Showing papers in "Strain in 1988"
TL;DR: A survey of these developments and the advances in polariscope design can be found in this article, where the authors provide a survey of recent developments in the field of automated and computer aided photoelastic analysis.
Abstract: Photoelastic stress analysis can be a long and tedious process. However recent and current developments in the field of automated and computer aided photoelastic analysis mean that it is becoming possible to do more complex analysis and to perform it more quickly. This paper provides a survey of these developments and the advances in polariscope design.
35 citations
TL;DR: In this paper, it is shown that the inertia error may also arise from the method of dynamic force measurement, and the theory for the latter is presented and its merits discussed, as well as the results of experiments to measure this error are presented.
Abstract: Loadcells for materials testing machines are calibrated statically by comparison with a transfer standard, traceable to the National Physical Laboratory. There is evidence to suggest that, under certain conditions, this static calibration may be insufficient for dynamic testing. The possibility of an error being generated by the inertia of the mass between the loadcell and the specimen is discussed and the results of experiments to measure this error are presented. For the case chosen it is shown that the inertia error may be predicted by calculation. Errors may also arise from the method of dynamic force measurement. The conventional DVM and the analogue peak hold voltmeter are widely used but are subject to errors in a practical machine situation due to their method of operation. Bandwidth limitations are also illustrated for a number of instruments with different sampling rates. A better, although more expensive and complicated solution is to digitise the signal and to use some form of spectral analysis such as the Fast Fourier Transform or the Cross Correlation Integral. The theory for the latter is presented and its merits discussed.
8 citations
TL;DR: Moire interferometry is used to simultaneously measure the in plane and out of plane displacement components in this article, where high sensitivity of displacement measurement is maintained and high contrast fringes are obtained without recourse to additional filtering.
Abstract: Moire interferometry is used to simultaneously measure the in plane and out of plane displacement components. The high sensitivity of displacement measurement is maintained and high contrast fringes are obtained without recourse to additional filtering.
8 citations
TL;DR: In this paper, a simple procedure to obtain very reliable estimates of the stress concentration at the root of a notch using only data from points beneath the notch root along its axis of symmetry is described.
Abstract: This paper describes a simple procedure to obtain very reliable estimates of the stress concentration at the root of a notch using only data from points beneath the notch root along its axis of symmetry. The advantages of the method are (i) data from only a few points are needed, (ii) the necessary computations require only a hand held calculator, (iii) inaccurate data becomes quite apparent to the analyst, and (iv) random experimental errors are largely compensated.
5 citations
TL;DR: In this article, the authors describe shakedown and relate it to pressure/strain observations during proof testing, and propose a shakedown approach based on shakedown to make judgments.
Abstract: A recent BSSM meeting organised by the Pressure Systems Technical Group discussed proof testing of pressure vessels, with particular reference to nozzles etc which fall outside the normal design route and require stress analysis testing. The references in BS 5500 to brittle lacquer, strain gauges and competent persons were of particular concern, as were the interpretation of pressure/strain plots.
The BS 5500 design route is based on a shakedown approach. The paper attempts to describe shakedown and relate it to pressure/strain observations during proof testing. In this way the reader should be more able to make judgments.
2 citations
TL;DR: In this article, the amplitude of the conditioned signals from the frictional strain gauge attached to the probe is described and the usefulness of the technique is discussed, as well as comparative tests of the performance of the FRG and bonded gauges on an axially loaded testpiece subjected to sinusoidal and random loading conditions.
Abstract: A probe for the measurement of surface strains on dynamically loaded structures has recently been tested at the National Engineering Laboratory (NEL). The procedure for estimating the amplitude of the conditioned signals from the frictional strain gauge attached to the probe is described and the usefulness of the technique is discussed. Calibration data are presented from comparative tests of the performance of the frictional gauge and bonded gauges on an axially loaded testpiece subjected to sinusoidal and random loading conditions.
2 citations
TL;DR: In this paper, the dynamic along-wind coefficient has been evaluated by means of a single-degree-of-freedom rectangular cylindrical model in a partial boundary layer wind tunnel.
Abstract: The dynamic alongwind coefficient has been evaluated by means of a single-degree-of-freedom rectangular cylindrical model in a partial boundary layer wind tunnel. Experimental results show a tendency that the ratio of dynamic alongwind force coefficient to the static one is considerably greater than unity in a low reduced velocity range and increases when the reduced velocity decreases, while it converges to a fairly constant value less than unity when the reduced velocity increases. This tendency can be explained by pressure correlation effects. Although the turbulence intensity and scale were found to have a significant effect on the static coefficient value the ratio of dynamic to static coefficient appears to be insensitive to those turbulence parameters.
2 citations
TL;DR: In this paper, several analytical methods are outlined to deal with the title problem when the vessel is free of external constraints, which correspond to the Haigh equation, which provides a nonlinear relationship between the induced circumferential stress and the applied internal pressure.
Abstract: Several analytical methods are outlined to deal with the title problem when the vessel is free of external constraints. In essence these correspond to the Haigh equation, which provides a nonlinear relationship between the induced circumferential stress and the applied internal pressure. To make use of these analyses a survey of the cross sectional profile is required. The approach using an internal swinging arm has been found most useful. The extent to which an improved Haigh equation is valid is examined with reference to the pneumatic loading of a twin saddle supported horizontal vessel which contains imperfections and restraints at the supports.
2 citations
TL;DR: In this article, some optical phenomena in three dimensional photoelastic media are analyzed and some misleading statements made in Ref. 1 relative to the experimental technique of integrated photo elasticity are analyzed.
Abstract: Some optical phenomena in three dimensional photoelastic media are analysed. Suggestions made in Ref. 1 relative to the experimental technique of integrated photoelasticity are analysed and some misleading statements of the latter paper are indicated.
1 citations
TL;DR: A pre-Congress - IMEKO (Houston)/SEM (Portland Or) 1938 to 1988 Strain Gauge Jubilee Celebration - publication by special arrangement with P K Stein co-ordinator as mentioned in this paper.
Abstract: A pre-Congress - IMEKO (Houston)/SEM (Portland Or) 1938 to 1988 Strain Gauge Jubilee Celebration - publication by special arrangement with P K Stein co-ordinator.
1 citations
TL;DR: In this article, the average effects of finite length gauges located on the boundary of a notch fillet are analyzed using a modal representation of the stress and strain fields in stress concentration regions.
Abstract: From a previously derived modal (i.e., series) representation of the stress and strain fields in stress concentration regions, exact analytical expressions are obtained for the averaging effects of finite length gauges located on the boundary of a notch fillet. A simple method of analysing such data is described. It is then applied to two problems to show i) how easily poor or faulty data can be detected and ii) how a very reliable estimate can be made of the magnitude and location of the peak stress (or strain), even when using data from gauges beyond the very highly stressed (strained) region.
TL;DR: A microprocessor based data acquisition and real time processing system used for in-situ agricultural machinery experimentation is introduced in this paper.
Abstract: A microprocessor based data acquisition and real time processing system used for in-situ agricultural machinery experimentation is introduced in this paper.
The devlopment, principle and error of the system are discussed, and some practical trials are related.
TL;DR: In this article, hole shapes have been optimized in diametrically loaded circular discs with two neighbouring holes leading to minimum stress concentration factor (s.c.f.). Two neighbouring holes symmetrically located side by side with the load axis perpendicular to the line joining the centres of the holes are considered.
Abstract: Using a two dimensional photoelastic technique, hole shapes have been optimised in diametrically loaded circular discs with two neighbouring holes leading to minimum stress concentration factor (s.c.f.). Two neighbouring holes symmetrically located side by side with the load axis perpendicular to the line joining the centres of the holes are considered. Results are given for a range of disc diameter/hole diameter ratios (11.44≥D/d≥4.16). Optimised quasi-trapezoidal hole geometries, stress distributions around these holes and the effect of tilting the load direction are presented. In comparison with circular holes, the s.c.fs. have been reduced up to about 14% with quasi-trapezoidal holes at regions of peak stresses and up to 23% at peak tensile stress regions.
TL;DR: In this article, the minimum normalised light intensity In is introduced as a reliable characteristic parameter, in three dimensional photoelasticity, whose measurement is rather comfortable, whose limits of a cited method are pointed out.
Abstract: The minimum normalised light intensity In is introduced as a reliable characteristic parameter, in three dimensional photoelasticity, whose measurement is rather comfortable. Spectral, stress components, angle of divergence of the stress components, and material dependence of In is investigated. Limits of a cited method are pointed out. Some misunderstandings that took place in Ref. (1) are highlighted. The basic concepts of two methods in integrated photoelasticity are compared.