Vol. 11, No. 5 (1955)
1955, 31 (5): 371-378. doi: 10.7498/aps.11.371
In this paper, a method of superposition in given for the determination of approximate stress function of prisin with small hole in torsion. The approximate stress function consists of two parts. The first part is the solution of torsion problem for a simply connected region bounded by the exterior boundary of the given prism. The second part is the solution of Von-Neumann problem in the exterior region of the small hole.The boundary value of second part on the small hole is determined so that the superposition of these two solution gives free boundary condition on the surface of hole. It can be shown that the effect of second solution are concentrated in around the neighbourhood of the small hole.
A new type of simple electronic timer and its operational principle are described. The method and circuits of calibration are explained. The experimental results are tabulated and plotted in comparison with calculated values. Finally, discussions on the circuit, its accuracy, range of operation and applications are presented.
INTERNAL FRICTION PEAKS ASSOCIATED WITH THE STRESS-INDUCED DIFFUSION OF CARBON IN FACECENTERED CUBIC ALLOY-STEELS AND METALS
1955, 31 (5): 387-402. doi: 10.7498/aps.11.387
Internal friction peaks asscciated with the presence of carbon in several types of f.c.c. alloy-steel (18/8 type stainless steel and high manganese steel) have been observed from measurements with a torsion pendulum. The temperature for maximum internal friction lies between 200-300℃with a frequency of vibration of about I cycle per second. The height uf the peak rises and the position of the peak shifts to a lower temperature with an increase of the carbon content. When the amount of carbon in solid solution is reduced by tempering the specimen at an elevated temperature, the height of the peak lowers and the peak shifts to a higher temperature. A comparison of the activation energy and the diffusion ccefficients determined by internal friction methods with those measured in conventional macro-diffusion experiments reveals that the observed internal friction peak is associated with the stress-indused diffusion of carbon in these face-centered cubic steels.Internal friction peaks associated with the stress-induced diffusion of carbon in a Ni-Al alloy and in pure nickel have also been observed. These experiments show that the appearance of an internal friction peak associated with the diffusion of carbon in f.c.c. metals may be a general phenomenon.
1955, 31 (5): 403-410. doi: 10.7498/aps.11.403
It is well-known that the stress-induced rotation of the magnetic domains in nickel gives rise to an internal friction peak (when internal friction is plotted as a function of temperature of measurement). An internal friction peak associated with the presence of carbon in nickel was recently observed in our laboratory. In this paper are described further experiments which demonstrate conclusively that this new internal friction peak is not connected with ferromagnetism of nickel but depends upon the amount of carbon in solid solution in nickel. More accurate determinations of the activation energy associated with this internal friction peak show that this activation energy is indeed very close to the activation energy for the diffusion of carbon in nickel. These experiments thus show that the new internal friction peak is associated with the stress-induced micro-diffusion of carbon in nickel.A brief discussion on the mechanism of this internal friction peak in terms of the existence of holes in the crystal lattice of nickel is given.
1955, 31 (5): 411-420. doi: 10.7498/aps.11.411
In frequency modulation system the change of the percentage modulation affects the bandwidth of the transmitted signal. Outside the critical sideband the amplitude of all the higher order sidebands is a positive decreasing function of the order of the sidebands. In this paper we give an approximate determination of amplitude of this critical sideband as given by equation (8) or fig. (2); given also are the approximate magnitude of any side band above the critical and the ratio of the amplitude of any sideband above the critical to that of the critical, equation (11). By means of these two equations we can design the bandwidth of the transmission system by retaining a certain number of significant sidebands above the critical.