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By Herbert Haas

1. INTRODUCTION COPPER matte is now converted into blister copper at a cost of only $5 per ton of copper, or, based on a 40 per cent. matte, $2 per ton of matte, which is the record of at least one large smelting Works; and it seems hardly likely that a further reduction, large enough to warrant, a change in existing practice, could be made in bessemerizing costs. But the new type of converter here described and the new practice proposed are intended, not so much for the treatment of mattes, as for the extension of, the process to the direct reduction in the copper-converter of pyrite ores

Jan 6, 1914

By N. S. Greensfelder

The firing of explosive charges by electricity dates back to 1745 when a Doctor Watson is said to have used an electric spark for igniting gunpowder. His method failed in practical application because, to ignite blasting powder, heat must be applied for a period longer than the duration of an electrostatic spark; Wheatstone found that this does not exceed 1/24000 sec. The usual result, therefore, of an electrical discharge in gunpowder is to scatter the grains, without igniting them. Benjamin Franklin partly overcame this difficulty by confining the powder and crushing grains that lay in the line of discharge. In 1822, after the primary cell had been discovered by Volta, Robert Hare, professor of chemistry at the University of Philadelphia, noticed the heating of a short piece of wire placed in the circuit of a voltaic battery. Later work by Oersted, Faraday, Wheatstone, and Henley resulted in the developmcnt of the magneto blasting machines. Fulminates of gold and silver are thought to have been discovcrcd by Cornelius Drebbel, about 1600. Pepys, in his diary for November 11, 1663, recounts a conversation with Doctor Allen, who told him about aurium fulminans "of which a grain ... put in a silver spoon and fired, will give a blow like a musquett and strike a hole through the silvel spoon downward, without the least force upward.'ll This fallacious belief that explosives act downwards only is still held by many who should know better. Fulminate of mercury was discovered by Howard in 1799. J. Shaw of Philadelphia is said to have invented a fulminate-of-mercury cap in 1814; his idea was later adopted by gunmakers in England and France. The principal advantages of mercury fulminate for use in detonators are the simplicity of exploding it and the great shock developed by its explosion.

Jan 1, 1923

By N. S. Greensfelder

The firing of explosive charges by electricity dates back to 1745 when a Doctor Watson is said to have used an electric spark for igniting gunpowder. His method failed in practical application because, to ignite blasting powder, heat must be applied for a period longer than the duration of an electrostatic spark; Wheatstone found that this does not exceed 1/24000 sec. The usual result, therefore, of an electrical discharge in gunpowder is to scatter the grains, without igniting them. Benjamin Franklin partly overcame this difficulty by confining the powder and crushing grains that lay in the line of discharge. In 1822, after the primary cell had been discovered by Volta, Robert Hare, professor of chemistry at the University of Philadelphia, noticed the heating of a short piece of wire placed in the circuit of a voltaic battery. Later work by Oersted, Faraday, Wheatstone, and Henley resulted in the developmcnt of the magneto blasting machines. Fulminates of gold and silver are thought to have been discovcrcd by Cornelius Drebbel, about 1600. Pepys, in his diary for November 11, 1663, recounts a conversation with Doctor Allen, who told him about aurium fulminans "of which a grain ... put in a silver spoon and fired, will give a blow like a musquett and strike a hole through the silvel spoon downward, without the least force upward.'ll This fallacious belief that explosives act downwards only is still held by many who should know better. Fulminate of mercury was discovered by Howard in 1799. J. Shaw of Philadelphia is said to have invented a fulminate-of-mercury cap in 1814; his idea was later adopted by gunmakers in England and France. The principal advantages of mercury fulminate for use in detonators are the simplicity of exploding it and the great shock developed by its explosion.

Jan 1, 1923

By M. Muskat R. D. Wyckoff

The phenomenon called "water-coning" is that, observed in many oil wells, in which bottom water gradually and frequently sudderlly displaces a part or all of the oil production when a certain rather critical production rate from the well is exceeded. To follow in detail the process of the formation of a water cone as it breaks through the oil zone and enters the well bore is a problem so complex as to make a theoretical analysis practically impossible. However, an analytical treatment of the flow system before the water has broken through and during the time that it lies statically beneath the oil zone with an elevated or "coned" surface can be carried through under certain approximations. To present an analysis which shows the essential characteristics of the coning mechanism is the purpose of the present discussion. Physical Basis of Theory and Meaning of Approximations As will always be true for flow systems where true water-coning is at all possible, the water will be supposed to lie beneath the oil zone because of its density contrast with respect to the oil. In fact, tinder the usual field conditions, when the pay horizon is reasonably homogeneous, the water most frequently enters the well through the lower zones, but even when it enters from intermediate zones it may, in the later life of the well, displace the bottom layers of oil, thus resulting in a system wherein the oil is effectively floating on the water.

Jan 1, 1935

By C. H. Lee, R. Maddin

The diffusion rates of Ag110 in cylindrical single crystals of 99.99 pct pure silver, which were twisted to a total surface strain of 0.91 during the diffusion anneal at temperatures of 700°, 750°, and 800°C, were measured by sectioning and counting as a function of the strain rates. The ratio of the diffusivities while strain ing occurred (Ds) to those of the unstrained specimens varies linearly with the rate of twisting and attains values of near 100 for some of the rates used. The enhancement of diffusion by straining is inversely proportional to the temperature at which diffusion occurs. The activation energy for diffusion determined from the data plotted as a function of the rate of twisting decreases from 44,090 cal per mole for zero strain, to an asymptotic value of 21,000 cal per mole for the strain rates of 22 x it)"5 see-l. Qualitative explanation for the observations based on the generation of nonequilibrium number of defects by plastic deformation will be discussed. The initial research of Buffington and cohen1 on self-diffusion in a iron under compressive stresses contributed the first quantitative information concerning the effect of applied stresses on diffusion. These results were obtained from radioactive Fe55 plated on one of the horizontal surfaces and compressing the large-grained specimens while the diffusion-anneal was occurring. Enhancement of diffusion of a maximum of seventeen times was observed provided the strain was in the tertiary stage of creep and the rates of straining were at least as fast as rates used in the normal creep test. On the other hand, Darby, Tomizuka, and Balluffi,2 extending silver single crystals up to 30 pct elongation at rates of straining about equal to those used by Buffington and Cohen observed no effect. For the past two and a half years at the University of Pennsylvania, we have been investigating the effect or torsional strains on self-diffusion in silver single crystals. If enhancement is observed as has been reported1 a possible explanation may be based upon the generation of fairly large numbers of point defects and their role in the diffusion process. Hence, since torsion should produce an abundance3 of point defects, an increase in the diffusivity while the crystal is being twisted should easily be measured. EXPERIMENTAL PROCEDURE Our research uses single crystals of silver prepared from 99.99 Ag by the Bridgman method in a dynamic vacuum of less than 25 µ. As grown, they are about 25 cm long by 1.3 cm in diam. The crystals are cut into 7.5 cm lengths with a jeweler's saw and machined to the shape shown in Fig. 1. The test length of the crystal is machined to a 0.6 cm diam after which the ends are masked and the test section etched heavily in HNO3, and KCN:(NH4),S2Os , solution to remove the effects of machining. The specimen is then annealed in vacuum for 8 to 12 hr at 800°C to remove any residual stresses and also to recrystallize the end sections. The recrystallized ends are necessary since experiments showed that single-crystalline end sections are too soft to transmit the desired torque. Occasionally, recrystalliza-

Jan 1, 1960

By B. E. Cornish

Most technical and statistical data published on pyrophyllite relating to production figures, uses, markets and sales, have in the past traditionally linked the mineral with talc and soapstone. This is due to several common superficial physical properties resulting in substitute uses and applications. However, these minerals are not similar in chemical composition and do not generally occur in a similar geological environment. Pyrophyllite now stands on its own in the marketplace-particularly in ceramic applications-due to the combination of excellent heat shock and creep resistance properties of the mineral. The increase in pyrophyllite use in the field of ceramics indicates the continuing realization of these marked unique properties. Several new fields of ceramic applications, previously the preserve of high-alumina materials, have been developed on the intrinsic properties of pyrophyllite. Pyrophyllite is an aluminum silicate with the molecular formula of AI2O34SiO2H2O. It would be more appropriate to group pyrophyllite with such materials as kyanite, diaspore, andalusite, and certain high-alumina clays in relation to its general applications (Stuckey, 1928). These materials all have good beat shock resistance properties at high temperatures and are widely used for the manufacture of refractories. For those reasons they are interchangeable in some applications. Pyrophyllite also has many uses in nonceramic applications, the most important to date being as a substitute for talc in fillers. The major pyrophyllite mining operations are located in the US, Japan, Korea, Canada, and Australia, where the mineral is widely used as a raw material for general ceramic, mineral filler, and dilutant applications. Commercial Applications Pyrophyllite was first used in the last century for lining stoves and fireplaces, and also in the carving and polishing of ornamental objects. The rise in industrial demand for new products and applications resulted in the introduction of pyrophyllite as an alternative, mainly for talc and soapstone. Industrial filler applications followed for paint, paper, cosmetics, rubber, pesticides, crayons and pencils, and bleaching soap. The first use of pyrophyllite in ceramic applications was prior to World War II, in the manufacture of ceramic cladding tiles in the US. This was followed by the production of kiln furniture refractories and whiteware when pyrophyllite was offered by suppliers in North Carolina as an alternative to some local clays. The largest tonnages of pyrophyllite used today are in refractory linings in steel ladles in Japan, as seen in Table 1. The consumption of pyrophyllite in Japan is second only to clay and chamotte among refractory raw materials used. Recently this technology has been adopted in Australia. Japanese and Australian practice has resulted in appreciable technical and economic benefits, particularly when pyrophyllite is used in combination with zircon. The potential growth for this application is substantial if US and European steelmakers follow. Investigation and research into the properties of pyrophyllite determined the following main advantages of pyrophyllite-based ceramics: high corrosion resistance for molten iron, steel, and slags; good heat shock resistance; good indices of deformation under load and hot creep resistance (refractories); and increase in mechanical strength of whiteware products promoted by a better distribution of mullite in finished products (also obtained at lower firing temperatures than normally required in production of triaxial ceramics). White cement

Jan 1, 1983

By C. R. Johnson, R. A. Greenkorn, E. G. Woods

A new method of reservoir evaluation called pulse-testins has been developed for describing formation properties between wells. Pulse-testing utilizes a sensitive differential-pressure gauge at a responding well to measure and record the response generated by a series of flow rate changes (pulses) at an adjacent or pulsing well. Since the pulse-test instruments have a sensitivity of about 0.001 psi, pulses of several hours or less in duration will generate a measurable response in most reservoirs. For this reason, many well pairs can be tested in a short period of time with little interference in field operations. Comparison of pulse-test results to conventional testing methods shows that the pulses obey unsteady-state, compressible-flow theory and thus provide a measure of both transmissibility (kh/µ) and storage (Fch). In additian, the method can be used qualitatively to describe communication across faults and between zones, and direction and tnagnitude of fracture trends. INTRODUCTION To obtain maximum usefulness of new reservoir analysis methods as well as to aid the field engineer in understanding local reservoir anomalies, improved methods are needed to describe heterogeneities in specific reservoirs. Optimum well spacing, equipment specifications, well completion design and especially the economics of pressure maintenance and secondary recovery programs depend on the extent and location of the heterogeneities that affect flow behavior in the field. One method for obtaining a measure of areal reservoir heterogeneity is an interference test. In the simplest interference test. constant-rate production or injection is initiated at one well and the effect of this flow is measured as pressure vs time at another well. Thus, during interference tests the flow characteristics of the formation are determined in situ. Despite their obvious usefulness in reservoir delineation. interference tests have not enjoyed frequent usage. Reasons for this have been the weeks or months required in many fields to obtain a pressure response measurable with conventional gauges, and the interruption of routine field operation during the field-wide shut-in normally required during these long times. Also, only average properties of the relatively large volume of the reservoir disturbed during these long times can normally be obtained — variations in properties between individual wells cannot be delineated. To eliminate these drawbacks of conventional tests, a special reservoir description technique called pulse testing' has been developed. Pulse-testing has several advantages that make it more convenient and practical for field use than interference tests. Valid tests are more certain because use of a series of flow disturbances gives rise to a diagnostic pressure response that can more readily be distinguished from unknown trends in reservoir pressure and other "noise." The time required is only a fraction of that for an interference test because a special, high-sensitivity differential pressure gauge can detect a much smaller pressure change. Variations in properties between individual wells can be delineated because of the relatively small volume of the reservoir disturbed during these short times. Finally, wells other than the pulsing and responding wells do not have to be shut in or carefully regulated.

Jan 1, 1967

By C. H. Curtis

THE valuable mineral content of the current feed to the Miami concentrator is as follows: copper, 0.7 pct total; molybdenum, 0.01. Flotation of this ore yields a sulphide concentrate containing: chalcocite, 44 pct; molybdenite, 0.5; pyrite, 50.0; insol, 5.5. A combination of potassium ethyl xanthate and pentasol amyl xanthate as collectors, and pine oil, as frother, are used in this flotation. Rejection of pyrite is encouraged by holding the amount of collectors used to the minimum consistent with copper recovery and by operating at high alkalinity (equivalent to 0.35-0.40 lb CaO per ton solution of pH 11.0).

Jan 1, 1950

By J. W. Spretnak, H. R. Ogden, A. G. Imgram

The effect of working reduction, stress-relief annealing, and recrystallized grain size on the tensile and notch-tensile properties of molybdenum and Mo-0.5 Ti was studied. It was found that increasing the amount of working reduction increased the strength and reduced the tendencies toward brittle behavior. Stress -relief annealing did not alter the strength but lowered the transition temperature. Increasing the recrystallized grain size lowered the strength and raised the transition temperature. The notch -unnotch strength ratio began to decrease with decreasing temperature at temperatures below those at which the notched ductility fell to zero for all of the micro structural conditions investigated. BEING bcc metals, the refractory metals in Groups Va and VIa (V, Cb, Ta, and Cr, Mo, W) undergo a ductile-to-brittle transition and exhibit brittle fractures at low temperatures. Previous research has shown that molybdenum and tungsten not only have higher transition temperatures than columbium and tantalum but show a marked sensitivity of transition temperature to structure as well.' Recrystallized materials become brittle at considerably higher temperatures than is the case with material having a worked or fibered micro-structure. Evidence of structure sensitivity has also been detected in columbium- and tantalum-base alloys containing appreciable amounts of molybdenum or tungsten such as F-48 (Cb-15W-5Mo-1Zr) and Ta-10w.2 This paper describes the results of research conducted to further evaluate the effects of metal. lurgical structure on the low-temperature tensile and notch-tensile properties of molybdenum and Mo-0.5Ti. The effects of rolling reduction, stress-relief annealing temperature, and recrystallized grain size were studied. Considerable progress has been made in explaining the fundamental mechanisms of the flow and fracture characteristics of bcc metals. Several of these concepts are helpful in interpreting the data obtained in this study. Brittle fractures occur when the highly temperature-sensitive yield strength equals, or exceeds, the temperature-insensitive brittle cleavage fracture stress.3 The rapid increase in yield strength with decreasing temperature, characteristic of all bcc metals, is therefore of primary concern. petch4 has described the yield strength, ay, (stress required to initiate plastic flow) of bcc metals by the expression where ai is the frictional resistance to slip, Ky is a constant numerically equal to the slope of a a vs curve, and 2d is the average grain diamefer. The oi term itself is thought to be composed of a temperature-insensitive component dependent on impurity content and second-phase particles and a temperature-sensitive component dependent on the Pierls-Nabarro force.5 This equation has also been demonstrated to hold for the flow stress (stress required to maintain continued plastic flow).' Brittle-crack nucleation is thought to occur by the coalescence of dislocations piled up in slip planes at sessile dislocations or twin and grain boundaries.7,8 These proposed mechanisms require that a large number of dislocations be released into the active slip planes so that sufficiently large stress concentrations are produced at the dislocation pile-ups to enable coalescence into a micro-crack. Therefore, at least a microscopic amount of slip must occur in some grains to facilitate initial crack formation. Cottrell 7 has predicted that brittle fracture, nucleated by slip, should occur when where ty is the shear yield strength, ß = 1 in un- notched xension, u is the shear modulus, and y is the effective surface energy. This equation incorporates the Griffith concept of fracture that a crack will propagate if the decrease in strain energy equals or exceeds the increase in surface energy.

Jan 1, 1964

By S. H. Penn

Preliminary experimental evidence seems to preclude the use of unlubricated mechanical force drills on the moon. Measured values of the coefficients of friction and adhesion between metallic and nonmetal-lic solids have been shown to increase in an ultra-high vacuum environment. The paucity of real knowledge of the influence of a hard lunar vacuum upon interacting solid surfaces, relegates current proposals to sample the moon with a mechanical force drill, to the equivalent of wildcatting on earth. Within a few years, drilling will be attempted on the lunar surface with tools that have been designed with parameters that are normally considered for most conventional terrestrial drills. Lunar drills must be light in weight, portable, have reasonable penetration rates, low manpower requirements, etc. Although the initial equipment cost is expected to be high, this will probably not be a critical factor. Early lunar drilling will be limited to shallow holes with depths of 10 ft or less. The primary function of these holes will be to furnish samples of lunar surface materials but they may also be utilized for other purposes, such as geophysical experiments. Instruments may be installed in them capable of measuring thermal diffusivity, gamma radiation, etc. As sampling will be the primary objective of the earliest holes, sample contamination is a parameter that effectively excludes such otherwise promising techniques as explosive or plasma jet drilling. The most desirable method is probably some form of mechanical force drilling that has the capability of operating in the extreme lunar thermal environment (125° to 37S°K), high vacuum (10- l3 torr range), and low gravity.

Jan 1, 1968

By Thomas V. Falkie

4.3-1. Introduction. DEFINITION OF PRODUCTION SYSTEMS ENGINEERING. Surface mines, like most other mining and manufacturing operations, are usually organized along functional departmental lines. Frequently a mine manager will have his responsibilities divided among production, maintenance, administrative, and engineering functions. Often these are separate departments, but various combinations and variations of these functions can be found in mining companies throughout the world. The production function is responsible for physically removing the ore from the ground, processing it, and shipping the product to its market. The production manager supervises and is responsible for all man-machine systems necessary to extract and process the ore. The maintenance function, which is sometimes included within the framework of production, has the task of insuring the maximum availability and longevity of equipment needed to produce the ore. The administrative function is responsible for accounting, personnel, industrial relations, purchasing, public relations, property, and other related staff functions. For purposes of this chapter, engineering can be described as the function which plans, designs, and supervises construction of physical plant and equipment. In this context engineering includes mechanical, civil, chemical, electrical, and mining engineering. However, another phase of engineering is to prepare plans to insure that the various man-machine components function in an optimum way towards the single most important goal of any enterprise-the maximization of return on the investors' money. Along with the planning, another duty of engineering is to audit all phases of the operation for the purpose of recommending improvements toward this same general goal. These latter two ideas form the basis for a discussion of production engineering and systems engineering. Production engineering is a catchall, problem-oriented function whose duties can include: 1) solution of day-to-day production problems, 2) short-

Jan 1, 1968

By H. Rosenthal, A. L. Jamieson

Stress-corrosion cracking of copper-base alloys is of considerable importance and has been the subject of many investigations which employed various accelerated tests and long-time service tests. The outstand¬ing accelerated tests used are variations of either the mercury cracking test reported by Rogers in 1905( 1)2 or the ammonia test reported in 1910(2). The ease of applica¬tion of the mercury test is probably the reason industry adopted it. Subsequent investigation of this test(3,4) revealed that a minimum threshold stress was necessary before mercury cracking could develop. Since season cracking has been found in some instances in caliber 0.3o ammunition which has passed the mercury test, it is evident that the threshold stress value of the mercury test may be too high for dis¬tinguishing between acceptable and un¬acceptable caliber 0.30 cartridge cases. This condition has naturally led to the study of an ammonia test with its ability to cause cracks with almost any stress level. But the lack of a definite threshold value means that standards are necessary for evaluating the results of the ammonia test.

Jan 1, 1945

By E. G. Leonardon, C. Schlumberger, M. Schlumberger

In the search for practical geological problems amenable to solution by the potential methods, the geophysicist is led to study mathematically various theoretical cases. In these idealistic discussions, the media under consideration are generally supposed to be homogeneous and iso-tropic. The geophysicist, of course, realizes perfectly that these conditions do not occur in their entirety in reality. However, the assumptions made are justified, because very often they are necessary in order to render possible an exhaustive study of a given problem, which otherwise would be too complicated, and would not lend itself to a complete mathematical analysis. Of the above two assumptions, that concerning the homogeneity of a given geological formation is satisfactorily realized except in so far as isotropy is concerned, since this property is not often encountered in practice. As a consequence, it is very desirable for the geophysicist to have quite an extensive knowledge of the properties of anisotropic formations, and of the laws that govern the propagation of electric current therein. With such principles in mind, he will be able to decide whether the conclusions arrived at in simple, isotropic conditions are still correct in more complex cases, or in what way they must be modified or adapted in order to constitute a sound basis for the interpretation of the results obtained in anisotropic media. On the other hand, the fact that in anisotropic formations the mobility of the ions is greater along the strike than perpendicular thereto can be utilized for determining the direction of the dip by induction measurements. We therefore propose to study in three successive chapters the following points: 1. Propagation of the electric current in anisotropic media. 2. Some consequences of the anisotropy of geological formations with reference to the surface electrical measurements, and their interpretation. 3. Determination of the direction of the dip of anisotropic formations by surface induction measurements.

Jan 1, 1934

By Adolph Knopf, L. G. Westgate

Pioche lies 240 miles southwest of Salt Lake City, in southeastern Nevada, 19 miles west of the Nevada-Utah line. It is at the end of a branch line (33 miles), which connects at Caliente with the Los Angeles and Salt Lake division of the Union Pacific System. Its commercial relations are with Salt Lake City and Los Angeles, chiefly with the former. The surrounding area is part of the Great Basin, an arid region of alternating mountain range and intermont plain, the latter floored with out-wash from the mountains. About Pioche the plain varies between 4700 and 6000 ft. above sea level. The town lies in a valley at the east base of a low northwest-southeast range (the Pioche Hills) 12 miles in length, which rises about 1000 ft. above the adjacent flat. West of the Pioche Hills is a higher north-south range consisting of two parts: to the south the Highland Range, between Bennett Pass and Stampede Gap; to the north the Bristol Range, from Stampede Gap to Bristol Pass. This double range reaches altitudes of 8000 to 9000 ft., or more (the highest point, Highland Peak, is 9395 ft.), and rises some 2500 ft. above the surrounding plain It is continued in lower hills to north and south. Smaller ranges rise from the flat west of the Highland and Bristol ranges. The area studied and shown on the map (Fig. 1) is covered by three inch-to-the-mile topographic sheets: the Highland Range, the Bristol Range, and the Panaca, the latter mapped in part only. The sedimentary rocks of the district include Paleozoic limestones, sandstones and shales, Pliocene tuffs, and modern wash. Igneous rocks are represented by intrusive dikes and stocks and by extensive lava flows of mid-Tertiary time.

Jan 1, 1927

By Robert E. Green, P. W. Kingman

Application of a constant geometry compression test to single crystals of aluminum of selected diameters from 1/4 to 1/64 in. showed the presence of a diameter-dependmt size effect. The most pronounced effects were found in those crystals oriented for single slip, while for specimens possessing orientations in the comers of the standard stereographic triangle virtually no size effect was exhibited. The yield stress of the crystals oriented for single slip was found to increase with decrease in specimen diameter, while the strain-hardening rate was found to be lower for the smaller specimens. The experimental results are in general agreement with those of other investigators obtained from lensile tests on copper and aluminum crystals. THE earliest systematic investigation of a possible size effect on the plasticity of metals was that of no,' who in 1926 performed tensile tests on cylindrical aluminum single crystals with diameters of 3 to 8 mm. Ono concluded that the gross stress-strain curve did not show a diameter dependence, but that the resistance to slip for strains of 0.1 pet and less appeared higher for 3-mm-diam crystals than for larger sizes. Later studies of aluminum by Maddin et al2 tentatively concluded that a size effect exists, but the conclusions were again open to question because of inconsistencies in the experimental data. Wu and Smoluchowski3 had previously shown that the slip system activated in a single-crystal sheet specimen of aluminum is a function of the specimen cross section in the slip direction, but no stress-strain data were obtained. Subsequently Fleischer and Chalmers4 studied the effect of the length of the slip direction of the primary-slip system on the stress-strain curve by testing aluminum crystals with geometrically dissimilar cross sections. In the course of this investigation a size effect was indicated in rather large crystals; however, the number of these tests was small. Other investigators have indicated that a size effect in aluminum is appreciable only for diameters of 0.5 mm or less.5, 6 Size-effect studies have also been carried out on copper crystals, the most detailed being that of Suzuki et a1.7 who performed tensile tests on specimens of many diameters ranging from 2 to 0.12 mm. Suzuki found a strong size dependence in the easy-glide region, both the extent of the easy glide and the hardening rate in easy glide were size-dependent, and the size effect was found to be orientation-dependent. Suzuki's results are in agreement with the less extensive observations of Pater-sonB and those of Garstone et al.9 A size effect was found by Rebstock using tubular copper crystals.'0 Size effects have also been noted in a brass,6, 11 in cadmium,12'19 and in hexagonal crystals.14 All the previously cited works have been entirely concerned with the variation of specimen cross section. The effects of specimen length and the change of specimen geometry which results from using progressively thinner specimens while maintaining the same specimen length have been largely ignored. A theoretical discussion of the effects of specimen length and geometry has been given by Hauser and Jackson,15 who predict a grip effect on easy glide as a function of specimen geometry provided that the specimen dimensions are large compared with the spacing between the slip bands, and by Fleischer and Chalmers,18 whose analysis of grip effects resulting from lattice rotation predicts an increase in easy glide with an increase in specimen length. A study of size and geometry effects in aluminum crystals by Kitajima and shimba17 indicated increasing amounts of easy glide in specimens of increasing length and identical cross section, and nearly identical stress-strain curves for specimens of different sizes having constant length-to-diameter ratios. Since the present study is primarily concerned with diameter dependence, the following factors were taken into account: specimen material, specimen geometry, testing method, range of sizes to be tested, and possible influence of surface and volume effects. Aluminum was chosen because of the present lack of conclusive results and the seeming possibility of size effects at relatively large diameters, the

Jan 1, 1964

By A. F. Meston

Centrifugal force has been used for centuries for separating liquids but machines for doing this are a comparatively recent development. The use of these machines is being extended into many industries but this paper is confined to their use in the oil industry. The centrifugal machine is found at the well where "cut oil" is dehydrated for acceptance by pipe lines; and in the refinery and byproduct plant. In fact, wherever finely divided suspended particles should be removed from an oil, there is a possible use for a centrifugal machine, if the particles have, or can be made to have, a specific gravity different from that of the oil. Centrifugal machines are also used for cleaning fuel and lubricating oils and dehydrating transformer oils. Applications and Results When oil comes from the well mixed with water, it is spoken of as cut oil. Settling often does not remove sufficient water for the oil to be accepted by pipe lines, thus necessitating chemical or other treatment. Centrifuging alone, or following chemical treatment, effectively prepares such oil for pipe lines, as is shown by the following data: WateR, Etc. Wat~R. Etc. Temperature, Oil to Pipe Line, aT StUt at Finish Degrees F. Bel. Per HouR PIE Cent. PEECent Oklahoma lease.... 160 10 10 0.25 Kansas lease....... 125 4 20 0.25 to 2 On the Oklahoma lease, the machine was cleaned of solid material once in 12 hr. At first, it was thought that chemical treatment was necessary to start separation and 1 qt. of prepared compound was added to each 100 bbl. of the cut oil before centrifuging. Later it was found that

Jan 1, 1924

By P. A. Witherspoon, S. P. Neuman

Evaluating the permeability of a caprock overlying a potential gas storage reservoir is a very critical problem. Pumping water from the reservoir can be used as an evaluation tool in analyzing this problem. Fluid level changes that occur in the aquifer us well as in the caprock can be measured with appropriately placed wells. If the leakage of water from the caprock into the aquifer is considerable, the effects will be apparent in the aquifer. If the leakage is slight, however, it will not be possible to detect it with certainty from observations in the aquifer alone. Fluid level measurements in the caprock must be relied upon. and improved methods of analyzing such effects have been developed which are based on a theoretical analysis of fluid flow through a caprock of infinite thickness. An example applying these methods to field data is discussed. INTRODUCTION One of the most critical problems in evaluating an aquifer gas storage project is determining the tightness of the caprock overlying the formation to be used as the storage reservoir. A formation that has previously held oil or gas obviously has a suitable caprock, but an aquifer that contains only water gives no such assurance. A number of aquifer projects in the United States have been troubled by gas leaking out of the intended storage zone, and the ensuing difficulties have led to the development of new evaluation methods. One of these new methods is pump testing wherein water is removed from the aquifer at some controlled rate prior to injection of gas. This fluid withdrawal causes a pressure drop to move out through the aquifer for considerable distances in a matter of days or weeks. Depending on the properties of the caprock, a pressure transient can also pass upward (as well as downward) through the caprock layers adjacent to the aquifer. Thus, if the operator has placed observation wells at appropriate distances from the pumping well, the rapidity with which the pressure transients reach different points in the system can be used to investigate the fluid transport properties of both the aquifer and its caprock. The usefulness of pump testing has been recognized by groundwater hydrologists for many years as a means of determining the potential yield and properties of aquifers used in water supply They have introduced the term "leaky aquifer" for a system in which an aquifer is overlain (or underlain) by semipermeable caprock layers. The ease with which water leaks into the aquifer during pumping can, of course, be very beneficial in bringing additional water to the pumped well. Hydrologists have therefore devoted considerable attention to this prob-lem. From the gas storage standpoint, however, the tighter the caprock layers that overlie the intended storage reservoir, the better are the conditions for minimizing or eliminating any vertical migration of gas. Thus, after a suitable geologic structure has been found, the emphasis in aquifer storage projects is in determining that the caprock is tight. Attention has recently been focused on the use of pump testing as one approach to solving this problem.23,24 This paper presents a further development on evaluating the permeability of a slightly leaky caprock when the caprock is of infinite thickness. From the practical standpoint, this means that the caprock layers are thick enough that pressure transients do not reach the outer boundaries of the system during the pumping test. In a subsequent paper, an analysis of the case where the caprock is of finite thickness will be presented. PREVIOUS WORK ON LEAKY AQUIFERS Jacob" developed a partial differential equation describing the flow of water in an aquifer of permeability k that is overlain by a leaky caprock of permeability k'. Fig. 1 shows a schematic cross-section of the system under consideration. One of his principle assumptions was that if k > > k', the direction of flow is essentially vertical in the caprock and horizontal in the aquifer. Neuman19 confirmed the validity of Jacob's assumption using a mathematical model. Another assumption was that a permeable source layer overlies the caprock (Fig. 1) and is able to maintain a constant hydraulic head at the upper boundary of the caprock. By neglecting the effects of compressibility within the caprock, Jacob1* developed a solution for a bounded circular aquifer. Later, Hantush and Jacobx5 used the same assumptions to solve the case of an infinite radial aquifer that is pumped at a constant rate. Their solution may be expressed in di-mensionless parameters by

By Per Kofstad, Hallstein Kjöllesdal

The oxidation behavior of niobium (columbium) has been studied in the temperature range 500° to 1200°C and at oxygen pressures of 760,100, 10, 1, and 0.1 mm of Hg. The work comprises kinetic studies of the oxidation as well as structural investigations of the oxidized specimens by means of X-ray diffraction, electron diffraclion, electron microscopy, and metal1ographic techniques. The oxidation reaction has a highly irregular temperature dependence and is unusually sensitive to changes in the oxygen pressure. The complex oxidation behavior is suggested to be due to formation of different Nb2O5 modifications in different temperature regions. During oxidation oxygen is also dissolved in the metal. Formation of oxide whiskers take place on the oxide surface at temperatures above approximately 800°C. VARIOUS aspects of the oxidation of niobium have been studied.l-12 The investigations show that niobium has a complex oxidation behavior, and the oxidation

Jan 1, 1962

By Herbert K. Kutter

This paper is concerned with the physical phenomena in the fracture process of presplitting and only indirectly with the establishment of the optimum presplitting parameters. Its nature is therefore qualitative, rather than quantitative. Before examining the problem of presplitting, it is first necessary to study the phenomena which occur when an explosive charge is detonated in a borehole. To do this it is desirable to consider the action of the explosion wave separately from that of the expanding gases.l In the theoretical analysis such a separation poses no problems. Experimentally this was accomplished by use of an underwater-spark discharge to generate the stress wave and by pressurized oil to simulate the pressure of the explosion products. The main role of the wave is to generate a densely radially fractured zone around the borehole. The subsequent gas pressure, exerted against the walls of a highly (radially) fractured cavity, generates a quasi-static stress field (henceforth referred to as static stress field). This stress field was found to be the same as that of a pressurized cylindrical "equivalent cavity" with a radius equal to that of the crack tips. Under these conditions the quasi-static stresses become appreciable and cause further extension of the radial cracks. It was further found that, under gas pressure, the longest of the radial cracks would extend first, and extension of two diametrically opposed radial cracks requires the least pressure. From these observations concerning the single shot the transition to a whole series of more or less simultaneous shots, as in presplitting, can readily be made. In the case of multiple shots, as in presplitting, exactly the same effects occur, but at numerous locations and sufficiently close in time that they interfere with

Jan 1, 1968

By Norman B. Pilling

Practical limitations to the usefulness of silicon steels are the hardness and brittleness silicon imparts to iron, making iron-silicon alloys of more than 8 per cent. silicon content unusable except where castings can be employed. In the use of commercial silicon steel, in thin rolled sheets, as in transformer construction, when the silicon content exceeds 4.2 per cent. the sheet is too brittle for satisfactory shaping by punching or similar operations. When such a brittle steel is sheared, it frequently breaks along a haphazard path in advance of the cutting tool. In Fig. 1 is shown a slightly enlarged view of the sheared edge of a 14-mil enameled sheet of nominally 4 per cent. silicon steel. In 5 in. along the sheared edge, only 44 per cent. was actually cut; the rest was torn, with the path of fracture varying widely from the path of travel between the shears. This is probably an extreme case of such brittle-ness, but a shearing or punching test is not necessary to reveal brittle-ness of this order; narrow strips will break when bent between the fingers. In Fig. 2, the proportion of actual cut edge is greater, but secondary fractures branch off at about 30" from the line of shearing in advance of the cut. Deprived of the support of adjacent parts of the sheet, the tips of the angles are bent out of the plane of the sheet by the shears, leaving a peculiar flared effect, like the set of the teeth on a saw. An end-on

Jan 1, 1923