Temperature Decrement Research Articles

Strain-Amplitude Dependent Internal Friction Studies of Dilute Alloys of Copper

This paper presents an investigation of the room temperature decrement in dilute polycrystalline alloys of copper as a function of strain amplitude and annealing at a frequency of about 1 cps. The characteristics of the internal friction measured are: (1) The internal friction and strain amplitude dependence of the internal friction decreases with increasing solute content. (2) The internal friction is reversibly dependent upon the preanneal temperature. (3) The internal friction is hysteretic with strain amplitude. From the effect of the solute concentration and annealing temperature on the decrement, values for the binding energy for Al and Si solute atoms to dislocations in copper were calculated. These values are compared to theoretical values calculated on the basis of strain and electrical interaction energies. The experimental binding energy is in good enough agreement with the theoretical values to conclude that the onset of a strain amplitude dependence of the internal friction is caused by the freeing of sufficient dislocations from their pinning solute atoms.

Temperature Dependence of Young's Modulus and Internal Friction of Single Crystals of Beta-Brass

The temperature variation of Young's modulus of beta-brass single crystals of 55 atomic percent copper has been determined. Comparison is made with previously reported results. Internal friction has been measured at 21 and 42 kilocycles per second at room temperature and as a function of temperature to slightly above the complete disappearance of order. The room temperature decrement is for all crystals of the order of 10−4 and mainly independent of amplitude of oscillation. The decrement as a function of temperature shows a ``relaxation peak.'' Zener's theory for alpha-brass is found to apply and the source of the relaxation is preferential orientation of pair axes of solute atoms in adjacent cells. The heat of activation is about 20×103 calories per mole. The relaxation peak is shown to be characteristic of the disordered state. There seems to be no relaxation phenomenon present in the ordered state. The effect of precipitation of the alpha-phase on Young's modulus and the internal friction has been found negligible unless a large amount of precipitation occurs.

Vertical Decrement of Temperature and Pressure

IN NATURE of March 10 (p. 437), Mr. Maxwell Hall gives an interesting table of the vertical distribution of temperature and pressure in Jamaica, and, apparently in happy ignorance of the dangers of the process known as extrapolation, goes on to apply the results of observations extending to a maximum height of only 7400 feet to the determination of the probable temperature of meteorites in extra-terrestrial space. As he expresses a desire to know whether any similar results have been found in India, and as I have on several occasions during the past ten years discussed the vertical distribution of temperature and pressure in this country, I gladly take this opportunity of referring him to my papers on the meteorology of the North-West Himalaya, and on the temperature of North-Western India, published in the “Indian Meteorological Memoirs,” vols. i. and ii. From the latter I extract the following table on the mean decrement of temperature up to a height of 12,000 feet, computed from the observations of twenty-five stations combined in various ways. For each month an interpolation formula of the form T = T0 + ah + bh2 + ch3, was computed, and by its means the decrements from sea-level to 1000 feet, 1000 to 2000 feet, &c., were calculated. Finally, the average decrement for the twelve months was computed, and is here given in an abridged form. The curves for the several months differ very widely from one another, those for the summer giving the most rapid decrement at sea-level, and the decrement increasing with altitude in winter: —

I. Numerical elements of Indian meteorology.— Series III. Temperatures of the atmosphere, and isothermal profiles of high Asia

The principal object of this paper was to trace the relation between the decrement of mean temperature and the increment of height above the level of the sea in different regions of High Asia, to connect the variations observed from the general mean of the whole (390 feet increase of height for a diminution of 1° F. in mean temperature) with the variations of season and of geographical position, and also to point out the cause of certain peculiarities in the climate of High Asia.

3. On the Diminution of Temperature with Height in the Atmosphere at different Seasons of the Year

The results communicated to the Society were obtained from nearly five years of simultaneous observations, made twice a-day at Colinton and at the Bonally reservoir five miles south-west from Edinburgh. The height of the former station above the level of the sea is 364 feet, of the latter 1100 feet exactly; the difference 736 feet. The mean annual difference of temperature amounted to 3°.22, giving 229 feet of ascent for a diminution of temperature of 1° Fahr. The influence of the seasons is briefly shewn by the following numbers:That the decrement of temperature is most rapid in summer, and least so in winter, has been long known.

XXV.—On the Diminution of Temperature with Height in the Atmosphere, at different seasons of the year

In the year 1830, I succeeded in establishing a Register of the Thermometer at the Bonally Reservoir, which formerly supplied the city water-works, being at a distance of five miles in a direction south-west from Edinburgh. This station is on the northern acclivity of the Pentland Hills, at a height of 1100 feet above the sea. The following year I obtained corresponding observations at the village of Colinton, situated a mile and a half north of the preceding station, and above 700 feet lower. Although this difference of level be not very considerable, yet, as these comparative registers have been kept for nearly five years with pretty uniform results, some confidence is evidently due to the conclusions, even although considerable difficulties opposed themselves to obtaining registers quite free from exception. The interest attaching to them is the greater, that, although registers have been kept at Leadhills and other elevated stations, I do not recollect any strictly comparative observations in Scotland, perhaps not even in Great Britain, at two stations near one another, and differing considerably in level, from which the important meteorological element of the decrement of temperature in the atmosphere could be deduced.