bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Integration of Test Methodology, Material Database, and Material Selection/Deselection Strategies for a Chemical-Material Compatibility Database System
Authors: Shuely WJ
Published: March 2009

The effect of chemical exposure on the degradation of material properties is important to material evaluation and selection for both commercial and military products. Described here are a set of enhancements to a traditional chemical-material compatibility database that were required to support the early selection of chemically resistant materials in a concurrent engineering environment. This initial phase in the development of an integrated chemical-material compatibility system included: organization of tests into a comprehensive scheme, test selection for the initial screening tests in the scheme, the increased standardization of test procedures and reports required to support database queries, and the control of data set flow from the test laboratory directly to the database. Emphasized here is the design of modular database files based on material, chemical, and test specification descriptors that are indexed to the resulting test properties database module. ASTM Committee E49 formats were employed where available. The polymeric material documentation has been implemented by development of a menu-driven laboratory database version of ASTM Guide for the Identification of Polymers (Excludes Thermoset Elastomers) in Computerized Material Property Data-bases (E 1308-92). Examples are provided from the screening test found in the initial section of the test method scheme. One is able to execute a rapid paperless transfer of predictive and experimental screening results to the chemical-material compatibility database, query the results to eliminate a substantial fraction of materials and rank a more limited set of candidate materials to provide a useful “deselection” capability.
Advanced Composite Material Property Data Modeling for Engineering Analysis and Design
Authors: Spainhour LK , Rasdorf WJ , Alberts JM
Published: March 2009

Awareness of fiber-reinforced plastics is increasing in the domain of civil engineering. However, much of the potential of these new materials is lost because of inefficient data management practices. The main focus of this research is the design of a formal conceptual data model that encompasses the data needs of civil and structural engineers throughout the life cycle of a composite material component. This data model can be used to support automated data exchange and database development. Other issues addressed in this research include assessing the suitability of the Entity-Relationship model for composite materials data, and modeling special types of data applicable to composite materials.
The Role of Corrosion in a Material Selector Expert System for Advanced Structural Ceramics
Authors: Munro RG
Published: March 2009

The primary goal in the development of advanced structural ceramics has been to provide high-strength, corrosion-resistant materials for use in high-temperature, aggressive environments. Much of the developmental effort has focused on heat exchangers for use in industrial gas- or coal-fueled systems with temperatures on the order of 1200 to 1400°C. while ceramics are often popularly described as inert to chemical degradation, the corrosion resistance of these materials actually ranges from excellent to very poor, depending especially on the compositions of the environment and the material. Understanding these dependencies is critical to the development of a materials selector expert system for advanced ceramics. The present paper examines the development of a set of rules for a material selector expert system based on relations among composition, microstructure, transport processes, operating conditions, and corrosion. The concurrent information requirements that must be provided in a computerized materials property database are discussed also.
The Development of a Corporate Information Bank for Materials Data Using Commercially Available Software
Authors: Agema KS
Published: March 2009

A materials information bank has been developed that contains generally accessible data on materials properties used in the electricity generating industry, along with more specific corporate material data, for example, failure analysis reports, research results, and evaluation reports. This information bank is based on the very latest developments in data storage systems suitable for personal computers. An extremely powerful information retrieval system has been created by linking various commercially available software packages.
Review of Materials Property Relationships for Use in Computerized Life Assessment
Authors: Jaske CE
Published: March 2009

The procedures for calculating estimates of the remaining life of key engineering components and the material properties used in those procedures are usually computerized. This paper reviews the properties that are typically needed for remaining life calculations and discusses how they should be computerized to properly interface with analytical methods. The properties include stress-strain and creep deformation behavior, fatigue and creep damage accumulation, tensile strength, crack-growth resistance, and fracture toughness. for remaining life calculations, computerized models of these properties should include the effect of aging caused by elevated-temperature service exposure. Typical methods for computerized modeling of material properties are illustrated by means of two specific examples: (1) the prediction of remaining creep-rupture life of fired furnace tubes and (2) the prediction of remaining creep-rupture and creep-crack-growth life of welded pipes and pressure vessels.
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.
Fire Resistive Joints -- A History in the Making
Authors: Nicholas JD
Published: March 2009

The international and national efforts to standardize fire resistive joints are nearing resolution. Understanding the differences between fire barriers for fire resistive joints and through-penetration fire stops were important in writing the documents. Dissemination of current information, pertaining to fire resistive joints, is critical to uniformity in building codes and fire test standards. Also recognizing the status of this industry and its ultimate goal will help minimize expense and optimize performance.
Validation of SHRP A-003A Flexural Beam Fatigue Test
Authors: Deacon JA , Tayebali AA , Rowe GM , Monismith CL
Published: March 2009

The recently completed Strategic Highway Research Program (SHRP) Project A-003A included the development of a flexural beam test for measuring fatigue of asphalt mixes and an analysis system based on multilayer elastic theory to estimate in-situ performance. The ability of laboratory measurements—coupled with simulations of load response in situ—to predict in-situ pavement performance is demonstrated. Specifically the current investigation shows that controlled-strain laboratory tests are suitable for pavement performance predictions; that A-003A test measurements are sensitive to a variety of fundamental mix properties known to affect fatigue performance and that they compare favorably with measurements using other state-of-the-art equipment; and that, using calibrations developed by the investigation, in-service pavement performance can be predicted for a variety of mixtures, climates, pavement structures, and traffic loadings. Attempts to simulate mixture performance under the accelerated testing of both laboratory wheel tracking and ALF experimentation yielded mixed results.
Engineering Properties of Asphalt Mixtures and their Relationship to Performance
Authors: Davis RL
Published: March 2009

Good performance for a highway, like any other product, is satisfaction of the user or customer. Most asphalt pavement users are well satisfied as long as the ride is smooth and the cost is low. The major purpose of this paper is to determine those engineering properties which result in a durable, smooth, low-cost asphalt pavement and to show how they can be controlled to assure continuing satisfaction of the road user. These properties are identified as being those that eliminate or reduce low-temperature cracking, reflection cracking, fatigue cracking, distortion and disintegration. Distortion or structural weakness can be eliminated by increasing the top size of the aggregate in the region of the weakness or increasing the thickness of the pavement depending on the type of distortion. Disintegration is controlled through softening the asphalt, increasing its content and the quality of the aggregate. Cracking is reduced through a combination of the foregoing factors. Proper management of these factors assures long term satisfaction.
Evaluation of Aging Characteristics of Modified Asphalt Mixtures
Authors: Huang S-C , Tia M , Ruth BE
Published: March 2009

A laboratory investigation using typical Florida dense-graded and open-graded mixtures was conducted to evaluate the effects of a few promising modifiers on the long-term aging characteristics of asphalt mixtures. Six types of modifiers including gilsonite, carbon black, fine ground tire rubber (GTR-80), styrene-butylene-rubber (SBR), ethylene vinyl acetate (EVA) and styrene-ethylene-butylene-styrene (SEBS) were used in this study. These modifiers were blended with AC-30, AC-20, and AC-5 base asphalts to produce a total of ten modified asphalts. These ten modified asphalt blends and the unmodified AC-30 were used to make Florida type S-1 structural course and type FC-2 friction course asphalt mixtures. These mixtures were compacted into Marshall specimens for age hardening and subsequent testing. A total of 416 compacted modified and unmodified asphalt mixture specimens were subjected to a forced-draft oven aging process for 90 days at 60 °C (140 °F), and natural sunlight for 6 months to simulate the long-term aging effects on these mixtures. These aged and unaged asphalt mixtures were evaluated by (1) resilient modulus tests at 5 and 25 °C (41 and 77 °F) and (2) indirect tensile tests at 5 and 25 °C (41 and 77 °F). The effects of cycle frequency used in the resilient modulus tests were also assessed. The test results indicate that the modified asphalt mixtures appear to have more pronounced delayed elastic behavior as compared with that of the unmodified asphalt mixtures. The fracture energy, which is characterized by means of the area of stress-strain curve, indicated that the modified binders using a base asphalt of AC-30 tend to be too brittle as they harden further with time. However, modified binders using a base asphalt of AC-5 appear to be softer than that of conventional AC-30 under typical Florida conditions.
Potential of Dynamic Creep to Predict Rutting
Authors: Mallick RB , Ahlrich R , Brown ER
Published: March 2009

Rutting is one of the predominant types of distresses observed in hot mix asphalt. Different versions of creep tests are used at present to evaluate rutting potential of hot mix asphalt mixtures. To evaluate the potential of dynamic creep to predict rutting, tests were conducted under representative conditions on laboratory samples with different levels of air voids and on field cores from pavements with known rut depths. Test were also conducted on mixes with different aggregates and aggregate gradations to identify mixes with rutting potential. When subjected to dynamic creep, samples with different air voids showed a similar response to that observed in field rutting. Good correlations were obtained between permanent creep strain and rutting rates of pavements. The dynamic creep test was able to quantify the effect of aggregate type and gradation on rutting potentials of mixes. Mixes with crushed aggregates performed better in the creep test than the mixes with uncrushed aggregates.
Comprehensive Characterization of Performance-Related Properties of Asphalt Concrete Mixtures Through Dynamic Testing
Authors: Chua KM , Roo MC
Published: March 2009

It is often desirable to be able to obtain a comprehensive characterization of the performance-related properties of asphalt concrete with as few tests as possible. The New Mexico State Highway and Transportation Department is interested in obtaining a comprehensive characterization of the performance-related properties of the four types of asphalt concrete mixtures that are commonly used in the state. These properties include: the strength, the resilient modulus, the rutting characteristics, and the fatigue/cracking characteristics. Typically, different tests are needed to determine these characteristics. However, the approach taken here to obtain the desired information is through dynamic testing with large (15 cm diameter × 30 cm high) cylindrical asphalt concrete specimens at four different load levels, frequencies, and temperatures. The load applied were 1112 N, 2224 N, 4448 N, and 8896 N; at frequencies of 1 Hz, 4 Hz, 8 Hz, and 16 Hz. Test temperatures were 4.4°C, 25°C, 37.8°C, and 60°C. Continuous haversine load cycles were applied for each test set and the response to the repeated loadings were recorded. Resilient modulus histories were obtained. Rutting characteristics of the material at different temperatures were obtained from the residual deformation histories. The thermal viscoelastic properties were determined from the deformation response at the different temperatures. The change in the damping characteristics with repeated loading were determined through analysis of the data in the frequency domain. Since damping properties can be related to the embrittlement and aging characteristics of materials, the fatigue properties were also inferred. Additionally, it is shown that the degree of susceptibility of the asphalt concrete to cracking and reflection cracking can also be estimated.
The Fate of Toxic Pollutants in Contaminated Sediments
Authors: Yong RN
Published: March 2009

Sediments function as “sinks” for various kinds of contaminants (pollutants and nonpollutants) discharged into the receiving waters. Toxic pollutants in the sediments constitute a significant concern inasmuch as they can infect the waters above the sediment if they are released from the sediments. Hence the persistence and fate of these toxic pollutants need to be determined. At least two sets of interests can be identified in the contamination of sediments as a whole: (1) assessment of the “storage” capacity (for contaminants) of the sediments, and the potential for “mobilization” or release of contaminants into the aqueous environment, particularly into the overlying water, and (2) development of a strategy for removal of the contaminants from the sediments that would be most appropriate (i.e., compatible with the manner in which the contaminants are retained in the sediment) and cost-effective. Both sets of interests require a knowledge of the distribution of the contaminants, i.e., characterization of the contaminants contained in the sediment, and the manner in which these are “held” within the sediment, i.e., “bonded” to the various sediment solid fractions (constituents).
Oxidation of Pyrite in Marine Clays and Zinc Adsorption by Clays
Authors: Ohtsubo M
Published: March 2009

The oxidation of pyrite in marine clays exposed to a subaerial environment was confirmed and was determined to be well correlated with decreased adsorption of zinc by the clays. The production of sulfuric acid and iron oxide by this oxidation and the accompanying decrease in pH was demonstrated based on an investigation of the chemistry of the marine clay profile and laboratory incubation tests for remoulded clay samples. Both pH decrease and the production of iron oxides reduced the zinc adsorption capability of the clays. This suggests that the zinc adsorbed by the marine clays would be released into the pore water due to exposure of the sediment surface to the atmosphere.
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.
Abating Coal Tar Seepage into Surface Water Bodies Using Sheet Piles with Sealed Interlocks
Authors: Collingwood BI , Boscardin MD , Murdock RF
Published: March 2009

A former coal tar processing facility processed crude coal tar supplied from manufactured gas plants in the area. Coal-tar-contaminated ground water from the site was observed seeping through an existing timber bulkhead along a tidal river and producing a multicolored sheen on the surface of the river. As part of a short-term measure to abate the seepage into the river, 64-m long anchored sheet pile wall with sheet pile wing walls at each end was constructed inland of the timber bulkhead. The sheet piles extended to low-permeability soils at depth and the interlocks of the sheet piles were provided with polyurethane rubber seals. Based on postconstruction observations for leakage and sheens related to leakage, the steel sheet piles with polyurethane rubber interlock seals appeared to provide a successful seal and abate coal-tar-contaminated ground water seepage into the river. The tie rod penetration sealing proved to be a more problematic detail, but through several postconstruction grouting episodes, an effective seal was produced.
Testing of a Cement-Bentonite Mix for a Low-Permeability Plastic Barrier
Authors: Deschênes J-H , Massiêra M , Tournier J-P
Published: March 2009

A laboratory investigation was carried out to determine the physical properties of a suitable mix of cement-bentonite for a low-permeability cutoff wall implemented in 1991 under the north dyke at the LG-1 hydroelectric site, which is part of the James Bay Development Project in Northern Quebec. The project specifications required the mix to have a hydraulic conductivity of less than 10-8 m/s and be able to sustain a plastic deformation of 6% without fissuring, as measured in a triaxial compression test with a lateral pressure of 100 kPa on a specimen cured for 90 days. A two-phase laboratory study was carried out. Phase 1 involved the determination of the mix design, while the second phase consisted of the laboratory control of the manufactured mixture. During phase 1, laboratory samples were prepared with different proportions of cement, bentonite, sand, and water. The permeability, triaxial compression, and unconfined compression tests were performed after curing periods ranging from 8 to 120 days. Once the appropriate mix was selected, it was tested to check if it met the specifications. During phase 2, or during actual production or construction, density and viscosity measurements of the cement-bentonite slurry were made routinely at the plant and at the discharge of the slurry pipe. Cylindrical specimens were molded using slurry from the discharge of the pipe and from the trench. Permeability, triaxial compression, and unconfined compression tests were performed on the specimens after curing periods ranging from 3 to 103 days.
Partnering for Environmental Restoration: The Port Hope Harbour Remedial Action Plan (RAP)
Authors: Weston SMC
Published: March 2009

A Remedial Action Plan (RAP) is being developed for Port Hope Harbour, one of 43 Areas of Concern (AOCs) identified by the International Joint Commission (IJC). The RAP, when implemented, will lead to the restoration and protection of desirable water conditions in Port Hope Harbour. The environmental concern associated with the harbour can be best viewed as a historical contaminated sediment problem. Approximately 90 000 m3 of sediment located in Port Hope Harbour's turning basin and west slip are contaminated by uranium and thorium series radionuclides, heavy metals, and PCBs. There are several groups contributing to the development of the RAP. All of these groups have the common goal of developing an environmentally sound plan that reflects the views of the community. Strategic partnerships have been established that recognize the need to integrate and coordinate the efforts of all agencies, stakeholders, and the community. The objective is to develop an environmentally sound remediation plan through an efficient and effective management framework.
Regulatory Strategies for Remediation of Contaminated Sediments
Authors: Zar H
Published: March 2009

A number of federal and state laws may be used to obtain remediation of contaminated sediments in the United States. Until recently, the most prominent approaches at the federal level were the use of Superfund authorities for sites on the National Priority List and navigational dredging activity by the Corps of Engineers. However, with the increasing concern about contaminated sediments, regional offices of the U.S. Environmental Protection Agency (EPA) and state agencies have begun to use a greater variety of regulatory approaches, both individually and in combination. These efforts have been particularly evident in the Great Lakes and are now being extended nationwide, as embodied in the EPA's Contaminated Sediment Management Strategy. This paper will describe some of the regulatory approaches being applied, case examples in the Great Lakes area, and the expected directions of these efforts, as embodied in the national strategy.
Patterns and Perspectives in Applied Fracture Mechanics
Authors: Merkle JG
Published: March 2009

This fifth Jerry L. Swedlow Memorial Lecture begins with a brief philosophical and historical overview of applied fracture mechanics, particularly as it pertains to the safety of pressure vessels. It then progresses to a more-or-less chronological panorama of experimental and analytical results pertaining to the important subject of constraint, a fundamental aspect of fracture mechanics in which Jerry Swedlow had a keen interest and to which he made valuable contributions. To be truly useful and dependable in application to the safety analysis of real structures, new analysis developments must be physically realistic. That means that they must accurately describe physical cause and effect. Consequently, before useful mathematical modeling can begin, a pattern of cause and effect must be established from experimental data. This can be a difficult and time consuming process, but it is worth the effort. Accordingly, a central theme of this paper is that, consistent with the scientific method, the search for patterns is constant and vital. This theme is well illustrated historically by the development of small, single-specimen, fracture toughness testing techniques. It is also illustrated, at the end of the present paper, by the development, based on two different published large-strain, elastic-plastic, three-dimensional finite-element analyses, of a hypothesis concerning three-dimensional loss of constraint. Specifically, it appears that, at least in standard compact specimens, when a generalization of Irwin's thickness-normalized plastic-zone parameter, β, reaches a value close to 2π, the through-thickness contraction strain at the apex of the near-tip logarithmic-spiral slip-line region becomes the dominant negative strain accommodating crack opening. Because slip lines passing from the midplane to the stress-free side surfaces do not have to curve, once these slip lines are established, stresses near the crack tip are only elevated by strain hardening and constraint becomes significantly relaxed. This hypothesis, based on published three-dimensional elastic-plastic analyses, provides a potentially valuable means for gaining additional insight into constraint effects on fracture toughness by considering the roles played by the plastic strains as well as the stresses that develop near a crack tip.
J-Integral for a Semi-Elliptical Surface Crack at a Bimaterial Interface
Authors: Sharobeam MH , Landes JD
Published: March 2009

Surface cracks are common defects in welded, bonded, and composite structures. The elastic-plastic fracture of these defects may be analyzed using the J-integral. The authors have recently developed a new approach to evaluate the J-integral for semi-elliptical surface cracks in panels made of homogeneous materials and subject to remote tension. This approach, which is based on load separation, allows the evaluation of J for such a three-dimensional geometry using a single specimen test record. It is analogous to the single specimen technique in two-dimensional geometries. In this article, the authors extend their study to surface cracks at bimaterial interfaces. A three-dimensional finite element model is developed to model such a crack. The J-integral is evaluated along the crack front using the virtual crack extension method. The elastic-plastic fracture behavior of the crack is studied. Load separation is also examined and the new single specimen approach for surface cracks in single material panels is extended to those at bimaterial interfaces. The study also includes a comparison between the results of surface cracks in single material panels and those at bimaterial interfaces.
Effects of Constraint on Upper Shelf Fracture Toughness
Authors: Joyce JA , Link RE
Published: March 2009

The upper shelf fracture toughness and tearing resistance of two structural steels, HY-100 and ASTM A533, Gr. B, were determined over a wide range of applied constraint. The constraint conditions were varied by changes in specimen geometry and loading mode. Bend specimens with shallow and deep cracks, compact specimens, and single and double edge notched tension specimens were used in this study. A rotation correction was developed for the single edge notch tension specimen which greatly improved the behavior of the J-R curves determined using this specimen. The experimental results were used to investigate the applicability of the Q and T stress parameters to the correlation of upper shelf initiation toughness, JIc, and tearing resistance, Tmat. The J-Q and J-T stress loci, and corresponding plots of material tearing resistance plotted against Q and T, were developed and compared with the expectations of the O'Dowd and Shih and the Betégon and Hancock analyses. The principle conclusions of this work are that JIc does not appear to be dependent on T stress or Q while the material tearing resistance, Tmat, is dependent on T stress and Q, with the tearing modulus increasing as constraint decreases.
Effects of 3-D Transverse Constraint on the Evolution of In-Plane Q-Stress
Authors: Shum DKM
Published: March 2009

This study examines the limits of validity of the Q ≈ 0 assumption under monotonic loading along the crack front in the “high constraint” 2-in.- and 4-in.-thick 4T-planform CT specimen geometries. Preliminary results indicate that progressive deviation of the in-plane crack-tip fields from Q ≈ 0 occurs with increasing load, along the crack front up to the symmetry plane of the geometries. The nature of the in-plane deviation can be described using J-Q theory. Significantly, no indication of possible 3-D transverse loss-of-constraint effects on the crack-tip fields is manifested in a 2-D plane strain analysis of the 4T-planform geometry. Uniformity of J or K values along the crack front does not imply either the existence of single-parameter-dominant conditions or the absence of substantial 3-D variations in the in-plane crack-tip fields. Preliminary results also suggest that current KIc-related size requirements in ASTM-E399 might be sufficient to preclude the onset of significant 3-D transverse Q-stress effects for the 4-in.-thick geometry. However, significant deviation from J-dominant conditions could occur within the existing JIc- and JR-related size requirements in ASTM-E813 and ASTM-E1152 for both geometries.
On the Effect of Mismatching on Structural Resistance of Welds
Authors: Eripret C , Franco C , Gilles P
Published: March 2009

The usual fracture mechanics based concepts available to assess structural integrity have been developed for homogeneous structures. When considering cracks in welds, these methods assume that cracks are located in a material of uniform properties and neglect any difference of strain carrying capacity due to mismatching effects. The French Cracked Weld Research Programme (FCWRP, conducted by CEA, EDF, and FRAMATOME) has been in progress for the last three years to investigate how the effects of weld metal mismatch may affect structural resistance of welded structures. This paper gives an overview of the conclusions and results drawn from this program.
Significance of Locally Intensified Strain Ageing to the Fracture Toughness of Welded Steel Structures
Authors: Dawes MG
Published: March 2009

A review of past studies shows that tests on specimens notched after welding can give overestimates of the fracture toughness that occurs at the tips of flaws present during welding. This situation results from locally intensified straining and ageing embrittlement (LISAE), which has been shown to trigger low stress brittle fractures in both notched and welded wide plate tension tests, and welded structures in service. Although the relative susceptibilities of steels to strain ageing embrittlement are sometimes assessed by testing bulk strained and aged samples, the results of such tests may be optimistic. A summary is given of work to develop a fracture toughness test method for LISAE. The new test will give increased confidence and accuracy in fracture assessments, be of use in selecting tough materials, and aid the development of materials that are resistant to LISAE.
Fracture Behaviour of Subclad Cracks
Authors: Hodulak L , Siegele D
Published: March 2009

An approximate calculation method for stress-intensity factors at the deepest point of finite-length subclad cracks accounting for plastic deformation of the cladding was reported elsewhere. An extension of this method for the part of the crack front near to interface and for infinitely long cracks is described in the first part of this paper. The second part of the paper deals with some applications of this calculation method.
Translaminar Fracture Toughness Test Methods and Results from Interlaboratory Tests of Carbon/Epoxy Laminates
Authors: Underwood JH , Kortschot MT , Lloyd WR , Eidinoff HL , Wilson DA , Ashbaugh N
Published: March 2009

Fracture tests were performed with carbon/polymer laminates and analyzed for the purpose of developing translaminar fracture toughness test and analysis procedures. Notched specimens were tested of two types of symmetrical layups — quasi-isotropic [0/45/90] and [0/90]; two carbon fiber/epoxy materials — a relatively brittle T300 fiber/976 epoxy and a tougher AS4 fiber/977-2 epoxy; two laminate thicknesses — 2 mm and 4 mm; and three specimen configurations — the standard three-point bend and compact configurations, and an extended compact specimen with arm-height to specimen-width ratio of 1.9. Stress and displacement expressions were obtained for the extended compact specimen, including those for stress intensity factor, K, and crack mouth opening displacement, V, in terms of relative notch length, a/W, and for a/W in terms of V. Relationships for the bending stresses that control self-similar and off-axis cracking for the extended compact specimen were derived.

Damage was characterized in the tests, including that associated with arm breakage in the standard compact specimen and load-point damage in the bend specimen. Two types of notch-tip damage were characterized using radiography, that which extends perpendicular to the notch in predominantly 0‡ fiber layups, and that which occurs ahead of the notch in quasi-isotropic and 90‡ fiber layups.

The applied K at maximum load, Kmax, determined in a way that took account of the effective crack growth up to the maximum load point, was used as a measure of fracture toughness. For deviations from the linear P-V plot corresponding to Δa/W ≤ 0.04, Kmax gave consistent measurements of fracture toughness. This criterion also excluded tests with damage of the type that violates the basic concept of fracture toughness measurement. Plots of Kmax vs δa/W showed increasing resistance to crack growth for quasi-isotropic layups and constant resistance to crack growth for predominantly 90‡ fiber layups.
Constraint Effect on Fracture Behaviour of Adhesive Joints with Different Bond Thickness
Authors: Daghyani HR , Ye L , Mai Y-W
Published: March 2009

The main aims of this work are to investigate the constraint effect of adherends on the fracture behaviour of adhesive joints and to study the fracture properties of aluminium-adhesive joints using a rubber-modified epoxy resin (GIc = 2.76 kJ/m2) as an adhesive material. Compact tension (CT) adhesive joints were manufactured for a wide range of bond thickness and fracture tests were conducted. The fracture energy was found to increase, though not monotonically, towards the fracture energy of the bulk adhesive as the bond thickness was increased. The constraint and stress triaxiality at the crack tip in the adhesive joints were also characterised for various bond thickness using elastic-plastic finite element method. It was found that as the adhesive bond thickness was increased, the stress triaxiality near the crack tip was relieved by the intensive deformation of the adhesive. Furthermore, the relationship between J-integral and crack-tip opening displacement (CTOD) was dependent on the constraint around the crack tip. Scanning electron microscopy (SEM) was used to examine the fracture surface morphology. Brittle fracture mechanisms were observed for thin bonds (0.04 < t < 0.5 mm) but tough fracture mechanisms were identified for thick bonds (t > 1 mm). The fracture energy of adhesive joints was proportional to the size of the crack tip plastic zone and the transfer of the bulk adhesive fracture toughness was governed by the constraint at the crack tip. Results from this work would improve integrity assessment of engineering adhesive joints.
Reduction of the Stresses in a Joint of Dissimilar Materials Using Graded Materials as Interlayer
Authors: Yang Y , Munz D
Published: March 2009

If two dissimilar materials are joined at high temperature, very high residual stresses develop near the free edge of the interface during cooling to room temperature. In most cases, the stresses are singular for elastic material behaviour. One method to avoid the stress singularities is to introduce a graded interfacial zone with a continuous change of all material properties between the two joined components. In this paper the distribution of the stresses in FGM has been calculated by FEM. The interlayer has continuous material properties, which means that the graded interlayer has not been treated as N layers. The value of the peak stress and the location of the peak stress in the joint have been investigated.
In-Plane Fracture Toughness Measurement of Paper
Authors: Mai Y-W , He H , Leung R , Seth RS
Published: March 2009

Paper sheet material has a high toughness and a low yield stress so that linear elastic fracture mechanics is inappropriate to measure its fracture resistance. Experiments have been conducted on single edge-notched tension SE(T) specimens using the J-integral analysis but there are difficulties in identifying the crack initiation, and the Jc value at 0.2 mm crack growth as required by ASTM E813-89 depends on the slope of the JR-curve which may be affected by specimen size and geometry effects. To overcome these problems the essential fracture work concept is applied to paper and an experimental technique developed to evaluate the specific fracture energy using deeply double-edge notched tension DE(T) specimens containing different ligament lengths. With this technique the fracture resistance of papers from hardwood and softwood pulps, the effects of level of bonding and recycling can be compared. It is recommended that the essential fracture work method be used for quality control of paper by the pulp and paper industry.
Fatigue Crack Growth Behavior of Ti-1100 at Elevated Temperature
Authors: Maxwell DC , Nicholas T
Published: March 2009

Effects of temperature, frequency, and cycles with superimposed hold times are evaluated in Ti-1100 in order to study the complex creep-fatigue-environment interactions in this material. Crack growth rate tests conducted at a cyclic loading frequency of 1.0 Hz show that raising the temperature from 593 to 650°C has only a slightly detrimental effect on crack growth rate, although these temperatures produce growth rates significantly higher than at room temperature. From constant △K tests, the effects of temperature at constant frequency show a minimum crack growth rate at 250°C. From the minimum crack growth rate at 250°C, the crack growth rate increases linearly with temperature. Increases in frequency at constant temperatures of 593 and 650°C produce a continuous decrease in growth rate in going from 0.001 to 1.0 Hz, although the behavior is primarily cycle dependent in this region. Tests at 1.0 Hz with superimposed hold times from 1 to 1000 s are used to evaluate creep-fatigue-environment interactions. Hold times at maximum load are found to initially decrease and then increase the cyclic crack growth rate with increasing duration. This is attributed to crack-tip blunting during short hold times and environmental degradation at long hold times. Hold times at minimum load show no change in growth rates, indicating that there is no net environmental degradation to the bulk material beyond that experienced during the baseline 1 Hz cycling.
Strain Rate and Inertial Effects on Impact Loaded Single-Edge Notch Bend Specimens
Authors: Vargas PM , Dodds RH
Published: March 2009

Many significant problems in fracture mechanics of ductile metals involve surface breaking defects (cracks) located in structures subjected to short-duration loading caused by impact or blast. When the severity of impact loads is sufficient to produce large inelastic deformations, the assessment of crack-tip conditions must include the effects of plasticity, strain rate and inertia. This work examines the interaction of impact loading, inelastic material deformation and rate sensitivity with the goal of improving the interpretation of ductile fracture toughness values measured under dynamic loading. We focus on shallow and deeply notched bend test specimens, SE(B)s, employed routinely to measure the static fracture toughness of a material. A thorough understanding of the test specimen's dynamic behavior is a prerequisite to the application of measured fracture properties in structural applications.

Three-dimensional, nonlinear dynamic analyses are performed for SE(B) fracture specimens (a/W= 0.5, 0.15, 0.0725) subjected to impact loading. Loading rates obtained in conventional drop tower tests (impact load-line velocities of = 6 m/sec) are applied in the analyses. An explicit time integration procedure coupled with an efficient (one-point) element integration scheme is employed to compute the dynamic response of the specimen. Strain-rate sensitivity is introduced via a new, efficient implementation of the Bodner-Partom viscoplastic constitutive model. Material properties for A533B steel (a medium strength pressure vessel steel) are used in the analyses. Static analyses of the SE(B) specimens provide baseline responses for assessment of inertial effects. Similarly, dy namic analyses using a strain-rate insensitive material provide reference responses for the assess ment of strain rate effects. Strains at key locations on the specimens and the support reactions (ap plied load) are extracted from the analyses to assess the accuracy of static formulas commonly used to estimate applied J values. Inertial effects on the applied J are quantified by examining the accelera tion component of J evaluated through a domain integral procedure
Validation of R6 Defect Assessment Methodology Using Experiments on Plates and Pipes with Surface Cracks
Authors: Hodulak L , Memhard D , Couterot C
Published: March 2009

Plates and pipes with surface cracks were loaded to a level at which a definite amount of stable crack growth was achieved. Nominal stresses necessary for stable crack extension in depth direction equal to that observed on fracture surfaces were calculated and compared to nominal stresses in experiments. Option 2 of the R6 supplied closer agreement with experiment than Option 1. All results calculated with Option 1 were conservative.
ASTM G-4 Twenty-Year Report Card: Keynote Address
Authors: Benz FJ
Published: March 2009

The ASTM G-4 Committee was established twenty years ago. The purpose of the Committee, then and now, is to provide for better test methods, standard practices, and education in oxygen-enriched atmospheres. Safety, efficiency, productivity, and legal-consequence aspects have made the contributions of this Committee an important part of the many industries that use oxygen. In this paper, the original charter of the Committee, along with the suggestions made by other Keynote Speakers, will be reviewed. The process to achieve the key aspects assigned to the Committee will be assessed and graded. Three areas will be considered: standardization of test methods, standardization of guidelines and practices, and education. Areas that need attention in the future by the Committee will also be identified.
The Seal Configuration Tester, a New Approach to the Evaluation of Elastomeric Materials for Oxygen Service
Authors: Haselmaier LH , Powell BA
Published: March 2009

A new approach for evaluating elastomeric materials for use in high pressure oxygen has been developed. Because this approach replicates the dynamic forces that occur in pressure systems and subjects a specimen to progressive wear, it allows the user to compare wearability and oxygen sensitivity. This method determines if a candidate material ignites before it mechanically fails and provides a relative wearability ranking for that material.

Existing mechanical impact test methods produce data which is useful in screening various materials for oxygen sensitivity. The pass/fail data produced from these tests do not easily translate into a suitable material selection for a particular oxygen application. This new evaluation technique produces both mechanical wear data in combination with sensitivity data which can easily be applied when selecting elastomeric materials for a particular oxygen application.

An explanation of the process as well as sample data are presented.