bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating overall returns to international agricultural research in Africa through benefit‐cost analysis: a “best‐evidence” approach
Authors: Maredia Mywish K. , Raitzer David Anthony
Published: January 2010

This study offers a “best evidence” approach to summarizing recent benefit‐cost analyses of international agricultural research in Africa. First, from an extensive literature review and the resulting global inventory of impact studies, 23 studies are identified that calculate aggregate rates of return for Consultative Group on International Agricultural Research (CGIAR) and partner investments in Sub‐Saharan Africa (SSA). These studies are then appraised against a review framework consisting of principles, criteria, and indicators for study rigor. Subsequently, the economic benefits reported by studies grouped on the basis of its analytical rigor are aggregated and set against total investment by the CGIAR and national agricultural research systems to determine if the total investment to date can be justified by documented benefits under a range of assumptions. As a result, the study finds that aggregate investment is justified under a fairly wide range of suppositions. Under all scenarios, the vast majority of documented benefits stem from a relatively limited array of activities with a majority of benefits stemming from biological control (80%). Close to 20% of total benefits result from crop genetic improvement, and less than 1% result from all other activities. The implications of these results for research investment strategies in SSA and impact assessment are discussed.
Student perspectives and opinions on their experience at an undergraduate outreach dental teaching centre at Cardiff: a 5‐year study
Authors: Lynch C. D. , Ash P. J. , Chadwick B. L.
Published: January 2010

Aim:  Outreach teaching is now regarded as a desirable component of undergraduate dental teaching programmes in the UK. A purpose‐built undergraduate dental outreach‐training centre was opened in Cardiff in 2002. The aim of this paper is to report student perspectives and opinions on their experience at this unit over a 5‐year period.

Methods:  Final year dental students at Cardiff University were invited to report their comments on the St David’s Primary Care Unit at various times during their placement there. Information was recorded for undergraduate students who commenced final year in 2003, 2004, 2005, 2006 and 2007 (n = 257).

Results:  After 1 year, the most common favourable aspects reported by students included the availability of a suitably trained nurse for all procedures (n = 191), ready access to helpful/approachable teaching staff (n = 145), and closeness of learning experience to subsequent practice (n = 122). Many students commented on their growing confidence in their own abilities whilst in the unit.

Conclusion:  Overwhelmingly, students reported their enthusiasm for training in an outreach teaching unit, preferring it to traditional dental school environments. Inherent in the comments recorded for each student was a sense of growing confidence in their abilities and development of reflective practice. Further work is needed to identify the impact of this form of dental student training on subsequent practices in Vocational Training and independent clinical careers.
A national study on the attitudes of Irish dental faculty members to faculty development
Authors: O’Sullivan E. M.
Published: January 2010

Introduction: International studies suggest that dental faculty are resistant to the concept and practice of faculty development. This paper analyses the demographic and educational profile of Irish Dental Faculty, exploring their attitudes to educational initiatives.

Methods and materials: Irish dental faculty were invited to participate in a national study on perceived educational needs. A custom‐designed questionnaire was distributed using a ‘mixed‐method’ approach, incorporating both quantitative and qualitative components. Overall response rate was 64.6%.

Results: Analysis of the demographic profile of Irish dental faculty reveals a male dominated regime (64%). Whilst faculty possess many professional qualifications and extensive clinical experience, most have little or no training inhowto teach. Many had attended teacher training programmes; however, 92% merely attended infrequent, informal sessions. Less than a third (30%) of the part‐time staff had attended teacher training (P ≤ 0.05), few faculty members had any formal teacher training. Whilst the study revealed a low level of engagement with existing teaching support services, there appeared to be considerable support for the concept of faculty development as 75% were willing to attend teacher training courses. This refutes previous suggestions that dental educators are resistant to educational concepts. Attitudes to faculty development varied significantly with age, gender and time since last qualification. This report presents a detailed analysis of learning needs, and a review of the perceived barriers/inducements to participation.

Conclusion: This study indicates that targeted educational interventions, with content and delivery tailored to the specific needs of recipients, are most likely to succeed.
Histological evaluation of periodontal regeneration in autogenous tooth transplantation in the dog: a comparison between one and two‐stage surgical techniques, a pilot study
Authors: Marques Ferreira Manuel , Filomena Botelho Maria , Lina Carvalho , Barbara Oliveiros , Palmeirão Carrilho Eunice Virgínia
Published: January 2010

Abstract –  Objective:  To compare the periodontal regeneration, associated with autogenous tooth transplantation in dogs, using either one‐ or two‐stage surgical techniques.

Methods:  The study group consisted of three Beagles, older than 5 months, in which six incisors and six premolars were transplanted to mechanically prepared recipient sockets. One group was transplanted using a one‐stage method to recipient beds prepared immediately before transplantation. The second group of teeth were transplanted using a two‐stage method in which the recipient beds were prepared and left to heal for 7 days before transplantation. Clinical examinations were done every week and the animals were euthanized 9 weeks later. Subsequently, decalcified sections were prepared for routine and imunohistochemical histological evaluation. Periodontal healing was evaluated by undertaking histomorphometric analysis and analyzed using the Mann–Whitney test (P = 0.05).

Results:  All the transplanted teeth in both groups survived. No statistically significant difference was found in the complete healing between the treatment groups (P = 0.053). There was no difference between the occurrence of inflammatory root resorption (P = 0.135) and replacement root resorption (P = 0.081).

Conclusions:  This study demonstrated that there was no difference between the two surgical techniques in terms of preventing root resorption in transplanted teeth.
Computer Simulation and Design of the Control System for a Wind Turbine Generator
Authors: Sambar H. , Pavelic V. , Warner R. J.
Published: January 2010

This project is a part of an overall study aimed at producing a new generation of wind turbine generators. The wind turbine generator proposed is a horizontal axis machine with three blades operating downwind. A hydraulic system actuates mechanical linkages to control blade pitch during operation. The blade pitch control concept provides active control of rotor rpm above the rated wind speed and during no load condition. The lowering of blade and tower loads while providing the capability for well tuned rotor control are its primary features. A hydraulic system, designed to control the pitch of the blades of a wind turbine generator, is simulated on the digital computer using the Runge-Kutta method. The control system subroutine is coupled with the aerodynamic subroutines of the blades to represent the model for the wind turbine generator. The response of the simulated wind turbine to a real wind case is shown to agree with the desired response.
Analysis of Coupled Vibration Response in a Rotating Flexible Shaft-Impeller System
Authors: Hagiwara N. , Sakata S. , Takayanagi M. , Kikuchi K. , Gyobu I.
Published: January 2010

This paper presents a way of analyzing the vibration of a rotor shaft system coupled with flexible impellers based on the transfer method. Each of the flexible impellers is modelled so that it comprises an inertia and an elastic hinge based on the assumption that any impeller’s vibration mode except its one-nodal diameter has no dynamical connection with a shaft. The stiffness of the hinge is based on the eigen frequency of its mode calculated by means of a finite element method, or obtained by experiment. The method developed allows the calculation of the vibration response of a rotor shaft system consisting of several flexible impellers and several bearings when it is subject to an out-of-balance force. Theoretical results are compared with experimental data and show very satisfactory agreement. This simple method appears therefore to be practical and efficient to predict the dynamical characteristics of a high speed rotor system with coupling of impeller flexibility.
Spline Coupling Induced Nonsynchronous Rotor Vibrations
Authors: Marmol R. A. , Smalley A. J. , Tecza J. A.
Published: January 2010

A mathematical model for predicting spline coupling induced nonsynchronous rotor vibrations is developed, and the predictions are compared with data from a rotor dynamics test rig. The special feature of the spline model is the characterization of the friction forces that are produced at the mating spline teeth surfaces and subsequent calculation of the internal damping coefficients. The spline internal damping and the resulting rotor instabilities are predicted for four different spline configurations and the solution results are correlated with measured data from a gas turbine rotor simulator test rig.
A Study of Induction Hardening Hole Surfaces in Clearance Fit Joints to Improve Fatigue Strength
Authors: Carlson D. L. , Pavelic V.
Published: January 2010

The feasibility of using induction hardening to improve the fatigue strength of clearance fit clevis-type joints was investigated. Clearance fit joints are desired to facilitate machine assembly and disassembly in applications where accessibility and safety are a problem. The purpose of induction hardening the hole surface was to induce compressive residual stress near the hole to reduce the mean stress and to increase material strength. According to the Goodman criterion for steel, a greater stress range is possible with a reduced mean stress. The residual stress distribution produced near the hole was estimated by induction hardening rings and using a modification of the Sachs boring out method. The hole surfaces of a typical link were induction hardened and tension-tension fatigue tested. The load stress distribution was estimated using strain gages. It was determined that the fatigue strength of a clearance fit joint can be increased by at least 100 percent by induction dardening the hole surfaces.
A Probabilistic Model of Size Effect in the Fatigue Strength of Rounds in Bending and Torsion
Authors: Mischke C. R.
Published: January 2010

The use of a probabilistic premise to establish the relation of size to the attenuation of endurance strength in rounds, such as shafts subjected to bending or torsion is investigated. The method allows the designer to construct the appropriate expression for Marin fatigue strength reduction factor, kb, directly from fatigue tests that have been ordered. For probabilistic design procedures, the mean and standard deivation of the Marin fatigue strength reduction factor are required, and the method described allows these estimates to be made.
A Method of Damping Synthesis From Substructure Tests
Authors: Jezequel L.
Published: January 2010

The assembly of damped linear structures along continual interfaces in order to achieve a damping synthesis may pose problems, because assembly methods are ill-conditioned when there is a high number of degrees of freedom at the interfaces. Moreover, identification methods using the smoothing of impedance curves do not give a Rayleigh-Ritz model. To overcome these difficulties this paper proposes a modal synthesis technique which uses two types of normal modes and a new orthogonalization of measured modes based on the Ritz-Galerkin method. It has given a real damping synthesis in the case of damped plate assembly.
Proximity Spectra of Oscillators Under Random Excitation
Authors: Masri S. F.
Published: January 2010

The transient mean-square response of an uncoupled two-degree-of-freedom system under spatially correlated nonstationary random excitation is determined. The excitation is modulated white noise with an intensity function that resembles the envelopes of typical earthquakes. Results of the analysis are used to investigate the effects of (a) cross correlation, (b) shape of the intensity function, (c) delay time associated with the arrival of the excitation at different parts of the system, and (d) dimensionless system parameters on the mean-square proximity spectra.
Vibration Analysis of Continuous Systems by Dynamic Discretization
Authors: Downs B.
Published: January 2010

An equivalent mass matrix may be defined, for a segment of a continuous system, as one which retains precisely the dynamic properties of the original segment in discretized form. Dynamic Discretization, which makes use of a particular form of Stodola iteration, progressively generates the equivalent mass matrix in ascending powers of frequency squared, whilst simultaneously generating deformation functions in a similar power series. The method is quasi-static and readily copes with shear deformation, rotary inertia and quite complex segment geometry. Accurate vibration analysis in terms of frequencies, mode shapes and corresponding stress distributions is achieved using an extremely coarse system subdivision for a variety of geometries.
Design and Automation
Authors: Ragsdell K. M.
Published: January 2010

The Design Automation Committee of the Design Engineering Division of ASME has now sponsored five Design Automation Conferences. This edition of the Journal of Mechanical Design contains 23 papers submitted by the design automation committee; most of which were presented at our last major meeting held in September 1979 in St. Louis. It seems timely and appropriate to comment on the relationship of these papers one to another, to papers given at previous Design Automation Conferences and to the goals of the committee, in terms of the several recognized functional areas of design automation: •Machine Design Applications •Design Optimization and Numerical Methods •Computer Graphics and Drafting •Hardware-Software System Evaluation •Man-Machine Interaction •Finite Element Analysis •CAD/CAM Systems •Intelligent Machines and Robotics We conclude by the number, quality and subject matter of papers in recent meetings that significant work in the areas of interest is occurring, but that care must be taken to ensure presentation of work in all areas of interest.
In-Plane Vibration of Annular Disks Using Finite Elements
Authors: Srinivasan V. , Ramamurti V.
Published: January 2010

The axisymmetric and asymmetric in-plane, free vibration of annular disks using the finite element method is discussed. The in-plane behavior is analyzed by annular ring segments using a Fourier series approach to model the problem asymmetries. Using displacement functions which are exact solutions to the in-plane static problem, the stiffness matrices corresponding to the 0th, 1st and nth harmonics are derived. By assuming that the static displacement functions closely represent the vibration modes, the mass matrices for various harmonics are also derived. These matrices can be readily coded into any special or general purpose structural analysis computer programs. Results of example problems are compared with exact solutions.
A Technical Theory of Dynamical Torsion for Beams of any Cross-Section Shapes
Authors: Gay D. , Boudet R.
Published: January 2010

In order to study the free torsional oscillations of beams, two parameters are introduced—a torsion parameter and a warping parameter—each of them by means of a statistical definition. Using the classical hypothesis of strength of materials, we reduce the dynamical comportment of the beam to a one-dimensional comportment. The four basic relations obtained present a similar form with those of bending motion of a Timoshenko beam. Hence equation of torsional motion is derived and usual cases of boundary conditions relevant to the problem are given. We conclude with a view of the possibilities of the theory, particularly in the numerical area of structural dynamics.
Design and Analysis of a High Pressure Apparatus
Authors: Rolle K. C. , Crisp J. N. , Palazotto A. N.
Published: January 2010

In the determination of equilibrium phase diagrams, i.e., pressure volume-temperature relations for lubricants at pressures up to 2800 MPa and temperatures of 378K, one must carry out a highly sophisticated design of a high pressure apparatus. In 1935 Bridgman designed a piston-displacement device and measured the compressibility of numerous materials at high pressures. However, in order to obtain accurate equilibrium phase diagrams for lubricants, Bridgman’s relatively crude analysis must be considerably refined. The authors have extended this original design using finite element techniques to accurately correct pertinent measurements which are in turn incorporated into the expressions used in determining the pressure-volume temperature relations of lubricants.
On the Measurement of Average Foot Pressure and Ground Reactions During Walking Cycle
Authors: Chandrasekaran H.
Published: January 2010

In a number of studies associated with the deformities of the foot in general and the occurance of plantar ulcer in particular it is required to have an accurate estimate of the average normal and shear pressure variation arising from ground reaction during the walking cycle. This necessitates the measurement of the instantanious area of contact between foot and ground along with the forces. The present paper describes for the first time such a system in which quantitative out-put of the following parameters can be monitored during the walking cycle. (1) Instantanious component forces of the foot-ground reaction (Fv, Fh and Fi) (2) Instantanious area of contact between foot and ground during the walking cycle (A) (3) Instantanious average normal and shear stress on the underside of foot during the walking cycle.
The Design of a Continuous Fiber Composite Surface Hip Replacement
Authors: Roberts J. C. , Ling F. F.
Published: January 2010

The design of a continuous fiber composite surface femoral shell having the same elastic properties as bone is presented. Contact between the femoral ball and acetabular cup was modeled as an elastic spherical ball loaded on an elastic semi-infinite body. The elastic constants of the composite were obtained by using empirically modified and experimentally verified rule-of-mixture equations relating the elastic properties of bone to those of both the fibers and matrix. The stresses were calculated for the contact problem and applied to a cross-ply laminate made up of orthotropic lamina. An interactive tensor failure criterion was used to select a safe design for polyimide, ultra-high molecular weight (U.H.M.W.), high density polyethylene, acrylic bone cement and epoxy composites using either glass or kevlar fibers. The safest composite design appears to be that made with a polyimide or epoxy matrix and glass or kevlar fibers.
The Design of Variable-Ratio Chain Drives for Bicycles and Ergometers—Application to a Maximum Power Bicycle Drive
Authors: Miller N. R. , Ross D.
Published: January 2010

This paper describes a technique for generating a chain drive capable of allowing a desired varying angular velocity function on the driving shaft while maintaining constant angular velocity of the driven shaft. The technique is closely related to the synthesis of cams with flat faced oscillating followers. The technique is illustrated by the synthesis of a drive train for increasing the power applied to the rear wheel of a bicycle. The synthesized drive train shows a theoretical 12.6 percent increase in delivered power. Comparisons with published experimental results, as well as a discussion of the assumptions used in the synthesis procedure are included.
A Wheelchair Dynamometer
Authors: Thacker J. G. , O’Reagan J. R. , Aylor J. H.
Published: January 2010

This paper describes the design of a low-cost wheelchair dynamometer used to evaluate patient performance while using their own wheelchairs. Specifications are listed and details of the overall system including controlling schemes are given. Representative clinical research is listed. The multiple uses of the dynamometer system are discussed.
Combined Fatigue Stress Concentration Factor Determination
Authors: Kurajian G. M. , Na T. Y.
Published: January 2010

The paper begins with a panoramic view of the state of the art embracing the spectrum of methods employed by different designers to account for all stress concentration effects in calculations for use in the design of machine elements and components subjected to combined/fatigue loadings. Then, on the basis of the widely accepted von Mises-Goodman approach, and the method deemed the best for incorporating combined stress concentration effects, a general expression is derived for the combined fatigue stress concentration factor which is applicable to any machine element or component subjected to any combination of fatigue loadings. Various load combinations are considered not only to illustrate the use of the derived expression, but also to demonstrate other methods which may lead to calculations which are incorrect depending upon the nature and magnitude of the parameters involved. The specific machine component, that of a stepped shaft subjected to combined fatigue loadings, is selected for particular, detailed and further demonstration. Demonstrative tables and a curve plot are also included.
The Split Nut: An Easy to Fit Nut with a Higher Inherent Strength
Authors: Cotterell B.
Published: January 2010

The split nut, invented by Commander P. Y. Williams, is easier to fit than the conventional nut and has a higher inherent strength. The two halves of the nut, which is coned at both ends, fit into a conical washer that forces them tightly onto the bolt. The positive clamping action increases the radial load on the threads, which reduces the tensile bending stress at the root of the thread. The load distribution in the threads is also improved, because the change in thread pitch caused by the axial deformation of the nut and bolt is partly compensated by a rotation of the nut halves about an axis normal to that of the bolt. These two effects reduce the maximum tensile stress at the root of the thread to about half of that in the conventional nut.
A Preliminary Design Tool for Pretwisted, Tapered Beams or Turbine Blades
Authors: Durocher L. L. , Kane J.
Published: January 2010

A strength-of-materials approach is used to develop an approximate stiffness matrix for a uniformly-pretwisted beam segment. The beam element is a 12 degree-of-freedom member that includes shear effects, eccentric loading effects, axial-torsional and bending-torsional coupling, and the torsional stiffening effect of the natural pretwist. The current formulation can be employed as an inexpensive preliminary design tool for pretwisted blading that is suitable for implementation on low-core computer graphics systems. After obtaining a workable geometry, final design optimization can be performed by utilizing more sophisticated, and expensive, three-dimensional finite element models.
Reliability Analysis of Truss Structures by Using Matrix Method
Authors: Murotsu Y. , Okada H. , Niwa K. , Miwa S.
Published: January 2010

This paper proposes a method of systematically generating the failure criteria of truss structures by using Matrix Method. The resulting criterion for a statically determinate truss is simple and its failure probability is easily evaluated. In case of a statically indeterminate truss, however, there are many possible modes or paths to complete failure of the structure and it is impossible in practice to generate all of them. Hence, the failure probability is estimated by evaluating its lower and upper bounds. The lower bound is evaluated by selecting the dominant modes of failure and calculating their probabilities. The upper bound is evaluated by assuming that the redundant truss behaves itself like a statically determinate truss, i.e., the structure fails if any one member is subject to failure. Numerical examples are provided to demonstrate the applicability of the propsed methods.
Dynamic Shear Response of Rectangular Plates with Initial Imperfections
Authors: Pasic H. , Herrmann G.
Published: January 2010

The paper presents an analysis of the elastic response of a simply supported, imperfect, rectangular plate subjected to an in-plane supercritical shear force, suddenly applied at one of the edges in the form of a square pulse. The influence of the initial plate irregularities on the overall response during both loading and postloading period is investigated. The averaged in-plane inertia forces are taken into account. The analysis is an extension of the studies of the response to in-plane normal forces of plates of infinite width and finite length given in [1], and of a finite plate given in [2]. The results indicate that the frequency spectra of free vibrations during the post-loading regime are controlled by the initial irregularities distribution, plate geometry and the load levels.
On the Analysis of Uniform Prismatic Columns
Authors: Herman H.
Published: January 2010

A number of well known methods of column analysis and their underlying reasoning are examined. A method of analysis is proposed which takes into account the reviewed literature. The method is based on analysis of elastic equilibrium, and provides for including the effects of load eccentricity and straightness imperfections, which are present in all real columns. The resultant explicit formula for the allowable column load is valid over the entire range of slenderness ratios and is extendable to the analysis of beam columns.
A Comparison Between Trochoidal, Rotary Vane and Reciprocating Expanders
Authors: Robinson F. J.
Published: January 2010

For the purpose of comparison, hypothetical designs for reciprocating and a rotary vane type expanders are considered in relation to a prototype trochoidal machine built and tested by the author. Geometrical and thermodynamic features of the three machines are discussed in addition to some of the practical problems associated with their configurations. Parameters such as chamber surface area to volume ratio and swept to bulk volume ratio have been evaluated for the designs considered and estimates are made for mechanical and diagram efficiencies likely to be achieved in each case. A new parameter is proposed whereby the instant turning moment at a given shaft angle may be determined as a function of chamber pressure and it is suggested that this parameter provides a convenient means for determining the optimum expansion ratio for various expander configurations.
The Analytical and Experimental Evaluation of Resonant Response in High-Speed, Lightweight, Highly Loaded Gearing
Authors: Drago R. J. , Brown F. W.
Published: January 2010

The resonant response of high-speed, lightweight gearing is of serious concern to the transmission specialist. Such gearing typically has several natural frequencies within its operating range. The existence of a resonant response in a range of interest is of itself not indicative of a potential failure; however, if the vibrational energy associated with that made is sufficient to cause stresses beyond the fatigue endurance limit, the gear will fail. These failures are usually rapid and destructive. Two approaches to this problem are possible: The gear may be damped or it may be redesigned to move its natural frequencies out of the operating range. This paper describes the causes and effects of gear resonance, experimental and analytical methods for identifying resonant frequencies and mode shapes, and methods for use in the design and hardware stages to avoid the coincidence of exciting and natural frequencies.
A Dynamic Absorber for Gear Systems Operating in Resonance and Instability Regions
Authors: Benton M. , Seireg A.
Published: January 2010

There are many practical situations where resonances and instabilities in pinion-gear systems are difficult to predict in the design stage due to the unreliability of estimating the mesh stiffness and damping parameters. This paper presents a procedure for the design of an optimal dynamic absorber system which can be used in conditions where preliminary analysis shows that high dynamic tooth loads are likely to occur. The optimal parameters for the absorber are given in a generalized form in order to simplify its design for a particular gear system.
Rotational Vibration With Backlash—Part 2
Authors: Wang C. C.
Published: January 2010

This paper is a continuation of a paper [1] previously published. In this paper, the experimental results for the 3-mass system as defined in Part I are presented. Physical simulation very close to an ideal limiting case where the driven pinion is linked to the output pulley with a very low stiffness shaft was performed. The nonlinear responses of a system with backlash and subject to impact and/or displacement excitation were obtained. The presence of multiple critical speeds for a single degree of freedom system under impact and/or displacement excitation has been analytically explained and experimentally confirmed. Computer solutions based on the piecewise linear iteration technique as outlined in Part 1 have achieved a considerable degree of success. Computer predictions agree well with actual responses in various speed ranges despite a series of bold assumptions that were made to simplify the numerical process.
Numerical Implementation of Complex Potentials for Gear Tooth Stress Analysis
Authors: Cardou A. , Tordion G. V.
Published: January 2010

Stresses in spur gear teeth can be calculated by the complex potentials method, using a generalization of Hirano’s conformal mapping. Mathematical programming is used to fit the transformation to a given profile as closely as desired. Complete formulas for stresses and displacements are given in terms of the transformation parameters. Results are compared with other published values.
Calculation of Contact Ratios for Plastic/Plastic or Plastic/Steel Spur Gear Pairs
Authors: Yelle H. , Burns D. J.
Published: January 2010

An analytical method is presented for calculating real contact ratios for plastic/plastic or plastic/steel spur gear pairs. A comparison is made with published experimental data and the method is used to explain the importance of load sharing in thermoplastic gearing.
Dynamic Continuous Path Synthesis of Industrial Robots Using ADAMS Computer Program
Authors: Orlandea N. , Berenyi T.
Published: January 2010

The ADAMS (Automatic Dynamic Analysis of Mechanical Systems) [3] is used to determine the laws of motion for the actuators of industrial robots when a continuous path and orientation for the gripper is prescribed. Simultaneously the dynamic loads in the system are determined. The results for a six degrees of freedom robot are described in animated form. The three-dimenional frames used in animation are colored and are completely computer generated.
The Application of Finite Element Methods to the Dynamic Analysis of Flexible Spatial and Co-Planar Linkage Systems
Authors: Sunada W. , Dubowsky S.
Published: January 2010

An analytical method is presented for the dynamics of spatial mechanisms containing complex-shaped, flexible links with application to both high-speed industrial machines and robotic manipulators. Existing NASTRAN-type finite element structural analysis programs are combined with 4 × 4 matrix dynamic analysis techniques and Component Mode Synthesis coordinate reduction to yield a procedure capable of analyzing complex, non-linear spatial mechanisms with irregularly shaped links in great detail, yet producing a system of equations small enough for efficient numerical integration. The method is applied to two examples.
Future Trends in Optimization
Authors: Johnson G. E.
Published: January 2010

The purpose of this article is to provide a permanent record of the major ideas and questions raised during the panel session entitled “Future Trends in Optimization” at the 1980 Design Engineering Technical Conference in Beverly Hills, California. The panel members were Professors D. J. Wilde of Stanford University, E. J. Haug of the University of Iowa, K. M. Ragsdell of Purdue University, J. N. Siddall of McMaster University, and F. Freudenstein of Columbia University. They spoke, respectively, on Optimal Design Under Uncertainty; Computer-aided Design Sensitivity Analysis and Optimization of Dynamic Systems; Optimization: The Future of Design, Integration of Optimization with the Design Process; and Optimization in Mechanisms: Past, Present, and Future. It is hoped that the article will prove useful in guiding future efforts in the area of optimal mechanical design.
Accessible Region and Synthesis of Robot Arms
Authors: Tsai Y. C. , Soni A. H.
Published: January 2010

The present paper deals with the study of determining accessible region for two and three-link robotic arms with pin-joints. Based on the derivation of the loci-curves traced by a two-link robotic arm, design charts are developed. Such design charts are utilized in determining the accessible regions of a three-link robotic arm. Following the analysis of the accessible regions of two and three-link robotic arms, the paper presents a synthesis procedure to synthesize two and three-link robotic arms. Given a set of end-positions of a two or three-link robot arm, the proposed synthesis procedure will yield the dimensions and the location of the robot arm which will enclose within its accessible region the design points. The same synthesis procedure is proposed to trace a specific planar point-path. The present paper further examines the potential application of the synthesis procedure of two and three-link robotic arms in synthesizing a closed-loop mechanism for point-path generation. The two-link robotic arm is examined for the case where the end positions lie on a fixed circle. This case leads to the synthesis of a four-bar mechanism for a special point-path curve. The synthesis procedure may be extended from the four-bar synthesis to a cam-follower (non-circular-cam) system where the follower is the two link robotic arm. A further extension of this procedure is demonstrated in synthesizing analytically the dual-cam mechanisms derived from the stephenson six-link mechanism. The present investigation examines all three possible cases of dual-cam mechanisms. For special cases, it is demonstrated that such dual-cam mechanism may be degenerated to synthesize a mechanism with one cam pair.
Kinematic Analysis of Spatial Mechanisms Using Train Components
Authors: Osman M. O. M. , Bahgat B. M. , Dukkipati R. V.
Published: January 2010

A useful method for the kinematic analysis of spatial mechanisms is presented. For the purpose of kinematic analysis, the mechanism is treated as a consist of a number of master train components. For each master train component, geometric constitutive equations for use in kinematic analysis of mechanisms are developed. The kinematic analysis of all train components consisting the mechanism are performed as parts of the master components using a mathematical programming procedure. The analysis is followed in sequence from one train component to another as they form the entire mechanism. Numerical examples are presented to illustrate the proposed technique.
On the Dynamic Simulation of Large Nonlinear Mechanical Systems. Part 2: The Time Integration Technique and Time Response Loop
Authors: Cipra R. J. , Uicker J. J.
Published: January 2010

Part 2 presents a time integration technique for nonlinear differential equations and illustrates its use in the time response loop of the simulation technique outlined in Part 1. The time integration method for nonlinear differential equations is based upon the repetitive analytical (modal) solution of a set of equations linearized about the current operating position. This linearized set of equations may include viscous damping. The method incorporates a variable time step suited to the degree of nonlinearity and as shown in an example problem, gives comparable agreement in results with a Runge-Kutta numerical technique. The time response loop of the simulation technique uniquely combines the concepts of substructuring, system synthesis, and frequency reduction discussed in Part 1 with the time integration method presented here to form the overall simulation technique.
Design Formulas for Expansion Bellows
Authors: Chand Satish , Garg S. B. L.
Published: January 2010

In this work the problem for S-type of bellows and U-type of bellows subjected to axial loading is treated by using plate theory and beam theory. The solutions found here are compared with those obtained by rigorous mathematical analysis and simplified expressions are developed for the use of designers. The results for maximum equivalent stresses and axial deflections are plotted for different geometric parameters of bellows.
Resonances and Instabilities in Dynamic Systems Incorporating a Cam
Authors: Cronin D. L. , LaBouff G. A.
Published: January 2010

A model consisting of two oscillators coupled through a kinematic constraint is employed in this paper to investigate resonances and instabilities in dynamic systems incorporating a cam. Examination of linearized motion equations exposes parameters governing system behavior. Explored using numerical integration, Floquet analyis, and approximate methods are coupling-induced modification of conventionally-predicted resonant behavior, and two categories of subharmonic and superharmonic instability. Approximate methods described in this paper for predicting resonances and instabilities appear to function reliably and offer the potential for reduced analysis cost.
Hybrid Computer-Aided Design of a Hydrostatic Vehicle Drive With Energy Accumulator
Authors: Svoboda J. V. , Sankar S. , Blach W.
Published: January 2010

The article presents the use of the hybrid computing technique in the design and optimization of a novel hydrostatic drive for urban vehicles. The vehicle system is modelled on the analog computer whereas the optimization algorithm and overall control is performed in the digital section. The ‘on-line’ features and the high computing speed of the analog model proves very advantageous in both the preliminary design and the system optimization process. The drive system consists of a small IC-engine, a hydrostatic transmission and a hydraulic accumulator energy storage. The hydraulic accumulator assists the engine during acceleration and allows for regenerative braking which results in a high overall efficiency in urban driving, where frequent stops occur. In the first stage of the design, the feasibility of the drive concept was evaluated. Thus preliminary designed system is repeatedly ‘driven’ through a short driving cycle under the control of the digital computer. A direct search optimization routine known as complex method evaluates the drive performance and readjusts four drive controller parameters. The objective of the optimization is to minimize the fuel consumption without any loss of drive dynamics. The comparison of the drive performance before and after optimization is presented and discussed.
Connection Force Analysis of Mechanisms Described by Explicit Equations of Motion in Generalized Coordinates
Authors: Allen R. R. , Harrell J. P.
Published: January 2010

Connection forces acting at the joints of a kinematic mechanism are derived from the generalized variables of the mechanism equation of motion using an equivalent-force analysis. The connection force calculation is numerically efficient and is independent of the formulation and solution of the equations of motion. A numerical example illustrates an application to a planar four-bar linkage.
Reduction of Instrumented Linkage Data for Simple Anatomical Joint Models
Authors: Kinzel G. L.
Published: January 2010

When measuring the total, six degree-of-freedom (dof) motion permitted by an anatomical joint, it is convenient to attach the ends of an instrumented linkage to the two bodies meeting at the joint and to measure six independent linkage variables as the bodies move. While this method gives a complete description of the motion, it does not permit the motion to be described in a quantifiable manner that non-technical personnel understand. It is therefore often desirable to model the joint as as simple joint which permits fewer than six dof’s, e.g., as a spherical or even a revolute joint. If this is done, a decision must be made as how the six-dof data will be used to define the motion data associated with these simple models. It is the purpose of this paper to present an approach for doing this based in part on optimization theory.
Analysis of Drive Shaft Speed Variations in a Scotch Yoke Mechanism
Authors: Wiederrich J. L.
Published: January 2010

Two analyses are presented for determining the drive shaft speed variations in a scotch yoke mechanism. The first analysis determines the speed variations when the mechanism is rigidly connected to a motor having a quadratic speed versus torque characteristic. The second analysis determines the speed variations when the mechanism is connected to a constant speed source through a flexible coupling. Together these models represent the two most common drive configurations. The results are of practical importance since they can be used in the preliminary calculations necessary in either the design of a main drive or the diagnosis of a drive problem in an existing machine. The methods are also of theoretical importance since they may be extended to the analysis of mechanisms having a greater harmonic content than the simple scotch yoke mechanism.
A Numerical Approach to the Stability of Rotor-Bearing Systems
Authors: Athre K. , Kurian J. , Gupta K. N. , Garg R. D.
Published: January 2010

The stability characteristics of a rotor-bearing system which indicate the threshold of instability are generally obtained by applying the Routh-Hurwitz criterion to the characteristic polynomial. Usually the characteristic polynomial is obtained analytically from the characteristic determinant. In the case of the generalized eigenvalue problems, this is practically impossible. To study the stability characteristics of a floating bush bearing, the characteristic polynomial is constructed from the generalized eigenvalue problem using a recently developed numerical technique. Results obtained through this computer package are compared with those already available in the literature.
Dynamic Response of a Rectangular Plate With Initial Imperfections Under Large In-Plane Forces
Authors: Pasic H. , Juricic D. , Herrmann G.
Published: January 2010

This paper presents an analysis of the response of an imperfect, finite, simply-supported, rectangular plate under an in-plane above-critical force applied during a short time at one of the edges in the direction perpendicular to the edge. The influence of the initial irregularities on the overall response during and after load application is analyzed. The results indicate that the frequency spectrum of free vibrations, after removal of the load, is controlled by the initial irregularity distribution, the plate geometry, and the load level.
Displacement Analysis of the General N-Bar, Single-Loop, Spatial Linkage—Part 2: Basic Displacement Equations in Matrix and Algebraic Form
Authors: Albala H.
Published: January 2010

The displacement analysis of the single-loop, N-bar, spatial linkage is presented—first in matrix form and next in algebraic form. The latter is achieved by means of some novel mathematical tools. The intermediate rotation angles are elminated through various stages. Thus, the general analysis of any particular spatial mechanism, seeking to obtain the input-output displacement equation in closed algebraic form, may be started at the end of the stage suited to this objective.
An Approximate Analysis of Circular Plates With Variable Thickness
Authors: Naghdi A. K.
Published: January 2010

Based on classic theory of beams and certain modifications, a simple technique is derived in order to obtain an approximate value of the maximum bending moment in a rotationally symmetric circular plate with a variable thickness. It is assumed that one of the two concentric boundaries of the plate is clamped, and the other is free. Numerical examples for both cases of constant and variable thickness plates subject to uniform pressure or rim line loading are presented.
Kinematic Synthesis of Planar Two-Gear Drives With Prescribed Dwell Characteristics
Authors: Lee T. W. , Shereshevsky Y.
Published: January 2010

This paper presents an analytical and computer-aided procedure on the kinematic synthesis of the planar two-gear drive. The drive is designed as a reversing mechanism and as a nonreversing mechanism either with or without dwell. Dwell characteristics of the mechanism are investigated using algebraic methods. It is found that the problem relates closely to the velocity-fluctuation of the four-bar linkage. Both general and specific dwell criteria are derived. An efficient computer-aided procedure can be used for the analysis of motion characteristics and for the development of a design chart. Numerical examples illustrate both analytical as well as graphical synthesis procedures.
Stability of Motion of Elastic Planar Linkages With Application to Slider Crank Mechanism
Authors: Tadjbakhsh I. G.
Published: January 2010

The problem of stability of motion of elastic planar linkages is considered in the context of the classical Euler-Bernoulli equations of motion. The case of slider-crank mechanism is considered in detail and the critical values of the dimensionless parameters measuring slenderness, speed, and length ratio which may cause instability are determined. The start-up and the steady-state solution of the mechanism without viscous damping and the effects of flexibility on piston force and efficiency is evaluated.
On the Dynamic Gear Tooth Loading as Affected by Bearing Clearances in High Speed Machinery
Authors: Bahgat B. M. , Osman M. O. M. , Sankar T. S.
Published: January 2010

The paper studies the effect of bearing clearances in the dynamic analysis of gear mechanisms in high speed machinery. For this purpose, an analytical model is developed based on the interdependence between kinematics and kinetic relationships that must be satisfied when contact is maintained between the journal and its bearing. The contact modes are formulated such that the bearing eccentricity vector must align itself with bearing normal force at the point of contact. The analysis mainly relies on determining the direction of the bearing eccentricity vector defined as the clearance angles βi at the bearing revolutes for each contact mode of the gear teeth. The governing equations of the clearance angles are developed using the geometrical constraints of the contact point location and the velocity ratio. The clearance angles and their derivatives are subsequently used to systematically evaluate kinematic and dynamic quantities of each gear as well as the dynamic tooth load. A pair of rigid tooth spur gears with two revolute clearances is analyzed to illustrate the procedure. The model presented in the paper provides a design method for investigating the effect of bearing tolerances and wear on the evaluation of dynamic tooth load in high speed gearing systems.