Applied Mechanics and Materials Vol. 612

Abstract: This paper presents the active control of vibrations of sandwich plates using piezoelectric composites (PZC). The top surface of the plate is integrated with the patches of active constrained layer damping treatment. Active fiber composite, one of the commercially available PZCs, is used as the material of the constraining layer of the patches and the constrained layer of the patch is composed of a viscoelastic material. Considering the first order shear deformation theory individually for each layer of the sandwich plate, a three-dimensional finite element model has been developed. The performance of active fiber composite for the smart vibration control of the sandwich plates has been studied and numerical results are presented. Emphasis has also been placed on investigating the effect of variation of piezoelectric fiber orientation angle in the constraining layer on the control authority of the patches.

Abstract: The automobile sector requires continuous progress in development of ‘Starter Motor’ by innovative approaches although significant progresses are made in the past. Development of Starter Motor has made it possible to start the engine by electrical means instead of doing it manually. The outstanding features of this motor are they can produce the maximum starting torque to crank the engine. In this case, we use electrical energy and convert it to mechanical energy in order to start the engine in motor vehicles. As the starter motor is mounted near the engine; vibrational disturbances produced due to either uneven road conditions or engine vibrations or both hampering the performance of starter motor which may result in breaking of component of motors. Vehicle will experience vibrations whose values are un-predictable at certain point of time causing random excitation and random vibrations. Aim of paper is to perform analytical formulation for Power Spectral Density function of Starter Motor by treating it as a cantilever beam and to find its response to random vibrations by using Finite Element Analysis (FEA).

Abstract: Cantilevered shaft-rotor systems consisting of multi disks and multi profiled shafts are considered. In this paper the procedures for the determination of the deflection, slope, shear force and bending moment at the extremities of the shaft are employed. Critical speeds or whirling frequency conditions are computed using transfer matrix method (TMM). For particular shaft-lengths, rotating speeds and shaft-profiles, the response of the system is determined for the establishment of the dynamic characteristics. A built-in shaft-rotor system consisting of two disks and two different profiled shafts is investigated for illustration purposes. Step response of the multi profiled shaft-rotor system is also found out.

Abstract: Vibrations are unwanted in most of the day today usage especially in mechanical machines, civil structures, aerospace industries and automotive parts. It is usually to get the rid of these vibrations by using magneto rheological fluids. A magneto rheological fluid provides viscous damping which gets added up when magnetic field is applied. The damping properties of fluid get multiplied and natural frequency of the body under observation also changes, using this technique the three layered MR fluid sandwich beam was fabricated and tested it for undamped and damped conditions. The controllability of variations in the various dynamic parameters like natural frequencies, vibration amplitudes and damping factors was observed. Keywords: Magnetorheological fluid, MRFluid sandwich Beam, Natural frequency, Damping factor, Damping coefficient.

Abstract: Dynamic behaviour of spindle system influences chatter stability of machine tool considerably. Self-excited vibrations of the tool results in unstable cutting process which leads to the chatter on the work surface and it reduces the productivity. In this paper, a system of coupled spindle bearing system is employed by considering the angular contact ball bearing forces on stability of machining. Using Timoshenko beam element formulation, the spindle unit is analyzed by including the gyroscopic and centrifugal terms. Frequency response functions at the tool-tip are obtained from the dynamic spindle model. In the second phase, solid model of the system is developed and its dynamic response is obtained from three dimensional finite element analysis. The works on analysis of the stability of milling processes focus on calculating the stability boundary of the machining parameters based on the dynamic models characterizing the milling processes. The stability lobe diagrams are generated from frequency response functions (FRF’s) lead to an stability limit prediction for the system at high speed ranges.

Abstract: For many years crack identification methods have been studied by number of researchers. The development of crack changes dynamic behavior of rotor system. It decreases the strength of object or material. Timely detection of a shaft crack by efficient condition monitoring system would avoid severe damage and expensive repairs due to failure of rotating machinery as well as assure the safety of personnel. The shaft crack is one of the most serious faults in high speed rotating machinery. It is important to detect them before they reach the critical size and cause total failure of the shaft. Hence attention to the study of rotating shaft with crack is required. This paper gives the general introduction to the vibration analysis method for crack detection with experimental set up. From software analysis it has shown that due to crack shaft gives different deformation values for different natural frequencies.

Abstract: The first part of this paper deals with the structural analysis of automobile frame and design modification to reduce weight of the chassis, the second part is the study of rolling over effect and the multiple axle drives with active bogies for chassis levelling and the final part is the implementation of the active bogies and multiple axle drives for the prevention of rolling over. A method has been suggested to overcome the rolling over by design modification of the chassis. Active weights are used in order to prevent the rolling over of a vehicle.

Abstract: This paper presents a 5-DoF articulated robot manipulator and proposes a strategy for solving its inverse kinematics. The Denavit – Hartenberg (D-H) parameterization has been used to model the kinematics of the manipulator. As degree of freedom of manipulator increases, the geometrical solution for inverse kinematics becomes difficult; hence an analytical method for the same is presented. Novelty in the method presented is that no approximations of trigonometric functions are used resulting in a theoretical positional accuracy of 10^-10mm of the end-effector. The articulated robotic manipulator developed makes use of integrated actuators and rapid prototyping technology enabling easy replication for educational purposes. The robot arm has been used for manipulation tasks in its workspace successfully.

Abstract: A Flexural mechanism uses flexibility of material for desired motion objectives. As compared rigid-body mechanisms where actuations are applied at the joints connecting rigid links, the manipulation of the Flexural mechanism relies on the deflection of internal flexible members. Flexural mechanisms have no relative moving parts (and thus involve no wear, backlash, noise and lubrication), are relatively compact in design as compared to rigid link mechanism. Double Flexural Manipulator (DFM) is basic building block for planar flexural mechanism. This paper explains working principle of DFM and its parametric modelling. DFM has three basic parameters which decides range of motion, actuator requirement (Peak force and continuous force). In this paper Parametric FEA analysis is carried on DFM and verified with Analytical Model. This parametric modelling can be further used for designing and developing a flexural mechanism for precision applications.