Solutions are needed for increasing the material removal rate without degrading surface quality in micro-electrical discharge machining (μ-EDM). This paper presents a new method that consists of suspending micro-MoS2 powder in dielectric fluid and using ultrasonic vibration during μ-EDM processes. The Taguchi method is adopted to ascertain the optimal process parameters to increase the material removal rate of dielectric fluid containing micro-powder in μ-EDM using a L18 orthogonal array. Pareto analysis of variance is employed to analyze the four machining process parameters: ultrasonic vibration of the dielectric fluid, concentration of micro-powder, tool electrode materials, and workpiece materials. The results show that the introduction of MoS2 micro-powder in dielectric fluid and using ultrasonic vibration significantly increase the material removal rate and improves surface quality by providing a flat surface free of black carbon spots. 相似文献
Recently, the ease of machining a workpiece by electrical discharge machining (EDM) processes has been determined by λ·θ theory, which is the product of the thermal conductivity (λ) and melting point (θ) of the workpiece in relation to the machining time. This paper presents a fundamental study of the total energy of discharge pulses required to machine different workpiece materials, and a new theory, referred to as λ·θ·ρ theory, is proposed, where ρ is the electrical resistivity of the workpiece. Unlike the λ·θ theory, the λ·θ·ρ theory includes the electrical resistivity of the workpiece material, because it involves the electric current transfer to create the discharge pulse. Using discharge pulse count monitoring, it was also revealed that the machining time cannot be used as a parameter to measure the ease of machining, since it is affected by many complications such as adhesion, cavitations, and short-circuiting. Parameters that are independent of machining complications are introduced in order to measure the ease of machining; the total energy of discharge pulses, discharge pulse number, average discharge pulse energy, discharge pulse density, and tool electrode wear. The results show that the coefficient of correlation for each parameter from the λ·θ·ρ theory is much higher than the λ·θ theory. Thus, the λ·θ·ρ theory is better than the λ·θ theory in determining the ease of EDM processes. 相似文献
This paper addresses the issue of robust reliable stabilization for a class of uncertain nonlinear stochastic systems with both discrete and distributed time-varying delays and possible occurrence of actuator faults. By constructing a new Lyapunov functional and using linear matrix inequality technique, a new set of sufficient conditions is established for the stochastic stability of the uncertain nonlinear stochastic systems. Then, sufficient conditions are obtained for the solvability of the robust stabilization problem via robust reliable controller. More precisely, the derived control law guarantees the robust stabilization of nonlinear stochastic systems in the presence of known actuator failure matrix and uncertainties. Further, the results are extended to study the stabilization of stochastic systems with unknown actuator failure matrix. Moreover, the obtained criteria are formulated in terms of LMIs and also the reliable controller can be designed in terms of the solutions to certain linear matrix inequalities. Finally, numerical examples with simulation result are presented to demonstrate the validity and less conservatism of the obtained results. 相似文献
In this paper, dynamic response of GFRP composite plate under ballistic impact has been studied by experimental tests and also by an efficient FE model. Material characterization of GFRP composite is performed as required for progressive damage analysis of laminate due to impact. Shock effect of impact is considered in the material modeling of composite plate. The influence of the target thickness on the ballistic performance of the composite plate is also studied by considering 3.12, 6.24 and 9.36 mm thick targets. Moreover, sandwich composite plate consisting of GFRP and Kevlar/epoxy in three different combinations of laminate layers is considered to obtain suitable combination for structural application that offer better penetration resistance. Damage pattern, contact force histories and stresses in composite plate are studied in addition to residual velocity and acceleration of projectile. Numerical results from present FE model in terms of residual velocities and damage patterns in composite plate show good agreement with the experimental results.
Due to the occurrences of debris, the ability of micro-EDM to produce precise dimension is degraded, hence positioning display indicator of micro-EDM machine is not accurately measure the real dimension. Therefore, imprecise workpiece dimension is happen. In order to overcome this problem, in this paper, the use of discharge pulse counting methods to correct this error is introduced. The dimension error from micro-EDM processes by using discharge pulse counting method is much smaller than when using the positioning display indicator of micro-EDM machine. Hence, by using discharge pulse counting method, high precision machining can be achieved. 相似文献
Abstract In this paper, a novel design of the flower pollination algorithm is presented for model identification problems in nonlinear active noise control systems. The recently introduced flower pollination based heuristics is implemented to minimize the mean squared error based merit/cost function representing the scenarios of active noise control system with linear/nonlinear and primary/secondary paths based on the sinusoidal signal, random and complex random signals as noise interferences. The flower pollination heuristics based active noise controllers are formulated through exploitation of nonlinear filtering with Volterra series. The comparative study on statistical observations in terms of accuracy, convergence and complexity measures demonstrates that the proposed meta-heuristic of flower pollination algorithm is reliable, accurate, stable as well as robust for active noise control system. The accuracy of the proposed nature inspired computing of flower pollination is in good agreement with the state of the art counterpart solvers based on variants of genetic algorithms, particle swarm optimization, backtracking search optimization algorithm, fireworks optimization algorithm along with their memetic combination with local search methodologies. Moreover, the central tendency and variation based statistical indices further validate the consistency and reliability of the proposed scheme mimic the mathematical model for the process of flower pollination systems. 相似文献
In this paper, we propose a new variable control chart under type II or failure‐censored reliability tests by assuming that the lifetime of a part follows the Weibull distribution with fixed and stable shape parameter. The purpose is to monitor the mean and the variance of a Weibull process. In fact, the mean and the variance are related to the scale parameter. The necessary measures are given to calculate the average run length (ARL) for in‐control and shifted processes. The tables of ARLs are presented for various shift constants and specified parameters. A simulation study is given to show the performance of the proposed control chart. The efficiency of the proposed control chart is compared with a control chart based on the conditional expected value under type II censoring. An example is also given for the illustration purpose. 相似文献