bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration of Parametric CAD and Dynamic Models for Industrial Robot Design and Optimization
Authors: Tarkian Mehdi , Lunde´n Bjo¨rn , O¨lvander Johan
Published: July 2009

This paper presents an approach of integration between multiple analysis tools that covers several engineering disciplines, used for robot design and optimization. There are three main components in this approach namely a highly flexible geometric model, a parametric dynamic simulation model, and a framework for integration of the models and execution of an optimization process through a user friendly interface. To illustrate the presented methodology an integrated analysis tool for an industrial robot is developed combining dynamic and geometric models in a parametric design approach. An optimization case is conducted to visualize the automation capabilities of the proposed framework, and enhance the early design phases for industrial robots.
Multi-Users Dynamic Maintenance Document for Complex Mechanical Products: Application for Automobile
Authors: Coulibaly Amadou , Huang Ying , Gardoni Mickae¨l , Maranzana R.
Published: July 2009

This article proposes a framework intended to provide customized electronic maintenance documents for complex mechanical products to be used in different typical contextual conditions. The customization takes into account the product usage profiles, the users’ behaviors and the environmental factors. Depending on these contextual aspects the approach allows to elaborate specific documents for different maintenance tasks to be performed either by the customers or by skilled technicians. The documents must be updated dynamically to follow the utilization conditions evolution. An application is outlined for the case of automobile. In conclusion, we point out future extension of this work to improve the product availability using the PLM (Product Lifecycle Management) systems to collect and reuse contextual field data at design stage.
Impedance Control of Cable-Driven Mechanisms
Authors: Rezazadeh Siavash , Behzadipour Saeed
Published: July 2009

In this work, an impedance control method is developed and applied to two cable-driven mechanisms. The first one is a classical problem of driving a rigid body in 3-D space by seven cables. Our approach is based on the impedance control of rigid link manipulators which is then extended to include the specific considerations of the cable-driven mechanisms such as maintaining the tensile force in the cables. The method is then extended to the serial multibody cable-driven mechanisms. The motivation for this problem is the possible application of cable-driven systems in the rehabilitative exercises such as physical and/or occupational therapies. In this case, the human body acts as a multibody system which is driven by cables attached. The impedance control in such application facilitates the comfort of the patient by providing the necessary compliance while moving the body parts. The formulation of the problem is developed using Lagrange’s equation and the control input (which is the cable forces) is calculated based on the position and/or force feedback from the multibody. Simulation results demonstrate the effectiveness of the presented method.
Development of a Self-Excited Oscillator for SI-Traceable Measurements in Atomic Force Microscopy
Authors: Vogl Gregory W. , Pratt Jon R.
Published: July 2009

A new self-excited micro-oscillator is proposed as a velocity reference that could aid the dissemination of nanonewton-level forces that are traceable to the International System of Units (SI). An analog control system is developed to keep the actuation side of the device oscillating sinusoidally with an amplitude that is fairly insensitive to the quality factor. Consequently, the device can be calibrated as a velocity reference in air and used in ultra-high vacuum with a velocity shift of less than one percent. Hence, the calibrated micro-oscillator could be used with electrostatic forces to calibrate cantilevers used for atomic force microscopy (AFM) as SI-traceable force transducers. Furthermore, the calibrated micro-oscillator could potentially be used as an AFM sensor to achieve atomic resolutions on par with those realized in frequency-modulation AFM (FM-AFM) with quartz tuning forks.
Information Management Capabilities of MDO Frameworks
Authors: Hiriyannaiah Santosh , Mocko Gregory M.
Published: July 2009

Multidisciplinary design optimization (MDO) is a methodology, which integrates analysis and optimization techniques to solve engineering design problems involving multiple disciplines. MDO frameworks have been developed which facilitate the integration of disciplinary analysis code and optimization techniques. Commonly used MDO frameworks include ModelCenter, iSIGHT, modeFRONTIER and FIDO. Recent advances in MDO framework have addressed issues related to data exchange, distributed computing, process integration and trade study. However managing, storing and sharing MDO problem information have not yet been addressed. Thus, the primary objective in this research is to propose a new configuration for MDO frameworks to enhance information management capabilities. This is achieved by (1) identifying requirements for managing decision-related information, (2) evaluating current MDO frameworks against the key information management requirements, and (3) extending current software to include a file information system and structured repository. Finally, a new configuration is developed augmenting a structured repository to enable reuse of information associated with the formulation of MDO problems.
A Study of Conditions That Affect the Distribution of Compliance in Compliant Mechanisms
Authors: Canfield Stephen L. , Chlarson Daniel L. , Shibakov Alexander , Richardson Joseph D. , Saxena Anupam
Published: July 2009

Researchers in the field of optimal synthesis of compliant mechanisms have been working to develop design tools that yield distributed compliant devices from a continuum design domain. However, it has been demonstrated in the literature that much of this work has resulted in mechanisms that localize compliance rather than distribute it as desired. Inaccurate representation of the stiffness or strain energy due to the existence of point flexures in the mechanism was identified as the cause of this behavior by early researchers. To eliminate this cause, several approaches have been tried to improve the design of distributed mechanisms, for example additional constraints on the optimization process, alternate parameterization techniques that avoid point flexures and additional objective functions evaluated as Pareto sets. In this paper, the authors further investigate the fundamental reasons for the prevalence of lumped designs. Representative simple compliant mechanisms are investigated analytically and numerically and the influence of various additional objectives on the final design is evaluated. To extrapolate these results to more complex mechanisms, examples are constructed that show evidence that a preference remains for lumped compliance, despite the countermeasures that have been applied. Pareto compatibility analysis developed by the authors is used to analyze the influence of various objectives on the distributive nature of the final design. These conditions that influence the distribution of compliance fall into two basic categories: those specific to the numerical methods applied and those of purely mechanical (i.e. fundamental) nature. This work will examine conditions of the latter type and will demonstrate that such a preference for lumped compliance exists. This preference is shown to be contained in the classic objectives; flexibility and stiffness. Based on these results, greater insight into the optimization process is gained and applied to improve the search for distributed compliant mechanisms.
End-Effector Trajectory Tracking of a Class of Flexible Link Manipulators
Authors: Vakil Mohammad , Fotouhi Reza , Nikiforuk P. N.
Published: July 2009

A new controller for the end-effector trajectory tracking (EETT) of a class of flexible link manipulators which composed of a chain of rigid links with an end-link flexible (CREF) is introduced. The dynamic model of the CREF is expressed into the standard singularly perturbed form; that is, the dynamic model is decomposed into slow and fast subsystems. The states of the slow subsystem are the joints’ rotations and their time derivatives, while the states of the fast subsystem are flexible variables, which model the lateral deflection of the end-link, and their time derivatives. For the slow subsystem, corrective torque is added to the computed torque control commands of the rigid link counterpart of the CREF to reduce the EETT error. This corrective torque is derived based on the concept of the integral manifold of the singularly perturbed differential equations. It was shown that this corrective term is of order ε2 where ε = 1/(2πf) and f is the smallest non-zero natural frequency of the CREF. To stabilize the fast subsystem, an observer-based controller is designed by the gain-scheduling technique. Due to the application of the observer-based controller there is no need for the measurement of the time derivative of the flexible variables, which their measurements are hardly practical. To facilitate the derivation and implementation of introduced controller here, several properties of the mass matrix of the CREF are introduced and used. The effectiveness and feasibility of the new controller are shown through the simulation and experimental studies.
Shape Comparison of 3D Models Based on Features and Parameters
Authors: Viswanathan Karthik , Chowdhury Sagar , Siddique Zahed
Published: July 2009

Computer-Aided Design (CAD) is used extensively during mechanical product design, which involves creating 3D models of components and then assembling them into modules and systems. Methods and tools to compare components and identify a common platform using these 3D CAD models of components would facilitate faster specification of product family architecture. Hence, there is a need to develop means for comparing component geometry, in order to identify the common and distinct features, determine component commonality, and identify a common platform for the set of components. This paper presents an approach to determine geometric commonality between components from their 3D solid models. The approach consists of performing a pair-wise comparison between components. To measure commonality for a pair of components, first all feature-pair’s dimensions and positions are measured, which then combined to give the overall component-pair commonality.
Feature Parameters Extraction of Blending Surfaces for CAD Geometry Models Compression
Authors: Liu Jun , Huang Yunbao , Wang Qifu , Chen Liping
Published: July 2009

In this paper, a CAD model compression approach is presented by representing blending surfaces with their spine curves and variation functions of blending radiuses. The core idea of this approach is to recognize blending surfaces from all B-spline surfaces in a CAD geometry model by analyzing their principle curvature curves, and then extracting their feature parameters i.e. spine curves and variation functions of blending radiuses. Experiments demonstrate that the geometry models including blending surfaces are greatly compressed, which benefits much to cooperative development of complex products, mass customization, and 3D geometry search over internet.
Robust Optimization With NURBS HyPerModels
Authors: Ajetunmobi Abiola M. , Turner Cameron J. , Crawford Richard H.
Published: July 2009

Engineering systems are generally susceptible to parameter uncertainties that influence real-time system performance and long-term system reliability. However, designers and engineers must design system solutions that are both optimal and dependable. Robust design techniques and robust optimization methods in particular, have emerged as promising methodologies to address the problem of dealing with parameter uncertainties. This research advances a robust optimization approach that exploits gradient information embedded in proximate NURBs control point clusters that are inherent in NURBs metamodel design space representations. The proximate control point clusters embody the target sensitivity profile and therefore include robust optimal solutions, thus enabling selective optimization within regions associated with the clusters. This robust optimization framework has been implemented and is demonstrated on unconstrained robust optimization problems from two test functions and a constrained robust optimization problem from a practical engineering design problem.
A Case Study in the Use of Design Exemplar as a Search and Retrieval Tool
Authors: Anandan Srinivasan , Srirangam Murty , Summers Joshua D.
Published: July 2009

This paper presents a case study examining the utility of design exemplar technology as a search and retrieval tool with respect to retrieving mold inserts for a tire manufacturing company. Limitations of using the geometric-based exemplar approach such as tediousness of authoring exemplars and time complexity are identified. These limitations are addressed by developing a new parametric-based exemplar approach. This approach calculates a set of maxima and minima based on the specifications of the query mold insert. The design exemplar is essentially useful to prototype the query mechanism. However due to time complexity, the parametric approach was implemented as a dedicated software package.
A Practical Robust and Efficient RBF Metamodel Method for Typical Engineering Problems
Authors: Fang Xingjie , Wang Liping , Beeson Don , Wiggs Gene
Published: July 2009

Radial Basis Function (RBF) metamodels have recently attracted increased interest due to their significant advantages over other types of non-parametric metamodels. However, because of the interpolation nature of the RBF mathematics, the accuracy of the model may dramatically deteriorate if the training data set used contains duplicate information, noise or outliers. Also constructing the metamodel may be time consuming whenever the training data sets are large or a high dimensional model is required. In this paper, we propose a robust and efficient RBF metamodeling approach based on data pre-processing techniques that alleviate the accuracy and efficiency issues commonly encountered when RBF models are used in typical real engineering situations. These techniques include 1) the removal of duplicate training data information, 2) the generation of smaller uniformly distributed subsets of training data from large data sets and 3) the quantification and identification of outliers by principal component analysis (PCA) and Hotelling statistics. Simulation results are used to validate the generalization accuracy and efficiency of the proposed approach.
Evolution of a Novel Finger Mechanism for Robust Industrial End Effectors
Authors: Dubey Venketesh N. , Crowder Richard M.
Published: July 2009

This paper presents design for a finger mechanism that has evolved from the stringent requirement of ruggedness and reliability in an industrial application. The paper initially describes the need for a special purpose end effector to operate in a constrained environment and then takes through the various stages of design modifications that were required to ensure safety and reliability. This resulted into a rigid link finger design, which is adaptive to different shapes and operated by a single actuator providing up to 3 degrees of freedom to the finger. A number of such finger mechanisms can be assembled together in different configurations to design special purpose end effectors. This paper covers two such designs and briefly discusses the grasping and control issues associated with the limited number of actuators built into the end effector, and evaluates their suitability in industrial environments. The design overcomes limitations of majority of existing tendon based end effectors requiring a large number of actuators to be controlled thus meeting the space and safety requirements for constrained industrial applications.
A Statically Balanced Gough/Stewart-Type Platform
Authors: Carricato Marco , Gosselin Cle´ment
Published: July 2009

Gravity compensation of spatial parallel manipulators is a relatively recent topic of investigation. Perfect balancing, by either counterweights or elastic elements, has been accomplished, so far, only for parallel mechanisms in which the weight of the moving platform is sustained by legs comprising purely rotational joints. Indeed, balancing of parallel mechanisms with translational actuators, which are among the most common and used ones, has been traditionally thought possible only by resorting to additional legs containing no prismatic joints between the base and the end-effector. This paper presents the conceptual and mechanical design of a balanced Gough/Stewart-type manipulator, in which the weight of the platform is entirely sustained by the legs comprising the extensible jacks. By the integrated action of both elastic elements and counterweights, each leg is statically balanced and it generates, at its tip, a constant force balancing the weight of the end-effector in any admissible configuration. If no elastic elements are used, the resulting manipulator is balanced with respect to the shaking force too. Two Appendices are also provided, presenting formal and novel derivations of the necessary and sufficient conditions allowing i) a body arbitrarily rotating in space to rest in a state of neutral equilibrium under the action of general constant-force generators, ii) a body pivoting about a universal joint and acted upon by a number of zero-free-length springs to exhibit constant potential energy regardless of its configuration.
Expanding the Product Realization Process to Incorporate Entrepreneurship and Innovation
Authors: Doepker Philip E.
Published: July 2009

This paper outlines our experiences in the implementation and evolution of the Product Realization Process (PRP) in industry sponsored capstone team design projects with an emphasis on developing business plans. Particular emphasis is placed on the incorporation of innovation and entrepreneurship since the Innovation Center was established two years ago. In 1996 we began using the PRP in our capstone courses with 6 projects from 3 companies. We now implement over 60 projects each year. The total number of companies that have sponsored projects is now over 80. Approximately 10 projects per year are related to innovation and entrepreneurship and include elements of market studies, patent searches, intellectual property investigations, cost estimating, manufacturing and the development of a business plan. This paper will address the following: • The evolution to multidisciplinary projects; • The enhancement of the conceptual design process to emphasize innovation; • The migration from a one semester course to a two semester sequence; • The development of partnerships with faculty and students in the School of Business and the Law School; • The parallel phases in the projects that include technical development and the development of a business plan.
The Duality of Biomimetics and Artiomimetics in the Creative Process of Design
Authors: Rodriguez-Leal Ernesto , Dai Jian S. , Pennock Gordon R.
Published: July 2009

This paper proposes a new model for the creative process of design. This model is developed by combining two of the most accepted models of creativity: the Wallas stage model and the Wertheimer productive thinking model. The paper discusses the importance of Biomimetics in design and presents examples of successful inventions produced when nature is imitated by designers. The role of Biomimetics in the new model for the creative process is discussed. For complementing the new model of creativity, this paper introduces the concept of Artiomimetics as the imitation of artifact structure, shape, features or motion to inspire the development of new inventions. This paper proposes that the incremental evolution of concepts that lead to invention is given by either the application of Biomimetics or Artiomimetics. This paper presents examples where the duality of biomimetic and artiomimetic approaches is used to effectively foster creativity resulting in breakthrough inventions.
Framework for Generating Modularized Product Designs With Assembly and Variety Considerations
Authors: Gupta Saraj , Okudan Gu¨l E.
Published: July 2009

Conceptual design is found to be the most ambiguous and creative phase of design. There exist only a few computational tools that aid designers at conceptual design stage, and mostly designers rely on personal experience or experience of coworkers to generate quality designs. The proposed framework aims at generating robust computerized conceptual designs by incorporating Modularity, Design for Assembly (DFA) and Design for Variety (DFV) principles at the conceptual stage. Conceptual design alternatives obtained from the proposed framework are ranked based on minimum assembly time, and are composed of modules in a way that future changes in customer needs are satisfied only by replacing certain modules. The framework involves searching a design repository of components by using functional-basis and pre-defined graph grammar rules, to generate all possible conceptual design alternatives. These design alternatives are ranked and filtered using a DFA index, and top two alternatives are selected. Selected designs are modularized and filtered using a DFV index to obtain the best design alternative. This paper provides a detailed discussion of the framework obtained by amalgamating Modularity, DFA, and DFV. Working of the proposed framework is demonstrated with the help of an electronic toothbrush design example.
An Exploratory Study Into Process Failures During the Voice of Customer Process in Product Development
Authors: Esterman Marcos , Zimmerman Roderick F. , Spano Joel , Pereda Diego A.
Published: July 2009

This paper examines the Voice of the Customer (VOC) as a functional process in order to better understand why the process fails and to generate insights into avoiding these pitfalls. The importance of the VOC in product development has been well documented. However, even with this understanding, many product development failures are still rooted in a failure to effectively integrate the VOC into the organization’s respective decision-making processes. It is the objective of this paper to study this issue more in depth. First the role of the VOC in product development will be explored and a functional model of the VOC process will be proposed. This functional model will serve as the basis to identify ways in which the process could fail. This analysis will be augmented with a case study that identifies additional failure modes of the VOC process. The paper concludes with some research questions to address these shortcomings that would be of interest to the product development community.
A Measure of Impact for Platform Changes
Authors: Rojas Alvaro J. , Esterman Marcos
Published: July 2009

In today’s product development environment, most companies develop product platforms rather than individual products due to the time and cost savings that are reaped from subsequent development efforts. Most of the product platform development literature focuses on the development decisions for a product platform while it is under development, which is logically where the biggest benefits would be gained. However when a new market or a new technology arises, firms often struggle to assess these opportunities within the context of their existing product platforms. There is relatively little work that examines the product platform decisions after the platform has been developed and new, unanticipated opportunities are presented to the development organization. The focus of this work is to leverage the existing literature to development an impact assessment process that explicitly accounts for the constraints of a preexisting product platform when considering new technology and/or market opportunities. In this paper, an overview of the overall assessment process is presented. This is followed by the development of the impact metrics and a case study to illustrate the assessment process. The paper concludes with the next step in this work.
Design of a Bio-Inspired Spherical Four-Bar Mechanism for Flapping-Wing Micro Air-Vehicle Applications
Authors: McDonald Matt , Agrawal Sunil K.
Published: July 2009

Design of flapping-wing micro air-vehicles presents many engineering challenges. As observed by biologists, insects and birds exhibit complex three-dimensional wing motions. It is believed that these unique patterns of wing motion create favorable aerodynamic forces that enable these species to fly forward, hover, and execute complex motions. From the perspective of micro air-vehicle applications, extremely lightweight designs that accomplish these motions of the wing, using just a single, or a few actuators, are preferable. This paper presents a method to design a spherical four-bar flapping mechanism that approximates a given spatial flapping motion of a wing, considered to have favorable aerodynamics. A spherical flapping mechanism was then constructed and its aerodynamic performance was compared to the original spatially moving wing using an instrumented robotic flapper with force sensors.
Optimization of a Planar Quadruped Dynamic Leap
Authors: Bhattacharya Subhrajit , Chitta Sachin , Kumar Vijay , Lee Daniel
Published: July 2009

Quadruped walking robots need to handle high obstacles like steps that are often not kinematically reachable. We present a dynamic leap that allows a quadruped robot to put its front legs up onto a high rock or ledge, a motion we have found is critical to being able to locomote over rough terrain. The leaping motion was optimized using a simulated planar quadruped model. We present experimental results for the implementation of this optimized motion on a real quadruped robot.
An Investigation of Impact of the Product Family Design on the Shop Floor Performance
Authors: Artar Hakan U. , Okudan Gu¨l
Published: July 2009

While many approaches have been proposed to optimize the product family design for measures of cost, revenue and performance, many of these approaches fail to incorporate the complexity of the manufacturing issues into family design decision-making. One of these issues is different approaches for assembly sequencing. This paper presents a computer simulation study by which the impact of two postponement strategies is investigated for a real-life product family case under various demand conditions. Overall, the results indicate that when the product family design takes into account the assembly sequencing decisions, the outcomes at the shop floor level improve. The results have implications for companies that are looking into increasing their revenue without increasing their investment in the shop floor.
Electrical Characterization of Single Carbon Nanowires
Authors: Samuel B. A. , Haque M. A.
Published: July 2009

We present experimental results on the electrical characterization of single semiconducting carbon nanowires using microfabricated electrodes. The material tested is classified as nanoporous carbon and is a class of amorphous carbonaceous material. Because of amorphous nature of this system the properties of the carbon nanowires are not similar to other crystalline carbon nanowire systems such as carbon nanotubes and graphitic carbon nanowires. Synthesis, experimental characterization techniques and the electron transport mechanism are discussed in this paper. Applications for this carbonaceous material include size-selective catalysis [1, 2], flexible electronic components and as gas sensors [3].
High Performance Utility Resource Deployment and Brokering for Scientific Applications
Authors: Cohen Jeremy , Darlington John
Published: July 2009

As computing power continues to grow and high performance computing use increases, ever bigger scientific experiments and tasks can be carried out. However, the management of the computing power necessary to support these ever growing tasks is getting more and more difficult. Increased power consumption, heat generation and space costs for the larger numbers of resources that are required can make local hosting of resources too expensive. Emergence of utility computing platforms offers a solution. We present our recent work to develop an update to our computational markets environment for support of application deployment and brokering across multiple utility computing environments. We develop a prototype to demonstrate the potential benefits of such an environment and look at the longer term changes in the use of computing that might be enabled by such developments.
Modelling and Simulation of a Cantilever-Paddle Beam Under the Effect of Capillary, Shock, and Electrostatic Forces
Authors: Ouakad Hassen M. , Younis Mohammad I.
Published: July 2009

In this paper, we present a mathematical model and analysis for a microbeam fixed at one end and coupled to a microplate at its other end under the effect of capillary, shock and electrostatic forces. The model considers the microbeam as a flexible structure, the plate as a rigid body. First, we subject the system to capillary force via a drop of fluid which is trapped underneath the microplate. We derive closed-form solutions to the static and eigenvalue problems associated with the microbeam-microplate system. We then subject the system to shock loads for both case (capillary and electrostatic forces). The Galerkin procedure is used to derive a set of nonlinear ordinary-differential equations that describe the microsystem dynamics. We investigate the influence of the fluid volume ratio and the applied DC voltage on the microbeam response. We find that the effect of capillary force has much more dominant role compared to shock and electrostatic forces.
An Open Architecture for Embedding VR-Based Mechanical Tools Into CAD Applications
Authors: Joshi Hrishikesh , Jayaram Sankar , Jayaram Uma , Varoz Larry
Published: July 2009

Virtual Reality (VR)-based assembly and disassembly analysis systems have been in use for several years. There have also been various efforts at creating bi-directional integration between CAD systems and VR-based assembly systems. The next step in this integration is to provide the capabilities of CAD and the immersive systems under one umbrella. This paper presents an open/extensible architecture for embedding VR-based mechanical tools within CAD systems to assist in assembly and disassembly analyses. The goal is to allow the user to perform immersive assembly/disassembly evaluations entirely within the CAD system. The architecture discussed in this paper is designed to leverage the inherent visualization and modeling capabilities provided by any commercial CAD system, while allowing the user to use any level of immersion ranging from simple tracking and stereo visualization to complete haptics devices. The focus is on providing assembly and disassembly capabilities using mechanical tools (e.g. wrenches, screwdrivers, etc.). The architecture is designed to be open (generic) for easy adaptation with any CAD system (through the API of the CAD system) and any haptic device (through the API of the haptic device). It provides a template consisting of modules and classes, which are relevant irrespective of the choice of the CAD system or the haptics system. The architecture is also designed to be extensible to include advanced interactions and simulations beyond the basic capabilities implemented in the system described in this paper. The CAD model library structure is leveraged for managing virtual tools and fasteners available to the user. The proposed architecture has been implemented to provide virtual assembly functionality within CATIA V5 using the VirtualHand™ Toolkit from Immersion Corporation. Examples of this implementation using threaded fasteners and tools are also presented. The extensibility of the architecture was tested by implementing a different suite of mechanical tools for a different simulation purpose.
Model Driven Vehicle System Engineering: Requirements, Issues and Challenges
Authors: Jennings Mark
Published: July 2009

The requirements, issues and challenges of establishing a model-driven vehicle system engineering (MD-VSE) process are explored. The needs for new methodologies, processes and infrastructure to address complex system level design issues are highlighted. The problem is viewed from the perspective of the relation between vehicle engineering domains and vehicle attribute and function requirements. With this view, an incremental approach to establishing a MD-VSE process is outlined. The approach consists of developing modeling frameworks to address critical attribute and function trade-off scenarios. The modeling frameworks would allow more formal and up front optimization and sensitivity analysis than is currently realized. In order to sustain these frameworks, a modeling cascade process has also been outlined. This would place formal requirements on VED’s to deliver models to support the MD-VSE process.
Operational Supports for Offshore Platforms: From System Integrity Monitoring to Marine Assurance and Safety
Authors: Prislin Igor , Goldhirsh Michael
Published: July 2009

The paper discusses typical full life-cycle of operational support for offshore platforms based on integrity monitoring systems, data management, and system maintenance services. The paper focuses on data management using a Client Data Center that provides offshore and onshore data hosting, postprocessing, and long term archive via the Internet. Properly selected, operational support provides elements to manage historical data critical to future assessments of the offshore-platform structural health, including the fatigue life of vital systems like mooring, tendons, and risers. The paper highlights the benefits of carrying out operational support continuously with the major goal — to make offshore platforms safe and profitable.
Interaction Between the Underwater Explosion Bubble and the Structure
Authors: Zhang A. M. , Yao X. L. , Shi D. Y. , Li J.
Published: July 2009

Based on the potential-flow assumption, BEM is applied to simulate the dynamic characteristics of underwater explosion bubble near boundaries and solve the interaction of bubble and elastic-plastic structure by coupling with FEM. A complete 3D program of underwater bubble analysis (UBA) is developed and the calculated error is within 10%. With this program, flat plate, cylinder and other simple structures are analyzed; the damages caused by retarded flow, pulsating pressure and jet and other loads on the structures are calculated, including different cases with free surface or without free surface. Results show that bubbles can cause great damage, and the specific cases can even cause greater damage. From the wall pressure and the stress curves of typical elements on the structure, it can be seen that the pressure peak occurs when the bubble collapses, which proves that the pressures caused by the bubble’s collapse and jet can result in great structure’s severe damage. It can provide reference for the research on the dynamic characteristics. The research in this paper aims to provide references for the correlated research on the dynamics of the underwater bubble.
Rogue Waves in Oceanic Turbulence
Authors: Fedele Francesco
Published: July 2009

A stochastic model of wave groups is presented to explain the occurrence of exceptionally large waves, usually referred to as rogue waves. The model leads to the description of the non-Gaussian statistics of large waves in oceanic turbulence and to a new asymptotic distribution of their crest heights in a form that generalizes the Tayfun model. The new model explains the unusually large crests observed in flume experiments of narrowband waves. However, comparisons with realistic oceanic measurements gathered in the North Sea during an intense storm indicate that the generalized model do not appear to improve upon the original Tayfun distribution.
Actual VIV Fatigue Response of Full Scale Drilling Risers: With and Without Suppression Devices
Authors: Tognarelli Michael A. , Taggart Samuel , Campbell Mike
Published: July 2009

In an effort to more effectively understand and manage vortex-induced vibration (VIV) fatigue integrity of its drilling risers, BP has instrumented several of them on a number of mobile offshore drilling units (MODUs) and offshore production platforms worldwide. This paper presents several aspects of the findings from those monitoring campaigns, with particular emphasis on the relatively more densely populated MODU data sets. In-situ monitoring has practical use as a realtime quantifier of accrued VIV fatigue damage to both drilling riser and wellhead casing over the course of a given monitoring period, a fundamental indicator of structural integrity. At present, this can be very useful to operators given that the gap between predicted and measured VIV fatigue damage can be very large. In this paper, the measured data are used to expose some of the physical details of full-scale riser response whose omission from predictive design tools and methods may contribute to this wide gap. To characterize the size of the gap, the data are compared to calculations using the most commonly used industry VIV analysis software. This demonstrates the inherent level of analysis over conservatism with respect to full-scale, unsuppressed drilling risers in the field when typical analysis parameters are utilized. A means of adjusting the parameters to reduce the over conservatism is then implemented. Finally, the data are used to reveal some performance indicators for VIV suppression devices that are presently being utilized in drilling operations.
Influence of Localized Geometric Imperfections i.e. Buckles and Wrinkles on the Integrity of Pipelines
Authors: Yang Zhengmao , Shashi Kumar , Tronskar Jens P.
Published: July 2009

Pipelines are relied upon to transport hazardous liquids and gasses over long distances. A major threat to the integrity of pipelines is mechanical damage, caused by outside natural forces. According to the AGA report [1], 39% of offshore and 37.7% land based natural gas pipeline failures were caused by outside force. During the installation of offshore pipelines the pipe wall at the 6 o’clock position sees large compressive strain and local buckling may occur. Dents may also occur by impact onto hard objects such as the rollers on the stinger or rocks on the seabed and by anchor impact etc. These kinds of imperfections change the local geometry of the pipe, and therefore, a stress concentration and local bending stress will be induced. The stress concentration factor can be up to 10 depending on the geometry of the imperfection. As a result, the local stresses will be much higher than the design stresses for the pipeline in operation subject to internal pressure and axial strain, and fracture and fatigue capacity of the pipelines with these imperfections will decrease dramatically. Because of the large local deformation, the materials in the deformed pipe region have undergone large local plastic strains i.e. 10–20% plastic deformation. The material properties of the pipe with large plastic strain will be drastically changed, and therefore the fracture resistance of the pipe is expected to be decreased, especially when the damage is located at the seam or girth welds. To assess the criticality of such damage which often can be associated with strain induced flaws in the heavily deformed parent metal and welds, ‘fitness-for-service’ assessment is required. The objective is to determine the severity of the flaws in the deformed pipe and to make the repair/replacement decision. At present there are no definitive assessment guidelines that consider these aspects and how to incorporate the behaviour and fracture capacity of the heavily deformed material. In this paper, a numerical model of typical local imperfections i.e. buckles and wrinkles was established from the in-situ geometry measurements. The local stress distributions of the pipes were analyzed. Based on this stress analyses, the stress concentration around the local imperfections in operation were obtained and the fracture capacity and fatigue life of the pipeline was assessed. The tensile and J R-curve data for deformed pipeline materials were obtained by the DNV Energy laboratory to study the influences of the large plastic strain on the material properties, and the fracture resistance and fatigue crack growth of the pipe. Based on the numerical analysis and test results, a fracture combined fatigue assessment was performed to decide on the mitigation and remediation strategies for the pipeline.
Research on Applicability of New Materials to Marine Structures in Tropical Climates: Exposure Test Project in Consideration of Actual State of Structural Members
Authors: Tomosawa Fuminori , Sekita Kinji , Ono Tadashi , Yonemaru Keisuke , Takizawa Shozo , Suzuki Takakazu
Published: July 2009

The application of lightweight and durable new structural materials to structural members of marine constructions in harsh environments, such as marine oil production facilities, is expected to reduce their running/maintenance cost, thereby reducing their life-cycle cost. The subject of the present project of serial studies is to elucidate the applicability of new materials that are expected to be applicable to structural materials for marine constructions by focusing on their durability. To this end, exposure tests of these new materials are conducted in Okino-tori-shima and Miyako-shima, which are prominently fierce marine environments in Japan. The specific purpose of this study is to accumulate basic date that will contribute to the durability design of structures using these materials. In the previous series of studies conducted from 1998 to 2005, 22 types of new materials were classified into five corrosion grades based on exposure test results to assess their applicability as structural materials. The present study is conducted with more emphasis on their practical uses. In consideration of economic efficiency and practical utility, one each was selected as specimens from the five grades of structural materials: an aluminum alloy, stainless steel, 9% nickel steel, common steel, and CFRP (Carbon Fiber Reinforced Plastic). Structural members of actual marine structures are exposed to a corrosive environment while being subjected to the loads of their own weight and external forces. However, few studies have investigated the durability of materials under stress. The authors conducted literature searching in regard to the selected five materials but scarcely found study results or data publicly available that can be utilized for durability design. The authors therefore planned exposure tests in which test pieces were to be exposed to marine environments while being subjected to axial forces. The ongoing study began in 2006 and is planned to last for five years. This paper reports on the outline of testing and the results of preliminary investigation.
Hydrodynamic Force Model on Free Spanning Pipeline Subjected to Seismic Excitations
Authors: Li Xin , Dong Rubo , Jin Qiao , Zhou Jing
Published: July 2009

Firstly, a series of model tests of free spanning submarine pipeline are carried out on an underwater shaking table in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. Hydrodynamic forces imposed on the span of submarine pipeline due to different direction excitations are studied. Secondly, finite element method on the base of the theory of interaction between fluid and structure is utilized to analyze the dynamic response of free spanning submarine pipelines subjected to earthquakes. Thirdly, based on Morison equation an improved hydrodynamic force model considering the effects of seismic exciting directions is proposed. Discretized equations of motion derived from the improved Morison equation is employed to analyze the dynamic response of free spanning submarine pipelines subjected to earthquakes. FE model is established to simulate the above experimental conditions. Finally, the comparison of numerical results with experimental results shows that the improved hydrodynamic force model could satisfactorily predict dynamic response on the free spanning submarine pipelines subjected to earthquakes.
Inspection of Clad and Plain Carbon Steel Girth Welds on Offshore Caisson Risers Using Semi-Mechanised Ultrasonic Testing (SMUT)
Authors: Conder Robert J. , McPherson Ryan , Kooren Ton , Parlane Allan
Published: July 2009

Caisson risers installed through drilling slots are an increasingly common method to add additional riser access to existing oil and gas production platforms. This paper describes the inspection methodology used for two new caisson risers on the Talisman Energy owned Tartan platform in the North Sea. The methodology for qualification of the inspection system for both plain carbon steels and Inconel 625 (UNS N06625) clad carbon steel is described. The offshore performance of the SMUT system is discussed and the time and safety benefits of this system are highlighted.
Comparison of Fatigue of Girth-Welds in Full-Scale Pipes and Small-Scale Strip Specimens
Authors: Maddox Stephen J. , Zhang Yan-Hui
Published: July 2009

As part of a study of fatigue in girth-welded steel pipes, tests were performed under constant amplitude loading on both full-scale pipes and strip specimens cut from such pipes. Significant differences were found in their high-cycle fatigue lives, which extended to around 108 cycles, and apparent fatigue endurance limits, the small-scale strips displaying superior fatigue properties. The reasons for this were investigated considering the fatigue crack initiation site, weld geometry, type of pipe, loading conditions, residual stresses, the re-testing of unfailed specimens and size effects. Fracture mechanics fatigue crack growth calculations were also performed using a K solution specially calculated by FEA for the girth weld. Conclusions are drawn about the suitability of strip fatigue test specimens for representing the fatigue behaviour of full-scale girth welded pipes and the scope for re-testing unfailed full-scale pipes.
Simulation of Boat Launching and Hoisting in a Seaway
Authors: So¨ding Heinrich , Reppenhagen Michael
Published: July 2009

For modeling the launching and hoisting of a small boat from/to a ship advancing in moderate seaway a software simulation system was developed. Its purpose is to test various procedures and the necessary equipment for such maneuvers. The software will be extended further as a ’federation’ within a ’high-level program architecture’ (HLA) using the commercial ’run-time infrastructure’ (RTI). It comprises a visualization of the water surface, the frigate, the boat and the cables connecting both vehicles during part of the maneuvers.
Modelling the Seasonality of Extreme Waves in the Gulf of Mexico
Authors: Jonathan Philip , Ewans Kevin
Published: July 2009

Statistics of storm peaks over threshold depend typically on a number of covariates including location, season and storm direction. Here, a non-homogeneous Poisson model is adopted to characterise storm peak events with respect to season for two Gulf of Mexico locations. The behaviour of storm peak significant wave height over threshold is characterised using a generalised Pareto model, the parameters of which vary smoothly with season using a Fourier form. The rate of occurrence of storm peaks is also modelled using a Poisson model with rate varying with season. A seasonally-varying extreme value threshold is estimated independently. The degree of smoothness of extreme value shape and scale, and the Poisson rate, with season, is regulated by roughness-penalised maximum likelihood; the optimal value of roughness selected by cross-validation. Despite the fact that only the peak significant wave height event for each storm is used for modelling, the influence of the whole period of a storm on design extremes for any seasonal interval is modelled using the concept of storm dissipation, providing a consistent means to estimate design criteria for arbitrary seasonal intervals. Characteristics of the 100-year storm peak significant wave height, estimated using the seasonal model, are examined and compared to those estimated ignoring seasonality.