Numerical simulation of edge effect in plasma arc forming of sheet metal
Edge effect was found in plasma arc forming process of sheet metal, which reduces the forming accuracy of sheet metal seriously. In order to reveal the forming mechanism and forming laws of the edge effect. A numerical model on forming of sheet metal using plasma arc with scanning along a straight line was established and the forming mechanism and forming laws of the edge effect were studied. The results showed that the upper material and the lower material of the edge were produced shrinkage along the scanning path and both shrinkage were different. The size relationship of the two shrinkage determines the direction of edge warp. The difference of the two shrinkage affects the warpage of the edge. In the comprehensive effect of shrinkage and warpage, the non scanning region in the both sides of the scanning path appears bulge or depression. The numerical analysis results were agree well with the experimental results. The conclusions provide a theoretical basis to reduce the effect of the edge effect on the accuracy of the sheet metal forming.
Study on flexible forming of sheet metal using plasma arc
The technology of flexible forming for sheet metal ultilized by thermal stress-strain now gradually becomes a focus of research both at home and abroad.Compared with another heating source,plasma arc is more economical,safe,flexible and practical.However,at present,researches on flexible forming of sheet metal using plasma arc are very limited,such as only using scanning path by straight line,investigating microstructure development in heat affecting zone of sheet metal,etc.The following issues have been investigated the mechanisms and characteristics theories,then through different shapes of sheet metal,researched the difference using scanning path through straight line and curve line,and the influence of different shapes by experiment and analysis.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.