bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Sensitivity Analysis of Machine Tool Spindle and Support System
Authors: Chandrupatla Tirupathi R.
Published: April 2021

The problem of selecting the bearing spacing for a machine tool spindle is considered. The main objective is to choose this spacing value at the design stage for minimizing the workpiece cylidricity error. The equations are derived in a general setting and optimum values are computed. The method presented can be extended to more complex spindle designs.
3-D Elasto-Plastic Contact Finite Element Analysis for Bearings Design
Authors: Shigang Wang , Jun Yu , Ji Zhou , Mingzhang Li
Published: April 2021

In this paper, A 3-D elasto-plastic contact problem in bearings is studied by Finite Element Method (FEM). A computer program has been developed for this purpose. A trial-error method is employed to cope with the geometrical nonlinearity and a tangential stiffness method is employed to tackle the material nonlinearity appeared in elasto-plastic contact problems. A frictionless contact problem of roller bearings is analysed, the result reveals that in 3-D elasto-plastic state the trend of the contact surface pressure distribution is similar to Hertz problem’s but flater.
Integrating Parametric Geometry, Features, and Variational Modeling for Conceptual Design
Authors: Keirouz Walid , Pabon Jahir , Young Robert
Published: April 2021

We describe an architecture for conceptual mechanical modeling. It combines tools for parametric geometry and variational modeling using a feature-based representation. Parametric geometry allows designers to represent families of components as a single parameterized model. Variational modeling allows designers to model mechanical concepts analytically using equational constraints, and to evaluate competing alternatives common during conceptual design. Feature definition facilities allow designers to build libraries of frequently used mechanical components, by collecting interacting components into single higher level entities (features), and defining ways to interact with them.

All of these capabilities are needed for conceptual design, and play complementary roles. Integrating them, and clarifying their inter-relationships, is essential to building an architecture supporting conceptual design. To this end, we have implemented this architecture in an experimental CAD system.
Representing and Recognizing Features in Mechanical Designs
Authors: Finger Susan , Safier Scott A.
Published: April 2021

When experts view an object, they perceive it in terms of their own expertise. For example, manufacturers see features that affect the processes used to fabricate a part, while structural engineers see sources of stresses and other features that tend to reduce the life of a part. Features can be geometric, such as slots or chamfers; they can be quantitative, such as distances between holes; they can be functional, such as alignment; or they can be qualitative, such as a rough surface finish. Research in feature-based design systems for mechanical designers has been motivated by the realization that geometric models represent the design in greater detail than can be utilized by designers, process planners, assembly planners, or by systems that emulate these activities. Features provide abstractions to facilitate the creation, representation, and analysis of designs.

Our goal is to enable designers to compose mechanical designs from high-level features that embody functional and geometric properties. In addition, we want to provide designers with feedback on the manufacturability, assemblability, functionality, cost, etc. of the design as it evolves. To support this process in an intelligent CAD environment requires the integration of geometric models, analysis tools, and synthesis tools so that all aspects of the design can be considered while it is in progress. We are developing a design environment based on a shared representation of the design in which we can extract and reason about features of the design from different perspectives.

Our approach is to represent both the design and the features using graph grammars. By representing the features using the same grammar as the design, we can recognize features by parsing a feature against the graph that represents the design. We are exploring grammars for behavior as well as geometry in order to provide a link between behavioral and geometric representations. In this paper, we focus on the representation and recognition of features.
Heuristic Design of a Material Processing Component
Authors: Jamalabad Vikram R. , Langrana Noshir A. , Jaluria Yogesh
Published: April 2021

The main thrust of this research is in developing a knowledge-based system for the design of a mechanical engineering process. The study concentrates on developing methodologies for initial design and redesign in a qualitative format. The component selected is a die for plastic extrusion. A design algorithm using best first heuristic search and expert knowledge, both in procedural and declarative form, forms the core of the process. Initial design and redesign methodologies are presented that can enable efficient design of a component using expert knowledge. Some generality has been accomplished by the implementation of the techniques to dies of different cross sectional shapes. The software is written in Lisp within an object oriented software package using analysis modules written in C.
Back to the Drawing Board?: Computer-Mediated Communication Tools for Engineers
Authors: Jakiela Mark J. , Orlikowski Wanda J.
Published: April 2021

This paper describes an exploratory research study that attempted to determine the nature of computer-mediated information that would be exchanged by engineers engaged in a process of product design and manufacture. The results suggest that computer-mediated communication tools supporting asynchronous, written modes of information exchange, are likely to have little utility for engineers engaged in design and manufacture. Substantial augmentation of these tools will be necessary before their wide-spread adoption and use by engineers can be expected.
Design Evolution Management: A Methodology for Representing and Utilizing Design Rationale
Authors: Thompson James B. , Lu Stephen C.-Y.
Published: April 2021

In conventional design practice, a detailed product description is the end-result of a design process. Usually these detailed product descriptions do not contain information linking their heritage from early-stage abstract product descriptions or the particular influence of different life-cycle perspectives. This “missing” information, a description of the multi-staged and multi-perspective design process, is termed a design evolution, and is a representation of the design rationale for a product description. This research focuses on the development of a methodology for Design Evolution Management, i.e. techniques for representation and subsequent utilization of a design evolution during a design process. Within this methodology, a design evolution is represented both at strategic and tactical levels. A prototype computer-based design environment called AIDEMS, based on this design methodology, has been built and is being tested in several design domains. This design environment provides design engineers a platform for expressing their design strategies and tactics and uses Artificial Intelligence programming techniques enabling semi-automated design assistance for: resource scheduling, explanation of design assertions, execution of design revisions, design inconsistency detection, and exploration of design alternatives.
Constraint Absorption and Relaxation Using a Design History
Authors: Meehan Edmund J. , Brown David C.
Published: April 2021

A simple mechanism has been implemented and demonstrated within a routine design expert system. It has a limited ability to adjust design constraints based on experience within the domain. The mechanism is activated in response to noticing an extended run of either constraint failures or constraint successes. It reasons about the validity of either relaxing or absorbing a constraint. This process is referred to as Constraint Absorption. We hope to improve the performance of the expert system by reducing the incidence of repeated constraint failure, and by eliminating redundant constraints.
Engineering Design Research in Japan
Authors: Tomiyama Tetsuo
Published: April 2021

This paper describes the historical development and the current situation of engineering design research in Japan. It reviews Japanese design theories and methodologies of significant importance in mechanical engineering. Future directions are also discussed.
Simulation of Probabilistic Wind Loads and Building Analysis
Authors: Shah Ashwin R. , Chamis Christos C.
Published: April 2021

Probabilistic wind loads likely to occur on a structure during its design life are predicted. This article describes a suitable multifactor interactive equation (MFIE) model and its use in the Composite Load Spectra (CLS) computer program to simulate the wind pressure cumulative distribution functions on four sides of a building. The simulated probabilistic wind pressure load was applied to a building frame, and cumulative distribution functions of sway displacements and concepts of reliability were demonstrated by computing the probability of overturning using NESSUS (Numerical Evaluation of Stochastic Structure Under Stress), a stochastic finite-element computer code. The geometry of the building and the properties of building members were also considered as random in the NESSUS analysis. The uncertainties of wind pressure, building geometry, and member section property were quantified in terms of their respective sensitivities on the structural response.
Incorporating Finite Element Analysis Into Component Life and Reliability
Authors: August Richard , Zaretsky Erwin V.
Published: April 2021

A method for calculating a component’s design survivability by incorporating finite element analysis and probabilistic material properties was developed. The method evaluates design parameters through direct comparisons of component survivability expressed in terms of Weibull parameters. The analysis was applied to a rotating disk with mounting bolt holes. The highest probability of failure occurred at, or near, the maximum shear stress region of the bolt holes. Distribution of material failure as a function of Weibull slope affects the probability of survival. Where Weibull parameters are unknown for a rotating disk, it may be permissible to assume Weibull parameters, as well as the stress-life exponent, in order to determine the effect of disk speed on the probability of survival.
Extensions to the Taguchi Method of Product Design
Authors: Otto Kevin N. , Antonsson Erik K.
Published: April 2021

The Taguchi method of product design is an experimental approximation to minimizing the expected value of target variance for certain classes of problems. Taguchi’s method is extended to designs which involve variables each of which has a range of values all of which must be satisfied (necessity), and designs which involve variables each of which has a range of values any of which might be used (possibility). Tuning parameters, as a part of the design process, are also introduced into Taguchi’s method. The method is also extended to solve design problems with constraints, invoking the methods of constrained optimization. Finally, the Taguchi method uses a factorial method to search the design space, with a confined definition of an optimal solution. This is compared with other methods of searching the design space and their definition of an optimal solution.
Capturing and Using Designer Intent in a Design-With-Features System
Authors: Nielsen Eric H. , Dixon John R. , Zinsmeister George E.
Published: April 2021

The goal of “intelligent” computer-aided-design (CAD) systems is to provide greater support for the process of design, as distinguished from drafting and analysis. More supportive design systems should provide a quick and simple means of creating and modifying design configurations, automating evaluation procedures (e.g., for manufacturing), and automating interfaces to analysis procedures.

In this paper we are concerned with the issues of representing in-progress designs so that such goals can be met. A feature-based representation is proposed in which features are defined as possessing not only form but also certain designer intentions regarding geometric relationships. A working experimental version of a design-with-features system using this representation for thin-walled components illustrates its use in composing a design as a configuration of feature-forms, in modifying the design geometry through automatic, intelligent incorporation and propagation of designer-initiated geometry changes, and in providing for the generation of user-defined features. In contrast to constraint-driven simultaneous equation solving methods, this system uses an intent-driven knowledge-based method to propagate and incorporate geometry modifications not only in fully-constrained designs, but also in over- and under-constrained designs. Issues of manageability, extensibility, and computationally efficiency were considered in the development of the core services of the system.
Life-Cycle Serviceability Design
Authors: Gershenson John , Ishii Kosuke
Published: April 2021

This research seeks to develop a systematic methodology to balance the serviceability, reliability, and modularity (SRM) of a design with other life-cycle costs. While design for assembly (DFA) and modular designs are stressed, SRM’s effects on post manufacturing life-cycle issues are often bypassed. In particular, a design without adequate consideration for serviceability could seriously affect service costs and customer satisfaction. This paper develops a systematic method to deploy the serviceability design guidelines during early stages of design. Our study, service mode analysis (SMA), involves a consistent representation of design rules, failure and service frequency data, and life-cycle service cost. This paper defines the steps used to complete the service mode analysis and proposes a means of expressing serviceability both quantitatively and qualitatively. The paper also shows a method to examine tradeoffs between serviceability costs and other life-cycle costs.
A Design Methodology for a Self-Maintenance Machine
Authors: Umeda Yasushi , Tomiyama Tetsuo , Yoshikawa Hiroyuki
Published: April 2021

This paper proposes a design methodology for a self-maintenance machine. The self-maintenance machine is a machine that can maintain its functions for a while, even though faults happen. In order to achieve functions for diagnosing and repair planning, a model based approach that employs qualitative physics is proposed. Regarding repair executing function, two types of repair strategies are proposed; viz., control type and functional redundancy type which is a strategy to add redundancy to a machine from a viewpoint of function. A prototype of the self-maintenance machine is developed. Because this machine uses the control type of repair strategy, it succeeded to maintain its functions as far as its structure does not change. A promising candidate for dealing with faults that involve structural changes is the functional redundancy type of repair.
Mathematical Foundations of Engineering Design Processes
Authors: Bell David G. , Taylor Dean L. , Hauck Paul D.
Published: April 2021

This work provides an overall framework for discovering fundamentals of engineering design processes, which can eventually be used to improve process performance. This framework is based on the hypothesis that design processes are dynamic systems, and that the large body of system analysis techniques can be applied. To use these techniques, design processes are described on structural, behavioral, and functional levels. It appears that the process structure involves paired methods and modeling schemata, and that the application of a set of these pairs implements an evolution of metamodels with iterative refinement. That is, products may evolve through a sequence of mapping and iterative redesign steps. Process behavior has been observed, and the requirements and beginnings of a mathematical model are described. Process function is briefly discussed as necessary for development of process performance measures. Such a deep understanding of processes is required to implement effective selection of method and modeling schema pairs, and to facilitate the development of new pairs.
Identifying the Fundamental Geometric Attributes of Design: An Application of Distinctive Feature Theory
Authors: Chovan John D. , Waldron Manjula B.
Published: April 2021

The identification of a basal set of geometric attributes used by designers to describe mechanical engineering design can provide useful information on the manner in which designers communicate information about mechanical design. In this paper, geometric attributes were identified from descriptions provided by five mechanical designers while they read and analyzed thirteen mechanical engineering drawings of varying complexity. From the verbal protocols, the geometric attributes were identified and then subject to a cluster analysis. A set of fifteen geometric attributes were identified as distinctive features since they were minimally sufficient to cluster the set of 61 design features contained in the drawings. These distinctive features provide insights into how designers reason about mechanical engineering drawings, which may be useful when designing human-machine interfaces for computer-aided design.
Quiescence in Internal Propagation
Authors: Sarma Sanjay E. , Rinderle James R.
Published: April 2021

Concurrent design often involves a large number of variables related through a complex network of constraints. This not only makes it difficult to find a design solution, but also to understand the design parameter trade-offs, trends and interactions. Precise estimates of all the design parameters which would facilitate the exploration of tradeoffs and interactions are generally not available, however, the allowable ranges or intervals of some design parameters are often known. Narrower, or more refined intervals, facilitate the inference of stronger conclusions and the more robust application of mathematical optimization and constraint reasoning tools. Refinement of intervals can be carried out conveniently by constraint propagation, however, direct constraint propagation is often a computationally slow process. In this paper we study constraint propagation at a fundamental level and identify certain properties of the process. We then propose an alternative method in which these properties are utilized to increase considerably the speed and accuracy with which the final quiescent state of constraint propagation can be computed.
A Dialectical Reasoning System for Design Documentation
Authors: Ruecker Lukas , Seering Warren P.
Published: April 2021

This paper presents results of our research in design documentation. We have focused on the problem of capturing and applying design knowledge during product development. We have developed a task- and domain-specific representation for dialectical semi-formal reasoning in design which enables us to capture relationships among pieces of design knowledge clearly and concisely and provide computational services aimed at making documentation easier to use, more powerful, and thus, more valuable.
An Automated and Interactive Approach for Fitting B-Spline Surfaces Through 3D Planar Visual Data
Authors: Theodoracatos Vassilios E. , Katti Ranganath R.
Published: April 2021

The work reported here is an integral part of a system developed for the automated reconstruction of arbitrary-shaped physical objects using vision systems, three dimensional computer graphics, and B-Spline surface approximation techniques. Digitized planar contour points are automatically fitted in the image and world space to define a minimum number of B-Spline control points using least-squares approximation techniques. The final set of points represent the B-Spline control net of the entire surface of the object. The resulting curves and surfaces can be further interactively modified until a satisfactory fit is obtained. Three parametrization techniques, viz., uniform, chord length, and affine invariant angle method are implemented and adjusted to their local minima using the Newton-Raphson iteration method. The effect of each method on the accuracy of the reconstructed surface is discussed. The techniques were tested using a clay model of a human face. The uniform parametrization performed better with the highest speed of convergence and best least-squares error characteristics. On the other hand, it was less effective in detecting sharp corners as compared to the other two methods. The results also show that there is a minimum number of control points for every surface beyond which there is no error improvement. This is useful in several industrial applications when checking surface accuracy of manufactured parts using Coordinate Measuring Machines (CMM).
Automatic Finite Element Mesh Generation Over Intersecting Rigid Body-Movable Subdomains for the Automation of Parametric Conceptual Design
Authors: Yang Hyunik , Hoeltzel David A.
Published: April 2021

An approach for the automatic generation and refinement of three dimensional finite element meshes subdivided by multiply connected, rigid body movable subdomains has been developed. A combination of computational geometry and geometric modeling techniques have been employed to implement parametric computer-aided design based on the finite element method. Nonconvexity of an overall three dimensional domain has been handled by combining convex geometric primitives as subdomains for the construction of a three dimensional domain. A clipping technique is employed for determining intersections points between subdomains bounded by triangulated surfaces, following their rigid body movements. To demonstrate the utility of this approach to parametric redesign, a series of meshes that model a hip joint prosthesis and a reciprocating internal combustion engine, as assemblies of parametrically-defined geometric primitives, have been developed.
High-Resolution Camera-Space Manipulation
Authors: Skaar S. B. , Chen W. Z. , Miller R. K.
Published: April 2021

The paper presents results from experiments conducted to test the limits on precision and versatility of the method of camera-space manipulation for manufacturing operations. The task used as the basis for the experiment is a close-tolerance rigid-body mating task. The receiving piece is stationary and arbitrarily positioned and oriented. Motion of the inserted piece requires six degrees of freedom for task completion. This is accomplished using the very large GMF S-400 manipulator. The maneuver is guided entirely by information from two uncalibrated cameras. Without the benefit of passive compliance, relative position resolution of the two pieces of about half a millimeter is achieved with considerable reliability. The experiment makes use of newly-developed “ring” cues (and associated image-analysis software) which are painted on the two bodies to be joined.
An Algorithm for Two-Dimensional Geometric Boundary Construction From Finite Element Node Displacement Data
Authors: Jablokow Andrei G. , Gilmore Brian J. , Clark Kent
Published: April 2021

This paper describes a system for constructing geometric models from elastically deflected finite element meshes. Two dimensional boundary curves are constructed by fitting B-Spline curves to the deflected Finite Element model. Cubic B-Splines are generated using least squares fitting techniques to the boundary curves of the Finite Element results. The fitted curves are connected end-to-end. The algorithm is useful after analysis for interfacing analysis results with design data in a shape optimization system based on Finite Element techniques.
A Solution to the Missing-View Problem for Polyhedral Solids
Authors: Srinivas Y. L. , Dutta Debasish
Published: April 2021

An algorithm for generating the missing view corresponding to a given pair of orthoghonal views of a polyhedral solid is presented. The solution involves reconstructing the solids from the partial information given and then generating the missing view. The input is a vertex connectivity matrix describing the given views. Reconstruction of solids from incomplete orthographic views will have applications in computer-aided design, machine vision and automated inspection systems.
Synthesis of Contact Surfaces of Spherical Cam-Oscillating Roller-Follower Mechanisms: A General Approach
Authors: González-Palacios Max Antonio , Angeles Jorge
Published: April 2021

A novel method of synthesis of the surface geometry of spherical cam-oscillating roller-follower mechanisms is introduced. The approach aims at zeroing the sliding velocity between the cam and the roller, their respective geometries being thus obtained as conical surfaces. The pressure angle is analyzed in detail. Specific results are presented for the application of this synthesis technique to indexing cam mechanisms.
Applications of Kinematic/Kinetic Performance Tools in Synthesis of Multi-D.O.F. Mechanisms
Authors: Lee Ming-Yih , Erdman Arthur G. , Gutman Yevsey
Published: April 2021

Analytical and graphical performance synthesis tools for multi-DOF mechanisms are developed in the companion of this two-part paper [1]. Various performance indices derived from the Jacobian matrix for analyzing performance characteristics of multi-DOF mechanisms were proposed. These performance indices are the local kinematic coupling index (inner product of the Jacobian column vectors), the local directional mobility index (ratio of the Jacobian’s eigenvalues), and the local efficiency index (product of the Jacobian’s eigenvalues). In this paper, effort is placed on the applicability of the proposed analytical and graphical synthesis tools used to aid the design of multi-DOF mechanisms. Two examples representing open and closed chain mechanisms will be used to illustrate the effectiveness and efficiency of proposed method. First, a two-link planar robotic manipulator is used to apply the the proposed method. Following that, a two DOF parallel drive road simulator illustrates applicability of the suggested tools. Through these examples, geometric parameters and joint range limits of the mechanism are optimized through the evaluation of performance indices, eigen-ellipse and intersection angle between trajectory contours.
A Semigraphical Method for the Solution of the Burmester Problem
Authors: Chang Ching Yu , Angeles Jorge , González-Palacios Max Antonio
Published: April 2021

The determination of the planar four-bar linkage intended to guide a rigid body through five finitely-separated configurations is known as the Burmester Problem. This is a nonlinear problem that involves finding the roots of a system of four bilinear equations in four unknowns. When solving this problem numerically, for it is evasive to other means, issues such as numerical conditioning, multiplicity of solutions and singularities must be considered. Here we present a semigraphical method of solution that reduces the problem to finding the intersections of two contours in the x-y plane of motion. The method not only produces all real solutions, by simple inspection, but also provides information about the numerical conditioning of those solutions.
The Stewart Platform of General Geometry Has 40 Configurations
Authors: Raghavan Madhusudan
Published: April 2021

The Stewart platform is a six-degrees-of-freedom, in-parallel linkage. It is used in automotive and flight simulators, positioning tables for assembly and robotic applications, and various other applications requiring linkages with high structural stiffness. It consists of a base link, a coupler link, and six adjustable-length legs supporting the coupler link. Each leg consists of a prismatic joint with ball-joint connections to the base and coupler respectively. The forward kinematics problem for the Stewart platform may be stated as follows: given the values of the six prismatic joint displacement inputs to the linkage, compute the position and orientation of the coupler link. This problem may be set up as a system of nonlinear multivariate polynomial equations. We solve this problem using a numerical technique known as polynomial continuation. We show that for Stewart platforms of general geometry (i.e., platforms in which the linkage parameters are arbitrary complex numbers) this problem has 40 distinct solutions.
Generalized and Actual Constraint Forces in the Inverse Dynamic Analysis of Spatial Flexible Mechanical Systems
Authors: Chen D. C. , Shabana A. A. , Rismantab-Sany J.
Published: April 2021

In this investigation, a procedure is developed for the determination of the actual system of constraint forces in spatial flexible mechanical systems. Expressions for the generalized reaction forces in terms of the constraint Jacobian matrices of the joints are presented. The effect of the elastic deformation on the actual reaction forces is also examined numerically using the spatial flexible multi-body RSSR mechanism that consists of a set of interconnected rigid and elastic bodies. The procedure described in this investigation can also be used to determine the joint torques in kinematically driven spatial elastic mechanism and manipulator systems.
Design Methods of Improving Robot Manipulator Performance
Authors: Ulrich Nathan , Kumar Vijay
Published: April 2021

Although industrial robot mechanisms are relatively mature, few manipulator arms are available for use outside of the factory. This paper presents several techniques of improving the performance of robot manipulators designed for use in unstructured or hazardous environments. These methods include a means of passive, mechanical, and energy-conservative gravity compensation, a remote actuation technique, and the use of tension-element transmission and speed reduction. In comparison with a conventional arm, an arm incorporating these techniques moves faster, handles a larger payload, and responds better to external forces. In addition, simulation results show that it consumes less than one-tenth the energy.
Parametric Excitation of Robotic Manipulators
Authors: Sankaranarayanan H. K. , Streit D. A. , Kim H. Y.
Published: April 2021

The predominant compliance in the dynamic response of the PUMA 560 robot manipulator arises in joints two and three. Considering compliance of these two joints, the effects of user controlled variables on system stability are studied using Floquet theory. Specifically, manipulator configuration, operating speed and trajectory amplitude are considered. For some configurations, instabilities are expected for ranges of operating frequencies which are significantly removed from the neighborhood of multiples of resonant frequencies of the stationary system. Results demonstrate overall trends in stability regions for several ranges of system configuration. Results also identify regions of rapidly changing stability of this industrial manipulator.
The Effects of JIT Manufacturing Philosophy on Machine Utilization and Tool Life
Authors: Asikele Edward E. , Soni A. H.
Published: April 2021

This paper examine how the applications of Just-in-Time (JIT) manufacturing philosophy create excess capacity if the rate of production in a machining center is greater than the rate of the demand for the products at a subsequent machining center. The excess machining capacity created can be reduced by operating the machine(s) with excess capacity at a lower speed up to a certain limit (in order to maintain efficiency). By operating the machine(s) with excess capacity at a lower speed, the machine utilization is increased as well as the tool life of the machine(s).
Theory for an Active Dynamic Vibration Absorber
Authors: Stephens L. S. , Rouch K. E. , Tewani S. G.
Published: April 2021

Research in dynamic vibration absorbers has yielded several fundamental designs. Among these are the tuned dynamic absorber, the Lanchester damper, and the impact damper. These designs utilize certain combinations of passive mechanical elements (springs and dampers) to reduce the vibrational amplitude of a system. However, with recent advances in motion sensing and actuating, the design of vibration absorbers that utilize actively actuated elements has become more attractive. This paper develops the theory for using a damped dynamic vibration absorber with an active control element to reduce the vibrational amplitude of a lumped mass system. A control law consisting of a linear combination of velocity and acceleration of the main mass is developed for the active element A closed-form solution is presented for the absorber tuning equation, and numerical methods are used to generate performance curves.
Modelling of Flexible Manipulators Employing a Spatially Translating and Rotating Beam Finite Element
Authors: Gaultier Philippe E. , Cleghorn William L.
Published: April 2021

The implementation and development of a spatially translating and rotating beam finite element for the purpose of modelling flexible manipulators is presented. Flexible manipulators are subject to dynamic loads from link and actuator masses undergoing acceleration, and structural or applied damping. To model these effects, a spatial beam element is developed which accounts for the effects of axial loads on lateral vibration, Rayleigh damping, and actuator and payload masses modelled as lumped masses. Hamilton’s principle is employed to derive the governing differential equations for the spatial beam element, and compatibility matrices are developed for their assembly. The method is generalised to facilitate application to manipulators of different geometry and applied joint motion, and proves to be very stable. Joint motions are utilised which produce smooth acceleration profiles as opposed to sharp profiles used in typical industrial manipulators. Comparisons with published data illustrate good agreement. The beam element presented shows promise as a useful design tool and a basis for further study in the implementation of flexible manipulators.
Observations of Subcritical Superharmonic and Chaotic Response in Rotordynamics
Authors: Ehrich Fredric
Published: April 2021

When a rotor, excited by unbalance, is operating eccentrically within a clearance and in local contact with the stator it behaves as a bilinear oscillator with a natural periodic motion that resembles bouncing. When excited by unbalance at a subcritical rotative speed which is exactly or nearly 1/Nsuper times its natural frequency, the nonlinear system will respond by bouncing at or nearly at its natural frequency, or super harmonically at a frequency exactly Nsuper times the operating speed, or forcing frequency. As in supercritical subharmonic response, there is a zone of with characteristics of chaotic behavior in the transition zone between any order of superharmonic response and the next highest order superharmonic response. There is also an intricate pattern of progressive bifurcations of the orbit on entry into this characteristically chaotic region and a reverse progression on exit from this region.

The response is a mirror image or reciprocal set of the more thoughly studied supercritical subharmonic response of the same bilinear oscillator system which, when excited by unbalance at a supercritical rotative speed which is exactly or nearly a whole number Nsub times its natural frequency, the nonlinear system will respond by bouncing at exactly or nearly its natural frequency at a frequency exactly 1/Nsub times the operating speed or forcing frequency. Such supercritical subharmonic response is also characterized by the appearance of characteristically chaotic behavior in the transition zone between successive orders of subharmonic response and by patterns of progressive bifurcations of the orbit on entry into and exit from each region of characteristically chaotic response.

Various aspects of subcritical superharmonic response are studied in a numerical model of the nonlinear system, and are compared to data taken on the core spool of an aircraft engine gas turbine. The engine data show many of the unique characteristics of response, wave form and spectral content predicted by the numerical model of the bilinear oscillator when operating at subcritical rotative speed.
Flexural Critical Speeds of a Two-Rotor Bearing System With One Overhang
Authors: Chow C. Y. , Wang I-Chih , Chow Rae
Published: April 2021

Power-train arrangements, such as a two-rotor system with one overhang, have a wide spectrum of industrial applications, from a workbench grinder to compressor-turbine unit. Based on a typical dimension, flexural critical speeds both in the forward and backward whirl are calculated by a commercial software package. These critical speeds are further analyzed by varying the shaft overhung, rotor inertia and gyroscopic effect. Parametric analysis would enable designers to make a trade-off study and obtain a satisfactory operation. In extreme conditions, results obtained have been verified with available analytical solutions.
Identification and Resolution of a One-Times Slip Frequency Synchronous Motor Field Start Up Problem
Authors: Wolff F. H. , Hustak J. F.
Published: April 2021

This paper describes how to detect the presence, and determine the magnitudes, of both one times slip frequency and two times-slip frequency torque pulsations. This is done by using test measurements on a 19000 hp (14168 kW), 1200 rpm (20 hz) synchronous motor/gear/compressor drive train which experienced a premature motor field excitation during commissioning.
Modelling of an Elastic Disk With Finite Hub Motions and Small Elastic Vibrations With Application to Rotordynamics
Authors: Flowers George T.
Published: April 2021

In the modelling of flexible structures undergoing large overall motion and small elastic vibrations, it is necessary to include elastic displacement effects up to second order if the resulting equations are to be consistent. Elastic displacements are typically modelled using mode shapes and generalized coordinates, an approach that neglects displacement effects that are higher than second order in the generalized coordinates. This study examines the implications of such effects in the modelling of an elastic disk with arbitrary base motions and small elastic vibrations. A general modelling procedure is described that is appropriate for the development of simulation models for such structures. An approximate technique is used to account for the second order elastic displacements. The model is specialized to the case of an elastic disk undergoing a constant axial spin and infinitesimal displacements for all other degrees of freedom. Comparisons are made between the natural frequencies of this model with and without foreshortening effects and some conclusions are drawn as to the relative importance of such terms in rotor disk modelling.
On the Dynamics of a Beam Rotating at Nonconstant Speed
Authors: Huang Yii-Mei , Lin Ming-Shang
Published: April 2021

The response and its stability of a beam rotating at nonconstant angular speed are studied. The rotating speed is assumed to be the combination of a constant angular speed and a small periodic perturbation. The axial and flexural deformations due to rotation are considered simultaneously. Thus, the rotating team at nonconstant speed yields a set of parametric excited partial differential equations of motion. Extended Galerkin’s method is employed for obtaining the discrete equations of motion. Then, the solution and the its stability are found by using the method of multiple scale.
The Influence of Mounting Compliance and Operating Conditions on the Radial Stiffness of Ball Bearings: Analytic and Test Results
Authors: Butner M. F. , Murphy B. T. , Akian R. A.
Published: April 2021

Ball bearing stiffness is significantly affected by internal clearance as well as the nature of applied loads and bearing ring mounting compliance. Since their stiffnesses are key to rotor critical speeds, it is important to obtain the most accurate possible radial stiffness prediction for shaft bearings during the machine design analysis process. Quasi-static analysis of spring-preloaded ball bearings predicted reduced radial stiffness when the outer ring is permitted to tilt rather than being assumed restrained from angular deflection. This effect was confirmed experimentally by observing resonant frequencies of a rotor supported on ball bearings of varied internal clearance, mounted with and without spring preloading. Analytic predictions of bearing stiffness are given, and test results presented for comparison.
Influence of Thermal Conductivity of Lubricant on the THD Characteristics of a Plain Journal Bearing
Authors: Rajalingham C. , Prabhu B. S. , Bhat R. B. , Xistris G. D.
Published: April 2021

The viscous heat generation in the lubricant film of a hydrodynamic journal bearing causes a rise in temperature of the fluid film. Considering the influence of the temperature variation along and across the film, the performance of a journal bearing is investigated under adiabatic conditions for different values of thermal conductivity of the lubricant. In this analysis, the temperature of the journal surface has been chosen to ensure that there is no net heat transfer from the lubricant The results show that the variation of temperature across the film affects bearing performance significantly and that an increase in lubricant thermal conductivity enhances bearing performance.
Jumping Phenomenon in Journal Bearing
Authors: Kryniski Krystof
Published: April 2021

Due to their reliability and low maintenance costs over an extended service time, the journal bearings, also known as fluid-film bearings, are commonly incorporated in the super-critical rotor systems. Together with proven balancing methods, they allow rotating machine to pass smoothly through the various of critical speeds, both during start-ups and shut-downs. However, journal bearings need to be designed very carefully, as at some operating conditions (speed and load), they may introduce the undesired effects, such as unstable operations or sub-harmonic resonances. The standard procedure leading to the optimum fluid-film bearing design is based on the bearing capacity, defined by the Sommerfield number [1][2]. When Sommerfield number is determined, all design parameters, such as viscosity, radial clearance, diameter and rotation speed, etc. are matched to satisfy the engineering requirements specified. The procedure is considered to be completely reliable and is commonly used in turbo-machinery and high-speed compressor design. However, the significant divergences between theory and practice were observed with the increase of a bearing radial clearance [3].
The Effect of Bistable Jump on the Reliability of Squeeze Film Damper
Authors: Changsheng Zhu
Published: April 2021

Based on lots of data from an experiment of a high-speed rotor supported on squeeze film dampers, this paper analyses that how the bistable jump affects the reliability of squeeze film dampers, if the rotor system has to frequently pass through the bistable oparation speed range. It is shown that the change of the rotor vibration amplitudes caused by times of passed through bistable operation speed range is more significant than that caused by steady operating time. The users must pay much attention to the bistable jump phenomenon in the successful application of squeeze film dampers.
Investigation on the Bistable Jump in Subcritical Speed Range of Rotor Supported on Uncentralized Squeeze Film Dampers
Authors: Changsheng Zhu , Xixuan Wang , Caigao Fu
Published: April 2021

This paper presents one of bistable jump phenomena observed in rotor system supported on uncentralized squeeze film dampers which occurs in the subcritical speed range of rotor. The jumping tendency of this bistable jump is jumping up in acceleration and jumping down in deceleration and is without the transposition of disk mass centre. The behaviors, especially the latter, are different from the bistable jump behaviors reported to date. The reason for occurrence of the subcritical speed bistable jump is explained by a Duffing equation with the varied stiffness and the exciting force which amplitude is proportional to the square of rotating speed of rotor.
Dynamic Torque Response of an Electro-Rheological Clutch
Authors: Firoozian R. , Bullough W. A. , Xiao S. , Hosseini-Sianaki A. , Johnson A. R. , Makin J.
Published: April 2021

The main potential advantage of electro-rheological fluid when used as the interface medium between electronics and actuators in high speed machines is its ability to respond quickly to a change in the control signal. The analysis reported in this paper shows that over the operating speed range the system has a time constant of less than one millisecond and for most practical applications it can be assumed that when a suitable control strategy is employed the output torque would be proportional to the control signal.

Most electro-mechanical torque transducers have time constant of over 10 milliseconds and therefore direct measurement of the torque produced by the electro-rheological clutch would be very expensive if not impractical. This paper reports a numerical method of identifying the torque response from the output of a conventional torque transducer which has a natural frequency of 110 Hz. The transfer function is first identified from a standard step input test, and the torque response of the clutch then is estimated from the measured signal. Although the noise on the signal will be always amplified with this method the use of a digital filter makes it possible to obtain an accurate estimate of the torque response.
Progressive Torsional-Axial Continued Vibrations in Crankshaft Systems: A Phenomenon of Coupled Vibration
Authors: Song X. G. , Song T. X. , Xue D. X. , Li B. Z.
Published: April 2021

It has been recognized that the effects of coupled vibrations are the most important when the natrural frequencies of torsional and axial vibrations are equal to each other or that axial natrural frequency is double of that of torsional. Especially the response of axial vibration, which frequency is double of that of torsional resonance, may become very serious.

Two types of coupled vibration between torsional & axial vibration in crankshafting are introduced. And the method to calculate the coupled vibrations at the same frequency and at the double frequency of axial to torsional is presented.

Dynamic model tests & torsional and axial vibration tests of practical crankshaftings on board have been performed. From the tests and calculations, a phenomenon of torsional-axial continued vibration, progressive in nature, as a result of coupled vibration are revealed.
A Review of the Dynamics of Independently Rotating Wheel Systems for Railway Vehicles
Authors: Swamy S. Narayana , Dukkipati R. V. , Osman M. O. M.
Published: April 2021

Major analytical and experimental efforts in the field of Independently Rotating Wheel systems (IRW) for railway vehicles have been reviewed. Various methods adopted by researchers to incorporate guidance capability to the system are discussed. Attention is focussed on the lateral stability and response characteristics of IRW systems and mathematical models developed to predict them. Some critical research needs are identified.