bluuebunny/crossref_metadata_2025 huggingface dataset:
The Discrete Topology Optimization of Structures Using the Modified Quadrilateral Discretization Model
Authors: Zhou Hong , Malela Ravinder G.
Published: September 2013

The modified quadrilateral discretization model is introduced for the discrete topology optimization of structures in this paper. The design domain is discretized into quadrilateral design cells. There is a certain location shift between two neighboring rows of quadrilateral design cells. This modified quadrilateral discretization model allows any two contiguous design cells to share an edge whether they are in the horizontal, vertical or diagonal direction. Point connection is eradicated. In the proposed discrete topology optimization method of structures, design variables are all binary and every design cell is either solid or void to prevent grey cell problem that is caused by intermediate material states. Local stress constraint is directly imposed on each analysis cell to make the optimized structure safe. The binary bit-array genetic algorithm is used to search for the optimal topology to circumvent the geometrical bias against the vertical design cells. No postprocessing is needed for topology uncertainty caused by point connection or grey cell. The presented discrete topology optimization procedure is illustrated by two topology optimization examples of structures.
Three-Dimensional Equilibria and Stability of Nonlinear Curved Beams Using Intrinsic Equations and Shooting
Authors: Karlson Kyle N. , Leamy Michael J.
Published: September 2013

This article describes a shooting method that provides numerical solutions to static equilibrium equations for intrinsically curved beams in three-dimensions. Notably, the method avoids iteration for cantilever beams subjected to distributed or point follower loads. This is due to the governing equations being given in first-order form such that the specification of a single boundary condition on the forced end results in automatic satisfaction of the fixed boundary condition. Also documented is a general procedure for finding all solutions to static beam problems with conservative loading. This is particularly useful in beam buckling problems where multiple stable and unstable solutions exist. The procedure for finding all solutions is built around the Picard-Lindelöf theorem on the uniqueness and existence of solutions to initial value problems. Using the presented approach, three-dimensional equilibrium solutions are generated for many loading cases and boundary conditions, including a three-dimensional helical beam, and are compared to similar solutions available in the literature. The stability of the generated solutions is assessed using a dynamic finite element code based on the same intrinsic beam equations. Due to the absent need for iteration, the presented approach may find application in model-based control for practical problems such as the control of equipment utilized in endoscopic surgeries and the control of spacecraft with robotic arms and long cables.
Motion Generation Using Combinations of Peaucellier Straight-Line Mechanisms
Authors: Nelson Carl A. , Padilla Christian A.
Published: September 2013

The Peaucellier linkage is one of only a handful of known, single-degree-of-freedom mechanisms that trace an exact straight line. Although the traced output is straight, the relation between input rotation angle and output position along the traced line is nonlinear. The purpose of this study is to investigate the composite motion of stacked Peaucellier straight-line mechanisms. After stacking, the original straight-line output transforms into a complex curve whose shape is dependent on the motion of all of the component mechanisms, their geometric parameters, and how the component Peaucellier cells are interconnected. MATLAB software was used to generate output curves considering different stacking configurations and mechanism sizes. MATLAB was also used to analyze the final data and identify correlations between the mechanism link sizes, stacking configurations, and relative output curves. Based on a polynomial fitting technique, resultant output of the stacked mechanisms was generally found to be of 6th order except when purposefully constrained. This is a first attempt to characterize kinematic trace curves for this type of stacked straight-line linkage system.
Developing a Taxonomy of Risk-Mitigating Actions From a Legacy Database of a Large Design Organization
Authors: Hsiao Chuck , Ruffino Michael , Malak Richard , Tumer Irem Y. , Doolen Toni
Published: September 2013

This paper presents a taxonomy for project-level risk-mitigating actions developed from a large design organization’s risk database. The taxonomy classifies actions according to their purpose and how they are embodied. The taxonomy along with the results of actions recorded in the database can be used to evaluate the effectiveness of different types of risk-mitigating actions. A methodology for refining the taxonomy based on analyzing mismatches between different coders using the taxonomy is also given. Because the taxonomy is based on an existing legacy database, this paper discusses related issues such as missing contextual information.

Developing this taxonomy will lead to further advances in empirically evaluating the usefulness of different risk-mitigating actions. This will allow for better understanding and improved prediction of how different types of risk-mitigating actions affect a project’s eventual outcomes such as cost and schedule, leading to future advances in decision-making approaches of risk-mitigating actions in complex environments.
On the Finding of Collinearity Circles for Force-Input Coupler-Driven Four-Bars
Authors: Chang Yin-ping , Her Innchyn
Published: September 2013

While there have been ample amount of publication on traditional four-bar transmission characteristics, little is found in the field relating to the transmission of a singular type of four-bar, namely, the force-input, coupler-driven variety. In contrast to the conventional torque-input, crank-driven four-bars, the use of this new category of linkage is only gradually surfacing. In this paper, a novel performance indicator called the Collinearity Circle is proposed, which is used to monitor the effectiveness of the transmission in a force-input, coupler-driven four-bar. The salient feature of this Collinearity Circle lies not only in its convenient shape, but also in its simple derivation, which can be shown to be merely geometry-dependent. Like the well known instant center, which is also only geometry-dependent, the proposed Collinearity Circle will be proved to be a handy addition to the kinematics toolbox for its power to enable speedy construction and ballpark estimations on the transmission properties of force-input, coupler-driven mechanisms.
Digging Trajectory Optimization for a New Excavating Mechanism of Electric Mining Shovel
Authors: Wei Baochen , Gao Feng
Published: September 2013

For traditional 2-DoF excavating mechanism of electric mining shovel, the log spiral trajectory is regarded as the optimal digging trajectory with less energy consumption. The design of new 3-DoF excavating mechanism is aimed for a mechanism more dexterous than the traditional 2-DoF one, thus reduces the digging energy consumption. The optimal trajectory of the new mechanism should be different from the traditional one. This paper considers different possibilities of excavating manners and different kind of digging trajectories. With the method of polynomial fitting, the approximately optimal trajectory is obtained. With the numerical simulation, it shows that the new 3-DOF excavating mechanism is energy-efficient compared with the traditional excavating mechanism.
State-of-the-Art in Geometric Modeling for Virtual Machining
Authors: Aras Eyyup , Yip-Hoi Derek
Published: September 2013

Advances in computer technology have made possible the integration of complex geometric and process modeling capabilities for use in engineering design and process planning. This is evident in the area of machining where it is now possible to integrate the physics of the machining process with changes that are taking place to the geometry of a work piece during the execution of complex operations. This capability is referred to as Virtual Machining (VM). Geometric modeling capabilities include the ability to generate complex swept volumes created during execution of tool path moves, to subtract these from a dynamically changing in-process work piece model, and to extract the instantaneous cutter/workpiece engagement as the tool moves in the feed direction. Process modeling includes the use of this engagement geometry to calculate cutting forces, deflection of structures, vibrations and to use these in process optimization.

This paper reviews advances in the first part of this tandem, the geometric modeling methods and techniques that make Virtual Machining possible. It further highlights important directions that can be taken to further advances in this field.
Decision-Based Design Using Time-Varying Preferences Represented by Stochastic Processes
Authors: Pandey Vijitashwa , Mourelatos Zissimos P.
Published: September 2013

Soliciting and expressing the preferences of a decision maker in engineering design is critical. In general, the preferences vary through time, complicating the design of engineering systems. In this article, we propose that if parameterized utility functions are used to model the preferences, the time-varying characteristics of the parameters can provide valuable information on the likely decisions the decision maker can make at a future time. To model the time-dependent uncertainty in preferences, we use parameterized utility functions with the parameters characterized by stochastic processes and demonstrate how the design process is affected by stationarity properties of the random parameters. We work in the normative utility theoretic domain and show a property of the multiplicative utility function that allows us to use the common Black-Scholes-Merton options pricing model from finance, to account for variability in preferences with time. Finally, we discuss how to modify the design process so that optimal products are ready when there is a future need for them. The applicability of our approach is demonstrated using a cell phone example.
Nonlinear Targeted Energy Transfer in Granular Chains
Authors: Hasan M. Arif , Starosvetsky Yuli , Vakakis Alexander F.
Published: September 2013

One of the prime focuses in the design of highly adaptive granular material is in ability to passively control the flow of energy through it by means of trapping, redirection and scattering. In this study we demonstrate that one of the possible mechanisms to achieve efficient control over the propagating shock wave in the material is the usage of weakly interacting, non-compressed granular chains. In the latest computational studies we have demonstrated that the shock waves initially localized on a finite amount of chains can be efficiently redirected to the neighboring granular chains. In this work, we present an analytical and numerical approach to the concept of targeted energy transfer (TET) in granular media. We consider two weakly coupled granular chains which have on-site potential. This on-site potential arises if the granular chains are mounted on linear elastic foundation. We propose two different mechanisms for TET in granular media: (i) decouple the coupling, and (ii) stratification of the foundation. Each mechanism provides an efficient way of localization of energy in one of the two chains. For the second mechanism, one chain with varying parameter is excited by an initial impulse but coupled with another chain with constant parameter is initially at rest and we transform the governing equation of the granular chain system into two coupled oscillators and thus made an analogy between strongly nonlinear granular chain with the quantum Landau-Zener tunneling. The revealed phenomena open up the possibility of designing granular media as shock mitigators by efficiently redirecting the incoming energy to the neighboring granular chain, i.e. it gives a passive control over the incoming energy by redirecting among the granular networks.
A Flexible Multibody Dynamic Approach for Virtual Shake Table Simulation
Authors: Das Manabendra , Mi Zan , Das Rajiv
Published: September 2013

A linear finite element (FE) analysis based on modal superposition techniques is often the tool of choice for response analysis of automobile and heavy machine sub-systems. Dynamic input loads cause various structures to vibrate and rattle, thereby inducing nonlinear interaction at the interfaces of these components. These nonlinear interactions cannot be modeled using a linear approach. On the other hand, fully nonlinear FE methods possess all the features that are required to capture nonlinear interactions but they demands enormous computation overhead for large system level models. A hybrid approach based on flexible multibody dynamics offers a viable solution to this problem. The system is divided into several sub-structures and each individual structure is represented as a separate flexible body. Modal superposition is used for each flexible body to reduce the size of the model. However, the interaction in-between various bodies or sub-structures is modeled using nonlinear force elements. Therefore, with this hybrid approach, the computation cost remains comparable to the linear FE method, without compromising the fidelity of the model.
Stabilization of Self-Excited Oscillation in a Flexible Fluid-Conveying-Pipe by Position Feedback Control
Authors: Kosaki Hideaki , Yabuno Hiroshi
Published: September 2013

Resonances in flexible fluid-conveying-pipes have been theoretically and experimentally analyzed from the practical and physical points of view. The excitation mechanisms for the resonances have been given considerable attention. In contrast with the analysis of the resonance phenomena, there are few studies on the stabilization control method for the self-excited oscillation of a flexible fluid-conveying-pipe. In this paper, we propose a control method for the self-excited oscillation in a fluid-conveying-pipe theoretically and experimentally. The unstable mode of the fluid-conveying-pipe is not any eigenmodes of the flexible pipe without flow because it is non-self adjoint system. In this paper, by not using the eigenmodes of the flexible pipe without flow deriving the unstable mode shape exactly, we propose a stabilization control method which actuates the unstable mode directly. Therefore, under the proposed control method, the spillover is avoidable and only one sensor is required.
Active Recovery of Contact-Free Levitation in Magnetic Bearing Systems
Authors: Li Peichao , Sahinkaya M. Necip , Keogh Patrick S.
Published: September 2013

The use of magnetic bearings allows rotor dynamic systems to be developed for high speed applications, including low pressure/vacuum environments. They provide an alternative to conventional journal, rolling element and gas bearings. The benefits of using magnetic bearings are well documented in terms of low friction operation, together with controllable dynamic characteristics such as stiffness and damping. Magnetic bearings are usually equipped with touchdown bearings to protect the system in cases of power failure, transient loadings, system faults or unexpected influences that may induce system control malfunction. A rotor assembly invariably exhibits residual unbalance due to manufacturing imperfections. The underlying unbalance forces have an influence of the rotor dynamics that arise from contact between a rotor and a touchdown bearing. When considered with the system dynamics, larger unbalance tends to increase the possibility that a rotor will be able to remain in persistent contact with a touchdown bearing. A system has therefore been developed in which the touchdown bearings may be actuated so as to induce the rotor to return to contact-free levitation. This paper provides an assessment of the touchdown bearing motions that will realistically achieve this goal.
Improvement, Optimization, and Prototyping of a Three Translational Degree of Freedom Parallel Robot
Authors: Hodgins Jonathan , Zhang Dan
Published: September 2013

This paper presents an evolutionarily design change for the Delta parallel robot. The proposed design change increases the useful workspace of the robot and aids in permanently avoiding singularities on the workspace. This is accomplished by means of a new intermediate parallel link.

This also simultaneously increases the total workspace volume and the stiffness at the outer limits of the workspace.

The design is analyzed and the inverse kinematics, stiffness and dexterity relations are formulated. Subsequently, an optimization problem is formulated that aims at taking advantage of the new attributes and illustrate its benefits to the robotic design. The results are clearly illustrated by comparing the robot with the new link to an equivalent robot without it.

Lastly, the developed design is 3D modeled to test and verify functionality.
A Structured Approach to Identify Styles in Designs
Authors: Chan Tian , Mihm Jürgen , Sosa Manuel
Published: September 2013

This paper introduces a structured approach, based on clustering analysis, to identify groups of visually similar designs (and potentially members of a design style) in a large set of unique designs. We implemented our approach on the population of design patents filed in the USA during the 1976–2010 period. Design patent data is used in our analysis for two reasons: (1) claims of design patents concern the visual aspects of classes of artifacts; (2) similarity between design patents is captured through a tightly controlled citation process. The cluster analysis is based on constructing a similarity index across all pairs of design patents, followed by applying a divisive graph clustering algorithm to organize design patents into a hierarchical tree. Identified clusters of potentially visually similar design patents are tested for positive association against other grouping criteria that are expected to contain similar designs such as design patents filed by the same designer, design patents filed by the same firm, and design patents assigned to the same patent class category. We discuss the implications of our findings for the study of the emergence and evolution of styles in design.
Structure Synthesis of Six-Bar Mechanisms for Aircraft High-Lift Surfaces
Authors: Wang Anngwo , Yan Hong-Sen , Kuo Chin-Hsing
Published: September 2013

Slat/flap driven mechanisms are essential transmission components of high lift systems and may contain combinations of linkages, ball screws, cam tracks and gears. This paper is, therefore, devoted to the structural synthesis of the aircraft slats/flaps driven mechanisms with six links. Based on the concept of generalization and specialization of mechanisms, all feasible new design alternatives are systematically derived and summarized as a complete atlas listed in Appendix. The provided atlas is useful for designers when considering alternative topological structures of the slats/flaps driven mechanisms in the future.
Limit-Cycle Analysis of Three Dimensional Rigid Rotor/Shaft/Autobalancer System With Symmetric Bearing Support
Authors: Jung DaeYi , DeSmidt Hans
Published: September 2013

In recent years, there has been much interest in the use of automatic balancing devices (ABDs) in rotating machinery. Autobalancers consist of several freely moving eccentric balancing masses mounted on the rotor, which, at certain operating speeds, act to cancel rotor imbalance. This “automatic balancing” phenomena occurs as a result of nonlinear dynamic interactions between the balancer and rotor wherein the balancer masses naturally synchronize with the rotor with appropriate phase to cancel the imbalance. However, due to inherent nonlinearity of the autobalancer, the potential for other undesirable non-synchronous limit-cycle behavior exists. In such situations, the balancer masses do not reach their desired synchronous balanced positions resulting in increased rotor vibration. Although several researchers have explored limit-cycle behavior of single-plane ABD-rotor systems, a limit-cycle analysis of a full three dimensional rigid ABD/shaft/rotor considering transverse deflection, out-plane tilting and gyroscopic effects has not been investigated. This paper considers an approximate harmonic analytical solution to describe the limit-cycle behavior in a three dimensional rigid rotor/ABD system. Essentially, the solutions presented here capture both in-plane transverse deflection and out-plane tilting motion of the system under the limit-cycle condition. Here the whirl speed of the ABD balancer masses is determined via the solution of a non-linear characteristic equation. Also, based upon the limit-cycle solutions, the limit-cycle stability is assessed via a perturbation and Floquet analysis exploring three main parameters; ABD balancer mass, ABD damping, and axial location of ABD along the shaft. The coexistence of the stable balanced synchronous condition and undesired non-synchronous limit-cycle is studied. It is found that for certain combinations of ABD parameters and rotor speeds, the non-synchronous limit-cycle can be made unstable thus guaranteeing global asymptotic stability of the synchronous balanced condition. Finally, the analysis is validated through numerical simulation. The findings in this paper yield important insights for researchers wishing to utilize automatic balancing devices in rotor/shaft systems and limit-cycle mitigation.
Designing B-Spline Surfaces With Haptics Based on Energy Minimization Method
Authors: Liu Xiaodong
Published: September 2013

Designing B-Spline Surfaces is difficult and cumbersome with traditional 2D based interfaces, e.g., a 2D mouse. Based on energy minimization or variational surfacing technique, the paper presents a technique for using a haptic device to design B-Spline surfaces. In our system, a haptic interface is used to directly manipulate/design key constraints in a natural 3D environment, and the system uses energy minimization method to generate the “smoothest” B-Spline surface that satisfies these constraints in real-time. The discussed technique is significantly much more efficient and powerful than previous research, and without any pre-calculation, it can solve a B-Spline surface with up to 20,000 control points in real-time and, at the same time, produce high quality B-Spline surfaces satisfying an arbitrary combination of point and curve constraints.
Analysis of Multi-Material Bonded Assemblies on a Non-Conforming Mesh
Authors: Kumar Goldy , Shapiro Vadim
Published: September 2013

Bonded multi-material assemblies arise frequently in design, manufacturing, architecture, and materials design. It is a common wisdom that finite element analysis of such assemblies usually requires all components to be represented by compatible finite element meshes; application of meshfree methods in such situations is often considered problematic due to the need to impose additional interface conditions. Neither approach scales to deal with realistically complex models arising in many applications.

We propose a simple extension of meshfree analysis on a non-conforming mesh for linear structural analysis of such multimaterial assemblies. The method is simple, can be implemented within most FEA packages and does not require either compatible meshing or complex interface boundary conditions. Our numerical experiments demonstrate that computed results are in good agreement with known analytical and computational results for well studied multi-material bonded assemblies (lap and butt joints). We also demonstrate application of the proposed method to realistically complex assembly of a mounted sculpture that cannot be easily analysed by other methods.
Ontology-Based Malfunction Forecast and Root Cause Analysis in Product Design
Authors: Chang Xiaomeng , Terpenny Janis
Published: September 2013

In product design, passing undetected errors to the downstream can cause error avalanche, could diminish product acceptance and largely increase the overall cost. Yet, it is difficult for designers to collect all the related potential errors from different departments in the initial design phase. In order to deal with these problems, this paper puts forward an ontology based method to integrate related history error data from different data sources of multiple departments in an enterprise. By using the advantages of ontologies and ontology-based information systems in knowledge management and semantic reasoning, the method enables the investigation of the root cause of the related potential malfunctions in the early product design phase. The framework can provide warnings and root causes of related potential errors in design based on history data and further continuously improve the product design. In this manner, this method is expected to reduce the knowledge limitation of designers in the initial design phase, help designers consider the problems in the whole enterprise and the product life cycle more completely, facilitate design improvement more accurately and efficiently, and further reduce the cost of the overall product life cycle.
A Combinatorial Packing Algorithm and Standard Trunk Geometry for ISO Luggage Packing
Authors: Shellshear Evan , Carlson Johan S. , Bohlin Robert
Published: September 2013

Automated packing algorithms for luggage compartments in automobiles are of great interest. The difficulty of automatically computing the volume of a mesh representation of a boot according to the ISO 3832 standard restricts the design of vehicles required to meet minimal trunk volume specifications and also increases the cost of physical and virtual verification of the original design specifications. In our paper we present a new heuristic combinatorial packing algorithm for the ISO luggage packing standard. The algorithm presents numerous advantages over previous algorithms in terms of its simplicity and speed as well as producing high density of packed objects. The algorithm also solves the problem of requiring a fixed grid structure to position discrete objects in the boot and can also be used as an additional optimization on existing algorithms. In addition, we also provide the first comparison of state of the art packing algorithms for a simplified trunk geometry and propose a standard trunk geometry to enable future researchers to compare their results with other packing algorithms.
A Network Flow Optimization Model for Automotive Glazing Recycling
Authors: Farel Romain , Saitou Kazuhiro , Leroy Yann , Yannou Bernard
Published: September 2013

In a recycling scheme such as the recycling of End of Life Vehicle (ELV) materials, the different stakeholders are expected to configure the operation process and the product distribution to maximize their own profits. However, these individual optimizations in many cases do not correspond to the maximal profit for the whole chain. In addition, the financial autonomy must be carefully studied beforehand and controlled so as to ensure an economically viable recycling chain. This paper proposes a cost-benefit parameterized model for the ELV glazing recycling scheme both for the network structure and the material flow sizing. The model is mapped onto real ground data from French industrial partners, and a linear optimization model is built to simulate the conditions of costs and benefits situations for the upcoming glazing recycling chain in 2015 in France.
Prognosis Informed Design Framework for Operation and Maintenance of Wind Turbines
Authors: Tamilselvan Prasanna , Wang Yibin , Wang Pingfeng
Published: September 2013

Advances in high performance sensing and signal processing technology enable the development of failure prognosis tools for wind turbines to detect, diagnose, and predict the system-wide effects of failure events. Although prognostics can provide valuable information for proactive actions in preventing system failures, the benefits have not been fully utilized for the operation and maintenance decision making of wind turbines. This paper presents a generic failure prognosis informed decision making tool for wind farm operation and maintenance while considering the predictive failure information of individual turbine and its uncertainty. In the presented approach, the probabilistic damage growth model is used to characterize individual wind turbine performance degradation and failure prognostics, whereas the economic loss measured by monetary values and environmental performance measured by unified carbon credits are considered in the decision making process. Based on the customized wind farm information inputs, the developed decision making methodology can be used to identify optimum and robust strategies for wind farm operation and maintenance in order to maximize the economic and environmental benefits concurrently. The efficacy of proposed prognosis informed maintenance strategy is compared with the condition based maintenance strategy and demonstrated with the case study.
Determining the Stability of Collaborative R&D Networks
Authors: Altfeld Nils , Hinckeldeyn Johannes , Kreutzfeldt Jochen , Gust Peter
Published: September 2013

To reduce the likelihood that R&D projects fail, companies tend to perform collaborative R&D activities in networks. A fundamental characteristic of networks is stability. This paper introduces a novel approach that theoretically determines the stability of R&D networks and combines the analysis of network topology with a two-layer simulation model.

Graph theory and measures from social network analysis are used to analyze the topology of collaborative R&D project networks. Our study enables us to identify the companies that play a key role in R&D networks. To ensure the right outcome of the collaborative R&D project, participants with a high betweenness centrality index should be monitored. These participants influence the stability of collaborative networks on a large scale. With these insights, an improved risk management approach can be set up.
Learn to Design by Mapping Information Among Several Methods
Authors: Rizzuti Sergio
Published: September 2013

The paper is based on the experience matured in ten years of teaching “Product Design and Development” at the Faculty of Engineering of the University of Calabria (Italy).

This paper is focused on the consideration that many of the methods employed during product design activity share a matrix formulation as a means of collecting and managing project data and that students must be familiarized with the use of this kind of data structure in a very different way from their previous experiences, because project management can be pursued by mapping information from one method to another.

Students are in fact guided to organize data related to the design on which they are involved in order to guarantee that the information can be mapped from one formulation to another, meaning that they have the whole design process under control. Attention will be paid to the pedagogic aspects and problems associated with the way how information can be collected and ranked and how a decision can be made.
Experimental Study on Pre-Stressed Circular Cylindrical Shell
Authors: Zippo Antonio , Barbieri Marco , Strozzi Matteo , Errede Vito , Pellicano Francesco
Published: September 2013

In this paper an experimental study on circular cylindrical shells subjected to axial compressive and periodic loads is presented. Even though many researchers have extensively studied nonlinear vibrations of cylindrical shells, experimental studies are rather limited in number. The experimental setup is explained and deeply described along with the analysis of preliminary results. The linear and the nonlinear dynamic behavior associated with a combined effect of compressive static and a periodic axial load have been investigated for different combinations of loads; moreover, a non stationary response of the structure has been observed close to one of the resonances. The linear shell behavior is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.
Polar Decomposition of Unit Dual Quaternions
Authors: Purwar Anurag , Ge Q. J.
Published: September 2013

This paper seeks to extend the notion of polar decomposition from matrix algebra to dual quaternion algebra. The goal is to obtain a simple, efficient and explicit method for determining the polar decompositions (PD) of spatial displacements in Euclidean three-space that belong to a special Euclidean Group known as SE(3). It has been known that such a decomposition is equivalent to the projection of an element of SE(3) onto SO(4) that yields hyper spherical displacements that best approximate rigid-body displacements. It is shown in this paper that a dual quaternion representing an element of SE(3) can be decomposed into a pair of unit quaternions, called double quaternion, that represents an element of SO(4). Furthermore, this decomposition process may be interpreted as the projection of a point in four-dimensional space onto a unit hypersphere. Examples are provided to illustrate that the results obtained from this dual-quaternion based polar decomposition are same as those obtained from the matrix based polar decomposition.
Distributed Actuation Effectiveness of Flexible Parabolic Cylindrical Panels
Authors: Hu S. D. , Li H. , Tzou H. S.
Published: September 2013

Open parabolic cylindrical panel plays a key role in radial collection and transmission applied to radar antennas, space reflectors, solar collectors, etc. Piezoelectric active vibration control can suppress unexpected fluctuation and maintain precision surface and operations. This study aims to investigate the distributed actuation behavior of adaptive open parabolic cylindrical panels using piezoelectric actuator patches. Motion equations of parabolic cylindrical panels laminated with a piezoelectric patch is presented first. Then, the actuator induced modal control force is derived with an assumed mode shape function. As the area of actuator patch varies due to the curvature change, the normalized actuation effectiveness (i.e., modal control force divided by actuator area) is further evaluated. When the actuator area shrinks to infinitesimal, the expression of microscopic point modal control force is obtained to theoretically predict the actuation distribution behavior. The actuation behaviors of the total control force and its components exhibit distinct characteristics with respect to shell geometries, modes and actuator properties. Analyses show that the control force component contributed by the membrane force dominates the total control effect. The bending-contributed component increases with corresponding vibration mode number, while the membrane-contributed component decreases. Three shell geometries from shallow to deep are evaluated in case studies. Analysis of optimal actuator location shows that actuators are preferred to locate where the curvature of shell panel is larger in order to maximize the control effectiveness.
Efficient Implementation of Extended Finite Element Method
Authors: Hotwani Vishal , Kumar Ashok V.
Published: September 2013

Extended finite element method (or XFEM) locally enriches the finite element solution using a priori known analytical solution. XFEM has been used extensively in fracture mechanics to compute stress concentration at crack tips. It is a mesh independent method that allows crack to be represented as an equation instead of using the mesh to approximate it. When this approach is used along with Implicit Boundary Finite Element Method (IBFEM) to apply boundary conditions, a fully mesh independent approach for studying crack tip stresses can be implemented. An efficient scheme for blending the enriched solution structure with the underlying finite element solution is presented. A ramped step function is introduced for modeling discontinuity or a crack within an element. Exact analytical solution is used as enrichment at the crack tip element to obtain the stress intensity factor (SIF) directly without any post processing or contour integral computation. Several examples are used to study the convergence and accuracy of the solution.
Using Model Uncertainty to Reduce Verification and Validation in Noise and Vibration Problems
Authors: Otto Kevin , Jacobson Clas
Published: September 2013

Verifying and validating that a mechanical system meets the design requirements is often a costly iterative activity. This is particularity true, for example, with complex vehicle systems that must meet noise and vibration requirements to ensure vehicle occupant comfort. We show here how analysis of model uncertainty can speed verification testing by bounding and guiding hardware prototype redesign. Vibration and acoustic model uncertainty and residual errors are estimated, and then analysis derived to ensure that this uncertainty range is covered by a planned set of design changes. We further use these results to define a complexity metric based on uncertainty, and an adaptability metric based on the domain of available adjustment. We then propose a capability metric by comparing the range of uncertainty against the range of adaptability provided. We demonstrate the efficacy with an example from the elevator system design, rapidly meeting noise and vibration requirements with only one prototype iteration.
Probabilistic Vision-Based Full-Field Displacement and Strain Measurement via Uncertainty Propagation
Authors: Furukawa Tomonari , Wada Yoshitaka , Michopoulos John G. , Iliopoulos Athanasios
Published: September 2013

This paper presents formulations that enable the vision-based measurement of displacement and strain fields extensively in a probabilistic manner. The proposed formulations are built on the dot centroid tracking (DCT) method by digital cameras, which measures the darkness of each pixel in gray scale, identify dots marked on a specimen, derives dot centroids using pixel darkness information and derives displacement and strain fields by tracking the centroids and interpolating the nodal displacements and strains. Under the Gaussian assumption, the proposed formulations analytically propagate the standard deviation of uncertainty in darkness measurement and estimate that in the displacement and strain field measurement. As the first step, the formulations were completed for continuous field measurement with triangular elements. Most advantageously, the proposed formulations allow discussion on measurement error bounds, which also enables the quantitative comparison of the DCT method to the other measurement techniques. For numerical validation, standard deviations of nodal displacements and strains estimated from the known darkness uncertainty were compared to those derived from large samples created with the same darkness uncertainty. The results show the validity of the proposed formulations and their potential in measurement with reliability.
Design Optimisation of a Nonlinear Energy Sink Embedded on a Harmonically Forced Linear Oscillator: Theoretical and Experimental Developments
Authors: Gourc Etienne , Michon Guilhem , Seguy Sébastien , Berlioz Alain
Published: September 2013

In this paper, the dynamic response of a harmonically forced Linear Oscillator (LO) strongly coupled to a Nonlinear Energy Sink (NES) is investigated theoretically and experimentally. The system studied comprises a linear oscillator subject to an imposed displacement with an embedded, purely cubic, NES. The behavior of the system is analyzed in the vicinity of 1:1 resonance. The complexification averaging technique is used to obtain modulation equations and the associated fixed points. These modulation equations are analyzed using asymptotic expansion to study the regimes related as relaxation oscillation of the slow flow called Strongly Modulated Response (SMR). The zones where SMR occur are computed using a mapping procedure. The Slow Invariant Manifolds (SIM) is used to derive a proper optimization procedure. It is shown that there exist an optimal zone in the parameter plane forcing amplitude–nonlinear stiffness, where SMR occurs without having a high amplitude detached resonance tongue. An experimental setup exhibits a strong mass asymmetry (mass ratio ≈ 1%). The cubic stiffness is realized geometrically with two linear spring that extend axially and are free to rotate. Using the previous optimized stiffness of the NES, different frequency response curves and associated zones of SMR are obtained for various forcing amplitude. Good agreement between theoretical and experimental results is observed. The reported experimental results confirm the design procedure, and the possible application of NES for vibration mitigation under periodic forcing.
Shape Characterization for Droplet Impingement Dynamics in Ink-Jet Deposition
Authors: Zhou Wenchao , Loney Drew , Fedorov Andrei G. , Degertekin F. Levent , Rosen David W.
Published: September 2013

The impact of droplets onto a substrate in ink-jet printing is critical for control and optimization of the droplet deposition process to improve part quality and accuracy and to reduce the manufacturing time. However, most previous research on droplet impingement dynamics mainly utilized one metric — the droplet spreading radius, which does not provide enough information for manufacturing purposes. This paper presents a new metric that is relevant to manufacturing by characterizing the droplet shape by measuring the similarity between the droplet shape and a desired shape over time. This enables a model of droplet shape evolution and optimization of the droplet deposition process to build desired geometries. Meanwhile, analyses with this shape metric aids understanding the physics of droplet shape evolution during impingement. A 2-D shape metric is first proposed and test cases are given to validate the effectiveness of the shape metric. Then the definition is extended to characterize 3-D droplet shape. Results also show the 3-D shape metric is effective and robust.
Near-Wall Dynamics and Photoresponse of Swimming Microbiorobots
Authors: Wong Denise , Steager Edward B. , Kumar Vijay
Published: September 2013

At the microscale, the ability to precisely move objects on the scale of microns is a challenge. One method is to use microbiorobots (MBRs), constructed of a neutrally-buoyant microstructure powered by a monolayer of swarmer flagellated bacteria adhered to the surface. The bacteria swim to propel the microstructure in a fluidic environment in the absence of external forces. The trajectory is a combination of translation and rotation, with the rotation generally observed to be clockwise when viewed from above. In order to create a dynamic model of the inherent motion of MBRs, we use UV light to immobilize the bacteria on different regions of an MBR and characterize the resultant motion. We show that the bacteria on the edge of the structure have different force contributions than those in the center of the microstructure where the flagella cannot interact with the surface under that MBR. This is a step towards improved accuracy in the control of MBRs when external forces are applied for manipulation.
High Dimensional Full Inverse Characterization of Fractal Volumes
Authors: Michopoulos John G. , Iliopoulos Athanasios
Published: September 2013

The present paper describes a methodology for the inverse identification of the complete set of parameters associated with the Weirstrass-Mandelbrot (W-M) function that can describe any fractal scalar field distribution of measured data defined within a volume. Our effort is motivated by the need to be able to describe a scalar field quantity distribution in a volume in order to be able to represent analytically various non-homogeneous material properties distributions for engineering and science applications. Our method involves utilizing a refactoring of the W-M function that permits defining the characterization problem as a high dimensional singular value decomposition problem for the determination of the so-called phases of the function. Coupled with this process is a second level exhaustive search that enables the determination of the density of the frequencies involved in defining the trigonometric functions involved in the definition of the W-M function. Numerical applications of the proposed method on both synthetic and actual volume data, validate the efficiency and the accuracy of the proposed approach. This approach constitutes a radical departure from the traditional fractal dimension characterization studies and opens the road for a very large number of applications and generalizes the approach developed by the authors for fractal surfaces to that of fractal volumes.
Multi-Sensor Defect Identification Under Sensor Uncertainties
Authors: Furukawa Tomonari , Koo Bonsung , Xu Fei , Michopoulos John G.
Published: September 2013

This paper presents a methodology for identifying defects by multiple sensors under the presence of both sensor and defect uncertainties. This methodology introduces a representation of the beliefs of both the locations of defects and the sensors each by a probability density function and updates them using the extended Kalman filter. Since the beliefs are recursively maintained while the sensor is moving and the associated observation data are updated, the proposed methodology considers not only the current observation data but also the prior knowledge, the past observation data and beliefs, which include both sensor and defect uncertainties. The concept of differential entropy also has been introduced and is utilized as a performance measure to evaluate the result of defect identification and handle the identification of multiple defects. The verification and evaluation of the proposed methodology performance were conducted via parametric numerical studies. The results have shown the successful identification of defects with reduced uncertainty when the number of measurements increases, even under the presence of large sensor uncertainties. Furthermore, the proposed methodology was applied to the more realistic problem of identifying multiple defects located on a specimen and have demonstrated its applicability to practical defect identification problems.
Optimization of Honeycomb Contact-Aided Compliant Cellular Mechanism for Strain Energy Absorption
Authors: Hyland Jennifer E. , Frecker Mary I. , Lesieutre George A.
Published: September 2013

This paper presents the optimization of hexagonal honeycomb structures with internal contact mechanisms for energy absorption applications. While extensive work has been reported in the literature on traditional honeycombs of varying geometries under dynamic and static loading, contact-aided compliant cellular mechanisms under quasi-static crushing or impact have not been previously considered. This paper addresses this void through the optimization of a hexagonal honeycomb unit cell containing a contact mechanism. An optimization problem is formulated that maximizes the strain energy per area of a contact-aided compliant cellular mechanism. Two- and three-variable optimization problems are considered, using variables that define the cell geometry and the initial contact gap. It is found that with the addition of a contact mechanism, more strain energy can be absorbed when compared to the same cell without a contact mechanism.