Abstract: The Solid Rocket Propellant in its crude form is a rubber like material. This rubber like material performs very interestingly when used to study crack propagation. Blunting of crack tips occurred in the composite when the load is applied, which is generally non-linear phenomenon. The crack propagation analysis for such case is generally taken for double edge cracks but the presence of central cracks in the composites cannot be ignored. This trend is nonlinear and complex. In order to simplify things, optical grade polyurethane material is used instead. The polyurethane material we used for our experimental work was PSM-4. In this research work, an extensive study is made regarding crack propagation analysis using the basic principles of fracture mechanics and its different techniques for finding out the parameter necessary for tracing crack propagation. Mode 1 (Opening Mode) is considered for the central crack propagation analysis. The objectives set in this context are the determination of Stress Intensity Factor of central crack in the specimen using photoelastic experimental data and simulation of central crack in softwares (ANSYS, Pro-e). For this purpose a rectangular plate with Central Crack was used to be experimented upon using the techniques of Photoelasticity. A comparative analysis technique is adopted to compare the effectiveness of results from experiments as well as software simulations.
Abstract: Brake dynamic groan noise which is a low frequency phenomena associated with brake stop condition or slow brake release. This phenomenon said to be a friction-speed characteristic and commonly associated with low speed events. Thus a high speed test regarding this phenomenon is done. In conjunction with speed, pressure relation is also tested. Analysis of groan occurrence in relation of the speed and pressure is performed. The pressure relation to this event is expected to widen the study of this phenomenon which currently confined to stick and slip motions.
Abstract: Performance analysis in term of identifying the system's transient response, stability and system's dynamical behavior in control system design is undeniably a must process. There are several ways in which a system can be analyzed. An example of well known techniques are using time domain and frequency domain approach. This paper is focused on the fundamental aspect of analysis of classical feedback controller in frequency domain of XY milling table ballscrew drive system. The controller used for the system is the basic PID controller using Matlab SISOTOOL graphical user interface. For this case, the frequency response function (FRF) of the system is used instead of using estimated model of transfer function to represent the real system. Result in simulation shows that after proper tuning of the controller, the system has been successfully being controlled accordingly. In addition, the result also fulfill the set requirement of frequency domain analysis in terms of the required gain and phase margin, the required maximum peak sensitivity and complimentary sensitivity function and the required stability.
Abstract: In recent years, the Swirling Fluidized Bed has been regarded as one of the novel designs in fluidization technology. This new technique features an annular blade distributor which injects the fluidizing gas through a certain inclination, is capable of fluidizing the bed and at the same time causes swirling motion of particles in a circular trajectory. In the present work, the fluidization characteristics and hydrodynamics of a swirling bed are studied using an experimental approach. The behavior of gas-particle interaction in a swirling bed in terms of operation regimes, trend of pressure drop across the bed and the hysteresis effect, are explored with varying bed configurations. Seven sets of particles, three in spherical shape, two in cylindrical shape and two in irregular shape, are used as bed material by considering bed weights from 500 g to 2000 g and blade overlap angles 18° for air velocities up to approximately 3.5 m/s and blade inclination of 10°. The results evidently showed that particle configurations dramatically affect the beds’ behavior.
Abstract: Parallel Manipulator has lot of applications in areas like flight/automobile simulators, earthquake simulators, milling machine, etc. Main disadvantage of parallel manipulator is the presence of singularities within the workspace. Due to this, entire workspace of a parallel manipulator cannot be used effectively. To overcome this disadvantage, an automated selective activation mechanism is proposed, designed and fabricated using solenoids, gear train and belt drive arrangement. By using this mechanism interior singularity are crossed and this enables the user to utilize the entire workspace. Selective activation mechanism with automation ability is designed in such a way that, depending on activation of solenoid, active joint of manipulator changes from one position to another, which subsequently changes the singularity curves. By changing active joint positions, 4 ways of operating manipulator are identified. For all type of operations, singularity curves are plotted using MATLAB.
Abstract: In the past few decades, Composite Sandwich Panel (CSP) technology significantly influenced the design and manufacturing of high performance structures. Although using CSP increases the reliability of structure, the important concern is to understand the complex deformation and damage evolution process. This study is focused on the mechanical behaviour of CSP under flexural loading condition. A setup of three-point bending test is prepared using three support span of 40, 60 and 80 mm. The loading was controlled by three different displacement rates of 1, 10 and 100 mm per minute to examine the effects of strain-rate on bending behaviour of CSP material. The beam span significantly affects the flexural stiffness of CSP panel. The load-deflection response of the panel shows two different portions, that representing equivalent elastic and plastic regions in both the core and facesheets components of CSP. The non-combustible mineral-filled core appears to be nonlinear in the elastic region, at high loading rate. Consequently the failure occurs as the core/facesheets interface suffers debonding.
Abstract: In the past few decades, underground railway systems as one of the accepted transportation system have become an integral part of populated cities, and consequently developing advanced structure to speed up the tunnels construction process become vital. Ceiling collapse is defined as the major failure in construction of tunnels that need to be concerned to prevent any hazardous on workers. Sprayed Concrete (SC) is the traditional structure that has been used for temporary support of tunnels under construction process. The disadvantages of SC such as tough preparation and installation process that is also time consuming procedure, is caused a necessary need to design new structure to be replaced by traditional cases. This study is concentrated on design and mechanical analysis of curvature polymer panel to be replaced by SC in tunnels. For this reason, Hard Density Polyethylene (HDPE) Polymer is selected due to its specific mechanical features such as high strength and stiffness to weight ratio. The tests of compression and tension are performed to extract the material properties and mechanical behaviour of HDPE polymer. A good study is done on mechanics of polymer materials to select an appropriate model accurate enough to model HDPE polymer. YEOH model is selected and utilized in Finite Element Analysis (FEA) using ABAQUS 6.9EF. Explicit Dynamic (ED) Procedure is used to simulate the hyperelastic deformation of HDPE polymer structures. The mathematical model and computational procedure are validated using simulation results of a three-dimensional (3D) model of a cubic HDPE polymer under compression load that compared well with experimental data. The established simulation procedure has applied on the proposed model of curvature HDPE polymer structure for temporary supports of tunnels. The actual loading and boundary condition in tunnels are tried to apply on the structure and the model is ran using FEM and ED procedure. The flexural strength response of structure is plotted as load-deflection curve to show the stiffness that can be tolerated with the curvature structure. A complete discussion is given on stress and hyperelastic deformation of the structure. The results are illustrating the advantage and disadvantage of designed structure and the possibility of utilize polymer materials in tunnelling process. The computational procedure is strongly recommended for design and analysis of polymer structures for different engineering application.
Abstract: To overcome the stalled effect and poor starting torque of fixed pitch Darrieus turbine, researchers invent variable pitch vertical axis tidal turbine (VATT). For tidal stream designers main challenge is that the design can sustain in hostile marine environment. Due to lift base design VATT is very critical for cavitation, so appropriate parameter selection can improve the hydrodynamic performance and life of the turbine. An attempt is made to optimize the design parameters of VATT for variable pitch using ANSYS CFX, hereafter CFX, which is based on a Reynolds-Averaged Navier-Stokes (RANS) model. A transient simulation is done for variable pitch VATT using Shear Stress Transport turbulence (SST) scheme. Main hydrodynamic parameters like torque T, combined moment CM, coefficients of performance CP and coefficient of torque CT, etc. are investigated. The modeling and meshing of turbine rotor is performed in ICEM-CFD. Mesh motion option is employed to achieve variable pitch phenomenon. This article is the one part of the ongoing research on turbine design and developments. The numerical simulation results are validated with analytical Matlab results performed by Edinburgh Design Ltd. The article concludes that CFX simulation is done accurately and major parameter selections for turbine development are feasible.
Abstract: The development of amorphous motors has been paid more and more attention. Different types of amorphous motors are designed, calculated, manufactured and tested. All of the motors achieve high efficiency and high torque density, especially in the high speed applications. However, few amorphous motors have been applied to practical applications. This paper reviews the newly development of amorphous motors. Several deficiencies limited the development of amorphous motors are discussed, and some effective improved methods are proposed.
Abstract: Power generation performance of a self-excited retarder determines whether the design goal of its braking torque could be achieved. The numerical analysis of transient electromagnetic field took magnetic vector potential as variable and made six reasonable assumptions to simplify calculation. Based on above, definite solution about transient electromagnetic field and the finite element received a detailed description. The external circuit and end effect of the power generation unit were taken into account so as to improve the calculation accuracy. Let the finite element equation and external circuit equation combine to form field-circuit coupled equations and then using Crank Nicolson method established its space-time discrete model. After verification by experiment, theoretical performance of the power generation unit was basically consistent to the experimental result for a 500Nm prototype. This showed that the numerical analysis as well as the model was feasible and the power generation unit could satisfy the requirement of braking unit for excitation current.