جستجوی مقالات مرتبط با کلیدواژه « نسبت سیگنال به نویز » در نشریات گروه « مواد و متالورژی »

In this research, the effect of electric discharge machining input parameters on the surface roughness of A413 composite reinforced with 2.5% Al2O3, in two cases with the presence of a magnetic field and without a magnetic field was investigated and compared. The research presented with Taguchi experiment design approach which is based on L9 orthogonal array and iterative surface technique. The input parameters of these experiments include voltage (two levels), current intensity (three levels), pulse on-time (three levels) and pulse off-time (three levels). Experiments results show machined surface roughness reduction in presence of magnetic field up to 32 percent. The analysis of the results included the determination of signal-to-noise ratio diagrams corresponding to each of the input parameters and analysis of variance by Minitab software. The results show that the surface quality of the workpiece improves in the presence of a magnetic field compared to machining conditions without a magnetic field. Also, based on the results of analysis of variance in both cases, the current intensity is the most effective input parameter on the surface roughness of the workpiece made of A413 composite reinforced with 2.5% Al2O3.

In this research, the effect of input parameters of Electrical Discharge Machining (EDM) on A356 nano-composite reinforced by 3.5% alumina (Al2O3) was examined and optimized by the Taguchi technique based on the L9 orthogonal array and duplicated levels technique. The input parameters of these experiments consisted of voltage (two-level), current intensity (three-level), pulse on-time (three-level), and pulse off-time (three-level). Moreover, the output parameters were comprised of the material removal rate of the workpiece, the tool wear rate of the machining, and the surface roughness of the workpiece. The analysis of the results and investigation of the signal-to-noise graphs (S/N) and variance analysis (ANOVA) were carried out by using software. Also, with the determination of the loss function of total normalized values of the output parameters based on appropriate weight coefficients, the optimum level of each input parameter was identified. Besides, with performing the variance analysis, the magnitude of contribution percentage of each of the input parameters in the total variance was calculated. Based on the obtained results, it was concluded that the most influential parameter on the material removal rate was the pulse off-time, on tool wear rate was the current intensity, and on the surface roughness was the pulse on-time. Furthermore, the first level of the voltage (80 V), the first level of the current intensity (10 A), the first level of the pulse on-time (35 µs), and the second level of the pulse off-time (70 µs) were determined as the optimum input parameters. The contribution percentage of the input parameters in the total variance for voltage, current intensity, pulse on-time, and pulse off-time was found to be 12.98, 20.96, 5.47, and 60.60, respectively.

Metal matrix composites, according to the type of reinforcement used, have a different machinability. 2024 Aluminum matrix composites reinforced with aluminum oxide is among the materials the machining of which through traditional methods leads to the rapid wear of the tool; hence, EDM is a suitable method for machining this class of materials. Given that this machining method has different parameters, optimal set of machining parameters has a major effect on machining time, surface quality and tool wear rate. Using calculation and analysis of the total normalized quality loss (TNQL) and simultaneous signal to noise ratio of the outputs, this research is an attempt to investigate the effect of EDM parameters including current intensity, voltage, pulse on-time, and pulse off-time on material removal rate, tool wear rate and surface roughness in a the states of with and without powder and rotary tool. The results showed that current intensity and then pulse on-time, pulse off-time, and voltage have respectively the most important effect on output parameters of machining. The use of aluminum oxide powder and rotary tool increases gap and creates a centrifugal force and hence moves particles away from the area of machining and finally increases MRR. The use of aluminum powder in collision with sparks makes the sparks smaller and reduces their penetration depth and, thus, reduces the surface roughness. The results of optimization without powder and rotary tool proposes the combination of parameters as A3B1C2D3 while with powder and rotary tool proposes the combination of parameters as A1B1C2D3.