Applied Mechanics and Materials Vols. 592-594

Abstract: In this study, the vibration analysis of a laminated composite magnetorheological elastomer (MRE) sandwich beam is presented. The governing differential equations of motion of a sandwich beam embedding a MRE layer as core layer and laminated composite beams as the face layers are presented in a finite element formulation. The validity of the developed finite element formulation is demonstrated by comparing results in terms of the natural frequencies derived from the present finite element formulation with those in the available literature. Various parametric studies are also performed to investigate the effect of a magnetic field on the variation of the natural frequencies and loss factors of the MR elastomer composite sandwich beam under various boundary conditions. Furthermore, the effect of the thickness of the MR elastomer layer on the variation of the natural frequencies and loss factors are studied. The study suggested that the natural frequency increases with increasing magnetic field, irrespective of the boundary conditions.

Abstract: The design of structures and machineries in present days are based on optimizing of multi-objectives such as maximum strength, maximum life, minimum weight and minimum cost. Due to this flexiblity they allow having a very high level of stresses. This leads to development of cracks in their elements. Due to long-term service many engineering structures may have structural defects such as cracks. So it is very much essential to know the property of structures and response of such structures in various cases. In this article the natural frequencies and mode shapes of an uncracked and cracked cantilever Timoshenko beam is studied by using finite element method (FEM) and MATLAB programme. The effect of crack on the natural frequencies of the uncracked and cracked Timoshenko beam is studied.

Abstract: The forced Duffing oscillator is investigated by time-delayed linear and nonlinear acceleration feedbacks. The method of Slowly Varying Parameter (SVP) can efficiently develop frequency response curves with stability of solutions. Appreciable reduction in peak value of response and gradual reduction in the skew-ness in frequency response curve is observed with the introduction of gain and delay. For some values of control parameters the entrainment phenomena are also observed. Appropriate choice of gain and delay parameters are made from the primary stability zone of linear stability analysis graph. The results obtained by this method are compared with numerical integration (NI) method and they are in good agreement.

Abstract: Tuned Vibration Absorber (TVA) is the best solution available to control/suppress vibrations of any dynamic systems. Dual mass Tuned Vibration Absorber are designed and implemented for the vibration control. Though the slab barker machine is operating at various natural frequencies, the Dual mass TVA can be designed to mitigate the vibrations depending on the position of mass. The experiments were carried out for various locations of mass. And it is found that the vibration /shock waves of slab breaker machine are absorbed by using a passive TVA system. By keeping the operating condition same it is practically found that at the location of 4cm the optimal vibration reduction obtained and the amplitude is found to be reduced by 37 %.

Abstract: The electronics package in a spacecraft is subjected to a variety of dynamic loads during launch phase and suitable thermal environment for the mission life. The dynamic and thermal analyses performed for a structurally reconfigured electronics package. Two different simulation models are developed to carry out the analyses. This paper discusses in two parts, in part-1, the vibration responses are determined at various critical locations, including on the Printed Circuit Board (PCB) for the vibration loads specified by launch vehicle using Finite Element Analysis (FEA). The mechanical properties of PCB are determined from the test specimens, which are then incorporated in the finite element model. In part-2, the steady-state temperature distributions on the components and on the PCB are determined, to check the effectiveness of heat transfer path from the components to the base of the package and to verify the predicted values are within the acceptable temperature limits specified. The predicted temperature values are then compared with on-orbit observations.

Abstract: Modal analysis plays an important role at design stage which helps in diagnosing problems related to structural vibration. This paper delineates about the experimental work to investigate the modal parameters, such as mode shapes and natural frequencies of a metallic container. The modal parameters have been experimentally determined for the empty container, the container filled with one liter of water and the container filled with two liters of water. Theoretical analysis is also carried out through finite element analysis using ANSYS workbench 14 for finding out modal parameters of the empty container only. The boundary conditions of the container in the experimental and FEM analysis have been kept same. The values of modal parameters obtained by the two methods then compared for their proximity

Abstract: With increased expectations for engineering products of high quality and safety standards, the need for accurate, fast and objective quality determination of these characteristics in engineering products continues to grow. Embedded vision provides one alternative for an automated, non-destructive, fast and cost-effective technique to accomplish these requirements. In this work, the authors are developed an integrated system which has two major components: an Embedded Vision System (EVS) and a Real Time Monitoring System (RTMS). This work describes design and development of prototyped Production Line System (PLS) based on a practical and fast approach using EVS and LabVIEW with IMAQ Vision Assistant as image processing tool. Experimental results show that this integrated system is faster and produces a lower error rate than humans produce in the quality inspection process.

Abstract: Flexibility plays a key role in robot based applications, where the ability to perform complex tasks in semi structured or even unstructured environments is strategic.Most industrial robot operates inside a security fence which separates them from human workers, but not all. Flexibility, lightness in relation to the mass to be displaced and energy efficiency are acquiring increasing significance in automation. We can achieve higher performance in robots by optimizing the parameters like high-speed operation, lower energy consumption, lighter weight and safer operation. In this paper a pick and place robot is designed and developed to achieve effective automation with higher safety and with greater ease. The main objectives of designing this flexible manipulator are to reduce its mass and to minimize its vibrations in the end-effector, which enhances good accuracy in positioning.This can be achieved by bringing down the number of working components and jointswhich reduce various losses. The greater mass can be transferred from one place to another place with relatively lesser mass of flexible three link manipulator. The various problems were encountered and rectified during the design and fabrication of flexible three link manipulator for pick and place application.

Abstract: This paper presents the development of a system for analyzing and adapting the Human Arm motion for virtual reality applications. The proposed system consists of number of Flex sensors, Inertial Measurement Units and Embedded Data Acquisition System, to record the joint angles for deriving the kinematic states (position, velocity and acceleration) of different parts of the human arm. A flexible structure is used for holding the sensors on the human arm at the required position, without hindering the movement. The embedded circuit utilizes a 32-bit Microcontroller to process the data from various sensors and transmits digitized data to the central computer for computing the various kinematics parameters. The system has been tested against standard motion tracking device and is found to perform close to the reference device with an average error of 6% . Such a device can be used to simulate critical operations in medicine and industry and analyze performance during various tasks.

Abstract: Pneumatic drives have many advantages over other actuators in terms of efficiency and safety which enable them to be used in many applications. In the present study, a new method of position manipulator with two pneumatic cylinders which are interconnected has been presented. Nonlinear mathematical model of the system has been formulated. Using Matlab-Simulink software, the system has been simulated. Fuzzy based control system has been designed for the system. From the various responses and indices it is observed that the fuzzy based control system has better performance than PID based control system. Also it is observed that the system with fuzzy controller has better setpoint tracking characteristics.