Search Documents

By A. C. D. Chaklader, Ashok K. Kakar

The basic density equation originally dericed ' to predict the increase in density of a compact of spherical particles with the progressive deformation at the points of contact has been further modified to include the yield strength of the material. This has been done by assuming that the contact areas grow to stable sizes under a fixed stress which is equal to three times the yield strength. The final equation has the form: where Do and D me the initial and final bulk densities of the compact, u is the applied pressure, and Y is the yield strength of the material. This equation was tested with the data obtained on spheres of lead, K-Monel, and sapphire. The calculated yield strength t~alues for lead and sapphire are within the range of values reported in the literature. A few of the earliest hot pressing models proposed to explain the mechanism by Murray, Livey, and williams2 and then by McClelland3 are based on a plastic flow mechanism. However, more recent investigations suggest that the overall densification process is a combination of several mechanisms, such as particle rearrangement, fragmentation, plastic flow, and stress-enhanced diffusional creep. While fragmentation and particle rearrangement are considered to be responsible for the densification in the early stages,"475 it has been concluded that the final stages of hot pressing are controlled by stress-enhanced diffusional creep.516 The manner in which the densification takes place, i.e., by fragmentation, particle rearrangement, plastic flow, or stress-enhanced diffusional creep, would depend upon the type of material, the temperature, and the stress level used during the hot-pressing experiments. Metal compacts can be expected to have a much greater contribution from plastic flow than ceramic oxides. Also, plastic flow would be a significant contributing factor to densification at high temperatures and high stresses. Most of these works, directed towards elucidation of densification mechanism, have dealt with kinetics of the process. The results of most of the authors vary from one another and they have proposed either new empirical or semiempirical equations to fit their data. The densification rate was found to vary with the type of the powder, shape and size of the powder, initial packing density of the compact, and a few other factors such as rate of heating, pressure, and so forth. Beyond the initial stages, the densification process has been considered to be as time-dependent flow, controlled by a diffusional process, e.g., Nabarro-Herring creep. Palm our, Bradley, and johnson' have attempted to use modified creep rate equations to interpret the data of densification under hot-pressing conditions. Beyond the initial stages, however, the densification would be controlled by a process depending upon the temperature, pressure, and size of the powders. It is the authors' belief that such densification cannot be exclusively controlled by a single process and so attempts should be made to study some observable phenomenon like microstructure, yield strength, and so forth. The emphasis of this work has been toward studying the densification problem from a more fundamental point of view. Some of the principal variables, like initial packing density, mode of packing, and size of the powders, have been controlled to a great extent. The total strain produced on pressure application (instantaneous) in such a case can be considered to be due to plastic and elastic deformation. The elastic component of the strain can be determined by decreasing the load to the initial value. The strain remaining then can be correlated with the contact areas produced by deformation and the corresponding applied load. In a previous paper,' the possible deformation behavior of spheres in a compact has been theoretically analyzed and experimentally tested. The change in contact area radius a relative to the particle radius R was related to the bulk density and the bulk strain for simple and systematic modes of packing. Tt was found that a density equation relating the above parameters can be represented by: where D and Do are the bulk densities of the compact at any value of a/R and a/R = 0, respectively. This basic equation should hold for any material as it was derived from geometrical considerations alone. An attempt has been made in this work to include the yield strength in the above density equation, so that a knowledge of the properties of any material can be used in predicting the densification behavior during the hot-pressing process. THEORETICAL CONSIDERATTONS The deformation of two spheres in contact under a static load can be compared to the deformation occurring between a hard spherical indentor and the flat face of a softer metal. Tt has been shown theoretically by both ~encky~ and lshlinskyg and experimentally by ~abor" that, for a material incapable of appreciable work hardening, the mean pressure required to produce plastic yielding (for deformation occurring between flat face and a hemispherical indentor) is approximately equal to three times the elastic limit, Y, of the material (in tension or compression experiments). Tabor has further observed that the same relationship is valid in the case of work-hardening materials, if the elastic limit at the edge of the indenta-

Jan 1, 1969

By G. W. White

Over the past several years, the steady progress of gas lift from a mysterious art into a developing science has been traceable through the many fine papers that have appeared in Journal of Petroleum Technology. Consequently, this magazine has rightly become a standard for the serious students of gas lift all over the world. The following discussion is offered in a sincere attempt to accurately present certain topics covered in the subject paper in the light of acknowledged state of the art procedures. INSTALLATION DESIGN The first point to be questioned is the author's installation design, beginning with Eq. 6. The use of 1,200 psi in the spacing equation instead of the 1,275 psi noted as available seems, at first glance, to be a simple arithmetic error. Upon further examination, it appears evident that both this 75 psi plus the 100-psi safety factor must be subtracted from available kickoff pressure because of conditions imposed by the characteristics of the ASC valve (see Fig. B-1). Pressure-charged valve design is incorrectly penalized by spacing the first valve using only 1,100 psi. The use of such a high back-pressure makes it appear that a typical ASC installation would require no more valves than a comparable conventional valve installation. Using a value of 100-psi tree pressure, the well could be valved to 11,000 ft very conservatively with seven pressure-operated valves, but would still require 11 ASC valves. The use of 400-B/D spacing gradient for a 140-B/D rate is not an accepted practice using precharged valves. The author would have done well to note the advantages to be gained by reducing the 500-psi tree pressure, which is clearly explained by Beadle, Harlan and Brown.' In Step 1 of Part III of the continuous flow discussion, the author incorrectly applies the Poettmann and Carpenter curves.2 Item 2 is an incorrect statement. An excellent reference on this point is the paper by Baxen-dell and Thomas.' VALVE MECHANICS The next topic relates to the mechanics of precharged valves. Eq. 2 for the ASC valve can be used to describe the condition of equilibrium, wherein the valve is closed with opening pending. When this equation is used to determine relative values of casing, dome and tubing pressure with conditions approaching the transition value, some strange results are obtained. The following uses the author's symbols and values given on page 689. Fig. B-1 shows the condition that exists at the moment an ASC valve has been uncovered during the unloading process (Condition I). The obvious result is a locked condition. The basis for the curve is shown on the figure which includes 1,000 psig casing pressure to uncover the valve. If injection gas is not bled off the casing until the pressure is decreased by an amount exceeding the stabilizer discharging valve pressure, upward adjustment of the casing pressure is mandatory for the valve to open and unloading operations to continue. In Condition I the dome pressure exceeds the casing pressure by 20 psi, and the tubing pressure required to open the valve is 1,212 psig. This tubing pressure would not exist under the assumed conditions. In Condition I1 the casing pressure is increased to the dome pressure, and the tubing pressure required to open the valve is 1,102 psig. It is apparent that the casing pressure must be increased to a value exceeding the dome pressure before unloading operations could continue. In Condition I11 a maximum casing pressure of 100 psi (stabilizer charging valve set pressure) above the dome pressure is reached, and the tubing pressure required to open the valve is 549 psig. The author's statement after Eq. 5 that "the minimum tubing pressure required to open an ASC valve is equal to the casing pressure at depth less the transition pressure of the valve" is incorrect except for Condition I11 only. Otherwise, the equation is invalid.

Jan 1, 1965

By E. Wysocki

In the production of magnesium oxide, dolomitic lime and magnesium chloride are reacted to produce an intermediate product, magnesium hydroxide. Consistent product quality requires close monitoring of the soluble calcium hydroxide level during the reaction. Traditionally, this analysis has been done by manual titration; however, the product quality could improve with more frequent analysis and better control. A feedback control system was developed based on frequent automatic titrations, and reactor modelling was used to discern a control strategy. The system development and implementation are described.

Jan 1, 1984

J. E. Stead, Middlesborough, England (communication to the author): Prof. Howe's valuable paper on cast-iron brings forward most prominently the correct explanation of the part played by combined carbon in pearlite and cementite, in determining the strength and hardness of cast-iron. On a previous occasion I haveoshown that castings made by melting a white Cleveland iron and glazed iron, one containing 1.5 and the other from 4 to 5 per cent. of silicon, and each about 3 per cent. of carbon, were stronger than those made of ordinary foundry-iron; the difference in the final castings being a differ-

Jan 1, 1902

By Edward Saibel

THE various theories that have been advanced to explain or predict the conditions under which a metal fractures may be divided into two categories: First, there are the macroscopic theories generally used in engineering practice. These are empirical in nature and limited in application. For example, the maximum normal stress criterion, which is quite satisfactory for a mild steel in simple tension at atmospheric pressure, no longer suffices when this steel is pulled under hydrostatic pressure.2 In all of these empirical theories, the critical condition characteristic of the material and of the loading conditions must be obtained experimentally. Secondly, there are the theories based on interatomic forces,3,4 or on the energy required to form new surface.5,6 These have all dealt with the theoretical evaluation of the tensile stress necessary to bring about rupture in a purely brittle manner; that is, without plastic flow preceding fracture. All of these attempts have led to values of the tensile strength of crystals or of polycrystalline bodies that are 100 to 1000 times higher than observed values. On this account, it has been thought necessary by some investigators to conceive of a microcrack structure or distribution of flaws throughout the specimen such that the resulting stress concentrations provide the factor necessary to bring about agreement between calculation and experiment. It has been pointed out by several observers7 that this point of view is highly unrealistic, in that the weakening effect of these flaws or microstructures must be very uniform from specimen to specimen, since the fracture stresses found for various specimens of the same material tested under similar conditions are so - nearly constant. Furthermore, since calculations based on atomic forces or atomic energy are for purely brittle fracture, a condition probably never satisfied in tests, agreement is hardly to be expected. Thermodynamic Theory Of Fürth In order to resolve this apparent discrepancy between the theoretical cohesive strengths and the observed fracture strengths, Fürth8 advanced a thermo- dynamic theory of the tensile strength of isotropic bodies based on work of Born9 relating to the melting of crystals. Assuming an isotropic material free from imperfections and flaws, behaving elastically up to the breaking point, and assuming a connection between rupture and the melt- ing phenomenon, Fürth obtains an expression for the rupture stress u, in the form [ ] where Q is the melting energy per unit mass, ? is the density, and µ is Poissons’ ratio. Fürth compares fracture stresses computed from Eq I with the fracture stresses of metals as given in the Landolt-Bernstein Tables (1927) and in the Hand-

Jan 1, 1947

IN order that you may be expert in every phase of this art of parting, I wish to caution you upon twelve points, all necessary, so that you may know beforehand what may happen to you and what provision you must make to obtain good results. Understand that the gain derived from this art lies in carrying out the work that you wish to do accurately and with profit, which means nothing other than working with certainty and seeing that there is no loss of gold or silver [69v] or substance of anything that is valuable in itself. For, since everything lost is silver or gold, it is valuable however little. it may be, and many little things obviously make one large one; for gain increases gain, and loss, loss. Therefore, you will have as your first task to seek to have the materials that you are to use for making the aqua fortis of as perfect a nature as possible. I tell you this because the saltpeter is often weaker and of worse quality than the alum. For this reason it is necessary to make an effort to have it not only well refined and free from earthiness but also of a nature as powerful as pig [dung] saltpeter, the color of which tends strongly toward yellow. In order to work better, you also refine this again before you put it to use, as I shall tell you in its place. Likewise, see if you can get alum of the red kind that comes from the Levant or from Cartagena, for it costs less and is more powerful. Furthermore; see that you have a good number of well-formed cucurbits of properly purified glass not too large and of, equal content and size. Above all, see that they contain, no indentations, bubbles, folds, or scratches, especially, in the, body or in the bottom, because they break easily and the nature and great force of the acid pierces them by eating away, and makes a little hole. For this reason, cucurbits. are always divided into four grades; one is taken for making aqua fortis, another for drying the waters when they are laden with silver, the third for recovering the acids from the separations, and the fourth are either rejected as useless or dangerous, or are saved for recovering the whites or for some other service. Whoever wishes to practice this art well should remember to keep a large supply of cucurbits, receivers, and alembics. The third is the precaution which one must take in luting them; first, to

Jan 1, 1942

By Paul L. Horrer

Costly damage by severe wave attack to many engineering structures has illustrated the need for a consideration of the nature of wave action in plans for offshore drilling operations. Using wave data it is possible to answer questions pertaining to engineering problems such as platform elevation, structure orientation, and expected wave forces. For locations where wave records are not available a technique can be used to obtain information about wave characteristics from past meteorological data and near shore submarine topography. Forces exerted on structures by waves may be divided into four parts. A completed study is given in which frequencies of various wave heights and maximum frictional drag forces are computed for a typical offshore drilling site. INTRODUCTION Waves of tremendous proportions accompanying hurricane winds crash against breakwaters and other offshore structures causing untold damages. Wave forces exerted on structures at these times are enormous, as shown by past records of incidents where massive portions of breakwaters have been broken off and moved by waves. On other similar occasions, whole structure; have been unloosed and smashed or floated away. These incidents, which seem almost incredible, serve to illustrate the great amount of energy contained in large waves, and to show that this energy results in powerful forces destructive to offshore installation~ which are not designed sufficiently strong to withstand wave attack. In the past the expected frequencies of waves having various characteristic.% have rarely been considered in the design of structure affected by wave action. As a result, many structures have failed to accomplish the purpose for which they were designed or have collapsed under wave attack. Others have been constructed to withstand greater wave energy than is ever encountered, with resulting waste of material and construction time. In this study an analysis is made of the frequencies of waves having different characteristics which affect the plans for offshore drilling installations. After such an analysis the erection of these structures can proceed with less risk involved and with more efficiency and economy. ENGINEERING ASPECTS In the offshore drilling program wave forces play an extremely important part in design and construction of drilling rigs in shallow water. The design of a platform or other structure from which drilling equipment is operated is critical, becauze any damage to the platform may endanger personnel and result in complete loss of equipment. Since a platform built too close to the water would be battered by breakers, and one built unnecessarily high would involve undue expense, it is necessary to know the most desirable elevation at which the platform should be erected. This is only one of many questions about structural planning which can be answered using existing technique for determining wave characteristics. The purpose of efficient design for the portions of many types of offshore structures which are acted upon by wave forces is the same as that of all designs which deal with frictional forces of a fluid on a solid. For these structures the problem is comparable to that encountered by undersea craft moving through water, except that in the case of a fixed structure the force is produced by the water moving past the model. For off shore sructures which are extremely rigid the frictional forces may be nearly negligible compared with the impact or shock forces imparted by breaking waves. In all case; the better design is that which offers the least resistance to the opposing forces. From a consideration of wave forces, each drilling structure varies in efficiency depending upon the type and amount of superstructure in contact with the waves. For example, round piling and bracing offer less resistance to wave forces than do I-shaped ones. All network superstructure such as cross bracing should be kept to a minimum and at as low an elevation as possible, so that it will not expecience the pressure exerted at the tops of breaking waves. Models of proposed structures can be tested in wave tanks and in the field to ascertain the efficiency of specific designs. Past experience in beach and shoreline engineering has shown that, although changes in the topography of the bottom very near shore do not seem to be occurring, the natural forces involved may be in a delicate balance such that a static state exists. Interruptions of any of these natural forces by erecting offshore structures are likely to cause undesirable effects. Changes in beach profile result partly from sediment being brought into suspension by the orbital motion of waves and partly from the transport of sediment by longshore currents. With the erection of an offshore structure and consequent change in the combined effects of these two forces, unfavorable deposition upon, or erosion of, the bottom at the site may occur. Therefore, combination wave and current studies are essential for the solution of problems involved in the design of most marine structures. TECHNIQUE FOR OBTAINING WAVE INFORMATION In determining the probable effect of wave action on an offshore drilling structure, it is first necessary to know the usual frequencies of certain wave types for the given location. A technique has been developed which provides a means for obtaining information about wave characteristics in the

Jan 1, 1949

By Paul L. Horrer

Costly damage by severe wave attack to many engineering structures has illustrated the need for a consideration of the nature of wave action in plans for offshore drilling operations. Using wave data it is possible to answer questions pertaining to engineering problems such as platform elevation, structure orientation, and expected wave forces. For locations where wave records are not available a technique can be used to obtain information about wave characteristics from past meteorological data and near shore submarine topography. Forces exerted on structures by waves may be divided into four parts. A completed study is given in which frequencies of various wave heights and maximum frictional drag forces are computed for a typical offshore drilling site. INTRODUCTION Waves of tremendous proportions accompanying hurricane winds crash against breakwaters and other offshore structures causing untold damages. Wave forces exerted on structures at these times are enormous, as shown by past records of incidents where massive portions of breakwaters have been broken off and moved by waves. On other similar occasions, whole structure; have been unloosed and smashed or floated away. These incidents, which seem almost incredible, serve to illustrate the great amount of energy contained in large waves, and to show that this energy results in powerful forces destructive to offshore installation~ which are not designed sufficiently strong to withstand wave attack. In the past the expected frequencies of waves having various characteristic.% have rarely been considered in the design of structure affected by wave action. As a result, many structures have failed to accomplish the purpose for which they were designed or have collapsed under wave attack. Others have been constructed to withstand greater wave energy than is ever encountered, with resulting waste of material and construction time. In this study an analysis is made of the frequencies of waves having different characteristics which affect the plans for offshore drilling installations. After such an analysis the erection of these structures can proceed with less risk involved and with more efficiency and economy. ENGINEERING ASPECTS In the offshore drilling program wave forces play an extremely important part in design and construction of drilling rigs in shallow water. The design of a platform or other structure from which drilling equipment is operated is critical, becauze any damage to the platform may endanger personnel and result in complete loss of equipment. Since a platform built too close to the water would be battered by breakers, and one built unnecessarily high would involve undue expense, it is necessary to know the most desirable elevation at which the platform should be erected. This is only one of many questions about structural planning which can be answered using existing technique for determining wave characteristics. The purpose of efficient design for the portions of many types of offshore structures which are acted upon by wave forces is the same as that of all designs which deal with frictional forces of a fluid on a solid. For these structures the problem is comparable to that encountered by undersea craft moving through water, except that in the case of a fixed structure the force is produced by the water moving past the model. For off shore sructures which are extremely rigid the frictional forces may be nearly negligible compared with the impact or shock forces imparted by breaking waves. In all case; the better design is that which offers the least resistance to the opposing forces. From a consideration of wave forces, each drilling structure varies in efficiency depending upon the type and amount of superstructure in contact with the waves. For example, round piling and bracing offer less resistance to wave forces than do I-shaped ones. All network superstructure such as cross bracing should be kept to a minimum and at as low an elevation as possible, so that it will not expecience the pressure exerted at the tops of breaking waves. Models of proposed structures can be tested in wave tanks and in the field to ascertain the efficiency of specific designs. Past experience in beach and shoreline engineering has shown that, although changes in the topography of the bottom very near shore do not seem to be occurring, the natural forces involved may be in a delicate balance such that a static state exists. Interruptions of any of these natural forces by erecting offshore structures are likely to cause undesirable effects. Changes in beach profile result partly from sediment being brought into suspension by the orbital motion of waves and partly from the transport of sediment by longshore currents. With the erection of an offshore structure and consequent change in the combined effects of these two forces, unfavorable deposition upon, or erosion of, the bottom at the site may occur. Therefore, combination wave and current studies are essential for the solution of problems involved in the design of most marine structures. TECHNIQUE FOR OBTAINING WAVE INFORMATION In determining the probable effect of wave action on an offshore drilling structure, it is first necessary to know the usual frequencies of certain wave types for the given location. A technique has been developed which provides a means for obtaining information about wave characteristics in the

Jan 1, 1949

By C. W. Spencer, B. F. Addis, G. H. Bishop, C. A. Steidel

STUDIES of the inter granular attack of metals by liquids have generally been confined to polycrys-talline specimens. This note reports the results of preliminary studies of the penetration of bismuth-rich Ni-Bi liquids into oriented bicrystal specimens of nickel. It is found that isothermal penetration follows a parabolic rate law and shows a definite anisatropy with respect to direction on the grain boundary surface. Nickel bicrystals containing < 100> tilt boundaries were grown using the Czochralski method. Relative misorientation of the parent crystals was controlled to ± 1deg. The boundaries are straight in the growth direction, i.e., the common <100>, and generally straight in the transverse direction, as shown in Fig. 1. The starting material, Inco HPM grade nickel was contained in a recrystallized alumina crucible and maintained under argon. Bicrystals typically contain 30 ppm C, less than 10 ppm S, O, N, and 50 ppm residual metallics, principally iron and silicon. Specimens, as schematically illustrated in Fig. l(c),were cut from bicrystal ingots using a thin water-cooled abrasive wheel. To insure removal of all residual strain, which accelerates the penetration, specimens were round through 600 grit silicon-carbide, chemically polished, and annealed for 4 hr at 1375°C under argon. The procedure described by Cheney et al.1 for exposing specimens to

Jan 1, 1962

By Charles H. Shamel

I fear most of the Institute members are already weary of the perennial controversy about the apex law. I feel that way about it myself now, though I have been guilty of considerable contribution- to the discussion in the past. The discussion does not seem to perceptibly influence previously held views and I would not again break into print on the subject but for the urgent invitation of the Chairman of our Law Committee. This energetic and able member has firmly determined to secure a revision of the mining law and among other things to eliminate the so-called apex provision from the U. S. mining statutes. He is, however, fair about it and has invited me to make ((the strongest possible argument in its favor." I am suspicious that he is acting on the psychological principle that it is usually easier to convince an audience against a cause vigorously but unsuccessfully defended than against one wholly mute. Nevertheless, I realize that personally he wishes me no harm, much as he hates the apex law, and so am willing that the Institute have whatever benefit may accrue from my taking up again the unpopular side of the discussion. I say this because the attitude of a large part of our "articulate" membership seems irreconcilably hostile; their minds are made up; favorable consideration is foreclosed; and they become impatient and even sarcastic at any attempt to elucidate a favorable view of the apex law. The exact question for discussion at the present time is not whether on abstract, or any other considerations, the apex law is the best possible rule, but the very different proposition whether, after nearly 50 years of statutory life and much longer as a practically universal miners&apos; custom, it is now just and expedient to repeal the apex law. At this point it seems to me that we may profitably devote a paragraph or two to the subject of the origin of law in general, as we are presumed to be considering the subject from the high viewpoint of the general welfare of the nation. The most comprehensive and accurate definition of law in the legal sense is, that it is the body of rules for the regulation of human conduct which is enforced by the State, that is, by the nation.l Legal

Jan 1, 1915

By T. H. Aldrich

The Aldrich Mining Go. holds under lease from the Illinois Central R. R. Co. about 14,000 acres, in the east half of Township 12, Range 12 W., in Marion county, Alabama, and owns other lands, of which about 1,000 acres adjoin this leased tract, making a total area of about 15,000 acres, all of which is underlain by the coal-seam upon which the company is operating. This seam is nearly horizontal; and a ravine, diagonally crossing the tract, exposes the outcrop on either side for about 2 miles. The territory has been so divided that nearly the whole of it can be worked out by two collieries. The mines at Brilliant were opened in the fall of 1898, and shipments began in the following spring. The original plan was to furnish steam-coal for locomotives to the Illinois Central R. R. Co.; and upon this expectation the investment of capital was made. The field was entirely new; and the softness of the coal at the outcrop induced the belief that it could be very cheaply mined. A contract for the delivery of a large quantity of coal to the railroad was accordingly executed. But with the advance of&apos; the entries to increasing distances from the outcrop, the coal proved so hard that it could no longer be drilled with a breast-auger; and the expense of mining became so great that the contract for cheap steam-coal had to be canceled. It became evident that the work must be done with machinery and explosives, if it could be profitably done at all. On the other hand, the excellent quality of this coal opened, at the same time, a possible market not specially contemplated at the outset—namely, that of a first-rate coal for domestic and general uses. Since no other deposit of such coal was known to exist on the line of the Illinois Central, or any other railroad

Jan 1, 1907

By Leroy Gardner

EVERY reader of this paper is well aware of the fact that the prolonged inhalation of large amounts of free silica dust results in fibrosis of the lungs, and that other inorganic dusts, except those of asbestos and the mineral poisons, are thought to be relatively harmless. But probably few have had opportunity to visualize the effects of silica, asbestos and other minerals upon living tissues. The ideal demonstration would be based upon sections of lungs from human beings that had inhaled com-parable concentrations of different dusts for a unit period of time. Such material is generally difficult to obtain and in some instances is of ques-tionable value because the subject has been exposed to more than one kind of dust. A demonstration could be prepared from the lungs of animals. However, so many months or even years are required to com-plete the exposure to each kind of dust that enough material has not been accumulated. For a general survey of the action of different types of dust, I am therefore compelled to use the tissues of animals that have been injected with suspensions of dust particles. The injection method offers certain advantages. The quantity, the particle size and the state of dispersion can be controlled with sufficient accuracy so that the tissue responses to different minerals can be accu-rately compared. The method insures contact between the tissues and the mineral particles; protective mechanisms, which may prevent the inhalation of certain types of foreign body, never come into play. If the pathway of injection be one that minimizes nonspecific injury, the tissue responses may simulate those produced by inhalation but they develop somewhat more rapidly. It should always be remembered that injection methods merely demonstrate the capacity of various kinds of minerals to provoke reaction in the tissues; whether the same substances are inhaled from atmospheric suspension and accumulate in the lungs in dangerous quantities can be demonstrated only by inhalation.

Jan 1, 1938

By J. Fred Johnson

COROMANT is the trade name of the alloy-steel drill rod tipped with a chisel-type tungsten-carbide bit manufactured by Sandvik Steel Works Co., Ltd. Other names, such as Swedish or air-leg method of drilling, are used in various localities. Coromant drilling in Sweden was the natural sequence of the adaptation of tungsten-carbide inserts to the already established routine of drilling. By the middle thirties the percussion drill had reached practically its highest attainable efficiency as a drilling machine. Since then improvement has been in metallurgy of component parts to increase life or lessen weight, in the development of pneumatic and automatic feeds, in the use of jumbos to more quickly and easily handle machines, and in changes in drill rods and bits. By 1937, drilling in the United States and Canada was done by relatively heavy mounted drifters with positive hand or automatic feeds. In Sweden, on the other hand, emphasis had been placed on light equipment and drifting was done with pneumatic bars and reverse-feed stopers. In 1938, one of the most prominent American drill manufacturers developed an air-leg for successfully drilling the extremely variable but relatively soft iron ores of some of the northern Michigan mines. Also in 1938, a comparative Swedish test, also in soft iron ore, of a 50-lb jackhammer mounted on an air-leg, against a 100-lb reverse-feed drifter on a pneumatic bar, showed the net drilling time was increased by the air-leg set-up from 51 to 71 pct, in drilling 6-ft rounds in a 6 1/2x6 1/2 ft drift. Miners were becoming scarce in Sweden even at that time and, since the lighter equipment made the work easier and more attractive, the airleg was then made use of in some types of soft rock. In 1940, for instance, a large tunnel for a hydroelectric plant was driven with this equipment. By 1943, when tungsten-carbide inserts came into the picture in Sweden, a great many of the kinks in percussion drilling with this hard-metal had been worked out in Germany under the stress of war conditions. However, only 10 pct of the drilling machines manufactured in Sweden were jackhammers for use on air-legs and only the one manufacturer made air-legs in the United States. American practice had largely supplanted integral forging of drill bits by the detachable steel bit. Canada and South Africa were using the one-pass throwaway bit but Sweden was still using the same old integral forged bit. After a long study of the trend toward simplicity

Jan 1, 1952

By T. V. Moore

DURING 1910, crude-oil production in the United States reached a record level averaging about 3.700,000 barrels daily. Export declined sharply while imports increased with the result that large quantities of crude oil were run to storage during the year. Imports consisted largely of residual fuel oil brought in from South America bit because of a shortage of that product in this country and of Mexican crude. The price of petroleum products followed the declining trend of the last three year resulting in serious disparity between crude and product prices. This condition was aggravated in some areas by the increasing production of distillate by recycling operations and by the high tanker rates prevalent in the last two months of the year. As a result two small purchasers found it necessary to reduce crude-oil price in the Corpus Christie area of Texas.

Jan 1, 1941

By Edward Saibel

The various theories that have been advanced to explain or predict the conditions under which a metal fractures may be divided into two categories: First, there are the macroscopic theories generally used in engineering practice. These are empirical in nature and limited in application. For example, the maximum normal stress criterion, which is quite satisfactory for a mild steel in simple tension at atmospheric pressure,&apos; no longer suffices when this steel is pulled under hydrostatic pressure.2 In all of these empirical theories, the critical condition characteristic of the material and of the loading conditions must be obtained experimentally. Secondly, there are the theories based on interatomic forces,3&apos;4 or on the energy required to form new surfaces.5,6 These have all dealt with the theoretical evaluation of the tensile stress necessary to bring about rupture in a purely brittle manner; that is, without plastic flow preceding fracture. All of these attempts have led to values of the tensile strength of crystals or of polycrystalline bodies that are 100 to 1000 times higher than observed values. On this account, it has been thought necessary by some investigators to conceive of a microcrack structure or distribution of flaws throughout the specimen such that the resulting stress concentrations provide the factor necessary to bring about agree- ment between calculation and experiment. It has been pointed out by several observers&apos; that this point of view is highly unrealistic, in that the weakening effect of these flaws or microstructures must be very uniform from specimen to specimen, since the fracture stresses found for various specimens of the same material tested under similar conditions are so nearly constant. Furthermore, since calculations based on atomic forces or atomic energy are for purely brittle fracture, a condition probably never satisfied in tests, agreement is hardly to be expected. Thermodynamic Theory of Fürth In order to resolve this apparent discrepancy between the theoretical cohesive strengths and the observed fracture strengths, Fürth8 advanced a thermodynamic theory of the tensile strength of isotropic bodies based on work of Born relating to the melting of crystals. Assuming an isotropic material free from imperfections and flaws, behaving elastically up to the breaking point, and assuming a connection between rupture and the melting phenomenon, Fürth obtains an expression for the rupture stress a, in the form where Q is the melting energy per unit mass, p is the density, and is Poisson&apos;s ratio. Furth compares fracture stresses computed from Eq I with the fracture stresses of metals as given in the Landolt-Bernstein Tables (1927) and in the Hand-

Jan 1, 1947

By Edward Saibel

The various theories that have been advanced to explain or predict the conditions under which a metal fractures may be divided into two categories: First, there are the macroscopic theories generally used in engineering practice. These are empirical in nature and limited in application. For example, the maximum normal stress criterion, which is quite satisfactory for a mild steel in simple tension at atmospheric pressure,&apos; no longer suffices when this steel is pulled under hydrostatic pressure.2 In all of these empirical theories, the critical condition characteristic of the material and of the loading conditions must be obtained experimentally. Secondly, there are the theories based on interatomic forces,3&apos;4 or on the energy required to form new surfaces.5,6 These have all dealt with the theoretical evaluation of the tensile stress necessary to bring about rupture in a purely brittle manner; that is, without plastic flow preceding fracture. All of these attempts have led to values of the tensile strength of crystals or of polycrystalline bodies that are 100 to 1000 times higher than observed values. On this account, it has been thought necessary by some investigators to conceive of a microcrack structure or distribution of flaws throughout the specimen such that the resulting stress concentrations provide the factor necessary to bring about agree- ment between calculation and experiment. It has been pointed out by several observers&apos; that this point of view is highly unrealistic, in that the weakening effect of these flaws or microstructures must be very uniform from specimen to specimen, since the fracture stresses found for various specimens of the same material tested under similar conditions are so nearly constant. Furthermore, since calculations based on atomic forces or atomic energy are for purely brittle fracture, a condition probably never satisfied in tests, agreement is hardly to be expected. Thermodynamic Theory of Fürth In order to resolve this apparent discrepancy between the theoretical cohesive strengths and the observed fracture strengths, Fürth8 advanced a thermodynamic theory of the tensile strength of isotropic bodies based on work of Born relating to the melting of crystals. Assuming an isotropic material free from imperfections and flaws, behaving elastically up to the breaking point, and assuming a connection between rupture and the melting phenomenon, Fürth obtains an expression for the rupture stress a, in the form where Q is the melting energy per unit mass, p is the density, and is Poisson&apos;s ratio. Furth compares fracture stresses computed from Eq I with the fracture stresses of metals as given in the Landolt-Bernstein Tables (1927) and in the Hand-

Jan 1, 1947

By Gordon M. Yocom

A PROPER consideration of the subject of this paper should include economic aspects as well as the technical phases of the metallurgy, production, and properties of the product. The metallurgical phases of the processing and properties of the product will be considered only from practical aspects and within the scope of the writer&apos;s experience with tonnage production. The Bessemer process was invented 85 years ago and became important because it put steel manufacture upon a larger and less costly basis. In America the Bessemer production has declined for many years and has not maintained its proportionate place with the rapid advances of the open hearth. The achievements in the open-hearth field were attained by the greater number of technical people attracted to that branch of the industry. The antipathy of technical students for the older and less popular Bessemer field gradually weakened the forces defending it and retarded the development of new and better methods. In Europe the economic advantage of the basic Bessemer process has not been overlooked and the tonnage usually is greater than that of the open hearth. The acid process has been the subject of renewed attention in America during the past few years and those who are more familiar with it are striving to show that the method is too valuable to abandon. A considerable tonnage of Bessemer-blown metal, in both molten and ingot forms, used in connection with the open-hearth practice makes it an important auxiliary unit to the industry. This practice aids in modifying the price level of heavy remelting scrap in addition to speeding up the open-hearth operation. The use of Bessemer steel has continued not only because of periodic economic advantages but also because of certain inherent qualities of machinability, weldability and stiffness, which are valuable for many applications. The properties of stiffness and rather high reaction to cold-work require some modification in order to meet the demands of modern methods of processing, which involve cold-reduction and cold-forming. At least one factor contributing to the stiffness of this steel is the relatively high phosphorus content of the acid product. The phosphorus content of the Thomas or basic Bessemer steel of Europe is considerably lower than the normal acid product in America. The American industry has continued the use of the acid process chiefly for the reason that the available ores are more easily adapted to this process from both metallurgical and economic standpoints. In European practice the basic process is necessary with the highly phosphoric ores available and it is sustained to some degree by the sale of the rich phosphate slag as a by-product. The basic process was used in this country at several plants many years ago, but was abandoned for economic reasons. A part of the past history of these trials is given here because the author believes it has not been published and it has some bearing on the subject of this paper. The information is authentic to the extent that

Jan 1, 1941

By Milton T. Pana

Computer techniques now have been applied to the solution of a wide variety of scientific and engineering problems in the mining industry, but generally not in great depth in any one area. In mining, the area covered in greatest depth and with the greatest success has probably been mine planning and to a lesser degree production scheduling. A rather comprehensive review of the literature related to mine planning and production scheduling indicates that contributions in these areas have been geographically, as well as organizationally, widespread. Of twenty-six papers reviewed, eleven were from industry, eight from educational institutions, four from computer vendors, two from the Bureau of Mines, and one from a private consultant. The conclusions that can be derived from the literature are: First, the-state-of-the art has advanced to the point that computing ore reserves and developing mining plans with the aid of the computer is now a routine practice; second, the application of the computer to mine planning problems has markedly improved our ability to estimate ore reserves, more accurately define pit limits, and determine an optimum mining sequence. MINE PLANNING The papers in this section deal essentially with the problem of determining the final pit limits of an orebody and the ore reserves associated with a given pit limit. The problem is probably best described by Soderberg25 and more recently by Reibell. 23. There are two techniques currently being applied to this problem by several mining companies: 1) the multiple-cone technique and 2) the Lerch-Grossman algorithm. The multiple-cone technique is the older of the two techniques and has the advantage of being more flexible, allowing an engineer to easily vary pit slopes in different sectors of the design. The technique can also be used to define intermediate pit contours. The Lerch-Grossman algorithm is appealing in that the final solution is given in the form of a true mathematical optimum. The technique is limited, however, in that the size of the blocks in the orebody model are a function of the desired

Jan 1, 1969

By M. F. Comerford

M. F. Comerford (Smithsonian Astrophysical Observatovy)- The authors&apos; concern about the effects of preferred orientation is justified and emphasizes a phenomenon that can be a source of serious error, but the cogency of their concluding statement bears close examination. They contend that comparison of intensities from parallel planes of the two phases, as proposed by Averbach, Comerford, and Bever,13 leads to incorrect results. The state- ment is based on the fact that, in Fig. 3, intensity measurements at extreme angles of tilt, (2, lead to different values than those given by the average of all the data. The proposed explanation is that unsuspected superpositions of (110), reflections spuriously enhance the martensite intensity. However, it can be shown on appropriate stereographic projections that no superpositions occur which can affect the reflections in question. Hence, the ex-

Jan 1, 1965

By Albert F. J. Bordeaux

Discussion of the paper of Albert F. J. Bordeaux (Bi-Monthly Bulletin, No. 23, September, 190S, pp. 629 to 640). A. H. BROMLY, Zihuatanejo, Guerrero, Mexico (communication to the Secretary*) :-The following criticism of what "is offered as a summary which may be found useful by mining engineers," is not dictated by any captious spirit, but in the interest of historical and scientific accuracy. The States of Queretaro and Oaxaca have produced sufficient silver to warrant more extended notice. Referring to Pachuca, State of Hidalgo, the somewhat loose and. inexact statement is made that "the ore-deposit is an andesite, intermixed with quartz-veins, rich from the surface." A better description would be,-the ore-deposits consist of quartz-veins in andesite. It is notable that many of the rich shoots worked in recent days did not come to surface. In consequence, Pachuca, is often quoted by the ill-informed as a camp in which values improve with depth, the truth being that the veins carry shoots, or clavos, some of which were exposed at surface and some not. The name of " electric plow," applied to the mechanical stirrer of recent use, is certainly not to be recommended. The stirrer, or agitator, consists essentially of a traversing gang-plow, operated by power through shafting, drums, and wire-rope. The fact that in certain plants the motive-power used is electricity does not make it an electric plow. Such a name suggests a machine of which the motor is an essential and integral part; which is not so in this case. A lathe in a factory driven by water-power is not called a hydraulic lathe. My experience agrees with Dr. Raymond&apos;s note as to azulaque, which in sortie districts is also applied to blue copper carbonate. The El Oro, Esperanza, and Mexico mines should be allocated to the State of Mexico; the Dos Estrellas being in Michoacan, as stated. The El Oro quartz certainly does not appeal to me

May 1, 1909