bluuebunny/crossref_metadata_2025 huggingface dataset:
CAD Data Representations for Haptic Virtual Prototyping
Authors: Stewart Paul , Buttolo Pietro , Chen Yifan
Published: February 2021

For many years designers have relied on visual feedback and two-dimensional pointing devices to interact with Computer-Aided Design (CAD) models. The “sense of touch”, that is fundamental to interaction and manipulation in everyday life, is not yet a part of the standard human-computer interface. An on-going project at the Ford Research Laboratory has created an immersive virtual prototyping system with which a designer can not only visualize a CAD model but also “touch” it using a force-feedback device. This paper will briefly introduce human perception of haptic information and then describe the process of haptically rendering an object. Then the issues involved with the correct selection of a data representation for haptic rendering will be addressed. Lastly, a brief description of the experimental system implemented at the Ford Research Laboratory will be given.
MMCs and PPCs As Constructs of Curvature Regions for Form Feature Determination
Authors: Sonthi Ratnakar , Gadh Rajit
Published: February 2021

Shape feature information about a part is required to analyze the part for downstream issues such as manufacturability and assemblability. One method of obtaining the feature information is feature recognition from the geometric model. This paper presents an approach called Curvature Region (CR) approach for feature determination in solid models. The CR-approach categorizes features into two primitive shape classes: protrusions and depressions. In the first step, these primitive shape classes are recognized from the solid model. In the next step, the primitive shape classes are analyzed using rules to obtain features. Primitive features are found by first converting the boundary representation (B-Rep) of the CAD model to a higher level of representation called Curvature Region Representation (CR-Rep). Curvature Regions are then grouped together to form Minus-Minus Centers (MMCs) and Plus-Plus Centers (PPCs). Primitive shapes are then defined in terms of these centers.
Use of Computational Techniques Applied to the Design and Performance Prediction of Diesel Engines
Authors: Campbell Niall A. F. , Hawley J. Gary , Wallace Frank J. , Wilson Mike , Banisoleiman Kian
Published: February 2021

Integrated computational techniques using cycle simulation, finite element analysis (FEA) and gas flow modelling are currently being applied to enhance the design of automotive diesel engines by obtaining more accurate representations of the thermal boundary conditions on the gas side of the combustion chamber. This paper details the methodology of such an approach focusing on the development of a zonal gas flow model, as opposed to a full CFD analysis, to provide a quicker and more flexible means of achieving spatial gas side heat transfer models.
An Algorithm for Designing Conventional and Fuzzy Logic Control Systems
Authors: Edwards Dean B. , Canning John R.
Published: February 2021

This paper presents an algorithm that can be used to design either conventional or fuzzy logic control systems. In order to use the algorithm, the engineer must first choose a performance index for the system which he or she wants to optimize relative to some specified design parameters. For conventional state space controllers, the design parameters are the feedback constants associated with the state variables of the system. For fuzzy logic controllers, the design parameters are the parameters used to define the fuzzy sets for the input state and control variables. We use the algorithm to design proportional plus derivative (PD) and proportional, integral, and derivative (PID) control systems and their equivalent fuzzy logic control systems. The algorithm therefore provides a unifying approach for designing either conventional or fuzzy logic control systems.
An Optimization Procedure in a Sirocco Fan Using Experimental Data
Authors: Min H. S. , Rew H. S. , Ahn C. O.
Published: February 2021

The flow rate and the specific noise level of 18 sirocco fans were measured and these data were analyzed by the Taguchi method and the neural network. The optimal design value obtained by the neural network generally showed good agreement with that by the Taguchi method. The effects of eight important design variables on the flow rate and the specific noise level were discussed.
Interval Arithmetics Based Numerical Solution of Linear Systems of Equations for Non-Deterministic Analysis of Structures
Authors: Delcroix Franck , Braibant Vincent , Oudshoorn Adrien
Published: February 2021

Industrial companies are being more and more interested in the non-deterministic aspects of system, structure and process design, and beyond, in the non-deterministic analysis and optimisation outcomes. The main difficulties of stochastic approaches lie in the evaluation of the statistical distributions of the structural responses. Current methods fall in two categories, with Monte-Carlo methods whose computational costs become prohibitive as the number of parameters increases or the expected confidence levels are high and Stochastic Finite Element methods whose assumptions may be restrictive. In order to calculate the statistical distributions of structural responses, an original method is proposed. The method, which uses interval arithmetics, seems promising in terms of performance and suitability for intensive numerical treatment.
Optimal Process Design for Maximum Heating and Cooling Rates of Pressure Vessels
Authors: Kok Schalk , Stander Nielen
Published: February 2021

Optimal pressure and ambient temperature profiles are calculated to allow the rapid heating and cooling of pressure vessels during startup and shutdown. The ordinates of the ambient temperature and pressure at equally spaced time intervals are chosen as the design variables. Cubic splines are fitted through the ordinates to describe the ambient temperature profile required for the convective heat transfer analysis, and the pressure profile required during the structural analysis. Response surface methodology is used to construct approximations to temperature and stress in the transient thermoelastic nonlinear analysis. Linear response surfaces were found to be sufficiently accurate, thereby minimizing the number of finite element analyses. Three problems are solved to illustrate the methodology.
An Approach to Integrated Product/Process Design via Virtual Prototyping
Authors: Bauer Matthew D. , Rosen David W.
Published: February 2021

With the introduction of virtual prototyping into the product development process, simultaneous product/process design is enabled. The research reported in this paper illustrates an integration of product and disassembly process design via virtual prototyping. In this context, a virtual prototype is an information model consisting of a product model and one or more process models. Virtual prototype generation is a hybrid process consisting of both automated and interactive tasks. Simultaneous product/process design is accomplished by formulating the integrated product/process design problem as a multiobjective optimization problem in which product/process requirements are evaluated via virtual prototyping. Solution of the integrated product/process design problems is achieved through the application of the MORPS algorithm. Application of the use of virtual prototypes is presented in the simultaneous product/process design of an automotive center console.
Methodology for Locking Feature Selection in Integral Snap-Fit Assembly
Authors: Genc Suat , Messler Robert W. , Gabriele Gary A.
Published: February 2021

While every step in a systematic approach to the design of an assembly for integral attachment using snap-fit features is important, none is more important than the selection of locking features. After all, it is these features that hold the assembly together. Comprised of a latch and catch component, locking pairs must themselves be selected using a systematic approach. This paper presents that approach as a six-step methodology, after defining and describing latch and catch components. It then demonstrates the methodology using a case study taken from real life.
Jamming Conditions for Multiple Peg and Hole Assemblies
Authors: Sathirakul Korntham , Sturges Robert H.
Published: February 2021

Multiple peg-in-hole insertion problems represent a practical assembly class. It is more complicated than single peg insertion since the interaction of all pegs with their holes need to be considered together. The physics of this class of assembly tasks needs to be analyzed, for us, to develop a fine-motion strategy, or to design devices to solve the insertion problems.

In this article, we present the geometric as well as quasi-static analyses of a dual peg-in-hole problem. We enumerate all the possible contact-states of the problem and derive the geometric conditions of each contact-state. We also derive the force-moment equations for static-equilibrium states of the dual-peg problem based on the quasi-static assumption, and obtain the jamming diagram of the problem. We find that pegs with different dimensions may have different jamming diagrams. A taxonomy of dual-peg problems is presented. Finally, we propose an approach to extend these results to general multiple-peg problems in 3 dimensions.
Automated Planning for Stacking of Bent Sheet Metal Parts
Authors: Ayyadevara Venkateswara R. , Sturges Robert H.
Published: February 2021

This paper deals with the automated generation of stacking plans for bent sheet metal parts which are difficult to stack due to their irregular geometry. A stacking plan consists of a set of homogeneous transformations describing the configuration of each constituent part of the stack with respect to a world coordinate system. Stacks are constructed incrementally by adding parts to an existing stack. The base part is positioned to maximize stability when placed on a special part buffer. Successive parts are added in a configuration minimizing the height of the stack c.g. and ensuring the stability of the stack and the constituent parts. Evaluation of part and stack stability and analysis of part-part interference and part instability are addressed. Three examples demonstrate the advantage of interference analysis, handling of non-90° part orientations, and effect of features like asymmetric flanges and large holes on computational efficiency.
Integration of Process Planning and Production Scheduling for Agile Manufacturing: A Case Study
Authors: Sadeh Norman M. , Hildum David W. , Smith Stephen F. , Kjenstad Dag , Laliberty Thomas J. , McA’Nulty John
Published: February 2021

As companies increasingly customize their products, move towards smaller lot production and experiment with more flexible customer/supplier arrangements, such as those made possible by Electronic Data Interchange (EDI), they increasingly require the ability to (1) respond quickly, accurately and competitively to customer requests for bids on new products and (2) efficiently work out supplier/subcontractor arrangements for these new products. This in turn requires the ability to (1) rapidly convert standard-based product specifications into process plans and (2) quickly integrate process plans for new orders into the existing production schedule to best accommodate the current state of the manufacturing enterprise.

This paper describes IP3S, an Integrated Process Planning/Production Scheduling shell for agile manufacturing. IP3S utilizes a blackboard architecture that supports (1) concurrent development and dynamic revision of integrated process planning/production scheduling solutions, (2) maintenance of multiple problem instances and solutions, (3) flexible user-oriented decision making, (4) declarative representation of control information, (5) the use of a common representation for exchanging information, (6) coordination with outside information sources and (7) portability and ease of integration with legacy systems. IP3S has been validated in the context of a large and highly dynamic machine shop at Raytheon’s Andover manufacturing facility. Empirical results show an average performance improvement of 23% in solution quality over a decoupled approach to building process planning/production scheduling solutions.
Analytical Method for the Prediction of Reliability and Maintainability Based Life-Cycle Labor Costs
Authors: Fitzpatrick Mark , Paasch Robert
Published: February 2021

In today’s competitive marketplace, the quality of a product is becoming increasingly more important. The informed customer not only weighs the ability of the product to meet his/her requirements, and the purchase price of the product, but also the money that must be expended to maintain the function of the product. Hence, lowering the life-cycle cost of a product will increase its value and attractiveness to the customer.
Spatial Synthesis of Electro-Mechanical Products
Authors: Madhusudan T. N. , Gupta S. K.
Published: February 2021

In automated synthesis of electro-mechanical systems, considering both behavioral and spatial information is a challenging problem. This paper describes an approach to generate first-cut spatial configurations of electro-mechanical assemblies that satisfy side-effect constraints and also adhere to the basic behavioral interconnectivity specified during conceptual design. This approach is based on the branch-and-bound search technique and tightly integrated with conceptual design of electro-mechanical systems. We believe that by integrating behavioral and spatial information, one can provide a framework for effective exploration of a large number of design alternatives and increase the effectiveness of solid modelling-based assembly tools.
Signal Processing Approach for Geometric Detail Suppression
Authors: Lee Yong-Gu , Lee Kunwoo
Published: February 2021

Given the widespread use of the Finite Element Method in strength analysis, automatic mesh generation is an important component in the computer-aided design of parts and assemblies. For a given resolution of geometric accuracy, the purpose of mesh generators is to discretize the continuous model of a part within this error limit. Sticking to this condition often produces many small elements around small features in spite that these regions are usually of little interest and computer resources are thus wasted. Therefore, it is desirable to selectively suppress small features from the model before discretization. This can be achieved by low-pass filtering a CAD model. In this paper a method to apply the techniques in signal processing to the manipulation of a 3D model is proposed.
Modeling and Evaluation of Product Design Problems in a Distributed Design Environment
Authors: Pahng Francis , Senin Nicola , Wallace David
Published: February 2021

This paper proposes a framework for the modeling and evaluation of product design problems in a computer network-oriented design environment. The framework is intended to integrate designer-specified mathematical models for multi-disciplinary and multi-objective design problems. The goal is to provide the ability to rapidly construct integrated design problem models to facilitate collaborative design work, improve product quality and reduce development time. Ultimately, it should allow specialized engineering applications and design problem models to operate under a common design environment.

A product design problem is modeled in terms of interacting objects, called modules, each representing a specific aspect of the problem. Modules interact with one another through services that allow the exchange of information. Modules can encapsulate engineering models and data or software applications. The method is extended to create a distributed object-based modeling and evaluation framework for design problems.
Experimental Study of the Behavior of Certain Connectors in a Vibratory Bowl Feeder
Authors: Rosario Lourdes M. , Hernández-Coronas José D.
Published: February 2021

The design and implementation of vibratory bowl feeders involves the analysis of the behavior of the parts as they are conveyed up the bowl track. This paper presents the results obtained in a series of experiments which study the effect of the vibration amplitude in the feeder on the dynamic orientations of a family of parts. The objective of the study is to investigate how complex parts behave in a vibratory bowl feeder and try to establish a relationship between the orientation of the parts and the vibration amplitude of the bowl feeder. The study consisted of experimenting with four types of connectors that were similar in shape but differ in proportions. By experimenting with a part family, we intend to establish and generalize in the near future a relationship between the tendency of the parts to fall in certain orientations, the amplitude of vibration in the feeder, and geometric features or mass properties. The acquired knowledge could then be incorporated in computer aided design programs, together with existing theory on feeder design, to specify orientation devices and operating parameters in the vibratory bowl feeder.
STEP Pilot Project: Consolidated Schema for Airframe Engineering Analysis
Authors: Liang Jian , Shah Jami J. , Urban Susan D. , Harter Edward , Bluhm Thomas
Published: February 2021

This paper addresses the data modeling aspect of an ongoing research project which is aimed at developing an integrated product data-sharing environment (IPDE) based on the international standard STEP. The data model involves multiple design and analysis applications including: Product Design, Computational Fluid Dynamics Analysis (CFD), Finite Element Analysis (FEA), and feature based manufacturability evaluation. The model makes use of multiple STEP Application Protocols (AP203, 209, 214, 224) and integrated resources from different parts of STEP. Extensions beyond STEP were necessary for CFD analysis, parametric geometry and constraints. The latter were imported from the ENGEN* Data Model and a new STEP-compliant model was created for CFD. The consolidated data model used for a prototype is presented in this paper.
Virtual Reality Sculpture Using Free-Form Surface Deformation
Authors: Furlong Todd J.
Published: February 2021

Free-form deformation allows a user to deform surfaces in an intuitive manner that has been compared to sculpting clay (Sederberg and Parry, 1986). This research investigates the use of this deformation technique to create virtual sculpture in the Iowa State University C2, a CAVE™-like apparatus. Emphasis is on intuitive and direct interaction with a surface in order to mold it into whatever shape the user has in mind. An icon-based menu is provided for changing modes of interaction, and a 3D paint tool allows users to add color to their models. Possible applications of this research include virtual art and conceptual or industrial design.
A Constraint Satisfaction Approach for Multi-Attribute Design Optimization Problems
Authors: D’Ambrosio Joseph , Darr Timothy , Birmingham William
Published: February 2021

In this paper, we describe a multi-attribute domain CSP approach for solving a class of discrete, constrained, optimization problems. The multi-attribute domain CSP formulation provides a compact representation for design problems characterized by multiple, conflicting attributes. Design trade-off information is represented by a multi-attribute value function. Necessary conditions for an optimal solution, defined in terms of the value function, are represented as constraints. This provides a uniform problem-solving approach (constraint satisfaction) for identifying solutions that are both feasible and of high value. We present and characterize a consistency algorithm for this type of CSP.
QFD Models for Research and Development of Future Car
Authors: Tsuda Yasuhisa
Published: February 2021

In succession to Tsuda (1995) in which 2 QFD models were proposed for Concurrent Engineering (CE) development of a complicated product such as an automobile, this report treats a study of QFD models for research and development of a future car. First it is discussed, how to approach a future car concept. As customers can not forecast the future, the market quality requirements do not exist which were the very starting point of the 2 QFD models proposed in Tsuda (1995). Instead, experts must find future quality requirements, which then need to be accepted by customers, together with their backgrounds. These circumstances are considered for modification of the 2 QFD models proposed in Tsuda (1995) into new QFD models. These models will then be compared with a research and development case of a future car which was pushed forward on the same basic concept as these models. This real case aimed at the research of both a future car and the methodology of its research and development. It included not only planning and development of a future car, but also customer researches using this concept car. As a result the 2 new QFD models are proven valid for the research and development of a future car.
Robust Tracking for Uncertain Flexible Structures Using Mixed Time-Optimal and Sliding Mode Control
Authors: Jalili Nader , Olgac Nejat
Published: February 2021

An improvement step in robust control is studied for uncertain (linear or nonlinear) systems. The proposed two-stage control scheme first modifies the original desired trajectory, and then imposes robustness against uncertainties in tracking this modified trajectory. For the trajectory modification stage, a simple scheme is considered : time optimal-rigid body motion (TO). The robustness stage is performed using Sliding Mode Control with Perturbation Estimation (SMCPE), an advanced form of SMC. This routine brings some strong features as demonstrated by examples. A rotating hub with flexible beam attachment is taken as the first example, and an undercontrolled two-mass system with a linear spring as the second. The comparative studies show superior results for the combination of TO-SMCPE over the basic SMCPE. Moreover, this two-stage control exhibits stable and highly advantages performance even for cases where H∞-type of robust control structure is declared unstable by earlier investigations.
Unified Approach of Active Panel Vibration and Flutter Controls Using Piezoelectric Actuation and Iterative Root Locus Method
Authors: Ho Ming T. , Chen Roger R. , Chu Li C.
Published: February 2021

Panel forced-vibration and panel flutter are controlled by using piezoelectric actuation and iterative root locus design method. Although forced-vibration and flutter are essentially two different physical phenomena, their limit-cycle behaviors can both be modeled by a non-linear stiffness driven either by a forcing input or by an aerodynamic load. A nonlinear finite element dynamic model which incorporates these two driving terms has been developed for an aluminum panel with one-sided surface-mounted piezoelectric actuators. The first-order piston theory type relation is used to provide an adequate representation of the supersonic aerodynamic load. Surface strains and their associated strain-rates at various pre-determined locations on the panel are the system outputs for feedback. Input and output filters are used in the control loop in order to avoid aliasing and to minimize effects of noise on unmodeled high frequency modes. The importance of including the filters in the model is also demonstrated. The root locus design method is used iteratively to search for the local optimal output feedback gains either to increase modal damping for the forced-vibration case or to increase critical dynamic pressure for the flutter case. Although the control design is linear, it is shown to work adequately for the numerical simulations using non-linear system model. An experiment is performed to verify the forced-vibration results which serves as an inexpensive way of checking and/or modifying the panel flutter control design before a very expensive wind tunnel testing is arranged.
Spatial Characteristics of Acoustic Boundary Control for Interior Noise Suppression
Authors: Hirsch S. M. , Sun J. Q.
Published: February 2021

Suppressing interior sound radiation in aircraft and automobiles is a important problem. There are two mainstream methods for this problem: active noise cancellation (ANC) and active structural acoustic controls (ASAC). An ANC system often requires a high dimensionality to achieve the level of global noise reduction in a three dimensional volume that ASAC systems with a relatively low dimensionality are capable of, while actuators for structural control systems are power intensive. There are also concerns that structural controls may cause damages to the structure. This paper develops an acoustic boundary actuation method that may retain the advantages of both methods. Steady-state optimal noise control in a rectangular enclosure is studied by using the proposed method. Simulation results are presented to demonstrate the ability of acoustic boundary controls to cancel noise fields due to various sources. A study of the spatial characteristics of the acoustic boundary control as a function of frequency and relative phase of disturbances is also presented. Numerical simulations uncover an interesting phenomenon on the variation of the optimal control vector which may have significant implications to the actuator grouping studies.
Adaptive Noise Cancellation in an Acoustic Duct
Authors: Ben-Amara Foued , Kabamba Pierre T. , Ulsoy A. Galip
Published: February 2021

The problem of adaptive noise cancellation in an acoustic duct is discussed. An adaptive controller design approach based on parametrizing the set of stabilizing controllers using the Youla parametrization and tuning the Youla parameter to achieve regulation is presented. Three controller adaptation algorithms are implemented to solve the noise cancellation problem in an acoustic duct. The experimental results indicate a mixed performance for each of the adaptation algorithms, with good performances observed only in some frequency ranges. The discrepancy between the expected and the observed performances is attributed to unmodeled nonlinearities in the speakers.
Vibration Reduction and Isolation by On-Off Control of Friction Force at Spring Support
Authors: Yamaguchi Hideya , Yashima Masahito , Hirayama Yoshinori
Published: February 2021

This paper presents a new method of on-off control for the spring support to reduce and isolate vibration transmitted to machines or structures. The procedure utilizes the auxiliary spring whose end is designed to control the clamping friction force with the brake mechanism. The clamping friction force is varied according to the switching law that is deduced from the variable structure systems (VSS) control theory taking into account the energy dissipation due to friction. The experiments and numerical simulations confirmed the effectiveness of the proposed method by investigating the transient response and the displacement transmissibility.
Application of Dynamic Vibration Absorbers to Mass Measurement
Authors: Mizuno Takeshi
Published: February 2021

A mass measurement system which uses a dynamic vibration absorber as measuring device is developed. It can measure mass even under weightless conditions like in space stations. In this system, an object to be measured is fixed to a rotating table (rotor) at a distance from the rotational axis. Since it makes the rotor unbalanced, a centrifugal force causes the supporting structure to vibrate during rotation. A dynamic vibration absorber attached to the structure is tuned or controlled to cancel the excitation force. When the structure does not vibrate, the amplitude of motion of the auxiliary mass equals the ratio of the amount of unbalance to the auxiliary mass. Therefore, the mass of the object is determined from the motion of the auxiliary mass. According to the measurement principles, the vibration of the supporting structure must be eliminated. A servocompensator with the performance of automatic frequency tracking is applied to reduce the vibration. Experimental results demonstrate that mass can be measured accurately with the developed measurement system.
Modeling and Feedback Control of Flexible Plate With Focus on the Modes Highly Coupled to Radiation Field
Authors: Ren Mingzhang , Seto Kazuto , Doi Fumio
Published: February 2021

A discretization method based on an inverse modal analysis process is presented for creating a lumped parameter model for actual structure. With the discrete system the standard optimal control law can be formulated in physical state space to design a controller. Furthermore, the method makes it easy to target the vibration modes with prominent sound radiation in control design, that is a simplified consideration of active structural acoustics control. The method is demonstrated and verified by vibration and noise control experiments of a clamped plate. Four highly radiating modes among the first twelve modes of the plate are well controlled by using three sensors and one actuator, based on a 9DOF lumped model of the plate.
High Performance Damping With a Semi-Active Spring
Authors: Bobrow James E.
Published: February 2021

In this paper an approach to vibration suppression is presented that does not use any form of viscous damper. That is, the force generated by the actuator has no velocity dependence. We give three different hardware configurations for an actuator that behaves effectively as a spring with an adjustable unstressed length. By adjusting this unstressed length on-line from feedback, it is possible to obtain fast settling times and superior shock isolation characteristics. At the instants when energy in the actuator is maximized, we discard this energy as heat in the working fluid by opening a low power solenoid valve for a short time interval. This sets the unstressed length of the actuator, or effective spring, to be zero. The total energy in the vibrating structure is therefore decreased at these instants of unstressed length adjustment. Analytical results and simulations are given that demonstrate the performance of our approach.
Actuator Selection for Vibration Control With Control Energy Constraints
Authors: Doki Hitoshi , Hiramoto Kazuhiko , Kaido Jun , Skelton Robert E.
Published: February 2021

This paper deals with a sensor/actuator placement problem in design of active vibration control systems for flexible structures. This problem is formulated as a minimization problem of the total energy which is defined as a sum of a kinetic and strain energy in a controlled structure with a constraint of control effort. The inequality constraint on the variance of the closed-loop control effort is adopted to represent the capacity (dynamic range) of the actuator. Using a design algorithm which iteratively tunes the weighting matrix of the quadratic performance index in the LQG problem, the controller which meets these specifications can be synthesized. The optimal location of the sensor/actuator is determined by calculating the total energy for each candidate under several energy constraints of the control effort. The optimal placement of the sensor/actuator depends on the control energy constraint. Simulations and experiments for a cantilevered beam are conducted. These results of the optimization can be used as a guide to the design of active vibration control system.
Phase Space Interpretation and Stability Analysis of a Self Excited, Friction Damped Turbine Airfoil
Authors: Pesheck E. , Pierre C.
Published: February 2021

The free response motion of a self excited, friction damped, single-degree of freedom, turbine airfoil model is determined utilizing both exact and asymptotic methods. A three-dimensional phase space representation is used to examine the system’s global stability, and to further intuitive understanding of the system dynamics. Conclusions are reached regarding the validity and application of stability predictions through comparison of approximate and exact solutions.
Micro-Scale Simulation of Adhesive Effects During Normal Impact
Authors: Streator Jeffrey L.
Published: February 2021

A numerical simulation is developed to investigate the role of adhesive forces during the normal impact of a rigid body against an elastic surface. The model consists of a rigid, 2D translating body and a surface that is composed of a flexible linear array of particles, coupled to a fixed base via linear springs. Adhesive effects are incorporated in the model by ascribing a Lennard-Jones type interaction potential between the surface and the body. Dynamical equations of motion for the interface are integrated numerically during an impact event. It is found that the coefficient of restitution decreases with increasing interaction strength and decreasing approach velocity. Above a certain interaction strength for given velocity and below a certain velocity for given interaction strength, the body is found not to rebound, but sticks to the surface. The simulation results are found to be in qualitative agreement with the impact model of Dahneke (1973, 1975). Quantitative discrepancies are explained by the effects of surface “plucking.”
The Surface Variational Principle: A Different Perspective for Structural Acoustic Modeling
Authors: Ginsberg J. H.
Published: February 2021

This paper surveys the development and application of the surface variational principle (SVP) governing the acoustic interaction between surface pressure and normal velocity. SVP is analogous to the method of assumed modes for vibration analysis, in that it represents the response in terms of a sequence of basis functions that are globally defined. The system equations governing the series coefficients are obtained by requiring that the value of the variational functional be stationary. In the wavenumber-based version of SVP, the pressure and velocity are represented by dual range Fourier series. A brief description of the steps entailed in formulating the SVP equations and coupling them to the equations for an elastic structure is provided. Then the computational requirements of an SVP analysis relative to conventional boundary element and finite element techniques are discussed. This is followed by an example illustrating the convergence properties of SVP. Another example is used to highlight the physical interpretation of the SVP representation of surface response. The evolution of the present version of SVP is surveyed, along with some of its applications. The paper closes with a brief discussion of possible future applications of the method.
Dynamic Responses of a Cylindrical Shell Subjected to Shock Wave Induced by Underwater Explosion
Authors: Weifang Zhong , Zhongzu Liu
Published: February 2021

The dynamic responses of a finite length cylindrical shell submerged in an infinite, inviscid, irrotational, incompressible fluid and subjected to shock waves induced to underwater explosion due to a spherical charge, are investigated in the view of method of modal superposition. Effects of shock wave pressure and hydrodynamic force are considered in shell equilibrium equations. By expanding distribution function of shock wave pressure into Fourier series and using method of Galerkin, the coupled equations of fluid-structure interaction problem are solved numerically. Finally, displacement re sponse of the shell is obtained.
Mode Localization and Delocalization in Constrained Strings and Beams
Authors: Riedel Chris H. , Tan Chin An
Published: February 2021

The free vibration response of a string and a Euler-Bernoulli beam supported by intermediate elastic constraints is studied and analyzed by the transfer function method. The constrained system consists of three subsystems coupled by constraints imposed at the subsystem interfaces. For both the string and beam systems, curve veering and mode localization are observed in the lower modes when the distance between the elastic constraints is varied. As the mode number increases, the modes of the system become extended indicating that the coupling springs have little effect on the system at higher modes. A wave analysis is employed to further investigate the behavior of the systems at high frequencies. Reflection and transmission coefficients are formulated to show the effects of the constraints on the coupling of the subsystems. The weakly bi-coupled beam produces an interesting phenomena where a particular mode experiences no localization while neighboring modes are localized. The frequency at which this occurs is termed the delocalization frequency. Only one delocalization frequency exists and it occurs where the reflection coefficient of the propagating wave becomes zero.
Interpreting Proper Orthogonal Modes in Vibrations
Authors: Feeny B. F.
Published: February 2021

We investigate the interpretation of proper orthogonal modes (POMs) of displacements in both linear and nonlinear vibrations. The POMs in undamped linear symmetric systems can represent linear natural modes if the mass distribution is known. This is appoximately true in a distributed system if it is discretized uniformly. If a single mode dominates, the dominant POM approximates the dominant mode. This is also true if a distributed system is discretized arbitrarily. Generally, the POMs represent the principal axes of inertia of the data in the coordinate space. For synchronous nonlinear normal modes, the dominant POM represents a best fit of the nonlinear modal curve. Linear and nonlinear simulation examples are presented.
Nonlinear Localization in Systems of Tautochronic Vibration Absorbers
Authors: Chao Chang-Po , Shaw Steven W.
Published: February 2021

The system considered consists of a rigid rotor and N centrifugal pendulum vibration absorbers (CPVAs) riding on epicycloidal paths tuned to order n, the same as the dominant order of the applied torque. An investigation is carried out to determine the effects that a dynamic instability of the synchronous motion of CPVAs has on the system performance. Using various co-ordinate transformations, including a group-theory-based transformation and an angular transformation, the system dynamics are modeled by a set of 2N first-order, averaged, autonomous differential equations. A bifurcation analysis of these equations shows that in the post-bifurcation dynamic, one of the N absorbers moves out of step and at a much larger amplitude than its partners. This localized response is dynamically stable and leads to the worst-case (that is, the smallest) operating torque range of all the possible post-critical steady-state solutions. Analytical estimates of the torque range and the rotor acceleration are derived based on a truncated version of the equations, and more accurate estimates are obtained from a numerical solution of the non-truncated equations. The results are found to be very accurate when compared to numerical simulations.
Stabilization of Inverted Coupled Pendula Using Parametric Excitation
Authors: Osada Reiko , Sato Chikara
Published: February 2021

Parametric stabilization of a single inverted pendulum has been extensively studied using the Mathieu equation and its corresponding stability diagram. The inverted single pendulum may be stabilized using parametric excitation at a specified frequency and amplitude given by a narrow stable region in the Mathieu diagram.

Coupled pendula with parametric excitation or corresponding resonant systems have been studied from mathematical view point (Cesari, 1959; Gambill, 1955; Richards, 1983), from electrical view point (Sato, 1962a; Sato, 1962b; Sato, 1971; Sato, 1975) and from mechanical view point (Sato, 1995). Coupled pendula with parametric excitation have been studied within a limited region by some researchers, including the authors. A study of inverted coupled pendula with parametric excitation has not been performed as far as the authors know. Usually it is assumed that inverted coupled pendula are unstable in the absence of any other stabilizing mechanism such as feedback. One question is whether the inverted coupled pendula could be stabilized only by parametric excitation? The present paper gives an affirmative answer to this question in a limited and finite region. The stability is also examined using the differential equations and other methods.
Parameter Excitation Effects in Gear Dynamics
Authors: Nataraj C. , Whitman Alan M.
Published: February 2021

A pair of spur gears with involute teeth is considered. Nondimensional expressions are derived for the dynamic tooth loading. The resulting parametrically excited equations are analyzed by the procedures of asymptotic analysis. The results show that instability regions can occur leading to large vibrations and failure. These instability regimes are presented as a function of speed and other parameters. Minimum damping values to prevent the instabilities are derived as a function of the gear ratio and number of pinion teeth. In addition, given some inherent damping, response amplitudes of the transmission error are presented as a function of nondimensional parameters.
Robustness of Time-Varying Systems
Authors: Colonius Fritz , Kliemann Wolfgang
Published: February 2021

The dynamics of many mechanical systems can be described, or approximated by smooth vector fields in d-dimensional space Rd. External and internal excitations as well as modeling uncertainties are incorporated in the vector fields as families of (time-varying) functions, possibly with their own dynamics. The problem then is to study the response behavior of the system under the given uncertainty structure. In this paper we analyze the stability of uncertain systems at an equilibrium point, using the concept of stability radii. Roughly, a stability radius is the smallest excitation range such that a (time-varying) perturbation within this range can render the system unstable. Since we consider time-varying perturbations, the precise stability radius of the system is determined by the maximal Lyapunov exponent of the linearization at the equilibrium point. Several examples illustrate the theory and compare the precise stability radius to the one obtained via Lyapunov function techniques.
Natural Frequencies of Stator in Induction Motors
Authors: Suzuki Isao , Noda Shinichi , Itomi Kazunobu , Ishibashi Fuminori
Published: February 2021

Totally enclosed induction motors in which the stator core is pressed in the frame are in general used in industrial machines and manufactured with similar construction around the world. These motors produce a strong electromagnetic noise, which is caused by resonance between the natural frequencies of the stator core and the harmonics of electromagnetic forces. Therefore, it is very important to estimate its natural frequencies at the stage of design. As the first stage of research to estimate the natural frequencies of the stator core pressed into the motor frame, the dual rings were chosen as the object of studies. They are similar to the motor in construction and are easy to use to solve the problems. The purpose of this study is to investigate the effects of the tight fit to the natural frequencies and to find an analytical method by FEM. The authors have found that the introduction of spring elements with radial and circumferential spring constants at the contact surfaces provides accurate calculated results of the natural frequency by FEM. This paper describes about the spring constants obtained from experiments and analysis. As a result, when the spring constants in the radial direction are infinite and those in the circumferential direction are variable, it is clear that the spring constants for natural frequency analysis by FEM were expressed as a function of contact pressure on the contact surfaces. In the second stage, the measurement and calculation of natural frequency in the actual stator core with a frame was performed, and these results showed good agreement. These spring constants will be useful in FEM analysis of stator cores pressed into cylindrical induction motor frames.
A Study on Electro-Magnetic Auto-Balancing System and its Balancing Method
Authors: Wang Xixuan , Zeng Sheng
Published: February 2021

A new type of on-line automatic balancing system — the electromagnetic balancing system is concerned in this composition. The balancing head in this system consists of two stators and two slide plates. Each slide plate, on which there is a correction mass, can be driven to move relative to the shaft in single direction by the electromagnetic force. The positions of both masses are able to be detected conveniently by corresponding sensors. The balancing method is a conventional one. The moving procedure of the correction mass to meet the slide’s single -direction rotating character is described. Experiment results of its application to flexible rotor are also included.
Influence of Bearing Alignment on Vibration of Multi-Span Rotor
Authors: Hirano Toshio , Yamashita Tatsuo
Published: February 2021

This paper describes the influence of bearing alignment (vertical position) on vibration of multi-rotor-bearing system. The rotor-bearing system used in this study consists of three rotors and six bearings. It is designed to have the equivalent dynamic characteristics to the turbo-generator-systems for utility power generation plant. And it is equipped with alignment setting devices which can set the bearing alignment in vertical direction precisely without disassembling the test rig.

It was confirmed that bearing alignment affects the rotor vibration. Some critical speeds and their peak amplitudes change. When the bearing alignment changes, the load of the bearing changes and it affects oil film characteristics. The calculated results considering this agree with the test results. The effect of the bearing alignment on the rotor vibration becomes large when the bearing load is about zero.
Gyroscopic Effects of a Vibrationally Isolated Rotating Disk and Shaft
Authors: Margolis Donald L.
Published: February 2021

An aircraft engine is an example of a rotating machine whose rotating imbalance will be transmitted as vibrational energy into the structure to which it is attached. There is considerable interest in understanding this energy transmission in order to design mounting systems, both passive and active, which can control this transmission the best possible way in order to reduce structurally borne noise in the cabin. It is a well established fact in acoustics[1] that in order to reduce perceived sound at the listener, the noise transmission path must be severed by 1) eliminating the source of the disturbance (usually difficult if not impossible), 2) preventing propagation of energy into the structure and ultimately to structural surfaces, 3) preventing radiation of sound energy from vibrating surfaces, and 4) preventing radiated sound from reaching the listener. In this paper we address only the prevention of energy transmission from the source into the supporting structure through use of some type of mounting system.
Flexural Vibration of a Viscoelastic Sandwich Beam in its Plane of Lamination
Authors: Nayfeh Samir A. , Slocum Alexander H.
Published: February 2021

When a laminated sandwich beam consisting of alternating elastic and viscoelastic layers bends in the plane normal to its plane of lamination, the relatively compliant viscoelastic layers are sheared between the adjoining elastic layers and energy is dissipated. This mechanism, known as constrained-layer or shear damping, is a proven method for damping flexural vibration, but only in the plane normal to the plane of lamination. For vibration parallel to the plane of lamination, the elastic layers need not deflect together, and the viscoelastic layers are sheared when adjoining elastic layers undergo different deflections. This mechanism of damping is discussed herein.

In this paper, we study the vibration of a symmetrically laminated five-layer sandwich beam in its plane of lamination. Taking the viscoelastic material to have frequency-independent hysteretic damping, we derive a boundary-value problem governing steady harmonic motion of the sandwich beam and then obtain its discretized counterpart. For the particular case of a beam with simply supported elastic layers, we obtain the resonant frequencies and loss factors of the composite beam, and study their dependence on geometric and material properties.