bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Cyclic Wetting and Drying on Corrosion of Zinc and Steel
Authors: Zhang XG , Tran HQ
Published: March 2009

Cyclic tests of solution spraying, water condensation, and air drying were conducted to study the corrosion rate and corrosion products of zinc and steel. The results demonstrate that wetting and drying pattern affects not only the corrosion rate but also the morphology of the corrosion products. The corrosion product formed on zinc under cyclic conditions was distinctively localized and had the effect of retarding the corrosion, while that formed on the steel surface was more uniform and had a less retarding effect.
Cleavage Fracture Quantified by J and A2
Authors: Chao YJ , Ji W
Published: March 2009

The analytical asymptotic solutions including higher order terms for stresses at a crack tip embedded in a power law elastic-plastic material are applied to the interpretation of cleavage fracture for a mild steel. It is demonstrated that fracture initiation can be determined by using two parameters J and A2 — J represents the level of loading and A2 quantifies the level of constraint. Constraint related issues such as size effect, transferability, and biaxial stress effect are investigated. The predicted results have the same trend as seen experimentally.
The Role of Geometry and Crack Growth on Constraint and Implications for Ductile/Brittle Fracture
Authors: O'Dowd NP , Shih CF , Dodds RH
Published: March 2009

A family of self-similar fields provides the two parameters required to characterize the full range of high- and low-triaxiality stress states that can exists near the tip of a mode I stationary crack. The two parameters, J and Q, have distinct roles: J sets the size scale of the zone of high stresses and large deformations, while Q scales the near-tip stress distribution relative to a high triaxiality reference stress state corresponding to a long crack in an infinitely large body.

The evolution of mode I near-tip fracture states under plane strain conditions is addressed in two parts. We begin by discussing crack geometry and load effects on near-tip constraint for a non-growing crack. Details aside, increased loading (plastic deformation) in finite size geometries is accompanied by a steady loss of constraint. This behavior is explained and quantified relative to a high triaxiality reference stress state, or the Q=0 state, using results from several crack geometries.

The second part of this work focuses on crack growth effects on constraint. Here steady-state crack growth provides a basic result. First, crack growth under well-contained yielding elevates near-tip constraint. Second, the maximum stress elevation due to growth is set by the steady-state high triaxiality stress state. The competing effects of constraint elevation due to crack growth and constraint loss due to increased plastic deformation in a finite size geometry offers insight into the transition to a brittle fracture mode after some amount of ductile tearing.
Prediction of Cleavage Fracture in the Brittle to Ductile Transition Region of a Ferritic Steel
Authors: Koers RWJ , Krom AHM , Bakker A
Published: March 2009

A model is presented to predict the event of cleavage fracture in the brittle to ductile transition region. In this region cleavage fracture could occur after some amount of ductile tearing. The model takes into account the competition between the nucleation of voids at second phase inclusions leading to ductile fracture and the nucleation of unstable micro cracks initiated at second phase inclusions leading to cleavage fracture. The model was tested on four point bend specimens of a ferritic steel tested in the brittle to ductile transition region. It was shown that there could be a significant amount of ductile crack growth before the specimens failed by cleavage. Two different crack growth simulations were performed to investigate the stresses ahead of a ductile growing crack. One simulation takes into account the softening of the material in the process zone, due to damage, around a quasistatically ductile growing crack. The second simulation neglects this damage. It was found that the crack opening stress near the crack tip in the process zone is significantly lower than in the analysis neglecting the effect of damage. Further from the crack tip, outside the damage zone the crack opening stresses are similar in both simulations.
A Comparison of J and CTOD as Elastic-Plastic Fracture Characterizing Parameters
Authors: Gordon JR , Neale BK , Wang Y-Y
Published: March 2009

This paper presents results of experimental and numerical analysis studies to investigate the relationship between J and CTOD and assess whether they are, indeed, both suitable elastic-plastic fracture characterizing parameters. Detailed elastic-plastic finite element analyses were undertaken for SE(B) specimens with a/W ratios of 0.1, 0.2, 0.3 and 0.5. Analyses were performed for a range of material stress-strain curves and yield strength levels to determine the influence of work hardening and yield strength on the J-CTOD relationship.

It was found that: 1. The standard CTOD estimation procedure can give rise to significant errors in the predicted CTOD for high work hardening materials (σTS/σYS > 1.5) .2. For SE(B) specimens, the following J-CTOD correlation can be used to relate J to CTOD J=mTSσTSCTOD where mTS = 1.21 + 0.95 (a/W) − 0.5 (a/W)2. 3. J and CTOD do not always produce consistent trends when used to characterize the fracture toughness of different materials, i.e., the toughness ranking based on J is not necessarily the same as the ranking obtained using CTOD.
Application of J-Q Fracture Methodology to the Analysis of Thermal-Shock Experiment TSE-5A
Authors: Shum DKM
Published: March 2009

The ORNL thermal-shock experiment TSE-5A is re-analyzed using the J-Q fracture methodology. The objective is to evaluate the hypothesis that potential toughness elevation associated with the shallow-flaw geometry in the TSE-5A cylinder is eliminated by the resence of a tensile axial stress that arises from the nearly equibiaxial nature of thermal-shock loading. Analysis results indicate that Q ≈ 0 for the TSE-5A experiment. Analysis and experimental results together suggest that neither the J-Q trajectory nor the Jc(Q) locus in the regime where Q ≈ 0 have been affected by the thermally-induced transverse load, relative to a situation with the axial stress absent. Therefore, the hypothesis under investigation is not supported by the analysis results and interpretation framework examined in this study.
The Role of Strike Marks on the Reproducibility of Charpy Impact Test Results
Authors: Schmieder AK , Purtscher PT , Vigliotti DP
Published: March 2009

Charpy V-notch specimens from one lot of high-strength steel were tested using three machines to determine reference values for three measures of toughness: absorbed energy, lateral expansion, and height of shear lips. The broken specimens were examined to determine the location and magnitude of changes in specimen features made during testing. The features of interest were the height and location of the shear lips, the location of the lateral expansion projections ranked by height, and the location, length, width, and angle of the first- and second-strike marks. Changes in these features were compared to the changes in average absorbed energy for each of the machines in its standard condition. To correlate changes in these features with intentional machine modifications, ten series of tests were made on a fourth machine. Patterns which could predict the direction of change in absorbed energy for most modifications were observed. The trends indicated by these data are: (1) each modification resulted in an increase in absorbed energy, (2) the distance between second-strike marks is a measure of the compliance of the striking edge and anvil, (3) the offset of the first-strike marks is largely due to lift-off of the specimen at the moment the striker hits the specimen, (4) offset and the angle of second-strike marks are measures of general asymmetry of loading, and (5) lateral expansion and shear lips are valuable as means to detect scale errors and excess losses not related to the work of fracture.
Effect of Surface Finish of Charpy Anvils and Striking Bits on Absorbed Energy
Authors: Ruth EA , Vigliotti DP , Siewert TA
Published: March 2009

Some new Charpy impact testing machines often report higher energy values than machines which have been in service for a period of time. An investigation into the cause of this phenomenon revealed that a major contributing factor was the surface finish of the Charpy anvils and the striking bit. Depending on the trajectory of the Charpy specimen halves after impact and the configuration of the testing machine, a considerable amount of friction may occur between the specimen and the anvils as the specimen is broken. Friction may also occur between the specimen and the striking bit as the specimen exits the machine. Polishing the anvils and the striking bit minimizes the friction between these parts. As a Charpy impact testing machine tests many samples, the striking bit and anvils become burnished and energy absorption due to friction is reduced. If new parts are highly polished prior to installation, the burnishing, normally caused by testing many samples, is simulated. In this way energy absorption associated with friction during the wear-in period is minimized and remains more constant during the life of the anvils and striking bit. ASTM Standard Test Methods for Notched Bar Impact Testing of Metallic Materials (E 23) requires the surface finish of the anvil and striking bit to be better than 4 μm (125 μin.). Specifying a 0.1 μm (4 μin.) surface finish as a requirement in E 23 will not only eliminate the wear-in period, but will minimize shifts in test results when anvils and/or striking bits are replaced in Charpy impact testing machines.
The Effect of Charpy V-Notch Striker Radii on the Absorbed Energy
Authors: Siewert TA , Vigliotti DP
Published: March 2009

The two most common Charpy V-notch striker designs (8-mm and 2-mm radii on the striking edge) were compared using verification (reference-grade) impact specimens. Other variables in the test matrix included two different brands of U-type pendulum machines and four different specimen energy ranges (near 18, 45, 100, and 200 J). In this comparative study, we found a very small difference between the two striker designs and an even smaller difference between the two brands of machines. At 200 J, the difference between the two striker designs was about 10 J. This difference might not be important in most production testing, but must be considered in verification testing where the acceptable range may be 5 %. The standard deviations of absorbed energy for the two strikers were similar, except at 200 J where the 2-mm striker produced standard deviations about 3 times higher than the 8-mm striker.
Effects of the Striking Edge Radius and Asymmetrical Strikes on Charpy Impact Test Results
Authors: Tanaka M , Ohno Y , Horigome H , Tani H , Shiota K , Misawa A
Published: March 2009

The effects of the striking edge radius of the Charpy impact test on the absorbed energy and lateral expansion were investigated. The effects of the changes of the length of test specimens and effects of symmetry of test specimens was also investigated. The absorbed energy of the 8mmR's was higher than the 2mmR's as in the study by Naniwa et al.[1]. For every machine tested, the absorbed energy was higher when the striking point did not contact the specimen opposite the notch. The effects of the length of test specimens were larger when the asymmetric test specimens were tested.
Correction of Charpy Impact Values for Kinetic Energy of Test Specimens
Authors: Chandavale RG , Dutta T
Published: March 2009

The Charpy impact test was studied theoretically and experimentally, to learn how much of the pendulum energy is imparted to the test specimen. The fracture was separated from the subsequent collision, and the collision was studied kinematically. Materials are known to have a standard coefficient of restitution between any two bodies [1]. If this value is known, the behavior of the two bodies can be predicted after collision for any two initial velocities of the colliding bodies. This parameter was measured on U-type pendulum impact testing machine at a known initial velocity of the pendulum. The error based on velocities of V-notched test specimens and pendulum were calculated at several different initial velocities of the pendulum corresponding to different energy levels. The error was also measured by experiment at different energy levels on machine. The results were in reasonable agreement with the calculated values. Various test conditions and material properties of the specimen that cause such error are also discussed.
Load Damping Absorbers and the Determination of Load/Displacement Data for Precracked Charpy Specimens
Authors: KarisAllen KJ , Matthews JR
Published: March 2009

A mechanical damping technique is described where a soft metal absorber attached to the leading edge of the striker is used to reduce the inertial oscillatory component of dynamic load time records. A technique is also presented which generates specimen load line displacement data indirectly from force/time information. A comparison of damped and undamped impact records indicates that the tested absorber configuration is an effective method of reducing inertial load oscillations. The experimental evidence indicates that the elastic and plastic machine load-displacement relationships can be accurately determined under the impact conditions generated in a precracked Charpy test. The procedure presented eliminates the requirement for using a dedicated device for the measurement of specimen displacement when absorbers are used to remove the inertially generated load oscillations.
Improved Load Ratio Method for Predicting Crack Length
Authors: Chen X , Albrecht P , Wright W , Joyce JA
Published: March 2009

The elastic compliance from unloading/reloading sequences in a load-displacement record estimates well crack length in elastic-plastic fracture toughness tests of compact tension [C(T)] and bending type specimens. The need for partial unloading of the specimen makes it difficult to run the test under static loading and impossible under either dynamic loading or very high temperatures. Furthermore, fracture toughness testing in which crack length is determined from elastic compliance requires high precision testing equipment and highly skilled technicians. As a result, such tests are confined usually to research laboratories and seldom used under production settings.

To eliminate these problems, an improved load ratio method of predicting crack length is proposed that utilizes only the recorded load versus load-line displacement curve (or load versus crack-mouth-opening displacement curve) without unloading/reloading sequences. As a result, the instrumentation is much simpler than in the elastic compliance or potential drop methods. If only a monotonic load-displacement record is to be measured the fracture toughness test becomes almost as simple to perform as a tension test.

The method described here improves in three ways the “original load ratio method” proposed by Hu et al. First, a blunting term is added to the crack length before maximum load. Second, a strain hardening correction is included after maximum load. And, third, the initial crack length and the physical (final) crack length measured at the end of the test serve to anchor the predicted crack lengths, forcing agreement between predicted and measured values.

The method predicts crack extension with excellent accuracy in specimens fabricated from A302, A508, and A533B piping and pressure vessel steels, A588 and A572 structural steels, and HY-80 ship steel.
Apparatus for Ultrasonic In Situ Accurate Crack Size Measurement on Laboratory Test Specimens
Authors: De Vadder D , Park Y , François D
Published: March 2009

Knowledge on the diffraction of ultrasonic waves by crack tips in the nondestructive testing (NDT) field of applications was used to develop a method and a device for the in situ crack size measurements in fatigue test specimens. This single device allows accurate measurements at every stage of the life of the test piece. The standard accuracy is 0.1 mm in the direction of propagation. In many cases we proved that it can reach 0.03 mm. Thanks to the possibility of measurements along the crack front, it is well suited for thick specimens. After some feasibility tests we designed a prototype ready for marketing. It has been used to study the local crack-tip behavior. We could not only trace evolution of the crack profile across the entire specimen thickness but also the crack closure length at any particular point versus increasing load. In this way we confirmed on A533 steel specimens different behaviors of fatigue cracks in the plane stress and in the plane strain regions. Crack closure, the blunting, and the retardation after an overload depend on the position along the front.
Characterization of a Crack in an Aluminum Bar Using an AC Magnetic Bridge
Authors: Schmidt WF , Zinke OH , Nasrazadani S
Published: March 2009

A hairline crack was introduced in a 27.9 cm long by 7.62 cm wide by 1.3 cm thick (11 by 3 by 0.5 in.) 6061-4 aluminum specimen by repeated bending. The size of the crack was limited by stopping the bending at the initial stage of crack formation. Measurements were then made using an AC magnetic bridge which detected the presence of the crack and enabled characterization of its form. The extent, the orientation, and the depth from the surface along the crack length were obtained from the measurement. This paper outlines the principle of the bridge operation and details related to interpreting the output from the bridge as the bridge is moved over the surface of the aluminum specimen. Verification of the bridge measurements was made by destructive evaluation of the specimen using a scanning electron microscopic examination.
A Study of Ventilation Measurement in an Office Building
Authors: Dols WS , Persily AK
Published: March 2009

The National Institute of Standards and Technology has conducted a study of ventilation and ventilation measurement techniques in the Bonneville Power Administration (BPA) Building in Portland, Oregon. The project involved the use of the following outdoor air ventilation measurement techniques: tracer gas decay measurements of whole-building air change rates, the determination of air change rates based on peak carbon dioxide (CO2) concentrations, the determination of percent outdoor air intake using tracer gas (sulfur hexafluoride and occupant-generated CO2), and direct airflow rate measurements within the air handling system. In addition, air change rate measurements made approximately three years apart with an automated tracer gas decay system were compared. Airflow rates were measured in the air handling system ductwork using pitot tube, hot-wire anemometer, and vane anemometer traverses, and good agreement was obtained between the different techniques. While accurate determinations of percent outdoor air intake were achieved using tracer gas techniques, the use of CO2 detector tubes yielded unreliable results. Reliable determinations of ventilation rates per person were made based on SF6 decay and direct airflow rate measurements, but the use of peak CO2 concentrations led to overestimations of building air change rates. The measured values of the whole-building air change rates, and their dependence on outdoor air temperature, did not change significantly over a three-year period. The whole-building air change rate under minimum outdoor air intake conditions was determined to be twice the outdoor air intake rate provided by the minimum outdoor air intake fans due to leakage through the main outdoor air intake dampers.
The Effect of Varying Levels of Induced Duct Leakage on Differential Pressures in a Florida House
Authors: Kozik AC , Oppenheim P , Hintenlang D
Published: March 2009

The objective of this research is to quantify the effect of varying levels of induced duct leakage on differential pressures and subsequent radon levels in a typical Florida residence. The heating and air conditioning (HAC) system of a residence was modified with the addition of a fresh air ventilation system. This modification provided the ability to simulate either a return leak or a supply leak in the HAC system. The amount of leakage induced can be varied using flow control dampers and an auxiliary fan located in the ventilation system ductwork.

The house was pressurized and depressurized by adding 0.06 m3/s of ventilation air into the return side and removing 0.05 m3/s of ventilation air from the supply side of the air handling system, respectively. The subsequent changes in house pressure and ventilation rates reduced the indoor radon concentrations from 1865 Bq/m3 to 170 Bq/m3 under pressurized conditions and to 305 Bq/m3 under depressurized conditions.
A Description of the New ASTM Test Method E 1424, Used for Measuring Fenestration Air Leakage at Differential Temperatures and Pressures
Authors: Kehrli DW
Published: March 2009

A new committee has been developed by ASTM Committee E6 for measuring air leakage rates of fenestration products under imposed conditions of differential pressures and temperatures. This new method is different from the long-standing, internationally referenced ASTM Method E 283 in that it is performed under temperature differentials across the test specimen similar to ASTM C 236 and C 1199, and AAMA 1503-88.

This new method will show the impacts of expansion and contraction, shrinkage, compression-set, fabrication and design integrity, and material and component interactions in the air leakage rates of window and doors products.

This paper compares the two methods and provides some typical test data.
Air Leakage Characteristics of Various Rough-Opening Sealing Methods for Windows and Doors
Authors: Proskiw G
Published: March 2009

The air leakage characteristics of eight methods of sealing, or otherwise treating, the rough openings (R/O) found around window and door frames were evaluated under laboratory conditions. The eight methods studied were: 1. no treatment (empty), 2. conventional (fiber glass), 3. densely packed, fiber glass, 4. backer rod, 5. casing tape, 6. poly-return, 7. poly-wrap, and 8. foamed-in-place urethane.

The untreated R/O (Method 1) displayed the greatest leakage while the second largest occurred using the conventional practice of packing fiber glass into the R/O space (Method 2). In contrast, Methods 5, 6, 7 and 8 were able to reduce R/O leakage to negligible levels.

To relate these results to the overall building leakage, an estimate was made of the percentage of the total building leakage which would occur through the R/Os in a typical 97 m2 (1040 ft2) bungalow. Two levels of total house airtightness were assumed: 1.5 air changes per hour at 50 Pa (ac/h50) representing tight construction and 5.0 ac/h50 (representing loose construction). For the tight house with Method 1 (no treatment), the R/O leakage accounted for 39% of the total house leakage; with Method 2 (conventional), this figure dropped to 14%. With each of Methods 5 to 8, the contribution of R/O leakage to total house leakage was less than 1%. For the loose house and Method 1, the R/O leakage was 12% of the total; with Method 2, it dropped to 4% and with Methods 4 to 8, it was less than 1%.

The incremental builder cost of each technique (i.e., exclusive of mark-up for overhead, profit, etc.) was estimated assuming Method 2 as conventional practice with a base cost of zero. Incremental costs ranged from a low of $18 per house for the urethane approach (Method 8) to $84 per house for the poly-wrap technique (Method 7).
Airflows and Moisture Conditions in Walls of Manufactured Homes
Authors: TenWolde A , Carll C , Malinauskas V
Published: March 2009

Unintentional airflow in exterior framed walls frequently causes diminished thermal performance. Furthermore, even very small infiltrative or exfiltrative airflows with little or no effect on the thermal performance are capable of voiding the moisture protection provided by a vapor retarder. Combined with high indoor or outdoor humidity, such walls may accumulate excessive amounts of moisture. However, more data were needed on airflows in and through wall assemblies and the effect of airflows on moisture conditions in walls. Twenty wood frame walls of ten different designs, characteristic of walls of manufactured homes, were constructed and installed in a test building near Madison, Wisconsin. In-place pressurization and depressurization tests were performed to separately determine airtightness of the interior and exterior membranes of the wall. This paper describes the methodology, equipment, and results of these measurements. Air pressure differences across these walls were monitored during an entire winter season, along with temperatures and moisture conditions in the walls. This paper describes the instrumentation and methodology used in these measurements. The measurements showed that providing wall cavity ventilation may cause pressurization of the wall cavity and can lead to a significant increase in air leakage and heat loss without reliably providing the intended protection from moisture accumulation in the cavity. Although several of the walls experienced condensation and mold growth, the moisture conditions in the walls showed no clear correlation with airtightness or with the amount of air flowing through the wall. Indoor humidity correlated strongly with wall cavity moisture conditions, suggesting that indoor humidity control is the most effective strategy to prevent excessive moisture accumulation in the exterior building envelope during winter.
Thermal Performance Characterization of Residential Wall Systems Using a Calibrated Hot Box with Airflow Induced by Differential Pressures
Authors: Jones DC , Ober DG , Goodrow JT
Published: March 2009

ASTM E 283 and ASTM E 1424 in conjunction with ASTM C 976 were used to study the effect of airflow on thermal performance of the wall. A typical residential 2 × 4 stud wall was constructed and placed on top of a subfloor, making a 2.44 × 2.74 m (8 by 9 ft) test specimen. This base wall assembly was then covered with two types of XPS sheathing, various housewraps, a 15# felt, and a polyethylene vapor retarder film in 40 different configurations and tested individually per ASTM E 283 and per ASTM C 976. For 24 of the 40 C 976 tests, a differential pressure was induced across the test wall as per and ASTM E 1424. Airflows ranged from undetectable airflow at 0 ∙ Pa ΔP to 1.63 L/s ∙ m2 for the base wall assembly alone. Difference in airflow resistance performance between the ASTM E 283 and ASTM E 1424 test methods were noted. Thermal testing results incorporating both ASTM C 976 and ASTM E 1424 for tests 1–28 produced apparent thermal conductances (C-values) in the range of 0.40 W/m2 ∙ K for a nondetectable airflow level to 1.81 W/m2 ∙ K for an airflow of 1.53 L/s ∙ m2 for the base wall assembly alone with a 20-Pa ΔP. The calculated C-value for this base wall assembly was 0.40 W/m2 ∙ K. Test results reveal that airflow rates as low as 0.2 L/s ∙ m2 could produce a 46% increase in apparent C-value. Similar thermal performance differences were revealed when thicker shiplap XPS sheathing was used. Tests were also conducted using an Air-Tight Drywall configuration showing the effect of “wind washing” on thermal performance. By sealing the gypsum drywall on the base wall assembly tested, the apparent C-value, when exposed to a 12.5 Pa wind pressure, was found to be equivalent to a base wall assembly configuration which allows 0.15 L/s ∙ m2 airflow to penetrate completely through.
Uncertainties in Fan Pressurization Measurements
Authors: Sherman M , Palmiter L
Published: March 2009

The ASTM Method for Determining Air Leakage Rates by Fan Pressurization Test (E 799-87) measures the airtightness of building envelopes using fan pressurization. Uncertainty is introduced in the process from the uncertainty of the airflow and pressure measurements as well as from nonlinearities in the system to be measured. This paper analyzes the precision and bias associated with making a measurement using E 779 in typical field situations. Model specification (or modelization) errors may also contribute significantly to the overall uncertainty in the estimates of the 4 Pa leakage; the sources and sizes of these modelization errors interact with the instrumentation errors in making a fan pressurization test. Insufficient field data exist to fully include the effects of modelization and other low-pressure phenomena, but the current standard can nevertheless by improved by tightening the instrumentations and procedural specifications and by judicious choice of pressure measurement stations.
Field Comparison of Alternative Techniques for Measuring Air Distribution System Leakage
Authors: Modera MP
Published: March 2009

ASTM has recently standardized a methodology for measuring the leakage of residential air distribution systems to unconditioned zones [ASTM Test Method for Determining the External Air Leakage of Air Distribution Systems by Fan Pressurization (E 1554-93)]. The standard includes two alternative leakage measurement techniques. One technique requires only a blower door, whereas the second technique requires a flow-capture hood as well as a blower door. This paper reports on the results of field measurements in 30 houses using both measurement techniques, and analyzes the relative strengths and weaknesses of the two techniques. The repeatability of each of the techniques, as well as the comparability of the results from the two techniques, is examined. A key issue addressed is the importance of duct pressure measurements in each of the two techniques. Analyses show that the leakage measured with the blower-door-only technique would have been negatively biased by 30% to 50% if the duct pressure had not been incorporated into the measurements and analyses as specified in the standard. Similarly, it is shown that supply leakage measurements with the flow-capture-hood technique would have been negatively biased by 33% if the envelope pressure differential had been used instead of the duct pressure differential.
An Approach to the Modelling of Atmospheric Corrosion
Authors: Lyon SB , Wong CW , Ajiboye P
Published: March 2009

Atmospheric corrosion is relatively complex involving interactions between a metallic substrate and a dynamic atmosphere. Modelling of other corrosion processes has been carried out with some success however, little advance has been made on the modelling of atmospheric corrosion. Successful models must incorporate a detailed understanding of the corrosion under the various deposition, evaporation and condensation regimes implicit in the diurnal cycle. A good model for atmospheric corrosion should also consider the electrochemical nature of corrosion and be able to predict the observed changes in corrosion rate during drying and re-wetting. This work develops a model based on a condensed droplet model with a central anode and a peripheral cathode and considers the effects of evaporation on the concentration of electrolyte, its conductivity and the effects of reducing droplet size on the variation in limiting oxygen reduction current. As the conductivity variation permits estimation of the anode to cathode resistance, the limiting oxygen reduction current can be used to estimate the maximum voltage drop due to resistive effects in the droplet. The model predicts that there is no significant resistive control in an evaporating droplet assuming the corrosion rate is that given by the limiting oxygen reduction current. However, in a condensate or adsorbate of uniform thickness resistive effects may become significant in layers less than 10 μm thick. In atmospheric corrosion, this has relevance with respect to repeated evaporation and condensation during wetting and drying, to the effects of rainwater washing and surface cleaning and also to micron or sub-micron thick adsorbates.
Analyses of Four Years of Exposure Data from the USA Contribution to ISO CORRAG Program
Authors: Dean SW
Published: March 2009

The USA part of ISO CORRAG Collaborative Atmospheric Exposure Program has completed 4 years. The purpose of this worldwide exposure program has been to obtain atmospheric and corrosion data on four metals to verify that the atmospheric classification system given in ISO standards ISO 9223, 9224, 9225, and 9226 are valid. Five sites were included in this program; 250 m lot at Kure Beach, Newark-Kearny, Point Reyes, Los Angeles, and the Fort Sherman coastal site in Panama. Flat panels and wire helices were used with triplicate specimens for six consecutive 1 year and single 2, 4 and 8 year exposures. The helices appear to corrode at significantly higher rates than the panels. The Fort Sherman coastal site was most corrosive to all alloys. The Newark Kearny site exhibited significantly lower corrosivity than in previous exposures. Multiple regression analyses showed that the environmental data accounted for a major portion of the variation in corrosion data for all metals except aluminum. The ISO classification system was accurate in 58% of the cases studied. In the other cases, it underestimated the corrosion rate about as often as it over-estimated the rate.
Effects of Silicon and Nickel Contents on the Atmospheric Corrosion Resistance of ASTM A588 Weathering Steel
Authors: Townsend HE
Published: March 2009

Nine ASTM A588 low-alloy weathering steels representing three levels of silicon and nickel were prepared by induction melting and hot rolling in the laboratory. Corrosion tests were conducted for eleven years at four atmospheric sites which included industrial, rural, and marine locations. The results were fitted to kinetic equations of the form, C= AtB, where C is the corrosion loss, t is time, and A and B are constants in accord with Method 1 of ASTM G101 “Standard Guide for Estimating the Atmospheric Corrosion Resistance of Low Alloy Steels.” Both silicon and nickel are shown to have a beneficial effect on the corrosion resistance of A588 weathering steel. For silicon, on average, each 0.1% increase results in a 4% decrease in corrosion loss after 11 years, a 6% decrease in corrosion rate after 11 years, and a 12% increase in the time to reach a 10-mil(250μm) penetration. For nickel, each 0.1% increase results in a 4% decrease in corrosion loss after 11 years, a 7% decrease in corrosion rate after 11 years, and a 15% increase in the time to reach a 10-mil (250(μm) penetration. By way of comparison, Method 2 of ASTM G101 predicts a 2% increase in the corrosion index for each 0.1% increase in silicon or nickel.
Atmospheric Corrosion Rates of Weathering Steels at Test Sites in the Eastern United States — Effect of Environment and Test-Panel Orientation
Authors: Coburn SK , Komp ME , Lore SC
Published: March 2009

To obtain long-term atmospheric corrosion data for weathering steels such as ASTM A 242 Type 1 (USS COR-TEN A) and ASTM A 588 Gr. A (USS COR-TEN B), an exposure program was initiated in which test panels were exposed for up to sixteen years at three corrosion test sites in the eastern United States. A unique feature of this program was that test panels were exposed in four different orientations (30°S, 30°N, 90°S, 90°N) at each site. The results confirmed the superior resistance of the weathering steels as compared to that of copper-bearing steel and carbon steel under virtually all the test conditions, with the A 242 steel being the most corrosion resistant. Overall, the rural test site (Potter County, PA), which is in line with the prevailing winds carrying acid-rain constituents from the middle western United States, was about twice as corrosive to these steels as was the urban-industrial site (Kearny, NJ), whereas the moderate-marine site (Kure Beach, NC, 250 m) was about ten times as corrosive as was the urban-industrial site. With respect to the effect of test panel orientation, the south-facing panels tended to show lower corrosion rates than did the north-facing panels at all the test sites. Also, in most cases, the inclined (30°) panels showed lower rates than did the vertical (90°) panels.
Corrosion Evaluation of Automotive Trim Material
Authors: Sabata A , Drigel GS , Cooper TL
Published: March 2009

Bright annealed ferritic stainless steel is used as automotive trim material. A 20% Cr ferritic stainless steel gave adequate corrosion protection in chloride atmospheres. Both 17% Cr materials, 434 and 436, need a Cr flash for good corrosion protection. Electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS) and Cyclic polarization curves were used to evaluate the corrosion performance. The corroded samples were analyzed with Time-of-flight Mass Spectrometer (TOFSIMS) and Scanning Electron Microscope (SEM). The 20% Cr ferritic stainless steel performed better than the 17% Cr materials in all the tests. Some differences in the corrosion products were observed between the accelerated tests and outdoor exposures.
The Influence of Marine Environments on Metals and Fabricated Coated Metal Products, Freely Exposed and Partially Sheltered
Authors: King GA , O'Brien DJ
Published: March 2009

Corrosivity surveys have demonstrated that in Australia marine environments represent by far the main corrosion hazard to metals and coated metal products. Also field inspection of some commercial product has revealed cases of very significant early corrosion in unwashed areas. Existing published data on the relative performance of metals and prepainted coated metals, especially as fabricated building products, is inadequate to meet the needs of those faced with decisions regarding product selection. A ten-year industrially funded project has been initiated to address this by studying the comparative performance of generic classes of metal products and alternative finishes, and this paper presents some interim results. Twenty-two commercial products based on galvanised steel, 5% and 55% aluminium-zinc coated steel, stainless steels and aluminium, were obtained from five countries, some prepainted with acrylic, polyester, silicon-modified polyester (SMP), or polyvinyldifluoride (PVF2) topcoats, and two with a polyvinylflouride (PVF) or polyvinylchloride (PVC) film laminate. All have been fabricated into ‘bent’ specimens, the test piece designed to simulate the types of distress metal products encounter during manufacture and building. Initial microcracking at bends and Erichsen domes was recorded photographically. A complex aluminium extrusion in four finishes was also exposed and measurements of initial colour and gloss were made for all specimens. Materials exposed for mass loss measurements include ‘mild’ steel, low-alloy copper-steel, zinc, 5% and 55% aluminium-zinc coated steel, and ‘wire-on-bolt’ assemblies. Specimens are exposed at three marine sites (severe, moderate and mild) both in the open and under a shelter designed to permit deposition of salt and particulates but prevent rainwashing. A glass canopy roof enables some UV degradation of the organic coatings. After one year the shelters have produced a remarkable deterioration of the coated steel products at the severe and moderate sites, the sheltered corrosion rates being up to seven times those in the open. Of the three coatings, the 55% aluminium-zinc consistently has the lowest corrosion rate which on average is about one-third that of zinc. Strong relationships have been established between the corrosion rates and the measured levels of airborne chloride.
Long-Term Atmospheric Corrosion in Spain: Results after 13–16 Years of Exposure and Comparison with Worldwide Data
Authors: Morcillo M , Simancas J , Feliu S
Published: March 2009

Available information on atmospheric corrosion over long periods of time (10–20 years or longer) is unfortunately very scanty despite its great usefulness; in fact, only from such type of data can reliable long-term atmospheric corrosion predictions be made. This paper reports the results obtained after 13–16 years of field exposure tests at various Spanish test sites including several types of atmosphere: rural (El Escorial), urban (Madrid, Zaragoza), industrial (Bilbao), and marine (Barcelona, Cadiz, Cabo Negro, Alicante). Panels of low-carbon steel, zinc, copper, and aluminum were removed from open-air racks after 1–6, 8, 10, 13, and 16 years of exposure, and their weight losses used to determine the corrosion rate. Long-term corrosion data were found to conform to a general equation, C = Atn, where A and C are the corrosion losses after one and t years of exposure, respectively, and n is a constant. Only mild steel in scarcely aggressive atmospheres of central Spain was found to fit a more complex equation. The results are compared with those found throughout the world, which were compiled in a comprehensive literature survey. Finally, an attempt was made at correlating exponent n with the type of atmosphere for each metal studied.
Effects of Weatherproofing Sealants on Building Aesthetics
Authors: O'Neil VK , Klosowski JM , Altes MG , Bergman LC
Published: March 2009

In today's commercial construction and renovation markets, the building owner desires a structure that remains both free of leaks and aesthetically pleasing for many years. It is assumed by many designers that within the group of high performance sealants “a silicone is a silicone”, indicating that a sealant in a generic class carries with it both the positive and negative characteristics associated with that class. Silicone is generally considered the premium performing material, exhibiting excellent durability. However, occasional appearance problems, generically assigned to silicones, have swayed some specifiers away from silicones on some substrates. The contributors to appearance problems are many, and only a few are specifically related to the sealant used.

This paper describes several sealant related phenomena which can contribute to building aesthetic problems. These include sealant dirt pick-up, substrate staining and fluid migration into porous substrates. Each of these terms is defined in detail. Laboratory and weathering tests are described which indicate how quickly and how severely aesthetic problems develop. Results are reported for sealants representative of the following types: plasticized silicones, unplasticized silicones, unplasticized surface-modified silicones, plasticized polyurethanes, unplasticized polyurethanes and plasticized modified polyethers. The influences of local environment, joint design and application technique are also discussed.
Primerless Polysulfide Building Sealants
Authors: Fiorillo AR , Harding JR
Published: March 2009

Polysulfide polymers have a long history of success as the base polymer in building sealants, but these sealants usually require the use of primers to ensure good adhesion to the various substrates used in building construction. Usually different primers are required for porous and non-porous substrates.

Whenever primers are required to achieve good adhesion, there is always the risk that the primer may be improperly applied or that some areas may be skipped during the priming. There is also the need to ensure that the primer does not get on the building surface and cause discoloration.

Polysulfide sealants have now been developed that incorporate adhesion promoters that eliminate the use of primers. These sealants have been tested against ASTM C-920-87, Specification for Elastomeric Joint Sealants, as a class 25 building sealant on glass, anodized aluminum and concrete and have easily met all the requirements.
In-situ Re-Glazing of Structural Sealant Glazing Joints a Case History
Authors: Wilson MD
Published: March 2009

Structural sealant glazing has attracted considerable attention due to its inherent glass retaining method which allows smooth exterior glass walls interrupted only by narrow weatherseal joints. The technique has become increasingly popular with owners and architects since its inception in the early 1970's.

In 1990 it was determined that a five story office building nearing completion had structurally glazed insulating glass units in multi-story bay windows that had been incorrectly installed. Verification of the required structural glazing design was performed to compare with the as-built conditions, and re-glazing the structural silicone glazing joints was indicated to be warranted.

The construction team desired to perform the re-glazing without removing the installed units for cost and time reasons. In-situ re-glazing of a single insulating glass unit was performed as a test of the proposed remedial technique. The test was deemed successful and the remaining defectively glazed units were re-glazed in-situ.

The design and construction circumstances that led to the situation requiring the re-glazing, the lessons learned during their resolution, the in-situ re-glazing techniques utilized, and comments on the need for potential re-glazing of structurally glazed systems are presented.
Laboratory Effectiveness Testing of Oil Spill Dispersants
Authors: Fingas MF , Kyle DA , Wang Z , Handfield D , Ianuzzi D , Ackerman F
Published: March 2009

Dispersant effectiveness tests are reviewed. Studies have been conducted of the variances among several standard regulatory tests. Three main causes of differences have been identified, oil-to-water ratio, settling time and energy. Energy can be partially compensated for in high energy tests by correcting for natural dispersion. With this correction and with high oil-to-water ratios and a settling time of at least 10 minutes, five apparatuses yield very similar results for a variety of oils and dispersants. Recent studies into the energy variation of dispersant tests show that the energy level varies in many apparatuses. The repeatability of energy levels in apparatus is largely responsible for the variation in dispersant effectiveness values in certain apparatus. Studies of analytical procedures show that traditional extraction and analysis methods cause a bias to results. Methods to overcome these difficulties are presented.
Understanding the Mechanism of Dispersion through Oil Droplet Size Measurements at Sea
Authors: Lunel T
Published: March 2009

Measuring the oil droplet sizes produced when oil is dispersed at sea is a critical stage in understanding the process of dispersion. A laser Phase Doppler Particle Analyzer (PDPA) with a measurement range 1–300μm has been developed which can distinguish between oil and the background signal from air bubbles, suspended sediment and plankton at sea. The resulting improvement in the signal to noise ratio has enabled us to measure oil droplet size in situ below an oil slick.

Measurements in the North Sea indicate that the droplet size distributions for a variety of oils and oil-dispersant combinations have a number median around 20 microns and are independent of the oil/oil-dispersant combination. Although the droplet size distribution is similar what is very different for these different oil-dispersant combinations is the number of droplets in the 1–70μm size range. n the basis of the measured size distribution and model predictions of the vertical movement of these droplets at sea we define dispersed droplets ⩽ 70μm and suspended droplets > 70μm. Efficient dispersants produce a large number of droplets in the 1–70μm size range while poor dispersants or an untreated slick produces a smaller number of oil droplets in this size range.

Comparison of the oil droplet size distribution of naturally and chemically dispersed oil indicates that the rate determining step in the process of dispersion is the splitting of large droplets (70–300μm diameter) to produce oil droplets in the size range 1–70μm. The consistency of the oil droplet size distribution for a variety of oil and oil-dispersant combinations suggests that the splitting process is via the shear forces imparted by microscale turbulence. The proposed mechanism has implications for both the modelling of the process at sea and the design of laboratory dispersant tests.