Search

An analysis technique for biological shape based on the concept of bending energy has been developed. The technique permits the calculation of the amount of energy (work) that would have to be expended to form typical biological shapes out of a linear, thin-shelled medium. In addition the development of this analysis procedure provides several new results concerning image processing including a sampling theorem for simply connected closed contours and a fast algorithm for calculation of the bending energy.

A probabilistic method is presented for the design of gear trains. By idealizing the gear train as a weakest-link kinematic chain, the design is made with respect to bending strength and surface wear resistance. The structural and the kinematic designs and the gear train are assumed to known. All the parameters affecting the design are considered as random variables. The design criterion is that the overall probability of failure of the gear drive in bending or by surface wear at nay particular speed of the output shaft must be equal to the given probability of failure. The design of a nine-speed lathe gear box has been considered as an example problem.

In this article an attempt is made to estimate the effects of some factors on the accuracy of results of model tests. As an example an analysis was performed upon the investigations on plate-type bridge structures made in the Bridge Department of the Technical University of Wroclaw (Politechnika Wroclawska) Poland. The methods of the model testing, errors in measurements resulting from the in-series connection of electrical extensometers of different initial resistances, as well as errors caused by inaccuracies in positioning extensometers on the model are discussed. Finally the effect of inaccuracies in measuring thicknesses of the model plates is estimated and the total error of the bending or twisting moment computed from the influence surfaces, as determined in model tests, is found.

The structure of the plain tricot knitted fabrics underlies two-bar tricots knitted fabrics. The biaxial tensile properties of the plain tricot fabric are calculated theoretically from the structure of fabric and some of mechanical properties of yarn, applying the method developed by S. Kawabata.The tensile process is divided into two regions, i.e., the bending effective region and the stretching effective region. The border of these two regions can be given by critical stretch ratios λc1 and λc2 where suffixes 1 and 2 indicate wale direction and course direction, respectively.The tensile properties in the two regions are analyzed by using a new model which is different in structure from single dembigh stitch. The model used for plain tricot stitch consists of needle loop and sinker loop, i.e., layer of front yarn and of back yarn. In this model are two yarn crossing points; one is of the front yarn layer and another is of the back yarn layer. It is assumed that these two crossing points are in contact with each other and do not seperate during deformation process before critical ratios, that is, in bending effective region, but, after the critical state, these two points are separated in proportion to λ2. The other analytical method is same as that of single dembigh fabric. Yarn frictional properties between crossing yarns are introduced and the accuracy of the calculation is much more enhanced due to this improvement, compared with the theory of single dembigh fabric.Using some of actual fabrics, the theoretical and experimental values are compared, in all deformation modes of biaxial extension, with good agreements.

Much theoretical and experimental work has been published on the flexure of pipe bends. Examination of the results to date show considerable differences between certain measured results and the predicted behaviour.The theoretical works relate mainly to long radius bends and all make many simplifying assumptions.This paper presents a more detailed theoretical study, for bending in the plane of the pipe bend. Examination of both typical and extreme cases and a comparison with the experimental evidence shows which of the various theoretical simplifications can be accepted for a given pipe bend.It is concluded that although complete stress distributions calculated by previous theories may be seriously in error over particular ranges of the variables, the peak stresses and flexibilities are, by a combination of circumstances, unlikely to be more than 5-10 per cent in error if certain factors introduced in the more recent of these theories are used.Manufacturing and other variations between nominally similar pipe bends, however, seem to preclude the possibility of predicting the behaviour of a particular bend to closer than ±20 per cent.

From the time the solidifying skin begins to form in the mold until well after solidification is complete, a continuously cast section is subjected to a complex history of thermal and mechanical stresses. Also, in most casting machines gross bending deformations are imparted to the cast strand, either to introduce or eliminate a curvature. The ability of the solidified material to withstand these stresses and strains is essential in permitting the casting operation to proceed, as well as in avoiding surface and internal tears that can lead to poor product quality or necessitate excessive conditioning. In this paper the nature of the stresses and strains that the cast section must withstand are discussed. Results of experimental studies of the strength and ductility of low-carbon steels in the range of temperatures and strain rates of concern in continuous casting are presented. Compositional effects in both simple tension tests and in bend tests are discussed, with special reference to the reduction in ductility observed in the temperature range of about 1500° to 2200°F following certain prior thermal histories. The implications of these results in the design and operation of continuous-casting machines are also discussed.

Tests were conducted to demonstrate the computational adjustment of strips of aerial photographs by independent models where the models are only approximately oriented in a stereoscopic instrument. The system is sparing of operator time, operator skill, and photogrammetric equipment, taking advantage of recent reductions in the cost of computer time. Most of the errors introduced in the approximate orientation are eliminated through the computation. Preliminary results show an improvement in results over the purely instrumental method. The breaks between models are smaller than those in which the model is finalized with the instrument. Residual bending of the strip conformed well to a parabolic adjustment.

1. The method proposed makes it possible to determine the residual stresses to a great depth, from the thinnest surface layer down to the unhardened material. 2. Induction hardening of gear teeth creates residual compressive stresses in the fillets; in the transition zone these become tensile stresses. Polishing usually creates residual tensile stresses in the hardened surface layer. 3. Polishing with removal of 0.2–0.3 mm from the hardened surface layer in the fillets reduced the endurance limit 20–30% by comparison with unpolished gears. Cutting of the teeth should produce a finish of at least ▿5, in which case cutting at the base of the teeth is inadmissible. 4. The endurance limit (bending) of the teeth of induction hardened gears made of 40KhN steel is higher than that of quenched 12KhN3A gears.

The bend parts of high pressure pipings by using high frequency induction heating are to be heat treated for stress relieving in compliance with many application standard, the requirements of the rules and regulations of classification societies and the power plant engineering standard for example.The new bending technique was developed in order to do away with heat treatment of the bend parts of steel pipings, which are satisfactory and adequate in mechanical property and change in wall thickness and shape of the bend parts.

The paper deals with those tests which are involved in specifications. The discussion is from the standpoint of the purpose and significance of the various standard tests which are made rather than that of the technique of the details of testing. A considerable number of data are given. The subjects treated are purpose and importance of tests of cable; insulation resistance test; high-voltage test; dielectric loss and power-factor test; ``ionization'' test; bending test; accelerated life test; preparation of samples for high-voltage tests and tests of components. The possible significance of wide variation in some of the properties of cable is discussed. The relation found between time and voltage based on a large number of tests of both three-conductor and single-conductor cable is discussed at considerable length. A test for stability of the impregnating compound is described as is also a proposed standard load for dielectric-loss testing. Some data are given showing the effect of repeated bending on lead and how that effect is influenced by the tensile stress in the lead. The paper concludes with a list of the ways by which, in the author's opinion, progress can be made in the improvement of the quality and the design of paper-insulated high-tension cable.

The mechanism of straightening of sections and rails by means of a roller straightener with axial adjustable rolls has not been clarified. The auther studied this problem analytically and derived the relations between the largest radii of bending necessary for straightening, at the points of the second and third rolls of straightener and the results of straightening, when the modulus of elasticity and curvature of sections before operating are known. The auther also shows, as a special case, that the sections can be straightened not only in horizontal plane, but also vertical plane in accordance with severe bending in even horizontal plane by the straightener rolls. The present paper deals with the repeated bending tests and the tension-compression tests for specimens of hard steel, mild steel and brass, as these characteristics of repeated cold works on these materials are the most important points for designing the straightening machine.

Techniques such as birefringent coatings, moiré, brittle lacquers, strain gauge, and holography can all be used on composites since they enable surface strains to be measured. However, a correct and accurate interpretation of results obtained by these methods is essential. The significance of this is demonstrated by observing the effect of the differences between the directions of principal stresses and strains. In addition the suitability of the birefringent-coating technique for application to fibre-composite materials is examined by considering the three-point flexure of a narrow rectangular beam of span/depth ratio 6 in some detail. Within the framework of the assumptions that stresses will be distributed in accordance with elementary bending theory and that the appropriate stress-strain relations for orthotropic materials are applicable, isochromatic and isoclinic patterns are predicted and compared with experimental results. A more precise solution is also obtained by employing the finite-element displacement method. From a qualitative standpoint the comparison is found to be good although more research is required before the birefringent-coating technique can be used in situations demanding a reliable quantitative appreciation.

Proceeding on the assumption that a guyed tower inclined bodily by the pressure of the wind should have the points of guy attachment remain in a straight line, methods are given for calculating the following quantities: guy tensions (for windward, leeward and perpendicular guys), horizontal and vertical forces acting on the top section of the tower, stresses in the middle section, stresses in the bottom section due to bending, design of flat-top and umbrella antennas, change in stresses due to temperature variation, and dimensions of foundations and anchorages. These methods are fully illustrated by the complete calculation of a 625-foot (190 meters) high hollow cylindrical guyed steel tower. Tables of all guy weights, tensions, and sags are given, together with the quantities which determine them.

A description is given of a quick and simple technique for checking, by means of the usual χ2; and Kolmogorov-Smirnov tests, the goodness of fit of Weibull's distribution to data relating to the fatigue of textile materials tested for abrasion, repeated extension, repeated bending, etc., or subjected to any type of action susceptible of being treated by means of such a distribution.

The design, fabrication, development, operation, calibration and results from reversed bending combined with steady-torque fatigue-research machines are presented. Fifteen-centimeter-long, notched, SAE 4340 steel specimens are subjected to various combinations of these stresses and cycled to failure. Failure occurs when the crack in the notch passes through the specimen automatically shutting down the test machine. These cycles-to-failure data are statistically analyzed to develop a probabilistic S-N diagram. These diagrams have many uses including the design of rotating components having minimum size and weight for a specified number of cycles and reliability.

Information obtained in an investigation of the effects of heat curving, and the results of a subsequent analysis of the bending behavior of heat-curved members, have been used to formulate criteria for heat curving rolled beams and welded girders. Two of the main provisions of the criteria are the requirements for: (1) A minimum radius; and (2) an increase in the usual vertical camber. The minimum-radius requirement was selected to prevent excessive web bowing due to the combined effects of the residual compressive stresses and shear stresses from applied loads. The requirement for increase in camber was selected to negate vertical residual deflections, or loss in camber, as a result of slight inelastic action under initial loading. A specification for heat curving, essentially in accordance with the criteria analyzed in this paper, was recently (1969) adopted by AASHO.

One of the basic problems of structural-model analysis, model photoelasticity and photoelastic coatings in the problem of mechanical and optical creep, relaxation and related phenomena. It is pointed out that, in spite of creep or relaxation, it is possible to achieve physical similarity between model and object if the model material behaves in a certain range as a linear viscoelastic material. Such a material is called a “momentarily linear material.” Several model materials behave in this way in a certain range of stress and time. Because of creep and relaxation, the common tensile tests are, in general, not quite adequate for evaluation of physical properties of plastics used for models. Also the bending test is not always adequate. It is shown how to obtain sufficiently accurate relations between stress, strain, birefringence and time, using tapered specimens. The problem of biaxial creep of model materials is discussed, and a simple method of evaluating the suitability of a given plastic as a model material is shown. Some conclusions concerning time-dependent factors are formulated, and some possible areas of investigation are shown.

Recent developements in analytical photogrammetry seem to be remarkable, especially with the expansion in the ield o its application, and also the demand or higheraccuracies in photogrammetric surveying is growing day by day, throwing beore us many interesting problems.Due to the recent developments in analytical photogrammetry, we have become convinced that these problems can be solved. Having been engaged in analytical photogrammetry during the past six years, we recently examined the inluence of the lens distortion on accuracies, and we ound that it was unexpectedly large. In this paper, we will discuss the problems which we had to deal with and the particular applications o the results.First o all, the method o analysis and the corrections or symmetric and asymmetric radial lens distortions will be shown and secondly we will make observations rom various standpoints on the phenomena which appeared in the actual examples when applied the lens distortion correction i. e. the inluence on a single model, on a strip and on the relation between the bending coeicient o a strip and the variations o orientation elements caused by the lens distortions.

The failure of rock materials in the form of rings subjected to line loadings on either their internal or external surfaces is studied. Formulae for the stresses and some numerical values are given. Experimental results for three fine-grained rocks are given and values of the tensile strengths so obtained are compared with those from direct tension, indirect tension (Brazilian) and bending tests. It is found that the calculated tensile stresses at failure for rings loaded in either fashion, and for bending tests, are considerably higher than those for direct tension or the indirect tensile (Brazilian) test. It is suggested that this is due to the fact that in the two latter cases the stresses are uniform (or nearly so) over the section in which failure takes place, while in the three former they vary almost linearly across it. This suggests that a criterion for failure must not simply involve the stresses at a point, but also their rate of change with position.

The helically corrugated, impervious, steel sheath is formed around the cable core, welded and corrugated in a continuous operation. This manufacturing method eliminates the thermal problems of the extrusion process, the length restrictions of the sinking or draw-down system, and also increases the pliability and the radial strength of the sheath. The sheath is an impervious barrier to gases and fluids which also gives mechanical protection to the cable core. Corrugation designs are based upon an engineering balance of weight, thickness of metal, pliability, compression strength, and ability to withstand internal and external pressures. The method of corrugating is flexible, and special designs can be made for specified service conditions. Even with thinner sheaths than commonly used for other types of impervious sheaths such as lead and aluminum, the corrugated steel sheath has improved radial strength and resistance to "sheath metal fatigue." Conduits, ducts, and similar accessories are not necessary to protect the cable. Service records and laboratory tests substantiate the fact that the corrugations do not damage cable cores either during the manufacturing process, installation, or service. Cables protected with the corrugated steel sheath have bending characteristics which permit them to be shipped on normal diameter reels and to meet the normal installation requirements of minimum radii and number of bends. The sheath can be bent much sharper without damage to itself than recommended by industry standards for various insulations and cores. Protective systems for the sheath have been developed for chemical and corrosive environments.

General Reluirements are stated for mat, bench walls, checker work, regenerator korbels, main flues, division walls, oven chambers and jamb blocks. The following Tests are described:—inspection, reheating tests on three qualities, bending test. Requirements and specifications are discussed. The latter part ofthe paper deals with Apparent density and Permanent expansion. It is shown that the relation between them is a linear one and a chart is given. The average of thirty-nine determinations gives an apparent density, for Western brick, 0.016 higher than for Pennsylvania brick, due to the fact that the Western ganister is slower to transform than the Eastern.

Data on the variation of the physicomechanical properties of sheet glass-reinforced plastics exposed over a four-year period to different climatic conditions are reported. Polyester and phenolic laminates were exposed to the climates of Moscow and Batum either in the open air or in unheated warehouses. The tensile and bending strengths were taken as the principal indicators of changes in the mechanical properties of the materials. The property fluctuations are more considerable under humid subtropical conditions (Batum).

Synopsis The Paper presents a new method for the determination of the collapse load for structures of any degree of complexity by a simple routine analysis. The method is limited only by the time which would be taken in the analysis for a large frame. It is shown, however, that a skilled analyst may be able to reduce the labour involved to a considerable extent. The method is contrasted with the method which is used at present, in which the designer guesses the locations of the plastic hinges which form when the structure collapses, and then adjusts his guesses in a systematic manner.

A transition piece used for super-heater tubes of power plants was made by friction weld holding an Inconel tube between an austenitic stainless steel tube and a 2.25 Ci-1Mo steel tube, them mechanical properties at room temperature of the tubular transition piece were examined and thermal cycle and creep rupture tests were carried out for practical use. The test results are as follows:1. Welded joints (730°C S.R) made by friction weld showed satisfactory tensile and bending properties.2. Under thermal stress by 230-650°C thermal cyclic heating and internal pressure, the tubular transition piece was ruptured within the 2.25 Cr-1Mo steel tube in every case.3. In the creep rupture test at 650°C, the tubular transition piece was ruptured within the 2.25 Cr-1Mo steel tube.

A computer program was developed to compute torsional and bending stresses in long bones. The input format for the program is designed to be as convenient to the user as possible, allowing him to transmit to the program only as many points as he feels are required to describe the cross-sectional geometry. The program permits the user to specify by which method torsional stresses are to be computed, what type of stresses are to be computed, and to what accuracy the results are desired. Computation times are of the order of 5 sec or less (on an IBM 360), making use of the program more economical than manual computations.

1. The brittleness of a nitrided case indented with a diamond pyramid (mean value of 10 imprints) can serve as a criterion to determine the layer's tendency to form “grit” during grinding. 2. The brittleness of the nitrided layer determined from the appearance of the diamond pyramid impression depends not only on the inherent brittle strength of the layer but also on the compressive stresses in it. Other conditions being equal, the higher these compressive stresses, the more brittle it is and grit formation during grinding is more likely. 3. The formation of grit on the nitrided layer is associated with compressive stresses caused by sudden surface heating. 4. With increasing core hardness of a nitrided steel part, the nitrogen content and compressive stresses in the case increase, thereby increasing its brittleness. 5. The more thorough the quench-hardening operation (the higher the as-quenched hardness), the less brittle is the nitrided case. Quenching from 900 instead of 950°C results not only in an increased brittle strength of the case in bending tests but also in a reduced brittleness in a diamond indentation test. 6. The decrease of brittleness with increasing nitriding temperature, as determined from a diamond pyramid test is connected with the reduced compressive stresses.

Repeated bending impact tests were carried out with test pieces of a rimmed steel at -40°C-30°C. It was found that, in the case where test pieces were broken at the repeated number fewer than 103, the transition temperature appeared at about 0°C. and did not appear at more than 103. The trasition domain of the case where the cleavage was assumed to be made by the last one impact under repeated impact test was higher than that in case of simple impact test.

The biaxial tensile property of warp knitted fabric of single tricot stitch with close lap has been calculated theoretically from yarn properties and fabric structure, by using the method introduced by Kawabata. In this analysis, two regions, i.e., the deformation regions of bended yarn and yarn stretching, are separated with a critical stretch ratio taken as a border and the properties in these regions are analyzed separately. Then the properties in these two regions are composed. That is:1. Calculating method of critical stretch ratios is introduced theoretically from fabric structure by putting a model in which yarn is straight and not stretched.2. The biaxial tensile properties in the bending effective region is calculated from fabric structure and the equilibrium of forces, assuming that the unit structure consists of three arcs in relaxed form and that friction between yarns can be neglected.3. Next, the biaxial tensile properties in the stretch effective region is calculated from the equilibrium of forces and the tensile property of yarn on assumption that yarn does not move from needle loop to sinker loop.4. Finally, some examples are calculated and examined the effects of some structure constants of the fabric on its tensile property.

Three series of standard two-quart pudding pans of different metal thicknesses, coated with one, two, and three coats, respectively, of enamel were tested for impact resistance, using the Enameled Utensil Manufacturers' Council standard impact test. The impact resistance of the pans was increased with increase (1) in metal thickness of the pans, (2) of the enamel thickness, and (3) in the size of the bottom radius. The size of the chip formed on impact also increased with increase in enamel thickness. The literature dealing with the fracture of glass and enamels is reviewed, and the factors influencing spontaneous chipping and chipping caused by bending and impact are discussed.

Up to the present, the investigations on the thermal fatigue have been carried out mainly under conditions of cyclic uniform heating and cooling in the cross-section of specimen, but in practice we meet with many cases in which the cross-section of materials are subjected to various transient temperature gradients, while studies in these cases have not been made sufficiently.Therefore, in order to investigate these problems we have constructed a new type of thermal fatigue testing machine. With this testing machine the wedge-shaped specimen was rapidly heated by high-frequency-induction, and then cooled in water reciprocally, so as to make transient temperature gradient in its cross-section. By this method, in the specimen the bending and the axial thermal strains were introduced. In our machine, the bending strain was restricted and the axial thermal strain was freely released. The average heating rate at heating surface may change from 50°C/sec to 300°C/sec, and in the range of 10mm along gage length of specimen the same temperature distribution is obtained.Some experimental results of 13Cr steel and 18-8 steel showed that our machine was suitable to the thermal fatigue testing under conditions of transient temperature gradient in cross-section.

It is currently believed in some parts of the world that the problem of structural fatigue in the case of aircraft having a modern multiple spar wing structure can be safely dealt with by allowing fatigue cracks to develop in service. The typical multiple spar wing has its bending tension area distributed between the “ caps “ of two or more spars and a large number of independent heavy stringers. It is believed in some quarters that complete failure in flight of any one spar boom or stringer due to fatigue will leave the wing with sufficient strength for the aircraft to land safely. This note does not discuss the validity of this belief, nor the level of safety so achieved, but attempts an objective assessment of a problem that arises as a consequence of this belief.

This paper deals with the contact pressure between a belt and the pulley to which it transmits force and with the bending and membrane stresses in the belt. The anticlastic configuration of the belt is also taken into consideration. The commonly known simplified approximate analysis of the pressure, as well as the results of a more elaborated theory, are presented. Also given in the paper are the description and evaluation of several experimental stress analyses methods that can be used to solve the problem. Two and three-dimensional photoelasticity, thickness measurements and electrical strain gages were found to be the most practical approaches. The correlation of results obtained using the theories and the experimental methods is discussed. It is estimated that the peak contact pressure is 3.5 times the one computed using the plane stress assumption. Results obtained will also have application in the design of wire-ropes or cables transmitting forces to sheaves, or drums.

The paper discusses existing practice of specifying temperature-rise of electrical machinery by thermometers, and points out that the B.E.S.A. Rules are more satisfactory but are not generally adopted, probably on account of the higher limits.The relations between surface temperatures and internal or hot-spot temperatures are discussed, together with the influence of the load on the temperatures of different parts of a machine.Location of hot spots in the axial direction is considered, as well as the heat flow through the insulation.The influence of the thickness of insulation on the relation between internal and surface temperatures is dealt with, and a diagram showing the radial temperature distribution is given. The importance of considering the voltage of a machine in connection with temperature-rise on account of the greater temperature gradient through the insulation is pointed out.Consideration is given to the question of operating large turbo plants on ultimate temperature rather than on temperature-rise, on account of the increased load obtainable at low air temperatures.A plea is made to operating engineers to call for the fitting of embedded temperature detectors, although temperature guarantees based on this method may not be obtainable. A series of tests on mica-insulated bars is described, including heating runs on bars insulated with mica wraps containing varying percentages of mica, and it is shown that the percentage of mica has a direct bearing on the breakdown voltage which the bars will stand after heating.The results of bending tests on bars before and after heating are shown. The conclusion arrived at is that mica insulation, as used in modern turbo-alternators, retains its mechanical and electrical properties at temperatures up to 200° C. It is suggested that the limit of the ultimate temperature should be raised to 160° C. instead of the usual value of 125°C.

A theory of the biaxial tensile properies of warp knitted fabrics was developed in previous paper. The biaxial tensile properties of single tricot stitches with a close lap is calculable if the mechanical properties of yarn and fabric structures are given.In this paper, the biaxial tensile properties of some actual fabrics have been calculated by using the theoretical formula presented in previous paper. The properties have also been measured by using a biaxial tensile tester for the purpose of comparing with the theoretical values.A good agreement has been obtained between theoretical curves of the biaxial load-extension relation and the measured curves over the whole range from the initial tensile region to the ultimate region.It is concluded that the biaxial tensile properties of single tricot fabrics are calculable with good accuracy if the tensile properties of yarn and the structure constants of knitted fabric are given.

In a garment, freedom from wrinkling depends upon the ability of the fabric to recover from bending deformations which occur during wear and laundering. During wear, the important variables are the ambient temperature and humidity and the activity of the wearer. Fabrics next to the wearer's body are exposed to temperatures of 90-95° F., to relative humidities of 60-95%, and to pressures up to 2 psi for various times. During laundering, the important conditions are temperatures of 100-140° F. while wet, pressure of 1-2 psi, and deformation times of 4-6 min. followed by temperature changes which may either set wrinkles in or remove them as in tumble drying. The mechanical agitation during washing does not cause wrinkling; it actually assists the fabric to recover from wear wrinkles. Centrifugal spinning to remove water is the major cause of wrinkling in automatic washing machines. Data and information on the above factors can be used in the design of laboratory tests which can currently prediet the performance of wash-wear fabrics. Several new and modified test procedures which are being developed along these lines are described.

Synopsis The Paper describes an investigation made for the Anglo-Iranian Oil Company in connexion with large diameter pipe-lines. Formulae are developed for the stresses in a fully restrained line arising from the pressure of the liquid in it, from general variations of temperature, and from differential heating. The loading on anchor-blocks and buttress-blocks ia considered. Formulae are given for the spacing of ring-supports necessary to keep the combined stresses due to bending, eccentricities in alignment, temperature changes, and fluid pressure, within safe limits when judged by the Mises-Hencky criterion. Lack of data on possible errors of alignment and straightness of pipes make these formulæ tentative in character, but the general analysis is independent of particular assumptions in these respects. Tables of formulæ are given both in general terms and in a simplified form for a particular pipe.

A comparison is drawn between numerical and analytical approaches to problems of plate bending and buckling. Certain analytical methods are reviewed and deficiencies are noted leading to a logical development of iterative numerical techniques for achieving essentially identical results. One such technique is presented for investigating the post-buckling behavior of circular plates possessing arbitrary boundary conditions under uniform edge loads. Although a relatively simple problem, it emphasizes the development of the computer program and the conditioning of certain classes of nonlinear differential equations to fit such a program. It is seen that such a procedure resolves a fundamental shortcoming of series solutions to simultaneous, nonlinear differential equations by avoiding arguments concerning the significant number of terms required to satisfy prescribed initial and final boundary conditions with sufficient accuracy. Instead, it replaces a two point boundary value problem with an initial value problem and a Runge-Kutta numerical integration process which may be carried out step-by-step to attain prescribed kinematic and geometric terminal conditions.

Summary: This paper gives the practical engineer a brief and somewhat unusual approach to the theory of prestressed concrete design, and thence develops the formulae essential to design. Analysis of the stresses in a designed section then follows, and the important moment-stress diagram is illustrated. The latter will be of particular interest to field engineers.

The synthetic-rubber O-ring seal is being used successfully for aircraft parts and general hydraulic systems in the cold district. However, satisfactory ones to be used for those conditions have not yet been produced in Japan. Therefore, tests or performance tests of trial productions have been made frequently and it is quite difficult to make these tests when the temperature is thirty or forty degrees below zero.According to JIS the cold flexibility of O-ring for industries in general is to be examined through the cold bending test, and as for those for aircrafts, that is to be tested through the cold elongation method. But both of these methods are not helpful to systematically find out the influence of temperature. The authors has made an apparatus utilizing the cold bending device. According to the experimental results, we obtained that the ratio of the diametral deflexion of O-ring to the load is connected with the hardness of O-ring measured by the JIS hardness tester for the rubber materials. Making use of this results, we propose to represent the so-called “cold flexibility” with variations of the hardness due to the difference of temperature.

Synopsis The Paper extends the plastic theory for plane frames of mild steel to cover the cases in which the detailed loading programmes of a set of independently variable loads are either wholly or partially unspecified and there is no restriction on the number of times each load may be applied. A general method for analysing framed structures of mild steel, under arbitrary loading programmes, is presented. A two-bay portal frame with rigid joints, subjected to three independent forces, is taken as the basis for discussion, and a complete numerical analysis of the “shake-down” problem for this frame is given to illustrate the general method. Once the elastic analysis has been made, the time required for the “shake-down” analysis will, in many cases, be not much longer than that which would be needed to make the analysis for plastic collapse. Limitations of the present theory are discussed, and some suggestions as to its probable applications to design problems are offered.

THE test about to be described has been in use in this company for about fifteen years, and has been adopted to some extent by the rubber industry, particularly for use with belting. However, in response to various requests for information regarding the details of the test as applied to tire-carcass materials, a brief description of the methods now in use in the company laboratories is given here. The tests consists of taking a strip composed of several plies of fabric and rubber, bending the strip around a hub until its two faces are nearly parallel, applying a weight to the hub so that the strip is pulled taut, and moving the jaws reciprocally so that the strip drives the hub and is moved back and forth around the hub. This is continued until a separation occurs between the plies of the strip. This test, if carried out under carefully controlled conditions, gives consistent results, and it is the purpose of this paper to outline these conditions.

In judging the feel or “handle” of a material, use is made of such sensations as stiffness or limpness, hardness or softness, and roughness or smoothness. It is desirable to devise physical tests that analyse and reflect the sensations felt and assign numerical values to the measurements. The present paper describes tests that reflect the first groups of sensations, namely, stiffness and hardness, whilst the sensation that is experienced in stroking a material, obviously connected with frictional properties, will be dealt with in another paper. An instrument is described on which it is possible to measure the angle through which a specimen of cloth droops when a definite length is held out over an edge. By means of a mathematical formula that is fully developed in an appendix to the paper this angle is converted into a term called the bending length of the material. This quantity may be defined as the length of fabric that will bend under its own weight to a definite extent. It is strictly a meas...

1. The selection of carburizing and diffusion chromizing conditions for low- and medium-carbon steels makes it possible to increase the surface hardness to HRC 60-50 after final heat treatment without quench cracks, which raises the fatigue limit several times as compared with the strength after chromizing without carburizing. 2. After carburizing and diffusion chromizing of steel 18KhGT the carbon concentration down to a depth of 0.6 mm amounts to 0.8–0.7%, and after quenching and low-temperature tempering the surface hardness is HV 1400-1650, HRC 58-59; the fatigue limit in symmetrical bending is σ −1, = 81 kg/mm2 σ−1c. 3. After chromizing of steel 18KhGT previously carburized, followed by quenching and low-temperature tempering the fatigue limit increased by 29% for samples carburized in active carburizer and by 57% for samples carburized in weak carburizer as compared with the same treatment but without chromizing. 4. Carburizing with subsequent diffusion chromizing can be used to increase the wear resistance of machine parts operating under high contact pressures and cyclic loads.

Circular tanks resting on compressible soils suffer ascisymmetrical settlement and the tank floor takes on a dish-shaped form. The paper gives the bending stresses in the tank floor and walls due to the differential settlement of the floor center with respect to the tank walls. The analysis is useful for the choice of foundations of such cases.

The paper describes the preparation of machine control tapes using a computer programme package, and the B.S.R.A. (British Ship Research Association) part-programming processor system. The comprehensive nature of the system, the development of a modular basis and the modification of the general engineering 2CL to provide a shipbuilding version are described. N.C. (Numerical Control) machines in use in shipbuilding include automatic draughting machines, several varieties of N.C. flame-cutting machines and their associated computer programmes, and a N.C. frame bending machine. The advantages of Numerical Control are listed and the importance of considering the system as a whole is emphasized.

The purpose of this research was to assess what improvements might be obtained in the bend ductility of beryllium sheet by starting with high purity commercial powder and consolidating it into sheet by techniques that minimized deformation and texturing. Sound sheet was achieved with reduction ratios from 2∶1 to 12∶1 at temperatures from 700° to 1050°C by forging, upsetting and compression rolling. Compression rolling is accomplished by successively changing the rolling direction by 30 deg after each pass so that no preferred rolling direction was developed. It was found that as the plastic bend ductility increased (up to 4 pct) the yield strength decreased. The higher bend ductilities corresponded to lower reduction ratios, lower degrees of preferred orientation and a larger subgrain size as determined by transmission electron microscopy. Sheet prepared by commercial rolling practices from the less pure commercial powder exhibited similar behavior. The ductile-to-brittle transition temperature for bending decreased with improved purity and reduced texture.

In previous paper, a biaxial tensile deformation theory was developed of a plain tricot fabric, a fundamental type for all two-bar tricot fabrics, .In the present paper, this theory is expanded and more generalized to calculate the properties of two-bar tricot fabrics. The structure of the model proposed for the plain tricot fabric is modified to make it adaptable to more complicated structure.When the number of wale spacings crossed by underlapping becomes large or when spun yarn is used, the original theory becomes more error-prone. To make the theory more precise, the compressive property of yarn should be introduced for calculation in stretching-effective region. In the new theory, a simple model where yarn is wound around a cylinder is used for the structure of the crossover region.Finally, some theoretical calculations have been done for various factors such as the tensile and the frictional properties of yarn, structural constants, and the number of wale spacings crossed by underlapping.

Of recent years, the progress of E. D. P. S. (Electronic Data Processing System) has been very remarkable, and this system is now considered very effective method for ship construction.In Yokohams Shipyard, I. B. M. 7090 Type which is installed in M. C. C. (Mitsubishi Computing Center) is used for mould loft calculation, such as calculation of developing off-sets for curved shell plates, bending off-sets for frames, and assembling off-sets for erection units etc.And this calculation system has been adopted for several kinds and type of actual ships, such as 40, 000 DWT oil tanker and 10, 000 DWT super liner cargo ship.The system is featured by many charactiristics, such as:1) The number of shell plates which can be dealt with by this system are approximately 150-200 pieces of plate for either one 40, 000 DWT oil tanker or 10, 000 DWT cargo ship, which is 90% of total curved shell plates.2) Only 1/1000 hours is needed to calculate the developing off-sets and bending off-sets for one plate.3) Error in calculation can be kept less than ± 2.5mm in average, which is more accurate than the provious 1/10 scale mould lofting.4) Since making input data is very simple, even unskilled worker can accomplish this work fast and without error.In this first report, calculation methon for curved shell plater and twisted longitudinal frames will be explained.