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By Carlos D. da Gama, Charles R. Nelson

Griffith’s theory of brittle fracture, as modified by McClintock and Walsh to fit rock behavior in cases of failure by compression, has been successfully applied in various fields of rock mechanics. Extension of the Griffith's criterion to rock blasting problems may also be more representative of rock behavior than the simple consideration of a criterion of failure based on the dynamic tensile strength of the material. If consideration is given to pre-existing cracks within rock structure, occurring not only because of the discontinuous properties of rocks, but also as a result of drilling operations that normally precede blasting, those cracks can be propagated under the action of the dynamic stresses (radial and tangential) induced by the passage of the wave emitted by the explosion. Conditions for initiation and propagation of pre-existing cracks are deduced in terms of rock properties and explosives performance. Influence of the different variables governing the phenomenon is discussed after considering an actual example. Results seem to be well correlated with experimental evidence of radial cracking observed in blasting with high explosives acting within hard rock.

Jan 1, 1971

By A. M. Gaudin, C. S. Chang

IN general, fatty acids or their alkali salts do not cause clean quartz to float. However, the presence of multivalent ions, such as the alkaline-earth metal ions and heavy-metal ions, can activate quartz and thus make it respond to soap flotation. The mechanism of activation and soap flotation of quartz has been studied.1-4 The problem was attacked by making flotation tests rather than by careful adsorption measurements on suspensions of ground quartz in solutions containing the activator and the collector. Attempts have been made to determine the adsorption of barium ion and calcium ion on quartz. The results have only qualitative value as the analytical methods were not adequately precise. Artificial radioactivity and progress in radioactivity detection have introduced a new analytical tool, which can have a sensitivity several orders of magnitude greater than that of other methods.5-6 In the experimental work described in this paper the radioactive tracers, barium 140 and carbon 14, were employed. Lauric acid was synthesized, having a radioactive carbon atom and was used with Ba140 to study the adsorption of barium and laurate ions from aqueous solution on ground quartz. Flotation tests, using the vacuum flotation technique,4 were run in conjunction with the adsorption experiments. The object of this investigation was to understand better the reaction mechanism of barium activation and soap flotation of quartz. Methods and Materials Quartz Sample Preparation: Lumps of hand picked quartz, washed free of stains, were reduced in size to -20 mesh in laboratory crushers. The product was boiled in concentrated hydrochloric acid to remove the abraded iron. The cleaned product then was ground dry in a laboratory porcelain mill, using siliceous pebbles, to pass through a 200 mesh screen. The ground product was deslimed by sedimentation at 37 microns. This -200 mesh +400 mesh material was subjected again to boiling with concentrated hydrochloric acid, followed by washing with distilled water and further desliming. The cycle was repeated until no trace of iron could be detected in the wash liquor. During the final washing, the pH of the wash water was checked to insure the complete removal of the acid from the mineral. The quartz then' was rinsed with conductivity water. The resulting product was dried in a drying oven and stored in mason jars. The impurities (spectrographic) were as follows: Al, 0.01 to 0.001 pct; Li, Mg, Mn,, Na, each less than 0.001 pct; Fe and Cu not detected. The specific surface of the quartz sample was determined by the krypton gas adsorption method.7 The average of two measurements was 881 sq cm per g. The calculated specific surface for 37/74 micron quartz particles, using a surface factor of 1.96,8 is 900 sq cm per g. This is in good agreement with the measured value of 881 sq cm per g. Beta-Counting Method: The radioactive isotope of barium used in the experimental work was barium 140. It has a sufficiently long half-life, 12.8 days, emits high-energy beta particles (up to 1.0

Jan 1, 1952

By P. Ramakrishnan, Ramjilal

Fine powders of lead zirconate titanate have been prepared by three different methods such as ball milling, conventional coprecipitation and spray drying. Different powders have also been prepared by changing the process variables in each method. These powders were analysed for particle size chemical composition and reactivity. DTA, TGA and x-ray analysis have been carried out to study the lead zirconate titanate formation with reference to calcination temperatures. The calcined powders were then consolidated by compaction and sintering. An attempt has bean made to explain the consolidation behaviour of these powders on the basis of powder characteristics.

Jan 1, 1980

By W. C. Elmore

THE magnetic powder method, long used. for roughly mapping mag-netic fields, has recently been refined 1,2 for investigating the microscopic variations in the surface magnetization of ferromagnetic crystals. Bitter2 first discovered regular powder patterns connected with the crystal structure of such specimens. Several other investigators3 have used Bitter's original technique, with slight modifications, to study the varia-tion of the patterns with variations in the magnetizing field applied parallel to the surface, and their dependence upon the state of strain, of polish and of crystal cut. All of the explanations of these patterns on metallic ferromagnetics have been couched in general terms. In a preliminary report we have described an improvement in the powder technique which led us to the discovery of a new effect throwing con-siderable light on the magnetic secondary structure of alpha iron4 and of nickels single crystals. We now report additional evidence confirming the existence and stability of a magnetic block secondary structure.

Jan 1, 1936

By Cyril Stanley Smith

Jan 1, 1949

By Cyril Stanley Smith

Jan 1, 1949

By J. A. Hutcheson

NO one questions that it is technically possible to achieve the controlled release of atomic energy in a form that can be converted into heat or electricity. However, before this is actually an accomplished fact a great amount of work must .be done. This work falls into two general classifications: research and engineering development. At present a research program is under way in this country, co-ordinated and directed by the Atomic Energy Commission, which, as time goes on, will uncover fundamental knowledge of this new science that is essential before industrial applications of atomic energy are practical. Undoubtedly therefore, as the store of available knowledge increases, a time will come when answers to the many questions relating to practicality of atomic energy in industry can be determined with reasonable certainty. That the application of atomic energy in industry will eventually be proved practical is assumed. What then are the engineering problems that must be solved before the first practical electric power generating station can be built?

Jan 1, 1948

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.' Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,' and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.' Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,' and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By D. R. Spink

In the preparation of zirconium and hafnium metals, there are many indications that impurity levels control the physical and chemical properties of the metal. The purpose of this work was to develop methods of producing pure raw materials that could be reduced to highly pure metals. Early work by the Carbomcndum Metals Co. and others indicated that certain fused salts were highly efficient in the removal of impurities from gaseous zirconium tetrachloride. We have developed workable fused salts along with a continuous and higly efficient scrubber design which can be used to produce very pure zirconium tetrachloride. Metal made from the purified tetrachloride has been shown to approach crystal bar metal in purity. Scrubber designs are discussed with recommended materials of construction. VARIOUS methods have been used to purify zirconium (and hafnium) tetrachloride. Most of these methods involve thermal degassing initially (the removal of more volatile compounds at temperatures below that where zirconium tetrachloride exhibits a significant vapor pressure) followed by a sublimation step (which conveniently leaves the nonvolatiles behind.) While these procedures effect definite purification, such processing is batchwise and does not result in optimum purification. Early work by The Carborundum Metals Co. and others indicated that fused salts were highly efficient in the removal of impurities from gaseous zirconium tetrachloride. The objective of this work was to develop a continuous fused-salt scrubbing process that would yield high-purity zirconium and hafnium tetrachlorides. The term "fused salt" refers to the molten state of ionic compounds and as used here, specifically refers to alkali metal and alkaline earth halides. Fused salts, because of their many valuable properties, are becoming increasingly im- portant industrially. These valuable properties of the fused salts are: 1) stability at elevated temperatures; 2)low vapor pressure; 3) low viscosity; 4) ability to dissolve many different materials; and 5) good elctctrical conductivity. All but the last property enhances the use of fused salts as scrubbing agents for zirconium and hafnium tetrachlorides. Fused-salt scrubbing may be defined for our purpose as the intimate contact between a gaseous compound and a molten salt with the purpose of removing impurities from the gaseous compound. In this case, the gaseous compound is zirconium tetrachloride which submlimes at 331°C. When this gas is contacted with a molten salt, impurities such as aluminum, iron, and titanium are removed and the resulting product is considered fused-salt scrubbed. Zirconium and hafnium are sold to a purity specification. Generally speaking, normal production without scrubbing is capable of meeting specifications. There are, however, several considerations That make the knowledge of methods of additional purification highly desirable. These are: 1) the control of product analysis; 2) the production of a pure product for special applications; 3) the salvaging of off-specification material; and 4) the use of raw materials with higher impurity levels than 1 he present raw materials. You will note that items 1 and 2 are somewhat complementary to each other and that item 4 assumes that The present process has impurity removal limitations. To better understand the part that fused-salt scrubbing of zirconium tetrachloride plays in the manufacture of zirconium, Fig. 1 contains an illustrated flow sheet of the industrial production of zirconium metal. In referring to Fig. 1, we can point out the specific benefits derived from our ability to purify zirconium tetrachloride. Purification of the crude (hafnium-containing) zirconium

Jan 1, 1962

By E. P. Miesch, P. B. Crawford

A study was made of the effect of permeable and impermeable lenses in a reservoir on the production capacity of a well. Both steady-state and unsteady-state data were obtained. An electrical resistivity model was used to obtain the steady-state data and thermal models. were constructed to obtain the unsteady-state data. The productivity of a well is affected very greatly only when the lenses are close to the well. The effect of circular lenses on the productivity ratio can be correlated with the distance from the center of the lens to the center of the well divided by the radius of the lens. When this dimensionless distance is equal to six or greater, the effect of the lenses on production capacity will be negligible. The pseudo steady-state productivity of a heterogeneous reservoir can be predicted using steady-state data. INTRODUCTION Many analytical solutions of reservoir behavior assume that reservoir rock is uniform and homogeneous. Although this assumption is used, all of the data from core analyses and well logging indicate that the reservoirs are heterogeneous. Very little work has been done on the performance of heterogeneous reservoirs. The work of Landrum,l et al. showed that transient phenomena in oil reservoirs could be studied with thermal models. Pickering and Cotman2 used thermal models to study flow in stratified reservoirs and investigated the effect of inhomo-geneities in oil reservoirs on transient flow performance. Loucks3 made a mathematical study of the pressure build-up in a system composed of two concentric regions of different permeability. Root, Silberberg and Pirson4 studied the effect of the growth of the flooded region on water influx predictions using a thermal model consisting of three concentric cylindrical regions of different thermal properties which simulated the aquifer, the flooded region and the unflooded portion of the original hydrocarbon region. Tomme, et a1.5 made a mathematical study of vertical fractures. The object of this investigation was to study the effect of highly permeable and impermeable lenses in the vicinity of the wellbore on the pressure depletion history of the well. Steady-state data were obtained for both conductive and nonconductive lenses that completely penetrated the formation. The lenses were symmetrically located at various distances from the wellbore. The unsteady-state data were obtained on seven thermal models. EXPERIMENTAL EQUIPMENT AND PROCEDURE STEADY-STATE DATA The steady-state data were obtained from an electrical resistivity model 30 in. in diameter and approximately 11/2 in. deep. The outside of the model was lined with a 30-in. diameter copper strip, which served as the outer boundary of the reservoir. The bottom was covered with a sheet of plexiglass so that it would be nonconductive. The model was filled with a slightly saline solution. The well size was varied from an 0.064-in. diameter copper wire to a 10-in. diameter copper cylinder. Readings were taken with an impedance bridge using AC current to prevent polarization at the contacts. Copper and wax lenses were used to represent infinitely conductive and nonconductive lenses, respectively. The resistance was first measured for each well diameter with no lenses in the reservoir. Then the conductive and nonconductive lenses were spaced symmetrically at various distances from the well and the resistance read from each lens location. The diameters of the conductive lenses were 3, 1.022 and 0.624 in., and those of the nonconductive lenses were 3, 2.25 and 1.563 in. The ratio of each resistance reading to the resistance reading with no lenses in the reservoir

Jan 1, 1965

By William E. Ford, Edward Salisbury Dana

WheweUite. Calcium oxalste CaCz04.Hz0. In small colorless monoclinic crystals. Optically +. j3 = 1.555. From haxony, with coal; also from Bohemia, and Akace. Oxammite. Ammonium oxelate, (N&)rC20r.2HzO. From the guano of the Gudape Isbnds, Peru.

Jan 1, 1922

By H. M. Morse

Tinsley Oil Field.—Mississippi joined the oil-producing states when on Sept. 13, 1939, the Union Producing Company's G. C. Woodruff well No. 1, sec. 13, T. 10 N., R. 3 W., Yazoo County, was completed after drilling plug at 4540 ft. in the Woodruff sand of the Eutaw formation of Cretaceous, producing 300 bbl. per day of 34.4" gravity oil through a ¼-in. choke, with a gas-oil ratio of 80 to 1 and bottom-hole pressure of 2045 lb. This was the discovery well in the Tinsley oil field. The well was drilled to a total depth of 4567 ft. and no salt water was encountered. The sand underlies the Selma chalk formation. Nine producing oil wells and one dry hole were drilled and completed by the end of 1939. Two producing sands have been found in the Eutaw and a third sand in the top of the Tuscaloosa formation, called the Woodbine sand in Louisiana and Texas. Faulting is an important factor in the Tinsley field. Total oil production has been approximately 250,000 bbl. from the nine flowing wells. Total depth to top of productive zone was 4540 ft.; to bottoms of productive wells, 4580 ft. Net thickness of the producing formation is 20 to 40 ft., and its porosity is 24 per cent. The deepest zone tested was the Tuscaloosa, in which the depth of hole was 6112 feet. Six hundred and forty acres has been proved for oil production. Jackson Gas Field.—The Jackson gas field has shown a steady decline in the number of wells but the pressure has been maintained. This field is a perfect example of a water-driven field and the time of wells going to salt water is predictable. Five wells were drilled in the Jackson field, of which only one produced. Amory Gas Field.—Interest was renewed in the Amory gas field, where a new well was started in the fall of 1939. Geological Formations.—The deepest well drilled in 1939 was the Willmut Gas and Oil Company's Cleve Love S. F. Johnson No. 1, sec. 29, T. 6 N., R. 1 W., Hinds County. This well encountered the Lower Cretaceous, Trinity series from 3770 to 6422 ft.; Lower Mesozoic from 6422 to 6484 ft. The geological correlations and nomenclature of the formations in Mississippi are shown in the accompanying strati-graphic section.

Jan 1, 1940

By H. M. Morse

Tinsley Oil Field.—Mississippi joined the oil-producing states when on Sept. 13, 1939, the Union Producing Company's G. C. Woodruff well No. 1, sec. 13, T. 10 N., R. 3 W., Yazoo County, was completed after drilling plug at 4540 ft. in the Woodruff sand of the Eutaw formation of Cretaceous, producing 300 bbl. per day of 34.4" gravity oil through a ¼-in. choke, with a gas-oil ratio of 80 to 1 and bottom-hole pressure of 2045 lb. This was the discovery well in the Tinsley oil field. The well was drilled to a total depth of 4567 ft. and no salt water was encountered. The sand underlies the Selma chalk formation. Nine producing oil wells and one dry hole were drilled and completed by the end of 1939. Two producing sands have been found in the Eutaw and a third sand in the top of the Tuscaloosa formation, called the Woodbine sand in Louisiana and Texas. Faulting is an important factor in the Tinsley field. Total oil production has been approximately 250,000 bbl. from the nine flowing wells. Total depth to top of productive zone was 4540 ft.; to bottoms of productive wells, 4580 ft. Net thickness of the producing formation is 20 to 40 ft., and its porosity is 24 per cent. The deepest zone tested was the Tuscaloosa, in which the depth of hole was 6112 feet. Six hundred and forty acres has been proved for oil production. Jackson Gas Field.—The Jackson gas field has shown a steady decline in the number of wells but the pressure has been maintained. This field is a perfect example of a water-driven field and the time of wells going to salt water is predictable. Five wells were drilled in the Jackson field, of which only one produced. Amory Gas Field.—Interest was renewed in the Amory gas field, where a new well was started in the fall of 1939. Geological Formations.—The deepest well drilled in 1939 was the Willmut Gas and Oil Company's Cleve Love S. F. Johnson No. 1, sec. 29, T. 6 N., R. 1 W., Hinds County. This well encountered the Lower Cretaceous, Trinity series from 3770 to 6422 ft.; Lower Mesozoic from 6422 to 6484 ft. The geological correlations and nomenclature of the formations in Mississippi are shown in the accompanying strati-graphic section.

Jan 1, 1940

By J. WILLIAM WETTER

WHEN the privilege was extended to me to address this meeting I could not help but make a mental review of my own activities and experiences in connection with association work. After having spent about 16 years in the mining engineering field, I entered into the operating branch of coal mining which afforded, about 12 years ago, my first opportunity of attending a meeting of our local Association and sitting in with the "big boys" of the industry. This was quite a thrilling experience because I had heard a great deal about the various operators who belonged to the Association and knew, or at least thought I knew, that a certain group dominated its affairs and that a "clique" was in control of a sizable "roller" which could be "steamed up" at will to flatten out any opposition which might appear upon the horizon or under it, too, for that matter. Now, I was to have the privilege of observing this "clique" at first hand, of seeing a small group making the policies and shaping the destinies of a great industry and planning the activities of an important Association while a large majority of the members would sit by either complacently or otherwise with the full knowledge that the "roller" was in waiting to reduce them to ribbons at the first sign of resistance.

Jan 1, 1930

By E. Gybbon Spilsbury

In a paper* read at the last meeting of the Institute, in Scranton, Pa., I referred to the proposed introduction at the Haile gold-mine, South Carolina, of a novel method of chlorination. I have since

Jan 1, 1888

By L. E. Paulson

INTRODUCTION The Northern Great Plains has 16 billion tons of strippable lignite (1). Presently, 15 million tons per year are mined; essentially all is used for generation of electrical power. In the future, additional large quantities will be consumed in the production of gaseous and liquid fuels. A major consideration in design and operability of power stations and conversion plants is the nature of the ash or inorganic constituents of the lignite used. These inorganic components cause fireside fouling in boilers, exert a catalytic effect in liquefaction and gasification, and contribute to particulate and SO2 emissions. Ash fouling on fireside boiler tubes cause reduced heat transfer and gas flow which limits boiler performance. Severe fouling can result in shutdown of the boiler. A comprehensive test program in both pilot plant and field studies at the Grand Forks Energy Technology Center (GFETC) has shown that ash fouling increases with increased sodium content of low-rank coals (2). The sodium in the coal can be

Jan 1, 1983

By N. A. D. Parlee, I. D. Shah

THIS communication reports the results of some work done on the effect of gold, palladium, and platinum on the liquid-gas-solid equilibrium in the Ag-O system,1,2 see Fig. 1. Recently several investigators3, 4, 5 have reported the effects of gold, palladium, platinum, and copper on the solubility of oxygen in liquid silver. This communication represents only a portion of the work done here on the solubility of oxygen in liquid silver and liquid Ag-Au, Ag-Pd, and Ag-Pt alloyss—the greater part having already been reprted. The apparatus, materials, and procedures used were similar to those of earlier work.' l The main precautions observed in obtaining these freezing points at constant temperature and PO2 = 1 atm were as follows: 1) The points were approached very slowly from higher temperatures. 2) In the very near vicinity of the L-G-S equilibrium point precautions were taken to see that the melt was in equilibrium with oxygen at one atm. Equilibrium was considered to have been attained when no more absorption of oxygen was observed in the last 15 min at a fixed temperature. 3) In the case of these alloys, the freezing point of the melt at 1 atm of oxygen and the equilibrium amount of oxygen absorbed by the liquid "infinitesimally" above this point were determined by lowering the temperature in very, very small steps, equilibrating at

Jan 1, 1969

The co-operation of the members of the Institute is earnestly sought by the Committee on Nominations, recently appointed by the Board of Directors, in its work of formulating a ticket for officers and places falling vacant in the Board of Directors in February, 1916. The Committee must present the official ticket of nominations to the Board of Directors at its October meeting. Members are, therefore, urged to send promptly their nominations for officers and Directors in order that the Committee may have an opportunity to give them full consideration. The officers to be elected at the annual meeting in February, 1916, are: One officer, known as Director and President. Two officers, known as Director and Vice-President. Five officers, known as Director. The officers of the Institute whose terms expire are as follows: President, William L. Saunders (not eligible for re-election). Past President, Charles F. Rand. Vice-Presidents, Thomas H. Leggett, District 0; Fred W. Denton, District 4.

Jan 9, 1915

By T. H. Alden

Using alternating tension-compression straining, the hardening of magnesium oxide single crystals was studied up to large stresses and strains. At 0.25 pct plastic strain amplitude, the hardening curve is approximately linear with slope 25,000 psi from the shear yield stress, 7 to 8000 psi, to 35,000psi. Above this stress, the slope decreases. The strain hardening behavior of MgO is considered qualitatively similar to that of metal single crystals. The relatively high stress attainable by strain hardening is associated apparently with the high yield stress on the cross-slip system, (001) <110>. Cleavage fracture during testing is uncommon. It is argued that the centers of high internal stress at glide band intersections, at which cracks tend to nucleate, are dispersed by cyclic strain. Special features of the glide band structure produced by cyclic strain and revealed by dislocation etch pits, support this view. Strain hardened MgO has mechanical properties greatly superior to the as-received material: yield stress, greater than 100,000 psi; elongation to fracture about 1 pct. A material is said to strain harden if the yield stress increases with an increment of plastic strain. This definition is usually applied for straining done in one direction, but is also applicable when the strain direction is periodically reversed, Fig. 1. For certain metal single crystals, data are available which permit a comparison of the hardening behavior for cyclic straining and for tension straining.&apos;-4 With certain qualifications, these data show that the same processes of hardening are operative in each type of test.5 Despite this fact, the importance of the technique is not immediately evident, although tension-compression studies of the common metals appear to suggest some deficiencies in theories of strain hardening developed exclusively on the basis of tensile tests. However, a recent observation suggests that the cyclic straining method may be very useful for studying semibrittle crystals in which large plastic strains are not accessible in unidirectional testing. The observation is that zinc crystals, when strained in tension-compression at -52°C, do not fail by cleavage at low stress (-500 psi)6 as they do in tension, but harden to a limiting stress of more than 5000 psi over a total plastic strain of about 600 pct.2 An important characteristic of the behavior of zinc crystals is the high stress, relative to the yield stress, attainable by strain hardening. By comparison, the hardening of aluminum single crystals tested by an identical technique saturates at 1100 psi. This difference is best explained by the cross-slip hypothesis of dynamic recovery.7,8 In zinc, cross slip is difficult because of the high yield stress for glide on planes other than the basal plane in the < 1120 > zone. The present work was undertaken in order to test whether these methods and ideas are applicable to other materials. Magnesium oxide single crystals, in common with most crystals of the rock-salt structure, deform plastically but fail by cleavage after a small strain when tested in tension. It was hoped that larger strains would be attained using tension-compression. There is, in addition, evidence 8a which shows that slip on the probable cross system, (001) < 110>, is difficult in magnesium oxide; it may therefore be possible to attain high stresses by strain hardening. 1) EXPERIMENTAL PROCEDURE Experimental methods used in this study were based in part on techniques reported in papers of Stokes, Johnston, and Li.&apos; MgO blocks, purchased from Norton Co., were used without further annealing. Specimens were cleaved to dimensions approximately 0.125 in. sq and 1 in. in length. The gage section, formed by chemical polishing, was sprinkled with 280 mesh silicon carbide particles in order to introduce fresh dislocations. The crystals were then cemented into cylindrical aluminum adapters and clamped in an Instron testing machine. One of two alternating straining programs was used. In the first, total cross-head travel was established and increased in steps after various numbers of cycles. In the second, a capacitance gage was used to directly measure the elongation of the specimen and the crosshead was controlled so as to keep the plastic strain amplitude constant. The straining was always symmetrical with respect to the initial, zero strain condition. While both procedures produce strain hardening, only the latter permits a measure of the total plastic strain so that hardening curves may be drawn. Constant plastic strain amplitude tests were done

Jan 1, 1963