Wyniki wyszukiwania - BazTech

1

Determination of the initial thickness of tubes subjected to bending. Part II. Discussion and analysis of obtained results

Śloderbach Z.

Engineering Transactions

|

2015

|

Vol. 63, iss. 4

497--507

EN

In this second part of the paper, applying epressions derived in Part I, the exemplary calculations of the initial thickness of a metallic tube subject to bending at bending machines are presented. The expressions for calculating of the initial thickness were presented for a suitable measure of the big actual radius Ri in the bending zone for an exact (general) solution and for three formal simplifications of the 1st, 2nd, and 3rd order. In the calculations the external or internal diameter of the tube subjected to bending is applied as a parameter. In this paper, the author shows that the calculated initial thickness of the tube (for the same parameters of bending) depending on the external diameter is lower than that calculated depending on the internal diameter. For example, the expression for calculation of deformations included in the UE Directive [1], contains dependence on dext not on dint. The results of the calculations are presented in the graphs and tables enclosed.

2

Wykorzystanie modelowania fizycznego i matematycznego do określenia odkształceń w nowym procesie walcowania pielgrzymowego rur na zimno

Pociecha D., Mroczkowski M., Osika J., Boryczko B.

Prace Naukowe Politechniki Warszawskiej. Mechanika

|

2013

|

z. 253

141--146

PL

W pracy przedstawiono wyniki modelowania fizycznego i matematycznego umożliwiające określenie odkształceń w nowym procesie walcowania pielgrzymowego rur na zimno. Modelowanie fizyczne przeprowadzono na prototypowej walcarce pielgrzymowej pracującej według koncepcji prof. nadzw. dra hab. inż. Jana Osiki. Materiałem badawczym były rury aluminiowe ze znacznikami pomiarowymi. Do określenia odkształceń wykorzystano system wizyjny, który umożliwia pomiar odkształceń z uwzględnieniem zmian grubości ścianki badanej rury. System umożliwia śledzenie odkształceń w jednym pełnym cyklu roboczym. Modelowania matematycznego dokonano przy użyciu programu Abaqus. W symulacjach procesu walcowania pielgrzymowego uwzględniona została pełna historia odkształcenia walcowanej rury umożliwiająca określenie odkształcenia materiału w całej kotlinie walcowniczej.

EN

The paper presents results of physical modelling and numerical simulation, which allows to determinate strain fields in the cold pilger rolling process. Physical modelling was carried out on prototype pilger mill, which work according to the conception of Professor Jan Osika. Aluminium tubes with copper wire inserts as markers have been investigated. To measure strain fields optical system, which take into account variation of tube thickness, was used. Strains were analysed during one full cycle of pilgering process. Abaqus software was used for numerical simulation. Taking into account history of deformation in the working zone, the strain fields have been calculated.

3

Impact of mismatch-related phenomena on a room-temperature operation of nitride VCSELs.

Maćkowiak W., Nakwaski W.

Optica Applicata

|

2000

|

Vol. 30, nr 1

125-140

EN

The influence of mismatch-related phenomena (mostly strain fields and structure defects) on a room-temperature (RT) operation of possible nitride VCSELs is examined using a simple but still detailed analytical model. Intentionally introduced stress fields within nitride VCSEL quantum-well (QW) active regions (band-gap engineering) are found to have a much weaker effect on their optical gain than in the case of conventional arsenide and phosphide VCSELs. Dislocation densities (including misfit dislocations), on the other hand, have a considerable harmful impact on VCSELs thresholds, mostly because of increasing scattering losses and decreasing internal quantum efficiency. Single-quantum-well nitride VCSELs are found to be very sensitive to the above impact. A reasonable increase in a number of QWs in multiple-quantum-well VCSELs tremendously improves their performance. In the case of relatively high dislocation densities, bulk double-heterostructure VCSELs may turn out to be the best nitride designs although they may also exhibit too high thresholds to lase at RT.