bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Protective Clothing: Development and Testing of Asbestos Substitutes
Authors: Dixit B
Published: December 2008

The origin of asbestos use is traced and its unique properties are discussed. A comparison of various substitutes available to replace asbestos shows that there is no single substitute. Development of an effective substitute from fiberglass is described. Lack of proper test methods for measuring the effectiveness of the substitutes in safety clothing required the development of new test methods, which are described. These tests show that Zetex, made from highly texturized fiberglass, offers insulation and strength properties superior to those of asbestos. Results of molten metal splash resistance tests on asbestos and Zetex and the effects of various treatments are discussed.
Some Characteristics of Fabrics for Heat Protective Garments
Authors: Krasny JF
Published: December 2008

Some principles of protection afforded by clothing in fire situations are reviewed briefly. Several examples of measurements of heat protective properties are given. The materials covered are single layers of fabrics appropriate for work uniforms, the same type of fabric combined with four popular underwear fabrics, and typical fire fighters' turnout coat assemblies, consisting of a shell fabric, vapor barrier, and thermal barrier. Such protective garment assemblies should not burn; they should retain their integrity, that is, not shrink, melt, or form brittle chars that break during the stresses induced by movement of the wearer; and they should provide as much insulation against heat on the fire scene as possible without interfering with the wearer's activities.
A Method for Testing Fabrics with Molten Metals
Authors: Jaynes PS
Published: December 2008

This paper describes a method for testing fabrics with molten metals. The test evaluates the fabric's ability to protect people who are accidentally splashed by metals such as molten iron, aluminum, or brass.

Some test results are discussed to illustrate the application of the test method. The test procedure is substantially the same as a test method for evaluating heat transfer through materials upon contact with molten substances, now being developed by ASTM Subcommittee F23.80 on Molten Substances, a subcommittee of ASTM Committee F-23 on Protective Clothing.
U.S. Navy Protective Clothing Program
Authors: Audet NF , Spindola KJ
Published: December 2008

The Navy Clothing and Textile Research Facility is involved in a major effort to develop fire retardant-heat protective clothing for Navy shipboard personnel encompassing both work and special protective clothing.

To determine the degree of protection afforded by the various articles of clothing being developed, both laboratory and field testing have been employed. Laboratory material tests have included vertical flammability resistance tests and protection time determinations for flame impingement exposure. Field tests have involved exposure of garments to total flame envelopment utilizing manikins equipped with paper tape temperature sensors to estimate the extent of burn injury sustained.

The usefulness of laboratory tests such as flame impingement tests to predict material/clothing performance under more realistic fire threat conditions is limited because of differences in exposure conditions between laboratory tests and full-scale fire tests. Laboratory tests do, however, provide an extremely useful screening tool to limit the number of candidate systems to be evaluated under field conditions.

This paper covers the nature of some of the clothing systems being developed, the laboratory and field evaluation procedures employed, and some of the laboratory and field test data accumulated on the materials and clothing items investigated.
A Dynamically Insulated Heat-Protective Clothing Assembly
Authors: Davies J
Published: December 2008

This paper describes the design development and evaluation of a thermally comfortable pressure suit and associated equipment, using the vortex cooling effect for use during access penetrations into the United Kingdom-designed, advanced gas-cooled nuclear reactor system (AGR). Also discussed is the method of assessment of clothing materials. The system design of a heat balance equation using the Ranque Hilsch cooling effect produced by a vortex cooling tube, used in conjunction with a ventile clothing assembly, and the operation of a system to achieve adequate protection for persons working for extended periods in abnormal environments are demonstrated.
Anthropometric Fit Testing and Evaluation
Authors: McConville JT
Published: December 2008

A major challenge facing designers and manufacturers of protective clothing and equipment is the establishment of a sizing system that will accommodate the body size variation of the user population as well as provide a good fit for individual users. This has been variously achieved by means ranging from hit-or-miss trial-and-error methods to the careful application of anthropometric design data. Ultimately, the success of the design and the sizing system can be established only by an anthropometric fit test in which garments or equipment are worn or used by subjects representing the size range of the user population and carefully evaluated for fit and function. Described here are guidelines for conducting such a fit test.
The Development of Improved Forgings for Modern Steam Turbines
Authors: Curran RM
Published: December 2008

This paper describes the developments that have taken place during the past 40 years in the manufacture of the large rotor forgings that are required for the turbine and generator sets in electric utility, central station applications. Modifications in steelmaking practices—such as the changes from open hearth to the electric practice, the introduction of vacuum pouring, and changes in ingot mold design—are discussed, as well as evaluations of newer remelt techniques such as vacuum consumable electrode melting, electroslag remelting, and electroslag hot topping. Changes in alloy content and heat-treating practices and the improvements that have resulted in the mechanical properties and fracture toughness are illustrated.

The progress that has been made in reducing the incidence of internal flaws and the improvements that have been made in nondestructive testing and evaluation to quantitatively appraise the effect of such flaws on the probable performance are discussed.

It is concluded that in low-pressure rotors, as a result of the improved cleanliness, detection methods, and fracture toughness, the probability of an undetected critical size defect has been decreased by several orders of magnitude. In the case of the high-temperature rotors, the improvements in properties, together with improved designs and operating procedures, have substantially improved the life expectancy of these rotors in spite of increases in forging size and unit ratings.

The important contributions that ASTM committees have made to this progress are described and acknowledged.
Influence of Advanced Steelmaking Technology on Specification Trends for Rotor Forgings
Authors: Steiner JE , Jaffee RI
Published: December 2008

Advanced steelmaking equipment and processes that are state of the art for the production of rotor forgings are described. The Electric Power Research Institute (EPRI) has sponsored a study on high-pressure (HP) rotor forgings of 1Cr-Mo-V steel with 0.001 to 0.002% sulfur content produced by conventional vacuum carbon deoxidation (VCD) and electroslag remelting processes. Low phosphorus, low hydrogen, and residual element control were also objectives of this study.

Laboratory studies show that combined low levels of manganese (Mn), phosphorus (P), silicon (Si), and residual elements improve the toughness and resistance to temper embrittlement of rotor steels. In a recent EPRI program with Vereinigte Edelstahlwerke, the process combination basic electric arc furnace melting and ladle furnace refining with vacuum treatment successfully produced a 25-metric-ton model rotor in which levels of 0.02Mn, 0.002P, 0.001S, 0.04Si, and 0.005Al at 27 ppm oxygen were achieved.

Specification implications of these trends to high-purity rotor steels suggest that requirements for Mn, Si, and sulfur (S) will trend to lower content levels.
Manufacture of Differentially Heat-Treated Turbine Rotor Forgings
Authors: Suzuki A , Kinoshita S , Kikuchi H
Published: December 2008

Using modified Cr-Mo-V steel with small additions of nickel and niobium and reduced silicon, four integral high pressure (HP) and low pressure (LP) combination turbine rotor forgings with 1240-mm maximum barrel diameter were manufactured. To obtain improved toughness in the LP portion and sufficient creep strength in the HP portion, the rotor forgings were differentially heat-treated; HP portions were austenitized at high temperatures and LP portions at low temperatures, followed by forced air cooling in the HP portions and by water spray quenching in the LP portions. Evaluation of the manufactured rotor forgings revealed that the toughness and the creep strength were sufficient in the LP and HP portions, respectively, the residual stress was sufficiently low, and the heat indication testing results were satisfactory in spite of the differential heat treatment.
Mechanical Properties of Advanced Technology 1Cr-Mo-V Steam Turbine Rotor Forgings
Authors: Swaminathan VP , Jaffee RI , Steiner JE
Published: December 2008

Three advanced steel melting process—low-sulfur vacuum silicon deoxidation, electroslag remelting, and vacuum carbon deoxidation—were applied to produce three 1Cr-Mo-V [ASTM Specification for Vacuum-Treated Carbon and Alloy Steel Forgings for Turbine Rotors and Shafts A 470-82, Class 8] steel forgings for steam turbine application. A detailed evaluation of the tensile properties up to 565°C (1050°F), fracture toughness (KIc and JIc), high-cycle and low-cycle fatigue properties, and stress rupture (creep) properties were determined for the three forgings.

Compared to conventionally produced forgings, the advanced technology forgings show better tensile ductility and uniformity along the radial and longitudinal directions. Charpy upper-shelf energy shows about 40% improvement, and no temper embrittlement was found using a step-cooled and isothermal aging treatment. Significant improvement in fracture toughness (factors of two to three higher) is realized for these forgings. Low-cycle fatigue life is better at high temperatures due to the absence of nonmetallic inclusions. Creep strength shows slight improvement. However, creep ductility probably is improved due to low residual elements. Especially, the VCD forging shows excellent creep ductility even at long lives. Both the toughness and creep properties are better than those of oil-quenched rotors produced by European practice. These improvements are attributed to cleaner steel, low residual elements (especially very low sulfur content), and the associated reduction of nonmetallic inclusions.
Soft-Martensitic Stainless Cr-Ni-Mo Steel for Turbine Rotors in Geothermic Power Stations
Authors: Schönfeld K , Potthast E
Published: December 2008

Steel Grade X5 Cr-Ni-Mo 12 6 containing 0.05% carbon, 12% chromium, 6% nickel, and 1.50% molybdenum is an advantageous material for turbine rotors in geothermic power stations because of its excellent strength and toughness properties in combination with good erosion and corrosion resistance.

In terms of the phase diagram, this soft-martensitic steel has its place at the martensite/austenite/ferrite interface. Therefore, its chemical composition must be chosen so as to have a completely martensitic structure after hardening. During tempering above 773 K (500°C), austenite is precipitated in finely dispersed form in the tempered martensite. This secondary austenite improves the toughness, is extremely stable, and does not transform even at temperatures down to approximately 73 K (-200°C).

The manufacture of and the mechanical properties of a turbine rotor 1200 mm in diameter by 5600 mm in length with a finished weight of approximately 21.5 tons are described in detail.
In-Service Inspection Test and Evaluation Techniques for Large Generator Rotors
Authors: Bellows RH , Zawoysky RJ , Walker DN
Published: December 2008

There is much interest on the part of utilities to pursue avenues for upgrading and for the life extension of electrical generating equipment. As an integral part of such an evaluation, the current condition of the generator rotor must be assessed fully to determine if the rotor can be expected to perform reliably for many additional years. A comprehensive nondestructive testing (NDT) and evaluation program has been developed by General Electric Co. to assess the condition of in-service generator rotors, to make predictions of remaining life, to set reasonable reinspection intervals, and, most importantly, to identify rotors that have a high probability of failure and to recommend that they be replaced or otherwise upgraded to minimize the chances of failure.

This paper will describe the inspection methods and analytical techniques that are used in the evaluation of in-service generator rotors and will provide a summary of recommendations that have been made to date.
18—18 Corrosion-Resistant Retaining Rings for Nuclear Power Plant Generators
Authors: Rambaud JB , Cazenave RH
Published: December 2008

Several years ago, the Pamiers Plant of the Compagnie Française de Forges et Fonderies (C3F) undertook a research program on the 18-18 corrosion-resistant grade for retaining rings.

An extensive testing program conducted in association with Electricite de France led to a decision to equip the 900- and 1300-MW generators of French nuclear power plants with NMF 18 retaining rings (NMF 18 is the C3F trademark for the 18-18 material).

To date, 20 rings have been manufactured in the following sizes: 1. Outer diameter: 1746 to 2040 mm (68.74 to 80.31 in.). 2. Thickness: 83 to 90 mm (3.27 to 3.74 in.). 3. Height: 700 to 775 mm (27.56 to 30.51 in.). 4. Weight: 2.5 to 3.5 metric tons.

The guaranteed yield strength at midwall is 750, 850, or 900 MPa (109, 123, or 130 ksi), depending on the type of ring.

After a review: (a) of the properties of the 18-18 grade and their comparison with the conventional 18-4 material and (b) of the principal results of the test program, we are describing the specifics of the manufacturing process and the facilities of these large rings.
Production of a 304 Stainless Steel Nuclear Reactor Forging from a Very Large Electroslag Refined Ingot
Authors: Watkins EJ , Tihansky EL
Published: December 2008

A four-loop, upper barrel flange forging for a nuclear reactor was produced from what the authors believe to be the largest 304H grade stainless steel electroslag refined (ESR) ingot ever refined. The ingot was refined in a 1524-mm-diameter, ingot withdrawaltype ESR furnace using a lime-bearing slag, low-frequency a-c power, and dry air protection. Five electrodes were remelted in order to produce the desired ingot weight. The ingot was subsequently forged in a five-step operation on a 6800-metric-ton press to produce the desired barrel flange configuration. Testing of the finished machined forging revealed excellent tensile ductility, excellent ultrasonic penetrability, and good chemical uniformity with no macrosegregation. Overall quality was judged to be superior to previously produced, conventionally melted forgings.
Cryogenic Mechanical Properties of A286 Alloy and 304LN Stainless Steel Used in Fabrication of Support Struts for Superconducting Magnets
Authors: Abe T , Kohno M , Suzuki A , Scanlan RM
Published: December 2008

A286 alloy and 304LN stainless steel were chosen for support struts used in the construction of a mirror fusion testing facility, which is subjected to the cryogenic temperature. Electroslag remelting technology (ESR) was adopted to manufacture A286 alloy. A program was initiated to investigate the cryogenic mechanical properties with emphasis on the effect of the grain size of A286 alloy.

The test results revealed that: (1) A286 alloy showed little effect of grain size on the tensile properties, while the fracture toughness properties were affected by the grain size, especially at 4 K; (2) 304LN stainless steel produced almost the same tensile and fracture toughness properties as A286 alloy.

The temperature dependence of the mechanical properties of 304LN stainless steel and A286 alloy also is discussed. The support strut forgings produced excellent quality, and the proof load test results were indicative of the no plastic deformation during applications.
High-Sensitivity, Immersion, Ultrasonic Testing of Steel Forgings
Authors: Gensure JG , Melilli AS , Brueggemann SM
Published: December 2008

Present industry-wide standards covering ultrasonic inspections of forgings such as ASTM Recommended Practice for Ultrasonic Examination of Heavy Steel Forgings (A 388-80) specify the contact method of inspection. Sensitivity settings vary as to inspection technique—longitudinal or shear wave (straight or angle beam). Normally, the sensitivity is established using a back reflection or test sample technique in order to resolve equivalent flat-bottom hole (EFBH) sizes of 3.175 mm (0.125 in.) at the centerline or bore surface of the forging. The assumption is made that most indications will be oriented parallel to the direction of the longitudinal axis of cylindrical forgings and in a circumferential plane of ring forgings.

On occasion, discontinuities occur in forgings that are different than normal, requiring changes in normal procedures and techniques. Size, orientation, location, and distribution require special considerations. This paper outlines how a high-sensitivity, immersion, ultrasonic technique is utilized to inspect a group of gear component and miscellaneous forgings suspected of having internal hydrogen flakes. The technique is successful in locating the discontinuities and distinguishing between the flakes and other types of discontinuities, specifically nonmetallic inclusions.
A New Wide Plate Arrest Test (SCA Test) on Weld Joints of Steels for Low Temperature Application
Authors: Tanaka K , Sato M , Ishikawa T , Takashima H
Published: December 2008

As a realistic and practical criterion for brittle fracture arrest in low temperature storage tanks, the present authors propose the short crack arrest (SCA) concept. This aims at arresting brittle fracture before propagation to a catastrophe. In order to investigate the capability of steel materials from the viewpoint of this concept, two types of wide plate tests, the SCA tests on weld heat-affected zone (HAZ) and base metal, were developed. These two test methods were designed to simulate the run-and-arrest phenomenon of brittle fracture in actual storage tanks.

The two types of tests, together with the compact crack arrest (CCA) test, were applied to base metals and welded joints of a wide range of steels for low temperature application. Efforts were made to clarify the effects of base metal chemical compositions and conditions for welding on the weld HAZ characteristics.

The results revealed that addition of about 3% nickel to the base metal significantly improved the weld HAZ arrest toughness. It was also shown that the SCA capability of steels could be predicted from the Ka values obtained by the CCA test.
Fracture Toughness of Ductile Iron and Cast Steel
Authors: Bradley WL , McKinney KE , Gerhardt PC
Published: December 2008

The dynamic fracture behavior of ductile cast iron and cast steel has been studied to better explain why blunt notched Charpy bars indicate ductile iron has a quite inferior fracture toughness compared with cast steel with similar tensile properties (15 versus 75 J) while fracture mechanics tests indicate a much less significant difference in fracture toughness between the two materials. Using standard and fatigue precracked side-grooved Charpy specimens, it has been shown that the different predictions are due to a difference in constraint, the standard Charpy bar experiencing loss of constraint for the cast steel but remaining fully constrained for the ductile iron. For fatigue precracked and side-grooved Charpy specimens, initial crack extension occurred in both materials under conditions of full constraint, and the cast steel upper shelf fracture toughness was found to be only modestly better than the upper shelf fracture toughness of the ductile iron. Because of its lower ductile-to-brittle transition temperature, ductile iron has been found to have a superior fracture toughness to cast steel with similar tensile properties at temperatures below ambient.
Resistance Curve Approach to Composite Materials Characterization
Authors: Ratwani MM , Deo RB
Published: December 2008

The delamination growth resistance of composites under Mode I (opening mode) has been investigated. It is shown that composites exhibit increasing resistance with increasing growth. The double cantilever beam specimen has been used to obtain delamination growth resistance curve over a wide range of delamination extension. The delamination growth resistance curve is shown to be path independent.

Delamination growth resistance curves have been obtained for current resin materials and high toughness materials. It is shown that the delamination growth resistance depends not only on the resin material but also on the fiber used. AS4/3501-6 material exhibits higher resistance than AS1/3501-6. The influences of temperature and porosity on delamination growth resistance have been investigated. It is found that AS1/3501-6 has lower resistance at -54° C (-65° F) than at room temperature ambient conditions. Porous laminates exhibit slightly lower resistance to delamination growth than nonporous laminates.
A Comparison of the Fracture Behavior of Thick Laminated Composites Utilizing Compact Tension, Three-Point Bend, and Center-Cracked Tension Specimens
Authors: Harris CE , Morris DH
Published: December 2008

An experimental study of the effects of specimen configuration and laminate thickness on the fracture behavior of notched laminated composites is presented. The behavior of [0/±45/90]ns, [0/90]ns, and [0/±45]ns graphite/epoxy T300/5208 laminates was studied. When fracture toughness was computed at the failing load of the center-cracked tension specimen, laminate thickness significantly influenced fracture toughness. If fracture toughness was computed at the interception of the 5% secant line with the load-COD record, fracture toughness was found to be independent of both laminate thickness and specimen configuration. Defined in this manner, fracture toughness can be physically interpreted as an indicator of the onset of significant notch-tip damage.
Residual Strength of Five Boron/Aluminum Laminates with Crack-Like Notches After Fatigue Loading
Authors: Simonds RA
Published: December 2008

Boron/aluminum specimens were made with crack-like slits in the center and with various proportions of 0° and ±45° plies. They were fatigue loaded and then fractured to determine their residual strengths. The fatigue loads were generally in the range of 60 to 80% of the static tensile strength of the specimen as determined from a previous study, and the stress ratio was 0.05. For virtually all of the specimens the fatigue loading was continued for 100 000 cycles. The spcimens were radiographed after the fatigue loading to determine the nature of the fatigue damage. A few specimens were sectioned and examined in a scanning electron microscope after being radiographed in order to verify the interpretation of the radiographs and also to get a better insight into the nature of the fatigue damage.

The results indicate that the fatiguing does not significantly affect the strength of the specimens tested. The results of the radiography and of the scanning electron microscopy indicate that the 45° plies suffer extensive damage in the form of split and broken fibers and matrix cracking in the vicinity of the ends of the slit. By contrast, the only significant damage to the 0° plies was a single 0° matrix crack growing from the ends of the slit.
Hold-Time Effects in Elevated Temperature Fatigue Crack Propagation
Authors: Nicholas T , Weerasooriya T
Published: December 2008

An experimental investigation was conducted to evaluate the effects of hold times on the fatigue crack growth rate of Inconel 718 at 649°C using compact tension specimens. Tests were run under computer-controlled constant K conditions using compliance to determine crack length. Hold times ranging from 5 to 50 s were applied at maximum, minimum, and intermediate load levels. The data show that the hold times at maximum load were the most damaging in terms of crack growth rate. Hold times greater than 5 s led to purely time-dependent crack growth behavior which was predictable from sustained load data using K as a correlating parameter. Hold times at minimum or intermediate load levels had little or no effect on crack growth rate. A linear cumulative damage model based solely on fatigue and sustained load data was found to be adequate for spectrum loading so long as the hold times were at maximum load.
An Application of Stress Intensity Factor to Fatigue Strength Analysis of Welded Invar Sheet for Cryogenic Use
Authors: Soya I , Takashima H , Tanaka Y
Published: December 2008

Fatigue strength of several types of welded Invar joints were investigated at room temperature and 111 K. Lap fillet welded joints, in which a 1.5 mm thick Invar sheet was welded to a 1.5 mm or 3.0 mm thick Invar sheet or 12 mm thick stainless steel, were made by tungsten-inert-gas (TIG) welding. A joint, in which a 0.5 mm thick Invar sheet was inserted between two overlapped 1.5 mm thick Invar sheets, was made by resistance seam welding. In these joints, the root of the weld is the region most susceptible to fatigue crack initiation.

Since S-N relationship depends upon the joint type, specimen size, and loading method in a fatigue test, a fatigue strength parameter independent of these conditions is necessary for the fatigue evaluation of structures. In this study, equivalent stress intensity factor range ΔKeq was adopted and investigated as such a parameter. By simulating the measured cyclic strain behaviors by elastic-plastic FEM analyses, the cyclic ranges of tensile, bending, and shear stresses that arise in the vicinity of the weld can be estimated. Using these ranges, ΔKI, ΔKII and accordingly ΔKeq were calculated for each specimen.

As a result, it was found that the relationships between ΔKeq and cycles-to-failure in the range above 104 cycles were well within a narrow scatter band, regardless of the type of joints. It was concluded that ΔKeq is a very effective parameter for prediction of fatigue strength when the sharp root of a weld is the problem.
An Experimental and Numerical Investigation of the Growth and Coalescence of Multiple Fatigue Cracks at Notches
Authors: Grandt AF , Thakker AB , Tritsch DE
Published: December 2008

This paper describes results of an experimental and numerical study concerned with the growth and coalescence of multiple fatigue cracks. A multi-degree-of-freedom algorithm is developed to predict the cyclic growth of separate cracks which develop along the bore of a circular notch. The crack shapes and sizes are allowed to develop naturally as they join into a single flaw which then propagates to failure. Experiments are described with multiflawed specimens of titanium and Waspaloy. The numerical model does an excellent job of predicting the crack coalescence life in all the specimens.
Near-Tip Crack Displacement Measurements During High-Temperature Fatigue
Authors: Sharpe WN , Lee JJ
Published: December 2008

A laser-based interferometric technique was used to measure crack opening displacements near the tips of fatigue cracks in superalloy compact tension specimens at 23 and 650°C. Measured compliances showed reasonable agreement with predictions of linear elastic fracture mechanics at both temperatures. The opening load ratios were easily determined by the minicomputer-controlled measurement system and where found to be independent of temperature, crack length, and precracking level when they were measured at positions more than half the specimen thickness away from the tip.
Viscoplastic Fatigue in a Superalloy at Elevated Temperatures
Authors: Wilson R , Palazotto A
Published: December 2008

This study involved extending existing analyses of the stress field and plastic zone ahead of a crack tip in a IN-100 compact tension specimen through a larger number of load cycles considering a frequency of 2.5 Hz and an R ratio of 0.1 at 732°C. The Bodner-Partom viscoplastic constitutive equations are utilized in describing the material behavior.
Fracture Testing With Arc Bend Specimens
Authors: Underwood JH , Kapp JA , Witherell MD
Published: December 2008

A limited review of existing stress, stress intensity factor, and displacement analyses was compared with new work in order to select arc bend geometries appropriate for fracture testing. Results from the literature for rectangular and arc bend specimens were compared with finite element and boundary collocation results from the present work.

Two series of comparative tests were performed, one with arc specimens cut from a steel forging with outer-to-inner radius ratio of 2.5, the other from an aluminum cylinder with outer-to-inner radius ratio of 1.3. Fracture toughness tests, KIc, and JIc when appropriate, were performed with standard arc tension specimens and with three-point arc bend specimens with both arc and chord support.

Conclusions were drawn regarding the appropriate stress intensity factor, crack mouth displacement, and load-line displacement solutions for arc bend fracture specimens. Recommendations were offered for practical ranges of specimen geometry and for reliable test procedures.
Influence of Partial Unloadings Range on the JI-R Curves of ASTM A106 and 3-Ni Steels
Authors: Sutton GE , Vassilaros MG
Published: December 2008

An investigation was performed to evaluate the effects of elastic unloadings on the J-integral-resistance curves of ASTM A106 Class C steel and 3-Ni steels. Compact specimens (1T) were tested using (1) the multispecimen technique, (2) the direct-current potential drop technique, and (3) an elastic unloading compliance technique with unloadings ranging from 10 to 90%. The two former techniques were 0% unloading procedures used to generate the reference J-R curves. These reference curves were compared with J-R curves obtained using elastic unloading for the two steels. Results indicated that use of the elastic unloading compliance technique caused no significant difference in the J-R curves.
Fracture Toughness Testing of Zircaloy-2 Pressure Tube Material with Radial Hydrides Using Direct-Current Potential Drop
Authors: Davies PH , Stearns CP
Published: December 2008

This paper addresses problems involved in measuring fracture toughness of thin pressure tube material which, in the presence of radial-axial hydrides, undergoes a significant brittle to ductile fracture transition. Compact tension specimens (∼5 mm thickness) are machined from flattened tensile strips of Zircaloy-2 in which radial hydrides (30 to 100 ppm hydrogen) are produced by precipitation under stress. Axial fracture toughness is determined for the unirradiated material between room temperature and 300°C using the dc potential drop method. At low and intermediate temperatures crack growth is governed predominantly by the presence of the radial hydrides, and the potential drop is shown to underestimate crack extension due to short-circuiting across tight crack faces. In the upper shelf regime where crack extension is governed mainly by the flow properties of the matrix, the potential drop overestimates crack extension due to through-thickness yielding. It is shown that good, reproducible results can be obtained by careful data analysis using individual specimen calibrations.
J-Resistance Curve Analysis for ASTM A106 Steel 8-Inch-Diameter Pipe and Compact Specimens
Authors: Vassilaros MG , Hays RA , Gudas JP
Published: December 2008

An experimental investigation was performed to evaluate the applicability of using J-integral resistance (J-R) curves from laboratory specimens to describe the fracture behavior of circumferentially cracked 8 in. diameter ASTM A106 steel pipe. The approach of the study was to perform J-integral tests on 48 in. long, 8 in. diameter, Schedule 80 ASTM A106 steel pipes and compare them with J-integral tests performed on 1/2T, 1T plan, and 2T plan compact specimens machined from the pipe wall. The pipes were tested in four-point bending and were monitored for load, crack opening displacement, bend angle, and electrical potential drop. Elastic compliance and direct-current potential drop (DCPD) techniques were used simultaneously to predict crack length during the tests. The compact tension specimens were tested in a conventional screw-driven testing machine while being monitored for load, load-line deflection, and electrical potential drop. Elastic compliance and DCPD techniques were also used for crack length predictions during these tests.

The results of this series of J-integral tests indicate that similar J-R curves result from the two types of specimens. However, small specimen tests cannot easily be used to predict full J-R curve behavior for larger, full-sized specimens owing to the modest amount of crack extension available in laboratory-sized specimens.
Influence of Crack Depth on Resistance Curves for Three-Point Bend Specimens in HY130
Authors: Towers OL , Garwood SJ
Published: December 2008

To obtain a better understanding of the behavior of shallow cracks in structures the influence of crack depth on fracture toughness has been studied. Fracture toughness tests were carried out on 50-mm thick three-point bend specimens sampling HY130 high strength steel. The mode of crack growth in all cases was tearing, and fracture toughness values at initiation of crack growth were evaluated as well as resistance (R) curves. Fracture toughness values were calculated in terms of both the crack tip opening displacement (CTOD) and the J integral. Crack extension was deduced from unloading or reloading compliance and by use of an alternating-current potential drop technique.

It was found that the fracture toughness values at initiation of crack growth, and the R-curve slopes, were consistently higher for crack depth to width (a/W) ratios of 0.3 or less than for the a/W ratio of 0.5 commonly used for routine fracture toughness tests. For very deep cracks, a/W ≃ 0.8, the fracture toughness at initiation of tearing was little different from that for a/W ≃ 0.5. The R-curve slope, however, was higher for a/W ≃ 0.8 than it was for a/W ≃ 0.5. The latter observation (and the observed increase in fracture toughness with decrease in crack length for a/W less than 0.3) is considered to be consistent with loss of constraint for very short and very deep cracks.
Computation of Stable Crack Growth Using the J-Integral
Authors: Carifo JE , Swedlow JL , Cho C-W
Published: December 2008

Crack growth of almost 8 mm in a standard C(T) specimen is computed in ten steps by tracking a J-resistance curve for 7475-T7351 aluminum. Some discussion is presented as to why the far-field J is preferable to near-field quantities for this procedure. The analysis did not track the companion force-displacement curve.
Plastic Energy Dissipation as a Parameter To Characterize Crack Growth
Authors: Watson TJ , Jolles MI
Published: December 2008

The global plastic energy dissipation for crack initiation and slow growth was experimentally determined for monotonic, quasi-static loading conditions utilizing compact tension and three-point bend specimens of HY-130 steel. For non-side-grooved specimens, the global plastic energy dissipation was linear with crack extension. For side-grooved specimens, however, the global plastic energy dissipation R-curves were not linear. Moreover, for non-side-grooved specimens, the values of the global plastic energy dissipation at crack growth initiation and the global plastic energy dissipation rate were found to be dependent on specimen size, geometry, and initial crack length. Although no tests were conducted to determine the sensitivity of side-grooved specimens to size or initial crack length, it was found that, for these specimens, the geometry dependence of the global plastic energy dissipation rate was minimized but not eliminated.
Weight Functions of Radial Cracks Emanating from a Circular Hole in a Plate
Authors: Sha GT , Yang C-T
Published: December 2008

Explicit nodal weight functions for a pair of symmetric radial cracks emanating from a hole in a plate are presented with special emphasis on the load-independent characteristics of the explicit weight functions that can obviate repeated calculations of the Mode I stress intensity factors (KI) under different loading conditions. An analytical expression, which relates the explicit crack-face weight function component for Mode I deformation to the radial distance from the crack tip along the crack face, is also provided to facilitate KI evaluation by combining the uncracked stress field and the explicit crack-face weight functions through the use of the linear superposition principle. The utilization of the explicit weight functions, which are obtained from a simple loading, for calculating KI under complex loading conditions such as biaxial loading and pin-joint loading with and without interference pressure, is uniquely demonstrated by combining the superposition principle and the weight function concept.
An Empirical Surface Crack Solution for Fatigue Propagation Analysis of Notched Components
Authors: Yau JF
Published: December 2008

A stress intensity factor solution for a surface crack in a finite solid subjected to an arbitrary stress field is presented. The solution was developed based on the superposition principle, the weight function technique, and a referenced finite body correction factor. An additional surface factor is identified when the solution is applied to the reduction of data from tests on surface flaw specimens.

Verification of the solution is first made by comparison with published results for problems with non-uniform stresses. The examples include a surface crack under pure bending load and a corner crack at a circular hole.

Another assessment was achieved by verifying the solution against the test results of ASTM round-robin test data for cracked fastener holes. Good correlation was obtained on all aspects of experimental observations such as the backtracked stress intensity factors, the measured residual lives, and the observed variation in crack aspect ratio.

It has been further demonstrated, from Air Force supported test programs, that the solution is accurate in predicting crack propagation behavior and residual life for subcomponent specimens under complex loadings. The test specimens are made of four different superalloys in various shapes of geometric discontinuities. The test conditions include various combinations of temperature, stress level, mean stress, and cycle profiles. The results have shown that the great majority of the measured life/predicted life ratios are within a factor of 1.5. It has also been demonstrated that the capability of the methodology is independent of the stress levels, specimen types, materials, and cycle profiles used in the study.
Dynamic Crack Propagation and Branching under Biaxial Loading
Authors: Shukla A , Anand S
Published: December 2008

A photoelastic study of high-speed crack propagation and crack branching is conducted under biaxial loading conditions. Cross-type specimens fabricated from Homalite 100 are loaded in a specially designed loading fixture where loads parallel and perpendicular to the crack can be controlled independently. The experimental data obtained are analyzed using dynamic stress field equations and multiple points to obtain the instantaneous stress intensity factor K, the stress field parallel to the crack σox, the crack velocity å, the branching stress intensity factor Kbr, and the branching angle θ. The results indicate a strong influence of the sign as well as the magnitude of σox on both crack propagation and branching.
Assessing the Dominant Mechanism for Size Effects on CTOD Values in the Ductile-to-Brittle Transition Region
Authors: Anderson TL , Williams S
Published: December 2008

There has been some uncertainty in the field of fracture mechanics as to whether shifts in the ductile-to-brittle transition with specimen size are caused by statistical sampling effects or constraint effects. Fracture toughness data for three carbon-manganese steels were analyzed to examine the effectiveness of each model in predicting the results of different sized specimens. The data set used in this investigation contains nearly 500 crack tip opening displacement (CTOD) values for various geometries of single edge notched bend (SENB) specimens with thicknesses ranging from 10 to 100 mm. A limited amount of data for single edged notched (SENT) specimens and side grooved SENB specimens was also included.

It was found that the mechanism which accounts for size effects most effectively depends on the amount of plastic flow prior to fracture. Under conditions of small scale yielding, high constraint is maintained in both small and large specimens. In this region the Landes and Shaffer statistical sampling model appears to work well for explaining the higher average toughness of small specimens. However, when the ligament yields prior to fracture, the shifts in transition observed with specimen size cannot be explained by statistical sampling effects alone.

The temperature at which net section yielding first occurs tends to shift upward as (1) the specimen thickness increases, (2) the ligament length is decreased (in a bend specimen), or (3) the mode of loading is changed from tension to bending. When the ligament yields, the plastic deformation relaxes the crack tip constraint and the brittle-to-ductile transition becomes steep. The relaxation of crack tip constraint occurs more rapidly and at lower temperatures in smaller specimens. This gives rise to a steeper transition curve and a shift in transition temperature which cannot be accounted for by statistical effects. Thus as the critical CTOD increases the relative contribution of statistical sampling on size effects decreases and constraint effects tend to dominate.
Dynamic J-R Curve Testing of a High Strength Steel Using the Key Curve and Multispecimen Techniques
Authors: Joyce JA , Hackett EM
Published: December 2008

J-integral R-curve tests were performed on three-point bend specimens of a 3-Ni steel at three loading rates: quasi-static, intermediate (25 mm/s), and drop tower (2.54 m/s). The key curve and multispecimen procedures were employed for the higher rate tests; this investigation is focused primarily on details of the test method development. The multispecimen and key curve techniques were found to yield upper shelf J-R curves which were in substantial agreement at the elevated loading rates. Numerical smoothing techniques required to apply a key curve method appear to separate the oscillatory high frequency component from the load-displacement record. For the 3-Ni steel tested for this investigation both JIc and T were found to be elevated with increasing loading rate.
Stress-intensity Factors for Circumferential Surface Cracks in Pipes and Rods under Tension and Bending Loads
Authors: Raju IS , Newman JC
Published: December 2008

Stress-intensity factors for a wide range of nearly semi-elliptical surface cracks in pipes and rods are presented. The surface cracks were oriented on a plane normal to the axis of pipes or rods. The configurations were subjected to either remote tension or bending loads. For pipes, the ratio of crack depth to crack length (a/c) ranged from 0.6 to 1, the ratio of crack depth to wall thickness (a/t) ranged from 0.2 to 0.8, and the ratio of internal radius to wall thickness (R/t) ranged from 1 to 10. For rods, the ratio of crack depth to crack length also ranged from 0.6 to 1, and the ratio of crack depth to rod diameter (a/D) ranged from 0.05 to 0.35. These particular crack configurations were chosen to cover the range of crack shapes (a/c) that have been observed in experiments conducted on pipes and rods under tension and bending fatigue loads. The stress-intensity factors were calculated by a three-dimensional finite-element method. The finite-element models employed singularity elements along the crack front and linear-strain elements elsewhere. The models had about 6500 degrees of freedom. The stress-intensity factors were evaluated using a nodal-force method.

The present results were compared with other analytical and experimental results for some of the crack configurations. The results generally agreed within 10%.

These results should be useful in predicting crack growth rates and fracture strengths, designing structural components, and establishing inspection intervals for pipes and rods.
Neutron Radiographic Detection of Corrosion
Authors: Berger H
Published: December 2008

Many nondestructive testing (NDT) methods for corrosion detection depend on the reduced thickness of the component following corrosive attack. This is normally the underlying concept for corrosion detection by NDT methods such as X-radiography, ultrasonics, and eddy currents. For neutron radiography, however, the basis for the detection is the neutron attenuation by the hydrogen in the corrosion product itself. This difference in the approach gives neutron radiography an advantage over many other NDT methods because of the potential for early detection of corrosion, before extensive attack and thinning of the material have occurred. Neutron radiographic methods are reviewed and some initial results are given for corrosion detection in aluminum. Practical neutron sources are becoming available and can be combined with established image detectors, including real-time detection systems. Corrosion in aluminum resulting from a 6.5-h supersaturated salt-water spray is shown to be detectable.
Acoustic Emission Capabilities and Applications in Monitoring Corrosion
Authors: Pollock AA
Published: December 2008

The physical processes of corrosion are examined as possible sources of acoustic emission (AE). Detectable emission is produced by film cracking, gas evolution, hydrogen-induced microcracking, plastic zone growth, and discontinuous crack movements in stress-corrosion cracking (SCC) and hydrogen-assisted cracking. By these mechanisms corrosion can be detected while it is occurring. Practical applications include rapid evaluation of the susceptibility of materials to corrosion, particularly to SCC. Apart from real-time monitoring of the corrosion process, the structural damage caused by corrosion can be detected after it has occurred by AE monitoring during application of stress. In this testing mode, emission is enhanced by surface degradation and corrosion products. Pipelines and aircraft structures have been tested in this way. In large structures it is generally more practical to detect the results of corrosion than to monitor the corrosion process itself. For success in field applications attention must be paid to issues such as background noise and wave attenuation, and operator training and experience is an important factor.