The Journal of Strain Analysis for Engineering Design

The distribution of the stress, strain, and strain rate in a long rod, one end of which has been given a fixed velocity, is analysed. Computer programmes have been written for three different classes of materials: purely rate-sensitive materials, purely strain-hardening materials, and materials exhibiting both strain hardening and speed effect. Where possible the results have been checked against known solutions.

It is well known that in approximate analysis of elasticity problems lower and upper bounds to the true strain-energy content can be obtained by the alternative assumptions of compatible displacement fields or of equilibrating stress fields. While formulations based on the first are relatively easy to achieve those based on the second present many difficulties. In this paper it is shown how by virtue of the analogy between plane-elasticity and slab-deflection problems compatible-displacement formulations in either one can be used to generate equilibrating formulations in the other. This should result in a direct application of existing programmes to a wider range of problems.

A review of some failure mechanisms of glass-reinforced plastics under single and repeated (fatigue) loading is presented. Published work of both an experimental and an analytical nature is included. There are several micrographs and a brief description of the component materials is given.

A simple redundant structure subjected to a non-uniform temperature distribution is simulated experimentally by means of two tensile-creep test machines holding specimens of Nimonic Alloy 90 at different temperatures in the range 800-900°C. The machines are linked together so that although the total load applied to the specimens is constant the share of that load taken by each varies owing to dissimilar creep rates, as it would in the structure. This redistribution of load is observed for several initial stress conditions and several temperature differences. In each case the results are compared with calculations based on creep-strain data obtained from constant-stress tests. An important practical feature of the results is the establishment of stable (fully redistributed) stresses. These stresses are insensitive to the initial conditions, can be estimated quite simply from constant-stress creep data, and are always more uniform than the thermal stresses appropriate to the same temperature difference. There is some indirect evidence that the creep process itself (primary creep in particular) is a manifestation of stress redistribution on a microscopic scale.

Thin cylindrical specimens, plain and with deep axial grooves, have been tested under pulsating pressure and under static pressure with cyclic axial straining. The test results, together with some supplementary information from other authors, show that Langer's method, based on an elastic-stress analysis, is applicable to the fatigue design of pressure vessels. Design curves for the establishment of the acceptable elastic-stress range corresponding to a given fatigue life are proposed. Attention is drawn to the limitations of Langer's method.

The discontinuity stresses in the vicinity of discrete supports welded to the hemispherical end of a pressure vessel under internal pressure have been measured. Four brackets fabricated from flat plates and three tubular supports were examined. Experimental stresses compared reasonably well with stresses estimated by approximate analytical methods which are suggested as standard design checks.

Investigations on the elastic properties and strength of sedimentary rocks in uniaxial and triaxial compression and on the tensile strength of sedimentary rocks are described. A brief account is given of the application of dimensionless analysis to scale-model roadway tests and of the properties of a scale-model material.

The frozen-stress photoelastic technique was used to determine the stresses around reinforced non-central holes in discs. Both circular bosses and a thickened annulus were used as reinforcements. Calculations by Green, Hooper, and Hetherington were found to predict the mean stresses (through the thickness) well but these calculations cannot predict the peak stresses. The latter were not significantly less than the values of the unreinforced perforated discs. The stresses in a taper disc were lower than in a disc of constant thickness.

Piezo-resistivity, ‘end’ effects, and transverse connections are taken into account in semi-quantitative formulae capable of reproducing observed magnitudes and systematic changes of gauge factor and cross-sensitivity in foil and wire gauges and of suggesting means for reducing cross-sensitivity.

The most general axially symmetrical thermal load is one in which a transient temperature distribution, varying axially and radially, is applied to an axially symmetrical system with an irregular axial boundary. When the thermal stress equations are applied to such a system, using the conventional Gauss-Siedel or Liebmann method, severe oscillation has been experienced making convergence impossible to achieve. The authors present in this paper a method which not only converts a diverging solution but also yields a rapid rate of convergence. This method has been successfully applied to the problem of a steam turbine rotor.