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By Sylvia Whitehead, G. M. Schwartz, J. N. Gundersen

Sylvia Whitehead (Petrologist, The Broken Hill Propriety Co. Ltd., Melbourne, Australia) — Examination of thin sections of jaspilites from numerous banded iron formations in Australia has revealed no evidence to suggest that silicate minerals have formed by reaction between magnetite and silica. Textural relations indicate that part of the magnetite crystallized very early in the history of the rocks, probably during diagenesis, and remained stable under conditions of metamorphism altering only to hematite or limonite under conditions of oxidation and weathering. Many jaspilites also contain later magnetite which is almost certainly of metamorphic origin. Wherever magnetite is present in quartz rich bands containing little or no silicate or carbonate, it is very fine grained and occurs generally as isolated, well formed octahedral crystals or as small crystalline aggregates. These show no evidence of corrosion or reaction with the quartz even in rocks where adjacent bands contain silicate minerals of moderate to high metamorphic grade. Concerning the silicate minerals, it is reasonably certain that bands of very fine grained stilpnomelane

Jan 1, 1963

By T. H. Alden

T. H. Alden (General Electric Research Laboratory)—This paper as well as earlier ones of Dr. Wood represent an important contribution to the experimental description of fatigue fracture. The mechanism of fracture proposed by the authors, however, is not established by this data nor supported by other data existing in the literature. Although taper section metallography provides a rather detailed picture of fatigue crack geometry, photographs so obtained must be interpreted with care. The narrow bands revealed by etching, frequently associated with surface notches, are labeled by the authors "fissures". Measurement shows, taking into account the 20 to 1 taper magnification, that the depth of these structures is at most 2 to 3 times the width. This distinction is important in the conception of a mechanism of crack formation. It is difficult, for example, to imagine a deep, narrow fissure arising from a "ratchet slip" model. A surface notch, on the other hand, may form easily by this mechanism. The notches observed in the present work are the subsurface evidence of the surface slip bands or striations in which fatigue cracks are known to originate.4-6 It is clear that an understanding of the structure of these slip bands is of key importance in understanding the mechanism of fracture. The evidence presented shows that these regions etch preferentially, possibly because they contain a high density of lattice defects, or as the authors state equivalently, because they are "abnormally distorted." However, it is not possible to conclude that the distortion consists of a high density of vacant lattice sites. The fact of a high total shear strain in itself does not assure a predominance of point defects as opposed to other defects, for example, dislocations. Other evidence in the literature which suggests unusual densities of point defects formed by fatigue7-' refers not to the striations or fissures, but to the material between fissures (the "matrix"). If a choice must be made, the preferential etching would seem to be evidence for a high dislocation density, since dislocations are known to encourage chemical attack in copper;g no such effect is known for the case of point defects. A third alternative is that the slip bands are actually cracked, but that near its tip the crack is too narrow to be detected by the authors' metal-lographic technique. In this case the rapid etching can be readily understood in terms of the increased chemical activity of surface atoms. Unless a vacancy mechanism is operative, the motion of dislocations to-and-fro on single slip planes will not lead to crack growth. Point defect or dislocation loop generation are the principal non-reversible effects predicted by this model. In any case, the nonuniform roughening of the surface in a slip band6 requires a flexibility of dislocation motion which is not a part of the to-and-fro fine slip idea. The same is probably true of crack growth by a shear mechanism. Either some dislocations must change their slip planes near the end of the band and return on different planes,'0 or dislocations of opposite sign annihilate." The mechanism by which these processes occur in copper at room temperature or below is that of cross slip. Thus cross slip appears to be essential to fatigue crack growth.6'10"12 The fact that a tensile stress opens the slip bands into broad cracks does not indicate the structure of the bands or the mechanism by which cracks form. The charactersitic concentration of slip into bands during fatigue shows a low resistance to shear strain in these regions. (This fact in itself may be inconsistent with a high concentration of vacancies.) The authors contend also that continuing shear produces an additional mechanical weakening so that the bands fracture easily (are pulled apart) under the influence of the superimposed tensile stress. It is equally possible that the only weakness is a weakness in shear, that the crack propagates by a shear mechanism, and that subsequently the tensile stress pulls the crack apart. Even the direct observation of bands opened by a tensile stress would not be conclusive since, as argued above, they may be fine cracks. The same argument applies to internal cracks, their existence in the presence of a tensile stress not indicating the mechanism of formation. Internal cracks originating in regions of heavy shear have also been seen following tensile deformation of OFHC copper,13 so that this mode of fracture is not unique to combined tensile and fatigue straining. The authors point out in their companion report14 that 90 pct of the cracks formed during pure tor-sional strain were within 8 deg of the normal to the specimen axis. If the tensile stress were an important factor in crack propagation, it is surprising that the cracks cluster about the plane in which the normal stress vanishes. Similarly, a study of zinc single crystals showed that for various orientations the life correlated well with the resolved shear stress on the basal plane,'= and was not dependent on the normal stress across this plane. W. A. Wood and H. M. Bendler (Authors' reply) -Dr. Alden's discussion emphasizes the essential point in the relation of slip band structure to

Jan 1, 1963

By H. C. Vacher, C. J. Newton

EXTENSIVE investigations in the field of residual strain measurement by X-ray diffraction have been made by Bollenrath, Hauk, and Osswald,1 by Smith and Wood,2'3 by Greenough; by Rosenthal and Norton." and many others. Since X-ray strain measuremeits apply only to those crystals of the test body which are of the proper condition and orientation to diffract and since the residual strains revealed may be accompanied by either body or tex-tural stresses, there has been considerable disagreement among investigators with respect to the validity of conclusions in this field. Although the experi-mentors have employed a variety of loading schemes, surface preparations, and X-ray wave lengths, the observations almost invariably have been made only on the outer surfaces of the specimens. The present note is not to be construed as an exposition of a new method of stress analysis by X-ray strain measurements on sections but as a presentation of some results which point to interesting possibilities for further experiments with sections. The two test rods used in this study were of ingot iron annealed at 910°C. The initial length of the gage section was 2 in. and the diameter was 0.415 in. Cross-sections were cut from the ends of the annealed rods to provide strain-free material. The tensile rod was axially loaded the desired amount in a commercial testing machine. A 1 in. portion of the gage length was cut from the other rod and was subjected to compression in the same machine. Details of this plastic straining of each rod are given in the upper half of Table I. A half-cylinder piece about 1/4 in. long was obtained by making a short longitudinal plane cut containing the axis of the rod near the center of the gage length. From adjacent material a disk about 1/8 in. thick was cut to provide the cross-section specimen. Later another section was cut from this same region with an angle of 30" between the normal to its surface and the axis of the test rod. A cross-section and a longitudinal section were cut from the compression rod in a similar manner. All of these as well as the strain-free cross-sections were mounted in Bakelite and used as specimens for the following X-ray strain measurements. During the course of the study, it became apparent that the condition of the surface of a specimen was a highly critical factor. One of the annealed strain-free specimens as a control was subjected to about 24 hr of polishing with fine alumina, interrupted about every 2 hr for etching with 1 pct nital. Its lattice parameter was determined at intervals from measurements on back-reflection X-ray diffraction patterns, which were calibrated with diffraction from tungsten powder. The parameter gradually approached the value found in the literature for strain-free iron and remained there, within the limits of the experimental error. This determined a long polishing and etching procedure which was adopted for all the specimens and which gave X-ray results from the surfaces believed to be representative of each specimen as a whole. A large number of back-reflection patterns were made with cobalt and chromium radiation, all at normal incidence. Except for some preliminary stationary exposures made to monitor the removal of cold work from the surfaces, each exposure was made with the specimen slowly translating and the film slowly rotating. In appropriate cases a thin layer of a standard metal powder, tungsten with cobalt radiation and silver with chromium, was dusted over a film of vaseline on the surface of the specimen to serve to calibrate the X-ray patterns. After the preliminary work, four films were made,

Jan 1, 1956

By C. F. Jenkins, G. V. Smith

Serrated plastic flow in stable austenitic alloys based on Fe/Ni has been shown to be related to the presence of carbon and/or chromium in the systems. Strength peaks and plateaus in the serrated-flow temperature region for a commercial alloy correlate with an increased dislocation content, arising, presumably, from enhanced multiplication as a result of a strong interaction between dislocations and solute atoms. The data generally support a mechanism controlled by migration of vacancies, with the energy for vacancy motion being modified by the presence of chromium. Chromium atom -dislocation interaction is responsible for effects above 500°C, whereas the defect interacting with dislocations between 200" and 500°C is suggested to be a carbon-vacancy Pair. ThE phenomenon of jerky flow, serrated flow, or the Portevin-le Chatelier (P-C) effect in austenitic stainless steels is usually attributed to substitutional at1,2 mospheres1,2 or to precipitates&apos;-4 which form at dislocations during plastic deformation. On the other hand, evidence exists which supports a direct inter-stitial-dislocation interaction mechanism for serrated flow in fcc Ni-C,5,6 Ni-H7-9 and in nickel-austenites containing carbon." The present work consists in a study of serrated plastic flow in stable austenitic al-loys. The effects of carbon and of chromium were investigated separately, and a commercial stainless steel with different levels of interstitial impurity concentration was studied in an attempt to delineate the combined effects of the alloying elements. EXPERIMENTAL TECHNIQUES a) Materials and Fabrication. A commercial AISI 330 stainless steel and several specially prepared aus-tenitic alloys have been studied. The experimental alloys were prepared by arc melting the constituents under purified argon. Analyses of the materials are given in Table I. The commercial alloy was obtained as 5/8 in. bar stock and rolled to 0.092 in. sq, with several intermediate anneals. At this stage some of the material was annealed in Pd-purified hydrogen at 1100°C to establish different levels of interstitial content. All other heat treatments were in vacuum (10-5 torr). The "pure" alloy ingots were swaged to 0.120-in. rod and annealed in Pd-purified hydrogen at 1100°C. The analyses for these conditions are also contained in Table I. Following the above treatment, the final wire sizes Table I. Chemical Analyses of Test Materials Hrin Hydrogen at Cr, Ni, Alloy 1lOO°C wt pct wt pct C, ppm* N, ppm* Type 330 As-received 14.78 33.25 430 300 Type 330 64 14.78 33.25 40 50 Type 330 200 14.78 33.25 27 21 Fe/35 Ni 72 - 35.10 <10 62 Fe/35 Ni 200 35.10 <I0 44 Fe/35 Nil15 Cr 72 14.95 34.94 <I0 61 Fe/35 Ni/15Cr 200 14.95 34.94 <10 45 Fe/35 Ni/C $ 35.OM 380 *Sensitivity: N t 5 ppm Ct10ppm. f Nominal Ni content. % A master NiC alloy was used in preparation of this material; courtesy of D.E. Sonon. were obtained by either swaging or cold drawing. The test results did not vary with these techniques. b) Specimen Preparation. Two sizes of specimen and two gripping systems were used. i) 0.070-in. wire with a chemically milled gage section: 0.75 in. long, 0.060 in. in diam. These were fastened into grips containing tapped grooves. ii) 0.050 in. wire, gage length 1.5 in. Ball bearings were welded to the ends of the wires and the gage length was taken to include all material between the welds. Socket-type grips were used with these specimens. With specimens of type ii), joining was performed in a specially constructed brass jig, under argon, and automatic timing was utilized in the procedure. No adverse effects of welding were noted. Specimens were encapsulated and solution treated for 1 hr at temperatures selected to produce the same average grain size, -50 µ. Annealing twin boundaries as well as normal crystal boundaries were counted. The temperatures used are listed in Table 11. Table 11. Specimen Size. Temperature of Heat Treatment and Resulting Grain Diameters for Test Materials Recrystallization Resulting Material Condition Temperature Grain Sue AISI 330 Not H purified 0.070 120O°C 45 to 55µ in, wire AlSl 330 H , pure, 0.070 in. 1150°C 45to55µ wire Fc/35Nil15Cr Pure, 0.070 in. wire 1000°C 45tossp Fe/Ni Pure. 0.070 in. wire 775°C 45 to 55µ Fe/Ni/C Pure, 0.050 in. wire 850°C 10 to 20p AlSl 330 Not purified, 0.050 1150CC 45to55p in. wire AlSl 330 ti, pure, 0.050 in. 1150°C 45to55p wire

Jan 1, 1970

By T. J. Koppenaal

The surface slip line structure has been investigated by optical microscopy during the easy glide deformation of Cu-A1 single crystals as a function of composition, testing temperature and prior thermal treatment. The slip line structure in alloys of 2.5 or less at. pct Al is similar to pure copper, while alloys of 5 or more at. pct Al show slip tracings typical of a brass. Cross slip is observed in the "a-brass type" crystals and the amount of this type of slip increases rapidly with aluminum content. The cross slip tendency in 14 at. pct Al crystals is signicantly higher when tested at 150°C as compared to 4.2" and 77°K. In addition, cross slip is more pronounced in this alloy in the furnace cooled condition than when quenched from 450°C. The cross slip behavior is analyzed in terms of existing models for this type of deformation. In two previous investigations, reports of yield points1 and solid solution strengthening2 in Cu-A1 single crystals have been given. This paper enlarges upon the brief description of the slip line structure discussed in these reports. Since the easy glide slip line pattern of copper changes markedly with the addition of -30 pct Zn (-brass),3 a study of slip lines as a function of solute additions in Cu solid solutions should help to explain some of these differences. In addition to composition variables, slip lines have also been studied as a function of testing temperature and prior thermal treatment. PROCEDURE The slip line observations were made on single crystals of 0.5 to 14 at. pct Al using a light microscope. Details concerning the preparation and basic testing procedure are given elsewhere.&apos; Prior to testing, each crystal was homogenized at 900°C for 24 hrs, furnace cooled, and electrolytically polished in a 60 pct phosphoric acid solution. The strain rate was-5 X 10 sec-I in each case. Unless otherwise stated, all observations reported upon here were made during the early stages of easy glide. RESULTS AND DISCUSSION The maximum magnification generally used was 1000X, and slip lines could be resolved down to about 105 cm (1000A). This resolution is appreciably less than obtainable with electron microscopy replica techniques where the replication can resolve slip lines down to about 40 A. Thus, while many qualitative features could be studied, the type of quantitative data obtainable with an electron microscopy replica study could not be made. Crystals containing 0.5 and 2.5 at. pct Al deform much like pure copper exhibiting a high density of fine slip lines that cover the entire gage length of the specimens. Fig. 1 shows the surface slip line pattern in a 2.5 at. pct A1 extended 0.01 shear strain at room temperature. Crystals having 5 to 14 at. pct A1 showed appreciably coarser slip lines that were generally concentrated at one end of the gage length. During easy glide these coarse slip lines propagate along the gage length in a manner similar to that observed in a-brass single crystals by Piercy, Cahn, and cottrel14 and refered to by them as a Lüders band propagation. Fig. 2 shows a typical area of these coarse slips in a 14 at. pct A1 crystal after a room temperature shear strain of 0.01. Two slip systems were apparently active. Using a method described by Cullity, the angles, between the specimen axis and the normals of the primary and secondary slip planes were determined to be 50 and 84 deg, respectively. &apos;From the Laue photograph, was 52, 81, 66, and 30 deg for the primary, cross, conjugate, and fourth slip planes, respectively. The secondary active plane in Fig. 2 is thus established as the cross slip plane, and the operative slip system is evidently the cross slip system, e.g., slip

Jan 1, 1963

By Alfred Siegel

Mineral pigments give color, opacity, or body to paint, stucco, plaster, mortar, cement, linoleum, rubber, and similar materials. They must be finely divided, substantially insoluble, and generally inert for such uses. Inorganic pigments may be grouped somewhat arbitrarily as follows: A. Natural mineral pigments dug from the earth. 1. Those consisting mostly of iron oxides, such as hematite and limonite. 2. Those containing large amounts of clay or noncoloring matter, such as ocher, sienna, umber, and colored shales. 3. Those whose color is not due to iron oxide, such as Vandyke brown (including sap brown, an alkali extract of Vandyke brown), graphite, and terre verte. B. Synthetic pigments. 1. Those containing iron oxide as the essential coloring matter, such as "pure" reds, yellows, and blacks, and Venetian reds. 2. Those not containing iron oxide, but rather such compounds as lithopone, zinc white, titanium white, ultramarine, Prussian blue, and the like. Only groups A and B-1 are discussed here. All the pigments in those two categories, except Vandyke brown, sap brown, and some of the carbonaceous slates, contain, as their essential color constituents, one or more compounds of iron; namely, an oxide-limonite (2Fe2O3.H2O to Fe2O3.4H20), hematite (Fe2O3), or magnetite (Fe2O3.FeO). Man&apos;s first permanent coloring materials were earth pigments-the ochers, iron oxides, and various iron-stained clays. The caves occupied by prehistoric man and the arts of the ancient Chaldean, Egyptian, and Cretan civilizations bear mute witness to this and also testify to the beauty and permanence of earth colors. As the Roman era developed, earth pigments were pushed from their pre-eminent position by white lead and red lead and in the Middle Ages by zinc oxide. Today, of course, the number of acceptable pigments is very large and on a value basis the group of natural and synthetic earth pigments stands forth with $16,000,000 per year; it is surpassed by titanium, lead and zinc pigments. Of this sum,21 natural pigments supplied 31 pct of the tonnage and 16 pct of the value of the total finished pigment in 1957, the remainder representing the tonnage and value of sales of the synthetic iron oxide colors. The average value of finished natural pigments in 1958 was $80.62 per ton. The average value of manufactured pigments in the same year was $202 per ton. Of the 60,000 tons of manufactured colored pigments sold in 1958, the reds comprised 76 pct of the market and the yellows 20 pct. The reds furnished 68 pct of the value and the yellows 24 pct. Of the finished iron oxide pigments (natural and manufactured) sold in 1958, the reds dominated the market with 66 pct of the quantity and 63 pct of the value; yellows supplied 17 pct of the quantity and 20 pct of the value, and browns furnished 11 pct of the quantity and 10 pct of the value. The average value of the reds was approximately $152, and the average value of the yellows $190 per ton. The highest valued pigment in 1958, with almost 12 pct of the total tonnage and 21 pct of the value of the iron oxide pigment market, was manufactured red from calcined copperas valued at $286 per ton.

Jan 1, 1960

By Douglas Baker

Zinc concentrates assaying approximately 54% zinc and 30% sulfur are roasted in a suspension type roaster to yield a zinc oxide calcine assaying about 65% zinc and 0.40% sulfur. This calcine is the feed material to the sulfuric acid leaching section of an Electrolytic Zinc Plant. The SO2 gases resulting from the elimination of sulfur from the concentrates are passed through a waste heat boiler for the generation of high pressure steam, cleaned by a baghouse, and delivered to the humidifying tower of a sulfuric acid plant system. The gases are then treated in a mist precipitator for final fume removal and then converted to sulfur trioxide in a three pass contact system using vanadium pentoxide catalyst for the manufacture of sulfuric acid. Waste heat steam is used to power the steam turbine which drives the acid plant blower.

Jan 1, 1970

By D. P. Seraphim

Single crystals of bee Li-Mg solid solution were grown and their internal friction was measured as a function of temperature, A peak of the Zener type was found in the damping spectrum. The activation energy for the relaxation process is 21.5 ± 1 kcal per mole and the frequency factor is 1015.7 ± 0.7 sec-1. ZENER internal-friction peaks which are observed for a wide range of solid solutions are attributed to stress-induced changes in local order.&apos; In the present work a Zener internal-friction peak, the first reported for a solid solution of an alkali metal, is

Jan 1, 1961

Jan 1, 1935

JOSEPH W. RICHARDS, Chairman. J. E. JOHNSON, JR., Vice-Chairman. ARTHUR S. CALLEN, Secretary, 453 Chestnut St., So. Bethlehem, Pa. SUB-COMMITTEES IRON ORE DWIGHT E. WOODBRIDGE, Chairman. ERNEST F. BURCHARD, WILLIAM KELLY, CHARLES F. RAND, FELIX A. VOGEL. BLAST FURNACES II. A. BRASSERT, Chairman. WILLIAM H. BLAUVELT, AMBROSE N. DIEHL, JAMES GAYLEY RICHARD V. McKAY. STEEL WORKS HENRY D. HIBBARD, Chairman. GUILLIAEM AERTSEN, C. F. W. RYS, .1. S. UNGER. FRANK D. CARNEY, A. A. STEVENSON, WILLIAM It. WALKER. MECHANICAL TREATMENT CHARLES A. BUCK, Chairman. ROBERT W. HUNT, GEORGE MESTA, FREDERICK W. WOOD.

Jan 6, 1915

Jan 1, 1910

By Dan A. Permenter

This paper assesses some of the critical factors that must be considered and addressed in the implementation of small computer systems for technical applications within a coal company. Aspects of hardware selection that are somewhat specific to the coal industry are discussed, and a table of potential areas of application is presented. The dilemma of internal software development is presented and a software development program based on a users group approach is outlined and discussed in detail.

Jan 1, 1983

By L. G. Schulz

THE possibility of using reflected X-rays to produce images of crystals was explored by Barrettl who developed simple experimental procedures for X-ray microscopy and who showed by numerous examples the great range of information that could be made available. In his method characteris radiation is used to produce an image of a limited area of the sample on fine-grained film, this image subsequently being enlarged approximately X100. A somewhat different method will be described here;&apos; white radiation from a fine-focus X-ray tube-"&apos; is used to produce an image of a relatively large area of a single-crystal surface. part of the sample; therefore, white radiation is needed. The resolution in the image formed on the photographic film will depend on the size of the focal spot of the X-ray tube. If the sample is made

Jan 1, 1955

By T. W. Peterson, J. W. White, E. E. Krist

In developing a minicomputer application for an industrial grinding circuit, the control program is usually coded and the compilation is debugged on a remote access computing system. Final debugging must wait for installation of the minicomputer. This work reports on an alternative. Here both compilation and execution bugs are eliminated before the hardware is installed by testing the control program against a dynamic simulation. Attention is directed toward development of a particular real-time control program for an industrial wet grinding circuit in a copper concentrator. Specific data were supplied by the Anamax Mining Co. for a grinding division consisting of a rod mill followed by two ball mills in parallel. This information was used to set up a plausible model structure.

Jan 1, 1977

By Guy R. Johnson

It is a common observation among those engaged in the ironbusiness, that the lower (i.e., the less graphitic) grades of pigiron show a rough face on the pig. As such irons are always low in silicon, the generally accepted belief is, that this rough face is due to the absence of silicon. Certain investigations, however, made by the writer on Embreville pig-iron, and extending over nearly a year&apos;s time, seem to indicate another cause, namely, the giving-off of included gases, particularly sulphurous oxide (SO2,). It is, of course, the tendency of such gases to rise through the iron, escaping into the air; and the more liquid the iron, and the longer it remains liquid, the greater the chance for such escape. The lower grades of iron, being always colder, tend to solidify early, and before the included gases can completely escape.

Jan 1, 1898

By S. C. Suboleski, C. B. Manula

In a high risk venture such as mining where capital is committed and contracts are signed on a minimum of information, decisions are based primarily on production forecasts derived through consideration of such factors as management-labor relations, mining practice, variations in physical conditions, and the equipment applied. Among these factors, the physical conditions offer the least opportunity for control, and, due to the wide range of mining conditions experienced, little effort has been made to develop objective methods for measuring their effects on mine output. This paper&apos;s aim is to demonstrate a method for assessing these relationships that can be applied under a wide range of conditions both in new mines and in working sections where there is a need to determine the impact of proposed operational modifications. Using empirical data from active underground mines, a mathematical model was developed to derive a set of regression equations for predicting production as a function of mining conditions.

Jan 1, 1982

By E. C. Wade, R. D. Valentine

This paper describes a computer applications engineering system and it&apos;s use to apply a thermal dryer fan motor in a coal preparation plant. The computer hardware and software systems are described to indicate the general approach taken and a specific case study is reviewed to show how computer power is brought to projects in the coal industry.

Jan 1, 1983

By D. M. Francois-Bongarcon

The idea of parameterizing reserves has only been formalized and scientifically applied for a few years. Its most fully developed application, that of open pits, has been operational only since 1976. Two new versions which have just been issued provide a complete solution to the problem and also a powerful tool for mine planning, and they open up a new field of investigation. This paper describes the basic principles for parameterizing reserves, their application for open-pit mines, the algorithm used, the physical interpretation of the results obtained, their economic use as well as the first prospects offered by a complete parameterization in tm of (I. ti), or of the metal price.

Jan 1, 1984

By Ronald R. MacDonald

There is an ongoing need for the abstracting and coding of new information in the energy and environmental studies field for addition to the BIRS system. There are approximately 3000 bibliographic entries coded into the BIRS system. The bibliographic retrieval system was designed to be run by the general data management System 2000. The information system with entries of coal research, land reclamation and other energy and environmental studies is up and on line. As more entries are coded they are loaded into the system.

Jan 1, 1977

By C. P. Parsons

CALIPER logging is a practice of measuring the variations in the diameter of the open hole in a well. This information is useful for many purposes, among which are: Determining the volumetric capacity of the portion of open hole to be cemented; the amount of gravel to be used for gravel-packing a well; the size and location of seat for a packer to be placed in a well; studying the effects of nitroglycerin shots; studying the effects of acidizing; studying the cause of drill-pipe failures; studying drilling technique; geological correlations. This is a new practice in oil fields and is eliminating considerable guesswork.

Jan 1, 1942