bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure of the Neutron Irradiated VVER-type Reactor Pressure Vessel Steels
Authors: Kočík J , Keilová E , Procházka I , Čížek J
Published: April 2008

Conventional transmission electron microscopy has been used to investigate the radiation-induced changes in the microstructure of VVER-type RPV steels. Specimens irradiated at ≈ 270 °C temperature in both the power light-water reactor (surveillance specimens) and the research reactor have been studied. In addition, the microstructure of the thermally aged specimens was analyzed too. Microstructural analysis has been supplemented by some preliminary results of the Doppler broadening and lifetime positron annihilation measurements.

Radiation-induced matrix defects visible by TEM in power reactor surveillance specimens consist of black dots, small dislocation loops and fine precipitates distributed heterogeneously with a dislocation substructure. Evolution of the radiation damage structure depends on the neutron fluence and the neutron flux. Only hardly discernible black dots were observed in specimens irradiated in the research reactor in NRI Řež. However, also in this case, the presence of a vacancy-rich component in the damage structure was suggested by positron lifetime measurements.
Two-Step Recovery Process of Irradiation Hardening in 1%Ni Doped 9%Cr-2%W Martensitic Steel
Authors: Kasada R , Morimura T , Matsui H , Narui M , Kimura A
Published: April 2008

The effect of nickel addition on irradiation-induced hardening has been investigated for reduced-activation martensitic steel (RAMS). Specimens were irradiated in the JMTR at 80°C and 220°C up to 0.15 dpa. There was no significant difference in the tensile properties between the steels with and without Ni addition after the irradiation at 220°C, while in the case of the irradiation below 170°C, the Ni-added RAMS showed a more than four times larger irradiation hardening than the steel without Ni addition. The recovery behavior of the irradiation hardening of Ni-added steel on post-irradiation annealing showed two-step recovery behavior; the first step was around 200°C and the second one was around 350°C, while only the single step of recovery was observed around 350°C in the steel without Ni addition. The mechanism of the recovery process of the tremendous irradiation hardening in Ni-added steel is discussed along with the behavior of vacancies, carbon atoms and their complexes investigated by means of positron annihilation lifetime spectrometry.
Microstructure and Hardening in Thermally Aged and Neutron-Irradiated Fe-Cu Model Alloy
Authors: Kawanishi H , Suzuki M
Published: April 2008

The microstructure of Fe-0.6 wt.% Cu alloys irradiated at 290°C to 0.0055 dpa in the Japan Materials Testing Reactor was examined using a conventional electron microscopy technique to study the precipitation behavior of copper in α-iron, in addition to those thermally aged at 500°C for 1000 h and unalloyed Fe. Hardness measurements were also carried out. Results showed that there were two kinds of copper precipitates in thermally aged alloys. The first one was an ultrathin untwinned precipitate that increased in thickness with aging, decreasing in size and number density. The second was small with twinning, that grew little until peak hardness. Age hardening, thus, was attributed to ultrathin copper precipitate. Irradiation, which induced a dramatic hardening in the alloys, eliminated the ultrathin precipitates while the small-twinned ones survived. Two (111) patterns appeared on a (110) selected area diffraction pattern of the α-iron matrix in the irradiated specimens with one (111) pattern analyzed to be due to (110)Cu3Fe reflections (forbidden reflections in fcc crystals) and the other (111) pattern to (220)Fe3O4 reflections. It was concluded that irradiation induced the formation of short range ordered domains of Cu3Fe-superlattice (L12-type) in Fe-Cu alloys, resulting in the dramatic hardening. The precipitation of FeSi was recognized to be enhanced by irradiations in unalloyed iron.
Mechanical Properties and Microstructure of HFR-Irradiated Ferritic/Martensitic Low-Activation Alloys
Authors: Materna-Morris EI , Rieth M , Ehrlich K
Published: April 2008

Within the framework of the European Fusion Technology Programme, a series of ferritic/martensitic developmental alloys have been investigated after irradiation in the HFR (Petten, Netherlands). These new 7–10%CrWVTa alloys have been optimized towards long-term activation and the properties are compared with the conventional 9–12% CrMoVNb steels. The comparison contains two alloys from FZK (OPTIFER - type), the commonly investigated IEA alloy F82H and an ORNL - 9Cr2WVTa material. The irradiation was carried out in the temperature range of 250 – 450 °C up to an accumulated dose of 0.8 dpa.

The mechanical properties of the unirradiated and irradiated specimens were determined by tensile and impact tests. Radiation hardening, shift in DBTT to higher temperatures and partially a reduction of upper shelf energy were observed. Selected samples have been investigated by means of metallographic, SEM and TEM methods. The micro-structures developed during neutron irradiation showed irradiation-induced precipitates, dislocation loops and He bubbles or small voids. These microstructures contribute to the observed irradiation-induced hardening and the changes of the fracture mode from transgranular to intergranular fractures.
Reanalysis of Swelling and Irradiation Creep Data on 316 Type Stainless Steels Irradiated in the FFTF and Phénix Fast Reactors
Authors: Toloczko MB , Garner FA
Published: April 2008

In comparing results of irradiation creep experiments conducted by researchers in France and those by researchers at Pacific Northwest National Laboratory in the United States, quite different values for the creep-swelling coupling coefficient were reported. The differing coefficients complicated the understanding of the growing data base on irradiation creep. However, upon careful consideration, the French and US results showed key differences in experimental technique and analysis. The French and US irradiation creep experiments were conducted with several important differences that were initially thought to be of little consequence. One difference was related to whether stress-free swelling or stress-enhanced swelling was measured and used in calculating the creep strains. Inspection of irradiation creep results published by the French also showed their technique for extracting the creep-swelling coupling coefficient was different than that used by the present authors. In an effort to better understand the origin of the differing creep coefficients, data from the French and US experiments was reanalyzed taking into account these differences. In performing this reanalysis, completely consistent results were obtained.
Microstructure Modeling of a 316L Stainless Steel Irradiated with Electrons
Authors: Henry J , Barbu A , Hardouin-Duparc A
Published: April 2008

The work presented here is a first step in an effort to develop a rate theory model useful for the prediction of microstructural evolution of austenitic stainless steels in typical irradiation conditions for PWR core internals. An important difficulty associated with this type of model is the lack of well known material parameters (apparent defect migration energies, bias factors, etc.), which depend on the composition of the alloy and on the presence of impurities. The approach adopted here consists in finding an adequate set of parameters which results in a good agreement between model predictions and microstructural data after irradiating a 316L stainless steel at different temperatures in a 1 MeV electron microscope. Model results can then be compared with microstructural data corresponding to different irradiation conditions. We have chosen here to perform irradiations at low damage rate using 3 MeV electrons, which is a simpler case compared for example with neutron irradiations. We have found that calculated and measured densities of interstitial loops are in good agreement if a small fraction of the generated defects is considered to be in the form of di-interstitials, in accordance with molecular dynamics results. In the future, we intend to modify the model for the case of neutron irradiations. The same procedure as implemented here for the choice of material parameters (i.e., 1 MeV electron irradiations) will be carried out for different types of austenitic stainless steels. Model predictions will then be compared with microstructural observations obtained after irradiations of the steels up to different doses in an experimental reactor.
Effects of Damage Rate on Formation of Voids and Dislocation Loops in Metals
Authors: Xu Q , Yoshiie T , Iseki M
Published: April 2008

Effects of damage rate on the formation of voids and interstitial type dislocation loops in pure metals, such as Au, Cu, Ni, Fe and V, and alloys of Ni and V, were investigated. The specimens were irradiated at the Kyoto University Reactor (KUR) with improved temperature control. The dose rates of neutron irradiation were 4.4×1015n/m2s (E > 0.1 MeV) and 3.9×1017 n/m2s (E > 0.1 MeV) at 573 K. By the total dose of about 7×1021 n/m2 (E > 0.1 MeV), the loop density increased with increasing dose rate, whereas the growth behavior of microvoids depended on the dose rate and irradiated materials. In Cu, Fe and V, the concentration and the size of microvoids increased with increasing dose rate. In Au, the difference of microvoid formation between two dose rates was small. While in Ni, Ni-Cu and Ni-Ge, the size of microvoids increased with decreasing dose rate. The behaviors of formation of microvoids and dislocation loops were analyzed by the rate theory. It was clarified that the microvoid formation strongly relates to the mobility of vacancies. The calculation also showed that the nucleation of dislocation loops increases with increasing dose rate.
Influence of Silicon or Titanium on the Microstructural Evolution of Fe-Cr-35Ni Alloys Irradiated with Neutrons or Self-Ions
Authors: Watanabe H , Garner FA
Published: April 2008

A series of Fe-Cr-35Ni alloys was irradiated to doses ranging from 12 to 36 dpa with fast neutrons at 375–600°C and to 59–117 dpa at 675°C with Ni+ ions. The primary purpose of this study was to examine the effect of silicon and titanium on both microstructural evolution and the tendency of Fe-Cr-35Ni alloys to spinodally decompose during irradiation. As expected, the addition of these solutes suppresses void swelling and alters the microstructural evolution. They do not appear, however, to suppress the tendency toward spinodal-like decomposition, but only to change somewhat the microstructural consequences of the decomposition.
A Composite Model for Segregation and Microstructural Evolution Under Electron Irradiation
Authors: Watanabe S , Sakaguchi N , Takahashi H , Ohnuki S
Published: April 2008

We have investigated radiation-induced segregation (RIS) near a grain boundary in an austenitic stainless steel under electron irradiation taking into account the simultaneous evolution of faulted dislocation loops and network dislocations by a composite model. It has been found that dislocation free zones (DLFZ) formed in the vicinity of the grain boundary by the irradiation, and we carried out direct observation of the DLFZ formation by in-situ irradiation in a high-voltage electron microscope (HVEM). Prediction of temperature and dose dependence of DLFZ formation agreed with experimental results. The inter-relationship between RIS and DLFZ formation near a grain boundary has been substantially clarified. RIS and DLFZ were understood considering point defect and solute flow associated with the excess defect to the grain boundary.
Measurement and Calculation of Helium Generation in Beryllium Pebbles Irradiated in EBR-II
Authors: Greenwood LR , Oliver BM , Gelles DS , Baldwin DL , Dalle Donne M , Kawamura H , Scaffidi-Argentina F
Published: April 2008

Beryllium pebbles are being evaluated for their potential use as a neutron multiplier in fusion power reactors. Commercially available pebbles were irradiated in the Experimental Breeder Reactor II to study property changes and gas production. Helium production rates from fast neutron irradiation are significantly higher in beryllium than in other metals due to the low neutron energy threshold and large (n,2n)2α nuclear cross section. Furthermore, the 9Be(n,α)6He(β) reaction breeds 6Li, which has a high thermal neutron cross section for producing helium and tritium. Calculations of helium and tritium production were performed based on neutron dosimetry measurements.

Stepped-anneal and total helium release measurements were conducted on single and multiple beryllium pebbles, from two different suppliers, Brush Wellman and Nippon Gashi Co.-Japan. The measurements were conducted to determine the total helium content for comparison with predictions, and to determine the helium release characteristics as a function of time and temperature. These data are required for fusion reactor design. Sequential helium analyses were conducted over a temperature range from 500°C to 1100°C in approximately 100°C steps. Observed helium release in both beryllium lots was nonlinear with time at each temperature interval, with each step being characterized by a rapid initial release rate, followed by a gradual slowing of the rate over time. Fractional helium release as a function of temperature was observed to be substantially different for the two lots.

Comparisons of the measured and calculated total helium production in the beryllium agree within ±5%. This agreement validates our understanding of the reaction mechanisms, nuclear cross sections, and neutron dosimetry results, thereby demonstrating that we can confidently predict helium generation and release characteristics for the design of fusion reactors.
Activation Spectra: Techniques and Applications to Stabilization and Stability Testing of Materials
Authors: Searle ND
Published: April 2008

The activation spectrum of a material represents the relative amount of damage caused by individual spectral regions of the source to which the material is exposed. Experimental techniques used to determine activation spectra include (1) narrow-band radiation utilizing interference filters or a grating or prism spectrograph and (2) polychromatic radiation with sharp cut-on UV/visible transmitting glass filters to define the relative effects of radiation by individual spectral regions during exposure to all wavelengths longer than the cut-on of the filter. The spectral effects of radiation on a material are determined by measurement of spectral changes, i.e., by UV, visible or infrared spectroscopy, and, if sample size permits, by changes in physical properties.

Applications of activation spectra include the development of light stable materials, the design of meaningful light stability tests, timing of exposures based on actinic radiation and prediction of service life by providing a means of determining effective dosage. Examples are given to demonstrate many of the applications of activation spectra and comparison is made with action spectra which represent the wavelength sensitivity of a material independent of the spectral emission properties of the radiation source.
Exposure Test Results for Inkjet Inks in Interior Light Environments
Authors: Fischer RM , Ketola W
Published: April 2008

A procedure for development of a simple, small-scale laboratory accelerated test based on the same light source used in the actual indoor application is described by Ketola et al., [1] “Stress Analysis and Accelerated Test Design for Interior Light Environment” as part of this STP 1385. The test parameters identified in that work were used to evaluate and compare the durability of “inkjet” inks in both actual exposure and accelerated conditions. The inks were also exposed to more traditional weathering tests that may also be used to evaluate the light stability of materials used indoors. Test results point out the importance of matching the spectral power distribution of the real environment for obtaining the most accurate durability assessment. An approach for estimating service life for these inks is also described.
Advances in Accelerated Weathering Instrumentation Technology Using Advanced Control Systems
Authors: Patel B , Tikhtman J , Lee F , Scott K
Published: April 2008

For laboratory weathering instruments to be most useful, they must have, among other qualities, the ability to conduct tests repeatably and reproducibility. Repeatability is the measure of a specific instrument's ability to duplicate results from one test to another. Reproducibility is the measure of the ability of instruments of the same model to duplicate test results. As users become more sophisticated, the demand for instruments capable of very good reproducibility and repeatability increases. Thus, instrument manufacturers are constantly challenged to deliver suitable instruments to the testing community. For those tests that are influenced by multiple parameters, some of which are synergistic, while others are offsetting, the challenge is even more pronounced.

This paper discusses the concepts and features incorporated in a particular type of xenon weathering instrument to control critical test parameters, whether they are mutually compatible or not.
Estimating the Durability of Roofing Systems
Authors: Cash CG
Published: April 2008

A method for the estimation of the durability of both steep and low sloped roofing systems is presented. The “thermal load” concept is defined. Each estimate is based on the thermal load at the exposure site, the presence of significant design, workmanship, and materials defects, and the generic roofing system proposed or selected. Examples show how to calculate the mean durability, and the durability adjusted for systemic defects for any of seventeen low- and steep-sloped roofing systems.

Thermal loads for many geographic locations and the thermal sensitivity factors for many roofing systems are provided.
A Review of Test Methods Used in the Selection of Materials for Oxygen Service: Keynote Address
Authors: Bryan CJ
Published: April 2008

This paper reviews the most frequently used methods to aid in the selection of materials for oxygen service. Many different test methods have been developed over the years. An engineer once said that all he needed was a match to determine if a material was suitable for oxygen use. Today, there are many tests available to the investigator as well as many different versions of the same test. A literature search revealed eleven tests for autogenous ignition, five tests for oxygen index, four tests for mechanical impact, eleven tests for pneumatic impact tests on materials and components, three heats of combustion, two for flat gasket combustion, two for oxygen aging of polymeric materials, one test specific for metals combustion, and five cleaning processes. This paper presents short summaries for many of these test procedures.
Polymer-Oxygen Compatibility Testing: Effect of Oxygen Aging on Ignition and Combustion Properties
Authors: Waller JM , Haas JP , Beeson HD
Published: April 2008

The oxygen (O2) compatibility of six polymers used in O2 service was evaluated after 48 h exposures at 121 °C (250 °F) to O2 pressures of 620 and 6200 kPa (90 and 900 psia). Three elastomers were tested: chloroprene rubber (C873-70), fluorocarbon rubber (Viton® A), and silicone rubber (MVQ type); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel® 42), polytetrafluoroethylene (PTFE Teflon® 500A), and polychlorotrifluoroethylene (Neoflon® CTFE M400H). Post-aged changes in mass, dimensions, tensile strength, elongation at break, durometer hardness, and thermomechanical properties were evaluated. For selected materials, gaseous nitrogen- (GN2-) aged controls were used to ascertain the effect of thermal versus oxidative degradation. Finally, the effect of O2 aging on selected ignition (AIT) and combustion (ΔHc) properties was determined. As expected, aged polymers were less ignitable and combustible. Special attention was given to Neoflon CTFE; namely, the possible effect of percent crystallinity (quick- versus slow-quenched) on the aging, ignition, and combustion behavior was evaluated.
Igniter Effects on Metals Combustion Testing
Authors: De Wit JR , Steinberg TA , Stoltzfus JM
Published: April 2008

The combustion of 0.32-cm-diameter pure iron rods in gaseous oxygen under normal and reduced gravity conditions has been investigated to determine whether the upward Regression Rate of the Melting Interface (RRMI) and other burning characteristics are affected by the type of igniter material (wire) used. The experiments performed involved igniting the samples in normal gravity with different types of igniter wire at the two separate test pressures of 0.69 and 6.9 MPa (100 and 1000 psia). The igniter wires used were pure aluminum wire, pure iron wire and aluminum-palladium (Pyrofuze®) wire. The results have shown that in normal gravity the RRMI is unaffected by the type of igniter wire used when measured after the first two drops of molten oxide products have detached from the burning sample. However, the ignition event and subsequent first stages of burning of the iron rods were significantly different for the different igniter wires. Post-test microanalysis of test samples showed that in normal gravity, no igniter material was present with the formed oxide products on the end of the test sample rod. However, post-test microanalysis of test samples burned in reduced gravity showed a film of palladium, introduced by the Pyrofuze® igniter wire, coating the interface between the melted and resolidified portion of the rod and the formed oxide products. The physical orientation and location of the palladium film and the fact that palladium acts as a catalyst in many oxidation reactions suggests that reduced gravity burning could be influenced by the choice of igniter wire and further experimentation is warranted. Additionally, the palladium present during the ignition event in normal gravity tests may act as a catalyst to further promote the ignition of the sample and influence the initial stages of burning.
A Fluid Flow Analysis of the Gaseous Impact Test
Authors: Ducrocq J , Barthelemy H , Roy D
Published: April 2008

The Gaseous Impact Test is simulated using fluid dynamics numerical models. Pressure overshoots observed at Centre de Technologies et d'Expertises are matched by one-dimensional computations. Peak temperatures are evaluated when including irreversible processes. Formation of a temperature gradient within the hot gas plug has been identified and an explanation is provided. The influence of geometrical design parameters is studied. Temperature history requires use of a two-dimensional model for it enables description of vortex-induced mixing as a consequence of the reflected shock bifurcation at the test tube end. A cellular structure is formed in the pressure field. Skin temperature of different wall materials has also been evaluated. Short versus long test tube effects are discussed.
Failure Investigation of a Welding Regulator Fire
Authors: Newton BE , Hull WC , Beeson H
Published: April 2008

This paper describes the investigation and failure analysis of a welding regulator fire that resulted in explosive energy release and injury to an operator. The failure analysis revealed that an organic contaminant in the form of an insect had entered the cylinder valve prior to attachment of the regulator. Ignition of the insect and nest materials led to an explosion-like overpressure that blew the high-pressure poppet through the nozzle and forcibly separated the regulator bonnet from the main body. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) on the residue from the fire-damaged components confirmed that insect nest material was present at the time of the fire. Autogenous Ignition Testing (AIT) on similar insect debris revealed a very low ignition temperature and probable high heat of combustion. The explosion-like energy release was felt to be related to a momentary containment of the fire in the early stages of the combustion event which led to greater involvement of the cylinder valve's nylon seat and resulted in increased reaction kinetics.
Tests of Combustion of Aluminum Packing and Trayed Columns
Authors: Fano E , Barthelemy H , Lehman J-Y
Published: April 2008

The flammability of structured packing made of thin aluminum sheet (0.2 mm) for use in oxygen service has been investigated by several companies and the results have been published since the first paper was given by Dunbobbin et al. [1]. All these previous tests involved small samples of about 100 g. The propagation on such small samples is quite difficult to analyze especially with LOX flowing down, as in actual operating conditions. The results of these tests have been published in STP 1197 [2]. Three sets of tests have been performed on larger samples to closely reproduce the operating conditions of cryogenic columns. The first set involved larger packing samples (650 g) above a LOX pool, heated to create a gas flow. The second set involved seven complete columns, 30 cm diameter × 2 m high, containing packing with LOX flowing down. The ignition pack was similar to the first set of samples. The third set involved twelve complete columns, 30 cm diameter × 2 m high, with 20 aluminum trays, in normal working conditions. The ignition cell failed in six tests so only six tests were significant. Results of this investigation performed on large samples were used when preparing the CGA pamphlet G-4.8 published in 1993 [3], which concluded that aluminum structured packing in ASUs introduces no additional risk, compared with aluminum trays.
AASHTO T307 — Background and Discussion
Authors: Groeger JL , Rada GR , Lopez A
Published: April 2008

The current AASHTO protocol for determination of resilient modulus of soils and aggregate material (T307-99) is based largely on Long Term Pavement Performance (LTPP) Protocol P46. The LTPP protocol evolved over a number of years and has had numerous contributors (including significant guidance and input from the authors of this paper). To-date, over 3000 samples have been tested with P46 and results of this testing effort will have far-reaching implications in the development of performance models for pavement structures. Many lessons were learned during development of P46 and this history is documented in a companion paper. The present paper provides a background of the reasons and rationale behind some of the major technical aspects of P46, and by direct association, AASHTO T307. The paper also offers suggestions for improvement or modification of T307. It is hoped that this discussion will lead to a deeper understanding of the test procedure and perhaps facilitate a discussion of the direction the T307 procedure should follow in the future.
A Fully Automated Computer Controlled Resilient Modulus Testing System
Authors: Marr WA , Hankour R , Werden SK
Published: April 2008

This paper describes a fully automated computer controlled testing system for performing resilient modulus tests. It describes the use of a PID adaptive controller to improve the quality of the test and reduce the labor required to run the test. It also addresses some of the difficulties and technical details for running a resilient modulus test according to current test specifications.
The Use of Continuous Intrusion Miniature Cone Penetration Testing in Estimating the Resilient Modulus of Cohesive Soils
Authors: Mohammad LN , Herath A , Titi HH
Published: April 2008

This paper presents an application of the continuous intrusion miniature cone penetration testing in evaluating the resilient modulus of cohesive soils. Four cohesive soils were selected for the field and laboratory testing program. The field tests were performed on these soils using the continuous intrusion miniature cone penetration test system. The laboratory testing program included repeated load triaxial tests on undisturbed soil samples, and soil physical and strength properties testing. A statistical analysis was performed on the test results of two soils to develop a correlation among the resilient modulus, cone penetration test parameters, in-situ stresses, and soil properties. The model was used to predict the resilient modulus of other two soils. The predicted and measured values of the resilient modulus were in agreement.
The Interaction and Performance of Commercial and Experimental Fluorosurfactants and Commercial Floor Polish
Authors: Cartwright BT
Published: April 2008

Recently, the leading fluorosurfactant used in floor polish applications has been removed from the market. In an effort to qualify replacements, a thorough study of the use of fluorosurfactants in floor polish applications has been conducted. Water based films have always been subject to temperature and humidity differences in real world applications. Floor polishes are formulated to be useful under these conditions of high or low humidity and high or low temperatures. Certain conditions will also affect the flow and leveling performance of these films. Stress conditions, those on the boundaries of real world examples, can define the performance of a floor polish in today's market. Under these stress conditions fluorosurfactants perform differently and affect the performance and characteristics of a floor polish, including failure.
Coefficient of Friction - An Overview of Floor Surfaces, Polishes and Maintenance Interaction
Authors: Hughes S
Published: April 2008

Floor care and slip resistance has been fundamentally accepted for centuries. The advent of scientific investigation of specific interactions between flooring materials and traction is a relatively new subject, being pioneered by Hunter during the 1920's and continued by James during the first half of the 20th century. This work established the standard utilized by Underwriters Laboratories, Inc., and eventually to the standard by ASTM D 21, the committee on Polishes. Continued scientific study, correlated with actual field experience solidified the importance of this work and established the benchmark for determining the static coefficient of friction of a polished surface, as well as creating a means for examining the relative slip resistance of other surfaces intended for pedestrian passage.
Historical Development and Future Prospects of Structural Silicone Sealants in China
Authors: Yue-lin W , Hong-min W , Li-min W
Published: April 2008

In China, the first four-sided structurally glazed curtain wall building, the Beijing Great Wall Hotel, was constructed in 1987. Since then, glass curtain wall buildings have become popular, and it is estimated that about 5 million m2 of coated glass are fabricated and installed by way of Structural Silicone Glazing (SSG) every year. Structural silicone sealants from Dow Coming and General Electric (GE) held the largest share of China's market until 1998. China developed and decreed its own national standard GB 16776-1997 for structural silicone sealants that is comparable with ASTM C 1184 but that has more stringent requirements in terms of tensile strength and adhesion to substrates. All structural silicone sealants, whether they are manufactured domestically or overseas, are required to be approved by the Chinese government based on the GB 16776 specification, and only certified products are permitted for use in Chinese glass curtain wall engineering. There are currently eight foreign structural silicone sealants and ten domestic products approved for installation of glass curtain walls in China. This paper covers China's market, national standard, and prospects of structural silicone sealants.
Moisture Conditions of Substrates and Effect on Adhesive Bond of Sealants
Authors: Kenney ME , Kenney RJ
Published: April 2008

The paper explores the relationship between elevated moisture in sealant substrates and the ability of sealants to develop and maintain adequate bond strength. Documented sealant adhesive failures, due to moisture conditions of substrates, and the use of various sealant primers and surface treatments on new construction and renovations of existing buildings are reviewed. Laboratory and field tests reveal that, typically, a low adhesive bond develops when elevated moisture levels are present, even when substrates feel dry to the touch, and particularly when certain primers are used. Laboratory tests further show that the use of certain primers, even when the sealant substrate is very damp, can greatly increase sealant bond strength and the ability of sealants to remain bonded even when sealants are immersed in water for extended periods after initial cure.
Effect of Foam Backer Rod on the Deep Section Cure of One-Part Sealants
Authors: Iglauer S , Hutchinson AR , Lee TCP
Published: April 2008

High performance elastomeric sealants are commonly used in cladding systems and curtain walling of modern high-rise buildings. Ideally, they should not stick to, or be affected by, the presence of a backer rod (foam). The cured skin thickness development for three one-part sealants (silicone, polyurethane, modified silicone) in combination with four different foams was examined. The influence of water (water immersion of the sealant and the use of wet foam) was also investigated. It was found that closed cell polyethylene foam clearly inhibited the cure, in some cases significantly, whilst open cell polyurethane foam did not influence the cure speed. It is predicted that a combination of very slow cure and movement during cure would result in significantly reduced joint performance.
Insights into the Use of Biocides in Silicones Sealants: Test Methods and Durability Aspects
Authors: de Buyl F , Gastaldi H
Published: April 2008

Especially in humid or wet environments, such as bathrooms and kitchens, silicone sealants must be protected by the use of biocides from the growth of microbiological agents, i.e. fungi (mould or yeast), bacteria, or algae, to ensure longevity of the aesthetic aspect of sealing joints. Environmental aspects of using biocides, efficacy of active ingredients, and appropriate test methods to be used in order to assess ultimate performance and predict service-life durability under various weathering conditions (underwater leaching, UV exposure, outdoor) are all important aspects that require careful consideration.

Based on the experiences acquired in Rohm and Haas and Dow Corning laboratories, respectively, we have shown the importance of pre-conditioning the specimens, and selecting the appropriate test method to assess the anti-fungal protection of sealants. Among the various methods developed for that purpose, i.e., CAN2-19.0-M77, Wallhauser test method, NFX 41-514, ISO 846 and ASTM G21-96, we have shown that ISO846, method B, is the most appropriate for assessing the efficacy of biocides in protecting sealants against fungus growth in sanitary environments. We also discuss the choice of the appropriate inoculums and challenge testing conditions, as well as the key aspects that are important for proper interpretation of the ratings resulting from the challenge tests.

Comparative testing carried out with various silicone sealant systems enabled the identification of active ingredients adequate to provide durable protection of a cured silicone sealant, in particular after underwater leach-out conditioning, which for weatherproof sealing in residential glazing and sanitary applications is an important requirement. Comparison of the ratings obtained before and after underwater leaching provides therefore insights that allow estimation of the decrease of anti-fungal efficacy over time during service-life. Key selection criteria that an effective biocide needs to fulfill are also suggested.
Durability of Horizontal Sealant Joints
Authors: Nicastro DH , Gorman PD
Published: April 2008

There is an epidemic of premature horizontal sealant joint failures throughout the United States; they appear to be even more prevalent than sealant failures in vertical (wall) joints. In addition to the usual problems (leakage, property damage, poor indoor air quality) associated with vertical joint failures, horizontal joint failures can result in personal injury from trip and fall incidents. This paper presents case histories of horizontal sealant joint failure investigations; a summary of research on the resistance of horizontal joints to concentrated loads; a test method for penetration resistance; data collected from numerous projects throughout the United States, including load resistance test results and observations of the joint configuration, materials, and condition after varying years of service; and recommendations for durable horizontal sealant joint design and installation.
Sealant Failure Morphology — The Important Criterion of Equipment Selection for Weathering Studies
Authors: Wypych G , Kuberski S , Lee F
Published: April 2008

The objective of this study is to identify criteria for the selection of laboratory equipment for weathering studies of sealants that allow improvements in the correlation of accelerated weathering results with outdoor exposure results.

The Approach of the study is to compare physical-chemical characteristics of sealants, which were exposed to various laboratory methods and outdoors. Polyurethane, silicone, polysulfide, and Kraton®-based sealants were selected for this study. Sealants were exposed outdoors to wet (Florida) and dry (Arizona) climatic conditions. The laboratory studies were conducted in a fully equipped xenon-arc weather-ometer simulating wet climate conditions, a xenon-arc tabletop device, simulating dry climatic conditions, and a fluorescent UV condensation weathering device.

The degradation of the sealant surface on exposure to both natural and laboratory conditions was compared on the basis of morphological changes. The following methods were used to study chemical and morphological changes: TGA, DSC, polarized light microscopy, and image analysis. The results of physical-chemical studies are related to the esthetic performance of sealants measured by an image analysis to determine the rate of crack formation and the development of characteristic morphological features of crack formation in different sealants.

In this analysis, the exposure to natural conditions is used as the point of reference. The physical-chemical changes due to weathering in laboratory devices are compared with outdoor exposure results to verify similarity of the failure morphology. A valid laboratory weathering procedure is expected to result in the same degradation mechanism and induce similar modes of failure as outdoor weathering.
Harmonization and Optimization of Weathering Test Methods for Building and Construction Sealants and Adhesives
Authors: Searle ND
Published: April 2008

Sealants and adhesives play a vital role in building engineering and are expected to perform well for at least 20 years. However, many fail prematurely, partly because of inadequate information on their long-term resistance to the effects of solar radiation, heat/cold, moisture, atmospheric pollutants and mechanical strain. The laboratory accelerated weathering tests, a necessity for determining in a short time whether products are suitable for the intended use, often fail to identify products with poor in-use performance. The validity of the test results depends on optimization of the test parameters so that aging effects of field conditions on sealants can be closely simulated. Simulation of the spectrum of solar radiation by the artificial light source is a critical factor. Simulation of the temperature, amount and type of moisture and mechanical strain that sealants experience under use conditions is also significant.
Evaluation of a Carbon Thermoplastic to Titanium Bonded Joint
Authors: Leon GF , Trezza MF , Hall JC , Bittick K
Published: April 2008

Carbon thermoplastic (AS4/APC-2) to Titanium (6Al-4V) bonded and bonded/bolted joint designs were developed for use in the marine, Composite Storage Module (CSM) for the Office of Naval Research. Finite element modeling of the design was done using PATRAN and subsequent analyses were performed using the ABAQUS finite element code. In order to validate the design and to provide a measure of confidence with the fabrication and assembly of the joint, three, full-scale test specimens were designed, fabricated and tested in a representative tensile load environment. The three joint specimens were fabricated by Production Products and tested at the Naval Surface Warfare Center, Carderock Division. The carbon specimens were 1.04 m (40.9 in.) in length by 0.254 m (10 in.) in width by 28.5 mm (1.12 in.) in thickness and captured in the 70 mm (2.75 in.) thick titanium. Two of the specimens were bonded joints and the third was a bonded/bolted joint. The specimens were subjected to three cycles of tensile loading on a 2447 kN (550 kip) MTS test machine with the last loading cycle to failure. One bonded joint specimen failed in the adhesive bondline at 378 kN (85 kips) and the second bonded joint failed at 600 kN (135 kips). The bonded/bolted joint specimen showed adhesive failure at 489 kN (110 kips) and complete failure in the bolts at 556 kN (125 kips). This paper discusses the theoretical predictions, experimental results and correlation.
Bolted Joint Analyses for Composite Structures — Current Empirical Methods and Future Scientific Prospects
Authors: Hart-Smith LJ
Published: April 2008

One purpose of this paper is to describe and explain some highlights in the history of the analysis and design of bolted or riveted joints in fiber-polymer composite laminates. The second is to project into the future, where it might become practical to replace today's empirical analytical tools, which need copious test data to enable them to be applied, with physics-based composite failure criteria of universal applicability that need very few intrinsic material properties. The paper focuses on the analysis tools and is not a compendium of available test data. The paper begins with a review of the governing geometric parameters, along with their influence on which failure mode will dominate. The concept of optimum joint geometries is introduced, to show how to maximize the gross-section laminate strength and, thereby, to minimize the weight of these structures. It progresses to the two widely used analysis tools, developed years ago at the Long Beach and St. Louis divisions of the former McDonnell Douglas Corporation. The Douglas model is applied via explicit formulae, in conjunction with an empirically established stress-concentration relief factor. The latest forms of these equations are presented here, having changed little since they were first proposed almost 30 years ago. The McDonnell model, identified by the code name BJSFM is also based on algebraic solutions, but is encoded to enable a more thorough assessment to be made of the entire stress field, rather than just the most critical two locations. This code also relies on empirically determined correlation factors, in the form of characteristic offset distances, sometimes mistakenly believed to be true material properties. These same factors can also be applied to modify the predictions of finite-element analyses. The importance of using simple comprehensible models is stressed. The former model can also be used with the non-linear multi-row computer code A4EJ, again with very little need of test data — provided that the fiber pattern does not differ excessively from the quasi-isotropic lay-up. Excessively orthotropic fiber patterns are shown to be unacceptably weak at bolt holes and in need of a disproportionately large number of experimental test data to cover the many additional failure modes that cannot occur for close-to-isotropic fiber patterns. The paper closes with a glimpse of what the new SIFT (Strain-Invariant Failure Theory) for fiber-polymer composites, developed within the Boeing Company and already accepted for use at many locations outside, might do for this technology in terms of finite element analyses that need only five intrinsic material properties for each fiber-polymer combination, regardless of fiber pattern and joint geometry. The opportunities for drastic reductions in the cost of test programs, and accelerated schedules through not having to wait for specific tests for each joint, are clearly very powerful.
Design of a Learning Binding for Alpine Skiing
Authors: Gulick DW , Mote CD
Published: April 2008

Advances in binding design for alpine skiing have been unable to eliminate injuries to the lower leg and knee. Studies to identify appropriate release settings have concluded that the maximum forces during skiing are not predictable using any measurable anthropometric parameters, and furthermore, that they are variable during skiing due to changes in snow conditions, skiing style, and other unmeasurable variables. This paper considers the feasibility of an alpine sking binding with variable release settings that adapt to changes in the force magnitudes during skiing. Release settings are determined according to difference equations involving previous and current force measurements. To facilitate comparison with contemporary commercial bindings, the learning binding design includes three release modes: external twist and internal twist governed by the lateral force component at the toe and forward lean governed by the vertical force component at the heel. Binding forces measured during more than 36 min of skiing experiments are used to determine values for the design parameters within the adaptive algorithm. Then the performance of the learning binding is judged by comparing the release settings to the settings recommended by ASTM Standard F 939-93.

The release settings of the learning binding algorithms are on average more than 22% less than the ASTM recommended settings for each skier, with a maximum reduction of 50% for one subject. No inadvertent releases are predicted throughout the skiing data. The reduced release settings adapt to temporal changes in forces and yield earlier releases in several falling scenarios experienced in the data. These results suggest that a learning binding can significantly improve the safety of alpine skiing.
Variable Influence in On-Snow Ski Boot Pressure Measurements
Authors: Goodwin DA , Ford K
Published: April 2008

This study compared the effects of several variables with respect to measurement of kinetic data collected during alpine skiing. The Novel Pedar System, a portable, in-shoe, pressure distribution measurement system, was used to directly collect field data. One subject with prior experience as a national level racer participated in the study. Statistical comparisons were made between dependent variables, such as contact time, maximum force, and force-time integral, and independent variables, such as instrumentation position and turn type. The results demonstrate that there were statistically significant differences between some of the independent and dependent variables. The kinetic results show agreement with previous studies and are, therefore, useful as elementary input data for empirical models, which could help estimate pressure distribution along the running surface of a ski during skiing. When alpine ski properties, ground (surface) conditions, and boot loading are considered collectively, these models could be used to help ski manufacturers predict ski performance earlier in the design and development stages and evaluate “risk of injury” situations.