bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Role of Analysis in Mechanics
Authors: Leipholz H.H.E.
Published: April 2018

Experimental mechanics and mathematics are closely interwoven. Experiments provide facts and data which have to be explained and made consistent by introducing hypotheses which are formulated in mathematical terms. Such hypotheses lead to new systematical experimentation and so on. The result will be a well founded theory in one of the fields of mechanics.

Realizing this interaction between the two disciplines, which should be of interest to reviewers, recent developments in mathematics, which have had and will probably have a great influence on mechanics, are briefly discussed in this article.
Local and Average Transfer Coefficients for Developing Laminar Flow Between Parallel Flat Plates
Authors: Fernandes E.C. , Saboya F.E.M.
Published: April 2018

Local and average mass transfer coefficients in the entrance region between parallel flat plates were experimentally determined. The mass transfer experiments were performed using the naphthalene sublimation technique. In accordance with the analogy between heat and mass transfer, the experimental conditions simulated the heat transfer situation characterized by laminar flow in a parallel plate channel, one wall being isothermal and the other insulated, The temperature and velocity fields were simultaneously developing. Results were obtained for Reynolds numbers from 100 to 1500 and plate length-to-equivalent diameter ratios from 5 to 20. By use of the reciprocal of the Graetz number as an independent variable, the data for the various test runs could be brought together. The experimental results were compared with analytical predictions and a very good agreement was observed. Overall mass transfer results were measured with a precision balance and compared with the integral local values; the two methods gave results that agree to within a few percent (typically 2%).
Vibration Problem of Visco-Elastically Damped Structures
Authors: Van Overmeire Marc
Published: April 2018

For the solution of vibrational problems, involving viscoelastic damping layers, the application of a modal superposition technique requires the solution of the eigenproblem, ([K(ω)] - ω2[M]) (u)=0, with frequency dependent stiffness matrix [K(ω)]. This paper presents a straightforward method, namely a slightly modified Sturm Sequence Method, for the solution of this eigenproblem.
Large Elasto-Plastic Deformations of Work-Hardening Metal Alloys
Authors: Voyiadjis G.Z. , Navaee S.
Published: April 2018

The work outlined in this research demonstrates the applicability and effectiveness of the elasto-plastic model presented by the First author in [1] in solving complex (i.e., any shape and any deformation) finite deformation problems. The use of the Lagrangian formulation in this work eliminates the controversy regarding the choice of the appropriate co-rotational stress rate, and provides a more convenient theory than the more common spatial formulation.

The aluminum alloy 2024 is used in this work as it closely displays the properties outlined by the proposed constitutive equations [1].

The problem of analysis of displacements, stresses, and strains in elements made of this material subject to arbitrarily large deformations under the conditions of plane strain or plane stress is formulated in terms of the finite element method. Numerical examples include the bending of a moderately thick plate and the stress concentration problem of a plate with a hole subjected to an uniform uniaxial loading.

Experimental verification is provided for the bending of the moderately thick plate.
A Study of Dynamic Holographic Photoelasticity Using Ruby Laser
Authors: Chia Y.C. , Tong J.W. , Tou C.T.
Published: April 2018

A solution to the problem of principal stress distribution on the boundary of a circular hole and on a section of the model in semi-infinite plate during passage of the stress wave is presented.

The solution was obtained experimentally by using a polyester material model, utilizing a double-pulsed Ruby Laser with energy/pulse of 0.25 joule. The stress pulse was applied by loading with reproducible falling weight of the pendulum. Utilizing an external event to initiate the firing order of Ruby Laser and using a different time delay, we have recorded, respectively, the isochromatic and isopachic fringes at one model using a Faraday Rotator.
Interaction Between a Subsonic Air Jet and a Sharp Edge
Authors: Ko N.W.M.
Published: April 2018

This paper describes an experimental investigation of a jet of Mach number 0.5 which is partially interrupted by an 180° sharp edge. Detailed Schlieren and pressure spectral measurements of the jet with the sharp edge located at different locations inside the jet have indicated the presence of the basic jet coherent structure, the axisymmetrical and azimuthal constituents and the resonances set up by the interaction of the jet flow and sharp edge. The resonances arc due not only to the interaction of the initial shear layer with the acoustic feedback from the basic coherent structure but also with the acoustic feedback from the wake vortices set up in the wake flow behind the sharp edge. For the former, dependence of the level of resonance on location of the sharp edge has also been found.
Deflection Estimates Using the Virtual Work Principle
Authors: Piché Robert
Published: April 2018

Well-established methods of approximate static analysis for linear statically indeterminate structures are combined with the method of virtual work to calculate approximate deflections. The method is more general than the method of minimum complementary energy, since deflections may be estimated at any point of the structure, and there may be any number of loads applied (including distributed loads). Error bounds are derived, and sufficient (verifiable) conditions for the method to yield upper-bound estimates are proved. Finally, two examples are worked out: a double-braced truss and a rigid plane frame.
The Calculation of Properties of the Flow over a Backward Facing Step With the k-ε Model of Turbulence
Authors: Hackman L.P. , Strong A.B. , Raithby G.D.
Published: April 2018

This paper reports predictions of the mean velocity, the turbulent kinetic energy and the pressure and skin friction coefficients for turbulent flow over a backward facing step based on the standard k – ε closure for the turbulence shear stresses. In previous publications, errors due to the numerical algorithm as distinct from the turbulence model have been carefully assessed using different numerical schemes and finite volume geometries and it is argued that the current results are numerically accurate. Thus one can now assess the accuracy of the k – ε model of turbulence independently of numerical error.

The results predicted herein were found to be in reasonable agreement with relevant experimental data.
Effectiveness of Active TMD for Buildings’ Control
Authors: Abdel-Rohman M.
Published: April 2018

This paper presents some numerical investigations obtained from studying the effectiveness of active tuned mass dampers (TMD) in suppressing the vibrations in buildings. The results of the study indicate that active TMDs are not effective for forced vibration control in buildings. However, active TMDs are very effective and economic in suppressing the free vibrations response. For typical wind excitation, it is thus recommended to use passive TMD for forced vibration control, and active TMD for free vibration control.
The Spectral Method of Calculation of Symmetric Structures of Finite Size
Authors: Dinkevich Solomon
Published: April 2018

This article suggests a method of computing linear problems for multi-element symmetric structures of finite size; i.e., the multi-element structures associated with symmetry groups of order h > 1. Every such symmetric structure corresponds to a symmetric matrix which may have other matrices as its elements; we call the original matrix the “block-matrix” and its elements “submatrices”.

In theory, every symmetric matrix can be diagonalized. In practice, however, the process of numerical diagonalization may require a prohibitive amount of computer time. If a combination of analytical and numerical decompositions of such matrices is available, it can be then utilized to substantially reduce the amount of calculation and the requirement of computer time.

One such method, which we call the “Spectral Method”, is offered herein. This method is subsequently used to solve both homogeneous and nonhomogeneous systems of linear equations and to invert corresponding matrices of such structures.
Observations on the Use of Computers in the Process Planning of Machined Components
Authors: Yellowley I. , Kusiak A.
Published: April 2018

The possibility of further integration of CAD/CAM systems is dependent upon a better understanding of the process planning function. Existing computer aids to process planning tend to stress a variant approach which does not easily allow for process evolution and optimisation.

The authors describe a new approach to the optimisation of multi-operation machining processes, which should allow the pursuit of generative planning methods at higher levels of the process planning function.

In order to demonstrate such an approach, the problem of optimising cost in the removal of discrete volumetric elements will be reviewed, with particular reference to the milling process. The additional problems which arise in practical cases, where several intersecting volumes must be removed are discussed. This more realistic problem is then formulated in a manner which allows the application of a simple, effective heuristic to find good results.
A Geometrically Consistent Linearization Method
Authors: Calisal S.M.
Published: April 2018

The study of irrotational incompressible flows about thin geometries can be carried out using the well known perturbation procedures. In two-dimensional flows exact solutions based on mappings can be used to compare the accuracy of first order solutions. For most airfoil sections a first order perturbation solution is not sufficiently accurate in representing the pressure and velocity distribution, especially about the leading edge. For three-dimensional flows exact solutions are rare and for more complex problems such as ship wave resistance formulations an exact solution does not exist for comparison of results. In this last case second-order solutions exist but are very difficult to calculate. Therefore, it would appear advantageous to improve first-order calculations. To this end a perturbation method that incorporates the geometric properties of the body is studied. This method is applied to a symmetric Joukowski airfoil and to an elipse. This method, here called the “geometrically-consistent linearization method” predicts the leading edge pressure variations correctly in the two cases studied and appears to be superior to the classical first order solutions. An iterative solution following this procedure further improves the calculation especially for thicker foils. The method discussed and the following iteration procedure seem to form an efficient numerical solution to airfoil flow problems.
A Review of Combustion of Single Coal Particles in Fluidized Beds
Authors: Basu Prabir
Published: April 2018

The state of the art of the theory of the process of combustion of single coal particles in fluidized beds is reviewed. The process of combustion of coal is divided into two stages: devolatilisation, and burning of the char. The devolatilisation and the subsequent combustion of the volatile matter takes an order of magnitude less time than that for burning of the char. Therefore, the burning of char dominates the characteristics and performance of the combustor. Generally, the combustion of char is found to be controlled by the mass transfer to and reaction on the external surface if the area of pores in the char is less than 0.3 × 106m2/m3. Existing information suggests that in a fluidized bed oxygen diffuses to the carbon surface and it enters into heterogeneous reaction with carbon producing mainly CO. The carbon monoxide burns to CO2 in a diffusion flame surrounding the char particle. The surface temperature of the char, which is always higher than the bed temperature, is found to increase with decreasing size of the char, but it may start decreasing again if the site of CO oxidation moves away from the char surface for very small char particles. The mass transfer rate to the char particles may be calculated by considering the radial variation of local voidages, but this effect is significant only in limited cases.
Structural Control Considering Time Delay Effect
Authors: Abdel-Rohman Mohamed
Published: April 2018

The time delay between measuring the structural response, and applying the designed active control forces may affect the controlled response of the structure if not taken into consideration. In this paper it is shown how to design the control forces to compensate for the delay effect. It is also shown that the time delay effect can be used as a criterion to judge the effectiveness of the proposed control mechanism. As an illustration of the theoretical consideration, a numerical example in which a tall building is controlled by means of active tendons is presented.
Optimization of Wheel Slips for Maximum Braking Effectiveness with a Directional Stability Constraint
Authors: Guntur Rao R. , Sankar S. , Sankar T.S.
Published: April 2018

In this paper the dynamic behaviour of road vehicles on two different roads during braking has been studied with the help of a mathematical model. An optimization method is used to determine wheel slips for maximum braking effectiveness. A directional stability constraint has been imposed in the optimization procedure. The results are useful as guidelines to designers of anti-lock braking systems. The results indicate that by trading off a small amount of braking effectiveness significant improvement in directional stability can be obtained.
The Stability of Fluid Filled, Circular Cylindrical Pipes Part I - Theoretical Solutions
Authors: Sherbourne A.N. , Urrutia-Galicia J.L.
Published: April 2018

It was shown previously that the usual engineering approach to the problem of shell stability conforms with the more general variational method. Whereas the former entails the equilibrium of all forces acting on an infinitesimal element at incipient buckling, the latter simply replaces the load terms in the general differential equations of equilibrium by equivalent “parametric” or “reduced” loads.

The theory is applied to the applied to the problem of the circular, thin walled pipe acting as a simply supported beam containing fluid to any arbitrary level. By expressing the displacements and compatible internal loads in doubly infinite Fourier series which satisfy geometric and natural boundary conditions and using a Bubnov-Galerkin technique, it is possible to obtain estimates of he critical fluid density required to buckle the shell. Two cases of buckling are examined involving full and partially loaded pipes and the solution is seen to be sensitive to the number and location of harmonics included in the numerical calculations. Some logarithmic relationships are proposed between the buckling load and the shell parameters defining length and sectional slenderness. It is shown that the results can be conveniently interpreted using the parameter K which defines the nature of the stress field.
Second-Law Analysis of Energy Processes Part IV: The Exergy of Hydrocarbon Fuels
Authors: Brzustowski T.A. , Brena A.
Published: April 2018

Exergy is the maximum amount of work that can be extracted from a thermodynamic system in a given environment. This thermodynamic function, which depends both on the state of the system and on the conditions in the environment, is the basis of convenient engineering methods of Second-Law analysis of energy processes. The present paper deals with the exergy of hydrocarbon fuels, for which the reference environment is the atmosphere. In the case of pure hydrocarbons or simple mixtures whose composition is known exactly, it can be calculated precisely. It turns out that the exergy B is linearly related to the lower heating value LHV of these substances, and depends only weakly on local atmospheric conditions. The relationship approaches the simple proportionality B/LHV = 1,065 as the molecular weight of the fuels increases. That proportionality was first suggested by the correlations between B and LHV for various families of pure fuels. Subsequently, both the proportionality and the value of the constant were derived. It is conjectured that the same proportionality holds for heavy complex hydrocarbon fuels of unknown composition.
Heat Convection from a Horizontal Cylinder Rotating in a Quiescent Fluid
Authors: Badr H.M. , Ahmed S.M.
Published: April 2018

The aim of this work is a theoretical investigation to the problem of heat transfer from an isothermal horizontal cylinder rotating in a quiescent fluid. The study is based on the solution of the conservation equations of mass, momentum and energy for two-dimensional flow of a Boussinesq fluid. The effects of the parameters which influence the heat transfer process namely the Reynolds number and Grashof number are considered while the Prandtl number is held constant. Streamline and isotherm patterns are obtained from the mathematical model and the results are compared with previous experimental data. A satisfactory agreement was found.
On the Flexibility of Spatial Kinematic Chains
Authors: Rao A.C.
Published: April 2018

A number of distinct or non-isomorphic kinematic chains exist for a specified number of links and joints. For example, sixteen distinct chains can be obtained with eight links and two hundred and thirty chains with ten links having a single degree of freedom. Similarly, many space mechanisms can be formed with four links and joints having different degrees of freedom. So far no measure is available to know which of these possesses greater mobility or flexibility. Flexibility is not to be confused with the degree of freedom. Intuitively one feels that a six-link chain has greater flexibility than a four-bar chain both having the same degrees of freedom. Though the mobility of a chain increases with the number of links one is not sure how the structural arrangement, type of links and joints, their numbers and sequence etc. influence the same. Combining graph theory with the concepts of probability, simple formulae are developed to investigate the relative merits of spatial and planar kinematic chains. The greater the flexibility or mobility of the chain, the higher is the ability to meet the motion requirements, i.e., a chain having greater entropy can be expected, say, to reproduce a given function more accurately.
Heat Transfer R & D in Support of CANDU Reactors
Authors: Carver M.B. , Groeneveld D.C.
Published: April 2018

The paper reviews various types of thermalhydraulic models used in computational analysis in support of reactor design, and concentrates on particular areas of research and development, fundamental to defining accurately the various modes of heat transfer upon which reactor operation depends.
Principal Axes Technique and Uniqueness Criterion - Buckling
Authors: Dubey R.N.
Published: April 2018

A uniqueness criterion for solids in finite deformation is developed. The criterion is used in conjunction with the principal axes technique to calculate the buckling stress in an elastic-plastic plate under uniaxial compression. The result is found to be significantly lower than the similar result obtained from the classical analysis.
Synthesis of the Dimensional Tolerances of a Four-bar Mechanism
Authors: Fu Jing-fan , Fenton R.G. , Cleghorn W.L.
Published: April 2018

This paper presents a procedure to determine allowable tolerances in the dimensions of a planar four-bar mechanism which ensure that the output motions are kept within required error bands from the untoleranced motions. Starting from a preliminary set of estimates of the errors allowed, an optimization search is employed to determine the set of link dimension tolerances required to satisfy the output motion requirements. By incorporating a set of weighting factors associated with the link dimensions, the optimization is reduced to involving one independent variable. Examples applied to function generating and coupler point path generating mechanisms have been included to illustrate this procedure.
Certain Heat Conduction Problems In a Perforated Circular Cyliner
Authors: Naghdi A.K.
Published: April 2018

Employing a new class of basis functions, certain steady-state two-dimensional heat conduction problems for a multihole circular cylinder are solved. It is assumed that the outer boundary of the cylinder is subject to convection, while the cases of the following inner boundary conditions are investigated. (1) The inner boundaries are subject to a constant temperature. (2) The inner boundaries are subject to convection. (3) The inner circular cylinders consist of a different material containing uniform heat sources. It is also assumed that the properties of the materials involved, and the factors such as the convection heat transfer coefficients are temperature independent. Numerical results for all of the three aforementioned cases are presented, and for a particular case, the result is compared with that of a previous investigator.
Vibration of a Plate with Attached Mass
Authors: Smirnov A.
Published: April 2018

The eigenvalue problem for a circular plate with an attached mass is considered. The receptance method and the finite element method are both used to solve the problem. The eigenvalue equation obtained with the receptance method allows for both numerical and asymptotic solutions. By means of the method of a small disturbance, the simple formulas for eigenvalues are evaluated and the accuracy of these formulas is estimated. The asymptotic formulas describe the influence of the attached mass, the stiffness of a spring and damping on eigenvalues. The results of the computations show that eigenvalues obtained with the different methods show good agreement.
Measured and Simulated Performance of a Solar Domestic Hot Water System
Authors: Naegele T. , Hay J.E.
Published: April 2018

A commercially available solar domestic hot water heating system installed in a private residence in Vancouver. Canada has has been intensively monitored over a four month period. Simulation of the system was performed using a modified version of the WATSUN-3 Domestic Hot Water (DHWA) model. Model predictions are compared against actual system measurements on an hourly and daily basis. Reults show that the model is able to consistently track thermal conditions within the system and is capable of predicting system performance to within 5 percent.
A LOWER BOUND FOR THE BUCKLING LOAD OF A DIVERGENT NON-CONSERVATIVE SYSTEM
Authors: LY B.L.
Published: April 2018

The divergent non-conservative problems considered in this paper are pseudo self-adjoint. It is shown that a self-adjoint eigenvalue problem is related to the original non-conservative problem. The smallest eigenvalue of this self-adjoint system provides a lower bound for the buckling load of the non-conservative system.
A CORRELATION BETWEEN DEVIATIONS IN FORM AND SIZE TOLERANCES
Authors: COGUN C.
Published: April 2018

It is often necessary to prescribe size and form tolerances when specific workpiece accuracy is demanded. On the basis of published data and investigations carried out by the author a correlation has been developed between deviations in form and International organization for Standardization (ISO) tolerances. The range of application is for nominal sizes up to 10000 mm and for tolerance grades 4-16. This correlation can help constructors and workshop workers to choose the size of form tolerances when a certain workpiece accuracy is damanded. The proposed correlation is verified by measurements of the fitting of workpieces for industrial production and the evaluation of measuring data.
EFFICIENT INVERSE DYNAMICS OF GENERAL N-AXIS ROBOTIC MANIPULATORS
Authors: CYRIL X. , ANGELES J. , MISRA A.
Published: April 2018

Presented in this paper is an efficient scheme to solve the inverse dynamics problem associated with robotic manipulators of arbitrary architecture, using the recursive Newton-Euler formulation. The scheme’s efficiency derives from the use of suitable coordinate frame to represent the vector quantities and the suitable manipulation of the vector operations. The computational complexities of this and other general dynamical formulations published so far are compared. In conclusion, it is observed that not only the dynamical formulation methodology, but also the judicious representation and manipulation of the vector quantities contribute to the computational efficiency of the algorithm. An example is presented to show the validity of the computational scheme.
MINIMIZATION OF VIBRATION OF AXIALLY MOVING BEAMS
Authors: KALAYCIOGULU S. , MISRA A.K.
Published: April 2018

The paper investigates the vibrations of axially moving beams which may represent appendages in the process of deployment from a spacecraft or a prismatic joint in a flexible manipulator. The existing dynamical analyses of axially moving beams assume a given deployment scheme (usually, uniform deployment rate) and determine the corresponding vibratory response. The present paper, however, attempts to determine deployment schemes so that vibrations are minimized. First, several deployment schemes (uniform, exponential, squared and sinusoidal) are compared and it is noticed that the sinusoidal scheme results in the least vibratory amplitude. This is followed by an actual minimization process using pontryagin’s principle. In this, deployment from a given initial length to a desired final length within a specified duration of time is considered and the square of the displacement, integrated over the length and over the given duration, is minimized. The two-point boundary-value problem obtained is solved numerically. The vibration during this optimum deployment scheme is much smaller than that during uniform or exponential deployment; the sinusoidal scheme, however, appears to be quite good and comparable to the optimal scheme.
DYNAMICS OF FLEXIBLE MULTIBODY MECHANICAL SYSTEMS
Authors: Cyril X. , Angeles J. , Misra A.
Published: April 2018

In this paper the formulation and simulation of the dynamical equations of multibody mechanical systems comprising of both rigid and flexible-links are accomplished in two steps: in the first step, each link is considered as an unconstrained body and hence, its Euler-Lagrange (EL) equations are derived disregarding the kinematic couplings; in the second step, the individual-link equations, along with the associated constraint forces, are assembled to obtain the constrained dynamical equations of the multibody system. These constraint forces are then efficiently eliminated by simple matrix multiplication of the said equations by the transpose of the natural orthogonal complement of kinematic velocity constraints to obtain the independent dynamical equations. The equations of motion are solved for the generalized accelerations using the Cholesky decomposition method and integrated using Gear’s method for stiff differential equations. Finally, the dynamical behaviour of the Shuttle Remote Manipulator when performing a typical manoeuvre is determined using the above approach.
DEFLECTION OF A FLEXURAL CANTILEVER BEAM
Authors: Sherbourne A.N. , Lu F.
Published: April 2018

The behaviour of a flexural elasto-plastic cantilever beam is investigated in which geometric nonlinearities are considered. The result of an elastica analysis by Frisch-Fay [1] is extended to include post-yield behaviour. Although a closed-form solution is not possible, as in the elastic case, simple algebraic equations are derived involving only one unknown variable, which can also be expressed in the standard form of elliptic integrals if so desired. The results, in comparison with those of the small deflection analyses, indicate that large deflection analyses are necessary when the relative depth of the beam is very small over the length. The present exact solution can be used as a reference by those who resort to a finite element method for more complicated problems. It can also serve as a building block to other beam problems such as a simply supported beam or a beam with multiple loads.
ATTITUDE DIAGRAMS FOR TORQUEFREE GYROS
Authors: Rimrott F.P.J. , Szczygielski W.M.
Published: April 2018

For studies of the attitude behaviour of torquefree gyros, the so-called attitude diagram gives the most comprehensive and instructive information. In setting up the relationship, the concepts of kinetic energy and complementary kinetic energy supply the essential foundation.

The paper begins with the fundamental equations of gyrodynamics, which are then reduced to expressions for torquefree gyros. After introduction of the attitude diagram, i.e. a Poincaré-type map of the gyro motion, it is shown that a different treatment of the available equations is indicated for cases where, the kinetic energy is high, and for cases where the kinetic energy is low.
A CO-ROTATIONAL FORMULATION FOR GEOMETRICALLY NONLINEAR FINITE ELEMENT ANALYSIS OF SPATIAL BEAMS
Authors: Jiang L. , Chernuka M.W.
Published: April 2018

A co-rotational procedure is presented in this paper for handling arbitrarily large three-dimensional rotations associated with geometrically nonlinear analysis of spatial beam structures. This procedure has been incorporated into two commonly used 3-D beam elements, the 2-node cubic beam element and the 3-node superparametric beam element, in our in-house general purpose finite element program, VAST. In the present procedure, the element tangent stiffness matrices are generated by using the standard updated Lagrangian formulation, while a co-rotational formulation is employed to update the internal force vectors during the Newton-Raphson iterations, A number of example problems have been analyzed and the result are in good agreement with analytical or published numerical solutions.
A NUMERICAL STUDY OF FREE CONVECTIVE HEAT TRANSFER FROM A HEATED HALF-CYLINDER IN AN ENCLOSURE
Authors: Oosthuizen P.H. , Paul J.T.
Published: April 2018

Two-dimensional free convective flow in an enclosure which has a heated half-cylinder on the floor has been numerically studied. The half-cylinder is kept at a uniform high temperature. The enclosure has horizontal upper and lower walls and inclined side-walls. The side-walls are also kept at uniform temperatures and the top and bottom surfaces are adiabatic. In general, the side-walls have been assumed to be at different temperatures. The situation considered is an approximate model of that which occurs in some simple crop dryers. The flow has been assumed to be steady and laminar. Fluid properties have been assumed constant except for the density change with temperature which has been treated using the Boussinesq approximation. The governing equations have been written in dimensionless form and solved using a finite element method. Results have been obtained for a wide range of the governing parameters for a Prandtl number of 0.7, i.e. for air, and the effects of these governing parameters on the heat transfer rate has been studied.
PROPERTIES OF AN INTERCONNECTED HYDRO-PNEUMATIC SUSPENSION SYSTEM
Authors: Liu P.J. , Rakheja S. , Ahmed A.K.W.
Published: April 2018

The static and dynamic properties of a vehicle suspension comprising hydraulic struts interconnected in the roll plane are investigated. The fundamental properties of the interconnected suspension are investigated and compared to those of the unconnected suspensions with and without the anti-roll bar, in terms of load-carrying capacity, suspension rate, roll stiffness as well as damping characteristics. The anti-roll performance of the interconnected suspension is analyzed for excitations encountered during directional manoeuvres. The ride quality performance is evaluated for excitations occurring at tire-road interface. It is concluded that the interconnected hydro-pneumatic suspension with inherent enhanced roll stiffness and damping characteristics can significantly restrict the body roll motion to achieve improved roll stability of a vehicle.
PROPAGATION OF HARMONIC WAVES IN AN INITIALLY STRESSED THIN ELASTIC TUBE FILLED WITH AN INVISCID FLUID
Authors: Demiray Hilmi , Dost Sadik
Published: April 2018

This article presents a theoretical analysis for the wave propagation in a thin walled prestressed elastic tube filled with an inviscid fluid. Considering the blood flow in human artery and its physiological conditions, the tube is assumed to be initially subjected to a mean pressure Pi and the axial stretch λ2. The governing equations of the tube and the fluid are obtained by adding a small incremental disturbance on this initial field. In the formulation, the interaction between the blood and its container is taken into account. A harmonic wave type of solution is sought for the field equations, and the associated dispersion relation is obtained by using appropriate boundary conditions. Some special cases as well as a general case are thoroughly discussed and the results of the present formulation is compared with those of the relevant literature.
STABILITY OF EULER, LAGRANGE AND KOVALEVSKAYA GYROS IN A NEWTONIAN CENTRAL FORCE FIELD WITH SECOND ORDER TERMS
Authors: Ge Zheng-Ming , Ku Fu-Neng
Published: April 2018

The stability of the permanent rotation of the Euler, Lagrange and Kovalevskaya gyros about a fixed point in the Newtonian central force field is investigated by Liapunov direct method, which improve Leimanis’ and Rumiantsev’s result of stability conditions. For the sake of high accuracy, the first and second order terms of R-1 expressed by potential energy of the Newtonian central force field have been considered, where the R is the distance from the fixed point to the center of attraction.
PREDICTING 800 TO 500 DEGREES C WELD COOLING TIMES BY USING BACKPROPAGATION NEURAL NETWORKS
Authors: Chan B. , Bibby M. , Holtz N.
Published: April 2018

Backpropagation network technology (BNT) for predicting submerged arc weld 800 to 500°C cooling times (T8/5) is evaluated in this study. The experimental data used for training are extracted from the works of Rodrgues et al [1], Van Adrichem et al [2], Bibby et at [3] and Bala et al [4], Trained networks are tested against the independent work of Kohno et al [5]. Reasonable agreement is found in most cases. Furthermore, cooling times predicted by BNT are compared with counterpart cooling times from the conventional Adams models [6,7] for this purpose. The comparison shows that cooling times determined from BNT compare more favorably with experiment (data base) than those obtained from the Adams calculations. The optimal network structure appears to be 2-hidden layers with 4 & 3-hidden nodes respectively, trained with 20 training data sets. Experience with a network consisting a single-hidden layer and 4-hidden nodes is also reported for comparison. Finally, the potential for backpropagation network generated values for replacing convention semi-empirical formula is discussed.
ACCELERATION OF CONVERGENCE OF WAVEFORM RELAXATION ITERATIONS FOR SECOND ORDER LINEAR SYSTEM
Authors: Jackiewicz Z. , Knap J.
Published: April 2018

The solution of second order linear systems of differential equations by waveform relaxation techniques is investigated. It is demonstrated that overlapping of components of the system improves significantly the speed of convergence of the resulting waveform relaxation iterations.
CURVATURE ANALYSIS OF VARIABLE PITCH LEAD SCREWS WITH CYLINDRICAL MESHING ELEMENTS
Authors: Kang Yaw-Hong , Yan Hong-Sen
Published: April 2018

Based on coordinate transformation matrices and theory of gearing, we derive the mathematical expressions of surface geometry and the location of contact point of variable pitch lead screws. According to curvature theory, we obtain the principal curvatures, the principal directions, and the orientation of the contacting line at any contact point. Furthermore, the condition of avoiding undercutting of the screw surface, the reduced radius of curvature along any tangential direction, and the angle between the normal of contact line and the relative velocity are also derived. The result of this work is necessary for the tasks of contact stress analysis and wear/lubrication analysis for variable pitch lead screws with cylindrical meshing elements.
EFFECT OF BAFFLES ON SLOSHING MODULATED FORCES AND TORQUES DISTURBANCES REACTED TO GRAVITY GRADIENT DOMINATED ACCELERATIONS
Authors: Hung R.J. , Pan H.L. , Long Y.T.
Published: April 2018

The behavior of sloshing dynamics modulated fluid systems driven by the orbital accelerations including gravity gradient and jitter accelerations have been studied. Partially liquid-filled rotating dewar applicable to a full-scale Gravity Probe-B Spacecraft container with and without baffle are considered. Results show that slosh waves excited along the liquid-vapor interface induced by gravity gradient dominated orbital accelerations provide torsional moment with tidal motion of bubble oscillations in the rotating dewar. Fluctuations of slosh reaction forces and torques exerted on the dewar wall driven by the orbital accelerations are also investigated. Since the viscous force between a liquid-solid interface, and the surface tension force between a liquid-vapor-solid interface can greatly contribute to the damping effect of slosh wave excitation, a rotating dewar with baffle provides more areas of liquid-solid and liquid-vapor-solid interfaces than that of rotating Dewar without the baffle. Results show that the damping effect provided by baffle reduces the amplitudes of slosh reactions forces and torques feedback from the fluids to the container, in particular, the components of fluctuations transverse to the direction of baffle.
LIFT AND DRAG OF A TWO-DIMENSIONAL PAD SLIDING UPON A POROUS SURFACE
Authors: Desseaux André , Menet Jean-Luc
Published: April 2018

We consider the influence of withdrawal or injection of a fluid through a porous surface on the flow limited by a long parallel slider. Due to the no-slip conditions, the flow lacks of symmetry. But, a choice for a vertical velocity independent on the gap between the two surfaces is equivalent to a classical similarity solution. Then, the governing equations are reduced to a set of three ordinary differential equations. The quasilinearization method is a powerful tool to resolve these equations as soon as a first approximate solution is known. In both cases of small and large values for Re, we present an asymptotic formulation and use these first solutions for the scheme. A comparison with our numerical results shows that, respectively, these two approximations can be used until Re<5 for the first one and if Re>25 for the second. The different numerical results (velocity profiles, pressure, lift and drag) as functions of Re are analysed and compared with other published values.
ON SOME VARIATIONAL FORMULATIONS FOR MINIMUM SURFACE
Authors: Popov E.V.
Published: April 2018

An approach to resolving the minimum surface problem based on the total energy balance of the nodal system is represented in this work. The approach leads to design of two or three (for 2D or 3D problems respectively) independent systems of linear algebraic equations with symmetrical matrices in the banded form similar to global stiffness matrix of FEM assemblage. The efficiency of the approach is demonstrated by some 2D and 3D numerical tests. The formulation allows one to minimize the surface embodied into non-plane and plane, closed and non-closed contours. If a contour is closed and plane it allows to correct the triangle network distortion.
STATIC AND DYNAMIC ANALYSIS OF FLEXIBLE BEAMS: A CONSISTENT UPDATED LAGRANGIAN FORMULATION
Authors: Behdinan K. , Stylianou M.C. , Tabarrok B.
Published: April 2018

A study of static and dynamic analysis of slender beams undergoing large deflections is undertaken here. the Euler-Bernoulli hypothesis is employed and the beam deforms with large rotations but small strains. Initially the static analysis, using the consistent updated Lagrangian techniques which accounts for full non-linearity of the beam is undertaken and is then extended to dynamic analysis. Several examples illustrating the implementation and the performance of the proposed formulation are included and a comparison with results obtained by the co-rotational method is provided.
EVALUATION OF DISCRETE ADAPTIVE FAIL-SAFE ACTIVE SUSPENSION
Authors: Dukkipati R.V. , Vallurupalli S.S. , Osman M.O.M.
Published: April 2018

Hardware implementation of discrete adaptive control for a full scale vehicular single degree of freedom (SDOF) active suspension has been discussed in this paper. This paper describes an experimental evaluation of full scale fail-safe adaptive active (SDOF) suspension system that has been performed for the first time. A servo hydraulic force actuator is installed along with passive suspension components to form a fail-safe active suspension. A discrete model reference adaptive control (DMRAC) approach with recursive least square (RLS) estimation and covariance modification has been used for the software/hardware based digital control. A real time computer controlled adaptive active suspension software which shows the experimental response and animation of the results has been developed.
DEVELOPMENT OF A ROLL DYNAMICS MODEL OF A LIQUID TANK VEHICLE
Authors: Ranganathan R.
Published: April 2018

The roll dynamics model of a liquid tank vehicle is developed by integrating an equivalent mechanical analogy model of the liquid cargo to the roll plane model of a heavy commercial vehicle. The mechanical analogy model of the fluid slosh is represented through an equivalent pendulum system derived from the potential flow theory for a cylindrical tank. The non-linear vehicle model equations are derived in the roll plane of the tank vehicle by the use of Lagrang’s equations. The fluid-vehicle interaction is hence dynamically coupled in order to investigate the directional behavior of the tank vehicle during typical highway maneuvers. Computer simulations are performed on the dynamic roll model of the tank vehicle under various fill conditions and dynamic maneuver conditions. The roll response of the tank vehicle is then compared to that of an equivalent rigid cargo vehicle to study the impact of fluid slosh behavior. The influence of fluid fill level, loading conditions and vehicle characteristics on the dynamic roll performance of the vehicle is also investigated.
FREE VIBRATION ANALYSIS OF NON-UNIFORM TIMOSHENKO BEAMS USING DIFFERENTIAL TRANSFORM
Authors: Chen Cha’o Kuang , Ho Shing Huei
Published: April 2018

This study introduces using differential transform to solve the free vibration problems of a general elastically end restrained non-uniform Timoshenko beam. First, differential transform is briefly introduced. Second, taking differential transform of a non-uniform Timoshenko beam vibration problem, a set of difference equations is derived. Doing some simple algebraic operations on these equations, we can determine any i-th natural frequency, the closed form series solution of any i-th normalized mode shape. Finally, three examples are given to illustrate the accuracy and efficiency of the present method.
NATURAL CONVECTION HEAT TRANSFER FROM A DISCRETE HEAT SOURCE COUPLED WITH CONDUCTION DOMINATED PHASE CHANGE
Authors: Lacroix M.
Published: April 2018

A numerical study has been conducted for the heat transfer from a discrete heat source by natural convection in air above coupled with conduction dominated melting of a phase change material (PCM) below via a wall of finite thermal diffusivity. Results indicate that the presence of a PCM layer underneath the wall significantly delays the temperature rise of the heat source. The time delay increases as the thermal diffusivity of the wail material decreases and as the thickness of the PCM layer increases. For high thermal conductivity wall materials [Formula: see text] the steady state heat source temperatures are similar and independent of the PCM layer. On the other hand, for [Formula: see text], the steady state temperatures are higher and dependent on the thickness of the PCM layer. A correlation is proposed in terms of the thickness of the PCM layer and the thermal conductivity ratio of the wall.
ANALYSIS OF CERAMIC MATRIX COMPOSITES WITH BRIDGING CRACKS IN THE PRESENCE OF CREEP
Authors: Birman V. , Byrd L.W.
Published: April 2018

Ceramic matrix composites (CMCs) represent an attractive class of materials, particularly in aerospace applications where a combination of thermal and mechanical loads may present a challenge for a designer. An important feature of these materials is their ability to withstand damage without immediate failure. This emphasizes a significance of studies of damaged CMCs, particularly at high temperatures. In particular, the analysis of creep of CMCs with matrix cracks is important to accurately predict the response and reliability of such materials. The solution presented in this paper concentrates on creep in the presence of bridging cracks and uniaxial tensile load. Residual thermal stresses and the effect of temperature on the rate of creep are incorporated into the formulation.
MICROMECHANICS OF FAILURE IN METAL MATRIX COMPOSITES
Authors: Rubeinstein A.A. , Wang P.
Published: April 2018

An analytical model of failure development in metal matrix composites is presented the model is based on a recently developed analytical method for the analysis of fracture process zone development in composites. We employ a classical fracture mechanics modelling technique using the process zone concept and a small-scale approach for the fracture resistance analysis. The method is based on an exact analytical solution of the corresponding boundary value problem representing the micromechanical processes taking place within the process zone. The considered composite consists of an elastic-ideally-plastic matrix and elastic fibres. The model and the analysis are based on explicit consideration of the discrete distribution of the reinforcing fibres. During the process zone development within each individual segment, we have regions experiencing elastic deformation, plastic yield and, eventually, void formation and growth. The void growth leads to failure. The developed analytical formulation may be applied to layered composites.
LOCALIZATION OF STRUCTURAL VIBRATION AND ACOUSTIC RADIATION THROUGH BOUNDARY CONDITIONING
Authors: Muthukumaran P. , Bhat R.B. , Stiharu I.
Published: April 2018

Structural response and the resulting sound radiation due to excitations applied at any point on the structure depend very strongly on the boundary condition. Constraining structural vibration to the local areas of interest and modifying vibrational behaviour of the entire structure have numerous application s in sound and vibration control engineering. A concept of boundary conditioning has been proposed here in order to manipulate and control the vibration behaviour of the structure. A plate structure has been analyzed for its response and numerical results demonstrate the localization of structural vibration to the region of excitation by creating additional boundaries and conditioning them to achieve proper stiffness. This study shows that it is possible to localize the vibration and to alter mode shapes by advntageously modifying the boundary stiffness values.