An analytical solution is presented for the case when an elastic sphere is pressed against an elastic half-space and twisted until complete slip occurs. Formulas are derived for the stress and displacement components, their evaluation is illustrated by numerical examples, and comparisons are made with the results of photoelastic tests. These tests also furnished an experimental verification of the assumption that the tangential-surface traction is proportional at every point to the normal pressure within the sliding-contact area, the proportionality constant being the coefficient of friction.

It is shown in this paper that along the root sections of filleted or notched bars there is a rapid rise in the transmitted shearing forces, and this may be regarded as the principal reason for the occurrence of stress peaks under these circumstances. By making a few assumptions concerning the distribution of these shear loads, the stress-concentration factors can be calculated with satisfactory accuracy for such cases which have been heretofore analytically intractable.

Six different nut designs have been investigated by the three-dimensional “stress freezing” photoelastic method, obtaining the maximum stress values at the bottom of the threads for each design. It has been found that by the application of either a tapered-thread nut or a nut with a tapered lip the strength of the fastening can be increased by more than 30 per cent. This improvement in strength can be expected only in cases where the type of loading or conditions of application are conducive to brittle failure, i.e., dynamic loads or static loads at elevated temperatures.

This paper deals with three particular problems in turbine-generator design, namely ( a ) stress concentrations in transverse grooves of two-pole generator rotors, ( b ) centrifugal stresses in rotors, and ( c ) stress concentrations in T-heads (bolts and blade fastenings). The connection between these problems is only their mutual sphere of application and the fact that in each case the solution has been obtained by photoelasticity. The problems have been investigated as two-dimensional ones, the first and third being analyzed by the standard photoelastic technique, while in the second problem the fundamentally three-dimensional method of “freezing” the stresses in bakelite samples was applied.

The method of three-dimensional photoelasticity is based on the experimental fact that samples of phenolic resins, such as Bakelite, Marblette, and Trolon, when annealed in a loaded condition show a complete preservation of ( a ) the elastic deformation and ( b ) the accompanying birefringence produced by the loading at the annealing temperature. After presenting a historical review of the method, the author discusses the current theory of the molecular structure of phenolic resins by which the phenomena observed in the annealing procedure can be explained. Test results are given which prove the elasticity of Bakelite at elevated temperatures. Applications of the method are also discussed.

A method is presented for the calculation of stresses and deflections in ring-shaped shells of circular cross section, subjected to axial forces. The solution is derived without the restriction imposed for toroidal shells by previous investigators, that the radius of curvature of the cross section is to be small in comparison with the mean radius of the torus. The range of applicability of the method is extended hereby to include the slightly arched convolutions used in the construction of welded bellows. By a rational reduction of the general solution approximate design formulas are obtained for the maximum stresses and deflections in bellows under axial forces and the calculated values are compared with experimental data.