Testing of Main Bearing Loads and Strains in Crankshafts Caused by Deviations in the Position of the Shaft Journal and Bearing Axes

Nozdrzykowski Krzysztof, Grządziel Zenon

Multidisciplinary Aspects of Production Engineering

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2020

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Vol. 3, Iss. 1

41--56

EN

This article presents the results of a simulation, testing the variation of main bearing loads and strains in crankshafts caused by geometrical deviations of the bearing system to justify the necessity and purposefulness of measurements of both the shape and axes position deviations of crankshaft journals. Measurements of these deviations at the existing level of applied measuring techniques are significantly limited. The research also accentuates the practical implementation of a measuring system equipped with the so-called flexible support system for the measured object, developed at the Maritime University of Szczecin. This system makes it possible to eliminate elastic deformations of the crankshaft due to its own weight, whereby the measurements of geometrical deformations of the crankshafts can be carried out with appropriate accuracy in conditions corresponding to the non-reference measurements when determining the object measured in counterpoints. The obtained results have fully confirmed the purposefulness of the conducted research and the validity of the theses.

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Static condensation in modeling roller guides with preload

Dunaj Paweł, Berczyński Stefan, Pawełko Piotr, Grządziel Zenon, Chodźko Marcin

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1072--1082

EN

This article presents the methodology for modeling the stiffness of a machine tool load-bearing system using the finite element method. A new, simplified model of stiffness of the linear guide with a preload based on equivalent contact model was proposed. An equivalent contract model was developed where the ball was replaced with four rod elements of equivalent stiffness, interconnecting the opposite ends of the face of cuboidal finite ele- ments. To shorten the computation time and facilitate modeling reduction and substructur-ing methods was used. The accuracy of the proposed model was compared with experimental results. In addition, the computation times were evaluated by comparing the simplified model with the full model and other equivalent models. Then, the model was used to determine the stiffness of the machine load-bearing system on the example of a machining table using the aforementioned methods and the obtained results were com-pared in terms of accuracy (less than 1% difference in maximum displacement value) and computation time with the classic approach (up to 97% in time reduction). This paper demonstrated the validity of the proposed model, allowing accurate and fast determination of the stiffness of machine tool load-bearing system.