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By Frances Jane Cromwell, D. J. McAdam, G. W. Geil

In a series of papers, the authors and their associates have shown that the technical cohesion limit is affected by the same four factors that affect the flow stress, namely, the stress system, plastic deformation, temperature, and the strain rate.16-28 Moreover, each of these factors affects the technical cohesion limit in the same way that it affects the flow stress,t The influence of any one of these factors may be represented by a curve of cohesion limits, although only one point on the curve may represent actual fracture. As the term ilfracture stress' has come into use with the same significance as 'ctechnical cohesion limit," the authors are here using the shorter term with the understanding that it does not always refer to actual fracture. This paper presents the results of an investigation of the flow of notched and unnotched specimens betqrcen yield and fracture, A study has thus been made of the flow and fracture of metals as affected by the stress system, and of the ductility of metals as affected by the stress system throughout plastic deformation. Since two of the principal stresses were equal (S2 = S3), the stress systems can be represented in terms of the radial stress ratio, the ratio of the transverse radial stress s3 to the longitudinal stress S1.* The results of the experiments are represented by a series of their flow-stress curves for each Of the metals investigated, and these diagrams have been used for the development Of Other diagrams Of various types. Ludwik was the first to suggest that fracture occurs when the flow stress becomes equal to a technical cohesion limit. Although Ludwik was incorrect in his view that the technical cohesion limit depends only on the amount of plastic deformation and not On the stress system, he was 'Orrect in his view that the flow-stress curve for any stress system terminates at a point representing a technical cohesion limit. The authors have seen some recent references to assertions by other investigators that a point representing the fracture stress need not be on the flow-stress curve. The Ludwik principle, however, "auld Seem to be axiomatic, provided that the flow Stress and fracture stress are properly defined and that the fracture stress is properly determined. Disregard Of this principle has led to some untenable theories Of criteria for fracture. When a metal is very ductile, the conventional method of determining the ductility and fracture stress by dividing the breaking load by the sectional area after fracture, generally gives values that are much too high. With some metals and in some conditions, the fracture stress thus determined may be two or more times the

Jan 1, 1949

By Robert B. Sosman

THE chance that a Howe Memorial Lecturer will be able to refer back to a personal contact with the distinguished metallurgist for whom this lectureship is named grows steadily smaller. I did not have the pleasure of his personal acquaintance, but I did receive from him in 1916, quite unexpectedly, a letter commenting on a paper that I had recently published27 on "Types of Prismatic Structure in Igneous Rocks." The paper was written for geologists and petrologists, but it had an application, naturally, to the crystallization of iron and steel in a mold. The letter impressed me at the time, and still does, with the breadth of Professor Howe's interests and his perseverance in keeping up with the progress of any branch of knowledge that had metallurgical connotations. SCOPE OF THE LECTURE During several years preceding the date mentioned I had worked in collaboration with Arthur L. Day and E. T. Allen8 at the Geophysical Laboratory, Carnegie Institution of Washington, on the temperature scale as defined by the nitrogen thermometer at high temperatures. Later (1928-1947) I had the opportunity of helping to apply this experience to the pyrometric problems of the steel industry. Because of the range of its temperatures, the multiplicity of the methods used, and the variety of its purposes, pyrometry in the open-hearth process has always offered a fertile field for both research and development. I am therefore devoting an hour to the subject of temperatures in the basic open-hearth furnace, the furnace that makes most of our steel in the United States. I would direct your attention particularly to the choice of the first two words in the title of the Lecture. One sometimes hears or reads of the "temperature of such-and-such a furnace," as if it were a single, measurable, characteristic quantity. I need hardly emphasize to any one who has ever operated a furnace or a kiln that "temperature of the furnace" is a meaningless phrase. Even if we confine our attention to the space enclosed by the roof, walls, and hearth of an open-hearth furnace, it is doubtful whether any such space has ever been so uniform in temperature that the phrase would have a meaning. In any furnace, there are many different temperatures, capable of being measured at many different places, and actually being measured for several different purposes. These pyrometric purposes, methods, and results, if given in detail, would expand this lecture into a book on the basic open-hearth process. I must therefore confine myself to a statement of the range of temperatures as they have been observed in various parts of the furnace, indicating in a general way why they are measured, and mentioning the methods that are available without attempting to describe these

Jan 1, 1948

By John F. Abel

AIME is closing the books on its first 100 years. In the next year the meetings and many papers will doubtless be filled with statistics on the growth of AIME, and, incidentally, on the mining industry. Let's try to keep our cool and avoid breaking our arms patting ourselves on the back. AIME, nationally and locally, runs on the drive and dynamism of a rather small number of its members. If you look at the annual SME Blue Book of national officers and committee members, you will be struck by the repetition of the same names throughout. Trend for a few men to shoulder the burdens and responsibilities can be seen on the local level, too.

Jan 1, 1970

By Joseph W. Mills

In 1956 the discovery of nickel on Jumbo Mountain, Snohomish County, Washington, focused attention on this part of the Cascade Range, far more renowned for its timber than for its mineral resources. Hand specimens assaying as high as 13 pct Ni encouraged Discovery Mines Inc. of Mount Vernon, Wash., to stake 12 claims in Township 31 North, Range 9 East of the Willamette Meridian. The property was leased to Climax Molybdenum Co. in January 1957. Trenching, sampling, and geologic studies were carried out during the late summer of 1957 when most of the snow had disappeared. Although the deposits are only about four miles south of the logging town of Darrington and about two miles, as the crow flies, southeast of the end of a good gravel road from that town, all camp supplies and equipment were air-dropped, owing to the extremely rugged nature of the terrain.

Jan 3, 1960

INTERNATIONAL ENGINEERING CONGRESS This Congress will be held under the auspices of five National Engineering Societies, of whi h the Institute is one. The sessions will be held in 11 sections and the proceedings will be published in 10 volumes of 500 pages each, of which Volume 8 will contain the papers and proceedings on Mining Engineering and Metallurgy. The membership fee of $5 will entitle the holder to the volume of General Proceedings and Index, and, in addition thereto, any other single volume chosen. Other volumes may be subscribed for according to a sliding scale depending upon the number of volumes taken. The Institute will have a meeting in San Francisco during 1915, and it is desirable for our members to join the International Engineering Congress at in early date in order that their support of the enterprise may be given in its early stages, when it is most needed.

Jan 2, 1914

By Freeman Bishop

The tight electric power supply is one of the most dramatic problems facing the mining industry in 1971. This is caused by rising demands for energy. Clean-fuel and air-pollution controls have contributed to the problems of producing energy from sulfur oil and coal. Coking coal has become scarce. One stimulating development is that coal is no longer the cinder in the mining industry's eye. In fact, it may be the favorite candidate as a base for fuel within a few years. Synthetic gas from coal is the watchword. In dedicating a multi-million- dollar project aimed at converting coal into oil and gas, Hollis M. Dole, Assistant Secretary of the Interior, recently made it clear that coal, which has been taking a back seat to nuclear fission research and study grants, is now coming into its own. Conversion pilot plants are being activated in all parts of the nation.

Jan 1, 1970

PICK AND SHOVEL CLUB, CASE SCHOOL OF APPLIED SCIENCE The last meeting of the year of the Pick and Shovel Club of Case School of Applied Science was held on May 20, 1919. The speaker, Dr. Zay Jeffries, gave a very instructive and interesting talk on the Metallography of Non-ferrous Metals. The club has had a very successful year in spite of the loss of a few months time through the S. A. T. C. Among the speakers for the year were Dr. F. R. Van Horn, Dr. C. H. Fulton, and Dr. W. R. Veazey of our school; Dr. E. S. Moore of Penn. State College; Dr. Ansel St. John, of the National Carbon Co.; and Mr. V. S. Bidle, of the W. S. Bidle Co. The graduating members wish the club the best of success for the coming year. BERTRAND R. WARMELING, Secretary.

Jan 7, 1919

By J. L. Wright

When management is confronted with the risk of constructing a waste disposal well, these are some of the questions which may arise. Should the company expand the present waste treatment plant? More lagoons will cut into valuable acreage which might be needed later, and yet the pollution engineer says he can guarantee results. On the other hand, does the formation being used for those successful disposal wells off to the west extend over far enough to be used for the company's own well? Will the formation be thick enough? Will it be too deep? Will it be porous and permeable enough? Apart from needing to make a profit on the products made at the plant, plant officials must sometimes act under pressure to comply with pollution standards. The manager must build the cost of the pollution control system into the price of the products made by the company.

Jan 1, 1970

By Robert B. Schlosser

Anaconda's Jackpile uranium mine is a multi- million-ton open pit sandstone deposit, producing some 3000 tpd for the company mill. With minor exceptions, the orebody is in equilibrium, and the backbone of ore-grade control is the radiometric assay, which fortunately is dependable. Preparatory Sample Drilling: Before it is stripped, the orebody is diamond-drilled on 200-ft centers N-S and 100-ft centers E-W. Drill core is logged, split, and assayed radiometrically, and several samples are assayed chemically to check the equilibrium status. This information establishes the pit outline and the first rough estimate of ore. After stripping, diamond drill data is supplemented by rotary drillholes on 50-ft centers. Dry chip samples, collected every 2 ft, are prepared and assayed radiometrically at the mine. Details of the orebody are then available for study, and the basic mining plan is drawn up.

Jan 10, 1958

By S. Webster, M. Karmis, C. Haycocks

Mining any seam can seriously affect subsequent operations in coal seams both above and below the one being mined. The effect is often detrimental to the recovery, cost and safety of mining the subsequent seams. This paper describes the ground control mechanisms involved in mining through a passive subsided zone or all actively subsiding trough. Data were extracted from case studies, primarily from the Appalachia region, for construction of empirical models to predict interaction problems that can occur in overlying seams. Inner-burden thickness, innerburden lithology, percentage extraction, lower seam height, time and overburden were analyzed to determine their effect on upper seam damage. Magnitude of upper seam subsidence was incorporated, together with a broad classification of rock types, to predict the type and range of damage that can occur in the upper seam. Results are summarized in graphically and nomogram form for use in. engineering design.

Jan 1, 1984

Would you give us a short biographical sketch including your birthplace, education and current activities? I was born Jan. 16, 1920 in Minneapolis, Minnesota, and lived there the first 22 years of my life. I also spent quite a bit of time on a farm about fifty miles north of Minneapolis owned by relatives. During the Depression, we lived off of ten cows and about fifty chickens. I'm a full-blooded Swede all along the line, and I'll be the last one in my family since my wife is not of Swedish descent. I attended Macalester College, a small school in St. Paul, to study for the ministry originally. However I soon realized that I really didn't have the talents for the ministry and I could probably do as much or more in a field where I did have some talent.

Jan 3, 1974

By John M. Pitt

Shear strength assessment and the associated variability in rock masses historically have been hindered by high costs and biases in laboratory testing programs. An in situ direct shear device was developed on the principle of the previous borehole shear device for soils. Using wedge action to simultaneously apply normal and shear stress to an envelope of material on the periphery of a borehole, the device develops a complete Mohr-Coulomb failure envelope. Tests performed in homogeneous materials show expected strengths and their variability equivalent to laboratory tests. However, tests in a structurally non- homogeneous coal did not display significant variability. A 38 mm diam borehole was used in this work; however, larger or smaller bore- holes may also be used within the size limits of the device. The device is employed in holes commonly drilled for rock bolt placement, at 1 to 2 minutes per test.

Jan 1, 1984

By A. Wahab Khair

This paper presents an analysis of fracture mechanisms in coal subjected to bi-axial state of stresses, indentation of laterally con- fined coal specimen. Coal specimens were loaded to failure by the straight wedge indenters at various lateral confinement pressures. Strain distribution and acoustic emission characteristics of coal specimens under stress were recorded. The influence lines of vertical forces acting on the horizontal straight boundary of the coal specimen for each type of wedge indenter have been established using holographic interferometry technique. The effects of wedge indenter angle, confinement pressure, and coal anisotropy on fracture types, failure modes, and post-failure conditions were studied. The results indicated that combined application of holographic interferometry and acoustic emission monitoring techniques is not only suitable for studying deformability of heterogeneous and microscopically discontinuous material under stress but it also enhances the mode of fracture during the post failure stage.

Jan 1, 1984

By S. E. Piper, E. M. Buchalter, R. P. King, E. T. Woodburn

The problems involved in an optimum decision making model for flotation circuit are, first of all, to characterize the feed material in terms of parameters which can quantitatively describe the network flotation action in terms of a feasible set of control actions. Once the characterization has been postulated, it is then necessary to devise tests relating to parameter sensitivity, in order that credibility of the model predictions can be assessed. Once a credible model is available, the optimum control set is determined by a hill climbing technique. Details will be reported as to the credibility of model predictions using the stochastic flotation model on a network and further, computational problems associated with hill climbing for a complex objective function are reviewed. Discussion is presented on use of the Rosenbrock technique with constraints and use of a modified objective function with constrained derivatives when employing Fletcher and Powell technique.

Jan 1, 1969

By Y. P. Chugh, R. A. Missavage

Moisture has been known to influence strata failures in coal mines for a long the. A concise review of what is known about effects of moisture on strata control with emphasis on the Illinois basin coal mines is presented in this paper. Some approaches to mitigate the effects of moisture-leaving coal in the roof, guniting, shotcreting, application of sealants-are then briefly discussed.

Jan 1, 1982

By D. H. R. Price

This paper presents two tentative models of the use of a notional metal in a country like Britian, which have been developed using the System Dynamics modelling method. Computer simulations have been carried out using one of the models. These show the effect on the recycling of the notional metal of a wide range of possible future values of world market price and demand for the metal.

Jan 1, 1977

By Alan K. Burton

An industry-wide demand for bigger and more efficient trucks, with their supposed economies of scale, is well established. Some trucks have been, and often are brought "off the shelf," with the manufacturer offering only certain minor options, much as in the private automobile industry. The market is well established; there is keen competition; in recent years there have been few significant changes, and few are expected. With large trucks (100-ton-capacity and over), however, the situation is different. Here, with an individual truck costing several hundred thousand dollars, there is an ever in- creasing trend to engineer a truck for a specific application. The body will be designed and sized for the material that the truck will carry; the engine and transmission will be geared to the haul profile, and tires will be designed to suit road conditions and work requirements. Early Truck Development Haulage trucks designed expressly for open-pit mine service were introduced during the 1930's. The first models to arrive on the scene hauled about 15 tons, and easily outperformed the modified highway trucks that had been used for mine haulage up to that time.

Jan 8, 1975

By H. A. Lequear, J. D. Lubahn

A sudden change from one constant strain rate to another during a tensile test causes an unusual transient in aluminum alloy 61ST. A sudden change from one constant stress to another during a creep test does not produce an unusual transient in this material. A specially devised test shows that the nature of the previous steady-state conditions, which the sudden change disturbs, is one of the factors affecting the transient behavior. Some of the observations may be explained in terms of strain aging. USUALLY a sudden change during a tensile test from one constant strain rate to another causes a small, abrupt vertical shift from one stress-strain curve to another, parallel one. This behavior is apparently characteristic of all metals at very low temperatures and of many metals for wide ranges of temperature. It is illustrated in Fig. 1 for some early data on 61ST tested at — 195oC, and in Fig. 2 for some recent data on copper at room temperature. The greater accuracy of the results of Fig. 2 over previous ones' is due to the equipment shown in Fig. 3. Three levers apply the bulk of the load, while the changes in the small remainder load are indicated sensitively by a low capacity load scale. Refs. 2 and 3 describe the recording equipment. A test like those in Figs. 1 and 2 provides the information necessary to determine the rate sensitizrity, n,4 of the metal. ( a log s ) ? log s n = ------------------------ ----------------------------= ( a logs e, ? log e logS2-logS1 log S2/S1 log i2 — log e1 log e2/e1 where S equals stress: e is logarithmic strain or natural logarithm of (final gage length/initial gage length);" i is strain rate or de/dt: and n is rate sensitivity, rate of change of log stress with log strain rate at a given strain, or (a log S/a log i),. Normally, the rate sensitivity, n, is positive, which means that an increase in stress causes an increase in rate. However, certain exceptions, attributed to strain aging,5 have been observed. Fig. 2 indicates how rate sensitivity values are derived from the measurements. Table I summarizes the rate sensitivity values derivable from Fig. 1. In contrast to the behavior of copper in Fig. 2, the aluminum alloy 61ST, which strain ages when tested near room temperature, exhibits an unusual transient when the strain rate is suddenly changed,' as shown in Fig. 4. Initially, there is a comparatively sudden vertical shift of the stress-strain curve in a direction corresponding to the rate change, but then the curve gradually shifts back again. The initial shift is not as sudden as might be expected, because the testing machine is unable to achieve the impressed rate change instantaneously, as illustrated in Fig. 2. The behavior shown in Fig. 4 will be referred to as a tensile transient, the word tensile implying that the behavior was observed in a tension type of test. The corresponding test, where the strain rate is maintained constant except for the sudden change, will be called a tensile transient test. A creep transient, by contrast, will be defined as a temporarily abnormal behavior in a creep transient test, where there is a sudden change from one constant load to another.' In Fig. 4, a naive look at the gradually decreasing and then increasing load after a sudden rate incre-

Jan 1, 1957

By C. R. Hayward

THE CHAIRMAN (ALBERT SAUVEUR, Boston, Mass.).-I am sure we are indebted to Prof: Hayward for his addition to our knowledge of the influence of sulphur on steel. As he has said in this paper, sulphur has had many defenders in recent years. It seems to me, however, that, while it may be old school to believe in the detrimental action of sulphur, it is not yet old school to believe in segregation; that while it may be that 0.1 per cent. of sulphur has no very great effect on the physical properties of steel, a ladle analysis of 0.1 per cent. of sulphur may readily result in 0.2 or 0.3 per cent. sulphur being present in the segregated portion of the ingot, and that, it seems to me, might be a rather serious matter. J. S. UNGER, Pittsburgh, Pa.-Prof. Hayward has presented the results of an investigation along a line to which I have devoted considerable time and attention, and I am particularly pleased to note that his results are in accord with my own and further tend to prove the fact that the old, established prejudice against sulphur is based more on belief than actual facts. I have felt for years that tooo much stress was placed on the harmful influence of certain elements in steel such as sulphur, phosphorus, copper, etc., but it has only been within recent years that efforts have been made to, establish the truth. Practically all the investigations made to date have proven that these elements within reasonable limits are harmless and, in fact, that for certain purposes the addition of these elements is beneficial. In referring to copper, J. E. Stead, Vice-President of the British Iron and Steel Institute, said at their last meeting: "Even today one comes across steel specifications in which copper is barred, which can only be regarded as ail indication of ignorance, if not stupidity, of those who prescribe the composition of steel, for it has been long ago proved that copper in steel, instead of being an evil, is quite harmless, and is sometimes distinctly beneficial." Sulphur owes its evil name to the early days of the manufacture of steel. Chemical analyses were crude, and failure due to either poor raw materials or metallurgical treatment were many. Sulphur being a comparatively easy element to determine with reasonable accuracy, particular attention was called to the amount of sulphur, and the failure was attributed to it, without giving any consideration to other causes. A pre-

Jan 4, 1917

By A. A. Smith, J. S. Smart

THE elements silver, cadmium, tin, antimony and tellurium either are found as impurities in commercial coppers or are intentionally added to produce coppers for special uses, When present in small quantities, each of these metals exerts a significant effect on the properties of copper, but despite considerable experience and investigation much remains to be learned about their specific behavior. The presence of extraneous elements, particularly oxygen, complicates the study of individual additions of impurities in the range 0 to 0.05 per cent, and the use of high-purity copper has been found extremely helpful in circumventing these difficulties. It has also been found that individual behavior can be satisfactorily determined from measurements of two commercially important properties, conductivity and softening temperature, according to methods that have been described previously.1,2 Data of this type, obtained in the course of a general investigation of the effects of impurities on the properties of both oxygen-bearing and oxygen-free copper are presented herewith. All samples except those containing cadmium were prepared as 3/8-in. continuously cast oxygen-free rod from pure copper and weighed amounts of a similarly synthesized master alloy. Composition was checked by chemical methods, which in every case verified the calculated analyses. Test wires were cold-drawn one B. and S. number per pass on a string-up machine using four 30-min. 600°C. anneals at 0.3125, 0.257, 0.204 and 0.162 in. and a final cold reduction of 75 per cent to 0.081 in. Some oxygen-bearing samples were produced directly from the 3/8-in. oxygen-free rods by diffusion from a surface scale at 850°C. and drawn to size as listed above, but most of the alloys were remelted in pure graphite and cast through air into a I-in. round mold, The slugs were then hot-rolled to 5/16 in., drawn to 0.162 in., annealed as listed above, and drawn to 0.081 inch. Conductivity wires were annealed for I hr. at 100°C. intervals between 300° and 800°F., using a hydrogen atmosphere for oxygen-free samples and purified nitrogen for the oxygen-bearing type, All samples were quenched from the annealing temperature in 10 per cent H2SO4 and conductivity was measured on a Hoopes bridge that had been checked against a Kelvin bridge. The softening temperatures represent the half-hard stage of the annealing curve as determined by a standard procedure.1 EFFECT OF SILVER Numerous excellent studies of the argentiferous coppers are found in the literature, and these have been adequately

Jan 1, 1943