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By S. R. Krom

IN Mr. Hoffman's papers, and in the discussions attending them, the claim is apparently made for the Sturtevant mill that it produces

Jan 1, 1893

By Arhtur T. Allen

THE Kingsport formation, a part of the Knox dolomite of Ordovician age, is composed of 538 ft of dolomite and limestone. Numerous bands, layers and nodules of chert, arenaceous and shale zones are present. The characteristics displayed by these features have been useful in mapping, prospecting and mining. Perhaps a better understanding of the origin of these zones will increase their usefulness.

Jan 1, 1947

ALTHOUGH iron ores occur in many parts of Sweden the two principal deposits are those at Grängesberg (see accompanying map) and at Kiirunavaara-Gellivare. Both of these deposits are con-trolled by a holding company, Trajikaktiebolaget Grängesberg-Oxelösund, which sells annually about one-half of, the iron in ore traded in world markets and has a fleet of 24 seagoing ore boats, with a total dead weight capacity of 172,500 tons. Because of its pre-eminence in international iron ore trade a brief outline of its operations will be of interest. ORE DEPOSITS OF GRÄNGESBERG The Grängesberg deposits have been known since the Middle Ages, but up to the middle of the nineteenth century the ore was transported from the mines to the furnaces in winter in. sleighs. Railway building began in 1853, and in 1873 the complicated structure of capital investment was tottering, but the basic bessemer process created a demand for ore high in phosphorus, as this is, and refinancing on the initiative of Sir Ernest Cassel put the principal operation on a firm footing. There are numerous property owners in the district, but they are all controlled by a joint administration board, and 90 per cent of the ore is produced by a subsidiary of the Grängesberg company from proper-ties which it either owns or leases. The ore, a mixture of magnetite and specular hematite, is in lenticular bodies, dipping about 70 E. in. fine-grained gneiss, and contains about 61 per cent Fe and 1 per. cent. P. There are two principal veins; the total ore reserves to a depth of 500 meters are estimated at 150,000,000 tons. As seen in the accompanying illustration, the ores were first worked in open cuts, but eventually underground shrinkage stoping was adopted. Difficulties were encountered in the support of the workings and from the freezing of the ore in the stopes, so slicing was adopted, although block-caving is used in one place. Most of the mining is now done at a depth "of 150 to 190 meters. The present annual output is about 1,400,-000 tons of crude ore, which yields about 1,000,000 tons of concentrate after being subjected to magnetic con-centration and jigging.

Jan 1, 1927

By George S. Rice

Those who for the first time see, at a mine, a great hole caused by subsidence; or, going underground, see an extensive fall of roof or hanging wall are apt to regard such an occurrence as an accident and not a normal condition of exhaustive mining. Moreover, the public is inclined to believe that a cave or subsidence of the surface is the result of carelcssness in mining or the rapacity of the mine operators in "robbing pillars," a tern too loosely used in descriptions of coal mining. This belief is fostered by the common-law requirement that an owner of the surface or of surface improvements is entitled to full support of the surface. Court decisions have upheld this law even when that owner has sold or leased the underlying mineral, unless a clause in the sale or lease contract exempts the mining company from paying the owner of the surface for damages that may result from mining. Another reason for this belief is the earlier practice (which is still extensively followed in this country) of leaving all coal pillars unmined, except as they have been thinned by so-called robbing; by not extracting the pillars, the surface may be supported by them for years, perhaps for generations. Inasmuch as the practice of leaving permanently in the mines from one-third to one-half of the mineral is wrong, with respect to conservation of a national resource, it behooves the mining engineers to assemble data and disseminate information on the subject, pointing out that subsidence must follow complete extraction, unless expensive methods of back-filling are employed, such as are used in Germany and France. These methods inevitably increase the cost of mining and the price of the mineral produced. It is popular to speak of "waste in mining" without a realization that much so-called wasting is unavoidable unless subsidence is accepted and provision made therefor where the surface is valuable, or else the only present known alternative of hydraulically placing sand or crushed stone filling in the excavations, at an increased cost of the mineral product to the consumer.

Jan 1, 1923

By George S. Rice

Those who for the first time see, at a mine, a great hole caused by subsidence; or, going underground, see an extensive fall of roof or hanging wall are apt to regard such an occurrence as an accident and not a normal condition of exhaustive mining. Moreover, the public is inclined to believe that a cave or subsidence of the surface is the result of carelcssness in mining or the rapacity of the mine operators in "robbing pillars," a tern too loosely used in descriptions of coal mining. This belief is fostered by the common-law requirement that an owner of the surface or of surface improvements is entitled to full support of the surface. Court decisions have upheld this law even when that owner has sold or leased the underlying mineral, unless a clause in the sale or lease contract exempts the mining company from paying the owner of the surface for damages that may result from mining. Another reason for this belief is the earlier practice (which is still extensively followed in this country) of leaving all coal pillars unmined, except as they have been thinned by so-called robbing; by not extracting the pillars, the surface may be supported by them for years, perhaps for generations. Inasmuch as the practice of leaving permanently in the mines from one-third to one-half of the mineral is wrong, with respect to conservation of a national resource, it behooves the mining engineers to assemble data and disseminate information on the subject, pointing out that subsidence must follow complete extraction, unless expensive methods of back-filling are employed, such as are used in Germany and France. These methods inevitably increase the cost of mining and the price of the mineral produced. It is popular to speak of "waste in mining" without a realization that much so-called wasting is unavoidable unless subsidence is accepted and provision made therefor where the surface is valuable, or else the only present known alternative of hydraulically placing sand or crushed stone filling in the excavations, at an increased cost of the mineral product to the consumer.

Jan 1, 1923

By Eric R. Morgan, J. C. Shyne

STRAIN aging is the name given to time-dependent changes which occur in the properties of cold-worked metals and alloys during storage. These changes are best observed through a study of mechanical properties, as illustrated in Fig. I for low-carbon steel. The effects of strain aging are usually regarded as being detrimental, particularly in deep-drawing steels. For example, an increase in yield strength and loss in ductility lead to buckling and tearing during drawing. At the same time the return of the yield point results in the formation of Luders bands or stretcher strains during the pressing operation. As a result of these effects many attempts have been made to eliminate strain aging from low-carbon steel. The problem still remains, however, because all known methods of preventing strain aging result in a more costly steel. The present work is an assessment of the situation in terms of theoretical, practical, and economic factors and suggests a new solution to the problem. Previous Work According to the Cottrell theory,' strain aging in a-iron may be regarded as the migration of interstitial atoms to free dislocations and the anchoring of dislocations by the resulting atmospheres. It may be concluded that the important factors which will govern the degree of strain aging are the diffusivity, the effective amount of interstitial element in solution, and the time of aging. The diffusivities and effective amounts of carbon and nitrogen in solution in low-carbon rimming steel are such that significant aging occurs in a few hours' storage at room temperature. Strain aging in deep-drawing steels cannot be controlled by controlling the time of aging because in commercial practice this is determined by economic factors concerned with inventories and may be several weeks. The diffusivity of nitrogen is twice that of carbon at room temperature but the diffusivities can be controlled by controlling the storage temperature. The retardation produced by only a 25 °C drop in temperature is significant but the cold storage of large steel inventories is an impractical solution to Table I. Analysis of Base Materials Alloy Pet C Yet 0 Pet N Vac 0.0037 0.052 0.0003 H 0.0044 0.013 0.0008 C 0.06 0.0014 0.0001 the problem. By far the most simple and effective ways to control strain aging are through control of the amount of carbon and nitrogen in solution. This may be effected through alloying, controlled precipitation, or by eliminating the carbon and nitrogen. Consider first the control of the amount of carbon in solution. The simplest approach would be alloy -ing in which strong carbide-forming elements are added. Examples of this approach are the additions of titanium' and niobium9 0 steel. These elements also combine with nitrogen and oxygen and when added in sufficient quantity result in a completely killed and non-aging steel. They are, however, impractical additions because they result in a costly steel. Carbon and nitrogen are often removed from iron on a laboratory scale by annealing in wet hydrogen, but because of cost this process has never been adopted on a commercial scale. In practice the amount of carbon in solution is controlled by the rate of cooling from the annealing temperature (710°C or 1310°F). In commercial box

Jan 1, 1958

Beyond the industrial suburbs of Melbourne to the southeast are brown coal deposits just under the fertile soil of the Latrobe Valley. These deposits rank as one of the wonders of the world. The manner in which this resource is put to use is one of the great engineering accomplishments of our time and also a prime example of Australian elan. The brown coal, with over 60% water content, occurs in beds from 200 to 400 ft thick, under 50 ft of cover. Fifty thousand tons of coal per day move in a nearly continuous stream from mining face to boilers. The power plants supply two thirds of the State of Victoria's requirements, about 800 megawatts. Surge capacity between mine and power plant is sufficient for 12 hr steaming time! Victorian brown coals have been known since the middle of the 19th century. However, it took a strike of bituminous coal miners in 1915 to bring brown coal permanently into the picture as a fuel for power generation. In Australia, power generation is a State function. The great development of brown coals has been under the State Electricity Commission of Victoria.

Jan 10, 1964

By J. J. Egan, A. B. Kinzel, W. Crafts

Advances in the production of quality steel have emphasized the need for greater knowledge of the amount and distribution of oxygen in the steel. Control of inclusion content and quality is largely dependent on such knowledge. While many analytical methods have been devised for the accomplishment of this end, few are without serious limitations in accuracy, convenience, or skill required in application. Usually at least two methods are necessary to determine total oxygen and constituent oxides. Because of the great importance of this problem and the specific interest in the application of such methods of analysis, the various procedures were carefully reviewed at the Union Carbide and Carbon Research Laboratories, with the view of developing a method free from the limitations mentioned above. Intensive experimentation finally led to an improved iodine extraction analysis described by Cunningham and Price.1 After this had been thoroughly checked from the standpoint of the analytical chemist, it was rechecked from that of the metallurgist. This involved preparation of a number of small heats of varying composition with determination of total oxygen in the molten metal by the alumina method2 and an analysis of the solidified material without the aluminum addition by means of iodine extraction; the oxides of iron, manganese, silicon and aluminum also being determined by the iodine analysis. The report of this work constitutes the subject of this paper. The Iodine Method Fundamentally the iodine method is well established. It is based on the procedure first described by Eggertz3 and depends upon the fact that iron, manganese, silicon and aluminum, as well as the metallic constituents of the pertinent sulfides, carbides and nitrides of these metals

Jan 1, 1933

By Stephen L. Bolivar, Susan H. Balog, Thomas A. Weaver

A data-classification scheme was developed to detect potential uranium mineralization in the Montrose l º x 2º quadrangle, Colorado. The methodology developed is a rapid and efficient method of resource evaluation on a reconnaissance scale. The necessary techniques were developed and refined to digitize, integrate, and register various large geological, geochemical, and geophysical data sets for the Montrose quadrangle, Colorado, using a grid resolution of 1 km. All data sets for the Montrose quadrangle were registered to the Universal Trans- verse Mercator projection. The data sets include hydrogeochemical and stream sediment analyses for 23 elements, uranium-to-thorium ratios, airborne geo- physical survey data, the locations of 90 uranium occurrences, and a geologic map (scale 1:250 000). Geochemical samples were collected from 3965 locations in the 19 200 km2 quadrangle; aerial data were collected on flight lines flown with 3-5 km spacings. These data sets were smoothed by universal kriging and interpolated to a 179 x 119 rectangular grid (each grid block is 1 km2). A mylar transparency of the geologic map was prepared and digitized. All possible combinations of three, for all data sets, were examined for general geologic correlations by utilizing a color microfilm output. Subsets of data were further examined for selected test areas. A classification scheme for uranium mineralization, based on selected test areas in the Cochetopa uranium district, is presented. Areas favorable for uranium mineralization, based on this scheme, were identified and are discussed.

Jan 1, 1982

By George Bell

THE mine and milling plant of Demonstration Gold Mines, Ltd., is near the city limits of Baguio, Mt. Province, P. I. The mine road connects with the main highway to Manila. The nearest railway point is near sea level, approximately 40 miles distant. The Baguio district is very mountainous and has one of the heaviest rainfalls in the world. It is therefore difficult to maintain roads or to impound tailings and mine dumps. All supplies are trucked into the district direct from Manila or the nearest railway point, which means uncertain deliveries and high freight rates. Installation of equipment is difficult and costly. The average elevation at the mine is 4000 ft. and the climatic condi-tions.are ideal except for a three months rainy season. The company generates its own power for mining and milling opera-tions with three 400-hp. Ruston Diesel engines direct connected to 250-kw. General Electric alternating current generators. Labor conditions have been excellent, although at present social security laws are causing some unrest. Labor receives a higher average wage rate in this district than other labor in the Islands. The com-pany also furnishes free living quarters, hospitalization and work-men's compensation. Taxation has been reasonable up to the present time, but some of the new mining legislation may make it difficult to operate and pay dividends. The future depends largely upon the continuation of $35 gold and the political outcome in the Islands.

Jan 1, 1939

By Frederick Beckett

WIDESPREAD experimentation has been conducted in recent years to devise a means of preventing intergranular corrosion in austenitic chromium-nickel steels of the 18 per cent chromium-8 per cent nickel type. Additions of titanium to these steels have been used commercially to overcome this difficulty, as advocated by Krupp of Germany, and the latest literature reference concerning improved details of this method is the article by Bain, Aborn and Rutherford.1 Extensive work by the present authors has shown columbium also to be a particularly valuable agent for inhibiting intergranular corrosion. This paper does not deal with steels that are largely or wholly aus-tenitic ; it is limited to a discussion of the results obtained through the use of titanium and columbium in plain high-chromium steels. For many years titanium has been used commercially by some steelmakers as a cleanser, and to a lesser extent as a hardener, but then in greater per-centages. The results of the work to be described disclose that titanium and columbium in proper proportions act as effective softeners in the high-chromium steels. It is well known that chromium intensifies the hardening effect of carbon in steel; it imparts pronounced air-hardening properties within a rather wide range of chromium content; it provides increased ductility in steels of given strength and hardness; and it enhances resistance to corrosion and oxidation at elevated temperatures to a marked degree. However, in applications requiring a combination of some of these valu-able properties great hardness is frequently a detriment rather than a merit. When the objective is a soft and ductile steel having optimum corrosion resistance, the producer strives for a carbon content as low as commercially practicable.

Jan 1, 1933

By Charles D. Hoyt

T IME studies and cost accounting were combined to increase the efficiency of the overall mining method and thereby reduce costs at the Titania mine of the National Lead Co. in southern Norway about 70 miles southeast of Stavanger. From these studies a more effective drilling system was developed, standards were adopted for setting base pay rates, shrinkage stoping was abandoned for open stoping, a new mechanical loading chute was adopted, and the loading and haulage system was changed. Ore minerals at the Titania mine are ilmenite and magnetite; gangue minerals are plagioclase and hyperstene with accessory minerals of biotite, pyrite, chalcopyrite, and spinel. The average content of the ore is 17 pct TiO2 and from 20 to 25 pct iron. The ilmenite crystals contain microscopic lamels of hematite, making it impossible to obtain a high TiO2 content in the concentrate. An ilmenite concentrate with 44 pct TiO2 and 36 pct Fe, and a magnetite concen-

Jan 9, 1950

By Charles B. Dudley

DEAR SIR: It is now nearly three years since my first report to you on the subject of steel rails was written. That report, as you will remember, dealt principally with the question of the relation between the chemical composition and physical properties of steel rails end their power to resist crushing and fracture in actual service. Other matters were referred to or touched upon in that report, but the main question was, Why do some rails crush or break in service while others do not? Yon will doubtless remember that the principal conclusion arrived at was, that the softer rails are less liable to Crush or break in service than the hard ones. Or, in other words, so far as conclusions could be drawn from the chemical analysis and physical test of 25 samples of steel rails which had actually been in service, these conclusions were that those rails which have the smaller amounts of carbon, phosphorus, silicon, and manganese are less liable to crush or break in service than those which have larger amounts of these elements. Or, again, looked at in the light

Jan 1, 1881

By Charles L. Mantell, B. G. Shah

SINCE the beginning of the industry, commercial electrolytic manganese has followed the Shelton patent' among others, which called for the addition of sulfur dioxide in controlled amounts, to a purified manganese sulfate-ammonium sulfate at a controlled pH. Every attempt to eliminate sulfur dioxide additions has resulted in operating difficulties, chiefly solution of the deposited metal and lowered current efficiencies. Many replacements for sulfur dioxide have been proposed and studied, chiefly sulfur compounds, urea, thiourea, and proteins similar to those employed successfully in copper refining. It has been suggested that sulfur dioxide is a re-ductant for higher-valence manganese compounds, or that it is reduced by manganese metal in the deposit to hyposulfites or its compounds, and that these might affect the cathode film or the deposition potential, or the overvoltage of manganese. The additives were studied following the method of Mantel1 and Ferment2 who determined the feasibility of current-potential curves as an analytical tool for monitoring manganese elec trowinning solutions for metallic impurities: nickel, cobalt, silver, copper, zinc, molybdenum, cadmium, magnesium, and sodium. The individual effect of each on the standard polarization was determined for a range of concentrations. Not all affected the polarization curve; cadmium, magnesium, and sodium had no effect. Nickel, cobalt, silver, copper, and zinc yielded a correlation between transition current and concentration of impurity.

Jan 1, 1968

By David W. Brunton

From the old-fashioned " grab-sample " to the modern timing-device, which takes a machine-sample with mathematical precision, there is a wide gap, which was only crossed by many years of toil and unremitting endeavor. Even to-day, notwithstanding the advancement in the art, " grab-sampling " is still practiced—sometimes to afford the unscrupulous mine-promoter a basis for fairy-tales with which to entrap the too-gullible investor, and often by milling and smelting companies to determine the amount of moisture in custom-ores. The latter practice is almost as reprehensible as the former, and it causes more trouble and ill-feeling between seller and buyer than all other factors put together. -NO reputable concern to-day would think of attempting to determine by grab-sampling the amount of gold, silver, lead, or copper contained in an ore, and yet many buyers expect the miner to accept the results of grab-sampling in the determination of the amount of water contained in the ore, forgetting that accurate results are just as necessary here as in the determination of the metals, because the result determines the percentage of weight of the ore which shall be excluded and considered to have no value whatever. Samples for the determination of moisture should be taken with as great care as samples for the determination of metallic content, and in order to avoid the extra expense of a separate operation moisture-samples should be taken from the sample-safe. As the sample reaches the sample-bin in a smaller stream and by a more circuitous route than the " reject" travels in its path to the outgoing car, it loses more moisture en route, and a constant should be added to compensate for this difference. Carefullg ,con ducted experiments have shown that the differ.elice in loss of moisture between the two routes does not exceed 10 per cent. in summer and 7 per cent. in winter. For instance,

Jan 1, 1910

By David B. Morris, Paul I. Eimon

Computer-assisted data storage and retrieval in the geosciences is coming of age. A growing awareness of the need of the geological and mining community for effective access to existing data has triggered studies and development programs on many levels; governments, professional societies, industrial concerns, and the academic world are all active in this field. Developments in the past decade in computer hardware and software lend hope to the geoscientist searching for a means of expediting the flow of data. The new concern of the earth sciences coming together with the blossoming child of technology, computing, has led to serious study of the geoscience information problem. Active system development is under way in several areas. The papers presented at this Symposium effectively sample the spectrum of present day activity in machine-based geologic data storage and retrieval. These papers show the reader where the action is in this field today. Both long-range studies and plans and operational systems are discussed. Several studies and research efforts have been undertaken on a national or international scale. Robinson discusses the activity of the international geological community in these Proceedings. He speaks from a position of authority as Chairman of the International Union of Geological Sciences' Committee on Storage, Automatic Processing and Retrieval of Geological Data. A study of a "coordinated information program for geological scientists in the United States" documented by Smith, et al.1 proposes a "long-range information program ... responsive to the entire geosciences community . . . (to) draw on the best of large-scale information systems technology." The European geologic community is embarked on project Geosemantica 70, started at the Ecole Nationale Superieure des Mines de Paris. Dixon discusses some results of this work in a following paper. The Canadian study of geological data storage and retrieval on a national scale is reported in a volume edited by Brisbin and Ediger.2 The Canadian report presents detailed recommendations for recording and coding geologic data for automatic process-

Jan 1, 1969

By C. C. Miller, A. B. Dyes

The cost of finding and developing new reserves is continually rising. We must meet these rising costs with more economical operations. This can he accomplished if we revise our ideas of proper well spacing and well allowable to consider the concept of optimum well spacing. According to this concept, the optimum spacing is the one which leads to the maximum present worth for a reservoir when ail factors affecting total cost and total revenue are considered and when the wells are produced in the most eficient manner. Application of this principle efficiently utilizes available well potential and properly considers the recovery eficiency in addition to fixing the spacing on the basis of the amount and value of the oil to he recovered. This Study presents an analysis of one producing zone containing low gravity crude to illustrate the effect of these factors on the present worth and on the optimum economic spacing under two production drives—-evolved gas and water drive. The maximum present worth occurs when the optimum number of wells for open-flow operation is employed. Frequently, this optimum development cal1s for very wide spacing and the ideal field rates are not unreasonable. Under other circumstance. where proration is necessary, an optimum combination of well spacing and well allowable exists which permits production at relatively high rates. The optimum well density in a field depends on the recovery efficiency and the valule of the oil. In solution gas-driven reservoirs this optimum spacing for operation at high producing rates can vary from extremely wide spacing to handle viscous low gravity oil in thin formations to relatively close spacing in thick sands where good recoveries are expected. Because of the better recovery from water-driven fields, the optimum spacing in these fields is closer than in solution gas-driven fields. Also, the water encroachment pattern is dependent upon the well spacing, and an adequate numher of wells is needed to assure a good sweep eficiency. The economic optimum well density in a water-driven field is high enough for this purpose. INTRODUCTION From year to year domestic oil becomes more difficult to find. The fields we do locate are frequently smaller and deeper than older fields and the costs for men, material and equipment are continually rising. To replenish our reserves we must continue to search for and develop new fields, but experience has shown we cannot expect prices to rise in proportion to costs. Consequently, we must meet increasing costs by more economical operations. A vigorous effort is being made within the industry to improve exploration methods, to cope with the problems of deeper drilling, and to obtain a secondary yield from older fields. Many significant contributions have resulted from these efforts. The economic operation of new fields can be further improved by developing these fields on optimum spacing and producing the wells at higher rates. This would avoid the drilling of unnecessary wells and provide additional capital for seeking new oil. While the benefits of these practices are obvious, the problem of defining the optimum development of a field for natural depletion can become very complex. A study of the effect of well spacing and several reservoir variables on economic worth of a specific field is reported here to illustrate the problem and to show the magnitude of the benefits to be realized. This study is necessarily limited to the field conditions selected and is not intended as a general solution of the well spacing problem. It does, however, indicate factors to be considered, the trends to be expected, and the direction in which we should proceed in developing new fields. NO consideration is given to land and legal considerations which might arise. METHOD OF ANALYSIS The optimum method of developing and producing a field is to use the combination of spacing and prora-tion which gives the maximum return. In addition, we do not want to lose recovery. These considerations of maximum return and maximum recovery present no serious conflict. The value of each method of operation is conveniently expressed in terms of its present worth. According to the present worth method of evaluation,' an acceptable annual percentage return is assigned to the operation, and all incomes, capital costs, and expenses are discounted at this rate to the start of the operation. This net value is the present worth. If we apply the same discount rate to several alternate methods of operation, the one yielding the greatest present worth is the best method. If we express net income in terms of price per barrel of oil produced, drilling and equipment costs on a well basis, and expenses as cost per well year, this evalu-

By Clarence Zener

Theoretical considerations by one of the authors have ledl to the prediction that the dynamic internal friction of annealed metals has a broad maximum at a certain grain size. This prediction they have verified2 for alpha brass. In the present paper the theory is extended to include the precise manner in which the internal friction varies with grain size on either side of the maximum. New experimental data are presented to test this extended theory. The physical basis for the type of internal friction that is being investigated lies in the interplay between stress and temperature. Just as local fluctuations in temperature give rise to local fluctuations in stress, so likewise fluctuations in stress give rise to fluctuations in temperature. But temperature gradients give rise to necessarily irreversible thermal currents, and hence to internal friction. The theory for this type of internal friction has been developed quantitatively,³ and has been experimentally verified,4,5 for the particularly simple case of the transverse thermal currents accompanying transverse vibrations. Of more fundamental importance are the intercrystalline thermal currents accompanying all types of vibration. The variation in stress across grain boundaries arises from the elastic anisotropy and at least partial random orientation of the individual crystallites. An exact quantitative treatment of the internal friction due to these thermal currents is of course out of the question. However, much information can be obtained from general arguments.1,6 Thus when the frequency of vibration f is low, or when the grain size d is small, adjacent grains remain nearly in thermal equilibrium, and vibration proceeds isothermally with little internal friction. Again, when the frequency is high, or the grain size large, the heat flow per cycle is small, the vibration proceeds adiabatically with little internal friction. The internal friction will become a maximum in the transition region. The degree of adiabatic-

Jan 1, 1940

By Clarence Zener

Theoretical considerations by one of the authors have ledl to the prediction that the dynamic internal friction of annealed metals has a broad maximum at a certain grain size. This prediction they have verified2 for alpha brass. In the present paper the theory is extended to include the precise manner in which the internal friction varies with grain size on either side of the maximum. New experimental data are presented to test this extended theory. The physical basis for the type of internal friction that is being investigated lies in the interplay between stress and temperature. Just as local fluctuations in temperature give rise to local fluctuations in stress, so likewise fluctuations in stress give rise to fluctuations in temperature. But temperature gradients give rise to necessarily irreversible thermal currents, and hence to internal friction. The theory for this type of internal friction has been developed quantitatively,³ and has been experimentally verified,4,5 for the particularly simple case of the transverse thermal currents accompanying transverse vibrations. Of more fundamental importance are the intercrystalline thermal currents accompanying all types of vibration. The variation in stress across grain boundaries arises from the elastic anisotropy and at least partial random orientation of the individual crystallites. An exact quantitative treatment of the internal friction due to these thermal currents is of course out of the question. However, much information can be obtained from general arguments.1,6 Thus when the frequency of vibration f is low, or when the grain size d is small, adjacent grains remain nearly in thermal equilibrium, and vibration proceeds isothermally with little internal friction. Again, when the frequency is high, or the grain size large, the heat flow per cycle is small, the vibration proceeds adiabatically with little internal friction. The internal friction will become a maximum in the transition region. The degree of adiabatic-

Jan 1, 1940

By C. P. Davenport, Garth Duell

What are the projected electrical power needs of the nation and of the Northwest during the next 15-20 years? No one who has researched the subject has reached a substantially different result than the following simple conclusion: electrical power requirements are doubling every decade. There are some who question the necessity of a power company's need to install capacity every ten years equal to what it has done during its entire previous history; there are even those who would argue that such growth should be arbitrarily curtailed. However, a power company must, by law, meet its responsibilities of providing the energy the public expects when the switch is thrown.

Jan 10, 1972