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By C. H. Mathewson

CONSIDERABLE progress has been made during the last few years in analyzing the action of plastic deformation in metallic crystals. This is due largely to the development of X-ray spectrographic methods for studying changes in the orientation of single crystals, or of conglomerates, as they occur during the process of plastic deformation, but partly to the widespread knowledge of suitable technique for preparing large (single or variously combined) crystals for direct crystallographic observation under stress or in various conditions of strain. These two methods of studying changes in the crystalline structure of metals may of course be used in conjunction with features of mutual support, but unfortunately the advantage of direct crystallographic observation is lost when we proceed to the study of severely cold-worked structures, owing to the occurrence of real or apparent crystalline discontinuities which become more and more complicated as the amount of plastic action increases. Furthermore, the X-ray methods do not appear to be adequate, at least in their present stage of development, to fix definitely the character of structural alteration in the parent crystal lattice by plastic deformation. The principal question at issue concerns the nature of the crystalline particles that remain after plastic deformation. These are generally known in our American metallurgical literature as crystalline fragments,' and they seem, indeed, to diffract as individuals causing the Hull pattern of a severely cold-worked metal to resemble the pattern of a fine powder,2 with certain features of preferred orientation among the particles deter- mined by the manner and intensity of cold working. We must freely concede that there are conceptions of lattice alteration, apart from that of simple fragmentation, which would account for an increasing number of lattice positions according to X-ray spectrographic observation as the degree of deformation increased.

Jan 1, 1927

By Walter R. Hibbard

THE increased strength of a polycrystal-line metallic aggregate compared with that of its individual crystals generally has been associated with complex stress distributions at the grain boundaries resulting from atomic irregularity between grains. This disregistry, together with the necessity for adjacent crystals to deform 'compatibly regardless of the single crystal crystallographic strain mechanism, complicates this mechanism so as to increase the metal's resistance to deformation. Although Taylor1 has shown from purely mechanical considerations the requirement for at least five active slip systems to absorb the complexities during the homogeneous deformation of polycrystalline face-centered cubic metals, experimental studies by Barrett and Levenson2 indicate that this is feasible only in a qualitative sense because of deviations from homogeneous deformation. Seitz and Read in their review3 state: "Unfortunately . . . present knowledge of the grain boundary influence is not sufficient to complement the work in single crystals and provide us with a good foundation for treating polycrystals." The purpose of this investigation was to attempt to clarify the gap between single crystals and crystalline aggregates by an analysis of the effects of deformational stresses. Some of the results were described by C. H. Mathewson in his 1943 Campbell Memorial Lecture.21 PREVIOUS INVESTIGATIONS Since the performance of single crystals deformed under pure stresses has been relatively thoroughly investigated, the most significant researches are concerned primarily with deviations from single crystal behavior of large grained specimens. Qualitative grain boundary effects involving the observed amount of slip were reported by Carpenter and Elam5 in 1921. Individual crystals in a two or three grained aluminum specimen deformed by tension acted in the normal manner described by Taylor and Elam4 except for marked modifications at the grain boundaries. There the power to withstand deformation was considerably increased, leaving a ridge on the specimen where decreased slip occurred, often noticeable 34 in: from the boundary. Adcock,6 Yamaguchi,7 Seumel,8 Hirst9 and others have also reported this phenomenon as a qualitative trend. Yet attempts by O'Neill10 and Ljunggren11 to measure a difference in hardness at grain boundaries in undeformed specimens were unsuccessful. Miller12 measured quantitatively the reduction in slip near the boundary between the single crystal and polycrystalline areas of zinc specimens. These effects consisted of two parts: I. Next to the polycrystalline interface the distribution of stresses was so altered

Jan 1, 1948

By J. T. Norton

As cold working is an important feature in a great many of the fabricating processes now applied, this paper presents some ideas of the nature and results of the plastic deformation produced in this operation. The art of manufacturing metal for practical uses is very old and has undergone very great development. The science of metals has also developed very rapidly recently and the various processes to which ,metals are submitted are much better understood now than they were even a short time ago. All the knowledge that can be obtained on this subject is useful because it promotes efficiency in converting metal into finished articles. ATOMIC ARRANGEMENT IN CRYSTALS In the solid state all metals are crystalline. The atoms are arranged in, a definite symmetrical configuration, which is repeated at regular intervals, and thereby defines what we may term a lattice. Presumably . the atoms exist as positive ions. The dissociated electrons place themselves between groups of positive ions, and thus define a second lattice, an "electron lattice." From such a point of view, the crystalline forces which hold a metal together are the electrostatic attractions between positive ions and negative electrons. The particular type of lattice into which a metal crystallizes depends on the number of these lattice electrons given up by each atom, and is thus connected very closely with the chemical valence of the metal.

Jan 12, 1926

By J. T., Norton

As cold working is an important feature in a great many of the fabricating processes now applied, this paper presents some ideas on the nature and results of the plastic deformation produced in this operation. The art of manufacturing metal for practical uses is very old and has undergone very great development. The science of metals has- also developed very rapidly recently and the various processes to which metals are submitted are much better understood now than they were even a short time ago. All the knowledge that can be obtained on this subject is useful because it promotes efficiency in converting metal into finished articles.

Jan 1, 1927

By L. R. Jackson, W. T. Lankford, K. F. Smith

COMMERCIAL steel sheet is prepared by a combination of hot and cold rolling and annealing. This treatment usually results in more or less pronounced anisotropy. The [ ] anisotropy may manifest itself both as preferred orientation and in the manner in which impurities, segregations, and the like, are aligned in the sheet. The type of preferred orientation and the organization of impurities or segregations may affect the elastic moduli, the yield strength, the tensile strength, and almost always the amount of ductility in different directions. In any case, the most important directions concerned in the anisotropy are along the rolling direction, along the width direction, and along the thickness direction. Considerable data exist on the anisotropy of sheet steel as demonstrated by conventional tensile tests; however, few attempts have been made to measure the constants of plastic anisotropy and use them to describe the flow of anisotropic sheet under combined stresses. [ ] In this paper, evidence is presented indicating that plastic flow in anisotropic sheet can be described by the shear-strain energy flow theory provided that the anisotropy is properly taken into account. MATERIALS USED IN THE INVESTIGATION Table I lists the sheet materials used in this investigation and describes the condition in which materials were tested. DESCRIPTION OF TESTS AND TEST METHODS Two types of tests were run-tensile tests and hydraulic-bulge tests. Characteristic parameters of anisotropy were determined from the tension tests by methods which will be described later. In all cases, the tensile test pieces were cut from the same quarter line and adjacent to the bulge test pieces in the sheet in order to minimize

Jan 1, 1948

By M. A. Keogh

This paper reviews the physical properties that make low-density polyethylene the most practical and economical material for launder• fabrication in the majority of mine and mill applications. The basic design features and use of other launcher• materials are also discussed.

Jan 1, 1976

By G. Scavino

A 0.5 wt.% C, 22 wt.% Mn austenitic steel, recently proposed for fabricating automotive body structures by cold sheet forming, due to favorable overall strength and ductility, exhibits plastic localizations during uniaxial tensile tests, whereas no localization happens during biaxial Erichsen cupping tests. Full-thickness tensile and Erichsen specimens, cut from as-produced sheets, were polished and tested at different strain rates. During the tensile tests, the plastic localization phenomena consist first of macroscopic deformation bands traveling along the tensile axis, and then of series of stationary deformation bands, each adjacent to the preceding ones; both types of bands involve the full specimen width and yield macroscopically observable surface relief. No comparable surface relief was observed during the standard Erichsen tests. The stress state being known to influence plastic localization phenomena, reduced-width Erichsen tests were performed with 10 to 30 mm width polished specimens, in order to explore the transition from biaxial to uniaxial loading.

Jan 1, 2009

By Magued G. Iskander

The deterioration of concrete, steel, and timber is a serious hindrance to construction in marine and corrosive environments. Composite materials such as fiber-reinforced polymers (FRP) can offer performance advantages for construction in these environments. In the last decade, piling made of FRP composites has been used experimentally throughout North America. However, composites face obstacles because they do not have a long track-record of use in civil engineering structures. A comprehensive review of the current experience in research, testing, design, and practice of composite piling is presented in this paper.

Jan 1, 2002

By Murali Gadde

The immediate floor bed in the Illinois Basin coal mines is often comprised of weak plastic underclay material. Operational and stability problems were encountered in the past due to the low strength characteristics of the underclay floor. Among several indicators of the nature of the floor, Atterberg limits are the most important ones that describe the plasticity behavior of these clayey materials. While several useful and interesting studies were conducted in the past on the Illinois Basin weak floor material, within the knowledge of the authors, a comprehensive database describing the plasticity characteristics of the floor material has never been published. In this paper, a large database comprising over 700 sets of Atterberg limits was put together from 39 inactive and active mines from all the three states covering the Basin. Analysis of this data shows several interesting trends related to the engineering behavior of the floor material. The paper also describes the practical implications of the trends shown by the Atterberg limits.

Jan 1, 2008

By Alan Morris

THE investigation of the hot-working properties of metals and alloys furnishes a problem which has been attacked in many ways. Tensile, impact and hardness tests on heated specimens have furnished interesting data, but in most cases either the tests are difficult to make or the results hard to translate into terms of practical value. Some investigators have used the drop hammer to advantage. It furnishes a rapid and simple method of comparing the plasticity of metals at elevated temperatures. The indications obtained by its use are of value only in so far as their significance is understood and they can be intelligently used to predict the behavior of a given metal under given hot-working conditions. The work reported here was undertaken not only to add-something to the existing volume of such data but also to contribute to our understanding of the results. Doerinckel and Trockels1 used cylindrical specimens and determined the work required to reduce the specimen to one-half the original height. Ellis2 studied the effect of constitution on the malleability of steel at high temperature. His method and that of Kent3 were similar to the one used in the present work. The tests described by Kent were made on samples of tin, zinc, aluminum, copper, lead, 70:30 and 60:40 brasses, with and without a small quantity of lead. He concluded that the test would "indicate whether a material can be forged at a given temperature without cracking." This interpretation must be used with caution. While it is probably true within limits, one must consider the severity of the forging operation. Again, it will not apply strictly to forms of hot working other than forging. For instance, an alloy running 61.0 per cent. copper, 3.25 per cent. lead, remainder zinc, will crack badly in the test, yet it is extruded commercially. When the possibility of hot-working a new alloy is being considered a study of its drop-hammer test should help

Jan 1, 1931

By William G., Pariseau

There are important phenomena in rock and soil mechanics that cannot be explained in terms of theories of homogeneous, isotropic materials. Subsidence of strata about mine openings is an example. In-situ stress measurements in nonisotropic sedimentary, and metamorphic rocks is another. Patterns of joints, faults, fractures, and similar geologic features impart directional mechanical properties to rock masses that are locally isotropic or anisotropic. On the geologic scale, the non-homogeneity of composite rock masses may, in certain instances, be dealt with as homogeneous anisotropy. The mechanics of large rock masses can, therefore, be expected to involve considerations of anisotropy. The source of the anisotropy is not relevant. Once the scale of observation is selected and the material is defined accordingly, the analysis of stress and deformation proceeds without regard to the numerical values of the material constants. There are also important phenomena in rock and soil mechanics that cannot be explained in terms of linear elasticity, theory. For the mechanical description of anisotropic geologic materials capable of de- forming beyond the limit of purely elastic strains, a plasticity theory is required.

Jan 1, 1972

By William G. Pariseau

There are important phenomena in rock and soil mechanics that cannot be explained in terms of theories of homogeneous, isotropic materials. Subsidence of strata about mine openings is an example. In-situ stress measurements in nonisotropic sedimentary and metamorphic rocks is another. Patterns of joints, faults, fractures, and similar geologic features impart directional mechanical properties to rock masses that are locally isotropic or anisotropic. On the geologic scale, the nonhomogeneity of composite rock masses may, in certain instances, be dealt with as homogeneous anisotropy. The mechanics of large rock masses can, therefore, be expected to involve considerations of anisotropy. The source of the anisotropy is not relevant. Once the scale of observation is selected and the material is defined accordingly, the analysis of stress and deformation proceeds without regard to the numerical values of the material constants. There are also important phenomena in rock and soil mechanics that cannot be explained in terms of linear elasticity, theory. For the mechanical description of anisotropic geologic materials capable of deforming beyond the limit of purely elastic strains, a plasticity theory is required. The purpose of this chapter is to present a plasticity theory for anisotropic rocks and soils. The proposed theory is based on the work of Hill in anisotropic metal plasticity and represents an extension of his work so as to include anisotropic geologic materials. The point of departure from metal plasticity theory begins with the inclusion of the normal stresses as linear terms in the yield condition, which plays a central role in plasticity. Once the yield condition is established, the plastic strain increments are obtained immediately through the principle of normality. For practical applications, some simplification of the three-dimensional theory is re-

Jan 1, 1972

Naturally occurring organic plastics have been in use for over 2,000 years. Plastics based on chemically modified organic polymers date back only about 100 years, and those based on synthetic polymers about 50 years. The development of ,these two latter groups up to the present day is outlined, and the basic techniques currently available for polymer-building and modi-fication (blending, copolymerisation, quantitative and qualitative struc-tural control, and'si de-group reactions)-are reviewed.

Jan 1, 1962

By S. Christiansen, G. R. Winslow, R. W. Kobler

Todays End of Life vehicles are shredded and their metal components recovered and recycled by standard methods. The remaining non-metallic fraction is shredder residue, and contains vast amounts of high value engineering plastics. None are today recovered. Discussed are the developmental approaches used in the first process to recover these valuable plastics. Examined are initial laboratory studies, pilot plant design and construction, product development, results, and flowchart explanations.

Jan 1, 2001

By S C. Dominy

This contribution examines the effect of feedstock sampling before the sorting stage of polyethylene terephtalate (PET) bottle recycling. Batches of waste PET bottles may contain non-PET bottles which need to be removed by sorting. Any residual presence of PVC is detrimental for the quality of products manufactured from recycled PET. The maximum tolerated concentration of PVC in cleaned PET is extremely low, which places high demands on the recovery of PVC achieved by sorting. To be confident of attaining the desired PET quality after sorting, acceptance sampling of truckloads of PET bottles may take place prior to sorting. It is shown that accounting for sampling uncertainty requires that the sorting process achieves a consistently high recovery of PVC bottles.CITATION:Glass, H J and Dominy, S C, 2017. Plastics recycling and sampling, in Proceedings Eighth World Conference on Sampling and Blending , pp 129–134 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By Don Masson

MUCH has been written and many prophecies made on the subject of plastics as a replacement for metal, and the extent to which these materials will compete with each other for peace- time markets. (Metal is used in a broad sense to include all types.) But although certain synthetic resin materials have made considerable headway in war production, this change to plastics can hardly be regarded as a serious threat to the mining and metallurgical industries. Even today, the total yearly tonnage of plastic materials is approximately only 1 per cent of that of steel, and only a small fraction of this might be considered as actually replacing steel. However, these figures must not be taken as indicating that the importance of plastics in fields hitherto considered exclusively the territory of metals is negligible-far from it. Considering the comparatively minute tonnage of plastics now being produced in comparison to the output of metals, the number of applications where plastics have augmented or aided the sale of metals is considerable.

Jan 1, 1944

By Hui Yongning

This paper presents a simulating test of constitutive relation of soil anchor in laboratory and puts forward a new plastoelastic mechanical model, on which a new calculating formula of elastic and plastic limit bearing capacity for soil anchor is suggested and two engineering projects verify that this method is adaptable.

Jan 1, 1991

By Jorge Olivari Ortega

"La plata fue un metal de apreciado valor para las sociedades pre-hispánicas -en tanto los mineros lo obtenían de forma pura y se beneficiaban como metales argentíferos. En ese sentido, el presente texto describe su historia y usos en las sociedades pre-hispánicas. La plata se encontraba en los filones hidrotermales, asociada a la argentita, un sulfuro de plata, y calcita, así como a diversos sulfuros y arseniuros de níquel-cobalto-bismuto. Asimismo, gracias a sus propiedades físicas como color, brillo y maleabilidad, se puede trabajar fácilmente y obtener bellos objetos zoomorfos (auquénidos andinos: llamas, alpacas y vicuñas) para los rituales de fertilidad del ganado."

Nov 1, 2016

By Edinson Terán, Delia Cieza

El Perú, enfrenta crisis y entrampamiento político institucional; sin embargo, las regiones evidencian diversos esfuerzos por superar las limitaciones políticas, mediante la participación del conjunto de actores en la gestión de su desarrollo. La presente experiencia parte de este proceso, Cajamarca tiene un especial significado considerando que se convirtió en el icono de las manifestaciones en contra de la minería en el 2011. Actualmente la región vive procesos de cambio con iniciativas de diversos actores que buscan nuevas condiciones para aprovechar sus recursos y convertirla en un territorio competitivo nacional e internacionalmente.

Sep 29, 2023

By Miguel Arancibia

El presente trabajo nos permitirá conocer sobre la actual relación comercial que tienen los negocios locales -NNLL - de nuestra zona de influencia como Antauta con las empresas contratistas de la unidad minera de San Rafael y la importancia de cerrar brechas digitales dentro de los procesos comerciales que ambos gestionan. Minsur como parte de su estrategia de sostenibilidad busca contribuir al progreso de nuestros grupos de interés, impulsando oportunidades de desarrollo para todos, siendo un principio dentro del Consejo Internacional de Minería y Metales -ICMM- y guiados por nuestro propósito “Mejorar la vida transformando minerales en bienestar”.

Sep 29, 2023