Search

This paper describes an apparatus used to investigate the temperature variable in fretting. Observations have been made on the nature of the wear, its appearance, and its extent in two atmospheres—air and argon. In argon, the wear is adhesive in nature and has been shown to be influenced by a change of material properties with temperature. With an air environment, the adherence and stability of the oxide product is temperature-dependent, thus affecting the wear rate. From a consideration of wear scar parameters it is shown that abrasion by α-Fe2O3debris is not the main cause of fretting wear.

The rolling-four-ball test, which closely simulates the rolling and sliding experienced in angular contact ball-bearings, has been used to study the influence of the steelmaking process on the rolling contact fatigue properties of steels used for rolling bearings. Commercially available balls, as well as specimens made from conventional En-31 and various special high-speed tool-steels manufactured by different processes, have been compared. Methods of improving steel quality, such as vacuum induction melting, vacuum consumable arc melting and vacuum degassing have been assessed. The same types of steel manufactured by similar methods by different steelmakers have been tested. Significant differences in performance have been found between different types of steel and between the same types of steel manufactured by different processes. Acid material was generally superior to basic material, and vacuum techniques were beneficial. Modifications in the steelmaking procedure which improved material properties gave increased resistance to rolling contact fatigue. The effect of the steelmaking process was found to be similar with all steelmakers. Observations of significance in the study of the mechanism of failure have been made.

The present state of knowledge of methods of hardening and of strengthening materials and the use of hard materials for tribological applications is summarized. The essential properties of materials for various types of mechanisms such as rolling bearings, gears, cams, etc. are reviewed. Mechanisms of failure and controlling factors are discussed.

Experimental structures have been built and tested which utilize polyester-impregnated, paper-laminated urethane foam board as the principal stress-resisting material. These structures have been found adequately strong for the construction of light industrial and residential buildings. Material properties are in some instances an advantage; in others a restriction. A two-story prototype building has been constructed which shows performance characteristics similar to conventional wood-frame structures.

Prediction of field service behavior of a bituminous mix on the basis of its composition or material ingredients, presents a difficult problem. In spite of this, research and experience have provided methods for practical mix designs which are adequate in most cases. The designs used at present are essentially trial and error in nature. The type and gradation of aggregate and the asphalt grade are chosen, then a number of asphalt contents are estimated which hopefully bracket the desired optimum conditions. Next follows the making of specimens and their testing to determine the optimum mix. If the combination of ingredients does not give the specified or desired properties (stability, voids, etc.), the components in the mix are changed and the tests are repeated. The assumption at the start of this investigation was that a knowledge of physical factors of the aggregate and the binder could lead to a more systematic and unified mix design procedure. The specific objectives of this research were: a. To define and measure quantitatively useful mix-design parameters for aggregates. b. To define and analyze the function of asphalt in a mix. c. To try to predict "strength" values for aggregate-asphalt mixtures from composition parameters. d. To initiate an approach to a unified mix design.

Many applications in the electrical industry require the use of materials that must sustain a mechanical load as well as provide electrical insulation. Applications such as these are electromechanical in nature, and include the armature bar support system in the stator, and the slot liner, blocking and retaining ring insulation in the rotor. In order to fill both the electrical and mechanical requirements of these applications, compromises have traditionally been necessitated in one of the material properties. The development of new materials has reduced the need for these compromises, as it has provided materials with increased mechanical strength without sacrificing insulating properties.

The paper presents the results of load tests on instrumented bored piles. Field measurements of load transfer in sand were made and design criteria are suggested for computing the tip and the side resistance of bored piles in sand as a function of soil properties. The behavior of bored piles in sands is a complex problem and more testing and related analytical studies are needed to achieve a better understanding of the problem. The side resistance of a bored pile in sand can be reasonably correlated with the integral on the periphery of the pile of the product. In this study, the correlation factor was found to be equal to about 0.7 for a penetration in sand less than 25 ft. Pending future progress, the curves showing tip load versus settlement for side shear transfer presented in this paper should be used cautiously by the practicing engineer.

Behavior of elastic-plastic structures under repetitive and fluctuating loads is considered in this paper. Plastic deformation either stabilizes after a finite number of cycles or continues during the cycling. In the first case the structure is said to have shaken down to the boundary at the loading program. If plastic deformation does not stabilize an elastic-plastic structure becomes unserviceable due to either alternating plasticity when yielding occurs repeatedly in the opposite senses or accumulation of plastic strains and progressive increase of permanent displacements. This paper attempts to survey the shakedown theory, including the accommodation of a structure to the prescribed loading range as well as inadaptation and unserviceability. The notion of shakedown, incremental collapse, ratchetting and alternating plastic deformation are first illustrated with examples. The fundamental theorems on shakedown and inadaptation are presented next, attention being directed to generalizations of the classical Melan and Koiter theorems. Applications of the theorems are given. Available methods for determining the shakedown range on generating self-equilibrated stress fields are discussed. Special techniques applicable to problems involving both dead and fluctuating loads are invoked. Recent studies accounting for inertia forces, geometrical changes, material hardening, variation of material properties with temperature, displacement assessment, etc. are referred to.

This paper describes how finite-difference procedures are used to solve axisymmetric thermal stress problems with the aid of an electronic digital computer. In this solution, elasticity theory is employed in a stress-function formulation that includes the effects of continuously varying temperatures in both the axial and radial directions. Variations of material properties with position are accounted for in a stepwise manner by dividing the solid into zones with independent properties. The finite-difference techniques permit details such as curved boundaries and multimaterial assemblies to be incorporated into the computer program. An extensive experimental test program was developed concurrently with the analysis, and solutions are compared with photoelastic model studies as well as with the measurements made on complete propellant-grain systems. Solutions to several typical propellant-grain problems also are presented in this paper to illustrate the general characteristics of these systems under transient thermal loadings. One of these problems is the transition between two steady-state storage temperatures which is a condition commonly encountered. Results indicate that under this loading the most critical structural condition is usually experienced by the grain at one of the steady-state end conditions. E / n, s, 8 =

Synopsis The Paper shows that to a first approximation the California bearing ratio (CBR) of a remoulded soil can be deduced from the estimated bearing capacity of the soil, which itself can be deduced from a knowledge of the suction of the remoulded soil and its true angle of friction. It is also shown that the suction of such a remoulded soil and its true angle of friction can be inferred from a knowledge of the liquid and plastic limits and moisture content of the soil, thus allowing the CBR and its variation with moisture content to be estimated from the results of the various plasticity tests. If the degree of saturation is known, the variation of CBR with air content can also be deduced. Worked examples are given showing how the method described in the Paper is used to estimate CBR values for a variety of practical conditions. L'Exposé fait apparaître qu'à une première approximation, le coefficient de charge de Californie (California bearing ratio (CBR)) d'un sol remanié peut être déduit à partir de la capacité de charge estimée du sol, qui peut elle-même être déduite de la connaissance de la suction du sol remané et de son angle réel de frottement. Il apparait aussi que la suction d'un tel sol remanié et son angle réel de frottement peuvent être déduits de la connaissance des limites de plasticité et de l'état liquide et de la teneur en eau du sol, permettant ainsi que le CBR et sa variation correspondant à la teneur en eau soient estimés à partir des résultats des différents essais de plasticité. Si le degré de saturation est connu, la variation du CBR selon la teneur en air peut aussi être déduite. Des exemples avec les opérations effectées sont donnés montrant comment la méthode qui est dérite dans l'exposé est employée pour estimer les valeurs CBR en fonction de conditions pratiques variées.

Bowing of multispan rod-type fuel elements depends upon axial thrust, heat generation gradients and variations in heat transfer processes. This paper presents the analysis needed to extend the results of an earlier paper to include the effects of interaction between rod deflections and coolant flow. It is assumed that the material properties of the rod can be adequately represented by material properties associated with an axisymmetric temperature distribution, and that perturbations to the flow field are small enough that linearized equations can be used.

In previous papers by Green & Rivlin[1, 2] and an earlier report [3], constitutive equations have been developed describing the mechanical properties of materials possessing memory. A similar topic has been discussed by Noll [4, 5]. In [1, 2] it is assumed that the stress at a fixed particle of the material is a functional of the displacement gradients at the instant of measurement and at times preceding the instant of measurement. In another paper, by Pipkin & Rivlin [6], constitutive equations have been developed governing certain types of physical properties of materials which may be described by the relation between a tensor of order µ on the one hand and the displacement gradients in the material and ν vectors on the other, all the quantities being measured simultaneously. In the present paper, these two problems are combined.

The advent of deep ocean technology has created a need of buoyancy at ever increasing depths. This paper concerns itself with two most widely used techniques for dewatering/deballasting, compressed air supplied by surface maintained compressors and high pressure gases contained in pressure vessels. The objective of the paper is to examine the effects on these two techniques of various parameters which, in the author's opinion, are often overlooked by design engineers. This results in a significant degradation of the system under actual operating conditions. The principal parameters involved are structural integrity, geometric properties, material properties and the variance with pressure of the real gas properties and sea water density. This paper is an attempt to appraise designers and users of the impact of the above considerations on proposed buoyancy systems.

The solution of problems in soil engineering requires a detailed knowledge of the mechanical properties of soils which are, perhaps, among the most complex materials to be studied from this point of view. The present paper endeavours to present a reasonably comprehensive account of the relations governing the response of soils to applied forces. An introductory presentation of the aspects involved and their place within the general framework of the study of material properties is followed by a discussion of relevant methods used in describing and classifying soils. A separate section treats the important subject of soil water and the factors influencing its movement through the channel network of the soil skeleton. The greater part of the paper is devoted to considerations regarding the fundamental stress-strain-time relationships. The important principle of effective stress is presented, followed by a discussion of stress-deformation relationships. The process of consolidation, i.e., the time-dependent dissipation of pore-water pressure after loading, is treated in some detail. The applicability, within a limited range, of linear stress-strain relations to soils is discussed followed by an account of failure criteria and shearing resistance with special emphasis on the prevailing drainage conditions. The influence of the strain rate on strength forms the subject of the last section of the treatment of stress-strain-time relations. In conclusion, several special topics are presented: a discussion of the pressures and volume changes in expansive clays, the behaviour associated with thixotropy and sensitivity and, lastly, the response of soils to dynamic forces.

The paper deals with current conceptions of cold working and its varied effects on the metal undergoing deformation. The mechanism and behaviour of single metal crystals and polycrystalline aggregates, whilst undergoing cold working deformation, are outlined. Two aspects are treated, namely, block slip and “twinning”. The X-ray examination of a polycrystalline metal under deforming stresses is mentioned, together with the formation of flow lines, better known as Lüder's lines. The effect of cold work on the mechanical, physical, electrical, and chemical properties of materials is then considered in some detail, together with the practical aspects of the changes wrought. The paper concludes with a brief summary of the subject, and the more important theories are reviewed in order to see how far they explain all the phenomena observed.

This paper concerns the propagation of elastic waves in materials reinforced by inextensible fibers. Slowness surfaces, energy fluxes and directions of propagation are determined and expressed in terms of material properties and fiber directions. The case of two domains of fiber-reinforced materials, similar in all respects except for fiber direction, and bonded together at a plane interface, is considered in detail. The misalignment in fiber directions that occurs at the bonded interface is shown to cause a significant scattering of mechanical energy. The range of validity of the mathematical model employed in this paper is indicated and it is shown that the results may be useful in practical cases. The existance of surface waves is also discussed.

In recognizing the increasing availability of various composite materials, this paper promotes a new approach to the design of the plate and shell structures. It is based on the loading and shape require ments of the structure to determine a particular composite whose constituents and their geometric arrangements are such that a certain design criterion will be satisfied. For the preliminary study of such an approach, a momentless criterion is adopted in the present paper for the design of axisymmetrically loaded shells of revolution. To maintain the shell in a momentless state, the general equation which governs the shape, loadings and the material properties of the shell, and the displacements equations have been derived. Applications to the pressure vessels with ellipsoidal bulkheads show that composite materials with variable elastic constants will be needed for constructing a momentless vessel. Numerical examples are presented to illustrate the proposed method of approach and provide as guidelines for the development of new composites.

SummaryStandard techniques of mass-transfer theory are used for the prediction of ablation rates; the thermodynamic and chemical-kinetic material properties are introduced by way of enthalpy-composition diagrams; the interface condition is given as the root of a single non-linear equation involving material properties. The paper treats both steady ablation and unsteady ablation, the latter by means of a quasi-steady assumption which confines transient effects to the solid phase.Detailed comparisons are made with the methods of Sutton, Bethe and Adams, and Lees. The formulations of the paper are shown to be equivalent to, but more general than, those of the earlier authors; it is suggested that they are simpler as well. Some improvements over previous practice are recommended in connection with the calculation of the shear stress at the interface.

The paper commences with a general treatment illustrating the advantages of writing the equation of state of a pure substance in characteristic (canonical or fundamental) form, from which expressions for all other thermodynamic properties can be written down in terms only of the characteristic function and its partial derivatives. In this way, thermodynamic consistency between the equations for the different properties is automatically ensured. The initial difficulties in constructing an equation of state in characteristic form are briefly discussed, and it is shown how the characteristic equation may be built up from an existing p-v-T equation of state and an equation for the specific heat capacity at zero pressure. An existing set of equations for the single-phase region of Refrigerant-12 is transformed in this way into a single characteristic equation of state from which, through given simple expressions, all other thermodynamic properties may be computed. The equation of state is expressed dimensionlessly in reduced co-ordinates so that it may be used with equal facility in any coherent system of units. For the sake of completeness, other existing equations for the saturation pressure and for the saturated liquid have been put into dimensionless form and are given in the paper.

Since the structure of simple fluids at high densities is largely determined by "hard-core" molecular repulsions, the properties of such fluids must be closely related to those of hard-sphere systems. In particular, the pair distribution function g(r), of a simple fluid must resemble that of a hard-sphere fluid. In this paper, general equations for the thermodynamic properties of real fluids are derived in terms of the pair distribution function for hard-sphere fluids. We have developed equations for the properties of real systems by neglecting higher order terms in the functional expansion of g(r) exp /?4(r) about its hard-sphere value (8). It was possible to demonstrate the applicability of this truncated expansion to dense fluids without detailed specification of the potential function +(r). After an outline of the derivation of thermodynamic relations, results are given for excess functions of concentrated solutions at constant volume. Towards the end of the paper, we present equations for partial molar properties at infinite dilution.

W recent years, considerable interest has developed in filament-reinforced plastics This new, composite material possesses many advantageous material properties including a high strength-to-weight ratio, which compares favorably with homogeneous metallic materials At one time, the fabrication of filament reinforced plastic pressme vessels presented itself as a formidable problem, but the difficulties have since been overcome There still remain some problems of analysis, but these too are being solved Conventional elasticity formulas are not applicable for use in analyzing filament-reinforced plastics because some of the material property assumptions of classical elasticity are invalid Instead, it is necessary to derive new relations based on suitable simplifying assumptions In recognition of this fact, Kitzmiller, DeHaven, and Young assumed in their analysis of a filament reinforced plastic pressure vessel that the resin is used as a binder with no force carrying capacity Their approach, commonly referred to as the netting analysis, was subsequently extended by Zickel and Read 3 In a later analysis of the problem Hoffman included the force carrying capacit}^ of the resin and derived formulas which contain orthotropic material constants The material constants of the composite material depend upon the properties and distribution of the filament and the resin Changes in its composition will affect the material constants in a way that may be studied experimentally, analytically, or by a combination of the two The analytic point of view will be developed in the present paper Bell, Brown, Ekvall, and Cutwater, to name a few, were motivated toward similar objectives All but one confined his analytical work to materials loaded in the direction of the reinforcing filaments They found relations similar to those presented at the beginning of the present paper Ekvall, on the other hand, also considered the complementary problem in which an external force was applied normal to the direction of the reinforcing filaments It is the purpose of the present paper to analyze the behavior of filament reinforced plastics from a solid mechanics point of view The study is directed toward an evaluation of the stress strain relations in the direction of and normal to the internal filaments Each analysis will be conducted with the aid of an equivalent model Unlike the work of the previous investigators, the present study will not be confined to the elastic range, but will include the elastic-plastic range as well To the best of the author's knowledge, HofTman is the only other investigator who has heretofore used a plastic yield condition in his analysis of a reinforced plastic

The properties of materials at high temperatures are receiving considerable study in the design of much industrial equipment. The present paper describes some fundamental considerations in this field by discussing the creep of metals in shear. Some theoretical and practical reasons for investigating creep in shear are given, test apparatus for this purpose is outlined, and some experimental information is included. Much more work in this type of study is desired and the paper may help to stimulate further research in this direction.

This paper describes new reinforced thermoplastic materials that have been developed for rigid exterior, painted automobile panels. Traditionally these panels have been fabricated from zinc die cast, steel, or more recently from sheet molding compound (SMC). Guide Lamp Division of General Motors is injection molding mineral filled nylon, fiber glass reinforced nylon, and fiber glass reinforced thermoplastic polyester rigid exterior automotive panels that are painted car color for 1974 Chevelles, Cadillacs, Pontiacs, Oldsmobiles and Buicks. The applications, material properties, paint performance, and design recommendations for these three reinforced thermoplastic materials are reviewed. (MM)

The authors of preceding tutorial papers in this volume have discussed the physical nature of shock-wave propagation in solids, the experimental techniques involved, and some aspects of transient mechanical behavior. The purpose of the present paper is to consider, firstly, the application of stress and shock waves to the technology of material fabrication and processing, and secondly, to assess the ensuing effects on material properties.

The subject of material science dealing with the macroscopic stress-strain behavior of engineering is generally called the “mechanical properties of materials.” In addition to solid state physics, an understanding of macroscopic mechanical properties is necessary in both the evaluation and improvement of material properties. Furthermore, these mechanical properties and the associated engineering theories defining stress-strain behavior still represent the only scientific basis for engineering design. This paper reviews recent developments in this field. New engineering theories for expressing the stress-strain behavior of materials under various environments are also considered. The paper does not attempt to outline the entire field, but the essential information on mechanical properties is briefly covered. Some areas of research on the experimental and theoretical macroscopic aspect of material science needing exploration are also indicated. In these evaluations, theories predicting the stress-strain relations for combined states of stress from uniaxial stress-strain relations are also summarized. Because of space limitations, this paper is restricted to static properties of materials, and dynamic loading conditions are excluded.

This paper describes how finite-difference procedures are used to solve axisymmetric thermal stress problems with the aid of an electronic digital computer. In this solution, elasticity theory is employed in a stress-function formulation that includes the effects of continuously varying temperatures in both the axial and radial directions. Variations of material properties with position are accounted for in a stepwise manner by dividing the solid into zones with independent properties. The finite-difference techniques permit details such as curved boundaries and multimaterial assemblies to be incorporated into the computer program. An extensive experimental test program was developed concurrently with the analysis, and solutions are compared with photoelastic model studies as well as with the measurements made on complete propellant-grain systems. Solutions to several typical propellant-grain problems also are presented in this paper to illustrate the general characteristics of these systems under transient thermal loadings. One of these problems is the transition between two steady-state storage temperatures which is a condition commonly encountered. Results indicate that under this loading the most critical structural condition is usually experienced by the grain at one of the steady-state end conditions. E / n, s, 8 =

THE WRITERS AGREE WITH HORN AND HENDRON THAT THE SLIDING WEDGE METHOD OF ANALYSIS IS IDEALLY SUITED FOR COMPUTER SOLUTION AND A FULL PARAMETER STUDY WOULD BE A USEFUL CONTRIBUTION. THE WRITERS AGREE THAT A RELATIVELY LOW VALUE OF THE UNIT WEIGHT OF THE SHELL MATERIAL WAS USED IN ANALYZING THE SECTION. A VALUE OF 104 PCF WAS USED FOR THE SOIL CHARACTERISTIC BECAUSE: (1) THE UNIT WEIGHT OF THIS MATERIAL HAS RELATIVELY LITTLE INFLUENCE ON THE COMPUTED FACTOR OF SAFETY, (2) PRIMARY INTEREST WAS IN THE STABILITY OF THE UPSTREAM SLOPE OF THE EMBANKMENT FOR A CONDITION OF FULL RESERVOIR, AND (3) THE ABUNDANCE OF ANALYTICAL DATA FOR UNIT WEIGHT OF 104 PCF MADE IT UNNECESSARY TO COMPUTE VALUES FOR OTHER UNIT WEIGHTS. THE WRITERS AGREE THAT THE COMPUTED FACTOR OF SAFETY IS RELATIVELY INSENSITIVE TO VARIATIONS IN THE POSITIONS OF THE ASSUMED FAILURE SURFACES WITHIN THE EMBANKMENT. HOWEVER, IT SHOULD BE NOTED THAT THE IN- SENSITIVITY OF THE COMPUTED FACTOR OF SAFETY TO CHANGES IN THE POSITION OF .0 EVEN AS LARGE AS 40 FEET HAVE RELATIVELY LITTLE INFLUENCE ON THE GENERAL LOCATION OF THE SLIP SURFACE WITHIN THE EMBANKMENT IN VIEW OF THE EMBANKMENT UNDER CONSIDERATION. IN CONNECTION WITH THE POSITION OF FAILURE SURFACES, THE WRITERS HAVE BEEN UNABLE TO FIND ANY DISCREPANCY IN THE VALUE REPORTED IN THE ORIGINAL PAPER. REFERENCES: STABILITY ANALYSES FOR A SLOPING CORE EMBANKMENT, H. BOLTON SEED, HASSAN A. SULTAN, ASCE, (PROC. PAPER 5308), JULY, 1967.

The damping effectiveness of a treatment utilizing the shear motion of a viscoelastic layer depends upon the stiffness of a constraining layer and the separation of the center of the constraining layer from the center of the base plate. A treatment which increases the latter factor through use of a spacer has been described previously by Kerwin [J. Acoust. Soc. Am. 31, 846(A) (1959), and Paper IC3 presented at III International Congress on Acoustics, Stuttgart, Germany, September 1, 1959]. An alternative method of achieving large separation is to combine the function of the spacer with that of the constraining layer in a “spacer‐foil.” The theory for such a treatment is given in the present paper, with relationships for the optimum thickness as a function of material properties.

THE WRITERS AGREE WITH OLSEN AND CHEN'S REMARKS REGARDING THE IMPORTANCE OF THE FREQUENCY CHARACTERISTICS OF THE INPUT BASE MOTIONS. THE WRITERS EXAMINED THE INFLUENCE OF THESE FREQUENCY CHARACTERISTICS IN A SUBSEQUENT PAPER. THE USE OF POWER SPECTRAL TECHNIQUES WOULD BE USEFUL PROVIDING THE APPROPRIATE DYNAMIC MATERIAL PROPERTIES OF THE SOILS ARE INCORPORATED IN THE ANALYSIS. SINCE THE EXAMPLE DOES NOT REPRESENT CORRECT MATERIAL PROPERTIES, IT IS SUGGESTED THAT ADDITIONAL ANALYSES ARE REQUIRED TO EXAMINE THE USEFULNESS OF POWER SPECTRAL TECHNIQUES FOR THE ANALYSIS OF SOIL DEPOSITS. REPORTS ISSUED: SEISMIC RESPONSE OF HORIZONTAL SOIL LAYERS, I.M. IDRISS, H. BOLTON SEED, ASCE PROC. PAPER 6043, JULY 1968.

The storage, retrieval, and manipulation of thermodynamic data with the aid of a computer requires accurate analytical representation of thermodynamic properties of solutions. In the present paper, a critical assessment is made of simple power series expansions and their limitations in representing thermodynamic properties over the entire composition range of a binary system. The advantages of certain orthogonal series as an alternative method of representation is also discussed. Particular emphasis is placed upon series representations which use Legendre polynomials due to their simplicity and the fact that their functional form is consistent with empirical observations of solution behavior. Since the coefficients of orthogonal series are independent of each other when the entire composition range of a binary system is represented, any thermodynamic property can be fitted to any desired degree of accuracy by a finite number of terms without the necessity of storing a large number of significant digits. Also, because the coefficients are uncorrelated, they are amenable to mathematical interpolation and extrapolation as well as to physical interpretation. The relationships between coefficients of series expansions of all partial and integral properties for the general case have been derived using the Gibbs-Duhem equation.

The question considered in this paper is the ultimate performance limitations of variable-reluctance stepping motors. It has been shown that solving the problem of matching a stepping motor to a load reveals two key parameters needed to characterize its performance for point-to-point positional control. These parameters are the work per step and the upper limit on stepping frequency when the motor runs free of its load. These parameters apply when certain operating conditions, termed ''Class I operation'', are satisfied. The electromagnetically limited performance capability of two types of stepping motors is examined in terms of the above two parameters. The types considered are machines with armature motion parallel to the air gap and those with armature motion normal to the air gap. Expressions are derived that relate the key performance parameters to the physical dimensions of the machines and to basic properties of materials. It is concluded that the machines with motion normal to the air gap potentially offer superior performance to those with parallel motion, at least over size ranges of greatest interest. However the full realization of this superior performance will not be possible until the mechanical problem of converting small linear displacements into shaft rotation is solved in an efficient manner.

Synopsis Polymer-impregnated concrete (PIC) impregnated with the most often used polymers, polymethyl methacrylate and polystyrene, shows little ductility. The ultimate strength is often three to four times higher than that of ordinary concrete, but failure comes without warning in a brittle, almost explosive manner. This paper reports an investigation designed to increase the ductility of PIC so that some plastic yielding can take place before and after the ultimate load is reached. Various percentages of monomer combinations of the methyl methacrylate were used with an elastomer, n-butyl-acrylate. The entire stress-strain relationship of the materials was determined by means of the splitting tensile and axial compression tests. The investigation shows that PIC can be modified to give either a material with high strength and little ductility or one with a somewhat lower strength and large ductility. Thus potentially material properties can be tailored to particular structural service requirements.

This paper is concerned with a special class of response functions for some of the constitutive equations in the nonlinear isothermal theory of elastic-plastic materials. Detailed attention is given to the development of special forms for the free energy and the stress response, motivated mainly by the mechanical behavior of ductile metals in the plastic range and in the presence of finite strains. After obtaining a properly invariant representation for the free energy response (and hence also for the stress) as a function of certain (easily interpretable) measures of deformation, the results are specialized to isotropic materials and are expressed in terms of the invariants of kinematic measures. Some special cases are elaborated upon and, by way of illustration, the influence of plastic deformation on the material properties of the stress response in a simple tension test is discussed.

This paper describes the development and verification of analysis procedures for predicting the performance of a wood joist floor system at service loads. The analysis procedure incorporates the interaction of the many material and system characteristics including interlayer slip, variable material properties, and composite and two-way action. Parameter studies showing the influence of major variables on floor system behavior are presented. Experimental results obtained from beam and floor tests are compared with predicted values calculated using the developed mathematical model. Floor behavior at overload levels is considered. The rational analysis procedures presented can form the basis for improved design procedures for wood joist structural systems with resulting important implications in housing and other construction.

Nondestructive test methods have traditionally been involved in the detection of localized or point defects such as cracks, voids, and inclusions. However, there has been an increasing demand for meaningful NDT methods that characterize material properties over large surface areas or within the entire volume of a component or structure. Infrared techniques, which lend themselves to area and volume coverage, have been refined for this purpose to a high degree. Simultaneously, there has been a major effort to increase the effectiveness and utility of the large amounts of data resulting from IR scans. This paper concentrates on data enhancement methods, using both real-time and computer-treatment techniques. The data reduction methods covered are significant departures from present NDT data presentations and are aimed primarily at the major ``IR customers''-the materials and design engineers.

By representing the time-dependent material properties by mechanical models, i.e. the generalized Maxwell and/or Voigt (or Kelvin) models, it is possible to formulate a consistent procedure to analyse the effect of material damping on dynamic response. As a continuation of the previous work which concerned the creep and relaxation of viscoelastic materials, the present paper applies this representation to the harmonic response analysis. The harmonic solution can be obtained by decomposing the relevant forces and displacements into real and imaginary parts and it is shown that the modal analysis by an appropriate eigensolution procedure is useful for obtaining the dependence of vibration amplitude on frequencies of sinusoidal external excitations.

This paper discusses stresses and deflections in anisotropic solid structures of revolution. It presents two methods based on finite-element techniques: one, a solid-of-revolution method in which material properties, applied forces, and temperatures are independent of angle, and two, a long-cylinder method in which these properties are independent of the longitudinal coordinate. These methods are postulated on uniform stress fields within the element, rather than on the usual functional displacement description within the element. A Fortran program has been written for both these methods, and ample test problems are presented to validate the methods. An application is presented for thermal stresses induced during the post-growth cooling stage of Czochralski-grown lithium tantalate crystals.

The present state of knowledge of the phase relations and thermodynamic properties of the uranium-nitrogen system is given. Emphasis is placed on the nonstoichiometric and thermodynamic properties of uranium sesquinitride. The present paper consists of two parts. The first part is on the phase relations; an equilibrium phase diagram is proposed, and the relationship between structure and lattice parameter for the α-U 2 N 3 -UN 2 system is shown. The second part deals with thermodynamic properties of UN and α-U 2 N 3 ; the data on decomposition pressures, specific heats, and heats and free energies of formation are summarized and evaluated.

Highway pavements are generally represented by a threelayer viscoelastic model. In this paper a two-part model is presented to account for damage accumulation in such structures. The first part of this model uses simulation techniques to relate the statistical characteristics of the system response to the variability of the operating environment and of the material properties. The stress, strain and deflection outputs are used in the second part of the model to yield the statistical characteristics of three damage indicators: rutting, roughness and cracking. This second part of the model is based on a closed-form probabilistic solution. The material properties as well as the operating conditions, i.e., temperature, loading patterns and velocities, are given in terms of their statistical characteristics. The structural integrity and reliability with respect to each of the damage indicators are measured. A special feature of the second part of the model is that the responses are given for varying temperatures. An example of application is provided.

This paper is concerned with a polar symmetric transient thermal problem for a hollow sphere of strain-hardening material, the inner boundary of the sphere being subjected to a sudden temperature rise. Thermal and material properties of the medium are dependent on temperature. An illustrative example, involving linear variation of conductivity, thermal expansion, yield stress and quadratic variation of elastic modulus with temperature, has been solved numerically. Stress and plastic strain distributions on loading and residual stress distributions on unloading have been presented.

This paper presents a technique that seems to calculate adequately, from first principles, the mound and cavity growth that occur during nuclear and high-explosive cratering events. The technique features a standard, numerical approach to high-intensity, stress-wave propagation coupled with a unique model of material behaviour in brittle failure. A preshot testing programme is presented which obtains the necessary material properties from logging tests in the medium and from laboratory tests of selected rock samples. In situ properties to be determined by field logging are density and elastic velocity (compressional and shear velocity). Sample properties to be determined by laboratory tests are hydrostatic compressibility (to at least 40 kb), triaxial data, tensile strength, Hugoniot elastic limit, and high-pressure Hugoniot data for the rock near the point of detonation (nuclear only). Calculations are presented for Project Hardhat (5 kt, nuclear in granite), Project Scooter (0·45 kt, high-explosive in alluvium), Project Danny Boy (0·42 kt, nuclear in basalt), Project Sulky (0·09 kt, nuclear in basalt), and three parameter studies featuring rhyolite equations-of-state. The Danny Boy calculation confirmed spalling to be the predominant, nuclear cratering mechanism in hard, dry rock. This observation permitted the construction of a free-fall, throw-out model which gave a reasonable estimate of crater radius and ejecta boundary. The rhyolite parameter studies give some insight into the importance of medium properties in determining crater geometry. Further effort in this area is required; however, the agreement between the above calculations and the field experiments indicates that the technique is capable of resolving this issue.

Many different impact test arrangements have been utilized to investigate the dynamic properties of metals. This paper discusses the applications and limitations of a one-dimensional theory of bar impact, particularly as it relates to a specific experimental configuration known as the ‘thin wafer’ or ‘split Hopkinson pressure-bar’ technique. An analysis of this experiment, which utilized a bilinear approximation for the stress-strain curve of the aluminium being tested, led previous investigators to demand the incorporation of strain rate effects in the constitutive relation of metals. However, the present nonlinear analysis of the same test demonstrates that the experimental data for this particular metal can be predicted from a strain rate independent theory. This new analysis indicates the influence of assumptions which neglect certain stress wave propagation phenomena. These mechanical effects are shown to be an important contribution to dynamic observations which had been attributed only to intrinsic material properties , such as strain rate dependence.