bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.