bluuebunny/crossref_metadata_2025 huggingface dataset:
A Reconsideration of Elastostatic Load Transfer Problems Involving a Half Space
Authors: Karasudhi P. , Rajapakse R.K.N.D. , Liyanage K.K.
Published: April 2018

This paper is a reconsideration of elastostatic load transfer problem of a long cylindrical elastic bar partially embedded in an elastic half space. Each problem is considered as consisting of two interacting systems, an extended half space and a one-dimensional fictitious bar. A compatibility condition is imposed near the interface of the interacting systems. In order to incorporate the real phenomenon of stress singularities at the ends of the bar, without carrying our a complicated derivation of the stress singularity factor, the basic unknown force at both ends of the fictitious bar is set to zero. However, the effects of the stress singularity are found to be not significant, especially for long bars and when the main concern is only on the force-displacement relationship at the top end of the bar.
An Integral Technique to Evaluate Opening Mode Stress Intensity Factors for Embedded Planar Cracks of Arbitrary Shape
Authors: Khattab M.A.A. , Burns D.J. , Pick R.J. , Thompson J.C.
Published: April 2018

In this paper, techniques are developed to handle the integrable singularities of the integral proposed by Burns and Oore for the estimation of opening mode stress intensity factors for embedded planar defects of arbitrary shape. The hybrid numerical-analytical integration techniques developed consider separately two crack front zones and one interior zone of the crack surface. Parameters are established for the sizing of the integration elements within each zone.

Studies of elliptical defects with aspect ratios between 1 and 10 demonstrate the accuracy and efficiency of this procedure for computing opening mode stress intensity factors. A simple method which compensates for the quadrature error associated with computationally inexpensive, coarse grids is outlined.
Numerical Solution for Liquid Storage Container on Euler-Winkler Elastic Foundation
Authors: D’Souza Giles , Oravas Gunhard AE.
Published: April 2018

Numerical solutions for a liquid storage container consisting of a cylindrical shell and a shallow conical shell base resting on a gravel foundation are presented. Solutions for the case of rotationally symmetric loading are given by the Finite Element and the Finite Difference Method. The effects of the value of the Subgrade Modulus on stresses and the appropriateness of the Asymptotic Solution in the analysis of structures is examined. This paper represents the concluding part of the study of a liquid storage tank resting on an elastic foundation, the first part of which was published in [1].
Ocean Wave Energy Conversion Devices Popular Today
Authors: Watts K.C. , Graham J.W.
Published: April 2018

Wave energy is one source of alternate energy that has fascinated man’s imagination throughout history yet has alluded his ability to tap it economically for domestic use. Considerable interest in harnessing wave energy exists today in a number of parts of the world, prompted to a large extent by the oil crisis of 1973.

This paper examines several wave energy devices which are currently being investigated in the United Kingdom, Japan, Norway and the U.S.A. Each is briefly examined in respect to its operating principles, efficiency, advantages, weaknesses and state of development. The devices discussed are: (1) the Kaimei, the floating ship off the coast of Japan; (2) Salter’s nodding duck with its gyroscopic reference frame; (3) the Lancaster flexible bag; (4) the SEA CLAM version of a flexible bag; (5) the NEL oscillating water column fixed rigidly to the ground; (6) the Vickers terminator and attenuator versions of the oscillating water column; (7) the Norwegian use of a “harbour” with an oscillating water column used to increase the device’s range of frequency response; (8) the latching buoy of Norway; and (9) the Bristol cylinder. Also presented are the studies at the Technical University of Nova Scotia of a two hinged floating raft, the DAM ATOLL of U.S.A. origin and a version of an oscillating water column device designed to increase its spectral response.
On the Effect of Residual Stresses in the Plastic Buckling of Columns - A Model Study
Authors: Camotim D. , Roorda J.
Published: April 2018

The bifurcation load and post-buckling behaviour of perfectly elastic columns is not affected by the presence of residual stresses. However, this is not the case when bifurcation occurs in the plastic range. In this paper, an analytical and experimental study of a column model is carried out, in order to investigate the influence of residual stresses in plastic buckling, namely, in the lowest bifurcation load and corresponding post-buckling behaviour. Initial geometrical imperfections are also taken into account and a sensitivity analysis is performed, in which the combined effect of both factors on the strength and maximum load supported by the structure is studied. Two elastic-plastic stress-strain relations are considered, with linear and nonlinear strain-hardening respectively. An experiment simulating the behaviour of the model is also presented. The experimental set-up is described and the experimental results are displayed and compared with the analysis.
Flow Pattern of Solid Particles in a Double Vortex Chamber
Authors: Georgantas A.I. , Krepec T. , Kwok C.K.
Published: April 2018

An experimentally determined air flow pattern in a double vortex chamber is utilized to predict the flow pattern of inserted solid particles. The minimum (critical) particle size retained in the vortex chamber is established in relation to different operating parameters. In view of possible applications of the double vortex chamber in combustion technology, an evaluation of the performance of the system at combustion operating conditions is also made. Experimental evidence of the predicted particle flow pattern is obtained for both cold and hot running conditions.
Interlayer Slip and Delamination Effect: A Hemivariational Inequality Approach
Authors: Panagiotopoulos P.D. , Koltsakis E.K.
Published: April 2018

In the present paper we formulate hemivariational inequalities describing the interlayer slip and delamination effect in elastic structures. After the formulation of the interface conditions which are of a nonmonotone multivalued nature, we derive hemivariational inequalities for the static and dynamic problems. Further some methods for the numerical treatment of the problems are given (regularisation method and substationarity-point method). Two numerical examples concerning simple adhesively connected elastic structures are given to illustrate the theory.
Heat Transfer Characteristics of Insulation Materials Available in Kuwait
Authors: Waked Adnan M.
Published: April 2018

Several insulation materials are being used in the construction of buildings in Kuwait. In this work the heat transfer characteristics of these insulation materials are being studied. It has been shown that the thermal diffusivity (α) of the insulation materials will significantly influence the characteristics of the heat flow through the material. The results show that materials with high thermal diffusivity, mainly materials with low densities, will have higher peak heat transfer loads than those of higher densities. Thus, the lower the value of (α) the better heat transfer characteristics the material will have.
On Elastic Systems Subjected to Configuration Dependent Loading and Certain Unilateral Constraints
Authors: Sadiku S. , Leipholz H.H.E.
Published: April 2018

The analysis of elastic systems supporting configuration dependent loading and subject to certain unilateral constraints is discussed. The problem is modelled as a variational inequality problem. Defining an inner product in a certain way, and hence a norm which is topologically equivalent to the Sobolev norm, existence and uniqueness of the variational problem have been proved. A finite-difference discretization of the system leads to a quadratic programming problem solvable by applying Crier’s version of the SOR method.
Discussion of Two Theories on the Penetration of Multilayer Metallic Targets
Authors: Nixdorff K.
Published: April 2018

A short survey of possible penetration theory approaches and possible penetration situations is given in order to show why a large number of different penetration theories can be found in the literature. Of this variety of theories, an empirical or quasianalytical theory and an approximate analytical one, used for estimating residual velocities and other parameters of the penetration of monolithic targets, are compared and applied to double layer and multilayer targets. The results are qualitatively in accordance, but differ quantitatively. The difference and some peculiarities are discussed.
Numerical Simulation of Oscillations in a Continuous Optical Discharge
Authors: Makomaski A.H.
Published: April 2018

A numerical method based on the assumptions of Forester and Emery is used to study the oscillatory behaviour of the plume and of the thermal wave associated with a point plasma, sustained by continuous optical discharge of a c.w. laser. Computations are carried out to simulate conditions in argon at 4 atm and initially at room temperature.

The numerical results explain or confirm many experimental features and generally quantitative agreement with experiment is good. Application of Kimura’s stability theory to the plume suggests aerodynamic instability as the origin of the oscillations. As for flames, these oscillations are associated with waves analogous to the Tollmien-Schlichting waves in laminar boundary layers.
Stagnation Point Flow of a Non-Newtonian Second Order Fluid
Authors: Teipel I.
Published: April 2018

In this paper the flow near a two-dimensional stagnation point for a particular non-Newtonian fluid has been studied. For a second order fluid the equation of motion for the stream function has been solved by using a similarity approach. A new parameter which is a combination of the Weissenberg number and the Reynolds number characterizes the visco-elastic effects. A fourth order differential equation has to be solved numerically. Only three boundary conditions are necessary. Results for various cases will be shown. In addition an approxamation theory has been derived in order to recognize the influence of the new parameter.
FLOW THROUGH A ROW OF CLOSELY-SPACED CIRCULAR CYLINDERS NORMAL TO A COLD WATER STREAM
Authors: LOCK G.S.H. , O’CALLAGHAN W.J.
Published: April 2018

Flow near a row of parallel circular cylinders standing normal to a cross flow has been investigated experimentally. The cylinders spanned the height of the test section in a water tunnel in which the temperature was maintained close to the freezing point. Reynolds numbers, based on the mean bulk water velocity and the cylinder diameter, ranged between 3 x 103 and 3 x 104. The gap-diameter ratio g/D was set at five nominal values: 0.49, 0.20, 0.15, 0.10 and 0.06.

For this range of conditions, static pressure readings were taken around the cylinder surfaces and at points well upstream and downstream of the cylinders. The overall static pressure change was converted into a pressure loss coefficient whose dependency on Reynolds number and gap-diameter ratio has been studied. The cylinder surface pressure profiles were used to determine flow behaviour in the gap region and in the wake. A critical transition at free stream Reynolds numbers much lower than that corresponding to a single cylinder was evident; a gap-diameter ratio near to 0.15 appeared to separate two different flow regimes. A cellular wake was often observed and found to be either metastable or bistable.
STRESS ANALYSIS OF CIRCULAR CYLINDRICAL SHELLS WITH FLANGE AND RIB ASSEMBLY
Authors: ANANDARAO M. , RAMAMURTI V. , DUKKIPATI R.V.
Published: April 2018

Static analysis of circular cylindrical shell with ribs and flange assembly subjected to axisymmetric and asymmetric loading is carried out. Finite element method using cyclic symmetric is used. The Potter’s method is modified to solve the simultaneous equation of cyclic symmetry analysis. An experimental model was tested for static axisymmetric and asymmetric loading. The results are compared with the theoretical ones.
BOUNDARY LAYER CALCULATIONS ON CYLINDERS OF RANKINE-OVAL SECTIONS
Authors: ABDULHADI M.
Published: April 2018

An approximate calculation of the boundary layer parameters around a long cylinder of Rankine-oval section is carried out. The calculations are undertaken as a step-by-step analysis using the finite-difference form of the integral formulations of the boundary layer equations. The separation line of the boundary layer for an oval of thickness = 0.2 is located in the rear portion of the oval in a plane making an angle of 137° with the direction of the flow.
FURTHER REMARKS ON RATES OF STRETCH TENSORS
Authors: Zhong-heng Guo , Lehmann Th. , Haoyun Liang
Published: April 2018

Using principal axis method, representation theory, fundamental theorem of symmetric polynomials and some special technique, the present paper obtains intrinsic expressions for rates of right and left stretch tensors and some new relations between these rates. The expression for the rate of the left stretch tensor is also new.
THE CONSTRAINED LEAST-SQUARE OPTIMIZATION OF SPHERICAL FOUR-BAR LINKAGES FOR RIGID-BODY GUIDANCE
Authors: Liu Zheng , Angeles J.
Published: April 2018

The synthesis of spherical four-bar linkages for rigid-body guidance consists of the computation of the relevant dimensions of this type of linkage so that it can guide its coupler link to attain a set of prescribed orientations, Generalized coupler curves are used to describe the specified orientations and to evaluate the linkage error, defined as the sum of the errors between the corresponding computed and prescribed orientations. A two-loop optimization procedure is set up to minimize this error, results being obtained resorting to the orthogonal decomposition algorithm, an iterative numerical scheme introduced elsewhere. Continuation and damping techniques are used in the numerical procedure to enhance the convergence likelihood and its rate. The optimization scheme is developed on a general basis and can handle the spherical rigid-body guidance problem for any number of prescribed orientations. A numerical example is included in the paper.
NUMERICAL STUDY OF LAMINAR CONVECTION AND THERMOSOLUTAL CONVECTION IN A TWO-DIMENSIONAL TRAPEZOIDAL CAVITY
Authors: Lacroix M.
Published: April 2018

Heat transfer driven by temperature gradients and simultaneous temperature and concentration gradients has been studied numerically for horizontal prismatic cavities of trapezoidal section having a hot horizontal base, a cool inclined top and insulated vertical walls. Results are presented for a cavity with width-to-mean height ratio of 4, thermal and concentration Rayleigh numbers up to 106 and 5.105 respectively, and top surface inclinations from 0 to 15 deg to the horizontal. The Prandtl and the Schmidt number used are 0.71 and 0.6 respectively. The governing equations are expressed in terms of stream function and vorticity and body-fitted coordinates are used for mapping the sloping top wall. As the inclination of the top surface is increased, the Nusselt and Sherwood numbers decrease. The effect of opposing thermal and concentration gradients on the Nusselt and Sherwood numbers is however more important than the effect of the inclination of the top surface. Theoretical Nusselt and Sherwood numbers are compared with available experimental data.
INELASTIC STRAIN CONCENTRATION IN DIRECTIONALLY SOLIDIFIED MATERIALS
Authors: Alwar R.S. , Babu Suresh
Published: April 2018

The application of Directionally Solidified (DS) materials in the construction of hot section parts (blades, vanes) of a gas turbine results in improvement in the engine performance and durability. Inelastic strain, an important parameter in low cycle fatigue (LCF) life prediction methodology, may be evaluated using simplified methods like Neuber’s rule and Equivalent Strain Energy Density Hypothesis. The objectives of the present investigation are to examine the validity of these methods in case of DS materials and to demonstrate using numerical methods that the low cycle fatigue life of DS materials is superior to isotropic materials.
THE DEVELOPMENT AND LINEAR STABILITY OF ROTATING BOUNDARY LAYERS
Authors: Prokop R.M. , Finlay W.H. , Chen P.
Published: April 2018

In this study, the effect of Coriolis force on the development and linear stability of the boundary layer on a rotating flat plate is examined. The parabolized governing equations are solved using a Legendre spectral element method with a marching scheme. The shape of the velocity profile is a function of the nondimensional rotation rate Rox/Rex, where Rox is the rotation number and Rex is the Reynolds number. For a given value of Rox/Rex, the base flow is self-similar, but the shape of the velocity profile changes when Rox/Rex is varied. These results are confirmed by demonstrating that the governing partial differential equations can be reduced to one ordinary differential equation by similitude analysis. The linear stability of the boundary layer to spanwise perturbations is also considered. The non-Blasius shape of the base flow velocity profile does not have any appreciable effect on the growth rate of the vortices compared to that obtained with a Blasius profile for all Rox/Rex ≤ l×l0-4 considered. Thus, the rotational Görtler number Re1/4Rox1/2(δ/δB)3/2 (where δ and δB are the actual and Blasius boundary layer thicknesses respectively) is the appropriate parameter to describe the growth of the vortices.
PSEUDO PROBABILISTIC APPROACH TO TEST ISOMORPHISM AMONG KINEMATIC CHAINS
Authors: Shubhashis S. , Choubey M. , Rao A.C.
Published: April 2018

There is no dearth of methods to test isomorphism amongst kinematic chains. Search for a computationally easier, logically simple and unique method is still on. Present work is in quest of a reliable test to detect isomorphism among kinematic chains. Work presented here is more versatile as it incorporates more features of the kinematic chain which were not included earlier such as number and type of links, their relative dispositions in the kinematic chain, nature of adjacent links etc. The method proposed is based on the concept of pseudo-probability (pseudo means it appears to be, but not exactly. The approach does not follow in-toto the principles of probability and considerable liberty has been taken in interpreting the word probability hence the word pseudo is used along with the probability schemes). Using the resemblance of different coloured balls in an urn for the number and type of links in a kinematic chain, a matrix (named P-Matrix) representing the kinematic chain in totality is generated. For the sake of comparison a numerical scheme named, pseudo probability scheme, P-Scheme, is developed from the above P-Matrix and is used for testing isomorphism. In fact the method is more powerful in the sense that each row of the proposed P-Matrix is capable of representing the respective kinematic chain distinctly and can be used to compare the kinematic chains with same link assortments, uniquely.

The proposed method, besides possessing the potential of testing the isomorphism among simple-joint, single degree of freedom kinematic chains is also capable of multi degrees of freedom and multiple-joint kinematic chains.
A METHODOLOGY FOR THE CONFIGURATION SYNTHESIS OF MACHINING CENTRES
Authors: Yan H.S. , Chen F.C.
Published: April 2018

The purpose of this paper is to present a design methodology for the configuration synthesis of machining centres with tool change mechanisms to meet required topology and motion requirements. This methodology is computerized and the machining centres with tool change mechanisms of up to ten links are synthesized. As the result the minimum number of links of the mechanism of machining centres is 8 and the numbers of configurations of machining centres with 8, 9 and 10 links are 75, 331 and 793, respectively. Furthermore, this work provides a systematic approach for synthesizing spatial open-type mechanisms with motion requirements.
STUDY OF DRIVER FACTORS AFFECTING THE DIRECTIONAL RESPONSE OF AN ARTICULATED VEHICLE USING NEURAL NETWORKS
Authors: Yang X. , Stiharu I. , Rakheja S.
Published: April 2018

A two-layer neural network with 12 neurons in the first layer is applied to model the directional control behaviour of a driver-articulated vehicle system. Six different training schemes are employed using combinations of input variables related to visual perception of tracking error in terms of position and orientation, and motion perception of the driver. The network is trained using the results derived from a comprehensive closed-loop analytical model under an obstacle avoidance manoeuvre. The input data to the neural network included: the coordinates of the previewed path, lateral position, velocity, and acceleration of the tractor and lateral acceleration of the trailer. The front wheel steer angle was considered as the desired output of the trained network. The effectiveness of the trained network describing the driver behaviour is investigated under different directional maneuvers of varying severity. It is concluded that the neural network can be trained to model the directional control behavior of the driver, while the effectiveness of the trained network depends upon the input variables supplied to train the network. The results show that the visual perception of the driver based on the position error contributes most significantly to the training of the network. The motion perception variables in terms of lateral accelerations of the articulated vehicle yield a more effective neural network model of the driver.
MODELLING OF RESIDENTIAL HOT WATER SYSTEMS
Authors: Pontikakis N. , Ruth D.W.
Published: April 2018

The design of residential hot-water plumbing supply systems was studied using computer models. The study consisted of two parts; first a flow analysis of the hot-water supply was undertaken and second the heat losses of the distribution pipes, and the hot-water tank were analyzed. The aim of the study was to find ways to conserve energy in the hot-water tank by using different designs to optimize the existing systems. From the current research it was found that a low-flow showerhead and the insulation of pipes can conserve energy, which results in customer financial savings. A low-flow showerhead contributes a 14-17% saving in the heat losses from the hot-water tank while the insulation of the pipes attributes another 1.5-1.7% saving.
NUMERICAL KINEMATIC ANALYSIS OF THE DOUBLE WISHBONE MOTOR-VEHICLE SUSPENSION SYSTEM
Authors: Attia H.A.
Published: April 2018

In this paper, an efficient numerical algorithm for the kinematic analysis of a double wishbone suspension is presented. The double wishbone suspension system is usually used for front wheel axles of rear wheel driven cars. The kinematic analysis of the one-DOF suspension mechanism is carried out in terms of the rectangular Cartesian coordinates of some defined points in the links and the joints. Geometric constraints that fix the distances between the points belonging to the same rigid link are introduced. Additional driving constraints are added as a function of the input driving variables. The nonlinear constraint equations are solved by iterative numerical methods. The corresponding linear equations of velocity and acceleration are solved numerically to yield the velocities and accelerations of the unknown points on the wheel knuckle. The velocities and accelerations of the other points of interest can be calculated if their positions are locally specified. In addition, the angular velocity and acceleration of any link in the mechanism are evaluated. The presented formulation in terms of the system of coordinates based on the presented formulation in terms of the system of coordinates based on Cartesian coordinates of specified link points is simple and involves only elementary mathematics. A numerical example is presented.
THE KINEMATIC SYNTHESIS OF STEERING MECHANISMS
Authors: Yao Jin , Angeles Jorge
Published: April 2018

We propose a computational-kinematics approach based on elimination procedures to synthesize a steering four-bar linkage. In this regard, we aim at minimizing the root-mean square error of the synthesized linkage in meeting the steering condition over a number of linkage configurations within the linkage range of motion. A minimization problem is thus formulated, whose normality conditions lead to two polynomial equations in two unknown design variables. Upon eliminating one of these two variables, a monovariate polynomial equation is obtained, whose roots yield all locally-optimum linkages. From these roots, the global optimum, as well as unfeasible local optima, are readily identified. The global optimum, however, turns out to be impractical because of the large differences in its link lengths, which we refer to as dimensional unbalance. To cope with this drawback, we use a kinematically-equivalent focal mechanism, i.e., a six-bar linkage with an input-output function identical to that of the four-bar linkage. Given that the synthesized linkage requires a rotational input, as opposed to most existing steering linkages, which require a translational input, we propose a spherical four-bar linkage to drive the steering linkage. The spherical linkage is synthesized so as to yield a speed reduction as close as possible to 2:1 and to have a maximum transmission quality.
LOW FREQUENCY VIBRATIONS OF A THIN CYLINDRICAL SHELL JOINED WITH AN ANNULAR THIN PLATE
Authors: Filippov Sergei B. , Haseganu Eliza M.
Published: April 2018

The low frequencies and vibration modes of a thin cylindrical shell joined with an annular thin plate are obtained in this paper by means of asymptotic and numerical methods. If the annulus is wide then the low-frequency vibrations are axisymmetric. For this case a new approximate approach is developed for the evaluation of the low frequencies. If the annulus is narrow, the low-frequency vibrations are non-axisymmetric, the narrow annulus is considered as a circular beam. The equations describing the vibrations of the cylindrical shell stiffened by a circular beam are solved with the help of asymptotic techniques. The asymptotic results are in good agreement with the numerical results obtained by sweep and finite element methods.
REAL-TIME SCHEDULING OF DISTRIBUTED MULTI-ROBOT MANIPULATOR SYSTEMS
Authors: Yuan P. , Moallem M. , Patel R.V.
Published: April 2018

This paper presents an online task-oriented scheduling method and an off-line scheduling algorithm that can be used for cooperative control of a distributed multi-robot manipulator system. Satisfaction of temporal deadlines and tasks-relative constraints are considered in this work. With the proposed algorithms, both the timing constraints and relative task dependencies can be satisfied when the worst-case execution time is unknown. The total execution time of the assembly tasks can be significantly improved compared with other known scheduling algorithms such as the First-In-First-Out and Round Robin scheduling methods. Experimental results are presented indicating that the proposed algorithm can be used for improving the performance of multi-robot systems in terms of timing and resource constraints.
DEVELOPMENT OF AN EXPERIMENTAL TECHNIQUE TO MODEL DEFLECTIONS IN SURFACE GRINDING
Authors: Bauer R. , Lin S. , Warkentin A.
Published: April 2018

Deflections in surface grinding can lead to geometrical inaccuracies in the components being ground and can also limit production rates in the grinding process. This paper develops and tests an experimental technique to indirectly measure the deflections in the surface grinding process by comparing the actual mass removed during a grinding pass to the mass that would have been removed if there were no deflections. The relationships between the spindle power, normal force and grinding deflections are then derived. The experimental technique was applied to both a Brown & Sharpe 824 Micromaster conventional surface grinding machine, as well as a Blohm Planomat 408 CNC creep-feed grinding machine in the Grinding Research Laboratory at Dalhousie University. For the Brown & Sharpe surface grinder, the experimental results show a linear relationship between the spindle power and the grinding deflections, which agree well with the literature. For the Blohm Planomat grinding machine, however, the relationship between the spindle power and the deflections is nonlinear. Further investigation revealed that this nonlinearity is primarily due to the presence of backlash in the spindle lead screw.
CONCEPTUAL DESIGN OF A TRANSLATIONAL HYBRID MECHANISM FOR AGILE MANUFACTURING
Authors: Côté Frédéric , Bouchard Nicolas , Gosselin Clément M.
Published: April 2018

The use of fixtures in manufacturing of automobile engines is a well established practice. The drawback of fixtures is that they must be redesigned and rebuilt whenever the part that they are supporting is modified. This operation is tedious, costly and limits the agility of the manufacturing process. In this paper, a flexible fixturing system accommodating an entire family of lightweight aluminum engine blocks is presented. The key element of this research is the use of parallel or quasi-parallel mechanisms (PMs) in the development of the fixturing system. PMs are known to have high stiffness, high payload and high precision qualities. By virtually eliminating the need for the redesign of fixtures, the flexible pallet presented in this paper may lead to significant improvements in their use in automobile manufacturing.
APPLICATION OF A TUNABLE ELECTROMAGNETIC DAMPER IN SUPPRESSION OF STRUCTURAL VIBRATION
Authors: Liu Kefu , Liu Jie , Liao Liang
Published: April 2018

An electromagnetic damper is developed to construct a tunable damped dynamic vibration absorber. The developed vibration absorber can suppress vibration of a structure subjected to a harmonic force with variable frequency. The damping of the vibration absorber can be adjusted on-line to cope with variation in the exciting frequency. The electromagnetic damper is composed of an electromagnet and a copper plate attached to the absorber mass. The relationship between the damping ratio and the damper current is discussed analytically. An experiment is conducted to determine the damping coefficients. A clamped-clamped beam is used as a primary system. The damper is connected between the absorber mass and the ground. This setup is referred to as skyhook dynamic vibration absorber in this study. The performance of a skyhook dynamic vibration absorber is compared with that of a groundhook dynamic vibration absorber where a damper is connected between the primary mass and the absorber mass. Two algorithms are proposed to tune the damper on-line. The first algorithm is FFT-based while the second one is rms-based. The control algorithms are tested against three frequency varying scenarios: multi-step change, linear change, and single-step change plus impact disturbance. Merits of each of the control algorithms are demonstrated.
A THEORETICAL BASIS FOR THE ANALYSIS OF LOGIX GEARS
Authors: Guran Liu , Quanhong Liu , Dongfu Zhao , Deyu Song , Chan C.Y.
Published: April 2018

A novel approach to gear design to produce so-called Logix gears is based on differential geometric methods and results in higher order contact parameters, i.e., reduced stress concentration. Profiles designed in this way admit concave-to-convex mating tooth surfaces and a simple two gear set with such properties is presented as an example. Once a pair of mating gears has been configured it is then shown how to design hobbing racks to cut these gears.
DEVELOPMENT OF SMART STRUCTURE SYSTEMS FOR HELICOPTER VIBRATION AND NOISE CONTROL
Authors: Chen Y. , Wickramasinghe V. , Zimcik D. G.
Published: April 2018

Helicopters are susceptible to high vibratory loads, excessive noise levels and poor flight stability compared to fixed-wing aircraft. The multidisciplinary nature of helicopter structures offers many opportunities for the innovative smart structure technology to improve helicopter performance. This paper provides a review of smart structures research at the National Research Council Canada for helicopter vibration and cabin noise control applications. The patented Smart Spring approach is developed to vary the blade impedance properties adaptively to reduce the vibratory hub loads transmitted to the fuselage by vibration reduction at the source. A smart gearbox strut and active structural acoustic control technologies are investigated to suppress the vibration and tonal gear meshing noise into the cabin either by modifying the vibration load transmission path, or weakening the coupling between exterior and cabin acoustic fields. Two adaptive seat mount concepts are proposed to reduce the vibration of the aircrew directly to improve ride quality of the vehicle.
INVESTIGATING THE EFFECT OF THE ORTHOTROPIC PROPERTY OF PIEZOELECTRIC PVDF
Authors: Sokhanvar S. , Zabihollah A. , Sedaghati R.
Published: April 2018

The applications of the piezoelectric Polyvinylidene Fluoride, PVDF, integrated with the beams, plates, and membranes, performing as sensor, actuator or combination have been received considerable attention in the recent years. However, not much work has been reported on the influence of the PVDF’s orthotropic behavior, particularly the effect of the orientation of the PVDF film in the host structure, on the performance of the system. In the present study, the effect of the piezoelectric PVDF film orientation on the output voltage, the actuation force, and the dynamic response of the integrated structures has been studied using the finite element method. In the sensory mode, the difference between the output voltages obtained from the biaxial piezoelectric PVDF film and uniaxial one, when the orientation of the film varies from 0 to 90 degree, is investigated. In each case the proportion contributions of the involved piezoelectric coefficients including d31, d32 and are studied. Alternatively, in the actuation mode, the effect of orthotropic behavior of the actuator on the nodal displacements has been taken into consideration. The influence of the material orthotropic property of the transducer on the free undamped response of the system is also investigated. Moreover an effective Young’s modulus and effective Poisson ratio for the uniaxial PVDF film has been introduced using an optimization procedure to minimize the error caused by isotropic assumption of uniaxial PVDF film.
MODELING AND PERFORMANCE EVALUATION OF OPTICAL SYSTEMS USING SKEW RAY TRACING
Authors: Liao Te-Tan , Lin Jing-Fung
Published: April 2018

This paper applies a computational geometric algebra approach based on a 4 x 4 homogeneous transformation matrix to model optical systems and to evaluate their performance. In the proposed approach, the directions of the refracted/reflected rays at each boundary in the optical system are determined using skew ray tracing based upon Snell’s law. The differential changes in the image coordinates caused by optical aberrations are derived for both polychromatic and monochromatic light by applying a sensitivity analysis approach. Finally, a merit function is constructed comprising five individual defect items in order to evaluate the overall performance of a generic optical system. The proposed analytical approach provides a comprehensive and robust approach for the modeling and evaluation of optical systems.
NUMERICAL ASSESSMENT AND OPTIMAL ALLOCATION PLAN FOR PLANT NOISE CONTROL
Authors: Lan Tian-Syung
Published: April 2018

Inadequate noise simulation, identification, and strategy often cause dreadful plant layout. This unacceptable abatement results in the tremendous cost and inefficiency of noise reduction. To minimize the influence of machine noise along the plant boundary, the advances of optimal allocation planning and appropriate noise abatement on machine are then progressed in this paper. By using a sixteen-station sound monitoring system and the gradient numerical method - EPFM (Exterior Penalty Function Method), the numerical assessment is thus achieved, accordingly. Introducing the optimal design data of equipment’s locations and noise reduction value into the ENM (Environmental Noise Model), a commercial sound simulation package, the predicted noise contour map of the plant is moreover accomplished. The noise check of noise map along plant’s boundary is then furthermore approached to confirm the accuracy and acceptance of the numerical result.

Noise control is important and essential in the process plant, where the noise level is restricted by both Occupational Safety & Health Act (OSHA) and local noise regulation. In this paper; we (1) develop a mathematical model for economic plant noise control system, (2) give the proper allocation, (3) simulate the acoustic distribution within the plant, and (4) compare noise levels with local noise regulations. The numerical technique in both adjusting the optimal allocations and searching for the best noise reduction to the machine is fully demonstrated; thereafter, the verification of plant’s noise is attained using ENM. With the simulated results, it is shown that this paper absolutely provides an approachable method, which is very effective, economical and applicable in plant’s noise control with profound insight.
SINGULARITIES OF REDUNDANT 4R POSITIONING MANIPULATORS
Authors: St-Pierre Luc , Zsombor-Murray Paul
Published: April 2018

Singularities can be elusive but geometric considerations can reveal the singularities of a redundant 4R manipulator for positioning tasks. Points on a line, called transversal, that intersects all R-joint axes, cannot move in the direction of this line. Conditions governing the existence of transversals to four lines will be discussed. A way to find transversals is developed and tested with a numerical example. A possible metric, or singularity proximity measure for this type of singularity is investigated. This metric is based on the shortest distance between a line and a quadric and various methods will be proposed to solve this geometric problem.
IDENTIFICATION OF THE NONLINEAR FRICTION CHARACTERISTICS IN A HYDRAULIC ACTUATOR USING THE EXTENDED KALMAN FILTER
Authors: Chinniah Yuvin , Burton Richard , Habibi Saeid , Sampson Eric
Published: April 2018

In this paper, the nonlinear friction characteristic of a custom made symmetrical linear hydraulic actuator is investigated using the Extended Kalman Filter (EKF). A new and very accurate characterization of friction is made by using a quadratic function of the piston velocity. Further to this proposed empirical friction model, the EKF is used to estimate the function coefficients. In this paper, an iterative approach is used to maintain system observability and render the estimation process more reliable. The study is conducted in simulation and by using measured experimental data. The estimated states and parameters by the EKF are found to be convergent to their known values in simulation and, further to experimental results, unique and repeatable. In addition, changes in the friction characteristics, which can occur in the physical system due to wear in the piston seals or degradation in the oil properties, are detected and accurately estimated by the EKF in simulation. This study presents an accurate nonlinear model for the representation of friction in a hydraulic actuator. It paves the way for the implementation of strategies for early fault detection in hydraulic systems.
A COMPREHENSIVE SOLUTION OF THE CLASSIC BURMESTER PROBLEM
Authors: Chen Chao , Bai Shaoping , Angeles Jorge
Published: April 2018

The classic Burmester problem aims at finding the geometric parameters of a planar four-bar linkage whose coupler link attains a prescribed set of finitely separated poses. The solution proposed is claimed to be comprehensive because it (a) includes all four types of dyads—RR (revolute-revolute), PR (prismatic-revolute), RP and PP—and (b) gives due consideration to the numerics behind the solution. A PR dyad is treated as a RR dyad with its fixed joint centre at infinity, similar interpretations applying to RP and PP dyads. The paper includes the synthesis of planar four-bar linkages in its full generality, that of dyads with P joints being given the utmost attention. Finally, the underlying numerics receives the attention seldom found in the literature on the subject, our main concern being numerical robustness.
EXPERIMENTAL INVESTIGATION OF THE PROPERTIES OF A NOVEL COMPLIANT AIR BEARING MATERIAL HANDLING SYSTEM
Authors: Chung J. , Townsend B. , Stras L. , Lee L. , Sullivan P. A.
Published: April 2018

An air bearing materials handling system supports its load on two compliant runners having the form of oval cylinders moving along shallow concave rails. Air is supplied by manifolds integral with the rails through nozzles spaced at intervals in the rail surface. Loads up to 3 tonnes can be moved with an effective coefficient of sliding friction of about 1%. Developed by trial-and-error, the system has incompletely understood features. Two are: the role of the system geometry in providing load support; and the construction of the runners, which consist of layers of cellulose fibre tissue wound onto a core, and enclosed in a plastic cover. Exploratory research aimed at establishing the effect of these features on the load fraction supported by air pressure is reviewed. Flat surface equivalents instrumented for pressure surveys are developed to assess the role of the tissue, and to suggest alternatives. The load fraction is determined, and the response to asymmetric loading is investigated. The minimum number of tissue layers necessary for bearing action is identified, and the performance of compliant alternatives is explored. The review concludes with a discussion of the elements required of a mathematical model suitable for guiding design improvement.
DESIGN OPTIMIZATION OF VEHICLE SUSPENSIONS WITH A QUARTER-VEHICLE MODEL
Authors: Chi Zhongzhe , He Yuping , Naterer Greg F.
Published: April 2018

This paper presents a comparative study of three optimization algorithms, namely Genetic Algorithms (GAs), Pattern Search Algorithm (PSA) and Sequential Quadratic Program (SQP), for the design optimization of vehicle suspensions based on a quarter-vehicle model. In the optimization, the three design criteria are vertical vehicle body acceleration, suspension working space, and dynamic tire load. To implement the design optimization, five parameters (sprung mass, un-sprung mass, suspension spring stiffness, suspension damping coefficient and tire stiffness) are selected as the design variables. The comparative study shows that the global search algorithm (GA) and the direct search algorithm (PSA) are more reliable than the gradient based local search algorithm (SQP). The numerical simulation results indicate that the design criteria are significantly improved through optimizing the selected design variables. The effect of vehicle speed and road irregularity on design variables for improving vehicle ride quality has been investigated. A potential design optimization approach to the vehicle speed and road irregularity dependent suspension design problem is recommended.
MULTI-PARAMETER ANN MODEL FOR FLAT-END MILLING
Authors: Mounayri Hazim El , Badar M. Affan , Rengifo Gustavo A.
Published: April 2018

The quality, productivity and safety of machining can be significantly improved through the optimization of cutting conditions. The first step in achieving such an objective is the development of accurate and reliable models for predicting the critical process parameters. In this paper, an innovative Artificial Neural Network (ANN) model that predicts both cutting force and surface roughness in end milling is developed and validated. A set of five input variables is selected to represent the machining conditions while twelve quantities representing two key process parameters, namely, cutting force and surface roughness, form the variables of the network output. Full factorial design of experiments is used to generate data for both training and validation. Successful training of the neural network is demonstrated through comparison of simulated and experimental results for four different output variables, namely cutting force, surface roughness, feed marks, and tooth passing frequency. The predictive ability of the model is verified experimentally by comparing simulated output variables with their experimental counterparts. A good agreement is observed.
A CHARACTERISTIC-BASED FINITE VOLUME ELEMENT METHOD FOR CONVECTION-DIFFUSION-REACTION EQUATION
Authors: Phongthanapanich Sutthisak , Dechaumphai Pramote
Published: April 2018

A two-dimensional convection-diffusion-reaction equation is discretized by the finite volume element method on triangular meshes. Time-dependent convection-diffusion-reaction equation is developed along the characteristic path using the characteristic-based scheme, while the finite volume method is employed for deriving the discretized equations. The concept of the finite element technique is applied to estimate the gradient quantities at the cell faces of the finite volume. Numerical test cases have shown that the method does not require any artificial diffusion to improve the solution stability. The robustness and the accuracy of the method have been evaluated by using available analytical and numerical solutions of the pure-convection, convection-diffusion and convection-diffusion-reaction problems.
INDICATORS FOR THE ENVIRONMENTAL IMPACT OF WASTE EMISSIONS: COMPARISON OF EXERGY AND OTHER INDICATORS
Authors: Rosen Marc A.
Published: April 2018

Exergy is compared with other indicators for the environmental impact of waste emissions in an effort to better understand its potential as, or as the basis for, an effective indicator of the potential of an emitted substance to impact the environment. Relations between environmental impact and exergy in general and chemical exergy of waste emissions in particular are observed to support the use of exergy as such an indicator. The measure of disequilibrium with respect to a reference environment provided by exergy is considered, along with the consequence that the exergy of unrestricted waste emissions has the potential to impact the environment. Exergy is observed to exhibit many characteristics of other indicators of environmental impact, which are mainly empirical in nature. An exergy-based indicator could contribute to the development of rational and objective procedures for assessing the harmful effects on the environment of a substance and predicting its potential for environmental impact. The potential usefulness of exergy in addressing environmental problems is concluded to be significant, but further research is needed to develop objective exergy-based indicators that are practical for the potential of a substance to impact on the environment.
BIDIMENSIONAL FINITE ELEMENT ANALYSIS OF SPUR GEAR: STUDY OF THE MESH STIFFNESS AND STRESS AT THE LEVEL OF THE TOOTH FOOT
Authors: Bettaieb Mohamed Nizar , Maatar Mohamed , Karra Chafik
Published: April 2018

The purpose of this work is to determine the spur gear mesh stiffness and the stress state at the level of the tooth foot. This mesh stiffness is derived from the calculation of the normal tooth displacements: local displacement where the load is applied, tooth bending displacement and body displacement [15]. The contribution of this work consists in, basing on previous works, developing optimal finite elements model in time calculation and results precision. This model permits the calculation of time varying mesh stiffness and the evaluation of stress state at the tooth foot. For these reasons a specific Fortran program was developed. It permit firstly, to obtain the gear geometric parameters (base radii, outside diameter,…) and to generate the data base of the finite element meshing of a tooth or a gear. This program is interfaced with the COSMOS/M finite element software to predict the stress and strain state and calculate the mesh stiffness of a gear system. It is noted that the mesh stiffness is periodic and its period is equal to the mesh period.