Sennosuke Sato

STUDIES ON THE MECHANICAL PROPERTIES OF HOT EXTRUDED BERYLLIUM AT ELEVATED TEMPERATURES.

The hot extruded beryllium of reactor grade purity was studied at elevated temperatures with respect to its tensile, hardness, elastic modulus and creep properties. The thus obtained results have been discussed in comparison with out previous report regarding hot rolled beryllium.The hardness was regarded as a macroscopic measure for the temperature dependencies of critical slip mechanisms in single crystal.The elastic modulus up to 1000°C were determined by means of an ultrasonic pulse propagation speed.The creep tests were carried out in two ways, namely the stress increment method at constant temperatures among the room temperature to 700°C and the temperature cycling method of the triangular temperature variation between 350 and 600°C at constant loads. In the stress increment creep, the steady creep rate and the rupture life in the Larson-Miller diagrams agree reasonably with the corresponding data at The Brush Beryllium Co. by ordinary method. The relation of steady creep rate e and the cycles-to-rupture NR in the temperature cycling creep was expressed as eNR0.70=constant. This equation is similar to the formura on strain controlled fatigue. The considerations in the temperature cycling creep of this material have been discussed in comparison with constant temperature creep.

An Approach to Torsion Problem of a Circular Shaft with Multiple-Notches

In this paper, an approximate solution is derived for a twisted shaft with circumferential notches periodically situated along its length. The solution for the extreme case where the dimensions of notches are infinitely small, has been obtained previously by Neuber. The present solution, however, is of sufficient accuracy for practical use even in the range of moderate dimensions of notches. The maximum torsional stress has been evaluated for various values of the radius of a notch. The ratio of maximum stress for multiple-notches to the corresponding one for a single-notch has been obtained, using two different formulas for a single-notch, previously obtained by Sonntag and Okubo respectively, and the validity of the two formulas is discussed.