Sanjib Kumar Acharyya

GA-Optimized Fuzzy-Feedforward-Bias Control of Motion by a Rugged Electrohydraulic System

An electrohydraulic system with a proportional valve and industry-grade cylinder has been used to target the servoclass tracking performance. Such systems have a wide range of heavy-duty applications, where the environment could be quite dirty along with the demands becoming faster and more precise every day. High static friction in the cylinder and large deadband of the valve in the system pose control challenges that are more severe than in a system with a servovalve and a low-friction cylinder. A fuzzy-feedforward-bias controller has been developed and a genetic algorithm has been used to optimize the controller parameters. The real-time control experiments revealed excellent tracking throughout the cycle for sinusoidal displacements beyond 1.5 Hz.

Optimal process design for laser transmission welding of acrylics using desirability function analysis and overlay contour plots

In this paper, an attempt is made to set the optimal laser transmission welding parameters to attain a desired weld seam with maximum joint strength. The earlier developed mathematical models are used to optimise the welding process. Design-expert software is used to optimise the process parameters, taking into account two proposed optimisation criteria. Numerical and graphical optimisation techniques are applied. The result of numerical optimisation predicts two pareto-optimal solution sets according to the planned optimisation criteria; whereas, graphical optimisation result produces overlay contour plots, which allow quick visual inspection of the area of desirable response values.

Static-Performance Based Computer-Aided Design of a DDV and its Sensitivity Analysis

Abstract Direct Drive valves (DDV) are gaining increasing acceptability for their simple configuration, low leakage, and low cost. Two major components of the present single-stage DDV are a spool valve and a linear force-motor. The objective of the present investigation was to formulate a design methodology and a static performance simulation tool for the DDV. The present work includes lumped and chiefly one-dimensional, non-linear field modelling of flow through the spool valve and magnetic flux in the motor. Detail modelling has been done only for leakage flow in the spool-bushing radial clearance of the spool valve, since it has critical bearing in the performance analysis. A computer-aided tool for designing a single stage valve, based on some additional simplifying assumptions of the lumped model, has been presented. The static performance algorithm was developed on SIMULINK, without invoking the design-level simplifications. The simulation tool has been used to carry out a design validation against the known performance of Moog Series D633 valve. Different designs of the valve, corresponding to different actuation specifications were obtained, and their static performances have been investigated. Also a sensitivity analysis has been carried out to study the effects of tractive air gap area ratio in the motor and port lap conditions in the spool valve.

An Experimental Determination of Johnson Cook Material and Failure Model Constants for Armour Steel

An experimental programme for determination of the Johnson Cook material and failure model constants for a typical armour steel material is reported. Tensile tests on specimens made from the armour material have been conducted at quasi-static and dynamic strain rates and at ambient and elevated temperatures. The analysis of the experimental data generates the model constants that are required as inputs during numerical simulation of dynamic events like armour impact using Johnson Cook constitutive relation and failure model implemented in most of the commercially available Finite Element codes.

A Correlation Study Between Mechanical Properties and Morphological Variation of 20MnMoNi55 Steel

Mechanical properties of nuclear reactor pressure vessel materials need to be assessed for degradation while operating under an irradiated condition, but conventional destructive tensile testing is not possible in such cases. In the present paper, a methodology is suggested which relates microstructural parameters to macro-mechanical properties of 20MnMoNi55 steel. Morphological variation of 20MnMoNi55 steel has been achieved through inter-critical heat treatment based on the phase fraction of constituent phases. The inter-critical temperature range of as-received material is determined through dilatometric testing. A color etching technique has been adopted for identification of different phases present in as-received and heat treated steel specimens. Vickers hardness values of each constituent phase as obtained from micro-hardness testing is correlated and standardized with the specified color code of each phase through image analysis of colored optical micrographs. Finally macro-hardness, obtained from the standard mixture rule based on micro-hardness and volume fraction of constituent phases, is correlated with tensile properties.

Effect of Microstructure Degradation on Fracture Toughness of 20MnMoNi55 Steel in DBT Region

The paper considers the effect of microstructure degradation on fracture toughness of 20MnMoNi55 pressure vessel steel. This degradation is reflected through the shift of fracture toughness vs. temperature curve along the temperature axis and rise in reference temperature in ductile to brittle transition (DBT) region. Hardness also depends on the microstructure of metallic alloys. The present study explores the correlation between hardness and fracture toughness for different microstructures in order to calibrate loss in toughness from hardness. The master curve reference temperature and microhardness for different microstructures are measured experimentally. It is observed that there exists a fair linear relation between microhardness and reference temperature.

Optimization of Primary Loop Pump Power of a Loop-type Liquid Metal Fast Breeder Reactor with Annular Fuel Using Genetic Algorithm

The present study focuses on the optimum design based on primary loop of a liquid metal fast breeder reactor (LMFBR). Inside the core annular fuel, rods are used for better heat transfer to the liquid sodium coolant. Value of the outlet temperature of the coolant from the core, surface temperature of the fuel pin, and pumping power at different volume flow rates are studied, and genetic algorithm (GA) is used to minimize pumping power required to maintain flow in the primary loop for an optimal design parameters.