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By Francis M. Walters, Irwin R. Kramer

The substitution of cobalt for part of the nickel in Invar was found by P. H. Brace1 to lower the coefficient 01 expansion. Scott1 extended the use of cobalt to alloys of higher inflection temperatures. Such alloys have a larger temperature range of low expansion than those without cobalt, and their use up to 400' or 500°C. offers decided advantages in certain applications. However, it has been found that the iron-nickel-cobalt alloys are not stable in this temperature range. Experimental Methods Two methods were used in studying the stability of the low-expansion iron -nickel-cobalt alloys. Dilatometer specimens were held at 480°C. for 9 months and the change in expansion characteristics was dctcr- mined. Filings were held for about 2 months at various temperatures and the change in structure was determined by X-ray diffraction. As shown by Table I, the alloys studied covered a wide range in nickel plus cobalt content (which determines the inflection temperature) as well as some variation in the ratio of nickel to iron (which controls the temperature of the gamma to alpha transformation). Included also are alloys containing carbon and vanadium, carbon and titanium and three with various amounts of copper. The alloys were melted in a high-frequency induction furnace with a magnesia crucible, using ingot iron, electrolytic nickel and commercial cobalt. Fifteen-pound heats were cast into iron molds after deoxidizing with silicon, or

Jan 1, 1942

By Francis M. Walters, Irwin R. Kramer

The substitution of cobalt for part of the nickel in Invar was found by P. H. Brace1 to lower the coefficient 01 expansion. Scott1 extended the use of cobalt to alloys of higher inflection temperatures. Such alloys have a larger temperature range of low expansion than those without cobalt, and their use up to 400' or 500°C. offers decided advantages in certain applications. However, it has been found that the iron-nickel-cobalt alloys are not stable in this temperature range. Experimental Methods Two methods were used in studying the stability of the low-expansion iron -nickel-cobalt alloys. Dilatometer specimens were held at 480°C. for 9 months and the change in expansion characteristics was dctcr- mined. Filings were held for about 2 months at various temperatures and the change in structure was determined by X-ray diffraction. As shown by Table I, the alloys studied covered a wide range in nickel plus cobalt content (which determines the inflection temperature) as well as some variation in the ratio of nickel to iron (which controls the temperature of the gamma to alpha transformation). Included also are alloys containing carbon and vanadium, carbon and titanium and three with various amounts of copper. The alloys were melted in a high-frequency induction furnace with a magnesia crucible, using ingot iron, electrolytic nickel and commercial cobalt. Fifteen-pound heats were cast into iron molds after deoxidizing with silicon, or

Jan 1, 1942

By Robert C. Sutter

In 1958, it became obvious to some of us in the solution mining business that there were certain problems in connection with our sodium chloride brining operations which were industry- wide. These were the types of problems which, while they were important to the safe and economical operation of our salt brining operations, were not such that their solutions would give an individual company a great competitive advantage over his competitor; and since they involve the safe and efficient mining of a natural resource, it was obvious that the answers would, in any event, be shared industry-wide. Since we were dealing with underground solution mining and, consequently, unseen and remotely controlled operations, the problems are formidable and the solutions difficult. While all of us were doing work to improve our operations, none of us could justify the expenditures necessary for basic research in these areas. Consequently, the idea was conceived of research sponsored by many companies with the same problems. In 1960, 11 companies entered into a' formal agreement to jointly support research on a specific problem of sodium chloride solution mining. The project to be undertaken was the development of a method for measuring the size and extent of underground solution cavities in sedimentary salt beds. It was agreed that all research was to be performed by independent research organizations. A part-time consultant or administrator was retained to administer the research contracts and to provide technical advice.

Jan 1, 1966

By C. Augustus Carlow

THE subject which has been allotted to me is so vast and far-reaching that it is impossible to deal adequately with it in the time available. A complete survey would occupy the spare time of any one man for many years, whereas the time available to me is measured in weeks In the circumstances, I have been fortunate in securing the aid of several willing collaborators, and shall endeavor to re present such information as presently exists in published form, examine the situation critically in the light of present-day conditions, and arrive at certain conclusions' which I shall venture to put forward for your consideration No one who has lived through the past 25 or 30 years, and who has witnessed the amazing achievements of recent scientific research, would venture to deny the possibility that new sources of energy-may yet become available, or to prophesy to what extent these may be harnessed to the service of mankind So far as we can see, however, coal, as a source not only of power and heat but also of that wonderful range of derivatives that form the raw materials of so many industrial processes, must continue to play a vital role in our economic life It is the chief mineral fuel, exceeding all other mineral resources in value, production and demand In value coal overshadows the industrial metals, while of the sources of energy-coal, oil, gas and water power-the first named is the most important Thus, for example, in the United States, coal as a fuel (that is, as a source of heat and power) is still predominant, the figures of percentage of

Jan 1, 1947

By B. K. Loveday, N. V. Ramlall

A study was carried out to evaluate various batch flotation models for the recovery of minerals in a UG2 platinum ore. The major minerals in a UG2ore can be grouped as platinum group minerals, chromite, and siliceous gangue. This study also examined the entrainment of minerals during flotation. The models were ranked using statistical methods and an analysis of model-fit residuals. Entrainment parameters obtained from model fitting were evaluated for logic using a simple mineral-to-water ratio versus time plot. The foremost conclusion from the study was the importance of entrainment modelling. The measurement of water recovery increased the size of the data-set, and the inclusion of a simple entrainment model was statistically significant. The overall fit to the data was improved, and the entrainment model provided logical information on the recovery of gangue minerals that were not considered to be floatable.

Jan 1, 2015

By Gherman Pavlovich Nikonov

Results of preliminary research on the use of small diameter water jets at high pressure for cutting rocks has demonstrated the possibility of effective cutting of anthracite. Detailed research has, therefore, been conducted at the Skotchinsky Institute of Mining to study the dynamics and structure of the small water jets and the mechanism by which they cut coal. One of the objects of this research was to obtain data for the design of a machine for cutting rock, based on the same principles as that for cutting coal. The productivity of water jet mining machines depends on the hydro- dynamic parameters of the jet. Therefore, the research on small diameter water jets was directed, initially to a study of the nature of the variation of these parameters, and to obtain a profile of dynamic pressure distribution over the section of the jet. As has been confirmed previously, the required jet pressure (to cut coal) lies in the range of 100 to 500 atmospheres. These pressures were utilized for the research. The diameter of the nozzle was changed as ~follows; 0.97; 1.24; 1.5; 2.17; 2.87; and 3.57 mm. Graphs showing dynamic pressures for each nozzle diameter and varied axial dynamic pressure were obtained over distances ranging from 2 to 70 cm from the nozzle. One of the most important hydrodynamic parameters of a jet, closely related to the dynamics of jet disturbance in air, is the magnitude of the axial dynhmic pressure. A study of the variation in this pressure with increasing distance from the nozzle led to the separation of the jet into three specific parts, which differ from each other not only in the nature of the change in dynamic pressure, but also in structural properties.

Jan 1, 1971

By Wen-Long Cai, A. Frederick Banfield

This paper investigates, through case studies on a porphyry copper and a coal deposit, the differences and relevances between an approximate production schedule approach, i.e., the best case and the worst case schedules and a practical production schedule approach. The comparisons were with regards to: 1) choosing an optimum ultimate pit size, 2) determining processing capacities, 3) selecting 'optimum' cutoff grades, and 4) blending. The comparison criteria was to maximize the project net present value. Conclusions were drawn based on the study results.

Jan 1, 1996

By J. Lehmann, H. Gaye

A brief review of Computational Thermodynamics software concerning the modeling and prediction of reactions involving metals, slags and fluxes is presented. Their application for various steelmaking treatments is discussed. Examples concern phosphorus removal in BOF and EAF, ladle steel desulfurization, and specific treatments for inclusions control in semi-killed or Al-killed carbon and stainless steels.

"Chairman: Mr W. S. GALLAGHERRapporteur: Professor A. M. STARFIELDPapers:Long-term mine production scheduling by G. C. S. BurneAn application of linear programming to investment analysis by A. ErlandssonOptimizing medium-term operational plans for a group of copper mines by M. Splaine, D. C. Atkinson, W. Davison and L. SmithThe simulation of underground stoping and transport operations in gold mining by F. H. Touwen and N. C. JoughinProduction planning is a subject that lies at the interface between the computing centre and mine management. Discus¬sion during this session was thus largely concerned, directly or indirectly, with communication between computing and mining personnel, and as such was relevant to the symposium as a whole.Mr A. Weiss set the tone of this discussion by referring to `user-orientated systems'. He congratulated Mr Burne in this regard, pointing out that his long-term production scheduling program, as a computer system, was similar in approach to the manual system it replaced, and was therefore easily understood by planning engineers. He asked whether the schedule engineer had his 'hands on' the system, to which Mr Burne replied that the engineer did in fact spend several days running alternative schemes through the computer. Mr Weiss commented on the advantage of having terminals on site for this sort of engineer-computer interaction. He also commented on the flexibility of Mr Burne's approach to scheduling and how preferable this was to a one-step optimization package. This was brought home by a question from Mr H. D. Small: Mr Burne's program sometimes found it necessary to temporarily halt an advancing face, and he asked whether the logic of the program could be altered to avoid this (e.g. by suitably slowing down the rate of face advance). Mr Burne replied that it was in fact easier for the planning engineer to sort this problem out manually. The way in which the computer results were presented made it particularly simple for the production engineer to see how to avoid or remedy a stopped face.On the technical side, both Mr Weiss and Mr H. M. Wells questioned Mr Burne on the handling of grade control by his program. From answers by Mr Burne and his colleague Mr K. H. Thomson it emerged that a spot-check on grade every now and then was all that was necessary at Mufulira, and that the idea of actual grade control was more a question of short-term than of long-term planning."

Jan 1, 2014

By Juan Ayza

Dado que la geología económica estudia las materias del reino mineral que el individuo extrae para sus necesidades vitales, el presente texto señala la relación de ciertos minerales (estaño, tunsgteno, antimonio, manganeso, oro, plata, cobre, zinc) de la zona minera sur del Perú, con la geología regional y sus contribuciones económicas a través de personalidades como Balta, Steinmann, Dueffas, Douglas, Bulman, G. Peteraen, Newell, Heim; Newell, Chronic y Roberts; Jenka, Ahlfeld y Bruggen. De acuerdo a este estudio geológico se infiere que tanto el oro y el hierro pertenecen a la costa, así como los yacimientos de plata, plomo y zinc son de la cordillera volcánica, la línea de tungsteno de Cabanillas se encuentra asociada a granitos, los depósitos telegramáticos de cobre, antimonio, mercurio y plata, se encuentran relacionados a líneas tectónicas en la depresión del Titicaca. Asimismo en el yacimiento oriental, tenemos el peri y apomagmáticos de calcopirita, plomo-zinc, plata, plomo-plata, antimonio, oro, tungsteno y estaño. Finalmente, la repartición de zonas mineralizadas responde a dos causas: la asociación a varias clases de intrusiones y la relación directa a distintas categorías de líneas y regiones tectónicas.

Jul 20, 1956

BESIDES air -water, sulphur, salt, coal, and lime-stone are the key nonmetallic raw materials used by the chemical industry and each came in for attention at the AIMF, Industrial Minerals Division meeting at Morgantown. W, Va., Sept. 13 to 15. West Virginia is a growing chemical producing area with sites along the Ohio and Kanawka Rivers being favored because of power, accessibility of raw materials (many in the State), water supply, and transportation.

Jan 10, 1951

By Eric Forssberg, Vigen Zeng

During mechanical grinding high intensity vibration is emitted that contains information on the mill's operating state. Tests, using a laboratory ball mill, studied the influence of operating parameters on the vibration signature. The parameters studied were: mill speed; powder filling; pulp density; grinding period; and pulp temperature. Vibration signals were detected by an accelerometer, amplified by a vibrometer and recorded onto digital audio tape. A digital oscilloscope converted the signals into IBM-compatible data format. Digital signal processing and multivariate data analysis were carried out with specially developed software. The power spectral density was estimated from the time-domain vibration signal. Four new latent variables were used to describe changes in the vibration spectra. A relationship was established between operating parameters and latent variables which could form the basis of a quick and automatic method of monitoring operating parameters in ball mill grinding.

Jan 4, 1993

By Jan E. Nesset, Julie Fournier, Jorge Torrealba, Colin Hardie

"Gas dispersion studies have been used to benchmark and optimize plant flotation performance for more than a decade, although this technology is not as widely in use as it likely should be based on the significant improvements that have been reported. Part of the reason may be a general lack of awareness within the industry of just what these improvements have been. This paper reviews a number of the reported case studies, groups them into categories of improvement, and draws some general conclusions. The paper will be of interest to plant engineers and technology providers seeking new approaches and tools for improving their own and clients’ processes.INTRODUCTIONThe sector of flotation hydrodynamics that is now known as gas dispersion technology, and the corresponding terminology, had its beginnings in the 1980’s and early 1990’s in the laboratories of McGill University where the students of Prof. J.A. Finch and Dr. C. Gomez conducted studies of gas holdup, superficial gas rate and water recovery on laboratory flotation columns (Laplante et al., 1983; Xu et al., 1991;, Banisi and Finch, 1994; Finch et al., 1999; Nesset, 2011). Sensors were developed for gas holdup (eg), gas rate (Jg) and bubble size (Db) distribution (Tavera et al., 1996: Finch et al., 1999; Dahlke et al., 2001; Chen at al., 2001; Hernandez-Aguilar et al, 2002, 2005). The sensor measurements were rapidly adapted for use in mechanical flotation machines in plant environments (Gomez and Finch, 2002; Gomez et al., 2003; Cooper et al, 2004; Torrealba-Vargas et al, 2004; Nesset et al., 2007). Somewhat parallel developments were being conducted by Gorain and colleagues at the University of Queensland’s JKMRC on pilot and industrial flotation machines using the McGill approach but utilizing alternate sensor designs for eg, Jg and Db (Gorain et al., 1997, 1999; Schwarz and Alexander, 2006) to link flotation kinetics to bubble surface area flux (Sb). Early industrial applications were those led by the university teams from McGill (Canada), the JKMRC (Australia) and the University of Santa Maria (Chile) at plants in North and South America, Australia, South Africa, Asia and Europe. Industrial organizations that brought the technology on-board in the early 2000’s included Teck Resources (then Teck Cominco), COREM, Vale (then Inco), Anglo American Platinum. Several of the major flotation cell manufacturers also purchased the McGill bubble viewer technology for their own equipment studies. The sensors have continued to evolve with multiple and continuous measurement of Jg (Torrealba-Vargas and Finch, 2006, Bartolacci et al., 2008), gas holdup by acoustic means (O’Keefe, 2007) and a combined Jg-Db device called the Anglo Bubble Sizer (Harbort and Schwarz, 2010). A review of the gas dispersion technology use and development have been provided by Gomez and Finch (2002), Harbort and Schwarz (2010) and Nesset (2010)."

Jan 1, 2015

By J. Gniel, L. King, C. Gaudin, C. O’Loughlin

"This paper presents some recent advancements in centrifuge modelling, which enable the installation of displacement piles to be performed in-flight while measuring ground responses. Details and results are provided from a series of experiments where 21 full-displacement piles were installed into a sample of consolidated kaolin clay at 40g. The piles were pushed into the sample at a constant rate of penetration, with installation reaction loads and pore pressures measured. Insight into the installation effects of the full-displacement piles was obtained by undertaking in-situ testing pre- and postinstallation of piles. The findings show that centrifuge testing has the potential to play an important role in furthering the current understanding of displacement pile behaviour and installation effects.INTRODUCTIONDisplacement piles and displacement ground improvement columns cause soil to undergo significant distortion and shearing during installation, which alters the soil properties. It is essential to consider these changes in soil properties to estimate the behaviour of pile foundations with higher degree of accuracy. However, the installation effects of displacement piles are widely considered as one of the most difficult geotechnical mechanisms to model, both analytically and numerically, and experimental data is needed to advance the current state of knowledge.Theories, analytical and semi-analytical, have been developed to describe the displacement pile installation process. Randolph et al. (1979) applied the cylindrical Cavity Expansion Method (CEM) to model the installation of a displacement pile in a fine grained cohesive soil. However, cylindrical CEM only considers the field variables in radial coordinates, and hence the soil-pile interface can only be modelled as a frictionless material. Baligh (1985) introduced the Strain Path Method (SPM), which assumes soil flows around the tip of a displacement pile. SPM was shown to model the stress and strain fields, particularly within close proximity to the pile, more accurately compared to the cylindrical CEM. While these methods account for the installation effects of a displacement pile and can be used to estimate a resulting ultimate bearing capacity, they are unable to describe the load-settlement behaviour of such piles. With the added complexity of group effects, existing analytical methods do not provide a means to accurately calculate the ground response to the installation of a group of displacement piles in a cohesive soil.The advancement of computational power, numerical techniques and constitutive models has improved the accuracy of numerical analysis, particularly in regard to modelling pile installation. However, even with advanced techniques, Finite Element Method (FEM) suffers a number of disadvantages due to the large deformations, which results in mesh distortion and tangling. Mesh-free methods such as Discrete Element Method (DEM), Smoothed Particle Hydrodynamics (SPH) and Material Point Method (MPM) are the next generation of computational techniques that are able to deal with large deformation problems. However, these advanced techniques are computationally expensive, complex and yet to be incorporated into commercial packages. Such methods are considered to still be in the development stage and are yet to provide a complete solution to pile installation problems."

Jan 1, 1900

By Gregory M. Molinda

Extremely difficult ground conditions were encountered in the main belt entry in a room and pillar mine in West Virginia. Several generations of supplemental support, including cable bolts, cribbing, and Heintzmann jacks and beams failed to halt roof falls that threatened workers safety and the life of the mine. Polyurethane (PUR) was injected into 27 intersections in the roof and the results were monitored by borehole video camera. The mine had averaged 2-3 falls in the beltway per year and, since the roof injection, no roof falls have occurred. Pre- and post injection monitoring of test holes showed that stability can be achieved without filling all of the existing void spaces. Video logging showed that the project goal of building a beam from 2-6 ft into the roof was successful. Pre-injection monitoring of roof fractures uphole can delineate the zones to target for reinforcement, and avoid pumping PUR into large voids to little effect. Multiple-injection zones can be identified, and the entire intersection drill hole array can be optimized based on knowledge of the fractured zones. In addition, pre-monitoring can prevent excessive hydrofracturing in solid zones. Polyurethane injection is a proven method of rock stabilization in even the weakest, most broken ground. Optimization of the injection design by pre-injection video diagnostics can greatly contribute to the successful and efficient roof stabilization.

The editorial expenses for the preparation of the manuscript of the second edition, as for the first, were provided by grants of the Engineering Foundation and the Open Hearth Steel Committee of the Iron and Steel Division, AIME ; the Seeley W. Mudd Memorial Fund again sponsored the publication of this volume. The companies and research or educational institutions with which the authors, reviewers, and editors are connected also contributed much to the writing and editing of this book through their generous donations of time and travel and office expenses. And finally, the authors and others have given countless hours of their own time with no recompense but the satisfaction of a job well done. In order to give credit to the companies or educational institutions which made it possible for the members of the Editorial Board to devote considerable time to the revision of this book, the names of these members and their affiliations are recorded here as follows W. O. Philbrook, Carnegie Institute of Technology M. B. Bever, Massachusetts Institute of Technology H. B. Emerick, Jones and Laughlin Steel Corporation B. M. Larsen, United States Steel Company A number of individuals suggested desirable changes in the book before rewriting was started. Almost all manuscripts were gone over critically by reviewers, and the resulting criticisms led to the correction of errors and omissions and greatly contributed to the accuracy and completeness of the text. Other people have supplied additional data or illustrations or assisted in other ways. While some of these contributors must remain anonymous because they are not known to the Editors, the cooperation of the following individuals is gratefully acknowledged: R. D. Allen, Republic Steel Corporation, Chicago Isadore Amdur, Massachusetts Institute of Technology Mary Baeyertz, Armour Research Foundation S. P. Bahmer, Republic Steel Corporation, Massillon E. C. Bain and Associates, United States Steel Company, Pittsburgh C. W. Briggs, Steel Founders' Society of America H. W. Briske, Wisconsin Steel Works

Jan 1, 1951

The editorial expenses for the preparation of the manuscript of the second edition, as for the first, were provided by grants of the Engineering Foundation and the Open Hearth Steel Committee of the Iron and Steel Division, AIME ; the Seeley W. Mudd Memorial Fund again sponsored the publication of this volume. The companies and research or educational institutions with which the authors, reviewers, and editors are connected also contributed much to the writing and editing of this book through their generous donations of time and travel and office expenses. And finally, the authors and others have given countless hours of their own time with no recompense but the satisfaction of a job well done. In order to give credit to the companies or educational institutions which made it possible for the members of the Editorial Board to devote considerable time to the revision of this book, the names of these members and their affiliations are recorded here as follows : W. O. Philbrook, Carnegie Institute of Technology M. B. Bever, Massachusetts Institute of Technology H. B. Emerick, Jones and Laughlin Steel Corporation B. M. Larsen, United States Steel Company A number of individuals suggested desirable changes in the book before rewriting was started. Almost all manuscripts were gone over critically by reviewers, and the resulting criticisms led to the correction of errors and omissions and greatly contributed to the accuracy and completeness of the text. Other people have supplied additional data or illustrations or assisted in other ways. While some of these contributors must remain anonymous because they are not known to the Editors, the cooperation of the following individuals is gratefully acknowledged : R. D. Allen, Republic Steel Corporation, Chicago Isadore Amdur, Massachusetts Institute of Technology Mary Baeyertz, Armour Research Foundation S. P. Bahmer, Republic Steel Corporation, Massillon E. C. Bain and Associates, United States Steel Company, Pittsburgh C. W. Briggs, Steel Founders' Society of America H. W. Briske, Wisconsin Steel Works

Jan 1, 1964

By R. Boom, K. C. Mills, S. Riaz

This paper details the recent trends in slag-related research from 1999 to 2003. The trends in thefollowing are outlined: • Annual publication rate • Geographical origin of the work • Nature of the research (e.g. thermodynamics, kinetics) • Nature of the slag studied. This study has revealed that slag research in the USA and Europe has decreased to about a half over the last 20 years and that there has been a significant decrease in Japanese research in this area in recent years. However, these decreases have been offset by significant increases in Chinese and Korean research activity. There has been a significant increase in the amount of work carried out on the recycling and environmental aspects of slags in recent years.

Jan 1, 2004

By Deepak Vidyarthi

This paper deals with various measures adopted in protecting a conveyor duct (named after a Conveyor Belt that was numbered as ‘02’) housing a 1600 mm (63 inches) belt conveyor system in a large, heavily mechanized open cast iron ore mine, producing about 20.0 million tones of ore per annum.

Jan 1, 2008

By F. D. Rosi

The slip and twinning behavior in extended titanium crystals were studied in some detail. The formation and appearance of coarse kink bands are discussed. Their crystallographic geometry was determined by X-ray analysis. A phenomenological interpretation of the complexities in kink band development is also presented. The critical resolved shear stress, coefficient of shear hardening, and plane of fracture were determined for several crystals extended at room temperature. THE slip and twinning elements observed in the room-temperature deformation of titanium were enumerated in a previous paper1 in which considerations were advanced regarding the nature and selection of these elements and their effect on the known mechanical properties of this metal. The present study concerns the crystallographic, microscopic, and mechanical aspects of flow in relation to the slip and twinning elements, and includes a prediction of slip systems, nature of slip and twin markings, inhomogeneities of plastic flow, and stress-strain characteristics. Unless otherwise noted, arc-melted titanium sponge (99.77 pct) was used in these experiments. The method of production of crystals, their dimensions, and the surface preparation for micrographic examination have been reported.&apos; For obtaining stress-strain characteristics, only those crystals which traversed the entire width of the specimen and were at least 8 mm in length were used. Tensile deformation of the crystals was performed with conventional grips for sheet specimens and a constant-stress loading beam, designed after the method of Andrade and Chalmers.&apos; The specimens were loaded by allowing sand to flow from a reservoir into a bucket suspended from the longer end of a balanced 6:1 lever arm at a rate controlled to load the specimen approximately 2 kg per min. Strain measurements were made using the Baldwin SR-4, bonded, resistance-wire strain gage, Type A-8, which permitted a reading accuracy of 2 microinches per inch. The formulas used in the evaluation of shear stress and shear strain, as in deriving the coefficient of shear hardening, are given by Schmid and Boasv n terms of the original orientation and change in length of the crystal. For calculating the critical resolved shear stress, the standard equation was used. The crystallographic nature of the unpredictable slip observed in a number of specimens was determined by the single-surface X-ray method of analysis as described in ref. 1. Experimental Results Prediction of Slip System: It was reported&apos; that room temperature slip in titanium takes place predominantly on {10i0} and in a <1120> direction, giving three potential slip systems. Hence, it should be possible to predict the operative primary system in the manner used by Taylor and Elam&apos; for alu- minum (i.e., the one with the greatest component of shear stress in the direction of slip). The stereo-graphic construction in Fig. 1 shows that this is true. In all cases, slip was found to occur initially on the (0110) plane and, in a number of cases, in the [21f0] direction. (The direction of slip was not determined for all orientations.) It follows that duplex slip can be expected when two slip systems are geometrically equally favorable for slip, as demonstrated in Fig. 2. In both crystals slip took place simultaneously on the (1700) and (olio) prismatic planes, as indicated by Fig. 2a and b. In the case of crystal B the movement of the specimen axis with increasing extension was toward the (10i0) direction, which represents the stable end orientation resulting from alternate slip on the [2ii0] and [1120] directions. This is analogous to the duplex slip process in face-centered cubic metals." Unpredictable Slip: In a number of crystals whose orientations were well within the operation of a single slip system, secondary slip occurred on planes not predicted by the criterion of maximum shear stress. Examples are shown in Fig. 3. In addition to

Jan 1, 1955