Department of Mechanical Engineering

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Euler angles describe rotations of a rigid body in three-dimensional Cartesian space, as can be obtained by, say, a spherical joint. The rotation carried out by a spherical joint can also be expressed by using three intersecting revolute joints that can be described using the popular Denavit-Hartenberg (DH) parameters. However, the motions of these revolute joints do not necessarily correspond to any set of the Euler angles. This paper attempts to correlate the Euler angles and DH parameters by introducing a concept of DH parameterization of Euler angels. A systematic approach is presented in order to obtain the DH parameters for any Euler angles set. This gives rise to the concept of Euler-angle-joints (EAJs), which provide rotations equivalent to a particular set of Euler angles. Such EAJs can be conveniently used for the modeling of multibody systems having multiple-degrees-of-freedom joints. Copyright © 2012 by ASME.

World University root node

Journal of Computational and Nonlinear Dynamics

Denavit-Hartenberg parameterization of Euler angles

The problem of controlling the vibration of a transversely excited cantilever beam with tip mass is analyzed within the framework of the Euler-Bernoulli beam theory. A sinusoidally varying transverse excitation is applied at the left end of the cantilever beam, while a payload is attached to the free end of the beam. An active control of the transverse vibration based on cubic velocity is studied. Here, cubic velocity feedback law is proposed as a devise to suppress the vibration of the system subjected to primary and subharmonic resonance conditions. Method of multiple scales as one of the perturbation technique is used to reduce the second-order temporal equation into a set of two first-order differential equations that govern the time variation of the amplitude and phase of the response. Then the stability and bifurcation of the system is investigated. Frequency-response curves are obtained numerically for primary and subharmonic resonance conditions for different values of controller gain. The numerical results portrayed that a significant amount of vibration reduction can be obtained actively by using a suitable value of controller gain. The response obtained using method of multiple scales is compared with those obtained by numerically solving the temporal equation of motion and are found to be in good agreement. Numerical simulation for amplitude is also obtained by integrating the equation of motion in the frequency range between 1 and 3. The developed results can be extensively used to suppress the vibration of a transversely excited cantilever beam with tip mass or similar systems actively. © 2011 Springer-Verlag.

Archive of Applied Mechanics

Vibration control of a transversely excited cantilever beam with tip mass

The objectives of this present work is to study the stability and bifurcation control of an idealized electrostatically actuated microcantilever MEMS device that can widely observe in the field MEMS application. Here, the cantilever based device has been modelled as a spring-mass-damper system considering both the linear and nonlinear spring and damper. Simultaneously, the cantilever based device is excited harmonically by applied voltages. The method of multiple scales is employed to obtain the reduced order equations in terms of amplitude and phase those are directly used to determine the approximate the solutions for different resonance conditions. The catastrophic failure of the system may occur due to the presence of saddle-node and pitchfork bifurcation points as it leads the jump phenomenon. Basins of attractions are plotted in order to find the initial condition for a specific solution in a region having more than one solution. The obtained results can successfully be used in designing the microcantilever based devices that depict typical realistic nonlinear characteristics in the field of MEMS application. (c) 2012 Elsevier Ltd....Selection and/or peer-review under responsibility of the Symposium Cracoviense Sp. z.o.o.

Tuning the Nonlinear Behaviour of Resonant MEMS Sensors Actuated Electrically

Cloud formation is a ubiquitous process and modeling it as a simplified experimental set-up may be an interesting and fruitful task. In this study different flow and thermal processes and fluid structures during cloud formation (especially Cumulus clouds1) are investigated through an experimental setup. Vapor coming out of a 20cm×20cm water surface at temperature 60-800C interacts inside a square plexiglas tube of vertical height 60cm with dry, cold air passing from above the tube. An air conditioner is used to supply cold air at temperature 180C over the plexiglas tube. Various parameters like rate of evaporation, speed of cold air are regulated as per requirements. Turbulent plume structure is observed through a sheet of light. Optical visualization method is adopted for observing the condensed water droplets. Movies of vertical and horizontal views of plume structure are taken. Observation of this entrainment process reveals the turbulent nature of convection related to it and the gradual growth of cloud (aggregation of condensed water particles) with drop of temperature as clouds move up. Our present study is also important for prediction of type of Cumulus cloud formed for known environmental conditions. © (2012) Trans Tech Publications, Switzerland.

Applied Mechanics and Materials

Experimental study of cloud formation

Energy is consumed at every stage of the cycle of water supply, treatment, use and disposal. The intensity of energy consumption (kW h/m 3) depends upon the specific technologies applied at each stage of the water cycle. For some technologies, the intensity may be relatively low, whereas the intensity of other technologies is substantially greater. This report surveys the available literature on energy intensity for water use in the municipal and agricultural sectors and separates the process into several stages. Water supply, water treatment, residential end use, wastewater treatment, and agriculture end use are considered. Representative values of the energy consumed per unit water are given for a broad range of processes. Water extraction and pumping from ground and surface sources is considered. The energy intensity of treatment required for different types of water source is found to vary widely between the extremes of relatively fresh surface waters, which use energy mainly in pumping, and seawater, which requires desalination. Energy usage for different methods of irrigation including pressurized as well as surface irrigation is studied. The energy intensity of residential end use is very high relative to other parts of the water supply cycle. Processes such as heating water, washing clothes and dishes, and cooking are briefly studied within the water end-use stage. Hot water usage is responsible for making end use the most energy intensive stage of the water cycle. Hot water use in different buildings is briefly reviewed. Wastewater treated with various processes is considered, and the energy intensity is found to be highest when advanced wastewater treatment methods are applied. Energy consumption in the agricultural sector, which is principally related to irrigation pumping, is generally of lower energy intensity than for the municipal treatment or end use. © 2012 Elsevier Ltd. All rights reserved.

Renewable and Sustainable Energy Reviews

Energy requirements for water production, treatment, end use, reclamation, and disposal

This work studied the ball indentation test at room temperature to characterize the local tensile properties of bi-metallic weld joints. The weld specimens used were fabricated by joining between SA 508 Gr. 3 ferritic steel and Type 304LN stainless steel with Alloy 82 buttering on the ferritic steel side and Alloy 82/182 weld metal. The test results showed that yield stress (YS) of weld metal was slightly higher than that of Type 304 and smaller than that of SA508 Gr.3, and ultimate tensile stress (UTS) of weld metal was similar as those of Type 304 and SA508 Gr.3 base metals. Also, the values of YS and UTS of buttering layer (Alloy 82) were nearly same as those of weld metal. Heat-affected-zones (HAZs) showed higher YS and UTS values compared to their base metals. © (2012) Trans Tech Publications, Switzerland.

Advanced Materials Research

Application of ball indentation technique for mechanical properties estimation of Bi-metallic weld

A generalized methodology is developed for thermal testing of various solar dryer designs operated for natural and forced air flow conditions. The steady state mathematical model based on heat balance concept of solar dryer without load is applied to identify the dimensionless parameter called no-load performance index (NLPI). Laboratory models of direct (cabinet), indirect and mixed mode solar dryer are designed and constructed to perform steady state thermal tests for natural and forced air circulation. The dryers with no-load are operated with air passage between absorber plate and glass cover for the range of 300-800W/m 2 and 0.009-0.026kg/s of absorbed thermal energy and air mass flow rate respectively under indoor simulation conditions. The present study reveals that the forced convection operated dryer provides higher NLPI in contrast to that of natural convection. The comparative performance analysis of dryers indicates that the mixed mode dryer exhibits maximum value of NLPI followed by indirect and cabinet ones for both natural and forced air circulation. It is also found that for any dryer operating at given air flow condition, almost invariable NLPI values have been obtained for a wide range of absorbed energy and ambient air temperature data, thus facilitating performance comparison between different dryer designs on equitable basis. The results of statistical analysis showing low standard errors of mean further demonstrate good consistency in NLPI values for various dryer designs. The uncertainty in NLPI due to error in measurement of several parameters by instruments ranges from 0.79 to 1.96% for various dryer designs operated under different conditions. © 2011 Elsevier Ltd.

Solar Energy

Testing method for thermal performance based rating of various solar dryer designs

The damaged response of a composite lamina depends on various mechanisms that take place at the microlevel, i.e., at the level of the fiber and matrix. The present work focuses on developing a ply level continuum damage model for point-wise stiffness degradation through simplified representation of the microlevel damage. A three dimensional micromechanical analysis of a single cell representative volume element is carried out for various volume fraction, and levels of damage. The model brings out the coupled effect of damage on the effective point-wise ply level stiffness. Further, the numerical results are employed to develop a functional continuum representation of stiffness degradation as a function of the damage parameters and fiber volume fraction perturbations. The micromechanics model is consistent with experimentally observed stiffness degradation, i.e., a strong influence of fiber breakage and fiber matrix debond, and a weak influence of normal cracking of matrix. The proposed model can be considered as an improved version of the widely accepted diffused (meso) damage models, i.e., DML. The study also gives a generalized and consistent definition for the free energy, which can be used for modeling growth of damage. © 2011 Elsevier Ltd.

Composite Structures

Micromechanics based ply level material degradation model for unidirectional composites

A generalized approach for adaptive finite element analysis of laminated composite structures is presented in this study. The approach quantifies and controls discretization and modeling error. The goal of this paper is to present an economical, easily computable and relatively robust error estimator. A patch recovery based discretization error estimator is used and a goal based one shot adaptive procedure is implemented to control the discretization error. An explicit indicator, for estimation of modeling error, has been proposed for the laminated composites. The quality of the discretization and modeling error estimators is studied through numerical examples. The effectiveness of the proposed approach is also demonstrated through the analysis of damaged laminates. The key advantage of the proposed approach is that the desired mesh and models in the laminate are adapted automatically to achieve the user specified error tolerances in discretization and modeling errors. © 2012 Elsevier Ltd. All rights reserved.

Computers and Structures

A generalized adaptive finite element analysis of laminated plates

Convection traditionally refers to heat transfer associated with a fluid which is in motion. When the fluid motion is caused by an external agency, for example, a fan or a “wind,” the convection is termed as forced convection. In free convection, in contrast, fluid motion is predominantly due to buoyancy forces caused by density differences in the fluid; the density difference is generally due to variations of temperature or variations of concentration of species or both. © 2013 CRC Press/Taylor & Francis Group, LLC.