bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of Three-Dimensional Surface Flaw Geometries During Fatigue Crack Growth in PMMA
Authors: Troha WA , Nicholas T , Grandt AF
Published: March 2009

A series of fatigue crack growth experiments was conducted on a transparent polymer (PMMA) using a surface flaw geometry in bending. A Newton interferometric technique was used to measure crack opening displacements and closure for four different loading histories. Results are presented for conditions of constant applied stress-intensity factor along the crack face free surface, at the crack tip in the depth direction, for constant applied load range, and for a block loading sequence.

Three distinct crack geometries are identified and are found to be a function of crack size. The crack opening displacement patterns are found to be strongly influenced by the formation of a void internal to the crack. Three distinct closure loads are identified and measured for surface flaws of various crack depths and aspect ratios. The various closure loads are used to define effective stress-intensity ranges. Life predictions, crack growth rates, and aspect ratios are used to evaluate the applicability of the various closure loads at different locations. It is found that the same closure load does not determine the best value of effective stress intensity at all points along the crack tip in the surface flaw geometry.
Some Special Computations and Experiments on Surface Crack Growth
Authors: Prodan M , Radon JC
Published: March 2009

The new method of surface crack growth calculation under linear elastic fracture mechanics (LEFM) conditions facilitates the use of stress-intensity factor K (and in particular its ΔK range) as a tool to estimate the fatigue life of cracked plates under tensile loads. This is made possible by determining a set of parameters in order to obtain equal ΔK values and analogous crack propagation rates in two widely different specimen geometries, a plate and a standard compact type (C(T)) specimen. A comparison of fatigue lives with equivalent crack growth for both types of specimen suggests that in using the proposed procedure, the significance of ΔK values in a part-through crack is closely related to that of a through crack in a C(T) specimen.

In analyzing the surface crack growth under elastic-plastic conditions, it should be necessary to use J values in a different way than in LEFM. Appropriate references to both problems are quoted.
Growth of Surface Cracks Under Fatigue and Monotonic Increasing Load
Authors: Hodulak L
Published: March 2009

An engineering assessment of the life time and failure conditions for components with surface cracks can be easily done using a personal computer program. The methods, assumptions and the modeling of surface crack growth used in the program are briefly described.

A more detailed comparison of calculated and observed growth of surface cracks under fatigue and monotonic increasing load shows some phenomena, which are not completely understood as yet. They are discussed in connection with the constraint variation along the crack front. Some results on constraint at the front of surface cracks and on the J-R curves for surface cracks in tension plates are given.
Petrographic Investigations of Concrete and Concrete Aggregates at the Bureau of Reclamation
Authors: DePuy GW
Published: March 2009

The Bureau of Reclamation has had a strong interest in the development and application of concrete technology to the design, construction, and maintenance of water resources development projects. The application of petrographic methods to concrete technology has been a natural outgrowth of Reclamation's involvement in the development of concrete technology. Reclamation's first petrographer was W. Y. Holland who, purely out of curiosity, employed petrographic techniques to see what types of rocks were failing in the sulfate soundness test for aggregates. As this provided useful information for the evaluation of the suitability of aggregates, Reclamation began to routinely perform petrographic examination of aggregate samples to provide information on the suitability of aggregates and to compare samples from different sources. The method was also used to examine concrete to identify rock types failing in the freeze-thaw test, and to determine the cause of distress in deteriorated concrete. The petrographic examination received its biggest impetus in the early 1940's in the investigations of alkali-aggregate reaction in concrete and the development of precautionary measures. Reclamation established its Petrographic Laboratory in 1941 to investigate deleterious chemical reactions in concrete. The petrographic method has become widely accepted and is now routinely applied in concrete technology investigations throughout the world. The main applications of petrographic methods are in the evaluation of concrete aggregates for use in concrete, the assessment of the quality of concrete and the diagnosis of the cause of distress in deteriorated concrete, and as a basic procedure in concrete research investigations.
The Use of Large-Area Thin Sectioning in the Petrographic Examination of Concrete
Authors: St.John DA
Published: March 2009

Large-area thin sectioning of a concrete core allows examination of micro-textural detail that is not observable by other petrographic techniques. Because the area of the section represents a large sampling of the core, this allows the relationship of faults and deterioration to both the outer surface and the internal texture to be determined and gives a good estimate of the degree of damage present in the concrete. The usefulness of the technique is illustrated by cases of alkali-aggregate reaction, soft water attack, high temperature corrosion and carbonation, and other textural faults in concrete. It is concluded that especially in the case of alkali-aggregate reaction the examination of large-area thin sections should be the preferred technique for microscopy as it appears to provide the range of textural information necessary for unequivocal diagnosis.
The Study of Alkali-Silica Reactions in Concrete by the Use Of Fluorescent Thin-Sections
Authors: Andersen KT , Thaulow N
Published: March 2009

Detailed thin-section examination of the concrete in a jetty affected by alkali-silica reactions shows that the varying reactivity of the aggregates can be ascribed to variations in porosity of these aggregates. Examination of the alkali-silica gel found in association with the reacting particles shows that the gel occurs in three different morphologies depending on the location of the gel in the concrete. The examination also shows that cracks induced by alkali-silica reactions are for a large part devoid of gel indicating that deterioration of concrete due to swelling of gel in cracks is an unlikely mechanism.
Alkali Silica Reaction of Concrete in Electrical Substation Piers Accelerated by Electric Current
Authors: Ozol MA
Published: March 2009

Concrete piers supporting towers at the corners of an electrical substation are expanded and severely cracked. Eight intermediate piers show no signs of expansion, cracking, or surface deterioration. All piers were constructed (1969) of the same concrete mixture.

The corner piers are connected to both ground and the above steel structure. The intermediate piers are grounded only and not connected to the above steel structure.

The coarse aggregate (CA) is a siliceous gravel composed essentially of quartz, quartzites, and cherts. The fine aggregate (FA) is a natural sand of essentially the same composition.

Cores taken from the corner piers exhibit: a) internally cracked CA particles with cracks extending into the mortar and connecting with cracks from other particles; b) reaction rims around CA particles with adjacent pockets of dried Alkali-Silica Reaction (ASR) gel that has breached through the reaction rim; c) peripheral separations around CA particles, with peripheral cracks in the adjacent mortar, and CA particles loose in their sockets; and, d) dried ASR gel in voids, cracks, and CA sockets, commonly in association with ettringite crystals.

The determined alkali contents of the corner pier, and intermediate pier concretes were the same; .06% NA2O and .05% K2O in each, as weight percents of the concrete.

Samples from the intermediate piers show these features of ASR to a minor degree: a) rim development on some chert and quartzite CA particles; b) small gel deposits within, and near, chert and quartzite CA particles; and, c) some chert and quartzite CA particles with internal cracks that do not extend out of the particles.

Since both concretes have ASR, one to an inconsequential degree and the other to a serious degree, the difference in the condition of the two concretes is attributable to a difference in the rate at which the ASR proceeded in one versus the other.

On-site measurements of electrical potential, by Cu/CuSO4 reference cell, between the steel structure and both the pier concretes and the surrounding soil show current flow from the concrete to the soil, with strong implications that, because of the corner piers being connected to the superstructure, the potential differences and current passing through the corner concrete was larger than through the intermediate concrete.

It is proposed that the reason for the difference in the degree of the ASR in the concretes is that the ASR has been accelerated in the corner piers by greater diffusion of alkali ions under the influence of a greater electrical potential gradient than is present in the intermediate piers.
The Importance of Petrological, Petrographical and Mineralogical Characteristics of Aggregates in Very High Strength Concrete
Authors: Sarkar SL , Aïtcin P-C
Published: March 2009

Aggregate intrinsic strength, particularly that of coarse aggregates, receives scant attention from concrete technologists and researchers as long as the w/c ratio falls within the 0.50-to-0.70 range, primarily due to the fact that the cement-aggregate bond or the hydrated cement paste fail long before aggregates do.

This, however, does not hold true for very high-strength concretes, with very low w/c ratios of 0.20 to 0.30. Compressive strength testing of very high-strength concrete has indicated that aggregates can assume the weaker role, exhibited in the form of transgranular fractures on the surface of failure, as has already been observed in some lightweight concretes.

The authors have carried out detailed petrological, petrographical and mineralogical characterization of twelve different coarse aggregates that have performed with variable success in very high-strength concrete in Canada and the United States. Suitability for such an application has been linked to a special set of lithological characteristics: the minerals must be strong, unaltered, and fine grained. Intra- and intergranular fissures, partially decomposed coarse-grained minerals, and the presence of cleavages and lamination planes tend to weaken the aggregate, and therefore the ultimate strength of the concrete.
Petrographic Examinations Aid in Establishing the Causes of Deterioration of Precast Concrete Sewer Manhole Sections
Authors: Cady PD , Weyers RE
Published: March 2009

This paper describes a forensic investigation to establish the causes for very severe, early deterioration of precast concrete sewer manhole sections. Petrographic examinations played a major role in determining the causes of the deterioration. Early on, it was established that the entrained air-void systems were severely inadequate in the affected sections. However, many manhole sections that were located well below the frost line still showed severe deterioration. In addition, crack patterns characteristic of expansive reactions (map cracking) were present along with the typical fracture planes parallel to exposed surfaces commonly associated with freezing and thawing attack. Petrographic examinations revealed that the MgO content of the portland cement in those sections was 3 1/2 times that of the unaffected sections and, at 9.1%, was more than 50% higher than is permitted in ASTM C-150.
Laser Excited Fluorescence in Criminalistics
Authors: Menzel ER
Published: March 2009

Applications of laser-excited fluorescence can be found in numerous areas of criminalistics, including document examination, fiber analysis, serology and latent fingerprint development. This paper focuses on the latter application. The present mature procedures for laser fingerprint detection are described to set the stage for discussion of current research, which primarily deals with time-resolved imaging to take advantage of the difference between the lifetimes of substrate and fingerprint fluorescences.

The principal procedure for laser detection of latent prints on smooth surfaces involves first the fuming with cyanoacrylate ester, which results in the formation of a polymer on the fingerprint residue. Thus stabilized latent prints can then be solution stained with fluorescent dyes. Porous items are treated with ninhydrin or its analogs, which react with amino acids of the fingerprint residue. Subsequent reaction with group II B metal salts yields intensely fluorescent products.

Time-resolved imaging involves modulated laser excitation and gated imaging with a microchannel plate image intensifier. The critical requirement for such imaging is the identification of reagents or stains that yield lifetimes which are longer than those of the substrates (typically 1 ns or less) and also at least comparable to the laser cutoff and image intensifier turn-on time (about 5 ns). Two general approaches are presented. One involves compounds that yield long-lived d-π* intramolecular charge transfer states. The other involves chemical reactions with fingerprint residue that lead to formation of organo-rare earth complexes which display long-lived rare earth emission. The structural and photophysical features which underlie the luminescence properties of fingerprints treated with ninhydrin or its analogs and subsequently with metal salts are discussed with the aim of providing guidelines for the design of optimized fingerprint detection reagents.
Temperature and Laser Intensity Effects in Highly Resolved Fluorescence Spectra of Tetracene in Cryogenic Matrices
Authors: Velthorst NH , Gooijer C , Hofstraat JW
Published: March 2009

Temperature and laser intensity effects on the highly resolved fluorescence spectra of the model compound tetracene in crystalline and in amorphous cryogenic solid solutions have been investigated.

In crystalline solid solutions, using lamp and selective laser excitation, the spectra show a strongly temperature dependent height, width and position of the narrow lines. Hence, accurate temperature control and stability are required for reliable identification and quantification. In amorphous solutions under laser excitation also the height and width of the narrow lines strongly depend on temperature; the line positions, however, are independent of the temperature and the choice of the matrix material.

The effect of the laser intensity on fluorescence line-narrowed spectra has been studied for tetracene in amorphous glassy and polymer matrices. It appears that already at relatively low laser powers the narrow lines show a nonlinear dependence of their fluorescence intensity, in particular when excitation is performed in regions with large absorption cross sections.

Moreover, attention will be paid to the temperature- and laser intensity dependence of hole-burning effects in laser excited spectra in amorphous matrices.
Laser Based Approaches to Increase Fiber-Optic-Based Selectivity: Dynamic Fluorescence Spectroscopy
Authors: Betts TA , Bright FV , Catena GC , Huang J , Litwiler KS , Paterniti DP
Published: March 2009

Over the last several decades the communications industry has developed small, high-light transmitting fiber-optic materials. Because of their inherently non-perturbing nature fiber optics have found wide spread use in many diverse areas of analytical spectroscopy. Of all the spectroscopic techniques, fiber-optic-based fluorescence has probably enjoyed the greatest popularity. Unfortunately, while successful analyses have been achieved via fiber-optic probes, only a fraction (that is, spectral information) of the total information content from the fluorescence process has been utilized. In this paper, recent results from our laboratory are presented for the successful implementation of the remaining dynamic and steady-state fluorimetric measurements in conjunction with fiber-optic sensing.
Laser Induced Luminescence Spectroscopy on Solid Substrates: An Overview
Authors: Vo-Dinh T
Published: March 2009

This paper provides an overview of the photophysical processes and analytical applications of high-resolution luminescence spectroscopy using solid samples. Experimental results are discussed within the framework of a theoretical model involving isolated guest molecules weakly interacting with the host solid substrate. Examples are given to illustrate the spectral structure of luminescence spectra exhibiting zero-phonon lines and phonon wings. Effects of experimental parameters such as temperature are discussed. Analytical considerations on the various laser-based techniques in fluorescence and phosphorescence analysis are reviewed and discussed in detail.
Subattomole Amino Acid Analysis by Laser-Induced Fluorescence: The Sheath Flow Cuvette Meets Capillary Zone Electrophoresis
Authors: Cheng YF , Dovichi NJ
Published: March 2009

Subattomole analysis of fluorescein isothiocyanate (FITC) derivatives of amino acids is produced by combining capillary zone electrophoresis for high-efficiency separation with laser-induced fluorescence for high sensitivity detection. To optimize the separation process, several buffer systems were investigated. A pH 10 carbonate buffer provided good separation of 14 FITC amino acids. Concentration detection limits range from 5 × 10-12 M for alanine to 9 × 10-11 M for lysine, injected onto the column; ∼9 × 10-21 mol of alanine is contained within the ∼1-nL injection volume at the detection limit. The alanine detection limit corresponds to less than 6000 molecules injected onto the column and represents a four order of magnitude improvement in the state of the art for fluorescent detection of amino acids and a six order of magnitude improvement in the state of the art for the detection limit for isothiocyanate derivatives of amino acids.
Thermal Analysis of Nonwoven Polyester Geotextiles
Authors: Thomas RW , Verschoor KL
Published: March 2009

Traditional methods of characterizing the durability of geotextiles often lack the precision and sensitivity needed in short-term aging tests. In an effort to differentiate between thermal and chemical effects, thermal analysis and physical property testing were used to study nonwoven, polyester geotextiles aged at ambient and elevated temperatures in controlled environments conducive to hydrolysis of polyester. Samples were exposed to deionized water, aqueous sodium hydroxide, and aqueous calcium hydroxide. Three thermal analytical techniques were used to characterize aged and unaged bulk samples of geotextiles: differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), and dynamic mechanical analysis (DMA). In addition to assessing changes in various physical properties, solution viscosities were performed on aged and unaged samples. In general, of the three thermal analytical techniques used, DSC is the most promising method for bulk geotextile characterization.
Stress Cracking Morphology of Polyethylene (PE) Geomembrane Seams
Authors: Halse YH , Koerner RM , Lord AE
Published: March 2009

The high crystallinity of polyethylene (PE) geomembranes offers an excellent chemical resistance to harsh chemical leachates, but can be problematic with regard to stress cracking. Particularly vulnerable are field seams due to their overlapping geometry, necessity for surface grinding for removal of oxide layers, and possibility of poor quality. Using laboratory test specimens under constant load (ASTM D 2552 [modified]) it was shown that field seams can be subjected to such stress cracking.

This paper presents a fracture surface morphological study of the cracked specimens from those particular tests. Five different seam types were evaluated, compared, and contrasted under different applied stress levels. Qualitatively, the morphology patterns were grouped into five categories: long fibrous, short fibrous, flake, hackle, and lamellar. These morphologies appear to be related to the magnitude of the applied global stress. The short fibers occurred at low stress, the long fibers at moderate stress, and the flake at high stress. Hackle often appears before the plastic failure as the cross-sectional area of the specimen decreases. Lamellar, the least common structure, may be caused by a combination of a low stress cracking with local plastic failure.

What remains now is to see if this tentative classification applies to stress-cracked specimens from large laboratory tests and for field situations. If the nature of the field failure can be ascertained by comparison with the laboratory-generated categories (small and large sizes), implications to optimal seam types and/or polymer compound type may become apparent.
Influence of Geotextile Structure on Pore Size Determination
Authors: Rigo JM , Lhote F , Rollin AL , Mlynarek J , Lombard G
Published: March 2009

Filtration performance of a geotextile is related to its capacity to retain soil particles over time without clogging. A pore size determination such as the filtration opening size (FOS) is used to assess the geotextile's filtration behavior. Standard hydrodynamic methods use a soil with a uniformity coefficient (Cu) greater than 6, with the coarser particle size value at least twice the estimated FOS value, and with a d10 four times smaller than the FOS value. The filtration opening size determination, using such a soil, is greatly influenced by the size of the coarser particles and by their fraction. Pore size has been overestimated because of these factors and because of the curve continuity. The soil nature of the gradation curve and the quantity of soil used in the test may distort pore size determination, hide some phenomena, and lead to errors in interpretation.

The geotextile structure can be characterized by the mass per unit area, thickness, density of fibers, fiber diameter, porosity, and fabrication process.

This report includes the first results of a laboratory study performed at the Polytechnical School of Montreal, the University of Liège, the University of Grenoble, CEMAGREF (Antony, France), ENEL (Milano, Italy) and the Ontario Ministry of Transports (Toronto, Canada) on the interaction between geotextile structure and filtration opening size (FOS).
Structural Study of Porometry and Filtration Opening Size of Geotextiles
Authors: Faure YH , Gourc JP , Gendrin P
Published: March 2009

The use of geotextiles as filters involves the prior determination of filter criteria. The filtration opening size, Of, is used as characteristic geotextile parameter for the retention criterion. Until now, Of has been determined by an experimental procedure. In this paper, the authors propose a theoretical approach, based on a structural model applied to nonwoven geotextiles. The geotextile is modelled on the basis of the Poissonian polyhedra method, and the distribution of “conduits” passing through the geotextile is defined and evaluated. Once the textile structure has been modelled, particular attention is given to the hydrodynamic sieving test, which provides a means of measuring Of. A theoretical approach is used to simulate cyclic test conditions and to propose a parametric study for optimizing test conditions. This theoretical approach is systematically supported by an experimental validation. The proposed method is the first of its kind to provide a realistic means of forecasting the filtration opening size of nonwoven geotextiles.
Effects of Freezing on the Microstructure of Geotextiles
Authors: Henry KS , Taylor S , Ingersoll JE
Published: March 2009

Examination with a scanning electron microscope (SEM) revealed that a single freeze-thaw cycle in distilled water did not damage the fibers of a needle-punched or a heat-bonded geotextile; however, significant soil particle contamination occurred in the needle-punched fabric after being frozen in soil in laboratory tests. (The heat-bonded fabric was not tested in this manner.) The presence of soil particles both in fabric pores and on fabric fibers suggests that the fabric's ability to reduce frost heave is degraded. Laboratory frost heaving tests showed that a fabric's ability to mitigate frost heave decreased after having been exposed to vertical water flow in soil prior to freezing. The flow is thought to have introduced soil fines into the fabric, but this idea was not confirmed by inspection before freezing. A pumping test conducted with soil in a triaxial cell, designed to simulate stresses on a pavement subgrade during thawing, did not noticeably contaminate the needle-punched fabric tested. Furthermore, fabrics subjected to the triaxial cell pumping performed as well as new fabrics in mitigating frost heave in laboratory soil freezing tests. Whether the triaxial cell pumping test and/or the vertical water flow procedures simulate field conditions has yet to be determined.
Towards Understanding the Behavior of Grave Emulsions by Means of Laboratory Study
Authors: Brennan MJ , Huet M , Lafon JF , Paute JL
Published: March 2009

The evolution of new grave emulsions rich in binder (about 4%) has permitted the coring of materials in situ for laboratory studies. The modulus of poorly conditioned grave emulsion was found to depend on the sum of the restraining forces in a repeated triaxial compression test. However, there was a trend for the modulus of the well-conditioned material to be stress independent. Moduli estimated from direct tension tests using cores of grave emulsion after more than five years service were of the order of one third of the value for a typical dense bitumen macadam. Gyratory compaction studies showed that grave emulsion requires double the compactive effort to achieve the same density as a dense bitumen macadam. Moreover, a compaction plant is less efficient on site with grave emulsion due to the limited ability of pneumatic-tired rollers to expel water from the material.
Classification of Emulsified Recycling Agents
Authors: Muncy SG
Published: March 2009

The use of pavement recycling has steadily gained momentum over the last ten years. This includes various methods of both hot and cold recycling. Recycling has proven to be a reliable alternative to conventional methods of rehabilitation. The end product is of high quality and may be compared to similar methods employing only virgin materials.

Though the use of these methods has increased, a method of selecting and specifying recycling agents has lagged behind. ASTM now has A Standard Practice for Classifying Hot Mix Recycling Agents (D 4552-87). A similar standard for emulsified products is now being investigated.

This paper presents a classification system for the selection and use of emulsified recycling agents. This classification system is derived from currently used practices and extensive field observation of the interaction between materials and methods. Terminology, methods for selection, and general use guidelines are discussed.

Recycling is an important part of any pavement management system (PMS). The Federal Highway Administration has mandated the adoption of a PMS for all states. A PMS will be used to select the appropriate rehabilitation and maintenance procedure based on accepted criteria. A standard system of classification and terminology will place recycling in its proper position within the PMS.

Several state DOTs have established specifications for emulsified recycling products. As needs vary, so have these specifications. States and regions have reduced the full spectrum of products to those serving local needs. The classification system will allow easier transfer of technology as the terminology is standardized.

The classification system defines the emulsified recycling agents by composition as well as by intended performance. With this system in place, engineers will be able to select products on the basis of equipment on hand, traffic constraints, and intended vehicle capacity. This system may be used in application from rural roads to interstate highways.
The Toxicity of Hydrogen Chloride and of the Smoke Generated by Poly (Vinyl Chloride), Including Effects on Various Animal Species, and the Implications for Fire Safety
Authors: Hinderer RK , Hirschler MM
Published: March 2009

Toxicity of smoke is only one of many factors determining the hazard or the risk resulting if a product were involved in a fire in a specific scenario. Other factors include: amount of smoke (i.e., concentration of combustion products in the atmosphere), rate and quantity of heat release, mass loss rate, and flame spread rate, as well as such “environmental” factors as ignition source characteristics, fire detection and suppression devices, building occupancy, and code enforcement. A factor almost specific to the smoke generated from burning poly (vinyl chloride) (PVC) is the decay of hydrogen chloride (HCl) by reaction with building surfaces. The values of smoke toxic potency measured will also be affected by a number of parameters, including combustion mode, exposure mode, toxicological end point, and statistical analysis of results.

A crucial factor, often overlooked, is the choice of an animal model appropriate as a surrogate for man, and its validation. Test animals are frequently chosen on the basis of convenience, cost, or other characteristics (e.g., sensitivity) rather than because of their similarity to man. This is particularly important in combustion toxicology, where one test species may not be a good model for all the major combustion products generated. Thus, comparisons of materials producing different major combustion products must be approached with caution to ensure that any apparent differences encountered in tests are not simply an artifact of test species.

Over recent years, increasing evidence has surfaced that some rodent species are poor models for the toxic response of man to irritant gases or to smoke-containing irritants. Studies on HCl (as a pure gas) and on the smoke generated from the burning of PVC have indicated that mice are much more sensitive than rats. More importantly, they are much more sensitive than primates. It has also been established that rats are a good model for primates in terms of the lethal effects of irritant products. Although primates have survived 15-min exposures to 10 000 ppm of HCl, 2500 ppm is lethal to mice. Moreover, under the same exposure conditions, mice will die at PVC smoke levels four to seven times lower and HCl levels seven to ten times lower than those at which rats will. In contrast, lethal doses of asphyxiants such as carbon monoxide (CO) are similar in rats and mice.

These results indicate that the response of the mouse significantly overestimates the toxic potency of HCl and of PVC smoke to man.
Performance Testing for the Corrosivity of Smoke
Authors: Ryan JD , Babrauskas V , O'Neill TJ , Hirschler MM
Published: March 2009

The corrosivity of combustion products has arisen as an issue for both product manufacturers and standards bodies. While many industries can have concerns in this area, electronic communications and control equipment are especially vulnerable to the problem. The best way to manage the smoke corrosivity issue is to avoid a fire. In the event a fire does occur, a number of actions must be taken. An important consideration is that the materials and products used should have been chosen with due consideration of their corrosion-causing potential. To do this requires a suitable corrosivity test.

It has traditionally been assumed that smoke corrosivity is directly correlated to the emission of acid gases. The results of recent experiments have shown that materials which do not release acid gases can, nevertheless, cause corrosion of metal surfaces, as determined by metal loss. In addition, for electrical equipment there are two other types of related nonthermal damage from combustion products which must be considered, viz., ohmic bridging and degradation of contacts.

Laboratory tests proposed to date to measure the corrosive effects of combustion products all have significant deficiencies: some methods are not performance-based at all and are merely tests for pH. In others, unrealistic specimen heating or unrealistic exposure targets are used. To facilitate the development of a better test, a series of criteria have been developed. A specific test method was evolved from these criteria. The method is performance-based and incorporates realistic fire heating conditions.
Quantitative Analysis of Fracture Surfaces Using Fractals
Authors: Alexander DJ
Published: March 2009

The concept of fractals was used to analyze fracture surface profiles to determine whether fracture surfaces are fractal in nature, and whether the fractal character can be related to either the mechanical properties or the microstructure of the specimens. Sections taken through the fracture surface of fracture toughness specimens were metallographically prepared and photographed, and the fracture profiles were digitized. Simple computer programs which used different techniques to measure the length of the fracture profiles with differing degrees of precision were used to analyze the profiles by generating a fractal plot of apparent profile length versus the measurement step size. The accuracy of the computer programs was verified by examining artificially generated profiles which had a known fractal character. The analyses indicated that fracture surface profiles are indeed fractal, at least over a limited range of detail. However, it was not possible to match the fractal dimension of the fracture profiles to either the mechanical properties of the metals or to their microstructures. In addition, different profiles taken from the same specimen had different fractal dimensions. Discontinuities in the fractal plot could not be related to the microstructural features. Therefore, although fracture surface profiles are fractal in nature, it appears that this information is not useful in understanding the relationship between the microstructure and the mechanical properties.
Fractographic and Metallographic Study of the Initiation of Brittle Fracture in Weldments
Authors: Harrison PL , Abson DJ , Jones AR , Sparkes DJ
Published: March 2009

A technique is described for establishing the microstructural features associated with the initiation of brittle fracture in weld metal and heat-affected zone (HAZ) crack-tip opening displacement (CTOD) test specimens. The technique involves detailed optical and scanning electron microscope examination of fractographic features to establish the local directions of fracture propagation at various locations on the fracture surface. This information is used to trace fracture propagation back to the region of initiation. In many instances, the precise initiating feature can be located and identified. Once identified, the fracture initiation position is marked and the specimen sectioned through this point to allow the region in which fracture initiated to be examined metallographically and related to the surrounding microstructure. Details of the technique are discussed.

Examination of steel weld metal and HAZ regions has revealed nonmetallic inclusions, pearlite colonies, second-phase regions (martensite, retained austenite, or carbide), and localized regions of intergranular fracture as the initiating features. The significance of these findings is considered with regard both to the size of features at which cleavage fracture initiates and to scatter in CTOD values.
The Determination of Calcium and Magnesium Carbonates in Soils and Aggregates
Authors: Choquet F , Ista E , Verhasselt AF
Published: March 2009

The determination of carbonates in soils and aggregates through the measurement of the “loss on ignition” by calcination at 1000°C does not make it possible to discriminate between calcium carbonate, magnesium carbonate, and the double carbonate of calcium and magnesium (“dolomite”).

The measured value may also include the crystallization water and constitutional water of certain compounds as well as any organic matter contained in the samples.

The operation procedure described in the paper is based on the hot acid attack of a test portion of the sample to disengage the carbon dioxide, which is caught in a titrated mixed solution of barium hydroxide and potassium hydroxide. In the acid attack solution, the calcium and magnesium ions are determined by complexometry (possibly by atomic emission or absorption).

The advantage of the method lies in the interpretation of the results. A comparison of these with the theoretical contents calculated for calcium carbonate, magnesium carbonate, and the double carbonate of calcium and magnesium generally makes it possible to discriminate between the various probable carbonates of the analyzed sample. In some cases, the presence of other calcium and magnesium salts can be demonstrated. A number of concrete and experienced examples are presented.
Slurry Wall Backfill Integrity and Desiccation
Authors: Khera RP , Thilliyar M
Published: March 2009

Experiments were conducted to study the effect of desiccation on backfill materials consisting of a sodium bentonite, kaolinite, and sand. The permeant consisted of water, aniline, phenol, and hydrochloric acid solutions. Soil specimens subjected to drying and wetting cycles snowed considerable cracking. The largest cracks were formed with phenol and the smallest with water. With increased kaolinite contents, the width and frequency of the cracks decreased. No cracks were formed with hydrochloric acid. The tests on cracked specimens indicated higher initial permeability which decreased with time and reached the same order of magnitude as uncracked specimens. Essentially all the cracks closed during the permeability tests. In the field, cracks are not likely to close and permeability is inclined to remain high or even increase if the soil in the cracks erodes.
Influence of Some Environmental Activities on Physical and Mechanical Behavior of Clays
Authors: Pamukcu S , Tuncan M , Fang H-Y
Published: March 2009

Chemical contamination of clays during depositional and postdepositional periods influences their physical and mechanical properties. Laboratory-prepared specimens mixed with various percentages of contaminating agents were tested to assess some of these influences. Municipal sludge, fly ash, and fuel oil were selected to represent the contaminating agents. The laboratory specimens were prepared using pure clay minerals or mixtures of them. A part of the specimens was prepared through consolidating the initial slurry, and part was prepared by sedimentation. Variation of shear modulus, permeability, and compressibility with increasing percentages of sludge and fly ash were analyzed for a number of consolidated kaolinite specimens. Some of the behavior was explained through influences of contamination on the formation of clay structure. Scanning electron micrographs were utilized to find evidence in support of the observed behavior. Similar studies were conducted on laboratory-prepared, consolidated marine clay samples. The shear modulus of both fuel oil and sludge mixed samples were found to decrease. The decrease was most significant in the fuel oil sample. This was attributed to the formation of an open, loose microstructure and the increased water-holding capacity of the specimen. The rate of settlement of sedimented clays were found to be influenced by the presence of contaminating agents.
A Modified Shear Strength Formulation for Swelling Clay Soils
Authors: Chatterji PK , Morgenstern NR
Published: March 2009

Physico-chemical forces of repulsion and attraction exist in swelling or active clay-water systems. A modified shear strength formulation that extends the classical Terzaghi effective stress relationship to include physico-chemical forces is proposed in this paper.

Residual shear strength comparisons were carried out for five carefully controlled, large-strain direct-shear tests on Na-montmorillonite before and after leaching with distilled water and under constant overall volume conditions. These tests indicated that the volume change and residual shear strength characteristics of Na-montmorillonite are governed by the true effective stress, σn*, defined in the modified effective stress relationship as the difference between the total stress, σn, and the summation of pore water pressure, uw, and the net physico-chemical forces of repulsion and attraction (R - A). Additional data available in the literature on residual strength of swelling clay minerals also appear to support the modified strength formulation.

Actual measurements of overall (R - A) forces during leaching of the samples appeared to agree well with theoretical estimation of the net physico-chemical forces.
Tracer Experiments in Saturated Sand by Computed Tomography and Inductively Coupled Plasma
Authors: Steude JS , Sullivan CP , Chaney RC , McKee M , O'Shea LE
Published: March 2009

The spreading of a tracer in saturated sand is important to the understanding of groundwater hydraulics and is fundamental to issues concerning groundwater quality. A thorough understanding of this spreading process is necessary for accurate forecasts of the behavior of groundwater resources. Computed tomography (CT) is a nondestructive testing technique developed for medical diagnostic purposes. Recently, soil scientists and petroleum engineers have used CT to measure a variety of soil properties including bulk density, porosity, water content, etc. Computed tomography scanning is based on attenuation measurements of X-ray beams which are directed through an object from many different angles. These measurements are numerically reconstructed with a digital computer to produce a tomogram or internal “picture” of the distribution of the X-ray attenuation in the object. This distribution can be correlated to the variation of other properties, such as those mentioned above. The time required to produce the tomogram is relatively short (seconds) compared to the duration of a typical flow experiment (minutes to hours); thus, CT scans can generate real-time data. The inductively coupled plasma (ICP) method is a standard method used in the analysis of groundwater for inorganic contaminants. It is based on the measurement of atomic emission by an optical spectroscopic technique. The objectives of this study are: (1) to use CT to develop a procedure that measures the spreading of saline tracers in saturated sand with X-ray attenuation measurements; (2) to test this procedure with laboratory flow experiments; and (3) to validate the CT flow experiments with chemical analyses of effluent samples using the standard ICP method. The results of statistical lack-of-fit analyses indicate that a linear model can be used to relate tracer concentration in saturated sand to X-ray attenuation. Breakthrough curves, plotted as relative concentration versus time, are obtained from flow experiments conducted with tracers and analyzed with CT technology. The results of this investigation indicate that existing medical CT technology can be used effectively to measure tracer concentration in flow experiments in saturated sand. The results of ICP analyses support the CT results. The ICP results also clarify the limitations of the CT procedure used here.
Thermomechanical Analysis in Materials Science
Authors: Neag CM
Published: March 2009

In thermomechanical analysis (TMA) changes in sample dimensions are measured as a function of time or temperature under a nonoscillatory load. When these changes are measured without an applied load the technique is referred to as thermodilatometry. Taken together, these techniques are used in describing the viscous and elastic properties of materials ranging from liquids to polymers to metals. While a wide variety of instrumentation is available, they differ primarily in probe type, the arrangement of the applied loads, the mode of detection (mechanical, optical, or electrical), and the degree of automation. This paper will provide an overview of the techniques, instrumentation, and applications of thermomechanical analysis in material science.
Temperature Calibration of Thermomechanical Analyzers: Part II—An Interlaboratory Test of the Calibration Procedure
Authors: Seyler RJ , Earnest CM
Published: March 2009

An interlaboratory “round robin” test study was conducted for the calibration method developed by ASTM Task Group E37.01.12, which is described in this paper. The interlaboratory test protocol was consistent with the requirements outlined in ASTM Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method (E 691). The results obtained by ten participating laboratories are reported. A precision and bias statement for the ASTM Test Method for Temperature Calibration of Thermomechanical Analyzers (E 1363) was developed from the statistical treatment of the data.
Material Characterization by Thermomechanical Analysis: Industrial Applications
Authors: Riga AT , Collins EA
Published: March 2009

Thermomechanical analysis (TMA) has been used to study a wide spectrum of materials over a broad range of temperatures in our laboratories. Polymers, motor oil-wax composites, ceramics, alloys, and metals have been studied from -100 to 600°C. The TMA properties that have been measured are the glass transition temperature, softening point, coefficients of linear expansion, heat deflection temperatures, creep modulus (compliance) and relaxation, degree of cure, viscoelastic behavior, dilatometric properties, melting temperature, Curie, and Neel magnetic transition temperatures and properties.

Polymer cure has been studied and is indicated by variations in the glass transition temperature and increased with heat cycling. A good correlation exists between ASTM Vicat softening temperatures and heat deflection temperatures under load with TMA transition temperatures, which approximate strength and Tg. A scheme has been developed to rank commercial polymers based on their creep modulus and creep recovery. There is a good correlation between the TMA creep properties and the known tensile properties of commercial polymers.

Additive-treated oil forms short stubby wax crystals, which lead to a low creep modulus oil-wax composite at -60°C. This soft composite (gel) melts at a depressed temperature. These TMA properties have been related to low-temperature pumpability and engine performance.

The critical magnetic transition temperatures (Curie and Neel) of a number of ceramics and alloys have been determined by TMA. There is a good correlation between the TMA, differential scanning calorimetry (DSC), and literature critical magnetic temperatures. The mechanism responsible for magnetic changes in the paramagnetic state has been elucidated from TMA expansion rates and DSC exothermicity.
Elasticity Characterization of Materials During Thermal Treatment by Thermal Mechanical Analysis
Authors: Wiedemann HG , Riesen R , Boller A
Published: March 2009

The viscoelastic behavior of natural and synthetic materials changes during thermal treatment. Thermomechanical analysis (TMA) is the method to determine these mechanical properties directly as a function of time and temperature. Depending on the selected measuring mode either the expansivity (dilatometry), the viscous flow (penetrometry), or the elastic behavior can be investigated. Young's modulus is calculated from flexure and compressive measurements.

To give an overview of these possibilities thermoplastic polymers, poly(methyl methacrylate) (PMMA) and polyethyleneterephthalate (PET), and rubber have been analyzed. The solid transition of α-β quartz revealed a minimum of the Modulus of Elasticity during the transition. Flexure measurements of wood specimens during degradation show the different elastic regions.