bluuebunny/crossref_metadata_2025 huggingface dataset:
The Response of Viscoelastic Materials to Slow Cyclic Stresses
Authors: McCammond D.
Published: April 2018

The response of viscoelastic materials to uniaxial cyclic stresses at low frequency is analysed theoretically using a Fourier series representation and dynamic compliance calculated from creep data. The theory is applied to sawtooth, square and rectangular wave forms on polymethylmethacrylate and polypropylene. Correlation between theory and experiment is good even when extended into the non-linear region for polypropylene.

It is suggested that this approach would require considerably less computation for general cyclic stress forms than an integral superposition method.
Boundary Layer Effects in a Wave Tank
Authors: Smith S.H.
Published: April 2018

When a progressive wave moves down a wave tank, it is known that the amplitude in the transverse direction is not exactly horizontal. A simple model is investigated and it is found that the variation from the constant value is of the order of(ν/ωa2)½ where ν is the kinematic viscosity, ω the wave frequency and a the width of the tank. Surface tension has negligible influence for the usual laboratory situations.
Comparison of Experimental Microlayer Thickness Results
Authors: Judd R.L.
Published: April 2018

The results of an interferometric study of the thickness of the microlayer underlying a dichloromethane vapour bubble which was observed during saturated nucleate boiling on a glass surface are reported. These results are compared with the experimental results of two other investigators.
A Regulated-Current Network Analog for Reactor Fuel End-Cap Temperatures
Authors: Rogers J. T. , Flemons R. S. , Barns G. M.
Published: April 2018

An analog of resistors and regulated-current sources has facilitated the thermal design of end caps for nuclear reactor fuel elements. The analog permits cylindrical-symmetric representation of the end caps, adjacent fuel, and sheath. With the analog, temperature distributions in various complex geometry end-cap designs can be readily determined. Non-uniform radial and axial heat source distributions, external uniform or non-uniform heat transfer coefficient distributions, and arbitrary internal contact conductance distributions between components can be treated.

A feature of the analog design is the regulation of currents to the nodal points within the simulated fuel region, insuring independence of the current loadings at other nodal points. This facilitates rapid setting of the required heat source distribution.

The analog has been used in the design of end caps of fuel elements for different fuel designs. Screening of proposed designs has been accomplished, and design configurations optimized.

The principles of the design can be applied to analogs used for many other purposes.
A Wall-Skew-Angle Correlatior for Flow in Curved Ducts
Authors: Young J.W.S. , Howard J.H.G.
Published: April 2018

A wall-skew-angle correlation is presented which, when combined with simple calculation procedure, allows the estimation of the boundary layer integral parameters on the end wall of a curved duct, requiring one measures, data point and the inlet and freestream conditions to be known. The major advantages of the formulation presented are simplicity and speed of solution.
Closed-Form Displacement Analysis of Five-Link R-C-R-C-P Spatial Mechanism
Authors: Dukkipati R. V.
Published: April 2018

Using (3 x 3) matrices with dual-number elements, closed-form displacement relationships are derived for a spatial five-link R-C-R-C-P mechanism. The input-output closed form displacement relationship is obtained as a second order polynomial in the output displacement. For each set of the input and output displacements obtained from the equation, all other variable parameters of the mechanism are uniquely determined. A numerical illustrative example is presented. The derived input-output relationship can be used to synthesize an R-C-R-C-P function generating mechanism for a maximum of 15 precision conditions.
Waveform, Confinement and Heater Thickness Effects on the Critical Heat Flux from Electrically-Heated Thin Strips
Authors: Fisk R. W. , McLaughlin M. H.
Published: April 2018

Three parameters affecting the critical heat flux from vertical, electrically heated, thin (0.051-0.254 mm) silver strips in R-113 (CC12F-CC1F2) are discussed.

The first is the reduction in critical heat flux (up to 32%) with decreasing ribbon thickness due to a lateral thermal conduction effect. The second is a reduced RMS heat flux for an AC sinusoidal waveform. The third is the reduced critical heat flux (up to 40%) from a vertical ribbon when confined between parallel plates, with no apparent dependence on ribbon length.
Nonlinear Bending of Inextensible Thin Rods Under Distributed and Concentrated Loads
Authors: Faulkner M. G. , Stredulinsky D. C.
Published: April 2018

A method is presented for the analysis of thin rods loaded by concentrated and distributed loads. The technique is also applicable to non-uniform rods. The solution of a nonlinear differential equation is avoided by considering the rod as a series of short rod segments. Each segment undergoes only small strains and small relative rotations so that the differential equation governing its shape is linear and easily solvable. The method is illustrated by two problems; the stiffened caternary and the tapered cantilever under distributed and concentrated loads.
Camber In Electron-Beam Welded Stainless Steel Sections
Authors: Bibby M. J. , Goldak J. A
Published: April 2018

Camber measurements in a series of small electron-beam (EB) welded stainless-steel Tee and bar sections are presented. The results are rationalized in terms of the semi-empirical deflection relationship for predicting camber in welded mild steel sections. It is demonstrated that the same relationship can be used for both austenitic stainless and carbon steel alloys. Some of the limits of camber predictability in terms of section size and heat input are discussed.
Variational Formulations for Linear Elastodynamics of Micropolar Media and the Associated Eigenvalue Bounds
Authors: Dost S. , Tabarrok B.
Published: April 2018

Governing equations for linear elastodynamic analysis of micropolar media are reviewed and are then cast in the framework of some variational statements. Starting from Hamilton’s principle, two mixed principles and a complementary energy principle are derived through a systematic procedure of relaxing some admissibility conditions and imposing others. The pertinent functionals represent the generalisations of the corresponding well-known functionals in the classical theory of linear elasticity. Finally, the case of free vibrations is considered and the nature of zero frequency modes, as obtained in the Hamiltonian and the complementary procedures, is discussed. The boundedness of eigenvalues in the two formulations is also examined and the corresponding Rayleigh quotients are compared.
Pressure Tubes: The Pressure Vessels in the CANDU Nuclear Power Reactor
Authors: Ross-Ross P.A.
Published: April 2018

One of the main engineering characteristics of the CANDU nuclear-power reactor is the use of pressure tubes rather than one large pressure vessel to contain the fuel and coolant. The power reactor basically consists of a calandria, which is a vessel containing the low pressure heavy water moderator, end shields, and an array of identical pressure tube assemblies which project through the end shields and calandria.

This paper briefly describes the CANDU reactor, some of the design and development, done in support of the pressure tube concept, and the Canadian experience with pressure tubes.
Stability of a Simply Supported or Clamped Silo Wall Subjected to Frictional Tangential Follower Loads
Authors: Leipholz H.H.E. , Bhalla K.D.
Published: April 2018

In this paper, the stability of a silo wall has been investigated without considering the edge effect caused by adjacent walls. The silo wall is assumed to be subjected to tangential, compressive, exponentially varying following loads. Janssen, in his publications, justified using such loads. Hence, since the turn of the century loading of such a type has been widely used for silo design.

The direct method of Liapunov is used for the stability investigation. Following this method, one determines the stability conditions without solving explicitly the boundary value problem of the system’s motion. Since no specific form for the solution is assumed when working with Liapunov’s approach, one does not know whether the structure will fail by buckling or by flutter. However, one does obtain the critical load beyond which the safety of the structure is endangered.

The results are obtained in the form of three stability conditions. Two of these conditions may be used to determine the dimensions of the silo. The third condition then prescribes the required material damping. The paper may be considered as a first attempt into the investigation of silo stability with Liapunov’s direct method. A complete investigation has to include edge effects and may be left for further research.
Pressure Rise Inside a Vessel Communicating with the Outside through an Orifice and Subject to an External Shock Wave of Arbitrary Positive Time Duration
Authors: Khosla A. , de Krasinski J.S.
Published: April 2018

A method has been developed to estimate the pressure rise in a closed vessel communicating with the outside through a small orifice and subject to an external shock wave of arbitrary positive time duration. The analysis consists of dividing the process into the dynamic component responsible for the first pressure peak with the oscillations which follow it, and the “quasi-static” component of filling the vessel due to the. long positive duration time of the wave acting at the orifice. Charts have been worked out for the subsonic and choked flow through the orifice. Complicated situations which may occur in reality can be analysed by combining various wave shapes discussed in the paper. The theoretical calculations are backed by numerous experimental data.
Analysis of Three-Lobe Bearings Having Non-Newtonian Lubricants by a Finite Element Method
Authors: Singh D.V. , Sinhasan R. , Tayal S.P.
Published: April 2018

Additives are extensively used in the commercial lubricants to improve their specific qualities. These lubricants are therefore non-Newtonian and their nonlinear relations between shear stress and shear strain rate are generally represented by cubic shear stress laws. The Navier-Stokes equations and the continuity equation in clindrical coordinates, representing the flow-field in the clearance space of each lobe of the three-lobe hydrodynamic journal bearings having Newtonian fluids, are solved by the finie element method using Galerkin’s technique. The solution for non-Newtonian lubricants is obtained by an iteration technique modifying the viscosity term in each iteration. The static performance characteristics have been obtained for both Newtonian and the non-Newtonian lubricants. The load capacity and friction of the bearing decrease with increase in the nonlinearity of the lubricant whereas the end flow is relatively unaffected.
Transverse Bending of Thin Concrete Conical Shells on Euler-Winkler Elastic Foundation
Authors: Oravas Gunhard AE. , Chung Kit-Man
Published: April 2018

Two approximate methods of analysis for thin elastic concrete shells on Euler-Winkler elastic foundation is presented in this paper. The approximate analytical solutions of the Geckeler-Bauersfeld type, and the asymptotic type are developed via a series of simplifying assumptions. The fundamental differential equation of the clastic conical shell is derived by means of approximations first introduced by Kann[1].

A case study of a tank consisting of a cylindrical shell and a shallow conical shell resting on gravel foundation is analysed by means of the approximate solutions, and the results are compared to the conventional solution of this tank problem, which ignores the elastic reaction of the foundation owing to the bending of the conical shell.
Vibration of Thick Circular Plate--Determination of Elastic Properties Through the Resonant Behaviour
Authors: Priolo P. , Sitzia C.
Published: April 2018

The authors examine, from two complementary points of view, the main problem deriving from the necessity of deducing elastic properties of materials by considering the resonant condition of transversely vibrating discs, that is the determination of the efficiency at high frequencies of finite elements formulated with the assumptions of the thick plate theory.

The first approach consists, having standardized the basic relations for various thick annular semi-analytical finite elements, in testing convergence and correspondence to known analytical solutions. The second consists in the experimental evaluation of the influence of thickness in deducing the Young’s modulus of a series of polycarbonate resin discs at frequencies corresponding to modes with up to eight nodal circles.
Turbulence in Flow with Circular Streamlines
Authors: Zak Michail
Published: April 2018

Based on the mathematical model of turbulence proposed in references [1-4], the formation of turbulence in flow with circular streamlines is analyzed.

The conditions of instability of a laminar flow with circular streamlines with respect to small pulsations are found. Special attention is paid to a steady turbulent regime.
An Experimental Investigation of a Low Heat Flux, Wickless Heat Pipe
Authors: Larkin B.S.
Published: April 2018

This paper reports tests on a wickless heat pipe to be used for transporting heat from the ground to protect an electronic package from low ambient temperatures. Evaporating heat transfer coefficients were measured for low heat fluxes where the behaviour of the evaporating film is unpredictable. The effects of type of working fluid, heat flux, charge quantity and tube inclination were investigated.
Prediction of the Efficiency of Non-Circular Spur Gears
Authors: Reinhart W.R. , Ferguson R.J. , Delaney R.G.
Published: April 2018

This paper reports predictions and test results which indicate the average loss rate per revolution for non-circular gears can be considered essentially the same as those for circular gears given similar specifications and operating conditions. There is, however, a significant variation in loss rate with respect to non-circular gear angular position.

The method of prediction was extended from a procedure developed by Anderson and Loewenthal for calculating the losses of external spur gears. The extended method is not restricted to non-circular gears as it can be used to calculate losses in rack and pinion and internal gear meshes.
A Development in the Use of Westergaard Stress Functions for the Solution of Griffith Crack Problems
Authors: Heng Zhang , McCammond D. , Tabarrok B.
Published: April 2018

Through some examples, it is shown that the use of Westergaard’s stress function in the solution of problems involving cracks in infinite plates may lead to erroneous results. The reasons are investigated in this paper and a procedure for avoiding such erroneous results is recommended.
Temperature Effects on the Fatigue Behaviour of an Aluminium-Silicon Aloy
Authors: Culver L.E. , Balthazar J.C. , Radon J.C.
Published: April 2018

The fatigue behaviour of BS1490 LM-30 aluminium-silicon alloy has been investigated at room temperature and at a comparatively high temperature of 250°C. ASTM type compact specimens have been used to gather information about the fatigue crack growth behaviour in this cast aluminium alloy at 250°C and a comparison made with the results of simitar tests at 20°C. The effect of stress ratio was investigated and fatigue crack growth thresholds were established for the stress ratios R=0.08, 0.5 and -1.0. The overall appearance of all the fractured surfaces was brittle and fractographic observations showed that the silicon precipitate determines the mode of fracture in the investigated temperature range.
Internal Gravity Waves in a Continuously Stratified Turbulent Flow Through Porous Media
Authors: Rudraiah N.
Published: April 2018

The attenuation of internal gravity waves propagating in a weakly stratified turbulent fluid flowing through a coarse porous medium is studied using a gradient-diffusion model. Small amplitude analysis is considered based on the assumption that the action of turbulence is parametrically represented by eddy mixing coefficients. By considering anisotropy of eddy coefficients, it is shown that the damping length and period increase are in general dependent on the porous parameter γ2, the Prandtl number Pr, thickness of the porous layer H, and eddy viscosity parameter Km 1 Subject quantitatively to the choice made for the eddy coefficients, it is shown that the effect of γ2 is to increase the frequency and to decrease the damping length of the waves as a result of energy dissipation due to friction in the bed. The damping is more rapid when H and Km 1 are large. The dependence of the relative damping length on H is in opposite directions for long and short waves. In particular, it is shown that the period increase and relative damping length present a minimum and maximum respectively at the intermediate wave lengths; the positions of these extrema depend on H, Km and Prγ2.
Liapunov’s Stability of Nonlinear Periodic Systems
Authors: Olas Andrzej
Published: April 2018

The goal of the paper is to propose a new procedure for the investigation of the Liapunov type stability of the zero-solution of a nonlinear periodic set. The procedure avoids either the use of Liapunov’s transformation or the occurrence of the nonstationary derivative V'(t,x)in the investigation. The critical subcase is analyzed when the solution of the linear part of the set is periodic. It is expected that a generalization of the procedure is possible. A 3-dimensional set is discussed as an example.
Heat Transfer in a Rectangular Plate Fin with Inner Circular Boundaries
Authors: Naghdi A.K.
Published: April 2018

Employing a special class of functions, the problem of steady-state heat transfer in a rectangular plate fin with 4N* inner circular boundaries are solved. It is assumed that the outer and inner boundaries of the plate are kept at different but uniform temperatures, and that the inner boundaries are symmetrically located with respect to the axes of symmetry of the plate. However, the N* inner boundaries in each quadrant do not have to be necessarily of the same size, nor must they be located in any orderly fashion. It is also assumed that the properties of the materials involved are temperature independent. Various numerical results for the rate of heat exchange and temperature distribution are presented.
Erosion of a Two-Dimensional Channel Bend by a Solid-Liquid Stream
Authors: Benchaita Mohamed T.
Published: April 2018

A theoretical study on “Erosion of a two-dimensional channel bend by a solid/liquid stream” is presented. The problem of erosion involves two interdependent phenomena: the fluid mechanics of the solid/liquid phase and the wear of materials by collisions and friction of solids on the metallic surface. By combining the theories of fluid mechanics of suspended particles in a liquid stream and a simple model of material weight loss by a single abrasive, one can determine the rate of erosion depth along the two-dimensional channel bend. The influence of erosion parameters such as abrasive size and stream velocity (at the bend inlet) is discussed.

The generalized model could then be used to evaluate erosion rates in industrial equipment such as pipe-bends, tees and elbows, catalytic cracking of oil, and oil-well casing.
The Development of Transition Pieces Using Triangulation
Authors: Pearce G.F.
Published: April 2018

A transition piece connecting a rectangular section to a circular section may be a warped or double-curved surface. This type of surface is, strictly speaking, undevelopable. However, the surface can be developed by considering it to be made up of a series of triangles. This paper is concerned with the selection of these triangles so that the result is a satisfactory development which avoids kinks in the final surface. Contour lines are used to indicate whether kinks will be present in the formed surface.
On the Derivation of Parametric Terms in the Equations of Elastic Stability of Thin Shells
Authors: Urrutia-Galicia J.L. , Sherbourne A.N.
Published: April 2018

In this paper, the parametric terms in the equations of elastic stability of thin shells will be derived in a way that appears to be simpler than those found in the literature. The result matches the solution given by Bolotin in 1967 but has been obtained by avoiding the energy functional of thin shell theory. The parametric terms account for the influence of prebuckling loads, membrane forces and their derivatives and are therefore of some significance in formulating the comprehensive stability equations for a variety of shell geometries.
On the Thermally Induced Flexural Deformation of an Anisotropic Visco-Elastic Plate Resting on an Elastic Foundation
Authors: Misra J.C. , Kar S.B. , Samanta S.C.
Published: April 2018

The object of the paper is to examine the role of anisotropicity in a visco-elastic plate subjected to an uneven temperature distribution. An expression for deflection of the particle at the middle section of a rectangular plate is found analytically. An attempt towards the quantitative analysis of the deflected central surface has been made and the results are compared with those for an identical isotropic plate.
An Indirect Method of Investigating Heat Transfer in Turbulent Flow in a Tube
Authors: Larkin B.S. , Savic P.
Published: April 2018

This paper describes a method of determining the correlation for heat transfer in turbulent flow in a tube, by measuring the heat transfer between water flowing through two similar tubes soldered together. This technique eliminates the need to measure surface temperature and minimizes thermocouple errors. Excellent consistency is obtained and it is argued that this implies accuracy of the same order. An analysis is given which describes the conduction of heat between the two tube surface/liquid interfaces.
A Time Marching Method for Internal Flows Using Curvilinear Coordinates
Authors: Reggio M. , Camarero R.
Published: April 2018

A time-marching method for flows with nozzle and blade-to-blade applications is presented. The approach developed consists of solving the basic conservation equations of gas dynamics in conservation form on a curvilinear grid.

The assumption of quasi-streamlines is satisfied by generating a body-fitted coordinate system. Stability is maintained by upwind differencing of the mass and momentum fluxes and downwind differencing of the pressure. The method is then applied to the solution of a plane and axisymmetric nozzle and to VKI’s gas turbine blade and compared to previous computations and experiments.
On Beltrami-Michell-Like Equations for Nonlinear Elastic Dielectrics
Authors: Dost S. , Glockner P.G.
Published: April 2018

Beltrami-Michell-like equations for nonlinear elastic dielectrics are obtained by choosing the deformation gradient, the polarization gradient and the polarization vector as independent field variables, so as to yield linear compatibility equations. The corresponding stress field also yields linear balance equations. Two simple examples for the case of semilinear isotropic elastic dielectrics are solved to illustrate the theory.
Nutation Accretion or Decay Due to Internal Energy Dissipation
Authors: Rimrott F.P.J.
Published: April 2018

In the present paper the secular attitude drift of a torquefree axisymmetric gyro is studied as a function of its attitude. By arguing that the gyro’s energy loss is due to the hystereses of its structural elements, an energy dissipation function is established, which is found to be proportional to an innate dissipativity of the gyro’s body and to the gyro’s attitude angle.

It is then shown that deformations of the gyro configuration are required, to facilitate the attitude drift induced by dissipation. The deformed gyro configuration is found to be a function of the (slowly drifting) attitude angle only, thus making it nearly constant. As a consequence the concept of rigidity, so essential for gyrodynamics, need not be abandoned.

The available experimental evidence is very sparse, but sufficient to show that typical satellites have innate dissipations in the order of microwatts due to structural hysteresis alone; and more, of course, when equipped with a nutation damper.
Advanced Experimental Mechanics in Modern Engineering Science and Technology
Authors: Pindera Jerzy T.
Published: April 2018

The explosive development of modern technology and the increasing societal awareness of technological risks are enforcing a more rigorous approach to the development of engineering theories, experiments, and design procedures. The recent progress in the theories and techniques of measurements has exposed various deficiencies of procedures of experimental and analytical mechanics. Major patterns of the rapidly emerging system of theories and experimental and analytical procedures based on scientific methodology -- which is called “advanced experimental mechanics” -- are outlined. The strong interdependence of advanced experimental mechanics, contemporary analytical mechanics and modern trends in applied materials science is illustrated by examples. Major issues are discussed within the framework of the modern scientific methodology formulated by Karl Popper, of Thomas Kuhn’s notion of paradigm in science, of Niels Bohr’s correspondence principle, and of the requirement of reliability of engineering procedures in mechanics imposed by socio-economic factors.
Further Results on the Stability of Viscoelastic Columns
Authors: Szyszkowski W. , Glockner P.G.
Published: April 2018

Recent results published by the authors on the stability behaviour of columns made of time-dependent materials are extended in a number of ways. Firstly, the closed-form expression obtained for the safe load limit of a simply supported column made of a linear three-element model material, is generalized for an arbitrary linearly viscoelastic constitutive law. The result, obtained by means of the static stability approach, is confirmed by an asymptotic solution of the dynamic stability equations. The same solution technique is used to generalize this expression for columns with arbitrary boundary conditions.

Even though columns as structural members exhibit stable post-buckling behaviour, there are structural configurations, involving compression members, the overall load deflection behaviour of which indicate unstable post-buckling characteristics. A simple example is used to alert the designer to the possibility of encountering such configurations and the danger associated with such post-buckling behaviour in the case of structures made of time-dependent materials.
Analytical Trajectory Optimization of Seven Degrees of Freedom Redundant Robots
Authors: Benhabib B. , Fenton R.G. , Goldenberg A.A.
Published: April 2018

The basic characteristic of kinematically redundant robots is that non-unique joint solutions may exist for a specified end effector location. Thus, trajectory planning for a kinematically redundant robot requires an optimization procedure to determine the joint displacements when solving the inverse kinematics relations. In this paper an analytical solution is developed for the trajectory optimization problem of redundant robots based on the classical Lagrange’s method. A detailed formulation is provided for seven degrees of freedom robots, which minimizes the Euclidean norm of joint dislacements for point-to-point motion trajectory planning.
The Use of Transformation and Superposition in the Solution of Multiply-connected Boundary Value Problems
Authors: Mioduchowski A. , Faulkner G. , Kim B.
Published: April 2018

The development of two general solution methods for linear multiple boundary value problems was considered in terms of the elastic torsion of multiply-connected inhomogenious prisms. Two mathematical techniques, the transformation and the superposition, are introduced, and, in conjunction with the finite element procedure, they were applied to several example problems for the purpose of verification of the accuracy/reliability. The results obtained indicated that the two methods are versatile, easily adaptable to any arbitrary multiply-connected linear boundary value problem, and provide reliable results.
A Method for Detection of Distinct Mechanisms of a Planar Kinematic Chain
Authors: Patel L.K. , Rao A.C.
Published: April 2018

This paper presents a computationally simple and efficient method for identification of distinct mechanisms of a planar kinematic chain having a single degree of freedom. It is proposed that velocity diagrams for all the inversions of a chain be drawn and the possible isomorphism among these velocity diagrams be detected. From the velocity diagram, a motion transfer point matrix can be prepared resulting in the development of a numerical scheme to be associated with a mechanism. Identical schemes lead to detection of isomorphism between mechanisms. The main advantage of this method is that, apart form detecteing isomorphism, it indicates which of the inversions is better kinematically e.g. higher the total number of vectors, better is the mechanism.
Stability Analysis of the Motion of a Tuned Gyroscope
Authors: Ge Zheng-Ming
Published: April 2018

In this paper, we use the Liapunov direct method to study the stability of motion of the rotor of a single-gimbal, elastically supported tuned gyroscope with the input rate ø̇1 = ø̇2 = 0 in three cases: (1) rotor-gimbal damping coefficients D1 = D2 = 0, rotor winding coefficient Dw = 0; (2) D1 ≠ 0, D2 ≠ 0, Dw = 0; (3) D1 ≠ 0, D2 ≠0, Dw ≠ 0.
Kinematic Analysis of Flexible Geneva Mechanisms
Authors: Fenton R.G. , Zhenbiao Wu
Published: April 2018

The deformation of Geneva wheels resulting from a unit normal unit force applied at the point of contact between the driving pin and the wheel is determined using the finite element method. The dynamic and static forces driving the Geneva wheel, and wheel deformations are computed. The output of the flexible Geneva wheel is determined with the help of an interpolating polynomial. An interactive process is used to update the dynamic component of the force based on the computed wheel acceleration values. Results indicate that the output of high speed flexible Geneva wheels is different from that obtained for Geneva mechanism having non-deforming links.
A COMPARATIVE STUDY OF CAM MOTIONS FOR HIGH-SPEED SEMI-RIGID FOLLOWER CAM SYSTEMS
Authors: GREWAL P.S. , NEWCOMBE W.R.
Published: April 2018

A study is presented on the comparison of all the popular cam motions based on a refined dynamic model which takes into account the effects of cam profile errors and most of the important factors that influence the dynamic performance for a semi-rigid follower cam system. A stochastic model is developed to simulate the input signal resulting from the cam motion, including the deviations due to profile errors. The performance criteria comprise the vibrational response at the follower and the dynamic characteristics at the cam. It has been established that, at high speeds, it is not the vibrational behaviour, but the follower tendency to jump and the maximum contact force and cam torque values which determine the dynamic performance. The Modified-Sine, Simple Harmonic and 3-4-5 Polynomial motions have been shown to exhibit superior high speed performance compared to that of the popular Cycloidal and Modified Trapezoidal motions. Higher-order Polynomial motions give very poor performance at high speeds.
EXPERIMENTAL RESULTS ON THE TENSILE STRENGTH OF ATMOSPHERIC ICE
Authors: DRUEZ J. , McCOMBER P. , TREMBLAY C.
Published: April 2018

The tensile strength of atmospheric ice samples (glaze and rime) obtained in an open type wind tunnel has been measured. Ice was grown from supercooled water droplets impinging on a rotating aluminium cylinder. In a first series of tests, the liquid water content of air was set at 0,8 g/m3 and the tensile strength of atmospheric ice was measured as a function of temperature ranging from −3 to −20°C, wind velocity during accretion ranging from 10 to 23 m/s and nominal strain rate ranging from 8, 70 × 10-7 to 1, 88 × 10-3 s-1. In a second series of tests, the liquid, water content of air was set at 1, 2 g/m3 and the wind velocity was maintained at 23 m/s. The tensile strength was measured as a function of temperature ranging from −3 to −20°C and larger nominal strain rate ranging from 7,25 × 10-8 to 7, 25 × 10−3 s−1. Maximum strengths, measured at −14°C, are found to be 5, 0 MPa at 1, 2 g/m3 liquid water content and 3, 1 MPa at 0, 8 g/m3 liquid water content. For the lowest temperatures used (−14 and −20°C), the atmospheric ice tensile strength increases with strain rate in the ductile range, i.e. strain rates lower than about 10−6 s−1. In these cases, the strength is found to be maximum for strain rate corresponding to the ductile-brittle transition and decreasing for higher strain rates. For the highest temperatures used (−3 and −8°C), the tensile strength of ice is found to be nearly constant as a function of strain rate.
ON THE DESIGN OF IMPELLER VANES OF CENTRIFUGAL PUMPS
Authors: TSANG L.
Published: April 2018

Empirical relations are employed in this paper to select blade (vane) angles, number and shapes for centrifugal pump impellers. A review of both the inlet and exit conditions of fluid in an impeller is given. Using Pearsall’s optimum inlet radius

[Formula: see text]

at the suction eye, together with Pfleiderer’s equation governing the number of vanes per impeller

[Formula: see text]

and the equation for slip (7.3), the whole geometry of the impeller can be defined.
LINEARIZED ROBOT MODELS IN JOINT AND CARTESIAN SPACES
Authors: BALAFOUTIS C.A. , PATEL R.V.
Published: April 2018

In this paper, linearization of the Newton-Euler formulation of robot dynamics is considered, and linearized robot models in joint and Cartesian spaces are presented. A new computational method for recursive evaluation of linearized dynamic robot models, about a nominal trajectory is given. The proposed algorithms are designed to evaluate the “sensitivity matrices” necessary to determine the linearised robot models and can be implemented numerically or symbolically. To achieve an efficient formulation for the coefficient sensitivity matrices, concepts from tensor algebra are used. A numerical implementation of the proposed linearized model shows that it has computational complexity of order N2.
BONDGRAPH MODELLING OF ROBOT DYNAMICS
Authors: El MARAGHY W.H. , El MARAGHY H.A. , IBRAHIM A.
Published: April 2018

Euler-Lagrange and Newton-Euler dynamic modelling become very involved and the equations quite complex even for a robot of few axes. For robot models, the bondgraph approach provides several advantages such as explicit bondgraph representation of the robot physical parameters and does not involve any complex equation writing or matrix inversion. In this paper, the use of the bondgraph method for modelling and simulating robot dynamics is presented. To illustrate the technique, a dynamic model for a SCARA robot is derived using bondgraph modelling. The causality conflict arising from the dependent inertias is solved by introducing structural and joint damping. Simulation results obtained using the developed model were in very close agreement with the analytical values obtained using the manipulator kinematic relations. Response due to impact excitation was obtained and is presented.
ADAPTIVITY-FLUIDS-LOCALIZATION: THE CHALLENGE TO COMPUTATIONAL MECHANICS
Authors: Zlenkiewicz O C
Published: April 2018

not available
ON THE FUNDAMENTAL FREQUENCIES AND MODES OF FREE VIBRATION OF CYLINDRICAL SHELLS
Authors: Urrutia-Galicia J.L. , Arango L.J.
Published: April 2018

The fundamental frequencies and modes of free vibration of simply supported circular cylindrical shells are explored. The results include the fundamental frequencies ωmn and the modes (m,n) of steel cylindrical shells which are presented in the form of a nomogram, see Figure 6. Besides, single more general formulas are given for cylindrical shells made out of any elastic material which turn out to be very suitable for design and analysis purposes.
ANALYSIS OF NATURAL CONVECTION HEAT TRANSFER BETWEEN TWO HORIZONTAL CYLINDERS AND THEIR ENCLOSURE
Authors: Lacroix M.
Published: April 2018

A numerical study has been conducted for natural convection heat transfer for air around two horizontal heated cylinders placed inside a rectangular enclosure cooled from the side. Three cylinder spacings were investigated. The local and overall Nusselt numbers were determined over the range of Rayleigh numbers from 104 to 106. It is found that the thermal performance of the unit is strongly influenced by the Rayleigh number and, to a lesser extent, by the cylinder spacing. A correlation is suggested for the overall Nusselt number.
THE STABILITY OF THE UNSYMMETRICAL HEAVY GYRO WITH DAMPING TORQUE
Authors: E Zheng-Ming , Chiu Shih-Ming
Published: April 2018

The conditions of the unsymmetrical heavy gyro are that A ≠ B ≠ C where, A, B and C are the principal moments of inertia of the rigid body and the center of gravity G of the rigid body does not coincide with the fixed point, i.e. zc ≠ 0, xc = yc = 0 in this paper. The conditions of the stability and of the instability of the unsymmetrical heavy gyro with and without linear or nonlinear damping torque are obtained by the direct method of Lyapunov.
MULTIPLE SOLUTIONS FOR INEXTENSIBLE ARCHES
Authors: Lipsett A.W. , Faulkner M.G. , Tam V.
Published: April 2018

The multiple equilibrium solutions of both deep and shallow inextensible arches is investigated through the use of a segmental shooting technique. The original nonlinear boundary value problem governing the large deformations of these arches is solved using a sequence of linear initial value problems which converge iteratively to the required boundary conditions. This method has proved successful in previous studies to analyse these large deformation problems when there is initially only one unknown at the beginning of the arch that must be assumed. Extension of this method to the problem with two initial unknowns is presented here. In either case all equilibrium solutions can be found in a systematic fashion. When there are three initial unkowns the present method is not able to determine the totality of equilibrium shapes for a given problem and loading. However, in this case, it is possible to determine a number of equilibrium shapes using engineering judgement for the values of the initial unknowns.
ROLE OF MECHANICS IN PLEX: A TECHNICAL PERSPECTIVE
Authors: Garud Y.S.
Published: April 2018

The mechanics of materials and structures plays an important role in majority of life prediction and structural integrity evaluations. In many industrial systems this role gets integrated with effects of service environment and material aging; corrosion, oxidation, and irradiation are examples of such effects which require an interdisciplinary approach. Degradation mechanisms related to these effects have been identified as potentially significant to plant life extension (PLEX). In-service inspection and component monitoring are some of the cost effective steps emphasized in the life extension works; usefulness of the results of these steps can be enhanced through the methods needed for the component condition assessment. These methods, therefore, demand an ever increasing accuracy and improvements requiring a better appreciation and integration of the mechanics.

The above aspects of PLEX are critically examined in this paper with a review of key degradation mechanisms elucidating the role of mechanics. Current design basis and recent developments in the life prediction techniques are discussed identifying areas of further work. Stress corrosion cracking, corrosion fatigue, pressurized thermal shock, and long term material stability under thermal and irradiation aging are some of the phenomena emphasized in this work. The significance of mechanics in treating the sub-critical crack growth due to these phenomena is discussed. Also, from the point of view of final failure step, the role of impact energy and fracture toughness is examined with consideration of the time dependent changes in these properties. The additional objective of this presentation is to provide a perspective on the assessment of remaining life and safety margins with particular reference to the needs and challenges of the plant life extension.
DAMAGE AND FUZZY RISK ASSESSMENT IN STEAM PLANTS
Authors: Cheung-Mak S.K.P. , Le May I.
Published: April 2018

The various methods of damage assessment in steam plants are reviewed. An example of estimating the remaining life of steam pipe welds containing cracks is discussed.

Modelling techniques provide a quantitative evaluation of the risk of failure. However, damage assessment is not an exact science. Thus the fuzzy set method of risk assessment is introduced. Most material data for creep are obtained from accelerated tests, and the extrapolation of shorter time data to longer times at different stresses and temperatures is used in the prediction of remaining life. Inexact knowledge of load and temperature variations in the operation of actual steam plant further complicates overall risk assessment.

Estimation of the overall risk of failure in the plant using the fuzzy set method requires identification of critical areas in different components at which damage may have accumulated, together with nondestructive testing, microstructural evaluation and other methods to define the extent of the damage. The importance of the particular component to the operation of the whole system must be assessed before a judgement can be made to provide a prediction of the plant’s remaining life.
INTEGRITY ASSESSMENT OF THICK WALLED INDUSTRIAL FURNACE TUBES
Authors: Kizhatil R.K. , Seshadri R.
Published: April 2018

This paper examines various simplified methods proposed to analyze stresses and predict damage and remaining life in furnace tubes subjected to sustained primary pressure stresses and cyclic secondary thermal stresses resulting from a typical furnace operation. Operational effects such as tube fouling, firing rates, startup-shutdown cycles are considered. Component integrity assessments are carried out using some recently developed techniques. A numerical example of a furnace tube made of HK-40 material is presented, and results obtained using a non-linear finite element analysis are compared with predictions obtained using the elastic-core method.
FLANGED JOINT ANALYSIS: A SIMPLIFIED METHOD BASED ON ELASTIC INTERACTION
Authors: Bouzid A. , Chaaban A.
Published: April 2018

Structurally sound bolted joints often fail due to loss of tightness. This is because the clamping load is affected by the application of the internal fluid pressure. A good design technique should therefore encompass most aspects of joint behaviour and produce efficient sealing performance within the clearly defined limits of the method used. This paper presents a simple analytical model based on an extension of the Taylor Forge approach taking into account flange rotation, flexibility of both the gasket and the bolts and, when applicable, the stiffness of the end closure. Examples will be discussed based on experimentally determined gasket properties.
LIMIT LOADS OF FRAMED STRUCTURES AND ARCHES USING THE GLOSS R-NODE METHOD
Authors: Fernando C.P.D. , Seshadri R.
Published: April 2018

An approximate method for determining limit loads of mechanical components and structures on the basis of two linear elastic finite element analyses is described. The load-control nature of the redistribution nodes (r-nodes) leads to considerable simplifications. The combined r-node equivalent stress, which can be obtained by invoking an appropriate multibar mode, can be identified with the reference stress. The method is applied to beam, framed and arched structures, and the limit load estimates obtained are reasonably accurate.
ACCURATE FREE VIBRATION ANALYSIS OF CLAMPED MINDLIN PLATES USING THE METHOD OF SUPERPOSITION
Authors: Yu S.D , Cleghorn W.L.
Published: April 2018

The method of superposition is further developed to analyze free flexural vibration of clamped rectangular Mindlin plates. Comparison of results given by Mindlin’s theory of plates with those previously obtained by Reissner’s theory has shown that the rotatory inertia does not significantly affect plate flexural vibration. Accurate eigenvalues are presented for a number of values of plate aspect ratio along with two representative values of thickness ratio.
FINITE ELEMENT MODELLING OF TILLAGE TOOL DESIGN
Authors: Kushwaha R.L.
Published: April 2018

A non-linear finite element model was developed for three dimensional soil cutting by tillage tools. A hyperbolic constitutive relation for soil was used in the model. Analysis was carried out to simulate soil cutting with rectangular flat and triangular tillage blades at different rake angles and with curved blades. Interface elements were used to model the adhesion and the friction between soil and blade surface. Soil forces obtained from the finite element model for the straight blades were verified with the results from laboratory tillage tests in the soil bin. The finite element model predicted draft force accurately for both tillage tools. Results indicated that the draft was a function of rake angle, tool shape and the curvature.
NATURAL FREQUENCIES OF A SHORT CURVED PIPE
Authors: Redekop D.
Published: April 2018

The natural frequencies are determine for a short curved pipe. A shell theory is developed in toroidal coordinates, based on the Mushtari-Vlasov-Donnell assumptions. The theory is specialized for the case of moderate curvature of the torus centre-line. To demonstrate the accuracy of the theory the end. exponential decay coefficients are calculated. These are compared with the corresponding coefficients for a straight pipe, and with values given previously for a curved pipe. The theory for the determination of the natural frequencies of vibration in symmetric and anti-symmetric modes is presented. Numerical results are computed using the theory, and these are compared with results for a comparable straight pipe.
DISPLACEMENT-IMPULSE COMPLEMENTARY IN ANALYTICAL MECHANICS
Authors: Rimrott F.P.J. , Tabarrok B. , Altenbach J.
Published: April 2018

Based on Euler’s linear momentum law, equations of motion of a mechanical system, consisting of a collection of point masses and force elements, such as springs or dashpots, are derived using generalized impulses, rather than generalized displacements, as coordinates. There are limitations to this approach involving both potential energy aspects and kinetic energy aspects. The present paper if of introductory nature and restricted to systems with translatory motion.
DYNAMICAL BEHAVIOUR OF ARTICULATED TRAIN CAR AND INFLUENCE ON VERTICAL COMFORT
Authors: Ravalard Y. , Coutellier D. , Masfrand S.
Published: April 2018

The aim of the study developed in this article is to stress the main physical phenomena linked to the articulation of vehicles from a systematic modeling of the railway train dynamics. Comfort has been, up to now, one of the main criteria in the specification sheets which any vehicle has to meet when being designed and even when answering an invitation to tender. Several solutions currently exist to determine the comfort levels inside railway vehicles but these solutions have always been reduced to the study of a single vehicle. The idea is to develop the research problematics in order to demonstrate the validity or not of the study of vehicles isolated in the articulated train cars; or in case of articulated train cars to show that the dynamical features are modified and have a non-neglectable influence on the comfort behaviour of the different vehicles of this train car. In the first place, a simple model will be made to represent correctly the behaviour of the vehicle. A modal analysis on models with several articulated vehicles will be made to underscore the phenomena related to the increase in vehicles. A forced response analysis will assess the phenomena and help to determine a solution with an integrated damper located in the joint.