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By Louis A. Panek

THE purpose of this paper is to present a method of designing safe and economical arch structures that are to be constructed of concrete or directly of original earth materials. The experimental data used to illustrate the design method are taken from Bucky and Fentress,1,2 and the application of the ideas presented by them is extended by obtaining an additional set of curves from which arch structures may be designed. This design method is based upon the following principles of similitude: A scalar model made of the same material as that of the full sized structure will behave similarly to its prototype if the density of the model is increased in the same proportion as its linear scale is decreased. Let R represent the scale or model ratio, namely, the ratio of a prototype linear dimension to the corresponding model linear dimension. The effect of increased density may be obtained by rotating the model in a centrifuge at a speed such that the centrifugal field exerts on the model an accelerative force R times the accelerative force of gravity. Under these conditions; (I) model unit stresses are equal to corresponding prototype unit stresses, (2) the ratio of the prototype deformation at a given point to the model deformation at a similar point is equal to the scale ratio, R, and (3) the model and the prototype will behave similarly within and beyond the elastic limits of strain. According to the above relations, such models can be used to solve the following problems: I. The dimensions of the most economical safe arch structure for a given load. 2. The maximum safe roof span underground for given geologic conditions. The procedure is described briefly as follows. Tests are made by rotating in a centrifuge a number of models that repIesent a variety of prototype loads and dimensions. From the experimental data, curves are plotted to show the relations between these loads and dimensions. The curves are used to solve directly the problems stated above. Structural design is based upon the working (safe) stress of the material of construction, which is established by applying a factor of safety to the experimentally determined ultimate strength of the material. In conformity with this principle, each model is gradually loaded until failure occurs. A safety factor is then applied to the results. If a safety factor of 4 is used, a given model at failure represents a safe prototype, the linear dimensions of which are equal to one-fourth the model ratio at failure times the corresponding model dimensions. The safe model ratio is computed from the following formula: [Safe R = (rl 47r2n2r _ 7r2n2r~r~ \4/ gg in which: n = centrifuge revolutions per second at model failure; r = radius of rotation of the model in feet; g = 32.2 ft/sect.]

Jan 1, 1947

By E. Miller, R. Geffken, K. L. Komarek

The thermodynamzc properties oJ liquid Cd-Sb alloys were investigated using the cell arrangement measurments were obtained every 2°C at a heating and cooling rate of 12°C per hr and at equilibrium every 2O0C frorn 500°C down through the stable liquidus. The S-shaped asCd US composition curve was used in the cotnposition regzon near Cd,Sb, to calculate a tempeerture-dependent inleraction coefficient from quasichemical theory. Rapid changes in a scd were observed at a transition temperature varying from 400" to 465°C depending on con/kosition. It could not be determined if the changes in aScd were discontinuous, but tlze composition dependeke of the magnitude of the change is indicative of a second-order phase transformation in the liquid. The values of the experimental changes in ASCd are in agreement with calculations from the slope of the transition temperature, using the concept that a second-ovdev phase transition occurs in liquid Cd-Sb alloys. II is suggested that the transformalion is associated with the formation of Cd4Sb3 molecules in the liquid. ThE structure of liquid alloys is the subject of many investigations. X-ray, resistivity, and thermody-namic data have been interpreted as indicating varying degrees of short-range order in the liquid in alloy systems forming inter metallic compounds. In general, the melting process is not a transition from an ordered to a completely disordered state, but some degree of order is retained in the liquid. Maximum ordering in the liquid state occurs close to the melting temperature of the compound and the arrangement of atoms becomes more random at higher temperatures. Of special interest in this respect is the Cd-Sb system. It is one of the few metallic systems which form both stable and metastable compounds when liquid alloys are cooled at normal rates. The stable system exhibits an intermetallic compound, CdSb, melting at 459"c.l A second compound, CdrSbs, has also been reported,' melting close to this temperature. The metastable system has one compound, CdsSbz, melting at 420"c.I Resistivity measurements on liquid Cd-Sb alloys close to the liquidus temperatures have been interpreted in terms of a complex ordering behavior which changes rapidly with increasing temperature.3 The resistivity-composition curve is characterized by two maxima corresponding in composition to CdSb and CdsSbz. The resistivity-temperature plots show sharp breaks for alloys in the composition range of 45 to 70 at. pct Cd on cooling through a transition temperature close to the stable liquidus. Fisher and phillips4 investigated the influence of temperature and composition on the viscosity of liquid CdSb alloys. The viscosity of some alloys increases sharply on supercooling below the stable liquidus. A maximum in the viscosity-composition curve occurs at the composition CdSb. The thermodynamic properties of liquid Cd-Sb alloys have been investigated by Seltz and ~e~itt' and Elliott and chipmane by the electromotive-force method and their results are in good agreement. However, these investigations were carried out at temperatures well above the liquidus temperatures of the alloys, and the temperature coefficients of the electromotive force, dE/dT, were obtained from experimental points for each alloy at a few temperatures considerably above the liquidus temperature. Scheil and ~aach' investigated the thermodynamic properties of this system by the dew point method in the temperature range from about 100°C above the stable liquidus down into the supercooled liquid region. They reported several anomalies, i.e., the activity of a melt on heating differed from that on cooling, and the activity increased sharply in the limited temperature interval immediately above the liquidus temperature of the stable alloy, followed by a sudden decrease below the liquidus. Values obtained on heating and cooling were not in agreement. A reinvesti-gation of a few alloys by Scheil and Kalkuhl' by the electromotive-force method failed to confirm these observations. The authors concluded that the anomalies were due to inhomogeneities in the starting alloys and they discarded their previous results. The present investigation was undertaken in order to obtain thermodynamic data close to the liquidus temperature and in the supercooled region where the anomalies were originally reported, employing the electro motive-force method. This method is quite precise and will most easily permit observations of small changes in activity and partial molar entropy with temperature. Measurements were taken every few degrees so that the dE/dT values could be calculated over the entire temperature range and small changes in the thermodynamic properties close to the liquidus temperature could be observed. I) EXPERIMENTAL PROCEDURE Specimens were prepared from 99.999+ pct Cd and Sb (Cominco). Surface oxide was removed by scraping and then melting the metals under vacuum and filtering through Pyrex wool. Appropriate amounts of the metals were weighed on an analytical balance to k0.1 mg, sealed in double Pyrex capsules under vacuum,

Jan 1, 1968

By G. P. Conard, E. H. Rennhack

The creep behavior of hot-rolled, hypoeutectic Zn-Ti alloys was investigated in the temperature range from 0.43 to 0.53 TM. Secondary flow was found to originate primarily from strain-induced gvain growth where grain boundary )nigvation served to relieve the strain energy of distortion introduced by slip, grain boundary sliding, and subgvain formation. The extent to which this recovery mechanism operated was determined by the ratio of grain width to the spacing between planar fibers of TiZn,, compound particles generated in these alloys during rolling. When this ratio was unity, creep resistance demonstrated a marked improvement. In this condition, which was fulfilled by annealing following rolling, structural stability was enhanced with decreasing grain size below the equicohesive temperature (-0.5Tm), while the reverse was true above this temperature. TITANIUM concentrations approaching the eutectic composition of 0.23 wt pctl have been shown to promote a significant increase in the creep resistance of rolled zinc,2 The alloying effect created with titanium is somewhat unique; a structure closely resembling that of a fiber-reinforced metal composite can be developed which selectively modifies creep strength in preference to other mechanical properties. In an earlier investigation,~ the present authors found that, while the fiber network, composed of individual TiZn,, compound particles, had a distinct influence on rolled texture, the crystallographic variations produced were of minor importance with respect to creep. Rather, creep resistance seemingly increased when the grain size appeared to coincide with the in-terfiber spacing. The work described here was undertaken to explore this effect in greater detail. EXPERIMENTAL PROCEDURE Three zinc-base alloys containing 0.05, 0.12, and 0.16 wt pct Ti were prepared from CP zinc and iodide titanium in the form of 4 by 2 by f in. chill-cast ingots. The melting and casting procedures for these alloys have been detailed el~ewhere.~ Individual ingots of each alloy were hot-rolled at 200°C (392°F) to total reductions of 10, 25, 50, 75, and 90 pct in from one to five passes, respectively, employing a 10-min reheat prior to each rolling pass. With grain, tensile-type creep specimens with a 1-in.-long, -in.-wide gage section were machined from the rolled strips for test purposes. Annealing studies to explore the influence of grain size on secondary creep flow were carried out at 400°C (752°F) in argon for times extending up to 60 min. The grain-size effect was evaluated in terms of average grain width and length values statistically derived from lineal intersection measurements.4 A similar method was applied in establishing the average interfiber spacing, i.e., average perpendicular distance between adjacent planar fibers. The creep characteristics of the alloys were investigated by means of constant-load and constant-stress creep tests. The former tests were conducted at 25°C (77°F) under an initial stress of 10,000 psi, while the latter were performed in the range from 25°C (77°F) to 90°C (194°F) at stress levels varying from 8000 to 22,000 psi. Total specimen strain, as determined with Budd HE-1161-B strain gages, was in excess of 0.10. Maintenance of constant stress was achieved through periodic load reductions made at 0.01 strain intervals to compensate for the attendant incremental reduction in specimen cross-sectional area. The maximum indicated error in the applied stress at these strain intervals was less than 3.0 pct. RESULTS AND DISCUSSION Constant-Load Creep. In an effort to clarify the in-terrelation between interfiber spacing and grain size with respect to the creep resistance of the Zn-Ti alloys, their separate effects on secondary creep rate were determined as a function of titanium content and rolling reduction. These results are set forth in Figs. 1 and 2, respectively. The average grain diameter plotted in Fig. 2 was resolved from average grain width and length values. No data are presented for reductions of less than 50 pct because of the inability to obtain consistent measurements on these strips. The curves of Fig. 1 indicated that, for a given titanium content, a decrease in interfiber spacing, as produced with increasing reduction, promoted a decrease in creep rate. Depending on titanium content, however, wide variations in creep rate occurred at the same interfiber spacing suggesting that interfiber spacing, by itself, has little or no influence on creep resistance. Grain size, on the other hand, decreased progressively with both increasing rolling reduction and titanium content, the effect of which led to a pronounced decrease in creep rate, particularly when the average grain diameter became smaller than 3.0 x 10"4 in., Fig. 2. The continuity of this relationship tended to support the view that grain size rather than interfiber spacing was predominant in controlling secondary creep. Annealing Effect. The observed dependence of creep flow on grain size suggested that a further contribution to creep resistance would result when the alloys were annealed to effect a coincidence between grain width and interfiber spacing, see Fig. 3(b). ~eiides creating an immediate barrier to grain boundary movement, annealing offered the possibility of providing increased structural stability by eliminating many high-energy, mobile grain boundaries.= To test this hypothesis, specimens from the Zn-0.16 Ti strips reduced 75 and

Jan 1, 1967

By John H. Holloman

In recent papers, O'Neill,' Vivian, and Zener and Hollomon3 have reviewed some of the information concerning the relations between stress and strain during plastic deformation. Since further information has been obtained since these reviews were published, this paper attempts to further coordinate and amplify the knowledge concerning the plastic deformation of metals in simple tension. Ordinarily the results of tensile tests of metals are presented as graphs in which the load divided by the original area is plotted as a function of the percentage of elongation measured over some specified gauge length. The interpretation of graphs of this sort is limited, since the stress required to deform the metal at any stage of the deformation is actually the load divided by the instantaneous rather than the original area. Furthermore, each increment of the deformation is performed on metal that has been previously deformed, and, as pointed out by Ludwik,4 the strain could be more effectively defined: where e is the strain and AO and A are, respectively, the original and instantaneous areas. The results of the tensile tests can be more effectively presented and interpreted if the stress* (load divided by actual area) is .lotted as a function of the strain as defined above. A schematic curve of this type is presented as Fig. I. In a previous paper,6 the concept of Ludwik7 concerning the flow and fracture of metals was successfully employed to explain some of the puzzling results of notched-bar impact tests of steel. It appears that the use of this concept ii; very fruitful and should be kept in mind in any study of the deformation charactcristics of metals. Ludwik considered that a flow stress-strain curve of a metal was essentially a locus of points that described the stress required for plastic flow of an infinite numbcr of specimens, each with a different strain history determined by the preceding part of the flow curve Each of these specimens can also be considered to have a fracture strength. Uniortunately (or fortunately depending upon the point of view), all the specimens, except the one deformed to the fracture strain, flow and do not fracture. Even though the metals do not fracture, the concept of a fracture-strength curve seems

Jan 1, 1945

By AIME AIME

LIFE in few countries is dominated by geographic conditions to the degree that it is in Peru. The broad plateau of the Andes, bordered by lofty ice-clad ranges with deeply eroded flanks, imposes a pattern on the region to which most human activities must conform. On the Pacific side, desert conditions prevail, interrupted only by irrigated valleys along rivers that descend from the highlands. Above seven or eight thousand feet the rocky ridges become grass covered, and the central zone is one of high pastures with cultivation in the valleys or on terraced slopes except at altitudes over 15,000 ft. where glaciated landscapes prevail. Each of the three belts has its own distinctive resources and climate, and each its own special ways in which its inhabitant, must make a living. The Pacific region is one of the most arid regions in the world. Except for the irrigation, the country is an unmiti¬gated desert. The climate, in spite of the tropical latitudes, is mild with the heat relieved by air from the adjoining cold ocean. Fogs are prevalent throughout the winter months but precipitation is scarcely measurable. Ideal conditions exist for cultivation of sugar and cotton which are the dominant crops. Lima, the capital. situated in one of the most productive valleys, is an impressive city which in its modern development is well maintaining the high position it held when it was the

Jan 1, 1945

By W. A. Sheaffer

Electric furnace installation and tough-pitch copper-casting operation at Canadian Copper Refiners Ltd. are described. General layout, power supply and control, refractories, induction pour hearth, casting equipment, metal temperature control, and oxygen-content control are discussed. E LECTRIC furnace at Canadian Copper Refiners Ltd. was put into operation in August 1949. The installation was designed primarily to melt electrolytic copper cathodes and to produce vertically cast tough-pitch shapes. To meet emergencies during reverberatory furnace shut-downs, provision was made for casting horizontal tough-pitch wire bars. Due to the ease with which metal temperatures, melting rates, oxygen content, and casting hours can be altered to suit production demands, the electric furnace has met the requirements admirably. General Layout The plant has been described by H. S. McKnight' and by J. H. Schloen and E. M. Elkin.2 Since these papers were written, the electric furnace has been installed in a 140 ft extension of the original casting building. The extension, 264 ft in width, is divided into one 24 ft and four 60 ft bays, each a continuation of similar bays in the older building. Fig. l, a partial floor plan of the extension, shows the location of major equipment. Power Supply and Control Power for the electric furnace and its auxiliary equipment is delivered by Quebec Hydro over two 12 kv three-phase, 60 cycle pole lines. One line is in use, while the second serves as an emergency standby. Connections for the electric furnace from these lines, which also feed the refinery power house, are made to a substation on Canadian Copper Refiners Ltd. property. Connections between this substation and the furnace transformer room are in underground conduit. The are-furnace transformer, 550 v auxiliary-equipment transformer, and 12 kv switchgear are in the transformer room near the furnace. Stepdown from 12 kv to are-furnace voltages is done by a 7500 kva oil-immersed water-cooled three-phase 60 cycle transformer. This unusually high kva rating is available because the arc furnace and transformer were adapted from a steel-melting unit. Secondary voltages are available in 16 steps between 251 and 95 v (across phases). A four-position tap changer, operated from the furnace switchboard is connected to taps yielding 199, 164.5, 127, and 115 v, respectively. The transformer primary feeder is equipped with a General Electric Magne-Blast circuit breaker. The pour hearth, casting wheel, bosh conveyor, and other auxiliary equipment are fed by a 12 kv to 550 v, 750 kva three-phase 60 cycle transformer. Graphite electrodes, 14 in., with tapered nipples are held in the are-furnace electrode arms with steel wedges. The arms, fed from the transformer secondary busbars by flexible cable bundles, are actuated by winch cables. Direct-current motors operating the winches are supplied by a 250 v motor-generator set. Power input to the furnace is controlled from the furnace switchboard. The board has the usual combination of remote controls for the 12 kv breaker and transformer tap changer, meters, overload relays, automatic and manual electrode motion controls, switchgear, etc. When power is on the furnace, automatic electrode feed is used; the power draw on a given voltage tap then is governed by current-limiting rheostats. The rheostats work through a Westinghouse bal-lanced-beam control circuit which, in turn, operates reversing contactors in the winch motor circuits. Arc Furnace The arc furnace is a standard-type NT Pittsburgh 'Lectromelt with inside shell diameter 12 ft 3¾ in. By hydraulic-lift cylinders, the furnace can be tilted forward to 39 ½ ° and backward to 5" from horizontal. A roof-swing cylinder is also installed but not used. Fig. 2 shows refractory-lining details. With the lining as shown, operating life between repairs is 6 to 9 months of two-shift casting operation. Charge slot, skim door, and roof refractories then are replaced completely, and any necessary repairs made to side walls. Bottom life is longer and the original under courses are still in service, while the top course was replaced in October 1951. The launder is lined with high chrome-magnesite trough brick backed by fireclay and insulating brick. The trough is covered with fireclay brick and asbestos sheet. At intervals, openings 12x6 in. are left in the permanent covering. These are covered with

Jan 1, 1956

By W. F. Hower, W. Brown

Large-scale sand consolidation tests were conducted in an effort to determine the reasons for the successes and failures of this method of sand control. Several different consolidating materials were used in treating both clean and bentonitic sands that were packed in a chamber having a capacity of 3.3 cu ft. The results were essentially the same for all of the different consolidating materials, The data show that low-viscosity consolidating materials pumped at a relatively slow rate gave the best results. Where the formation has produced sand, the treating fluids can compress the formation, thus permitting the channeling of fluids to another horizon. Pressure-packing these zones before attempting to consolidate is recommended. Sands containing more than 4 per cent of water-swelling clays are not good candidates for consolidation. It is indicated that loose sand, particularly when it is bentonitic, can be fractured during the placement of the treating fluids. INTRODUCTION Sand production in oil and gas wells has plagued the industry for many years, and numerous cures for this problem have been suggested. Most methods have been successful to a certain degree, but the great variety of well conditions that exist in the different areas has magni- fied the problem and limited the successful use of the various systems. Four review papers1-4 present a wealth of information concerning the degrees of success that have been obtained by the different sand-control methods. The bridging of sand grains by the use of gravel packs and screens has been quite successful. However, these methods do not leave the casing clear for all types of multiple completions, and the cure does not last for the production life of the well in some instance:;. The control of loose sands by sand consolidation with resins has never been as successful as desired. It has always been hoped that such a treatment would eliminate all sand problems for the life of the well, but. initial applications, starting in the middle 1940's, were only moderately successful. Lott, et a1,3 reported a success ratio of approximately 50 per cent and made the following conclusions. The highest percentage of successes were obtained where: a. Consolidation of a zone was made at the time of initial completion or prior to the production of sand. b. The interval treated was less than 12 ft in length. c. Between 30 and 50 gill plastic/ft of producing interval was displaced through the perforations. REASONS FOR SAND CONSOLIDATION FAILURES Our own experiences in the field of sand consolidation point toward the following conditions as the major reasons for the failure of sand consolidation attempts. 1. Mud-plugged perforations and mud invasion of the formation. 2. Sand in the casing covering all or part of the perforations. This sand could be either formation sand or one of the coarser sands used as propping agents in hydraulic fracturing. 3. Holes in the casing. 4. Channels behind the casing. 5. Attempting to treat too long a perforated section. 6. Too high a percentage of water-swelling clays in the formation. 7. Formations that have produced sand. Recent attempts were made to treat perforated sections ranging from 10 to 30 ft, in wells that have produced sand, by using a straddle packer that was raised and lowered through the perforations as the consolidating material was being pumped. In most instances, the pressure required to pump fluid into the formation varied considerably as the tool was raised and lowered. This suggested the possibility that significant differences in permeability were present or that only part of the formation had produced sand. There were times when a sudden break in pressure indicated that a fracture was being formed. Research conducted several years ago concerning the problem of the control of water in air and gas drilling indicated that shale sections could be fractured quite easily. In addition, it was determined that it was easier to pump fluids into shale bodies by fracturing the shale itself, or the interface between the shale and sand, than to pump into a fluid-saturated formation. Formations that produce sand are usually adjacent to shale bodies and frequently have shale streaks of various thicknesses inter-bedded in the sand. Therefore, where shale is exposed to fluid pressure it

By E. Z. Lajtai

The probability distribution of fracture data from a rock mechanics test contains information about the effectiveness of the testing procedure and/or about the nature of the operating failure mechanism. The tensile strength of Lac du Bonnet granite forms a bimodal probability distribution when determined through line loading as in the Brazilian test. The same data obtained from three point bends tests are unimodal. The bimodality can in part be removed by distributing the line load over a finite area. Moisture has the anticipated effect in lowering both the average compressive and the average tensile strength of Lac du Bonnet granite. The reduction in strength however is not uniform within the probability distribution; the change is the largest at low and the smallest at high strength. Conversely, long-term loading is more damaging to the high strength members of the distribution. The large scatter of failure times in static fatigue experiments can in part be removed or even utilized when the probability distribution of instantaneous strength is taken into account.

Jan 1, 1982

By Leonard Larson

DURING several years immediately preceding the adoption of wet-charge smelting at McGill, various necessary conditions affecting this procedure, such as plant rearrangement and the metallurgical nature of the concentrate produced at the concentrator, were fully considered. Wet-charge smelting is not altogether novel to the recently reconstructed smelter at McGill. A number of years prior to this improvement, when flotation methods were initiated at the concentrator, large tonnages of wet and (at that time) sticky flotation concentrate were charged directly into the reverberatory furnaces, because of the difficulty in handling the entire tonnage in the roasters. The plant had excess reverberatory units and this surplus furnace capacity was utilized to smelt raw flotation concentrate. During the years 1927 and 1928, a number of actual operating furnace test runs were made to determine in principle the feasibility of wet-smelting operation. Results were encouraging, and in November 1932 the roasting plant was shut down. For some time thereafter the wet feed was delivered directly to the reverberatory side-charging calcine hoppers already in place. Feeding the wet material through the old calcine hoppers and charge holes into the furnace involved considerable labor, but under the conditions existing at that time it was desirable to continue wet smelting even under the handicap of this laborious procedure. The smelting plant during this period was on a curtailed production basis, operating only about 15 days per month. The alternate starting up and shutting down of the roasting plant presented a difficult problem and charging the wet material directly to the furnace entirely eliminated this difficulty. The roasting plant was never operated thereafter. EARLY PROCEDURE Fig. 1 shows the general layout of the smelting plant before the smelter was remodeled. Under this arrangement, all concentrates and fluxes except converter flux were delivered in cars to wooden storage bins, which paralleled the roaster building. The material to be roasted was dis-

Jan 1, 1938

By Fun-Den, Wang

An open pit rock structure usually contains geological planes of weakness. They are formed by joints, faults, bedding planes, fractures, and cleavages. Rock slope failures often occur in the form of sliding of rock blocks along a plane or several planes. Such a rock block has three- dimensional geometry, and consequently a vector method of analysis has been found useful in evaluating its stability. Rock blocks of a tetrahedral shape with one free surface have been analyzed by Londe. Rock blocks formed by sets of parallel joints have been analyzed by Wittke. The present chapter presents the analysis of rock blocks formed by planes of weakness of arbitrary orientation, and of three-dimensional geometry.

Jan 1, 1972

By W. Mckewan, W. M. Fassell

The oxidation rates of copper have been determined at temperatures from 600" to 900°C in oxygen from 14.7 to 400 psi total oxygen pressure. The oxidation rate of copper is unchanged by oxygen pressures within the range studied. The observed data extend Feit-knecht's conclusion concerning the pressure independence of copper from atmospheric pressure to 400 psi. All samples studied in the above-mentioned temperature and pressure range have both Cu2O and CuO present in the oxide film. NUMEROUS papers have been published on the oxidation of copper, some of which have noted the effect of oxygen pressure on the oxidation rate of copper. It must be noted, however, that no data on the oxidation rates of copper at pressure in excess of 1 atm have been reported in the literature. (Le Chatelier¹ reported that a black oxide of silver was formed at 300°C and 15 atm pressure.) This is likewise true for the other metals. This investigation was initiated to obtain experimental oxidation rate constants for pure metals at elevated temperatures and high oxygen pressure. Copper was selected as the first metal since probably more reliable data are available on its oxidation rates and related physical and chemical properties than for any other metal or alloy. As a general summary, the following conclusions appear well established for the oxidation of copper: 1—The oxide coating consists of Cu2O with a superficial coating of CuO providing the ambient oxygen pressure exceeds the equilibrium pressure for the coexistence of Cu2O and CuO.² The following sequence of phases is then Cu/Cu2O/CuO/O2 (gas). The Cu2O consists of large crystals that have no relation to the orientation of the metal crystals, except for a very thin layer adjacent to the metal." The CuO consists of very fine crystals randomly oriented. If the oxygen pressure is below the equilibrium pressure for the coexistence of Cu2O and CuO, the coating consists of Cu,O only. 2—The rate-determining factor in the parabolic oxidation of copper is the diffusion of Cu+ ions through the Cu,O layer.4,6,7 The Cu+ ions are accompanied by electrons to maintain electrical neutrality. The mechanism of the reaction at the Cu2O/CuO interface and the method of growth of the CuO is in some doubt. 3—On copper, there are three reported pressure effects: (a) At pressures below 0.3 mm Hg oxygen pressure, the oxidation rate increases directly with pressure.', ' .Vxygen starvation at the surface may account for this effect. (b) At oxygen pressures from 0.3 to 63 mm, the oxidation rate increases as the 7th root of the oxygen pressure providing the temperature is such that only Cu2O is present in the film. (c) At pressures from above the equilibrium pressure for the coexistence of Cu2O and CuO (varies with temperature) to atmospheric pressure, the oxidation rate is independent of the oxygen pressure.' Equipment In order to determine the oxidation rates of metals in an oxidizing atmosphere at pressures up to 400 psi, the equipment is somewhat different than for low pressure work as is shown in Figs. 1 and 2. A Leeds and Northrup Micromax recording controller (A) is used to control the temperature of the Ni-chrome furnace winding in conjunction with a Micromax electric drive unit. The drive unit adjusts a 20 amp Variac (variable transformer) to control the power input into the Nichrome furnace winding. Due to the "self heating" of the sample by oxidation, frequently encountered in oxidation rate studies, it is essential that the sample temperature be measured independently. This is done by means of a series of six chromel-alumel calibrated thermocouples located spirally around the oxidizing metal sample. Each thermocouple is partially shielded from the direct radiation of the furnace wall by

Jan 1, 1954

By T. J. Koppenaal

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

Jan 1, 1963

By Francis F. Lucas

A microscope objective of given numerical aperture, when used with light of given wave length, has some fixed limit of resolution. This may be expressed as potential resolving ability—the ability to resolve is inherent in the lens but whether this limit is achieved in practice is quite another matter. Nearly 50 years ago Abbe evolved theoretical considerations which indicated that the ability of a lens to resolve detail is directly proportional to twice the numerical aperture of the objective and inversely proportional to the wave length of the light used. It is true, unquestionably, that as the numerical aperture of the objective is increased the potential resolving ability of the lens is increased and likewise when the wave length of the light used is decreased, the degree of resolution is increased. Whether Abbe's formula expresses the exact relationship is not a matter of great concern. It suffices to know that to improve resolution, other things being equal, two avenues of approach are available. Either the numerical aperture of the objective may be increased or the wave length of the light decreased. With the apochromatic system it is possible to employ successfully wave lengths from 400 to 500 uu and still secure reasonably short exposures. The present limit for numerical aperture is 1.40 N. A. although objectives of 1.60 N. A. are now an experimental possibility for metallurgical work. Thus certain well defined limits are set for those who work within the range of the visible spectrum. In order to take advantage of the increase in resolving power which accompanies a decrease in the wave length of light employed, Dr. A. Kohler and Dr. M. Von Rohr of the Zeiss Scientific Staff developed the "monochromats." These are quartz objectives corrected for the single wave length 275 uu which lies in the ultra-violet region of the spectrum. They also developed a series of quartz oculars and a complete photo-micrographic equipment with which to use the quartz optics. Quartz must be used for the optical parts because glass absorbs ultra-violet light almost completely. Thus there was made available about 20 years

Jan 1, 1926

By W. E. Coxe

In 1857 the Philadelphia and Reading Railroad Company, whose main line extended from Philadelphia to Pottsville, Pennsylvania, with branches into the coal regions of Schuylliill County, made a contract with the Fairmount Rolling Mill, at Philadelphia, for the rerolling of some four thousand tons of iron rails. The essential features of the agreement were that the old rails should be piled with puddled iron and rolled into flats for the rail pile, which latter was • to be of a section seven inches square, and after being heated, and reduced, by rolling, to a bloom of a section about fire inches by six inches, was to be reheated, before being finished into the rail of the T pattern, four inches high, weighing sixty-four pounds per yard. Great care was exercised in the execution of this contract, and the rails being distributed over all parts of the road, gave general satisfaction by their excellent wear. Five years afterward, the principal proprietor and manager of the Fairmount Rolling Mill was elected President of the Reading Railroad, and very many of the rails made under his supervision were still in use in the tracks of the company, of which he had just assumed the management. His first efforts were, therefore, directed to the procuring of more rails of the same quality wherewith to replace those worn out. Here he encountered some trouble, makers refusing to bid because of the details in the specification, the required reheating being the objectionable feature, for which it was generally intimated they would not be sufficiently remunerated for the increased labor, extra coal consumed, and the changes necessary from the established methods of working. Most of the new rails were, therefore, bought, and the old rails rerolled without regard to any particulars as to the manner of piling, heating, etc., each manufacturer furnishing what he deemed the best article possible for the money. As a consequence, rails of all imaginable grades were placed in the tracks, some giving out in six

By W. E. C. Coxe

IN 1857 the Philadelphia and Reading Railroad Company, whose main line extended from Philadelphia to Pottsville, Pennsylvania, with branches into the coal regions of Schuylkill County, made a contract with the Fairmount Rolling Mill, at Philadelphia, for the rerolling of some four thousand tons of iron rails. The essential features of the agreement were that the old rails should be piled with puddled iron and rolled into flats for the rail pile, which latter was to be of a section seven inches square, and after being heated, and reduced, by rolling, to a bloom of a section about five inches by six inches, was to be reheated, before being finished into the rail of the T pattern, four inches high, weighing sixty-four pounds per yard. Great care was exercised in the execution of this contract, and the rails being distributed over all parts of the road, gave general satis¬faction by their excellent wear. Five years afterward, the principal proprietor and manager of the Fairmount Rolling Mill was elected President of the Reading Railroad, and very many of the rails made under his supervision were still in use in the tracks of the company, of which he had just assumed the management. His first efforts were, therefore, directed to the procuring of more rails of the same quality wherewith to replace those worn out. Here he encountered some trouble, makers refusing to bid because of the details in the specification, the required reheating being the objectionable feature, for which it was generally intimated they would not be sufficiently remunerated for the increased labor, extra coal consumed, and the changes necessary from the established methods of working. Most of the new rails were, therefore, bought, and the old rails rerolled without regard to any particulars as to the manner of piling, heating, etc., each manufacturer furnishing what he deemed the best article possible for the money. As a consequence, rails of all imaginable grades were placed in the tracks, some giving out in six

Jan 1, 1877

By Eugene F. Broome, Hugh A. Walls

Self-diffusion coefficients were measured using the modified shear cell technique over a temperature range from 31" to 401°C. These data agree within experimental error with those of Petit and Nachtrieb, which were determined from 30°to 99°C. LIQUID self-diffusion behavior in gallium has been studied previously by Petit and Nachtrieb&apos; using their shear cell technique.&apos; Data were obtained in that investigation over temperatures ranging from 30.6 to 98.7"C, and these comprise the only published data for liquid gallium. In the work reported here, diffusion data were obtained from 30.8 to 400-9.Cusing a shear cell technique different from that of Petit and Nachtrieb. This modified shear cell method and the mathematical analysis for diffusion in a finite capillary geometry have been previously described.3 PROCEDURES AND ANALYSIS The segments of the modified shear cell were fabricated from types 304 and 316 stainless steel. No corrosion problems with gallium were encountered until attempts were made to obtain data at 500°C. The diffusion capillary diameter was 1.59 mm and capillary lengths for the four sets of cell segments used are given in Table I. Gallium with a purity of 99.999 wt pct was obtained from Var-Lac-Oid Chemical Co. The gallium-72 isotope used to measure the self-diffusion coefficients was produced from this inert gallium by irradiation in The University of Texas Reactor Facility, and was checked for radiochemical purity. Following a period of isothermal diffusion controlled to within 0.0l°C, the contents of each capillary section were emptied into a counting planchet, weighed to assure that gallium had not been lost during handling, and the radioactivity determined by windowless gas-flow proportional counting. Great care was taken to obtain a reproducible counting geometry for the samples. Diffusion coefficients were obtained from the solu-tion3 to the diffusion equation for the modified shear cell problem, viz.: in which B2= C2(t)Li + L2)- CSL1-COL2 P* (C0-Cs)(L1+ L2) and L, and L2 are the capillary segment lengths. The step-function initial concentration distribution was expressed as C(x,O) = C, for -L1 = x < 0 and C(x,O) = Co for 0 < x 5 L?. Also, C2(0 = ^- fcix,t)dx Computation of the diffusion coefficients was done numerically as described in our earlier paper.3 Because of the short half-life of gallium-72 (14.1 hr) and the relatively long counting times taken to give a precise value of the diffusion coefficient, it was necessary to account for the radioactive decay both during the actual count and between counts for different samples (before and after diffusion). Thus, the average count rate Cz(t) for a second sample counted from times t3 to t4 can be made consistent with the average rate Co determined for a first sample counted from times t1 to t2 by the relationship: N(e-»i-e-M») , , C2(f) " &-«,)(*-«.-«-»«) [21 in which N is the total number of counts taken and is the decay constant. RESULTS AND DISCUSSION The self-diffusion coefficients determined in this investigation are listed in Table 11. Values of the parameters used to calculate the coefficients are given in the table, as are values of the random counting error &apos; for the concentration ratio pz and the corresponding expected random variation AD in the diffusion coefficient. The quantity is calculable from: &apos;Cg — C2(t)} , „ ,2 .-„¦, M co-csl(ACs)J W in which AC is the error in the individual count rate. The mean values of the diffusion coefficients within each temperature group are also given in Table 11. Such temperature groupings of data are reasonable because of the small variations between the temperature~.~

Jan 1, 1970

By I. E. Campbell, R. I. Jaffe

Oxygen, nitrogen, and hydrogen are known to be absorbed by titanium at elevated temperatures. Ehrlichl reports that about 30 at. pct oxygen can be dissolved in solid solution by alpha-titanium. Nitrogen also has a solid solubility in alpha-titanium, but there is no information as to its extent. The solid solubility of hydrogen in titanium also is high. Kirshfeld and Sieverts2 report 50 at. pct soluble, while Hägg3 reports about 33 at. pct hydrogen to be soluble in alpha-titanium. General statements are made in the literature that oxygen, nitrogen, and hydrogen embrittle titanium, but no quantitative measurements have been made of the effect of these gases on the mechanical properties of the metal. One reason for this is the lack of a source of titanium pure enough to be considered a suitable starting material. Iodide-refined titanium, made by thermal decomposition of titanium iodide vapor on an incandescent wire,4 contains small amounts of carbon, silicon, iron, and aluminum, but is very low in oxygen, nitrogen, and hydrogen content, and, therefore, was used in this work. A further reason for the lack of quantitative information on the effect of these gases, particularly oxygen, is the difficulty of carrying out accurate analytical determinations at the low concentrations of interest in this work. For this reason, the oxygen, nitrogen, and hydrogen were added in measured amounts as gases, and diffused into the titanium, to avoid the necessity of chemical analysis. The purpose of the work reported here was to isolate and measure the effects of oxygen, nitrogen, and hydrogen on titanium of the highest purity available at the time. The concentrations studied were 0.25, 0.5, and 1 at. pct in each case. Experimental Work One-half of a 24-in. hairpin of iodide-refined titanium was available for this work. The rod was approximately 0.25-in. in diam and had a 0.003-in.tung sten core. From chemical and spectro-graphic analyses, the purity of the sample was estimated to be between 99.80 and 99.95 wt pct. The chief impurities (aside from the tungsten core) were iron (0.04 pct), silicon (0.01-0.1 pct), aluminum (0.05 pct), carbon (0.03 pct). The tungsten core constituted 0.05 pct by weight of the sample. Although some alloying undoubtedly took place between the tungsten and the titanium during the deposition reaction, the core remained substantially intact in the deposited metal. The initial average hardness of the titanium as deposited was 105 Vickers (10-kg load). The maximum hardness was 116 Vickers and the minimum 91 Vickers. The metal was somewhat harder than that currently being obtained by the iodide process, that is, 75-90 Vickers. The rod was cold swaged to ¼-in. diam and then cold rolled in diamond shaped rolls to about 0.080-in. square, using reductions of 15 pct in area per pass. The 0.080-in.-square wire was cut into 6-in. lengths for the preparation of the alloys by the gaseous absorption and diffusion method. ADDITION OF OXYGEN, NITROGEN, AND HYDROGEN TO TITANIUM A modified Sieverts&apos; absorption apparatus, shown in Fig 1, was used in

Jan 1, 1950

By William Braden

IT is obvious that the choice of the method to be employed in the handling of blast-furnace slags and mattes depends upon local facilities and conditions which may indicate as advisable some particular plan. As a result of the variety of such conditions hardly any two smelters use identically the same method, though they be located only a few hundred feet apart. For instance, of the several plants in Leadville, Colorado, each has a more or less distinctive system. The same is true of Salt Lake City and vicinity. In view of this it is evident that the existing diversity of practice cannot be accepted, prima facia, as evidence

Jan 1, 1897

By Robert Lowrie

Nine intermetallic compounds were tested in tension at various temperatures. Seven exhibited extensive plastic deformation at elevated temperatures. Correlations of tensile strength and elongation are attempted with melting (decomposition) temperature, valence electron configurations of the component elements, heat of formation, crystal structure, density, and volume decrease accompanying compound formation. A LTHOUGH intermetallic compounds have been -tX known for many years, the study of their mechanical properties, particularly in tension, is just beginning. The problem has been unattractive because of the well-known, erratic behavior of brittle materials tested in tension. The strong influence of surface or internal flaws as stress raisers in non-ductile materials and the effect of eccentricity of loading in superimposing bending stresses on the state of tension in the specimen are extremely difficult to mitigate and impossible to completely eliminate. Thus, tensile properties determined for brittle materials, such as intermetallic compounds at temperatures low in comparison to their melting points, are at best only general guides to the values to be expected in an ideal test of a perfect specimen of the material. It is, nevertheless, surprising that apparently no attempt was made to follow up the pioneer work of Tammann and Dahl1 in this field. Working with crude apparatus, these investigators succeeded in showing unequivocally that at temperatures sufficiently close to their melting points (from 75" to 400°C for the compounds tested) intermetallic compounds did exhibit plasticity. This was indicated by the appearance of slip lines on the surface of the specimen. No observations of strength were made in these tests, which were of a compressive or indentation type. Rossi2 in 1932 attempted to study the physical and mechanical properties of single crystals of a group of intermetallic compounds. However, he was able to prepare only one material, Cu2Z8,, in the form of large, defect-free, single crystals. Thus, he was able to report only the relative fragility of the compounds at room temperature. He reported one compound, Ag,Zn,, to be somewhat plastic at room temperature and Cu,Si to be friable, the latter in agreement with results reported herein. Although test results are available only in classified literature, it has also been announced that MoSi, possesses some ductility at elevated temperatures." In 1948 and 1949 Savitskii and Savitskii and Baron -ublished their work on the hot extrusion of Mg-Zn, Al-Mg, and Cu-Zn compounds. Under the favorable state of stress existing for this process MgZn, MgZn,, MgZn,, ß (Al-Mg), ? (Al-Mg) and 0 (Cu-Zn) could be reduced by amounts up to 90 pct at elevated temperatures. These authors also report that hardnesses of Mg-Zn compounds decrease from room temperature values of about 300 kg per sq mm to 30 to 50 kg per sq mm at 325°C. They found that alloys consisting solely of one Mg-Zn compound were most resistant to softening on heating, mixtures of a compound and eutectic less resistant, and mixtures of two compounds least resistant. The more rapid softening of mixtures of

Jan 1, 1953

By Courtenay DeKalb

Revision of the United States mining law is needed chiefly because of the following reasons: 1. The conceptions as to the characteristics of orebodies that were held at the time the statute of 1872 was enacted have since proved to be in many respects erroneous. 2. The operation of the existing law has been found to work unnecessary hardship upon many claimants to mineral land. 3. The existing statute fails in large degree to encourage development of mineral resources. 4. The existing law often produces conflict between placer and lode-claim rights, working unnecessary injustice to placer claimants. 5. The methods of establishing the rights of locators on United States mineral land are defective, and are not uniform throughout the States within which such lands exist. Law of the Apex The objections to the so-called "law of the apex" are so well known as to require no detailed statement. It is sufficient to point out that the apex rule was based upon the notion that ore deposits consisted of well-formed veins included between definite walls, like the slice of ham in a sandwich. The fact is that veins conforming to that simple type are rare. Irregularity is the rule, and the chief metal production of the United States comes from mass? which bear no resemblance to the tabular form of vein. Manifestly the law of the apex fails completely in such cases. Moreover, the tendency is constantly toward the exploitation of ores of lower grade than could formerly be worked, and such deposits exist mainly in the form of large irregular impregnated zones and masses, so that the future development of our mineral resources would be continuously embarrassed by shadowy claims to extra-lateral rights by the locators of so-called apexes.

Jan 1, 1915