In-service Operation Research Articles

Modeling and Simulation in Support of System Level Design for High Acceleration Linear Motors

Software tools offer powerful support in the areas of engineering specification, design, implementation, and test. The tools are at their most potent when they actively promote agility and responsiveness throughout a product life cycle <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">and</i> leave a legacy of knowledge to inform future product development. Model-based design facilitates these benefits by considering a simulation of the system under development as an executable specification. This executable specification may be regarded as ldquoone truthrdquo across engineering teams with the simulation being abstracted or enhanced as appropriate. First-principle, data-driven, and physical modeling further strengthens model-based design, by allowing the agility and responsiveness afforded by model-based design to be relevant for both algorithmic <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">and</i> nonalgorithmic design considerations. Indeed, models are a powerful means to offer support for in-service operation, diagnostics of unintended operations and assessment and upgrades of control systems and/or system architectures during the entire life-cycle of a product. This paper will consider the benefits of physical modeling and model-based design through an example of a high acceleration linear motor. The motor type, power electronic-drive switching strategy, and power-electronic drive architecture will be considered. Finally, the use of parallel computing within the context of this application will be discussed, in particular as an effective means to generate results for a large number of operational scenarios in a time-effective manner.

Heat Transfer Prediction of In-Service Welding in a Forced Flow of Fluid

An algorithm for heat transfer prediction of in-service welding operations in a forced flow of fluid is presented. The algorithm presented is derived from Rosenthal’s 3D heat flow equation and boundary layer approximations. This was possible by the introduction of an apparent thermal conductivity kPL, which is a function of the boundary layer’s heat transfer coefficient αf and the base material’s thickness δ. This implies that a weld cooling time ΔtT1/T2 in a forced flow of fluid can now be calculated by an ordinary engineering calculator and thus enabling suitable welding parameters to be determined. The magnitude of kPL(αf,δ) was established by regression analysis of results from a parametric finite element analysis series of a total number of 112 numerical simulations. Furthermore, the result of the regression analysis was validated and verified by a welding experiment series accomplished on an in-house designed and constructed in-service welding rig. The principle design of the welding rig as well as its instrumentation, a PC based Data Acquisition system, is described. In addition, a method to measure the weld metals cooling time ΔtT1/T2 by means of thermocouple elements is described. Finally, the algorithm presented in this study proved feasible for industrial in-service welding operations of fine-grained Carbon and Carbon–Manganese steels with a maximum Carbon Equivalent (IIW) (CE) of 0.32.

Simulation of Very High Temperature Overheating During Isothermal Creep of Single Crystal Ni‐Base Superalloy

This paper presents an experimental set-up developed for the simulation of overheatings under load representative of One Engine Inoperative events which can be encountered during in-service operation of turboshaft engines. These experiments provide several breakthroughs over classical testing equipments for the non-isothermal testing conditions of single crystal Ni-based superalloys. It was shown a major effect of thermal transition rates on the material behavior which was explained by microstructural evolutions.

A physical probabilistic model to predict failure rates in buried PVC pipelines

For older water pipeline materials such as cast iron and asbestos cement, future pipe failure rates can be extrapolated from large volumes of existing historical failure data held by water utilities. However, for newer pipeline materials such as polyvinyl chloride (PVC), only limited failure data exists and confident forecasts of future pipe failures cannot be made from historical data alone. To solve this problem, this paper presents a physical probabilistic model, which has been developed to estimate failure rates in buried PVC pipelines as they age. The model assumes that under in-service operating conditions, crack initiation can occur from inherent defects located in the pipe wall. Linear elastic fracture mechanics theory is used to predict the time to brittle fracture for pipes with internal defects subjected to combined internal pressure and soil deflection loading together with through-wall residual stress. To include uncertainty in the failure process, inherent defect size is treated as a stochastic variable, and modelled with an appropriate probability distribution. Microscopic examination of fracture surfaces from field failures in Australian PVC pipes suggests that the 2-parameter Weibull distribution can be applied. Monte Carlo simulation is then used to estimate lifetime probability distributions for pipes with internal defects, subjected to typical operating conditions. As with inherent defect size, the 2-parameter Weibull distribution is shown to be appropriate to model uncertainty in predicted pipe lifetime. The Weibull hazard function for pipe lifetime is then used to estimate the expected failure rate (per pipe length/per year) as a function of pipe age. To validate the model, predicted failure rates are compared to aggregated failure data from 17 UK water utilities obtained from the United Kingdom Water Industry Research (UKWIR) National Mains Failure Database. In the absence of actual operating pressure data in the UKWIR database, typical values from Australian water utilities were assumed to apply. While the physical probabilistic failure model shows good agreement with data recorded by UK water utilities, actual operating pressures from the UK is required to complete the model validation.

Blistering of a terrazzo floor in a university campus building

This paper concerns the blistering of a terrazzo flooring system in a university campus building. The terrazzo began to blister only ten months after installation and became increasingly worse with time. A typical failure analysis sequence was applied to this nonmetallurgical problem in order to determine the cause of the blisters. It was determined that a vapor pressure differential caused moisture to travel up through the concrete slab subfloor and become trapped beneath the terrazzo, creating blisters. This differential in above-slab and below-slab vapor pressure was attributed to a lack of circulating conditioned air in the building at the time of terrazzo installation. Although acceptable moisture measurements of the concrete slab were taken prior to terrazzo installation, they were invalid due to this lack of circulating conditioned air. It was recommended that the entire terrazzo flooring system be removed and an additional curing time be employed to ensure the concrete slab is acceptable to receive a new terrazzo flooring system. It was emphasized that the above-slab air conditions must closely match in-service operating conditions in order to eliminate the vapor pressure differential.

Quantification and Prediction of Pilot Workload in the Helicopter/Ship Dynamic Interface

The evaluation, early in the design cycle, of the limits for operating aircraft from ships in a wide range of sea states and atmospheric conditions has become an important issue for two main reasons. First, the simultaneous entry into service of new helicopter types and new naval platforms has generated an enormous task in the development of appropriate Ship Helicopter Operating Limits for in-service operations. Second, it has become clear that such operational factors need to be addressed at the design stage - which of necessity involves developing a predictive capacity in all of the areas which influence operational capability. These considerations need to take place in the context of technological advances which seek to assist the pilot in operations from ships. Improved radar for ship approaches and enhanced cueing, located around hangars and landing spots, are both areas which are being continually developed in association with upgraded aircraft systems for guidance, control, and stability augmentation. Ultimately, however, the situation comes down to the pilot's assessment of the workload involved in any task and the handling qualities of the vehicle being controlled. For this reason there has been a growing interest in two related areas: (i) the development of metrics to provide a consistent indicator of pilot workload and (ii) the enhancement of existing pilot models to generate authentic control activity in the aircraft/ship dynamic interface. This article describes recent techniques for extracting workload metrics from control activity and indicates the extent to which acceptably accurate workload predictions can be made. Some advances in pilot modelling are also described and examples are given to demonstrate the capability and limitations of currently available methods. Finally, the present state of integration of the two aspects into a robust tool for ship and aircraft system design is discussed. The focus of this article is, of necessity, on helicopter operations because that is where most of the current work has been centred.

The Application Of Lean Principles To In-Service Support: A Comparison Between Construction And The Aerospace And Defense Sectors.

Lean principles have shaped the automotive sector’s success in reducing costs and improving performance. Other industry sectors such as aerospace and construction in the U.K. have pursued similar benefits by similar means with differing degrees of success. An acknowledged vein of research in the transaction cost economics and relational contracting fields, emphasises the importance of informal norms and formal, legal documents and doctrines in commercial relations. This research illustrates that written agreements are influenced by the parties’ past relations, each one’s perception of the other’s reputation, future business prospects, as well as influences from the external environment. This paper argues that a successful and thorough application of lean principles is predicated on establishing these relational contracting norms and formal contracts which, we argue, promote an environment for fully rendering lean principles. We present a comparison of the construction and aerospace and defense sectors which have attempted to follow the automotive lead and apply lean principles in somewhat different environments. Their experiences in aftermarket and in-service support operations provide preliminary evidence supporting the paper’s central hypothesis. In effect, the construction and aerospace and defense sectors have adopted different positions relating to the importance of contractual structures in the pursuit of business improvement and as a result, have had varying success in the implementation of ‘lean’ approaches.

NO and NO2Emission Ratios Measured from In-Use Commercial Aircraft during Taxi and Takeoff

In August 2001, the Aerodyne Mobile Laboratory simultaneously measured NO, NO2, and CO2 within 350 m of a taxiway and 550 m of a runway at John F. Kennedy Airport. The meteorological conditions were such that taxi and takeoff plumes from individual aircraft were clearly resolved against background levels. NO and NO2 concentrations were measured with 1 s time resolution using a dual tunable infrared laser differential absorption spectroscopy instrument, utilizing an astigmatic multipass Herriott cell. The CO2 measurements were also obtained at 1 s time resolution using a commercial non-dispersive infrared absorption instrument. Plumes were measured from over 30 individual planes, ranging from turbo props to jumbo jets. NOx emission indices were determined by examining the correlation between NOx (NO + NO2) and CO2 during the plume measurements. Several aircraft tail numbers were unambiguously identified, allowing those specific airframe/engine combinations to be determined. The resulting NOx emission indices from positively identified in-service operating airplanes are compared with the published International Civil Aviation Organization engine certification test database collected on new engines in certification test cells.

Scale levels for fatigue fracture mechanisms of in-service crack growth in longerons of helicopter rotor blades

Cases of in-service fatigue crack growth in aluminium longerons of helicopter Mi-8 rotor blades were reviewed. Fatigue fracture surface patterns for micro- and meso-scale levels of crack growth mechanisms for in-service fatigued longerons are discussed. Meso-beach-marks were used to estimate the fatigue crack growth period in one of the damaged longerons with the least crack size. Results of these estimations showed the effectiveness of the special device in in-service operation, which was used in longerons for in-service fatigue crack detection.

Slip Transfer across Hetero-Interfaces in two-phase Titanium Aluminum Intermetallics

AbstractThe role of slip transfer processes across the heterophase interfaces in two-phase TiAl intermetallics has been studied. Polysynthetically twinned crystals of TiAl (PST-TiAl) have been used as model systems for individual grains in technologically relevant polycrystalline lamellar TiAl alloys. Compressive plastic loads have been applied for orientations of the lamellar interfaces parallel and perpendicular to the loading directions to produce hard mode slip activity. Transmission electron microscopy has been used to determine the active deformation modes in the constituent phases and to study the slip transfer across heterophase interfaces. The results are discussed with respect to the mechanical behavior of PST-TiAl and lamellar TiAl alloys, which is of relevance to in-service performance and metallurgical processing operations.

Slip Transfer across Hetero-Interfaces in two-phase Titanium Aluminum Intermetallics

AbstractThe role of slip transfer processes across the heterophase interfaces in two-phase TiAl intermetallics has been studied. Polysynthetically twinned crystals of TiAl (PST-TiAl) have been used as model systems for individual grains in technologically relevant polycrystalline lamellar TiAl alloys. Compressive plastic loads have been applied for orientations of the lamellar interfaces parallel and perpendicular to the loading directions to produce hard mode slip activity. Transmission electron microscopy has been used to determine the active deformation modes in the constituent phases and to study the slip transfer across heterophase interfaces. The results are discussed with respect to the mechanical behavior of PST-TiAl and lamellar TiAl alloys, which is of relevance to in-service performance and metallurgical processing operations.

Application of Fiber-Optic Distributed Sensors to Health Monitoring for Full-Scale Composite Structures

The purpose of structural health monitoring (SHM) is to lead a structure to be safer at lower cost. SHM systems capable of assessing structural integrity during manufacture and in-service operation would allow timely maintenance actions to increase safety and lifetime of structures. In such systems, it is important to evaluate the actual state of a structure. Recently, fiber-optic sensors have been actively developed, and one can measure many kinds of the physical measurands by them. Since they also have excellent characteristic, such as immunity of electromagnetic interference, durability and capability to realize distributed sensing, they are supposed to be suitable sensors for SHM systems. We installed fiber-optic sensors into full-scale composite structures to monitor strain or temperature during manufacture or to monitor in-service structural performance, i.e., stiffness. The structures applied with the sensors are International America's Cup Class (IACC) yachts and a Japanese experimental reentry vehicle, namely, HOPE-X, that are made of carbon fiber reinforced plastic. The fiber-optic sensors used in this study are two kinds of distributed sensors using Brillouin scattering and Raman scattering, respectively. The former can measure strain or temperature and the latter can measure temperature at an arbitrary region along an optical fiber. We could successfully measure strain or temperature of the full-scale composite structures in field and access the structural state. The results of this study demonstrate the great potential of fiber-optic distributed sensors for practical applications to large composite structures.

High temperature environmental attack and mechanical degradation of coatings in gas turbine blades

This paper examines how in-service and thermal environmental attack influence the mechanical properties (22–950°C) of CoNiCrAlY coatings over René 80 substrates in gas turbine blades using a small punch (SP) testing technique in conjunction with scanning Auger microprobe analysis. SP tests have clearly demonstrated strong dependence of mechanical degradation of near surface coatings on the elevated temperature environmental condition. The room temperature (RT) ductility in blade coatings decreased with increasing operating time under combined fuels of kerosene and liquefied natural gas (LNG) despite softening in used coatings. All the coatings depicted lower ductility at 825°C in air than at RT but not in vacuum so that the oxidizing environment would produce deleterious effects. In-service operation under the combined fuels led to a two-fold increase in the ductile—brittle transition temperature (DBTT) over coatings observed under mainly LNG because of more extensive oxidation and grain boundary sulfidation. However, the DBTT of coating did not change during thermal ageing at 870°C in air that produced only oxidation. These findings imply that the grain boundary sulfidation would exert a stronger embrittling effect on the CoNiCiAlY coatings than the oxidation.

Creep Deformation of a Fully Lamellar Gamma Based Titanium Aluminide Alloy

ABSTRACTA complex two phase γ-TiAl alloy, Ti-47Al-lCr-1Mn-2Ta-0.2Si (at.%) in a fully lamellar condition, has been creep tested at a stress of 200MPa and a temperature of 700°C. This simulates the in-service operating conditions for several potential gas turbine aero engine applications where creep resistance is a design limiting material property. The results have indicate that reduction in lamellae thickness and avoidance of feathery type microstructures contribute to improved creep resistance.

Productivity measurement in service operations: a case study from the health‐care environment

Examines the issue of productivity measurement in service operations. Proposes a dynamic model for productivity measurement in service operations. This model is based on the idea that the intangible output for service operations is the quality of their services and the input is the level of skill of their employees. Both the skill level and the quality are measured on the same scale. Bases the measurement of service quality on the five dimensions suggested by Zeithaml and also bases the measurement of the skill level of employees on a six‐dimensional instrument which is developed here.

The influence of morphology and distribution of α phase on the properties of polycrystalline CuZnAl shape memory alloy: Liu, W.G., Zhu, M., Yang, D.S. and Wang, Z.G. Metall. Trans. A Oct. 1992 23A, (10), 2939–2941

The work reported in this paper describes a simulation of the manufacture, through-life operation and limiting defect size assessment of a pipework joint in a nuclear powerplant boiler. The objective of this work is to understand the critical factors that influence the integrity of the joint in-service and support accurate predictions of service life. This work differs from typical structural integrity assessments in that advanced modelling techniques have been used throughout the assessment process and include detailed simulations of the manufacturing process, a simulation of the entire in-service operating history including predictions of creep-fatigue damage and cracked body analysis to determine limiting defect sizes.Residual stresses resulting from the manufacturing process can be a key driver for creep and creep-fatigue damage. The calculation of creep-fatigue damage for assessment purposes is typically undertaken within the framework of an appropriate assessment code, such as EDF Energy's R5. The standard assessment approach usually requires calculation of stresses using elastic finite element analysis followed by hand calculations to calculate the damage.A combination of explicit and implicit finite element methods are employed to simulate a range of manufacturing processes which influence the in-service structural integrity of a branched pipework joint. Where available, test data have been compared to the results to assess the validity of the simulation. The simulation results then feed into a finite element based structural integrity assessment. The methods follow the principles outlined in the EDF Energy R5 assessment code but use the inelastic strains calculated directly from analysis. The methods are based around the general purpose finite element code Abaqus.The residual stresses generated during manufacture may adversely affect the critical defect sizes for the pipework joint. However, the complex geometry and loading complicate the assessment of the cracked body. Therefore, a finite element analysis representing the cracked body has been carried out on the pipework joint to evaluate the J-integrals at the locations of interest and hence calculate the critical defect sizes. The analysis considers the residual stresses determined from the finite element analysis of the manufacturing processes.

Expert Systems in Service Operations

Despite previous work on expert systems in the manufacturing sector very few articles relate to a classification scheme for the application of Expert Systems (ES) in the service operations area. Based on a review of more than 200 abstracts from the ABI/INFORM database, seeks to provide a categorization of ES in the service sector and also to detail future needs in the application of this vital information technology in service operations. Enhances the manager′s understanding of ES technology and provides a perspective on how ES have been used in service operations.

In-service health monitoring of composite structures : Proceedings of the 1990 SEM Spring Conference on Experimental Mechanics, Albuquerque, New Mexico (United States), 4–6 Jun. 1990. pp. 304–309. Society for Experimental Mechanics (1990)

The aerospace industry is witnessing a vast utilization of composites in critical structural applications and anticipates even more use of them in future aircraft. Therefore, a definite need exists for a composite health monitoring expert system to meet today's current needs and tomorrow's future demands. The primary goal for this conceptual health monitoring system is functional reliably for in-service operation in the environments of various composite structures. The underlying philosophy of this system is to utilize proven vibration techniques to assess the structural integrity of a fibrous composite. Statistical methods are used to determine if the variances in the measured data are acceptable for making a reliable decision on the health status of the composite. The flexible system allows for algorithms describing any composite fatigue or damage behavior characteristic to be provided as an input to the system. Alert thresholds and variances can also be provided as an input to this system and may be updated to allow for future changes/refinements in the composite's structural integrity behavior.

Structural Materials in Aerospace Applications

In the selection of materials for aerospace applications, consideration is given to factors, such as strength and weight, as well as to economics and energy requirements for both manufacture and in-service operation of the completed structure. The proper combination of all factors must be considered before new applications can be undertaken. Aerospace structural materials cover a wide range of both metal alloys and nonmetallics. Because coverage of all materials is not feasible, for the civil engineer who is probably not familiar with many of these materials, three major metal alloying systems—steel, aluminum, and titanium—are examined. Heat treatments, fabrication, product forms and applications are reviewed to give the reader a broad introduction to some materials that could satisfactorily meet future structural requirements.

Development of a Reduced Wall 138kV HPOF Pipe Type Cable and Joints for RE-Conductoring of Existing 69kV Lines on the Florida Power&amp;Light Company System

A 138kV pipe type cable with 348 mils (8.8mm) of paper insulation and two types of joints have been developed for re-conductoring existing 69kV HPOF pipe type cable circuits installed in 6-5/8 inch (168mm) pipes on the Florida Power & Light Company system. A cost saving of 60 percent or $11.7 million will be realized in the re-conductoring of 15.9 miles (25.6km) of circuit compared to installation of new 138kV cables in 8-5/8 inch (219mm) pipe. Laboratory test data on cable as manufactured and on cable returned after one year in-service operation at the Florida Power & Light test site validate the adequacy of the optimized design.