bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue-Crack Propagation Behavior of Incoloy 800 at Elevated Temperatures
Authors: James L. A.
Published: November 2010

Linear-elastic fracture mechanics techniques were used to characterize the fatigue-crack propagation behavior of Incoloy 800 in an air environment over the temperature range 75 to 1200 deg F (24 to 649 deg F). Crack growth rates were measured over the range 5×10−7 to 5×10−5 in./cycle. Material Grades 1 and 2 were found to exhibit essentially the same behavior over this range. In general, crack growth rates increased with increasing test temperature, although the increases were less then previously noted for austenitic stainless steels. This difference is probably related to the superior oxidation resistance of Incoloy 800.
Pipe Deformation During a Running Shear Fracture in Line Pipe
Authors: Ives K. D. , Shoemaker A. K. , McCartney R. F.
Published: November 2010

Under sponsorship of the American Iron and Steel Institute, U. S. Steel Research has been conducting full-scale burst tests of large-diameter submerged-arc-welded line pipe to determine the toughness required to arrest running shear fractures for different design conditions. As part of that program, the pipe were instrumented with crack detectors, strain gages, and pressure transducers to determine the crack velocities and the actual pipe deformation and strain fields associated with the shear fracture propagating along the top of the pipe. This paper summarizes the test data that document the manner in which the pipe deforms during this type of crack propagation. The data show that for a propagating shear fracture, each of four different locations along the pipe length (relative to the crack tip) has a distinctive type of pipe deformation. For a location many pipe diameters ahead of the crack tip, the circumferential strain first decreases because of flexural waves associated with the initiation process and then continues to decrease in proportion to the local gas decompression; however, the longitudinal strain continuously increases because of a longitudinal “tongue” of tensile straining on the top of the pipe caused by pressure-induced opening of the flaps of the pipe on both sides of the fracture behind the crack tip. At a distance about two diameters ahead of the crack tip, the pipe cross section becomes oval, and in the presence of this deformation the strain field is no longer determined by the local pressure; in fact, the circumferential strain is near zero at a distance two diameters ahead of the crack. The oval pipe shape ahead of the crack tip is caused by the venting of the gas behind the crack tip which creates a downward reactive force on the bottom portion of the pipe. Opening at the crack tip is the result of tensile straining caused by circumferential and radial displacement of the flaps behind the crack tip. Thus it is believed that the action of the pipe-wall flaps behind the crack tip provides the primary force driving the crack down the top of the pipe.
Experimental Determination of Side Boundary Effects on Stress Intensity Factors in Surface Flaws
Authors: Jolles M. , McGowan J. J. , Smith C. W.
Published: November 2010

A technique consisting of stress-freezing photoelasticity coupled with a Taylor Series Expansion of the maximum local in-plane shearing stress known as the Taylor Series Correction Method (TSCM) is applied to the determination of stress intensity factors (SIF’s) in flat bottomed surface flaws of flaw depth/length ratios of approximately 0.033. Flaw depth/thickness ratios of approximately 0.20 and 0.40 were studied as were plate width/crack length ratios of approximately 2.33 and 1.25, the former of which corresponded to a nearly infinite width. Agreement to well within 10 percent was found with the Rice-Levy and Newman theories using a depth-modified secant correction and equivalent flaw depth/length ratios. The Shah-Kobayashi Theory, when compared on the same basis, was lower than the experimental results. Using a modified net section stress correction suggested by Shah, agreement with the Shah-Kobayashi Theory was greatly improved but agreement with the other theories was poorer. On the basis of the experiments alone, it was found that the SIF was intensified by about 10 percent by decreasing the plate width/crack length from 2.33 to 1.25.
Formability of Aluminum Alloy Sheets
Authors: Hecker S. S.
Published: November 2010

High strength-to-weight ratio materials are becoming of increasing importance in the automotive industry. Some aluminum alloy sheets offer strength equivalent to low-carbon sheet steel at one third of the weight. However, for these alloys no production stamping experience exists and little meaningful laboratory data have been accumulated. This study was conducted to provide such laboratory information. Complete tensile properties and forming limit curves (FLC), as measured by a laboratory technique developed by the author, were determined for the aluminum alloys with a wide range of properties and were compared to the properties of low-carbon steel. All the aluminum alloys were found to have lower FLC’s, lower r values and equal or lower strain hardening capacities than sheet steel. Therefore their formabilities will be less than those of steel for all modes of sheet forming. This predicted press performance was verified for some of these alloys in limited press trials on a deck lid (inner panel) stamping.
Simulation of the Heading Process
Authors: Vickers G. W. , Plumtree A. , Sowerby R. , Duncan J. L.
Published: November 2010

Plasticine, Commercially Pure Lead and 6061T6 Aluminum have been used as model materials to simulate some of the forming processes that can arise during a first blow axisymmetric heading operation namely; upsetting, forming into a die cavity and the free flow operation. The deformation characteristics have been studied in each of these operations and some gross internal flow patterns have been determined using multilayer plasticine workpieces. The influence of both the operation and the workpiece geometry on the heading forces was also investigated. Some simple analytical models based mainly on the Load Bounding Techniques have been employed to predict the heading forces. Reasonable agreement was observed between the theoretical and experimental results.
Effect of Residual Elements on Fracture Characteristics and Creep
Ductility of Type 308 Stainless Steel Weld Metal
Authors: Stiegler J. O. , King R. T. , Goodwin G. M.
Published: November 2010

Previous studies had shown that conventional type 308 stainless steel weld metal can have low creep ductility (< 1 percent total elongation) at 650 deg C. This paper demonstrates that the low ductility results from internal cracks that develop at austenite-sigma phase boundaries and propagate under the test conditions. The sigma phase is formed from ferrite present in the as-deposited weld metal. Type 308 stainless steel weld metal containing controlled amounts of the residual elements B, P, and Ti also contains sigma phase, but phase boundary cracking has not been observed even after 5000 hr. The controlled residual element weld metal is significantly more ductile (> 10 percent total elongation) than the conventional weld metals for which data are available.
Influence of Specimen Features on the Strength of
Boron/Epoxy-Reinforced Metal
Authors: Herakovich C. T. , Renieri M. P. , Davis J. G.
Published: November 2010

Experimental results are presented which indicate that the ultimate tensile strength of aluminum reinforced with boron/epoxy composite may be significantly affected by the configuration of the specimen, and whether it was individually laid-up or cut from a larger piece of material. Coupon specimens which were individually laid-up exhibited strengths close to that predicted by theory. However, specimens cut from large plates had strengths about 36 percent of predicted values. All specimens had a one-half inch (12.7 mm) wide gage section. For individually laid-up specimens, it was found that specimens which were loaded through fiberglass tabs yielded higher ultimate tensile strengths than modified dogbone specimens with load introduction through stepped load-transfer regions. Machining along the edges was found to have little influence on the strength of the specimens used in this study.
The Initiation and Propagation of Ductile Fracture in Low Strength Steels
Authors: Green G. , Knott J. F.
Published: November 2010

The effects of work hardening rate and inclusion content on the initiation and propagation of ductile fracture in low strength steels have been investigated. A model has been proposed based on these results, which describes the difference between the energy required for initiation and propagation of ductile fractures in such steels.
The Effect of Carburization in Sodium on the Mechanical Properties of Austenitic Stainless Steels
Authors: Krankota J. L.
Published: November 2010

Conventional mechanical properties tests (tensile, stress/rupture, and impact toughness) have been performed on annealed specimens of austenitic stainless steels (0.152 cm thick, 0.635 cm wide) which have been carburized in high temperature (538–593°C) sodium for times up to 2000 hr. Included in the work were alloys which might have been more resistant to carburization than conventional alloys, Type 310SS, 18-8-2, Uranus-S and Inconel-601. Results indicate that the tensile and stress rupture ductility of all the alloys decreased to less than 5 percent in tests at 538–593°C when the bulk carbon content of the specimens was 0.4 percent or greater. The decrease in ductility of surface-carburized specimens is much greater than that of alloys of the same nominal composition and same bulk carbon content but with the carbides homogeneously distributed throughout the specimen. It is shown that the brittle surface layer fractures in a transgranular, cleavage mode while the center of the specimens fail in the normal shear mode.
A Recovery-Athermal Glide Creep Model
Authors: Ostrom P. , Lagneborg R.
Published: November 2010

A theoretical recovery-creep model which takes the distribution of dislocation link lengths into account is developed. The recovery process is assumed to be climb controlled. The glide process is critically discussed and is found to be an athermal process. As a consequence of the athermal glide process the model predicts a time interval with the strain rate equal to zero after a small stress reduction. The model is able to simulate the strain-time behavior both in the primary and secondary stage and to simulate the distribution of dislocation link lengths. The stress dependence of the model is evaluated.
Finite Element Solutions for Crack-Tip Behavior in Small-Scale Yielding
Authors: Tracey D. M.
Published: November 2010

The subject considered is the stress and deformation fields in a cracked elastic-plastic power law hardening material under plane strain tensile loading. An incremental plasticity finite element formulation is developed for accurate analysis of the complete field problem including the extensively deformed near tip region, the elastic-plastic region, and the remote elastic region. The formulation has general applicability and was used to solve the small scale yielding problem for a set of material hardening exponents. Distributions of stress, strain, and crack opening displacement at the crack tip and through the elastic-plastic zone are presented as a function of the elastic stress intensity factor and material properties.
Constitutive Relations for the Nonelastic Deformation of Metals
Authors: Hart E. W.
Published: November 2010

Constitutive relations for metal nonelastic deformation are proposed. The descriptiion is entirely in terms of real time strain rate. The equations are fully three-dimensional, and the description is incremental. Changes of loading direction are treated in a simple manner. The current deformation state of the metal is characterized by a set of state variables that themselves evolve by well defined laws. The experimental background for the theory is also described.
Some Questions Regarding the Interaction of Creep and Fatigue
Authors: James L. A.
Published: November 2010

Data are presented from fatigue-crack growth tests conducted on Type 304 S.S. in inert environments at elevated temperatures which show that the thermal-activation noted in similar tests run in air environments is not present in the inert environment. Similar observations from the literature are reviewed, including the observation that the time-dependency noted in tests conducted in elevated temperature air environments is also greatly suppressed in inert environments. These findings suggest that an interaction between the fatigue process and the corrosive air environments is responsible for the thermally-activated time-dependent behavior often attributed to creep-fatigue interaction. Data are also presented which show that the fatigue-crack growth behavior of Type 304 S.S. subjected to significant creep damage prior to fatigue testing does not differ appreciably from the behavior of material not subjected to prior creep damage; again indicating minimal interaction between creep and fatigue. It is suggested that in the temperature range where pressure vessels and piping are generally designed to operate (i.e. below about one-half the absolute melting temperature of the alloy), the interaction between creep and fatigue is far less significant than once supposed, and that the major parameter interacting with the fatigue process is that of high temperature corrosion.
The Application of “Strain Range Partitioning Method” to Torsional Creep-Fatigue Interaction
Authors: Zamrik S. Y. , Bilir O. G.
Published: November 2010

The method of strain range partitioning was applied to a series of torsional fatigue tests conducted on tubular 304 stainless steel specimens at 1200°F (649°C). Creep strain was superimposed on cycling strain, and the resulting strain range was partitioned into four components; completely reversed plastic shear strain, plastic shear strain followed by creep strain, creep strain followed by plastic strain and completely reversed creep strain. Each strain component was related to the cyclic life of the material. The paper describes the experimental procedure used to achieve strain partitioning and the torsional test results are compared to those obtained from axial tests. The damaging effects of the individual strain components were expressed by a linear life fraction rule. The shear strain plastic component showed the least detrimental factor when compared to creep strain reversed by plastic strain. In the latter case, a reduction of torsional fatigue life in the order of magnitude of 1.5 was observed.
Fracture Mechanics and Fractography of Creep and Fatigue Crack Propagation at Elevated Temperature
Authors: Koterazawa R. , Iwata Y.
Published: November 2010

A fracture mechanics and fractographic study was conducted on creep and fatigue crack propagation of a 304 stainless steel under constant and repeated tensile stress at a temperature of 650°C. Linear elastic fracture mechanics could be applied to the test data fairly successfully in spite of the fact that the tests were conducted under creep conditions. A comparison with data in a literature indicated that this is not true for bending-type specimens such as the compact tension specimen because of redistribution of bending stress due to creep, and therefore a specimen geometry which avoids bending stress is preferred for creep crack testing. Under repeated stress, the crack generally started as a transgranular fatigue crack and changed to an intergranular creep crack at some length of the crack. The transition point moved to a later stage of crack propagation as the period of repeated stress increased. This transition phenomenon could be explained by assuming that the two crack propagation processes, the transgranular fatigue crack and the intergranular creep crack, are possible under repeated stress condition and that the one with the higher rate actually occurs.
Utility of Surface-Flawed Tensile Bars in Cyclic Life Studies
Authors: Coles A. , Johnson R. E. , Popp H. G.
Published: November 2010

Surface-flawed tensile bar specimens were developed and tested to investigate the applicability of fracture mechanics to relatively small crack sizes under varying stress-time-temperature conditions and to derive ths stress intensity relationships for such surface cracks. The geometric influences on continuous cycling, as well as time-dependent, creep/fatigue, crack propagation were observed and characterized for Inconel 718. The influence of stress ratio on cyclic crack growth rate curves was examined, and the equivalent stress intensity concept was substantiated. A residual life calculation method was developed, and verification test results were obtained wherein equal accuracy in calculated lives (following precracking) was observed for flat tensile specimens and simple cylindrical rotating disks. The verification tests established the viability of the elastic fracture mechanics method for predicting crack growth under conditions near the elastic/plastic limit, provided that pertinent material data are used and careful attention is paid to stress redistribution.
The Effect of Strain Rate Upon the Bending Behavior of Materials
Authors: Davies R. G. , Magee C. L.
Published: November 2010

The maximum loads sustainable in both four-point bending and prebent hinge collapse tests of several materials have been determined at crosshead rates from 4.2 × 10−3 mm/s to 4.2 m/s (10−2–104 in./min). All the materials exhibit a logarithmic dependence of flow stress on crosshead rate; this dependence is consistent with that previously reported for tensile deformation. Although there are some minor differences in the dynamic stress factors obtained by the bending and tensile methods, all the methods rank the materials in the same order. Thus, for materials evaluation the most convenient test method, which is usually the tensile test, can be chosen. For more complex loading geometries than considered here, scale model testing would yield the most reliable results.
Static and Dynamic Stress Intensity Factors by the Method of Transmitted Caustics
Authors: Katsamanis F. , Raftopoulos D. , Theocaris P. S.
Published: November 2010

The stress intensity factors in plexiglas plates containing an edge crack and subjected to static or dynamic loading are determined by the optical method of caustics. Measurements of the applied load were accomplished by means of a piezoelectric transducer and the caustics obtained in the experiments were photographed during the process of loading by using a Cranz-Schardin high speed camera. It has been found that the stress intensity factors for a dynamic loading are always higher than the corresponding stress intensity factors for a static loading of the same magnitude.
X-Ray Diffraction Study of Low Cycle Fatigue Damage in Plain Carbon Steel
Authors: Nagao Masato , Weiss Volker
Published: November 2010

An X-Ray diffraction analysis of low cycle bending fatigue was conducted on plain carbon steel (SAE 1008) in three conditions, as received (annealed) 20 percent prestrained, and strain aged. The decrease of the surface stresses at maximum and minimum strains, a reduction of the residual surface stress after unloading from the tension cycle, and a decrease of the half-value breadth during the first 20–30 cycles indicate rapid cyclic softening during the initial stages of strain cycling. After this initial period the microstructure of all specimens was found to be independent of the initial material condition. Similarly, the fatigue life as a function of strain range was also independent of the initial condition. X-Ray diffraction line analysis shows no changes for the major portion of the specimen life, from 0.1 Nf to 0.75 Nf. However, a linear relationship between half-value breadth and strain range is noted. It is suggested that this relationship can be utilized for monitoring and diagnostic purposes, particularly to determine the strain range to which a critical part has been subjected.
Effects of Surface Hardness and Other Material Properties on Erosive Wear of Metals by Solid Particles
Authors: Sheldon G. L.
Published: November 2010

Erosion of a material from a metal surface by the action of impinging SiC particles is studied. In a brief review, it is shown that investigators have correlated erosion wear with several material properties. These include fully annealed properties such as surface hardness, or properties relating to atomic band strength such as modulus of elasticity. In this paper, which studies the erosion wear for a number of pure ductile materials as well as alloys in the copper-nickel system, it is shown that a better correlation with erosion wear is achieved by using the Vickers hardness value of the fully work-hardened surface of the material. This quantity is probably the best material parameter to use in predictions of erosion resistance of metals and in the modelling of the erosion process.
Temperature Dependences of the Elastic Constants of Precipitation-Hardened Aluminum Alloys 2014 and 2219
Authors: Read D. T. , Ledbetter H. M.
Published: November 2010

Elastic properties of precipitation-hardened aluminum alloys 2014 and 2219 were studied between 4 and 300 K using ultrasonic pulse techniques. Both the longitudinal and transverse sound velocities were measured. Also reported are the Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio. For both alloys, the Young’s moduli are about ten percent higher than for unalloyed aluminum, and they increase about ten percent on cooling from 300 to 4 K. All the elastic constants show normal temperature dependence.
A Weakest-Link Model for the Prediction of Fatigue Crack Growth Rate
Authors: Oh Kong Ping
Published: November 2010

A weakest-link theory is proposed for analyzing the rate of fatigue crack growth. The joint probability density of a fatigue crack growing an amount X between x and x+dx, and in time η between N and N+dN cycles is derived from an initial probability function. The rate of crack growth is then obtained as the expectation of the random variable (X/η). It is shown that the average rate of crack growth obeys the power law for small ΔK, and that the power is a function of the shape parameter in the Weibull distribution.
The Effect of Plastic Strain Followed by Aging on the Torsion Fatigue Resistance of Quenched and Tempered 4340 Steel
Authors: Lyman John , Madden Carroll
Published: November 2010

The torsion fatigue limit of 4340 steel in the quenched and tempered condition is compared with the quenched, tempered and strain-aged condition. Previous experimental work by the authors indicated that strain-aging of tempered martensite of 4340 improved the tensile strength, yield strength and tensile elastic limit. Other workers have shown that the tensile elastic limit and rotating beam fatigue limit of 4340 steel were related at high hardness. The results of this work show that strainaging tempered martensite of 4340 at a hardness of 54-55 Rockwell C does not improve the high cycle torsion fatigue limit.
Assessment of Weld Heat-Affected Zones in a Reactor Vessel Material
Authors: Marston T. U. , Server W.
Published: November 2010

The mechanical properties of weld heat-affected zones (HAZ’s) associated with the heavy section, nuclear quality weldments are evaluated and found to be superior to those of the parent base material. The nil ductility transition temperature (NDTT), Charpy impact and static and dynamic fracture toughness properties of a HAZ associated with a submerged arc weld and one associated with a manual metal arc weld are directly compared with those of the parent base material. It is concluded that the stigma normally associated with HAZ is not justified for this grade and quality of material and weld procedure.
A Plastic-Strain, Mean-Stress Criterion for Ductile Fracture
Authors: Norris D. M. , Reaugh J. E. , Moran B. , Quin˜ones D. F.
Published: November 2010

We describe a computer model for predicting ductile-fracture initiation and propagation. The model is based on plastic strain. Fracture starts or a crack extends when the integrated product of the equivalent plastic-strain increment and a function of the mean stress exceeds a critical value over a critical length. This critical length is characteristic of the microstructure of the material. The computer fracture model is calibrated by computer simulation of simple and notched round-bar tension tests and a precracked compact tension test. The model is then used to predict fracture initiation and propagation is the standard Charpy V-notch specimen. The computed results are compared with experiments. The model predicts fracture toughness from tests of standard surveillance specimens from nuclear-reactor pressure vessels and can be applied to fracture calculations for these vessels.
Long-Life Notch Strength Reduction Due to Local Biaxial State of Stress
Authors: Leis B. N. , Topper T. H.
Published: November 2010

An explanation for the observed difference between the values of the long-life, fatigue-notch strength-reduction factor (Kf) and the elastic stress concentration factor based on the influence of biaxial-notch root stresses is presented for a limited class of problems for which the local stresses are elastic. Results of three-dimensional linear elasticity solutions for notch stresses are reviewed and then used in conjunction with a biaxial fatigue criterion suitable for elastic straining to predict values of Kf for a variety of notched components for which values have been experimentally determined. Comparison of actual and predicted values of Kf indicates a close correspondence suggesting that the influence of local biaxial stresses on the life to crack initiation of notched components is responsible for the reduced notch severity observed in many of the experimental investigations of long-life (fatigue) notch sensitivity.
Theory of Superplastic Flow in Two-Phase Materials: Roles of Interphase-Boundary Dislocations, Ledges, and Diffusion
Authors: Gittus J. H.
Published: November 2010

A new theory is developed to explain superplastic flow in two-phase materials. It is postulated that boundary-dislocations, piled up in dislocation-Interphase-Boundaries (IPBs) climb away into disordered regions of the IPB. Sliding then occurs at an IPB as dislocations glide toward the head of the pile up to replace those which have climbed into disordered regions of the boundary. An energy barrier which would otherwise render sliding virtually impossible on dislocation-IPBs can, it is shown, be largely eliminated if the dislocations glide in pairs. The disorder (actually an antiphase domain boundary) which is created by the passage of the leading dislocation is then repaired by passage of its successor. The threshold stress for superplastic flow is provisionally identified with the stress which pins IPB dislocations to boundary ledges. The activation energy is theoretically that for IPB diffusion. Good agreement is obtained between the theoretical equation for superplastic flow and the results of published experiments.
The Influence of Strain Hardening and Strain-Rate Sensitivity on Sheet Metal Forming
Authors: Ghosh A. K.
Published: November 2010

The current understanding of sheet metal stamping processes is discussed in the light of materials’ ability to distribute plastic strains in uniaxial and biaxial deformation. The focus is on the plastic flow properties, namely strain hardening and strain-rate sensitivity. Distribution of strain from uniaxial tensile specimens and sheets stretched over a rigid punch are presented for a number of sheet materials to illustrate the importance of these properties. Some effects of deformation rate are also presented.
Blunting of a Plane Strain Crack Tip Into a Shape With Vertices
Authors: McMeeking Robert M.
Published: November 2010

When monotonically increasing tensile opening loads are applied to a cracked, plane strain, elastic-plastic body, the crack tip will blunt until fracture occurs. At least within the rigid-plastic model for nonhardening material, the shape of the blunted tip is not unique. The blunted tip shape may have two or more sharp corners, or be smoothly curved. When the shape involves corners, the opening is predominantly accommodated by shearing of the material at the corners. This shearing transports material from the interior of the body onto the crack surface. In contrast, the smoothly blunted crack tip involves no such transfer of material points from the interior. However, the smoothly blunted crack, which was originally sharp, involves infinite strains on the crack tip surface. The crack with corners on the tip has large but finite strains on the crack tip surface. The stress and deformation field in front of a crack with two corners and with three corners on the tip, as calculated using the slip line method, is presented for the nonhardening, fully plastic, deeply cracked, double edge-notched thick panel. As in the case of the smoothly blunted crack tip, the elevated stress between the crack tips cannot be maintained very close to the crack tip, due to a lack of constraint. The stress distribution in the case of the crack tip with vertices on it differs from that of the smoothly blunted crack tip case. In particular, immediately in front of the crack tip with three corners, the stress is higher than that immediately in front of the smoothly blunted crack tip. An approximation for a power law hardening material indicates that the maximum stresses near the blunted crack tip is much the same for a crack with vertices on the tip as for a smoothly blunted crack tip. The details of the stress distribution, though, will depend on the mechanism by which the crack blunts. These results for stress and strain and some calculations of the growth of voids near the crack tips indicate the same fracture process could lead to different fracture toughnesses, depending on the type of mechanism by which the crack blunts.
Enhancement of Fatigue Crack Growth and Fracture Resistance in Ti-6Al-4V and Ti-6Al-6V-2Sn Through Microstructural Modification
Authors: Yoder G. R. , Cooley L. A. , Crooker T. W.
Published: November 2010

Significant enhancement in fatigue crack propagation resistance and plane strain fracture toughness was obtained in commercial purity Ti-6Al-4V and Ti-6Al-6V-2Sn through microstructural modification. Alloys studied were in the form of 25.4 mm-thick plate with interstitial oxygen contents of 0.20 and 0.17 weight percent, respectively. Heat treatments were chosen to provide widely varied microstructures; these included a mill anneal, recrystallization anneal and a beta anneal. The most beneficial heat treatment for improving these crack tolerance properties was found to be the beta anneal. However, the beta anneal resulted in yield strength reductions of 9 to 14 percent, from levels associated with the original mill anneal. The recrystallization anneal provided significant enhancement of plane strain fracture toughness and marginal improvement in fatigue crack propagation resistance with negligible loss of yield strength.
Strain Rate Effects on the Elevated-Temperature Tensile Behavior of a Bainitic 2-1/4 Cr-1 Mo Steel
Authors: Klueh R. L. , Oakes R. E.
Published: November 2010

The tensile properties of a normalized-and-tempered 2-1/4 Cr-1 Mo steel were determined from 25 to 566° C and the strain rate 2.67 × 10−6 to 144/s. The specimens were taken from a 1-in. thick plate and had a microstructure that was essentially 100 percent bainite. Except at 25 and 566° C, the 0.2 percent yield stress was little affected by strain rate; at 25 and 566° C, the yield stress increased with increasing strain rate. At a constant strain rate, the yield stress decreased with increasing temperature. The effect of strain rate and temperature on the ultimate tensile strength was somewhat more complicated. A strength peak that resulted from dynamic strain aging was observed in the ultimate tensile strength-temperature relationship. The position of these peaks moved to higher temperatures with increasing strain rate. Total elongation and reduction of area were relatively constant over the range of test variables, except at 566° C, where they increased with decreasing strain rate. However, uniform elongation decreased with decreasing strain rate at 510 and 566° C, dropping to 1 and 0.6 percent, respectively.
Elevated-Temperature Mechanical Behavior of a Carbon-Manganese Pressure Vessel Steel
Authors: Early J. G.
Published: November 2010

The short-time effects of stress and temperature on the mechanical properties of a carbon-manganese pressure vessel steel were investigated using room- and elevated-temperature tensile tests and short-time creep-rupture tests. The tensile test results indicated that strain aging effects were not Significant in the temperature range 593 to 677 C (1100 to 1250 F). Analysis of the creep-rupture data, in the range 621 to 677 (1150 to 1250 F), by the Larson-Miller method using the procedure of Manson and Mendelson yielded a value of 20.7 for the material constant, C. In the temperature and stress regime studied, a linear relationship was observed between log (stress) and log (time-to-rupture). Fractographic analyses revealed a common fracture mode in all specimens tested. The fracture mode is described as an intermediate type, containing features of both transgranular and intergranular fracture.
Current Progress in Materials Development for Coal Conversion
Authors: Samans C. H. , Hulsizer W. R.
Published: November 2010

A coal gasification materials program directed at developing engineering data on materials is described. Included are initial results on materials exposed in 6.9 MPa (1000 psi) simulated gasifier atmospheres at 755° K (900° F), 1089° K (1500° F), and 1255° K (1800° F); a 1 MPa (150 psi) simulated regenerator atmosphere at 1285° K (1850° F); and in pressurized aqueous environments simulating gasifier quench towers. Erosion/corrosion tests, scheduled to begin in the near future, are also described. Comparison of simulated exposure results with data from early interrupted exposures in two operating pilot plants are reported indicating reasonable agreement except for a few pilot plant specimens which appeared to deteriorate rapidly because of operating conditions not thought previously to be corrosive.
Combustion Roar of Turbulent Diffusion Flames
Authors: Giammar R. D. , Putnam A. A.
Published: November 2010

Pertinent literature is reviewed and experimental data on the combustion roar of turbulent, natural-gas, diffusion flames are presented. These data were obtained on two experimental burner rigs, one that consisted of two impinging fuel jets, and one that consisted of eight almost impinging fuel jets. Variables considered include the effect of firing rate up to several hundred thousand btu/hr, spud size, spud spacing and orientation, on both overall noise level and noise spectrum. The data are compared to similar observations from industrial combustors. Some speculations as to the specific source of the combustion roar are made.
The Transpiration-Cooled Gas Turbine
Authors: Bayley F. J. , Turner A. B.
Published: November 2010

This paper describes a program of experimental and analytical research designed to evaluate the aerodynamic and thermodynamic performance of transpiration-cooled porous surfaces in the high-temperature gas turbine. The aerodynamic penalties of effusing coolant through a set of nozzle blades are shown to be small, particularly when compared with the thermodynamic advantages which accrue from the effective cooling obtained. Although the effusing coolant can in certain circumstances increase gas to blade heat transfer rates by destabilizing a laminar boundary layer, in the turbulent boundary layers which predominate in turbine practice there is inevitably a reduction in heat transfer which can be satisfactorily predicted theoretically. In the combustion system of the gas turbine, transpiration cooling appears also to be very attractive, but much work remains to be done on heat transfer rates in the flame-tube.
Laminar Incompressible Flow in the Entrance Region of Ducts of Arbitrary Cross Section
Authors: Miller James A.
Published: November 2010

A combination of the numerical technique of Chorin for the solution of the Navier-Stokes equations and a transformation of the initial value problem to a boundary value problem is shown to allow calculation of the laminar hydrodynamic entrance region of ducts of arbitrary cross section. Numerical examples consisting of the solution for ducts of square and triangular cross sections are presented along with the associated friction factors.
The Buzz-Saw Noise Generated by a High Duty Transonic Compressor
Authors: Philpot M. G.
Published: November 2010

The buzz-saw noise made by a two-stage transonic research compressor has been investigated experimentally over a range of tip relative Mach numbers up to 1.56. The results show that the phenomenon is due to the propagation at supersonic relative tip speeds of the steady rotating pressure field associated with the first-stage rotor blades. The flow entering the tip section of the rotor has been analyzed theoretically and the circumferential pressure fluctuations computed, with good agreement with near-field measurements. The analysis leads to a clearer understanding of the dependence of the noise on inlet Mach number and three-dimensional effects and indicates the types of rotor irregularity which will most influence the harmonic content.
Thermal Energy Requirements of Air-Conditioning Systems
Authors: Lackey M. E.
Published: November 2010

The thermal energy requirements for air conditioning by compressive and absorption methods were determined for light-water, thermal-breeder, and fast-breeder reactors. The energy required to produce a ton-hour of refrigeration varied from 5100 Btu to 13,100 Btu by absorption and from 5600 to 8800 Btu by compression. The amount of waste heat dissipated to the environment at the reactor site as a consequence of producing a ton-hour of air conditioning ranged from an increase of 21,000 Btu for the electric-motor-driven refrigeration system to a decrease of 6000 Btu for the absorption refrigeration system.
Analysis of Changes in the Performance Characteristics of Steam Turbines
Authors: Cotton K. C. , Schofield P.
Published: November 2010

The proper analysis of routine steam turbine performance test data can afford valuable information on the internal condition of a steam turbine. This paper outlines the theory behind the analysis of test data together with several case histories illustrating the use of the analysis to pinpoint various steam turbine problems.
Analysis of the Dynamics of Gas Turbines and Their Control Systems
Authors: Sarantsev L. B.
Published: November 2010

The gas turbine units designed by the Neva Works named after V. I. Lenin (NZL) are intended for driving the gas trunkline compressors and electrical generators, and are also used in chemical and metallurgical industry for heat recovery. By July 1, 1969, 320 gas turbines manufactured by NZL had operated under load more than 4.5 million hr and produced over 20 million MWH. Two-shaft and single-shaft gas turbine units manufactured by the NZL are intended for open cycle operation with heat regeneration. The two-shaft arrangements are designed and built to operate with a free power turbine. The specifications for these gas turbine units are given in Table 1. The modern gas turbine units are equipped with control and protection systems which accomplish the automatic control of the unit at its starting and stopping as well as its operating duties. The hydraulic, pneumatic, and electric instruments and regulators are widely used in these systems. The indication and recording of main parameters of the unit are performed by a complete set of these instruments.
Gas Turbine Blade Heat Transfer Augmentation by Impingement of Air Jets Having Various Configurations
Authors: Tabakoff W. , Clevenger W.
Published: November 2010

An experimental investigation of heat transfer characteristics for various configurations of air jets impinging on the leading edge inner surface of the blade wall is presented. Three configurations were investigated, namely a slot jet, a round jet row and an array of round jets. The effect on the heat transfer coefficient of injecting solid particles into the air flow is considered. The study treats an important class of turbine blade cooling for which small cooling mass flow rates are of interest. The experimental facility and procedures are described in detail. A theoretical technique is introduced for predicting the heat transfer in the case of the slot jet configuration. The results are compared to experimental data.
A Proposed New Concept for a Solar-Energy Converter
Authors: Bailey R. L.
Published: November 2010

The potential advantages of terrestrially utilizing nonpolluting solar energy are well-known. One of the more promising approaches to achieving the desired high solar-electrical conversion efficiency is the direct process, avoiding Carnot efficiency limitations of heat engines. The chief present-art example is the large area silicon solar cell based on utilization of quantum properties of light. In the United States it is now an established technology created from the space program. This paper presents the results of some preliminary new research exploring the possibilities of creating high efficiency solar-electricity converters utilizing wave-like properties of radiation interacting with absorber-converter elements. The concept is revealed for what is believed to be a new, unique, and potentially useful pyramidical solar radiation absorber-converter structure. It is based on the possibility of extending concepts of power absorbing antennas and converters to the visible light range. The resulting proposed converter structure would have a rough surface texture and yield a d-c output. It may have, if subsequently researched, significant efficiency, cost, and fabricating advantages, particularly for large-scale terrestrial utilization of solar energy. The concept is called an Electromagnetic Wave Energy Converter (EWEC). Concept validity evidences of a preliminary kind at both microwave and near light wavelengths are presented.
Average Pressure Measurement in Low-Velocity Nonuniform Gas Flows
Authors: Gilbert G. B.
Published: November 2010

An accurate measurement of the average stagnation pressure at a duct cross section is necessary when trying to determine the loss characteristics of low-pressure loss components such as power plant ducts and electrostatic precipitators. In these components, the pressure loss is usually of the same order of magnitude as the gas velocity head. This paper describes how to calculate average stagnation pressure for flows with nonuniform velocity profiles. Guidelines are presented on the techniques needed to achieve an acceptable measure of the average stagnation pressure. These guidelines were developed for use by power plant engineers and experimental flow-model investigators. The required mathematical techniques, a computer program, and some experimental model results are presented.
Nonlinear Analysis of Rotating Stall
Authors: Takata H. , Nagano S.
Published: November 2010

A new stall model to describe rotating stall in axial-flow compressors is established, where blade rows are replaced by semiactuator disks, flow fluctuations are permitted to be finite and nonsteady, and blade row characteristics are taken into consideration in nonlinear and nonsteady forms. Through numerical analysis using the finite difference method, it is attempted to make clear the aspects of rotating stall—such as number of stall cells, stall propagation velocity, wave shape and magnitude of disturbance and their variations with flow rate through the compressor, and the mechanisms which control them. Most of the aims are achieved by taking into consideration the effects of blade row interference and the nonlinearities of blade row characteristics.
Performance of MONEL Alloy 400 in Feedwater Heaters
Authors: Rahoi D. W. , Scarberry R. C. , Crum J. R. , Morris P. E.
Published: November 2010

With access to data on more than thirty years service experience with MONEL alloy 400 tubing in high-pressure feedwater heaters, the Huntington Alloy Products Division conducted an extensive laboratory investigation on mechanisms and corrodents contributing to stress-corrosion cracking in this application. A mechanism by which copper-nickel and nickel-copper alloys fail through stress-corrosion cracking is proposed. Changes in manufacturing procedures make it possible to achieve material highly resistant to failure by this mechanism.
Further Development of the Burning Profile
Authors: Wagoner C. L. , Winegartner E. C.
Published: November 2010

In 1967, Messrs, Wagoner and Duzy presented a paper at the Winter Annual Meeting of the ASME entitled “Burning Profiles for Solid Fuels”, in which they described a derivative thermogravimetric procedure for evaluating the burning characteristics of coal and similar materials. Since that time, others, including Esso Research and Engineering Company, have attempted to duplicate this test in their own laboratories with varying degrees of success. The present paper describes some of the precautions required in setting up the test in other laboratories and gives further information on details of the test procedure which must be followed to obtain comparable results. Burning profiles of three chars obtained from the U. S. Bureau of Mines and of several petroleum cokes are also included.
Experiences of a Multiple Gas Turbine Machinery in Fast Patrol Craft
Authors: Hafstro¨m H. G.
Published: November 2010

The Swedish Spica-class torpedo boats have been in service now for some years. The experiences of the craft are reported good and some details are given in this paper of the results with the propulsion gas turbine, the gearing, the controllable pitch propeller, and the generator set gas turbine. Air intake problems in small craft are discussed as well as other problems connected with the multiple shaft installation.
Some Generalizations in Compressible Flow Characteristics
Authors: Benedict R. P.
Published: November 2010

Certain generalizations in compressible flow characteristics are first reviewed including specific solutions to flow with losses in the absence of heat transfer (i.e., Fanno flow), in terms of an empirical loss coefficient, Kf. The analysis is then extended to specific solutions to flow with heat transfer, with and without losses (i.e., isothermal and Rayleigh flows), in terms of an empirical heat transfer coefficient, Kq. All solutions are mapped on generalized plots which, in addition to their utility, exhibit a certain beauty of symmetry and continuity.
Thermal Stresses and Initial Deformation of Heated Condenser Tubes
Authors: Soler A. I.
Published: November 2010

A condenser tube bank with individual tubes axially and laterally restrained at the ends by tube sheets, and laterally restrained at intermediate locations by support plates is subjected to a uniform temperature rise. In the interior of the bank, the tube sheet flexibility is sufficient to allow absorption of the thermal growth without buildup of high compressive loads in the tube. Around the periphery of the tube bank the tube sheet is attached to a massive fixed water box; hence, in this vicinity, axial growth of the tubes is prevented and high tube compressive loadings can ensue. Accompanying such high tube loadings are two potentially severe problems: (1) buckling of the tube with attendant lateral growth and large bending stresses; and (2) failure of the tube-tube sheet attachment due to the high compressive loading. In this work we develop relations to predict the build-up of tube load and deformation as a function of initial deformation parameters. We show that the presence of initial deformation serves to reduce the magnitude of the direct compression load in the tube, but does so at the expense of building up large tube bending stresses. Thus, tube design to minimize the occurrence of tube failure at the tube sheet connection point may lead to severe tube bending between support plates. Typical tube geometries are investigated and numerical results presented; the results of these investigations suggest certain directions for tube design for particular operating configurations.