bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Unifying Principle for Evaluating Fracture Toughness in the Elastic and Plastic Regimes with Planar Fracture Specimens
Authors: Donoso JR , Landes JD 
Published: April 2008

Recently, Donoso and Landes proposed the existence of a common format equation (CFE) for developing calibration functions for two-dimensional fracture specimens. In the CFE approach, the relation between load, plastic displacement, and uncracked ligament size is expressed as the product of three terms: (1) a constraint factor, (2) a geometry and crack length-dependent function (G), and (3) a hardening function (H). The history-dependent component of the calibration functions, namely H, has been explored by the same authors, using two different hardening functions: a power law and a three-parameter function, designated as the LMN function. For the geometry function G, on the other hand, a power-law dependence on normalized ligament length, i.e., G ∝ (b/W)m (where W is the specimen width), is used for all of the classical two-dimensional fracture specimens. This type of behavior for G has been derived from the GE EPRI Handbook equations and has also been observed experimentally. From such a relationship, a crack-length independent value of eta plastic, ηpl is obtained that is equal to the exponent m.
The application of a ductile fracture methodology requires, in addition to the calibration functions, the fracture toughness of the material, usually given by the J-R curve. The computation of J, according to standard procedures, needs both its elastic and plastic contributions. The elastic component is normally evaluated in terms of K, the stress-intensity factor for the geometry and test conditions. The plastic component of J, on the other hand, is equal to the area under the load-plastic displacement curve per unit net section area of specimen, multiplied by the plastic eta factor, ηpl. The purpose of this work is to extend the use of the CFE approach to the elastic region of the load-displacement curve of standard frac-ture specimens, focusing on both their elastic compliances and their elastic eta factors, ηel. The elastic compliances and the G functions of the predominantly bend-type geometries, i.e., SE(B), C(T), and SE(T) specimens, are compared, showing that the elastic and the plastic eta factors are practically equal. This allows one to evaluate J in these geometries in terms of total displacement. The same does not apply, however, to the tensile M(T) and DE(T) geometries. In addition, K factors will be derived for the bend-type geometries based on the dependence of the elastic compliance with ligament size.
Method for Predicting J-R Curves from Charpy Impact Energy
Authors: Gioielli PC , Landes JD , Paris PC , Tada H , Loushin L 
Published: April 2008

In this paper a mechanistic rationale for the fracture process is applied to the CVN impact test so that the J-R curve fracture toughness could be estimated for materials that have only a CVN energy value as the fracture toughness characterization. The method assumes that the fit to the J-R curve can be given a standard form by assuming that the product of J and the tearing modulus, T, is a constant. Given this standard fitting form, the CVN energy is used to estimate a point on the J-R curve. Using this single point and the constant J × T product, the J-R curve is estimated with the two-parameter power law fit specified in ASTM standards. The procedure is applied to metals that undergo purely ductile fracture, that is, those that have CVN energy that would be characterized as “upper shelf” or 100% shear.
The method requires a calibration between impact energy, which has energy contributions from factors other than the fracture process, and the J-R curve point used in the fit. It is calibrated using three steel alloys where both CVN energy on the upper shelf and J-R curve fracture toughness data exist. The results show that a consistent calibration factor can be assumed that applies to all of the steels. Using that factor and the standard J-R curve fit, the prediction was good for all the steels examined. From these J-R curves, the initiation toughness value JIC can also be determined using the JIC construction from ASTM Standard Method E 1820. The resulting determination of JIC shows why the simple process of fitting data sets does not give a universal prediction of toughness. The material tensile strength plays a role in the determination of JIC.
Fracture Mechanics Validity Limits and Physical Evidence of Constraint in Fracture
Authors: Lambert DM , Ernst HA 
Published: April 2008

The consideration of fracture behavior should be a matter of vital concern in current design efforts. Many materials exhibit grossly different behavior when discontinuities are present in the structure. These may be inherent in the material or may stem from poor manufacturing, handling, and /or design practices. Inclusion of fracture behavior in the design models is the subject of fracture mechanics. Ultimately, a knowledge of fatigue and fracture becomes very important in avoiding disaster.
This paper is written with two primary purposes: to characterize the physical nature of fracture, and to dramatize the need to characterize the central flat fracture differently from the surface, shear fracture. To this end, the contents of the paper are organized as follows: (1) validity limits of fracture mechanics: this information was originally developed for the purpose of extracting similar fracture data and will be used here to help characterize bulk constraint effects and to establish the existence of the surface effect; (2) analysis of crack face displacements of planar specimens subjected to loads: this includes actual crack-, separation-, and stretch-profiles; and (3) consideration of three-dimensional fracture in light of the existence of two distinct fracture zones that exhibit different failure mechanisms; for this purpose, G and J as a function of depth below surface are discussed, as well as several constraint factors as a function of depth.
Safety in Ice Hockey: Third Volume
Authors: Ashare AB 
Published: April 2008

Description
The latest volume in this series enhances our understanding of both the injuries incurred in the game of ice hockey and of the techniques used to decrease the risk of these injuries.
25 peer-reviewed papers cover:
• Injury Surveillance--discusses the injury surveillance system and the principles of ice hockey injury research.
• Protective Equipment--focuses on the certification of protective equipment for ice hockey in the U.S., and the designs and standards for various forms of ice hockey headgear.
• Spinal Injuries and Concussions--explores various aspects of these types of injuries, including care and transport of injured players and a three-decade perspective.
• Penalties, Injuries, and Pressures--examines psychosocial and psychological aspects of aggressive play, views and assessments of rule infractions and penalties, and liability issues facing the in-line skating industry.
This volume is a valuable resource for hockey equipment manufacturers, academic sports biomechanics, all hockey coaches and administrators, sports medicine physicians, and athletic trainers.
The Effect of Biaxial Strain Ratio and Periodic Compressive Overstrains on Fatigue Crack Growth Mode and Crack Growth Rate
Authors: Varvani-Farahani A , Topper TH 
Published: April 2008

Biaxial fatigue tests were performed on thin-walled tubular 1045 steel specimens in a test fixture that applied internal and external pressure and axial load. There were two test series, one in which constant amplitude fully reversed strains were applied and another in which large periodic compressive strain cycles causing strains normal to the crack plane were inserted in a constant amplitude history of smaller strain cycles. Ratios of hoop strain to axial strain of λ = - 1 (pure shear), λ = -0.625, λ = - v (uniaxial straining), and λ = +1 (equibiaxial straining) were used in each test series. A confocal scanning laser microscopy (CSLM) image processing technique that gave a resolution of 0.25 μm was developed and used to obtain three-dimensional images of small cracks as they were opened under load. The information in the images was used to construct cross sections of cracks from which crack depth, shape and crack opening stress were obtained.
For pure shear straining tests (λ = -1) and for tests at a strain ratio of λ - 0.625 surface cracks rapidly initiated on planes of maximum shear in both constant amplitude and overstrain tests but did not increase significantly in length until near the end of the tests. Instead they grew into the specimen until they were semi-circular in shape. This phase occupied approximately 90% of the fatigue life. Then they began to grow in length as well as depth and linked up to cause failure.
In the uniaxial and equibiaxial straining tests, crack growth initiated on planes of maximum shear at 45° to the surface of the specimens (Stage I crack growth) before changing to Stage II growth perpendicular to the applied stress. The cracks once initiated grew continuously in both the length and depth direction until failure took place.
The magnitude and frequency of application of the periodic compressive overstrain cycles in the second test series was chosen to reduce the crack opening stress level below the minimum stress level of the constant amplitude cycles so that they experienced closure-free crack growth. The compressive overstrains significantly increased crack growth rates and decreased the threshold strain intensity for the smaller constant amplitude cycles. They also caused a large decrease in the small cycle fatigue resistance as measured by their equivalent strain-life curves.
Determination of Ct-Parameter Considering Effects of Accumulated Creep Deformation During Loading Period
Authors: Lee JH , Kim YJ , Yoon KB 
Published: April 2008

Most of the assessment equations for Ct, which is a well-known fracture parameter characterizing creep and creep-fatigue crack growth rates, have limited applicability to constant load conditions. However, crack growth due to creep can also occur under varying load conditions when the load rate is slow enough such that accumulated creep deformation near the crack tip can't be neglected. An estimation equation of the Ct-parameter that can be applied to the case of slow load rising was derived by the authors and denoted as (Ct)r.
In this paper, correlation between (Ct)r at the end of the load-rising period and Ct at the beginning of the succeeding load hold period is shown. And a new Ct estimation equation that can be applied to the load hold period following a slow load rising period is derived using the relation between (Ct)r and Ct. Finite element analyses of several cases with various load-rising conditions were performed. The results support accuracy of the proposed Ct estimation scheme. General applicability of the equation is also discussed.
Resistance Curves for the Threshold of Fatigue Crack Propagation in Particle Reinforced Aluminium Alloys
Authors: Tabernig B , Powell P , Pippan R 
Published: April 2008

The threshold of stress intensity factor range ΔKth increases with increasing crack extension until it reaches the constant value of long cracks. Such curves can be interpreted as resistance curves for the threshold of fatigue crack propagation.
In the paper a very simple method to measure such R-curves is presented and a concept based on the R-curve is used to describe the propagation/non-propagation behavior of physically small cracks. The application of the R-curve technique results in the Kitagawa diagram where one can estimate the fatigue limit of components containing “small” flaws. R-curve tests and standard fatigue experiments at different stress ratios were performed on a 20 vol% SiC particle reinforced 359 T6 cast aluminum alloy which contains naturally small flaws up to 400 μm. Application of the R-curve concept is demonstrated and the estimations are compared with experimental results of the fatigue tests. Good agreement between the predicted and measured failure behavior was found.
Effect of an Overload on the Threshold Level of Ti-6-22-22
Authors: McEvily AJ , Ohashi M , Shover R , DeCarmine A 
Published: April 2008

The effects of overloads on the fatigue crack growth behavior of the high trength α/β titanium alloy Ti-6-22-22 have been investigated. Fatigue cracks were grown at a baseline R level of 0.1, and single overloads, ranging in magnitude from 2–3 times the baseline level, were applied to determine the effect of the overloads on subsequent fatigue crack growth behavior. Because of the high yield strength of the alloy, 1225 MPa, the number of delay cycles following an overload was not as pronounced as in alloys of lesser strength. A principal effect of an overload in this titanium alloy was to increase the threshold for fatigue crack growth. An experimental procedure based upon the increase in threshold level was adopted to determine the maximum level of crack closure resulting from an overload.
The novel observation was made that following a sufficiently high overload the rocess of further crack growth involved the emergence of a surface crack ahead of the preexisting crack. It was also observed that the crack growth behavior at distances well beyond the overload plastic zone size could be sensitive to prior overload history.
Relation Between Endurance Limits and Thresholds in the Field of Gigacycle Fatigue
Authors: Bathias C 
Published: April 2008

In order to predict fatigue crack propagation at very long life a piezoelectric fatigue machine was built in our laboratory. This device is able to fail specimen at 1010 cycles and to determine thresholds up to 109 mm/cycle. The originality of this machine resides in the possibility to apply simultaneously to a specimen a constant tension effect and longitudinal ultrasonic vibratory effort with adjustable amplitude. That is to say, the R ratio can be varied from -1 to 0.9.
It appears that the fatigue thresholds are about the same in conventional fatigue and in resonant fatigue if the computation of the stress intensity factor K is correct. But there is a very large difference between the endurance limits at 106 cycles and 109 cycles. It means about 10% for steels and 30% for aluminium and nickel-based alloys.
To improve the relation between thresholds and fatigue limits, the gigacycle fatigue is studied in a Ni alloy manufactured by powder metallurgy with two sizes of inclusions. The testing temperature is 450°C. The first conclusion is that there is not any infinite fatigue limit until 109 cycles. The second conclusion is a possible correlation between the fatigue limit and the threshold at R ratio = 0. This relation is much more improbable for R = -1 because an incubation phenomenon exists around an inclusion or a porosity loaded at low stress level.
ASTM Committee D09—A History of Success
Authors: Mathes KN 
Published: April 2008

Historical Aspects: A long history of continued, active use is in itself a measure of success. Methods D 149 (1922), D 150 (1922), D 257 (1925) on electrical tests have been used extensively and even today are being periodically revised and updated. Much the same is true for D 115 (1941) varnish, D 202 (1924) paper and D 229 (1925) rigid sheet and plate plastics. D 495 (1938) dry tracking is generally now recognized as a technical failure, but a commercial success. This standard is still widely used and referenced! Standards D 69 (1920) friction tape, D 295 (1928) varnished cotton fabric and D 748 (1961) shellac, were once very important, are still needed, but today are seldom used.
Technical Concepts and Materials: In 1948 two technical papers, one by Ken Mathes on functional tests and another by Tom Dakin on thermal aging provided a basis for the adequate acceptance and use of the many new insulating materials that were becoming available. First, the Electrical Institute of Electrical Engineers, AIEE (now the Institute of Electrical and Electronic Engineers, IEEE), and then ASTM committee D09 followed with the much needed new approaches and standards—then and still outstanding successes. Tremendous growth in the use of plastics led to the formation of Technical Committee ASTM D20 from subcommittee status in D09. Committee D27 on Insulating Liquids and Gases also split away from D09. New elastomeric materials for cable led to their incorporation as Subcommittee 18 of D09 from their origins in ASTM D11 on rubber.
The subjects of treeing and surface failure (tracking) are extremely important, but today are still, to some extent, goals rather than completed accomplishments.
Instrumentation: The Electronic revolution has been successfully incorporated by D09 in many electrical, mechanical, and physical tests for insulating materials. Methods for very high resistance are an example. Organizational and Government Support: Public Utilities, the Electrical Industry, NIST (originally NBS), the US Navy, NEMA, NASA, and UL have periodically been responsible for outstanding accomplishments in D09. UL continues in the forefront especially in thermal aging. D09 participation in the International Electrotechnical Commission (IEC) is of particular importance. Publications: Symposia, Publications like STPs and Research Reports have often highlighted D09 activity and success.
Individuals: Success is possible only with the technical and organizational skills of dedicated individuals. Many ASTM awards have recognized such accomplishment.
Summary: This abstract can only touch on the foregoing aspects, which are described with more detail in the following paper.
New Ways of Disruptive Discharge Recognition in Insulation Testing Devices
Authors: Mathis H-J , Baur M , Blank R , Woschitz R , Überfall T 
Published: April 2008

The dielectric testing of gaseous and liquid insulation has a long tradition and devices for breakdown testing have improved during the past 40 years. Special liquids like silicone oil, have made it necessary to develop special methods. As a result, methods to recognize the disruptive discharge have changed, as have methods to determine switchoff characteristics and to generate test voltages.
The dielectric breakdown voltage is a variable with a statistical distribution. The test procedure involves a number of single test sequences. To get reliable results, it is of paramount importance to have a minimum of influence from one sequence to the next. This depends on breakdown energy and therefore on breakdown recognition, maximum short-circuit current and also on the switch-off characteristic of the testing device. The development of new, sensitive testing devices enable the energy which is sent into a test sample to be kept at a very low level. This permits a clear differentiation between partial discharge and disruptive discharge.
Investigations in breakdown characteristics and switch-off methods of devices with different techniques across several gaseous and liquid samples with special consideration of the comparability of testing results have been made to improve testing. This article describes new ways of breakdown recognition and switch-off techniques, discusses advantages and disadvantages of the new and better-known methods and discusses the problems of standardization.
Wide-Width Geomembrane Testing
Authors: Koerner GR 
Published: April 2008

Geomembranes are the most widely used components of liner and cover systems throughout the world. Arguably they are the most critical components of such systems. Millions of square meters of geomembrane have been used as liquid barriers over the past 20 years. However, there is debate over how to properly determine the performance tensile characteristic of these materials. This paper attempts to shed some light on obtaining uniaxial performance responses of commercially available geomembranes via ASTM D 4885, Standard Test Method for Determining Performance Strength of Geomembranes by the Wide Strip Tensile Method.
Over the past ten years since the test method was issued, several inconsistencies have been identified with the method. Such inconsistencies make it difficult for laboratories to generate comparable results while utilizing the standard. Areas of concern are specimen preparation, clamping, strain rates and data reduction. It is hoped that the paper may help promote uniform and consistent wide-width geomembrane testing. This paper contends that wide-width geomembrane testing is a performance test and that it should only be used for the purpose of design and research.
Laboratory Techniques for Service History Estimations of High Strength Fastener Failures
Authors: Gaudett M , Tregoning R , Focht E , Zhang XJ , Aylor D 
Published: April 2008

Two fastener failures have been analyzed to determine both failure mode and service loading history. The analyses were conducted through careful fractographic investigation and laboratory simulation to assess the integrity of the assembly design and to evaluate the role of unintended environmental effects in these failures. The first case involves Monel K-500 bolts that failed due to fatigue loading, terminated by overload fracture. The fatigue mode was intergranular (IG) at initiation, and then transitioned to classical transgranular fatigue prior to overload failure. Intergranular cracking in Monel K-500 is usually associated with environmentally assisted cracking (EAC). However, simulated service testing of several bolts under both fatigue and slow strain rate loading revealed that IG fatigue cracking could occur at low applied ΔK in air. Transgranular fatigue is associated with higher ΔK levels. Therefore, EAC was not the root cause of these failures.
The second case examines the fatigue failure of several IN625 studs. The stud stresses are estimated from fatigue striation measurements using a representative fatigue crack growth behavior and driving force equation. The inferred applied stress is greater than the material yield strength, which is indicative of a basic deficiency in the original joint design. Laboratory testing verifies the relative accuracy of this stress estimation method for both simple and complex loading histories. The accuracy can be most significantly improved through fatigue crack growth testing of the actual failed material under relevant service conditions.
Thread Lap Behavior Determination Using Finite-Element Analysis and Fracture Mechanics Techniques
Authors: Hukari RJ 
Published: April 2008

A new aerospace bolt thread lap inspection criterion is proposed based on fatigue crack propagation trajectories predicted by finite-element analysis (FEA) and fracture mechanics techniques.
Fastener producers and end users incur high costs due to thread lap problems. Current thread lap inspection criteria are 30 to 40-years-old, and are based on an intuitive understanding of potential thread lap behavior. These inspection criteria are ambiguous and make inspection difficult. Some costs can be avoided and quality can be improved by redefining acceptable and unacceptable thread laps. Specifically, these inspection criteria can be improved by using fracture mechanics and FEA techniques developed in the last 30 years.
Two-dimensional, axisymmetric, full nut-bolt-joint geometry, FEA models with elastic-plastic material properties, and contact elements at the thread interfaces were analyzed using ANSYS FEA software. Singular crack tip elements were used. Laps of expected geometries were built into the models, and then assumed to propagate as fatigue cracks. Cracks were iteratively grown using the maximum tangential principal stress criterion to determine the direction of crack propagation. Certain types of thread laps were shown to propagate in such a way that bolt failure would not occur. Conversely, other types of laps were predicted to propagate in such a way that bolt failure would be expected.
A simpler, less subjective criterion for inspecting laps is presented. This criterion takes advantage of the benign laps. The proposed method allows any lap contained entirely within a particular zone to be acceptable.