bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Procedure for Estimating the High Cycle Fatigue Strength of Some High Temperature Structural Alloys
Authors: Soo P. , Chow J. G. Y.
Published: October 2009

The generation of strain controlled fatigue data, for the standard strain rate of 4 × 10−3 s−1, presents a problem when the cycles to failure exceed 105 because of the prohibitively long test times involved. In an attempt to circumvent this difficulty an evaluation has been made of a test procedure involving a fast cycling rate (40 Hz) and load contolled conditions. The validity of this procedure for extending current fatigue curves from 105 to 108 cycles and beyond, hinges upon the selection of an appropriate strain value, since the strain range can change rapidly during the early stages of fatigue. Results from annealed 2 1/4 Cr-1 Mo, Type 304 stainless steel, Incoloy 800 H and Hastelloy X, tested over a wide range of temperatures, show that the strain measured at Nf/2 is a reasonable estimate since it gives an excellent correlation between the strain and load controlled tests in the 105 range where the data overlap. It seems clear that the differences in cycling rate and early stress-strain history for the two tests do not significantly affect the correlation. It may, therefore, be concluded that such load control test procedures may be used as a valid fast way for extending currently available fatigue curves from 105 to 108 cycles, and beyond.
Endochronic Description of Cyclic Hardening Behavior for Metallic Materials
Authors: Wu H. C. , Yip M. C.
Published: October 2009

The cyclic hardening behavior of metallic materials at a prescribed constant plastic strain rate is investigated. The development is within the framework of the endochronic theory of viscoplasticity. It has been shown that a cyclic steady state can be attained theoretically, in agreement with the experimental finding. A general expression for describing the stress-strain relation for all cycles of a fatigue test with fixed total strain amplitude is presented and the peak stress of each cycle at different specified total strain level is also investigated.
The Effects of Periodic High Loads on Fretting Fatigue
Authors: Kantimathi A. , Alic J. A.
Published: October 2009

Fretting fatigue tests have been conducted on 7075-T7351 aluminum alloy coupons with fretting pads of the same material. Three different stress ratios were used, the otherwise constant amplitude axial loads being interrupted every 1000 cycles by either tensile overloads to 400 MPa or compressive underloads to −200 MPa. Tensile overloads greatly prolonged fatigue life for low stresses where the overload ratios were 1.6 and above; compressive underloads had comparatively little effect. The results are discussed in terms of crack growth retardation phenomena.
The Creep Rupture Properties of ASME SA 516 (Grade 55) Steel in the Range 426°C to 872°C
Authors: Cowgill M. G. , Thomas K. C.
Published: October 2009

The in-air creep-rupture properties of SA-516 (Grade 55) steel have been investigated in the temperature range 426–872°C (800–1600°F). The rupture time and creep rate data have been correlated using the Larson-Miller method, and relationships have been developed between the time to onset of tertiary creep and the time to rupture. Interpretation of the data involved consideration of the microstructural changes above and below the eutectoid temperature, and in which decarburization was an important factor.
Strength of the Surface Layer of Mild Steel
Authors: Sasaki H. , Sato Y.
Published: October 2009

The load-strain curves of thin-walled hollow cylinders of mild steel under compression, bending or torsion and rectangular cross-sectional beams with small height under bending deviate from the elastic line before reaching the lower yield point. In this paper these experimental results are attributed to yielding of the surface layer of the material. It is concluded that the surface yeild stress is 3/4 of the inherent yield stress of bulk material under uniform stress such as simple tension or compression.
Plastic Deformation Behavior of Mild Steel Along Orthogonal Trilinear Strain Trajectories in Three-Dimensional Vector Space of Strain Deviator
Authors: Ohashi Y. , Tanaka E.
Published: October 2009

An experiment was performed on the plastic deformation of mild steel S15C by applying combined loads to thin-walled tubular specimens so that the deformation developed along orthogonal trilinear strain trajectories in the three-dimensional vector space. Scalar and vectorial history effects on the stress vector σ in the deformation along the third branch are examined for 28 kinds of trajectory combined of various values of an angle θe between the first and third branches and a length sl of the second branch.
Complete Numerical Solution of the Axisymmetrical Deep-Drawing Problem
Authors: Kaftanog˘lu B. , Tekkaya A. E.
Published: October 2009

The present study introduces a finite difference method to obtain the complete numerical solution of the axisymmetrical deep-drawing of a circular blank. The theory includes nonlinear strain-hardening, normal plastic anisotropy, prestrain, variable coefficient of friction as a function of deformation, an approximation to the thickness stress, and an instability criterion. Using a computer program, distributions of any variable such as stress or strain can be obtained at any stage. Theoretical solutions are in good agreement with experimental ones. The method of solution slightly overestimates the limiting drawing ratio, which can be improved by adding the effects of bending and unbending at the die.
A Review of the Recent Literature on the Unlubricated Sliding Wear of Dissimilar Metals
Authors: Glardon R. , Finnie I.
Published: October 2009

A survey is presented of recent theories of the wear which occurs when dissimilar unlubricated metals slide on one another. Such sliding wear is not only of practical importance, but is also of academic interest. The classical explanation for this form of wear, based on adhesion, has been questioned as improved experimental techniques have become available. In the present review, emphasis is placed on what is known as severe sliding wear and the state of present knowledge is summarized.
Fracture and Wear of Diamond Cutting Tools
Authors: Wong C. J.
Published: October 2009

This paper describes the performance of diamond cutting tools during high speed precision machining. Experimental data collected from a very large sample size showed that the tool life varied at random and was very close to exponential distribution. Tool wear can be characterized into normal wear, chipping, setting problems, line effects, chip dragging and fracture by inclusions in the workpiece. The tooling data showed that the effects of crystallographic orientations on tool life is insignificant. Experiments also indicated that tools with extremely short life have strong absorption band with maxima at 1365 cm−1. This seems to show the existence of N-O bond in the diamond crystal lattices. The presence of N-O bond appears to be correlated to premature tool failure.
A Study of Strain and Strain-Rate Dependent Properties of a Superplastic Zn-Al Alloy Under Biaxial Stresses
Authors: Hsu T. C. , Bidhendi I. M.
Published: October 2009

A superplastic Zn-Al alloy in sheet form is formed into a bulge over a circular hole by pneumatic pressure. The geometry, the stress, the strain, and the strain-rate are determined at various points covering the whole specimen and at various stages of the forming process. The complicated shape, and its complicated changes, are represented by introducing an index for the local geometry, called “prolateness,” which is also related to the local stress ratio in a simple way. The biaxial stress is analyzed into a strain-proportional and a strain-rate-proportional component, which represent, respectively, the quasi-solid and the quasi-liquid behavior of the superplastic material.
Optical Measurement of the Plastic Strain Concentration at a Crack Tip in a Ductile Steel Plate
Authors: Rosakis A. J. , Freund L. B.
Published: October 2009

The shadow spot method has been established as a valuable experimental procedure for measuring elastic stress intensity factors in planar fracture specimens. It is noted here that if the crack-tip deformation field in specimens of ductile materials can be characterized by means of a single plastic intensity factor, analogous to the stress intensity factor in linear elastic fracture mechanics, then the shadow spot method has potential for use in measuring this intensity factor. The value of the J-integral is adopted as the plastic strain intensity factor, and the lateral contraction of an elastic-ideally plastic planar specimen is calculated in terms of J from the nonhardening limit of the HRR asymptotic field of elastic-plastic fracture mechanics. The theoretical caustic curve which would be generated by geometrical reflection of normally incident parallel light from points of the deformed specimen surface lying well within the plastic zone is determined, and it is shown that the value of J is proportional to the maximum transverse diameter of the shadow spot to the third power. Results of preliminary experiments, in which values of J for a given single edge notched steel plate specimen are inferred from measurements peformed separately from the elastically and plastically deforming parts of the specimen, are also reported.
The Plastic Deformation of Mild Steel in Metal Cutting
Authors: Hau-Bracamonte J. L. , Wallbank J. , Wise M. L. H.
Published: October 2009

The effect of subcritical quenching and room temperature aging on the cutting behavior of mild steel has been studied by optical and electron microscopy. Carbon and nitrogen in supersaturated solid solution and/or as submicroscopic precipitates greatly increase the dynamic strength of the steel and, hence, reduce the rate of metal removal when machining with high speed steel tools. When compared with a steel with a carbon and nitrogen-depleted or precipitation-free ferrite matrix, it is clear that the effect is caused by an increase in the high-strain work-hardening rate and a reduction in dynamic recovery. Because these submicroscopical precipitates are redissolved upon straining, variation of particle size and spacing has little effect upon the rate of metal removal, hence there are no significant differences between the machining behaviour of the steel in the solution heat treated, quench-aged and overaged condition. Transmission and scanning electron microscopy were used to examine the high-strain deformation structure of chips. Subzero cutting, at liquid nitrogen temperature, was used to control the temperature in the primary shear zone and to “freeze” pre-existing structure in the flow-zone.
Wear of Tool Steels as Cropping Blades
Authors: Lui S. W. , Das M. K.
Published: October 2009

Wear performance of some tool steels such as cold working steel (AISI D2) and high speed steel (AISI M2) in high speed cropping are investigated for four groups of work materials, viz., (i) low carbon steel (AISI 1023), (ii) medium carbon steel (AISI 1039), (iii) ball bearing steel (AISI 52100), and (iv) austenitic stainless steel. The tool wear profiles and wear volumes are monitored through a digital technique at long intervals and the resulting deterioration of the billet quality was noted. The results confirm the trend found in other fabrication processes that the wear is much lower for the materials in Groups a and b as compared to the other two groups containing high alloying elements. The wear mechanisms, as observed through SEM images, are found to be quite different for these cases. Another observation relates to the fact that within the range investigated, the billet quality remains unaffected with the exception of the blade face angularity. Thus, the blades have surprisingly high tool life.
High-Strain Multiaxial Fatigue
Authors: Ellyin F. , Valaire B.
Published: October 2009

The aim of this investigation was to develop a method for the prediction of the high-strain multiaxial fatigue life (low-cycle fatigue) of a steel, based on high-strain uniaxial fatigue data. In this study, thinwalled cylindrical specimens were subjected to fully reversed high biaxial strains using differential pressure and axial load. The directions of the principal strains were maintained parallel and perpendicular to the specimen axes. Five different strain ratios were investigated covering both the inphase and fully out-of-phase conditions. The material selected for this investigation was a medium carbon steel; C-1018. It was found that a maximum principal strain theory, based on the plastic components of the applied strains, taking into account the strain in the thickness direction, resulted in a correlation between the biaxial and uniaxial results which was either good or conservative. Under inphase conditions the low-cycle fatigue life could be predicted using Nf = Nf0 a(ε1+ε2) and under fully out-of-phase conditions using Nf = Nf0 aε1 where ε1 and ε2 are the ordered applied plastic strains and the constants “Nf0” and “a” are obtained from uniaxial high-strain fatigue tests.
Fatigue of Small Helical Extension Springs Subjected to Static Torsion and Alternating Lateral Deflection
Authors: Gluck J. V.
Published: October 2009

Multiaxial fatigue studies of peened helical extension springs made of music wire were performed in a specially designed testing machine. The test regime imposed static torsion and alternating laterial deflection, with the spring ends held parallel. The maximum stresses, which were primarily due to bending, occurred in the first turn out of the specimen grip at an end of the coil axis normal to the direction of lateral motion. The stresses in the middle turn ranged between 88-94 percent of those in the ends turns. The practical fatigue limit was about 100,000-300,000 cycles, with the principal tensile stress averaging 50 percent of initial wire tensile strength and maximum shear stress averaging 28 percent of initial wire tensile strength. For static stresses up to 32 percent of tensile strength, the alternating stress at the fatigue limit was essentially invariant, as predicted by Sines’ criterion for multiaxial fatigue.
A Comparison of J Estimating Procedures for a Solid Subjected to Bending Loads
Authors: Smith E.
Published: October 2009

Zahoor and Kanninen have recently developed a simple procedure for estimating the magnitude of the J-integral for through-wall cracks in pipes subjected to bending loads. This paper gives consideration to their procedure, but to check its predictions against available numerical results, it is explored in detail for the case of a crack in a solid deforming under plane-strain bending conditions. In this case, an implicit assumption in the procedure is that the plastic rotation depends on the ligament size, and not on any other geometrical dimension. This assumption is strictly valid only for deep cracks, and this paper shows the degree of inaccuracy obtained when it is applied to shallow cracks. The assumption is also shown to correlate with the existence of a unique relation, independent of geometrical parameters, between the ligament net-section stress and the J-integral, and also with the existence of Turner’s plastic η factors.
Analysis of Test System Misalignment in the Creep Test
Authors: Wu Han C. , Wang T. P.
Published: October 2009

An analysis of test system misalignment is presented for the creep test. Sheet type rectangular 1100-0 aluminum specimens are used for discussion. It is found that the creep strain at the geometric centerline of the specimen is different than that at the neutral axis. However, this difference in the creep strain decreases with time. Generally, the effect of misalignment decreases with creep time. Creep tests conducted with long pullrods and large initial strain level (high creep stress) will tend to minimize the effect of misalignment.
A Study of the Friction and Wear of Cartridge and Free-Cutting Brass
Authors: Glardon R. , Finnie I.
Published: October 2009

Friction and wear experiments on brasses with and without lead particles are presented and compared. Quantitative results are given for the dimensions of the wear tracks and of the subsurface layers. Differences in the behavior of the two alloys are treated in terms of deformation characteristics and microstructure and the role of a dispersion of lead particles on friction and wear is discussed.
A Comparative Investigation of the Sliding Wear of Some FCC Metals
Authors: Glardon R. , Finnie I.
Published: October 2009

Experimental investigations of the friction and wear of four copper alloys and pure nickel are presented. Measurements of the shape and dimensions of the wear tracks and of the extent of subsurface layers are also reported. The results are discussed in terms of mechanical behavior and possible correlations with conventional mechanical properties are considered. The role of cyclic plastic deformation is emphasized and areas of interest for future research are suggested.
Response of Various Metals to Large Torsional Strains Over a Large Range of Strain Rates—Part 2: Less Ductile Metals
Authors: Johnson G. R. , Hoegfeldt J. M. , Lindholm U. S. , Nagy A.
Published: October 2009

This paper presents torsional test results for six metals subjected to large shear strains and high strain rates. Included are 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, tungsten alloy and DU-.75Ti (Depleted Uranium). The specimens are strained to fracture at strain rates from quasi-static to over 100 s−1. All of the materials exhibit strain hardening and strain rate hardening. At the higher strain rates some of the materials develop shear instabilities and localizations. Constitutive relationships are derived from the test data and finite element computations of the tests are performed.
Hardening and Degradation Rules for Metals Under Monotonic and Cyclic Loading
Authors: Mro´z Z.
Published: October 2009

In order to describe inelastic response of metals at room or elevated temperatures for complex loading histories, the combined isotropic-kinematic hardening model is discussed. The monotonic and cyclic loading histories are associated with variation of two different hardening parameters and the maximal prestress is assumed to affect essentially the material response. First, the hardening model is applied within time-independent plasticity and next the elevated temperature creep deformation is studied for both monotonic and cyclic loading. The degradation rules are briefly discussed in the last part of the paper.
A Study on the Notch Effect on the Low Cycle Fatigue of Metals in Creep-Fatigue Interacting Conditions at Elevated Temperature
Authors: Sakane M. , Ohnami M.
Published: October 2009

Frequency and hold-time effects on fatigue lives of cylindrical notched specimens of SUS 316 stainless steel were studied at 600° C in air. From the tests, the following conclusions were obtained: Neuber’s rule, as used in the ASME N-47 Code, predicts very conservatively the life of notched specimens in tests without a hold-time. But it gives a nonconservative estimate for the reduction in the life of the material by the introduction of a hold-time. An empirical formula of a “frequency-elastic stress concentration factor modified equation” was obtained by analysing the experimental data. It predicts accurately the life of the notched specimen tested at different frequencies.
Notion of Continuum Damage Mechanics and its Application to Anisotropic Creep Damage Theory
Authors: Murakami S.
Published: October 2009

After discussing the notion and the practical procedures of continuum damage mechanics, their utility is elucidated by applying them to formulate an anisotropic creep damage theory for nonsteady multiaxial states of stress. By taking account of the mechanisms of microstructural change of materials due to creep, it is shown that the creep damage state can be described by a second rank symmetric damage tensor, while the effects of material damage on creep deformation of damaged materials should be expressed by a fourth rank tensor formed from the damage tensor. Validity of the creep theory formulated in terms of these damage variables is examined by performing model tests. Specialization of the proposed theory is also discussed.
In-Process Tool Fracture Detection
Authors: Lan M. S. , Dornfeld D. A.
Published: October 2009

This paper investigates the feasibility of using acoustic emission (AE) signal analysis for the detection of the breakage as well as the chipping of a cutting tool during machining. Experiments were conducted on a lathe using conventional carbide insert tools under realistic cutting conditions. The tangential and feed forces were also measured for comparisons. The sensitivities of the AE signal and cutting forces to insert chipping and fracture are illustrated. The relationship between acoustic emission energy and the combined effect of fracture surface area and cutting load is discussed.
The Effects of Plate Stress-Strain Behavior and Pipemaking Variables on the Yield Strength of Large-Diameter DSAW Line Pipe
Authors: Shoemaker A. K.
Published: October 2009

Recent stringent specifications for large-diameter double-submerged-arc-welded gas-transmission line pipe include requirements that limit the range of allowable pipe yield strengths instead of the previous requirement of a minimum yield-strength value. These restricted pipe yield-strength ranges require control of the range of the yield strength in the plate used to make the pipe, knowledge of the relationship between the plate and pipe yield strength, and the effect of pipemaking (forming) variables on this relationship. The present study was conducted to determine the interrelationships among plate yield strength, plate stress-strain properties, pipe-forming variables, and pipe yield strength. In the first part of this work, pipe-forming strains were measured after each forming operating during actual pipe fabrication and the strains compared to the calculated values. The experimental and analytical values were in good agreement; thus, the cyclic straining of the original plate material during pipe forming was determined. In the second part of the program, specimens of typical line-pipe steels were cyclically loaded in the laboratory according to the cyclic histories that sections in the plate would experience when fabricated into pipe. The results showed a significant effect of the plate stress-strain behavior, as well as the amount of straining (or forming) on the resulting yield strength. Because of the complexities of all these interrelationships and the strain gradients developed through the pipe wall during pipemaking, a series of pipe were fabricated from steels having different plate stress-strain properties and the plate and pipe yield strengths were compared. Varying amounts of sinking (compressive straining) in the pipe O press and of pipe expansion were examined. Correlation of the plate and pipe yield strengths showed that, as a first order approximation, the pipe yield strength equated to the flow stress in the plate at a strain level equal to the total accumulated strain that occurs at the neutral axis of the pipe during the pipemaking operation. This approximation can only be made if work hardening occurs in the plate material at that total accumulated strain level. Otherwise, it can only be stated that the pipe yield strength will be less than that of the original steel plate.
Redundant Deformation Factor Evaluation Through the Hardness Profile Method in Round Section Bar Drawing
Authors: Cetlin Paulo Roberto
Published: October 2009

The increase in strength of bars caused by drawing is associated to the average deformation (ε) imparted to the material by processing. This paper discusses the hardness profile method for evaluating the redundant deformation factor φ, which in turn allows the calculation of ε. For one drawing pass the results obtained are compatible with those from other theories, but it seems that a previous experimental hardness profile evaluation of ε in the literature involved improper calculations. For two successive passes a generalized definition of φ is forwarded. These passes work harden the material less than expected by the external deformation in the bar, and no current theories for φ calculation are adequate for more than one drawing pass.
On the Microstructural Basis of Cleavage Fracture Initiation in Ferritic and Bainitic Steels
Authors: Saario T. , Wallin K. , To¨rro¨nen K.
Published: October 2009

The microstructural basis of the critical tensile stress criterion of cleavage fracture is discussed. It is shown that cleavage can be carbide induced in bainitic steels as well as in ferritic steels. The plastic work expended in brittle crack propagation is shown to be somewhat smaller for bainitic steels than for ferritic steels. This is proposed to be caused by the much higher dislocation density of the bainitic microstructure. The statistical nature of the cleavage fracture initiation process is shown to result in a test piece geometry dependent cleavage fracture stress.
Material Response and Continuum Relations; or From Microscales to Macroscales
Authors: Drucker D. C.
Published: October 2009

Brief qualitative assessments are presented of a few approaches to macroscopic stress-strain relations for structural metals, alloys, and composites and some remarks are made about fracture. Ignoring the scale and applying continuum mechanics to the microstructure lies at one extreme, the dislocation scale treatment of single crystals and simple polycrystals at another. When, as for structural aluminum alloys, the shear stress required for continuing plastic deformation is so much higher than for the constituent single crystals, it seems unlikely that the latter approach is able to exhibit the salient features of macroscopic behavior.
Plastic Response of Polycrystalline Metals Subjected to Complex Deformation History
Authors: Kratochvil Jan , Tokuda Masataka
Published: October 2009

We attempt to formulate the elasto-plastic constitutive equations which reflect the basic features of the microscopic mechanism of plastic deformation and at the same time remains sufficiently simple to be applicable in FEM solution of the practical problems. The constitutive equations are based on a simplified verison of polycrystal plasticity. In modeling of the properties of single crystal grains of the polycrystal attention is paid to active and latent hardenings, and especially to the Bauschinger effect. The stress response along three sets of typical examples of complex deformation histories are predicted and compared with precise data of tension-torsion tests. The predictions are in good agreement with the observed behavior.
Transition of Plastic Behavior From Single Crystal to Polycrystal Under Pure Tension, and the Effect of Multislip
Authors: Chiang C. R. , Weng G. J.
Published: October 2009

Based on a series representation the tensile stress-strain relation of a polycrystal is derived explicitly in terms of the plasticity of its constituent grains. This derivation assumes Taylor’s linear isotropic hardening law for slip systems and Berveiller and Zaoui’s modification of Hill’s self-consistent relation for grain interactions. It is taken that Taylor’s theory implies equal shears for the active systems, and this assumption leads to a simple micro equation for each grain. With the aid of self-consistent relation the average of these micro equations readily gives rise to a macro one for the aggregate, which is given analytically in terms of crystalline structure νij, slip modulus h and the number of active systems n. At a given n it is shown that, although the behavior of a polycrystal under partial yielding is sensitive to the interaction, or self-consistent model selected, the asymptotic state under full yielding is not. This simple theory is also shown to be in line with the classical ones of Taylor, Bishop and Hill, Hershey and Kocks. Comparison with Jaoul’s experiments on the hardening modulus further suggests that most crystals tend to deform with 2∼4, but not 5, active slip systems in the fully plastic range.
On the Microstructural Origin of Certain Inelastic Models
Authors: Aifantis E. C.
Published: October 2009

A unifying program modeling the evolution of microstructures and their effects on the macroscopic response of materials is outlined. The new physical assumption introduced is the distinction among “normal” states associated with the parent lattice and “excited” states associated with the occurring microstructures. Both states are described by the usual balance laws of continuum mechanics properly modified to account for their mechanical interaction (mass and momentum exchange). Emphasis is put on the spatial evolution of the microstructures and its nonconvex character which is stabilized by considering gradient effects. The program can lead to predictive models for the localization of microstructures and its relation to the localization of macroscopic deformation. Moreover, it provides a rigorous microstructural justification of macroscopic theories of plasticity and viscoplasticity, including isotropic and kinematic hardening, as well as various current inelastic models. Finally, it suggests a proper frame for considering large deformation and rotation effects.
A Thermo-Viscoplastic Constitutive Equation Based on Hyperbolic-Shape Thermo-Activated Barriers
Authors: Wang Li-Lih
Published: October 2009

A thermo-viscoplastic constitutive equation is proposed on the basis of thermoactivated mechanism with a spectrum of hyperbolic-shape barriers, suitable for a wide range of strain rate and temperature. Relations with other existing models or rate theories, which may be regarded a special cases of present model, are examined. Good agreement with experimental data for both fcc and bcc metals is shown. The activation volume is found dependent on temperature according to an exponential law. A simple parameter, which describes the equivalence between strain rate effects and temperature effects on flow stress, is suggested similar to Zener-Hollomon parameters
Improved Constitutive Equations for Modeling Strain Softening—Part I: Conceptual Development
Authors: Lowe T. C. , Miller A. K.
Published: October 2009

A microstructurally based model of nonelastic deformation is proposed which is capable of predicting strain softening as well as a wide range of other deformation behaviors. The model, an extension of the MATMOD constitutive equations, now includes representations of both short range and long range internal stresses, strengthening due to homogeneous and heterogeneous microstructures, and dynamic recovery. Additional conceptual improvements regarding the interactions between various sources of work hardening and the influence of straining direction upon deformation induced microstructures are also introduced. The physical origins of these extensions, their relationship to strain softening, and their implementation in the new model, MATMOD-4V, are presented.
Continuum Foundations of Endochronic Plasticity
Authors: Valanis K. C.
Published: October 2009

In this paper a number of issues are addressed. The proper measure of intrinsic time is shown to be the norm of the increment of the plastic strain tensor, if the memory path is a line in the cojoint stress-strain space and elasticity at reversal points is stipulated. The convexity of the kernel function suffices to show that a periodic plastic strain history will give rise to a periodic stress history—as is observed. Standard tests are then established for the unequivocal experimental determination of the kernel and hardening function, valid for use in general three-dimensional histories.
The Hardening and Rate-Dependent Behavior of Fully Annealed AISI Type 304 Stainless Steel Under Biaxial In-Phase and Out-of-Phase Strain Cycling at Room Temperature
Authors: Krempl E. , Lu H.
Published: October 2009

Thin-walled tubes were subjected to fully reversed strain-controlled axial (A), torsional (T), in-phase (I) and out-of-phase (O) loading. A computer controlled MTS axial-torsion servocontrolled testing machine and strain measurement on the uniform section of the specimen were used in all tests. Each of four specimens was subjected to combinations of A, T, and I segments, of two hundred cycles each, followed by an O-segment. In between every segment, axial, and torsional check-tests were performed to obtain information on hardening and rate dependence. During cycling the normalized stress amplitude was observed to increase nearly threefold. Even if cyclic saturation was reached during a segment, a change in loading direction caused further hardening followed by subsequent softening which rapidly subsided. Only the O-segment showed hardening exclusively. After the A, T, and I segments, a “cross-effect” was observed which disappeared after the final O-segment. Compared to the considerable hardening, rate dependence as measured by relaxation and strain-rate change tests varied little during cycling.
Variable Temperature Creep and Creep Recovery of 304 Stainless Steel
Authors: Cho U. W. , Findley W. N.
Published: October 2009

Creep and creep recovery data are reported for pure tension of 304 stainless steel under variable temperature between 593°C and 649°C. Varying temperature experiments involved multiple steps of abrupt temperature increase and decrease at a constant stress of 86.2 MPa (12.5 ksi). A temperature-compensated time proposed by Sherby and Dorn was employed to represent the effect of temperature. The temperature history dependent theory combined with the modified superposition principle was used to predict the variable temperature creep and creep recovery from data under constant temperature. The test data were predicted reasonably well by the theory.
Experimental Evaluation of Creep Constitutive Equations for Type 304 Stainless Steel Under Non-Steady Multiaxial States of Stress
Authors: Murakami S. , Ohno N. , Tagami H.
Published: October 2009

In order to evaluate the validity and limitations of the creep-hardening surface model proposed by the present authors, a series of creep tests for type 304 stainless steel were performed at 600°C under various non-steady multiaxial loadings. The test time and the interval of stress change were 960 hr and 48 or 96 hr, respectively, and five kinds of stress histories consisting of randomly varying stress magnitude, stress direction and interval of stress change were employed. It was found that the creep-hardening surface model describes sufficiently well the creep behavior observed in this work.
A Mechanistic Perspective of the Biaxial Strength of Paperboard
Authors: Gunderson Dennis E. , Bendtsen Lee A. , Rowlands Robert E.
Published: October 2009

Prior research has demonstrated the practical significance of biaxial strength and established methods for measuring and predicting biaxial properties. Analytical models have been shown to accurately predict failure conditions, but do not identify the mode of failure. The present research develops a method for modeling the biaxial strength of paperboard based on criteria which infer a specific mechanism or mode of failure. In this approach, one or more criteria comprise a model which is evaluated iteratively at multiple states of stress to construct a failure envelope. Analytical results are graphically compared with experimental data. While some models evaluated in this report do not adequately represent the data, one comprised of both stress and strain limiting criteria yields an acceptable fit. We conclude that the modeling approach proposed is practical and useful for distinguishing between “potentially correct” and “inadequate” concepts of biaxial strength. Results suggest that transverse compressive strain may play a role in limiting tensile strength and that paperboard may not fail in an in-plane shear mode unique from normal tensile and compressive failure.
Study on Tensile Strength of Resin Mortar
Authors: Morimitsu Takenori , Yabuta Tetsuro , Tsujimura Takeshi , Yamaguchi Kotaro
Published: October 2009

A new resin mortar has been developed to facilitate a small-diameter shield tunneling method. The breaking elongation, Young’s modulus and tensile strength of the resin mortar are measured and studied. This paper clarifies the relationship between the mechanical properties of the resin mortar and the ones of its constituent materials, using a three-spring model. The mechanical properties of the resin mortar predicted from the model proposed in this paper agree with the measured values.
Effect of Yield Stress and Grain Size on Threshold and Fatigue Limit
Authors: Mutoh Y. , Radhakrishnan V. M.
Published: October 2009

Experimental investigations have been carried out to study the effects of grain size and yield stress on fatigue limit and threshold stress intensity range. The relations between fatigue limit and grain size and yield stress and those between threshold stress intensity range and grain size and yield stress which were predicted according to the model proposed in the previous paper agreed quite well with the experimental data. The difference in the dependence of fatigue limit and threshold stress intensity range on yield stress was discussed based on the analytical relations between them.
Observations of Material Behavior Under Isothermal and Thermo-Mechanical Loading
Authors: Sehitoglu Huseyin , Karasek M.
Published: October 2009

Deformation and damage behavior of a 1070 steel (class U wheel steel) under thermo-mechanical and isothermal loading have been examined. Fatigue lives under thermo-mechanical and isothermal loading were compared for similar conditions of strain and temperature. For most cases, maximum tensile stresses developed in thermo-mechanical tests exceeded those obtained under isothermal conditions (at Tmin) for the same strain amplitude. Cyclic hardening was observed at 200 to 300°C in isothermal tests. Under thermo-mechanical loading, static strain aging resulted in added hardening due to alternate exposure of the material to high and low temperatures. When thermal recovery effects become dominant at the high temperature end, strengthening upon cooling was suppressed. Oxide scales readily formed at high temperatures (≥400°C) and resulted in an increase in damage accumulation rates. Oxygen penetration into crack flanks and the ensuing loss of carbon was identified using Auger spectroscopy. The severity of oxide penetration into the base metal increased with increase in surface crack density, longer oxidation times and higher temperatures.
Residual Stress Distribution in Machining Annealed 18 Percent Nickel Maraging Steel
Authors: Jeelani Shaik , Bailey J. A.
Published: October 2009

A novel electrolytic etching technique is used to determine the residual stress distribution in the machining of annealed 18 percent nickel maraging steel. Ring shaped specimens were machined under unlubricated orthogonal conditions with carbide cutting tools having wear lands of 0.125, 0.25, and 0.5 mm length at cutting speeds ranging between 0.05 and 1.60 ms−1. The results of the investigation show that the residual stresses are tensile at the machined surface and decrease with an increase in depth beneath the machined surface. The maximum (near surface) residual stress and depth of the severely stressed region increase with an increase in cutting speed and tool wear land length. The results are interpreted in terms of the variations in the amount of surface region deformation produced by changes in cutting conditions.
A Comparison of Crack-Tip Field Parameters for Large and Small Fatigue Cracks
Authors: Chan K. S. , Lankford J. , Davidson D. L.
Published: October 2009

A comparison of the elastic-plastic crack-tip fields of large and small fatigue cracks has been made using the ΔJ-integral approach. Using experimental strain and displacement range measurements obtained by means of the stereoimaging technique, the ΔJ-integral has been computed for an aluminum alloy containing either large or small fatigue cracks, by performing line-contour integration along a variety of rectangular paths around the crack tip. These calculations reveal that for both large and small cracks the ΔJ-integral is path-dependent, and that the value of ΔJ increases with decreasing distance from the crack tip. Using an average local ΔJ or one estimated from the CTOD, the enhanced crack growth rates associated with small fatigue cracks can be explained on the basis of the large average ΔJ-integral within the cyclic plastic zone. The effect of crack closure on the computed local ΔJ (or ΔK) and crack growth is discussed.
Modeling Plastic Deformation of Mild Steel Under Nonproportional Deformation Path
Authors: Gilat A.
Published: October 2009

An elastic/viscoplastic theory that includes anisotropic strain hardening is used in the analysis of a nonproportional biaxial torsion-tension loading test. The theory is a combination of the formulation of Perzyna [5] and the anisotropic hardening model of Mro´z [6], and is applied in modeling the behavior of mild steel in a nonproportional deformation test reported by Meguid and Malvern [2]. The results show that the theory predicts the material response well. Especially, the theory models adequately the noncoaxiality between the plastic strain rate and the deviatoric stress vectors following an abrupt change in the deformation path.
The Coefficients of Thermal Expansion of La2O3, TaVO5 and Ta16W18O94 Below Room Temperature
Authors: Chu C. N. , Saka N. , Suh N. P.
Published: October 2009

The coefficients of thermal expansion (CTE) of La2O3, TaVO5 and Ta16W18O94 were measured in the temperature range 150–300 K for space applications. Hot pressed La2O3 showed a positive CTE of 8.6 × 10−6 K−1. Sintered TaVO5 had a positive and extraordinarily large CTE (50 × 10−6 K−1), but the CTE was negative (−4.0 × 10−6 K−1) in the temperature range 340–380 K. The thermal expansion data suggest a reversible phase transformation near 260 K. The CTE of hot pressed Ta16W18O94 was −1.52 × 10−6 K−1. Sintered Ta16W18O94 showed slight hysteresis, but the CTE was about −1.0 × 10−6 K−1.
Notch Effect in Low-Cycle Fatigue at Elevated Temperatures—Life Prediction From Crack Initiation and Propagation Considerations
Authors: Sakane Masao , Ohnami Masateru
Published: October 2009

This paper describes the notch effect in low-cycle fatigue of an austenitic stainless steel SUS 304 at 873 K in air. Total strain range-controlled tests were carried out using a round unnotched and three round notched specimens. A prediction method for low-cycle fatigue lives of notched specimens was developed by predicting the crack initiation and propagation periods separately. To predict the former Neuber’s rule was applied and a nominal stress/strain criterion was developed to predict the latter. Failure lives, obtained by adding the two prediction lives, closely agree with observed failure lives.
Characterization of Optical and Surface Parameters During Particle Impact Damage
Authors: Rao P. Veerabhadra
Published: October 2009

The damage caused by sand impingement can be severe and detrimental to canopies, radomes, wind screens, and structural components resulting in loss of transmittance, communications, and premature failure. Extensive parametric studies were conducted to characterize the optical transmittance characteristics of polymethyl methacrylate and polycarbonate surfaces as functions of (1) velocity of impact, (2) exposure time (3) distance of the nozzle (4) angle of impingement, and (5) mass flow rate of the erodent. Particle damage was caused by a jet of high speed spherical and (crushed glass and silicon carbide) angular particles. The relationship between the optical and surface characteristics are discussed.
An Analysis of Drawbeads in Sheet Metal Forming: Part I—Problem Formulation
Authors: Triantafyllidis N. , Maker B. , Samanta Shyam K.
Published: October 2009

The development of a one-dimensional finite strain elasto-plastic shell model appropriate for use in modelling straight drawbeads is outlined. Numerical results obtained using a finite element technique are shown for practical bead designs. The sheet deformation is divided into two phases: that when the binder locks the sheet metal to form the bead, and that when the punch advances to form the panel, pulling the sheet and (possibly) drawing material through the bead. The effects of friction coefficient, bead geometry, and material properties are investigated, resulting in strain distribution diagrams and force-displacement curves for several bead designs.
Tensile and Fracture Properties of an Fe-18Cr-20Ni-5Mn-0.16N Fully Austenitic Weld Metal at 4 K
Authors: McCowan C. N. , Siewert T. A. , Tobler R. L.
Published: October 2009

The 4-K tensile and fracture toughess properties of a fully austenitic stainless steel weld are reported. One tensile and two compact tension fracture specimens were tested. The weld was produced by gas metal arc welding using an Fe-18Cr-20Ni-5Mn-0.16N electrode and a 98 percent argon-2 percent oxygen shielding gas mixture. The yield strength of 1015 MPa and average fracture toughness, KIc (J), of 203 MPa•m are higher than those of welds produced with 308L and 316L electrodes and compare favorably with base metal properties. Examination of the fracture surfaces of all samples by scanning electron microscopy showed ductile failure by microvoid coalescence. The suitability of this alloy for welding cryogenic structures is discussed.
Parametric Study of Stress-Intensity Factors in Bonded Composite Stringer Panels
Authors: Bigelow C. A.
Published: October 2009

Stress-intensity factors are determined for an infinite cracked orthotropic sheet adhesively bonded to an orthotropic stringer. Since the stringer is modeled as a semi-infinite sheet, the solution is most appropriate for a crack tip located near a stringer edge. Both adherends are treated as homogeneous, orthotropic media which are representative of many fiber-reinforced composite materials. The complex variable theory of elasticity was used to obtain a set of integral equations describing the problem. The integral equations are replaced by an equivalent set of algebraic equations, which are solved to obtain the shear stress distribution in the adhesive layer. From these adhesive stresses, the stress-intensity factors are found. A parametric study is conducted to determine the sensitivity of the system to material properties and specimen configuration. Unless the crack tip is very close to or under the stringer, the stress-intensity factor is approximately that of the unstiffened sheet. However, as the crack propagates beneath the stringer, the stress-intensity factor decreases significantly. Increasing the stringer stiffness or the adhesive stiffness also decreases the stress-intensity factor.
Dynamic Response of Curved Laminated Plates Subjected to Low Velocity Impact
Authors: Ramkumar R. L. , Thakar Y. R.
Published: October 2009

An analysis to predict the transient response of a thin, curved laminated plate subjected to low velocity transverse impact by a rigid object is presented. The contact force history due to the impact phenomenon is assumed to be a known imput to the analysis. The coupled governing equations, in terms of the Airy stress function and shell deformation, are solved using Fourier series expansions for the variables. Closed-form analytical solutions for plate deflections and strains are compared with available impact test results for flat plates. Outer ply strains are used to predict fiber failures and matrix splitting between fibers in the impacted laminate.
On the Influence of Strain-Path in Multiaxial Fatigue Failure
Authors: Wu Han C. , Yang C. C.
Published: October 2009

A set of strain-controlled experiments has been performed on tubular specimens of annealed stainless steel. The strain-paths are designed to highlight the characteristics of path-dependence in the axial-torsional fatigue tests. Fatigue life, directions of crack initiation, and propagation are the subjects of interest in this investigation. They have been observed to be strongly influenced by the strain-path. For all the specimens tested, crack initiation was in the tensile mode.