Showing papers in "Strain in 1985"
TL;DR: There is an array of full field experimental stress analysis techniques available to aid the designer or the engineer investigating service failures as discussed by the authors, including photoelasticity, moire, laser holography, brittle lacquer and SPATE.
Abstract: 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, moire, laser holography, brittle lacquer and SPATE) and assesses their relative merits in practical applications.
7 citations
TL;DR: In this article, the conventional finite element method has been modified to allow the elastic stresses along the fibre matrix interfaces of a composite to be determined with improved accuracy, and the results obtained by this modified method are compared with both a photoelastic and some traditional finite element solutions.
Abstract: The conventional finite element method has been modified to allow the elastic stresses along the fibre matrix interfaces of a composite to be determined with improved accuracy. The results obtained by this ‘modified’ method are compared with both a photoelastic and some traditional finite element solutions.
6 citations
TL;DR: In this article, the use of an automatic recording microdensitometer in conjunction with a fringe multiplying polariscope for analysing small portions of slices from frozen stress photoelastic models is described in detail.
Abstract: The use of an automatic recording microdensitometer in conjunction with a fringe multiplying polariscope for analysing small portions of slices from frozen stress photoelastic models is described in detail. The method is used to find the load distribution in the threads of a 30 mm ISO nut and bolt model. The accuracy is discussed and shown to be comparable to that of conventional photoelastic techniques.
3 citations
TL;DR: In this paper, three extensometers are described which have been used respectively for testing high strain fatigue in steels, fatigue crack propagation and fracture of a glass reinforced polyester composite.
Abstract: Of a number of methods for testing materials under biaxial stress conditions, the cruciform specimen with tension/compression loading of the arms allows exploration of the whole in-plane failure envelope. This paper highlights the problems arising in the measuring, monitoring and control of strains in cruciform specimens subject to static and cyclic biaxial loading. Three extensometers are described which have been used respectively for testing high strain fatigue in steels, fatigue crack propagation in steels and fatigue and fracture of a glass reinforced polyester composite. Each extensometer uses a full bridge resistance strain gauge circuit; two are based on bending of a beam and the third on deformation of a thin ring. Examples are shown of stress/strain loops for equibiaxial and shear conditions from fatigue tests on a steel and g.r.p.
3 citations
TL;DR: Considering one-axial strain fields in the penetration depth of X-rays, the corresponding measurement distribution of e versus sin2 ψ are calculated for 24 different oneaxial strains as mentioned in this paper.
Abstract: Considering one-axial strain fields in the penetration depth of X-rays, the corresponding measurement distribution of e versus sin2 ψ are calculated for 24 different one-axial strains. The parameter is the measurement direction. The deformations of neighbouring points are calculated with Taylor series and described with linear expressions. There are five different types of curves, which can be combined linearly. The calculations are only applicable for plane surfaces.
2 citations
TL;DR: In this article, the inner and outer boundaries of circular rings under internal diametral tension using two dimensional photoelasticity were optimized to reduce the stress concentration factor and weight.
Abstract: Optimisation of inner and outer boundaries of circular rings under internal diametral tension using two dimensional photoelasticity is presented. It is shown that, when shape optimisation of only one of the two boundaries in the field is carried out, there is an increase in the stresses on the other boundary. However, optimisation of both the boundaries is found to be beneficial with significant reduction in stress concentration factor and weight.
2 citations
TL;DR: In this article, the authors described the development and evaluation of temperature compensated high elongation resistance strain gauges for use from room temperature to 250°C, which could be temperature-compensated on steels with coefficient of thermal expansion α = 11 ppm/°C.
Abstract: The paper describes the development and evaluation of temperature compensated high elongation resistance strain gauges for use from room temperature to 250°C. These gauges could be temperature-compensated on steels with coefficient of thermal expansion α = 11 ppm/°C. Thermal output within 250°C was about 1 μm/m/°C and maximum standard deviation of 5 gauges was 34 μm/m. Strain limit was > 4% at room temperature and at 250°C. Gauge factors of different strain ranges at R.T. and at 250°C are tabulated. Some applications are stated.
1 citations
TL;DR: In this article, an insight into strain gauge telemetry techniques explaining why telemetry can offer interesting advantages over conventional strain gauge systems is discussed together with the importance of a.c. transmission in the avoidance of drifts and parasitic effects applicable to d.c systems.
Abstract: An insight into strain gauge telemetry techniques explaining why telemetry can offer interesting advantages over conventional strain gauge systems. The difference between a.c. strain gauge measurements and analogue to digital conversion followed by a.c. transmission is discussed together with the importance of a.c. transmission in the avoidance of drifts and parasitic effects applicable to d.c. systems.
A comparison between frequency modulation (FM) and time or pulse duration modulation (PDM) explains why PDM can offer significant advantages.
1 citations
TL;DR: In this article, the stress concentration during the loading and unloading processes of transient creep is investigated for a strip with semi circular notches by means of the photo-viscoplasticity, using specimens of celluloid at 65dC.
Abstract: The stress concentration during the loading and unloading processes of transient creep is investigated for a strip with semi circular notches by means of the photo-viscoplasticity, using specimens of celluloid at 65dC. The relations between the stress concentration factor, the geometries of strips, and time during the loading and unloading processes are derived from the time dependent variations of isochromatic fringe orders. Such trends cannot be analysed by the ordinary photoplasticity in which the time effect is not taken into account.
1 citations
TL;DR: This paper considers each of these areas and identifies where progress has occurred in engineering metrology and concludes with a few new predictions for the next decade or so.
Abstract: In 1952 Mr F. H. Rolt, one of the pioneers of engineering metrology, who had worked at NPL for over 40 years reviewed the progress in this area during the first half of the 20th century. He concluded his lecture by identifying eight topics on which progress could be expected.
This paper considers each of these areas and identifies where progress has occurred. The paper concludes with a few new predictions for the next decade or so.
TL;DR: 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 as mentioned in this paper.
Abstract: 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.
TL;DR: In this article, internal diaphragms were installed to provide support for the horizontal sand filter bed running the full length of the vessel, by means of four cylindrical plastic models.
Abstract: The model work presented in this paper was stimulated by investigations carried out on 3.7 m diameter horizontal cylindrical vessels used as oily water separators. In these, internal diaphragms were installed to provide support for the horizontal sand filter bed running the full length of the vessel. By means of four cylindrical plastic models two different designs for the diaphragm are considered. On the basis of strain gauge investigations, conclusions are drawn which should provide a design approach for these components whereby certain peak stresses can be avoided.