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By Murray F. Hawkins, W. J. Ainsworth

In all types of subsurface pressure gauges the extension which occurs in the pressure-sensitive element is a function of the difference between the external (well or calibration) pressure and the internal pressure within the gauge, rather than a function of the external pressure only. The internal pressure is near atmospheric and depends upon (a) the quantity of air sealed within the gauge at the time of calibration or measurement, (b) the quantity of moisture (liquid water), if any, sealed within the gauge, and (c) the temperature at which the calibration or well measurement is made. Part of this correction for the change of internal pressure with temperature is taken care of by the customary temperature coefficient of the gauge. However, part of it is not, and while this portion may be only a few psi, it is nevertheless predictable or preventable, and should be considered in precision measurements. ERROR NO. 1 If air is sealed in the gauge at the same temperature and pressure for both the calibration and the well measurements, the usual temperature correction will take care of any difference between calibration and well measurement temperatures. However, if air is sealed within the gauge at temperature T1 and pressure P1 at calibration but at temperature T2 and pressure P2 for a well measurement, because different amounts of air are sealed within the gauge in each case, the internal pressure at. or corrected to, calibration temperature Tr will he different by where all temperatures and pressures are absolute. The calibration temperature is used, and not the well measurement temperature, because the usual temperature correction reduces the well measurements to calibration temperature. The correction term as calculated by the above equation is separate from. and in addition to, the usual temperature correction. Example: T, = 540°R, sealing temperature at calibration P, = 14.7 psia, sealing pressure at calibration T2 = 460°R, sealing temperature at well P2 = 14.7 psia, sealing pressure at well Tr = 660°R, calibration temperature AP = 660 [14.7/460 — 14.7/540] = 3.1 psi While this error is small even under these somewhat maximal conditions, it nevertheless represents a practical situation which did occur, and which as a matter of fact gave rise to this note. Where AP is positive, as above, the correction is added to the measured pressure; where negative, subtracted from the measured pressure. This correction should also be considered in successive calibration runs where the gauge, for example, may be warm from a previous calibration at an elevated temperature. ERROR NO. 2 Where a small quantity of moisture (liquid water) is sealed within the gauge at atmospheric conditions, the increased vapor pressure of the water at higher well or calibration temperatures will cause an increase in internal pressure. This moisture will come presumably from condensation within the gauge following temperature changes, from moisture on the operator's hands, and from atmospheric moisture (rain, mist, fog, etc.). Calculation shows that approximately 0.2 cc of water (three to four drops) is sufficient to saturate the air within an Amerada RPG-3 Gauge at 160°F, at which temperature the vapor pressure of water is about 5 psia. As the vaporization occurs in a sealed volume, the increase in internal pressure will be in excess of this 5 psi. At higher temperatures the pressures will be higher; however more water will be required to saturate the air within the gauge. Some experimental work was carried out with an Amerada RPG-3 Gauge at 200°F fitted with a 1,000 psi element, both with a dry recording chamber and with a small amount of water added. The results directly proved the existence of the error due to the presence of moisture, and, it is felt, indirectly, due to the differences in sealing temperatures and pressures, as both effects may be ascribed simply to an increase in the moles of gas within the recording chamber. SUMMARY In precision measurements the error introduced by sealing the gauge during a well test at a different temperature and pressure from that of calibration may be corrected for by using the equation presented, or it may be prevented by taking care always to seal the gauge at near calibration conditions. The error introduced by sealing moisture in the gauge may be prevented by taking care to keep moisture out of the gauge, or by removing the moisture by either warming or evacuating the gauge. Both of these errors are independent of the range of pressure measurement and the type of gauge, and are in addition to the usual temperature correction. ACKNOWLEDGMENT Appreciation is expressed to W. B. Kendall, Geophysical Research Corp., Tulsa, Okla., who pointed out the error from differences in sealing temperatures during some winter work in Canada. ***

Jan 1, 1956

By T. A. Simpson

The search for ore continued at its relentless pace throughout 1967. Canada, South Africa and Australia plus a few scattered localities on the globe reported minerals finds of significant importance. Many of the reported finds were not high grade ore, but they nonetheless will assist in sup- plying a highly industrialized, mineral hungry world. No longer does inaccessibility and remoteness close an area to mineral exploration and development. The communication and transportation systems of today have closed the gap and, moreover, the demand for essential mineral commodities is causing price shifts which encourage exploitation of deposits heretofore considered uneconomical.

Jan 2, 1968

By A. Blake Caldwell

Tyrone-a complete mining and concentrating facility built by Phelps Dodge Corp.-straddles the Continental Divide where surface water on either side flows in opposite directions although all water is taken from and returned on the northwest side of the Divide. At the outset, Tyrone was saddled with a problem of an adequate water supply, and the Gila River some 23 miles distant appeared to be the logical source. This in itself presented a major obstacle to Phelps Dodge because of the distance water had to be pumped and because of an adverse head which had to be overcome between the Gila River and the two 4-million-gal-capacity terminal water supply tanks at the mill. Having acquired water rights on the Gila River and in order to control the seasonal fluctuations in water volume, the company built the Bill Evans, off stream, earth-filled dam. This reservoir will contain 2100 acre-ft of water when full and it was constructed by the Hamilton Construction Co. for Phelps Dodge. The dam impounds fresh water for the Tyrone plant's use and four vertical turbine pumps (4500 gpm each) lift the water 275 ft from the Gila River into the reservoir. Since construction, Phelps Dodge has optioned the lake to the New Mexico State Game Commission for recreational purposes. In addition to the lake, land around the reservoir has been optioned to the State Game Commission for public use. The lake has already been stocked with trout and by next summer some keepers should be available for the taking.

Jan 12, 1969

By E. R. Kaiser

COAL research during 1941 had a marked increase in activity on problems bearing directly on furthering the increased and improved use of coal in homes and industry. Coal producers and fuel engineers expressed a greater interest in its practical possibilities and the coal laboratories have shown an increased interest in applied research, of value at once or in the near future to industry and the public. A large volume of accomplishment in mining, coal analysis, and the fundamentals of coal constitution and coal chemistry also continued to fill the storehouse from which applied research and fuel engineering of the future can draw valuable data.

Jan 1, 1942

By Philip S. Mathews

THE tremendous stimulus given to the mining industry by the gold and silver policy of the present administration has found the capital market for mines ill prepared to afford practical means of financing. Particularly has this been true of the host of abandoned high-cost producers and prospects which increased gold and silver prices have made potentially profitable. In a comparatively short time, experience has demonstrated abundantly that valuable properties have frequently failed to secure capital, while questionable properties have drawn to themselves and their promoters more of the public moneys than their prospects justify. Singularly enough the fault is usually attributable to faulty financing. Discussion and study of this problem are vital to the industry.

Jan 1, 1936

By J. R. Linney

THE Eastern magnetite industry has not failed in its contribution to the war program during the past year. Man-power shortage was the critical problem in maintaining production and for the last half of the year, owing to lack of man power, it was necessary for some mines to change from seven to six days per week schedule. At Cornwall, Pa., the mine operated by the Bethlehem Steel Co. produced approximately 2,000,000 tons of crude ore and 1,200,000 tons of iron ore concentrates, a decrease of about 10 per-cent compared with the previous year. Railroad haulage in the open-pit at this mine was discontinued, being replaced by Mack trucks of approximately 30 tons' capacity. At the Mt. Hope mine in New Jersey, the Warren Foundry and Pipe Corp. produced about 195,000 long tons of crude ore obtaining 70.000 long tons of lump ore and 35,800 long tons of concentrates. An additional 24,500 long tons of concentrates was produced from a stock pile of 47.000 long tons of crude ore accumulated during the latter half of 1943, following the fire in their old dry mill. All of this material was handled through their Brown

Jan 1, 1945

By C. J. Rodgers

The present day success of gravel packs to prevent or retard the migration of unconsolidated sands into the well bore is due to: (I) the use of a saline or non-aqueous, nonsolids drill fluid, (2) proper preparation of the well bore prior to gravel packing, and (3) pressure placement of the gravel. The experience gained from the "pressure pack" method of gravel packing indicates that sand-free fluid production can be maintained for a length of time sufficient to make the operation economically attractive. Data pertaining to the first 15 wells so completed by Gulf indicate that for each dollar spent to effect the completion, there will be a return of more than $2.92. The pressure pack technique of gravel packing is essentially the placing of gravel in and adjacent to the producing formations. This is done with fluid pressure and by the use of a drill fluid that will permit partial or complete loss of returns to the formation during placement. This technique was first intentionally used by Gulf in May, 1950, and since that time has been applied in more than 90 wells. Other advantages claimed for this type of completion are that the pressure placement of the gravel has a scouring effect on the casing perforations, that additional drainage channels to the well bore are created, and that the possibility of shifting of the formations adjacent to the casing is minimized and possibly prevented. During the past few years, the use of gravel to prevent or retard the migration of unconsolidated sands into the well bore has met with a favorable degree of success. Numerous methods and techniques of "gravel packing" have been used, each having its own relative merits, and with varying results. M. L. Cashion1 in 1939 ably reviewed the history of gravel packing to that time. As stated in his paper, ". .. the idea of gravel packing wells is not new." During the period 1939 to 1949, very little if any progress or change in technique in this type of completion was made. However, it was noted in some cases that during the placement of gravel, if there was a loss of drill fluid to the formation, there was a corresponding loss of gravel to the formation. Also, it was noted that in those gravel-packed completions (opposite casing perforations) that "sanded up," there was found to be an absence of gravel in the annular space between the liner and casing, although gravel had previously been placed in this space and no gravel had been removed from the well at the surface. These findings resulted in the placement of gravel with fluid pressure and by the use of a drill fluid that would permit partial or complete loss of returns to the formation during placement. Pressure placement of gravel became an accepted practice in late 1949 and early 1950. Another fact brought to light that has contributed to the current success of gravel pack completions is that drilling fluids containing solids will to some extent cause plugging of the screening medium or blocking of the producing section. The removal of these solids by chemical action, mechanical action, or a combination of the

Jan 1, 1955

By G. W. LAAiIBOURNE

FEW mines possess a history of more fascinating interest than the Ontario at Park City, Utah. The famous Bonanza's production record of over $50,000,000; the great extent of its workings; the remarkable character of its mineralization; the fact that recent discoveries have shattered preconceived theories of the geology of the camp practically assuring the half-century old property a future as active and as prosperous as the past make the Ontario one of the unique mines of the world. A mere accounting of the wealth created by this historic property not only exemplifies the great profits

Jan 1, 1925

By AIME AIME

THE second session on geophysical prospecting at the February meeting of the Institute was a discussion of the mining law and the bearing of the new method of search on location of claims and assessment work thereon. Allen H. Rogers was chairman of the meeting, which he opened by reviewing the present law and the proposed changes. W. R. Ingalls commented (by letter) on the Arentz bill, as introduced into the House of Representatives in 1921 and the need for revision of the present mining law. L. W. Douglas explained (by letter) the bill that he introduced and which has been passed by the House. SAMUEL S. ARENTZ, Nevada: It is my opinion that if the American Institute of Mining and Metallurgical Engineers is to sell this proposition to the people in the West, they have to sell it to the lawyers, because, after all, they are heard loudly when it comes to speaking in Congress. One man tells the other, "This thing is a vicious piece of legislation"; it might not be, but they will pass it on if it affects them. If the Institute would impress on the people affected that we need a re-codification of the mining law and that such is necessary along certain lines; that things have changed during the past decade or two, so today instead of doing our prospecting alone through the sinking of a shaft, through a discovery that may be seen, we are now moving on to more modern means of discovery through geophysics, through the churn-drill, through geology, through geological inference, I think we could get somewhere.

Jan 1, 1929

By Eugene McAuliffe

THE heavy shrinkage in the production of bituminous coal has reflected adversely in the matter of tonnage produced by stripping arid mechanical loading machinery. The purchase of stripping and underground loading equipment has likewise been circumscribed. How- .ever a growing percentage of bituminous coal is being loaded by stripping and mechanical loading machinery. This situation is due to the fact that numerous strip pits were able to operate in Illinois and Indiana when under- cover mines were subjected to labor interference, a further advantage gained by their ability to produce and market coal at a price below that of the undercover mines. The mines equipped with mechanical loading. apparatus have enjoyed more continued operation for the double reason that the companies using coal-loading machinery are, generally speaking, more substantial and in better financial condition than many of the smaller properties who maintain hand-loading methods, and the market advantage due to lower production costs also reflects to the advantage of the undercover mines using mechanical loading equipment. Where a number of mines are con- trolled by one company, those not equipped with loading machinery and suffering from higher producing costs have often been closed, with the available tonnage concentrated in the more modernly equipped mines.

Jan 1, 1933

By R. B. Tippin

Laboratory and pilot plant studies showed that supergrade iron ore concentrates (containing less than 2% SiO2) can be made from standard grade magnetic iron ore products by cationic silica flotation. Continuous tests were run using various flowsheet arrangements. whereby (1) super and standard grade products were made simultaneously or (2) only a superconcentrate was produced. After a caustic scrub and desliming pretreatment, the silica in a magnetic taconite concentrate was reduced to 1.8% SiO2 by amine flotation. Approximately 75% of the iron was recovered in the single flotation stage, and by additional beneficiation 95% of the total iron was ultimately recovered,

Jan 1, 1973

By Alan E. Gallie

SHERRITT Gordon Co. was formed in 1927 to exploit a copper zinc orebody located in the bush 90 miles north of The Pas, Manitoba. The mine went into production in 1931, operated for a year and a half, and closed because of the low price of copper. Reopened in 1937, it operated continuously until mined out in 1951, producing 8.5 million tons of ore. From 1937 on Sherritt Gordon conducted an energetic prospecting program throughout northern Manitoba, giving particular attention to the belt of favorable greenstone rocks north of the Churchill River. From 1937 to 1941 a number of gold showings were located but nothing of economic value was found.

Jan 3, 1957

By C. B. Barlow, T. A. Mekelburg

Due to a tight ash constraint on the clean coal product and difficult middlings washability characteristics, a considerable amount of coal was being lost in the jig middlings at the Monterey No. 2 Mine. An investigation was conducted into circuitry to recover this lost coal with minimal effect on the total clean coal ash. A reverse two-stage hydrocyclone system cleaning at low specific gravities was selected. This system is currently recovering approximately 5.8 kg/s (23 stph) of 11.5% to 12.5% ash coal. The specific gravity of separation for the system is about 1.5 and the probable error is 0.13.

Jan 1, 1986

By C. H. Curtis

The Esperanza mine of the Copper Division of Duval Sulphur & Potash Co. is located in the Twin Buttes District, 32 miles southwest of Tucson, Ariz. Records of mining activity in this vicinity date back to the 1850's. The New Year's Eve mine, which was last active briefly during the years of World War II, made the first actual penetration into what is now Duval's Esperanza property. Duval's exploration department became interested in the Esperanza in the fall of 1954. The first test hole was started on May 8, 1955. Two years of intensive exploration work together with metallurgical studies developed the basis for the decision to establish an operation.

Jan 11, 1961

Feb. 5. Society for Applied Spectroscopy, 6 pm, supper, Tosca's; 8 pm, meeting, Socony-Vacuum Training Center, 63 Park Row, New York. Feb. 6, AIME, Chicago Section, Chicago Bar Assn., 29 S. La Salle St., Chicago. Feb. 18-21, AIME, annual meeting, Hotel Statler, New York. Feb. 19, Michigan College of Mining and Technology, alumni reunion, Skytop Room, Hotel Statler, New York. Feb. 21, AIME, Utah Section, Newhouse Hotel, Salt Lake City. Feb. 28, Bituminous Coal Research, Inc., annual meeting, Edgewater Beach Hotel, Chicago. Mar. 3-7, ASTM, spring meeting and committee week, Hotel Statler, Cleveland. Mar. 5, AIME, Chicago Section, Ladies' Night, Chicago.

Jan 1, 1952

By R. G. Johnson

The prevailing system of locating wells on a rectangular basis, as shown in Fig. 1-A, has developed because of the exigencies of offsetting at boundary lines. When, however, a very large tract is being drilled, it is often possible to abandon this inferior method for the superior arrange- ment known as "staggering," which is illustrated in Fig. 1, B and C. The advantages of the triangular over the rectangular method are evident from Fig. 2, computed on the basis of one well to 10 acres (4 ha.). With the triangular system, no land is more than 409.4 ft. (124.8 m.) from a

Jan 1, 1920

By G. H. Kesler, J. E. Oberele, C. E. Dryden, J. H. Oxley

Heat-transfer rates were measured in a model of a multifilament vapor-deposition bulb fo the preparation of high-purzty metals. Local transfer coefficients for heat transfer frow the filaments to the circuates process stream were determined as a functiol of gas flow rates and bulb, inlet, and filament, geowzetvies. These results a-e then convertted to n mass-t7,ansfer basis to provide a method of correlating vapor-deposition rates and to predict the performance of commercial urzits. The firm1 cor?,elating equation for mass transfer was found to be- wheve k, is the mass-transfer coefficient; D, is bze gas difficsivity : P is the system pressure; R is the gas constant; T is the gas temperature; Df, DB, and Di ave tlze diameters of the filament, bulb, and inlet, respectively; k is the gas conductivity; C, is the specific heat of the gas, M is the wzolecular zleight of the gas; Npr . N,,, NRe a7'e the Prandtl, Schmidt, and Reynolds numbem of the system, respectively; LB is the height of the bulb; and SB and Sf are the total suyiace area of the bulb and filaments, respectively. ONE of the more conventional methods of preparing very high-purity metals is the vapor deposition of the metal upon heated filaments. The reactions which can be employed in such a process generally fall into two classes: 1) Pyrolysis of a volatile metal compound. Generally because of their instabilities, metal iodides are used; however, other metal halides and hydrides have been employed. These processes are frequently carried out under vacuum conditions, and the filaments are maintained at high temperatures. 2) Hydrogen reduction of a volatile metal compound. A metal chloride is normally the preferred feed for these processes, but other halides are sometimes used under special conditions. These hydro- gen-reduction processes are usually operated at atmospheric pressure. Many of the current processes for the production of semiconductor materials are actually vapor-deposition processes. However, the vapor-deposition process itself is relatively old, and almost all metals can be prepared in a state of very high purity by the use of vapor-deposition techniques. Loonam has recently given an excellent review of the iodide process for metal deposition,' and Owen has started some detailed studies with a carbonyl system.' A more general treatment of all vapor-deposition processes has been outlined by Powell, Campbell, and Gonser.3 Despite the fact that vapor-deposition techniques have been employed since 1890, there is a surprising lack of fundamental information regarding the transport characteristics of even the simplest deposition system, the heated filament. The purpose of the investigation described in this paper was to extend some of the earlier data obtained at Battelle to predict deposition rates and the uniformity of deposition in large-diameter, multifilament deposition bulbs under forced convection conditions.4'5 A number of other investigators have already presented a simplified treatment of the deposition process under non-flow conditions, i.e., pure diffusion.6"9 To obtain information on the transport characteristics of a deposition bulb, a model of a typical plant deposition unit was constructed, and local heat-transfer coefficients from the filaments to a circulating air stream were determined under various conditions of air-flow rates and bulb, inlet, and filament geometries. These results were then converted to a mass-transfer basis, and consequently provided a method to correlate experimental vapor-deposition rates and to design commercial deposition units. EXPERIMENTAL WORK Description of Model. The apparatus which was used in this work was a scaled model of one type of deposition bulb. It was constructed of Lucite and was easily altered to give several combinations of diameter of bulb liner, inlet size and location, number of filaments, and outlet geometry. The model is shown in Figs. 1 and 2. The bulb shell was made octagonal for convenience in construction and observation, and the bulb liners were cylindrical. Air, introduced through one of several different jet inlets, was used as the test fluid in these model studies. Filaments for deposition of metal were simulated by metal rods 1/4-in. in diam. Two of the rods could be heated by passing electrical current through them ¦ while the remaining rods could not be heated. This procedure minimized the amount of heat which was

Jan 1, 1962

By O. D. Gonzalez, H. A. Wriedt

Alloys ranging from pure iron to pure nickel were saturated with nitrogen gas at 918°, 999°, and 1217°C and analyzed. The solubility of nitrogen at 1-atm pressure was obtained as a function of nickel content for the whole range of iron-nickel alloys and the temperature dependence of solubility is shown for the experimental alloy compositions. The heat of solution and the entropy of solution of nitrogen in the alloys as func-tiom of composition up to 41 pct Ni are given. 1 HE acquisition of more exact thermodynamic information for systems composed of iron with various alloying elements continues to interest ferrous metallurgists. The interstitial alloying elements, especially carbon, hydrogen, and nitrogen, comprise a field of particularly intense study. A recent investigation of carbon solubility in Fe-Ni alloys held at 1000°C in gases of fixed carbon activity showed an unpredicted minimum in the solubility near 72 pct Ni.1 The present investigation was undertaken to see if a similar anomaly in solubility existed for nitrogen in Fe-Ni alloys. The solubility of nitrogen in ? iron at known nitrogen activities has been measured several times.&apos;-&apos; Corresponding information for the solubility of nitrogen in solid Ni and Fe-Ni alloys is not available. Juza and sachsze9 reported that metallic nickel dissolved 0.07 pct N in equilibrium with Ni3N at 445°C. This result was regarded as dubious by Turkdogan and Ignatowicz10 who found less than 0.0004 pct N in nickel specimens equilibrated at 600°C with ammonia-hydrogen mixtures having fugacities of N2 gas up to 35,000 atm. Such fragmentary reports indicate only that nitrogen gas has a very much lower solubility in nickel than in iron. MATERIALS A purified iron from Battelle Memorial Institute was used for solubility measurements. This grade contained more than 99.95 pct Fe, the highest content of any measured individual impurity being 50 ppm for each of As, C, Cu, and Pb. The nickel and iron-nickel alloys, supplied by the International Nickel Co., contained 0.02 to 0.04 pct C, 0.17 to 0.19 pct Mn, 0.04 to 0.08 pct Si, < 0.01 pct P, <0.03 pct S, and <0.20 pct Co as principal impurities. The Fe-0.59 pct Mn alloy was of zone-melted quality, the highest concentration of any individual impurity being 15 ppm Al. The "prepurified" grade of nitrogen gas from Matheson Co. had a nominal nitrogen content of 99.996 pct. An "electrolytic" grade of hydrogen gas from National Cylinder Gas. CO. in which the principal impurity is water vapor was admixed with the nitrogen to prevent oxidation of these specimens. This grade was preferred to a purer grade because the presence of some oxygen helps in suppressing contamination of the specimens, for instance, by silicon from the porcelain furnace tube. EXPERIMENTAL PROCEDURE The specimens were equilibrated in vertical tube furnaces through which a 99 pct N2-1 pct H2 gas was passed at ambient pressure. For the 915", 918", and 999°C runs, a wound-resistance furnace was used, and for the 1217°C runs, a furnace with a tubular silicon carbide element was used. The temperature control system on both furnaces was similar: a Weston "Celectray" controller with a modulator, responding to the electromotive force of a thermocouple with its hot junction in the furnace, switched the furnace current between high and low settings. The temperature distributions in the working zones of the furnaces were determined with calibrated Pt/Pt-10 pct Rh thermocouples. The overall uncertainty in temperature was estimated to be ±3° at 915° to 999°C and ±5° at 1217°C . Consideration of the small temperature coefficients of the equilibria studied, together with the error limits in the method of analyzing for nitrogen, showed that further refinement in temperature uniformity would give no improvement in resultant accuracy. The reactive gas was generated by mixing together "prepurified" nitrogen and "electrolytic" hydrogen directly from cylinders commercially supplied. The flow rates of nitrogen and of hydrogen were fixed by setting with bleeders the pressure drops across the individual calibrated flow meters of constant resistance. For any given alloy, the solubility of nitrogen at 1-atm pressure (% N) was obtained from the analyzed nitrogen content of equilibrated specimens (% Na)according to Sieverts&apos; law, thus

Jan 1, 1962

By R. E. Zinkham

An investigation has been conducted to compare short transverse and longitudinal fatigue and fracture properties in 4.25-in.-thick, high strength aluminum alloy plates. One plate was produced using standard rolling techniques while the other was pre.forged before rolling. Little difference was shown in fatigue strength of longitudinal specimens taken from mid-thickness of the plate. Howeuer, in the short transverse orientation fatigue strengths at 107 cycles were about 25 and 50 pct less, respectively, for the preforged and standard rolled plate. Differences in fatigue strengths were attributed to grain size and shape as well US orientation of constituents. Fatigue crack propagation rates and fracture toughness were compared at three different stress intensity (K) levels, using a constant compliance, double cantilever, wedge-shaped specimen. In a given plate, comparable fatigue crack Propagation rates were observed in the longitudinal (i9W) and short transverse (TW) orientations. Somezuhat gveater rates were observed in the short transzerse (TR) orientation. The preforged plute gave a lower rate for all three directions. Considerable secondary cracking developed, at times, over portions of the fatigue crack in both plates, particularly at the lower stress intensity levels in the short transverse specimens. Micro structure revealed constituent stringers as possible causes of the crack branching. Fracture toughness was considerably less in both plates in the short transuerse orientation. It is concluded that preforging not only improved directional tensile properties but also the fatigue and fracture properties in general. On occasion, aluminum plates have been milled away for hinges or bolted connections and stressed through the thickness or short transverse direction. Little or no information is available concerning fatigue characteristics or fracture toughness in this loading orientation in aluminum plate, or of the effect of fabrication on these properties. It was the intent of this project to examine, develop, and apply a unique specimen that has been advocated by others to study the fatigue characteristics and fracture toughness of two differently fabricated high strength aluminum plates. Linear elastic fracture mechanics criteria may be applied to the specimen so that the fatigue crack propagation rate and fracture toughness data may be of use for design or inspection applications. Fatigue characteristics are generally measured in the longtudinal or long transverse direction, where fairly large specimens such as center notched panels,&apos; are usually employed. Limitations are evident due to plate thickness, however, in the type and size of specimen that may be tested in the short transverse direction without extensions. Therefore, a specimen that is to be loaded in this direction should, for convenience, be compact. The general type of fatigue crack propagation specimens discussed and employed herein meet this requirement. These specimens are commonly called double cantilever beam specimens and lately "crackline-loaded edge-crack specimens".2 They may vary from a slope of zero (parallel-sides) to a wedge shape, the type employed herein. In general for most specimens the stress intensity KI at the tip of a crack is a function of the load, P and crack length, a. Some varieties of the wedge shaped specimen, however, give essentially a constant stress intensity KI over a considerable range of crack length.&apos; This feature can be a valuable asset in fatigue crack propagation experiments because the stress-intensity can be controlled simply by controlling the load without regard to crack length. MATERIAL AND METHODS Material. A standard rolled (light pass reduction) and a ~reforged and rolled (heavy pass reduction) plate of 7179-T651 material were used for the evaluation. The chemistry, processing history and average tensile properties are shown in Table I. Specimen Selection and Preparation. The specimen selected for the generation of fatigue initiation or S-N data was an axial tension type and is shown in Fig. 1. Specimens were taken from mid-thickness in the longitudinal and short transverse directions from both plates. Specimens were polished with 500 grit paper in a direction parallel to the loading axis. For the fatigue crack propagation tests, the specimen shown in Fig. 2 was used. This is similar to a specimen that has been employed by Mostovoy3 for fracture toughness studies on 7075-T6 aluminum alloy. It also fortuitiously agrees quite well with the dimensions of a specimen for which Srawley and Gross2

Jan 1, 1970

By Paul J. Fopiano

SOME relationships between the flow characteristics of iron single crystals of 99.9 pct purity and the behavior of imperfections have been investigated. X-ray rocking-curve measurements and etch-pit counts were made as a function of plastic strain, and compared to the stress-strain curve obtained on a modified Polyani tensile machine. Crystals grown from rolled strips of vacuum-melted iron by the strain-anneal method1 had a high preference for a (110) longitudinal direction and a (211) face normal. The tensile specimens were prepared from 2 by i by 0.040 in. single crystals having a gage area of 3 by \ in. Rocking-curve measurements were carried out with a highly perfect germanium monochromating crystal in which the dazz spacing was matched to that of the dZl1 in the ir0n.l Well-collimated CuKal radiation was used throughout. These procedures practically eliminated errors due to geometrical and wavelength resolution. Inasmuch as the rocking-curve half breadth may vary markedly from point to point in the specimen being irradiated, the crystals were strained in place by mounting a hydraulic loading device on the double-crystal spectrometer. The rocking curves were taken after each increment of strain in the unloaded condition, since no observable difference was found in the rocking-curves between the loaded and unloaded states. The rocking-curve half breadths of the as-grown specimens were in the range 90 to 120 sec of arc when the beam irradiated an area of about -£ by -& in. on the specimen. DeMarco and weiss3 have shown that, for a well-colli- mated X-ray beam, irradiating about 10"! sq in. of the very same material, half breadths within 10 pct of the Darwin natural half breadth were observed. Since the rocking-curve specimens were stressed by the load-unload technique, the strain achieved at any given stress depended on the time of holding because of low-temperature creep. Fig. 1 shows the rocking-curve half breadth (also area/peak height) as a function of plastic strain for a relatively short holding time (2 to 5 min) at each stress level. For strains less than 0.1 pct the rocking-curve breadth is essentially constant; it is only for larger strains that there occurs a significant increase in this breadth. Where the holding times at each stress level were longer (by well over an order of magnitude) there occurs a significant increase in the rocking-curve breadth only after plastic strains of the order of 0.6 pct had been introduced into the specimen. This observation is related to the time dependence of creep phenomena and emphasizes the difficulty in comparing data obtained by two such different straining methods. Etch-pit results were obtained using a 2 pct nital etch on specimens strained in the range of 0 to 1 pct. Prior to etching, all specimens were annealed for 3 hr at 150°C, the carbon content being sufficient to decorate the dislocations for strains of at least 1 p~t.~ The data points were all taken from parts of the same single crystal which had been strained with short holding times at stress in increments of strain of the order of tenths of 1 pct. The (211) plane is particularly difficult to etch-pit in vacuum-melted iron and therefore it is felt that these values are as much as an order of magnitude low. Fig. 2 shows the etch-pit density as a function of plastic strain. The smooth curve passing through the data points is not meant to infer a quantitative correlation with the rocking-curve data. What is of interest, however, is the change in etch-pit density in the region of 0.2 pct plastic strain. The first three increments in strain (points 2,3, and 4) did not produce a measurable change in the etch-pit density while subsequent increments did produce a measurable change. While the absolute values of these results do not appear to be cor-

Jan 1, 1967