bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining the Yield Strength of In-Service Pipe Using Hardness Testing
Authors: Radmard Shadie , Berg Monique
Published: April 2011

Enbridge Energy Partners (EEP) (“Enbridge”) purchased a Tank Storage Facility in Cushing, Oklahoma in 2004. After the acquisition, it was discovered that pipe records were incomplete and hydrotest documents were unavailable for some of the pipe segments in the tank facility. In order to comply with the Code of Federal Regulations (CFR) 49 Part 195, it was determined that piping at the Cushing Facility should be operating under “low stress” conditions. To determine if this condition could be met, the internal design pressure and yield strength (“YS”) were required for each pipe segment. Without pipe records, neither the internal design pressure, nor the YS was known. In 2007, a project was undertaken by Enbridge to inspect and test all pipe segments identified to have missing pipe records. The project’s objectives were: (1) To establish procedure and process for nondestructive evaluation of tensile properties of in-service pipe; (2) To collect pipe characteristic information (i.e. diameter, wall thickness); (3) To determine if the piping could be considered low stress piping; and (4) If the piping could not be considered low stress, to select a course of action from the following options: a. Lower the Maximum Operating Pressure (MOP), b. Hydrotest the piping, c. Remove/Abandon all unnecessary lines. Two existing reports justified the use of hardness as a means of determining the YS of in-situ piping. Based on these reports, Enbridge developed the following project scope: (1) For all piping with missing records: a. to collect hardness data of in-situ pipe using two portable hardness testers (any hardness measurements taken with these portable hardness testers are hereinafter referred to as “field hardness”), b. to measure wall thickness of in-situ pipe; (2) To collect field hardness, lab hardness, YS and tensile strength data of pipe coupons of various diameters in order to establish a field hardness to YS correlation; (3) To determine the YS of the in-situ pipe using field hardness measurements and the established field hardness to YS correlation determined above; (4) To determine if the pipe could be considered low stress at existing operating pressures; (5) For pipe segments not deemed low stress at existing operating pressures, to calculate an internal design pressure (Allowable Working Pressure or “AWP”) required to maintain low stress conditions. This paper will describe the method used to determine YS and AWP of in-service piping using field hardness and compare the results obtained using this method to the YS and AWP determined using CFR Title 49 Part 195.106.
Is the 80% Leak Criterion Always Appropriate?
Authors: Haines Harvey , McNealy Rick , Rosenfeld M. J.
Published: April 2011

When evaluating corrosion ASME B31G recommends an upper limit of 80 percent of the wall thickness for evaluating metal loss depth. Although corrosion deeper than this can still be acceptable for maintaining a safe pipeline, the primary concern was for the effect of error in the corrosion depth measurement and the need to offer conservative criteria. If the measurement error is understood and the treatment of these errors can be handled in a routine and practical manner, then corrosion depths greater than 80 percent could potentially be acceptable. Examples of well understood measurement error are ILI tools where published values exist for commercial tools, in addition the error can be reassessed using in-the-ditch measurements when remediating occurs. The 80 percent maximum is also limiting for low pressure applications such as barge and tank lines, or natural gas distribution lines, where the pressure on a system is often only a fraction of the pressure carrying capability of full wall thickness pipe. This paper will demonstrate a method for assessing deep corrosion which is acceptable for low pressure lines and accounts for measurement error using other known sources of measurement error.
Prioritization of a Portfolio of Projects
Authors: Modica Jose Eduardo , Rabechini Roque , Martins Braun Edison
Published: April 2011

The high competitiveness in the oil sector, the velocity of changes in the world and the increasingly short life cycles of projects, have forced the large companies in this sector to maintain extensive project portfolios in engineering. These demand efficient management and balancing, because otherwise the competitive position relative to other companies is placed at risk. These companies have the challenge of developing appropriate methodologies to manage the portfolios and provide support to the decision makers, aiming at maximizing the results of the projects. One of the activities of portfolio management, and perhaps the most difficult, is the adequate prioritization of the projects, because it involves great subjectivity in the direct comparison of highly different projects, with different objectives and at times contrary in the use of criteria that depend on sensitivity evaluations. An example is the improvement in society’s perception of the company’s image that a project may provide. For the prioritization of these projects, it becomes necessary to employ multiple-criteria analyses, and for this, the organization needs to define how many, and which criteria are going to be utilized, together with their relative importance. This article has the purpose of describing the implantation of a prioritization methodology for projects utilizing the Analytic Hierarchy Process (AHP) analysis technique in a regional office of the largest logistics company in South America, Transpetro. The company forms part of the Brazilian oil system; more specifically in the transport and storage of oil and oil products. The company operates a fleet of 55 ships having the transport capacity of 2.9 million deadweight tons, 7,033 km of oil pipelines and 3,600 km of gas pipelines, 20 land-based terminals and 26 water-based terminals. The dynamic of the implantation will be presented as the results, demonstrating a preliminary sensitivity analysis, the choice of analytical technique utilizing multiple criteria, the development of a tool and the result of prioritizing the portfolio. In addition, the results of the analysis of this prioritization relative to the existing portfolio will be presented.
Remaining Local Buckling Resistance of Corroded Pipelines
Authors: Chen Qishi , Khoo Heng Aik , Cheng Roger , Zhou Joe
Published: April 2011

This paper describes a multi-year PRCI research program that investigated the local buckling (or wrinkling) of onshore pipelines with metal-loss corrosion. The dependence of local buckling resistance on wall thickness suggests that metal-loss defects will considerably reduce such resistance. Due to the lack of experimental data, overly conservative assumptions such as a uniform wall thickness reduction over the entire pipe circumference based on the defect depth have been used in practice. The objective of this research work was to develop local buckling criteria for pipelines with corrosion defects. The work related to local buckling was carried out in three phases by C-FER and the University of Alberta. The first phase included a comprehensive finite element analysis to evaluate the influence of various corrosion defect features and to rank key parameters. Based on the outcome of Phase 1 work, a test matrix was developed and ten full-scale tests were carried out in Phase 2 to collect data for model verification. In Phase 3, over 150 parametric cases were analyzed using finite element models to develop assessment criteria for maximum moment and compressive strain limit. Each criterion includes a set of partial safety factors that were calibrated to meet target reliabilities selected based on recent research related to pipeline code development. The proposed criteria were applied to in-service pipeline examples with general corrosion features to estimate the remaining load-carrying capacity and to assess the conservatism of current practice.
Influence of the Material Plasticity on the Characteristic Behavior of Sandwich Pipes
Authors: Arjomandi Kaveh , Taheri Farid
Published: April 2011

Sandwich Pipes (SP) can be considered as an enhanced design configuration for Pipe in Pipe (PIP) systems. By improving the structural properties of the core layer and the components’ interface adhesion, SP systems can be an effective design alternative for deepwater applications. However, designing such a hybrid structure demands more knowledge of the response of the system under the governing loading and environmental conditions. A SP system would be a suitable design alternative for offshore pipelines that are subjected to very large hydrostatic pressure in deepwater. Therefore, full understanding of the behavior of such systems under the external hydrostatic pressure is a prerequisite for designing optimum SPs. In this paper a set of parametric models are generated based on practical design configurations. The Finite Element (FE) software package, ABAQUS, is used to create the models and analyze them. The FE models are analyzed through eigenvalue buckling and post-buckling analyses with the assumptions of linear and nonlinear buckling. Appropriate initial imperfections and FE parameters are administered. Moreover, the integrity of FE models is investigated through a mesh convergence study and also by considering various types of element locking mechanism. The results of these three methods of analysis are compared and the discrepancy between the results obtained through the linear analysis in comparison to the nonlinear post-buckling analysis is highlighted. Moreover, the influence of using various material plasticity models on the buckling and post-buckling responses is also investigated. Different models describing the materials stress-strain curves in the form of the elastic perfectly plastic, elastic followed by plastic exponential hardening, as well as the existence of the Lu¨der’s bands are also considered. Furthermore, the effect of core material’s stiffness on the buckling and post-buckling response of the system is also examined. Based on the equivalent plastic strain, it will be shown that in order to ensure system’s effective composite sandwich action, the core must have a certain minimal stiffness. Finally, the influence of the enhancement in the steel grade used to form either the internal or external pipe on the stability response of both PIP and SP systems will be illustrated.
Increasing Productivity and Safety of Pipe Lowering Through Finite Element Analyses
Authors: Carneiro Daniel , Rosito Roberta , Carvalho Guilherme
Published: April 2011

It is common practice in the construction of buried pipelines that pipe sections are welded together at surface level and then lowered into a trench. The stresses induced to the pipe during lowering operation are seldom evaluated or considered in the pipeline design. Scarce industry guidelines and procedures are empirical. Simplistic (while not always conservative) calculations typically used to prevent yielding lead to restrictive spacing between lift points. This paper shows that the use of finite element analyses to realistically simulate the pipe lowering operations can significantly increase the distance between side booms (and hence the productivity) while increasing safety. Case study analyses were performed using data from a real pipeline under construction, showing that limiting the pipe span length is not sufficient to prevent yielding, while by adequately studying the lowering procedure, significantly larger spacing between lift points was achieved. The analyses were performed using a commercial software package widely used in offshore pipeline analyses. The effect in terms of induced stresses of additional issues such as route curves, which are difficult to evaluate in simple calculations, was also discussed. Further advantage can be taken from being aware of the actual stresses imposed to the pipe during its construction, for example by using weld defect acceptance criteria based on fracture mechanics rather than workmanship.
Fitness for Service Document Comparison: API 579 vs. PDAM
Authors: Jaske Carl E. , Rubal Melissa J.
Published: April 2011

Assessing the Fitness for Service (FFS) of deficient pipeline segments or facilities is an important step in managing the mechanical integrity and safety of pipeline systems. However, FFS can be determined according to several documents, including API 579-1/ASME FFS-1 2007 Fitness-For-Service (API 579) and the Pipeline Defect Assessment Manual (PDAM). The document contents and assessment methodologies of API 579 and PDAM are reviewed and compared for several common damage mechanisms. API 579 was originally developed for the refining and petrochemical industries but is currently applied to a broad range of equipment and systems. In contrast, PDAM was developed under a joint industry project to assess defects specifically in petrochemical pipelines. While PDAM refers the reader to API 579 for the assessment of several damage mechanisms, including gouges, manufacturing defects, weld defects, and cracks, the authors of PDAM claim that API 579 is generic, biased towards pipes in process plants, and can be overly conservative for the assessment of other pipeline defects. Understanding and comparing the current FFS documents can lead to an enhanced allocation of available resources and can improve the level of FFS assessments in the pipeline industry. The methods used to assess corrosion of components with static internal pressures, dents, dent-gouge combinations, and cracks are compared.
Risk Assessment of Underground Natural Gas Storage Station
Authors: Wang Ke , Zhao Xinwei , Luo Jinheng , Dong Baosheng , Li Lifeng , Cai Ke
Published: April 2011

With the development of West-East projects construction, China’s natural gas production and consumption is increasing. But it must be to ensure to supply a continuous gas to users despite pipelines were meeting an accident, solve the inconsistency between storing excess gas during the using troughs and complementing insufficient gas during the using peak, and regulate the gas distribution imbalance caused by gas consumption by day and night and seasonal changes. Underground natural gas storage has unique advantages compared with other methods of peak regulation. The station, as its important part, has many complicated facilities, and the assessment will be extremely important. The paper divided the station into three elements, assessed the risk based on API581. The paper also applied the method to assess these facilities on the station of one gas storage. At last, it presented the suggestive measures to control risks.
Low Cycle Fatigue of Corroded Pipes Under Cyclic Bending and Internal Pressure
Authors: Lourenc¸o Marcelo Igor , Netto Theodoro A.
Published: April 2011

Corroded pipes for oil transportation can eventually experience low cycle fatigue failure after some years of operation. The evaluation of the defects caused by corrosion in these pipes is important when deciding for the repair of the line or continuity in operation. Under normal operational conditions, these pipes are subject to constant internal pressure and cyclic load due to bending and/or tension. Under such loading conditions, the region in the pipes with thickness reduction due to corrosion could experience the phenomenon known as ratcheting. The objective of this paper is to present a revision of the available numerical models to treat the ratcheting phenomenon. Experimental tests were developed allowing the evaluation of occurrence of ratcheting in corroded pipes under typical operational load conditions as well as small-scale cyclic tests to obtain the material parameters. Numerical and experimental tests results are compared.
Optimizing Pipeline Transportation Using a Fuzzy Controller
Authors: Aramaki Thiago L. , Montalva˜o Anto´nio F. F. , Correa Joa˜o L. L.
Published: April 2011

This paper describes a case of a Proportional Integral (PI) Fuzzy controller development, in order to optimize pipeline transportation capacity. Real process data were acquired so that a real pipeline could be simulated. The fuzzy adaptive PI controller system was developed and interacts with a hydraulic simulator, working on the set-point of a conventional PI controller. A conducted research prior to this work has shown that holding the intermediate delivery valves open as much time as possible, even if this results in a low flow delivering, is better than do a fast delivering in terms of pipeline transportation capacity. The objective of this system is to control the amount of products to be delivered to intermediate stations in such a way that the control valve remains open while the batch is running. Besides that, the control valve opening fraction is changed very smoothly preventing transients in the pipe, until it is closed, which occurs when the station has received the expected demand. In order to accomplish that some information have to be loaded in the software like product demand per station, operational limits of the valve being controlled (minimum and maximum flow, the flow meter operational limits were also observed) and products transported at the segment monitored. The software developed can be easily deployed as a specialist system generating logic to be embedded in SCADA Systems or standalone software.
Composite Repairs of High Pressure Steel Pipelines
Authors: Laughlin Shawn , Leewis Keith
Published: April 2011

This paper provides a review of the performance considerations for effective mitigation of metal loss defects on high pressure steel pipelines. Special emphasis is placed on the non-trivial issues which are often not considered by practitioners of pipeline integrity efforts.
On the Comparison of Different Multiphase Flow Kernels for Gas Pipeline Real Time Advanced Functions
Authors: Baptista Renan Martins , Figueiredo Aline Barbosa , Bodstein Gustavo C. R.
Published: April 2011

The nature of real time advanced functions or systems for gas pipelines carrying two phase mixtures is complex, especially when the dominant phase is gaseous. In this case, the flow quite often requires periodic pig runs, among several other specific operational procedures. Thus, a robust, accurate, reliable and fast kernel is mandatory for good performance on leak detection, location and quantification, as well as any other real time function such as virtual instrumentation or inventory management and reconciliation. This work aims at comparing different transient two-phase one-dimensional kernels under the perspective highlighted above. Specifically, one may cite: (i) a two-fluid model, implemented in 20 years consolidated commercial flow simulator, bringing a kernel of first order in time and second-order in space, three continuity equations, and three momentum equations, where 2 different pressures are possible to be calculated; (ii) a simple two-fluid model to serve as the basis of a different way to approach the same problem. The main focus of this paper is on real time applications, then its main goal is to provide considerations and comparisons on accuracy, reliability and processing speed (CPU performance) coming from six different numerical methods and schemes. The commercial flow simulator is then being used as the basis of comparison, as it is considered highly reliable and robust by the market.
Plan of Communications and Relationship With Third Parties for the Bolivia-Brazil Pipeline Right-of-Way
Authors: Cauduro Ma´rcia
Published: April 2011

Objective: This work aims to present to the Plan of Communications and Relationship with Communities implemented by TBG as a tool for the Bolivia-Brazil Pipeline integrity management. Scope: In studies carried out by the European Gas Pipeline Incident Data Group (EGIG), global statistics demonstrate that most accidents involving pipelines are caused by improper actions of third parties. The expansion of sugar cane crops and the improvements in utilities, such as telephone, electricity, water and sewage services in the cities along the pipeline have increased the number of events of interference in the right-of-way. These facts have evidenced the need for creating a Plan of Communications and Relationship with landowners and neighboring communities to assure the continuous monitoring of the Bolivia-Brazil Pipeline right-of-way. The Plan of Communications and Relationship with Communities is designed to reduce the risk of accidents caused by the improper action of third parties. The strategy of action is focused on strengthening the relationships among the right-of-way technical staff, TBG subcontractors, and other publics affected by the pipeline. It also encourages the use of the toll-free Gas Hotline (0800 026 0400) - TBG main communication channel with communities. The intensive publicity targeted at specific audiences ensures that local populations and other relevant publics raise their awareness on the importance of preserving the right-of-way, and the precautions that must be taken in their neighborhoods, mainly in cases of interferences, such as urban improvement projects and farming activities by keeping permanent contact with TBG through the Gas Hotline. This work will also present the interfaces among the right-of-way technical staff, the corporate communications team, and specific target audiences; communication resources, guidelines, technical training programs, Gas Hotline monitoring and management plans, indicators of services provided to the communities and landowners, and the results of the Gas Pipeline Management Program.
Enbridge Northern Pipeline: 25 Years of Operation, Successes and Challenges
Authors: Pederson Ingrid , Sen Millan , Bidwell Andrew , Yoosef-Ghodsi Nader
Published: April 2011

Enbridge Pipelines Inc. has operated a 324 mm diameter, 870 km crude oil pipeline from Norman Wells, Northwest Territories to Zama, Alberta since 1985. This pipeline is the first completely buried oil pipeline constructed within the discontinuous permafrost zone of Canada. This pipeline was constructed over two winter seasons, and since 1985 has transported roughly 200 million barrels of crude oil to southern markets without significant interruption. This paper will review the design, construction, and operational challenges of this pipeline through the past 25 years. Unique and innovative aspects of this pipeline include measures taken during construction to minimize thermal disturbance to the soil, insulating permafrost slopes to minimize post-construction thaw, operating at temperatures that minimize thermal effects on the surrounding ground, accommodating ground movement caused by frost heave/thaw and slope instabilities, and evaluating the effects of moving water bodies adjacent to the pipeline right-of-way. The use of in-line inspection tools (GEOPIG) has been valuable as a supplement to conventional geotechnical monitoring, for the evaluation and assessment the effects of ground movement to the pipeline. Finite element pipe/soil interaction models have been developed for selected sites in order to assess the potential for slope movement to generate strains in the buried pipeline that exceed the strain capacity. This paper will review new monitoring data and findings since previous publications. In addition, the implications of long-term trends of increasing ground temperatures and associated changes to the geotechnical and permafrost conditions along the pipeline route will also be discussed and are relevant to other proposed pipeline and linear infrastructure projects along the Mackenzie Valley.
Study on Acceptable Risk for Oil and Gas Pipelines in China
Authors: Zhang Hua , Luo Jinheng , Chen Juanli , Zhao Xinwei , Zhang Guangli
Published: April 2011

Risk assessment is basis to put pipeline integrity management in practice and the acceptable risk level is important criteria to execute risk assessment and constitute maintenance safeguard. So it is very important to establish a rational and practicable acceptable criterion and present a specific acceptable risk level. It is just for this need that the present paper gave a review of all the available research around the acceptable risk level and analyzed various domestic and overseas standards and documentation concerning how to define the acceptable risk criteria. As a result, a criterion suitable for oil and gas pipeline was presented and recommended acceptable risk level was gave.
Evaluating a Corrosion Assisted Pipeline Rupture
Authors: Pussegoda L. N. , Semiga V.
Published: April 2011

An in-service failure was associated with an NPS 12, 6.35 nominal wall API 5L X42 grade pipe. This segment of the pipeline had been in service since 1957 and had a tar coating. The pipe was manufactured by piercing followed by rolling/extrusion to produce a seamless pipe. The pipeline has always carried refined petroleum products. The rupture event was captured by pressure history records that recorded an overpressure experienced during a sudden valve closure event. The section of pipe removed included portions of the upstream and downstream pipe sections to carryout a failure investigation. The paper presents the findings from the investigation. The paper presents the observations from inspection and experimental testing carried out on the removed pipe section. These included NDE, fracture surface examinations and destructive examination such as metallography that helped in obtaining information on the reduction in the resistance of the material to withstand the in-service pressure conditions. The above observations together with results from mechanical testing was used to estimate failure pressures based on a “deterministic” primary flaw size, using assessment methods (ECA) applicable to the failure case under consideration. The investigation of the failure indicated that the major contributing factors were: (a) the corrosion feature at the failure site that reduced the remaining wall thickness below 2mm, and the overpressure caused by the valve closure down stream in the vicinity of the failure site. Pipe specification checks from material removed from the section of the failed pipe, indicate that the pipe meets the API 5L X42 specification requirements.
Reliability Life Span of Fatigue Cracks
Authors: Rout Cameron , Mihell James , Adams Keith , Len Nathan
Published: April 2011

Reliability analysis has become widely used as a method of accounting for uncertainty in the sizing of metal loss features in pipeline integrity management programs. As inline inspection (ILI) technology for crack detection becomes more widely available, the opportunity to use reliability methods in a manner similar to that already adopted for metal loss features presents itself. Nevertheless, the technical challenges to the application of reliability analysis of cracks are distinct from those that are relevant to the reliability analysis of metal loss features. Calculating the time-dependent threat of failure due to fatigue or corrosion fatigue must address different parameters than it would for metal loss features, and consequently this presents new challenges in developing statistical analysis tools. Such challenges include predicting operational pressure cycling, accounting for uncertainty in ILI crack sizing, and characterizing crack growth behaviour type. This paper provides an overview of some important parameters to be considered in reliability-based fatigue or corrosion fatigue analysis with some examples of how they have been addressed in work to date by Dynamic Risk Assessment Systems, Inc.
A Comparison of Two Major Linepipe Specifications and Possibilities for Harmonization
Authors: Millwood N. A. , Andrews R. M. , Knauf G. , Howard R. , Roovers P.
Published: April 2011

A fundamental building block of all pipeline systems is the linepipe used to construct the pipeline. The specification for this pipe is the means of ensuring that the designer’s and owner’s requirements are communicated to the pipe mill and then ensuring that the correct pipe is delivered. The most widely used specification is probably API 5L; this has recently been harmonized with the corresponding ISO specification, ISO 3183:2007. Within Europe, EN 10208-2 has been widely used, particularly for onshore gas transmission pipelines. This standard was revised in 2009. There are presently differences between these specifications. Development of a single document could reduce costs for producers and users, as all parties will be working from a common baseline and a wider range of markets and sources of material will be available. The European Pipeline Research Group (EPRG) has carried out a comparison of the harmonized API/ISO and the EN specifications. This was intended to assist the drafting committees in working towards a single standard without compromising safety or increasing costs. The study has identified the areas of agreement and differences between the documents. The results of this comparison are presented in this paper, including recommendations for changes to achieve the goal of a common specification. The implications of possible changes for costs and safety are also considered.
Spill Consequence Analysis: A Method to Prioritize Integrity Excavations of Liquid Pipelines
Authors: Haggins Jana M. , Cote Edgar I. , Morgan Kristine , Shaheen Ehab
Published: April 2011

Corrosion and stress corrosion cracking (SCC) control programs are elements of pipeline integrity management. These programs often include in-line inspections (ILI’s) to identify, characterize and size anomalies, followed by field excavations to repair defects, remediate coating failures, and establish tool sizing accuracy. The highest priority excavations target anomalies with the lowest predicted remaining strength or deepest flaws. In cases where loss of pipeline integrity is highly consequential, selection of additional excavation sites based on the risk of failure is warranted. As specified in Annex B of CSA Z662-07, the risk of failure combines probability (typically based on the predicted remaining life of known corrosion or cracking features) with an evaluation of consequence along the pipeline length. Consequence evaluation typically considers the impacts of health and safety, environmental, property damage, public disruption, service interruption and financial loss. A practical methodology for evaluating consequence for liquid pipelines was developed for the NPS 10 Alberta Products Pipeline (APPL) in Alberta, Canada. Comprising of three (3) parts, the methodology starts with an evaluation of spill volume along the pipeline based on valve closure times and pipeline inventory drawdown. Combined with soil absorption data and topography, the spill volumes are used to model spill areas along the pipeline. Finally, the spill areas are overlaid on a classification of land use along the pipeline to quantify the relative spill consequence. The land use classification developed for this analysis has commonalities with the definitions for High Consequence Areas (HCA) and Unusually Sensitive Areas (USA) within U.S. Code of Federal Regulations (49 CFR, Part 195). Prioritized segments of the pipeline with elevated consequence levels were identified and used with the probability of failure to calculate risk and prioritize sites for ILI excavation programs.
Identifying and Mitigating Flow-Induced Vibration in Recycle Loop Gas Piping at a Centrifugal Compressor Station
Authors: Broerman Eugene L. , Gatewood Jason T. , O’Grady James T. , Troy Russell F. , Rand Charles L. , Stroud Gary T.
Published: April 2011

The South East Supply Header (SESH) is a relatively new pipeline placed into service in September of 2008. The 42″/36″ pipeline originates near Delhi, Louisiana and ends near Coden, Alabama. The pipeline has a nominal capacity of 1 BSCFD and includes three (3) mainline compressor stations, two (2) booster stations and numerous meter stations.
Understanding Magnetic Flux Leakage Signals From Gouges
Authors: Clapham Lynann , Babbar Vijay , Chen Jian Dien , Alexander Chris
Published: April 2011

The Magnetic Flux Leakage (MFL) technique is sensitive both to pipe wall geometry and pipe wall strain, therefore MFL inspection tools have the potential to locate and characterize mechanical damage in pipelines. The present work is the first stage of a study focused on developing an understanding of how MFL signals arise from pipeline gouges. A defect set of 10 gouges were introduced into sections of 12″diameter, 5m long, end capped and pressurized X60 grade pipe sections. The gouging tool displacement ranged (before tool removal) between 2.5 to 12.5mm. Gouges were approximately 50mm in length. The shallowest indentation created only a very slight scratch on the pipe surface, the deepest created a very significant gouge. All gouges were axially oriented. Experimental MFL measurements were made on the external pipe wall surface (pressurized) as well as the internal surface (unpressurized). The early results of the experimental MFL studies, and a hypothesis for the origin of the MFLaxial signal “dipole” are discussed in this paper.
Use of Multiple SMA Wires for Morphing of Inflatable Wings
Authors: McDonald Anthony D. , Walker Scott J. I.
Published: April 2011

The concept of inflatable wings has design heritage and they have recently seen renewed interest, largely due to the increased demand in unmanned aerial vehicles (UAVs). They offer design advantages over conventional wings, particularly with regard to stowage and portability, since they can be tightly packed when undeployed. Unfortunately current methods of flight control involve the use of additional control surfaces attached to the trailing edge of the wing, adversely affecting the stowage capabilities. One way of overcoming this restriction is to use the wing itself as a control surface, by morphing the very shape of the wing to achieve the desired results. This article outlines the research performed at the University of Southampton into differing configurations of Shape Memory Alloy (SMA) wires as a controllable actuator for the wing morphing. Specifically the use of multiple wires to further enhance this control was the focus of this work. A simple test rig was constructed in order to evaluate the pulling force achievable by combinations of SMA wires in a number of configurations. The most promising of these configurations was then attached to an inflatable wing model for further testing. Both static testing and wind tunnel testing was undertaken, evaluating the authority of flight control such a system could achieve. The test results are presented in this paper, giving an initial performance assessment of the proposed control method.
Vibration Measurements for Membrane Structures by Using Laser Excitation System
Authors: Obara Kenya , Kajiwara Itsuro
Published: April 2011

The purpose of this study is to establish a measurement method to get vibration characteristics of membrane structures. An impulse hammer or a vibration exciter have been traditionally used to measure the vibration response of constructions and mechanical systems, but this method is not appropriate to apply the impulse force for the membrane structures due to its lightness and flexibility. Consequently, non-contact impulse excitation is applied by using laser excitation system and is absolutely suitable for the vibration measurement of the membrane structures. The proposed method makes the precise measurement of the frequency response in wide frequency range possible because an ideal impulse force is applied to a point on the structure. Moreover, a health monitoring system can be constructed by combining this vibration testing system and damage detection system. Damage of structures can be identified by detecting fluctuations of vibration responses with this health monitoring system.
Structural Damage Identification With Performance-Based Uncertainty Quantification
Authors: Lew Jiann-Shiun
Published: April 2011

This paper presents an investigation of damage detection of a structure with significant uncertainty. The proposed approach integrates the performance-based uncertainty quantification and feedback control techniques for damage identification. A singular value decomposition (SVD) technique is used to decompose parameter variations into principal components that are weighted with the sensitivity of the performance metric for damage detection. This SVD technique can be used to differentiate between dominant uncertainties and minor uncertainties corresponding to damage identification. To improve the performance of damage identification under uncertainty, a feedback controller is incorporated into the structure to reduce the effect of the quantified uncertainty. The probability framework, based on Monte Carlo simulation, is used to predict the false identification of damage. Examples based on the structural dynamics challenge problem issued by Sandia National Laboratories are used to demonstrate the proposed techniques.
Dynamic Characterization of a Magnetoelectric Cantilever for Actuation and Sensing
Authors: Clarke Joshua , Sundaresan Vishnu Baba
Published: April 2011

This article continues our work to develop magnetoelectric materials as self-sensing actuators. Our research is directed at developing a two-segment cantilever device with closed-loop control. The actuator under study is fabricated as a laminated composite of the magnetostrictive material Iron-Gallium (Galfenol) and a Lead-Zirconate-Titanate piezoelectric material (PZT-5H). The mechanical and electrical characteristics of a single-segment cantilever are modeled using the equation of motion developed from variational principles in earlier work and are compared with experimental data from other groups. Additionally, parametric analysis is performed to determine the effect of varying the thickness fraction of the piezoelectric layer on the frequency response characteristics of the actuator. When applied to the dynamic behavior of the actuator, the model predicts behavior that closely resembles experimental results published by other groups. Parametric analysis of the piezoelectric layer thickness fraction indicates that the design of a magnetoelectric cantilever self-sensing actuator can be optimized by varying the thickness fraction.
Improvement on Thermal Shock Resistance of Ceramic Components by Using Self-Healing
Authors: Nakao Wataru
Published: April 2011

Availability of self-healing on the thermal shock resistance of ceramic components was investigated. Using gas quenching method, the crack-healed alumina-18 vol% SiC composite, which has excellent self-healing ability, was applied to thermal shock of the arbitrary quenching rate. The procedure could give rise to the thermal stress fracture at high temperature. The critical quenching rate at thermal stress fracture of the healed specimen was found to be 6.47 K/s, corresponding to the thermal stress of 452.3 MPa. Alternatively, that of the cracked specimen was found to be 5.02 K/s, corresponding to the thermal stress of 350 MPa. From the obtained results, usage of self-healing was confirmed to improve extremely thermal shock resistance. The present result suggests that usage of self-healing gives a large advantage to design the high temperature ceramic components, because the mechanically reliable design and thermal shock resistance cannot coexist due to low thermal conductivity.
On the Development of the En Masse Elimination Algorithm for Actuator Grouping Optimization in Adaptive Structures
Authors: Hill Jeffrey R. , Wang K. W.
Published: April 2011

As large arrays of actuators become increasingly common in smart structures, many systems do not have enough power supplies to control each actuator individually due to design, weight, or cost constraints. This issue can be addressed by grouping multiple actuators together and powering each group with a single power supply. As this is done, it is important to determine which actuators to group together. For best performance, the grouping of actuators must be optimized. Currently, genetic algorithms and other heuristic algorithms are used to determine this grouping, but a global optimum is not guaranteed. In order to accurately group the actuators and guarantee that the global optimum is found, we have developed a new method to achieve such purpose — the En Masse Elimination (EME) technique. This is an optimization algorithm used to determine the grouping of actuators when there is a constraint on the number of power supplies, specifically when there are more actuators than power supplies present. The first step in this method is for a solution that satisfies the power supply limitation to be found. The required control authority is determined for this solution. Next, some actuators are grouped while the power supply constraint is temporarily relaxed for all the other actuators. If the control authority of this solution is no better than the control authority of the acceptable solution, than large areas of the design space can be eliminated. This process is continued until the entire design space has been searched, and the global optimum is found. Unlike other methods, the global optimum is found without having to examine every possible combination. In this paper, a detailed explanation of the EME algorithm is given and the efficacy of this method is demonstrated. An example consisting of a beam with static deformation, multiple actuators, and varying constraints on the number of power supplies is used to illustrate the concept.
Multidisciplinary Design Optimization of Actuator Arrangements, Lay-Up Configurations and Control Systems for Smart Laminated Composite Structures
Authors: Honda Shinya , Kajiwara Itsuro , Narita Yoshihiro
Published: April 2011

Structures and control systems of smart laminated composites consisting of graphite-epoxy composites and piezoelectric actuators are designed optimally for the vibration suppression. Placements of piezoelectric actuators, lay-up configurations of laminated composite plates and the H2 control system are employed as design variables and are optimized simultaneously by a simple genetic algorithm (SGA). An objective function is H2 performance with assuming that the state feedback is available. A multidisciplinary design optimization is performed with above three design variables and then the output feedback system is reconstructed with the dynamic compensator based on the linear matrix inequality (LMI) approach. Optimization results show that the optimized smart composite successfully realizes vibration suppression of the system and it is confirmed that the present multidisciplinary design optimization technique is quite efficient to the smart composites.
Development of Biomimetic Intelligent Material Applying Bio-SMA Honeycomb Structures
Authors: Yamamoto Hidetake , Onishi Kiyoshi
Published: April 2011

Our research purpose is to develop biomimetic intelligent material system applying biphasic composites of biocompatible Shape Memory Alloy (bio-SMA) honeycomb and inert gas in order to create the multifunctional effects of solid-fluid dispersion for cancellous bone and shock absorption for muscle fibril and so on. This paper reports on modeling and manufacturing bio-SMA honeycomb to constitute active shock absorption and measurement of recovery forces depend on super-elastic deformation of hexagonal cell unit with heating. Consequently, load-displacement curves with heating of bio-SMA honeycombs were a likely step shape under in-plane indentation. Recovery forces of single cell-layered honeycomb were from 3.1 to 3.8 N and the forces of double cell-layered one were from 5.0 to 6.5 N. It was cleared that the force linearly increased as layer number of cells was larger. The curve of triple cell-layered one looked to be likely two-step shape depend on the distribution of in-plane cell deformation.
The Modelling of Hysteresis in Magnetorheological Dampers Using a Generalised Prandtl-Ishlinskii Approach
Authors: Wang Kun , Zhang Ying , Jones Richard W.
Published: April 2011

The major drawback of magnetorheological dampers (MR) lies in their non-linear and hysteretic force-velocity response. To take full advantage of the operating characteristics of these devices a high fidelity model is required for control analysis and design. In this contribution the ability of a generalised PI operator-based model to represent the characteristics of a commercially available MR damper is examined. This approach allows the user to define the PI operator to best match the hysteresis characteristics. For the MR damper the force-velcoity hysteresis characteristic is ‘S’ shaped and constrained. Two possibilities will be examined here for the generalised play operator; an hyperbolic tan function and a symmetric sigmoid function.
Configuration of Control System for an Adaptive Tensegrity Structure
Authors: Korkmaz Sinan , Bel Hadj Ali Nizar , Smith Ian F. C.
Published: April 2011

Tensegrity structures are attractive due to their potential for deployability, ease of tuning and high precision control. Since tensegrity structures have highly coupled behavior, placement of actuators is a primary concern when designing active control systems. This study investigates the active control performance of cable members of a tensegrity bridge. The actuation efficiencies of cable members are evaluated through a multi-criteria approach. The configuration of the control system is thus identified through outranking candidate active members. A multi-objective damage tolerance strategy is then proposed and optimally directed control solutions are identified using stochastic search. Case studies for several damage scenarios are examined to validate results. The most efficient active cable configuration is compared with that needed for deployment. Results indicate that the control strategy for deployment is a near-optimal solution for damage tolerance.
Free Vibration Analysis of Kirchhoff Plates With Damaged Boundaries by the Chebyshev Collocation and Perturbation Methods
Authors: Sari Ma’en , Nazari Morad , Butcher Eric A.
Published: April 2011

In order to compare numerical and analytical results for the free vibration analysis of Kirchoff plates with both mixed and damaged boundaries, the Chebyshev collocation and perturbation methods are utilized in this paper, where the damaged boundaries are represented by distributed translational and torsional springs. In the Chebyshev collocation method, the convergence studies are performed to determine the sufficient number of the grid points used. In the analytical method, the small perturbation parameter is defined in terms of the damage parameter of the plate, and a sequence of recurrent linear boundary value problems is obtained which is further solved by the separation of variables technique. The results of the two methods are in good agreement for small values of the damage parameter as well as with the results in the literature for the undamaged case. This study can lead to an efficient technique for structural health monitoring (SHM).
Effective Reduction of Peak Frequency in Hydraulic Engine Mounts
Authors: Tikani Reza , Vahdati Nader , Ziaei-Rad Saeed
Published: April 2011

Hydraulic engine mounts are generally applied to the aerospace and the automotive applications for the purpose of cabin noise and vibration reduction. By careful selection of hydraulic mount design parameters, at a certain frequency, namely the notch frequency, the dynamic stiffness will be smaller than the static stiffness and cabin vibration and noise reduction is provided at that frequency. Literature review indicates that in all previous hydraulic engine mount designs, the dynamic stiffness increases after the notch frequency. This phenomenon is not desirable because of the increase in transmitted force to the air-frame. Here in this paper, a new hydraulic engine mount design is proposed that uses two working fluids. This new design has two notch frequencies and two peak frequencies. In this study, effective reduction of the peak frequencies has been demonstrated by using a controllable fluid as one of the mount’s working fluids and a non-controllable fluid as the 2nd working fluid. As a result, one can obtain a hydraulic engine mount design with only one notch frequency but no peak frequency. The new hydraulic engine mount design and its mathematical model are presented in details and some discussions on the simulation results are also included.