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By M. P. E. Desvaux, P. Charsley

OLIP-line observations on copper alloys, using the electron microscope, have been made by a number of workers,13 but this work has been confined to a brass. In a CuAl alloys Koppenaal4 and Koppenaal and Fine5 have made observations with the optical microscope and by the use of interferometry. They found that the observed slip step heights inside the Liiders bands accounted for only 42 pet of the total macroscopic strain. The suggestion was put forward that optically unresolvable slip in other parts of the specimen accounted for a major part of the macroscopic strain. This is surprising since it is known from other workers that slip in a brass is inhomogeneous; i.e., large amounts of slip occur on individual {lll) closelys paced than being shared by a large number of closely spaced planes. Furthermore, a brass and a CuAl alloys with high concentration of aluminum exhibit similar deformation characteristics and slip-line patterns. Prior to investigations into the behavior of copper and a CuAl alloys under reversed stresses in tension and compression, some preliminary experiments have yielded results which the authors think resolve this discrepancy, and throw some further light on the behavior of a CuAl in tension. An experiment was carried out on a 10 at. pet CuAl single crystal, of gage length 7.5 cm, diameter 3.1 mm, and orientation shown in Fig. 3 (inset), for the purpose of resolving the above discrepancy. The specimen gage length was electropolished for 10 min in a 50:50 orthophosphoric acid (SG=1.75)-distilled water system, with 2 v across the cell and a current density of 0.5 amp per sq cm. The cathode was made of copper. After a tensile strain of 0.067 ± 0.001, intense slip was observed over a length 2 cm of the gage length whilst the rest of the specimen was relatively undeformed. In the lightly deformed region, slip bands of mean width 20 /x were spaced about 1 mm apart on average. The transition from the heavily slipped region (usually called a Liiders band) to the lightly deformed region was gradual, the slip-band density increasing as the "Liiders band" was approached. In the latter, the slip bands became so close together that, to the naked eye, the specimen appeared to be continously slipped, and the typical microtopography of this region is shown in Fig. 1. Twelve electron micrographs were taken at random from replicas of the Liiders-band region, and the widths of the slip lines were measured. The slip lines account for an over-all tensile deformation of 7.0 ± 0.7 pet, after allowing for the lengths of the un-slipped regions, which is in good agreement with the macroscopic strain. The distribution of slip-line widths was also measured and is shown in Fig. 3. Since Koppenaal could not resolve slip lines with height less than 540A (limit of resolution represented by dashed line), then it was deduced that he could have measured only about 50 pet of the deformation within the 'Liiders Band'. It is concluded, contrary to the suggestion of Koppenaal,5 that virtually all the macroscopic strain is accommodated within the "Luders band" and that there is no need to invoke fine slip distributed uniformly over the gage length.

Jan 1, 1967

By G. F. Fix

Oil and gas activity reached a higher peak in Indiana during 1940 than for any like period during the past decade. Major activity, as during 1939, was in the southwestern part of the state, the Indiana portion of the Eastern Interior Coal Basin, where most of the increase was due to field drilling in previously proven areas. The amount of wildcat drilling was about the same as for 1939. No new fields of any apparent consequence were discovered during the year, with the possible exception of the College pool, in southwest Posey County. Only one well had been completed in this area at the end of the year. About 10 ft. of saturated Aux Vases sandstone was drilled in this well and the initial production was I00 bbl. of oil a day. Other discoveries during the year 1940 include: St. Thomas, in southwestern Knox County, where four McClosky wells, ranging from I00 to 300 bbl. a day initially, were com-pleted; Buff kin, in central Posey County, with 11 oil wells and 5 gas wells completed; and new developments in two old areas —Randolph County (part of the old Trenton field) and Gentryville, northwestern Spencer County, where some oil was found many years ago. The St. Thomas field proved disappoint-ing, with very spotty production from the McClosky horizon of the St. Genevieve limestone at a depth of about 1875 ft. The discovery well flowed 362 bbl. a day ini-tially. At the end of the year the field was pretty well outlined by dry holes and some inside locations were dry. The Buffkin pool also proved spotty, with production from shallow Pennsylvanian sands and from the Basal Pennsylvanian Mansfield sandstone, the latter at a depth of approximately I175 ft., with small production from the Cypress sandstone of Chester age. Oil wells in this pool are small, ranging from 25 to 75 bbl. a day. The Randolph County area, on the east side of the Trenton gas field, showed some promise for a commercial gas field, with four completed gas wells having cumulative initial flows of about 1,200,ooo cu. ft. a day. The area appar-ently was not depleted during the Trenton boom at the turn of the century, since casing pressures are about as high as the virgin pressure in the old field. Elsewhere the pressure has dropped as low as 5 pounds. The Griffin field received most of the drilling during 1940, with 163 completed oil wells. This field now covers about 3200 acres on the Indiana side of the Wabash River and is not as yet completely delimited. It produced the major part of Indiana's oil during the year—a total of 3,594,000 bbl. At the end of 1940, there were 253 producing wells in Griffin. New Harmony had five completions for a total of 24. The Rockport field, in Spencer County, continued to be actively developed and had a total of 45 gas wells and 9 oil wells at the end of the year. Oil in commercial quantities had not been found in the field previous to 1940. Total gas production for the year was 394,470,000 cubic feet. In all, 521 wells were drilled in the state during 1940, as compared to 377 for 1939. Of this number 248 were oil wells, 77 were gas wells and 196 were dry. Divided into

Jan 1, 1941

By H. A. Wahl

This paper presents methods of designing hydraulic fracture treatments in formations saturated with slightly compressible liquids. Howard and Fast describe the fluid-loss control resulting from the viscosity and compressibility effects of the reservoir fluid in terms of a fracturing fluid coefficient. However, for horizontal fractures, this coefficient is applicable to infinitely thick reservoirs. These methods of evaluating fluid loss from horizontal fractures during treatment differ from previous methods in that: (I) formation thickness is incorporated in the velocity function describing the rate of fluid loss to the formation; and (2) for a given thickness the relative position of the fracture to the horizontal boundaries of the reservoir or any interrnediate permeability barrier is incorporated in the design procedure. This theory is applied to several actual and hypothetical field cases. The results of these calculations demonstrate that the eflect of formation thickness on fluid loss from horizontal fractures may result in fractures several times larger than predicted by other methods. INTRODUCTION Hydraulic fracturing has been the dominating well-stimulation technique during the last decade. From the time it was commercially available, fracturing has had a very favorable success ratio compared to other stimulation methods. However, numerous wells that were successfully stimulated remained economic failures. Only in the last few years has the oil industry recognized the importance of designing treatments for each well which will yield the maximum profit. This implies that for a given set of treatment conditions the size and general physical characteristics of the fracture can be determined. One of the outstanding contributions in the field of fracture design was presented by Howard and Fast.' In their paper, three flow mechanisms that control fluid loss from the fracture to the formation are defined: (1) viscosity effects of the fracturing fluid, (2) viscosity and compressibility effects of the reservoir fluid, and (3) wall-building effects of a treated fracturing fluid. The rate of fluid loss to the formation adjacent to a fracture is shown to be a function of time. For each flow mechanism the velocity function v(t) is expressed as a constant or fracturing fluid coefficient divided by the square root of time. This form of v(t) can be used in the Carter equation, as developed in the Howard and Fasc paper, to estimate the areal extent of fractures. This equation may be written as In the following sections the effect of formation thickness on fluid loss from horizontal fractures is evaluated when the controlling flow mechanism is the viscosity and compressibility of the reservoir fluids. The major assumptions inherent in the Carter equation are brought out in subsequent mathematical developments. THE EFFECT OF RESERVOIR FLUIDS ON FRACTURE EXTENSION When a fracture treatment is performed using a fracturing fluid identical to the reservoir fluid, the only flow mechanism controlling fluid loss is the viscosity and compressibility effects of the reservoir fluids. In developing a fracturing fluid coefficient for this mechanism, Howard and Fast considered a segment of the formation bounded by a unit area on the fracture face and extending to infinity in the direction of leak-off as shown in Fig. 1(a). The direction of leak-off z is normal to the fracture face. The equation governing the linear isothermal flow of fluid into this segment is where a = Eq. 2 is a form of the diffusivity equation. It is derived from the equation of continuity, Darcy's law and Eq. 3

By P. E. Baker

An improved method of logging formation density has been developed in which the formation is bombarded with a collimuted beam of gamma rays. By means of a scintillation detector and pulse height discriminator, the gamma-ray energy band is accepted and recorded which corresponds to deepest penetration into the formation. Laboratory tests on a field tool revealed no borehole diameter effect for smooth holes and no effect of formation chemistry, except insofar as chemistry affects density. In extensive field tests, the density log has exhibited satisfactory agree-ment with core measurements and has correlated accurately with other logs. INTRODUCTION This paper describes an improved method of logging formation density by means of back-scattered gamma rays to penetrate the formation together with energy discrimination to select only that energy (or frequency) range corresponding to deepest penetration into the forma- tion. This method of density logging was developed at the La Habra laboratory of California Research Corp.* Field instruments have been built and tested by McCullough Tool Co. and commercial service has begun in some areas. All of the data discussed here were obtained for the original field tool. The density log can be a valuable adjunct to existing logs because of its use in determining porosity quantitatively. It is useful also in connection with seismic and gravity surveys where formation density information is of interest. PHYSICAL PRINCIPLES The intensity, I, of a beam of gamma rays after traversing a distance, x, in an absorbing medium is given by I = loe -ax where I, is the intensity of the beam entering the medium and a the attenuation constant or macroscopic cross section of the medium for gamma-ray absorption. The macroscopic cross section depends on the number and types of atoms per unit volume and the gamma-ray energy. In brief, it is the sum of the atomic cross sections of all atoms per cubic centimeter. The density of the material is the sum of the masses of all atoms per cubic centimeter. Thus, the density and the macroscopic cross section for gam-ma-ray absorption vary in propor- tion to the number of atoms per cubic centimeter. The density of the material increases, of course, if the atomic masses increase without a change in the number of atoms per cubic centimeter. When the density increases in this latter way, the macroscopic cross section increases also, but disproportionately. This results from the fact that part of the gamma-ray absorption arises from the photoelectric effect and the pair-production effect**, which are proportional to the sixth and to the second power, respectively, of the atomic number of the absorber. The remainder of the absorption results from the Compton effect, and is directly proportional to the atomic number. The gamma rays that undergo Compton scattering are not immediately absorbed. Since these rays are scattered in all directions, a fraction will emerge from the face of the medium at which they entered. If a gamma-ray shield is placed between the source and detector, most gamma rays reaching the detector will be those scattered out of the medium. The intensity will depend on absorption and scattering in the medium, and so indicates the density of the medium. For gamma rays for which Compton scattering prevails, the intensity

Jan 1, 1958

By R. T. Hukki

The purpose of this paper is to present an analysis of the unit operation of grinding and the circulating load, of the unit operation of classification and the circulating load, and of the two superimposed into one operation to clarify the overall trend of events relating the circulating load to the capacity of the closed circuit grinding system, to the specific surface area of the final fine product, and to the energy consumption in the closed circuit grinding process. The capacity of the closed circuit is frequently, if not always, determined by the classifier, not by the mill." With these words a startling idea was expressed in 1934 by Dorr and Anable.1 Today, some 30 years later, grinding in closed circuit is universally accepted. The basic curve presenting the capacity factor versus circulating load by Dorr and Anable has obviously been so convincing that not a single authoritative investigation regarding its validity seems to have been conducted. The only major subject of discussion appears to have been the relative merits of the 'high' and 'low' circulating loads. It seems to be universally agreed that much still remains to be hoped for regarding sharpness of classification. BASIC CURVES FOR CONSTANT MILL LOADING Fig. 1 presents a series of basic curves for constant mill loadings in function of new feed rate and circulating load. The mill loading indicated by each curve is the sum of hourly tonnages of new feed and circulating load. For example, at point 0 where the new feed rate is 100 t/h and the circulating load 300%, or 300 t/h, the mill loading is 400 t/h. In closed circuit grinding, the new feed rate corresponds to the rate of finished classified material produced. Although at this stage the effect of classification is excluded in construction of the basic curves, the trend indicated by these curves is strongly in favor of closed circuit operation under relatively small circulating loads. A study of the curves reveals that, e.g., a mill operating under a load of 200 t/h at point P where the new feed rate is 50 t/h and the circulating load 300% will also operate under the same total load at point Q where the new feed rate is 100 t/h and the circulating load 100%. In other words, a reduction of circulating load from 300% to 100% would lead to doubling of the new feed rate and doubling of the rate of production of finished material, without a change in the total mill loading. The obvious question is, is it also possible by a reduction of the circulating load in a closed industrial grinding circuit to increase the production of finished classified material and, if so, how and to what extent? GRINDING TESTS BY DORR AND ANABLE In a series of open circuit grinding tests reported by Dorr and Anable1 limestone was ground at various feed rates in a 3-ft ball mill. The original data are reproduced in Table I. It can be seen that with the increased feed rate production of -65-mesh material increased and the energy consumption per unit weight of the -65-mesh product decreased in the reverse ratio. The data shown in Table I have been reproduced for our purposes in Table II for a scale corresponding to grinding in a large industrial mill. This reproduction

Jan 1, 1968

By W. A. Backofen, B. B. Hundy

THE pole figure interpretation in a recent paper' on the torsion texture of copper was questioned in discussion,2 nd a simpler alternative interpretation was proposed. In the hope of reaching a positive decision in favor of one or the other, further studies were undertaken with 70-30 brass and Armco iron. This additional work has not answered all the questions about torsion textures, but the new pole figures do offer support for the original interpretation and show that the texture is more complicated than the alternative suggests. From the previous paper,' the appropriate method of describing the texture in a twisted bar is known to be a pole figure plotted on a plane tangent to the surface of the bar. The axes of the pole figure are chosen to coincide with directions in the tangent plane which are parallel and at right angles to the bar axis (the longitudinal direction, L.D., and the transverse direction, T.D.), for these directions define symmetry axes of the texture. Therefore any ideal orientation that might be selected to represent the texture gives the crystallographic plane parallel to the tangent plane and the crystallographic direction parallel to the axis of the torsion specimen. A unique texture was assumed in the original interpretation, and the four ideal orientations, (112) [111], (111) [112], (110) [001], and (112) [131], were used in its description. Of the four orientations, the first three provide possible slip directions along the direction labeled T.D. in the pole figure, which is one of maximum shear stress in a specimen being twisted. The alternative, however, simply considered the texture to be made up of two components, one a [Ill] alignment along the specimen axis with a random orientation about the axis as in the wire texture, and the other a superimposed orientation (110) [0011. Experimental evidence for this simpler interpretation was derived from two observations: 1—twisting did not alter the orientation of a single-crystal torsion specimen of a brass in which an octahedral plane was perpendicular (and a [Ill] direction parallel) to the axis, and 2—deformation bands with approximately the (110) [001] orientation were seen to develop in the crystal during the test. The new pole figures were obtained with a brass and an iron torsion specimen of 3/4 and 1 in. gage length diameter, respectively. After annealing, polishing, and twisting, seven rods, about 0.030 in. in diameter and with different orientations, were prepared from material near the surface of each specimen; these were required for the method of constructing pole figures by using a Geiger counter as developed by Norton.5 Since the shear strain gradient in plastic torsion is linear, it was readily computed that the material supplying the brass rods had been subjected to a shear strain of about 3.2, and that supplying the iron rods had received a shear strain of about 2. All details concerning specimen design, testing procedure, rod preparation, and use of the Norton technique can be found in ref. 1. Only this procedure was followed in working out the (111) and (100) pole figures for brass, Figs. 1 and 2. However, X-ray photograms were also involved in the construction of the (110) pole figure for Armco iron, Fig. 3. The photograms were made according to the conventional transmission diffraction technique using a small sheet taken parallel to the specimen surface and etched to a thickness of about 0.0025 in. They were especially important in locating the boundaries

Jan 1, 1954

By Pol Duwez, Paul Pietrokowsky

Titanium and vanadium form a complete series of solid solutions at temperatures above 885°C. Below 885°C, vanadium is slightly soluble in a titanium (about 1.5 pct V at 650°C) and a two-phase a plus ß region extends to 18.5 pct V at 650°C. The alloys up to 15.0 pct V transform into a supersaturated a solid solution upon rapid cooling from the ß phase. Above 15 pct V the ß phase may be retained. The temperature at which the ß to a' martensite-type transformation takes place decreases steadily from 850°C for 0.5 pct V to 325°C for 12.7 pct V. IN the transition series of the periodic table, the six elements that have a body-centered cubic structure at all temperatures, namely chromium, vanadium, molybdenum, columbium, tungsten, and tantalum, fulfill the conditions required for the existence of complete series of solid solutions with the high temperature (ß) form of titanium. Up to the present time, complete solubility at temperatures above the a to ß transformation of titanium has been observed in the systems Ti-MO,1,2 Ti-Cb,2 Ti-W,³ and Ti-Ta.³ The two remaining elements, vanadium and chromium, have atomic diameters which are not as near that of titanium as the atomic diameters of the four other elements. Both are smaller than titanium and the difference, expressed in percentage of the titanium atomic diameter, is 12.3 pct for chromium and 8.2 pct for vanadium. On this basis, the least favorable conditions for solid-solution formation are therefore encountered in the Ti-Cr system. The early work on the Ti-Cr system4 revealed that up to about 1100°C the solubility of chromium in ß titanium is limited, and an intermetallic phase exists near the stoichiometric composition TiCr2. It was found later' that a continuous series of solid solutions extends across the diagram at higher temperatures, and TiCr2 forms by solid state reaction. It became apparent therefore that complete solubility would also be present in the Ti-V system. The present investigation confirms this possibility. The iodide-refined titanium used in this investigation was purchased from the New Jersey Zinc Co., New York. According to the manufacturer, a typical analysis of this product is 0.0065 pct Mn, 0.0022 pct Fe, 0.0015 pct Cu, and 0.0042 pct Pb. The Vickers hardness number (10 kg load) of the crystalline bar varies between 55 and 80. The vanadium metal was purchased from the Westinghouse Electric Corp., Lamp Div., Bloomfield, N. J. The purity of this metal is probably above 99 pct V. The oxygen content must have been quite low, since a bar about 1/4 in. square could be cold rolled into a ribbon 0.020 in. thick. To prepare the various alloys on the titanium-rich side of the diagram, the titanium rod was machined into cups 1 cm in diam and about 1.5 cm high. Pieces of vanadium, of the proper weight, were cut from the square bars and placed within the cups prior to melting. On the vanadium-rich end of the diagram, single pieces of the metals, in the proper weight pro-

Jan 1, 1953

By Roscoe E. Bell

BETWEEN 1945 and 1948 the author made studies of the western phosphate industry and its potentialities. These included an appraisal of the opportunities for western development of the industry, studies of production costs, of market potentials, of transportation economics, and of industry location. This paper will be directed toward pointing up the factors which have an important bearing on the establishment of fertilizer plants in the western area. Industry Location Factors: There are, of course, an infinite number of possible organizational setups which might require consideration. However, the phosphate industry is simple enough so that studies of the most probable alternatives can be made conveniently. The salient factors which require special consideration in such a study are: (I) the location of the raw materials, (2) the location, size, and character of the present and potential markets, (3) the location of energy sources and materials required for fertilizer processing, (4) the location and capacity of present manufacturing facilities, (5) the cost of assembling the materials and energy needed in manufacturing, and (6) the cost of distributing the manufactured product. Raw Material Supplies: Rock phosphate is the raw material for the manufacturing of phosphate fertilizer. In the United States the important known deposits of this material are located in three general areas (fig. 1). The western deposits, comprising about 60 pct of the nation's supply, are in the four-state area—Idaho, Wyoming, Utah, and Montana. The Florida deposits comprise roughly 38 pct of the national supply. The Tennessee deposits, comprising about 2 pct of the national supply, have been the most important source until recent years. The western deposits, which are virtually undeveloped, have not been used to any extent to meet the nation's need for phosphate rock and phosphate fertilizer. Fertilizer Markets: The large national markets for fertilizer are in the midwestern and eastern United States (fig. 2). The principal far-western markets are along the Pacific Coast, especially in California. Until recent years the western markets have been extremely limited, whereas the markets in the eastern United States have long been established and manufacturing facilities have been provided to meet these needs (fig. 3). In recent years the western markets have expanded very rapidly, continuing to grow throughout the war years and postwar period at a similar rate. The question always arises as to whether this is a temporary war-swollen market which will shrink back to its original size as soon as the present agricultural price levels drop. In order to answer this question consideration must be given to the character of the market (fig. 4). I have considered seventeen western and midwestern states in the western market area where transportation costs from the western deposits are equal to or lower than those from Florida. They include all states west of a line drawn through Chicago, Kansas City and the western boundary of New Mexico. In the mewar period this was a small market totaling only 37,000 tons of P,O, annually. The 1946 total for this same area was approximately 200,000 tons. Considerably more fertilizer would have been used in 1946 had adequate supplies been available. Estimates of future markets are difficult to make, but we do have some indices that are useful. The

Jan 1, 1951

By A. M. Gaudin, D. W. Fuerstenau

IN concentration of certain ores by soap flotation, prevention of quartz flotation is desired; the contrary is true in treatment of some oxide iron ores. Experimental study of the flotation of quartz goes back at least a quarter of a century.' Clean quartz does not float with fatty acids or soaps but does float when activated by one of many metallic salts. Control of pH is important. Broadly speaking the problem of quartz flotation has been approached from the empirical side, as was the related topic of flocculation or dispersion of quartz suspensions? Empirical studies indicated the existence of critical relationships between the additions of collector and activator. These additions were not stoichiometric for the formation of soaps of the activator cation. For example, Gaudin and Rizo-Patrona found optimum quartz flotation at pH 10.6 using barium activation and oleate collection when the molar ratio of oleate to barium was 1 to 1 instead of 2 to 1, as would be called for formation of Ba(OL),. Cooke and Digre" ' found that if calcium is the activator, a minimum quantity of that agent is required for effective flotation when the pH is 11.5. In other words, if the concentration of Na' exceeds 10 -2.5 mols per liter or if the concentration of H exceeds 10-11 mols per liter, the concentration of Ca++ in solution required for quartz activation is increased. This suggests that H+ is much more effective than Na+ on 10-2.5 quartz, perhaps in the ratio ofp or 108. Schuh- mann and Prakash6 studied anew the activation of quartz by barium, calcium, aluminum, and ferric iron. Salts of these metals are activators provided they are in stoichiometric excess over the collector used with them. Alkaline-earth salts are effective only in alkaline circuits. Important as they are in giving data on the effect of various agents on quartz, all these studies fail to give information on the detailed structure of the quartz-solution interface. A beginning in this direction was made by Gaudin and Chang,? who measured the adsorption of radioactively marked barium and laurate ions at quartz surfaces, and by Gaudin. Spedden, and Laxen,8 ho measured the adsorption of radioactively marked sodium at quartz surfaces. Work has also been done by Bell0 n measurement of the adsorption of sodium ion and chloride ion at quartz-solution interfaces. In all these experimental measurements of adsorption, the solid was centrifuged or filtered from the bulk of the liquor with which it had been associated; and the composition of the solid surface was ascertained by analysis, after allowance was made for the ionic composition of the liquor included with the centrifuged solids on the assumption that it is identical to the bulk liquid. Adsorption measurements give only the total amount of collector adsorbed at the quartz-solution interface; they give no indication of the distribution of these adsorbed ions at the interfacial layer. It is the ionic structure of the solid-solution interface and its importance to flotation that is the subject of this paper. The structure of this interfacial layer can be investigated by means of electrokinetic methods so that by combining electrokinetic studies with adsorption measurements, a more complete picture of the quartz surface may be obtained. The following studies were made to ascertain how electrolytes used in the soap flotation

Jan 1, 1956

By P. E. Schauer

During the initial nine-year deple-tion of the McKamie-Patton pool gas-condensate reservoir, the pressure behavior and fluid analyses indicated pressure maintenance by gas injection would be attractive relative to continued pressure depletion. As a result, a gas cycling program was inaugurated in Aug., 1949, which has since maintained reservoir pressure. In order to evaluate the benefits of this program, the recoveries for natural depletion and for cycling followed by blowdown were determined by calculating the fractional balance of the molar quantities of vapor and liquid remaining in the reservoir and produced at the surface for various stages of depletion. The results of the investigation show theoretical ultimate recovery due to the cycling program will be 42 per cent greater than would be realized under pressure depletion type operation. INTRODUCTION The benefits of gas injection pressure maintenance programs in condensate reservoirs have been recognized and qualitatively described in several papers1-8 during the past 15 years. Some of these papers also describe methods for calculating the increased recovery realized from cycling; however, as a rule, hypothetical reservoirs were used as examples".'.. This paper presents an evaluation of the pressure maintenance program for the McKamie-Patton condensate reservoir and includes a description of the fractional balance method employed to determine the benefits. Reservoir Development and Characteristics The McKamie-Patton pool, Lafayette County, Ark., was opened in June, 1940, with production obtained from the oolitic Smackover lime at a depth of approximately 9,300 ft. The structure is an anticline 8 miles long by 1 to 2 miles wide, and is one of many productive Smackover structures in Southern Arkansas. Of predominant importance is the condensate-bearing gas cap portion of the reservoir, which covers approximately 4,000 acres, attains a maximum thickness of some 200 ft, and has an average thickness of 90 ft. Development of the cap was accomplished with 21 wells drilled on 160 acre spacing. An isopach map of the cap is shown in Fig. 1. In addition, an oil rim is present along most of the periphery of the pool. Production practice includes field separation of black oil, and a high pressure gathering system which carries total well stream from gas cap wells to a plant where condensate is separated and the gas is processed for recovery of natural gasoline, butane, and propane. Since the gas contains appreciable hydrogen sulfide, it is removed by amine contact, after which free sulfur is produced by the Claus process. Core analyses from 1,767 gas cap formation samples averaged 14.2 per cent porosity and 379 md dry air permeability. Connate water was restored on seven samples of gas cap rock by air-brine capillary techniques, from which the interpreted water saturation averaged 28.17 per cent. During the early life of the field, it was believed the recovery mechanism, based on several of the other regional Smackover reservoirs, might be a natural water drive. However, subsequent production and pressure history revealed that the gas cap would not be produced by water drive, but would behave as a closed reservoir. In this respect, during the nine-year period of natural depletion from initial production to Aug., 1949, the cap production of 84.3 billion

Jan 1, 1958

By W. A. Ver Wiebe

Spurred on by the very high demands for new crude supplies resulting from World War 11, the oil men of Kansas strained every effort in 1943 to find as many new pools as possible. In all, 1761 test wells were drilled, ,of which 895 were successful in finding new oil supplies and 32 in finding new gas supplies. The total number of wildcat wells drilled in Kansas was 577, including the so-called "extension wildcats," which are located less than 2 miles from production. As a result of the very determined effort to find new oil reserves, 49 of the wildcat test wells found new oil pools in western Kansas and 7 found new oil pools in eastern Kansas. There were 289 rank wildcat tests, and among these 28 were successful ventures. They are responsible for 26 of the new oil pools recorded for the year and 2 of the new gas pools recorded. The ratio of dry holes to producing wells among such rank wildcats is thus approximately 10 to I (289 dry and 28 good). This compares with a ratio of II: I in 1942 and 6:1 in 1941; the same in 1940 and 5:Iin 1939. With nearly all wells flowing to their maximum economic capacity, the total production for Kansas during 1943 reached a new high; that is, 107,700,000 bbl., compared with 97,000,000 during the previous year. Similarly, the amount of gas sold during 1943 made a new high point on the production curve. The total amount was 122 billion cubic feet, compared with about 98 1/2 billion cubic feet for the year previous. As usual, the large Hugoton field of south- western Kansas accounted for approximately half of the total gas production. Highlights of the Year Despite the fact that 56 new pools were found in Kansas during 1943, it must be admitted that the future reserves of the state have not been increased greatly. Most of the new pools seem to be of minor value, although it is admittedly impossible to gauge the future production of any pool in Kansas with any exactitude. Judging by the later performance of some of the pools found in 1942 and in 1941, less than five of the new pools are likely to make any great contribution to the state's future oil reserves. Taking up the counties of Kansas in alphabetical order, the following statements summarize the highlights of the year. In Graham County, the Morel pool was extended to the southeast and this pool now promises to become one of the important pools of western Kansas. Several of the older wells have already contributed more than I000,000 bbl. of oil, and such a figure is considered very satisfactory in Kansas. In McPherson County, important new reserves were found by persistent drilling in township 17 S., R. I. W., the most northeastern township of the county. Many new wells in older pools and discovery wells in new pools make this region look promising. The Lindsborg pool, which had a sensational revival during 1942, was also extended in a number of directions and has now become a rather large producing area with a fairly high future potential capacity.

Jan 1, 1944

By A. F. Henderson, C. F. Cornell, A. F. Dunyon, D. A. Dahlstrom

IN processing magnetic taconites several steps of crushing, grinding, classification, and magnetic separation are required to produce a 60' pct Fe concentrate. Usually the final concentrate is in a slurry form of 55 to 70 pct solids by weight and is further characterized by a particle size of 60+ pct —325 mesh. In taconite plants already completed or under construction the conventional method used to obtain pellets suitable for blast furnaces is to filter the concentrate slurry, ball the filter cake, and then harden the green pellets in a traveling grate or in a vertical shaft furnace. Large tonnages must be handled in minimum floor space, with reduced maintenance and lowest possible operating cost. Filtration must therefore achieve two objectives: I) high filtration rate—in terms of pounds of dry solids per hour per square foot of filtration area—at a low filtrate solids concentration, and 2) a filter cake moisture that will always permit efficient balling within the normal fluctuations of ' plant operating conditions. If moisture contents are too high, balling may be impossible or result in a mushy ball .without enough green strength for the firing operation. Development work has met these objectives. At low investment and operating costs, filtration rates of 250 to 600 dry lb per hr per ft2 have been attained for concentrates of 60' pct —325 mesh. By combining the disk-type continuous filter with proper agitation, the Agidisc filter produces a homogeneous filter cake, easily discharged from the disk sectors. This application provides the lowest initial cost per square foot of filtration area, minimizes floor space, reduces down time for changing filter media to a negligible factor, and simplifies process control and maintenance for the operator. It is now possible to predict very closely the taconite concentrate filtration rates for a wide variety of conditions—either by experience or with a few simple leaf tests. When balling and pelletizing operations began on a continuous basis, it became apparent that moisture content of the filter cake was a critical factor and must always be controlled by the filter operator below some maximum allowable value. Accordingly the Reserve Mining Co. and the Eimco Corp. joined in a study of the many variables affecting filter cake moisture content. The study was conducted at the Reserve Mining Co. taconite plant at Babbitt, Minn. To process plant tonnage the Babbitt plant utilizes a 6-ft diam Agidisc filter with six disks and an 8-ft diam drum filter with 10-ft face. However, most of the plant filter investigations were made on the Agidisc because of its superior performance. A considerable amount of small-scale test work was first carried out to study more closely the individual variables and ascertain their effect on filter cake moisture content. A general correlation method was then developed which allowed reasonable prediction of moisture content at any operating conditions. This step was made necessary by the fact that in full-scale filtering, operating variables usually interact to produce a combined rather than a singular effect. Studies were then made on the full-scale filters to prove the validity of the correlations developed, and past operating records were examined to ascertain whether or not significant variations could be traced to any single factor or to a combination of factors.

Jan 1, 1958

By E. E. Wahlstrom

The Harold D. Roberts tunnel, in Summit and Park Counties, Colorado, is a concrete-lined pressure tunnel finished to a circular cross section of 10.25 ft diam. The tunnel is 23.3 miles long and is designed to transport water for domestic use by the City and County of Denver from reservoir storage at Dillon to a tributary of the South Platte River at Grant. The tunnel passes beneath the Continental Divide at the crest of the Front Range and intersects rocks of diverse types and origins and geologic structures of extreme complexity. Geologic investigations preceded and were continued during construction and contributed materially to the safe and economical advance of the tunnel headings. Geological data obtained and evaluated during construction include plans and sections on a scale of 1 in. to 50 ft, rock temperatures at 2000-ft intervals, records of progress related to geology, records of ground-water conditions, summaries of the use of steel and timber supports, and summaries of grouting operations. Adverse conditions required use of steel and timber supports for 71.74% of the total length of the tunnel. Most supported sections reached a condition of equilibrium within a few hours to a few months after being excavated, and the concrete lining serves chiefly to provide an additional safety factor and to provide necessary hydraulic characteristics to the tunnel. Efforts to attain a maximum rate of advance of the tunnel headings necessitated use of more steel and timber supports than would have been required in a less accelerated tunneling operation. This report summarizes geologic investigations prior to and during construction of the Harold D. Roberts tunnel in Summit and Park Counties, Colorado (Fig. 1) and analyzes the tunneling operation as it is related to the various kinds of geologic conditions encountered in the tunnel. The tunnel is concrete lined to a circular cross section of 10.25 ft and is designed to transport 788 sec ft from reservoir storage at Dillon 23.3 miles along a dog-leg course passing under the Continental Divide to outlet and control works at Grant, Colo. The primary purpose of the tunnel is to augment the domestic water supply of the City and County of Denver, but plans include provisions for power generation at the outlet portal at a future date. Location of the tunnel was made after extensive preliminary geologic and engineering investigations by the Board of Water Commissioners of the City and County of Denver, and the U.S. Bureau of Reclamation. In 1946 the Board of Water Commissioners started tunnel driving on a limited scale from the east (outlet) portal and by 1955 had completed 9986 ft of tunnel. An urgent need for additional sources of water supply required acceleration of the tunneling operation, and, in 1955, Tipton and Kalmbach Inc. of Denver were assigned the responsibility of reviewing the project and preparing plans and specifications for the tunnel and appurtenant features. Additional geologic studies were made, and the geology of several possible alternate tunnel lines were compared before determining that the tunnel should be driven along the course previously adopted by the Board of Water Commissioners. On July 12, 1956, a contract for construction was awarded to Blue River Constructors Inc., a combine

Jan 1, 1962

By Rollin E. Hook, Attwell M. Adair

The yield and fracture behavior of recrystallized chromiztm have been studied in order to gain an understanding of the recrystallization embrittlement-rheotropic recovery phenomenon. The duc tile-brittle tensile transition temperature of recrystallized chromium was found to vary from 225 ° to -80°C as the ratio of specimen diameter/mean planar grain size decreased. The applicability of this observation to other bcc metals is briefly discussed. Brittle fracture in recrystallized chromium was found to be initiated predominately from intercrystalline rupture nuclei. Single crystals exhibit a high degree of ductility at 23 "C. The experimental data indicate that grain boundaries play a significant part in the yield and fracture behavim. Pres training significantly reduces the transition temperature, and high temperature aging does not result in re-embrittle-ment until complete recovery or re crystallization occurs. SEVERAL theories have been used to explain the recrystallization embrittlement-rheotropic recovery phenomenon in chromium. Wain, Henderson, and ohnstone' propose a Cottrell dislocation locking mechanism due to nitrogen, and Weaver and Gross and weaver 3 propose a strain-induced precipitation mechanism involving a chromium nitride precipitate. The researches of many investigators seem to leave little doubt that brittleness in chromium is promoted by interstitial impurities. Smith and seybolt4 have shown that the ductile-brittle transition temperature is lowered as the interstitial content is reduced. weaver3 provides evidence for a 150°C reduction in the tensile transition temperature as the nitrogen content is reduced from 20 to 5 ppm. Maykuth and affee' have suggested that the amount and orientation of grain boundary impurities may be responsible for the brittle nature of recrystallized chromium. This suggestion was based on their findings that wrought iodide chromium possessing a fiberous grain structure is ductile in tension at room temperature while a recrystallized grain structure is completely brittle. Previous investigations have not studied this phenomenon sufficiently to determine its cause. Perhaps this has been largely due to previous experimental findings that brittle fracture observed in chromium has been almost entirely transgranular.' In addition McNeil and imb,' who investigated coarse-grained as-cast chromium, describe the point of initiation of fracture as cleavage, close to the (100) plane, near or at grain bound-daries, or at included particles or voids. However, Hook, Adair, and ipsitt found that fracture in coarse-grained recrystallized chromium is initiated by intergranular rupture and then propagates nearly entirely by cleavage. This result, together with their finding that room temperature ductility in bending is observed for single crystals and coarse-grained polycrystalline specimens for which the number of grains through the specimen diameter is small, suggests that grain boundaries may play an important role in the brittle behavior of chromium. The recrystallization embrittlement problem can be resolved into two questions. These are, whether the controlling mechanism is predominately one of crack initiation or crack propagation, and whether brittle fracture is initiated predominately by slip or twin induced intergranular rupture or by cleavage. The following research was designed to study the role of grain boundaries on the brittle fracture of chromium in an effort to resolve these questions. EXPERIMENTAL PROCEDURES, RESULTS, AND DISCUSSION General Procedure. All tensile specimens (except 0.04 in. diam wires) were prepared from 1/4 in. diam swaged rod fabricated from one ingot. Details of fabrication are given elewhere. The results of impurity analysis for the swaged rod and for the

Jan 1, 1963

By W. A. Ver Wiebe

Spurred on by the very high demands for new crude supplies resulting from World War 11, the oil men of Kansas strained every effort in 1943 to find as many new pools as possible. In all, 1761 test wells were drilled, ,of which 895 were successful in finding new oil supplies and 32 in finding new gas supplies. The total number of wildcat wells drilled in Kansas was 577, including the so-called "extension wildcats," which are located less than 2 miles from production. As a result of the very determined effort to find new oil reserves, 49 of the wildcat test wells found new oil pools in western Kansas and 7 found new oil pools in eastern Kansas. There were 289 rank wildcat tests, and among these 28 were successful ventures. They are responsible for 26 of the new oil pools recorded for the year and 2 of the new gas pools recorded. The ratio of dry holes to producing wells among such rank wildcats is thus approximately 10 to I (289 dry and 28 good). This compares with a ratio of II: I in 1942 and 6:1 in 1941; the same in 1940 and 5:Iin 1939. With nearly all wells flowing to their maximum economic capacity, the total production for Kansas during 1943 reached a new high; that is, 107,700,000 bbl., compared with 97,000,000 during the previous year. Similarly, the amount of gas sold during 1943 made a new high point on the production curve. The total amount was 122 billion cubic feet, compared with about 98 1/2 billion cubic feet for the year previous. As usual, the large Hugoton field of south- western Kansas accounted for approximately half of the total gas production. Highlights of the Year Despite the fact that 56 new pools were found in Kansas during 1943, it must be admitted that the future reserves of the state have not been increased greatly. Most of the new pools seem to be of minor value, although it is admittedly impossible to gauge the future production of any pool in Kansas with any exactitude. Judging by the later performance of some of the pools found in 1942 and in 1941, less than five of the new pools are likely to make any great contribution to the state's future oil reserves. Taking up the counties of Kansas in alphabetical order, the following statements summarize the highlights of the year. In Graham County, the Morel pool was extended to the southeast and this pool now promises to become one of the important pools of western Kansas. Several of the older wells have already contributed more than I000,000 bbl. of oil, and such a figure is considered very satisfactory in Kansas. In McPherson County, important new reserves were found by persistent drilling in township 17 S., R. I. W., the most northeastern township of the county. Many new wells in older pools and discovery wells in new pools make this region look promising. The Lindsborg pool, which had a sensational revival during 1942, was also extended in a number of directions and has now become a rather large producing area with a fairly high future potential capacity.

Jan 1, 1944

By F. G. Miller, R. C. McFarlane, T. D. Mueller

During the process of gas storage in pressure-depleted oil reservoirs, it has been observed that in some instances additional liquid oil is recovered and that the composition of the storage gas is materially altered. A mathematical study was made of the dynamic behavior of such a depleted oil reservoir undergoing gas injection. The important variable considered in this study, not included in previously published work, was that of compositional effects on the phase behavior of two-phase flow. Pressure, saturation and component composition profiles were developed for a linear, horizontal and homogeneous porous medium containing oil and gas but undergoing dry gas injection. Special new techniques were developed to overcome the problems of numerical smoothing which arise in the solution of the equations representing such systems. The method of solution includes the development of partial differential equations describing the behavior of the system, representing these equations by finite difference approximations, making certain simplifying assumptions and, finally, applying methods of numerical analysis with the aid of a high-speed digital computer. In an example calculation, results using the mathematical model are compared with field observations made on a gas storage project in Clay County, Tex. This field project involved a depleted oil reservoir used 'for gas storage and gas cycling purposes. As a result of these processes, the reservoir yielded substantial amounts of secondary oil, both in the form of stock tank oil and as vaporized products in the produced gas. The methods derived in this study may be applied to a variety of oil reservoir problems which are dependent on compositional effects. In recent years the number of oil reservoirs being used for gas storage purposes has increased greatly, and there has been at least one published account of additional oil recovery resulting from gas cycling a depleted oil reservoir after repressur-ing with dry gas for storage purposes. Additional oil recovery from oil reservoirs resulting from gas storage operations could become an important secondary recovery process. This is especially true since the use of natural gas in large metropolitan areas continues to increase and more gas storage volume near these areas is needed. These facts provided the motivation for the work reported here. This paper reports on a study of the inter-relations of composition, saturation and pressure changes which occur when hydrocarbon gas is injected into an oil reservoir system. From an understanding of the process, prediction methods may be developed for use in forecasting the secondary recovery products from gas storage operations in oil reservoirs and, consequently, .the economics of such projects can be developed. The process of storing hydrocarbon gas in an oil reservoir and the cycling process both involve the transient multi-phase flow of oil reservoir fluids with changing fluid compositions. There is a scarcity of work published on the subject. One of the first laboratory models developed to study a problem similar to the one posed here was published in 1948 by Standing, Lindblad and Parsons. l They developed a model to study gas condensate recovery by gas cycling, including the effect of heterogeneous reservoir permeability. Their results showed the compositional effects of injecting a gas of known composition into a two-phase condensate reservoir of known composition. A major finding of their study indicated that maximum oil recoveries from gas cycling projects result when low cycling pressures are used. Previous to their work it was generally considered

By V. Koump, T. F. Perzak, R. G. Olsson

The vate of dissolutioz of carbon in molten Fe-C alloys urns studied by votating- cylindrical g-vaphite sairlples in a stationary crucible containing the melt. The rate of dissolltion was determdined from the change in the bnth co)npositiorz. Alccss-tvansfev coeffi'cients, calcilated with the assurlption that the inte)yacial liquid ulas saturated with carbon, were found to be in agreement with an existing Correlation fov mass transfer jroni votating cylinders. It is corzcllrded tlat, itz the wnge of- Reynolds' numbers itzvestigated (790 to 18,000), the vate of dissolutio of carborz in Fe-C alloys is controlled by tile rate of carbon difirsion from the interface. The dissolution of carbon in molten Fe-C alloys has been the subject of a number of investigations. Most of these investigations have been inconclusive because of poorly defined experimental variables. Two of the more sophisticated studies are summarized below. Dahlke and Knacke' studied the phenomenon by, in part, immersing graphite rods into 0.5 pct carbon-steel for different lengths of time. Since the experiments were conducted in air or in CO atmospheres, the melt was strongly agitated by gas evolution. It was concluded that the change in bath composition as a function of immersion time was in agreement with the assumption that the dissolution process was transport-controlled. The hydrodynamic conditions in these experiments, however, were not well-defined and gave no indication of the nature of the dissolution process at higher fluid velocities. In a recent study Shurygin and ruk investigated the dissolution of carbon in molten Fe-C, Fe-Si, Fe-P, and Fe-Ni alloys. Small graphite disks were rotated in a crucible containing molten alloys under such conditions that only the lower face of the disk was exposed to the melt. The results of this investigation indicate that, over the range of velocities (100 to 1000 rpm) and bulk liquid concentrations (0.7 to 4.5 wt pct C) considered, the dissolution of carbon in the iron alloys is limited by the diffusion of carbon from the interface to the bulk liquid (a transport mechanism). For the particular geometry used by these authors, exact analytical solutions of hydrodynamic and diffusion problems are aailable. Hence the experimental results obtained by Shurygin and Kryuk permit the evaluation of diffusion coefficients of carbon in the four systems investigated. In the present investigation a series of experiments were conducted in which the rate of dissolution of carbon in Fe-C alloys was measured under conditions which permitted wide variation of the fluid velocity and the carbon concentration of the bulk liquid. Graphite cylinders were rotated at different speeds in a stationary concentric crucible containing various molten Fe-C alloys. THEORETICAL DEVELOPMENT In general, the resistance to mass transfer from a solid interface to a turbulent liquid is assumed to reside in a laminar boundary layer adjacent to the interface. If it is also assumed that the diffusion coefficient is independent of concentration, the steady-state rate of dissolution for the case of arbitrary liquid and solid densities can be obtained from the integration of the equations of continuity. The derivation is similar to that used by Lommel and chalmers4 for the case of pl = ps. The solution, expressed in terms where N = rate of diffusion of the solute from the interface. Exact analytical solutions of the hydrodynamic equation for the boundary layer thickness are available for only a limited number of geometries. Consequently, a mass-transfer coefficient, k, is usually

Jan 1, 1967

By B. L. Averbach, Morris Cohen, S. A. Kulin

The martensitic transformation can be initiated by elastic stresses at temperatures above M. in a steel containing 20 pct Ni and 0.5 pct C. Shear strains and normal tensile strains acting on a potential habit plane promote the transformation but compressive strains oppose it. THE strain sensitivity of the martensitic transformation has long been recognized. It is now well known that martensite formation can be induced by plastic deformation at temperatures below, and not too far above, the M, point.' However, the exact role of elastic vs. plastic strains and of the concomitant stresses has proved to be a very elusive matter. Many investigators2-' of the steel hardening reaction have made use of the stresses resulting from volume changes to account for such observations as the existence of retained austenite and its variation across the section of a bar, the change in the amount of retained austenite with quenching rate, and the self-stopping nature of the transformation when the cooling is stopped. The effect of applied strain as an independent variable has been studied in 70 pct Fe-30 pct Ni alloys by Scheil7 and McReynolds.8 Some data are also available for lithium and Li-Mg alloys,9 Cu-Zn,10 Cu-Sn and Cu-A1 alloys," and aus-tenitic stainless steels."-" It has been found that martensite formation can be induced isothermally, even at temperatures above M,, by mechanical deformation of the parent phase. The competitive nature of plastic yielding by slip and by the martensitic reaction has been depicted by Scheil.7 Basically, Scheil postulated that: 1—at temperatures not too far above M, (where austenite is less stable than martensite), a critical resolved shear stress (within the elastic range) is required to promote the transformation to martensite; 2—at and below M,, the austenite lattice becomes mechanically, as well as thermodynamically, unstable and shears over spontaneously into martensite without the application of external stress; and 3—at temperatures sufficiently far above M8, the critical resolved shear stress for martensite formation increases to a level above that required for slip, and plastic flow then supersedes the transformation when external stress is applied. Scheil's concepts were tested by McReyno1ds8 ho found no change in the elastic moduli (measured both statically and dynamically) of 71 pct Fe-29 pct Ni alloys in the vicinity of the M, temperature. Since the moduli did not approach zero or become negative on cooling to M,, it was concluded that the austenite lattice does not become mechanically unstable at M2, as postulated by Scheil. McReynolds also reported that M, is not raised by elastic stresses. Accordingly, plastic deformation was considered to stimulate the transformation by generating martensite nuclei in the distorted regions of the parent phase. The above issues with regard to the role of applied stress require clarification, if a basic understanding of the martensitic transformation is to be obtained. For example, in the reaction-path theory,'"," it is postulated that strain embryos exist in the austenite that provide part of the activation energy for the nucleation process. These embryos are visualized to be regions of localized strain in which the atoms in the austenite lattice are displaced part way along the path to their ultimate positions in the martensite. Consequently, it would

Jan 1, 1953

By J. M. McDowell, E. C. Doty, F. Morgan

Improvements in the X-ray method of measuring liquid saturation and saturation distribution are presented. Two identical direct current amplifiers have been added to measure continuously the intensities of the X-ray tube output and the beam which has passed through the core under test. The ratio of these intensities is automatically recorded on a modified Brown Electronik Recorder. Arrangements have been made to drive the core automatically and in synchronism with the recorder chart so as to give a continuous curve showing the variation of liquid saturation along the length of the core. By determining the ratio of the two X-ray beam intensities simultaneously the measurements are made essentially independent of small fluctuation in voltage and current supplied to the tube. This improved technique has been used for investigating the fluid distribution along the length of cores and core assemblies when one fluid is displaced by another. Typical results of these studies are shown. INTRODUCTION In a previous publication' a method was described for measuring the oil saturation in cores which was based on the absorption of X-rays by the fluid content of the core. While that technique is capable of yielding accurate results, the original apparatus was not especially convenient for determining the fluid distribution along the length of a core. This was primarily due to the slow response of the amplifier and galvanometer and the necessity of making a point by point survey of the material under investigation. It was, therefore, not only possible for sections of the core having a variable or unusual saturation distribution to escape observation entirely, but changes in output of the X-ray generator between readings on the unknown and the monitor introduced errors in the measurements that could be avoided only by further stabilization of the source or by taking a large number of readings. This paper describes a method and apparatus for recording continuously and automatically the intensity of the X-ray beam that is transmitted by a core. The variation of saturation with time at a given section of the core may thus be found, or by scanning the core by driving it in synchronism with the recorder the saturation distribution may readily be determined. As indicated in the previous paper, the X-ray method possesses an advantage over the weighing technique in relative permeability experimentation in that the core need not be removed from the holder for the purpose of making a saturation measurement. Furthermore, the actual distribution of fluid and the effects upon that distribution of inflow and outflow heads may be investigated. And errors due to gas bubbles or loss of liquid that are frequently sources of error in volumetric methods of saturation determination are avoided. PRINCIPLE OF THE METHOD The energy in an X-ray beam that has passed through an absorbing material is expressed by the well known formula: E = E0, e-cd (1) where E, is the energy in the incident beam, µ the mass absorption coefficient, c the density or concentration of absorbing material, and d is the length of path of the beam in the absorber. The coefficient µ varies with the wavelength of the radiation as well as with the absorbing material. The output of an X-ray tube varies in an approximately linear manner with the tube current, but to the second or higher power of the anode voltage. Moreover, the quality or wavelength distribution of the radiation varies with the voltage.

Jan 1, 1950

By F. V. Lenel, G. S. Ansell

The creep behavior of an aluminum -aluminum oxide alloy, A T 400, fabricated by compacting an atomized aluminum powder, extruding the compact, cold working, and recrystallizing the extrusion, was investigated. This alloy has a dispersion spacing of 1 . Previously Ansell and Weertman determined the steady-state creep rate of a recrystallized aluminum-aluminum oxide SAP-type alloy, MD 2100, with a 0.48-p dispersion. This alloy was found to have a steady-state creep rate of less than 10-6 min-1, too small to be measured accurately. By employing a more sensitive method of measuring creep rate, it was possible to determine the steady-state creep rate of AT 400 alloy, which is somewhat faster than that of MD 2100, at a series of temperature and applied stresses. Above a stress of Burger's vector, A = dispersion spacing, u = is a shear modulus) the rate follms an equation of the type: Steady-state creep rate K = A exp. where A is a constant, Q is the activation energy for sey-diffusion, and is the applied stress. At stresses lower than the steady-state creep rate drops off sharply and is no longer in agreement with this equation. This behavior is in good agreement with that predicted by the model for dispersion strengthened alloys in the stress and temperature range investigated. The absolute value of the creep rate is, however, four orders of magnitude lower than that predicted if the normal number of active dislocation sources are assumed to be present. It is concluded that in this SAP-type alloy the usual three-dimensional dislocation network is not present. Instead, short dislocation segments extending from one dispersed particle and terminating at a neighboring particle may act as dislocation sources. With this provision the creep model proposed by Ansell and Weertman reasonably accounts for the creep behavior which was observed. RECENTLY, Ansell and Weertman1 proposed a dislocation model from which they derived creep equations to describe the steady-state creep behavior of dispersion - strengthened alloys. Following Schoeck,2 they assumed that the rate controlling process for steady-state creep is the climb of dislocations over the dispersed particles. In order to verify their creep model, Ansell and Weertman determined the steady-state creep behavior of an aluminum-aluminum oxide SAP-type alloy, MD-2100, in both the fine-grained as-extruded, and coarse-grained recrystallized conditions. Since the grain size was the order of the dispersion-spacing, their model was not applicable for the as-ex- truded alloy. It should, however, be applicable to the coarse-grained recrystallized alloy. The results they obtained were rather unexpected. No meas-ureable steady-state creep was observed for the recrystallized MD-2100 alloy. If their model is correct, and if the second-phase particles act solely to hinder dislocation motion, then some measureable steady-state creep would have been expected. On this basis, they postulated that, in this SAP-type alloy, the main effect of the fine dispersion was to inactivate dislocation sources rather than to hinder the movement of dislocations. In order to understand more fully this unusual creep behavior, and to determine the validity of the model proposed,' the steady-state creep behavior of an aluminum-aluminum oxide recrystallized SAP-type alloy, with a somewhat coarser dispersion spacing, was investigated. The results of this study are presented in this paper.

Jan 1, 1962