Showing 3 results for Nikravan
Ali Reza Nikravan, Farhad Kolahan,
Volume 15, Issue 9 (11-2015)
Abstract
The use of TI-6AL-4V alloy is increasing in various industries, due to its characteristics such as high strength to weight ratio and excellent creep and corrosion resistance. However, because of titanium alloys poor machinability, non-traditional machining is usually used in shaping them. In this research, the wire cut machining of Ti-6Al-4V alloy has been investigated. In this regard, the effects of 8 process parameters and their optimal values are determined, for two process characteristics, cutting rate and surface roughness. One of the innovative aspects of the current study is the consideration of cutting height as one of the main parameters affecting the process output quality. Therefore, for three different cutting heights (each with two replicates), the L18 Taguchi matrix is employed to gather the required experimental data. Then, using the 108 data, statistical analysis, including signal to noise and analysis of variance were carried out in order to determine optimal process parameters and their effects on the two process outputs. Optimal process parameters values for maximum cutting rate and minimum surface roughness were verified by validation experiments. The results illustrate that the cutting height would alter the effects of process parameters and their optimal values. Finally, multi-objective optimization was performed to determine optimal parameters settings based on relative importance of process outputs for cutting heights of 30, 60 and 90 mm, in the form of technology table. The contribution of uncontrolled parameters and errors were less than 10% in all cases, which indicate the accuracy of the proposed technique.
Ayyoub Nikravan, Foad Farhani,
Volume 17, Issue 10 (1-2018)
Abstract
In recent years, capability of FPGA hardware for accelerating the solution of differential equations has attracted wide attention. However, complexities associated with the implementation and development of these equations on FPGA has precluded the wider application of this hardware among the users in the field of CFD. In this research, a software framework has been developed, which enables users to develop an FPGA based coprocessor for solving implicit PDE equations, quickly and with minimum complexity. Using this framework, the user defines the solution network and the algebraic equations, and the framework manages other operations such as construction of the solver IP, interface between the CPU and the coprocessor, memory layers and links among various parts. The framework consists of different sections for defining the architecture of the coprocessor using HLS and VIVADO software, and the links with CPU consisting of operating system drivers and operational functions for adjusting initial and boundary conditions and receiving the results through the PCIe port. Simplicity of the developed framework has been demonstrated by the construction of a coprocessor for solving two-dimensional Laplace equation. Comparison of speed of solution on CPU with the FPGA based coprocessor shows a 22-fold increase in the speed of solution of Laplace equation, and if fixed point operation is used in the construction of the coprocessor, the speed will even increase 65-fold.
Ali Reza Nikravan, Farhad Kolahan, Mahmoud Shariati,
Volume 22, Issue 8 (August 2022)
Abstract
Due to the importance of the joints in the pressurized instruments and the abilities of the laser welding in this study, the welding of AISI316L tubes have been studied and analyzed. In this regard a fixture has been drawn in order to positioning of the tubes and fixed on the welding desk. The welding input parameters includes the laser welding adjusting variables, includes (welding current, welding pulse width, and welding frequency). Moreover, the effect of the two other variables (rotating speed and the force applied to the welding seam) has also been studied. The welding output characteristics comprises the welding width, depth of penetration and welding strength. The experimental data has been collected using L27 Taguchi design. The relation between the process input variables and output characteristics has been established using different regression models. Based on the analysis of variance (ANOVA) results, pulse width and welding current with 70% contribution have an influential effect on all the three response characteristics. Moreover, the seam force has only the influential effect on the depth of penetration and strength. Next, in optimization step based on the importance of the process characteristics (strength, depth of penetration, welding width), the optimized levels have been determined. At the end, the optimized condition has been conducted using laser welding, in comparison of which the samples in the design matrix, the welding depth has a close relation with the thickness of the wall, the welding boundaries smother and the strength has a close value to the base metal.
