bluuebunny/crossref_metadata_2025 huggingface dataset:
Collaborative Optimization of Systems Involving Discrete Design at the Discipline Level
Authors: Balling Richard J. , Gale Dallas L.
Published: February 2021

The multidisciplinary design optimization technique known as collaborative optimization is extended to multidisciplinary systems in which disciplines employ discrete search strategies. A particular test case is examined in which discrete disciplinary design is accomplished via exhaustive search. Even though non-gradient-based search strategies are used for disciplinary design, a procedure is developed in which gradient-based nonlinear programming algorithms can be used at the system level to coordinate the work of the disciplines.
Dynamic Force Analysis of the Carpal Wrist
Authors: Canfield Stephen L. , Soper R. Randall , Reinholtz Charles F.
Published: February 2021

The Carpal Wrist is a novel, parallel-architecture device that exhibits many features desirable in a robotic wrist. Previous static analysis has verified the large, singularity-free workspace and the excellent force-bearing ability of the Carpal Wrist. Here, the parallel structure is shown to be particularly advantageous when considered dynamically due to its lightweight structure and multiple load bearing members. The dynamic equations of motion are derived in closed form by direct application of Lagrange’s equations to the kinematic model. The model assumes a relatively massive tool and includes all gravitational, inertial, and gyroscopic effects. The equations of motion provide closed-form evaluation of the actuation moments based on general tool trajectories.
Optimal Fuel Cell System Design Considering Functional Performance and Production Costs
Authors: Xue Deyi , Dong Zuomin
Published: February 2021

In this work the optimization-based, integrated concurrent design method is extended to a general mechanical system — the transportation fuel cell system. A general optimal design model considering both functional performance and production costs is first introduced. Mathematical models of the functional performance and production costs of the Ballard fuel cell system are then discussed. A joint performance and cost optimization is carried out using the Ballard fuel cell system to demonstrate the approach. The optimization concurrently takes into account of two functional performance aspects and production costs to identify the optimal values of two key design variables. The work is a continuation of the authors’ earlier research on integrated concurrent engineering design.
The Problem of Size in Robust Design
Authors: Koch Patrick N. , Allen Janet K. , Mistree Farrokh , Mavris Dimitri
Published: February 2021

To facilitate the effective solution of multidisciplinary, multiobjective complex design problems, a departure from the traditional parametric design analysis and single objective optimization approaches is necessary in the preliminary stages of design. A necessary tradeoff becomes one of efficiency vs. accuracy as approximate models are sought to allow fast analysis and effective exploration of a preliminary design space. In this paper we apply a general robust design approach for efficient and comprehensive preliminary design to a large complex system: a high speed civil transport (HSCT) aircraft. Specifically, we investigate the HSCT wing configuration design, incorporating life cycle economic uncertainties to identify economically robust solutions. The approach is built on the foundation of statistical experimentation and modeling techniques and robust design principles, and is specialized through incorporation of the compromise Decision Support Problem for multiobjective design. For large problems however, as in the HSCT example, this robust design approach developed for efficient and comprehensive design breaks down with the problem of size — combinatorial explosion in experimentation and model building with number of variables — and both efficiency and accuracy are sacrificed. Our focus in this paper is on identifying and discussing the implications and open issues associated with the problem of size for the preliminary design of large complex systems.
Analysis of the Transmission Error of Face-Gear Drives
Authors: Chung S. D. , Chang S. H. , Lu S. S.
Published: February 2021

Based on the face-gear generation process, the analytical geometry of face-gear drive with its mathematical model for tooth contact analysis of face-gear and spur pinion meshing was derived. In this paper, contact path and transmission error due to assembly misalignment were analyzed by using the proposed mathematical model and the tooth contact analysis. The effect of assembly error along the axis of face-gear, misalignment of crossed and angular displacement between axes of spur pinion and face-gear were all investigated. The results are illustrated by several examples.
The Creation of Assembly Geometry From Functional Definitions
Authors: Brady Doug , Juster Neal P.
Published: February 2021

Modern CAD systems are able to represent the geometry of engineering components proficiently. This aids the later stages of the design process but does not help during conceptual design. This paper outlines a suite of programs known as the Conceptual Assembly Design Tool which allows designers to create outline assembly geometry from function structures, thus providing a potential bridge between conceptual and embodiment design. The paper includes a case study showing how the system may be used during the resign of a moderately complex product.
A Constraint-Based Algorithm for Reasoning About the Shape Producing Capabilities of Cutting Tools in Machined Parts
Authors: Gaines Daniel M. , Hayes Caroline C.
Published: February 2021

The tools and processes available in a given shop greatly influence the way in which manufacturers view a part and the way in which they decompose it into manufacturable volumes (features). It would be very useful to manufacturers to have an automated process planning assistant that would allow them 1) to specify their own, possibly special purpose, and 2) show them the impact that adding those tools will have on the way in which the part can be decomposed into features and on the manufacturing methods that can be used in the process plan. In this paper, we present 1) Tool-Editor, which allows users to enter their own tool shapes in a specification derived from the National Institute of Standards and Technologies’ specification for manufacturing resources; and 2) Tool-Mapper, a method for identifying the regions of the part that each tool can produce and generating a method which describes how the tools can make the identified shapes. If the first stage of traditional process planning can be viewed as translating features into processes, then Tool-Mapper can be viewed as the reverse process in which tools are translated into shapes. The benefit offered by tool-mapping is that it provides a mechanism for allowing users to input tools specific to their shop, without requiring them to reprogram the system, or to perform more knowledge acquisition to determine the impact of changing the tools.
Admissible Tool Orientation Control of 5-Axis Complex Surface Machining for CAD/CAM Systems
Authors: Lee Yuan-Shin
Published: February 2021

This paper presents a methodology and algorithms of admissible tool orientation control for gouging avoidance in 5-axis machining. A method is proposed to find the admissible tool orientation by considering both local and global surface shapes. A filleted endmill is used in this study for 5-axis machining. Based on the evaluation of local surface shape, a geometry analysis method is developed to first find a feasible tool orientation for gouging avoidance along two orthogonal cutting planes. Adjacent geometry is then taken into consideration for detecting possible rear gouging. A localization algorithm is developed for filleted endmills to identify potential rear gouging area. Both the circular approximation and the detailed gouging checking methods are proposed for rear gouging correction. The techniques presented in this paper can be used to eliminate errors of tool paths as they are generated. Unlike the traditional graphical verification and user-interactive correction of tool path generation, the proposed methodology can be used to automate the planning and programming of cutter path generation for 5-axis machining.
Concurrent Decomposition for Sheet-Metal Products
Authors: Wang Cheng-Hua , Bourne David A.
Published: February 2021

During the product development stage, designers often face the task of partitioning a product into functioning parts. Unfortunately, most decomposition decisions are made based on product functionality while the product manufacturability is usually ignored. As a result, the resulting parts can be too expensive to manufacture or sometimes impossible to make.

In this paper, we present a systematic approach to help designers decompose sheet-metal products. This approach is primarily driven by product manufacturability. It takes into account the manufacturability of sheet metal cutting, bending and assembly processes, while trying to minimize the number of parts. To overcome the combinatorial nature of the decomposition problem, a develop-first-decompose-later strategy is used. The decomposition goes back and forth between the design and decomposition modules to achieve sub-optimal results. The decomposition results are sent to the corresponding process planners and a complete production plan is produced.

A prototype system has been developed to demonstrate the proposed approach. Several decomposition examples are also presented.
Process Planner’s Assistant: An Interactive and Iterative Approach to Automating Process Planning
Authors: Li Xiaomin , Kambhampati Subbarao , Hirode Kartheek , Shah Jami
Published: February 2021

Most existing approaches to computer aided process planning aim for full automation by searching for a plan that is optimal with respect to a pre-specified objective function. Such full automation is often infeasible in practice for three reasons: (i) the search space of potential plans is huge, (ii) optimality metrics are often context sensitive and can only be elicited through user interaction, (iii) because of the importance of process planning, organizations are more interested in process planning assistants that support human expert process planners rather than standalone process planners.

In this paper, we present a “process planner’s assistant”, which helps the human process planning experts in coming up with process plans. In order to achieve this, the process planner’s assistant must have access to the full search space of process plans, and the ability to modify plans in response to human criticism. The former is provided by basing our system on ASU Features Testbed, a comprehensive and systematic framework for recognizing and reasoning with features in machinable parts. To support the latter, the system is equipped with an incremental and interactive search mechanism. We will discuss the operational details of the resultant system, called ASUPPA.
The Process Capability Matrix: A Tool for Manufacturing Variation Analysis at the Systems Level
Authors: Frey Daniel D. , Otto Kevin N.
Published: February 2021

This paper introduces the concept of a process capability matrix — an ordered set of dimensionless parameters that capture information on a manufacturing system’s response to noises. The matrix captures information on the magnitude of noise, sensitivity to noise, and tolerance to variation. Algorithms and equations are presented that use the matrix to compute the yield of a manufacturing system. The method proves to be accurate on real engineering problems for which existing techniques are inadequate due to statistical correlation among product acceptance criteria. The process capability matrix also proves useful in a new type of block diagram of production systems. The block diagrams are shown to be useful in evaluating the effectiveness of feedforward control strategies for variation reduction. An electronics assembly process serves as an example of the algorithms and their use in design decision making.
A Case Study in Multi-Disciplinary Distributed Collaborative Design
Authors: Riesenfeld Richard , Fish Russell , Drake Samuel
Published: February 2021

Researchers at the University of North Carolina at Chapel Hill and the University of Utah participated in a collaborative, remote, rapid design and manufacturing experiment. Several domain experts at widely distributed geographical locations worked on a challenging multi-disciplinary design problem producing a rugged, compact and light-weight housing for a Video See-Through Head-Mounted Display to be used in image-guided surgical procedures. This was used as a case study to validate and motivate ongoing research in a distributed engineering design and manufacturing system.

The hypothesis was that Net-based use of a highly supportive integrated, collaborative design and manufacturing environment would dramatically expedite the design and manufacturing process. Using the already existing Alpha_1 design and manufacturing environment as a platform, we embarked on a project to collapse the normal six-month cycle of design and prototype iterations into a single three-week period of collaborative design. The lessons learned demonstrate the potential success of the hypothesis, and also provide a basis for further research into tools and environments needed to support integrated collaborative design, engineering, and manufacture.

We discuss the results of the experiment, application of the existing distributed design system, the supporting system architecture, and possible future research issues brought to light by the experiment.
Constraint-Based Reverse Engineering From Ultrasound Cross-Sections
Authors: Menon Jai , Desai Ranjit , Buckey Jay
Published: February 2021

This paper extends the “cross-sectional” approach for reverse engineering, used abundantly in biomedical applications, to the mechanical domain. We propose a combination of “projective” and cross-sectional algorithms for handling physical artifacts with complex topology and geometry. In addition, the paper introduces the concept of constraint-based reverse engineering, where the constraint parameters could include one or more of the following: time, storage (memory, disk-space), network bandwidth, Quality of Service (output-resolution), and so forth.

We describe a specific reverse-engineering application which uses ultrasound (tilt-echo) imaging to reverse engineer spatial enumeration (volume) representations from cross-sectional data. The constraint here is time, and we summarize how our implementation can satisfy real-time reconstruction for distribution of the volume data on the internet. We present results that show volume representations computed from static objects. Since the algorithms are tuned to satisfy time constraints, this method is extendable to reverse engineer temporally-varying (elastic) objects. The current reverse engineering processing time is constrained by the data-acquisition (tilt-echo imaging) process, and the entire reverse engineering pipeline has been optimized to compute incremental volume representations in the order of 3 seconds on a network of four processors.
Tactile Display for a Surface Texture Sensation
Authors: Ikei Yasushi , Fukuda Shuichi
Published: February 2021

The authors have developed tactile displays which have vibrating pins to convey the surface texture sensation of object surfaces to the user’s fingertip. The tactile sensation intensity scaling was performed to obtain a sensation scale of the display by means of the JND (just noticeable difference) method. One dimensional curves on the scale were displayed to investigate the human sensitivity to an intensity change rate. A tactile texture presentation method based on the image of an object surface is introduced. Two kinds of experiment were performed to discuss the feature of the method. Texture discrimination is the first one, in which the effect of texture element size to the correct separation was discussed. Then the sensations produced by the display and those by real objects were compared regarding several samples that had a major feature of vertical lines and of not containing low frequencies. The results are summarized, which is followed by the future research work.
Perspective Browsing: An Approach to Concurrent Design Support System
Authors: Ito Teruaki , Fukuda Shuichi
Published: February 2021

An approach of perspective browsing to concurrent design support system is presented based on the methodology of browsing design using the concept of perspective and the data structure called hypergraph. Hypergraph (HG) presents the high functional navigation for browsing design. The perspective model (PERMO) implemented using HG represents designer’s views and is designed to manipulate them in browsing design.

An example of bicycle design for the aged people using a prototype of bicycle design support system shows how to conduct perspective browsing in browsing design and its simulation shows the validity of our approach to concurrent design support system.
Advanced Failure Modes and Effects Analysis Using Behavior Modeling
Authors: Eubanks Charles F. , Kmenta Steven , Ishii Kosuke
Published: February 2021

This paper presents a systematic method applicable at the early stages of design to enhance life-cycle quality of ownership: Advanced Failure Modes and Effect Analysis (AFMEA). The proposed method uses behavior modeling to simulate device operations and helps identify failure and customer dissatisfaction modes beyond component failures. The behavior model reasons about conditions that cause departures from normal operation and provides a framework for analyzing the consequences of failures. The paper shows how Advanced FMEA applies readily to the early stages of design and captures failure modes normally missed by conventional FMEA. The result is a systematic method capable of capturing a wider range of failure modes and effects early in the design cycle. An automatic ice maker from a domestic refrigerator serves as an illustrative example.
Automated Knowledge Acquisition in Proactive Design
Authors: Arciszewski Tomasz , Ardayfio David , Doulamis John
Published: February 2021

This paper discusses automated knowledge acquisition in the context of proactive design. It presents the results of a feasibility study conducted as a University-Industry collaboration involving the Chrysler Technology Center and George Mason University’s Laboratory for Machine Learning and Inference. The subject of the study was the acquisition of design knowledge for proactive design. Conclusions of the research conducted are provided.
A Goal-Oriented Design Evaluation Model
Authors: Kim Jun B. , Wallace David
Published: February 2021

This paper presents a prescriptive goal-oriented design evaluation model. The approach uses goals or targets as is commonly observed in design practice. After providing motivation for a goal-oriented approach in the early stages of product design the concept and method, based upon subjective probabilities of acceptance, are formalized. A unidimensional acceptability function is defined and the mathematical construction of a multidimensional acceptability function is presented. Issues related to simplicity and measurement accuracy are discussed. Finally, the significance of uncertainty in relation to design improvement potential is discussed. The proposed method is then applied to an engine concept selection problem.
Generation of Component Degrees of Freedom From Assembly Surface Mating Constraints
Authors: Rajan Venkat N. , Lyons Kevin W. , Sreerangam Raj
Published: February 2021

Most products are assemblies of components. The number of components can range from a few tens to a few millions. Assembly design involves the specification of component locations and orientations and the types of joints between them to achieve certain functional requirements. Current approaches to assembly modeling provide the designer the ability to specify high-level mating constraints between components which are then used to generate their locations and orientations. However, this provides little information about what types of joints have been created which have direct relevance to the functional performance of the product.

In this paper, we present a new methodology for computing component degrees of freedom from the specified high-level mating constraints. Two types of surface mating constraints are considered: fits and against. We show how multiple constraints of these two types constrain the component degrees of freedom. If the assembly being designed has a grounded component, the components’ degrees of freedom can be used to compute the joints that exist in the assembly. Eleven different types of constrained component degrees of freedom are defined ranging from unconstrained to completely constrained. An example is presented to illustrate some of the degrees of freedom.
Simultaneous Engineering of Quality Through Integrated Modeling
Authors: Soyucayli Soykan , Otto Kevin N.
Published: February 2021

Simultaneous engineering has become the means to ensure quality through incorporation of manufacturing. This proves difficult without quantitative support tools. We present here a modeling based approach to simultaneously design a product and its production process. We demonstrate an approach of examining sensitivities of output to all inputs of a system, from product design specifications, process variables, and material specifications. We further develop mathematics of estimating the effects of in-line process control changes to increase quality. We demonstrate a method to choose noise sources to measure and process variables to control in-line based upon these measurements, and estimate the error reduction that such process control changes will provide. The tool allows simultaneous engineering of the product and process to increase quality.
A Prescription for Information Prospecting, Data Mining, and Design Refinement
Authors: Wood William H. , Agogino Alice M.
Published: February 2021

We present a prescriptive methodology for conceptual design based on a process of information gathering and refinement. While these activities are generic to conceptual design, a mathematical framework is developed toward structuring the design space, approximating the design space by generalizing design data, and formalizing the iterative process of narrowing the design space while refining the level detail in the design specification. As a prescription for conceptual design, this method formalizes the conceptual design process around a key tradeoff — the value to be gained by making design commitments balanced against the reduction in size of design space these commitments bring. Because conceptual design decisions carry tremendous leverage through to all downstream processes, formalizing conceptual design toward reducing arbitrary design decisions and focusing attention on the most critical design concerns holds the potential to improve greatly the ultimate product of the overall design process.
On a Case-Based Reasoning Technique Based on Similarity Methods and its Use in Engineering Design
Authors: Rudolph Stephan
Published: February 2021

In the field of case-based reasoning (CBR), the derivation of so-called ‘similarity measures’ is an unresolved open question. In this work dimensional analysis is used to derive appropriate similarity conditions for a CBR technique. For the subclass of all case descriptions consisting of real-valued quantities with physical units, it is shown how the Pi-Theorem can be used to construct similarity conditions from these case descriptions. Within this approach a proof for the correctness of the CBR technique can be derived.

The properties of the CBR technique using dimensionless groups indicate that it bears some potential in engineering design, where knowledge in the form of analytical equations is not always available. Often only pointwise and/or incomplete knowledge about the future design object in the form of previous designs, prototypes or simulation results is available and appears in certain cases to be sufficient for the new CBR technique.
The Influence of Information Characteristics on Preliminary Design Concepts
Authors: Knoop Willem G.
Published: February 2021

An experimental approach to discover the use of information in conceptual design will give a realistic insight of the information requirements. This can be used to specify future computer support systems, and improve their performance, especially in the conceptual stages of design. A method to observe the use of information in a conceptual design process has recently been developed. The method has been tested and fine-tuned through the observation of 10 design sessions. Valuable empirical data resides from this experiment. Data has been analysed in several perspectives. This paper presents the results of the activity/information analysis in relation with the quality of the design concept for which a rating system has been defined. A significant positive correlation was found between the amount of communicated information and the rating of the design. Furthermore, a discussion is given on the relation between information and the activities of the designer. Analysis activities are more communication intensive compared to synthesis and evaluation tasks.
Life Algorithm: A New Tool to Develop a Distributed Autonomous System
Authors: Fukuda Shuichi , Konishi Fumikazu
Published: February 2021

Recently an autonomous system that meets the growing demand for solving a problem in a diversifying environment has been desired in order to secure more robustness and flexibility. As a first step towards establishing such an autonomous system, we developed Life Algorithm (LA). Life Algorithm is fundamentally an extension of Genetic Algorithm (GA). While the conventional GA approach is based on genes and is homogeneous in its essence, LA is something more like a genome and realizes more diversity. A group of genes with different evaluation function is considered and these constitute agents. Thus, more individuality and more interaction between these agents can be taken into account and more robustness to cope with the widely and quickly changing environment can be realized. This paper demonstrates the usefulness of an LA approach by illustrating the example of power plant operation through simulation and an experiment of a solar cell system. The solar cell experiment demonstrates LA’s great flexibility and adaptability as a tool for developing such an autonomous system.
Support for Handling Complexity During Product Development
Authors: Tegel Oliver
Published: February 2021

In this paper, the influences of product complexity and process complexity as well as complexity of documentation on the way products are developed are discussed and conceptual solutions for methodological support and IT support are presented. The issues are described with examples from the automotive industry. Nevertheless, most statements are valid through many industrial areas and products as well.
Characteristics of Enhanced Active Constrained Layer Damping Treatments With Edge Elements: Part I — Finite Element Model Development and Validation
Authors: Liao W. H. , Wang K. W.
Published: February 2021

This paper is concerned with the enhanced active constrained layer (EACL) damping treatment with edge elements. A finite element time-domain-based model (FEM) is developed for the beam structure with partially covered EACL. The edge elements are modeled as equivalent springs mounted at the boundaries of the piezoelectric layer. The transverse, axial, and shear motions are included. The energy method in combination with the Golla-Hughes-McTavish (GHM) viscoelastic modeling method is used. The GHM dissipation coordinates can describe the frequency-dependent viscoelastic material properties. This model becomes the current active constrained layer (ACL) system model as the stiffness of the edge elements approaches zero. Without the edge elements and viscoelastic materials, the purely active system model can also be obtained from the EACL model as a special case. Lab tests are conducted to validate the models. The frequency responses of the EACL, current ACL, and purely active systems predicted by the FEM match the test results closely. Utilizing these models, analysis results are illustrated and discussed in Part (II) of this paper.
Adaptive LMS Model-Following Control Applied Inside a Closed-Loop
Authors: Smith Bradley R. , Robertshaw H. H.
Published: February 2021

A Least Mean Squares (LMS)-style algorithm is derived for the feedback control problem. The algorithm allows a tap delay line within the closed loop to be used for control applications. This paper derives the algorithm and applies the algorithm to two simple control problems for which the solution is known and to one problem with an unknown solution. The first problem is a stable second-order system. The second problem is a unstable second-order system which is initially stabilized with the feedback loop. In both problems, the weights converge to the expected values. The stable problem is used again with an inaccurate model that has 50% more damping than the actual plant. The weights converge to a solution which increases the performance of the controller.
Reduction of Ship Vibration by the Dynamic Absorber
Authors: Hsueh Wen-Jeng
Published: February 2021

The reduction of main hull vibration of ships by a semiactive dynamic absorber is investigated. The dynamic absorber system includes a moving mass, support springs, dynamic dampers and a control system. Only small electrical power supply is needed for the valve control of the damper and the operation of the control system. In this investigation, the operation theory of the dynamic absorber is first described. Then, a suboptimal control law for the absorber is derived based on the optimal theory. The numerical simulation results show that the dynamic absorber achieves better efficiency in hull vibration reduction than the passive type absorber during critical periodical excitation from the propeller. The vibration caused by multi-frequency excitation can also be suppressed by the dynamic absorber.
Passive Vibration and Noise Control of a Fuselage With the Floor Effect
Authors: Huang Yii-Mei , Dai Kuo-Wen
Published: February 2021

Using dynamic absorbers for reducing the vibration and the interior noise of an aircraft’s fuselage is studied. In this paper, the fuselage is modeled as a circular panel connected to a plate. The fuselage’s floor effect is considered herein via including the plate in the model. The source caused the vibration and the interior noise is a set of external pressures to the fuselage. Several dynamic absorbers are then attached to the fuselage for vibration and noise control. The dynamic response of the fuselage and its interior sound pressure are analytically formulated. From the numerical results, the absorbers are found to be effective in decreasing the vibration of the fuselage and the resultant interior acoustic pressure. Some general guidelines on absorber design are also suggested in the conclusions.
Minimization of Radiated Sound Power From Vibrating Shells by Optimal Placement of Lumped Masses
Authors: Belegundu A. D. , Koopmann G. H. , Constans E. W.
Published: February 2021

By optimally placing lumped masses on vibrating shells, it is shown that big reductions in sound power levels are achievable. The lumped masses, which weigh less than 10% of that of the structure, change the mode shapes of vibration such that the radiated noise is reduced. An example showing the mode shapes before and after optimization are included in this paper. What is interesting is that a perfectly symmetric vibrating structure admits a non-symmetric optimal mass placement. Total power from first four modes is reduced by over 13 dB.
Regenerative Damper With an Optimally Tuned Resonant Circuit
Authors: Okada Yohji , Yonemura Jun-ichi , Shibata Masa-aki
Published: February 2021

A new energy regenerative type vibration damper and suspension systems have been introduced by the authors. However, it produces higher harmonic disturbing force to the vibrating system caused by the nonlinear property of regenerative circuit. For the small amplitude, it does not produce damping force and the energy is not regenerated. This paper introduces a new idea of using a resonant circuit between the actuator and the regenerative circuit. For the frequency range near the resonancy, the regenerative voltage is amplified and the efficiency will be improved. The circuit also decreases the undesirable higher harmonics to the damping force. For analitical simplicity, a resistance is installed instead of regenerative circuit and an optimal tuning condition of the resonant circuit is developed. A simple experimental setup is made. The results are showing high potential of improving the regenerative damper by using resonant circuit.
Modeling and Active Vibration Control for Bridge Tower Structures Under Construction
Authors: Seto Kazuto , Doi Fumio , Ren Mingzhang
Published: February 2021

For controlling multi-modes of vibration of flexible bridge towers under construction, a lumped mass modeling method and a new method of simple robust control are proposed. Although the robust control theory such as H∞ theory is useful for controlling systems with unknown factors and variable parameters, it is not effective to control multi-modes of vibration of flexible structures. This proposed methods are specified by combining the suboptimal control theory for reducing sensor number and filtering technique for preventing spillover of neglected high modes of vibration. Effectiveness of the method is demonstrated by showing that the first five modes of vibration of a model structure of flexible bridge tower are well controlled without spillover of neglected high modes.
On the Efficacy of Magnetorheological Dampers for Seismic Response Reduction
Authors: Dyke S. J. , Spencer B. F. , Sain M. K. , Carlson J. D.
Published: February 2021

In this paper, the efficacy of magnetorheological (MR) dampers for seismic protection of structures is investigated through a series of experiments in which an MR damper is used to control a three story test structure subjected to a one-dimensional earthquake motion. Because of the intrinsic nonlinearity of the MR damper, several earthquake amplitudes are considered to investigate the performance, in terms of both peak and rms responses, of this control systems over a range of loading conditions. The results indicate that the MR damper is quite effective for structural response reduction over a wide class of seismic excitations.
A Method for Large-Scale Structural-Acoustic Analysis
Authors: Shiohata K. , Nemoto K. , Iwatsubo T.
Published: February 2021

This paper presents a method for large-scale structural-acoustic analysis in which a cavity is divided into several acoustic fields, and a transfer-function method is used to solve the acoustics efficiently. By solving simultaneous equations using the Gaussian elimination method sequentially for each pair of neighboring acoustic sub-fields, the calculation time and memory requirements are reduced. Calculation accuracy is the same as when calculating the entire acoustic field without first dividing it. We created two kinds of closed acoustic models (cavity models) and carried out numerical simulations. The results showed that the proposed method is effective for large-scale structural-acoustic analysis.
Comparison of Refined Beam Theory and FEM for Piezo-Actuated Structures
Authors: Seemann Wolfgang E. , Wolf Kai , Hagedorn Peter
Published: February 2021

For piezo-actuated structures a refined beam theory is introduced. In order to compare the analysis with previous investigations also the simple pin-force models are presented. The results obtained by these simple models for the static deflection agree well with the results obtained by the refined beam theory. However, the simple models are unable to predict the shear stress distribution in the bonding layer. Assuming ideal bonding between the piezoceramic elements and the beam a first approximation of the stress distribution in the bonding layer may be obtained by the refined beam theory. The results for the static case can be compared with results obtained by FEM. Especially for transient excitation of the piezoceramics the refined beam theory seems to have advantages in comparison with FEM.
Closed-Form Transient Response of One-Dimensional Continua
Authors: Wu Xuqiang , Yang Bingen
Published: February 2021

Exact and closed-form transient response of general one-dimensional distributed dynamic systems subject to arbitrary external, initial and boundary disturbances is determined. Non-self-adjoint operators characterizing damping, gyroscopic and circulatory effects, and eigenvalue-dependent boundary conditions are considered. Through introduction of augmented operators, a closed-form modal expansion of the displacement and internal forces of the distributed system is derived. The eigenfunction expansion is realized in a spatial state-space formulation, which systematically yields exact eigensolutions, eigenfunction normalization coefficients, and modal coordinates. The proposed method is illustrated on a cantilever beam with end mass, damper and spring.
An Analysis of a Friction Damped System Using Two Component Mode Methods
Authors: Pesheck E. , Pierre C.
Published: February 2021

Herein, two component mode methods are employed to investigate the forced dynamics of a cantilevered beam with an attached flexible friction damper. The first, traditional modal analysis, uses the free vibration modes of the unconstrained beam, while the second, a component mode synthesis approach, uses an alternative set of modes which confines the friction non-linearity to a single component mode. The convergence and efficiency of the two methods are compared for a particular case, and the component mode synthesis approach is found to converge at least as fast as, and usually faster than, the traditional modal analysis approach. Further analysis of the beam system is conducted and discussed using the component mode synthesis formulation.
Two-Dimensional Gas Pulsation Modeling of Compressor Manifolds
Authors: Lai Peter C.-C. , Soedel Werner
Published: February 2021

A general procedure for the analysis of curved or flat, thin two dimensional gas cavities such as thin compressor or engine manifolds or so-called thin shell type muffler elements, which can efficiently utilize the limited space of hermetically sealed compressors or small engine compartments, was developed. The basic assumption is that the thickness of the cavities is sufficiently small compared to the shortest wavelength of interest. The two dimensional inhomogeneous wave equation, which takes nonuniform thickness into account, is expressed in two dimensional curvilinear coordinates by the application of Hamilton’s principle. Four pole parameters are formulated from the pressure response solutions using the modal series expansion method and orthogonality property. Three gas cavities with simple geometries including a cylindrical thin cavity, a thin disk cavity and a thin spherical gas cavity are analyzed as examples. The convergence of the modal superposition is investigated. The transfer function of the thin disk cavity case is measured experimentally and compared to the theoretical results for verification. Because the back pressure at the valve location of a compressor or engine discharge port is an important issue for practical design applications, the input port impedance of the thin disk cavity from both theoretical and experimental approaches is compared. In addition, this particular thin disk model is successfully applied to a specific compressor head cavity. Both theoretical and experimental results are presented in this paper. Finally, active pulsation cancellation in the thin gas cavity can be achieved with the assistance of the above modeling procedure.
Friction Induced Vibrations: Experiments, Modelling and Analysis
Authors: Hinrichs N. , Oestreich M. , Popp K.
Published: February 2021

In the present paper, the dynamics of a nonsmooth friction oscillator under self and external excitation is investigated. The rich bifurcational behaviour predicted by numerical simulations is compared to experimental results. In order to predict the period and amplitude of the friction induced vibrations, the friction force can be modeled by means of friction characteristics. A more detailed look at the nonsmooth transition points of the trajectories shows that an extension of the friction model is necessary. For that aim, a bristle model, a friction contact with tangential stiffness and damping and a stochastic friction model are investigated.
Stability Analysis of Rotordynamic Systems Using Floquet Methods
Authors: Marghitu Dan B. , Flowers George T. , Szász György
Published: February 2021

A method of quantifying the relative stability of rotordynamic oscillations is developed. The approach is based upon application of Floquet theory, in conjunction with Poincaré mapping, to measured (and periodic) vibration data. Detailed knowledge of a dynamic model or of the internal dynamics of the system is not required. Example cases are evaluated for a rotor interacting with a clearance bearing in order to demonstrate the method. Results are presented and discussed for simulation data (obtained from a simplified model for the example system) and for measured data from an experimental test rig.
Relationships Between Acoustic Radiation Modes, Complex Acoustic Power, and Radiation Efficiency
Authors: Chen Pei-Tai
Published: February 2021

The paper explores the physical meaning underlying the surface complex acoustic power of a vibrating body, and its relationship to radiation efficiency under mono-frequency oscillations. The vibrating can be the entire wetted surface, or only a part of the surface with the remaining surface being held rigid. The surface complex acoustic power can be computed by the surface integral of pressure multiplying the complex conjugate of normal velocity. Based on the Gaussian Divergence theorem, it is shown that the real part of the complex power is the power radiated into a far field, while that the imaginary part pertains to the volume integral of the difference between the acoustic kinetic energy density with the potential energy density over the volume between the vibrating surface and the far field. The dynamical behavior of the acoustic field can be viewed as an infinite degree of freedom mass/spring/dashpot system, where the mass and spring are the inertia effects and acoustic compression effects of the acoustic particles and the dashpot is due to the plane wave relationship of the pressure waves at the far field that the acoustic energy propagates away from the acoustic field. By the model of the mass /spring/dashpot system, the phase angle of the complex acoustic power is identified as an indication of the ability of the vibrating surface to radiate acoustic power. The phase angle of the complex power depends on the distribution of the surface normal velocity. In order to study the normal velocity profile in relation to the ability to radiate acoustic energy, the previously established radiation mode (Chen and Ginsberg, 1995) is introduced and extended to situations in which a part of the surface is held rigid. An orthogonal condition for the velocity radiation modes is also established such that arbitrary velocity profiles can be decomposed into radiation modes. The acoustic modal radiation efficiency, defined as the radiated modal acoustic power divided by the surface integral of mean square normal velocity, is investigated in terms of the acoustic eigenvalue of that mode. Several different geometries of vibrating bodies are used to demonstrate the correlation of radiation efficiencies to eigenvalues of radiation modes, which include a rectangular baffled vibrating membrane, a box with only one of the six surfaces vibrating, a slender spheroidal body, and a spherical body. This correlation of acoustic radiation characteristics for different geometries is also demonstrated for a spheroidal body vibrating at some areas with other areas being held rigid.
Analytic Study of Discreteness Effects in a String Resting on a Periodic Array of Vibro-Impact Supports
Authors: Salenger Gary D. , Vakakis Alexander F.
Published: February 2021

We analyze the forced oscillations of an infinite string supported by an array of vibro-impact supports. The envelope of the excitation possesses ‘slow’ and ‘fast’ scales and is periodic with respect to the ‘fast’ scale. The ‘fast’ spatial scale is defined by the distance between adjacent nonlinear supports. To eliminate the singularities from the governing equations of motion that arise due to the discrete nature of the supports, we employ the nonsmooth transformations of the spatial variable first introduced in (Pilipchuk, 1985) and (Pilipchuk, 1988). Thus, we convert the problem to a set of two nonhomogeneous nonlinear boundary value problems which we solve by means of perturbation theory. The boundary conditions of these problems arise from ‘smoothness conditions’ that are imposed to guarantee sufficient differentiability of the results. The transformed system of equations is simplified using regular perturbation and harmonic balancing. Standing solitary wave solutions reflecting the discreteness effects inherent in the discrete foundation are calculated numerically for the unforced system.
Numerical and Experimental Analysis of the Nonlinear Dynamics due to Impacts of a Continuous Overhung Rotor
Authors: Azeez Mohammed F. Abdul , Vakakis Alexander F.
Published: February 2021

This work is aimed at obtaining the transient response of an overhung rotor when there are impacts occurring in the system. An overhung rotor clamped on one end, with a flywheel on the other and impacts occurring in between, due to a bearing with clearance, is considered. The system is modeled as a continuous rotor system and the governing partial differential equations are set up and solved. The method of assumed modes is used to discretize the system in order to solve the partial differential equations. Using this method numerical experiments are run and a few of the results are presented. The different numerical issues involved are also discussed. An experimental setup was built to run experiments and validate the results. Preliminary experimental observations are presented to show qualitative comparison of theory and experiments.
Control Effectiveness of Segmented Actuators Laminated on Ring-Shells
Authors: Ye R. , Bahrami H. , Tzou H. S.
Published: February 2021

Distributed control effectiveness of ring-shells laminated with segmented actuators is investigated in this paper. A new laminated quadratic piezoelastic triangular shell FE is developed using the layerwise constant shear angle theory. Element and system equations are also derived. The developed piezoelastic triangular shell element is used to model a semi-circular ring shell with various segments of distributed piezoelectric actuators. Finite element (triangular shell FE) solutions are compared with the theoretical, experimental, and finite element first. Natural frequencies and distributed control effects of the ring shell with different length of piezoelectric actuators are also studied. Control effectiveness is evaluated and optimal length of the actuator is recommended.