bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Stress Relief Time on the Transition Temperature of Linde 80 Welds
Authors: Hall JB , Yoon KK 
Published: September 2004

Abstract
The Babcock & Wilcox Company used Mn-Mo-Ni automatic submerged-arc welds with the Linde 80 flux type for the fabrication of 14 currently operating PWR reactor vessels. Due to the fact that the weld wire was copper-coated (high copper content) and that they have low upper-shelf toughness properties, the welds are limiting with respect to pressurized thermal shock analysis. The welds (reactor vessel, surveillance, and nozzle dropouts) were exposed to stress relief times (postweld heat treatment) ranging from 10–53 h between 593°C (1100°F) and 621°C (1150°F). In analyzing recently acquired master curve reference temperature data (ASTM E1921), it was discovered that there is a stress relief time effect on the transition temperature. The stress relief time effect can be seen in the drop weight TNDT data, but its effect is less clear in the 41 J (30ft-lb) Charpy impact data. In addition, the stress relief time has an effect on yield stress. The stress relief time may have an effect on the irradiation embrittlement of the welds, but the trend is not conclusive. Since there is an effect of stress relief time on the initial transition temperature, it is felt that it is important to test surveillance welds with similar stress relief times as the vessel welds that are being evaluated. Surveillance welds with longer stress relief times can be used to conservatively represent the vessel welds.
Irradiation Creep and Swelling of Russian Ferritic-Martensitic Steels Irradiated to Very High Exposures in the BN-350 Fast Reactor at 305–335°C
Authors: Konobeev YV , Dvoriashin AM , Porollo SI , Shulepin SV , Budylkin NI , Mironova EG , Garner FA 
Published: September 2004

Abstract
Russian ferritic/martensitic (F/M) steels EP-450, EP-852, and EP-823 were irradiated in the BN-350 fast reactor in the form of gas-pressurized creep tubes. The first steel is used in Russia for hexagonal wrappers in fast reactors. The other steels were developed for compatibility with Pb-Bi coolants and serve to enhance our understanding of the general behavior of this class of steels.
In an earlier paper we published data on irradiation creep of EP-450 and EP-823 at temperatures between 390–520°C, with dpa levels ranging from 20–60 dpa. In the current paper, new data on the irradiation creep and swelling of EP-450 and EP-852 at temperatures between 305–335°C and doses ranging from 61–89 dpa are presented. Where comparisons are possible, it appears that these steels exhibit behavior that is very consistent with that of Western steels. Swelling is relatively low at high neutron exposure and confined to temperatures &lt; 420°C, but it may be camouflaged somewhat by precipitation-related densification. These irradiation creep studies confirm that the creep compliance of F/M steels is about one-half that of austenitic steels.
Grain Boundary Phosphorous Segregation and Its Influence on the Ductile Brittle Transition Temperature in Reactor Pressure Vessel Steels
Authors: Kimura A , Shibata M , Kasada R , Nakata H , Fujii K , Fukuya K 
Published: September 2004

AbstractThe materials used for this work were two sorts of reactor pressure vessel (RPV) steels, which contain different amounts of phosphorous (P), namely 0.011 and 0.002 wt%. The specimens for Charpy V-notch (CVN) impact test, Auger electron spectroscopy (AES), and tensile test were thermally aged at 400, 450, and 500°C for 1000, 3000, and 5000 h. After the thermal aging, the AES specimens were broken in the AES chamber to measure the P concentration at grain boundaries. The AES measurements for as-received specimens were carried out following hydrogen charging so that grain boundary facets were available even without P segregation. The AES measurements revealed that the peak height ratio (PHR) of P/Fe at the grain boundaries of the high-P steel were 0.066, 0.141, and 0.120 in the specimens aged at 400°C for 3000 h, 450°C for 3000 h, and 500°C for 1000 h, respectively. The ductile-brittle transition temperature (DBTT) was measured for the aged specimens, and the ΔDBTT of 15K was observed only for the specimen aged at 450°C for 3000 h, although no changes in the hardness and tensile properties were observed. The grain boundary fracture ratio (GBFR) increased with increasing the PHR of P/Fe. Grain boundary fracture mode was located at the area close to the V-notch root. There was a good relationship among PHR, GBFR, and DBTT, indicating directly that the shift in the DBTT was due to grain boundary embrittlement caused by P segregation.
The Prediction of Fatigue Life Distributions from the Analysis of Plain Specimen Data
Authors: Shepherd DP 
Published: September 2004

Abstract
For any structurally critical component subject to fatigue, the safety of the structure depends on an accurate prediction of the life under this failure mode. However, in such circumstances it is insufficient to consider only the mean behavior of the material. To ensure structural integrity, a model for the distribution of life to failure is required, which will allow lives to be assessed relative to acceptable safety levels.
In previous work, a methodology for deriving fatigue life estimates for arbitrary specimen and component geometries from plain specimen data has been developed [4]. The methodology is based on a procedure for developing a model for the initiation behavior of the material from the specimen data and for applying this to an arbitrary material geometry or stress field. In the current paper, this method is further developed to allow for the associated distribution of fatigue lives to be calculated. This involves direct consideration of the statistical relationship between crack initiation and crack propagation, so that the distribution of initiation lives can be derived accurately. However, incorporating these considerations directly into the methodology reveals some inconsistencies in the formulation of the original model. These relate to the fact that, at high stresses, the specimens will fail in tension rather than classical fracture, thus altering the interpretation of the data. It is shown that a more robust model can be developed, but only by including the distribution of tensile strength as an additional variable, and by considering the statistical relationship between this and the other fundamental variables.
The methodology which arises from the incorporation of these considerations into the basic calculation scheme is then developed, including a means for estimating the distribution of life to failure at all points on the stress against cyclic life curve.
Probabilistic Fatigue: Computational Simulation
Authors: Chamis CC , Pai SS 
Published: September 2004

Abstract
Probabilistic computational simulation of fatigue-life is illustrated in terms of several sample cases that have been generated over the past ten years. The cases are selected to illustrate applications to multi-scale, multi-discipline, and multi-physics. These cases include composite laminate; coupled thermal, mechanical, fatigue, and creep, pressurized tank; engine blades; engine rotor; and composite combustor liner. The fundamentals for probabilistic computational fatigue are briefly described, and general comments are included on what it takes to perform probabilistic computational fatigue and to validate it. Typical results show that fatigue-life can be evaluated for complex components and for complex loadings. Probability of survival curves can be generated, and probabilistic sensitivities influencing fatigue-life can be determined. The paper describes what can be done rather than details of a specific case.
A Software Framework for Probabilistic Fatigue Life Assessment of Gas Turbine Engine Rotors
Authors: McClung RC , Enright MP , Millwater HR , Leverant GR , Hudak SJ 
Published: September 2004

Abstract
An enhanced life management process based on probabilistic damage tolerance methods has been developed to address material anomalies in titanium rotating components of gas turbine engines. Related methods are being used as tools to investigate the impact of engine monitoring and usage variability on prognosis for field readiness and life management. This paper begins with an overview of the process of probabilistic damage tolerant design, using the DARWIN® computer program to illustrate the interplay between various random variables and the conventional elements of structural design and life prediction. Special attention is then given to the initial distribution of material anomalies, scatter in fatigue crack growth data, and variability in complex mission histories. The significance of each source of variability for different applications is discussed.
Fatigue Life Variability Prediction Based on Crack Forming Inclusions in a High Strength Alloy Steel
Authors: Sharpe PS , Hillberry BM , Craig BA 
Published: September 2004

Abstract
Fatigue cracks in metals have been observed to form at nonmetallic inclusions in the matrix of the material, with the size of such features influencing fatigue life. A probabilistic method was used to predict the variability of fatigue life in quenched and tempered AISI 4340 steel. Crack growth analyses, presented as cumulative distribution functions of probability of failure, were made at two stress levels by growing inclusion size fracture mechanics flaws using an existing linear elastic fracture mechanics crack growth model. Initial flaw sizes were obtained from two separate distributions: one representing the overall inclusion population, and the other a subdistribution representing crack forming inclusions. In general, analyses correlated well with experimental lives, typically being within 25 %. The two initial flaw size distributions produced similar results; however, predictions based on the total inclusion distribution were heavily dependent on the threshold value. With the appropriate value of crack growth threshold, good correlation with variability can be made without requiring fatigue testing, particularly for the more critical shorter lives.
Corrosion Risk Assessment of Aircraft Structures
Authors: Liao M , Komorowski JP 
Published: September 2004

Abstract
This paper presents a comprehensive summary of IAR/NRC research on risk assessment of aging aircraft structures in the presence of corrosion and fatigue. Extensive test data, especially for fuselage splices containing corrosion and multiple site fatigue damage (MSD) and coupons cut from service exposed aircraft lap joints, have been generated under previous projects. Based on these test data, an empirical stochastic crack growth model was first developed to analyze the probabilistic fatigue characteristics of the splices. Risk analysis was then performed on the fuselage splices using the computer codes PRISM (Bombardier Aerospace, Inc.) and PROF (United States Air Force). Holistic life assessment methodology (HLAM), which aims to quantify structural integrity in the entire life cycle by addressing the interaction effects of corrosion and fatigue, has advanced considerably during the past five years. Risk analysis based on HLAM was carried out on the fuselage splices. The analytical results, which were obtained at different stages, are compared with the test results. It is shown that corrosion in lap joints, even at the levels less than the typical maintenance limit (i.e., 10 % material loss), could significantly increase the risk level of structural failure.
A Methodology for Assessing Fatigue Crack Growth Reliability of Railroad Tank Cars
Authors: Zhao W , Sutton MA , Penã J 
Published: September 2004

AbstractA methodology for assessing structural reliability of railroad tank cars undergoing fatigue crack growth is being developed. A three-degree-of freedom (3-dof) surface crack is employed to account for an asymmetric stress field existing at a fatigue critical location in tank car structures. A fatigue life prediction program using the Walker equation to account for stress ratio effects is developed for the 3-dof surface crack model. A component reliability problem is formulated as a limit state function and solved using a first-order reliability method along with importance sampling method within the commercial reliability software, STRUREL. The methodology is demonstrated using illustrative railroad tank car examples. The results show that: (a) failure probability, Pf, increases as tank car mileage increases; (b) welding residual stresses in the tank structure can significantly increase Pf; (c) uncertainty in the stress amplitude also has a significant effect on Pf; and (d) the correlation between initial crack depth and initial crack aspect ratio is an important parameter.
Predicting the Reliability of Ceramics Under Transient Loads and Temperatures with CARES/Life
Authors: Nemeth NN , Jadaan OM , Palfi T , Baker EH 
Published: September 2004

Abstract
A methodology is shown for predicting the time-dependent reliability of ceramic components against catastrophic rupture when subjected to transient thermomechanical loads (including cyclic loads). The methodology takes into account the changes in material response that can occur with temperature or time (i.e., changing fatigue and Weibull parameters with temperature or time). This capability has been added to the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code. The code has been modified to have the ability to interface with commercially available finite element analysis (FEA) codes executed for transient load histories. Examples are provided to demonstrate the features of the methodology as implemented in the CARES/Life program.
Artificial Weathering and Cyclic Movement Test Results Based on the RILEM TC139-DBS Durability Test Method for Construction Sealants
Authors: Miyauchi H , Enomoto N , Sugiyama S , Tanaka K 
Published: September 2004

Abstract
The purpose of this study was to assess the effect of artificial weathering and cyclic movement in a laboratory test based on the RILEM Technical Recommendation (RTR) “Durability Test Method for Curtain Wall Joint Sealants.” Eleven sealants being used in Japan were tested, including two silicones, two silicon-modified polyethers, two polysulfides, two polyurethanes — each as one- and two-part products — one two-part silicon-modified polyisobutylene, one two-part urethane cure acrylic, and one one-part water-borne acrylic. The two-part polyurethane, the two-part urethane-cure acrylic, and the one-part water-borne acrylic were also evaluated with and without painting the sealant surface. Test specimens were prepared using anodized aluminum and mortar as substrate materials; primers were used for all sealant/substrate combinations as recommended by the manufacturers. All sealant specimens were conditioned according to Method A. The durability test, consisting of weathering and thermo-mechanical cycling, was carried out both with and without the influence of fatigue cycling. The durability cycles were repeated three times. Weathering was conducted in a fully automatic weathering machine using a xenon arc light source. Sealants without painting were observed to chalk and craze at an earlier stage in the durability cycles than the ones with painted surfaces, confirming the effectiveness of painting the sealant surface in protecting organic sealants from aging. A substantial difference in the behavior of sealants was observed for exposures with and without fatigue cycling, confirming the importance of fatigue cycling in the degradation of sealants. In order to obtain a good correlation between accelerated weathering and actual service performance, a proper balance of degradation factors is essential.
Estimation of the Fatigue Resistance of Sealants to Movement at Intersections of Sealed Joints and Improvements in the Joint Design Method
Authors: Miyauchi H , Tanaka K 
Published: September 2004

Abstract
The paper investigates the fatigue resistance of sealants to movement at the intersections of sealed joints and proposes improvements to the method of joint design. As a first step, the fatigue resistance of sealed joint intersections to shear movement caused by the sliding motion of curtain wall panels was studied experimentally. Three types of building sealants were evaluated. Shear movement consistently deformed both the intersectional and linear sectional areas of joint specimens. Cracks formed within the intersectional area earlier than in the linear sections of the joints. As a second step, the fatigue resistance of sealed joint intersections to the rocking motion of curtain wall panels was studied experimentally. Two rocking motion types were evaluated. A rocking fatigue apparatus for the intersectional joint specimens was developed, and the number of cycles until crack formation was determined for given movements. We successfully obtained data on fatigue resistance of sealants using the new apparatus. Fatigue resistance of sealed joints is lower in the intersectional area than in the linear sections of the joints and is particularly lowest with simultaneous movements occurring in longitudinal and horizontal joints. Finally, the effect of curvature radii of curtain wall panel corners on fatigue resistance was studied at intersections of sealed joints. The fatigue test was carried out employing specimens with curvature radii varying from 0–8 mm. Shear movement consistently deformed the intersectional area of the joint specimens. A relation was found between curvature radius and the number of cycles to crack formation, i.e., the larger the curvature radius was, the higher the observed fatigue resistance was to joint movement.
Investigation of Burning Aluminum in Oxygen-Enriched Atmospheres through Microanalysis Techniques
Authors: Suvorovs T , DeWit JR , Osborne BP , Steinberg TA 
Published: September 2004

Abstract
Promoted-ignition testing of 3.2 mm diameter aluminum rods in high purity oxygen was performed. The rod and detached drops of both self-extinguished and water quenched samples were examined using scanning electron microscopy and electron probe microanalysis to analyze the physical structure of the sample and gather compositional data. A comparison of the micrographs of self-extinguished and quenched samples reveals clear differences in the extent of melted and re-solidified (unreacted) material and the thickness of the oxide layer, highlighting the effect of cooling rate on the burning system. A qualitative physical model for the burning of bulk aluminum in gaseous oxygen is presented. The model, incorporating a molten drop growth and detachment cycle, is based on an initial heterogeneous burning phase leading to a second phase of combined heterogeneous and homogeneous burning.
On the Causes of Deviation from the Palmgren-Miner Rule
Authors: McEvily AJ , Ishihara S , Endo M 
Published: September 2004

Abstract
Based upon considerations of fatigue crack growth, explanations for the observation that the Palmgren-Miner damage summation often deviates from unity can be established. It is assumed that the fatigue lifetime is taken up entirely in fatigue crack propagation, that is the number of cycles spent in crack initiation is a negligibly small fraction of the total lifetime. This assumption permits the fatigue lifetime to be analyzed in terms of a basic constitutive relation for the rate of fatigue crack growth that is given by: dadN=A(ΔKeff−ΔKeffth)2where a is the crack length, N is the number of cycles, A is a material-environmental constant, ΔKeff is the effective range of the stress intensity factor, i. e., Kmax - Kop, where Kmax is the maximum value of the stress intensity factor in a loading cycle, Kop is the stress intensity factor at the crack opening level, and ΔKeffth is the effective value of the stress intensity factor at the threshold level.
Three variable amplitude loading conditions are considered: two-step loading, multiple two-step loading, and overload and underload loading. In each case, the cause for deviation from a Palmgren-Miner damage summation of unity is clarified.
Degradation Parameters and Two-Stress Block Fatigue of Angle-Ply Carbon Fiber Reinforced Epoxy
Authors: Petermann J , Hinz S , Schulte K 
Published: September 2004

Abstract
Experimental studies on carbon/epoxy angle-ply laminates were conducted to prove different variables for their suitability as degradation parameters and to investigate frequency and load sequence effects. Within the investigated limits, the material did not behave in a frequency dependent manner. Although different damage mechanisms dominate at R = 0.1 and R = −1, the same degradation of fatigue strength per life decade was found. The variation of longitudinal stiffness and Poisson's ratio during fatigue life (the latter being considered superior to detect delaminations) exhibited load dependent characteristics. Under two-stress block fatigue, a significant effect of the load sequence on the fatigue life was found and different mechanisms were discussed.
Spectrum Coupon Testing of Fatigue-Resistant Fasteners for an Aging Military Aircraft
Authors: McMaster FJ , McKeighan PC 
Published: September 2004

Abstract
An experimental program of work was undertaken to assess the life improvement gained through utilizing cold expansion technology to enhance the resistance of cracking at fatigue critical locations (FCLs) in an aging military trainer aircraft. The FCLs considered included a countersunk hole and nutplate on two different wing spars. The overall goal of the experimental work was to provide a comparative assessment of the influence of the major variables examined, which included cold expansion method and process, hole size, countersink size, nutplate geometry, flight spectrum, and joint configurations. The results of this work clearly illustrated the inherent sensitivity of life improvement factors to the myriad of variables involved. Nevertheless, the foregoing experimental work clearly demonstrated the valuable life improvement that is provided by cold expansion for nearly all cases examined.
Fatigue Life of a SG Cast Iron under Real Loading Spectra: Effect of the Correlation Factor Between Bending and Torsion
Authors: Banvillet A , Palin-Luc T , Vittori J-F 
Published: September 2004

Abstract
This paper deals with the effect on life of the desynchronism between two variable amplitude load sequences in combined bending and torsion. Experiments were carried out on smooth specimens made of the EN-GJS800-2 cast iron. The comparison between experimental lives and predicted ones with the following fatigue life calculation methods is presented: Smith-Watson-Topper, Fatemi and Socie (method proposed by Bannantine), Wang and Brown, Socie's proposal for high cycle fatigue, and Morel. If the scatter of experiments is considered, these experiments show a low effect of the correlation factor on life. All the simulated fatigue life calculation methods give good results for proportional loads, but their predictions are not good for non-proportional loads. Morel's proposal seems to be the best to predict life of the tested material with our non-proportional fatigue test conditions.
Comparisons of Analytical Crack Closure Models and Experimental Results Under Flight Spectrum Loading
Authors: McClung RC , McMaster FJ , Feiger JH 
Published: September 2004

Abstract
Spectrum FCG data were generated with corner cracks at center holes for three contrasting spectrum types and two aluminum alloys, 2124-T851 and 7475-T7351. Existing strip-yield crack closure models for FCG analysis under spectrum loading were evaluated in comparison to conventional FCG models and enhanced as needed. Spectrum editing methods based on closure behavior were developed to reduce both computational and experimental time. FASTRAN was modified to address apparent differences in closure behavior between the surface and bore tips for compression-dominated spectra. Strip yield models successfully predicted FCG lives for contrasting spectra with a common constraint factor, unlike conventional models.