The paper presents an aproximate analytic method for determination of the stored energy of plastic deformation during cold bending of metal tubes at bending machines. Calculations were performed for outer points of the tube layers subjected to tension and compression (the points of maximum strains). The percentage of stored energy related to the plastic strain work was determined and the results were presented in graphs. The influence and importance of the stored energy of plastic deformation on the service life of pipeline bends are discussed.
Z. Śloderbach and J. Pająk
Z. Śloderbach and J. Pająk
A simplified analytical method to determine the range of the heat affected zone and its components during welding is presented. Heat affected zone (HAZ) is an area formed during welding in which, as the result of temperature, some structural changes in the welded material occured. Knowledge of the area and sub-areas of HA Z is important from practical point of view, since the area of the fine-grained HAZ is a critical place in terms of creep strength and thermal fatigue. Heat affected zone is often the cause of future damage of many devices in which welding technology was used for their repair.
Małgorzata P. Majewska, Jan Rawa, Janusz J. Pająk, Jacek Skomiał, Zofia Długołęcka and Barbara Kowalik
The aim of the study was to determine the effect of various forms of sunflower oil in the diet with protein degraded at different rates in the rumen on pancreatic juice secretion and activity. The experiment was conducted on 24 adult Corriedale rams weighing about 40 ± 1.5 kg, catheterized in the pancreatic and bile ducts and fistulated in the duodenum. The animals were fed diets consisting of meadow hay, potato starch, different degradable protein (casein or maize gluten, a source of zein) and different forms of sunflower oil (calcium salts, seeds and oil). It was stated that addition of various forms of fat to the diet did not significantly influence the secretion of pancreatic juice, regardless of the source of protein. However, sunflower seeds and oil used in the diet had a significant effect on bile secretion, protein content, proteolytic activity of trypsin and plasma lipid indices. No significant differences were observed in the lipolytic activity of the pancreatic juice, although lipase activity was higher when zein was used as the main protein source. It was concluded that dietary addition of certain combinations of protected or unprotected sunflower oil and different degradable protein may improve pancreatic activity and probably affect plasma lipid indices in sheep.