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By C. Perez-Rosales

A statistical method for determining simultaneously some of the basic geometrical characteristics of porous media such as porsity, specific surface* mean pore width, mean grain thickness and absolute permeability is presented. The proposed method is characterized by its simplicity and the minimum amount of laboratory equipment that it requires. The experimental procedure used to evaluate the various geometrical characteristics is based 'pan the 'surface analysis Of a a In view of this fact the app1icability Of the method is limited to homogeneous and isotropic materials. INTRODUCTION The behavior of a fluid flowing through a porous medium depends, among other things, upon the internal geometry of the medium; hence the importance of developing efficient methods to determine the geometrical properties of porous materials. This paper describes a statistical method to determine simultaneously some of the basic geometrical properties of porous materials such as porosity, specific surface, mean pore width, mean grain thickness and absolute permeability. The mathematical formulation has been developed that the data required to calculate the various geometrical characteristics of a sample can be easily measured by analyzing a section of the sample with an evenly spaced grid. THEORY A simple way of obtaining information about the internal geometry of a porous material is to throw a point at random over a cross-section of a sample. l-Through this procedure the porosity can be detemined.l,2 By considering that the material is homogeneous and isotropic, and that the point is dropped many times, the porosity 4 is given by where N is the total number of times the point is thrown and n is he number of times the point falls within pore areas. Another simple manner of analyzing the structural characteristics of a porous material is to superimpose an arbitrarily long line on a cross-section so that its length is evenly distributed over the surface area. Through this procedure the porosity can also be determined. If L is the total length of the line, and 1 is the sum of the lengths of the line segments within void spaces, the porosity is given by 4 = —.1.............. (2) The advantage of this type of analysis is that geometrical characteristics other than porosity can be obtained. Thus, if c represents the number of intersections between the line and the perimeter of pores, it can be shown3 that the specific surface, defined as he surface area of pores per unit bulk volume, is given by To give a proper description of the internal geometry of a porous medium, it is necessary to define quantities that characterize the notions of pore size and grain size. Unfortunately, because of the complexity of porous materials, it is difficult to give exact geometrical definitions of what is meant by the ConCePtS of "poresl' and "grains", especially when dealing with consolidated materials. Never theless, one often talks about the "size of pores" and the "size of grains" without defining accurately the terms. A possible solution to this problem follows. Assume that an arbitrarily long line is placed on a section of a sample so that the line is evenly distributed over the surface area (see Fig. 1). 1n a system like this, each line segment within a void space will be, by definition, the pore width in a given location and direction. Consequently, if the

Jan 1, 1970

By W. White, C. S. Barrett, R. M. Mueller

THIS communication reports film-recorded low-energy (-100 kev) proton blocking patterns'-3 for hcp and wurtzite crystals. In particular the sequence of relative line intensities* (corresponding to planar blocking) of common hcp metals is compared with those of the wurtzite semiconductors CdS and CdSe. The results show that the sequence is characteristic of structure. For closely similar structures such as those of CdS and CdSe, differences of line intensity attributable to the difference in atomic number, 2, of the scattering centers may also be seen. The apparatus and techniques used in this work were identical with those reported previously in a study of cubic systems.3 All metals were given standard metal-lographic etches, and the semiconductors cleaved, immediately prior to introduction to the vacuum system. Fig. 1 shows the unit cell of the wurtzite structure, and the geometry used to obtain the [1120] and [0001] patterns of Fig. 2. The axial ratio, c/a, for all ma- terials of Fig. 2 is close to 1.63. The patterns are then directly comparable in linear dimensions inasmuch as they have been reproduced at the same overall magnification of the patterns. (Overall magnification is proportional to the product of film-to-target distance and printing magnification. Thus the 1/6-in.-diam beam passage hole in the center of the film need not appear of uniform size in the prints.) The patterns for a given orientation, though similar

Jan 1, 1970

By Anal J. Mehta, Theodore D. Tiemann

Growing demand for steel and increasing dependence upon foreign ore makes the need for developing the technology for treatment of low-grade iron ores greater than ever before• Representative of these added interests were the studies carried on at the University of Wisconsin• These studies included among others: anionic and cationic flotation, magnetic separation, roasting followed by magnetic separation, electrostatic separation, a hydrogen reduction process,6,7 and caustic digestion• The idea of removing silica by caustic extraction is not new•-1; The principle of concentrating siliceous iron ores by this method is based on the fact that silica is soluble in sodium hydroxide solution while iron oxides are essentially insoluble• For this process to be economically feasible, it is believed that some method of recovering silica from solution as a marketable by-product, with recycling of spent liquor is necessary. Precipitation of silica with carbon dioxide will allow subsequent causticizing of the spent liquor with lime• Caustic thus produced can be recycled for digestion• A flowsheet of the envisioned process is given in [Fig• 1] The purpose of this paper is to describe results obtained from the investigation of carbon dioxide precipitation of silica from sodium silicate solutions, which could be later applied to the caustic extraction process to treat low grade siliceous iron ores, particularly taconites.15 Theoretical Considerations The soluble silicates of sodium include sodium orthosilicate (2Na2O•SiO2), sodium metasilicate (Na20•SiO2), sodium disilicate (Na1O•2SiO2), and more highly siliceous products approaching Na2O•4SiO2• These materials have been described in detail by Vail•16 Stones has reported that the extraction of silica is not significantly affected by the amount of silica in solution until the Si02/Na20 ratio exceeds that of orthosilicate (Ratio = 1/2)• However, as the Si02/Na2O ratio exceeds that of metasilicate (Ratio = 1), silica extraction is significantly impaired• The present experimental work was confined to orthosilicate and metasilicate solutions, as to be successful the envisioned commercial process for the extraction of silica from siliceous iron ores would operate in this region. The mechanism of extraction of silica from aqueous sodium silicate solutions is complex in nature. For the carbon dioxide process-18 of core and mold making in which silica is also precipitated from sodium silicate solutions by gassing with carbon dioxide, the reaction of aqueous silicates with gaseous carbon dioxide has been represented by the equations: [ ] However, these equations are very much oversimplified• It has been shown that the reaction between aqueous sodium silicates and carbon dioxide gas is ionic in nature 18 Considering this fact and the mechanism for digestion of silica in aqueous sodium hydroxide, the overall conversion of aqueous sodium silicates to solid silica may be represented in ionic form by the following equations: [ ] Silicon in the silicate ion is shown here with a coordination number of 6• This may be in doubt, but it is known that ion (SiF°)-2 exists; it seems logical that the Si (OH) e 2 ion should be equally capable of existence•

Jan 1, 1977

Reno, Nevada. J A Fulton, Director For publications of either the Mackay School of Mines or the State Bureau of Mines, address the School of Mines at the given address. Except where the contrary is indicated in the following list, available publications are sent free From the Mackay School of Mines. Bulletin 1, The identification of Nevada's common minerals, 50 cents; 3, Notes on the ore deposits of Cave Valley mining district, Lincoln County, 4, A preliminary survey of the Scossa mining district, Pershing County, 5, Ore deposits of the Gold Circle mining district, Elko County, 6, Bedded deposits of manganese oxides near Las Vegas, 7, Spruce Mountain district, Elko County, and Cherry Creek (Egan Canyon) district, White Pine County From the State Bureau of Mines: Bulletin 1, Mineral resources of southern Nevada One volume: Mining districts and mineral resources of Nevada, by F C. Lincoln (1923), $1.50.

Jan 1, 1933

By W. L. Remick

WHEN the senior author of this paper presented an article on Fine Coal Cleaning by the Hydrotator Process,1 at the February, 1927, meeting, that process had been developed in the anthracite region only to clean what is known as "slush" or "silt." This size constitutes all of the material passing the finest screen used at any particular colliery. Some use a 3/32 -in. round-hole screen and others use a 1/16 -in. round hole. Practice varies throughout the anthracite region, but the tendency seems to be toward the finer screen.

Jan 1, 1929

By C. C. Hatch, A. L. Mular

The methodology employed to develop a digital simulation of the Brenda Mines Ltd., Peachland, B. C., secondary crushing plant is described. Methodology includes data acquisition, data adjustment, model building, and the construction of a simulator structure. The simulator was utilized to study the effects of secondary and tertiary crusher close side settings, secondary screen opening, plant feed rate, and percent + 1 in. in the feed on the following responses: percent - 1/2 in. in the final product, plant reduction ratio, circulating load ratio, and screen efficiency. Results are presented in graphical form.

Jan 1, 1983

By W. G. Scott

SINCE devising the incline top-slicing method in use It the Coronado mine,1 I have had numerous inquiries is to how the same system could be adapted to larger orebodies. Based upon our experience here, 1 have outlined below some suggestions for its, application to orebodies of larger size. Modifications and extensions, of course, would have to be made to take care of different dimensions and irregularities. In order that one may have a better understanding of the scheme, a brief description of the Coronado method will he given first.

Jan 11, 1917

By Rodney P. Smith

The solubility of niobium carbide in y iron has been determined for the temperature range 1000" to 1300°C from the carbon content of a series of Fe-Nb alloys equilibrated with hydrogen-methane mixtures. The method is similar to that used by Darken, Smith, and Filer 1 to determine the solubility of aluminum nitride in y iron and by smith2 to determine the solubility of niobium nitride in y iron. The samples* were strips 1.2 by 3 by 0.035 cm. The niobium oxide.* For samples of composition slightly

Jan 1, 1967

By D. J. McAdam

RESULTS of investigation of corrosion-fatigue of metals at the U. S. Naval Engineering Experiment Station, Annapolis, Md., have been discussed by the writer in several recent papers. 1.2.3.1 In those papers references were also given to the work of Haigh in 1917.6 Efforts by the writer to obtain a better understanding of some of the factors involved in corrosion-fatigue finally developed into a general investigation of the effect of time and cyclic stress on corrosion of metals. Corrosion fatigue of Metals As described in the papers mentioned, rotating-cantilever specimens, conically tapered so that the stress is nearly uniform over a length of about 1.5 in., were subjected to simultaneous fatigue and corrosion. For this purpose a stream of water was diagonally applied so as to sweep the specimen from the outer to the inner fillet and surround the stressed surface with water. The fresh water is a calcium carbonate water, the composition of which has been given in a previous paper .2 The salt water is Severn River water having a saline content about one-third that of sea water. The previous papers described results obtained with ferrous and nonferrous metals. The experiments showed that even slight corrosion simultaneous with fatigue may cause failure at nominal stresses far

Jan 1, 1928

By Walter O. Snelling

In combating mine-fires the use of carbon dioxide as a means of producing an atmosphere in which combustion cannot be sustained, has been many times suggested and frequently tried, generally with a fair degree of success. The carbon dioxide is produced by acting on limestone with dilute sulphuric acid, large wooden boxes being used to hold the limestone, and arranged in such a manner that one box may be cleaned and refilled with blocks of limestone while another is being used in generating the carbon dioxide.. The gas is led by means of pipes of large diameter to the location of the fire, tight brattices having been previously put up as close to the fire as possible on every side, so as to limit the space to be filled with the gas to the smallest possible volume. The cost of producing carbon dioxide has been, however, a decided draw-hack to the use of this method, and the danger of producing carbon monoxide by the reduction of the carbon dioxide by heated carbon, and consequently bringing about an explosion, has also tended to prevent the application of this method. The use of sulphur dioxide in combating mine-fires has not, I believe, been previously suggested or tried, and yet the method presents such decided advantages over the use of carbon dioxide that it seems proper to suggest the advisability of considering it as a cheap, convenient, and safe means of fightr ing stubborn mine-fires. 1. Cost, Preparation, etc.—One ton of brimstone, costing from $20 to $30, will produce about 25,000 cu. ft. of sulphur dioxide gas, and allowing for all sources of loss it is probable that sulphur dioxide gas can be produced for about $1,300 per 1,000,000 cu. ft. For carbon dioxide gas, produced by the action of sulphuric acid on limestone, a good estimate would be $4,000 per 1,000,000 cu. ft., provided that sulphuric acid

Jan 1, 1909

By J. L. Gregg

A study of copper-base and silver-base alloys was made with the object of finding, if possible, useful alloys subject to dispersion hardening. These studies led to the discovery of several alloys showing considerable dispersion hardening, the most important of which, the alloys of copper with iron, nickel, cobalt and chromium silicides, have since been very ably reported by M. G. Corson.l This paper is offered as a few notes covering alloys other than those described by Corson and some further data on the silicide alloys. Copper Alloys For the purpose of making a rapid survey of copper alloys that might show useful dispersion-hardening phenomena, various alloys were prepared containing 3 per cent. of additional elements added in such proportion that possible compounds could be formed without an excess of either added element. These alloys in the form of rolled or forged pieces were quenched in water from a temperature of 871" C. (1800" F.) and subsequently aged at various lower temperatures for l-hr. periods. The comparison of the Rockwell hardness of the quenched alloys with the maximum hardness of the alloys after aging was used as a measure of the dispersion hardening. Table 1 shows the Rockwell "E" hardness 1/8-in. ball, 100-kg. load) of the quenched alloys, together with the maximum hardness resulting from aging. The reheating temperature given in this table is the aging temperature at which maximum hardness resulted from a l-hr. sojourn. From this table it may be observed that only the silicide alloys showed significant dispersion hardening. Of these, the only one not described by Corson is the Cu-Be-Si alloy. This alloy contained 1.35 per cent. beryllium and 1.78 per cent. silicon, which is approximately equivalent to 3 per cent. Be2Si. It had a yellow color and scaled much less than the other silicide alloys upon heating. It could be worked easily either hot or cold but hardened very rapidly on cold working. The annealed alloy upon drawing from a diameter

Jan 1, 1929

By J. L. Gregg

A study of copper-base and silver-base alloys was made with the object of finding, if possible, useful alloys subject to dispersion hardening. These studies led to the discovery of several alloys showing considerable dispersion hardening, the most important of which, the alloys of copper with iron, nickel, cobalt and chromium silicides, have since been very ably reported by M. G. Corson.l This paper is offered as a few notes covering alloys other than those described by Corson and some further data on the silicide alloys. Copper Alloys For the purpose of making a rapid survey of copper alloys that might show useful dispersion-hardening phenomena, various alloys were prepared containing 3 per cent. of additional elements added in such proportion that possible compounds could be formed without an excess of either added element. These alloys in the form of rolled or forged pieces were quenched in water from a temperature of 871" C. (1800" F.) and subsequently aged at various lower temperatures for l-hr. periods. The comparison of the Rockwell hardness of the quenched alloys with the maximum hardness of the alloys after aging was used as a measure of the dispersion hardening. Table 1 shows the Rockwell "E" hardness 1/8-in. ball, 100-kg. load) of the quenched alloys, together with the maximum hardness resulting from aging. The reheating temperature given in this table is the aging temperature at which maximum hardness resulted from a l-hr. sojourn. From this table it may be observed that only the silicide alloys showed significant dispersion hardening. Of these, the only one not described by Corson is the Cu-Be-Si alloy. This alloy contained 1.35 per cent. beryllium and 1.78 per cent. silicon, which is approximately equivalent to 3 per cent. Be2Si. It had a yellow color and scaled much less than the other silicide alloys upon heating. It could be worked easily either hot or cold but hardened very rapidly on cold working. The annealed alloy upon drawing from a diameter

Jan 1, 1929

By Roy A. Koski

INTRODUCTION Cleveland-Cliffs Iron Company, and its subsidiary companies, operate and manage mining, beneficiation, and pelletizing operations in the Upper Peninsula of Michigan, the province of Ontario, Canada, and the State of Western Australia, Australia. The concentrates and natural ores vary mineralogically, physically and chemically. This paper describes the techniques employed in pelletizing the various concentrates and ore fines. The plant operations described are the Republic, Humboldt, Tilden, Empire and Pioneer in Michigan, the Adams and Sherman in Ontario, and the Robe River in Western Australia. Table 1 contains further details regarding design and operating capacities, commissioning dates, and participant ownerships. Allis-Chalmers grate-kiln systems are utilized in Michigan and Ontario, and Dravo straight-grate systems in Western Australia. Currently, the Empire and Tilden operations are being expanded. At Empire the additional pelletizing unit, identified as Unit IV, will have a design capacity of 8 996 metric tonne/d and is scheduled for startup May 1, 1979. The Tilden operation is being doubled with the additional pelletizing unit, identified as Unit 11, having a de- sign capacity of 12 599 metric tonne/d. Startup is scheduled for January 1, 1980. MINERALOGY OF CONCENTRATES AND NATURAL ORES In the Upper Peninsula of Michigan, the operations process ores from the Negaunee iron formation of the Marquette Range. The

Jan 1, 1977

By Gilbert P. Moore

Petroleum operations in Bolivia are still limited to those of the subsidiaries of the Standard Oil Co. of New Jersey. Development work is being carried on at Sanandita and at Bermejo and testing operations in the north. Five wells have been completed at Sanandita. Wells 1 and 2 are producers, 3 and 5, which are north of 1 and 2, are poor wells, and well 4, to the south, was dry. In the Bermejo field, well 5 has just been completed. No information as to the production is obtainable. In the north one string was operated at each of the following locations: Machareti, Camatindi and Camiri. The well completed at Machareti during the year was a failure. The result of the others is not known. It is reported on good authority that a pipe line will be completed in 1931 to connect the Sanandita field with the Lomitas field in the Argentine. This will place Bolivia among the ranks of the producing countries of South America for the first time. This development indicates that some arrangement has been arrived at with the Argentine Government for the importation of Bolivian oil. During 1930 the Bolivian Government declared in effect the new Petroleum Law which had been expected for such a long time. One of the first acts of the military junta, which rose to power through a coup d'état, was to cancel this law, so that Bolivian oil operations are still under the old law of 1921. One new local company was formed to exploit 1,500,000 hectares near the town of Cochabamba. The Bolivia Concessions, Ltd., which had a concession permitting the selection of 17,000,000 acres in eastern Bolivia, is reported to have failed in 1930 and is now being liquidated. Chile During 1930 the Chilean Government entered into a contract with an individual to explore in five distinct zones of the Republic. According to the contract, geologists must be at work there by May 1 of this year and a well must be started by the end of 1931. If the operations are

Jan 1, 1931

By C. E. Reistle, G. L. Nye

The East Texas field is in Smith, Rusk, Gregg, Upshur and Cherokee counties, Texas. The discovery well was completed Sept. 8, 1930, near the eastern limit of the field. Within less than one year the new field became the dominant factor in the world production of crude oil. On Aug. 16, 1931, eleven months after completion of the discovery well, there were 1644 wells in the field, and the average daily production was 584,475 bbl. Since that time the number of wells has increased to 8195 on Oct. 1, 1933, and the field has produced 385,979,691 bbl. of oil. The geology of the East Texas field has been discussed by Lahee,1 Levorsen,2 Minor and Hanna3 and others, and it will not be discussed in detail here. The field is a structure of the monocline type on the westward dipping homocline between the Sabine uplift and the East Texas geosyncline. Production is obtained from the Woodbine group, which has been truncated and then sealed by the Austin chalk, which rests unconformably upon it. The oil-saturated part of the sand lies bettween a sub-sea depth of 3050 ft. on the east side of the field, where the Woodbine sand stops and the Austin chalk rests directly upon older formations, and a sub-sea depth of 3320 ft., which was the average depth of the water table in the sand at the time the field was discovered. The field is about 40 miles long and has an average width of approximately 4 1/2 miles. The area within the proven limits of the field is close to 116,580 acres and the normal Woodbine water underlies nearly 62,000 acres on the western side of the field at the present time. The field is unusual in several respects: (1) the tremendous size of the reservoir system and the quantity of oil in place; (2) the large area of the oil and water contact, which makes water movement possible into the oil-bearing part of the structure; (3) the absence of free gas within the main producing sand of the field. Changes in the reservoir pressure during the production history of the field have been greatly affected by

Jan 1, 1934

By Edward J. Way

+1KLEINFONTEIN GROUP CENTRAL ADMlNISTRATION, BENONI, TRANSVAAL, S. AFRICA. The cost and the speed of sinking a shaft are factors of so great importance in operating a mine, that the data given in Table I., herewith published, will be of interest and value to all engaged in practical mining; and for this reason the data are communicated for permanent and accessible record in our Transactions. The figures 'of cost cover the period from January 1, 1903, to May 31, 1903, during which time the total depth sunk was 858 ft. So far as I know, the cost of sinking per foot (£13,15s., 11.04d.) of a shaft of the dimensions 21 ft. by 6 ft. in hard rock, is the cheapest yet on record; and the speed of 213.5 ft. per month, which was attained during May, 1903, is also the best record for speed in sinking in rock so hard as that of this shaft. During the period from January 1 to May 31, 1903, there were 144 rounds worked, involving 4,032 holes, of a total depth of 28,963 ft. 2.4 in., which is equivalent to an average depth of 7 ft. 2.2 in. per hole bored. These data are of added interest from the fact that the work was done practically by native labor.

Jan 1, 1905

By Lawrence Addicks

ONE of the properties of copper, which has done much to give it its present prominent place among the useful metals, is its electrical conductivity, a property which has now become the chief criterion of 'the value of the commerical product. In pursuance of that distinctively American principle that, 1' the best is none too good," metal of the highest conductivity is usually called for even where such extreme purity is of no advantage, for instance, in the making of brass and other alloys. The average brass-founder feels nervous unless his copper is so very pure that it shows a conductivity of 99 or 100 per cent., while the character of the zinc used is usually overlooked in his anxiety. Electrolytic refining has made it possible to produce copper of a' very high degree of purity, the metallic impurities averaging but a few thousandths of 1 per cent.; oxygen, usually present in the form of cuprous oxide, bringing the total up to about a tenth of 1 per cent. The published data bearing upon the relationship between chemical purity and electrical conductivity is, however, very scant,' nearly all the work that has been done having dealt with alloys carrying considerable quantities of the foreign elements. In this paper I have brought together the results of experiments extending over a period of several years that have been carried out with the idea of determining the amount of various elements which would lower the conductivity 3 or 4 per cent.-a series of impure coppers rather than alloys. There are many precautions necessary to keep the conditions

Mar 1, 1905

By P. D. Merica

The remarkable phenomena exhibited by the aluminum alloy known as duralumin were discovered during the years 1903-1911 by A. Wilm1,2 and have been described by him and by others. 3 4 5 6 The unusual feature of this alloy is the fact, as was shown by Wilm, that it can be hardened quite appreciably by quenching from temperatures below its melting point followed by aging at ordinary temperatures, which consists merely f allowing the material to stand at these temperatures. The hardness is not produced by the quenching alone but increases during the period of aging, which may be from one to three days. Cohn3, 5 gives data showing the increase of hardness of duralumin during aging, after quenching in water from about 450° C. Upon annealing, the alloy so hardened by aging is softened exactly as is hardened steel. The composition of this alloy usually varies within the following limits: Copper, 3 to 4.5 per cent.; magnesium, 0.4 to 1.0 per cent.; manganese, 0 to 0.7 per cent.; aluminum, balance; iron (as impurities), 0.4 to 1 per cent.; silicon, 0.3 to 0.6 per cent. Its density is about 2.85. It is used only in the forged or rolled condition. This alloy has been produced for some years commercially and is in demand for the fabrication of parts for which both lightness and strength are required, such as for aircraft. Its tensile strength will average 50,000 to 60,000 lb. per. sq. in. (3515 to 4218, kg. per sq. cm.) after appropriate heat treatment, such as that described by Wilm.

Jan 6, 1919

By A. Arrott, G. S. Ansell

A model is proposed to account for the observed strengthening behazlior of ferrous martensites. me model is based upon the inheritance of carbon-rich regions by the martensite which were present in the FERROUS martensite is formed by a nucleation and shear mechanism when austenite is cooled, at a rate which is fast enough to suppress the formation of pearlite, below a critical temperature (Ms ). Although the mechanism of the transformation process appears to be well understood,1,2 the mechanism re- austenite prior to transformation. These carbon-rich regions strengthen the martensite in a manner analogous to the strengthening effect due to a finely dispersed second phase. sponsible for the observed high strengths exhibited by ferrous martensites is uncertain. In this paper, a model is proposed to account for the strengthening of ferrous martensite. MODEL The maximum solubility of carbon in austenite is 1.98 wt pct as compared with a maximum solubility of 0.025 wt pct in ferrite. Prior to transformation, the carbon in the austenite is nonuniformly dis-

Jan 1, 1963

By David Sinclair, Philip B. Bucky

THE dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests.§ None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their application in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I THE PHOTOELASTIC METHOD The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution. GENERAL EXPLANATION The stress at any point 0 in a structure (Fig. 1), may be resolved into two components, P and Q, each a pure tension or compression, at right angles to each other, called principal stresses.1 To fully identify the stress, the values of P and Q and their directions or angle [0] must be known.

Jan 1, 1940