bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties and NDE of a HIP'ed Silicon Nitride
Authors: Khandelwal PK
Published: March 2009

Life prediction analytical methodology for ceramic gas turbine engine components requires the incorporation of time- temperature-stress dependent behavior and properties of the structural material. Injection molded and hot isostatic pressed PY6 silicon nitride with 6% yttria was used for this study. The room temperature fast fracture modulus-of-rupture (MOR) strength of 812.9 MPa degraded at 1400°C to 465.6 MPa. The monotonic tensile strength at room temperature was 407.9 MPa, which degraded to 303.3 MPa at 1400°C. Scanning electron microscopy (SEM) indicated that MOR specimens predominantly failed from surface flaws at room temperature, whereas the tensile specimens failed from volume defects. At higher temperatures, however, the failures occurred from surface and volume flaws in both the MOR bars and tensile specimens. Tensile creep data between 1260°C and 1400°C resulted in a stress exponent (n) of 7.8 ± 1.0 with an apparent activation energy of 957 ± 149 kj/mole. SEM revealed that the material between 1300°C and 1400°C failed due to the formation, linking, and growth of cavities that caused the material to creep. At lower temperatures, failure was controlled both by slow crack growth and creep.

Microfocus X-ray detected 50 micron laser drilled surface holes in flat and button-head cylindrical specimens with a thickness sensitivity of 1% to 2%. Surface wave acoustic microscopy detected 10 micron surface holes in button-head tensile specimens.
Application of Mixed-Mode Fracture Criteria for Weakest-Link Failure Prediction for Ceramic Materials
Authors: Scholten HF , Dortmans LJ , deWith G
Published: March 2009

A set of combined experimental and numerical data is presented for the prediction of multiaxial strength for ceramics. Uniaxial and biaxial bend tests were performed on ten different materials. The strength predicted with various mixed-mode fracture criteria was compared with the measured values. A main conclusion was that with the introduction of an additional parameter, a “size-independent strength”, all tests were predicted within 3% accuracy. However, different criteria had to be used, which could not be interchanged between the various materials. The “size-independent strength” parameter is interpreted as a measure for the applicability of the weakest-link concept. Its physical meaning is yet uncertain, but predictions on materials for which the porosity was less than one percent showed that for these materials the deviations are largest. This could indicate that basic assumptions in the weakest-link models applied with respect to defect density are violated for these materials.
Time-Dependent Strength Degradation and Reliability of an Alumina Ceramic Subjected to Biaxial Flexure
Authors: ChaoL Y , Shetty DK
Published: March 2009

Fracture stresses of a sintered alumina ceramic were assessed in qualified uniaxial (three- and four-point) and biaxial (uniform pressure-on-disk) flexure tests under inert conditions (dry N2, 100 MPa/s stressing rate) and in deionized water at a low stressing rate (1 MPa/s). The size and stress-state effects on the inert fracture stresses of the alumina ceramic could be explained by a reliability analysis based on randomly oriented surface flaws and a mixed-mode fracture criterion. The decreased fracture stresses measured in both uniaxial and biaxial flexure tests in water were consistent with subcritical crack growth behavior inferred from dynamic fatigue tests in water. The reliability analysis of the size- and stress-state effects on and time-dependent degradation of fracture stresses included consideration of the statistical uncertainties (90 % confidence bands) of the estimated Weibull (Weibull modulus, m, and characteristic strength, σɵ) and slow-crack-growth (stress-intensity exponent, N, and critical crack growth rate, Vc) parameters. Results suggested that subcritical crack growth and strength degradation were more severe in biaxial flexure than in uniaxial flexure, which implies an interaction between stress state and subcritical crack growth.
Determination of Defect Distributions for Use in Failure Theories of Load Bearing Ceramics
Authors: Margetson J
Published: March 2009

Probabilistic failure theories have been developed for predicting the structural reliability of complex components subjected to conditions of multiaxial stress. Embodied in these theories are material failure characteristics which describe the statistical variation of defects within the volume and over the surface of the material. In this paper a method is presented for analysing the strength data. It is shown how the respective volume and surface defect distributions can be analysed to yield the strength parameters required by the various probabilistic multiaxial failure stress theories.
Probabilistic Methods for Ceramic Component Design and Implications for Standards
Authors: Cuccio J , Peralta A , Song J , Brehm P , Johnson C , Tucker W , Fang H
Published: March 2009

Probabilistic methods developed at Garrett Auxiliary Power Division of Allied-Signal Aerospace Company under the “Life Prediction Methodology for Ceramic Components of Advanced Heat Engines” program sponsored by The Department of Energy/Oak Ridge National Laboratory (DOE/ORNL) under contract No. 86X-SC674C (WBS Element 3.2.2.3) are presented. Statistical methods have been developed to estimate Weibull strength parameters and component reliability with confidence limits for structural ceramics. Estimates can be made using pooled strength data from specimens of multiple sizes and loading conditions, from multiple test temperatures, and from material with multiple strength distributions. Bootstrap and likelihood ratio techniques are used to calculate confidence intervals on parameters and reliability estimates from these complex pooled data sets. A large database was generated on one ceramic (NT154 silicon nitride) to verify the methods. These statistical methods guide the development of standards for more accurate parameter estimation, to define component reliability requirements with confidence limits, and to plan specimen tests for more efficient estimation of Weibull parameters and component reliability.
Evaluation of Tests for Measuring the Strength of Ceramic Tubes
Authors: Kranendonk WGT , Sinnema S
Published: March 2009

To measure the strength of ceramic tubes the C- and O-ring tests have been proposed. In the analysis of these tests, assumptions have been made, which can not always be fulfilled in practice. With computer simulations we investigated the stress distribution in C- and O-rings. We found that for C- and O-rings with a length to wall- thickness ratio of 6 the plane stress assumption fails and that axial stresses are not negligible. Also we investigated the influence of the load angle on the stress distribution in an O-ring test.
Head and Neck Injuries in Equestrian Sports
Authors: Bixby-Hammett DM
Published: March 2009

Horse activities have a large number of participants in the United States. Most accident occur in leisure activities making record keeping difficult. Horse activities are relatively safety ranking 67 in the number of admissions to hospital emergency rooms in the USA. Injuries when they occur to equestrians tends to be severe.

Statistics from Medical Examiners in the United States and morbidity studies from Australia and New Zealand are given as well as statistics from four sources: the National Electronic Surveillance System (NEISS), the Justin Sportsmedicine Program, the National Park System visitor and employee injuries and the United States Pony Clubs.

The figures show head/face/neck injuries in horseback riding are frequent and severe and can be prevented or reduced in severity by wearing secured ASTM SEI protective helmet. The horse and academic community by communication and cooperation should design studies which can provide information needed to prevent these injuries.
Psychological Characteristics of the Chronically Injured Athlete
Authors: Duffy FM
Published: March 2009

The helpseeking literature is used to provide a theoretical framework from which to study athletic injuries. The literature suggests that athletes possess specific characteristics (high self-esteem, high need to achieve, internal locus of control, masculine sex-role orientation, independence) which highlight the negative aspects of seeking and receiving aid and athletes performing at a higher competitive level have a higher degree of these characteristics. In addition, the literature supports that people with these characteristics perceive seeking and receiving help as very threatening. It is hypothesized that this threat is manifested by the following: a) delay in seeking help; b) less use of help; c) more self help; d) non-compliance; and e) a high rate of drop out in rehabilitation. It is also hypothesized that these behaviors create an injury-prone athlete.
Impact Postures and Neck Loading in Head First Collisions: A Review
Authors: Bishop PJ
Published: March 2009

Axial compression of the cervical spine is a significant source of spinal cord trauma and quadriplegia. This paper summarizes a number of studies related to injury mechanisms and potential strategies for reducing the risk of trauma. Head first collisions at 1.8 m.s-1 were conducted with a mechanical test dummy fitted with a force and moment transducer in the neck. Films taken at 500 fps confirmed that the head-neck-torso system was decelerated in stages rather than uniformly, so that the neck became trapped between the fixed head and moving torso. Compression forces were about 4800N for the neutral neck and 3800N for the flexed neck. Further analysis with a post-processing computer model of the cervical spine revealed compressive forces in excess of 5000N in the lower regions (C5, C6, C7) for both the flexed and neutral postures. Simulations with the neck extended suggest that the anterior longitudinal ligament, the neural arches and spinous processes would likely be damaged. When the ATD was subjected to blows that produced side bending of the head and neck the compressive force output from the transducer was 50% lower when compared to direct axial loading. This side bending posture appears to offer some promise in reducing the compressive loads on the spine due to head first collisions.
30 Plus Years of Head and Neck Injuries - Primate and Human Models' Responses to Energy Load and Forces
Authors: Unterharnscheidt FJ
Published: March 2009

This paper reports on a carefully controlled series of 4 groups of experiments using animal models, examining head and spinal cord injuries. In the first group of experiments, animals were subjected to both direct single and repeated applications of direct controlled impact to the head, using the concussion gun designed by Foltz, et al. causing translational (linear) acceleration. In a second group of experiments controlled nondeforming rotational acceleration was directed through a known path near C7-T1, using Head Acceleration Device II (HADII). The third group consisted of animal experiments using Rhesus monkeys undergoing -Gx impact vector acceleration of the restraint torsi but freely movable head and neck, and in the fourth group the same type of indirect impact acceleration was undertaken using +Gx impact vector acceleration. In each group detailed histological examinations were carried out using a Spielmeyer assortment.
Experimental Production of Head-Neck Injuries Under Dynamic Forces
Authors: Pintar FA , Yoganandan N , Sances A , Cusick JF
Published: March 2009

Compression related mechanisms of injury are common in sports and recreational trauma to the human cervical spine. The purpose of these studies was to experimentally reproduce common clinically seen injuries of the head-neck complex. A total of 19 preparations (8 quasistatic, 11 dynamic) were used to obtain strength and motion information correlated to pathology. The quasistatic studies served to develope a method to kinematically monitor the localized deformations in the tissue as injury occurs. It was observed that significant relaxation of the tissues occur post-traumatically and the kinematic analysis quantified the true extent of the deformations to the cervical spine components. Under dynamic loading, mid to lower cervical spine compression-related trauma occurred. To reproduce these kinds of injuries, the pre-existing lordosis was removed and the head-neck complex was dynamically impacted. Parallel studies on the Hybrid III anthropomorphic manikin head-neck indicated a substantially different response in compression compared to the human cadaver specimens.
The Incidence of Spearing by Ball Carriers and Their Tacklers During a High School Football Season.
Authors: Heck JF
Published: March 2009

This study established the cumulative incidence per season of ball carrier spearing and concurrent defensive spearing by tacklers for a New Jersey high school football season. Spearing (flexing the neck and initiating contact with the top of the helmet) is a significant cause of injury to the head and neck in football. To reduce the risk of head and neck injuries in football all types of spearing must be explored. Nine game films from the 1989 football season were viewed to determine the incidence of ball carrier spearing and concurrent defensive spearing. There were 167 incidents of ball carrier spearing (1 per 5.1 plays) and 72 incidents of concurrent defensive spearing (1 per 2.3 ball carrier spears). Officials can now penalize any player who initiates contact with his head. However, there were no spearing penalties called throughout the 1989 season. This study detected a surprisingly high cumulative incidence of ball carrier spearing and concurrent defensive spearing, along with poor enforcement of the spearing rule. To further reduce the risk of head and neck injuries officials should acknowledge ball carrier spearing as a rule infraction and enforce existing spearing rules during the tackling process. Coaches also should teach and drill correct technique with ball carriers, tacklers, and blockers throughout the season.
Head Injured Patients Who Talk Before Deterioration or Death: The TADD Syndrome
Authors: Ommaya AK , Thibault LE , Boock RJ , Meaney DF
Published: March 2009

A review of a class of head injured patients who display a lucid interval before onset of coma which defines an important category of brain trauma. A hypothesis explaining the mechanism of this syndrome (T.A.D.D.) is developed on the basis of in-vitro testing of venous and arterial responses to tensile strains and the relevant clinico-pathologic data are reviewed. Venospasm is proposed as the cause of secondary ischemic hypoxia associated with a high incidence of acute subdural hematomas and brain swelling. Suggestions for further testing of this hypothesis and implications for preventive management are discussed.
Measurement of Sensory Functioning and Integration Following Closed Head Injury
Authors: Ingersoll CD
Published: March 2009

A protocol for measuring sensory functioning and integration is discussed along with different approaches for examining the information collected. This protocol involves performing six variations of the Romberg test on a force platform. The six test conditions either eliminate sensory input or produce inaccurate visual and/or surface orientation inputs. Total, anterior-posterior, and medial-lateral sway are calculated from force platform center of pressure data. Five Romberg coefficients were formulated to determine the relative destabilizing effects of the last five test conditions. Center of pressure data were also subjected to a Fast Fourier Transform to examine the frequency spectrum associated with postural sway. Five frequency bands representing visual input, semicircular canal function, otolith function, and somatosensory input are evaluated. The results of studies examining each of these methods of evaluating sensory function and integration are presented.
ASTM F-1292 as a Tool for Playground Injury Severity Reduction
Authors: Shiffer RC
Published: March 2009

In 1986 an activity was undertaken by ASTM Committee F08 to develop a standard specification for testing playground surfaces impact attenuation. This activity resulted in the 1991 publication of ASTM F-1292 “Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment.” This specification sought to clarify the 1981 United States Consumer Product Safety Commission (CPSC) guideline recommendation of instrumented headform deceleration levels less than 200 G-max when tested at accelerations equal to play equipment critical heights. As such, it specifies test methodology to be used for surface testing to be conducted both in the laboratory and in the field and allows the determination of the maximum drop height at which G-max does not exceed 200. In the 1991 CPSC guideline recommendation, a second criteria of less than 1000 Head Injury Criteria (HIC) was added to the 200 G-max requirement. Revisions to ASTM F-1292 are currently being balloted to include this 1000 HIC requirement and attendant acquisition methodology.
Problems Prompt a Quest for High Quality Standards
Authors: Cullen WC
Published: March 2009

Roofing problems can be traced to a lack of standards, inadequacies in standards, non-conformance to or non-enforcement of standards. It follows that the occurrence of certain problems can be reduced or eliminated by producing appropriate, quality standards that are adhered to by the specified products. Five case studies are examined that focus on roof performance problems dealing with specific roofing materials described by ASTM standard specifications.

Suggestions are offered for revising specific standards by adding requirements based on available research results. Packaging and labeling requirements as well as precision and bias statements are also discussed.
A New Analytical Method for Determining the Distribution of Components in Asphalt Coated Felts and Shingles
Authors: Cash CG
Published: March 2009

This paper describes a new analytical method for determining the mean and standard deviation of the mass of each component of all asphalt coated felt products, excluding APP (atactic polypropylene) modified bituminous products (APP and other polypropylenes are relatively insoluble in 1,1,1 trichloroethane).

Methods for estimating the composition of products manufactured on asphalt saturated organic and asbestos felts are well known. Until now, similar analytical methods have not been available for products made with glass fiber felts. This new method adapts and improves on the older methods, to provide more refined and precise data for products made with most felt types, and which may lead to new concepts about the performance of these products.

Specific examples include comparative analyses of the exposed and unexposed segments of a typical 3-tab strip asphalt shingle manufactured on glass fiber felts, the top part of a laminated asphalt shingle manufactured on glass fiber felts, an SBS (styrene-butadiene-styrene) modified asphalt sheet, a conventional asphalt shingle manufactured on organic felt, and an SBS modified shingle made on a glass fiber felt.
Tear Resistance of Roofing Membranes
Authors: Dutt O , Paroli RM , Lei W , Mebrahtu H
Published: March 2009

Roofing membranes are subjected to a tear stress when stretched near a notch, cut, or nail hole. The force required to initiate or propagate tears in roofing membranes was studied using various standard test methods. The materials used in the study included reinforced EPDM (ethylene propylene diene monomer), PVC (polyvinyl chloride), and MBM (modified bitumen). The results were obtained from the load-displacement diagrams using the mean of three or five peaks on the test charts, as required. The tests showed significant differences in the values obtained by various methods. Five methods were used to investigate the tearing mechanism: four were existing standard methods and a fifth method involved grips designed at the National Research Council of Canada (NRCC). In this new method, the specimen is held in a top and bottom pair of grips that swivel as the tearing progresses. The gripping configuration in the tensile tester produces stress concentration in a very small area around the root of a tear and minimizes the tearing effort. Each membrane sample was tested with all five methods. Comparison of the results suggests that the swivel grips provide a more realistic simulation of tearing phenomena because tearing occurs at the lowest applied force.
Three Modified Bitumen Roofing Membranes at Fort Polk: Preliminary Field Test Results
Authors: Bailey DM , Rossiter WJ , Seiler JF
Published: March 2009

The results of the first five years of a 10-year field evaluation on three modified bitumen roofing systems at Fort Polk, LA are presented. This work is part of a research effort being conducted by the U.S. Army Construction Engineering Research Laboratories (USACERL) to investigate long-term performance of single-ply membrane roofing materials.

In 1987, three different modified bitumen roofing systems were installed on Building 920 at Fort Polk: a torch-applied atactic polypropylene (APP), a hot-mopped styrene-butadiene-styrene (SBS) and a self-adhering SBS membrane. At the time of installation, the roof membrane materials were tested for initial properties to provide a basis for comparison with later samples. Test samples for each roofing system were taken during the initial installation and at years 1,2,3, and 5. A total of nine tests measuring mechanical and physical properties of the membranes were performed on each of the sets of samples. The properties being evaluated were those considered essential to good roofing performance. For most properties, American Society of Testing and Materials (ASTM) standard test methods were used. In addition to the membrane testing, the roofs have been visually inspected once each year. Preliminary findings indicate that the test roofs are performing well.
Maximum Tensile Load and Elongation Properties of Heated Built-Up Roofing Membranes at Selected Cold Temperatures
Authors: Stenman HK , Mech MN , Paroli RM , Lei W
Published: March 2009

The effect of heat-conditioning on the maximum tensile load and elongation properties at cold temperature of glass and organic felt, 4-ply reinforced asphalt built-up roofing (BUR) membranes was determined. Specimens were heat-conditioned at 65°C (150°F) for 1, 7, and 28 days. Both the conditioned and the unconditioned membranes were tested for maximum tensile load and elongation. The specimens were prepared in both the machine and cross-machine directions. The tests were conducted at room temperature and at seven temperatures ranging from 0 to -60°C (32 to -75°F). In general, glass-felt BUR membranes showed higher elongations than the organic-felt BUR. The maximum tensile loads for both membranes were in the same range for the machine direction. The glass-felt BUR was stronger in the machine direction. The maximum tensile load and elongation of glass felt BUR are affected neither by heating time nor by testing temperatures below -10°C (14°F). The maximum tensile load of organic-felt BUR increases and elongation decreases with cold testing temperatures.
The Effects of Acrylic Maintenance Coatings on Reducing Weathering Deterioration of Asphaltic Roofing Materials
Authors: Antrim R , Johnson C , Kirn W , Platek W , Sabo K
Published: March 2009

Acrylic maintenance coatings are applied over aged organic asphalt shingle and built-up roofs and allowed to weather for 6–10 years. Test cut samples are analyzed chemically and via optical and scanning electron microscopy techniques and compared to uncoated areas subject to the same weathering. A mechanism for explaining weathering of asphaltic roofing materials is proposed, and the effect of acrylic maintenance coatings in reducing weathering is also clearly elucidated and documented.
Enhancement of the Standard for PVC Roof Membrane Material with the use of Mechanical and Chemical Analysis
Authors: Paroli RM , Dutt O , Smith TL , Whelan BJ
Published: March 2009

Samples of reinforced and unreinforced PVC roofing membranes were studied using dynamic mechanical analysis and tensile testing. Preliminary work has shown that the glass-transition temperature provides an indication of the relative stability of the membranes and may assist in understanding the shattering phenomenon.

This study discusses the utility of using the glass-transition temperature in standards for the reinforced PVC roofing membranes. It is shown that Tg values are easily obtained from dynamic mechanical analysis (DMA) and that DMA should be considered in the standards for roofing membranes.

Based upon the characterization of samples from shattered roofs, as well as reinforced materials subjected to artificial weathering, recommendations for enhancing the ASTM Standard D4434 are presented.
Short Term Moisture Gain Behavior of Perlite Rigid Insulation
Authors: Dupuis RM , Ilievsky O
Published: March 2009

Perlite rigid board insulation is in wide use as a primary insulation board in built-up roofing systems. Perlite insulation board is also used as a cover or overlayment board with foam insulation boards such as polyisocyanurate. The standard methods of attaching the perlite boards are to either mechanically fasten them or attach with hot asphalt as an adhesive. Quite often the first layer is mechanically fastened and the second layer is attached with hot asphalt. Recent field problems have developed wherein the use of perlite boards attached with hot asphalt and then covered with a fiberglass felt roof membrane have led to blistering. The blistering is isolated in occurrence, but severe when it occurs. A testing program undertaken to examine this behavior has uncovered the fact that perlite has a precipitously fast moisture gain/release behavior, depending apparently on the cellulose filler. The current test methodology and resulting data point to a need to revise the ASTM standards for these boards. This paper will provide the data, background, and technical motivation for reaching a better understanding of this phenomena. The time sequence for short term moisture vapor migration was found to be in 60 seconds or less. Perlite recover boards with higher cellulose contents were found to have a faster rate of water vapor migration at temperatures in the 400° Fahrenheit range (204° C).
Foam Failure in the Near-Facer Region in Polyisocyanurate Insulation Foams
Authors: Gaddy GD
Published: March 2009

Field experience has shown that facer delamination, or more accurately, foam failure in the near facer region, occurs in polyisocyanurate insulated roofing systems. This paper examined the conditions which may lead to foam failure in the near-facer region, defined here as the first two to seven cell layers of foam from the facer. The study examines delamination in faced polyisocyanurate (PIR) foam boards. These boards were blown with blowing agents including CFC-11 and HCFC-141b. The samples were tested before and after in-service exposure. Tensile strength and Young's modulus were determined as was the site of foam failure. Light microscopy was used to analyze the near-facer region both before and after failure and to determine the aspect ratio in the foam. Failure was found to occur in the near-facer region in all faced samples tested. Failure occurred in the faced foams at one half the stresses found in the unfaced samples. Additionally, the samples were found to have distinctly different tensile strengths near the upper facer than in the bulk of the foam.
Predicting Performance of Adhesively Bonded Joints Based on Acousto-Ultrasonic Evaluation
Authors: Karhnak SJ , Duke JC
Published: March 2009

Prediction of the performance of adhesively bonded joints is essential to the acceptance of this mode of fastening. In situations where the bonding is uniform throughout the joint the stress distribution depends primarily on the joint geometry. A knowledge of the bond properties and the stress distribution and magnitude can be used to determine failure initiation, subsequent load redistribution, changes in stress, additional regions of failure, and ultimately when the bonded joint will separate. However, in many actual situations the bonding is not uniform throughout the joint, and even the properties of the adhesive may vary. This paper describes work that addresses this situation. Acoustic microscopy has been used to provide a detailed image of the bonded joint, while acousto-ultrasonic measurements have been used to evaluate the stress transfer capability of modified lap shear adhesively bonded joints. The adhesively bonded composite material specimens were mechanically tested and performance correlated with NDE results.
The Durability of Adhesive Bonded Epoxy Carbon Fibre Composite
Authors: Parker BM
Published: March 2009

Two methods commonly used to measure the durability of adhesive bonded joints, namely the lap shear joint and the wedge test, are compared for carbon fibre reinforced epoxy matrix composite. For unaged joints, where bond strength varies due to surface contamination, it is shown that lap shear strength and initial crack length are related when failure is interfacial between adhesive and adherend. When these joints are used for durability testing, by exposure to constant hot/wet laboratory conditions, the results do not appear to be comparable because the changes measured are attributable to changes in the adhesive properties rather than in the adhesive-adherend interfacial region. The lap shear strength can be related to the calculated moisture content and distribution in the joint.
Advances in MIC Testing
Authors: Little BJ , Wagner PA
Published: March 2009

The study of microbiologically influenced corrosion (MIC) has progressed from phenomenological case histories to a mature interdisciplinary science including electrochemical, metallurgical, surface analytical, microbiological, biotechnological, and biophysical techniques. With microelectrodes and gene probes it is now possible to measure interfacial dissolved oxygen, dissolved sulfide and pH, and to determine microbial species responsible for localized chemistry. Biofilms can be tailored to contain consortia of specific microorganisms and naturally-occurring biofilms can be dissected into cellular and extracellular constituents. Scanning vibrating electrodes can be used to map the distribution of anodic electrochemical activity. Electrochemical impedance spectroscopy and electrochemical noise analysis techniques have been developed to non-destructively evaluate localized corrosion due to MIC. The development of environmental scanning electron, atomic force, and laser confocal microscopy makes it possible to image cells on surfaces and to accurately determine the spatial relationship between microorganisms and localized phenomena. Transport of nutrients through biofilms can be modeled using techniques including optical density measurements to precisely locate the water/biofilm interface and nuclear magnetic resonance imaging to visualize flow characteristics near surfaces colonized with microorganisms. The ways in which new techniques can be used to understand fundamental mechanisms and to discriminate MIC will be discussed in this paper.
The Use of Field Tests and Electrochemical Noise to Define Conditions for Accelerated Microbiologically Influenced Corrosion (MIC) Testing
Authors: Brennenstuhl AM , Gendron TS
Published: March 2009

The problem associated with the development of an accelerated test for assessing the susceptibility of materials to microbiologically influenced corrosion (MIC) is an uncommonly difficult one, The usual methods of accelerating corrosion such as increasing the temperature and concentration of aggressive species cannot be used. Both these factors have to be maintained within relatively tight limits, otherwise unacceptable changes in the biology of the system will result. Conventional, anodic polarization techniques can produce misleading information because the very high fields produced at the metal surface during polarization are incompatible with the maintenance of viable microorganisms. Other methods of acceleration and detection must therefore be sought.

A combination of failure analyses, laboratory studies, and field simulations has been useful to determine the mechanism of corrosion of Ontario Hydro's freshwater cooled heat exchangers (HXs) and to identify the most detrimental operating conditions. During field simulations of the worst conditions, electrochemical noise monitoring has identified a reproducible response that could be an MIC signature. This signature may be used to verify the relevance of proposed accelerated MIC tests to field operation.

This paper describes the methods and results of field experiments using electrochemical noise monitoring and their implications for accelerated MIC testing.
Review of Effects of Biofilms on the Probability of Localized Corrosion of Stainless Steels in Seawater
Authors: Salvago G , Taccani G , Fumagalli G
Published: March 2009

Measurements have been made of pH values in the layer adjacent to finemeshed screens immersed in artificial and natural seawater. The results obtained on platinum, bronze, nickel-based alloys, stainless-steel and carbon-steel screens indicate that acidic environments can be formed beneath the biofilm on even cathodically polarized metallic materials. From an examination of data regarding the exposure of different materials in galvanic couples to natural and artificial environments, it seems clear that stainless steels exposed to the acidification of the artificial environment: (1) leads to depolarization phenomena of the cathodic processes, with effects qualitatively but not quantitatively similar to those observed in natural seawater; and (2) enhances the localized corrosion onset probability, though the attack penetration depth is lower than values observed in natural seawater.

The different procedures for obtaining polarization curves in seawater, as well as the significance of the numeric values achieved, are discussed herein. The electrochemical complexity of biofilms is emphasized. Some aspects of the biofilms formed on stainless steel exposed to seawater are similar to those observed for conductive polymer films, such as polypyrroles.
Developments in On-Line Fouling and Corrosion Surveillance
Authors: Stokes PSN , Winters MA , Zuniga PO , Schlottenmier DJ
Published: March 2009

Corrosion and fouling impact the operation of cooling water systems in terms of reduced heat-transfer capability, increased maintenance cost, loss of plant availability, and water contamination. Conventional test methods have focused separately on measurement of fouling build-up by electrically-heated or pressure-drop apparatus and corrosion detection by electrical resistance or electrochemical methods. A major drawback of conventional fouling monitors has been the inability to indicate real-time corrosion activity beneath surface deposits. Consequently, it has been necessary to destructively evaluate test heat exchanger tubes and/ or rely upon use of corrosion coupons and probes, or both, under nonheat flux conditions. A recent test method, focusing on two simultaneous effects, monitors localized corrosion (pitting, etc.) promoted beneath a fouled heat exchanger tube. The corrosion tendency of a surface under heat flux differs from corresponding surfaces without heat transfer in two respects. First, higher temperature increases the rate of corrosion reaction kinetics. Secondly, scales or biofilms prevent uniform corrosion and promote localized attack, often in the form of pitting. Furthermore, the presence of deposits creates a microenvironment at the heat transfer interface that can prevent the ingress of certain species (inhibitors, biocides) and increase the concentration of others (acidity, bacteria). Contrary to expectation, the presence of scales or biofilms will often exacerbate damage, not prevent it. An overview of the test method and recent field results carried out at Amoco Chemical Company's Chocolate Bayou Plant are presented and discussed.
The Characterization of Sulfate-Reducing Bacteria in Heavy Oil Waterflood Operations
Authors: Jack TR , Rogoz E , Bramhill B , Roberge PR
Published: March 2009

This study was carried out in an oilfield waterflood operation in which produced brine is reinjected to displace oil from the reservoir. Significant corrosion problems are associated with bacterial colonization of the water handling system. Previous work has focused on optimizing biocide treatments, but there are limits to what is economically achievable by this approach.

This report describes results of an audit of chemical, biological and corrosion parameters measured across the Wainwright waterflood operation over a 30-month period. The intent of the audit was to provide a basis for understanding and improving monitoring and control practices in such operations.

Corrosion-monitoring methods generally failed to correlate in a simple way with corrosion failures. Failure frequency correlated with several water chemistry parameters. Common treatment chemicals showed evidence of promoting bacterial growth. Sulfate-reducing bacterial numbers were found to be a function of position in the system, population composition and water chemistry.

Based on the insights obtained, a series of runs was carried out in a special test facility to assess the effects of trace nitrate, oxygen scavenger, and nutrient addition on the sessile bacterial populations present in an operating unit. Results are briefly described.
An Electrochemical Method for On-Line Monitoring of Biofilm Activity in Cooling Water Using the BloGEORGE™ Probe
Authors: Licina GJ , Nekoksa G , Howard RL
Published: March 2009

The presence of active microorganisms on piping and components in cooling water systems can have a profound effect on the corrosion performance of such systems. Microbiologically influenced corrosion (MIC) can result in premature failures of critical and support systems, increased downtime of equipment for repairs and maintenance, and increased operating costs associated with mitigation measures. In some cases, MIC has forced premature replacement of tanks, heat exchangers, and piping systems with a severe effect on plant availability.

Monitoring methods that alert plant operators that biofilm formation is occurring on pipe work and components permit the operators to initiate mitigation actions before biofouling becomes severe or MIC has occurred. The effectiveness of common water treatment chemicals is also increased substantially by prompt actions. Unfortunately, most monitoring activities rely upon process controls or batch methods that are too slow or of insufficient sensitivity to permit reliable control and implementation of mitigation techniques. Those methods are also too slow to be utilized for process controls of biocide additions, hence, mitigation activities are often excessively costly, both environmentally and in terms of direct costs of antimicrobial chemicals.

An electrochemical probe to permit on-line monitoring of biofilm activity under power plant or other industrial exposure conditions is under development. This device, the BIoGEORGE electrochemical biofilm monitor, permits on-line evaluations of the effects of biofilm formation upon the surfaces of passive alloys such as stainless steels exposed to cooling water environments. Benchtop experiments have shown that biofilm formation on stainless steel surfaces can be detected by an electrochemical indication well in advance of any visual evidence of biofilm or corrosion on the electrodes. The probe may be used to provide an early warning to plant operators to take appropriate actions such that biofouling and MIC may be avoided. The simplicity of the design and operation sequence are such that probes may be installed and left to operate unattended for extended periods with only minimal operator interaction.

The design of the probe, results of benchtop experiments, and a description of its installation at the Browns Ferry Nuclear Plant are described.
Surface Analytical Techniques for Microbiologically Influenced Corrosion—A Review
Authors: Wagner PA , Ray RI
Published: March 2009

Microbiologically influenced corrosion (MIC) has received increasing attention from engineers, materials scientists, and corrosion specialists. In field and laboratory studies, basic surface analytical examinations must be correlated to knowledge of the overall corroding system in order to conclude the presence of MIC. Preliminary observations and microbiological, chemical, microscopic, and metallurgical techniques are discussed.
Thermodynamic Prediction of Microbiologically Influenced Corrosion (MIC) by Sulfate-Reducing Bacteria (SRB)
Authors: McNeil MB , Odom AL
Published: March 2009

Sulfiding corrosion induced by the action of consortia containing sulfate-reducing bacteria (SRB) in biofilms is a problem with most common engineering materials. It is now possible to use a model based on basic thermodynamic reasoning and information on complexation and alteration kinetics to make some predictions about the mineralogy and form of the corrosion products. This analysis, applied to a variety of materials, gives predictions in agreement with experimentation.
Sulfur Isotope Fractionation in Sulfide Corrosion Products as an Indicator for Microbiologically Influenced Corrosion (MIC)
Authors: Little BJ , Wagner P , Jones-Meehan J
Published: March 2009

Sulfur isotope fractionation was demonstrated in corrosion products resulting from the activities of sulfate-reducing bacteria within biofilms on copper surfaces. 32S accumulated in corrosion products, while 34S was concentrated in the culture medium due to fractionation. The accumulation of the lighter isotope was related to surface derivatization or corrosion as measured by weight loss.
Application of Reverse Sample Genome Probing to the Identification of Sulfate-Reducing Bacteria
Authors: Voordouw G , Jack TR , Foght JM , Fedorak PM , Westlake DWS
Published: March 2009

Reverse sample genome probing (RSGP) has been used for the analysis of sulfate-reducing bacteria (SRB) in samples obtained from heavy oil operations in the Wain-wright/Wildmere fields in Western Canada. These reservoirs are shallow (600 m), roughly 25°C, and host a 6% brine. Master filters containing up to 35 independently hybridizing SRB standards were used for analysis of DNA prepared from the samples. The standards represented the diversity of SRB that is now recognized, for example, SRB using lactate, ethanol, benzoate, propionate, decanoate, or acetate as their carbon and energy source. These had previously been isolated from Alberta oil and gas field environments either by single colony purification or by liquid culture enrichment. Twenty four sites were analyzed by RSGP following liquid culture enrichment of SRB on media with one of these six carbon sources. Combination of the results of this method for all enrichments indicated on average the presence of six different SRB at each site. No significant differences were observed in the types of SRB cultured from the two fields. Also, the same SRB standards were recovered by growth of either sessile or planktonic samples. Some oil field production waters were analyzed by direct extraction of DNA from the bacterial population and RSGP analysis. This indicated that the natural population is dominated by lactate- and benzoate-utilizers. Oil fields therefore harbor a variety of SRB. Biocide treatment schemes should ideally take into account this variety and be based on identification of the SRB involved, their known effects on field operations, and their documented biocide sensitivity. In this scheme, RSGP can help in the rapid identification of SRB and others, for example, acid-producing bacteria associated with corrosion.
Microbiologically Influenced Corrosion (MIC) Accelerated Testing Using a Flow-Through System
Authors: Luo JS , Campaignolle X , White DC
Published: March 2009

Microbes recovered from sediments, slime, tubercles, or corrosion coupons were characterized into functional groups, identified by fatty acid patterns and used in a flow-through test system. Test solutions were prepared as field conditions and supplemented with nutrients for the growth of microbes. Four-sided working electrodes were fabricated to simplify experimental design by combining four steel disks from the same stock into one probe. Concentric electrodes were made to simulate localized corrosion and study the effect of bacteria upon stability of localized corrosion. Electrochemical techniques such as: open circuit potential, electrochemical impedance spectroscopy, and galvanic current measurements were performed to evaluate the corrosion of mild steel in solutions containing different combinations of bacteria. Actual microbial community on the electrode surface was recovered by culture methods for viable counts upon termination of experiments. Preliminary results indicated that this test system provided an accelerated testing to simulate field exposures.
Fire Tests and Interior Furnishings
Authors: Hirschler MM
Published: March 2009

Interior furnishings are consumer products found in various occupancies. They include furniture, bedding, curtains and drapes, surface finishes (wall, ceiling and floor coverings), and cabinetry. Among the features they have in common is the fact that they are rarely a single material, but that they generally involve various layers. This characteristic is important because it explains why testing of their individual components usually does not give adequate answers.

A survey of the development of such fire tests, and of the present status, is presented here. Special focus will be placed on upholstered furniture tests.

The flammability of upholstered furniture has been under a microscope since it was first discovered to be an important issue, in the late 1960s and early 1970s. However, relatively few tests have been developed and standardized, either in the United States or in other countries. The initial focus was on cigarette ignition and on component testing, resulting in tests such as the NBS mockups and the UFAC test (ASTM E 1352 or NFPA 261 and ASTM E 1353 or NFPA 262, respectively). This was followed by testing of entire chairs with cigarettes (CA TB 116). Eventually, composite component testing with small flames started, pioneered by British standard BS 5852. Parallel to this, material testing continued, using a variety of mostly small-scale tests (the most frequently used tests being CS 191-53 and CA TB 117). In the mid 1980s, tests started to appear for the flaming behavior of complete upholstered furniture items, CA TB 133 being among the most notable ones. The fire community has now understood that the most important fire property is the heat release rate, and this has been incorporated into contents and furnishings tests, as in ASTM E 1537. The next step is the attempt to predict the results of such tests with bench-scale heat release tests and fire models. This work is still in progress.

Fire tests for other interior furnishings have also undergone a complex history, which is reviewed. Tests for the different products are in various stages of development. It would appear that the fire testing of furnishings and contents in the future will entail mostly finished products and heat release equipment.

A flurry of activity is characterizing the present emphasis on furnishings. Moreover, the majority of the new tests being developed generate results that can be used as input for models to carry out fire hazard or fire risk assessments.