bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of extensometers with spherically pointed pin ends for accurate determination of material qualities
Authors: BERGQVIST B.
Published: October 2008

Highly accurate FFA 10 mm inductive extensometers with spherical tips are used for materials testing. The pin ends are ground conical and spherically pointed ends of 16tm radius are then honed. The specimen is indented with a slightly greater cone angle and with the same nose radius by a similar conical‐spherical taper shank. The extensometer is mounted in these indentations under a spring pressure that plasticises the spherical contact area and squeezes out unevennesses.

The shear modulus of steel was evaluated from four values of Young's modulus and four of Poisson's ratio in tension and compression, determined with such extensometers in 16 different tests under dead weights calibrated by the official standards institute. The four shear modulus values obtained have root mean square errors within ±0.5%.
Elimination of isochromatics in photoholoelasticity
Authors: HOVANESIAN J. Der
Published: October 2008

This paper shows how isochromatics can be eliminated in double exposure photoholoelasticity so that sharp unmodulated and doubled isopachics are obtained for the unambiguous determination of principal stress sums. A quartz rotator is used to rotate by 90° the polarization of the beam emerging from the model. The rotated beam is redirected again through the model in a reverse direction and finally impinges on the hologram plate. Analytical and experimental analysis shows that the reconstruction of a double exposure hologram by this method yields isopachics only.
Note on the effect of cross‐sensitivity in the determination of stress
Authors: VASUDEVAN M.
Published: October 2008

The concentric Mohr circles of modified apparent strain, true strain and stress permit quick visualisation and calculation of true strains and stresses from readings of gauges with known cross‐sensitivities.
Instrumentation techniques for strain measurements in concrete pressure vessels and similar structures
Authors: HORNBY I. W.
Published: October 2008

This paper describes instruments and techniques that have been employed by the Central Electricity Generating Board for short and long term strain measurements in prestressed concrete pressure vessels, and the methods adopted for data logging and subsequent data reduction. The measurements and tests on samples required to interpret the site readings are also described.
Piezo‐resistive semi‐conductor gauges
Authors: WALLACE R. H.
Published: October 2008

Though the piezo–resistive semi–conductor strain gauge has a very high gauge factor compared with wire or foil resistance strain gauges, some precautions ate necessary in its use if a reasonable degree of stability and accuracy are to be attained. The introduction of thermistors in the bridge circuit can compensate for errors caused by temperature changes.
A note on the arrangement of strain gauges and the sensitivity of strain measurement
Authors: HSU CHENG–TZU
Published: October 2008

A discussion for investigating the yield surface of metal is described. The paper also presents the discussions of the accuracy of strain measurements and the arrangement of three–element 45° strain gauges on a thin–walled tube under combined loadings.
Impacts on steel and graphite
Authors: McCalvey L. F.
Published: October 2008

Although it has been accepted for some time that the damage criterion for impact of falling objects is the velocity at impact, there has been little acceptance of the view that velocity at impact determines damage in radial impacts such as occur in charge/discharge of fuel elements or gas induced vibrations in pins in elements. Most A.G.R. tests to date have been based upon interpretation of results from accelerometers to establish acceleration or deceleration values at impact. It is suggested that this practice is misleading. Variation in material properties due to temperature changes affect the stresses set up by impact. This effect is considered in relation to graphite and stainless steel.
Dynamic response of a vertical cantilever structure in the natural wind
Authors: DUTT A. J.
Published: October 2008

The paper describes an investigation in which the dynamic response of a vertical cantilever structure exposed to the natural turbulent wind was observed. The structure consisted of a steel tube 2 743 m (9 ft) high on the top of which was mounted a closed drum 609 6 mm (2 ft) diameter by 609 6 mm (2 ft) high. The deflexions of the drum on two orthogonal axes were measured and also the strains near the lower end of the steel tube. Wind velocity was measured with a hot–wire anemometer and all the measurements were recorded on a high speed ultraviolet recording galvanometer. The results are considered in two parts: (a) the response transverse to the wind direction (b) the response in the direction of the wind. The transverse displacements are accounted for by vortex shedding and the longitudinal displacements can be calculated from the wind velocity trace, given the requisite structural parameters. Many engineering structures can be considered as structures of one degree of freedom and it appears that the behaviour of all such structures can be predicted by the method used in this investigation.
The measurement of thermal strain using self–temperature compensated strain gauges
Authors: BARROWMAN E. M.
Published: October 2008

The effect of a temperature change on a strain gauge installation may be to produce strain readings of a magnitude greater than the mechanical strain being recorded. This paper discusses some of the difficulties encountered in the measurement of strain. In particular, the selection of the most suitable type of self–temperature compensated strain gauge for a particular specimen and its associated wiring technique are considered.
A critical evaluation of the centre hole technique for the measurement of residual stresses
Authors: BEANEY E. M. , PROCTER E.
Published: October 2008

The principle of the centre hole technique for determination of residual stresses and its practical application are described. The sources of error are discussed individually and a clear statement is given of the maximum possible errors in uniform stress fields when applying the recommended methods. Results from calibration exercises are shown. It is concluded that the technique has good reliability and, subject to the choice of method for hole forming, will have an accuracy better than 10%. Further investigations are to be made at Berkeley Nuclear Laboratories into the methods of hole forming and the performance of the technique in stress gradients is to be studied.
Linear strain–displacement interpretation of thin shells of revolution
Authors: DELPAK R. , PREECE B. W.
Published: October 2008

The general strain–displacement equations of Novozhilov have been simplified for the particular case of a shell of revolution. The simplified equations. with one exception, agree with those obtained by Klein. Each of the expressions has been investigated in an effort to attach physical significance to every term.

The equations have finally been transformed from a local co–ordinate system to a global system. This latter form is ideally suited to numerical procedures.
The acquisition and processing of torque–twist data in torsion testing with overstrain
Authors: SWIFT W. A. C.
Published: October 2008

A description is given of tests carried out on torsion bars and tubes of spring steel subjected to various degrees of overstraining. The results of the tests on tubes involving loading into the plastic region, unloading and reverse–loading, again into the plastic region, were combined for a number of spring steels in order to produce Bauschinger Charts. To make them more convenient for use in the prediction of the residual stress distribution in overstrained bars, the charts were then subjected to a ‘standardising’ process by constructing lines at equal increments of strain.

In order to obtain torque–twist data, an autographic recording rig operating over a known gauge length, was designed and manufactured. This rig could be converted to a trace reader so as to digitise the torque–twist data.
A computer program for calculating post–yield stresses from strains measured on strain hardening materials
Authors: MORETON D. N. , MOFFAT D. G.
Published: October 2008

Details are presented of a computer program developed to calculate the biaxial post–yield stress history from strain gauge readings on components made of strain hardening materials, without knowledge of the material's post–yield stress/strain behaviour. The accuracy of the program is illustrated by using it to predict the stresses in a tensile test on stain/ess steel.
Correcting for the effects of temperature on strain gauges —‐use of computer–logger on Milford Haven Bridge project
Authors: CULLINGTON D. W. , HOAR M. C. P.
Published: October 2008

The effects of temperature changes on strain gauge readings depend partly on the characteristics of the gauge and measuring equipment, and partly on the thermal properties of the structure being tested. The effect on the gauge can be numerically corrected, or compensated for by experimental techniques, and if required, the effect of temperature changes on the structure can be reduced by careful selection of the time of reading. Correction of Demec, vibrating wire and electrical resistance strain gauge outputs is discussed.

Experience with a computer controlled data logger used to correct for thermal effects on a 1/4‐bridge electrical resistance strain gauge installation is described. The use of this system on the Milford Haven Bridge is estimated to have reduced potential temperature errors from between ±100 to 200 μstrain to about ±20 to 30 μstrain.
On the asymptotic character of the stresses near notches in plane problems
Authors: THOMPSON J. C.
Published: October 2008

Analytical expressions are derived by the conformal mapping techniques of Muskhelishvili for the asymptotic character of the stress fields at the root of notches, re‐entrant corners, etc. in plane bodies. It is shown that the stress field can be expressed as the product of a rapidly varying term, which depends only on the known geometry, and a slowly varying term which is associated with the nominal stresses. Using the derived expressions, together with a few stress, strain, or photoe/astic measurements at arbitrary points within the notch region, the entire stress field around the notch can be predicted. This includes the location and magnitude of maximum stress. The suggested technique is applied to a notch with parabolic shape and is shown to yield highly accurate results.
Measurements of internal strains by nine‐gauge devices
Authors: BABUT R. , BRANDT A. M.
Published: October 2008

An assembly of nine vibrating‐wire strain gauges designed for the measurement of internal strain is described. Tests have been carried out on concrete specimens containing nine‐gauge devices of different size and stiffness. The processing of the gauge readings is outlined and the results of the test series are critically discussed.
A strain gauging technique for monitoring fracture mechanics specimens during environmental testing
Authors: DEANS W. F. , JOLLY C. B. , POYNTON W. A. , WATSON W.
Published: October 2008

A strain gauging technique has been developed for monitoring fracture mechanics specimens during environmental testing. It provides a means of determining and monitoring the specimen load, and detecting crack initiation. It is more sensitive than conventional monitoring methods and also much cheaper, especially for multiple testing.
Diametrical compression of rings
Authors: Rosenfield A. R.
Published: October 2008

Strains generated during large plastic deformation of diametrically‐compressed rings were measured using surface grid distortions. For rings sufficiently thick in the axial direction, the deformation pattern approximates plane strain bending. A strain/displacement relation is suggested and applications to the study of workability illustrated.
Separation of principal stresses in photoelasticity by means of a computer
Authors: KUSKE ALBRECHT
Published: October 2008

It is shown that a separation of principal stresses with different types of experiments using computers is more valid and economical for methods based on the condition of compatibility than for those based on the conditions of equilibrium. This means that first the sum of the principal stresses is determined which combined with their differences gives their values separately. In this method several equations are used of the finite difference type and all can be solved by means of an iteration procedure in computer program form.
Stress distribution around holes in wedges
Authors: SARNA Dr S. P. , ALI Dr S. M. J.
Published: October 2008

This paper deals with the study of stress distribution around holes in wedges. Ling and Hsu have reported a theoretical analysis for an infinite wedge of uniform thickness and variable depth (with a circular hole), using stress functions. In the present investigation, a large number of electrical resistance strain gauges of small gauge length (3 mm) were used for obtaining the distribution of stresses in a cantilevered wedge of uniform thickness and variable depth, with a circular hole subjected to end loading. The wedge was made of perspex. The results obtained indicate a maximum stress concentration factor of 1.7 using Timoshenko's method of calculating the nominal stress in the wedge at the hole boundary (using his theory of calculating stresses in a wedge without a hole). The experiments on the cantilevered wedge indicate a lower stress‐concentration factor compared with the results obtained theoretically by Ling and Hsu for an infinite wedge. In addition to vertical loading, stress distribution with a load inclined to the vertical was also obtained.
A semidestructive method for three dimensional photoelasticity
Authors: SRINATH L. S. , KESHAVAN S. Y.
Published: October 2008

Using the principle of optical equivalence and the experimentally determined characteristic parameters, it is possible to determine the variations of the secondary principal stresses and their directions across the thickness of a slice taken from a three dimensional photoelastic model. With these data, the shear difference method can be applied without cutting the slice into a subslice. This technique is applied to determine the stresses along a general line in a cone subjected to a compressive load at the apex. In practice, a fairly thick slice can be taken for analysis.
Transverse vibration of a cylindrical shell with torispherical head: model tests and stress analysis
Authors: BARRON R. , VILLAIMUEVA C.
Published: October 2008

As an aid in the design of vessels or containers in a process undergoing dynamic loading, the dynamic characteristics of a cylindrical scale model vessel have been investigated by the method of resonance testing. The scale model is 1/10th scale of a vessel in a process, comprising a cylinder and torispherical head of steel.

The dynamic characteristics of the scale model vessel and the normalised principal bending stresses are calculated and tabulated for a number of circumferential modes of vibration, for an empty vessel.

Practical problems associated with the method of vibration testing are discussed and a practical example shown of the use of the method of dynamic similarity and the scale model results, as an aid in the design of a full scale vessel.
Determination of thermal stress in concrete pavements by means of measurement of in‐situ strains
Authors: HSIANG‐TE TU
Published: October 2008

A new method of determining the thermal stress of concrete pavement in‐situ has been developed and applied to engineering practice with success. It consists of three parts:

1. A system of theorems was established on the basis of mathematical modelisation that both temperature and thermal strain were sine functions of t, the time of observation, owing to the daily fluctuations of temperature and consequently the corresponding thermal strain. It was found that there exist a time phase and an angle of axes rotation between temperature and thermal strain.

2. A bridge circuit with a strain block and specially designed equipment ‘free body’ was introduced. The strain transducer for every test point consists of one strain gauge in the strain block and one in the ‘free body’, the former is used as the active gauge in the bridge circuit and the latter as the dummy. A temperature probe of resistance type was inserted nearby each of the gauges. Arrangement of observations and procedure of the data treatment were stated.
Assessing the deterioration of plain and fibrous concrete subjected to flexural fatigue
Authors: BUTLER J. E. , KEATING J.
Published: October 2008

A flexural cyclic loading machine has been developed for an investigation into the fatigue characteristics of concrete containing small proportions of small steel fibres. Deterioration of large concrete beams caused by cracking was monitored by observation of changes in central deflection, variation of strain across the beam depth, midspan, electrodynamic modulus and ultrasonic pulse velocity. Typical results derived from ultimate load tests whose duration ranged from 0 02 seconds to several minutes and long term fatigue tests have been provided.
The prediction and measurement of axial forces, bending moments and accelerations in an engine connecting rod
Authors: Tilbury R. J.
Published: October 2008

The graphs, numbered 1–5 reproduced below, were omitted from the above paper. Any inconvenience to the readers is regretted.

The author wishes also to acknowledge with grateful thanks the assistance given to him by, the Department of Mechanical Engineering, Lanchester College of Technology, Coventry, where the work was carried out.
On the use of hardness tests to estimate the extent of plastic deformation
Authors: Steel J. M. , Spence J.
Published: October 2008

The standard hardness test result is dependent to some extent on the surface condition of the material being assessed. In particular, since the measurement involves permanent deformation of the surface the state of stress or strain in the material will influence the result. Consequently the hardness test may be used as an indicator of prior plastic deformation. The present investigation was concerned with the phenomenon of buckle propagation in undersea pipelines and a theoretical model of the collapse process was developed. The model predicted the extent of the developing plastic zones around the cross‐section of the collapsing pipe. Hardness measurements on the cross‐sections of collapsed pipe have been used to estimate the extent of the plastic zones and comparisons with the theoretical analysis are given.
Some proposals for the application of liquid crystals to photoelastic instrumentation
Authors: HEARN E. J. , GORMAN B.
Published: October 2008

Liquid crystal displays (L.C.D.'s) are well known for their application to electronic watches, calculators, games and digital thermometers, the technology involved being derived from electro‐optic effects observed in liquid crystals since about 1968. This paper describes proposals for a totally different application of one particular class of liquid crystal, as an optical element in a photoelastic transmission or reflective polariscope.

The proposals are currently under development* and considerable work remains before this particular application of liquid crystals is perfected. Early results are promising and if successful they could well produce a revolution in the design of optical equipment with particular attraction to automatic systems incorporating microcomputer control.
Forced vibration of a beam system with autoparametric coupling effects
Authors: Roberts J. W. , Cartmell M. P.
Published: October 2008

Small non‐linear interactions of the type referred to as autoparametric may have a considerable effect on the pattern of forced vibration response of certain categories of structures exhibiting low damping characteristics. Under conditions of internal resonance these may bring about a complete neutralisation of the normal forced vibration resonance curve with a transfer of energy to an indirectly excited mode. The paper examines non‐linear interactions between a pair of beam modes in forced vibration of a simple structure. Steady state solutions are obtained for the non‐linear system equations. Measurements of vibratory acceleration and strain on a laboratory model are shown to give good confirmation of the analytical results and show clearly the substantial effects of internal resonance.
The use of vibrating wire strain gauges for long term measurements on buried gas mains
Authors: Osborne G.
Published: October 2008

A trial agreement concerned with the effect of adjacent deep excavations on the risk of failure of buried cast iron gas and water mains was implemented by British Gas and National Water Council on 1 January 1983. To complement this agreement, field experiments are being carried out at selected sites throughout the UK. The British Gas Engineering Research Station (ERS) is working in cooperation with the Water Research Centre to install instrumentation to measure pipe strains, joint movement, ground temperature and ground movement.

Field measurements impose environmental and operating conditions of much greater severity than those encountered in a laboratory. This note outlines the site techniques developed by ERS which allow reasonably quick and reliable installation of equipment capable of withstanding the adverse conditions typical of backfilled trenches. The principle of operation of the VW gauge, its method of fixing, the factors affecting its output and the interpretation of the readings themselves are described.
Relative assessment of full field experimental stress analysis techniques
Authors: Harwood N.
Published: October 2008

There is an array of full field experimental stress analysis techniques available to aid the designer or the engineer investigating service failures. This note reviews currently available methods (i.e. photoelasticity, moiré, laser holography, brittle lacquer and SPATE) and assesses their relative merits in practical applications.
Photographic evaluation techniques in photoelasticity—Part 2
Authors: Meyer M. L. , Mehrotra L.
Published: October 2008

In Part 1, boundaries between black and white on high contrast photographs (e.g. Fig. 10) and lines on Agfacontour photographs (e.g. Fig. 15) have both been called E‐lines. On any given photograph of isochromatics, each E‐line denotes a specific fractional fringe order N = Ni|δN|, with integer orders Nit and all E‐lines have the same fractional order modulus. |δN| (0 ≤ |δN| ≤ 1/2). Exposure or processing changes lead to photographs with different E‐lines and |δN| values.

Part 2 treats evaluation and calibration of isochromatic E‐lines, gives examples and notes on illustrations of Part 1, discusses applications to isoclinics, and summarises some main features.
Random errors caused by temperature in magnitude of principal strains evaluated ith 3‐element strain gauge rosettes
Authors: Cappa P.
Published: October 2008

The effects of the uncertainties associated ith the apparent strain and gauge factor data, given by the manufacturer, in the evaluation of principal strains are examined. Principal strains are obtained by a reduction of the strains measured ith electrical resistance strain gauge rectangular or delta rosettes. The theoretical analysis points out the relevance of the effects caused.
Moiré interferometry for shear strain measurement
Authors: Asundi A.
Published: October 2008

Moiré interferometry maps the in plane displacement components with very high sensitivity. However, in most applications only normal strain components are derived from these contour maps. With the advent of composite materials and adhesive bonded joints measurement of shear strain is becoming increasingly important. This paper looks at measurement errors likely to occur in shear strain derivation.
Design optimisation for weight, stress and cost on Airbus using epoxy resin models
Authors: O'Brien E W
Published: October 2008

Scale modelling is used to perform experimental stress analysis on aircraft components in order to iteratively reduce stress peaks and remove material in low stress areas. The scaling technique used is to model the components in CT200 epoxy resin and analyse them using reflective photoelastic coatings. This technique leads to structurally efficient or optimised components early in the design programme. Costs are reduced by obviating stress problems which would normally only be found much later during the fatigue testing of the real component, by that time of course expensive tooling will have been made and forgings produced. It is also sometimes possible that a less expensive manufacturing technique may be employed as a result of the high confidence stress data produced. Loading rigs etc. are also much lighter and cheaper than the equivalent for testing the metal components.
The use of photoelastic coatings to investigate the pelvic strain variations resulting from the introduction of cementless metal backed acetabular cups
Authors: Slemon D , O'Donnell P , Little E
Published: October 2008

An in vitro photoelastic coating study was initiated to investigate the influence of metal backed cementless acetabular cups on pelvic strain conditions in the immediately post operative state, for comparison with those related to normal hip joint conditions. A single dried bone hemipelvis was loaded to simulate the pelvic orientation at both the 47% stance and single leg stance. The problems associated with use of the photoelastic coating technique are discussed, particularly in relation to the analysis of the anisotropic pelvic bone. A number of critical areas were highlighted on the pelvis where high shearing strains occurred after the introduction of cementless metal backed acetabular cups.
A study on the induced drilling stresses in the centre hole method of residual stress measurement
Authors: Weng C. C. , Lin Y.C. , Chou C.P.
Published: October 2008

This paper aims at the improvement of the accuracy of the centre hole method of residual stress measurement by reducing the error caused by the drilling itself. Based on the results of an intensive experimental investigation, a new approach is proposed for the determination of the induced drilling stresses caused by the mechanical drilling process. In this study, the electric discharge machining (EDM) technique was utilised to obtain a stress free sample from the bulk material. As compared to the annealing heat treatment method for obtaining a stress free sample, it was found that the EDM technique does not cause the changes of the structures and machining properties of the parent material. Thus, the induced drilling stresses in centre hole method can be evaluated more accurately by using a stress free sample obtained by EDM technique than by using an annealed one.
The dispersion of birefringence in photoelastic materials
Authors: Haake S. J. , Patterson E. A.
Published: October 2008

A spectral analyser was used to determine the variation with wavelength known as the dispersion of birefringence of the fringe constant f and the stress optic coefficient C for photoelastic materials. A disc was loaded diametrically and was subjected to the stress freezing thermal cycle. The intensity was measured along the diameter perpendicular to the load for wavelengths between 450 and 850 nm at 5 nm intervals. Using the theoretical solution to the stresses it was possible to calculate the stress optic coefficient for all wavelengths employed. A similar technique was used for an identical disc that was loaded at room temperature.

It was found that the fringe constant was extremely linear with wavelength for both types of loading and for the materials CT200, CT1200 and MY750. The stress optic coefficient did not change much between sheets of the same material but was markedly different between materials. The dispersion of birefringence was found to be approximately constant but showed evidence of anomalous dispersion.
Use of displacement data to calculate strain gauge response in non‐uniform strain fields
Authors: Schajer Gary S.
Published: October 2008

A simple and effective method is described for calculating the strain indicated by a practical strain gauge mounted in a nonuniform strain field. The method uses integration or summation of the displacement field along the perimeter of the strain gauge area. This procedure gives results which are equivalent to those obtained by much lengthier calculations involving double integration of the strain field within the strain gauge area. The displacement summation method can easily take into account significant strain gauge design details such as number, length, width and spacing of the grid lines. The method also demonstrates that a strain gauge can be used as a displacement sensor as well as a strain sensor.
Plastic strain determination using peak speckle pattern intensity
Authors: Tay C.J. , Shang H.M. , Xu C.L.
Published: October 2008

This paper presents an integrated peak spectral intensity method for the measurement of plastic deformation in metallic materials. The method employs a laser speckle technique and a computer based image processing system. Test results on aluminium, brass and copper sheets subjected to bi‐axial stretching using the hydroforming process shows a correlation between the integrated peak spectral intensity coefficient Hi and the equivalent strain. In addition, the use of the parameter Hi requires less computation and enables measurement of plastic strains of up to 30%.
The behaviour of pressurised plain pipework subjected to simulated seismic loading
Authors: Moreton D.N. , Yahiaoui K. , Moffat D.G. , Machin H.C. , Amesbury L.A.
Published: October 2008

A series of simulated seismic tests have been conducted using mild steel and stainless steel plain pipe specimens. These specimens were pressurised and subjected to fully reversed cyclic bending moments at frequencies of about 5 Hz. The bending moments and surface strains on the pipe wall were monitored and are reported here. Significant ratchetting was observed which, in the case of the mild steel specimens, lead to gross swelling and eventual failure. Although ratchetting was observed in the stainless steel specimens it was not so pronounced and failure appeared to be by low cycle fatigue.
The role of strain measurement technology in structural evaluation
Authors: Thomson J.F.
Published: October 2008

This paper describes the importance of structural evaluation to the process of design assessment and outlines the significant role played by strain measurement technology in extending the scope of strain history data collection and facilitating strain monitoring of full‐scale structures in the laboratory. After some general discussion of the various models of structural behaviour, it then proceeds to give a brief historical account and outlines the principles of thermoelastic stress analysis (TSA). A general desciption is provided of a specific TSA technique namely Stress Pattern Analysis by Thermal Emission (SPATE).

Despite the level of innovation and development in strain measurement technology, the use of bonded strain gauge elements is still by far the most commonly used strain measurement and monitoring technique in structural evaluation work at NEL. The paper highlights several recent test programmes carried out at NEL in the form of case studies which demonstrate different aspects of measuring, monitoring and validation of this and other strain measurement techniques; and verification of analytical models.
Strain measurements using real time X‐ray images
Authors: Rutland Craig A. , Wang Ming L.
Published: October 2008

Recent tests have shown that changes in densities within specimens can he seen when X‐ray images of the specimen are enhanced and compared. Prism specimens of aluminium and cement mortar were tested in uniaxial compression and simultaneously X‐rayed. The grey levels within images taken during loading are compared. Results show that the strains in the specimen can be determined from the change in grey levels.
Further assessment of numerical procedures for the study of fluid‐structure interaction
Authors: Haxton R.S , El‐Deeb K.M.M. , Royles R. , Hunter I.T.
Published: October 2008

Synopsis

A study of the doubly asymptotic approach (DAA) to fluid‐structure interaction was carried out using the PAFEC/Dolphins and STAGS/USA suites of programs. The particular problem simulated was that of a ring stiffened circular cylindrical underwater structure subjected to explosive pulses at standoff distances of the order of the diameter of the structure. The method of discretisation is described and response data obtained for selected nodes on the structure. Typical responses in the form of velocity‐time history and power spectral density are presented. Response in terms of stress is given also for a particular node as derived from adjacent elements in order to provide a check on the quality of the PAFEC/Dolphins numerical model. A coarse and fine modelling exercise with the STAGS/USA program demonstrated little change in the structural response in the areas of interest. Comparisons are made between the predictions of the two numerical codes, and a brief description is given of the experimental validation of the STAG/USA program. Future developments are discussed.
Local stiffening effect of ‘double deck’ bending strain gauges: part 1
Authors: Chen J.F. , Ooi J.Y. , Rotter J.M.
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 presents an approximate, analytical solution for the local stiffening effect of a DD gauge and quantifies the errors in the strain measurement. Part 2, to appear subsequently in Strain, will present 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.
Measurement of Y‐notch tip plastic zone by the laser speckle technique
Authors: Tay C.J. , Tay T.E. , Shang H.M.
Published: October 2008

This paper presents a laser speckle method for the measurement of plastic zone ahead of a Y‐notch tip on metallic specimens. The method employs an unexpanded laser beam to illuminate the test object. Diffracted images are captured on a ground glass and recorded using a CCD camera. The recorded images were digitised and subsequently analysed on a personal computer. The plastic strain at the notch tip was correlated with its corresponding speckle image using a recently proposed parameter known as the integrated peak spectral intensity coefficient. Specimens containing Y‐notches of various angles were tested and the resu Its compared well with that predicted by theory.
A single exposure reflection moiré interferometric technique for complete curvature analysis of bent plates
Authors: Subramanian G. , Subramanian A.
Published: October 2008

Most known moiré methods need to be repeated three times for getting curvature information in three different in plane directions, for the complete analysis. To overcome this difficulty, a new single exposure moiré interferometric technique is proposed that maps completely partial curvature contours in three different directions of laterally loaded specularly reflecting plate models. Converging HeNe laser light is diffracted by a lens plane cross grating. The 00, + 10 and the +01 diffraction orders are permitted through the Fourier transform (FT) plane and collimated to illuminate the plate model. The reflected light from the loaded model records the model with the inherent deformed interferometric cross grating superimposed on it. A posteriori Fourier filtering of the developed recording (moirégram) gives partial curvature contours pertaining to three different in plane directions from which the principal curvatures and the principal directions are obtained. Also, this technique, being a single exposure technique, has the potential for complete bending analysis of plates subjected to lateral impact loading and destructive loading applications, where the repeatability of the event may not be possible.
Analysis of loaded mandible behaviour using speckle pattern interferometry
Authors: Roman J. F. , Petzing J. N. , Tyrer J. R.
Published: October 2008

Orthognatic surgeons have a requirement for the measurement of stress distribution within the human lower jaw, in order to aid and improve surgical procedures. Validation of finite element modelling data describing mandible behaviour which has previously been attempted using holographic interferometry. Electronic speckle pattern interferometry (ESPI), a whole field non‐contact optical technique has been applied to the study of a dry human mandible under load. This technique improves over previous methods by generating discrete quantitative displacement and strain components. The optical analysis of a dry mandible is described, with the results viewed in ‘real time’ as progressively greater forces were applied on the lower border of the chin, in the upwards (impact) direction with biting boundary conditions included in the experimental model. This has shown that the bone tissue holding the front teeth transmits the forces impacting on the chin, which are absorbed by the basal bone of the mandible.
Measurement of strain concentration factor of composites plate using moiré interferometry
Authors: Feng Wang , Huimin Xie , Fulong Dai , Weibo Qu
Published: October 2008

In this paper, using a 1200 lines/mm replicated grating, the moiré interferometry method was applied to study the strain concentration factor of a carbon fibre composites plate with a central hole. The rules of strain concentration factors were determined under different loads.
Developments in rapid thermoelastic analysis
Authors: Calvert G.C.
Published: October 2008

This paper describes the work carried out by Rover's Experimental Analysis Department on developing the thermoelastic stress analysis technique for use with rapid prototype models. The paper discusses the business issues, which drove the research into a new “rapid” design validation technique, and the detailed work required to ensure the validity of the stress results.
Thermal deformation measurement of the solder joints in electronic packages using electron moiré method
Authors: Huimin Xie , Kishimoto Satoshi , Shinya Norio , Fulong Dai , Daqing Zou , Sheng Liu
Published: October 2008

In this paper, electron moiré method is used to measure the thermal deformation of electronic packages. In order to observe the electron moiré fringe, a holographic grid was replicated on the cross section of the BGA type package at 150°C. This grid was fabricated on a glass plate using a moving point holographic system, and was replicated to measured area at high temperature. Under SEM, the holographic grid(specimen grid) and a programmed electron beam scan(master grid) interfere and form electron moiré patterns. The shear strain measurement technique using electron moiré method is described. Using the electron moiré method, the shear strains in the different solder joints were measured and analysed. Some useful results were obtained.
Photoelastic inverse problem solution for a biaxially loaded infinite plate with a hole
Authors: Cárdenas‐Garcia Jaime F.
Published: October 2008

This paper presents an inverse problem solution for the case of photoelastic isochromatic fringes around the hole of a biaxially uniformly loaded infinite plate for two problems. Problem 1 relates to an infinite plate in which the circular hole is drilled first and then the loads are applied. Problem 2 is the residual stress problem in which the hole is drilled after the biaxial load is applied to the infinite plate. This “hole method” solution may be used for all cases of biaxial, far field uniform loading conditions.
Optical Fibre‐based Vectoral Shape Sensor
Authors: Burnett J.G. , Blanchard P.M. , Greenaway A.H.
Published: October 2008

Abstract: Optically broadband interferometric techniques have been developed into cost effective and practical systems that enable the discrimination of strain and temperature in fibre optic sensors. Recent developments of temperature‐insensitive strain and shape‐sensing fibre‐optic sensors are described. A variety of approaches are discussed that have led to recent development of multicore, temperature‐insensitive vector bend sensors.
Finite Element Analysis of Laminated Beams Under Transverse Loading
Authors: Wasti S.T. , Utku M.
Published: October 2008

Abstract: Laminated beams fabricated from strips with intermediate adhesive bonding layers are frequently used. The evaluation of the shear and normal stresses in the adhesive layer along the length of the beam is important and both analytical as well as experimental investigations for these stresses have been previously documented. In the present paper, an attempt has been made to compare the analytical shear stress values in the adhesive layer obtained in previous analytical work with those obtained by modelling the laminated beam using finite elements. It is also shown that the analytical approach may be extended to the approximate analysis of coupled twin shear walls.
Three Optical Procedures for Local Large‐Strain Measurement
Authors: Rotinat R. , bi Tié R. , Valle V. , Dupré J.‐C.
Published: October 2008

Abstract: Optical methods have been developed to measure large strains. Two alternatives are presented: the first one uses a cross grating, obtained by an innovative manufacturing process and the second one uses a mark‐tracking technique. The production of the grating is based on the deposit of a thin film through a master grid under vacuum. This creates small studs independent of each other, on the specimen surface. For the grid interrogation two techniques are discussed, one using the analysis of the optical diffraction figure and the other one the Fast Fourier Transform algorithm. Markers are simply deposited on the studied surface with a pen and strain determination is then obtained by mark‐tracking. The experimental validation consists of several simple tensile tests. Experimental results for polymers and latex materials confirm the quality of measurement. Strains are measured for values up to 1,200% without loss of information, with a strain accuracy close to 5times10‐4 at minimum gauge lengths of 0.125 mm.
Simulation of Error in Digital Photoelasticity by Jones Calculus
Authors: Tamrakar D. K. , Ramesh K.
Published: October 2008

Abstract: The accuracy of parameter evaluation by automated photoelastic techniques depends on both their theoretical formulation and experimental procedure. The sensitivity of techniques such as phase shifting and load stepping to error in optical misalignment and quarter‐wave plate mismatch would be of interest. A generic approach to simulation of error in digital photoelasticity is presented. The simulation has showed how to associate the errors in the phase map to the misalignment of optical elements.
Surface Contouring of Reflecting Plates Using Intensity Integration Technique
Authors: Subramanian G. , Jagannath V.R.
Published: October 2008

Abstract: An intensity‐based image processing method termed the Intensity Integration Technique (IIT) is proposed to obtain the slope and curvature of loaded reflecting plates. It employs divergent beam illumination to cover a large plate area. The deformation field is established by applying cumulative (integrated) intensity as the correlation parameter to relate the reflected images from the undeformed and deformed states of the object. The method is suited to modern computing environment and requires a simple experimental set‐up. It obtains absolute values of slope and curvature.
EM Design Technology for Topside Antenna System Integration
Authors: Rockway J. W. , Li S. T. , Russell L. C. , Manry C. W. , McGee J. B. , Meloling J. H.
Published: October 2008

Topside Antenna System Integration is one of the most important technology challenges for future Navy ship designs. This is due to dual mission requirements of increasing capability while reducing the overall signatures of a ship. Often these two goals are in conflict. Because of these conflicting design issues, new and innovative techniques are required. In order to maximize performance, accurate numerical modeling and simulation are required. By using modeling and simulation tools a thorough investigation of system performance can be obtained. This information can then be used to make informed design decisions. This paper describes the design procedure and engineering tools used for Navy topside antenna system integration. The approach is an iterative process by which topside designs and antenna system architectures can be analyzed and performance assessed.
Evolution of the Engineering Duty Officer in the United States Navy
Authors: Fee Jerome J.
Published: October 2008

The engineering duty officers (EDOs) are today part of the line of the United States Navy and wear the same uniform without any distinguishing marks. The EDs of the past were not always in the close relationship to their line officer counterparts. It is necessary to trace the heritage of the current EDs back almost 200 years to show how the EDs present position has developed. For the first 160 years, the predecessors of today's EDs were split between two communities: engineers and constructors. So it is necessary to trace the development of both communities simultaneously until their merger. During the last 40 years the combat systems officer has emerged. Since most readers know this more recent development, it will not be dealt with in the same detail as the EDs, “ancient history.”
Logistics In French Naval Programs
Authors: Le Moigne Jacques
Published: October 2008

This article gives a short description of recent progress accomplished in order to integrate logistics through the entire life cycle activities, the strategy implemented for maintaining efficient operational availability in our future ships, and the present areas of research concerning maintenance concepts.
Defining the Future of the Navy in the New Century and at the Turn of the New Millennium
Authors: Sacks Stephen
Published: October 2008

The process of defining the future Navy, with platforms built to last a long time yet technology rapidly evolving, is discussed in this paper. It is suggested that taking appropriate account of known long term trends can play an important part in the definition process. Several examples are presented showing the potential contribution of trend analysis.