bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of Fatigue Crack Growth under Irregular Loading
Authors: Nelson DV , Fuchs HO 
Published: March 2009

Fatigue crack growth under irregular loading is calculated from constant-amplitude test data. The results of such calculations are compared with measurements of crack growth in modified compact tension specimens made of two commonly used structural steels and subjected to three different irregular load histories, each applied at several load levels.
Two crack growth rate relations are utilized: I, the Forman relation, and II, a relation based on an effective stress intensity range concept. The Forman relation is used with two different methods of “counting” load ranges, that is, crack growth is calculated: (a) for all rising tensile load ranges as they occur in the load history and (b) for the load history condensed by a method which forms overall ranges and includes only the top decile of all rising tensile ranges. Crack growth rate Relation II is used only with counting Method a. The three resulting prediction methods are designated Ia, Ib, and II. Methods Ia and Ib disregard sequence effects, while Method II includes them.
Predictions of crack growth using Methods Ia and Ib agree with average test lives to within a factor of two in nearly all cases, with the exception of those instances where large compressive loads cause gross yielding and accelerated growth. Predictions based on Method II are superior to those for Ia and Ib when such gross yielding occurs and are comparably good for the other cases investigated here.
Neutron Gaging Systems
Authors: Reynolds GM 
Published: March 2009

A review is presented of neutron gaging concepts and applications. The gaging systems are restricted to those that measure elastic or inelastic scattered source neutrons, in either a transmission or scattering geometry. Neutron gaging, in this sense, is not selective. It cannot identify particular materials, but is useful in monitoring particular isotopes (hydrogen, boron) in otherwise known matrices.
Discussions are given of the many areas where neutron gaging has been applied: moisture measurements in soil, food, and the steel industry; detonating cord; metals; nonmetallic mines; well logging; and explosive ordnance and fuzes.
Although neutron gaging is inherently more sensitive than neutron radiography and presents the results in real-time, it is less commonly used than radiography. The advent of digital imaging tubes could allow two-dimensional information to be obtained from gaging systems and thereby increase their relative importance.
Neutron Radiography of Fuel Pins
Authors: Jackson CN , Powers HG , Burgess CA 
Published: March 2009

Neutron radiography performed with a reactor source has been shown to be a superior radiographic method for the examination of unirradiated mixed oxide fuel pins at the Hanford Engineering Development Laboratory. Approximately 1700 fuel pins were contained in a sample that demonstrated the capability of the method for detecting laminations, structural flaws, fissile density variation, hydrogenous inclusions, and voids in assembled fuel pins.
The nature, extent, and importance of the detected conditions are substantiated by gamma autoradiography and by destructive analysis employing alpha autoradiography, electron microprobe, and visual inspection. Also, a series of radiographs illustrate the response of neutron radiography as compared to low-voltage and high-voltage X-ray and gamma source iridium-192 radiography.
Resistance to Plane-Stress Fracture (R-Curve Behavior) of A572 Structural Steel
Authors: Novak SR 
Published: March 2009

The R-curve behavior of A572 Grade 50 steel was established over the temperature range-40 to +72°F by using state-of-the-art procedures. Both linear-elastic-fracture-mechanics (LEFM) and crack-opening-stretch (COS) analytical techniques were used in assessing experimental results obtained under load-control and displacement-control testing conditions. This study represents a pioneer effort in that it is the first known attempt to evaluate the R-curve behavior of a low-strength structural steel in some depth.
Results showed a steep Kc transition behavior for 1.5-in.-thick (38 mm) plate, with minimum Kc values of 57, 155, and 318 ksi √in (63,171, and 350 MNm-3/2) obtained at-40, +40, and +72°F (-40, +4.5, and + 22°C), respectively. A similar behavior was observed for 0.5-in.-thick (12.7 mm) plate, with minimum Kc values of 150, 273, and &gt;380 ksi √in. (165, 300, and &gt;418 MNm-3/2) obtained at the corresponding test temperatures. The results are discussed in relation to the influence of material and testing method, as well as in relation to earlier KIc results obtained at cryogenic temperatures.
The minimum Kc values measured demonstrate extensive crack tolerance for A572 Grade 50 steel under all combinations of the test conditions studied. With one exception, these minimum behaviors can be translated into total critical flaw lengths that are at least seven times the plate thickness (2acr ≧ 7B) for cracks embedded in large planar structures and subjected to tensile-stress levels equal to three fourths the yield strength. The applicability of acr calculations obtained from R-curve measurements generally, and on the A572 Grade 50 steel specifically, is discussed in relation to typical structural members such as H-beams.
A Finite-Element Analysis of Fatigue Crack Closure
Authors: Newman JC 
Published: March 2009

Experiments have shown that fatigue cracks close at positive loads during constant-amplitude load cycling. The crack-closure phenomenon is caused by residual plastic deformations remaining in the wake of an advancing crack tip. The present paper is concerned with the application of a two-dimensional, nonlinear, finite-element analysis using an incremental theory of plasticity to predict crack-closure and crack-opening stresses during the crack-growth process under cyclic loading.
A two-dimensional finite-element computer program, which accounts for both elastic-plastic material behavior and changing boundary conditions associated with crack extension and intermittent contact of the crack surfaces under cyclic loading, has been developed. An efficient technique to account for changing boundary conditions under cyclic loading was also incorporated into the nonlinear analysis program. This program was used subsequently to study crack extension and crack closure behavior in a center-cracked panel under constant-amplitude and two-level block loading. The calculated crack-opening stresses were found to be quantitatively consistent with experimental measurements.
Practical Method for Calculating Stress-Intensity Factors Through Weight Functions
Authors: Labbens R , Pellissier-Tanon A , Heliot J 
Published: March 2009

The existence for a plane or axisymmetric cracked body of an influence or Green's function, depending on the geometry of the body, allows calculation by means of a simple integral of the stress intensity factor. In this way the respective influence of geometry and load in K calculation are separated. The relationship between this function and the compliance for a concentrated force applied on the crack is shown.
Starting from complex mathematical considerations, Bueckner defined weight functions equivalent to the influence functions and of particular advantage for analytic as well as numerical purposes. Moreover he showed that weight functions behave like d-½ at the distance d from the crack tip. In the sequel we shall refer to weight functions, since they are studied more deeply from a mathematical point of view and are known more widely than influence functions.
A practical calculation method of weight functions by finite elements is shown. This method can be used for any bidimensional cracked body, plane or axisymmetric. Curves of nondimensional weight functions are given for cylindrical geometries currently used in engineering.
It is pointed up that this method is more flexible than the use of handbooks which, in spite of their great interest, cannot foresee all the geometries and loads which are met in engineering problems.
Stress Intensity Factor Solutions for Continuous Surface Flaws in Reactor Pressure Vessels
Authors: Buchalet CB , Bamford WH 
Published: March 2009

A two-dimensional finite element method is used to develop stress intensity factor solutions for continuous surface flaws in structures subjected to an arbitrary loading. The arbitrary loading produces a stress profile σ acting perpendicularly to a given section S of the structure. The stress profile is represented by a third degree polynomial σ=A0+A1x+A2x2+A3x3
Stress intensity factor solutions are developed for continuous surface flaws introduced in particular sections S in the structure considered. Solutions are developed for a surface flaw in a flat plate, for both circumferential and longitudinal flaws inside a cylindrical vessel, and for circumferential flaws at several locations inside a reactor vessel nozzle.
The superposition principle is used, and the crack surface is subjected successively to uniform (σ = A0), linear (σ = A1x), quadratic (σ = A2x2), and cubic (σ = A3x3) stress profiles. The corresponding stress intensity factors (KI(0), KI(1), KI(2), KI(3)) are then derived for various crack depths using the calculated stress profile in the region of the crack tip. The total stress intensity factor corresponding to the cracked structure subjected to the arbitrary stress profile is expressed as the sum of the partial stress intensity factors for each type of loading. KI=KI(0)+KI(1)+KI(2)+KI(3)=πa[K0F1+2aπA1F2+a22A2F3+4a23πA3F4] where, a is the crack depth and F1, F2, F3, and F4 are the magnification factors relative to the geometry considered. The results are presented in terms of magnification factors versus fractional distance through the wall (a/t) and reveal the strong influence of the geometry of the structure and of the crack orientation.
The stress intensity factor solutions obtained using this method are compared to solutions obtained using other methods, when available. In the case of the plate geometry, the solution obtained for the linear loading (σ = A0 + A1x) is shown to agree well with the boundary collocation solution reported by Brown and Srawley. The stress intensity factor solutions for the circumferential and longitudinal cracks in the cylindrical vessel compare well with solutions obtained by Labbeins et al using the weight functions method proposed by Bueckner, and are also in good agreement with the solution for uniform loading (σ = A0) obtained using the line spring method proposed by Rice.
Predicting Spacecraft Multilayer Insulation Performance from Heat Transfer Measurements
Authors: Stimpson LD , Hagemeyer WA 
Published: March 2009

One of the most commonly utilized insulation systems for National Aeronautics and Space Administration spacecraft is multilayer insulation (MLI). The problem of predicting performance of MLI blankets containing discontinuities is described. Design data and test techniques are required which allow correlation of heat leaks through discontinuities with measurable parameters. Some of these design data are obtained using the Jet Propulsion Laboratory's calorimetric testing program.
New materials and testing approaches will be required for more extreme environments of future spacecraft. Both higher and lower environmental temperatures are anticipated. Insulation performance must meet these demands, at the same time avoiding excessive weight.
Design Criteria for Guarded Hot Plate Apparatus
Authors: De Ponte F , Di Filippo P 
Published: March 2009

A procedure is suggested, in this paper, for a rational design of guarded hot plate apparatus of assigned performances.
The dimensions of the hot plate, of the guard ring, and of the maximum specimen thickness are derived from the computation of edge heat losses and unbalance errors.
The problem of the best location of the unbalance detectors along the gap is discussed, and some solutions are proposed.
The elements for the design of the cold plates are given for both liquid cooled and gas cooled plates.
Thermal Conductance of Pipe Insulation—A Large-Scale Test Apparatus
Authors: Kimball LR 
Published: March 2009

Thermal conductance measurements were carried out for pipe insulation on a large-scale test apparatus. A pipe 18 in. (0.457 m) in diameter and 20 ft (6.08 m) long was used. A chamber cooled to −70°F (−56.7°C) by expansion of liquid nitrogen surrounded the pipe. Water inside the pipe was heated to 160°F (71.1°C) by electrical resistance heaters. Several steady-state tests were made using air and water inside the pipe. A transient heat loss test was also made using water inside the pipe.
Close agreement was found between the theoretical steady-state thermal conductance factor and that experimentally measured. The numerical difference can be explained by center joint heat losses. Close agreement was also found in the transient response of the system to a loss of heat inside the pipe as experimentally recorded and compared to a theoretical approach.
Calibrated Hot Box: An Effective Means for Measuring Thermal Conductance in Large Wall Sections
Authors: Mumaw JR 
Published: March 2009

A large calibrated hot box apparatus, utilizing highly thermal resistant walls, has been constructed to permit fast and accurate thermal conductance measurements for large vertical sections. The test wall section, nominally 9 by 14 ft (2.7 by 4.2 m), is placed between two chambers maintained at different temperatures. The net heat flow through the test wall is the algebraic sum of the measured input electrical energy and the chamber wall heat transfer which is measured using a heat meter technique. With the use of high thermal resistance walls, the correction for chamber heat flow is generally less than 1 percent. Other data required for the final calculations are obtained using an automatic data monitoring and recording system. Data analysis and report preparation are performed using a computerized program written especially for the equipment.
These, and additional design features, permit a wide variation in mean temperature capability (0 to 100° F), air infiltration measurement capability (0 to 54 standard cubic feet per minute (scfm) at up to 10 in. H2° ΔP), and efficient usage of manpower by automating control, data taking, and analysis (test frequency of three per week for a manpower requirement of 1 to 2 h per day, excluding specimen construction).
Close agreement was found between the expected and measured thermal results, using calibration specimens measured in the ASTM Test for Thermal Conductivity of Materials by Means of the Guarded Hot Plate (C 177-63). Data in support of the basic conclusions of the paper are presented with the addition of suggestions for including the calibrated hot box as a useful ASTM test standard.
Three-Dimensional Analysis of Laminar Composites with Through Cracks
Authors: Hilton PD , Sin GC 
Published: March 2009

The variational principle of minimum complementary potential energy is employed to develop an approximate three-dimensional model for the stress distribution in laminar composites. This approximate theory is applied to the problem of a symmetric composite plate containing a through crack subjected to in-plane loading. Asymptotic solutions are obtained for the stress components in the vicinity of the leading crack edge. These solutions are in complete agreement with information obtained from an exact three-dimensional asymptotic analysis; that is, the in-plane variation of the stress components within each layer is described by the singular portion of the elastic, plane-strain crack solution. However, because of the three-dimensional character of the problem, the amplitude of the singular solution for the stress components varies along the leading crack edge. A two-parameter model incorporating the concept of surface and interfacial boundary layers is used to describe this transverse variation.
Results from the modeling and analysis performed here include a description of the through-the-thickness variation of the near-tip stress field, which has already proven to be of use in conjunction with photoelastic measurements, and an average or effective stress intensity factor for finite thickness homogeneous plates and laminates.
Mode I Stress Intensity Factors for Symmetrically-Cracked Orthotropic Strips
Authors: Konish HJ 
Published: March 2009

The effects of material anisotropy on the stress intensity factor are investigated numerically for both double-edge-cracked and center-cracked orthotropic tensile strips. The material properties employed correspond to homogeneous material models of mid-plane symmetric fiber composite laminates of varying ply orientation and ply properties.
The effects of anisotropy are found to be dependent on both specimen geometry and material properties. Complete decoupling of these geometric and material influences does not appear possible. However, the principal geometric parameter seems to be the distance from the crack tip to the free edge of the specimen; the effects of material properties appear to correlate with the in-plane elastic shear modulus. It is suggested that anisotropic effects can be sufficiently controlled, by means of specimen geometry, to justify the use of the known isotropic stress intensity factor as a reasonable (and usually conservative) estimate of the anisotropic value in most materials.
Crack Arrestment of Laminated Composites
Authors: Bhatia NM , Verette RM 
Published: March 2009

In this paper the potential of the buffer strip concept for providing fracture control in graphite/epoxy laminated composite panels subjected to uniaxial tension static and fatigue loads is evaluated. The specific buffer strip design consists of replacing the 0-deg and 90-deg plies in a π/4 laminate with ±45-deg plies along strips parallel to the uniaxial load direction. A number of specimens were fabricated and tested. The specimens were 8 by 20-in. panels of 8-ply (0, ±45, 90)s Thornel 300/SP286 graphite/epoxy laminates. Two 1-in. wide buffer strips were symmetrically placed 2 in. apart (3 in. center-to-center) and parallel to the longer sides of the panels. Initial flaws consisting of slits and circular holes of various sizes and orientations were machined at the midsection between the two buffer strips. Initial fracture and ultimate failure strengths of the panels were determined. In addition, several panels were fatigue cycled prior to static failure to assess the influence of fatigue loads on post-fatigue performance.
The static tests of the panels not previously fatigue tested showed that crack arrestment occurred when the initial flaw size exceeded 0.50 in. That is, the crack arrest capability was found to depend on the initial flaw size. For panels with 0.75 and 1.00-in. flaws, an initial fast crack was arrested in the buffer strips and the panels subsequently withstood approximately 20 percent more load. The crack initiation load for the panels which were previously fatigue cycled increased by approximately 10 percent as compared to the crack initiation load for an identical panel not previously fatigued. The improvement is attributed to development of zones of crazing and delamination in the crack tip region during fatigue cycling which reduce the local stiffness and the stress concentration. Fractographic examination of the failure surfaces confirmed the existence of this zone.
Engine Oil Viscosity Classifications-Past, Present, and Future
Authors: McMillan ML 
Published: March 2009

An extensive effort is under way to revise the SAE Engine Oil Viscosity Classification System to reflect user needs more realistically. To understand how the present system evolved, the history of the classification is traced, from the original version first published in 1911 to the present 1976 version. Reasons for both high- and low-temperature viscosity grades, multigrading, and footnotes to the viscosity table are discussed, as well as other classification systems which have been discarded over the years.
A critical assessment of the present classification is made from opinions offered at an SAE Open Forum last year. It is pointed out that the system has become quite complicated with four low-temperature and four high-temperature grades, five footnotes, and an appendix. Moreover, the high-temperature viscosity grades are based on an unrealistically low temperature of 98.9°C (210°F) and an unrealistically low-shear (kinematic) viscosity compared with engine operating conditions.
Several suggestions for improving the system are offered, although no one particular approach is advocated. It is concluded that to adequately reflect the effects of oil viscosity on engine performance in the field, the classification system must be revised to include a measure of low-temperature oil fluidity and a high-temperature, high-shear measure of viscosity which correlates with engine performance — a measure which has not yet been developed.
European Activity Concerning Engine Oil Viscosity Classification
Authors: Cassiani Ingoni AA , DiLelio GF , Eberan Eberhorst CGA 
Published: March 2009

The growing interest and concern over the problem of the high temperature viscosity of engine oils and its effect on the engine performance, following the proposal for revision of the SAE J 300, pushed the CEC Engine Lubricant Technical Committee to establish an Investigation Group (IGL 9) to investigate the subject of Viscosity Measurements at High Temperature.
The Low Temperature aspects are mainly covered by the CEC Investigation Group IGL 8 and the German National Organization DKA Study Group.
The IGL 9 Group agreed to circulate a questionnaire which was gratified with high degree of attention; 31 companies answered confirming the importance of the investigation and the requirement of viscosity measurements more realistic and in line with to day's engine operating conditions.
A first screening work carried out on some reference oils has demonstrated the possibility of correlation among different bench measuring techniques and an engine. The second stage now underway sees a new set of 9 test oils formulated using different polymer species commercially available, to be submitted to 22 “engine viscosity” and “viscosity rig” tests to define correlations where possible.
Bacterial Indicators and Standards for Water Quality in the Federal Republic of Germany
Authors: Müller G 
Published: March 2009

In the Federal Republic of Germany, the choice of the indicator differs with the water that has to be examined. For drinking water, the classical parameters are the total colony count and the Escherichia coli test.
While the colony count seems to be considered of less importance in other European countries, the German legislation contains mandatory limits. Furthermore, E. coli must not be present in 100 ml of drinking water. Fecal streptococci and Pseudomonas aeruginosa are good indicators for the examination of swimming water in pools which have been treated by flocculation, filtration, and chlorination.