bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain gauge performance during fatigue testing
Authors: Middleton J. C.
Published: October 2008

Strain gauges are used extensively to measure the changes in magnitude and distribution of dynamic stresses during fatigue testing. Over 200 000 fatigue cycles at high strains (4000 ± 2000/u/m) have to be withstood under certain conditions such as when evaluating the performance of heavy vehicle springs. In this work, various types of commercial strain gauges have been evaluated to determine the most appropriate installation for severe applications.

The best results were obtained using a constantan metal foil element strain gauge with phenolic glass backing.

Tests on heavy vehicle, multi‐leaf, Taperlite springs, manufactured by Tinsley Bridge Limited (formerly BSC Light Products), have demonstrated the suitability of the chosen system and showed that the dynamic stresses remained essentially constant during fatigue testing.
Rapid data acquisition using a data logger interfaced to a microcomputer
Authors: Thomas D. P. ,   British Gas, Bromfield M. A. , Evans W. T.
Published: October 2008

A description of the interface protocol is given and a method outlined to enable one way communication between the units without the necessity of additional hardware.

The system can easily be adapted for processing data for other sensor types simply by modifying the computer software.
Simultaneous combination resonances in a parametrically excited cantilever beam
Authors: Cartmell M. P. , Roberts J. W.
Published: October 2008

The effects of parametric excitation of a simple structure are such that very large responses may be generated in a plane perpendicular to that of the excitation as a result of relatively small accelerations, provided that the frequency of the excitation is related to that of the excited mode or modes in a certain manner. It is shown that it is possible for two or more resonances to be excited simultaneously, and that an effect generated by a weaker type of coupling can in fact modify that of a stronger coupling to a significant extent. A vertically oriented, thin and flexible cantilever beam of rectangular uniform cross‐section with a lumped end inertia, is modelled both to first and second order of approximation, and theoretical and experimental results for the stability zoning of the resonances are presented. An additional model is proposed which examines the combined effect of two resonances for two tuning cases, and this is compared with measurements of vibratory responses and strain on an experimental system. It is thus shown that the theoretical model postulated for the simultaneous excitation of two resonances accurately predicts the observed behaviour of the laboratory system within a specific range of excitation accelerations.
A modern approach to principal stresses and strains
Authors: Milner P. R.
Published: October 2008

A simple formal method of evaluating principal stresses and directions using eigenvalues and eigenvectors of the stress matrix is presented. The method is equally applicable to 2–d and 3–d stress systems and does much to eliminate any risk of undetected errors in calculation or mistakes in assigning a principal stress to its corresponding direction. The method is extended to analysis of the 45d̀strain gauge rosette.
Contact stress distributions in a turbine disc dovetail type joint ‐ a comparison of photoelastic and finite element results
Authors: Kenny B. , Patterson E A , Said M. , Aradhya K S S
Published: October 2008

Two dimensional photoelastic frozen stress techniques were used to investigate the stress distributions of an axially loaded dovetail joint as is found in the design of some turbine blade‐disc fixings. The internal stress distributions were obtained by the shear difference method and were compared to results obtained by using the finite element method. It was found that steep principal stress gradients were present immediately below the contact surfaces in the zone adjacent to the fillet radius of the dovetail fixing, which could be an important consideration in the fatigue strength of the joint. The finite element model used gave the same trends of stress as the photoelastic model, predicted higher peak principal stresses and did not exhibit the same detailed variations of stress distribution.
A theoretical and photoelastic contact stress analysis relevant to orthopaedic knee prostheses
Authors: Whelan M. P. , Little E. G.
Published: October 2008

This study is based on a theoretical and photoelastic static contact stress analysis, relevant to the design of the plastic tibial plateau in an orthopaedic knee prosthesis. It involves the review of existing theoretical analyses concerned with the contact mechanics of layered elastic systems and, where possible, the validation of any relevant findings using two dimensional photoelasticity. Significant findings include the identification of a general minimum recommendable design thickness for the plastic tibial plateau, the endorsement of using the Hertzian contact theory to predict contact stress levels in the tibial plateau of certain knee implants and the slight improvement in contact conditions in the plastic when the plateau is perfectly bonded to its supporting metal tray.
The determination of principal stresses from photoelastic data
Authors: Haake S. J. , Patterson E. A.
Published: October 2008

Current developments in the automation of photoelastic analysis have enabled the fast and accurate collection of the isochromatic and isoclinic parametersl from photoelastic specimens. Since the isochromatic parameter yields the difference in the principal stresses then a suitable procedure has to be used for their separation. This paper provides a survey of the stress separation techniques available with a view to incorporating the most suitable method into an automated full field polariscope.
Photoelastic stress analysis of reinforced polycarbonate orthodontic brackets
Authors: Rushforth C.D.J. , Bearn D.R. , Aird J.C.
Published: October 2008

A photoelastic investigation of the stresses in polycarbonate orthodontic brackets reinforced with stainless steel inserts is reported. Three inserts with different profiles are investigated. They are ranked with respect to the stresses generated at the interfaces of the metallic inserts and the polycarbonate material. Comparison of insert designs is quantified.
A low cost calibration conditioner for dynamic strain gauge measurements
Authors: Iaconis Francesco M. , D'Emilia Giuilio
Published: October 2008

A conditioner for dynamic strain measurements that allows for a series of calibration signals with periodic and predefined time occurrence, during the whole period in which the measurements have to be carried out, is presented in this work. The calibration signals, having suitable size ratios between them, allow one to evaluate the linearity of the entire measurement chain.
Measuring simultaneously linear and angular acceleration during a crash
Authors: Bill Bernie
Published: October 2008

The new translational/angular accelerometer presented in this paper consists of a pair of identical preloaded quartz shear elements inside a metal housing. Integrated impedance converters transform the piezoelectric signals to low impedance voltages. The rugged sensor is mounted on the surface of the structure under test by fixing it with four screws. It allows the simultaneous measurement of translational and angular acceleration. Due to its construction, the small and light weight sensor is suited for shock application, e.g. during crashes. An example of linear and angular acceleration acting on a dummy head during a crash is presented.
Investigation of contact stresses of a rotating cam by a digital photoelastic method
Authors: Wang Ming‐Jong , Wang Wei‐Chung
Published: October 2008

The maximum contact shear stresses (MCSS) and their locations of a rotating cam during rise and at a specific rotation speed were sought by a self‐developed digital phototelastic system with added functions of syncronous trigger and continuous image taking. Also found were the MCSS of a camduring rise under static state. The difference between the dynamic and static states were compared and investigated.
Sealing Fuji Prescale pressure sensitive film for protection against fluid damage: the effect on its response
Authors: Liggins A.B. , Surry K. , Finlay J.B.
Published: October 2008

Fuji Prescale pressure sensitive film will record pressures as a characteristic pink stain; the optical density response of these stains can be calibrated to allow subsequent conversion into full field pressure data. Due to its ease of use, Fujifilm has been employed extensively within animal joints. For this application, the potential disruption to the stain producing mechanism posed by the presence of joint fluids has led to the widespread use of fluid proof materials, within which the Fujifilm is protected; however, little data have been presented on the effect of protective materials on the subsequent stain response. This paper presents a quantitative assessment of the mean optical density responses of both protected film and a control group of unprotected film; the first group consisted of Fujifilm sealed between two layers of a readily available self‐adhesive material, forming sealed packets. The results indicated significant differences between groups (p<0.05); however, the effect of these differences is dependent on the method used to produce pressure data. Qualitative observations indicated that sealing reduced stain uniformity; preliminary qualitative observations regarding data manipulation methods to overcome this phenomenon are presented. Consequently, this work indicates the importance of validating methods for protecting Fuji film from fluid damage and their associated methods of data manipulation.
Application of the shadow optical method to fatigue and crack closure studies
Authors: Hermann R. , Bull C.
Published: October 2008

In this paper it will be shown that crack closure and related crack shielding mechanisms can be studied successfully by applying the shadow optical method, also known as the method of caustics. It is shown that at least one mechanism ‐ plasticity induced crack closure ‐ can be identified and determined from measurements of the transverse diameter of the caustic in the crack tip region. For given fatigue conditions at which crack closure occurs, several experiments have been performed to investigate the effectiveness of the crack opening in a typical fatigue cycle.

Two different methods of closure determination have been used. A comparison is made between one of the most currently used methods of back face strain (BFS) compliance measurement and the shadow optical method (SOM). The underlying features of these two experimental techniques provide the key to finding the extent of the load in the fatigue cycles over which the crack is actually open. This redefines the value of Kmin and the meaning of ΔK. The driving force, ΔKeff is shown to be reduced in or near the fatigue threshold of the alloy, because crack closure is most effective in this part of fatigue loading. The introduction of SOM to fatigue crack closure provides a suitable alternative for finding the effective part of the stress intensity range between the minimum and maximum loads. Conclusions drawn from this work were that in addition to determining that part of the fatigue cycle over which the crack is actually open, the shadow optical method allowed an accurate interpretation of the entire fatigue cycle between Kmax and Kmin
A simple finite element for beams on elastic foundations
Authors: Wasti S. Tanvir , Senkaya Ender
Published: October 2008

A simple “routine” beam on elastic foundation finite element using a polynomial displacement function has been developed which yields acceptably accurate deflection, shear and bending moment values for prismatic or non‐prismatic beams of elastic material resting on foundations with varying or nonlinear subgrade reactions. Limited extension of the formulation to an “exact” finite element using the exact displacement function of a beam on elastic foundation has also been carried out. The subgrade is represented by a non‐homogeneous solid medium to include nonlinear parameters if required. The iterative solution is extended to cases where the beam may uplift because the foundation is a no tension material. The model is also suitable for calculating the elastic deflections, membrane. and bending stress resultants for axisymmetrically loaded variable thickness shells of revolution. A computer program called FEBEF [finite element: beam on elastic foundation] incorporating the routine finite element has been prepared for the solution of beams on elastic foundations and axi symmetrically loaded shells of revolution.
Determination of necking zone using laser speckle
Authors: Tay C.J. , Shang H.M. , Kang B.L.
Published: October 2008

This paper presents a whole field laser speckle method for the measurement of the necking zone on the surface of metallic specimens. The method employs an expanded laser beam to illuminate the test object. Diffracted images are recorded on a high resolution photographic film and subsequently filtered using point wise filtering. The intensity of the diffracted halo is measured with a photo‐sensor and the intensity distribution on the specimen yields information on the necking zone of the test object. The technique is applied to aflat tensile specimen with two circular notches at the central portion. Measured necking zone is compared with results obtained by other conventional methods.
Verification of the duplex gauge using variable strains and temperatures
Authors: Cappa P. , Sciuto S.A. , McConnell K. , Zachary L.
Published: October 2008

Four steel specimens were equipped with “duplex nances”, a recently proposed transducer based on two different electrical resistance strain gauges, capable of correcting the effects induced by temperature. The examined innovative transducer, in comparison with traditional strain measuring systems, has the advantage of utilising two strain gauge channels of the same type, which significantly simplifies automatic measuring systems. The specimens were subjected to temperature and strain field variations in the ranges of=30–150°Cand=100–700μm/m respectively The temperature and strain values obtained from the duplex gauges were compared with those measured by means of traditional methodology, i.e. a strain gauge and a thermocouple.
Local stiffening effect of ‘double deck1 bending strain gauges: part 2
Authors: Chen J.F. , She K.M. , Rotter J.M. , Ooi J.Y.
Published: October 2008

In stress measurement where it is difficult or impossible to access the inside surface of the structure, “double deck” (DD) or “sandwich” bending strain gauges can be used to measure both the membrane and bending strains. A DD gauge consists of a pair of constituent foil gauges which are bonded on the upper and lower surfaces of a plastic base or filling. It is mounted on the external surface of the test specimen to measure the external surface strain, and by extrapolation, the internal surface strain of the. specimen. The. sensitivity of the DD bending gauge increases when the separation between the pair of constituent foil gauges increases. However, this also increases the stiffness of the whole gauge. If the stiffness of the DD gauge is significant compared with that of the plate to which it is attached, the presence of the gauge may cause significant changes in local stiffness and result in errors of strain interpretation. This study is presented in two papers. Part I, appeared in the Feburary 1996 issue of Strain, presented an approximate analytical solution for the local stiffening effect of a DD gauge, and quantifies the errors in the strain measurement. Part 2 (this paper) presents the verification of the. solution using a three‐dimensional finite element calculation, a parametric study and a correction method that can be applied easily. The extrapolation errors due to the stiffening effect and random reading noises are also explored. The figure and equation numbers in this part are continuedfrom Part 1, but the reference numbering is specific to Part 2.
Curvature contours of flexed plates by a multiple illumination moiré shearing interferometer
Authors: Subramanian G. , Subramanian A.
Published: October 2008

A new moiré method is proposed to map partial slope, partial curvature and twist curvature contours of laterally loaded specularly reflecting plate models. Converging HeNe laser light is diffracted by a lens plane cross grating, different combinations of orders are selectively permitted through the Fourier transform plane and collimated to illuminate the plate model. This technique eliminates the difficulties involved in Fourier filtering in the imaging optics, thereby extending the reflection moiré’ interferomelry to general plate structures and loading. The slope contours are obtained still by double exposure.
Bending analysis of a finite beam on a reinforced halfplane
Authors: Chandrashekhara K. , Antony S. Joseph , Mondal Debashish
Published: October 2008

This paper deals with an experimental study, using the photoelastic method, on the bending analysis of a centrally loaded finite free‐free beam resting on a partly reinforced (horizontally) elastic halfplane. In the experimental study the interface between the beam and partly reinforced halfplane has been made both frictionless and fully bonded. An experimental‐numerical hybrid method, developed earlier by the authors has been used to determine the contact pressure distribution. The contact pressure distribution thus obtained has been compared with the results obtained using an analytical‐numerical procedure in which two different modellings have been used for the reinforced region viz., (i) equivalent orthotropic (composite approach); and (ii) layered system (discrete approach). Results of contact pressure distribution as well as bending stress distribution in the beam have been presented for several cases. The experimental procedure presented here is easy to apply to such complex practical problems and could be of interest to design engineers.
Case study of safe lowering of an in service gas pipeline
Authors: Khadakkar Anil G. , Sankar K. Ravi , Rathinam P. , Narayanan R. , Rao S. P. , Popli J. K.
Published: October 2008

This paper describes an experimental investigation carried out involving instrumentation, measurement and monitoring of stresses in a large diameter gas pipeline during its lowering operations. It also highlights the ingenious techniques developed and adopted to overcome the difficulties pertaining to long leadwires, measurement of existing strains on the curved surface of a pipeline and protection of strain gauge installations. These novel methods were used to ensure smooth and proper functioning of strain gauge instrumentation even under the severe field conditions at site for more than two weeks, till the lowering operations and pipeline monitoring was successfully completed.
Measurement of cheek/tooth forces during speech production
Authors: Cama G. , Cappa P. , Kaitsas V. , Mastrantonio F. , Scluto S.A.
Published: October 2008

This paper deals with the “in vivo” evaluation of the forces exerted by perioral muscles on dental arches and describes the relationship between these loads and the acoustic emission, during speech production. To carry out the research two miniaturised load cells were placed on the upper incisors' vestibular surface of 12 patients (6 male, 6 female age ranging from 19 to 25 years) to monitor the contact forces generated during the pronunciation of three phonemes containing labio‐dental sounds. The acoustic pressure was gathered by means of a capacitive microphone. From the obtained results it is shown that some values of the force applied during speaking are of significance in corrective orthodontics; in fact, the maxima of the recorded values were approximately 2.7N and 1.0N for female and male subjects, respectively. Also a tendency was observed for a logarithmic dependence between the loads exerted by perioral muscles on teeth and the acoustic pressure level due to the voice; in fact, the correlation coefficients R were, for some of the examined patients, >0.9, even if values of 0.4 also were observed.
Stress concentrations arising from a slot in a plate under biaxial stress
Authors: Rees D.W.A.
Published: October 2008

The stress distributions around a straight blunt slot under biaxial stress are found by adapting the classical solution to the stress concentration around an elliptical hole in an infinite plate under uniaxial stress. Firstly, the slot was converted into an equivalent thin ellipse of large major:minor axis ratio with its major equal to the length of the slot. The principle of superposition was then employed to find the stress state on an axis of symmetry at near and far locations from the notch tip. Stress states were found for any ratio of remotely applied stresses in directions perpendicular and parallel to the notch axis. The solutions were verified experimentally for specific tensile stress ratios by bonding strain gauges to an aluminium plate under hydraulic pressure.
Past, present and future in UK aerospace
Authors: Barrington Norman A.
Published: October 2008

The account which follows covers developments in the aircraft industry at Filton over the last forty to fifty years and future prospects.
A new approach to triaxial residual stress evaluation by the hole drilling method
Authors: Wern H.
Published: October 2008

A new analysis technique is introduced to resolve the triaxial residual stress profiles from measurements using the conventional strain gauges for the hole drilling or ring core method extended with a displacement transducer to measure the out of plane displacement. The new technique uses an inverse formulation with wavelets.
Determination of material constants in creep continuum damage constitutive equations
Authors: Hyde T.H. , Sun W. , Tang A.
Published: October 2008

Experimental creep and creep rupture data are presented for copper at 150, 200 and 250°C and for 0.5Cr0.5Mo0.25V steel at 640°C. Creep continuum damage constitutive equations have been shown to be capable of accurately representing the creep behaviour of both materials. A six variable optimisation program, which was developed to efficiently obtain the material constants, is described.
Theoretical design of calibration beams for strain gauge factor measuring apparatus
Authors: Zubin Deng
Published: October 2008

By starting with theoretical analysis and combining with the needs of practical applications, this article carries out a preliminary theoretical investigation of optimum design of the cross sectional shape and dimensions of calibration beams for strain gauge factor measuring apparatus. A new formula is derived in this paper that shows the quantitative relationship among strains on the beam surfaces, the strain non‐uniformity within a certain range of the beam and beam thickness, which provides a theoretical basis for the accuracy improvement of the measuring apparatus and for correct application of the calibration beams, and also for drawing up and improving items concerning with calibration beams in strain gauge standards internationally. It is proven through experiments that the neutral axis of the bent calibration beam of rectangular cross section under pure bending moments is actually not circular but parabolic.
Experimental analysis of surgically corrected knee joint
Authors: Bedzinski R. , Scigala K.
Published: October 2008

Holographic interferometry, speckle photography and photoelasticity have been employed in the experimental investigations of the knee joint in four conditions ‐ anatomically normal joint, varus joint, joint after Coventry popliteal osteotomy and joint after correction made using a new variety of the Coventry procedure1. The studies included the investigations of the displacements of the bone in the sagittal plane, the displacements of points on the bone's surface in the frontal plane and the three dimensional state of stress. The obtained results show to what degree changes in the lower limb geometry affect the knee joint and in particular, its stability, functionality and the way in which it carries loads.
Vibratory weld conditioning — the effect of rigid body motion vibration during welding
Authors: Munsi A.S.M.Y. , Waddell A.J. , Walker C.A.
Published: October 2008

Previous studies suggested that the state of residual stress in a weld may be modified by vibration during and after the welding process. In this study, the effect of rigid body motion vibration on welding residual stresses was investigated. The specimens were welded while they were being vibrated in a rigid body motion mode. The specimens were vibrated using two different frequencies (50 Hz and 500 Hz). At the lower frequency vibration (50 Hz), small changes in the residual stresses were found, with no particular trend. At the high frequency vibration, no significant reductions in the residual stresses were observed in the longitudinal stresses or in the transverse direction. Some initial results are presented also regarding flexural vibration effects.
Mechanical Properties of a Typical Stereolithography Resin
Authors: Dulieu‐Barton J.M. , Fulton M.C.
Published: October 2008

Abstract: The mechanical properties of a typical stereolithography resin are determined. The effect of environmental variations, post‐cure time and batch to batch variations on the properties is investigated and discussed in detail. The amount ofanisotropy in the cured material is evaluated for each batch of material and the implications discussed in the context of experimental stress analysis.
Distributed Measurement of Strain using Optical‐fibre Backscatter Polarimetry
Authors: Rogers A.J.
Published: October 2008

Abstract: Fully‐distributed optical‐fibre sensing (FDOFS) systems are developing rapidly and are offering significant advantages for measurement functions in a variety of structural applications, especially in the oil industry, the power supply industry, the aerospace industries and civil engineering construction.

Polarization techniques are well established in FDOFS, and in the analysis of polarization‐mode dispersion (PMD) for optical‐fibre telecommunications. However, a major problem has been that of determining, from one end of the fibre, the distribution of the full polarization properties of a monomode optical fibre, along its length, with some specific spatial resolution.

This paper will present a new technique for providing this full information, and thus for measuring the distribution of any parameter, external to the fibre, which can modify its polarization behaviour. As a result, for example, it becomes possible to measure simultaneously the distributions of temperature and of a strain field comprising, in the latter case, the longitudinal and the two transverse components of direct strain, plus the transverse shear strain.

The technique comprises an extension of polarization‐optical time domain reflectometry (POTDR) [16], and necessitates on‐line processing. Details of the physical principles, the algorithms and the polarimetry will be presented, together with results illustrating the measurement accuracies which can be achieved.
Application Issues Using Fibre Bragg Gratings as Strain Sensors in Fibre Composites
Authors: Wei C.Y. , James S.W. , Ye C.C. , Tatam R.P. , Irving P.E.
Published: October 2008

Abstract: Fibre Bragg grating sensors have been developed as a strain measurement technique. With regard to practical applications, there is growing knowledge and experience. However, many application issues remain unsolved. These issues include signal interpretation, confidence in measurement accuracy, calibration, and zero‐strain definition. This paper reports some issues which have been encountered in practical measurements and application trials. The investigation covers various aspects of strain measurement. The measurement accuracy in a composite laminate is found to be influenced by the formation of cracks in adjoined layers, interface between fibre sensor and host materials and nonuniform stress fields.
Local Finite Element and Experimental Limit Loads of Cracked Piping Elbows Under Opening Bending
Authors: Yahiaoui K. , Moreton D.N. , Moffat D.G.
Published: October 2008

Abstract: Finite element (FE) and experimental data of cracked, 88.9 mm outside diameter, 5.49 mm thick, short radius, carbon steel piping elbows under displacement controlled, opening bending are reported. Short and long defects with depth‐to‐thickness ratios ranging from shallow to through‐wall, axially or circumferentially centred about the bend crown centreline or intrados respectively, are considered.

The FE predicted general deformation mechanisms and overall strain distributions compare well with the experimental observations. Also, the strains agree well with the experimental values away from the defects. However, in the immediate vicinity of the defect, the FE strain data give much more detail about the initiation and spread of plasticity as the loading is increased towards plastic collapse of the component, but specific integration point strain data reveals that the variations are large and that steep strain gradients are evident even within individual elements. This explains the poor comparisons with experimental data in these regions. Using the above type of data, in conjunction with the twice‐elastic slope (TES) method for the determination of plastic loads for the cases investigated, it has been shown that values lower than those obtained from similar global measurements (load‐displacement plots) are consistently obtained.
Gas Turbine Propulsion Plant Control
Authors: Whalley R. , Ebrahimi M.
Published: October 2008

A model of a gas turbine variable pitch propeller propulsion system for a warship is considered. The system inputs, for control purposes, are demanded fuel flow and propeller pitch angle. The principal output which is to be regulated is the propulsion shaft speed while shaft torque changes are to be suitably confined. An optimum, multivariable, minimum control effort regulation strategy is proposed enabling improved transient and constrained output interaction to be achieved. Simple passive feedback elements are employed. System regulation at full and half power is investigated.
Watch Turnover Support for Future Surface Combatants
Authors: Springs John , Weaver Melissa
Published: October 2008

During watch turnover in the Combat Information Center, warfighters rely upon verbal communications, standardized procedures, and personal memory to build the situation awareness needed to perform their jobs. The design and implementation of the systems they use require operators to integrate information through procedures. A user interface prototype for an automated watch turnover support system has been developed at the Integrated Command Environment (ICE) Lab at the Naval Surface Warfare Center in Dahlgren, Virginia. This prototype demonstrates how information from multiple shipboard systems could be integrated to a single source of information, enabling a more efficient and effective watch turnover process. An iterative development process allowed the documentation of watchstander information requirements, a categorization of information, and definition of user interface requirements.
Statistical Methods for Planning Diesel Engine Overhauls in the U. S. Coast Guard
Authors: Milkie C. M. , Perakis A. N.
Published: October 2008

The United States Coast Guard has recently investigated new strategies to maintain cutter propulsion diesel engines. Reliability centered maintenance with statistical methods may allow the time between costly scheduled overhauls to be increased. One indicator of engine aging is the number of failures experienced with increasing operating hours. The purpose of this paper is to investigate the failure‐time relationship of the ALCO 251 marine diesel propulsion engine operated on Reliance class cutters. This analysis used exponential, Weibull, and three‐part composite Weibull failure density functions to model engine casualty data dating back to 1978. The data does not indicate the source of the engine failure, but every failure had a significant operational impact. Results indicate an increasing failure rate as the engine ages to the 24,000 hour overhaul time. The evidence indicates a constant failure useful life region, but the increasing failure rate from the Weibull models suggests that the periodic over‐hauls do not prevent wearout failures. As a result, the Coast Guard should consider refining diesel engine overhaul policy in order to prevent increasing age‐related failures.
Engineering the Total Ship: A System Perspective on Warships
Authors: Holden Richard
Published: October 2008

This paper describes warships as manmade systems. A discussion of systems in terms of their characteristics and behavior is given and used as a foundation for a perspective of a warship as an integrated whole and an element of the naval force. The symposium series titled “Engineering the Total Ship” is used as a source of technical material to describe warships, naval operations, and the Navy organization. A system perspective is provided that defines warships as an integrated whole made up of interacting parts. The relationship of the Navy organization to the characteristics of warships is discussed.
Instabilities of Nonreturn Valves in Low-Speed Air Systems
Authors: Potter Mark , Bacic Marko , Ligrani Phil , Plackett Matthew
Published: October 2008

Practical observations of the nonreturn valve wear in aero-engine cabin-bleed systems suggest that such valves are subject to unstable behavior. A theoretical model for the prediction of nonreturn valve instabilities in air systems is proposed and a nonlinear state-space model of the nonreturn valve and air volume interaction is derived from first principles. Experimental work is used to identify both the dynamic characteristics and the flow properties of the valve, which are used to identify the coefficients within the model. Through frequency analysis of valve oscillatory behavior, the levels of damping within the system are identified. Finally, using a local linearization of the state-space model an explicit mathematical prediction of valve stability is derived based on system parameters. These predictions are used to generate a map of the transition from stable to unstable system behavior for low-speed air flow, which is in excellent agreement with experimental data.
Robust Machine Tool Thermal Error Modeling Through Thermal Mode Concept
Authors: Zhu Jie , Ni Jun , Shih Albert J.
Published: October 2008

Thermal errors are among the most significant contributors to machine tool errors. Successful reduction in thermal errors has been realized through thermal error compensation techniques in the past few decades. The effectiveness of thermal error models directly determines the compensation results. Most of the current thermal error modeling methods are empirical and highly rely on the collected data under specific working conditions, neglecting the insight into the underlying mechanisms that result in thermal deformations. In this paper, an innovative temperature sensor placement scheme and thermal error modeling strategy are proposed based on the thermal mode concept. The modeling procedures for both position independent and position dependent thermal errors are illustrated through numerical simulation and experiments. Satisfactory results have been achieved in terms of model accuracy and robustness.
Experiments and Models of the Magneto Rheological Behavior of High Weight Percent Suspensions of Carbonyl Iron Particles in Silicone Oil
Authors: Ahmadkhanlou Farzad , Mahboob Monon , Bechtel Stephen , Washington Gregory
Published: October 2008

Flow properties of magnetorheological (MR) fluids are greatly altered by the application of a magnetic field. The design, optimization, and control of novel devices that exploit MR fluid behavior in multidegree of freedom applications require three dimensional models characterizing the coupling of magnetic behavior to mechanical behavior in MR fluids. The authors have derived 3D MR fluid models based on multiscale kinetic theory. The underlying bases of the models are summarized, with phenomenological empiricism distinguished from multiscale first principles, and the models’ ability to capture the experimentally measured mechanical response of a MR fluid-based damper to specified magnetic fields is assessed. The results of this comparison are that the kinetic theory-based models both relate macroscale MR fluid behavior to a first-principles description of magnetomechanical coupling at the microscale and possess the flexibility to best match the measured behavior of a particular MR fluid device observed in our experiments.
Prediction of Form Errors in Rings of Nonuniform Cross Section Due to Workholding and Machining Loads
Authors: Golden Christopher L. , Melkote Shreyes N.
Published: October 2008

This paper presents a method for the prediction of final peak-to-valley (PTV) surface profile variation for face turning of rings of nonuniform cross section. An analytical method relates initial part form, part deflection during workholding and machining, and part elastic recovery to final PTV surface profile variation. Finite element method is used to supplement the analytical model, and experiments are conducted to validate both the analytical and finite element approaches. The analytical and finite element results correspond well with the experimental observations, with average relative errors of 11.6% and 7.2%, respectively.
Experimental Study on the Amplitude of a Free Surface Fluctuation
Authors: Nam Ho-Yun , Choi Byoung-Hae , Kim Jong-Man , Kim Byung-Ho
Published: October 2008

An experimental study was performed to measure the fluctuation phenomena of a free surface in a vessel with or without an internal structure. A flow enters from the bottom and flows out of the side wall nozzles. Characteristics of the free surface fluctuation are investigated in terms of the geometry factors of the vessel and the flow rate. A modified Froude number is proposed to describe the amplitude of a free surface fluctuation. The fluctuation amplitude increases stably with an increase in the ratio of the vessel diameter to the water level in a vessel without an internal structure. When the ratio is greater than about 2, the fluctuation decreases suddenly with an increase in the ratio and it becomes unstable. The fluctuation amplitude is linearly proportional to the square of the Froude number. The amplitude of a free surface fluctuation increases with an increase in the height of an internal structure, but this increasing ratio is reduced when the height becomes higher. Two correlations were developed in terms of the Froude number and geometry factors to predict the amplitude of the free surface fluctuation in a vessel with or without an internal structure.
Piping System Noise Issues: Multiple Noise Sources
Authors: Karczub Denis G. , Catron Fred W. , DePenning Charles , Fagerlund Allen C.
Published: October 2008

Noise levels in power plants continue to be exceeded on occasion in spite of recent developments such as industry wide use of the International Electrotechnical Commission (IEC) control valve standard 534-8-3. There are several reasons for this related to the specific piping system under consideration. This paper presents flow test data showing the addition of sound powers and the resultant increase in noise due to multiple control valves discharging into a common manifold pipe.
Technology Growth and Cost Trends of Power Stations in India
Authors: Ray Arjun Sarathi
Published: October 2008

Although a developing nation, India has acquired a high level of competence in design and construction of power stations. This paper presents a post-occurence review of the growth of thermal power station technology in India and the trend of power station construction costs. The data presented in this paper were gathered during a survey of twenty power stations built during the last two and half decades of the 20th century in different parts of this country. The survey revealed that the rise in power project costs, which was comparatively steeper during the last two decades of the 20th century, has not been simply because of the rise in costs of basic materials of construction, labour charges or secondary costs like interest on institutional loans. The other, and equally important, reason is that there has been major changes in the design and construction during this time. The change was necessary for various reasons: to suit plans for gradual indigenisation of technology, to take care of the feedback from operating plants, to keep pace with latest concepts in plant design and to meet environmental requirements. Obviously, the consequent changes also caused increase in costs.
Characteristics of a Laminar Diffusion Flame in a Cross-Flow of Combustion Products
Authors: Simon M. A. , Baird B. D. , Gollahalli S. R.
Published: October 2008

This study was an investigation of the characteristics of a horizontal laminar diffusion flame established from a tubular burner in a buoyant vertical flow vitiated with combustion products created by a flat flame. The effects of varying flat flame equivalence ratio on these characteristics were studied. Applications of this study include exhaust gas recirculation (EGR), staged combustion in furnaces, and afterburners in jet engines. The fuel used for both the horizontal (cross-flow flame) and the flat flame in this study was propane. For a range of flat flame burner equivalence ratio (0.6 to 0.9), measurements of cross-flow flame length, and global emissions of NO were made. The mass flow rate of propane delivered to the cross-flow flame was held constant during these measurements. The flames were photographed with a digital camera. Profiles of combustion species concentrations and temperature were taken at 25% and 50% of the cross-flow flame length for flat flame burner equivalence ratios of 0.6 and 0.8, and for a non-combustion case (air flow only) in the flat flame. It was found that increasing the flat flame burner equivalence ratio caused an increase in the length of the cross-flow flame. The maximum temperature of the cross-flow flame decreased with increasing flat flame burner equivalence ratio. The introduction of the cross-flow flame increased the NO production in a flat flame with an equivalence ratio of 0.6, but did not significantly affect the NO production in a flat flame of an equivalence ratios of 0.7 or 0.8, and reduced it (by as much as 25%) in a flat flame of equivalence ratio of 0.9. This reduction of NO production and flame temperature and increase in flame length with increasing flat flame equivalence ratio was attributed to the reduction of oxygen available to the cross-flow flame. These results were supported with the in-flame combustion species concentration profiles.
In-Site Machining of Steam Turbine High-Pressure Casing-Case History
Authors: Mazur Zdzislaw , Herna´ndez Alejandro , Luna Alberto , Nieblas Enrique , Ferna´ndez Rafael
Published: October 2008

In-site machining of a high-pressure casing of a 75 MW steam turbine, which experienced severe deformation after a long period of service is fully described. The casing deformation was measured using an optical instrument (transit) which revealed a bottom casing concavity of about of 4.4 mm and top casing convexity about of 2.8 mm. This deformation caused rotor-stator rubbing, an increase in steam path radial clearances, turbine efficiency deterioration and maintenance problems. To restore the casing horizontal joint surface flatness in the top and bottom casing halves, a special portable milling machine tool was used, which was supported directly on the casing. Also due to its deformation, the casing central guide bores of the diaphragms carriers needed to be re-machined. This was made by using a special rotary arm supporting an electrical angle grinder which was centred individually for each guide bore. The casing restoration was made without any needs for welding. Due to the machining of the horizontal joint, the casing joint surface was displaced approximately 6 mm in the vertical direction without needing to change the turbine rotor axis position. After the re-machining, the casing was put back into service reaching the design operational conditions without any problems.
Microgrid Viability for Small-Scale Cooling, Heating, and Power
Authors: Ribarov Lubomir A. , Liscinsky David S.
Published: October 2008

Cooling, Heating, and Power (CHP) energy systems provide higher fuel efficiency than conventional systems, resulting in reduced emissions and other environmental benefits. Until recently the focus of CHP system development has been primarily on medium-scale commercial applications in a limited number of market segments where clear value propositions lead to short term payback. Small-scale integrated CHP systems that show promise of achieving economic viability through significant improvements in fuel utilization have received increased attention lately. In this paper the economic potential is quantified for small-scale (micro-grid) integrated CHP systems suitable for groups of buildings with aggregate electric loads in the 15 kW–120 kW range. Technologies are evaluated for community building groups (CBGs) consisting of aggregation of pure residential entities and combined residential and light commercial entities. Emphasis is on determination of the minimum load size (i.e. the smallest electric and thermal load for a given CBG that is supplied with electric, heating, cooling power from a CHP) for which a micro-grid CHP system is both technically and economically viable. In this paper, the operation of the CHP system is parallel with the public utility grid at all times, i.e. the grid is interconnected. Evaluations of CHP technology options using simulation studies in a “three-dimensional” space (CHP technology option, CBG load aggregation, and geographical location in the USA) were evaluated based on comparisons of net present value (NPV). The simulations indicated that as electric load increases, the viability of the CHP system (independent of the system’s size) becomes more favorable. Exceeding a system runtime (utilization) of 70% was shown to pass the break-even line in the NPV analysis. Finally, geographic location was found to have a relatively weak effect on the reported trends. These results suggest that micro grid CHP systems have the potential to be economically viable with relative independence of geographic location if adequately sized to match the load requirements.
An Integrated Cooling Water Intake System Enhancement Strategy
Authors: Jones Jeffrey M. , Mayer Bert
Published: October 2008

Cooling water intake problems come in many forms. These problems can include large schools of fish or jellyfish, seaweed, lake grass, sand, and silt buildup or carryover in the cooling water intake and screen house. Lower lake levels and higher average temperatures, zebra mussel infestation, and non-uniform flow rates between traveling water screen (TWS) bays and circulating water pump bays due to under-sized intake structures can also affect cooling water intake. Downstream of the cooling water intake, flow imbalances caused by entrained debris challenge heat exchanger designs and aging equipment. One Midwestern plant developed an integrated approach to improve the overall performance of the cooling water intake which will result in increased operating efficiency. For the subject plant, this paper will discuss specific modifications planned or undertaken and their benefits and limitations, flow modeling and design margin analyses completed and in process, anticipated reduction in debris carryover, impingement, and entrainment, and suggested further improvements. The majority of modifications undertaken or planned at the subject plant are generally intended to minimize debris carryover and to reduce problems associated with system blockages and heat exchanger tube fouling. Specific modifications to be discussed include: an acoustic fish deterrent system at the inlet tunnel entrance, replacement of the flow-through TWS’s with an industry first-of-a-kind design screen technology, screen wash, and debris transport and removal system modifications, service water system strainer basket modifications, service water system heat exchanger repairs and modifications, and installation of a sodium hypochlorite system.