bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress and Energy Based Fracture Conditions for Fiber-Wise Splitting in Composites
Authors: Suresh N , Wang ASD 
Published: March 2009

This paper discusses the critical conditions for an interface-related fracture in epoxy-based graphite fiber-reinforced structural laminates. The specific fracture mode under consideration is that of a splitting crack along the fiber direction. Fiber-wise splitting often occurs in laminates that have holes, sharp notches, or cutouts due to stress concentration near these locations. The problem has been treated as an interface shear-dominated fracture, and methods of fracture mechanics are frequently employed for the purpose of analysis. Within this context, suitable mixed-mode fracture criteria are required. Past studies have used the strain energy release rates in the formulation of the desired criteria, and, depending on the test model used, the formulated criteria came in a variety of forms. Among several possible forms, the one form involving the total strain energy release rate (GI + GII) = constant has often been recommended. Recently, however, a form employing the stress intensity factors KI and KII has been deduced from a set of fiber-wise splitting test data. An apparent difference existed between criterion deduced based on G and that deduced based on K. Theoretically, of course, the two deduced criteria should be mutually equivalent.
This paper discusses the reasons for the apparent difference and offers a consistent interpretation of the respective set of test data. When this is done, a unified criterion, be it expressed in G or in K, can then be deduced without contradiction.
Stacking Sequence Effects and Delamination Growth in Graphite/Epoxy Laminates Under Compression-Dominated Fatigue Loading
Authors: Komorowski JP , Lefebvre D , Roy C , Randon C 
Published: March 2009

The effect of free-edge stresses on the fatigue of graphite/epoxy laminates was evaluated numerically and experimentally. Reported are results of static and compression-dominated (R = -3.75) fatigue tests on AS4/3501-6 and IM6/5245C using unnotched specimens. Two different stacking sequences of 18-ply laminates were tested. The lamination was (0°/45°/90°) (44.4%, 44.4%, 11.1%). Damage development was monitored using ultrasonic C-scans, photoelastic coatings, and optical microscopy.
Stacking sequence had a significant influence on compressive failure strength. Differences in the fatigue lives of the two stacking sequences were close to two orders of magnitude. Damage always initiated at the edge and was related to the magnitude of interlaminar shear stresses. Well-defined stages of the fatigue process leading to final failure were observed.
A computer code was used to predict the life of the specimens. The code has yet to be calibrated for an unnotched delamination failure mode.
The Role of Geometry and Crack Growth on Constraint and Implications for Ductile/Brittle Fracture
Authors: O'Dowd NP , Shih CF , Dodds RH 
Published: March 2009

A family of self-similar fields provides the two parameters required to characterize the full range of high- and low-triaxiality stress states that can exists near the tip of a mode I stationary crack. The two parameters, J and Q, have distinct roles: J sets the size scale of the zone of high stresses and large deformations, while Q scales the near-tip stress distribution relative to a high triaxiality reference stress state corresponding to a long crack in an infinitely large body.
The evolution of mode I near-tip fracture states under plane strain conditions is addressed in two parts. We begin by discussing crack geometry and load effects on near-tip constraint for a non-growing crack. Details aside, increased loading (plastic deformation) in finite size geometries is accompanied by a steady loss of constraint. This behavior is explained and quantified relative to a high triaxiality reference stress state, or the Q=0 state, using results from several crack geometries.
The second part of this work focuses on crack growth effects on constraint. Here steady-state crack growth provides a basic result. First, crack growth under well-contained yielding elevates near-tip constraint. Second, the maximum stress elevation due to growth is set by the steady-state high triaxiality stress state. The competing effects of constraint elevation due to crack growth and constraint loss due to increased plastic deformation in a finite size geometry offers insight into the transition to a brittle fracture mode after some amount of ductile tearing.
A Comparison of J and CTOD as Elastic-Plastic Fracture Characterizing Parameters
Authors: Gordon JR , Neale BK , Wang Y-Y 
Published: March 2009

This paper presents results of experimental and numerical analysis studies to investigate the relationship between J and CTOD and assess whether they are, indeed, both suitable elastic-plastic fracture characterizing parameters. Detailed elastic-plastic finite element analyses were undertaken for SE(B) specimens with a/W ratios of 0.1, 0.2, 0.3 and 0.5. Analyses were performed for a range of material stress-strain curves and yield strength levels to determine the influence of work hardening and yield strength on the J-CTOD relationship.
It was found that: 1. The standard CTOD estimation procedure can give rise to significant errors in the predicted CTOD for high work hardening materials (σTS/σYS &gt; 1.5) .2. For SE(B) specimens, the following J-CTOD correlation can be used to relate J to CTOD J=mTSσTSCTOD where mTS = 1.21 + 0.95 (a/W) − 0.5 (a/W)2. 3. J and CTOD do not always produce consistent trends when used to characterize the fracture toughness of different materials, i.e., the toughness ranking based on J is not necessarily the same as the ranking obtained using CTOD.
Improved Load Ratio Method for Predicting Crack Length
Authors: Chen X , Albrecht P , Wright W , Joyce JA 
Published: March 2009

The elastic compliance from unloading/reloading sequences in a load-displacement record estimates well crack length in elastic-plastic fracture toughness tests of compact tension [C(T)] and bending type specimens. The need for partial unloading of the specimen makes it difficult to run the test under static loading and impossible under either dynamic loading or very high temperatures. Furthermore, fracture toughness testing in which crack length is determined from elastic compliance requires high precision testing equipment and highly skilled technicians. As a result, such tests are confined usually to research laboratories and seldom used under production settings.
To eliminate these problems, an improved load ratio method of predicting crack length is proposed that utilizes only the recorded load versus load-line displacement curve (or load versus crack-mouth-opening displacement curve) without unloading/reloading sequences. As a result, the instrumentation is much simpler than in the elastic compliance or potential drop methods. If only a monotonic load-displacement record is to be measured the fracture toughness test becomes almost as simple to perform as a tension test.
The method described here improves in three ways the “original load ratio method” proposed by Hu et al. First, a blunting term is added to the crack length before maximum load. Second, a strain hardening correction is included after maximum load. And, third, the initial crack length and the physical (final) crack length measured at the end of the test serve to anchor the predicted crack lengths, forcing agreement between predicted and measured values.
The method predicts crack extension with excellent accuracy in specimens fabricated from A302, A508, and A533B piping and pressure vessel steels, A588 and A572 structural steels, and HY-80 ship steel.
The Effect of Varying Levels of Induced Duct Leakage on Differential Pressures in a Florida House
Authors: Kozik AC , Oppenheim P , Hintenlang D 
Published: March 2009

The objective of this research is to quantify the effect of varying levels of induced duct leakage on differential pressures and subsequent radon levels in a typical Florida residence. The heating and air conditioning (HAC) system of a residence was modified with the addition of a fresh air ventilation system. This modification provided the ability to simulate either a return leak or a supply leak in the HAC system. The amount of leakage induced can be varied using flow control dampers and an auxiliary fan located in the ventilation system ductwork.
The house was pressurized and depressurized by adding 0.06 m3/s of ventilation air into the return side and removing 0.05 m3/s of ventilation air from the supply side of the air handling system, respectively. The subsequent changes in house pressure and ventilation rates reduced the indoor radon concentrations from 1865 Bq/m3 to 170 Bq/m3 under pressurized conditions and to 305 Bq/m3 under depressurized conditions.
A Description of the New ASTM Test Method E 1424, Used for Measuring Fenestration Air Leakage at Differential Temperatures and Pressures
Authors: Kehrli DW 
Published: March 2009

A new committee has been developed by ASTM Committee E6 for measuring air leakage rates of fenestration products under imposed conditions of differential pressures and temperatures. This new method is different from the long-standing, internationally referenced ASTM Method E 283 in that it is performed under temperature differentials across the test specimen similar to ASTM C 236 and C 1199, and AAMA 1503-88.
This new method will show the impacts of expansion and contraction, shrinkage, compression-set, fabrication and design integrity, and material and component interactions in the air leakage rates of window and doors products.
This paper compares the two methods and provides some typical test data.
Air Leakage Characteristics of Various Rough-Opening Sealing Methods for Windows and Doors
Authors: Proskiw G 
Published: March 2009

The air leakage characteristics of eight methods of sealing, or otherwise treating, the rough openings (R/O) found around window and door frames were evaluated under laboratory conditions. The eight methods studied were: 1. no treatment (empty), 2. conventional (fiber glass), 3. densely packed, fiber glass, 4. backer rod, 5. casing tape, 6. poly-return, 7. poly-wrap, and 8. foamed-in-place urethane.
The untreated R/O (Method 1) displayed the greatest leakage while the second largest occurred using the conventional practice of packing fiber glass into the R/O space (Method 2). In contrast, Methods 5, 6, 7 and 8 were able to reduce R/O leakage to negligible levels.
To relate these results to the overall building leakage, an estimate was made of the percentage of the total building leakage which would occur through the R/Os in a typical 97 m2 (1040 ft2) bungalow. Two levels of total house airtightness were assumed: 1.5 air changes per hour at 50 Pa (ac/h50) representing tight construction and 5.0 ac/h50 (representing loose construction). For the tight house with Method 1 (no treatment), the R/O leakage accounted for 39% of the total house leakage; with Method 2 (conventional), this figure dropped to 14%. With each of Methods 5 to 8, the contribution of R/O leakage to total house leakage was less than 1%. For the loose house and Method 1, the R/O leakage was 12% of the total; with Method 2, it dropped to 4% and with Methods 4 to 8, it was less than 1%.
The incremental builder cost of each technique (i.e., exclusive of mark-up for overhead, profit, etc.) was estimated assuming Method 2 as conventional practice with a base cost of zero. Incremental costs ranged from a low of $18 per house for the urethane approach (Method 8) to $84 per house for the poly-wrap technique (Method 7).
Effects of Weatherproofing Sealants on Building Aesthetics
Authors: O'Neil VK , Klosowski JM , Altes MG , Bergman LC 
Published: March 2009

In today's commercial construction and renovation markets, the building owner desires a structure that remains both free of leaks and aesthetically pleasing for many years. It is assumed by many designers that within the group of high performance sealants “a silicone is a silicone”, indicating that a sealant in a generic class carries with it both the positive and negative characteristics associated with that class. Silicone is generally considered the premium performing material, exhibiting excellent durability. However, occasional appearance problems, generically assigned to silicones, have swayed some specifiers away from silicones on some substrates. The contributors to appearance problems are many, and only a few are specifically related to the sealant used.
This paper describes several sealant related phenomena which can contribute to building aesthetic problems. These include sealant dirt pick-up, substrate staining and fluid migration into porous substrates. Each of these terms is defined in detail. Laboratory and weathering tests are described which indicate how quickly and how severely aesthetic problems develop. Results are reported for sealants representative of the following types: plasticized silicones, unplasticized silicones, unplasticized surface-modified silicones, plasticized polyurethanes, unplasticized polyurethanes and plasticized modified polyethers. The influences of local environment, joint design and application technique are also discussed.
Primerless Polysulfide Building Sealants
Authors: Fiorillo AR , Harding JR 
Published: March 2009

Polysulfide polymers have a long history of success as the base polymer in building sealants, but these sealants usually require the use of primers to ensure good adhesion to the various substrates used in building construction. Usually different primers are required for porous and non-porous substrates.
Whenever primers are required to achieve good adhesion, there is always the risk that the primer may be improperly applied or that some areas may be skipped during the priming. There is also the need to ensure that the primer does not get on the building surface and cause discoloration.
Polysulfide sealants have now been developed that incorporate adhesion promoters that eliminate the use of primers. These sealants have been tested against ASTM C-920-87, Specification for Elastomeric Joint Sealants, as a class 25 building sealant on glass, anodized aluminum and concrete and have easily met all the requirements.
In-situ Re-Glazing of Structural Sealant Glazing Joints a Case History
Authors: Wilson MD 
Published: March 2009

Structural sealant glazing has attracted considerable attention due to its inherent glass retaining method which allows smooth exterior glass walls interrupted only by narrow weatherseal joints. The technique has become increasingly popular with owners and architects since its inception in the early 1970's.
In 1990 it was determined that a five story office building nearing completion had structurally glazed insulating glass units in multi-story bay windows that had been incorrectly installed. Verification of the required structural glazing design was performed to compare with the as-built conditions, and re-glazing the structural silicone glazing joints was indicated to be warranted.
The construction team desired to perform the re-glazing without removing the installed units for cost and time reasons. In-situ re-glazing of a single insulating glass unit was performed as a test of the proposed remedial technique. The test was deemed successful and the remaining defectively glazed units were re-glazed in-situ.
The design and construction circumstances that led to the situation requiring the re-glazing, the lessons learned during their resolution, the in-situ re-glazing techniques utilized, and comments on the need for potential re-glazing of structurally glazed systems are presented.
Understanding the Mechanism of Dispersion through Oil Droplet Size Measurements at Sea
Authors: Lunel T 
Published: March 2009

Measuring the oil droplet sizes produced when oil is dispersed at sea is a critical stage in understanding the process of dispersion. A laser Phase Doppler Particle Analyzer (PDPA) with a measurement range 1–300μm has been developed which can distinguish between oil and the background signal from air bubbles, suspended sediment and plankton at sea. The resulting improvement in the signal to noise ratio has enabled us to measure oil droplet size in situ below an oil slick.
Measurements in the North Sea indicate that the droplet size distributions for a variety of oils and oil-dispersant combinations have a number median around 20 microns and are independent of the oil/oil-dispersant combination. Although the droplet size distribution is similar what is very different for these different oil-dispersant combinations is the number of droplets in the 1–70μm size range. n the basis of the measured size distribution and model predictions of the vertical movement of these droplets at sea we define dispersed droplets ⩽ 70μm and suspended droplets &gt; 70μm. Efficient dispersants produce a large number of droplets in the 1–70μm size range while poor dispersants or an untreated slick produces a smaller number of oil droplets in this size range.
Comparison of the oil droplet size distribution of naturally and chemically dispersed oil indicates that the rate determining step in the process of dispersion is the splitting of large droplets (70–300μm diameter) to produce oil droplets in the size range 1–70μm. The consistency of the oil droplet size distribution for a variety of oil and oil-dispersant combinations suggests that the splitting process is via the shear forces imparted by microscale turbulence. The proposed mechanism has implications for both the modelling of the process at sea and the design of laboratory dispersant tests.
The Effectiveness Testing of Oil Spill-Treating Agents
Authors: Fingas MF , Kyle DA , Laroche N , Fieldhouse B , Sergy G , Stoodley G 
Published: March 2009

Laboratory effectiveness tests have been developed for four classes of oil pill treating agents: solidifiers, demulsifying agents, surface-washing agents and dispersants. Several treating agent products in these four categories have been tested for effectiveness. The aquatic toxicity of these agents is an important factor and has been measured for many products. These results are presented.
Solidifiers or gelling agents solidify oil. Test results show that solidifiers require etween 16% and 200% of agent by weight compared to the oil. De-emulsifying agents or emulsion breakers prevent the formation of or break water-in-oil emulsions.
Surfactant-containing materials are of two types, surface-washing agents and dispersants. Testing has shown that effectiveness is orthogonal for these two types of treating agents. Tests of surface washing agents show that only a few agents have effectiveness of 25 to 55%, where this is defined as the percentage of oil removed from a test surface. Dispersant effectiveness results using the “swirling flask” test are reported. Heavy oils show effectiveness values of about 1%, medium crudes of about 10%, light crude oils of about 30% and very light oils of about 90%.
Effectiveness of Chemical Dispersants under Breaking Wave Conditions
Authors: Mackay D 
Published: March 2009

A study is described in which the effectiveness of Corexit 9527 on Alaskan North Slope crude oil was assessed by conducting laboratory and wave basin tests. Three laboratory dispersant test systems were used: the MNS, Labofina and EXDET procedures. It was concluded that for the present purposes the EXDET system was most suitable, and it was used for subsequent tests. The dependence of effectiveness on dispersant to oil ratio, extent of weathering, temperature, water salinity, energy level and the presence of emulsified water (mousse) were determined.
The results were used to guide a subsequent program of tests at the Esso Resources Canada Ltd. Wave Basin in Calgary in which the effectiveness was determined under breaking wave conditions. From the results a correlating equation was developed to express effectiveness as a function of dispersant to oil ratio and delay time between dispersant application and the onset of breaking waves. Significant quantities of oil were dispersed under breaking wave conditions, even at what are conventionally regarded as low dispersant to oil ratios.
The implications of the results for assessing the actual and potential extent of chemical dispersion following the EXXON VALDEZ spill in March 1989 are discussed. Assuming that the dispersion efficiencies from the wave basin could have been achieved at the incident, it is believed that because of the onset of the storm with breaking wave conditions some 60 hours after the grounding, approximately 38% of the spilled oil could have been dispersed had available dispersants been applied to the spilled oil in the days following the grounding.
Neural Networks for Materials Data Analysis: Development Guidelines
Authors: Smets HMG , Bogaerts WFL 
Published: March 2009

Although the basic concepts of neural networks date from 1943, it is only in the last decade, with the discovery of new robust learning algorithms, that the research in the area of neurocomputing has boomed, resulting in a myriad of new and practical applications. Especially in the area of data analysis, with the ultimate goal to extract concentrated value from diffuse and intrinsically less valuable raw data, neural networks seem prone to success. In this context, neural networks have become mainstream technology in the domain of materials data.
Since about three years, research on the applicability of neural networks in the corrosion domain has been conducted at our department. Several networks were successfully trained to predict the corrosion risk of materials in various environments. They form part of the knowledge incorporated in an expert system for corrosion troubleshooting and intelligent risk determination.
In this paper, we will discuss some of the bottlenecks encountered when developing neural networks for data modeling. Tips will be given on how to find a good neural network architecture. However, as most of the failures of neural networks can be brought back to inappropriate data selection and representation, attention will mainly be focused on this topic. The problems that can be experienced will be illustrated by means of an example from the corrosion domain, and possible solutions will be given. Some basic rules to keep in mind during the development of a neural network will then be formulated.
Factors Influencing the Development of a Biostimulant for the In-Situ Anaerobic Dechlorination of Polychlorinated Biphenyls in Fox River, Wisconsin Sediments
Authors: Hollifield MB , Park JK , Boyle WC , Fritschel PR 
Published: March 2009

Polychlorinated biphenyl (PCB) contaminated sediments were collected from the Fox River, Wisconsin, and analyzed for the possible occurrence of reductive dechlorination. Evidence of in-situ dechlorination was observed. However, the extent of this in-situ dechlorination was less than that typically reported in the literature, suggesting that stimulation of further dechlorination was possible.
The use of nutrients and surfactants was explored for stimulating additional dechlorination. The nutrient amendment reported here was found to be inhibitory. Surfactants had varying effects, but none significantly improved dechlorination over control treatments. The most significant factors were observed to be the initial extent of dechlorination and PCB concentration. Additional dechlorination was most likely to be observed in sediments with higher PCB concentration and less initial dechlorination. All sediments converged on a common dechlorination level regardless of the initial state of the sediments.