bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture Toughness and Atom Probe Characterization of a Highly Embrittled RPV Weld
Authors: Sokolov MA , Nanstad RK , Miller MK
Published: September 2004

The Heavy-Section Steel Irradiation Program at Oak Ridge National Laboratory (ORNL) includes a task to investigate the shape of the fracture toughness master curve for reactor pressure vessel steel highly embrittled as a consequence of irradiation exposure. A radiation-sensitive reactor pressure vessel (RPV) weld with intentionally enhanced copper content, designed KS-01, is characterized in terms of static initiation (KIc, KJc) and Charpy impact toughness in the unirradiated and irradiated conditions. The objective of this project is to investigate the ability of highly embrittled material to maintain the shape of the unirradiated transition fracture toughness curve, as well as to examine the ability of the Charpy 41-J shift to predict the fracture toughness shift at such a high level of embrittlement. Irradiation of this weld was performed at the University of Michigan Ford Reactor. Specimens of KS-01 weld were irradiated to about 0.74 × 1019 neutron/cm2 at 288°C. Irradiation resulted in Charpy ductile-to-brittle transition temperature (DBTT) shift of 169°C. It was anticipated that this shift would result in a fracture toughness transition temperature (at 100 MPa√m) in the irradiated condition near or slightly above the pressurized thermal shock screening criterion for weld metals, ToPTS = 129°C. The fracture toughness characterization of KS-01 weld in the unirradiated and irradiated conditions was mainly performed by testing 1T C(T), although some 0.5T C(T) and precracked Charpy specimens were used in this study. The master curve analysis showed that this material exhibited shift of reference fracture toughness transition temperature, To, of 165°C as result of radiation, which is in remarkable agreement with Charpy DBTT shift. The absolute value of To in the irradiated condition was determined to be equal to 139°C. This weld exhibited a low ductile initiation toughness (JQ) after irradiation. It left a relatively narrow temperature window to examine the shape of the transition region. Irradiated median fracture toughness values up to 148 MPa√m follow the master curve shape. However, low toughness brittle fractures occurred at temperatures further above To (To + 61°C) than expected with a leveling of the KJc data from the master curve shape. The microstructure of the weld was characterized with the ORNL's energy-compensated optical position-sensitive atom probe. Atom probe tomography revealed a high number density (∼3 × 1024 m−3) of Cu-, Mn-, Ni-, Si-, and P-enriched precipitates and a lower number density (∼1 × 1023 m−3) of P clusters.
Effect of Stress Relief Time on the Transition Temperature of Linde 80 Welds
Authors: Hall JB , Yoon KK
Published: September 2004

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

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 < 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

The 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

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

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

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

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

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

A 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

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

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

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

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

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

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

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

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

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.
Development of a DCPD Calibration for Evaluation of Crack Growth in Corner-Notched, Open-Hole Specimens
Authors: George K , Reemsnyder HS , Donald JK , Bucci RJ
Published: September 2004

A direct current potential drop (DCPD) calibration was developed for an open-hole specimen to characterize fatigue crack growth (FCG) behavior of cracks initiating from a small corner flaw and transitioning to a through-thickness crack. A single Mode I stress intensity (KI) solution was derived covering the entire range of crack growth. The purpose of using this specimen geometry was to: 1) capture short crack behavior for specific crack length intervals of damage tolerance criteria and 2) use the data to evaluate predictive FCG methodology. Driven by these objectives, a non-standard specimen was chosen that better simulated the geometry and stress state of the component of interest: an aircraft wing design detail. Thin panels of selected 7XXX and 2XXX aluminum alloys were prepared with a centrally located open-hole with a corner notch of 0.13 mm (∼0.005 in.) to serve as a crack initiation site. Testing was conducted in high-humidity air under constant and variable amplitude loading. Short crack results agreed well with existing, closure-corrected, long crack data. Duplicate tests of the 7XXX alloys confirmed repeatability. The 2XXX alloys exhibited greater variability than the 7XXX alloys in the short crack regime. Evaluation of the predictive methods is beyond the scope of this paper and will be published separately.
Fuzzy Probabilistic Assessment of Aging Aircraft Structures Subjected to Multiple Site Fatigue Damage
Authors: Akpan UO , Rushton PA , Dunbar TE , Koko TS
Published: September 2004

A strategy is developed for fuzzy probabilistic assessment of the fatigue resistance of aging aircraft structures due to multiple site fatigue damage (MSD). The residual strength of an aircraft structure may be significantly reduced by the existence of fatigue damage at multiple locations. Depending on the level of subjectivity and degree of knowledge, MSD-related parameters may be represented as either purely random variables or fuzzy random variables. The membership functions of probabilistic characteristics of fuzzy random variables, namely mean values and standard deviations, are developed. Mechanistic and probabilistic models used to evaluate multi-site fatigue damage are also presented. A probabilistic solution strategy, employing the first order reliability method (FORM), is combined with the response surface-based fuzzy modeling approach to develop possibility distributions of the probabilistic response quantities (namely reliability indices and failure probabilities) for components subjected to multiple site fatigue damage. Instead of providing the traditional single valued, purely probabilistic measure for reliability, the present formulation proves its merit in its ability to combine experimental data with expert knowledge to provide confidence bounds on the structural integrity of aging aircraft. Moreover, the predicted bounds are dependent on the level of knowledge regarding the fuzzy input parameters, with a higher degree of knowledge resulting in more narrow bounds. An example problem is used to demonstrate the advantages of the proposed methodology.
Calculation of Stress Intensity Factors for Cracks in Structural and Mechanical Components Subjected to Complex Stress Fields
Authors: Wu Z , Glinka G , Jakubczak H , Nilsson L
Published: September 2004

One of the difficulties in using fracture mechanics is in determining stress intensity factors of cracked structural and mechanical components. The cracks are often subjected to complex stress fields induced by external loads and residual stresses resulting from the surface treatment. Both stress fields are characterized by non-uniform distributions, and handbook stress intensity factor solutions are seldom available in such cases. The method presented below is based on the generalized weight function technique enabling the stress intensity factors to be calculated for any Mode I loading applied to a planar semi-elliptical surface crack. The stress intensity factor can be determined at any point on the crack tip contour by using the general weight function. The calculation is carried out by integrating the product of the stress field and the weight function over the crack area.

Several examples of point-load weight functions and resulting stress intensity factors are presented in the paper. The method is particularly suitable for modeling fatigue crack growth in the presence of complex stress fields.
Apparent Molar Volumes and Adiabatic Compressibilities of Some Amino Acids in Aqueous Sucrose Solutions at 298.15 K
Authors: Pal Amalendu , Kumar Suresh
Published: September 2004

Apparent molar volumes V
ϕ and adiabatic compressibilities K
ϕ,

s
of L-glycine, L-alanine, and L-valine in aqueous sucrose solutions ranging from pure water to 25 mass% of sucrose have been determined at 298.15 K from precise density and sound speed measurements. Partial molar volumes V
ϕ
0 and partial molar adiabatic compressibilities K
ϕ,

s

0 of these amino acids at infinite dilution were evaluated. These values are required for calculating hydration number n
H of amino acids. Transfer volumes ΔV
ϕ
0 and transfer adiabatic compressibilities ΔK
ϕ,

s

0 at infinite dilution from water to aqueous sucrose solutions have been calculated. Transfer parameters have been discussed in terms of solute-cosolute interaction on the basis of a cosphere overlap model. Group contributions for the partial molar volumes and adiabatic compressibilities have been determined from the amino acids. All these results indicate that hydrophilic ionic group interactions are stronger than the hydrophilic-hydrophobic interactions in all the amino acids over the whole concentration range of sucrose solutions and decrease with the increase in size of side chain of amino acids.
Electron Spin Resonance Studies of Kinetic Effects of Substituent and Crown Ether on Intramolecular Sodium Cation Exchange in 2,5-Di-Tert-Amyl- and 2,5-Di-Tert-Butyl-1,4-Benzoquinone Radical Anions
Authors: Sueishi Yoshimi , Kasahara Masamichi , Okawa Kayo , Yamamoto Shunzo
Published: September 2004

Upon an addition of crown ethers to a solution of 2,5-di-tert-amyl-1,4-benzoquinone (2,5-DAQ) and 2,5-di-tert-butyl-1,4-benzoquinone (2,5-DBQ) radical anions, the significant broadening of the two-center lines was observed in their electron spin resonance (ESR) spectra. The formation constants for the complexation of sodium cation with three kinds of crown ethers in 2,5-DAQ and 2,5-DBQ radical ion pairs were estimated, and the intramolecular two-site jumping rates of sodium cation complexed with crown ethers were determined. Differential effects of steric and crown ether were found in the intramolecular sodium cation migration. The stabilization of inclusion complex of sodium cation with crown ethers gives rise to the acceleration effects on the rates of intramolecular migration of cation/crown-ether complex. Based on the results, a kinetic explanation for the intramolecular sodium cation migration in the presence of crown ethers was given.
Alkanolamines from Olefin Oxides and Ammonia
Authors: Jones Carol , Edens Martha R. , Lochary J. Fred
Published: September 2004

Ethylene oxide, propylene oxide, or butylene oxide react with ammonia to produce alkanolamines. Ethanolamines, NH3-n(C2H4OH)n(C2HOH)n(n = 1,2,3, mono‐, di‐, and tri‐), are derived from the reaction of ammonia with ethylene oxide. Isopropanolamines, NH3-n(CH2CHOHCH3)n(mono‐, di‐, and tri‐), result from the reaction of ammonia with propylene oxide. Secondary butanolamines, NH3-n(CH2CHOHCH2CH3)n(mono‐, di‐, and tri‐), are the result of the reaction of ammonia with butylene oxide. Mixed alkanolamines can be produced from a mixture of oxides reacting with ammonia. Ethanolamines have been commercially available for over 50 years and isopropanolamines, for over 40 years.sec‐Butanolamines have been prepared in research quantities, but are not available commercially. A variety of substituted alkanolamines are also available commercially, but have not reached the volume popularity of the ethanolamines and isopropanolamines. The freezing points of alkanolamines are moderately high. The ethanolamines are colorless liquids at or near room temperature. Alkanolamines are bifunctional molecules because of the alcohol and the amine functional groups in the same compound. This allows them to react in a wide variety of ways. Consumption of ethanolamines in the United States in chemical processing intermediates (captive use for ethyleneamine and surfactant applications) has increased significantly since the 1960s. Alkanolamines generally have low acute oral toxicity, but swallowing substantial quantities could have serious toxic effects. Exposure of the eye to undiluted alkanolamines can cause serious injury. Monoethanolamine and monoisopropanolamine are skin irritants, capable of producing serious injury in concentrations of 10% or higher. Alkanolamines and their derivatives are used in a wide variety of household and industrial applications. The amides are useful as foam stabilizers and aid cleaning in laundry detergents, dishwashing liquids, etc. Reaction of alkanolamines with a fatty acid at room temperature produces neutral alkanolamine soaps, found in cosmetics, polishes, household cleaners, and pharmaceuticals. Alkanolamine salts add to the surfactants line used in detergents, cosmetics, textiles, polishes, agricultural sprays, household cleaners, and metalworking compounds. Salts of alkanolamines and inorganic acids are useful chemical intermediates, and are used in corrosion inhibitors and antistatic agents, among other products.
Initiators, Anionic
Authors: Quirk Roderic P. , Monroy Victor M.
Published: September 2004

Anionic initiators for chain‐reaction polymerization are described. The general relationship between monomer structure, pKa, and appropriate initiating species is discussed. The scope and limitations of the use of alkali metals, aromatic radical anions, nuclides, alkyllithium, and other organoalkali compounds, organomagnesium and organobarium compounds, diphenylmethyl carbanions, fluorenyl carbanions, enolate anions, metal free compounds, and alkoxides as initiators are presented. The uniqueness of alkyllithium initiators in hydrocarbon solvents for controlled, living, anionic polymerization is discussed.
Ethylene Oxide Polymers
Authors: Back Darlene M. , Schmitt Robert L.
Published: September 2004

Ethylene oxide polymers are high molecular weight (>100,000) water‐soluble thermoplastic polymers. This article reviews the effect of shear, pH, salt, and temperature on the physical and chemical properties of poly(ethylene oxide) solutions and melts. Industrial uses of the unique properties of poly(ethylene oxide) in fields such as flocculation, pharmaceutical excipients, adhesives, coatings, and personal care are summarized.
Explosives and Propellants
Authors: Akhavan Jacqueline
Published: September 2004

Explosives and propellants are chemical compounds that undergo chemical decomposition reactions at very fast speeds, producing gaseous products, and a great deal of heat. In some circumstances a blast wave can be produced. The information provided here gives an introduction to this process covering the theory of detonation and deflagration. Explosives can be divided into three classes, (1) primary explosives, (2) secondary explosives, and (3) propellants. The behavior and performance of these three classes of explosives is discussed. Physical and chemical data on primary and secondary explosives is given together with details of new high temperature explosives. Lastly future developments in explosives technology are presented with regards to enhancing the performance, insensitive munitions and demilitarization.
Gasoline and Other Motor Fuels
Authors: Hochhauser Albert M.
Published: September 2004

Gasoline and Other Motor Fuels. Albert M. Hochhauser (ExxonMobil Research and Engineering Co.). Gasoline and other motor fuels comprise the largest single use of energy in the U.S. The cost of this energy continues to be a primary factor in the national economy. The fraction of resources from which these fuels come that is provided by foreign sources is a matter of political concern. Rapid increases in the price of crude oil has led to programs for developing alternative sources of fuels such as biomass and natural gas. Alternative fuels are being considered for their potential to reduce greenhouse gas emissions and the desire to reduce dependence on petroleum based fuels.

All motor fuels in the U.S. are manufactured by private companies. Many participate in other aspects such as refining or marketing. Gasoline demand is determined by the numbers of cars, paved roads, population, and economic growth. Gasoline must meet exacting specifications and vary according to location, temperature and altitudes at which the product is used. Octane is probably the single most recognized measure of gasoline quality. Petroleum refining begins with distillation of crude oil into many fractions. Most gasoline in the U.S. is obtained by catalytic cracking. Reforming increases octane. Gasoline additives (eg, dyes, antioxidants, detergents, etc.) are used to improve performance. Stricter emission standards have resulted in changes in vehicle hardware. Diesel fuel, second to gasoline, is used in a wide variety of engines. The ability of diesel fuel to burn properly is described by its cetane number. Diesel manufacturers have found it difficult to meet emission standards. Alternative fuels include biomass based liquids, natural gas (either compressed or converted to liquids) and liquefied petroleum gas.
Flame Retardants, Halogenated
Authors: Mack Arthur G.
Published: September 2004

Brominated, and chlorinated organic flame retardants are widely used to reduce the flammability and ignitability of plastics; this use is growing because of increasingly strict flammability regulations. Brominated and chlorinated aliphatic and brominated aromatic compounds are used as additives in both thermoset and thermoplastic polymers. Brominated aliphatic, brominated aromatic and chlorinated aromatic compounds are used as reactive flame retardants in both thermoset and thermoplastic polymers. In many applications, antimony oxide is used as a synergist, interacting with halogenated flame retardants to produce a more effective system. The largest volume brominated flame retardants are the brominated aromatics, Tetrabromobisphenol‐A and decabromodiphenyl oxide. The largest volume chlorinated flame retardants are the chlorinated paraffins.
Environmental Impact Assessment
Authors: Lawrence David P.
Published: September 2004

The field of environmental impact assessment (EIA) is increasingly important to the chemical industry and to industries using chemical technologies. Such industries are sometimes directly subject to EIA requirements. Industrial decision‐making (eg, locations, management practices) also can be affected by EIA requirements, documents and methodology. It is prudent practice to be aware of this rapidly evolving field and of its implications for the chemical industry. This starts with understanding the meaning, origins, objectives and types of EIA. It entails appreciating EIA institutional arrangements, as reflected in EIA legislation, regulations and guidelines, as applied in EIA regulatory systems, and as expressed through regulatory reform. It requires awareness of EIA processes (activities and process design choices) and methods (for activities, for EIA specialties). It means recognizing new EIA directions and emerging priorities (eg, the link toEMS, the lessons of EIA quality, effectiveness, and good practice, how the field is being re‐oriented to better integrate social and economic concerns, procedural and outcome fairness, sustainability, uncertainty and collaborative planning). It underscores the need to know where to go to obtain detailed and up‐to‐date information and insights about EIA requirements, theory and practice.
Do early interviews affect children's long‐term event recall?
Authors: Pipe Margaret‐Ellen , Sutherland Rachel , Webster Nalini , Jones Carolyn , Rooy David La
Published: September 2004

The present study examined the effects of the timing of an initial interview on children's recall of an event over delays of 1 and 2 years. Fifty‐five children who had originally participated in a novel event when they were between 5‐ and 6‐years old and had been interviewed about it following either short (1 week or less) or long (1 or 6 month) delays were re‐interviewed 1 and 2 years after the original experience. An additional 20 children not interviewed prior to the 1‐year interview were included as a no‐prior‐interview control group. Long delays to the initial interview led to better open‐ended recall at the 1‐year delay than short delays to initial interview or no prior interview. However, initial interviews that followed short delays had a greater impact on children's responses to specific questions. The results suggest that prior interview history is an important consideration when examining the effects of long delays on children's event reports, and that the effects of the timing of an initial interview depend on the nature of the information recalled. Copyright © 2004 John Wiley & Sons, Ltd.
Event frequency and children's suggestibility: a study of cued recall responses
Authors: Price Heather L. , Connolly Deborah A.
Published: September 2004

Research examining the effect of repeated experience on children's suggestibility for particular kinds of information has produced differing results. In one study, responses to recognition questions revealed heightened suggestibility for variable details in children who repeatedly experienced an event compared to children who experienced an event once. In other studies, no such effect was found with cued recall. In this study, 4–5‐year old children engaged in one or four play sessions. Children were later given a biasing interview wherein half of the details were incorrectly represented. Children were then given a final memory test using free and cued recall prompts that was preceded by one of three instruction types: no special instructions, moderate instructions, or opposition instructions. Children in the repeated‐event condition were more suggestible than those in the single‐event condition, regardless of instructions. No significant differences in suggestibility were found across instructions conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Childhood visits to animal buildings and atopic diseases in adulthood: An age‐dependent relationship
Authors: Radon Katja , Ehrenstein Vera , Praml Georg , Nowak Dennis
Published: September 2004

Background

Several studies reported protective effects of farming environments against atopic diseases. Therefore, we aimed to establish the relevant timing of exposure in early life.

Methods

A cross‐sectional study was carried out in a rural town. Overall, 4,537 inhabitants aged 18–44 years were eligible. Of these, 3,112 (69%) responded to a postal questionnaire on atopic diseases, life‐time exposure to farming environments, and potential confounders.

Results

Those with regular childhood exposure to animal buildings had a significantly reduced risk of nasal allergies. The greatest reduction in risk was seen for respondents starting regular visits to animal stables during the 1st year of life or between ages 3 and 5. Participants reporting start of exposure after age 5 remained at a lower risk for nasal allergies (0.70, 0.49–1.01).

Conclusions

The preventive effect of animal buildings' exposure against atopic respiratory diseases continues into adulthood. The magnitude of the effect appears to be age‐dependent. Am. J. Ind. Med. 46:349–356, 2004. © 2004 Wiley‐Liss, Inc.
Experimental human exposure to inhaled grain dust and ammonia: Towards a model of concentrated animal feeding operations
Authors: Sigurdarson Sigurdur T. , O'Shaughnessy Patrick T. , Watt Janet A. , Kline Joel N.
Published: September 2004

Background

Ammonia and endotoxin‐rich dust are present in high concentrations in swine confinement facilities; exposure to this environment is linked to workers' respiratory problems. We hypothesized that experimental exposure to ammonia and dust would impair pulmonary function, and that these exposures would be synergistic.

Methods

We exposed six normal subjects and eight subjects with mild asthma to ammonia (16–25 ppm) and/or endotoxin‐rich grain dust (4 mg/m3). Pulmonary function and exhaled NOx were measured before and after exposure.

Results

There was no significant change in pulmonary function in the normal subjects following any of the exposure conditions. Among asthmatics, a significant transient decrease in FEV1 was induced by grain dust, but was not altered by ammonia; increased bronchial hyperreactivity was also noted in this group.

Conclusion

In a vulnerable population, exposure to grain dust results in transient airflow obstruction. Short‐term exposure to ammonia does not increase this response. Am. J. Ind. Med. 46:345–348, 2004. © 2004 Wiley‐Liss, Inc.
Organic dusts and disease: A continuous research challenge
Authors: Rylander Ragnar
Published: September 2004

Research on organic dust during recent years has revealed major clinical effects and some causative agents. Many of the symptoms reported are caused by an inflammation in the airways, characterized by a neutrophil response. This condition can cause a non‐allergic asthma. There are also reactions characterized by lymphocyte accumulation and by specific IgE antibody formation. Causative agents identified as bacterial endotoxins, molds, and different allergens. Am. J. Ind. Med. 46:323–326, 2004. © 2004 Wiley‐Liss, Inc.