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By Jack L. Taylor

Single crystals of tungsten grown from powder -metallurgy swaged rod by high-temperative annealing were deformed in tetzsion at temperatures from 2500 to 5000 OF. Orientation of specittzen tensile axis, strained ratrix, and defortnation bands was determined optically by reflections from {110} etch pits. Slip traces meve analyzed and slip directiorz determined. Results indicate that {110}(111) , {112){111}. and {123}{111} type slip occur in tungsten over the terpe,atuve rutge investigated. Slip is orientation-dependent occuvring on tCuzt cowzbitzation oj slip plane and direction which has the highest critical resolved shear stvess. Overshooting appears to be a general occurrence between 2500' and 5000°F. Dejornatiotz bands show rotation in a directiorz opposite to the yotation of tire tensile axis. DEFORMATION in bcc metals has been reviewed by Maddin and Chen,' Keh and eissman,' and most recently by Nabarro, Basinski, and olt. From these reviews it is apparent that some disagreement exists concerning the crystallography of plastic deformation in bcc metals. There is evidence of noncrystallo-graphic slip, the crystal slipping on or near a noncrys-tallographic plane in the (111) zone for which the resolved shear stress is greatest. There is also evidence to indicate that crystallographic slip occurs in the planes of the same zone. On the other hand, there is agreement that the close-packed direction ( 111) is the slip direction in bcc metals. Further, in pure bcc metals4 and alloys the operative crystallographic slip systems are strongly dependent on temperature. Both crystallographic and noncrystallographic slip have been reportede8 in tungsten, a group VIA bcc metal. The number of slip families which operate in the case of crystallographic slip, however, has been in question. The earliest study by oucher' of single-crystal tungsten tested at temperatures of 1800 to 5000°F led to the conclusion that only {112)( 111) type slip operated. Raymond and eumann recently reached the same conclusion studying deformation by rolling of plasma-flame single crystals at 1800°F; however, only [loo] and [110] orientations were studied. Work at high temperatures by Leber and Pughs on tungsten and Chen and Maddin9 on molybdenum suggests that conjugate slip on nonparallel (110) planes may account for the slip on (112) and (123) planes found by others working with bcc metals. The present paper presents evidence of three families or modes of slip in tungsten in the temperature EXPERIMENTAL PROCEDURE Material. Standard microtensile specimens, 0.160 in. diam by 0.640 in. gage length, were ground from commercial powder-metallurgy swaged tungsten rod, type MK. Specimens were heated for 10 min at 5150°F or 6 hr at 5400°F in vacuum of 1 x 105 Torr or less to produce single crystals. At the lower temperature an average of two out of seven specimens heated in a group developed single crystals throughout the specimen length as shown in Fig. 1, the rest remaining wholly poly crystalline. At the higher temperature, three or four out of seven specimens became single crystal. Other than to note that Laue X-ray photographs generally showed sharp, well-defined spots, no attempt was made to assess crystal perfection or measure dislocation density. Two tungsten single crystals grown from the melt by the plasma-arc process were also used for this study.

Jan 1, 1967

By M. H. Childs, K. E. Merklin

Blast furnace feed specifications are being revolutionized because of the large increase in iron pellet production from low-grade ores of the Lake Superior region. Recent laboratory findings aimed at a better understanding of factors influencing the physical quality of pellets produced from taconite concentrates are reviewed. Tests for determining better product quality, the effects of additives, and production factors are discussed. The current revolution in specifications for blast furnace feed is typified to a great extent by the recent tremendous growth in iron ore pellet production from low grade ores of the Lake Superior region. Indeed, pellets are responsible, at least in part, for many of the stringent new requirements that are being placed on the suppliers of furnace raw materials. As the tonnage of pellets going to the steel mills increases, more and more attention is being turned to the detailed characteristics that make this product an ideal blast furnace feed. Control of quality in pellets is similar to that of any other product. A basic understanding of the factors that are encountered in their production, from the crude ore through to the finished product, is required, along with careful process supervision and frequent quality checks. Normally, chemical grade is not a problem. This usually can be controlled within the desired specifications by minor operating variations in the con- centrator. While future changes in requirements may result in the need for self-fluxing pellets1 or other chemical changes, today's quality demands center primarily around the physical characteristics of the pellets. It is in this area that many of the recent laboratory studies have proven helpful to the operating plants. A better understanding of the physical factors involved in pelletizing has provided the basis for a continuing program of quality improvement. Tigerschiold and Ilmoni2 and Cooke with various associates are responsible for the development of much of the basic understanding of the pelletiz-ing process. These earlier findings have served as a most useful background for this work. LABORATORY PROCEDURES Magnetite concentrates produced from eastern Mesabi Range magnetic taconites were used for all of the work reported herein. The sizing and chemical analysis of a random sample are shown in Table t Additives usually are mixed with the concentrates in taconite plants before pelletizing to improve the strength characteristics of the unfired balls. Ben-tonite, soda ash, and coal are in common use. The bentonite used in these studies was of the Wyoming sodium type; the soda ash was a standard commercia1 brand. Anthrafines were used where coal was called for. The procedure for making batches of balls at the Hibbing Laboratory is as follows: In an especially designed mulling equipment 2800 g of dry ore are mixed for 10 min with the desired additives. Water is added and mixing continued for 1 1/2 min. The charge is removed from the muller and put through a mechanical shredder to break down any lumps that may have formed. sixty previously formed seed balls are placed in the balling drum, which is in fact a 6 x 16-in. diam airplane tire turning at 53 Wm. Two thousand grams of the shredded concentrate and additive mix are fed by hand into the tire at a con-

Jan 1, 1961

By A. T. Tye

WHEN the roughing tables operated in 1923 were abandoned, all the coarse iron pyrite for-merly removed by the tables had to be ground to flotation size, which caused an increased power con-sumption of 2 kw.-hr. per ton. Recently, by increasing the tonnage, this has been reduced to a total of 16.6 kw.-hr. per ton. The cost of repairs has been slightly reduced by using an alkaline circuit instead of the acid mine water used in 1923. Other economies from elim-inating roughing tables and the finishing tables have more than compensated for the extra grinding and the total costs have remained practically the same, until the first part of 1927, when, with increased tonnage, the total cost has decreased to 72 cents and the repair cost to 9 cents. In 1923, with a combined gravity and bulk flotation flowsheet, the grade of concentrate was only 4.38 per cent copper. With preferential flotation this has in-creased to over 17 per cent copper. The tailing has decreased from 0.29 per cent -copper to 0.18 per cent. The copper recovery, instead of decreasing; as might be expected, has increased from 87.4 per cent to, 91.5 per cent. The silver recovery has also increased from 88

Jan 8, 1927

By J. R. Linney

APPROXIMATELY 5,788,000 long tons of crude ore was produced by the Eastern magnetite industry in 1946, or a drop of 26 per cent compared -with 1945. Decrease in production -throughout the industry varied from :8 per cent for the mine with the lowest reduction to 49 per cent for the mine -with the highest reduction. At the Chateaugay mine, operated by :the Republic Steel Corp. at Lyon Mountain, N. Y., 426,900 long tons of crude ,ore was produced, yielding 129,500 long tons of concentrates or a reduction of 46 per cent compared with the previous year. Owing to a strike the mine was closed down from Jan. 21 to July 29. At the Mineville mines, also operated by Republic Steel, output was 755,000 long tons of crude ore or a reduction of 49 per cent compared with 1945. The yield from the crude ore production consisted of 51,500 long tons of lump ore and 380,000 long tons of concentrates. The Mineville plant did not operate from March 17 through July 28, on account of the strike. The Fisher Hill mine, which produced 93,000 long tons of crude ore, included in the above figures, has not operated since March 17, 1946.

Jan 1, 1947

By M. W. Clegg

The application of the Laplace transformation to problems in the flow of compressible fluids in porous media has provided a large number of exact solutions. For plane radial flow, however, these solutions are either complex integrals or infinite series and are of little value to the field engineer. In the case of production at constant well pressure, the available approximate solutions me valid for large times only. In this paper it is shown that an approximate inversion formula for the Laplace transform, developed for the solution of viscoelastic problems, is applicable to radial flow problems and provides simple analytical solutions to constant terminal pressure problems. The method may be used to obtain approximate solutions to many problems, including media with radial permeability discontinuities, multi-layer formations and pressure buildup in wells after shut-in. The results are compared with the few available computer solutions as well as the large time solutions, and it is shown that this approximate method greatly extends the time interval over which a simple analytical solution is acceptable. INTRODUCTION The study of transient problems in the flow of fluids through porous media has benefited greatly from the application of transform methods. The use of the Laplace transformation for solving parabolic equations has been widely discussed in the field of heat conduction and diffusion as well as in the petroleum literature. Removal of the time variable with the Laplace transformation generally reduces the problem to a boundary value problem which may be solved by standard techniques. A much more formidable problem then faces the engineer, however, for frequently the transform does not possess a simple inverse. The result is that the general inversion integral must be used and this leads to either an infinite integral or an infinite series, both of which are difficult to handle from a computational standpoint. Asymptotic approximations for the inverse have been known for some time and these yield approximate inverse functions that are valid for very large or very small times — but frequently the times of interest lie somewhere between these two extremes. Therefore, some acceptable approximation valid over a larger interval of time is desirable. During the past few years a number of methods for achieving this have been developed and some of these are discussed briefly in this paper. The relative merits of the various methods are not evaluated here, but some general conclusions reached by other authors are given. One of these methods has been applied to problems associated with the radial flow of compressible liquids to producing wells. In the case of production at constant well pressure, the method leads to simple analytical solutions for a number of standard problems; e.g., homogeneous formation, permeability discontinuities, pressure buildup. These solutions greatly extend the range of validity of the asymptotic ones (valid for large times only) and should be of value in studying the behavior of wells producing under constant pressure conditions. METHOD FOR THE APPROXIMATE INVERSION OF LAPLACE TRANSFORMS Much of the work that has been done on the approximate inversion of Laplace transforms has originated in viscoelastic problems. Apart from the asymptotic approximations,1 one of the first approximate methods was due to Alfrey.2 If (s) is the Laplace transform of f(t) defined by

Members whose deaths were reported from Apr. 5, 1920, to Apr. 9, 1921. Elected Died 1916 ALLAN, FERGUS L 1920 1916 ATKINSON, CHESTER 1921 1920 BARBERENA, RAUL R 1920 1918 BARKER, F. L 1920 1914 BELL, D. A. S 1920 1920 BREWSTER, GEORGE AUGUSTUS 1920 1917 BRIGHAM, EDMUND D 1921 1915 CARROLL, D. J 1920 1897 CHAPMAN, ROBERT H 1920 1919 COOPER, W. G 1920 1918 CRITCHLOW, EDWARD B 1920 1917 CURTIS, WILLIAM L 1920 1893 DARSIE, JAMES 1920 1892 DELANO, WARREN 1920 1877 DEWEY, FREDERIC P 1921 1917 ENEBO, BENJAMIN A 1920 1896 FAWCETT, JAMES H 1920 1906 FRASER, A LEXANDER J . 1920 1889 GARLICHS, HERMAN 1921 1893 GILLET, LORENZO M 1920 1886 HALDEMAN, HORACE L 1920 1914 HALL, HARRY E 1919 1905 CHART, C. R 1920 1906 HART, PHILIP E 1920 1877 HARTRANFT, SAMUEL S 1921 1914 HICKMAN, E C 1920 1919 || INMAN, WILLIAM ELLIOTT 1921 1920 JETER, J. TINSLEY 1920 1918 JOHNSON, CHARLES W 1920 1916 JOHNSON, FRANK E 1920 1913 KING, FREDERICK G 1921 1887 KNAPP, GEORGE F 1920 1902 LAMB, RICHARD 1920 1880 LANE, J. S 1920 1920 LECKIE, WILLIAM 1920 1887 LEVAT, DAVID 1921 1882 LAWRENCE, BENJAMIN B 1918 1916 LEYNER, J GEORGE 1920 1871 LYMAN, BENJAMIN S 1920 1903 MCCHRYSTAL, JOHN H1920

Jan 1, 1923

APPROXIMATELY 90 per cent of the steel that is melted and refined in the United States and poured into ingots is made in basic open-hearth furnaces, as shown in Table 1-1. The annual ingot capacity of the steel industry reported January 1, 1950, by the American Iron and Steel Institute3* was 99,040,160 tons, of which the basic open-hearth process accounted for 85,896,580 tons, 86.7 per cent of the .total. The capacity of the individual furnaces varies over a wide range, a large majority falling within limits of 50 to 200 tons (Fig 1-1). Most of the units constructed [ ] since 1942 are in the larger size groups, between 175 and 225 tons capacity.

Jan 1, 1964

By T. N. Andersen, K. J. Richards, C. N. Wright

The kinetics of the important reactions occurring in an electrowinning cell have been determined. This information has been used to quantify relationships between the operating variables of current density, solution composition, agitation, and temperature and the resulting current efficiency and deposit quality. Analysis of these results has shown (1) the importance of dissolved iron in determining maximum possible current efficiency and corrosion rate at the cathode suspension loop, (2) the role of agitation, current density, inert salts and temperature in*determining deposit quality and (3) the effects of non-uniformity in the hydrodynamic conditions from the bottom to top of the cell. The significance of the results of this study to the operation of a commercial plant directly treating acid leach solutions is discussed.

Jan 1, 1973

NEW MEMBERS The following list comprises the names of those persons who became members during the period July 10 to Aug. 10, 1914: Members BAKER, FRED SHERMAN Tabowie, Unsan, Korea. BISSET, DANIEL GEORGE, Engr., 142 3d Ave., N. W., Edmonton So., Alberta, Canada.. BRANDT, MAURICE SHELDON, Chief Engr., White Eagle Mining & Milling Co., Box 298, Boulder, Colo. BROWNING, EDWARD, Min. Engr., Asst. to Supt., Cornwall Ore Bank Co., Cornwall, Pa. CASTLETON, WILLIAM ARTHUR, Mill Supt., East Butte Copper Mining Co., Butte, Mont. CHIDESTER, WALTER BARCLAY, Min. Engr., Care Mother Lode Mine, Greenwood, B. C., Canada. CLARK, EDWARD HARDY Mgr.,.Hearst Estate, 15 Broad St., New York, N. Y. CLARK, FREDERICK P., Chief Chem., International Lead Refining Co., East Chicago, Ind.

Jan 9, 1914

By R. E. Holmes, T. W. Leland

The solution to the unsteady-state mass- and heat-transfer equations describing the adsorption of a dilute component from a gas stream flowing through a packed bed is readily applicable to the design of hydrocarbon recovery units. The solution to these equations depends on the assumption of a linear equilibrium equation to relate concentrations on the surface to concentrations in the gas. This assumption is shown to be justifiable for components which are very dilute in the gas stream. This approach permits the prediction of the effects of bed shape and size, cycle time, and gas mass velocity on the recovery of each component. It also allows the time and gas flow rate needed for regeneration to be determined. The equations involve a constant for each component and another constant characterized by the type of adsorbent. These constants must be evaluated from operating data. Values of these constants determined for silica gel are presented. This paper points out the type of experitrrental data needed for a thorough design of hydrocarbon adsorption units. INTRODUCTION The growing importance of adsorption processes to recover hydrocarbons from natural-gas streams has created an urgent need for better methods to design and predict the performance of these processes. Since the original use of solid adsorbents in natural-gas processing was for dehydration, most of the current design methods for hydrocarbon recovery re extensions of those developed earlier for dehydration. These methods are based on an adsorptivity or bed loading factor defined as the amount of a particular component adsorbed per unit weight or per unit volume of the packed bed. The recovery of a given component is then expressed as an empirical function of its adsorptivity on a given adsorbent. In spite of the simplicity and initial utility of these methods, they are not completely satisfactory in that they do not predict the effect of the dimensions of the bed in relation to flow rate and cycle time, and do not predict the distribution of various components along the length of the bed. It is possible, however, to make a considerable improvement in the design of these processes by applying the basic equations of mass and heat transfer applicable to gases containing small concentrations of adsorbing components flowing through granular beds. These equations have been developed and solved by Anzelius,' Furnas,% nd Hougen and Marshall." where G = mass velocity of the inert constituents (assumed to be methane), lb/hr-sq ft, y = weight of an adsorbing component in the gas per unit weight of inert, lb of a given constituent per lb of methane, x = bed length, ft, p, = packed bed density, lb/cu ft, P, = gas density, Ib/cu ft, f = void fraction in the bed, t = time, hours, and w = weight of a given component adsorbed per unit weight of adsorbate free solid, Ib/lb pure adsorbent. The term on the left side of Eq. 1 represents the flow rate per unit bed volume of a component entering less the flow rate per unit bed volume of that component leaving the differential bed length. The terms on the right side represent, respectively, the accumulation rates per unit bed volume on the solid and in the gas phase within the differential bed section. The last term is negligible for this application since pgfv is quite small in comparison with p, and G. The partial differential is determined by the mass-transfer rate between gas and solid in the differential section.

By C. V. O. Hughes

Florida phosphate operations are unique in the ways standard mining equipment is made to meet specialized problems. Hydraulic mining and transportation has evolved in meeting three such special problems: 1) surface mining of a shallow, poorly consolidated but wet material; 2) high pro¬duction rates, necessary because of low prices for phosphate rock in a highly competitive market; and 3) preparation of the value-bearing rock, or matrix, for washing and flotation. The magnitude of the problems is better appreciated if the reader understands the size of operations in the area. The Florida phosphate field produces and ships about 10 million tons per year of phosphate rock. All of this has to be concentrated to its shipping grade, either by scrubbing and screening or by flotation.

Jan 1, 1956

By Dan E. Lewis, William E. Saegart

Similarities of certain geologic and mineralogic parameters are recognized among the various Philippine porphyry copper deposits. Lowell and Guilbert3 described a model of the typical porphyry copper deposit as the result of comparing numerous Western Hemisphere occurrences. Many of the characteristics of the Philippine porphyry copper deposits differ from the model developed by Lowell and Guilbert. A model of the typical porphyry copper deposit is presented and the characteristics of the Philippine model are compared with those of the Western Hemisphere model. Estimated Philippine copper production in 1975 was 242 446 mt. The total in 1948 was 2091 mt. This represents a 116-fold increase in copper production during the 28-yr period. The Philippines now rank seventh in total world production of copper.

Jan 1, 1978

By F. H. Willcox

THE CHAIRMAN (HENRY D. HIBBARD, Plainfield, N. J.).-This paper is timely because of the changed conditions due to the great war, but apparently its scope is limited to oxidation process steels. Referring to the four numbered observations on page 199: No. 1 seems to ignore Johnson's discoveries about oxygen in cast iron. No. 2 ignores crucible steel. No. 3 ignores red short steel containing enough gas solvents to make it solid, while No. 4 assumes that a deoxidizer is necessarily a gas decomposer or solvent and vice versa, which it not always is. From these observations it is deduced. that the only hole-forming gas in steel is an oxide of carbon (CO presumably is meant), which is not true.

Jan 4, 1917

By P. Somasundaran

An experimental and theoretical treatment of the depressing effect of inorganic electrolytes on the amine flotation of quartz is presented. Experimental data obtained for the amine flotation of quartz as a function of pH with potassium nitrate as depressant was used to test the models for the effectiveness of inorganic ions as depressants. The validity of commonly used assumptions are examined. The surface tension data obtained for dodecylammonium acetate solutions as a function of KNO3, concentration indicated that the collector adsorption on bubble cannot be neglected in the treatments, since this adsorption changes significantly with the addition of the inorganic electrolyte. It also indicated the possibility of significant changes in the specific adsorption potential of the collector occurring with the addition of inorganic electrolytes.

Jan 1, 1975

By William Price

DURING the past three or four years, the fabricators of silicon-bronze alloys have endeavored to induce risers of phosphor bronze to use instead the silicon-bronze alloys, claiming that the silicon bronzes are superior to the phosphor bronzes for switches and springs, or where high fatigue resistance is desired. This paper gives the results of tests comparing several phosphor bronzes with a 3 per cent silicon bronze and a copper-nickel-tin alloy (Adnic), all processed by the Scovill Manufacturing Co. So far as the authors are aware, sheet-metal fatigue tests have not been made on any of the alloys included in this report, except on one phosphor bronze, material C, Table 1, which was tested by Townsend and Greenall1.

Jan 1, 1937

By Olin G. Bell

During the year 1928 ten new producing areas have been discovered and several extensions in oil and gas fields have been found in southwestern Texas. This year, however, will reveal itself as one of small profits in spite of considerable increase in production for the area as a whole over the previous years. At the beginning of 1928 the fields in this area (Fig. 1) were producing a daily average of 7500 bbl. from 730 wells, whereas at the close of the year the daily average had increased to approximately 14,000 bbl. from 827 wells. Production for the year was 3,453,938 bbl. The total oil produced in Southwest Texas since its discovery has been 16,955,-388 barrels. (Table 1.)

Jan 1, 1929

SULFURIC ACID U.S. 4,070,260 - Sulfuric acid leaching of willemite, hemimorphite, or other zinc silicate ore. Ore is leached with at least a stoichiometric amount of a IN to 6N sulfuric acid solution at a temperature near its boiling point to form a gelatinous mass of hydrated silica and zinc sulfate, the water in the mass partially evaporated to crystallize all of the silica, the mass treated with hot water to dissolve substantially all of the zinc sulfate, the suspension filtered, and zinc values recovered from the filtrate by electrolysis. N. Dreulle, assigned to Compagnie Royale Asturienne des Mines. Jan. 24, 1978. 3 pp. (204-119). Filed: 2-10-76 (656,966) . Priority: France, 2-14-75 (75/04594) .

Jan 1, 1979

By Carl H. Schmuck

The terms "cable bolting," "extended ground support," and "grouted cable" are synonymous, and they have been popping up with much more regularity in the mining engineer s vocabulary. In simplest terms, lengths of u itensioned cable up to 18.3 m (60 ft) are grouted in drill holes prior to mining. This permits radical departures from mining practices that rely on conventional rock reinforcement. For example, by placing a pattern of cable bolts in the back of an open stope, ore can be mined in successive slices. After each slice is taken the protruding cable; are simply cut off and mining proceeds. When about 4.6 m (15 ft) of reinforced back remains, a crew places a new par tern of cable bolts in the ore.

Jan 12, 1979

By V. Vahatalo, E. Hakapaa, H. Tanner

Recently modernized, the surface plant of the Outokumpu mine in Finland incorporates a number of ideas meriting close scrutiny from this side of the Atlantic. The mining methods make extensive use of concrete in some unusual ways. Design of the headframe and surface plant represents the latest thinking of European engineers and includes an integral Koepe hoist. The deposit is in eastern Finland, province of North Karelia, 30 miles west northwest of Joensuu and at 60'44' N, latitude. Pyrrhotite, pyrite, chalcopyrite, and sphalerite mineralization occurs in a shear zone in quartzite near a body of serpentinite. Two lenses have a total length over 12.000 ft, with remaining reserves of the 3 to 4 pct Cu ore estimated at about 15 million metric tons.

Jul 1, 1955

By John E. Willson, Ben L. Seegmiller

A portable electronic instrument was designed and constructed to detect unknown stress magnitudes in rocks. The principle used to detect stress is based on the propagation velocity method. This method allows the stress in a rock subjected to a load of unknown magnitude to be determined, provided that the wave velocity-stress relationship for similar rock is known. This is accomplished by measuring the travel time of longitudinal mechanical waves passing between two points a set distance apart in a rock. The velocity of the wave is calculated and the stress determined from the wave velocity-stress relationship. If the sending and receiving transducer spacing is constant, a time vs. stress relationship rather than the velocity-stress relationship may be used. The method is nondestructive and tests can be made without drilling or otherwise disturbing the rocks. The first studies undertaken in the United States to determine stress in rocks using propagation velocity techniques were reported by Obert1,2 in 1939 and 1940. The Soviet Union first reported using propagation methods to study rock pressures in 1951.8 Success of the method led to the development of a pulse-type ultrasonic seismoscope4 in 1953. Using this instrument, Ivanov and Betaneli5,6 in 1963 succeeded in devising and testing under field conditions a method of investigating coal pillar stresses. In 1967 Osipova7 reported results of similar studies in the Nakhichevan salt mines. In France, Tincelin8 has used the propagation velocity method to study the stress distribution in iron ore pillars. Uhlmann9 has investigated stresses in salt and potash pillars in Germany, using velocity techniques. Determination of uniaxial stress by propagation velocity methods is limited to rocks which have readily detectable wave velocity-stress variations. The present stress detection instrument is restricted in application to rocks which have a velocity change under stress of at least 300 fps. Examples of rocks which meet this requirement are sandstones, coal, and possibly some limestones. Testing of this instrument was limited to a laboratory study and the results may or may not be indicative of what would be found in a field test. A program of field experiments to study the feasibility of using this instrument to determine mine pillar and tunnel stresses is in progress. Instrument Design The instrument has two main components: A probe and a control-display unit. The probe is a hand-held device to which two identical rodlike transducers are rigidly mounted. Coaxial cable connects the probe to the control-display unit which is mounted in an enclosed carrying case measuring 7 % x 9 x 13 in. The instrument is designed so it may be carried and operated by one man. Weight of the probe and enclosed control-display unit is approximately 20.1b. The probe consists of two transducers identical in construction. One transducer is used to convert electronic pulses to mechanical waves and transmit these waves into a rock. The other detects the transmitted waves in the rock and converts them back into electronic signals. The basic element in both transducers is a piezoelectric crystal. The crystal is a disk made of lead titanate zirconate and has a natural resonant frequency of 400 kHz ±1% in the thickness mode. A schematic of one of the two identical transducing elements is shown in [Fig. 1.] A spacing of 6 in. between sending and receiving transducers has been found to be most satisfactory. The control-display unit consists of a pulse generator and a 1-in. oscilloscope. Various electronic devices are used for the power supply, amplification, and calibration. The amplitude of the square wave from the pulse generator can be continuously varied between 0 and +20 vdc. Pulse width can be set at 1, 2, 3, or 4 µsec. The repetition rate of the pulse can have the following values: 50, 75, 100, 150, 200, 250, 300, 400, 500, 750, and 1000 Hz. The oscilloscope delay system allows the travel time of the longitudinal wave passing through a rock to be measured to an accuracy ±0.1 µsec in the range from 0 to 995 µsec. Fig. 2 is a schematic of the various electronic sections in the control-display unit. Laboratory Testing The first step in using the instrument is to develop a velocity-stress or a time-stress curve for the par-

Jan 1, 1972