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By A. M. Strauss

This contribution illustrates the application of the theory of period doubling to the description of the formation of microcracks in rocks. The fundamental mathematics is described and a method of prediction is proposed. The invariance (universal constants) of a generic microfracturing (damage) process is described. Finally, the method is presented as a deterministic method of predicting the failure of an engineering material while keeping track of the amount of damage that has occured at any point.

Jan 1, 1984

The following correspondence relating to a paper bearing the above title, presented by J. F. Wolff, at the New York meeting in February, 1917, and published in the Transactions, Volume LVI, page 142, has passed between the author of the paper, and Mr. Anson G. Betts, and is interesting, although it was received much too late for incorporation in its proper place in Volume LVI. ANSON CT. BETTS, Asheville, N. C.-1. I should like to ask Mr. Wolff if he finds-from analysis of the iron formation and of the iron ore, and from the relative amounts of each in each unit area of the formation, unleached and after leaching, that the iron remains entirely insoluble and the total quantity still remains present; or whether he finds that some of the iron is removed, or possibly even added by deposition from the water passing through the formation. 2. The water that passed into the iron formation had to go somewhere; was it absorbed by underlying formations through hydration, or, after passing through the ore formation, did it come to the surface in springs at a lower elevation, or how did it escape from the ground? 3. I should like to ask Mr. Wolff whether he finds that the iron formation in the sedimentary series does not, come next to the quartzites and generally between the quartzites and slates. J. F. WOLFF, Duluth, Minn.-1. In common with others, you appear to have some hesitancy in accepting the fact of the removal, by solution, of the enormous quantity of silica which has been leached out of portions of the Biwabik iron formation, thus forming orebodies of merchantable iron ore. I believe that even Dr. Waldemar Lindgren once hesitated to accept this fact. However, the evidence is so simple and absolutely conclusive that the fact is established beyond all question. At the contact of orebodies with their rock walls, the bands of iron ore in the orebody can be seen in contact with the corresponding bands of original iron oxide in the rock wall, and the chert layers in the rock wall can be seen to give place to fine granular material (fine silica and iron oxide) and pore space. This is especially noticeable where slumping at the rock walls his not been so great as to displace the layers in the orebody from their contact with their corresponding layers in the rock wall.

Jan 9, 1918

By Edmund Kirby

This meeting marks the point at which the long-standing dissatisfaction with the mineral-land laves, the innumerable protests against them, and the many isolated efforts to obtain relief, have developed into a general movement for the: revision. That part of the mining industry which is affected by these laws has three general organizations to speak for it: the American Institute of Mining Engineers, Mining and Metallurgical Society of America, and the American "A Mining Congress: all of which are represented in this meeting. In the series of able and thoughtful presented here, prominent men have discussed the evils of the present laws aid some of the reforms which should be made in them. We all appreciate fully the ultimate value of these studies; but we are also painfully aware of the fact that discussion of this kind has been going on for a quarter of a century without any other effect than a steady increase in the mass of printed records stored on library shelves. In order to get any practical result we must induce an indifferent government at Washington to act, and to do this we must unite in pushing some practical plan whereby it may act in a simple and effective way and with the least possible amount of criticism or opposition. The actual question before us is not whether the mining laws are bad; for their evils and absurdities are not only beyond discussion but also beyond the resources of a temperate and dignified vocabulary. It is not what particular changes ought to be made; for it is premature to make specific recommendations until there is some one to listen to them. Moreover, we all know that there are wisdom and experience enough available, and awaiting that time, for the creation of a code which would be a model to the mining world. The practical question now is, how to obtain the revision; and since the American Mining Congress has of late restricted its attention to this phase of the problem I wish as one of its representatives here to present its views upon the matter.

Jan 6, 1914

By A. Taylor

IN a previous communication,l the quaternary system Ni-Cr-Ti-A1 was described in detail and it was shown how certain alloys used for high-temperature applications could be construed as consisting of Ni,Cr suitably modified by the addition of aluminum and titanium in relatively small amounts. With the correct aging treatment, the ordered face-centered-cubic Berthollide phase, y'-Ni,Al, could be precipitated from the face-centered-cubic primary y-solid solution. By increasing the proportion of titanium with respect to aluminum, it was also possible to precipitate the very brittle hexagonal-close-packed Daltonide phase, ?-Ni,Ti. From the nature of the system it seems reasonable to expect the y and y'-phases to take appreciable amounts of cobalt and iron into solid solution. In the case of the present investigation it was decided to confine the work to iron additions only. This element may be introduced in two quite distinct ways: 1) as a simple replacement for nickel; and 2) as a replacement for chromium, titanium, and aluminum. The second method of iron addition forms the basis of the present investigation, which is, in effect, a study of the pseudo-quaternary system Ni,Cr-NiPe-Ni,Ti-NLAl. For purposes of reference, Figs. 1, 2, and 3 have been included and illustrate the quaternary system Ni-Cr-Ti-A1 described in the previous paper along with sections through N&Cr-Ni,Ti-Ni,Al at 750" and 1000 "C respectively. As will be shown below, the pseudo-quaternary system with components Ni,Cr, NiPe, Ni,Ti, Nihl is remarkably similar in many ways to the face defined by Ni,Cr-Ni,Ti-Ni,Al because of iron re-

Jan 1, 1958

By W. L. Austin

The advance made in recent times in this branch of metallurgy is indicated by the attention the subject is receiving from important American copper-producing companies. Reference to the files of publications devoted to the mining industry discloses that some 20 American companies are actively investigating the amenability of their ore, or other material, to leaching methods, and that plants of varying capacities up to 10,000 tons per day arc under construction or are projected. Several leaching works are in commercial operation. It has been frequently pointed out that no method of leaching is universally applicable, for the reason that each ore differs in some particular from apparently similar ore found elsewhere, and also because local conditions are rarely the same even where the ore closely approximates in character that being worked at some other point. For this reason the older companies are approaching the matter in a conservative manner, experimentally determining for themselves the salient features in each instance. In considering a leaching proposition three factors at once fix the attention: (1) disengaging the metal from mineralized forms in which it is found in nature; (2) recovering the metal in a commercial state after it has been dissolved; (3) the apparatus best adapted to carrying out the several operations. Bringing the Metal into Solution This feature.has been found to present no serious difficulties. Numerous solvents for copper are known, and it has been repeatedly demonstrated on a commercial scale that from 80 to 90 per cent. of the metal contained in an ore can be rapidly brought into solution. It is interesting to note, however, that all of the companies above referred to have selected sulphuric acid as the basis for a lixiviant. Where oxidized ore practically free from precious metals is treated simple leaching with

Jan 1, 1915

By M. H. Cullender

The performance characteristics 01 gas wells producing from formations which fail to stabilize within a relatively short period of time are obscured by the interrelation of the coefficient (C) and the slope "n" of the conventional back-pressure curve q = C(P2 f- p2s)n An empirical method is presented whereby the characteristic or true slope (11) of the back-pressure curve may be determined for a particular gas well. For those gas wells which do not stabilize within a relatively short period of time, the coefficient (C) is considered as a variable with respect to time and as a constant only with respect to a specific time. Thus, the back-presrure performance of such a well is presented as a series of parallel curve5, each curve representing the performance of the well at the end of a given time interval. Through use of the method presented, a simple presture gradient is developed and maintained within the drainage area around a producing gas well during the test period in order that the variation of the coefficient (C) with respect to time does not obscure the true value of the lope. INTRODUCTION The back-pressure method of testing gas wells as set forth by Schellhardt and Rawlins1 is dependent upon the requirement that a series of flow rates and corresponding pressure data be obtained under stabilized conditions. These data arc then plotted on logarithmic coordinates of flow rate (Q) vs difference in squared pressures (P2f — P2s) in order to determine the constants (C) and (n) for Equation 1. With respect to this method of presenting the performance characteristics of a gas well, it should be pointed out that although Equation 1 is an empirical relationship, the form of the equation was justified to a considerable extent by an independent development by Muskat and Botset.2 This development was theoretical in nature; however, certain assumptions with respect to the type of flow existing (viscous vs non-viscous) were madc which may or may not be correct. As the use of the method presented by Schellhardt and Rawlins spread through the industry, it became evident that the method of testing was applicable for those wells which approached stabilized prbducing conditions within a relatively short period of time. Performance characteristics could not be determined by this method, however, for wells which approached stabilized protlucing conditions slowly over a considerable period of time. This characteristic of "slow stabilization" has generally been associated with gas wells producing frorn reservoirs of low permeability. As the demand for natural gas continued to grow through the years, a great number of wells were completed in reservoirs of low permeability which exhibited "slow stabiliz:~tion" characteristics. Consequently, the problem of determining the true performancc characteristics of these wells became more apparent. It is with this problem in mind that the isochronal performance method of determining the flow characteristics of gas wells is presented.

Jan 1, 1956

By W. R. Crane

MINING of the red iron ores of the Birmingham district has been carried on energetically during the past 50, years, and their development has created a large iron and steel manufacturing, center, the only important one in the South. The district produces approximately 10 per cent. of all the iron ore of the United States (80 per cent. of the Alabama ore mined is red ore) ; also, 43 of the 419 blast furnaces of the country are in the district tributary to Birmingham. The rapid growth of the district has been made possible through investigations that resulted in radical changes in furnace practice, and a still greater impetus will come from the study of the low-grade, high-silica ores, as a result of which they will be made amenable to treatment by concentration. Mining practice in this district has been comparatively simple because of the occurrence of the ore; but with the-rapid extension of the work-ings and the disturbed condition of the ore bed at some distance from the outcrop, more difficult conditions are encountered and the tendency is toward worse rather than better conditions. Should the high-silica ores of the lower bench of the Big Seam become available through beneficiation, mining practice will have to be modified to meet the new conditions, which will be rendered more difficult by the increased weight of cover that will exist at considerable distances from the outcrop. Support of workings will require greater attention and the efficient and economical operation of the mines will depend largely on the successful solution of the problems of working-and handling the ore.

Jan 9, 1924

By T. W. Guy

DuRing recent years, tremendous strides have been made in the economical use of coal. This has resulted in, and to some extent has been a result of, making the fuel specifications more and more rigid. For this reason, all producers have found it necessary to improve their preparation materially, both as to sizing and the elimination of impurities, either by more effective preparation underground or at the tipple and cleaning plant, or both. This cause and its effect in all producing fields seem likely to continue for several years at least. The splendid inherent qualities of the Pocahontas and New River coals are known all over the world, but their good reputation is only partly due to inherent qualities, and to natural conditions which generally favor loading coal comparatively free from impurities; it is due in large measure to the care and skill used, either with or without the aid of mechanical devices, to ship products consistently low in ash. The first coal from the West Virginia smokeless fields was mined and shipped near Quinnimont, on New River, in 1871, while the first shipments from the Pocahontas field were in 1883. The development of both fields progressed rapidly. At first activities followed the main lines of the Chesapeake & Ohio and Norfolk & Western railroads, and were extended later as branch lines were built from these roads. The Virginian R. R., about 1907, opened up the Winding Gulf territory, which has since become a large producer of smokeless coals from the Pocahontas and the New River measures. Early Cleaning Methods In the early days, the tipples were simple wooden structures, with bar screens for separating the fines from the lump coal. All cleaning was done by the miners at the face, or by pickers in the railroad cars. Gates were provided in the chutes by which the flow of coal could be stopped when necessary while the pickers raked the surface of the coal in the car and picked out the impurities. A large percentage of the fine coal or slack was used for making coke at the mines in beehive ovens. The

Jan 1, 1932

By M. A. El-Aouar

Drilling muds are complex colloidal systems. In an effort to analyze the physical properties that affect their performance at high temperature, an investigation was made of the hydrothermal stability of the monoionic hydrogen, calcium and magnesium forms of montmorillonite and attapulgite. Samples were heated to 400°1F in a simple autoclave and analyzed for cation exchange capacity, c-axis X-ray diffraction spacing and pH factor us sodium hydroxide titration dependence. Out of the six monoionic clay minerals tested, calcium montmorillonite and magnesium attapulgite showed the least base exchange capacities and were relatively unaffected to heat. It is concluded that, of the six clays studied, these two clays were the most suitable forms for use in drilling fluids. INTRODUCTION The drilling of deep wells is dependent upon the drilling mud, and problems frequently arise concerning the effect of mud temperature and prolonged heating. Drilling muds are complex colloidal systems. In an effort to analyze their behavior in deep, hot boreholes, it was thought desirable in this investigation to study suspension of pure, monoionic montmorillonite and attapulgite clays before and after hydrothermal heating. Chemically, clays are hydrated aluminum silicates, such as montmorillonites and attapulgites. The structure of montmorillonite is composed of units made up of two silica tetrahedral sheets with a central alumina octahedral sheet. Attapulgite consists of double silica chains running parallel to the c-axis with the chains linked together at their longitudinal edges. The apexes of the tetrahedrons in successive chains point in opposite direc-tions.4,7,10 One of the most important characteristics of clay minerals is their property of sorbing certain anions and cations and retaining them in exchangeable state. The property of exchange capacity is measured in terms of milliequivalents (meq) per 100 gm of clay. The cation-exchange capacities are taken at pH 7 from titration curves which show the relation between pH and milliequivalents of added NaoH.9,11 The following are causes of cation exchange: (1) broken bonds around the edges of the silica alumina units would give rise to unsatisfied charges, which would be balanced by adsorbed cations; (2) substitution within the lattice structure of trivalent aluminum for quadrivalent silicon in the tetrahedral sheet and of ions of lower valence; and (3) the hydrogen of exposed hydroxyls may be replaced by a cation which would be exchangeable. The primary techniques employed to study the effects of hydrothermal treatment were titration curves and X-ray diffraction analyses. Titration curves were useful in characterizing the nature of the clay mineral surface and the stability of the various samples to attack by acid or alkali before and after hydrothermal treatment. X-ray diffraction analyses were used to determine changes in the nature and crystal structure of the minerals present and to determine the cations in exchange positions on the montmorillonite samples. EXPERMENTAL PROCEDURE PREPARATION OF SAMPLES Selected samples of Wyoming bentonite and attapulgite clay from mines along the Georgia and Florida border were purified by centrifugation to remove all particles larger than 2 microns. In preparing magnesium attapulgite, first a 1.00-normal solution of magnesium acetate was prepared. The pH of the solution was adjusted to 7.0 by adding magnesium oxide. One hundred grams of attapulgite clay were mixed in a blender for 30 minutes with the magnesium acetate solution. The attapulgite solution was left overnight, and then filtered in a Buchner funnel. The suspension was leached with further quantity of magnesium acetate solution and then washed with distilled water for 20 days, after which the filtrate was free from magnesium ions. The concentration of magnesium attapulgite in the clay slurry was adjusted and determined quantita-

By Thomas H. Sheldon

In the zeal for opening up new ore-bodies, or for extracting the ore from attractive bodies already opened up, we very often lose sight of the fact, that, after all, the operation of a mine is a business proposition, pure and simple, and, for the best working-results, should be treated upon a strict business basis. Of course, in every mine of consequence, a record is kept of expenditures and receipts, and such glittering generalities as " gross receipts," " net receipts," " mining expenses," and a per cent. profit," can be told to the cent; but does this record show economy of management, as compared either with the same record of other months, or with the record of other mines of the same class ? Moreover, if such a record shows that the cost of mining is high, does it in any way enable the manager to put his finger on the leakage ? Does it necessarily follow that a mine which makes a profit of, say, 40 per cent. on 25-dollar ore, is doing less economical mining than one which saves 60 per cent. on 80-dollar ore ? Of course the figures in the latter case look the more attractive; yet when it comes to the point of saving everything which can be saved, and of cutting down expenses to the lowest possible cost of operation, the former mine is doubtless on the firmer and more economical financial basis. But as to the relative merits of the system of mining in the two cases, nothing could be decided without a basis of detailed comparison ; if one system is more economical than the other, why is it so, and wherein does the advantage lie ? This can be shown only by keeping accurately the cost of each mining operation. And no matter how dissimilar two mines may be in character and operation, yet there are a few general heads common to all mining operations. In the first place, it is necessary to break the ore from the solid ground;

Jan 1, 1907

By N. J. Grant, A. W. Mullendore, Y. Ishida

Creep tests were performed at 500°F on polished specimens of A1-3 pct Cu at stresses of 2000, 4000, and 6000 psi. The effects of the size and distnbution of the second phase were studied in connection with the mechanisms of deformation, especially grain boundary sliding. Although the amount of grain boundary sliding varied considerably for the different heat treatments, yestriction of grain boundary sliding is not due primarily to precipitate on the grain boundary. NUMEROUS prior investigations of grain boundary sliding, notably those of McLean, 1 Rachinger, 2 Rhines, Bond, and Kissel, 3 and Brunner and Grant,4 have established the importance of this phenomenon in the deformation of pure aluminum and its solid-solution alloys at elevated temperatures. An extension of this kind of study to the case of a simple two-phase structure is an important step towards understanding the deformation behavior of more complex alloys. A two-phase A1-3 pct Cu alloy was selected for this study. The creep behavior of alloys in this system has been studied by Sully and Hardy,5 by Underwood, Marsh, and Manning,' and by Pelloux, Chaudhuri, and Grant.7 In these studies, the prior heat treatments were such that some precipitation took place during the tests in most cases. Pelloux, Chaudhuri, and Grant7 studied the creep of A1-2 and 3 pct Cu alloys in the overaged condition. Their results indicated that the structure most effective in promoting high-temperature strength consisted of a fine, closely spaced grain precipitate and large, widely spaced particles on the grain boundary. The present work consists of quantitative meas- urements of grain boundary sliding during creep of an A1-3 pct CU alloy with four different precipitate distributions. The aims were to quantitatively define the role of the second phase on grain boundary sliding, and to obtain information regarding the mechanism of grain boundary sliding. MATERIALS AND PROCEDURE A high-purity A1-3 pct Cu alloy, kindly supplied by Alcoa, was used in this investigation. The composition of the alloy in weight percent was as shown in Table I. This composition is such that A12Cu exists as a second phase at temperatures below 850°F. A homogeneous grain size of 0.6 to 0.8 mm was obtained by annealing the machined test bars for 5 min at 1000°F, furnace cooling to 930°F, and homogenizing for 5 hr. Following the recrystalli-zation and homogenizing anneal, four different heat treatments shown in Fig. 1 were utilized. The F7 and F5 treatments utilize a furnace cool to the aging temperature while Q7 and Q5 have a water quench from the homogenization temperature before aging. Figs. 2 to 5, and Table 11, show the size and shape of precipitate dispersions obtained with the above heat treatments. The heat treatments produce variations in the dispersion both in the grains and along the grain boundaries. Precipitate particles along the grain boundaries are rounded and large (about 1.5 p diameter) in the F5 and F7 structures (Figs. 3 and 5). The grain boundary precipitate was somewhat smaller (0.9 p diameter) in the Q7 structure and no grain boundary precipitate was detected in the Q5 structure using light microscopy. The pre-

Jan 1, 1964

By Arthur O. Gates

RittingeR's law of the energy expended in crushing is, as roughly stated by Profcssor Richards,' that the work of crushing is proportional to the reduction in diameter; or, as I have more fully expressed it: "The work done in crushing is proportional to the surface exposed by the operation; or, better expressed for this purpose, the work done on a given mass of rock is proportional to the reciprocal of the diameter of the final product—assuming that all the mass has been reduced to one exact sine, which is only theoretically possible."² Kick's law is stated by H. Stadler as follows :3 "The energy required for producing analogous changes of configuration of geometrically similar bodies of equal technological state varies as the volumes or weights of these bodies." In other words, the energy expended is proportional to the volume reduction, instead of the diameter reduction. That these two laws would give widely different results may be shown by a simple imaginary case. A ton of 16-in. cubes is broken to 1-in. cubes at the first operation, and these are broken to 1/16. cubes at a second operation. Since the first operation produces only one-sixteenth as much new surface as the second, the ratio of energy expended in the two operations would be by Rittinger's law as 1 to 16. By Kick's law, since the volume-reduction ratio is the same in both cases, the ratio of energy would be 1 to 1. This discrepancy is great enough to challenge a test by actual experiment, of which there has been, hitherto, but little compared with the amount of argument. The present paper is the record

Jan 1, 1916

By B. H. Kear, S. M. Copley

A dynamic theory of precipitation hardening in alloys containing cohevenl, stvess-.free, ordered particles is developed. The yield stvess is predicted from the stress dependence of the plastic strain vale, which is related to a derived dislocation velocity-stress function. The theory is shown to predict the magnilude and temperature dependence of the yield stress of a commercial nickel-base superalloy as well as many details of its slip structure. GLEITER and Hornbogen have developed a theory of the yield stress in alloys hardened by coherent, stress-free ordered ptrticles based on the observation that dislocations (b = a/2 (110)) glide in pairs.' When a dislocation pair shears through an ordered particle, the glide motion of the leading dislocation is impeded since it must create antiphase boundary (APB), whereas the motion of the trailing dislocation is assisted because it annihilates APB produced by the first one. Taking into account the APB energy, the size, and spacing of the particles, G-H predict the observed yielding behavior in Ni/18.8 Cr/6.2 A1 alloys composed of a matrix phase y '(nickel-solid solution) and particles of y' (basically Ni3A1). The G-H theory, as well as all previous theories of hardening by coherent ordered particles, do not include the details of dislocation motion; the present dynamic theory is an attempt to overcome this limitation. In the dynamic theory, the yield stress is predicted from the stress dependence of the plastic strain rate, which is related to a derived dislocation velocity-stress function. This function can be evaluated if the structure of the alloy, the APB energy of the ordered phase, and the characteristic drag or frictional stresses of the matrix and precipitate phases are known. The theory is shown to account for the observed temperature dependence of the yield stress in a commercial nickel-base superalloy. 1) NICKEL-BASE SUPERALLOYS Although their compositions are complex, the nickel-base superalloys have remarkably simple structures. A detailed examination of the commercial superalloy

Jan 1, 1968

By D. Roberts

SUMMARY In order to accommodate a new plant in a limestone quarry in the Mendip Hills, it became necessary to excavate a potentially unstable disused face of the quarry. A simple two-dimensional graphical method was used to analyse a failure, which occurred during a period of exceptionally heavy rain in 1968, and the results of this analysis were used in estimating the stability of the proposed excavation. The presence of water in vertical fissures and tension cracks was found to be a dominant factor in determining the stability of these faces. The results of this approximate analysis were used as a guide in deciding upon the final slope design and the purpose of presenting this example is to illustrate how the various factors involved in arriving at this design were weighed to arrive at a compromise between theoretical recommendations and practical considerations. INTRODUCTION The successful outcome of a geological and geochemical survey to prove adequate re- serves of high quality limestone, suitable for producing burnt lime, led to planning for the installation of the necessary plant at Amalgamated Roadstone Corporation's Batts Combe Quarry at Cheddar in Somerset. Topographic and property boundary limits added to restrictions which were likely to be imposed by any forthcoming planning consents and restricted the choice of plant location to one site. The particular site is, in fact, the main floor area of the original quarry which, like many hillside quarries, had been worked with just one face. Before a benching scheme had been introduced on higher ground, the original face had attained a height of 230 ft. and sloped at angles of 58º to 64º. Fig. I shows the present configuration of the disused quarry face and the present working area above. The floor area below the disused face accommodates the existing crushing, conveying, and screening plant. The new facilities for lime burning are to be in addition to the existing main line business of producing roadstone and concrete aggregates and, although a new aggregate production plant would be included in the new installation, no disturbance of current production was to be contemplated.

Jan 1, 1972

By W. R. Finlay, W. R. Jr. Hibbard

The key feature of the lattice coherency theory of precipitation hardening1 is the forced coherence between matrix and precipitate which elastically strains both lattices and is believed to be the major source of strengthening in precipitation hardening. In systems exhibiting age hardening, the atom movements leading to precipitation are not at all extensive and are such as to require the minimum amount of energy to produce the interface; that is, the new lattice forms in such a way as to be as nearly as possible a continuation of the old with a matched, coherent plane at the interface at least during the initiation of the precipitation. The crystallographic sequence whereby regions of the matrix change to the precipitate lattice usually can be resolved into a set of shearing operations.6'6 Conversely, the perhaps novel speculation is made that solution of a second phase is accompanied by shearing movements which are possibly the reverse of the precipitation shearing movements. A basic premise of the investigation reported in this paper is that precipitation and solution shearing movements constitute structural weaknesses which might cooperate with applied stresses to facilitate plastic deformation. Another basic premise of the investigation is that the application of hydrostatic pressure to a precipitation hardening system will significantly alter the degree of disregistry across the matrix-precipitate interface and thereby significantly affect the course of age hardening. Two binary precipitation hardening systems were investigated: rz pct zinc in aluminum which undergoes transformations, both precipitation and solution, by a simple crystallographic mechanism; and 4 pet copper in aluminum which undergoes a complex transformation in precipitating and dissolving a second phase. The effects of the application of uniaxial tensile creep stress during elevated temperature aging of both systems and of hydrostatic pressure during the elevated temperature aging of 12 pct aluminum-zinc were then investigated. Previous Investigations Van Wert in 1935,~ studied the effect of hydrostatic pressure on the room temperature age hardening of a few precipitation hardening systems. The latter were rather unfortunately selected since none is known to exhibit any marked volume change on aging and the majority were complex commercial alloys the precipitation mechanisms of which are not known. Jenkins, Bucknall and Jenkins~n,~ in 1944, applied tensile creep stresses to a complex copper. nickel-silicon alloy at various temperatures. The complexity of the alloy and the industrial objective of the work did not permit an appreciable addition to the theoretical understanding of either deformation or precipitation hardening.

Jan 1, 1949

By P. Nelson, K. L. Gunsallus, A. R. Ingraffea, J. F. Beech

INTRODUCTION Fracture toughness, KIC, is an intrinsic material property and is a measure of the energy required to create new surface area in a material. Fracture toughness measurements can be made for a wide range of rock types (Ouchterlony, 1980). As a measure of energy of comminution, fracture toughness might be used for more sensitive predictions of Tunnel Boring Machine (TRM) performance than are possible with other index measures in current use. This paper describes part of an ongoing, comprehensive, analytical/experimental program aimed at evaluation of KIC in such a role. The program includes efforts to: 1. Provide a firm analytical basis for a test specimen geometry: the core-derived short-rod. 2. Develop simple, inexpensive testing equipment and techniques. 3. Evaluate the accuracy of the above by testing rock and other materials and comparing the measured fracture toughness with those obtained by other methods. 4. Measure fracture toughness of a substantial number of different rocks from three ongoing TBM projects. 5. Compare fracture toughness results with other strength measures. 6. Compare all test results with observed TBM performance in the three projects. Presented here are summaries of all but the last of these efforts. Comparative evaluation of KIC as a more senstive rock property for TBM performance prediction will be the subject of the oral presentation and a subsequent paper.

Jan 1, 1982

By W. O. Philbrook, H. W. Hosking, N. B. Melcher

A simple and inexpensive mercury-tracer method has been develohed to study rates and Patterns of gas flow in blast furnaces. A Pulse of mercury is injected into the hot blast, and its arrival at the sampling Point is recorded by an electronic circuit that measures resonant absorbtion of ultraviolet light by mercury vapor in the gas aspirated .through the detecting. cell. A rapidly developing interest in blast-furnace technology in recent years has created a strong demand for precise knowledge of the rates and patterns of gas movement through the stock column. Classical fluid-flow theory cannot supply the desired information because the complexity of the blast-furnace situation precludes the accurate determination of many of the parameters required for solution of the equations. In fact some of the terms employed in fluid-flow treatments become almost meaningless under blast-furnace conditions. The void fraction of the stock column, for example, varies widely from place to place and is affected by the segregation of charge materials, attrition of lumps during descent, and channeling. Gas density varies with changes in local pressure, temperature, and composition, while viscosity varies with temperature and composition. Even if mean values for these functions were acceptable, they would be either impossible or extremely difficult to determine with a high degree of accuracy since the value of the mean for all gas properties would depend upon the flow distribution itself. Attempts to study gas movement by the pitot-tube determination of kinetic pressures have met with little acceptance. Reproducibility of results is extremely difficult to achieve in a situation where alignment of the tube orifice with respect to the flow direction in tortuous channels cannot be guaranteed. Because of these difficulties it would appear that progress can be achieved only with a direct method of measuring gas velocities and determining the shape of flow paths through the stock. The establishment of such a method is described in this paper. SELECTION OF METHOD Direct measurement suggests the use of a tracer by means of which the progress of a "parcel" of gas can be followed through the furnace. Several requirements must be met before any selected material can be considered a suitable tracer. First of all, it must be a substance not normally present in blastfurnace gas or dust; otherwise its presence in a gas sample will have little significance. It should be volatile at temperatures normally existing within the furnace, to ensure that it will travel with the gas, as a gas. It should possess special properties enabling its presence in the gas to be detected readily, and it should not undergo exchange reactions with any material normally present within the furnace, including refractories and coke as well as all components of the metal and slag. Radioactive materials naturally are considered because their radioactivity renders them susceptible to detection. However, of the many radioactive materials available, almost all are eliminated from final consideration by their unsuitability in terms of other properties. Radioactive silicon, carbon, calcium, phosphorus, and many others have been considered and discarded, either because they are not volatile over the whole range of significant temperatures, or because they could be expected to undergo exchange reactions with burden or refractory materials. Others which might be suitable in terms of these properties are eliminated because of a low activity, short half life, or the necessity for fragile counting apparatus. Of the many elements available in radioactive form, perhaps radon is the only one suitable for blast-furnace gas-flow studies. This has been used in several investigations1-4 with considerable success. The use of radiotracers has certain inherent disadvantages. One is the cost. An appreciable sum must be allowed for materials each time a test is made. Also, special methods of handling must be employed, and very often the progress of an investigation must be governed by the availability of isotopes and the delivery arrangements that can be made for them. An advantage is immediately gained if the tracer material can be a substance which can

Jan 1, 1960

University of Kansas, Department of Mining Engineering, Lawrence, Kansas Professor C. M Young The Department of Mining Engineering of the University lists two publications issued separately from the State Geological Survey: Engineering Bulletin 11, A chemical survey of the natural gases of Kansas and Oklahoma, by H C. Allen and E E Lyder. Engineering Experiment Station Bulletin 13, Kansas coal, by C. M. Young and H. C. Allen.

Jan 1, 1933

By J. A. Collins

THE process of plastic extension of face-centered cubic single crystal-line rods is so well understood, since the notable studies of Taylor and Elam,1 that the change in orientation of any crystal by slip and rotation may be predicted from the measured elongation. It is customary to assume a very homogeneous deformation, wherein gliding lamellae are free to rotate so that their slip direction continually approaches the axis of the rod, until a second slip system comes into operation; whereupon conjugate slip proceeds quantitatively to an end adjustment with the [112] direction in the axis of the rod. This process has been checked in many face-centered cubic materials and readily permits the preparation of specimens that have been sub-jected to various determinable amounts of shearing action. It is clearly of interest to study in such measurably strained specimens the development of a recrystallized structure on annealing and if possible detect the source of nuclei from which the new crystals grow. Strain-annealing experiments of this character have been performed by others but not in detail sufficient to permit a study, for example, of the number of recrystallized grains vs, the amount of shear. In the experiments now reported, this was done with a wide variety of orientations covering nearly the entire range of slip on a single system and corresponding to amounts of shear (ratio of shearing distance to distance between lamellae) at the conclusion of a test of from 0.08 to 0.57. A particular point was made of determining the crystallite rotation, or small angular range assumed by the octahedral slip plane after these various amounts of shear. The mechanism of recrystallization and the magnitude and effect of recovery on the recrystallization process was investigated.

Jan 1, 1940

By W. J. Parton

The efficient recovery and preparation of small sizes of anthracite called No. 4 Buckwheat (3/32 by 1/32 in.) and No. 5 Buckwheat (1/32 in. by 0), pre-sent a difficult problem to the anthracite operators. In many instances preparation of these sizes, particularly No. 5 anthracite, is extremely inefficient. In many of the older preparation plants, inadequate facilities, and often none at all, were provided as an integral part of the plant for cleaning this fine anthracite. Consequently, much of the material smaller than 3/32 in. was discarded. As the demand for these sizes increased, facilities for preparing the fine sizes were often crowded into existing structures with consequent sacrifices of capacities and efficiency. In addition to this condition, the methods of preparing the finest sizes are being developed in an attempt to improve their efficiencies. Because the demand for small sizes of anthracite still is increasing, many operators would benefit by investigating and improving the cleaning equipment employed on these sizes. The object of this paper is to de- scribe a stationary screen device from which the underflow is restricted by orifices, called a launder screen, along with operating results of several applications of this screen; a settling tank in which two classified products are produced by the installation of a cylindrical partition of smaller diameter than the original tank, one product being recovered from the small tank created by the partition and one product from the space between the inner and outer tank walls; a small pocket classifier or hydraulic trap for use in removing high ash particles from a sludge flow; the classification or segregation of sludge solids occurring in a 16 in. diam pipe flow by analysis of samples procured at different zones; and the operating results of a Fahrenwald sizer, as well as the performance of the concentrating tables handling the classified products. These simple devices were employed at the collieries of the Lehigh Navigation Coal Company Incorporated, Lansford. Pa., in order to improve preparation results on the fine sizes of anthracite. Launder Screens The launder screen is a screening and dewatering device which probably could be used advantageously in the flow diagram of many fine coal plants. Fig 1 shows that it consists of a stationary screen constructed by placing 6 in. high partitions every 6 in. along a launder. Holes are then drilled on 6-in. centers across the bottom of the launder to receive pipe bushings of the desired diameter. The screen cloth is tacked on top of the partitions. When water and solids are fed to the screen, only a small portion of the total water is removed through the orifices in each compartment so that the water in the feed is distributed evenly over the whole length of the screen. The screening action which results is very efficient because the solids are kept in a fluid condition for the full length of the screen. Blinding of the screen can be minimized by the use of screen cloth

Jan 1, 1950