Rajeev Srivastava

Modeling simulation and control of active suspension system in Matlab Simulink environment

This paper proposes the study of automobile active suspension system for the purpose of improving ride comfort to passengers and simultaneously improving the stability of vehicle by reducing vibration effects on suspension system. With the increased demand of fine control of parameters, the mechatronic controller is being used for increasing the comfort of vehicle with their application to the suspension system of the vehicle. This is the prime location for the consideration of inclusion of controller. The modeling and simulation is carried out in Simulink environment and the PID (Proportional Integral derivative) controller is introduced for improving the performance of the suspension system. The active control of the suspension system is being carried out by proper tuning of the controller. The dynamic performance of the integrated system is improved significantly by using the controller.

Influence of Solid Fraction Casting on Microstructure of Aluminum Alloy 6061

Semi-solid processing of AA6061 alloy near liquidus temperature with the addition of micro- and nanoparticles of same alloy may be highly attractive for small intricate shapes due to excellent mechanical properties. The present work utilizes semi-solid behavior of AA6061 alloy, which reduces macro- and nanosegregation of particles, porosity, and forming forces during the shaping process. The experiment utilizes the semi-solid slurry of different solid fractions mixed with a melt at pouring temperature range of 400 − 640°C. The potential of solid fraction to produce semi-solid slurry has been investigated with the help of microstructure analysis, which is a crucial need for aluminum industries. The result shows that during the stirring, every dendrite modified itself to fine solid grains and dispersion of these grains takes place inside the molten metal. Alloy cooled directly from semi-solid state results in higher relative density with respect to conventional casting. With increase of solid fraction to 25%, the un-melted solid structure inside the pores and cavities in the direction of elongated grains results in the subsequent enhancement in the impact strength, hardness, and compressive strength as 19 kJ/m2, 93 BHN, and 550 MPa, respectively, without any alteration in the basic metal matrix composite.

Friction, Wear and Mechanical Properties of Al-Si LM6 Cast Alloy Processed in Semi-solid Stage

Dry sliding wear characteristics, mechanical properties and microstructural behavior of powder-chip based reinforcement silicon rich LM6 aluminum alloy, fabricated by semi-solid casting were investigated. Wear tests were conducted on powder-chip reinforced cast samples using the pin on disc apparatus under 5, 10 and 15 N with 0.4, 0.8 and 1.2 m/s sliding speeds for 250, 500 and 750 m sliding distances versus EN31 tool steel hardened to 62 HRC. An observation from the microstructure images indicated that the porosity of the cast composite reduces due to the distribution of un-melted chips inside the short cavities by the addition of reinforcement and confirmed with the obtained results of density. The fracture in cast specimens indicates that the micro-cracks were prevalently propagated along the broken eutectic silicon particles. Additionally, wear resistance was increased reasonably due to the inclusion of reinforcement under metallic wear environment. Worn surfaces SEM, EDS, XRD and, AFM analysis suggests that surfaces plastically deformed along with silicon brittle asperities which stuck on the softer surface of the contact layers, while dominant wear mechanisms were found from these surfaces and wear debris.

Influence of processing parameters on microstructure and mechanical response of a high-pressure die cast aluminum alloy

ABSTRACT Motor sealing brackets were fabricated by pressurized die casting (PDC) process under 408 MPa pressure via semisolid thick slurry of Aluminum Alloy 6061 base metal and 20% powder-chip of similar composition (average 500 μm). Initially, 81 microns powder (40% by weight) and micro-size chips (60% by weight) were mixed by stirring near 300°C until the diffusion of powder takes place and then refined by ball milling process. Influence of thick semisolid slurry modified by powder-chip reinforcement was investigated according to unmelted chip distribution inside the formed cavities, reinforcement incorporation factor (RIF), density measurement, blister formation along the surfaces and microhardness. The obtained results reveal that the unmelted particles significantly improved the microhardness value and density as 134.85 HV and 2.71 g/cm3, respectively, also with the reduction in the size of cavities. Refined microstructures were observed at several locations of the components due to the effect of processing parameters.

Improving surface roughness of the 3D printed part using electroless plating

The effect of electroless metallic coating on 3D printed acrylonitrile–butadiene–styrene plastic parts surface has been studied. Owing to its excellent toughness, good-dimensional reliability, good-process capability, chemical resistance and cost-effectiveness, acrylonitrile–butadiene–styrene is used for fabrication of parts using a 3D open source printer. These parts are further metallic coated using electroless copper deposition technique. Two different surface preparation processes, namely aluminium paint paste and aluminium epoxy paste have been used for electroless coating. After the surface conditioning of parts using these methods, copper is deposited electrolessly using acidic solution, containing 12.5 wt% copper sulphate with 7.5 wt% of sulphuric acid. Deposition of copper, for two different methods, has been carried out using different temperature conditions and different time of deposition. In the first case, the temperature of the solution is initially kept at 45±2 ℃ and is allowed to come to the room temperature as the deposition is completed. In the second case, the temperature of the solution is maintained at room temperature throughout the process. Further, copper-deposited 3D printed parts were characterized based on their surface roughness measurement, electrical conductivity measurement, scanning electron microscopy, energy dispersive spectroscopy and adhesion evaluation test. It has been found that both the methods used for coating show better electrical performance and more uniform copper deposition. Adhesion between copper layers and 3D printed acrylonitrile–butadiene–styrene substrates is found to have good strength for Al-Epoxy-coated parts.

Parametric study on the performance of active suspension system for variable passenger size and repeated road bumps

Efforts are made to investigate the behavior of active suspension system with application of fuzzy logic controller, for better performance against uncertain operating environment. Comprehensive analysis of the complex four degree of freedom system, for derived mathematical model, is performed with the application of Simulink, and a fuzzy logic controller is tested and suggested to improve the performance for different operating aspects. Mathematical model has the adequate flexibility for simulation fidelity to attain the desired degree of accuracy and to meet the objectives and desired outcomes. The imposed effective parameters of analysis are vertical body movements, body acceleration, actuating force in addition to time to regain the stability, which are thoroughly analyzed for great number of specifications. Simulation results indicate the feasibility of modeled fuzzy logic controller tested for randomly profiled road as well as changeable loading conditions.

Dimensional accuracy improvement of part fabricated by low cost 3D open source printer for industrial application

3D open source printer (3D-OSP) based on fused deposition modelling (FDM) technique is one of the newly developed rapid prototyping (RP) process for the fabrication of parts. It has been observed from research finding that the contribution of parameter such as raster width, slice height, and path speed are the most significant to the dimensional accuracy of 3D open source product. In this paper, an attempt has been made to find out the influence of the process parameter along with their interactions on the 3D-OSP. Taguchi parameter design has been used to find out the optimum parameters level to minimize percentage change in length (L1), length (L2) and height (H) of test specimens. Experimental result reveals that there is different optimal parameters level setting for each dimensional characteristic namely change in length (L1), length (L2) and height (H). Therefore, grey relational method is used to obtain optimum factor level of each dimensional characteristic simultaneously. From obtain result it is conclude that appropriate control of machine process parameters improve the dimensional accuracy of parts fabricated by a low cost 3D open source printer for industrial/commercial application.

Mechatronic design of Magneto-rheological damper for automobiles

The greater challenges for automobile manufacturer are to meet the ever-increasing demand for ultra safe, comfortable and multimedia vehicle which is increasingly intelligent and smarter. For the purpose there is need of modify and adopt best control strategic device for finer control. The vehicle vibration is one of key property which has to be controlled by intelligent damper application. The study focuses on designing of damper by means of parallel plate model and visualise the effect of different structural and fluid parameter on shear force and hence, on dynamic range. The optimization and FEM analysis of magnetic circuit, is also carried out by means of ANSYS(Ansoft). The present study and approach is to design high dynamic range MR-damper for the Indian road condition. The study will also incorporate the accumulator influence during the design of MR-damper. It has also been observed during the design of MR-damper that controllable force and dynamic range are key parameters to evaluate damper effectiveness which are mainly dependent of gap ratio. The effect of gap ratio on dynamic range and shear force is carried out through the programming in MATLAB.