bluuebunny/crossref_metadata_2025 huggingface dataset:
Fixture Configuration Design for Sheet Metal Laser Welding With a Two-Stage Response Surface Methodology
Authors: Li Bing , Shiu Boon-wai , Lau Kwok-jing
Published: November 2020

In this paper a two-stage response surface methodology is developed for the robust fixture configuration design of sheet metal laser welding. The first stage is to optimally determine the Robust Design Space (RDS) where the relatively less-sensitive design over the entire feasible design space can be obtained. A weighted objective function combining both robustness and performance are taken in this stage. The degree of metal fit-up is taken as performance characteristic. Within RDS a second-order response surface model is fitted by a 3k fractional factorial design in the second stage. Thus, based on the new methodology the robust design results under the new fixturing scheme can be obtained. Illustrative example shows that the presented method can lead to a robust fixturing scheme and the influential design locators can be detected.
Optimal Smart Actuator Integration to Reduce Vibration in High Speed Mechanical Systems
Authors: Rastegar J. , Yuan L. , Hua L.
Published: November 2020

A systematic method is presented for optimal integration of smart actuators into the structure of robot manipulators for the purpose of enabling them to perform smooth object manipulation with smooth actuated joint motions. Here, the motions are considered to be smooth if they do not contain high harmonic components. For optimal positioning of smart actuators in the structure of robot manipulators, a method is developed based on the evaluation of the transmissibility of displacement (velocity and/or force) from the smart actuators to the robot manipulator joint motions and the end-effector displacements (velocity and/or force). A method is then presented for synthesizing actuated joint and object motions to achieve trajectories that do not contain high harmonic components. By minimizing the high harmonic components of the required joint and object motions with properly sized and placed smart actuators, such computer-controlled machines can operate at relatively higher speeds and achieve greater tracking precision with minimal vibration and control problems. A number of numerical examples are provided.
The Influence of Optimization in the Problems of Waves Propagation in Cylindrical Shells
Authors: Sarkisyan A.
Published: November 2020

The wave propagation in cylindrical shell under the influence of the different factors, such as visco-elasticity, magneto-elasticity, presence of temperature field and fluid, the layerness and anisotropy of the shell is a very interesting problem. Composite materials posses different properties, giving a push to further development of the theory of elasticity of anisotropic bodies, in particular theory of anisotropic plates and shells. For different thin shells, made from different materials, based on dispersion equations received dependencies of wave velocity to the angle between physical and geometrical axes of the shell are constructed. Anisotropic shells, containing fluid: compressed and incompressible, are considered. Constructed the surfaces, showing change of velocities depending on angle between physical and geometrical axes of shell and length of wave. Comparison of all received results is resulted which reveals the stabilizing role of fluid. The behavior of three layered orthotropic shell on the example of arteries is investigated. On the same example comparison with the similar shell is resulted and analysis of this comparison is given. Analysis shows that the velocity in a layered shell much more decreases in comparison with one layered.
Optimal Structural Topology Design for Energy Absorption: A Heuristic Approach
Authors: Soto Ciro A.
Published: November 2020

A new approach to design the topology for structures under crash events is presented. The approach is heuristic in essence, but numerical experiments have shown its uses in real problems. Using an interpolation between porous and solid (non-porous) materials plus a re-design rule to by-pass gradient computations the new approach is able to determine better locations of material and density in a given structural domain for kinetic energy dissipation. An example is presented to illustrate the methodology.
Effectiveness of Haptic Sensation for the Evaluation of Virtual Prototypes
Authors: Volkov Sergei A. , Vance Judy M.
Published: November 2020

Virtual Reality techniques provide a unique new way to interact with three-dimensional digital objects. Virtual prototyping refers to the use of virtual reality to obtain evaluations of designs while they are still in digital form before physical prototypes are built. While the current state-of-the-art in virtual reality relies mainly on the use of stereo viewing and auditory feedback, commercial haptic devices have recently become available that can be integrated into the virtual environment to provide force feedback to the user. This paper outlines a study that was performed to determine whether the addition of force feedback to the virtual prototyping task improved the ability of the participants to make design decisions. The specific task involved comparing the location and movement of two virtual parking brakes located in the virtual cockpit of an automobile. The paper describes the purpose, methods and results of the study.
Web-Based Interactive Design of Freeform Motions
Authors: Li S. T. , Ge Q. J. , Varshney A.
Published: November 2020

This paper deals with the development of a software system for web-based geometric design of freeform motions. The Virtual Reality Modeling Language (VRML) is used to describe static and animated 3D objects. The Common Gateway Interface (CGI) is used as an interface for client/server communication, parsing user input from the web browser and returning information based on user input. This work extends the web server’s functionality to include geometric design of freeform motions and automatic generation of VRML models by porting our existing C++ implementation of motion approximation and interpolation algorithms to the internet using platform- and language-independent CGI scripting. Examples are provided for geometric design of line-symmetric motions over the internet.
The Computation of 3D Pattern Matching As a Tool for Conceptual Freeform Shape Design
Authors: Vergeest Joris S. M. , Spanjaard Sander
Published: November 2020

Freeform feature fitting is a technique underlying different applications, including reverse engineering, object recognition and conceptual shape design. The latter application poses specific requirements to the fitting technique with regard to speed, robustness and interactivity. On the other hand, the spatial accuracy and the density of the input data can be permitted to be relatively low. We have performed freeform feature fitting to physical shapes using both a high-density mechanical scanning device and a low-cost desktop laser scanner. The performance of these technologies have been compared. The fitting technique is based on direct template matching, where a template is a 3D shape feature under control of 6 placement parameters (defining the ridged body transformation) and a number of intrinsic form parameters. We found that template matching remained reliable even for sparse and partly missing data. A low-cost, high-speed scanner can hence function as a 3D digital shape copier and be a supportive tool for conceptual product design. Limitations and extension of the technology are addressed.
Structure Synthesis of 4-DOF (3-Translation and 1-Rotation) Parallel Robot Mechanisms Based on the Units of Single-Opened-Chain
Authors: Yang Ting-Li , Jin Qiong , Liu An-Xin , Yao Fang-Hua , Luo Yu-Feng
Published: November 2020

Based on the units of single-opened-chain limb, some topological characteristics of rank-degenerate parallel robot mechanisms are revealed, and a systematic and effective new method for structure synthesis of 4-DOF (3-translation and 1-rotation) parallel robot mechanism is put forward in this paper. 50 new mechanisms are synthesized and classified. The method proposed in this paper is of universal significance and has been used for the structure synthesis of rank-degenerate parallel robot mechanisms with other kinematics output types.
Adaptive Slicing for a Five-Axis Laser Aided Manufacturing Process
Authors: Zhang Jun , Liou F. W.
Published: November 2020

The Laser Aided Manufacturing Process (LAMP) is an additive process similar to laser cladding. It can produce fully functional parts because the process is material independent. The traditional layered manufacturing (LM) processes with fixed build direction have a limited surface accuracy and their build time is often long due to the deposition of sacrificial support structure. The multiple degrees of freedom allow the LAMP system to build a part without support structure and with better surface quality; however, an automated method for path planning of such a multi-axis system is necessary. An algorithm of adaptive slicing for five-axis LAMP is presented in this paper, which can generate optimal slices to achieve deposition without support structures. Different from the current adaptive slicing, this technique varies not only in layer thickness but also in slicing direction. The slicing direction is determined by a marching algorithm, which is based on the surface normal of points on the side surface of the current slice. Two techniques are adapted to build the overhang between two adjacent layers: thin wall deposition and direct overhang deposition based on surface tension.
Concepts and Applications of Probabilistic Design
Authors: Booker Julian D.
Published: November 2020

Deterministic design fails to provide the necessary understanding of the variability associated with the properties of materials, manufacturing tolerances and in-service loading. Probabilistic design offers much potential in this area, providing an effective way of determining product life-time estimates, reducing failure costs and aiding the process of weight optimization in product design, but has yet to be taken up widely by manufacturing industry. In this paper, case studies are used to explore some important probabilistic design concepts and introduce methods that allow reliability performance measures to be assessed for product designs early in the product development process. The methods described are used in conjunction with Failure Mode and Effects Analysis (FMEA) to facilitate the setting of reliability targets for design proposals.
Computer Aided GD&T Advisor Based on Y14.5 Conformance and Good Practice
Authors: Ramaswamy Sanjay , Shah Jami J. , Davidson Joseph K.
Published: November 2020

Contemporary CAD systems support GD&T specifications simply as textual attributes which does not facilitate validation of dimensioning and tolerancing. The Y14.5 tolerance standard is quite complex and many engineers are not quite familiar with all this intricacies. A few expert systems have been developed for GD&T support but they typically focus on tolerance values and their cost consequences. This paper presents the design and implementation of an integrated system for specification and automatic validation of dimensioning and tolerancing schemes in conformance with Y14.5. The validation includes not only tolerance values but choice of datums and datum reference frames. Additionally, the GD&T specifications are checked against good practice rules. This paper also provides a compilation of such rules from a variety of sources.
Assembly/Disassembly Simulation Early During a Design Process
Authors: Léon Jean-Claude , Rejneri Nicolas , Debarbouillé Gilles
Published: November 2020

In this article, a method is presented which can automatically generate all feasible disassembly sequences of a product both from geometric and technological points of views. The components of the assembly are modelled with accurate B-Rep models and the mobility between them is modelled as effective translations, rotations or helical movements.

In order to reduce the algorithm complexity inherited from such models, i.e. the number of geometrically feasible sequences and the complexity of the movements, this approach is based on technological data associated to the geometric description of components.

The geometric and technological data are taken into account to create associations of components, i.e. the number of components is reduced, and to define criteria for the evaluation and selection of disassembly sequences in order to reduce the number of sequences effectively built and hence the algorithm complexity. Then, user criteria are incorporated to select the best component to mount/dismount for each operation and produce assembly/disassembly sequences. A path trajectory planner is coupled with the sequencing process to generate paths in 3D that avoid obstacles.

This approach incorporates geometric models of components as well as technological data, which may be available early during a design process. All these data are not strictly required for the simulation process. Therefore, the simulation can be continuously enriched during the design process and can be initiated early in this process.
Design Process Error-Proofing: International Industry Survey and Research Roadmap
Authors: Chao Lawrence P. , Beiter Kurt A. , Ishii Kosuke
Published: November 2020

This paper presents the results of a survey on the use of error management methods during the design process at several leading corporations in the United States and Japan. The survey reveals that although many companies are aware of the benefits of structured design processes, and although most have implemented systematic design practices to some level, many companies are still reliant on reactive tools (such as design reviews and checklists) to manage design-related errors. This paper discusses the survey methodology, the results of the survey, and the authors’ proposed work to address the existing lack of a systematic approach to design process error-proofing.
Product Development Process Modeling Using Advanced Simulation
Authors: Cho Soo-Haeng , Eppinger Steven D.
Published: November 2020

This paper presents a product development process modeling and analysis technique using advanced simulation. The model computes the probability distribution of lead time in a resource-constrained project network where iterations take place among sequential, parallel and overlapped tasks. The model uses the design structure matrix representation to capture the information flows between tasks. In each simulation run, the expected durations of tasks are initially sampled using the Latin Hypercube Sampling method and decrease over time as the model simulates the progress of dynamic stochastic processes. It is assumed that the rework of a task occurs for the following reasons: (1) new information is obtained from overlapped tasks after starting to work with preliminary inputs, (2) inputs change when other tasks are reworked, and (3) outputs fail to meet established criteria. The model can be used for better project planning and control by identifying leverage points for process improvements and evaluating alternative planning and execution strategies. An industrial example is used to illustrate the utility of the model.
On Defining Product Requirements: A Case Study in the UK Health Care Sector
Authors: Agouridas Vassilis , Baxter Jim , McKay Alison , de Pennington Alan
Published: November 2020

Design is one of the core business processes involved in product development, and approaches such as Quality Function Deployment (QFD) and Axiomatic Design (AD) have been developed for improving its effectiveness and efficiency. However, they are limited in their provision of structure and formalism to the mapping of customer needs to product requirements. This is in part due to lack of identifying characteristics of customer needs. The characteristics of Solution Space™, consisting of pairs of opportunities and constraints, address partially this by providing a framework for identifying sources of product requirements. This paper reports the results of a case study, within the UK health care sector, related to the design of an artificial knee joint. In particular, it is shown how AD and the framework consisting of pairs of opportunities and constraints can be used in conjunction with each other to establish a view of the system of which the artificial knee joint forms part. The development of such a view helps to ensure that characteristics of potential stakeholders’ needs are more appropriately identified. This is a prerequisite for the establishment of more formal relationships between stakeholders’ needs and product requirements.
RedesignIT: A Constraint-Based Tool for Managing Design Changes
Authors: Ollinger Gabriel Aguirre , Stahovich Thomas F.
Published: November 2020

RedesignIT is a computer program that uses model-based reasoning to generate and evaluate proposals of redesign plans for engineered devices. These proposals describe how the design parameters could be changed to achieve a specified performance goal. Equally important, the program proposes complementary modifications that may be necessary to counteract the undesirable side effects of the primary changes. RedesignIT is intended for use during the first stages of a redesign project, when engineers need to make a quick, yet accurate assessment of the overall effects of a particular design change. The program uses qualitative device models, which allow it to compute redesign plans efficiently. With its ability to predict the collateral, and probably undesirable, effects of a design change, the program is well suited to aid product designers in deciding on the feasibility of introducing design changes to a product. RedesignIT employs methods of artificial intelligence, especially qualitative reasoning, causal reasoning, and heuristic search.
Towards Logical Framework for Sequential Design
Authors: Dzbor Martin , Zdrahal Zdenek
Published: November 2020

Engineering design is usually seen as a knowledge-intensive process that driven by certain objectives eventually delivers an artefact having the desired properties or functions. Design is inherently iterative and the design goals evolve together with the solutions. Many current design theories present more or less efficient ways for finding a suitable solution to the given goals. However, they often leave open the question of the ‘solution talkback’. Under ‘solution talkback’ we understand the reasoning process that is able to infer what formal amendments to the initial design specification need to be made in order to produce a feasible solution. Modified explicit design specification would in turn enable designers to refine the solutions to their design problems. This paper suggests an early-stage theory that incorporates some typical features of design problems, and defines a reasoning framework for the reflection on the actions in design. First, the key terms are defined that are elaborated later with the focus on generation of new design goals through the reflection on the partial design solutions.
Tolerance Optimization: A Decomposition Scheme, Variance Reduction and Fractional Approximation
Authors: Gadallah Mohamed H.
Published: November 2020

Development of involved optimization algorithms is not an easy task for several reasons: First, every analyst is interested in a specific problem; Second, the capabilities of these methods may not be fully understood a priori; Third, coding of multi-purpose and more involved algorithms is not an easy job.

In this paper, the optimization problem employing the near to global optimum algorithm is studied (Gadallah, M.H., 2000). The focus is to exploit 2 ideas: First, the algorithm can be modified to act as a variance reduction technique; Second, the algorithm can be modified to tackle the problem of system decomposition. Both ideas are novel within the context of statistical design of experiments. The first, if fully proved experimentally could yield the simultaneous integration of nominal and variance optimization possible. The second, can be extended to deal with multi-dimensional highly constrained systems with ease. These two ideas are explained wife the use of a simple example to illustrate the idea. An algorithm is developed that deal with the problem in several stages according to a predetermined decomposition scheme. The original objective and constraint functions are dealt with to suit each stage. Accordingly, all NP hard problems can ideally be transformed into NP complete ones with a consequence on the number of stages resulting from decomposition. Several decomposition scenarios are used and their results are compared numerically. Two orthogonal arrays and four composite arrays are used to plan experimentation; these are L27OA and L54OA and their subfamilies. These arrays are compared with respect to their statistical measures.

The algorithm as such, is very promising optimization tool, especially for coupling system decomposition and variance reduction. Past work focused on either decomposition or statistical optimization. This work offers both capabilities. Several studies are reviewed and conclusions are drawn.
Computation of Time-Varying Cross-Spectra by Harmonic Wavelets
Authors: Newland David E.
Published: November 2020

Harmonic wavelets provide an organised method for local computations of the cross-spectra between two signals. Each signal is analysed into its wavelet expansion. The product of the (complex) amplitudes of corresponding terms in each expansion is then a measure of the time varying cross-spectral density between the two signals. To ensure adequate discrimination at low frequencies, it is necessary introduce additional terms into the expansion by intentionally oversampling, but the principle remains unchanged and the method allows the amplitude and phase of time-varying cross-spectra to be identified at closely-spaced time intervals. Some examples illustrate the procedure, which can be programmed simply using an FFT algorithm.
Optimizing Parameters of a Two-Degree-of-Freedom Maglev System
Authors: Xu Zhixiang , Seto Kunisato , Tamura Hideyuki
Published: November 2020

Because a repulsive maglev vehicle only has extremely small uncontrollable damping force in its magnetically levitated gap, its vibration is a considerable problem. The one solution of this problem is to add a secondary suspension to the main system that is now practically used for Japanese type maglev train. In this paper, we first simplified the repulsive magnetic levitation vehicle with secondary suspension into a two-degree-of-freedom vibration model, and then analyzed the vibration properties of the system. Especially, we investigated the influence of the system parameters on the frequency responses of the system in detail, and found out that there are four fixed-points both in the frequency responses of car-body and truck. Similarly to the technique for dynamic absorber, but contrary to the aim of dynamic absorber with which to suppress the vibration of main mass, we successfully optimized the system parameters to suppress the car-body’s vibration that is equivalent to that of the additional mass of dynamic absorber by arranging the positions of the fixed-points.
A Relative Nodal Coordinate Formulation for Finite Element Nonlinear Analysis
Authors: Park J. H. , Choi J. H. , Bae D. S.
Published: November 2020

Nodal coordinates are referred to a fixed configuration in the conventional equations of equilibrium. Nodal coordinates are referred to the initial configuration in the total Lagrangian formulation and to the last calculated configuration in the updated Lagrangian formulation. This research proposes to use the relative nodal coordinates in representing the position and orientation for a node. Since the nodal coordinates are measured relative to its adjacent nodal reference frame, they are still small for a structure undergoing large deformations if the element sizes are small. As a consequence, many element formulations developed under small deformation assumptions are still valid for structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph form, respectively. Closed loops are opened to form a tree topology by cutting edges. Two computational sequences are defined in a graph. One is the forward path sequence that is used to recover the Cartesian nodal deformations from relative nodal displacements and traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One open loop and one closed loop structure undergoing large displacements are analyzed to demonstrate the efficiency and validity of the proposed method.
Dynamics of Rolling Wheel With Contact Rigidity and Slip
Authors: Terumichi Yoshiaki , Suda Yoshihiro , Sogabe Kiyoshi
Published: November 2020

In this paper, we discuss the dynamics of a rolling wheel with contact rigidity and slip. We propose the approach, using the distance between the center of the wheel and the contact point as an index to the elastic contact for this problem. We discussed about the generation and disappearance condition of slip with dynamic load and initial vertical displacement, using some results for simple cases. It is shown that contact rigidity influences on the time when slip generates or disappears and duration time of slip. It is also clarified that when the friction force reaches the tangent force after slip, slip does not always stop.
A New Plate Element Based on the Absolute Nodal Coordinate Formulation
Authors: Mikkola Aki M. , Shabana Ahmed A.
Published: November 2020

In this investigation, a method for the finite rotation and large deformation analysis of plates is presented. The method, which is based on the absolute nodal coordinate formulation, leads to a plate element capable of representing exact rigid body motion. In this method, continuity conditions on all the displacement gradients are imposed. Therefore, non-smoothness of the plate mid-surface at the nodal points is avoided. By developing such a plate element, a constant mass matrix is obtained, and as a consequence, the centrifugal and Coriolis forces are equal to zero. Generalization of the formulation to the case of shell elements is discussed. Numerical results are presented in order to demonstrate the use of the proposed method in the large rotation and deformation analysis of plates and shells.
Dynamics of Flexible Beam Using a Component Mode Synthesis Based Formulation
Authors: Kobayashi Nobuyuki , Sugiyama Hiroyuki , Watanabe Masahiro
Published: November 2020

This paper establishes a new formulation strategy for a flexible beam with large rotational motion. The finite element based formulation, which was previously developed for the analysis of the ‘Spaghetti Problem’ by the present authors, is extended to realize a low order and high accuracy beam model using a kind of component mode synthesis method. The deformation of the flexible beam is modeled by a combination of a static mode represented by a shape function and an analytically evaluated vibration mode clamed at both ends with respect to the body coordinate system. The body coordinate system satisfies the condition that the x-axis connects both ends of the beam. To demonstrate the efficiency and validity of the flexible beam model in multibody dynamics, a 2-link flexible robot arm is modeled as a flexible multibody system consisting of some rigid bodies and two flexible beams. Its validity is indicated by good agreement between numerical simulations and the experimental results.
Utilization of Coupled Simulation in the Fatigue Loads Prediction of a Hydraulically Driven Log Crane
Authors: Mikkola Aki M.
Published: November 2020

Welded structures, such as hydraulically driven booms, are disposed to fatigue damage. Design against fatigue requires information on the fatigue resistance of a structure’s critical details and the fatigue loads that act on each detail. The present paper introduces a method based on dynamic simulation for determining the fatigue loads in a hydraulically driven log crane. The detailed simulation model was built up in the MBS-software environment in which the flexible mechanism model and the equations describing the hydraulic system were combined. The complete simulation model was verified by comparing measurements to numerical results. This comparison shows that there is a clear correspondence between the simulated and measured results. It was thus shown that it is possible to create a simulation model which can be used realistically for determining stresses in fatigue analysis. The model was employed in the study of the fatigue loads, which are formed when the crane is being loaded.
Basin of Attraction of the Simplest Walking Model
Authors: Schwab A. L. , Wisse M.
Published: November 2020

Passive dynamic walking is an important development for walking robots, supplying natural, energy-efficient motions. In practice, the cyclic gait of passive dynamic prototypes appears to be stable, only for small disturbances. Therefore, in this paper we research the basin of attraction of the cyclic walking motion for the simplest walking model. Furthermore, we present a general method for deriving the equations of motion and impact equations for the analysis of multibody systems, as in walking models. Application of the cell mapping method shows the basin of attraction to be a small, thin area. It is shown that the basin of attraction is not directly related to the stability of the cyclic motion.
A Numerical Method for Multibody System Frictional Impact Simulation
Authors: Zakhariev Evtim V.
Published: November 2020

In the paper a numerical algorithm for modeling of impact of rigid and flexible multibody systems considering the nonlinear Coulomb friction is presented. The algorithm is developed on the basis of the kinematic decomposition of the contacting surfaces. The possible motion along the normal direction of the contact point tangential plane is considered generalized coordinate. The impulse-momentum equations are derived using a general algorithm for dynamics modeling and solved consequently for the two stages, compression and restitution, of the impact process. Rigid body impact theory and analysis of the contacting point relative velocity are applied for effective modeling of the events sliding-stiction and reverse sliding. The method presented considers either Newton’s or Poisson’s hypothesis for the coefficient of restitution. The same approach is used for flexible systems that are discretized using finite element theory. It is pointed out that, if rigid multibody systems are considered, the coefficient of restitution does not reveal the true picture of the impact process. Several examples are solved and compared with the results obtained in other treatments.
Analysis of Electromagnetic Excitation Sources of Noise and Vibration in Interior Permanent Magnet Motor
Authors: Ko Hong-Seok , Kim Kwang-Joon
Published: November 2020

The purpose of this paper is to characterize electromagnetic excitation forces in an IPM (Interior Permanent Magnet) motor and to analyze their effects on noise and vibration. To do this, the electromagnetic excitation forces are classified into three parts and contribution of each to the noise and vibration is investigated. The first is cogging torque; in order to overcome drawbacks of finite element method in the initial design stage, an analytical method is proposed. The second is electrical torque ripple due to current harmonics; a simple equation for characterizing the current harmonics with respect to the electrical torque ripple is developed. The third is the excitation force related to distribution of electromagnetic forces in air-gap; existence of this force is understood by finite element method.

The influence of the electromagnetic forces on the noise and vibration is investigated by doing modal analysis and operational deflection shape analysis.
Bayesian Updating of Nonlinear Model Predictions Using Markov Chain Monte Carlo Simulation
Authors: Beck James L. , Au S. K. , Yuen K.-V.
Published: November 2020

The usual practice in system identification is to use system data to identify one model from a set of possible models and then to use this model for predicting system behavior. In contrast, the present robust predictive approach rigorously combines the predictions of all the possible models, appropriately weighted by their updated probabilities based on the data. This Bayesian system identification approach is applied to update the robust reliability of a dynamical system based on its measured response time histories. A Markov chain simulation method based on the Metropolis-Hastings algorithm and an adaptive scheme is proposed to evaluate the robust reliability integrals. An example for updating the reliability of a Duffing oscillator is given to illustrate the proposed method.
Modeling Damping Effect due to High Transient Motion Using the Riemannian Space
Authors: Al Majid Ahmad , Dufour Régis
Published: November 2020

An original method for evaluating the dissipative effect in SDOF systems due to the transient phenomenon was presented in a previous article (Al Majid and Dufour, 2000). This method based on the use of an additional dimension, and the general relativity concept was validated experimentally. However, the function of the forcing frequency required to establish the metric of the space was identified using an experimental transfer function. In the present paper the main objective is to solve the geodesic equations in order to avoid the experimental identification of the function contained in the metric. The variational problem of the metric of Riemannian space gives three geodesic equations for the SDOF system studied. Solving these equations gives in particular the transient forced response which, when compared with experimental results, permits validating the proposed method and therefore proving that the transient motion bends the space-time.
Active Control of Wind-Induced Building Vibration Using a Linear Coupling Strategy
Authors: Hashemi S. Mohammad , Golnaraghi M. F.
Published: November 2020

The active control of building vibration is addressed. The aeroelastic lumped mass model of a building is designed to be used as the test bed for the active control system. The five story lumped parameter model was modeled as a cantilever beam exhibiting planar vibration. A Linear Coupling Control (LCC) strategy was implemented to eliminate the vibrations. An active (moving) mass damper (AMD) was first designed and experimentally implemented to control the first mode vibration of the system. An alternative pendulum control system was then designed and implemented. The proposed pendulum, having three times smaller mass than the AMD, was found to be more effective in reducing the building vibrations.
Dynamics of Towed Cables During Transient Motions
Authors: Ng Leslie , Rand Richard , Keith William
Published: November 2020

This work concerns the problem of determining the relative position of a towed cable when the towing vessel is moving in an arbitrary given fashion. In particular we are concerned with avoiding the tangling of individual towed cables when the towing vessel is towing multiple cables. A model is developed to describe the dynamics of the tow cables for arbitrary motions of the towing vessel. The model is then analyzed for constant speed circular motions of the towing vessel. A combination of analytic and numerical techniques are used in the analysis of the resulting differential equations.
A Refined Model for a Piezoelectric Transformer
Authors: Seemann Wolfgang E. , Gausmann Rainer
Published: November 2020

This paper is dedicated to Prof. Peter Hagedorn, Darmstadt University of Technology, Germany, on the occasion of his 60th birthday.

Usually piezoelectric actuators are nowadays simulated with the help of finite element codes. Analytical models are only used for very simple geometries like beams and plates or in those cases where piezoelectric patches are bonded to a beam or plate. Examples can be found in literature. However, it has to be kept in mind that there are still some problems for which standard finite element codes like ANSYS might get difficulties. One such problem is a piezoelectric transformer with an arbitrary load impedance connected to the electrodes of one of the piezoceramics. Such a system is investigated in this paper. To obtain results which are still valid if the diameter of the rod is not small compared to the wave length, a refined rod theory is used which takes into consideration also the inertia effects due to transverse contraction. To derive the equations of motion and the boundary conditions for such a system Hamilton’s principle for electromechanical systems is used. The equations of motion are solved and compared with experimental results. A comparison with results of a finite element analysis is also given for one special case which could be handled by ANSYS.
Investigation of the Dynamic Behavior of Railway Ballast Using Molecular Dynamics Simulations
Authors: Kruse Holger , Popp Karl
Published: November 2020

The molecular dynamics method (MD method) is a powerful tool for the investigation of granular materials like the railway ballast. The characteristics of this method are explained in detail. In contrast to a continuum description, each single stone of the ballast is taken into account. Since the ballast settlement is strongly influenced by the shape of the stones, in the two-dimensional model polygonal particles are used. These particles are surrounded by fixed boundary walls. At the top of the ballast particle layer, a single sleeper is positioned which is loaded by forces occurring at the real track. The contact forces are calculated from the overlap area of the particle geometries.

The paper includes information about the sensitivity of the model behavior on initial conditions and contact law parameters. Furthermore, the contact network, the quasi-static stiffness of the ballast layer and its long-term behavior are addressed. Particular emphasis is put on the description of current difficulties and challenges in applying the MD method.
Identification of a Micro-Slip Friction Damping Function Using Directed Genetic Programming
Authors: Gregory Julie J. , Paez Thomas L. , Coleman Ronald G. , Gregory Danny L.
Published: November 2020

This paper describes the application of directed genetic programming to explore the functional form of non-linear restoring forces that arise due to micro-slip friction. Data are obtained from an experiment to investigate the friction forces in a simple shear interface subjected to a vibration environment. A candidate functional form is proposed to model this friction, and a genetic search is then performed which seeks optimal parameters for the function. The resulting parameters provide the best fit of the proposed functional to the experimental data.
Large Deflection Dynamics and Control for Planar Continuum Robots
Authors: Gravagne Ian A. , Walker Ian D. , Rahn Christopher D.
Published: November 2020

This paper focuses on a class of robot manipulators termed “continuum” robots — robots that exhibit behavior similar to tentacles, trunks, and snakes. In previous work, we studied details of the mechanical design, kinematics, path-planning and small-deflection dynamics for continuum robots such as the Clemson “Tentacle Manipulator.” In this work, we discuss the dynamics of a planar continuum backbone section, incorporating a large-deflection dynamic model. Based on these dynamics, we formulate a vibration-damping setpoint controller, and include experimental results to illustrate the efficacy of the proposed controller.
Structural Diagnostics Using Nonlinear Analysis (SDNA) With Smart Sensor Arrays
Authors: Adams Douglas E. , Bono Richard W.
Published: November 2020

There are compelling needs to develop and install smart online monitoring and diagnostic tools for complex dynamic systems. Automated internal diagnostics and prognostics will help to extend service and design lives for new and aging aircraft, civil infrastructure, mission critical aerospace structures, automotive systems, and industrial machinery. The most innovative aspects of a proposed approach to smart structural diagnostics using nonlinear analysis (sDNA) are discussed here including the sensor array architecture and networked processing platform. A diagnostic technique using transmissibility functions is described for pinpointing the location and extent of damage. Since damage is spatial in nature, these transmissibility functions are well suited for analyzing either passive operating data or active forced response data. Strain gauges installed in sensor array packets are described as ideal for monitoring usage and characterizing damage while accommodating nonlinearity and uncertainty in the system and boundary conditions.
Identification of Pedestal Parameters in Rotor-Bearing-Pedestal Systems Using Known Unbalance
Authors: Feng Ningsheng , Hahn Eric J.
Published: November 2020

This paper details a new technique for identifying the pedestal/foundation vibration parameters, viz. the pedestal or foundation stiffness, damping and mass matrices, of rotor-bearing-pedestal systems. Earlier approaches which relied on a knowledge of the hydrodynamic bearing forces as calculated from Reynolds equation, though promising in theory, proved unsatisfactory in practice. With this new approach on the other hand, at the expense of an additional run to enable the unbalance excitation to be correctly determined and assuming a knowledge of the rotor model, the uncertainties associated with bearing models are bypassed completely. It is shown both numerically and experimentally, that provided corresponding data are sampled at the same speed, good identification of pedestal parameters can be achieved even for pedestals supporting non-linear hydrodynamic bearings.
Theoretical and Experimental Study of the Dynamics of the Tripod-Ball Sliding Joint With Clearance
Authors: Xiaohong Jia , Linhong Ji , Dewen Jin , Jichuan Zhang
Published: November 2020

Clearance is inevitable in the kinematic joints of mechanisms. In this paper the dynamic behavior of a crank-slider mechanism with clearance in its tripod-ball sliding joint is investigated theoretically and experimentally. The mathematical model of this new-type joint is established, and the new concepts of basal system and active system are put forward. Based on the mode-change criterion established in this paper, the consistent equations of motion in full-scale are derived by using Kane method. The experimental rig was set up to measure the effects of the clearance on the dynamic response. Corresponding experimental studies verify the theoretical results satisfactorily. In addition, due to the nonlinear elements in the improved mathematical model of the joint with clearance, the chaotic responses are found in numerical simulation.
Analytical Solution of Forced Vibration of a Column Subjected to Conservative and Nonconservative Forces
Authors: Xu Zhixiang , Seto Kunisato , Tamura Hideyuki
Published: November 2020

This paper presents analytical results of forced transverse vibration of a column with a mass attached at free-end subjected to a tangential follower force and a transverse distributed excitation force, that is a simplified model of some structures in civil and mechanical engineering, e.g., a column of a suspension bridge, a launched rocket in the atmosphere. Because the tangential follower force is nonconservative, it is very difficult to get the analytical solution of the problem by usually-used analysis methods with which the adjoint boundary value problem can not be directly obtained. However, by applying the finite integral transform technique, we directly obtained the adjoint boundary value problem in the analysis process, and successfully obtained the analytical solution of the column’s vibration excited by the transverse distributed force.
Rocking Vibration of Rotating Disk and Spindle Systems With Asymmetric Bearings
Authors: Park Jung Seo , Shen I. Y. , Ku C.-P. Roger
Published: November 2020

This paper studies how bearing asymmetry affects natural frequencies and mode shapes of a rotating disk/spindle system through a numerical simulation and a perturbation analysis. Existing literature has shown that rocking motion of a rotating disk/spindle system with symmetric bearings consists of rigid body rocking of the spindle, one-nodal-diameter modes of each disk, and deformation of spindle bearings. The rocking motion, characterized by (0,1) unbalanced modes, has repeated natural frequencies when the spindle is stationary, because the disk/spindle system is axisymmetric. For a rotating spindle, (0,1) unbalanced modes evolve into forward and backward precession with circular orbits. In this paper, the numerical simulation shows that bearing asymmetry splits a pair of repeated (0,1) unbalanced modes into two modes with distinct frequencies when the spindle is stationary. Moreover, when the rotational speed increases from zero, the (0,1) unbalanced mode with lower frequency evolves into backward precession and the (0,1) unbalanced mode with higher frequency evolves into forward precession. The precession orbits are elliptical because of the bearing asymmetry. Two perturbation schemes are developed to prove the phenomena observed in the numerical simulation. For low rotational speed, a stationary disk/spindle system with symmetric bearings serves as the unperturbed system. Both the bearing asymmetry and gyroscopic effects from rotation form the perturbation. A contraction iteration predicts the effects of bearing asymmetry on natural frequencies and mode shapes. For high rotational speed, a rotating (gyroscopic) disk/spindle system with symmetric bearings serves as the unperturbed system. The bearing asymmetry forms the perturbation. To obtain a perturbation solution, the solvability condition is first derived for the unperturbed gyroscopic system. Lindsted-Poincaré approach then predicts the effects of bearing asymmetry on natural frequencies and mode shapes of the rotating disk/spindle system.
Determination of External Forces: Application to the Calibration of an Electromagnetic Actuator
Authors: Bucher Izhak , Rozenstain Moshe
Published: November 2020

A method for obtaining an accurate estimate of electromagnetic forces acting upon a vibrating structure is derived in this paper. The method was developed as a means for calibrating an electromagnetic excitation device where the electromagnetic force was sought to be estimated. The unique features of the proposed method are: (a) Compensation of inertial effects; (b) The method relies on indirect measurement of forces and displacements that are fed into an experimentally calibrated dynamical model. The calibration process allows us to precisely estimate distributed inertia and elastic forces and this allows us to model the relationship between the actually applied forces and various measurable physical parameters affected by the external forces. In the case of an electromagnetic device the affected parameters will be air-gap, current and magnetic flux. The lack of information in this case has lead us to a threefold approach where experimental data is combined with an analytical approach together with state-of-the-art measurement-techniques. The necessity to obtain an accurate account of the distribution of inertia in the structure necessitates a precise spatial model that was generated by means of a scanning laser-Doppler sensor. The analytical part involves the implicit estimation of Lagrange multipliers from an extended principal of virtual work.