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| Polak K. |
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| No 2 (2006), p. 111-118 |
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| Pernis R. |
| CALCULATION OF WALL THICKNESS AT TUBE SINKING |
Abstract
The technology of tube sinking has been generally used in end draws of technological method of tube production. Usually, it is due to the reason that internal diameter of the tube is small and the use of a mandrel is problematic or impossible. However, when using this method, it is necessary to know how the wall thickness will change after tube sinking. This submission attempts to answer this question. It introduces a review of published relationships for calculation of the tube wall thickness, which are determined by empirical or semi-empirical assumptions. Stated mathematical model of tube sinking is determined from the theory of metal forming and it is in the form of differential equations. Visualization of both equations is produced in a form of graphs, which mention the impact of individual technological parameters for the change of tube wall thickness at tube sinking. The most important impact on the tube wall thickness is thick-wallness of a tube that is the ratio of tube wall thickness to its diameter t0/r0. Regularity of changes in tube wall thickness completely coincides with the technical practice in the production of tube sinking. This fact is confirmed by implemented analysis of functional dependence on the basis of defined differential equations. The deciding impact in tube wall thickness in sinked tubes has its initial thick-wallness. In general, the higher initial ratio t0/r0, the lower growth of tube wall thickness, and in particular conditions at tube sinking, the tube wall thickness can start to decrease. The die angle impact on tube wall thickness is also documented. Similar to the thick-wallness of sinked tubes, also the die angle impacts on the change in tube wall thickness. Again, in general it can be said that with increasing die angle, the growth in tube wall thickness increases and can even cause a weakening of the tube wall to the increase wall thickness. On the other hand, the friction coefficient between sinked tube and die somewhat support the decrease in wall thickness. On the most important change in tube wall thickness at tube sinking impacts the degree of deformation. The implemented analysis shows that at certain conditions the degree of deformation can support the thickening of the wall as well as weakening of the wall.
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| Keywords: tube thick-wallness|tube sinking|change in tube wall thickness|die angle|friction coefficient| |
| No 2 (2006), p. 191-201 |
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