bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Optimal Robot Manipulator Motion Planning for Solid Freeform Fabrication by Thermal Spraying
Authors: Rastegar J. , Qin Y. , Tu Q. 
Published: March 2021

Abstract
A novel approach to optimal robot manipulator motion planning for Solid Freeform Fabrication (SFF) by thermal spraying is presented. In this approach, given the desired spatial geometry of the object, the motion of the spray gun relative to a forming platform is synthesized for minimal masking requirements considering the probabilistic nature of the thermal spraying process. The material build-up rate can be planned to achieve the desired distribution of the physical/material properties within the object volume. Examples of optimal motion planning for the generation of some basic solid objects and computer simulation of the effectiveness of the developed methodology are presented.
Inverse Kinematics of Serial Redundant Manipulators With Locked Articulations
Authors: Perreault Louis , Gosselin Clément M. 
Published: March 2021

Abstract
This paper presents an algorithm for the solution of the inverse kinematics of a serial redundant manipulator with one (or more) locked joint(s). To this end, a general procedure is developed for the determination of the equivalent Denavit-Hartenberg parameters of a serial manipulator with locked joints. This procedure can be applied to any serial architecture. The solution of the inverse kinematic problem for the three cases which can arise is then addressed. An example of the application of the method to a SARCOS 7-DOF manipulator is also given.
An Algorithm for Enveloping Linear Structural Response With Application to Spacecraft Stress Analysis
Authors: Kunt Cengiz O. , Mignosa Lawrence J. , Pontius James T. 
Published: March 2021

Abstract
An algorithm and a computer program are developed for spacecraft structural analysis to determine the maximum linear static response (stress, deformation, etc.) and the corresponding “worst direction” of the loading. Compared to the brute force approach of repeating the structural analysis to cover all the possible orientations of the load vector, the proposed approach is faster, more accurate, and computationally more efficient. Maximum structural response determination is illustrated through a case study of stress analysis conducted for the TRMM (Tropical Rainfall Measuring Mission) payload developed by NASA Goddard Space Flight Center and NASDA (National Space Development Agency of Japan). The paper includes part of the structural analysis conducted in sizing the Upper Instrument Support Platform, which provides support for two of TRMM’s major instruments.
The Study of Design Theory and Methodology in Mechanical Engineering: A Commentary
Authors: Karandikar Harshavardhan , Shupe Jon 
Published: March 2021

Abstract
Our aim in this paper is to examine the study of design theory and methodology (DTM) in the field of mechanical engineering design and to assess its impact. Rather than review the work of a growing number of individual researchers essential research themes have been distilled by an analysis of the conference papers in the area and through a survey of the research and practicing community. On the basis of the survey some commonly understood goals and products of the DTM research community are identified. We seek to understand the extent to which the goals of the research community been met and whether the products have benefited the customers. To maintain continuity and some perspective this commentary builds upon past reviews.
Managing Risk by Reordering Tasks in Engineering Design
Authors: Smith Robert P. 
Published: March 2021

Abstract
This paper describes a model of how reordering tasks in the engineering design and development process affects resource usage in a risky environment. All development projects are risky; their outcome and level of success is unpredictable. Many projects are canceled at some time during the development process, or never produce a working product or produce a product that fails in the marketplace. Doing engineering development is expensive; it requires high-cost labor as well as other potentially expensive resources. To some extent the magnitude of the risk is estimable; it is possible to predict now much resources (time, labor or other costs) any particular development task will consume as well as some estimate of whether or not an insurmountable technical problem is likely to be discovered. Also, development tasks are not independent; there are constraints on their ordering due to needed technical knowledge. The model presented in this paper uses those estimates to suggest an ordering of the tasks in an attempt to minimize the expected resource consumption for those projects that run a risk of cancellation.
A Study on Heredity and Evolution of Designs Considering Kansei by Using Genetic Algorithms
Authors: Yamakawa Hiroshi , Arakawa Masao , Katsuyama Nobuyuki 
Published: March 2021

Abstract
A new concept on the heredity and evolution of designs was proposed and an optimum design method based on the concept was developed newly by one of the authors. Several kinds of needs for designs may exist and users of some products are not satisfied with the functions of the products but also with their sensuous beauties or impressions of shapes and materials. To consider such sensous quality of the products was called “Kansei designs” in Japan and have become of interest and important lately (Nagamachi, 1989). In this study we introduce the same concept on heredity and evolution of designs as in the previous reports shown in Fig.1 (Yamakawa, 1994) and present a general design method to consider the Kansei design into ordinary, design process by making use of both SD (Semantic Differential) and the Genetic Algorithms. In order to support designer’s impressions, we also consider to take for other features Kansei estimation, which is similar to the original feature and easier to take “Kansei”, into account and developed an interface system which can show the transition of feature during GA process. Front view designs of a car are taken as simple numerical examples and the effectiveness of the proposed method is examined.
Frank Whittle and the Jet Engine
Authors: Smith Charles O. 
Published: March 2021

Abstract
The inertia of society is so stubborn that no one will move against it, if he cannot believe that it can be more easily overcome than is actually the case. And no one will suffer the perils and pains involved in the process of radical social change, if he cannot believe in the possibility of a purer and fairer society than will ever be established. These illusions are dangerous because they justify fanaticism, but their abandonment is perilous because it inclines to inertia.
Application of DFA to Telecommunications Equipment: One of the Most Successful Cases in AT&T
Authors: Kim B. Sung , Stanfill Karen Owens , Carus Bryce W. 
Published: March 2021

Abstract
A new telecommunications power distribution frame was developed to reduce costs, meet new international market requirements and enhance performance. DFA was thoroughly applied and resulted in a dramatic customer price reduction, fewer parts, less assembly time, and a lower defect rate.
Coding and Classification of Geometric Models
Authors: Qamhiyah A. Z. , Benhabib B. , Venter R. D. 
Published: March 2021

Abstract
For the efficient manipulation of information in support of design and manufacturing one would need to access large active databases. In this context, it is envisioned that 3-D object models must be easily retrieved for modification, or for simply reviewing related information. This paper addresses the development of a classification system for the efficient retrieval of 3-D object CAD models. For the design of a new object the user would access the database to locate the most similar object model and, if worthwhile, modify it to attain a model for the new object under consideration.
The proposed classification procedure comprises three main stages: First, 3-D geometrical data, sufficient for classification, is determined and extracted from a selected model of the object, and a primary representation domain is determined. Contours, were selected as the basic descriptive units. Based on this selection, relationships defined by descriptor elements were established between (a) two solid contours; (b) a solid and a hollow contour; and, (c) two hollow contours. In order to facilitate the use of the descriptor elements, a simple alpha-numeric coding system was developed.
In the second stage, the description of the object is mapped from the geometrical domain into a numerical-factor domain, where each contour is represented by a numerical value.
In the final stage, a code is generated based on the factor-domain representation in the form of a Fourier signature. Classification is then carried out according to the similarity of the generated Fourier signatures.
Experimental Analysis of the Finite Dynamics of a Suspended Cable
Authors: Benedettini F. , Rega G. , Alaggio R. 
Published: March 2021

Abstract
An experimental model of clastic cable carrying eight concentrated masses and hanging at vertically moving supports is considered. The system parameters are adjusted to realize multiple 1:1 e 2:1 internal resonance conditions involving planar and nonplanar, symmetric and antisymmetric, modes. Systematic response measurements are made in a large frequency range including meaningful external resonance conditions. Frequency-response plots and overall behaviour charts in the control parameter space highlight rich picture of often coexisting planar and nonplanar regular responses, as well as the occurrence of regions of quasiperiodic and chaotic motions which are characterized both qualitatively and quantitatively.
An Extrapolation Method to Compute Far-Field Pressures From Near-Field Pressures Obtained by Finite Element Method
Authors: Assaad Jamal , Bruneel Christian , Rouvaen Jean-Michel , Bossut Régis 
Published: March 2021

Abstract
The finite element method is widely used for the modeling of piezoelectric transducers. With respect to the radiation loading, the fluid is meshed and terminated by an external nonreflecting surface. This reflecting surface can be made up with dipolar damping elements that absorb approximately the outgoing acoustic wave. In fact, with dipolar dampers the fluid mesh can be quite limited. This method can provides a direct computation of the near-field pressure inside the selected external boundary. This paper describes an original extrapolation method to compute far-field pressures from near-field pressures in the two-dimensional (2-D) case. In fact, using the 2-D Helmholtz equation and its solution obeying the Sommerfeld radiation condition, the far-field directivity pattern can be expressed in terms of the near-field directivity pattern. These developments are valid for any radiation problem in 2D. One test example is described which consists of a finite width planar source mounted in a rigid or a soft baffle. Experimental results concerning the far-field directivity pattern of lithium niobate bars (Y-cut) are also presented.
Frequency Window Implementation of Adaptive Multi-Level Substructuring
Authors: Bennighof Jeffrey K. , Kaplan Matthew F. 
Published: March 2021

Abstract
Adaptive multi-level substructuring (AMLS) is a method for reducing the order of models of complex structures by orders of magnitude, while ensuring that the accuracy available from the original finite element model is preserved. A structure’s finite element model is transformed to a much more efficient representation in terms of approximate vibration modes for substructures on multiple levels. An adaptive procedure constructs an optimal model for satisfying a user-specified error tolerance, by determining which modes should be included in the model. In this paper, a frequency window implementation of AMLS is developed, in which frequency response analysis can be done over a frequency window at little additional cost beyond that of the solution at the center frequency. A numerical example is presented.
Control of Structure-Borne Sound Using Periodically Varying Rigidity
Authors: Hawwa Muhammad A. , Nayfeh Ali H. 
Published: March 2021

Abstract
Subsonic modes may cause significant radiation when they scatter at a discontinuity. In this study, we suggest an approach to filter out subsonic waves before they reach the discontinuities on the structure. This is done by imposing a material (parametric) periodicity in a fluid-loaded structure, which leads to a strong stopband interaction under a Bragg condition. The interaction is analytically described by the coupled-mode equations, derived using the method of multiple scales. Numerical illustrations are given in terms of the transmission loss for different fluid-loaded plates. The results can be utilized to suppress the undesired acoustic radiation generated by fluid-loaded structures.
Windowed-Transform Processing of Acoustic Beam Scattering From Fluid-Immersed Elastic Structures
Authors: Zeroug Smaine , Felsen Leopold B. 
Published: March 2021

Abstract
Acoustic beam scattering from submerged bulk and layered elastic structures is of interest for applications ranging from determining material properties to locating and identifying interior defects. Nonspecular reflection, which occurs when the incident beam is phase matched to leaky waves (LW) supported by the structure, constitutes an effective sensor for such applications. Forward frequency domain modeling based on a robust asymptotic hybrid beam-LW algorithm [Zeroug and Felsen, 1992] has shown that the nonspecular data, which is established by interference between specular reflection and LWs, depends strongly on the collimation of the incident beam, the number and leakage strengths of the excited LWs, and the curvature of the insonified structure. The present contribution addresses the inverse problem of extracting this phenomenology via wave-oriented processing, which is implemented by subjecting the scattered field data to a Gaussian-windowed Fourier transform (GWT) along spatial tracks parallel to the fluid-structure interface. For the fluid-immersed elastic configurations of: 1) solid half-spaces, 2) plates, 3) solid cylinders, and 4) cylindrical shells, the GWT-generated local wavenumber phase-space distributions footprint the correct wave physics, but with resolutions that are limited by the configuration-spectrum tradeoff. Examples demonstrate how the resolution is influenced by the GWT window size. The paper also includes preliminary results on application of a Prony superresolution algorithm for extraction of LW phase velocities and leakage rates.
Acoustic Behavior of Near Periodic Elastic Structures
Authors: Photiadis Douglas M. 
Published: March 2021

Abstract
Near periodic arrays of discontinuities have been predicted to have a significant impact on the acoustic properties of elastic structures. The discontinuities in the elastic properties of the structure produce a characteristic signature in the acoustic scattering cross section of the structure via two distinct mechanisms; a direct interaction producing acoustic Bragg scattering, and an indirect interaction wherein the discontinuities fundamentally alter the free waves of the structure. The locally propagating states of the pseudo-periodic system are Floquet or Bloch wave packets and the locations of the highlights in the cross section may be determined simply from the Bloch wavenumber via a phase matching argument. Predicting the resulting scattering levels requires an understanding of the propagation of the Bloch wave packets in the finite, pseudo-periodic structure. In the case of a thin ribbed cylindrical shell or plate this scattering mechanism can arise from flexural waves, and recent experimental results obtained at Naval Research Laboratory have demonstrated the importance of both this mechanism and Bragg scattering on the acoustic far field over a broad frequency range. In this paper, these results and the underlying theoretical development will be discussed.
Free Acoustic Oscillations Inside a Triaxial Ellipsoid
Authors: Levitina Tatyana V. 
Published: March 2021

Abstract
If a Dirichlet or Neumann condition is imposed on the surface of the ellipsoid, the variables are separated in the scalar wave equation in ellipsoidal coordinates, and the problem in hand is reduced to a system of three identical ordinary differential equations, each being defined on a separate interval and subject to its own boundary conditions. Thus, the three-parameter self-adjoint Sturm-Liouville problem arises: the equations are coupled by two separation constants and the eigen frequency of the ellipsoid, i. e., the spectral parameters, which must be so chosen that all the equations of the system have simultaneously nontrivial solutions, each satisfying the corresponding boundary conditions. The effective globally converging numerical algorithm is proposed for calculating eigen frequencies and separation constants. When the modes of an ellipsoid are found, the caustic surfaces can be easily determined. The merit of the method is illustrated on the example of several calculations of the sound field and caustic surfaces in an ellipsoid.
Selling, Designing, and Producing Products That Sound Good
Authors: Lyon Richard H. 
Published: March 2021

Abstract
“Sound Quality” has become a product feature that is becoming more important to customers and companies. Although the precise meaning of the term can vary, companies must respond when customers react to products that sound better. The purpose of this paper is to discuss some of the marketing and design issues involved in product sound, some tools that are available to determine what Sound Quality (SQ) is for any particular product, and how engineering design can be brought to bear on this product attribute. The author’s view is that SQ is amenable to good and rational procedures, just like the other methods used in product planning and engineering design.
The Method of Structure Dynamic Modification With Tested Modal Parameters: FEM Full Mode
Authors: Chen Shiyu , Dimentberg M. F. , Noori M. , Hou Zhikun , Wang Fengquan 
Published: March 2021

Abstract
This paper offers a new method for Structure Dynamic Modification, it is called the Modal Parameters–FEM Full Mode Method. With the FEM of the structure and the tested modal parameters, the rotational displacement information and the full mode can be got by full mode computation. After structure modification, the dynamic character of the modified structure can be calculated with the full mode.
Critical Speeds Resulting From Unbalance Excitation of Backward Whirl Modes
Authors: Greenhill Lyn M. , Cornejo Guillermo A. 
Published: March 2021

Abstract
Most rotordynamic analyses typically ignore the potential for critical speeds to be created by traversing a backward precessional whirl mode. While not commonly recognized, a backward mode can be excited using unbalance as the driving force. Based on the analysis of a Jeffcott rotor-bearing model, it was found that the condition for this response to occur is strongly dependent on stiffness asymmetry in the rotordynamic coefficients at the supports. To illustrate the application of this result, a rotordynamic analysis on actual hardware is presented, in which the unbalance excited backward mode resonance is calculated to occur. Test data is also given indicating the presence of the predicted critical speed. It is important to note that although the resonance is due to the backward mode, the precessional direction is forward. Several recommendations are offered with respect to rotor-bearing design so that this unique critical speed situation may be avoided.
A Numerical Method for the Dynamic Analysis of Rotating Flexible Blade-Disc-Shaft Assemblies
Authors: Jacquet-Richardet Georges , Ferraris Guy , Rieutord Pierre 
Published: March 2021

Abstract
A numerical method is proposed to compute the natural frequencies and mode shapes of rotating flexible blade-disc-shaft assemblies The formulation is based on a modal finite element analysis of the rotating system. The mode shapes used for the modal reduction are those associated to the global non-rotating undamped structure. To compute these modes, the size of the problem is reduced using both wave propagation and component mode techniques. An application is presented. The results obtained show that the chosen reductions do not reduce the quality of the model and illustrate its capability to deal with rotating shafts usually calculated using the rotordynamic approach. Finally, the possible dynamic interactions between shaft and disc components are described.
Modal Balancing of Quasi-Rigid Jet Engine Rotors With Exchangeable Rotor Modules
Authors: Schneider Hatto 
Published: March 2021

Abstract
Flexible rotor assemblies often consist of two or more rotor modules which are index-balanced against each other with the purpose of eliminating the need for re-balancing if a module should have to be exchanged. However, the index procedure may cause vibration problems because it ignores certain flexible rotor balancing requirements. This paper describes a modal balancing approach based on jet engine rotors which are typically balanced as ISO Class 2 (quasi-rigid) rotors. Appreciation is expressed to Prof. R. Gasch of TU Berlin for his valuable suggestions.
H2 Optimal Tuning of Passive Isolators and Absorbers
Authors: Van Pelt Tobin H. , Bernstein Dennis S. 
Published: March 2021

Abstract
Isolators and absorbers have been studied extensively as a means of passively suppressing vibration in mechanical systems. This paper derives the optimal tuning parameters for these passive suppression schemes with an H2 performance criterion. The H2 norm of a system is briefly reviewed, and its selection as a performance criterion is motivated. The optimal tuning scheme in the case of the absorber is then compared to the classical work of Den Hartog [1] and Snowdon [2]. The comparison shows little improvement in the H2 cost over the classical scheme, which suggests that the approximately optimal H∞ analysis of the absorber respects the optimal H2 cost. However, the reverse is generally not true, as in the case with increasing absorber masses.
Active Boundary Control of Elastic Cables
Authors: Baicu Catalin F. , Rahn Christopher D. 
Published: March 2021

Abstract
Cables are lightweight structural elements used in a variety of engineering applications. This paper introduces an active boundary control approach that damps undesirable vibrations in a cable. Using Hamilton’s principle, the governing nonlinear partial differential equations for an elastic cable are derived, including the natural boundary conditions associated with boundary force control. Based on Lyapunov theory, passive and active vibration controllers are developed. A Galerkin approach generates the linearized, closed loop, modal dynamics equations for out-of-plane vibration. Simulations demonstrate the improved damping provided by the passive and active controllers.
Optimum Structural Vibration Control With Bounds on Control Forces
Authors: Bolonkin Alexander A. , Veley Duane E. , Khot Narendra S. 
Published: March 2021

Abstract
This paper describes an approach for designing a structure-control system based on the linear quadratic regulator (LQR) which suppresses vibrations in structures. Bounds are placed on the control forces to simulate real actuators. The control system is optimized with an objective function of the total weight of the control devices. The design variables are the bounds (which are proportional to the weight of the control devices) on each control force with a constraint on the time to reduce the energy of the vibration to 5% of its initial value. As an example to illustrate the application of an approach, a wing box idealized by rod elements is used. Control systems are designed for this structure using four and eight actuators for several locations.