No abstract

No abstract

A nonequilibrium molecular dynamics ͑MD͒ simulation study is reported of the structural and rheological properties of confined n-decane between two Au͑111͒ surfaces in contact with its bulk under constant normal loads or constant heights. In the constant-load MD simulations, it was observed that fluid molecules were squeezed out of the pore continuously in a single simulation upon compression, whereas fluid molecules in the bulk were soaked into the pore when applied normal load was released. Pore separation depends on bulk pressure under the same normal load and approaches a steady value as normal load increases. In the constant-height simulations, density, velocity, and orientational profiles of the confined film were accumulated along the Z ͑perpendicular to the walls͒ and Y ͑parallel to the walls and finite due to the bulk͒ directions. These distributions are not uniform not only along the Z direction but also along the Y direction, particularly for weak fluid-wall interactions. The shear-thinning behavior and ''slip'' boundary conditions were also studied in this work. Even though the shear-thinning behavior was reported by several previous studies, the number of particles was fixed and the bulk condition was unknown in those simulations. The simulation geometry employed in this work is closer to that of surface-force apparatus ͑SFA͒ experiments and of engine lubricating systems where confined liquid is in contact with its bulk.

No abstract

This work investigates the cut quality characteristics of SS321 using plasma arc cutting. The SS321 has a wide range of applications such as in chemical storage, exhaust manifolds of automotives and aircraft. The intricate shapes for this material are very difficult to cut using conventional machining process. Hence, plasma arc cutting is used. The input cutting parameters are cutting speed, current, stand off distance and gas pressure. For each input parameter, three levels are considered and, therefore, total numbers of experimental runs are 3 9 3 9 3 9 3 = 81. To minimize the number of runs, the Taguchi L9 orthogonal array is proposed which is having advantages of both minimum and maximum trial runs. The output parameters are surface roughness, kerf width and heat-affected zone. The experiments are carried out in Micro Step spol S.R.O. Plasma arc cutting machine. To find the best cutting parameters, the regression models are given as input of Matlab-Genetic Algorithm. The test results show that ANOVA models are significant. It is inferred that lower values of current and Standoff Distance give better surface roughness and minimum heat-affected zone.