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1

‎ An extended contact model of the angular bearing

Kosmol Jan

Journal of Theoretical and Applied Mechanics

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2019

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Vol. 57 nr 1

59--72

EN

The article presents a new contact model of an angular bearing, called the extended model. The model takes account of the effects of centrifugal load caused by thr rotating ring of the bearing and the issue of elasticity. Present models, encountered in literature and referred to in the article as classical, consider the centrifugal force caused by the rotating ball only. Results of analytical research on the extended model and of FEM simulation show explicitly that the contact angles of bearings, and thus contact loads, differ very much from those values obtained in the classical model. These differences are disadvantageous for designing bearing assemblies, since contact loads are greater than those obtained in the classical model. This means, among others, that the present structures with angular contact bearings are in reality subject to greater loads than the constructor has envisaged. The motto of the article is to design analytical calculation models in such a form which would enable the constructor to estimate contact loads, just using a standard scientific calculator or MS Excel type applications; so that there would be no need for solving complex models using numerical methods.

2

The modelling of loading, unloading and reloading of the elastic-plastic contact of rough surfaces

Kostek R.

Journal of Theoretical and Applied Mechanics

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2012

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Vol. 50 nr 2

509-530

EN

This paper presents a non-linear mathematical model describing the hysteresis of dry contact of rough surfaces loaded in the normal direction. A number of characteristic phenomena appear during the initial loading, unloading and reloading of the contact interface. The contact is most flexible during the first loading, and its plastic deflection is significant, whereas the characteristic curve of unloading is stiffer and is mainly elastic in nature. The reloading characteristic is similar to the unloading characteristic, and thus a hysteresis loop is observed. The non-linear model of contact presented in this paper, which has been validated by experimental data, describes the aforementioned phenomena. The model is dedicated to the finite element method (FEM), the discrete element method (DEM), and simulations of multi-body systems (MBS), where accurate and effective contact models are preferred. The presentation of the model is supported by examples of applications to contact problems.

PL

W artykule przedstawiono nieliniowy matematyczny model opisujący histerezę suchego kontaktu ciał chropowatych, który został obciążony w kierunku normalnym. Kilka charakterystycznych zjawisk pojawia się podczas pierwszego obciążania, odciążania i powtórnego obciążania. Kontakt ciał jest najbardziej podatny podczas pierwszego obciążania, a jego plastyczne odkształcenie jest znaczne. Natomiast charakterystyka uzyskana podczas odciążania jest sztywniejsza, a odkształcenia mają głównie charakter sprężysty. Podobną charakterystykę uzyskuje się podczas ponownego obciążania, tak więc obserwowana jest pewna pętla histerezy. Zweryfikowany doświadczalnie model kontaktu, opisujący wyżej wymienione nieliniowe zjawiska, został przedstawiony w artykule. Model ten został opracowany z myślą o: metodzie elementów skończonych, metodzie elementów dyskretnych i układach wieloczłonowych. W praktyce obliczeniowej potrzebne są dokładne modele kontaktu, które nie wymagają jednak kosztownych obliczeń. Prezentację tego modelu wzbogacono przykładami obliczeniowymi.

3

Investigation on the Dynamics of Tool Grinding

Payrebrune K. M., Kröger M., Deichmueller M., Denkena B.

Machine Dynamics Problems

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2009

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Vol. 33, No. 2

92-104

EN

The manufacturing of high-performance carbide tools, like drills or milling cutters, is realized by a grinding process because of the strength and hardness of the used material. Due to the process forces and the cantilevering clamped workpiece, the blank bends and unwanted geometry errors occur. Additionally, great efforts are made to find optimal parameters for stable process conditions. In this work the interaction phenomena of tool grinding process and machine structure are analyzed and modelled. Thereby, the dynamic behaviour of workpiece, grinding wheel, and machine structure is experimentally investigated. Additionally, force signals of the grinding processes are measured and analyzed in time and frequency domain.

4

On Chater Vibrations in Cylindrical Grinding

Schütte O., Heimann B.

Machine Dynamics Problems

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2001

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Vol. 25, No. 3/4

135-137

XX

[Extended abstract] The problem of chatter vibrations still has a high relevance for the handling of high precision finishing systems in manugacturing. This article shortly summarizes papers of the authors that deal with the modeling of chatter in the process of external cylindrical plunge grinding...