Search Documents

By T. F. McCormick

THIS year, 1950, is the golden anniversary of the construction and operation in this country of a tube mill for the sole purpose of fabricating aluminum alloy tubing. For a short period prior to the beginning of this mill, aluminum alloy tubing was obtained from foreign sources or produced in mills fabricating other metals. Indeed, it was a very short period because aluminum itself was a newcomer in the field of metals. The first sheet rolling mill had been in operation just eight years and a rod rolling mill for the production of wire and cable had been functioning one year. The first tube mill for aluminum was built by the Aluminum Co. of America in May 1900 and started production with four draw benches and five men, including the mill superintendent. The building itself was a lean-to attached to a sheet-rolling mill at New Kensington, Pa. The cost of equipment, including the draw benches, dies, mandrels, and other tools, was about $5000. This figure seems absurd in the present day but nevertheless it was questioned at that time whether or not such a large sum should be spent to embark on a new and uncertain venture. The initial production system for the new mill consisted of casting round hollow ingots in a tilting-type iron mold, reducing the ingots to bloom size outside the plant, and finally drawing to size on the draw benches. This method of producing aluminum alloy tubing survived just two years, as blooms of satisfactory quality were not obtained consistently. It was superseded by the cupping method in which a 24-in. diam circle cut from a rolled plate was formed into a tube bloom using first a small cupping press and then a push bench. It was stated that tubing so produced was limited to a maximum diameter of 2 3/4 in. and to wall thicknesses varying from 12 to 24 gage. However, for the first time all the operations were performed at one plant and the result was a quality product. Later larger cupping presses and push benches were obtained and the method continued to be the principal one for aluminum alloy tubing for almost a quarter of a century. During the interim the use of a Alan Mannesmann -type billet piercer was explored and it was used to some extent, but failed to produce consistently a smooth inside surface suitable for drawing with aluminum alloys. Experiments started during the latter stages of World War I in the production of tube blooms with a hydraulic extrusion press, led to the use of this type of equipment to make tube blooms for further drawing during a change-over period extending from 1925 until 1930. At this time the cupping method was discarded completely. From these humble beginnings, the aluminum alloy tubing business expanded until well over six million pounds were produced in a single month in the United States during World War II. The major portion of this production was in strong alloys which did not appear in the tubing picture until 1022, when 17S alloy tubing was introduced for aircraft construction.

Jan 1, 1951

By Larry J. Tucker

INTRODUCTION The orebody at Pea Ridge strikes NE-SW and dips at about 800 to the SE. The ore and surrounding rocks are Pre-Cambrian in age. These rocks are usually very competent. Locally strong jointing has caused problems and toward the hangingwall dikes have caused particular problems during or after the open stoping phase of production. About 396 m of sediments lie over the ore. The shape and mineral content of the orebody has been fairly consistent so far with production areas lying from the 1375 to the 2475 levels. The deeper limits of the ore- body haven't been found yet. The ore is high grade magnetite with a strike length of over 600 m and a maximum width of over 180 m on some levels at the center of the orebody. Production at Pea Ridge for the first three years of operation came from two types of open stopes. The original stopes were recovered with horizontal production rings being drilled and blasted from vertical raises. Later a more typical sublevel stoping method using vertical production rings from one or more drilling sub- levels was used. There were a number of reasons for the selection of open stoping as the initial production method at Pea Ridge. First, it was judged that the ore was not of a block cave quality. After fifteen years of production, this assumption can be verified. There was some concern during the planning days for the potential for high flow rates of water into the mine from aquifers in the sediments lying over the orebody. Dewatering wells from surface and underground were put in as a precaution and nothing came of this potential problem. Open stoping and its resulting pillar structure put off this problem by supporting the sediments a few years longer. For a moderate investment in level development some production from open stoping was quickly realized. The first open stopes were brought in on what was then the bottom mine production level (2275), near the shaft pillar and situated on the footwall. This production practice of stoping on the heels of development from shaft pillar westward and from footwall to hangingwall continued through the open stope phases of production at Pea Ridge for many years. From the standpoint of mine efficiency and pillar stability, this would not seem to be a recommended mining practice. 74 570 w electric slushers, using 1.37 m dippers, pulled the open stope ore out into 18 ton bottom dump cars. Ordinarily five of these cars made up a train, which was pulled to the dump area by a trolley powered electric locomotive. Open stoping had the disadvantage that 100% of the recoverable portions of the orebody had to be developed in order to recover 33% of the ore. 67% of the ore was left behind in a large pillar system. For many years we had no planned method for recovery of these pillars. Mining methods are of course, limited by the existing technology. Advancing technology, coupled with the limited production capabilities of open stoping, low efficiencies and high relative cost early in the history of the operation recommended that other mining methods be looked at. In Sweden, considerable practical experience, coupled with a large amount of theoretical work had become available on sublevel caving. To Pea Ridge it offered the apparent benefits of: 1) The flexibility of diesel powered trackless haulage. 2) The efficiency of two machines to one operator on longhole drilling. 3) A multilevel production picture with a large number of drawpoints for ore recovery. 4) 100% recovery of the mineable portion of the orebody in one production pass, with no pillar recovery problems left behind. This paper outlines the experiments and experiences which Pea Ridge has gone through with sublevel caving from 1967 to this date.

Jan 1, 1981

By C. Elbaum

Specimens consisting of several crystals, each with a prescribed geometry and a controlled orientation with respect to both the extermally intposed stress and the highboring crystals, werer deformed in tension at room temperature. It is shown that the influence of a grain boundary on the plastic defolrmation of a mullicrystal depends on the extent to which the presence of the grain boundary, contributes to the necessity 01. multiple slip in the component crystals. MANY investigations were carried out in the past on the plastic deformation of aluminum single crystals, bicrystals, and polycrystals. The various studies of bicrystals aimed primarily at elucidating the influence of grain boundaries on the mechanisms of plastic deformation. In the earlier studies the emphasis was placed primarily on finding the "strength" contributed by a grain boundary. In more recent investigations it became apparent that the grain boundary does not contribute any strength per se but rather acts by influencing the mechanism of plastic deformation in the adjoining grains. The concept thus emerged of the plastic properties of a bi-crystal, and by extension of a polycrystal. depending solely on the mechanism of deformation prevailing in each grain. The contribution of the grain boundaries thus becomes limited to the type of restrictions imposed on each grain by its neighbors. The present investigation of the behavior of specimens consisting of more than two crystals was designed for the purpose of studying the influence of the grain boundary in simple aggregates. The findings of this study further support the concept that the restriction imposed on a deforming crystal by its neighbor constitutes the predominant factor in the plastic deformation of polycrystals. The term "multicrystal", in contrast with single and polycrystals, is used to describe specimens consisting of several crystals. Each one of the component crystals has a prescribed geometry and a controlled orientation with respect to both the externally imposed stress and the neighboring crystals. Two groups of multicrystals were prepared. All the component crystals of both groups of multicrystals had the axial orientation (isoaxial multicrystals) shown in Fig. 2, with the primary slip plane and slip direction both at 45 deg to the specimen axis. In the first group (hereafter referred to as group I) the component crystals were symmetrically oriented with respect to the plane of the grain boundary; the primary slip plane and slip direction were respectively at an angle of 60 and 30 deg to this plane. For the second group (group 11) the axial orientation remained the same and the relative positions of the primary slip plane and slip direction are shown in Fig. 3. EXPERIMENTAL METHODS The material used was aluminum 99.993 pct pure, according to the manufacturer. The specimens were produced by growth from the melt in a horizontal graphite container. In order to maintain the prescribed geometry of the individual crystals of a multicrystal, a technique described elsewhere was used.' The specimens were grown under a small, positive pressure of helium at a rate of approximately 1 mm per min. annealed in air for 24 hr at 640°C and cooled over a period of several hours to room temperature. All the multi-crystals were rectangular in cross-section, 6 by 18 mm (see Fig. 1) and from 150 to 170 mm long. In each group bicrystals, tricrystals and quadru-crystals were prepared as shown in Figs. 1 and 4.

Jan 1, 1961

By P. Nelson, K. L. Gunsallus, A. R. Ingraffea, J. F. Beech

INTRODUCTION Fracture toughness, KIC, is an intrinsic material property and is a measure of the energy required to create new surface area in a material. Fracture toughness measurements can be made for a wide range of rock types (Ouchterlony, 1980). As a measure of energy of comminution, fracture toughness might be used for more sensitive predictions of Tunnel Boring Machine (TRM) performance than are possible with other index measures in current use. This paper describes part of an ongoing, comprehensive, analytical/experimental program aimed at evaluation of KIC in such a role. The program includes efforts to: 1. Provide a firm analytical basis for a test specimen geometry: the core-derived short-rod. 2. Develop simple, inexpensive testing equipment and techniques. 3. Evaluate the accuracy of the above by testing rock and other materials and comparing the measured fracture toughness with those obtained by other methods. 4. Measure fracture toughness of a substantial number of different rocks from three ongoing TBM projects. 5. Compare fracture toughness results with other strength measures. 6. Compare all test results with observed TBM performance in the three projects. Presented here are summaries of all but the last of these efforts. Comparative evaluation of KIC as a more senstive rock property for TBM performance prediction will be the subject of the oral presentation and a subsequent paper.

Jan 1, 1982

By W. S. Ayres

[Secretary's Note.—At the Spokane meeting of the Institute, in discussion of President Brunton's address on "Modern Progress in Mining and Metallurgy in the Western United States," and at the request of members present, Mr. Ayres gave an oral account of his new separator, which is here published as an independent paper, partly because of its inherent importance and partly because it describes an improvement which did not originate in the Western United States, and therefore does not fall, strictly speaking, under the title of President Urunton's address.—R. W. R.] A brief history of the growth of the anthracite-coal preparation will give a better view-point from which to judge the present problem of separating slate from coal. At the beginning of the commercial value of anthracite, 70 years ago, only the pure portions, or " splits," of the veins were mined and shipped to market, and without any preparation or screening other than the selection, while loading, of the glassy lumps, and the rejection of the fine material and the slate that had strayed accidentally into the coal. The next step was the crushing or breaking of the coal (hence the name "breaker" as applied to the preparation-building), and the sizing of it by means of bars or revolving screens. This stage of its development marked the advent of the " breaker-boy " as a slate-picker, with his ever-increasing capriciousness. As the richer veins or a splits " became exhausted and the market demanded a still greater output, the less-pure " splits " and the thinner veins were utilized to produce the coal. Carrying as they do a far greater percentage of impurities, particularly when removing the pillars, it became necessary to build new and better equipped preparation-plants. Finally, we are now at the highest stage of complicatioii yet known to the art of coal-preparation. We are dealing with varying specific gravities, frictional difference, hardness, structure, and form in the pieces of coal and slate coming from many different veins, and

Jan 1, 1910

By F. D. Rosi

The slip and twinning behavior in extended titanium crystals were studied in some detail. The formation and appearance of coarse kink bands are discussed. Their crystallographic geometry was determined by X-ray analysis. A phenomenological interpretation of the complexities in kink band development is also presented. The critical resolved shear stress, coefficient of shear hardening, and plane of fracture were determined for several crystals extended at room temperature. THE slip and twinning elements observed in the room-temperature deformation of titanium were enumerated in a previous paper1 in which considerations were advanced regarding the nature and selection of these elements and their effect on the known mechanical properties of this metal. The present study concerns the crystallographic, microscopic, and mechanical aspects of flow in relation to the slip and twinning elements, and includes a prediction of slip systems, nature of slip and twin markings, inhomogeneities of plastic flow, and stress-strain characteristics. Unless otherwise noted, arc-melted titanium sponge (99.77 pct) was used in these experiments. The method of production of crystals, their dimensions, and the surface preparation for micrographic examination have been reported.&apos; For obtaining stress-strain characteristics, only those crystals which traversed the entire width of the specimen and were at least 8 mm in length were used. Tensile deformation of the crystals was performed with conventional grips for sheet specimens and a constant-stress loading beam, designed after the method of Andrade and Chalmers.&apos; The specimens were loaded by allowing sand to flow from a reservoir into a bucket suspended from the longer end of a balanced 6:1 lever arm at a rate controlled to load the specimen approximately 2 kg per min. Strain measurements were made using the Baldwin SR-4, bonded, resistance-wire strain gage, Type A-8, which permitted a reading accuracy of 2 microinches per inch. The formulas used in the evaluation of shear stress and shear strain, as in deriving the coefficient of shear hardening, are given by Schmid and Boasv n terms of the original orientation and change in length of the crystal. For calculating the critical resolved shear stress, the standard equation was used. The crystallographic nature of the unpredictable slip observed in a number of specimens was determined by the single-surface X-ray method of analysis as described in ref. 1. Experimental Results Prediction of Slip System: It was reported&apos; that room temperature slip in titanium takes place predominantly on {10i0} and in a <1120> direction, giving three potential slip systems. Hence, it should be possible to predict the operative primary system in the manner used by Taylor and Elam&apos; for alu- minum (i.e., the one with the greatest component of shear stress in the direction of slip). The stereo-graphic construction in Fig. 1 shows that this is true. In all cases, slip was found to occur initially on the (0110) plane and, in a number of cases, in the [21f0] direction. (The direction of slip was not determined for all orientations.) It follows that duplex slip can be expected when two slip systems are geometrically equally favorable for slip, as demonstrated in Fig. 2. In both crystals slip took place simultaneously on the (1700) and (olio) prismatic planes, as indicated by Fig. 2a and b. In the case of crystal B the movement of the specimen axis with increasing extension was toward the (10i0) direction, which represents the stable end orientation resulting from alternate slip on the [2ii0] and [1120] directions. This is analogous to the duplex slip process in face-centered cubic metals." Unpredictable Slip: In a number of crystals whose orientations were well within the operation of a single slip system, secondary slip occurred on planes not predicted by the criterion of maximum shear stress. Examples are shown in Fig. 3. In addition to

Jan 1, 1955

By Roswell H. Johnson, W. E. Bernard

To know the rate of declinc of oil wells is very important, yet ordinarily we are prevented from getting this rate because the oil from several wells is put into one or a few tanks as soon as the wells have been connected to the power. The object of doing this is economy of tanks, pipes, labor, and accounting. But we are making a great sacrifice for this small economy. The advantages of the individual records are that we would know better: 1. When the well has ceased to be profitable. 2. When a well has gotten into bad condition. 3. The real record of the yield per acre and the rate of decline of the wells. The lease total is too mixed as to age of the wells for existing records to have much significance. To obtain such individual well records and more accurate logs are the great desiderata of satisfactory management of oil properties. 4. Which wells show the slowest decline—information which is valuable in locating new wells or purchasing adjoining leases. The truth of this statement is evident, when we reflect upon the large number of purchases of producing property. Intelligent appraisal is of the utmost advantage and it is impossible without individual well-pro-

Jan 1, 1918

By Otto C. Kopp, Thomas B. Crattie, Dennis R. Owen

Whole-rock analyses of limestones, fine-gralned dolostones and coarser-grained dolostones adjacent to mineralized breccias (Coy mine, Mascot-Jefferson City district) were compared with similar lithologies adjacent to apparently non-mineralized breccias at the new Thorn Hill section located approximately 39 km north of the Coy mine. Specimens were analyzed for Ca, Mg, Si, Al, K, Fe, Mn, Sr, Br, C1, S, Ti and P using X-ray fluorescence analysis. The concentrations of the major and most minor elements for Thorn Hill specimens fall within the range of concentrations for Coy mine specimens; however, significant differences (probability < 0.05) were noted for Fe, C1 and Br for fine-grained dolostones and for MgO, Fe and Mn for the coarser-grained dolostones. No significant differences were detected for the limestones.

Jan 1, 1985

ROSWELL H. JOHNSON,* Pittsburgh, Pa.-The industry, I think, has suffered very severely from the lack of just such work as has been done by Messrs. Lewis and Beal. I think we owe a great deal to the Bureau of Mines for at last undertaking this much needed work, even though it is so belated. It could have been of very great assistance in so many properties where its usefulness has now passed. I think it is perhaps well to sound a note of caution, owing to the fact that so much of this information was derived from eastern Oklahoma; but with the new bulletin giving the decline for many fields, there will be far less danger of falling into error through assuming too much uniformity. The cumulative percentage curve seems to &apos;me to be a. particularly splendid idea. It should have a very important -influence, especially as the authors have themselves pointed out several variables that ought to be taken into consideration. The thickness, I think, is going to be an especially important one to work out along the general lines of method that they have advanced. Probably the most surprising thing in the paper is the general rule that the decline of a well is more correlated with its size than with its age. I can&apos;t help but think that that generalization, important as it is, is rather rough and will not apply so clearly when we have a larger number of fields before us. Still the generalization, rough as it is, is of very great importance, since the industry has been very largely basing a great many of its ideas on the ignorance of that principle. It leads to certain corollaries that are of great consequence. The first is that the undrilled portion of the property must be appraised on a. different basis from that used for the drilled portion.

Jan 4, 1918

By Oliver Bowles

WHEN a new type of equipment revolutionizes methods of quarrying one kind of stone, producers of other kinds focus their attention on its potentialities in their particular fields. The purpose of this paper is to discuss the accomplishments of the wire saw in slate, to show its more limited attainments in other kinds of stone, and to point out the possibili-ties of much wider application. A wire saw consists of a 3/16-in. or 1/4-in. three-strand wire cable that runs as a belt and cuts the rock by abrasion. (Fig. 1.) The teeth of the saw are sand grains carried in the grooves between the strands.

Jan 1, 1936

By William P. Blake

THE use of diamonds upon a large scale in drilling rocks, and the substitution to a certain degree of rotary diamond drills for the ordinary steel percussion drills, marks a new era in the art of mining. Since the invention by Leschot of the diamond drill, it has steadily advanced in its utility and range of application, and in the appreciation of miners and engineers. It must be claimed as one of the many gifts of science to the arts ; and it is, in particular, one of the fruits of the scientific education given at the Ecole Centrale, at Paris. Members are all, doubtless, more or less familiar with the construction of the drill and of the machinery by which it is applied in boring. It is, therefore, my present purpose only to direct your attention to some recent marked improvements, made by the American Diamond Drill Company, by which the economy and efficiency of the machines have been increased. Form of Bit. The annular or ring form of the drill-head or bit was, I believe, the earliest; and it is still in use, without essential modification, wherever it is desired to obtain a sample "core" or specimen of the rock traversed. But for mere drilling, regardless of the preservation of a test-core, a solid-head bit is preferred, except for very large holes. Until recently, these solid-head bits were made with a pointed cutting face shaped like an obtuse cone. This form was assumed to be the best, being most in accordance with the experience obtained with percussion drills. It is found, however, that the exact reverse

Jan 1, 1873

A GREAT and incomparable speculation is whether the discovery of A compounding the powder used for guns came to its first inventor from the demons or by chance. With this invention he certainly far surpassed all men of every age from the creation of the world up to that day when it was announced by him-men so very learned, indeed like angels and of divine intellect, powerful in every knowledge and power. These had not only revived-arts and sciences and discovered new ones with their intellects, but they had information about all natural

Jan 1, 1942

By E. DeGolyer

PROSPECTING for new deposits is a part of the ordinary routine business of the petroleum industry to an extent that is not true for any other mineral industry. The health of the industry depends upon whether we are successful or unsuccessful. How many know what it costs to find oil today and what it has cost in the past? Very few, I will wager. The industry is not well informed upon this extremely important point. We cannot deal in averages for lack of information. Does it cost more or less than previously? Prospect wells are increasingly deeper and, since the introduction of the core drill, prospecting techniques have required increasingly expensive field oper-

Jan 1, 1939

SMELTING is a thing essential to the end for which ores are sought, for without it every ore is a useless stone. This art is especially needed by those who, drawn on by hope, have mined ores in large quantities with great expense and effort. For this reason it is worth while to use one&apos;s wits and, if ordinary ways should not suffice, to consider how to find new ways of smelting the ores in order to extract the metals and to purge them of their earthiness. For this reason I shall now tell you of blast and other furnaces, and I shall also tell you, in order that you may be warned, that whoever wishes to do this well must first look at the nature and quality of the ore. You will already have had enlightenment on this from the experiments on assaying and with this as guiding star it is necessary to make ingenious structures and to provide for-the other needs as necessary, for one ore requires iron and another lead. Since I have already spoken of these in their own places on their ores, it is not necessary at present that I repeat, but here I wish to speak only of copper ore as a companion of silver and gold, and of where art is most required and where difficulties chiefly appear. For these things a machine must be built that is convenient to a good water supply in order to continue the work more easily. Its wheels should be large and easily moved, constructed in such a way that the force of the water lifts the bellows that are placed at the tuyère to direct the blast inside the furnaces that are to smelt the ores. For this, attention must first be given to the site of the machine, the quantity of water, and its fall; then to the wood for building the machine and for making charcoal; then to the stones that are used for the blast furnaces; then to the provision of good bellows that are wide, long, and full in their sides and made of cloth, for the better these are, the more they quicken the power of the charcoal

Jan 1, 1942

By Frederick C. Hull

THE grain size of a metal or alloy is one of the most important factors determining its properties. In steels, for example, grain size affects hardenability, toughness and machinability; in brasses, grain size is related to hardness and deep-drawing quality. In the field of heat-resistant alloys, grain size has a marked effect on ductility, creep and endurance strength. In order to determine these effects, as well as to control the properties of materials, many accurate and rapid measurements of grain size must be made. This paper presents a new and improved method for the estimation of grain size. USUAL METHODS of EVALUATING GRAIN SIZE A frequently used method of estimating grain size is that of comparing the image of a polished and etched specimen on the ground-glass screen of a metallographic microscope with standard grain-size charts. Several types of standards are available for use with different classes of microstructures. Geometric Grids.-The Metals Handbook1 has a series of hexagonal grids ranging in size from ASTM No. I to 8. Idealized Grain Networks.-Idealized grain-boundary networks for ASTM grain sizes I to 8 are included in the American Society for Testing Materials Tentative Standard E19-39T. Standard Micrographs.- The Metals Handbook and ASTM Tentative Standard EI9-39T contain micrographs of hypoeutectoid and hypereutectoid steels ranging in grain size from No. I to 8. The grain size of annealed brass (diam¬eter of the average grain in millimeters) is obtained by comparison with 10 micrographs of varying grain size in ASTM Tentative Standard Es-39T. A handicap to accurate evaluation of grain size by this method is the fact that it is difficult to compare photographs in a dimly lighted room with the image on the ground-glass screen, or, if the general illumination is increased so that the printed standards may be clearly seen, the contrast of the image of the unknown is decreased. It is easier to estimate grain size by comparing a micrograph of the unknown with the grain-size standards. However, photographing every specimen on which the grain size is desired is too costly in time and materials to be practicable. For hardened steels, the Shepherd or Jernkontoret fracture grain-size standards are very accurate and useful, but this method obviously cannot be applied to ductile alloys such as brass, stainless steels and austenitic heat-resistant alloys. Jeffries&apos; method for grain-size measurements consists of counting the number

Jan 1, 1947

The first National Industrial Conference was disbanded without accomplishing the results hoped for. A second conference is to be called in the near future. In response to suggestions of members of the Founder Societies, the following telegram was sent, Oct. 29, to the President and each member of his cabinet. "Engineering Council respectfully recommends appointing on new Industrial Conference two or more engineers familiar with industrial problems. Council represents five national societies of professional engineers having forty-one thousand members. Washington office in McLachlen Building."

Jan 12, 1919

By William D. Mayercheck

Introduction of continuous mining machines in the late 1940s created a new production bottleneck in room-and-pillar sections-the shuttle car. While continuous miners could cut and load coal at a nearly constant rate, the mining sequence was repeatedly interrupted as fully loaded shuttle cars changed places with empty ones. This wait-for-the-shuttle delay period forced the coal industry to reassess the shuttle&apos;s batch-type procedure with an eve toward continuous haulage systems that would allow uninterrupted coal flow from face to portal.

Jan 7, 1979

By William Kent

Mr. ASHBURNER&apos;s paper on the Classification and Composition of Pennsylvania Anthracites, read at this meeting, well shows the need of new and accurate determinations of the heating value of these coals. A similar need exists for the determination of the value of bituminous coals, since the variation in quality of the latter is greater than the variation in anthracites. The recent extensive use of liquid and gaseous fuels, " patent" fuels, tan-bark, and other refuse fuels, also makes a necessity fix some correct method of determining the relative values of each of these fuels. Mr. Ashburner has recommended that tests of coals should be undertaken by the Second Geological Survey of Pennsylvania, and Professor Dewey, as stated in Mr. Ashbnrner&apos;s paper, has suggested a plan for tests of American coals, by the Smithsonian Institution, for which an appropriation by Congress will be asked. It is to be hoped that if any extensive series of tests of coals is carried on under either Government or State auspices, the erroneous methods of test which were followed by Professor Johnson in 1842, and by Quartermaster-General Meigs in 1882, will not be adopted.* The first requisite in determining the heating-power of a fuel is proper apparatus, such as has not been used in any of the tests of American coals yet reported. In the hope that more accurate means may be used in future tests, the writer desires to call attention to an apparatus which he has designed for the purpose. Not having had opportunity for making a trial of it, nor even of having it criticised by others, he does not offer it as the best possible apparatus; but if it contains any points of value, and leads to the design of still more suitable devices by others, the object of the presentation of this paper will be accomplished. The tests by Professor Johnson and General Meigs were made by evaporating water into steam in ordinary steam-boilers. A steamboiler of ordinary construction is not a good apparatus for determining the heating power of a fuel, for the following reasons:

Jan 1, 1886

By E. W. Mehal, R. H. Cox

A planar Gunn oscillator was developed for use in a monolithic microwave integrated circuit. The device was designed to operate in the frequency range of 20 to 30 GHz with a continuous wave output. Selective epitaxial deposition was used to form the n+n-n+ device structure in (111)-B semi-insuluting GaAs. The active n- region was about 5 µ thick and was doped to about 2 x 1015 electrons per cu cm by the reactor background. The mobility was -5000 sq cm v-1 sec-1. The n+ epitaxial deposits were doped to 1 x 10" electrons per cu cm using S2Cl2. Planarity of the three DURING the past few years, new microwave devices in discrete form have been developed utilizing GaAs. The next logical step is to combine these devices in a successive deposits was quite good; total overgrowth was less than 1 µ. Metal ohmic contacts were applied to the n+ or n- regions using a Ag-In-Ge alloy. The n+n-n+ devices had symmetric IV characteristics and could be operated C. W. for both directions of device bias. Metal ohmic contacts made directly to the n-region always Produced asymmetric devices. C. W. operation was obtained over the 22 to 28 GHz frequency range. The best performance obtained was 1.5 mw C. LV. output at 28 GHz. microwave integrated circuit. A potential application would be a radar receiver operating in the millimeter wavelength region. The key component in such an integrated circuit is a microwave oscillator, recently described by Gunn.1, 2 Under the influence of a large electric field, high-resistivity GaAs exhibits a bulk negative resistance, and high-frequency current oscillations result. Since relatively high voltage and

Jan 1, 1969

By R. A. Esmonde

This paper describes the building and testing of a prototype welded aluminum truck body to a new design concept. The results of these tests are given along with an outline of further developments in the design and field application of aluminum bodies. The results of field service history are recorded with special reference to types of mining operations, service performance, wear, maintenance and economics of operation. Mention is made of current U.S. usage and predictions given as to future development of aluminum bodies in the mining industry. The use of aluminum for off-highway truck bodies in hauling rock for the mining and construction industries is by no means the novelty that it may seem. In 1932 an aluminum unit proved very satisfactory in service on the Hoover Dam project but at that time the only high strength aluminum alloys available were not weldable and with the high cost of construction, a sound economic case for an aluminum body could not be made. After World War I1 great advances in aluminum welding techniques, using the inert gas shield, combined with the development of high strength alloys with good welded properties and welding characteristics changed the whole picture. Welded aluminum bodies were rapidly developed and by 1958 attention was again focused on the use of aluminum for off-highway truck bodies. EARLY DEVELOPMENT WORK In 1959 Alcan, the Aluminum Co. of Canada, embarked on an extensive development program to prove the durability and economics of aluminum truck bodies for the mining and construction industries. The first step was to design a prototype aluminum body which took particular advantage of the fact that the modulus of aluminum is only one third that of steel. This means that within the elastic range, aluminum moves three times as much as steel which makes it more flexible and capable of absorbing much greater impact shocks. A body was built and mounted on a 22-ton truck and taken to the Jeffery Mine of Canadian Johns Manville Company at Asbestos, P.Q., Canada. Very little information was available as to the order of stresses that were set up in off-highway truck bodies and so it was therefore decided to carry out a test program to find out this information.

Jan 1, 1969