Volume 16, Issue 5, 01 May 1945
Index of content:
16(1945); http://dx.doi.org/10.1063/1.1707586View Description Hide Description
An analysis of the chip geometry and the force system found in the case of orthogonal cutting accompanied by a type 2 chip has yielded a collection of useful equations which make possible the study of actual machining operations in terms of basic mechanical quantities. The shearing strain undergone by the metal during chip formation, and the velocities of shear and of chip flow are among the geometrical quantities which can be quantitatively determined. The force relationships permit calculation of such quantities as the various significant force components, stresses, the coefficient of friction between chip and cutting tool, and the work done in shearing the metal and in overcoming friction on the tool face. The experimental methods by which such analyses can be readily made are described. Observed and calculated values from typical tests are presented.
16(1945); http://dx.doi.org/10.1063/1.1707587View Description Hide Description
The purpose of this note is to present the formulae for calculation of optimum height of horizontal flight of winged rocket‐ or jet‐bomb in an elementary way. First, the elementary principles of rocket‐propulsion are given, i.e., the momentary coefficient of external efficiency, which represents the part of the total energy of the propulsive material imparted to the rocket, the mass of the rocket after a certain time, the actual acceleration and the average acceleration of the rocket, and the average coefficient of external efficiency over a certain period of time. Next, the horizontal flight of a rocket in atmosphere at a certain height is considered and the formulae for the optimum height of flight are derived in two cases: (a) constant velocity of flight, (b) constant mass of the outflowing gases. The calculations refer to the case of adiabatic flow in the nozzle but may be applied easily to the case of any polytropic flow. The considerations are repeated in the same order for jet‐propulsion. The formulae are derived under the simplifying assumption that the difference in pressures in the wake behind the bomb in flight‐in which the pressure is smaller than in the free air‐and in the free air may be disregarded, since it is assumed that at the mouth of the nozzle the pressure equals the pressure in the free air. The difference between rocket‐ and jet‐propulsion is presumed to be known. In the former type of propulsion the propulsive material contains in itself the oxygen necessary for the combustion process, while in the latter the oxygen is taken from the outside air. The type of propulsion in which oxygen is contained, separately from the fuel, within the rocket in a compressed or liquid state, should be included in the rocket group.
16(1945); http://dx.doi.org/10.1063/1.1707588View Description Hide Description
The deflection angle θ of a cathode‐ray beam accelerated by a potential V is shown to be proportional to the linear charge density ρ transverse to the beam on the interior of the electrostatic deflection system, θ=ρ/2Vε0. The voltage deflection sensitivity depends on the plate‐to‐plate capacitancec per unit width, θ/E=c/2Vε0. This includes edge effects and permits a determination of the sensitivity from capacitance measurements or a simple graphical evaluation from the dimensions of the deflection system. The use of parallel‐wire lines as a deflection system is suggested, and its deflection sensitivity evaluated. Such lines have low transit time error and are either easily tuned, or can be operated non‐resonant with resistive termination.
16(1945); http://dx.doi.org/10.1063/1.1707589View Description Hide Description
When a gas is allowed to flow out along the radius in a rapidly rotating enclosure, it is compressed and therefore heated. The enclosure may be supplied with a coil of pipe carrying a cooling liquid to remove the heat of compression as formed in the gas. On guiding the gas back to the axis, it is cooled by its own expansion, and a maximum ΔT of about 150°C occurs. The work of expansion is determined by the rotor demand, not by the gas temperature or by the gas volume change. Both warm and cold fluids enter and leave the enclosure axially. Analysis shows that the cooling, ΔT, is given by ω2 r 2/2Cp . The rotational energy of the enclosure is not drawn upon by the steady fluid flows. The cooling liquid moves convectively through its circuit but the gas must enter the enclosure at a pressure somewhat above that at exit. A possible mechanical design is sketched. Maximum peripheral speeds allow 19 cal./gram to be extracted from the gas flow giving for air a drop of 77°C from room temperature. This is more than sufficient for most commercial refrigeration. Use of a favorable gas in the rotor gives sufficient ΔT to be very effective in gas liquefaction. Rotors may have their flows in series to increase the ΔT, and the gas may be at a supercritical pressure to keep it homogenous till released from the pressure. The device is expected to have high efficiency as a refrigerator. By utilizing the rejected heat, as Kelvin suggested, the device may be used for domestic heating.
16(1945); http://dx.doi.org/10.1063/1.1707590View Description Hide Description
The theory of stresses and displacements for layered soil systems is extended in this paper to cover the more general case of three layers with full continuity across the interfaces between the layers. The three‐layer system gives a closer approximation to the actual soil conditions encountered. Only the settlement equation at the surface of the ground is derived at this time, because it has a more direct application to the practical problems of foundation and airport engineering.
16(1945); http://dx.doi.org/10.1063/1.1707591View Description Hide Description
The persistence of an arc in an experimental tube with a pool type cathode has been studied. The mean life under carefully controlled operating conditions is determined by statistical analysis of a hundred or more observed lives and is taken as a measure of the stability. The dependence of mean life upon both the ambient temperature of the cathode pool and the current is determined. The arc is found to be most stable at an optimum ambient temperature. In the first observations the cathode spot was free; later observations were made with the cathode spot anchored in contact with a tungsten film. In both cases the results indicate that the mean life rises exponentially with the arc current in the ranges used. If I represents the arc current and L represents its average duration, the results suggest a relationship of the form,where F stands for some functional relationship depending on the mercuryvapor pressurep calculated from the ambient temperature, and upon other parameters such as x, y, and z, at present undetermined. For the proportionality constant k, the data give (2.46±0.06) ampere−1 when the cathode spot is free and (19.92±0.47) ampere−1 when the cathode spot is anchored. F(p, x, y, z, …) appears to be smaller with the cathode spot anchored than with it free, but the probable error in the function is relatively large.
16(1945); http://dx.doi.org/10.1063/1.1707592View Description Hide Description
A  pole figure for cold‐rolled and annealedsilicon steel, constructed from data obtained with an integrating x‐ray camera, is compared with a stereographic projection of  poles for one hundred individual grains in the same samples. From this comparison, it is concluded that pole figures are accurate enough to determine preferred orientations when the exact percentage of crystals in each orientation is not required.