bluuebunny/crossref_metadata_2025 huggingface dataset:
Proper Orthogonal Decomposition for Nonlinear Radiative Heat Transfer Problems
Authors: Hickey Daryl , Masset Luc , Kerschen Gaetan , Bru¨ls Olivier
Published: June 2012

Analysing large scale, nonlinear, multiphysical, dynamical structures, by using mathematical modelling and simulation, e.g. Finite Element Modelling (FEM), can be computationally very expensive, especially if the number of degrees-of-freedom is high. This paper develops modal reduction techniques for such nonlinear multiphysical systems. The paper focuses on Proper Orthogonal Decomposition (POD), a multivariate statistical method that obtains a compact representation of a data set by reducing a large number of interdependent variables to a much smaller number of uncorrelated variables. A fully coupled, thermomechanical model consisting of a multilayered, cantilever beam is described and analysed. This linear benchmark is then extended by adding nonlinear radiative heat exchanges between the beam and an enclosing box. The radiative view factors, present in the equations governing the heat fluxes between beam and box elements, are obtained with a ray-tracing method. A reduction procedure is proposed for this fully coupled nonlinear, multiphysical, thermomechanical system. Two alternative approaches to the reduction are investigated, a monolithic approach incorporating a scaling factor to the equations, and a partitioned approach that treats the individual physical modes separately. The paper builds on previous work presented previously by the authors. The results are given for the RMS error between either approach and the original, full solution.
Support of Product Innovation With a Modular Framework for Knowledge Management: A Case Study
Authors: Eddy Douglas , Krishnamurty Sundar , Grosse Ian , Wileden Jack
Published: June 2012

This paper presents an e-Design framework for knowledge management through its application in an engineering design case study. The e-Design framework enables the implementation of integrated design information throughout the entire design process. It facilitates the ease of sharing real time information across multiple individual designers, departments, or organizations as would be required in large scale design efforts. Similarly, it allows for the ease of use of technical tools integral to the design process that small design departments depend upon. Thus, regardless of the scale, the efficiency of engineering design can be improved with the use of the e-Design framework. The many features of the e-Design framework are exemplified through its application in a practical industry design problem. The case study in this paper addresses the utility and ease of use of this framework and provides one potential implementation method. This study involves a representative application of an innovative new mast design to elevate a surveillance camera on a military vehicle. The design process utilizes the NIST functional basis [3] to improve effectiveness and efficiency during conceptual design. The decision tool module of the e-Design framework is then used to evaluate and select the best conceptual design based on product design criteria. We use this case study to illustrate information quality and the clarity of design intent throughout the entire design process. The results reveal a usable design process method that can improve the transparency of design knowledge from design conception to completion. Additional benefits include storing of the information generated at the early stages for sharing and reuse throughout the entire design process. Most of all, improved transparent communication throughout the design process will reduce duplication of efforts and trial and error occurrences.
Enabling Computational Dynamics in Distributed Computing Environments Using a Heterogeneous Computing Template
Authors: Heyn Toby , Seidl Andrew , Mazhar Hammad , Lamb David , Tasora Alessandro , Negrut Dan
Published: June 2012

This paper describes a software infrastructure made up of tools and libraries designed to assist developers in implementing computational dynamics applications running on heterogeneous and distributed computing environments. Together, these tools and libraries compose a so called Heterogeneous Computing Template (HCT). The heterogeneous and distributed computing hardware infrastructure is assumed herein to be made up of a combination of CPUs and GPUs. The computational dynamics applications targeted to execute on such a hardware topology include many-body dynamics, smoothed-particle hydrodynamics (SPH) fluid simulation, and fluid-solid interaction analysis. The underlying theme of the solution approach embraced by HCT is that of partitioning the domain of interest into a number of sub-domains that are each managed by a separate core/accelerator (CPU/GPU) pair. Five components at the core of HCT enable the envisioned distributed computing approach to large-scale dynamical system simulation: (a) a method for the geometric domain decomposition and mapping onto heterogeneous hardware; (b) methods for proximity computation or collision detection; (c) support for moving data among the corresponding hardware as elements move from subdomain to subdomain; (d) numerical methods for solving the specific dynamics problem of interest; and (e) tools for performing visualization and post-processing in a distributed manner. In this contribution the components (a) and (c) of the HCT are demonstrated via the example of the Discrete Element Method (DEM) for rigid body dynamics with friction and contact. The collision detection task required in frictional-contact dynamics; i.e., task (b) above, is discussed separately and in the context of GPU computing. This task is shown to benefit of a two order of magnitude gain in efficiency when compared to traditional sequential implementations. Note: Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not imply its endorsement, recommendation, or favoring by the US Army. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Army, and shall not be used for advertising or product endorsement purposes.
Vertically-Aligned Springless Energy Harvester
Authors: Bendame Mohamed , Elrayes Karim , Mahmoud Mohamed , Abdel-Rahman Eihab M. , El-Saadany Ehab , Mansour Raafat
Published: June 2012

This paper analyzes a new configuration of a recently proposed “springless” vibration energy harvester. In this study, the harvester is positioned so that its oscillations are aligned vertically acting against gravity. The MPG response is investigated experimentally. Test results show that the VEH behaves as a softening nonlinear oscillator even for small excitations. A mathematical model of the underlying impact oscillator is also derived and its parameters are estimated.
Nonlinear Free Vibration of Nanobeams With Surface Effects Considerations
Authors: Fallah Ali , Firoozbakhsh Keikhosrow , Kahrobaiyan Mohammad Hossein , Pasharavesh Abdolreza
Published: June 2012

In this paper, simple analytical expressions are presented for geometrically non-linear vibration analysis of thin nanobeams with both simply supported and clamped boundary conditions. Gurtin-Murdoch surface elasticity together with Euler-Bernoulli beam theory is used to obtain the governing equations of motions of the nanobeam with surface effects consideration. The governing nonlinear partial differential equation is reduced to a single nonlinear ordinary differential equation using Galerkin technique. He’s variational approach is employed to obtain analytical solution for the resulted nonlinear governing equation. The effects of different parameters such as vibration amplitude, boundary conditions, and beam dimensions on the natural frequencies of nanobeams are investigated and results are presented for future studies.
Multibody Dynamics in Generalized Divide and Conquer Algorithm (GDCA) Scheme
Authors: Poursina Mohammad , Anderson Kurt S.
Published: June 2012

Generalized divide and conquer algorithm (GDCA) is presented in this paper. In this new formulation, generalized forces appear explicitly in handle equations in addition to the spatial forces, absolute and generalized coordinates which have already been used in the original version of DCA. To accommodate these generalized forces in handle equations, a transformation is presented in this paper which provides an equivalent spatial force as an explicit function of a given generalized force. Each generalized force is then replaced by its equivalent spatial force applied from the appropriate parent body to its child body at the connecting joint without violating the dynamics of the original system. GDCA can be widely used in multibody problems in which a part of the forcing information is provided in generalized format. Herein, the application of the GDCA in controlling multibody systems in which the known generalized forces are fedback to the system is explained. It is also demonstrated that in inverse dynamics and closed-loop control problems in which the imposed constraints are often expressed in terms of generalized coordinates, a set of unknown generalized forces must be considered in the dynamics of system. As such, using both spatial and generalized forces, GDCA can be widely used to model these complicated multibody systems if it is desired to benefit from the computational advantages of the DCA.
Analysis and Design of an In-Pipe System for Water Leak Detection
Authors: Chatzigeorgiou Dimitris M. , Youcef-Toumi Kamal , Khalifa Atia E. , Ben-Mansour Rached
Published: June 2012

In most cases the deleterious effects associated with the occurrence of leaks may present serious problems and therefore, leaks must be quickly detected, located and repaired. The problem of leakage becomes even more serious when it is concerned with the vital supply of fresh water to the community. In addition to waste of resources, contaminants may infiltrate into the water supply. The possibility of environmental health disasters due to delay in detection of water pipeline leaks has spurred research into the development of methods for pipeline leak and contamination detection. Leaking in water networks has been a very significant problem worldwide, especially in developing countries, where water is sparse. Many different techniques have been developed to detect leaks, either from the inside or from the outside of the pipe; each one of them with their advantages, complexities but also limitations. To overcome those limitations we focus our work on the development of an in-pipe-floating sensor. The present paper discusses the design considerations of a novel autonomous system for in-pipe water leak detection. The system is carefully designed to be minimally invasive to the flow within the pipe and thus not to affect the delicate leak signal. One of its characteristics is the controllable motion inside the pipe. The system is capable of pinpointing leaks in pipes while operating in real network conditions, i.e. pressurized pipes and high water flow rates, which are major challenges.
Towards a Formal Representation Model of Problem Formulation in Design
Authors: Dinar Mahmoud , Shah Jami , Hunt Glen , Campana Ellen , Langley Pat
Published: June 2012

Studies on design, show that problem formulation plays a major role in creative design. We plan to construct an interactive computer system that aids problem formulation. In the current stage, to improve our understanding of problem formulation, we have conducted exploratory protocol studies of novice designers and collected data from an expert designer in the form of a depositional interview. A formal representation of the design problem is needed to improve our empirical investigation. We propose a preliminary framework for such a model and we call it a problem map. It provides a basis for comparing how different designers perceive a problem. Our study is based on the design of a model aircraft for the AIAA student design competition. This preliminary analysis shows the evolution of the problem and the solution spaces in the elaboration of the problem maps through time. The problem maps also show a richer representation of attended attributes and relations for the expert and more attributes left in vacuum for the novices.
Kinematics and Dynamics of a Sliding/Bouncing Two Mass System
Authors: Gharib Mohamed , Tavakoli Ali , Hurmuzlu Yildirim
Published: June 2012

This paper presents the solution of the impact problem for a sliding/bouncing baton on flat and inclined planes subject to surface friction. The baton is assumed to have unilaterally constrained motion, which means one end slides on the ground while the other end collides with the ground. We use the impulse momentum approach and incorporate the impulse correlation ratio (ICR) hypothesis to solve the ground impact problem when the system has unilaterally constrained dynamics. Parametric investigations were carried out to examine the effect of the baton’s length and the inclined wall slope angle on the impulse correlation ratio. Numerical simulation and experiments were carried out to validate the model.
Robust Design for Profit Maximization Under Uncertainty of Consumer Choice Model Parameters Using the Delta Method
Authors: Resende Camilo B. , Heckmann C. Grace , Michalek Jeremy J.
Published: June 2012

In new product design, risk averse firms must consider downside risk in addition to expected profitability, since some designs are associated with greater market uncertainty than others. We propose an approach to robust optimal product design for profit maximization by introducing an α-profit metric to manage expected profitability vs. downside risk due to uncertainty in market share predictions. Our goal is to maximize profit at a firm-specified level of risk tolerance. Specifically, we find the design that maximizes the α-profit: the value that the firm has a (1−α) chance of exceeding, given the distribution of possible outcomes. The parameter α∈[0,1] is set by the firm to reflect sensitivity to downside risk (or upside gain), and parametric study of α reveals the sensitivity of optimal design choices to firm risk preference. We account here only for uncertainty of choice model parameter estimates due to finite data sampling when the choice model is assumed to be correctly specified (no misspecification error). We apply the delta method to estimate the mapping from uncertainty in discrete choice model parameters to uncertainty of profit outcomes and identify the estimated α-profit as a closed form function of design decision variables. This process is described for the multinomial logit model, and a case study demonstrates implementation of the method to find the optimal design characteristics of a midsize consumer automobile.
Approximate Surfacing of Curve Clouds for Conceptual Shape Creation and Evaluation
Authors: Arisoy Erhan Batuhan , Orbay Gunay , Kara Levent Burak
Published: June 2012

In product design, designers often create a multitude of concept sketches as part of the ideation process. Transforming such sketches to 3D digital models usually require special expertise and effort due to a lack of suitable Computer Aided Design (CAD) tools. Although recent advances in sketch-based user interfaces and immersive environments (such as augmented/virtual reality) have introduced novel curve design tools, rapid surfacing of such data remains an open challenge. To this end, we propose a new method that enables a quick construction of approximate surfaces from a cloud of 3D curves that need not be connected to one another. Our method first calculates a vector field by discretizing the space in which the curve cloud appears into a voxel image. This vector field drives a deformable surface onto the 3D curve cloud thus producing a closed surface. The surface smoothness is achieved through a set of surface smoothing and subdivision operations. Our studies show that the proposed technique can be particularly useful for early visualization and assessment of design ideas.
Controlling Modular Reconfigurable Robots With Handheld Smart Devices
Authors: Ko David , Kahawatte Nalaka , Cheng Harry H.
Published: June 2012

Highly reconfigurable modular robots face unique teleoperation challenges due to their geometry, configurability, high number of degrees of freedom and complexity. Current methodology for controlling reconfigurable modular robots typically use gait tables to control the modules. Gait tables are static data structures and do not readily support realtime teleoperation. Teleoperation techniques for traditional wheeled, flying, or submerged robots typically use a set of joysticks to control the robots. However, these traditional methods of robot teleoperation are not suitable for reconfigurable modular robotic systems which may have dozens of controllable degrees of freedom. This research shows that modern cell phones serve as highly effective control platforms for modular robots because of their programmability, flexibility, wireless communication capabilities, and increased processing power. As a result of this research, a versatile Graphical User Interface, a set of libraries and tools have been developed which even a novice robotics enthusiast can use to easily program their mobile phones to control their hobby project. These libraries will be beneficial in any situation where it is effective for the operator to use an off-the-shelf, relatively inexpensive, hand-held mobile phone as a remote controller rather than a considerably heavy and bulky remote controllers which are popular today. Several usage examples and experiments are presented which demonstrate the controller’s ability to effectively control a modular robot to perform a series of complex gaits and poses, as well as navigating a module through an obstacle course.
An Improved Support Vector Domain Description Method for Modeling Valid Search Domains in Engineering Design Problems
Authors: Roach Erin , Parker Robert R. , Malak Richard J.
Published: June 2012

Predictive modeling is an important tool in engineering design and optimization. Designers can develop a predictive model to replace a computationally-intensive physics-based model (a practice referred to as meta-modeling or response-surface modeling) or to model systems based on empirically-obtained data. However, such models typically have a limited domain of validity—that is, only certain combinations of model inputs yield predictions that are trustable. Consequently, designers must take care to bound the search space of optimization algorithms that otherwise would be unable to distinguish between valid and invalid predictions. Prior research has found that the valid input domain of a model can be shaped irregularly and difficult to model using simple bounds on input variables. The Support Vector Domain Description (SVDD) method was shown to be an effective approach for modeling such boundaries. However, the method used previously for generating the domain description is slow and scales poorly as the size of the training data set grows. This paper describes a new incremental method for generating a SVDD using a point-by-point comparison in place of considering all data points at once. This method is observed to be over 1000 times faster than the original method. This makes the overall approach attractive on problems of practical scale. We describe the new method, explore its characteristics, and demonstrate it on a design example for the selection of component concepts for a commercial power generation plant.
Using Product Archaeology to Integrate Global, Economic, Environmental, and Societal Factors in Introductory Design Education
Authors: Devendorf Erich , Cormier Phil , Moore-Russo Deborah , Lewis Kemper
Published: June 2012

Design education has traditionally been incorporated into the engineering curriculum in the junior or senior year through upper level mechanical design courses and capstone design projects. However, there is a general trend in engineering education to incorporate design activities at the freshman and sophomore level. The design aspects of these courses provide a unique opportunity to integrate global, economic, environmental, and societal factors with traditional design considerations. Incorporating these early in an engineering curriculum supports a broad engineering education in accordance with ABET required Outcome h. In this paper we introduce global, economic, environmental, and societal factors into a sophomore level engineering design course using strategies adapted from a Product Archaeology paradigm. Specifically, functional modeling is synthesized with a product dissection platform to create a foundation to demonstrate the broader impacts of engineering design decisions. The effectiveness of using Product Archaeology-based educational strategies to facilitate the learning objectives of Outcome h is evaluated using student surveys taken over a two year period.
Generating Interest for Engineering in Early Childhood Education Through a Book About Dissection
Authors: Chase Maya , McCallen Kevin , Martin Jackie , Kim Charles
Published: June 2012

In today’s world, it is critical to continually improve and develop new educational practices. Compared to developed and developing countries around the world, especially in science, mathematics, and engineering, the United States is falling behind. One of the most prominent reasons is the lack of interest in these subjects. In order to reverse this trend, it is important to develop new ways to creatively spark interest in engineering and natural sciences early on in a student’s educational career. The scope of this project was to develop a children’s book that introduced mechanical dissections. Along with the book, an in class presentation was developed for early elementary students in Kindergarten and 1st grade, with the goal of inspiring interest in engineering as a whole. This presentation was then used in local elementary school classrooms to gauge how such a program would fare in a typical elementary level classroom. Overall the project produced successful results. Not only were the students intrigued and excited to see the presentation, but they also learned more of the information than was originally expected. Through different media, the students were able to explore and question how and why a household appliance worked. This interaction with engineering concepts at a young age could prove to be very beneficial in the future.
Model-Based Optimal H∞ Controller on the Stability of a 2-DoF Quadrotor
Authors: Sampaio Rafael C. , Becker Marcelo , Siqueira Adriano A. G. , Breganon Ricardo , de Salvi Fa´bio , Belo Eduardo M.
Published: June 2012

In this work the synthesis of a MIMO (Multiple Input Multiple Output) robust optimal model-based H∞ controller is proposed. The whole process takes into account the dynamic equations of a 2-DoF quadrotor Mini Aerial Vehicle (MAV) attached to a steel stand. We consider the gamma-iteration algorithm to find the controller. Our analysis focuses on the control of roll and pitch axes, thereby neglecting the yaw axis control. As our goal is, a priori, to observe the behavior of the H∞ controller while it is controlling the four motors individually in order to stabilize our MAV, this set up provides us with the possibility of a very close overview of the aircraft. Indeed, it allows the easy insertion of disturbances in both axes (individually and simultaneously) and then closely observe the behavior of the platform. Besides, and most important at any laboratory environment, it is an extremely safe mode to run indoor tests, avoiding the quadrotor from causing harm to the crew if any technical problem occurs. The optimal H∞ robust controller presents a high capability of rejecting noises and disturbances. The controller can also suppress the uncertainties of our model. Besides presenting the dynamical model of our MAV, we present the experimental results of both roll and pitch control using the dSpace™ 1103 high performance controller board to embed the designed H∞ MIMO controller.
Empirically Derived Heuristics to Assist Designers With Satisfying Consumer Variation in Product Design
Authors: Cormier Phil , Literman Brian , Lewis Kemper
Published: June 2012

With markets becoming increasingly heterogeneous, design firms have strived to develop solutions to address the variation between consumers. This has led to the development of different design methodologies and tools, handling tasks from scoping of the problem to assisting with individual design steps. However, a limited amount of work has been done in identifying heuristics that can be used by designers to facilitate identifying viable concepts to meet different types of consumer variation. This work examines a range of product categories and individual products to identify how different types of consumer variation are addressed. Heuristics are then developed by examining the correlations between the solution and variation. Further, consumer variation that is not addressed is noted as well. These heuristics are intended to be used in the early stages of design to assist designers with the problem of addressing consumer variation.
Exogenous Force Estimation Using Disturbance Modeling for Optical Trap Experiments
Authors: Pickel Jason G. , Cole Daniel G.
Published: June 2012

In many optical trapping experiments, exogenous forces are estimated by assuming the exogenous force is balanced with the optical force. These optical forces are measured using Hooke’s law, and the displacement of the particle is low-pass filtered to minimize the effects of Brownian noise. This paper explores a different approach that uses a disturbance model approach for estimating exogenous forces using a Kalman filter. The state estimate is then used in a LQG structure to manipulate the relative position of a dielectric particle within an optical trap. The exogenous force estimate using a Kalman filter has been shown to have a higher SNR than the force estimation using Hooke’s Law. In addition to force estimation, the control structure can also manipulate the relative displacement of the particle to satisfy experimental conditions. A simulation is presented to demonstrate the performance of the LQG control structure.
Mobility Analysis and Inverse Kinematics of a Novel 2R1T Parallel Manipulator
Authors: Cuan-Urquizo Enrique , Rodriguez-Leal Ernesto , Dai Jian S.
Published: June 2012

This paper presents a novel parallel robot constructed with a three-limb CUP architecture. The mobility of the mechanism is obtained using screw theory, showing that the platform has three degrees of freedom, namely: (i) translation along the Z axis; and (ii) two rotations. The position analysis investigates the loop-closure equation resulting in a unique solution for the inverse kinematics problem and the identification of parasitic motions of the platform. The paper validates the analytical solution with a numerical example, where the results are compared with motion simulations of the manipulator using a commercially available software package.
Suppressing Features to Generate Simplified Models for Finite Element Analysis
Authors: Russ Brian , Dabbeeru Madan M. , Chorney Andrew S. , Skelley Daniel , Gupta Satyandra K.
Published: June 2012

Analyzing complex 3D models using finite element analysis software requires suppressing parts that are not likely to influence the analysis results, but may significantly improve the computational performance both in terms of mesh size and mesh quality. The feature suppression step often depends on the context and application. Currently, most analysts perform this step manually. This step can take a long time to perform on a complex model and can be tedious in nature. In this paper, we present a rule-based approach to feature suppression. We have developed a decision-tree based representation for capturing feature suppression rules. We have also developed utilities in Pro/Engineer CAD system to identify features that meet these rules and suppress them. We present several examples to illustrate the value of the proposed approach.
Nonlinear Force Analysis of Atomic Force Microscopy
Authors: Mahmoodi S. Nima , Salehi-Khojin Amin , Ahmadian Mehdi
Published: June 2012

The objective of this work is to highlight and discuss some critical conditions in which the imprecision of atomic force microscopy (AFM) system will be intensified. To precisely address these issues, we developed a complete close form solution for a non-linear motion of AFM system subjected to non-linear contact and van der Waals forces. Galerkin method and multiple time scale approach are used to solve the governing non-linear differential equation of the AFM system. A nonlinear frequency-response equation is then obtained as a function of displacement excitation, resonance frequency and associated response amplitude. By simulation of the AFM response under different tip-sample interaction force and distance, it is shown that jump phenomenon takes place due to the non-linear motion of microcantilever at certain operating frequencies. This case can be avoided via operating the AFM in a right frequency region; however the error associated with it must be compensated by a post-processing of collected data.
Effect of ACL Laxity on ACL Loading: Dynamic Simulation Using Impulsive Loads
Authors: Parekh Jesal , McLean Scott , Palmer Mark
Published: June 2012

Noncontact ACL injuries are among the most common, potentially traumatic and costly sport-related injuries, approximately 200,000 injuries occurring each year. Female athletes exhibit a trend toward higher rates of ACL injuries suggesting the influence of gender-specific characteristics. ACL laxity, a direct manifestation of hormonal cycling is a crucial differentiating factor between males and females that influences the strength and compliance of ACL when stressed. However, the mechanism through which ACL laxity implicates within an injury is unknown. Therefore, using FE methods, we tested the hypothesis that a lax ACL fails to adequately restrain the tibia during dynamic activities, resulting in lower intersegmental decelerations and subsequently, higher strain in the ACL. A 2D computational model of bones, meniscus, cartilage and ACL in sagittal plane was created. An impulse load was applied for 100ms (peak:1200N at 35ms) to simulate drop landing. Multiple simulations were run with varying ACL laxity. We observed that as stiffness increased from 50% to 150%, intersegmental deceleration increased by 10.9% and ACL strain reduced by 19.4%. These results indicate that relative peak deceleration of tibia can be used to predict ACL strain and is a potential clinical measure for identifying female athletes at risk for injury.
Dynamics Simulation of a Circular Membrane With an Eccentric Circular Areal Constraint
Authors: AlSahlani Assaad , Mukherjee Ranjan
Published: June 2012

We investigate the dynamics of a circular membrane with an eccentric circular areal constraint under arbitrary initial conditions. The membrane is assumed to be fixed at its outer boundary and the constraint is assumed to impose zero displacement over a circular area of the membrane. The symmetric and antisymmetric modes of vibration of the membrane are derived and their orthogonality properties are established. Using the orthogonality conditions established in this paper, the complete solution to the constrained vibratory motion of the membrane is determined for arbitrary initial conditions. Two sets of numerical simulation results are presented.
Integration of Life Cycle Inventories Incorporating Manufacturing Unit Processes
Authors: Campanelli Mark , Berglund Jonatan , Rachuri Sudarsan
Published: June 2012

Sustainable manufacturing (SM) concerns the manufacture of products with regard to environmental, social, and economic impacts over the entire life cycle. With a primary focus on environmental concerns, life cycle assessment (LCA) can support SM practices. The life cycle inventory (LCI) is a key phase of LCA, and this paper considers the integration of manufacturing unit processes (MUPs) into system-level LCIs, which requires consideration of process flow diagrams at different levels of abstraction. Furthermore, uncertainty quantification is an important component of LCA interpretation, and this paper proposes a method to synthesize LCIs from the process-level to the system-level that consistently quantifies uncertainty in the inventories. The method can incorporate MUP data derived from measurements and/or modeling and simulation. Further development towards a complete methodology is discussed.
Suppression of Machine Tool Chatter Using Nonlinear Energy Sink
Authors: Nankali Amir , Surampalli Harsheeta , Lee Young S. , Kalma´r-Nagy Tama´s
Published: June 2012

Suppression of regenerative instability in a single-degree-of-freedom (SDOF) machine tool model was studied by means of targeted energy transfers (TETs). The regenerative cutting force generates time-delay effects in the tool equation of motion, which retained the nonlinear terms up to the third order in this work. Then, an ungrounded nonlinear energy sink (NES) was coupled to the SDOF tool, by which biased energy transfers from the tool to the NES and efficient dissipation can be realized whenever regenerative effects invoke instability in the tool. Shifts of the stability boundary (i.e., Hopf bifurcation point) with respect to chip thickness were examined for various NES parameters. There seems to exist an optimal value of damping for a fixed mass ratio to shift the stability boundary for stably cutting more material off by increasing chip thickness; on the other hand, the larger the mass ratio becomes, the further the occurrence of Hopf bifurcation is delayed. The limit cycle oscillation (LCO) due to the regenerative instability appears as being subcritical, which can be (locally) eliminated or attenuated at a fixed rotational speed of a workpiece by the nonlinear modal interactions with an NES (i.e., by means of TETs). Three suppression mechanisms have been identified; that is, recurrent burstouts and suppressions, partial and complete suppressions of regenerative instabilities in a machine tool model. Each suppression mechanism was characterized numerically by time histories of displacements, and wavelet transforms and instantaneous energies. Furthermore, analytical study was performed by employing the complexification-averaging technique to yield a time-delayed slow-flow model. Finally, regenerative instability suppression in a more practical machine tool model was examined by considering contact-loss conditions.
A New Approach for Explicit Construction of Moldability Based Feasibility Boundary for Polymer Heat Exchangers
Authors: Hall Timothy , Dabbeeru Madan Mohan , Gupta Satyandra K.
Published: June 2012

Incorporating manufacturing feasibility is a very important consideration during the design optimization process and this paper is interested in investigating the molding feasibility of polymer heat exchangers. This application requires the explicit construction of the boundary, represented as a surface based on the parameter space, which separates the feasible and infeasible design space. The feasibility boundary for injection molding in terms of the design parameters is quite complex due to the highly nonlinear process physics, which, consequently, makes molding simulation computationally-intensive and time-consuming. Moreover, in heat exchanger applications, the optimal design often lies on the feasibility boundary. This paper presents a new approach for the explicit construction of a moldability-based feasibility boundary for polymer heat exchangers. The proposed approach takes inspiration from intelligent design of experiments and incorporates ideas from the field of active learning to minimize the number of computational experiments needed to construct the feasibility boundary. Our results show that the proposed approach leads to significant reduction in the number of computational experiments needed to build an accurate model of the feasibility boundary.
Vibration Structure of Gyroscopic Planetary Gears
Authors: Cooley Christopher G. , Parker Robert G.
Published: June 2012

This study investigates the vibration structure of high-speed, gyroscopic planetary gears. The vibration modes of these systems are complex-valued and speed dependent. Three mode types exist, and these are classified as planet, rotational, and translational modes. Each mode type is mathematically proven by the use of a candidate mode method. Reduced eigenvalue problems are determined for each mode type. The eigenvalues for an example high-speed planetary gear are determined over a wide range of carrier speeds. Divergence and flutter instabilities are observed at extremely high speeds.
Kinematic Motion Constraints of the Protein Molecule Chains
Authors: Shahbazi Zahra , Ilies¸ Horea T. , Kazerounian Kazem
Published: June 2012

The function of protein molecules is defined by their 3-D geometry, as well as their internal mobility, which is heavily influenced by the internal hydrogen bonds. The correct identification of these hydrogen bonds and the prediction of their effect on the mobility of protein molecules can provide an invaluable mechanism to understand protein behavior. Applications of this study ranges from nano-engineering to new drug design. We are extending our recent approach from identifying main-chain main-chain hydrogen bonds to all types of hydrogen bonds that occur in protein structures, such as α-helices and β-sheets. We use the Gru¨bler-Kutzbach kinematic mobility criterion to determine the degrees of freedom of all closed loops (rigid loops as well as closed loops of one or more degrees of freedom) formed by Hydrogen bonds. Furthermore, we systematically develop constraint equations for non-rigid closed loops. Several examples of protein molecules from PDB are used to show that these additions both improve the accuracy of mobility analysis and enable us to study a broader range of the motion of protein molecules. This approach offers theoretical insight as well as extensive numerical efficiencies in protein simulations.
Ground Reaction Forces for Various Standing Tasks Considering Generic Terrain
Authors: Howard Brad , Yang Jingzhou James
Published: June 2012

Many of the tasks presented to people in everyday life include standing on terrain that is not level or coplanar. Uneven terrain can affect the way in which people distribute their weight between their feet. This paper proposes a method for predicting human standing posture and the associated ground reaction forces (GRFs) taking into account a generic orientation of the ground support plane. Postures are predicted using multi-objective optimization (MOO) techniques and a 55 DOF digital human model. The human performance measures used in the cost function include musculoskeletal discomfort, delta potential energy, and visual displacement. The GRF are determined by a linear distribution model derived from the zero moment point (ZMP) and the Lagrangian recursive dynamic formulation. Postural stability based on the location of the ZMP will be discussed. Three postural cases are considered: standing on flat ground, standing with one foot on a stair, and standing with arbitrary support plane angles. Three different simulations are carried out for each case representing different tasks. Predicted GRFs have realistic values and follow the general trends expected for each of the postural cases.
An Integrated Approach to Design of Enhanced Polymer Heat Exchangers
Authors: Cevallos Juan , Gupta S. K. , Bar-Cohen Avram
Published: June 2012

Recently available formulations of thermally enhanced polymers are attractive in heat exchanger applications due to their low cost and improved corrosion resistance compared to the conventional metal options. This paper presents a systematic approach to the design of plate-fin heat exchangers made out of thermally enhanced polymers. We have formulated the design problem as the life cycle cost minimization problem. The integrated design model introduced here accounts for heat transfer performance, molding cost, and assembly costs. We have adopted well known models to develop individual parametric models that describe how heat transfer performance, molding cost, and assembly cost varies as a function of the geometric parameters of the heat exchanger. Thermally enhanced polymers behave differently from the conventional polymers during the molding process. The desired thin walled large structures are expected to pose challenges during the filling phase of the molding process. Hence we have utilized experimentally validated simulations to develop a metamodel to identify difficult and impossible to mold design configurations. This metamodel has been integrated within the overall formulation to address the manufacturability considerations. This paper also presents several case studies that show how the material and labor cost strongly influence the final design.
Optimizing the Shear Beam of a Non-Pneumatic Wheel for Low Rolling Resistance
Authors: Thyagaraja Niranjan , Shankar Prabhu , Fadel Georges , Guarneri Paolo
Published: June 2012

The design requirements of a low rolling loss non-pneumatic wheel are determined through a systematic optimization approach. In order to reduce the rolling resistance, linear elastic materials are considered instead of elastomers. To achieve an adequate compliance level, a metamaterial needs to be designed. The required metamaterial properties are determined as a result of an optimization where the metamaterial tensor components as well as the geometric dimensions are the design variables. This way the metamaterial can be designed such that the overall behavior of the non pneumatic wheel achieves the best performance in terms of compliance and contact patch pressure distribution. The resulting constitutive metamaterial properties of the shear layer can be used as prescribed constitutive properties to tailor the periodic mesostructure of a material by means of topology optimization.
Servo-Constraint Based Computed Torque Control of Underactuated Mechanical Systems
Authors: Kova´cs La´szlo´ L. , Ko¨vecses Jo´zsef , Zelei Ambrus , Bencsik La´szlo´ , Ste´pan Ga´bor
Published: June 2012

This paper aims to generalize the computed torque control method for underactuated systems which are modeled by a non-minimum set of generalized coordinates subjected to geometric constraints. The control task of the underactuated robot is defined in the form of servo constraint equations that have the same number as the number of independent control inputs. A PD controller is synthesized based on projecting the equations of motion into the nullspace of the distribution matrix of the actuator forces/torques. The results are demonstrated by numerical simulation and experiments conducted on a two degrees-of-freedom device.
A Hybrid Grasp Matrix for Cooperative Robotic Object Manipulation
Authors: Ringold Tyson L. , Cipra Raymond J.
Published: June 2012

When several robots work cooperatively to manipulate an object, redundancies naturally arise due to the increased number of applied contact forces, and as a result, many sets of joint torques exist that will realize the same motion. If the cooperating robots are kinematically deficient, their inability to directly control all of their applied forces presents difficulty in determining the optimal set of torques. To address this difficulty, two concepts from the robotic hand community are utilized: the grasp matrix and the stiffness matrix. These concepts are briefly reviewed with particular focus on the shortcomings of each. In order to solve the problem of choosing optimal joint torques, the grasp matrix and stiffness matrix are combined into a hybrid grasp matrix which resolves the indeterminacies caused by the kinematic deficiencies of the robots while maintaining a form that readily allows for a straightforward choice among the many possible torques. This concept is then applied to an example of four mobile robots cooperatively supporting a single object.
System of System Based Sociotechnical Complexity Challenges in Product and Process Design
Authors: Ali-Qureshi Zulfiqar
Published: June 2012

Unique characteristic of system of system based product life cycle challenges evolves different level of systems. This means the product design system and process level system consideration are very important besides the system level issues for product and process development which are part of systems of system. These core issues include the physical elements, assembly process and its related cognitive elements of component to that particular assembly and its process at Sub system level which are fundamental of System of system in holistic perspective of new product and process design. Any system level change or variety affects the next adjacent system in the same product as a member of same family of a system of system. In this paper the aspect of Hybrid electric car battery has been explored to reduce the system of system level sociotecnical complexity in product design. In this context, the affect of changeability in the assembly system level has been explored and DFA analysis and the complexity Index of the product at physical structure, assembly process and cognitive system level been discussed to draw analogy for making an understanding of similar nature of the system in platform based product and process family development.
Convex Estimators for Optimization of Kriging Model Problems
Authors: Hamza Karim , Shalaby Mohammed
Published: June 2012

This paper presents a framework for identification of the global optimum of Kriging models. The framework is based on a branch and bound scheme for sub-division of the search space into hypercubes while constructing convex under-estimators of the Kriging models. The convex under-estimators, which are a key development in this paper, provide a relaxation of the original problem. The relaxed problem has two key features: i) convex optimization algorithms such as sequential quadratic programming (SQP) are guaranteed to find the global optimum of the relaxed problem, and ii) objective value of the relaxed problem is a lower bound on the best attainable solution within a hypercube for the original (Kriging model) problem. The convex under-estimators improve in accuracy as the size of a hypercube gets smaller via the branching search. Termination of a hypercube branch is done when either: i) solution of the relaxed problem within the hypercube is no better than current best solution of the original problem, or ii) best solution of the original problem and that of the relaxed problem are within tolerance limits. To assess the significance of the proposed framework, comparison studies against genetic algorithm (GA) are conducted using Kriging models that approximate standard nonlinear test functions, as well as application problems of water desalination and vehicle crashworthiness. Results of the studies show the proposed framework deterministically providing a solution within tolerance limits from the global optimum, while GA is observed to not reliably discover the best solutions in problems with larger number of design variables.
Controlled Kinetic Monte Carlo Simulation of Nanomanufacturing Processes
Authors: Wang Yan
Published: June 2012

Kinetic Monte Carlo (KMC) is regarded as an efficient tool for rare event simulation and has been used to simulate bottom-up self-assembly processes of nanomanufacturing. Yet, it cannot simulate top-down processes. In this paper, a new and generalized KMC mechanism, called controlled KMC or cKMC, is proposed to simulate complete physical and chemical processes. This generalization is enabled by the introduction of controlled events. In contrast to the traditional self-assembly events in KMC, controlled events occur at certain times, locations, or directions, which allows all events to be modeled. The applications of cKMC to several top-down and bottom-up processes are demonstrated.