bluuebunny/crossref_metadata_2025 huggingface dataset:
Problems in Predicting the Thermal Properties of Faced Polyurethane Foams
Authors: Bomberg M
Published: March 2009

The thermal properties of polyurethane foams vary during service life depending on environmental conditions, the manner in which they are enclosed in the building partition, or if covered with facing membranes during their production. The effect of facing materials on thermal performance of the composites may range from a slight improvement of dimensional stability to a substantial reduction in the rate of loss of thermal resistance. Faced polyurethanes should be tested as composite materials, using a method that simulates performance conditions as closely as possible. Such a test method should include determination of cell gas composition as a measure of the aging process. Determination of cell gas composition after a period of exposure to different service conditions would allow an approximate correlation of laboratory results with in situ performance. The paper gives background information on effects of environmental factors and aging simulations on thermal resistance of polyurethanes and provides a starting point for discussion of the testing method.
Initial Rate of Absorption and Mortar Bond
Authors: Yorkdale AH
Published: March 2009

An examination is made of the effect of the initial rate of absorption (IRA) of structural clay units on the bonding ability of mortars to those units. This paper examines relatively recent data on the effect of IRA on the bond between mortar and structural clay masonry units. Included is a summary of data for both small-scale prisms and full-size walls from several sources. The paper also suggests areas and methods of research to more specifically identify the mechanisms of mortar bond to brick and other clay masonry units.
Growth of Physically Short Corner Cracks at Circular Notches
Authors: Leis BN , Galliher RD
Published: March 2009

This paper presents and discusses experimental results concerning the initiation and continued growth of cracks in thin circularly notched sheets. Data are reported for specimens and test conditions selected to examine the influence of (1) free surface and (2) inelastic action on the behavior of cracks at notch roots. Results of the study suggest that proximity to a free surface causes first a decrease and then an increase in the growth rate of physically short cracks at notches. This is postulated as being due to blunting of very short cracks and growth in a plane stress field, respectively. Inelastic action at notch roots, by contrast, is associated with increased growth rate within the notch plastic field. Its influence, therefore, is felt over distances equal to the plastic zone size so that its effect need not be restricted to physically short cracks. It is shown that current models which attempt to account for the influence of inelastic action and free surface on crack growth rate through empirical modifications to linear elastic fracture mechanics analysis are, in general, both inappropriate and inadequate.
Use of Low-Cycle Fatigue Data for Pressure Vessel Design
Authors: Lawton CW
Published: March 2009

Pressure vessels are usually designed for only a few thousand stress cycles and seldom for more than 105 cycles. For fatigue analysis to be practical for most of the ASME Code applications, a concept has been developed different from the practice used in machine design for high-cycle fatigue in rotating machinery. The concept uses fatigue design curves developed for the different materials. The curves account for most of the factors that reduce fatigue life as shown by a comparison with fatigue data generated with laboratory specimens. Because most pressure vessels are of welded fabrication, the fatigue design curves have full corrections for tensile mean stress in the applicable region to account for tensile residual stresses. For corrosive conditions, the fatigue design curves may require further corrections. A modified concept of strain range partitioning has been developed for the analysis of the creep and fatigue interaction for high-temperature design. The concept uses the strain difference range to calculate creep and fatigue damage, which is similar to the shear stress failure used in lower temperature design.

The use of the fatigue design curves is demonstrated with the evaluation for fatigue life of two fossil-fuel boiler components. One of these components illustrates the difference in use of the fatigue design curves when creep is a further consideration.
Slag Utilization in Pavement Construction
Authors: Emery JJ
Published: March 2009

An overall review of the current and potential utilization of ferrous, nonferrous, and boiler slags in pavement structures is given. It would appear that the optimum uses for iron blast furnace slag are in cements and base stabilization processes that take advantage of the energy “invested” in the suitably vitrified slag (granulated or pelletized), rather than bulk aggregate applications. Steelmaking slag that is not recycled can be used to advantage in asphaltic concrete (high stability and skid resistance), and may have applications in base and shoulder stabilization and construction (noting the expansion potential). Nonferrous slags such as copper and nickel slag can be used in granular base and structural fill construction, and related applications such as ballast. Boiler slags are used in a number of applications such as seal coat, asphaltic concrete, and granular base construction. While most ferrous slag is utilized, there is still much scope to utilize nonferrous and boiler slags that are often disposed of with consequent environmental impact. With the present indications of materials and energy shortages, there is a new concern that all byproduct slags be utilized effectively.
Atmospheric Corrosion of Copper Alloys Exposed for 15 to 20 Years
Authors: Costas LP
Published: March 2009

Copper alloys were exposed for 15 to 20 years at two marine, one industrial, and one rural location. Based on average corrosion rates for 13 alloys, the industrial corrosion rate was 1.4 µm/year whereas the rate for the other sites was approximately 0.7 µm/year. As expected, alloying agents affected the corrosion rates by a factor of 2 to 3.

General attack was the predominant form of corrosion. Dezincification was positively identified in C260 alloy and intergranular attack was noted in C642. Pitting was not a factor for any alloy.
Atmospheric Corrosion Test Results for Metallic-Coated Steel Panels Exposed in 1960
Authors: Tonini DE
Published: March 2009

Results of an ASTM-sponsored 20-year exposure of corrugated metallic-coated steel panels at five locations in the United States are reported. A total of 19 panels was placed at each exposure site, including at least one specimen from each of six types of continuous galvanizing lines in use when the test was initiated, five sheets galvanized using equipment similar to that used to prepare specimens for a similar test series initiated in 1926, one panel coated with pure aluminum, one panel coated with an aluminum-silicon alloy, and one panel coated with terne metal.

The analysis of the galvanized coatings data suggests the presence of nonlinear effects in the performance of the coatings. However, it was not possible to establish whether these effects were the result of nonlinearities in the coating performance itself or if they were the consequence of uncontrollable external factors which occurred during the exposure period.

The aluminized sheets were found to be essentially without failure at all test locations. In general, coating degradation beyond minor pinholing was not found.

The terne-coated sheets evidenced early rusting at all except the most aggressive of the test sites. Despite nearly total coating depletion, none of the test sheets have perforated.
Corrosion Performance of Decorative Electrodeposited Nickel and Nickel-Iron Alloy Coatings
Authors: DiBari GA , Hawks G , Baker EA
Published: March 2009

The corrosion performance of chromium-electroplated, decorative nickel and nickel-iron alloy electrodeposits has been studied in marine and industrial atmospheres and by means of copper-accelerated acetic acid-salt spray testing (CASS). Decorative nickel coatings, 15 and 30 μm thick, gave better overall corrosion performance than comparable decorative nickel-iron alloy coatings. Because of the rapid staining that occurs in marine and industrial atmospheres, nickel-iron alloy deposits are not suitable for decorative applications involving moderate and severe corrosion service. Decorative nickel-iron alloy deposits, 7.6 µm thick, appear suitable for mild corrosion service on the basis of CASS test results, but results were affected by iron content and type of electrodeposited chromium. The relatively good performance of thin alloy deposits accounts for established applications in mildly corrosive environments.

The performance of the decorative electrodeposited nickel coatings was influenced by the activity of bright nickel. Low-activity single-layer bright nickel (15 μm) performed better than high-activity bright nickel when used with microporous or microcracked chromium. High-activity double-layer nickel (30 µm) protected low-current-density areas of contoured steel panels better than low-activity double-layer nickel, either with microporous or microcracked chromium. Microporous chromium was more effective in this program; microcracked chromium was more effective in a previous study.
Comments on the Corrosion Performance of Decorative Nickel-Iron Coatings
Authors: Clauss RJ
Published: March 2009

The durability of decorative nickel-iron coatings in various types of exposure is discussed in detail. It has been determined that these coatings, as part of a specific multiple deposit system, perform acceptably for exterior automotive applications. It is necessary that a microdiscontinuous chromium be present in the composite coating to achieve optimum results and it is desirable to use a copper underlayer to the nickel-iron electrodeposits. Corrosion test results are also reported which establish that static tests cannot be relied upon to predict actual mobile service performance.
Calibration of Atmospheric Corrosion Test Sites
Authors: Baker EA , Lee TS
Published: March 2009

Inherent in the ability to accurately assess the performance of a material exposed in the atmosphere is an understanding of the relative corrosivity of that environment. The most reliable of present test methods for ranking materials' corrosion behavior have necessarily utilized long-term exposures to the natural environment in question. Given the variable nature of many atmospheric factors, it becomes important to determine the relative stability in the corrosivity of an atmospheric exposure site. Only in this way can the desired credence be given to atmospheric corrosion data generated for a variety of materials over an extended duration.

A review is provided of the major factors which must be considered in establishing a program to monitor and calibrate an atmospheric test site. These factors include both environmental assessments and corrosion evaluations. Consideration is given to the specific environmental parameters which could be monitored as well as experimental procedures which affect the atmospheric corrosion behavior of materials.
Reproducbility of Electrochemical Measurements of Atmospheric Corrosion Phenomena
Authors: Mansfeld F , Tsai S , Jeanjaquet S , Meyer E , Fertig K , Ogden C
Published: March 2009

A brief discussion is given of recent efforts to use electrochemical techniques for monitoring of atmospheric corrosion phenomena. Problems existing with the interpretation of time-of-wetness measurements are identified, and the finding that electrochemical sensors in their present design and application determine only fractions of the true corrosion rate is discussed. In order to resolve some of these difficulties, a statistically designed experiment is being carried out to evaluate the reproducibility of electrochemical measurements of atmospheric corrosion phenomena and to determine the effects of sensor design on time-of-wetness and cell efficiency. Results are presented for the first phase of this project, in which 15 atmospheric corrosion monitors (ACM) of the copper/steel and 15 ACM's of the steel/steel type, have been fabricated with steel and copper from three different heats. These ACM's have been tested in triplicate runs by exposure to aqueous 1-mM sodium chloride at a relative humidity of 45 percent until the surface had dried out, followed by additional exposure to either a moist air environment at three levels of relative humidity (65, 80 and 95 percent) or a sodium dioxide (SO2) test at three levels of SO2 ≈ 0, 0.2, and 1.1 ppm. During each test, steel plates from each heat were exposed to determine weight loss data. At present, only the drying-out data have been analyzed by statistical methods. It has been found both from electrochemical and weight loss data that the heat of the steel plays an important role, with one heat corroding at a higher rate than the other two which have equal corrosion rates. No differences were found between the five sensors of one heat. Additional factors that influence the measurement are day-to-day variations of the environment in the test chamber and to some extent the position of the ACM's in the test chamber. By comparing the electrochemical and weight loss data, a cell efficiency of about 20 percent was found for copper/steel and about 7 percent for steel/steel. This low cell factor is considered to be due mainly to local cell action on individual plates and to uncompensated ohmic drop in the electrolyte.

The copper/steel and steel/steel ACM's are being exposed on the Rockwell International Science Center roof for an aging period of three months, after which another series of laboratory tests will be conducted.
Effect of Atmospheric Pollutant Gases on the Formation of Corrosive Condensate on Aluminum
Authors: Byrne SC , Miller AC
Published: March 2009

As part of a program to develop predictive methods to estimate the long-term durability of aluminum parts, a methodology was developed to calculate the chemical composition of condensates formed on aluminum exposed to polluted air.

In this study, it is proposed that the maximum concentrations of ionic species in a condensate must be limited by the equilibrium condition established between the dissolved ions and the gases from which they formed.
Soil Capacity for Supporting Deep Foundation Members in Clay
Authors: Esrig MI , Kirby RC
Published: March 2009

A review and evaluation of the commonly used (state-of-practice) methods for analysis of ultimate capacity, load-deflection behavior, and driveability for driven piles in clay is presented. The evaluation suggests that significant progress has been made in modeling those portions of the problem amenable to conventional methods for structural analysis, but that remarkably little progress has been made toward realistically modeling soil behavior. A general effective stress method (state-of-art) for estimation of ultimate pile capacity is also presented and evaluated. The evaluation suggests that the general effective stress method has promise but is still in the process of development.
Development of a Teflon Helix Continuous Liquid-Liquid Extraction Apparatus and Its Application for the Analysis of Organic Pollutants in Drinking Water
Authors: Yohe TL , Suffet IH , Grochowski RJ
Published: March 2009

A continuous liquid-liquid extractor (CLLE) applicable for isolation and enrichment of trace organic constituents found in drinking water is described. The CLLE is automated for unattended operation and accomplishes the mixing, separation, and solvent recovery operations sequentially. Solvent recycle is employed to minimize solvent usage. The optimization procedures and evaluative criteria for the CLLE are presented along with two specific examples of drinking water applications.

The variability of the final evaporation step for highly volatile organics limits the use of this system for quantification of “low boilers”; however, purge and trap analyses can be utilized to quantify these compounds.
Flash Point Methods Applicable to Jet Fuels
Authors: Gibbons TR
Published: March 2009

The Abel, Pensky-Martens, Tag, and Setaflash testers are described with emphasis on differences in apparatus and procedure. The methods are classified into equilibrium and dynamic tests. Finally, the paper lists the differences in results that can be expected when a kerosine-type aviation turbine fuel is evaluated in all four test methods. These differences are large enough to require consideration when setting specification limits.
Response of Infrared Transmitting Materials to High-Velocity Impact by Water Drops
Authors: Hackworth JV , Kocher LH , Snell IC
Published: March 2009

An experimental and analytical program was performed to investigate the response of zinc selenide, zinc sulfide, and gallium arsenide to water drop impact. The experiments consisted of single-drop impact (0.7, 2.0, and 2.5-mm-diameter drops and impact velocities of 222 and 341 m/s); overlapping drop impacts (2.0-mm drops at 222 m/s); and exposure at 222 m/s to the standard rainfield (1.8-mm drops, 2.54-cm/h rainfall rate). An analytical model was used to compute stresses induced in the materials by a single water drop impact.

Within the conditions tested, each single-drop impact produced a ring fracture pattern characteristic of the material. Resistance to damage increased in the order zinc selenide, gallium arsenide, and zinc sulfide. The superior performance of zinc sulfide with respect to zinc selenide is attributed to the order-of-magnitude smaller grain size of zinc sulfide. Comparison with experimental results showed the analytical model to be a reasonable representation of the drop impact process.

The rainfield test of zinc sulfide showed that transmittance loss at short wavelengths (0.5 to 2.1 μm) was linear with exposure time, indicating a dependence on the extent of subsurface damage. At wavelengths above 2.5 μm, there was an incubation period before loss of transmittance. The end of the incubation period and the start of transmittance loss were associated with the nucleation of surface pits.
Influence of Crystal Structure on the Failure Mode of Metals by Cavitation Erosion
Authors: Preece CM , Vaidya S , Dakshinamoorthy S
Published: March 2009

The cavitation-induced deformation and erosion of metals of the three common crystal structures, face centered cubic, body centered cubic, and hexagonal close packed (fcc, bcc, hcp), have been investigated. It is shown that the shock-loading conditions encountered by the metal during cavitation enhances the effects of different deformation modes and strain-rate sensitivity arising from differences in crystal structure. This, in turn, results in a complex crystal orientation and grain size dependence of erosion rates.

These factors, which are highlighted under cavitation conditions and minimized under quasi-static loading, are considered responsible for the lack of any correlation between erosion rates and conventional mechanical properties such as strength and hardness.
Influence of Test Paraments in Vibratory Cavitation Erosion Tests
Authors: Matsumura M
Published: March 2009

A series of tests on iron and steel in a water tunnel system, which simulated field conditions quite closely, showed that each material has its own process of erosion, and that in general the fracture of metals by cavitation turns from ductile to brittle with the lapse of testing time.

Fractures of iron and steel in the vibratory method turned, as in the water tunnel, from ductile to brittle. It was found also that the ductile-brittle transition is decisively influenced by experimental parameters such as temperature of the test liquid, frequency of the vibration, and corrosiveness of the test liquid.

Based on these experimental results, it was concluded that, in the vibratory test, the process of damage of a material can be changed to a great extent by choosing appropriate conditions of the test.
Dual-Orifice Waterjet Predictions and Experiments
Authors: Selberg BP , Barker CR
Published: March 2009

A simplified dual-orifice circular jet analysis is developed to predict maximum velocity and pressure profile capabilities of waterjets. The analysis is applied to nozzles having total exit diameters of 1.016 mm operating at stagnation pressures of 2.812 MN/m2. These conditions result in flow rates of less than 2.27 × 10-1m3/s of water. Dual-orifice converging nozzles with 2- and 10-deg included convergence angles are analyzed as well as dual-orifice diverging nozzles with 8, 10, and 20-deg included divergence angles. The control-volume form of the conservation of mass and the conservation of momentum equations is applied to the converging dual-jet case. Velocity profiles prior to jet mixing, after Schlichting and Tollmien, are used as profile input to the conservation equations. Profile shapes after Schlichting are used downstream of the jet mixing process. Linear jet diameter growth laws are applied to predict jet diameters before and after the mixing process. The merged jet profiles are calculated downstream of the nozzle at representative stations and compared with a single-orifice jet profile of the same energy input. Diverging dual-orifice jet profiles are generated using the same profile and diameter growth equations as for the converging dual-orifice nozzle jet. Velocity and pressure profiles, generated at representative stations downstream of the nozzle exit, are compared with single-orifice nozzle profiles of the same total energy input. Experimental comparisons are made with 2- and 10-deg included-convergence-angle converging nozzles and with 8, 10, and 20-deg included angle diverging nozzles at 2.812 MN/m2 stagnation pressure. All nozzle shapes consist of a 13-deg converging cone followed by a straight section of length 2.5 exit diameters. A pressure transducer, fixed to the traveling carriage of a lathe and oriented so that the nozzle axis is in line with the transducer axis, is used for profiling studies. A hardened steel shield with a 5.00 × 10-1 mm central hole protects the transducer for the pressure profile studies. These pressure profile measurements are made at the same representative stations as the analytical results. Discussion of the agreement between analytical and experimental results is made with emphasis on limitations of the analytical model, the experimental tests, and on suggested improvements in nozzle design which will bring the analytical predictions and experimental results closer together.
Static and Dynamic Fibrous Initiation Toughness Results for Nine Pressure Vessel Materials
Authors: Server WL
Published: March 2009

The upper-shelf toughness regime corresponds to the normal operating temperature for ferritic nuclear pressure vessels. However, actual fibrous initiation toughness data have not been available for a wide variety of heats of steels and weldments. In fact, much of the data available have assumed that fracture initiation occurred at maximum load (equivalent energy approach), which is not the case for most materials tested on the upper shelf. Multispecimen (25.4 mm thickness compact or bend) initiation tests were, therefore, performed in the upper shelf temperature region to determine JIc for five base metal (two A533B-1, one A508-2, and two A302B) and four weld metal (two manual arc and two submerged arc) heats of nuclear ferritic steel. All of the heats were investigated under quasi-static loading (loading time ∼ 100 s) and under either closed-loop hydraulic loading (loading time ∼ 100 ms) or controlled impact loading (loading time ∼ 1 ms). For all materials investigated, crack initiation occurred prior to maximum load, and initiation toughness values (KJc) were up to 50 percent less than the equivalent energy (maximum load) toughness values. The initiation toughness results at 177°C also increased with decreasing loading time for all but one heat tested. HSST Plate 02 (A533B-1 steel) was tested at 71°C using all three loading rates; there were little differences observed for the Plate 02 tests due to loading rate, although the intermediate loading rate results were slightly lower than the rest. The data were analyzed using a simple statistical approach to obtain approximate confidence limits for the JIc values obtained. A comparison of JIc values obtained using three-point and nine-point fibrous crack length averages across the specimen thickness was made. The nine-point average generally gave higher values of JIc, but the variance about the regression line was not consistently lower than for the three-point average.
Quantitative Microscopy and Fatigue Mechanisms
Authors: Rhines FN
Published: March 2009

During the 135 years since Hood rightly associated fatigue failure with the internal structure of a metal by wrongly concluding that the metal had “crystallized,” there have been many hundreds of metallographic studies of fatigue that have deluged us with observations from which we have not yet been able to extract a really satisfying understanding of the basic principles involved in fatigue. It seems that the time is ripe for the application of the recently developed methods of quantitative microscopy. In so doing, it is important to appreciate, however, that there exists a mathematically rigorous geometry of microstructure which directs and limits the kinds of observations that can yield exact relationships between microstructure and physical properties. Additive geometric properties, such as total volume or total area of surface, are shape-insensitive and, hence, are readily measured and related to additive physical properties like density or hardness. Conversely, the average geometric properties, such as grain size, or average curvature of surface, are shape-sensitive and are limited in their application to a situation in which a regularity of shape prevails. Of particular interest in the field of fatigue are the geometrical extrema that are associated with localized mechanical effects, such as fracture. These are observable after the fact, chiefly in the two-dimensional parameters of the fracture surface. The scope of the application of quantitative microscopy to the study of fatigue is broad and the prospect of obtaining useful results is excellent.
Persistent Slipbands in Fatigued Face-Centered and Body-Centered Cubic Metals
Authors: Mughbrabi H , Ackermann F , Herz K
Published: March 2009

The cyclic stress-strain response, the development of persistent slipbands (PSB's), and the related dislocation microstructures have been investigated on single crystals of face-centered-cubic (fee) copper, nickel, and silver and of body-centered-cubic (bee) α-iron and niobium at room temperature. The formation of PSB's as a bulk phenomenon appears to be a general feature in fee metal single crystals and can be described remarkably well in a simple model based largely on Winter's work. The present work clarifies and emphasizes the special roles of cross slip and of long-range internal stresses in the formation of the matrix structure, in the nucleation of PSB's, and in the steady-state deformation occurring in the PSB's. In pure bee metals, on the other hand, PSB's are not found to be a feature of comparable generality. Under typical testing conditions, cyclic deformation of bee metals occurs by the low-temperature deformation mode, characterized by the low mobility of the screw dislocations and impeded dislocation multiplication. However, a deformation mode similar to that in fee metals, accompanied in some cases by the formation of PSB's as a bulk feature, is found under special conditions: low strain rate, elevated temperature (below the regime of self-diffusion), and the presence of interstitial impurity atoms. In conclusion, some general requirements that appear essential to the development of PSB's in fatigued metals are formulated.
Grain Size Effect on Crack Nucleation and Growth in Long-Life Fatigue of Low-Carbon Steel
Authors: Taira S , Tanaka K , Hoshina M
Published: March 2009

The ratios of the number of cycles to slipband formation and to crack nucleation to the total life were determined experimentally in fatigue tests of smooth specimens of low-carbon steel with several grain sizes. The number of cycles spent in propagating a nucleated fatigue crack was predicted by an analysis based upon the results of a through-crack growth study. The change of crystal deformation with number of cycles was studied by the X-ray microbeam diffraction technique, and the characteristics of cyclically induced substructure were discussed in comparison with substructure due to monotonic deformation. A micromechanistic model for the fatigue limit was proposed to interpret the Petch-type relation between fatigue limit and grain size under the assumption of the critical value of microscopic stress intensity factor at the tip of cracks blocked by the grain boundary. From through-crack growth experiments at several values of the stress ratio R, it was found that the threshold stress intensity factor ΔΚth increased linearly with the square root of the grain size l for each R-value, and the relation between the effective value of ΔΚth and l was independent of R-value. In order to interpret these findings, a model for the threshold of crack growth was proposed under the assumption that the threshold condition was determined by whether the slipband near the crack tip propagated into an adjacent grain or not.
Low-Cycle Fatigue Damage Mechanisms at High Temperature
Authors: Sidey D , Coffin LF
Published: March 2009

Observed effects of wave shape on low-cycle fatigue resistance and on concomitant fracture appearance at elevated temperature are summarized. Additionally, previously unreported tests on oxygen-free high conductivity (OFHC) copper at 673 K, as well as available published results, are examined using unequal strain rates to produce the wave shape. For OFHC copper, the fatigue lifetimes decreased by an order of magnitude as the tensile-going strain rate was reduced from 1.7 × 10 -3 s -1 to 1.7 × 10 -5 s -1 with a constant cyclic period. Accompanying this reduction in lifetime, the fracture mode changed from a transgranular fracture for the fast-slow wave shape to an intergranular single-crack fracture for equal ramp rates to interior cavitation for the slow-fast test.

Based on these findings and related work of other investigators, a qualitative model is presented to predict the ranking in fatigue resistance and in fracture mode as a function of wave shape and environment, for a given temperature, strain range and overall frequency. Essential features of this model include the assumption of grain boundary cavity size variability depending on the magnitudes of the tensile-going and compressive-going strain rates of the hysteresis loop and recognition of the important role of environment in degrading life and affecting fracture mode, especially when tensile- and compressive-going strain rates are equal.
Micromechanics Theory of Fatigue Crack Initiation Applied to Time-Dependent Fatigue
Authors: Lin TH , Lin SR
Published: March 2009

Different theories of fatigue crack initiation for time-independent fatigue are briefly reviewed. The micromechanics theory for time-independent fatigue proposed by Lin and Ito is shown to be applicable also for time-dependent fatigue. Three closely located parallel thin slices in a most favorably oriented crystal located at a free surface of a polycrystal are assumed to have small initial resolved shear stresses of opposite signs. From the slip rate versus resolved shear stress data of aluminum single crystals, the increases of local creep strains in the slices with cycles of stress loading were calculated by using the analogy between creep strain gradient and body force. This calculation was made for loading frequencies of 0.1 to 1000 cpm. It was found that the creep shear strain in the slices depends on the time of loading for frequencies greater than 10 cpm and becomes more dependent on cycles of loading at lower frequencies. The method is applicable also to loadings with given alternate strains instead of stresses.
On Understanding Environment-Enhanced Fatigue Crack Growth — A Fundamental Approach
Authors: Wei RP
Published: March 2009

Corrosion fatigue is a generic term that is used to describe the phenomenon of cracking (including environment-enhanced fatigue crack growth) in materials under the combined actions of an applied cyclic stress and a corrosive (aggressive) environment. Quantitative characterization and understanding have been hampered by the complexity of the problem, difficulties in separating the effects associated with crack initiation and crack growth, and by the absence of a truly interdisciplinary attack of the problem. With the development of fracture mechanics technology and sophisticated techniques such as Auger electron spectroscopy and low-energy electron diffraction analysis, quantification of environment-enhanced fatigue crack growth has now been placed on a reasonably firm basis in terms of both steady-state and transient responses. Understanding of the chemical processes that control environment-enhanced fatigue crack growth is beginning to emerge from coordinated mechanical, metallurgical, and chemical studies. A fundamental approach that underlies these studies and recent progress using this approach are described. Areas and directions for future research are discussed.
Symposium Summary and an Assessment of Research Progress in Fatigue Mechanisms
Authors: LeMay I
Published: March 2009

In his introduction to the 1958 Symposium on Basic Mechanisms of Fatigue, Professor Dolan noted that a great deal was known about fatigue failure and the basic mechanisms of fatigue, but that it was impossible to evolve an exact design on a quantitative basis largely because of the statistical nature of the phenomenon. A review of the papers of that symposium [1]2 shows clearly that a great deal was indeed known at that time concerning basic fatigue mechanisms without the benefit of thin-foil transmission electron microscopy (TEM) and other sophisticated techniques which we regard today as being essential tools in such studies, but there is no question whatsoever that we are today in a position of having an understanding in detail which may be considered to be several orders of magnitude greater than that obtaining in 1958. This has come about through the many specialized studies made over the past 20 years and through the use of much more sophisticated techniques such as thin-foil TEM, scanning electron microscopy (SEM), electron channeling, and Auger spectroscopy, as have been discussed and illustrated in the papers of the present symposium. However, despite all this progress in detail we are still faced with considerable uncertainties when attempting to design a component or structure to avoid the occurrence of fatigue failure or in predicting its fatigue life. This was well brought out by Fong [2] and it certainly appears shocking (at first sight, at least) to be considering a scatter factor of 20 in the fatigue life or of 2 in the mean strain range for fatigue failure of pressure vessels [3].
Fundamental Aspects of the Corrosion of Metallic Implants
Authors: Kruger J
Published: March 2009

The corrosion of metals in the aqueous environments of body fluids involves the setting up of electrochemical corrosion cells. The corrosion produced by these cells is controlled by thermodynamic and kinetic factors. The thermodynamic factors determine the corrosion tendencies; the kinetic factors determine the rate. Galvanic corrosion is affected by both thermodynamic and kinetic factors and occurs when two metals with widely differing potentials are placed in contact with each other. Other forms of corrosion depend more directly on factors controlling the rate of corrosion. For most alloys used in implants the corrosion rate is mainly dependent on the protective properties of the thin passive films that exist on the surfaces of these alloys. The quality of the protection afforded by passive films is related to their ability to resist chemical breakdown by damaging species and, once broken down, their ability to reform rapidly (repassivate). The interplay between breakdown and repassivation is important in determining the susceptibility of metallic implants to pitting, crevice corrosion, stress corrosion, corrosion fatigue, intergranular corrosion, and fretting corrosion.
A Critique of Dosage Type Measures of Community Noise
Authors: Allen JD
Published: March 2009

A highway traffic noise simulator is employed to generate statistical descriptions of the A-weigh ted instantaneous sound levels at several observer positions. It is suggested that some kinds of noise impact are more appropriately described by instantaneous criteria than by cumulative criteria. It is shown that if such instantaneous criteria are assumed, one obtains a significantly different evaluation of the relative contributions of different noise sources than would be obtained from an evaluation based upon cumulative criteria. The actual quantification of the relative contributions of different noise sources is quite sensitive to the choice of instantaneous criterion.
Community Noise Measures
Authors: Gales RS
Published: March 2009

Various scales and methods for rating community noise and its contributing sources are described. These have been derived from considerations relating the physical properties of sound to human auditory response. Particularly important are the frequency response and temporal response characteristics of human hearing. Community noise descriptors in five categories are evaluated in terms of application and complexity. Time integral measures, such as sound exposure level (SEL), also called single event noise exposure level (SENEL) are discussed, as well as time averaging methods such as equivalent continuous sound level (Leq) and some of its derivatives, such as day-night average sound level (Ldn) and community noise equivalent level (CNEL). A general evaluation is given of the utility of these descriptors for measuring community noise from various sources. It is noted that although researchers have proposed various corrections to A-weighted sound level for sounds with tonal, impulsive, and time-varying properties, there is no unanimity as to the general applicability of these corrections.
Considerations of Community Noise Impact on Hearing Health
Authors: Lipscomb DM
Published: March 2009

Potential contributors to hearing impairment due to community noise sources are discussed. These include: (a) the predisposing effect of moderately intense (70 dBA) average background sound levels; (b) the “effective quiet” concept that identifies sound levels that neither cause a temporary threshold shift (TTS) nor impede recovery from TTS; (c) community noise source stress reaction as a further predisposing influence during dangerously high level noise exposures; and (d) attitudinal factors involved in noise experience discussed in terms of a “pleasure principle.”
Community Annoyance with Transportation Noise
Authors: Schultz TJ
Published: March 2009

A comparison of the results from a number of social surveys on public response to transportation noise suggests that those studies agree sufficiently well with one another that a single relationship between noise exposure and annoyance can be determined that is valid for all kinds of transportation noise. A curve is proposed.
Predictors of Adverse Human Responses to Traffic Noise
Authors: Bradley JS
Published: March 2009

A field study was carried out measuring the responses to traffic noise of 1150 subjects at 46 different sites. The merits of a number of statistical noise measures were compared in terms of the accuracy with which they predicted responses. Measures most representative of only local traffic noise were most successful and included L10 and Leq values. The inclusion of measures of noise level fluctuations was found to be of minimal importance, and suggested that increased levels of fluctuations decreased adverse responses. The difference between day and night time noise levels also had only a small influence on responses and was largely due to the more disturbing nature of night time noise. Vehicle flow measures, particularly the logarithm of the total vehicle flow rate, were found to quite accurately predict responses. Results supported the concept of disturbance relating to noise measures representative of the energy equivalent level of only the particular noise in question (here traffic noise) as a potentially unifying basis for a wide range of statistical noise measures.
Laboratory Experiments on Traffic Noise Annoyance
Authors: Cermak GW
Published: March 2009

Four laboratory experiments were conducted to determine which attributes of traffic noise contribute most to human judgments associated with annoyance and perception. Results of these experiments showed that the energy equivalent sound level (Leq) was the best acoustical predictor of annoyance and perceptual responses. Secondary predictors were also identified, but extensive analysis showed that they did not add significantly to the predictive power of Leq.
The Cost of Uncertainty in Acoustic Measurements
Authors: Eldred KM , Kane JA
Published: March 2009

The cost of uncertainty in noise measurements is reviewed in order to address real tangible costs borne both by firms that have to quiet plant equipment to noise levels below the regulations, and by individuals who are exposed to noise levels above the regulations. The potential annual costs of uncertainties in just one case study—potential product noise regulations—are shown to be of the order of 300 to 500 million dollars, on a present value basis over a ten year period, although substantial uncertainty in these estimates is probable. The economic implications of noise measurement uncertainty are related to the purposes of noise measurement standards, and the significance of measurement uncertainty for the use and consequences of standards in noise regulations is discussed.
Practical Methods of Environmental Noise Assessment
Authors: McGaughey JW , Dennison EE , Ying SP
Published: March 2009

The 1977 document by the Committee on Hearing, Bioacoustics and Biomechanics (CHABA) Working-Group 69 titled “Guidelines for Preparing Environmental Impact Statements on Noise” is a welcome relief from the proliferation of environmental impact statement requirements of state and Federal agencies. A more unified approach is badly needed to permit a ready exchange of information between these agencies. However, extensive field noise surveys have shown that the concept of an annual day-night average sound level may be too general. Significant seasonal effects are shown which negate the usefulness of the annual day-night sound level concept. An alternative noise descriptor is suggested. In addition, road and highway noise, usually a major element of the community noise picture, contains an inherent measurement problem which should be addressed in a uniform manner. Finally, meteorological effects exist which must be accounted for by the guidelines. Practical measurement experience should be incorporated into the guidelines for the preparation of environmental impact statements on noise.
Toward More Effective Evaluation and Control of Airport Noise
Authors: Miller RL , Wood EW
Published: March 2009

This paper addresses the need for a single measure of noise exposure in evaluating the noise environment at airports. Unnecessary confusion and inconsistency often occur as a result of the many different measures available. Furthermore, noise exposure measures seldom play an active role in identifying reasonable noise abatement alternatives. The paper discusses three projects which have effectively employed game playing in the development of noise abatement actions.
Railroad Noise Impact on Residential Land Planning
Authors: Campanella AJ
Published: March 2009

A method of test for residential land use in the vicinity of a railroad using on-site noise level measurements is described. This was applied in the Columbus, Ohio area to optimize residential land utilization in the vicinity of a cross-country railroad. Acceptability criteria are those expressed in the Department of Housing and Urban Development (DHUD) Circular 1390.2 and a criterion developed for this special case. Measurement variables include the peak A-weighted sound pressure level (dBA), the energy equivalent sound level (Leq), the day-night average sound level (Ldn), train passage frequency and distance from the railroad's right-of-way centerline. Peak A-level observations made with a hand-held sound level meter are compared with a 24-h community noise meter's peak and Leq observations. A continuous 24-h strip chart technique was developed to validate digital data.
Factors Affecting the Design and Implementation of a Workable Community Noise Ordinance
Authors: Gatley WS
Published: March 2009

Municipal governments have the power to restrict the operation and use of many noise sources within their areas of jurisdiction. The success of programs to regulate community noise depends upon a number of factors: (a) identification of major noise sources; (b) training of personnel; (c) funding available for implementation and continued enforcement; (d) success in overcoming legal challenges; and (e) education of and support from the public.

This paper summarizes the types of noise legislation available to communities and describes their primary features. Design of effective and enforceable noise regulations for smaller communities with limited resources is emphasized. Methods for avoiding community noise problems, including prediction of noise levels, land-use planning, and zoning ordinances, are discussed briefly.
Biochemical Measurements of Microbial Mass and Activity from Environmental Samples
Authors: White DC , Bobbie RJ , Herron JS , King JD , Morrison SJ
Published: March 2009

Accurate measurement of the mass and activities of environmental microbial assemblies requires methods that differ from those of classical microbiology. Using the leaf-litter detrital microflora recovered after incubation in a semitropical estuary, biochemical assays of multiple components can be made which give reasonably similar estimates of microbial mass, using normalization values from bacterial monocultures. The assays involve recovery of adenosine triphosphate, the unique bacterial cell wall mucopeptide component muramic acid, the uniquely prokaryotic endogenous storage material poly-β-hydroxybutyrate, a series of exoesterase activities, and the extractable lipids, primarily the phospholipids and the glycolipids. If the sampling conditions are such that incorporation of radiosotopes into the microflora is possible, these assays become extraordinarily sensitive. If radioisotope usage can be coupled with the purification of particular lipids, it is possible to gain information on the structure and dynamics of the microbial population.
Measurement of Bacterial Biomass as Lipopolysaccharide
Authors: Watson SW , Hobbie JE
Published: March 2009

The biomass of bacteria in various waters can be estimated by measuring the amount of cellular bound lipopolysaccharide (LPS). LPS, which is present in the cell walls of gram-negative bacteria, including cyanobacteria, can be quantitated by using an extract of Limulus amebocytes. In one special environment, an oceanic water column below the euphotic zone, the results of the LPS technique agreed very well with those of the direct count and adenosine triphosphate techniques for measuring bacterial biomass.