bluuebunny/crossref_metadata_2025_split huggingface dataset:
The multi‐load method of determining discrete system parameters in a loaded three dimensional photoelastic model
Authors: Keshavan S.Y. 
Published: October 2008

AbstractThe determination of the secondary principal stress difference and their orientations for a discrete slice of thickness dz along a particular light path in a loaded three dimensional photoelastic model is discussed in this paper. It is well known that once the geometry of the loaded member and the geometry of loading on the member are fixed, the secondary principal stress directions at any particular point along any line of consideration remain constant. The secondary principal stress values will get multiplied by the factor through which the loading on the component is increased. This has been made use of in the present method and from the characteristic parameters obtained at the end of any light path for different loadings on the three dimensional model, the secondary principal stress difference and their orientations are obtained. The method proposed is a fully non‐destructive method of testing and involves measurements only on a transmission polariscope.
The laser strain gauge: micro machining of diffraction gratings using an Excimer laser
Authors: Wileman P. , Coupland J.M. , Creasey C.D. , Rowley D.M. , Halliwell N.A. 
Published: October 2008

AbstractThe laser strain gauge is a recently developed instrument for the single point measurement of surface strain to a resolution of 1 μm. It measures the deformation of a diffraction grating adhered to or etched into the surface of various substrates. In comparison with a conventional electrical resistance strain gauge the new gauge offers greater thermal stability and avoids the inconvenience of electrical connections. When gratings are etched directly into the surface of a component absolute strain measurements over its lifetime are possible.High frequency (1000 lines/mm) diffraction gratings can be etched into the surface of various substrates including carbon steels, polymers and ceramics using an Excimer laser. This paper describes the optical beam delivery system necessary for this application and demonstrates the feasibility of this exciting new technique.
An assessment of simple photoelastic models in aircraft design
Authors: Albiol R. 
Published: October 2008

AbstractPolyurethane sheet material has excellent properties for the manufacture of quick, cost effective design stress models. It is easy to model using very sharp instruments such as a scalpel with water lubrication. Because of its low stiffness, loading rigs can be constructed from engineering ply‐wood and other similar materials with the load being applied by means of dead weights or screw devices. The principle of the ‘self calibrating model’ developed by the ESA Group at Filton makes the results to be fully quantifiable. It is very rare that the opportunity arises in aircraft design and manufacture when the results of the simplified stress model can be validated against the behaviour of the real component. This paper reports on such an occasion when very good correlation was demonstrated. The correlation of the results, which was not known before, was established to be good. The conclusion is that the method for the type of problem analysed is cost effective and reliable.
Alternative calibration techniques for quantitative thermoelastic stress analysis
Authors: Dulieu‐Smith J.M. 
Published: October 2008

AbstractIn recent years thermoelastic stress analysis has been established as an important experimental technique. The SPATE (Stress Pattern Analysis by Thermal Emissions) system, marketed by Ometron Ltd., is the standard equipment for thermoelastic stress analysis. The signal obtained from the SPATE equipment is directly proportional to the sum of the principal stress on the surface of the structure under evaluation. For quantitative stress analysis accurate calibration constants must be obtained; these are dependent on the radiometric properties of the SPATE system detector and the material properties and condition of the surface in question. This paper describes a number of calibration techniques commonly in use. The factors which affect the accuracy of each technique are discussed in detail. An experimental calibration study of a “steel” is also included.
Automatic ordering of isochromatic fringes ‐ a new methodology
Authors: Ramesh K. , Kelkar Asish A. 
Published: October 2008

AbstractThe intensity variations in the isochromatic fringe field are significant and even minute variations can be recorded using the modern day CCD cameras. The sodium vapour source (589. 3 nm) used in general has upto 4% of another wavelength of 589. 6 nm. In view of this, the minimum intensity forming a fringe is affected and is significant at high density fringe zones. This aspect is used to identify sources and sinks in the fringe field and a new methodology for fringe ordering is proposed. It requires only one image to be processed and hence is equally applicable for static and dynamic problems.
Finite strain analysis by image processing: smoothing techniques
Authors: Amodio D. , Broggiato G.B. , Salvini P. 
Published: October 2008

AbstractThis paper is concerned with a methodology for measuring large strain fields based on digital image processing and numerical computations. The facility, already described in a previous paper by the authors, is based on a stereoscopic‐procedure, which returns the locations of a dot grid, previously etched on the surface of the work piece, in a three dimensional space. The markers are acquired by two CCD cameras from two different viewpoints. The data are then processed by a procedure based on shape function analysis. Tlie strain field is described by a plane Lagrangian referential co‐ordinate system, so that it is possible to take into account large displacements and finite rotations. Thus, the definition of a strain tensor on a 3‐D surface is widely discussed. The present paper faces the question of the noise propagation through the post‐processing algorithm. The method proposed is able to supply the confidence limits of the returned measurements.The strain analysis procedure was tested by a numerical input. A set of data were simulated, as returned by the acquisition system, for a specific strain problem. In this way the statistical parameters of the data can be easily controlled to explore a wide surrounding of cases. The complete post‐processing procedure was then applied to an experimental case concerning a high strain tensile test.
TV‐shearography for measuring 3D‐strains
Authors: Steinchen W. , Yang L.X. , Schuth M. 
Published: October 2008

AbstractThe shearographic interferometry is employed as a nondestructive full field, optical testing and measuring method without contact. Fringes of constant strain (so called isotase, tasis (Greek)=strain) can he observed in real time on the surface of the investigated machine parts and structures of any material and are represented by the shearogram. Using shearography two states of “deformation are recorded by doubly exposing a Holotesl film in an ordinary camera or stored by an electronic image processing system. In the lens of the camera a shearing element inside or outside the focus is integrated or the lateral Michelson shearing interferometer is used. Rigid body motions of the object are not recorded. Local deformation irregularities caused by a defect under or on the surface of the specimen create, strain concentrations; the homogeneous surrounding is poorly superimposed by an interference pattern. The shearogram shows dark and bright fringes which are the functions of the displacement derivative. The holographic interferometry measures the out of plane deformations directly. Terms of the out of plane strain can be determined by the shearographic method as well as the in plane strain fringes which are described in the following.
A technique for smoothing interior thermoelastic data and enhancing boundary information
Authors: Barone S. 
Published: October 2008

AbstractThis paper presents a technique by which it is possible to smooth thermoelastically measured interior information and to enhance edge data from non‐boundary measured values. The methodology is based on the compatibility equation and an iterative procedure. The technique has been successfully applied to correctly quantify the stress concentration around a hole in an araldite plate.
Contact stresses for a footing on an orthotropic elastic medium
Authors: Antony S.J. , Chandrashekhara K. 
Published: October 2008

AbstractThis paper deals with the contact stress analysis for a strip footing interacting with (i) a homogeneous orthotropic halfplane and (ii) multilayered orthotropic halfplane. The contact stresses have been obtained using a combined approach(finite element method‐analytical)in which the stiffness matrix for the footing has been obtained using the finite element method(F.E.M) while for the different cases of orthotropic medium(halfplane) considered here, suitable analytical solutions have been used. The halfplane needs to be discretised only along the contact length. Hence the solution can be obtained with a minimum input data and also the solution scheme is computationally efficient. Results have been presented for the contact stress distribution, displacement profile and bending stress distribution in the footing.
Factors affecting the intensity distribution in high stress gradient zones in digital photoelasticity
Authors: Mangal S. K. , Ramesh K. 
Published: October 2008

AbstractIn digital photoelastic analysis it is observed that in high stress gradient zones the fringes become brighter. It leads to erroneous results, if not accounted for, in those techniques which use quantitative values of intensity to evaluate the experimental parameters. In this note, the reasons for the above phenomenon is investigated and suitable recommendations are given.
Thermoelasticity for the analysis of crack tip stress fields — a review
Authors: Tomlinson R. A. , Olden E. J. 
Published: October 2008

AbstractA comprehensive review is given of methods to determine the stress intensity factor at crack tips using thermoelastic stress analysis. In order to obtain accurate results a number of areas of experimental procedure need to be considered and these are discussed in detail. The paper concludes with a discussion on the future potential of the use of thermoelasticity for the analysis of cracks.
The development of simultaneous thermo‐ and photo‐elasticity for principal stress analyses
Authors: Barone S. , Patterson E. A. 
Published: October 2008

AbstractA technique is developed for determining the individual principal stresses by measuring experimentally the sum and the difference of the principal stresses over a surface of an engineering component. This application, which results from previous research on the thermoelastic response of polycarbonate coatings typically used in reflection photoelasticity, is based upon the simultaneous use of thermoelastic stress analysis and automated photoelasticity. Full field patterns of the individual principal stresses can be evaluated, even over complex geometric surfaces, by properly processing the data obtained by the independent experimental techniques.
Design for prestressing tendons layout in stiffening walls via an experimental technique
Authors: Paloto J.C. , Ortega N.F. 
Published: October 2008

AbstractThe present paper describes the implementation of an experimental technique that allows one to optimise the efficiency of layout design for ropes, tendons, etc in prestressed structures. An application with a certain grade of complexity has been developed, i.e. a stiffening partition wall in hollow sections, with a central opening. This structural typology is normally used in bridges.
Study of Hull Angle Influence on SWATH Heave and Pitch Motions
Authors: Latorre R. , Vasconsellos J. 
Published: October 2008

ABSTRACTThe interest in Small Waterplane Twin Hull (SWATH) vessels has lead to the refinement in SWATH design. This paper examines the heave and pitch motion of a SWATH model with different side hull angles in head, quarter, and beam seas. The results show that maximum heave and pitch motions occur when the hulls are canted (angled) to 45° in head seas. Qualitative agreement was obtained with seakeeping calculations performed using Hooft's method. While the overall agreement is good, the comparison of the experiments and calculation results show the importance of viscous damping in the prediction of the maximum heave and pitch motion values.
Utilization of Root Cause Failure Analysis in the Investigation of Marine Deck Fitting Failures
Authors: Huff D. S. , Lynaugh K. M. 
Published: October 2008

ABSTRACTCracking was discovered in the openings of cargo deck tie down fittings on ships under construction. There was a distinct possibility that these cracks could propagate through the fittings and into the strength deck plating, affecting the ships hull integrity. With more than 14,000 fittings installed on each ship, the appearance of approximately 400 cracks at the mid‐ship area of the main and lower decks raised production and operational concerns. This paper will discuss the successful application of a Root Cause Failure Analysis (RCFA) methodology employed by a Corrective Action Team (CAT) established to solve the problem. Through their efforts and the systematic application of RCFA, various failure hypotheses were validated or discounted and consensus was achieved on the appropriate corrective action.
Survey of Reduced Workload and Crewing Strategies for Ocean Patrol Vessels
Authors: Baker C. , Krull R. , Snyder G. , Lincoln W. , Malone T. B. 
Published: October 2008

ABSTRACTThe U.S. Coast Guard is in the concept exploration phase of its Integrated Deepwater System (IDS) acquisition project. This project will define the next generation of surface, air and command, control, communications, computers, intelligence, surveillance, and reconnaissance (C4ISR) assets used to perform the Coast Guard's missions in the IDS environment (>50 NM off the U.S. coastline). As part of early technology investigations, the needs exist to: (1) analyze the workload requirements of the IDS, (2) identify alternative means to perform ship's work, and (3) optimize ship manning consistent with ship workload, performance criteria, and the available tools and equipment aboard. To reduce shipboard work requires an understanding of the mission and support requirements placed on the vessel and crew, how these requirements are currently met, and how requirements might otherwise be met to reduce workload and crew size. This study examined currently implemented workload and manpower reducing approaches of commercial maritime fleets, U.S. and foreign navies, and foreign coast guards. These approaches were analyzed according to evaluation criteria approved by the IDS acquisition project team. From this, strategies for shipboard work reduction that may be considered for adoption by the IDS were identified and analyzed according to performance and costs factors. Ten workload‐reducing strategies were identified: damage control, bridge, multiple crewing, engineering, risk acceptance, modularity, deck, enabling technologies, ship/personnel readiness, and operability and maintainability.
System Performance Modeling in C4ISR/Weapon System Design and Development
Authors: Froggett S. , Liu S. 
Published: October 2008

ABSTRACTThis paper describes an effective process for development of engineering models and discrete event simulations as part of the system engineering effort supporting Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance (C4ISR) and weapon system development. Application of modeling and simulation techniques throughout the system life cycle has been directed as an element of defense acquisition reform, and has been demonstrated to be effective in reducing cost and risk and improving system performance. Development of an executable model of the proposed system, which encompasses the functional architecture, process models, rules, and a data representation, allows the architect to ensure the design concept meets functional requirements. When this is carried a step further by developing a simulation of the architecture, or architectural components, it becomes possible to assess performance capabilities. A virtual model of the system can be executed to predict these characteristics and validate its likely fulfillment of operational requirements. This paper provides a step‐by‐step discussion of a process for developing system performance models and simulations, concluding with a synopsis of key areas for program manager attention.
Application of Guns in Naval Force Protection
Authors: Bradick Andrew 
Published: October 2008

ABSTRACTAny warship operating in a littoral environment is highly susceptible to attack from surface raider craft — the so called “Boghammer” threat. The NAVSEA close in gun system (CIGS) requirement stipulates a ten target scenario based on ONI analysis. The purpose of this paper is to discuss those sub‐elements of a gun‐based system that in combination will maximize performance by minimizing engagement time per threat. Modern gun and ammunition designs offer a new option for multipurpose self‐defense on all classes of combatant ships as well as an effective and economical solution to their inner layer defense requirements.The modern designs include: ▪ Medium caliber with high rates of fire, e.g.,1000 rounds per minute (RPM)▪ Extremely accurate fuse technologies combined with muzzle velocity measurement and correction calculations that permit densely delivered payloads.▪ Air bursting ammunition with high lethality from tailored sub‐projectile pay loads that is also impervious to ECM/decoys.▪ Extended engagement ranges from two to six km.A combination of all these features offers a lethality mechanism to defeat any threat by delivering a dense wall of steel between the ship and the threat target.Independently verified modeling has shown that these modern gun systems are able to engage ten targets with a maximum keepout‐range of 2600 m.
Structural Testing of Navy Vessels Using Bragg Gratings and a Prototype Digital Spatial Wavelength Domain Multiplexing (DSWDM) System
Authors: Baldwin Chris , Niemczuk John , Kiddy Jason , Chen Peter , Christiansen Martin , Chen Shiping 
Published: October 2008

ABSTRACTRepairing and maintaining the Fleet have been long‐standing problems for the Navy. In recent years, decreasing resources and Fleet assets have made repair and maintenance an even more difficult problem. In response to these pressures, Navy personnel have been seeking new methods to reduce overall maintenance costs. One such approach has been to instrument ships during operation with resistance strain gage technology in order to provide information for estimating the structural health of ship hulls. To date, a limited number of naval ships have been instrumented in this way, and have collected data to validate computer models that predict damage accumulation over the expected service life of the vessel (Adamchak 1984; Sikora 1983). The Navy is currently developing a new ship structural health monitoring system based on fiber optic technology. Application of this new health monitoring system to U.S. Navy vessels will improve maintenance programs by predicting need‐based maintenance schedules, thereby eliminating costly cyclic preventative maintenance schedules. This new system will also increase operational availability and ship survivability by providing ship operators real‐time information concerning the state of the ship structure. This paper describes the operational capabilities of this new system and recent test results on large‐scale naval structures including a U.S. Navy Landing Platform Dock 17 (LPD 17) ship propeller.
Reliability‐Based Load and Resistance Factor Design (LRFD) Guidelines for Unstiffened Panels of Ship Structures
Authors: Assakkaf Ibrahim A. , Ayyub Bilal M. , Hess Paul E. , Knight David E. 
Published: October 2008

ABSTRACTThe main objective of ship structural design is to ensure safety, functional, and performance requirements of the structural element for target reliability levels and for a specified time period. As this must be accomplished under conditions of uncertainty, probabilistic analyses are necessary in the development of such reliability‐based designs of unstiffened panels for ship structures. The load and resistance factor design (LRFD) format is developed in this paper for unstiffened panels. Partial safety factors are determined to account for the uncertainties in strength and load effects. In developing these factors, Monte Carlo simulation is used to assess the probabilistic characteristics of strength models by generating basic random variables that define the strength and substituting them in these models. The First‐Order Reliability Method (FORM) is used to determine the partial safety factors based on prescribed probabilistic characteristics of load effects. Also, strength factors are computed for a set of load factors to meet a target reliability level.
Reliability‐Based Design Guidelines for Fatigue of Ship Structures
Authors: Ayyub Bilal M. , Assakkaf Ibrahim A. , Kihl David P. , Siev Michael W. 
Published: October 2008

ABSTRACTMarine and offshore structures are subjected to fatigue loadings primarily due to the action of seawater waves and the sea environment in general. The load cycles in such an environment can be in the order of a million cycles per year. Fatigue failures in these structures can take place at sites of high stress concentration that can be classified by two major categories: baseplate and weldments. The former includes locations of high stress concentration such as openings, sharp re‐entry corners, and plate edges. In general, the mechanisms behind these failures are described by the general approaches to fatigue life prediction as discussed in this paper. There are two major approaches for predicting fatigue life: (1) the S‐N curve approach and (2) the fracture mechanics (FM) approach. The S‐N curve approach is based on experimental measurement of fatigue life in terms of cycles to failure for different loading levels and specimen geometries, while the fracture mechanics (FM) approach is based on the existence of an initial crack and subsequent crack propagation under cyclic load. The objective of this paper is to develop reliability‐based methods for determining the fatigue life of structural details associated with conventional displacement type surface monohull ships based on the S‐N approach and on the assumption that fatigue damage accumulation is a linear phenomenon (i.e., that follows Miner's rule). The methods are also based on structural reliability theory and can be applied either in direct reliability‐based design or in a load and resistance factor design (LRFD) format. The resulting design methods are referred to as the reliability‐based design approach for fatigue of marine structures. These design methods were developed according to the following requirements: (1) spectral analysis of wave induced loads, (2) use of conventional fatigue design codes, (3) nominal strength and load values, and (4) achieving target reliability levels. The first‐order reliability method (FORM) was used to perform reliability assessments and to develop the partial safety factors (PSFs) for fatigue limit state equations.