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Analysis of the nonstability states during bending processes of metallic tubes at bending machines. P. 1, Derivation of the basic expressions and relationships

Śloderbach Z.

Engineering Transactions

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2016

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Vol. 64, iss. 3

311--330

EN

In this paper the derivation of expressions for admissible values of strains and stresses for vertex points of layers subjected to tension during tube bending at bending machines is presented. The conditions of the dispersed and located loss of stability of the bent tube and the cracking criterion based on the technological index A5 (five fold sample) were assumed as criteria of instability. The original element of this paper is the extension of the criterion of strain location in a form of possible initiation of a neck or furrow (introduced by Marciniak for thin plates [1]) to bending thin- and thick-walled metal tubes at bending machines. Occurrence of loss of stability (especially that in a localised form) during tube bending can strongly reduce the service life. Thus, it is recommended to avoid such states during tube bending for elbows for pipelines or pipe installations.

2

A derivation of the generalized model of strains during bending of metal tubes at bending machines

Śloderbach Z.

International Journal of Applied Mechanics and Engineering

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2014

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Vol. 19, no. 1

145--163

EN

According to the postulate concerning a local change of the “actual active radius” with a bending angle in the bend zone, a generalized model of strain during metal tube bending was derived. The tubes should be subjected to bending at tube bending machines by the method of wrapping at the rotating template and with the use of a lubricated steel mandrel. The model is represented by three components of strain in the analytic form, including displacement of the neutral axis. Generalization of the model during bending metal tubes at the tube bending machines as compared with the existing papers (Śloderbach, 1999; Śloderbach and Rechul, 2000) consists in including the neutral axis displacement and possibility of determination of strains at each point along the thickness of the wall of the bent tube in the bending and bend zone. The derived scheme of strain satisfies initial and boundary kinematic conditions of the bending process, conditions of continuity and inseparability of strains. The obtained analytic expressions can be classified as acceptable from the kinematic point of view.

3

Nowa technologia i maszyna do produkcji znaków drogowych

Drenger T., Wiśniewski J., Nowacki Ł., Ulatowski Z.

Obróbka Plastyczna Metali

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2004

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T. 15, nr 1

23-26

PL

W artykule opisano stosowane rozwiązania konstrukcyjne znaków drogowych o kształcie niekołowym oraz nowoczesne konstrukcje znaków, odpowiadające wymaganiom Unii Europejskiej. Opisano technologie produkcji podkładu metalowego będącego podstawowym elementem znaku drogowego. Przedstawiono technologię oraz maszynę do produkcji znaków drogowych o dowolnych kształtach z podwójnie zagiętym obrzeżem, zaprojektowaną i wykonaną w Instytucie Obróbki Plastycznej w Poznaniu.

EN

The paper describes currently applied design solutions of noncircular road signs as well as modern sign designs, meeting the requirements of the European Union. The technologies of producing the metal background, the basic element of a road sign, have been described. A new technology and a machine for manufacturing road signs of any shape with double periphery bending has been presented. The machine has been designed and executed by the Metal Forming Institute in Poznań.

4

Analityczna określanie zmagazynowej energii deformacji plastycznej podczas gięcia metalowych rur na giętarkach

Śloderbach Z.

Przegląd Mechaniczny

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2000

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nr 9

15-20

PL

Przedstawiono podstawowe wiadomości o ukrytej energii deformacji plastycznej gromadzonej w metalach i stopach w procesach ich plastycznego odkształcania oraz skrótowo metody badań doświadczalnych i sposoby analitycznego opisu za pomocą odpowiednich wyrażeń i makroskopowych parametrów oraz odpowiednie wyrażenia służące do analitycznego określania wartości gęstości zmagazynowanej energii deformacji plastycznej podczas procesu gięcia metalowych rur na giętarkach w zależności od wartości kąta gięcia.

EN

Basic information on the latent energy of plastic deformation accumulated in metals and alloys while being plastically deformes. Methods of experimental tests and analystical description by means of suitable expressions and macroscopic parameters. Expressions for analytical determination of the density of the stores energy of plastic deformation while bending metal pipes on bending machines depending on the bending angle. Calculations were made for the outer middle points of the tensioned and compressed layers in the pipe being bent. Determination of the percentage ratio of the energy of plastic deformation to the delivered work of this deformation depending on the being angle.