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By N. J. Grant, D. S. Bloom

THE development of high temperature, high stress alloys had proceeded with such rapidity during the war, and for a short time afterward, that our knowledge of the constitution of the alloys had become seriously inadequate. To interpret correctly alloy behavior it is not only necessary to recognize the phases present, but also to know the properties of the phases under all varieties of conditions and treatments. Chromium in these high temperature alloys holds the unique distinction of being the only one element which must be present when an oxidizing or generally corrosive atmosphere is present and when a long life is desired in service. Carbon and nitrogen must also be considered where chromium is present. Carbon is always present, either as an impurity in the raw alloying elements, or as a deliberate addition agent to increase the strength. Nitrogen is generally picked up from the atmosphere during melting or may be added as an alloying element. The effect of nitrogen additions is not too dissimilar to that of carbon additions. As such, chromium carbides and nitrides become of great interest since they are present in a very large number of alloys, including alloy steels, stainless steels, super alloys, and the like. In the chromium-carbon system there are three accepted, carbides: Cr,C, Cr7C8, and Cr3C2. The existence of one more carbide, a still higher carbon form CrC, has been advanced. The phase diagrams of chromium and carbon as published by Friemann and Sauerwald² and by Tofaute, Kuttner and But- tinghaus³ -do not extend beyond the carbide Cr3C2, which contains 13.3 pct carbon; but Hatsuta has extended the diagram up to 20 pct carbon, and in doing so hypothesized, with the use of some questionable experimental results, the compound CrC. This carbide would contain 18.75 pct carbon, 81.25 pct chromium, by weight. It is further known that as the chromium carbides increase in carbon the acid resistance increases but the oxidation resistance decreases4,5 This is of great importance in high temperature alloys where time-temperature stability, as well as oxidation resistance, is of prime importance. The possible existence of a carbide of the formula CrC thus becomes of prime importance and it was considered important to recheck the chromium-carbon binary constitutional diagram for such a compound. In view of the wide spread of values listed for the melting point of chromium (1500° to 1850°C) and 1930°C8, it was considered .that the liquidus temperatures might well be redetermined more ac-

Jan 1, 1951

By AIME AIME

PRIZES totaling $450 were awarded at the Annual Meeting luncheon on Monday, Feb. 9, to the winners of the third national student prize paper contest. The undergraduate prizewinners, each of whom received a check for $100, were as follows: Mayo W. Lanning, Lafayette College, for his paper entitled ?Some Aspects of the Mining Methods Employed at the Scrub Oak Mines of the Alan Wood Steel Company,? (entered by the Lehigh Valley Section). Charles F. Parent, Montana School of Mines, for his paper entitled ?Relationships of Manganese Minerals in the Butte District,? (entered by the Montana Section). Harry Czyzewski, University of Illinois, for his paper entitled ?A Metallurgical Study of Cast Irons Used for Glass Molds,? (entered by the Chicago Section).

Jan 1, 1942

By David Hall

IN October, 1926, the Inspiration Consolidated Copper Co. began the operation of its new leaching plant, which has a capacity to handle 8600 dry tons of ore daily and produce therefrom approximately 160,000 lb. of electrolytic copper per day. (See Fig. 1.) The energy for the leaching process is supplied by three motor generator sets (Fig. 2), each set consisting of one 5450-hp., 6600-volt, three FIG. 1.-LEACHING PLANT OF INSPIRATION CONSOLIDATED COPPER CO. AT INSPIRATION, Ariz. phase, 25-cycle, 500-r.p.m. synchronous motor and two 1920-kw., 150 to 320-volt, 6000-amp.,12-pole, d. c. generators, and one 70-kw., 125-volt d, c. exciter. The capacity of the three sets is 36,000 amp. at 320 volts. A description of the metallurgical processes of this plant was. given in a paper by H. W. Aldrich,1 and from his paper we quote the following figures for the month of July, 1927:

Jan 1, 1928

By James F. McConnell, Charles W. Statler

Pennsylvania's existing large coal-fired units are limited to 2.0, 1.8, or 0.6 lb of sulfur per million Btu fired, depending on site location. Multi-stream coal preparation can be employed on system basis to extract the highest quality fraction of coal for use in units requiring the lowest sulfur. The middling fraction can be directed to units permitted higher sulfur. General Public Utilities Corp. has concluded that it is feasible to advance the state-of-the-art of heavy media coal preparation to produce an intensively cleaned primary product of 1.3 sp gr of less than 0.6 lb of sulfur per million Btu for the new unit and a middling product of 2.0 lb of sulfur per million Btu for existing units.

Jan 1, 1977

By G. B. Craig, G. L. Montgomery

A simple technique has been developed which reveals glide dislocations in zone-refined aluminum as etch pits. The technique has been tested quantitatively by making dislocation counts on aluminum single crystals deformed in pure bending. The method has the advantage of being insensitive to the orientation of the surface under examination. A number of etchants which will reveal dislocations in annealed aluminum have been reported.'-' These etchants apparently depend on decoration of the dislocations by an impurity (probably iron) and cannot, therefore, be used to reveal fresh glide dislocations. In addition, it is unlikely that screw dislocations will be etched because of their small attraction for impurity atoms. Amelinckx6 has reported that glide dislocations located along slip traces can be revealed by fluo-rated aqua regia. This work indicated that dislocations themselves, irrespective of decoration by impurity atoms, are responsible for the etch pits. However, as a result of additional etching experiments, Wyon and Marchin7 concluded that dislocations alone are not sufficient to explain the localization of etch pits on slip lines in aluminum using chemical etch-pitting techniques. In addition, their results show that glide dislocations are revealed only on surfaces approximately parallel to a (100) axis and that not all slip systems are attacked. These observations have been confirmed by the present authors. The technique described in this article is insensitive to the orientation of the surface, and reveals dislocations on all glide systems. Fig. 1 shows a deformed region in the neighborhood of a scratch. Dislocations can be seen along three slip traces. In the present work, single crystals of zone-refined aluminum are polished for from 2 to 5 min in a chemical polishing reagent held at 100°C, as described by Herenguel and second:' H2Sol 60 pct H3PO4 30 pct HNO3 10 pet The samples are then coated with a thin oxide film by annealing in air at 450°C for 1 hr and cooling in the furnace. After deformation, dislocation etch pits are developed by immersing the specimen in the same polishing solution which is now held at a temperature of 50°C. The formation of small hydrogen bubbles indicates that etching has occurred. The sample is immediately removed from the solution. Prolonged etching results in enlargement of the pits and, in regions of high dislocation density, the overlapping and loss of resolution of individual pits. It is the experience of the authors that contact with iron will ruinously contaminate the reagent. With careful etching, dislocations separated by half a micron can be resolved optically and the method has been shown to be sufficiently sensitive to reveal dislocations produced during the pre-easy glide region of deformation, Fig. 2. A few examples of glide-dislocation configurations, as revealed by this technique, are shown in Figs. 1 to 4.

Jan 1, 1964

By W. J. Uren, Charles R. Kuzell

The industries engaged in winning minerals from the earth, because of their widespread dissemination, are faced with perhaps as wide a variety of labor-management problems as may be found in any other broad sphere of productive activity. Those problems are continually increasing in volume and complexity, and management has become aware of their growing importance. For the past quarter century at least, labor-management problems have largely been union-management problems. During this period tremendous assistance has been given labor unions through legislation and administrative and political action. In the United States, legislation favorable to unions has come about in the form of the now defunct National Industrial Recovery Act; the Wagner Act, most of which has been carried forward in the Taft-Hartley Act and the Landrum-Griffin Act; the Norris-La Guardia Act, the Wage and Hour Law, the Walsh-Healey Act, and others. The result has been to transfer from the hands of management to those who direct the affairs of the unions a large share of control over the industry and to hamper in many ways the remaining control left to management. In the United States there are many examples of the power of unions to injure whole industries seriously without regard to the interests of management, the employes, or the public. During 1958 and 1959 revelations of corruption and coercion in labor unions made before the McClellan Committee of the U. S. Senate generated considerable public sentiment in favor of legislation to protect the interests of employes and the public. However, the resulting legislation, the Labor-Management Reporting and Disclosure Act of 1959 (Landrum-Griffin Act), demonstrated quite clearly that the political power of the labor union leaders was adequate to prevent adoption of effective measures in this field.

Jan 1, 1964

By Wayne P. Myers

Electricity, as normally thought of by a layman's definition, is a manmade force that has no color, no odor, is not visible, cannot be heard, yet man can control it and make it perform his work for him. A person dare not cheat on it, for it then will master him. It has laws, rules, and regulations that must be strictly adhered to if it is to perform in the safest, most reliable, and economical manner. In the early days of coal mining the power source was man himself. Later man employed steam and compressed air to reduce his muscle power requirements needed in the extraction of coal. By the turn of the 20th century, electricity had become the most common source of power for the coal industry. Steam and compressed air are still found in use in isolated cases today for specific applications; however, they are rapidly being replaced by electricity. Electrical laws and regulations are quite extensive and somewhat complex for the proper generation and use of electricity. Man-made laws, rules, and regulations for the care and handling of electricity, designed for man's safety, are rigidly enforced by the U.S. Bureau of Mines, as well as the various state departments of mines. BACKGROUND Until recent years most underground coal mines used direct current exclusively for all movable and for some stationary equipment. Exceptions were for permanent pumps, tipple, fan, and outside buildings where alternating current was normally employed. However, over 60 years ago there were mines with dual systems. Alternating current was used for cutting machines, drills, and pumps, direct current for locomotives. There were no other machines as these were hand-loading mines. Later, during early mechanization in the 1920s, alternating current was also applied to loading machines at some mines. Use of dual electric systems then declined until fairly recently when

Jan 1, 1973

By Charles H. Fulton

The process of crushing ore in cyanide solution was first used at the Crown mine, New Zealand, in 1897, by Mr. F. R. W. Daw; and, two years later, Mr. John Hinton tried it experimentally at the old Dakota plant, Central City, South Dakota. To Mr. Hinton belongs the credit of introducing this important modification in the Black Hills, this being its first successful application in the U. S., and its results have been so satisfactory that it has become established as the proper manner in which to treat the dense oxidized siliceous ores of this district. Five mills are now crushing ore in cyanide solution, namely, the Horseshoe, 120 stamps (60 in operation); the Dakota, 30 stamps; the Maitland, 40 stamps; the Hidden Fortune, 60 stamps; the Lundberg, Dorr & Wilson, one 6-ft. Monadnock roller-mill; and several others intend to adopt this practice. The dry-crushing process still holds its place for the treatment of the more porous and open siliceous ores; and two mills continue to dry-crush dense siliceous ores. Character of the Ores. The occurrence of the ores of the Cambrian strata in the northern Black Hills has been frequently described.' In practice they are classified, according to their appearance, into " red " and " blue " ores, the former being oxidized and the latter unoxidized. At the present time, usually the red ores only are treated at the mills, although occasionally small quantities of blue ore, which have become intimately mixed with the red in mining, are included. Generally the extraction of values by the direct treatment of raw ore is from 70 to 75 per cent. for red ores, and from 25 to 50 per cent. for blue ores. The ores consist mainly of a siliceous matrix containing, as a +1SOUTH DAKOTA SCHOOL OF MINES, RAPID CITY, SO. DAK.

Jan 1, 1905

By R. N. Dokken, J. F. Elliott

A high-temperature solution calorimeter was used to measure directly the partial molar heat of mixing of nickel in the Cu-Ni system, 0 to 15 at. pct Ni and 1200°C; of silver in the Cu-Ag system, 0 to 50 at. pct Ag and 1100°C; and of cobalt in the Cu-Co system, 0 to 6 at. pct Co and 1200°C. The heats of fusion of copper and silver were also detervnined directly. The results of these investigations are as follows: Cu-Ni: HM = [2.64 + 0.25Xm JXNiXCy kcal/g-U~OI Cu-Ag: HM =[4.00 + 0.31XAglXAgXCu kcal/g-atom Cu-Co: HF~ = [8- 5X~,]X& kcal/g-atotn Cu, AH, = 3290 * 275 cal/g-atom Ag, AH, = 2890 * 250 cal/g-atom The performance of the calorimeter was enhanced by improving the operational and control procedures, particularly the temperature-wieasuren~ent method and the solute-addition practice. The interpretation of the experimental data was improved by developing machine computational techniques that increased the speed, flexibility, and accuracy of the treatment of the data. THIS paper reports further measurements of the heats of solution of liquid metals with the high-tem- perature solution ca1orimeter.l Measurements were made of the partial molar heats of mixing in the following liquid alloys: Cu-Ni, Cu-Ag, and Cu-Co. In addition the heats of fusion of copper and silver were also determined. The apparatus and the experimental procedure were essentially those of Benz and Elliott.2 Several modifications in the experimental method and the means for interpreting the data were incorporated in this study to improve the results. The operation of the calorimeter and its characteristics will be described only briefly here. The

Jan 1, 1965

By Bevan Presley

THERE has been developed at Latouche a rather unusual system of mining which, for want of a better name, has been called the "Latouche system of mining." It is a modified form of shrinkage stoping applicable to orebodies of large or fairly large size where the ground is such that timbering would not be required in stoping. Mention has been made of this method of mining by Birch,1 who gave no details as it had been in use only a short time and the final outcome undetermined. The system, however, has proved to be entirely successful and it is thought that a paper covering it might be of general interest. Before proceeding with a detailed description of the "Latouche system" a brief description of the property and the various mining methods previously used will be given. LOCATION The Beatson mine of the Kennecott Copper Corp. is situated on the west coast of Latouche Island-, in Prince William Sound, Southwestern Alaska, 45 miles east of Seward, the coast terminus of the U. S. Government Railroad. It is a regular port of call for ships on the Southwestern Alaska run. The island is about 12 miles long and 3 miles wide. A ridge of mountains runs the entire length with a maximum elevation of 2500 feet. CLIMATE Latouche has to contend with possibly the greatest amount of precipitation on the North American continent. The annual average precipitation for the past 4 years has been 188 in., with 248 in. for the year 1926. A rainfall of 4 in. per day is not uncommon. In the winter the thermometer rarely falls below +20° F. and the snowfall is usually heavy during the months of March and April.

Jan 1, 1927

By T. L. Joseph

LARGE deposits of manganiferous iron ores, representing several million tons of metallic manganese, occur in the United States. The Minnesota deposits of such ore-are of outstanding importance because of their size, state of development, ease of mining and proximity to the Great Lakes, which permits water transportation to steel centers. In' view of the fact that our steel industry requires large quantities of manganese, for which no satisfactory substitute-has been found, and because our reserves of ferro-grade ore are comparatively small, the development of methods that will make our large deposits of manganiferous iron ores available as a source of ferromanganese is an important problem. Realizing the importance of this problem, some years ago the North Central Station of the U. S. Bureau of Mines and the Minnesota School of Mines Experiment Station undertook jointly the development of methods for recovering the manganese content of manganiferous iron ores in a: form suitable for the production of ferromanganese, the 80 per cent. alloy indispensable in producing steel. Two types of manganiferous iron ores have been described in previous reports. I The brown ores are higher in iron and lower in manganese than the black ores; the black ores are more siliceous but contain less phosphorus. The utilization of the iron content of the brown ores in the production of steel appears to furnish the best basis for their treat-ment. The method of attack has been to work out modifications in iron and steel practice so as to recover manganese in the form of slag comparable to ferro-grade ores. The greater part of the experimental work has been conducted with a 6-ton blast furnace and a Y2-ton basic open hearth. This paper is devoted mainly to open-hearth tests in which high-phosphorus spiegel

Jan 1, 1930

By David J. Dunn, Richard G. Martin

Of many physical parameters critical to design of grinding processes, impact of grinding media is among the most difficult to measure or predict. Yet impact of falling grinding balls, pebbles, or rods accomplishes the fine grinding essential to metallurgical recovery of most important minerals. Unfortunately, the same impacts that break ore fragments deform or crack grinding mill liners. A project was undertaken at Climax Molybdenum Company to measure impact forces in operating ball mills so that they might be used to calculate stresses in liner materials and be correlated with service performance of mill liner alloys. Towards that end, a method of measuring impact forces on ball mill liners using an instrumented grinding ball has been developed. Preliminary tests show that impact forces and contact stresses imposed on bare mill liners are quite high but are greatly reduced by cushioning when coarse ore particles are crushed between balls and liners.

Jan 4, 1978

By C. B. Foraker

THE Magma mine, of the Magma Copper Co., at Superior, Pinal County, Arizona, is 68 miles east of Phoenix and 21 miles west of Miami, Arizona, on highway U. S. 180. TEMPERATURES AND UNDERGROUND WATERS Surface Temperatures.-The average surface dry-bulb temperature at Superior is 72.4º; wet-bulb, 57.4º; with an indicated relative humidity of 38 per cent. The average yearly rainfall from 1921 to 1936, inclusive, was 18.74 in. The maximum condition of the atmosphere is in June, July and August, and the minimum is in January and February. The surface temperatures, of course, influence the temperatures of the down- cast shafts; however, the variation between winter and summer causes a difference of only 2º to 3º in the stopes and working places that are not close to the intake shafts. Average atmospheric conditions are shown in Fig. 1. Rock Temperatures.-Rock temperatures on the deeper levels of the mine are as follows: [ ] There appears to be no difference in rock temperature for any particular horizon of the various formations or in the vein. Water encountered is always the same temperature as the rock from which it flows, and for this reason it is thought that the water is heated by the rock; not the rock by the water. The country rock apparently has been heated by the various intrusions, perhaps the vein itself, and has not yet had time to cool off. The geothermal gradient (Fig. 2) as indicated by the rock temperatures given above is 1 ½ º per 100 feet. Underground Waters.-The underground water varies from 350 to 565 gal. per min., depending on the rainfall. The limestone and other

Jan 1, 1938

By J. J. Mulligan, F. F. Colcord, E. F. Kern

The electrolytic separation of silver and gold has been practiced by the refineries in the United States for a good many years, and probably because of frequent visiting between officials of plants and the consequent exchange of views, operations in the various silver and gold refineries are very similar. We find, for instance, they practically all use electrolytes of approximately the same composition, which, no doubt, is more the result of experience than of studies of electrolytes. At the new electrolytic parting plant of the U. S. S. Lead Refinery, Inc., East Chicago, Ind., considerable attention has been given to the composition of electrolytes, especially to their conductivity and their effect on the character of the silver deposit. We are not aware that anything has been recently published on this subject and are, therefore, presenting such data as we have with the idea that, although it will not be wholly new, it may stimulate interest in the subject. Effect of Copper Content on Conductivity The first work was to determine the specific conductivity of silver nitrate and copper nitrate solutions. Concentrated solutions of silver nitrate and copper nitrate were prepared by dissolving analyzed chemically-pure salts in distilled water, and determining the silver and copper in each. Definite amounts of the concentrated solutions were taken, mixed and diluted to a definite volume. The silver and the copper were determined in each of these solutions and the conductivity was then determined. The plotted results are shown in Figs. 1 and 2. The effect of increasing quantities of silver and copper is readily seen. A comparison of the two sets of curves shows conclusively the benefit of holding the copper content of the electrolyte above 5C g. per liter, as its effect is to increase greatly the conductivity in an approximate propor-

Jan 1, 1926

By H. P. Greenwald, H. C. Howarth

The rapidly increasing use in coal mines of portable auxiliary fans, which are generally 'blowers" employed in connection with canvas tubing, raises questions concerning the hazards of such equipment, especially where the practices are opposed to established methods of ventilating face workings. Half a dozen or more coal-mine explosions and some fires have been attributed to the use of auxiliary fans; moreover, competent mining engineers have found many dangerous installations and methods of use-for example, intermittent running of the fans in gassy mines with consequent accumulations of firedamp at the faces. These facts have led the U. S. Bureau of Mines to issue this recommendation: "In the interest of safety, the Bureau of Mines, Department of Commerce, recommends that auxiliary fans or blowers should not be used in coal mines as a substitute for methods of regular and continuous coursing of the air to every face in the mine." The comparatively recent introduction of new types of mining machines, mechanical loaders, face conveyors, and slabbing machines has encouraged the trial of new systems of face mining, all of which have for their object the rapid advance of the faces. Although the latter has certain economic advantages, in gassy mines the rate at which gas is given off is generally found to increase in proportion to the speed of advance into new territory, which in turn increases the difficulties of efficient ventilation of the face workings. Some of the systems of advance mining being tried in connection with new mechanizing methods practically compel the use of blower fans and tubing, as single narrow places arc now driven 300 ft. or more without crosscuts. In some instances a series of parallel headings are driven without crosscuts pre-

Jan 1, 1928

By James H. Hance

Several years ago the writer was connected with the Mint and Assay Service of the Federal Government as Assistant Assayer at the Salt Lake Assay Office. At that time cyanide bars formed approximately half of the bullion purchased by that office. Disagreement in valuat,ion between the producer and the office was not infrequent and to a lesser extent between the Assay Office and the Mint, this latter issue being soon obviated, however, by adopting uniform methods of sampling the bars. A nice problem seemed to offer itself for research and the writer began a series of experiments which were soon terminated, however, by his going into other work, and which he regrets have not since been completed. The results attained may suggest lines of approach to this problem and are, therefore, offered in this article. Frederic P. Dewey, Assayer of the Mint Scrvice, U. 5. Treasury, has had abundant opportunity to study this phase of metallurgy, and has published several articles relative thereto.1 In the last article cited Dewey quotes analyses of cyanide bullion similar in content to that with which the writer worked, and which show some of the variations met with. In the discussion of these papers,2 comparison has been made in terms of copper bullion, but to the writer this seems of questionable value. Copper bullion may resemble silver bullion, but its similarity to gold bullion with little or no silver content is another thing. The freezing-point diagram of Roozeboom, reproduced on page 881 of the discussion cited, is for the gold-silver series as stated. The original problem under discussion, however, is not this alloy but gold with base metals other than copper. As for the statement that the corners are the worst places or

Jan 1, 1916

By L. D. Dougan, J. V. N. Dorr

PaGE Geological Conditions......................... 78 Development of Elko Prince Property.................. 78 Prince Vein.............................. 79 Mining Practice.............*.'.......:...... SO Milling Practice............................ 84 Power Plant............................... 96 Construction Costs.......................... 97 Geological Conditions The Elko Prince mine is in the Gold Circle district, Nevada, about 155 miles (2. 4 km.) from the town of Midas, 55 miles (88.5 km.) west of Battle Mountain and 50 miles (8.5 km.) northeast of Golconda. The district is described by Emmons in U. S. Geological Survey Bulletin 408, 1910. Little was said of the Elko Prince, however, as only a small amount of work had then been completed. The geological structure of the region is simple. The oldest exposed formation, covering most of the area, is rhyolite, which has a light-colored devitrified groundmass enclosing phenocrysts of feldspar, quartz, and magnetite. It has been somewhat weathered and partially stained with oxide of iron. There are several outcrops of andesite which cut the rhyolite. The ore deposits occur as fissure veins, replacement veins, and sheeted zones. The Elko Prince vein is of the first type. The rhyolite near the veins is silicified, stained with oxide of iron, and, at some localities, replaced by ore, or is so permeated by metals as to be classed as ore. The vein filling consists chiefly of quartz, and the values consist entirely of gold and silver. Part of the gold exists as the native metal and part is associated with pyrite. Silver occurs free and as argentite in banded streaks through the vein. These veins trend in a northwesterly direction, with dips varying from 65' to vertical. Development of Elko Prince Property Gold was discovered in the district in the Fall of 1907, and a charac-stic rush followed The town of Midas was laid out and shortly had

Jan 1, 1919

By C. H. Herty

During the past few years frequent reference has been made to a certain type of iron known generally as "bad iron," "dirty iron," etc., both by steelmakers and producers of iron castings.' Open-hearth operators have claimed that such iron was entirely within the specified limits as to ordinary analysis but it was difficult to make good steel from it. It has been suggested that unreduced material in the iron is responsible, also that most trouble is experienced with the iron when the blast furnace is delivering a product whose analysis is more or less variable. Other reasons suggested are the use of scrap or borings, unsintered flue dust in the burden, a cold hearth, too high a proportion of unsuitable grade of ore, or the form of the carbon in the iron. Accordingly, a subcommittee was appoint at the fall meeting of the Open-hearth Committee of the Americ m Institute of Mining and Metallurgical Engineers held in Pittsburgh in October, 1926, to investigate the reasons for the occurrence of this bad iron and suggest methods for preventing its appearance. This committee enlisted the cooperation of the U. S. Bureau of Mines Experiment Station at Pittsburgh in undertaking a study of pig-iron quality as affecting the open hearth. The following is a report of the findings to date: Method of Testing Inasmuch as a "spell" of dirty iron occurs without warning and may be of short duration, it was deemed advisable to attempt to simulate the conditions existing before and during such a period and compare the quality of the steel made with the normal and with the dirty iron. The Bourne-Fuller Co., of Cleveland, which has a single furnace that supplies

Jan 1, 1929

By L. Adler

A relatively simple and effective technique is proposed to deal with the failure of geologic masses containing weakness planes. This technique, termed irextended" rupture envelope, provides a means to clearly distinguish rock and soil from fractured rock and, on a theoretical level, considers a matrix-inclusion system. It may also constitute the link between Mohr's and Griffith's failure theories. Included in the article are five sample problems concerning site location, structural design, strengthening the plane of weakness, changing the magnitudes of major and minor principal stresses and changing the orientations of major and minor principal stresses. Engineers trying to solve design problems in rock and soil mechanics have often assumed an iso-tropic and homogeneous medium. For naturally occurring geologic masses this assumption has always been viewed with regret. The following analysis which deals with the effects of plane anisotropy on failure presents a solution to this. The planes of weakness are joints, faults, bedding planes, fracture and cleavage (natural and induced), foliation and schistosity. The physical properties of these weakness planes include an undulating surface, frictional resistance, discontinuous extent, filling material, tightness and presence of water to cause a hydrostatic pore pressure. All of these properties relating to failure can be summarized in Mohr's rupture envelope for the plane of weakness. This, along with the geometrical orientation, strike and dip, of the plane of weakness produces what is termed an irextended" rupture envelope. MOHR'S STRESS CIRCLE AND RUPTURE ENVELOPE The significant features of these concepts are listed below.' 1) A point on the u - r coordinate plane represents the normal and tangential stress components on a reference area in the material. This area can have any orientation. (Fig. la)

Jan 1, 1963

By D. J. Jr. McAdam

Fort the past five years, an investigation of the endurance properties of metals has been in progress at the U. S. Naval Engineering Experiment Station, Annapolis, Md. As a result of the investigations at this Station1-5 and other laboratories6-11 "endurance limits" of practically all kinds of carbon and alloy steels have been determined and have been correlated with other physical properties, especially with tensile strength. About a year and a half ago, the investigation at the Naval Experiment Station was shifted to non-ferrous metals. As a result, several papers discussing the endurance properties of numerous non-ferrous metals and alloys, especially the alloys of nickel and of copper12-16 have been published. In these papers, stress-cycle graphs illustrate. the endurance properties of each individual metal and alloy, and other graphs illustrate the effect of cold working, heat treatment, and chemical composition on endurance and other physical properties. Endurance tests of non-ferrous metals were made by the machines used in the endurance tests of ferrous metals. 1-4 The specimen for the rotating-cantilever tests, which has been described, 1,2,13 has a conical surface, with taper so adjusted that the stress is nearly uniform over a length of about 1 ½ in. Alternating torsion tests were made with the machine of the inertia types17 and usually by an accelerated-fatigue method.12 As the rotating-cantilever endurance limits of metals are about twice the alternating-torsion endurance limits, the former values are more generally useful in correlating the endurance properties of nonferrous metals. In several recent papers by the writer13-16 correlation of the endurance properties of a number of non-ferrous metals has been discussed.

Jan 10, 1925