bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation of Organic Materials from in Situ Oil Shale Retort Water Using Macroreticular Resins, Ion Exchange Resins, and Activated Carbons
Authors: Huffman EWD
Published: March 2009

Organic materials in an oil shale retort water produced in situ were fractionated using macroreticular resins, ion exchange resins, and activated carbon Approximately 50 percent of the material was adsorbed on the macroreticular resin. Of the materials adsorbed on the macroreticular resin, 26 percent were basic, 36 percent were acidic, and 38 percent were of neutral character. Of materials passing through the resin, 21 percent were adsorbed on a cation exchange resin (basic), 58 percent were adsorbed on anion exchange resins (acidic), and 20 percent were not adsorbed (neutral). Activated carbon adsorbed quantities of material similar to those adsorbed by the ion exchangers if the sample was acidified before adsorption. Based on these fractionation experiments, a procedure to perform a preparative scale fractionation of an oil shale retort water produced in situ into representative organic compound classes has been developed. The four primary fractions isolated include hydrophobic bases, hydrophobic neutrals, carbon adsorbables, and nonadsorbables.
Aspect Ratio Variability in Part-Through Crack Life Analysis
Authors: Engle RM
Published: March 2009

A survey of various analytical solutions currently used in part-through crack life prediction is presented. Solutions are included which account for shape change effects as well as constant shape solutions. Comparisons of these solutions with constant amplitude experimental data are examined. Results are presented for three different materials: 2219-T851 aluminum, 6A1-4V (β annealed) titanium and 9Ni-4Co-0.20C steel.
Prediction of Constant Amplitude Fatigue Crack Propagation in Surface Flaws
Authors: Johnson WS
Published: March 2009

A technique used to predict constant amplitude crack growth in a surface flaw is presented. Various aspects of this technique that are discussed include: constant amplitude crack growth data, crack growth models, crack growth accumulation/ integration routine, surface flaw stress intensity factors, surface flaw transition to a through crack and the definition of failure/fracture of a specimen. The author's predictions and the results of a round-robin effort are discussed.
Jet Fuel Flash Point Reduction
Authors: Strauss KH
Published: March 2009

Forecasts of petroleum product demands show greater growth rates for distillates including jet fuels than for gasolines. Jet fuels are in direct competition with other distillates for the same part of the barrel; increasing jet fuel volume by incorporating gasoline fractions would decrease flash point. Consideration of a flash point reduction in jet fuel specifications is a controversial subject. A survey conducted by ASTM Technical Division J on Aviation Fuels of Committee D02 on Petroleum Products and Lubricants showed wide disagreement on the technical factors governing flash point in specifications. The symposium was developed to respond to the findings of this survey.
Effect of Flash Point on the Design and Operation of SST Aircraft
Authors: Boucher HT
Published: March 2009

The effect of flash point reduction and, therefore, the increase of vapor pressure on the design and operation of a supersonic transport (SST) is examined in detail. Considering an SST design, which has been optimized on the basis of a kerosine flash point of 38°C (100°F), the effect on design criteria of lowering flash point by 5.5°C (10°F) is equivalent to a cost penalty, to each SST aircraft in the order of $45 000 per year. A further 5.5°C (10°F) lowering would increase the penalty to some $125 000 per year. The penalty is not incurred in full where existing designs have included a margin to allow for lower flash points fuels.

The main effect of lower flash point fuels upon the safety of supersonic aircraft lies in the greater flame speed across pools of fuel which might be spilled in crash landings.
On-Line Safety Monitoring of a Large High Pressure High Temperature Autoclave
Authors: Tatro CA , Brown AE , Freeman TH , Yanes G
Published: March 2009

Four years of experience with on-line monitoring of a large autoclave used primarily for forming bonds and material densification is reported. The purpose of this work is to confirm that no flaws are growing in the autoclave during operation. Failure of this device during operation could endanger personnel and would damage property. Its loss would seriously curtail several ongoing research efforts.

The vessel is monitored with a commercial minicomputerized flaw location system. Four 4-sensor arrays are attached to the exterior of the device to receive acoustic emission signals. Computed locations are stored on cassette tape and selected portions can be displayed on a cathode ray screen. It is shown that although the minicomputer is implemented with two dimensional location software, the information can be reprocessed in a central computer to produce locations in three dimensions.

Long-term storage of data, data display, noise analysis, calibration, and computerized location error analysis is discussed.

No degradation by flaw growth has been detected in this device to date. This is the expected result, since it has an estimated 30-year life.
Acoustic Monitoring for Leak Detection in Pressurized Water Reactors
Authors: Smith JR , Rao GV , Gopal R
Published: March 2009

Acoustic emission (AE) offers significant promise for the monitoring of the structural integrity of nuclear power plants. The capabilities of acoustic monitoring for monitoring primary leaks in pressurized water reactors (PWR) are investigated in the current study on the basis of laboratory evaluation studies conducted under simulated plant conditions and on the basis of several plant monitoring experiences. The laboratory studies included a variety of localized steam leaks through circular orifices and fatigue-generated, through-wall cracks in pressurized pipe systems. The results are considered in light of an aerodynamic energy model. Also included in the study are leaks through a number of defective valves. Under plant monitoring studies, signal attenuation measurements on reactor pipe systems, tests on controlled leaks, and detection of natural plant leaks are considered. A modified plant heat-up method is suggested that will greatly enhance signal-to-noise ratio during the critical period of pressurization, when most AE would be expected.
A High Signal-to-Noise Oscillator for Contactless Measurement of Photoinduced Carrier Lifetimes
Authors: Curtis HW , Verkuil RL
Published: March 2009

A wide-band apparatus for contactless measurement of small changes in photoinduced carrier population is described. Since for some phenomena the signals of interest have very low amplitude, and since the generator supplying energy for the measurement is an oscillator loosely coupled electromagnetically to the semiconductor, very-low-noise circuitry is required. Further, sensitivity to minute conductivity changes is enhanced when the oscillation amplitude is made directly proportional to the figure of merit, Q, of the coupled oscillator resonant parallel inductance-capacitance (LC) tank. The circuit to approximate the desired dependence, amplitude = kQ, contains only two field-effect transistors and is basically an oscillator supplied by a constant current rather than by a constant voltage source. Its operation is analyzed via modeling that specifies the output signal as a function of device and circuit parameters; excellent correspondence with empirical data is shown.

The oscillator also operates as an infinite impedance detector of its own amplitude; this amplitude is shown to be linearly dependent on carrier concentration over significant ranges. Thus, the oscillator steady-state and transient responses may be directly related to wafer conductivity, induced carrier amplitude, and lifetime. The described apparatus is sensitive to carrier concentration changes of less than 1011 electrons or holes per cubic centimetre of silicon and will provide measurement of lifetimes from a microsecond to several seconds.
Multiparticle Erosion of Pyrex Glass
Authors: Sargent GA , Mehrotra PK , Conrad H
Published: March 2009

Multiparticle erosion tests were performed on Corning 7740 Pyrex glass using alumina powder of two grit sizes. Erosion was measured as a dimensionless parameter in terms of the loss in weight of the target per unit weight of particles impinged. The erosion characteristics of the Pyrex glass were investigated over a range of particle velocities, angles of impingement, and times of erosion.

It was found that maximum erosion occurred at a normal angle of impact for the 240-grit powder (mean particle size ≃ 30 μm); however, with the 400-grit powder (mean particle size ≃ 10 μm), the maximum was found to occur at a slightly lower angle of about 80 deg. At all angles of impingement it was found that amount of erosion decreased as the erosion time increased.

Erosion (E) was found to be dependent on the average particle velocity (V) by a power relationship of the form EαVn where n is a material constant. The values of the velocity exponent, n, in the present experiments were found to be between 2.2 and 2.7 and were independent of time of erosion.

The time (t) dependence of erosion was also found to obey a power law relationship of the form Eαtc where c is a material constant. The time exponent c was found to be -0.1 under all conditions of velocity, particle size, and angle of impingement. The decrease in erosion with increase in time has been interpreted in terms of a change in the surface roughness. Scanning electron microscopy (SEM) has been used to establish that the effective average angle of impingement decreased as time of erosion increased until a constant surface roughness was achieved, at which time it was found that the average angle of impingement was about 55 deg instead of 90 deg.

The experimental data obtained in the present work are discussed in terms of existing theories for the erosion of brittle materials.
Influence of Materials Construction Variables on the Rain Erosion Performance of Carbon-Carbon Composites
Authors: Schmitt GF
Published: March 2009

The influence of materials construction variables and environmental parameter effects on the rain erosion behavior of carbon-carbon reentry vehicle nosetip thermal protection materials has been investigated at velocities of 1220 to 1675 m/s by firing rocket sleds equipped with special specimen holders through the artificial rain-field at Holloman Air Force Base.

A high percentage of axial reinforcement (fibers end-on to the surface) is desirable in carbon-carbon composites for improved erosion resistance. One-dimensional reinforcement of this type would provide maximum erosion resistance, but the need for structural properties in reentry vehicle applications requires a combination of this high axial loading with fine-weave orthogonal 3-dimensionally reinforced construction for enhanced erosion-resistance and balanced performance. The small unit cell size is essential for good resistance. Increased in-plane isotropy in these composites by rotating the X-Y plies reduced the macroroughness development which is typical of the carbon-carbon composites in the multiple rain environment.

Improvements in weaving, impregnation, pyrolysis, and graphitization are reflected in a reduction in the mass loss ratio of composites which have similar Z bundle area fractions, but were made at different chronological times.

It was determined that Thornel 50 fiber composites gave better performance than Thornel 75, C-1000, C-3000, and other fibers. The introduction of intermediate chemical vapor deposition (CVD) of carbon coupled with low- or high-pressure pitch processing provided matrices for composites with improved erosion resistance compared with pyrolyzed resin or pitch-only processes.

Empirical relationships were determined to govern the erosion rate as a function of velocity and impingement angle.
Elastic-Plastic Fracture Toughness Based on the COD and J-Contour Integral Concepts
Authors: Dawes MG
Published: March 2009

The paper reviews the definition, fracture characterizing roles, and measurement of critical COD and J-values. It is proposed that COD should be defined as the opening displacement at the original crack tip position. This definition avoids much of the ambiguity of previous definitions based on the crack tip profile and the elastic-plastic interface. Attention is drawn to a fundamental problem which limits the general application of the J-contour integral concept to elastic-plastic descriptions of the crack tip environment when cracks occur in overmatching yield strength weld regions. A comparison of recent three-point single-edge notch bend (SENB) testing techniques, based on the standard instrumentation used in KIc tests, shows there is a close mathematical link between the estimated values of COD and J.

Experimental data, obtained over a wide range of temperatures, are used to demonstrate how the critical values of COD and J for unstable fracture are affected by variations in specimen geometry. Also, it is shown that measurements of JIc may lead to overestimates of KIc in materials having yield strengths less than approximately 700 N/mm2.
Effect of Size on the J Fracture Criterion
Authors: Milne I , Chell GG
Published: March 2009

Experimental evidence showing the size dependence of JIc in ferritic steels is presented. This behavior is described in terms of a relatively simple mechanistic model for cleavage fracture. It is shown that the mechanisms of cleavage fracture and ductile slow crack growth are always in competition and this leads to the behavior frequently encountered in fracture tests where initially ductile crack extension leads to fast brittle failure. The size effect is also discussed in terms of a shift in the ductile brittle transition temperature. The implications on failure assessment procedures are mentioned.
A Procedure for Incorporating Thermal and Residual Stresses into the Concept of a Failure Assessment Diagram
Authors: Chell GG
Published: March 2009

The Failure Assessment Curve proposed by Harrison, Loosemore, and Milne has been rederived and interpreted in terms of an equivalent J-integral analysis. Comparison with computed values of J indicates that the curve is a good approximation to a lower-bound failure criterion for mechanical loading. The J-integral interpretation enables thermal, residual, and secondary stresses to be included within the concepts of the Failure Assessment Diagram. A procedure is introduced which transforms points on a failure diagram obtained, for instance, from a J-integral analysis, into approximately equivalent points on the Failure Assessment Diagram. This procedure is particularly useful for failure assessments involving thermal, residual, or secondary stresses where a plastic collapse parameter is not definable. The procedure assumes that a plastic stress intensity factor can be estimated. A method of assessing the severity of a mechanical load superposed on an initial constant load is also presented. Examples showing the applications and advantages of the technique are given.
Elastic-Plastic Fracture Mechanics Analyses of Notches
Authors: Hammouda MM , Miller KJ
Published: March 2009

Fatigue failures invariably start at a surface notch. Crack initiation is due to plasticity while crack propagation can continue in an elastically stressed material due to the crack generating its own crack tip plasticity.

From elastic-plastic analyses, it is possible to predict the effect of notch plasticity on the behavior of short propagating cracks. Elastic-plastic finite-element analysis solutions to cracks in notch fields indicate that a crack will initially propagate at a decreasing rate until the crack can generate a crack tip plasticity that is greater than the elastic threshold stress intensity condition.
Determination of Sample Size in Flight Loads Programs
Authors: Berens AP
Published: March 2009

This paper describes the application of a statistical model of a cumulative damage index to the problem of determining the number of flights to be monitored in aircraft operational usage programs based on samples of flights. The method can be used to calculate the optimum number of flights to achieve given precision and confidence under stratified sampling. It also provides a method for determining precision at any level of confidence given a sample size. Examples of the use of the techniques are provided using data from the operational usage programs of three aircraft types.
Flight Spectra Development for Fighter Aircraft
Authors: Sandlin NH , Lauridia RR , White DJ
Published: March 2009

A method is presented for deriving realistic flight-by-flight stress spectra which are valid for any point in the structure of fighter or attack type aircraft. This method uses regression equations to define the relationships among stresses and flight parameters. The statistical distributions of aircraft motion parameters are derived and defined in multi-parameter response tables. These tables are combined with assigned mission profile data to establish all of the required flight parameters which are used in the regression equations to develop stress spectra. These spectra then are sequenced into a flight-by-flight order which can be used as input to a damage determination model or as a load program for laboratory testing.
Simulation and Monitoring of Loads in Crane Beams
Authors: Weiss MP
Published: March 2009

The fracture mechanics approach to design of steel structures uses the stress range distribution function as the main parameter that governs crack propagation and possible failures. It is an accepted fact that all welded structures contain existing small cracks that propagate as a function of varying stress ranges and stress intensity factors. The main problem is to predict correctly the nature of the varying stresses and to analyze them for fatigue evaluation.

Crane structures are exposed constantly to different static and dynamic loads and their stress distribution is quite complex. In this study, stress distributions in an overhead travelling bridge crane beam are evaluated by computer simulation and by monitoring real structures with a specially developed test setup.

The simulation starts with generating beta distributed random loads, and random loading and unloading places in the service area. These points are generated by means of a new general distribution model. Stress peaks and ranges are calculated and counted per each loading cycle.

The test setup uses regular load cells, with specially designed fixtures and A/D converters, to record data on perforated tapes.

The simulations were used to plot general distributions of stress peaks and ranges. The test results are special cases of the general distributions.

The results of this study are being used currently to evaluate fatigue lives and safe stresses in crane structures, and to update design codes.
Fatigue Mechanism—An Historical Perspective
Authors: Coffin LF
Published: March 2009

Following a note of welcome to the symposium participants, the activities of the ASTM Committee E9 on Fatigue are described. To place the 1978 symposium on fatigue mechanisms in perspective, some general comments on a symposium held in 1958 and some specific comments on each of the technical papers presented at that meeting are made. The conclusion one draws from a review of that symposium is that many investigators were seeking to understand fatigue by the use of special materials. Lithium fluoride, silver chloride, single crystals, and so forth, were the tools that could be used to increase our powers of observation on the basic behavior that was involved. Since then, the study of fatigue has advanced not so much from the aspect of mechanism, but more from phenomenology, including low-cycle fatigue, crack propagation, environment-enhanced fatigue, etc. It remains for this symposium to indicate whether we have gained more understanding of the basic mechanisms of fatigue during the past 20 years, and whether the proceedings will yield some new insight leading to a breakthrough in fatigue research.
On the Process of Subsurface Fatigue Crack Initiation in Ti-6Al-4V
Authors: Ruppen J , Bhowal P , Eylon D , McEvily AJ
Published: March 2009

The process of subsurface crack initiation in Ti-6AI-4V has been investigated in some detail. At low stress amplitudes, slip occurs primarily on prism planes and is blocked at α-β interfaces. The piled-up dislocations induce slip in the β-phase under cyclic loading which can lead to the formation of a Cottrell cleavage knife and thereby provide a site for subsurface crack initiation. At high stress amplitudes, pyramidal slip becomes operative and as a consequence a more compatible type of plastic deformation between the two phases can develop. Under these circumstances the tendency for subsurface crack initiation may be reduced.
Mechanisms of Fatigue and Environmentally Assisted Fatigue
Authors: Lynch SP
Published: March 2009

Fatigue cracks often initiate either by formation and development of coarse slip steps or by extensive deformation in localized soft bands producing intrusions and extrusions. Microstructural changes induced by fatigue, for example, formation of fine subgrain structures within soft bands, are probably necessary for intrusion, extrusion, and for subsequent Stage I crack growth. Stage II crack growth involves plastic-blunting/alternate-slip processes at crack tips. Increments of crack growth per cycle, for a given effective crack-opening displacement, depend mainly on the distribution of slip around crack tips during loading; this distribution is determined by both the microstructure and the environment. The effects of aggressive environments on crack growth can be explained, in many cases, on the basis that chemisorption of environmental species influences interatomic bonds and thereby facilitates nucleation of dislocations at crack tips. Striations ('ductile' and 'brittle' types) on fracture surfaces are produced because unloading deforms part of the fracture surface produced during loading.
Experiments Concerning Brittle, Ductile, and Environmentally Controlled Fatigue Crack Growth
Authors: Neumann P , Fuhlrott H , Vehoff H
Published: March 2009

Various experiments were carried out in copper and Fe-3Si under as simple as possible conditions in order to get unequivocal information about the mechanisms which are relevant for crack initiation and propagation. New results are reported about the conditions for Stage I crack growth. It is pointed out how extrusion-intrusion pairs can form as a consequence on Stage I cracks. Furthermore, the strain distribution around Stage II cracks is described in detail. Environmental effects on Stage I and Stage II crack propagation are reported and evidence is presented for rewelding during the compressive phases. Finally, a new experimental approach to study brittle crack initiation at plastified cracks is described.
Some Observations on the Role of Cellular Enzymes in the In-Vivo Degradation of Polymers
Authors: Williams DF
Published: March 2009

The in vivo and in vitro degradation of some suture materials, especially polyglycolic acid sutures, has been studied in an attempt to determine whether cellular enzymes have any influence on the degradation of polymers. The test protocols included a novel method for varying the type of tissue response to a material so that the in-vivo behavior of the material under different conditions could be followed.

It has been found that the hydrolysis of polyglycolic acid takes place by essentially the same mechanism in vivo and in vitro—that is, by hydrolysis in an aqueous environment—but that the initiation of this process is greatly enhanced by the in-vivo environment. The cells of an acute response to implant material appear to favor hydrolysis slightly more than do cells of a chronic response. A similar but more significant difference in tissue environmental effect is noted with the use of polyamide sutures, but the situation is reversed when silk sutures are used; then the chronic inflammatory cells have a greater effect on the suture materials than do the acute inflammatory cells.
Descriptors of Auditory Magnitude and Methods of Rating Community Noise
Authors: Goldstein J
Published: March 2009

A principal reason for measuring sound is to relate our acoustic environment to measures of human response. Characterization of the relevant relationships between physical exposure and the effects of noise on people has been fostered through the use of a wide variety of sound descriptors. Many of these descriptors were historically derived from sets of contours representing judgments of loudness, noisiness, or acceptability of sound. Many of these evolved merely as variations of one another. The apparent differences between the many assorted descriptors are simply due to differences in treatment of the many acoustic and non-acoustic parameters which are known or thought to influence human response to sound. The purpose of this tutorial paper is to review some of the more common sound descriptors used to portray our acoustic environment, as well as their derivations, formulation, applicability, and limitations.
Speech Interference and Community Annoyance
Authors: Sanford F
Published: March 2009

A prescriptive rather than descriptive approach to modeling community reaction to noise exposure is suggested, based on the strong relationship usually observed in social surveys between extensity of speech interference and prevalence of annoyance. Parallels between the suggested approach and another prescriptive theory of human behavior are drawn, and the advantages of such a systematic approach are discussed.
Errors Due to Temporal Sampling
Authors: Mansbach PA , Corley DM
Published: March 2009

Statistical techniques allow the prediction of the error (expressed as a standard deviation about the measured energy equivalent sound level (Leq) or time exceedance level (Lx)) due to temporal sampling of a time-varying signal. To first approximation, σ(Leq)=4.3σ(p2)/N, where σ(p2) is the standard deviation of pressure squared about its mean 〈 p2 〉, and N is the number of independent data points in the sample. These predicted standard deviations are compared with experimentally determined values, obtained by computer sampling of large sets of actual field data recorded at a highway, an airport, a suburban road, and a rural residence. The predicted standard deviations, for the example given, of sampling at 30 s intervals for 1 h, range from 0.3 to 8 dB. These values agree closely with the experimentally determined values, and the small remaining discrepancies are explained. For “continuous” (or very frequent) sampling, an “effective number” of independent samples is used, computed from the autocorrelation in the time-varying signal.
Aircraft Noise-Induced Building Vibrations
Authors: Stephens DG , Mayes WH
Published: March 2009

Community noise surveys have often identified building vibration as a source of annoyance in airport communities. Most recently, concern for building vibration has been associated with the introduction of the Concorde supersonic transport into the United States because of the relatively high levels of noise. The objective of this paper is to describe a study of building vibration resulting from aircraft and non-aircraft events in the vicinity of Dulles and John F. Kennedy International Airports. The measurement, quantification, and assessment of the noise and the associated vibration of windows, walls, and floors are described for several homes. Results include relationships between aircraft noise and building vibration and between vibration and human response. Comparisons of building vibration data with existing criteria for building damage and human response are also included.
Prediction of Community Noise from Rail Systems
Authors: Kurzweil LG
Published: March 2009

This paper presents a simple procedure for predicting noise in the vicinity of rail lines including intercity freight and passenger services and metropolitan systems. The procedure accounts for the effects of speed; wheel and rail condition; travel on bridges and elevated transit structures; geometrical spreading of sound energy; excess attenuation due to propagation over the ground and through the air; and barrier attenuation by sound screens, cuttings, embankments, and houses. Aweighted sound pressure level is the basic quantity predicted; equations are given to determine various noise exposure measures such as the 24-hour energy equivalent sound level (Leq (24h)), the day-night average sound level (Ldn) and the community noise equivalent level (CNEL).
L10 versus Leq—A User's Perspective
Authors: Cohn LF , McColl W
Published: March 2009

The Federal Highway Administration (FHWA) regulation tor highway traffic noise analysis, FHPM 7-7-3, allows for the use of either L10 (sound level exceeded 10 percent of the time) or Leq (energy equivalent sound level). Therefore, state highway agencies have the responsibility to empirically determine the preferable descriptor (L10 or Leq) for typical highway projects.

As such, the New York State Department of Transportation (NYSDOT) has performed several such studies in recent years. Among those are an analysis of two major prediction methodologies (National Cooperative Highway Research Program (NCHRP) Reports 117 and 174), and a long term measurement study of the Youngmann Expressway Noise Abatement Project in Buffalo, N.Y.

Results of these two studies indicate that both L10 and Leq are satisfactory descriptors for proposed highway projects. However, for vehicular flow rates of somewhere less than 400 automobiles per hour, L10 becomes suspect because the assumption of equal vehicular spacing becomes non-valid. For long-term studies, Leq is very sensitive to equipment malfunction, but is superior to L10 in its ability to consider short duration, random occurrences.
California's Noise Insulation Standards for Multi-Family Residential Construction
Authors: Van Houten JJ
Published: March 2009

Requirements for noise insulation are included in the design of all new multi-family dwelling units to be constructed in California after August 1974. Noise Insulation Standards are part of the California Administrative Code (Title 25, Section 1092) and are enforced by local building departments throughout the state. The standards apply to all new multi-family dwelling units, such as hotels, apartments, duplexes, townhouses, and condominium units. Detached single-family dwellings are specifically excluded.

The standards establish minimum requirements for the isolation of interior spaces from exterior noise and set minimum ratings for noise insulation of partitions between dwelling units. The community noise equivalent level (CNEL) of 45 dB is set as the maximum for intrusive noise from exterior sources. ASTM testing procedures for party wall and floor/ceiling system sound transmission provide the basis for setting minimum acceptable performance of separations between units.

Based on a study of numerous (over 200) residential projects, it has been found that a certification that the final design complies with the standards is generally required and provided as part of the consulting effort. Field tests are required when the sound transmission performance of the completed structure is questioned by the building official.

The paper provides a brief description of the standards, their enforcement, pitfalls and an assessment of their impact on residential construction in California.
Abatement of Aircraft Noise and Related Regulatory Actions
Authors: Sperry WC
Published: March 2009

In conformance with the Noise Control Act of 1972, the Environmental Protection Agency (EPA) has proposed to the Federal Aviation Administration (FAA) for promulgation eleven regulations for the control of aircraft noise and is considering several more. The EPA's proposed regulations logically fall into three categories defined by the segment of the aviation community that would be regulated, that is, manufacturers, aircraft operators, and airport operators. Those categories can be interpreted, with some liberties taken to suit the subject (aviation), to represent the source, path, and receiver noise control options which are commonly used in the discipline of acoustics as a technique for subdividing complex noise control problems into managable parts. Also, where noise control capability is highly dependent upon technology, which is always true for source control of aircraft noise, the EPA's proposed regulations are time-phased. That is, the noise requirements are based upon the results of past, present, and future programs of research, development, and demonstration which can be classified in terms of current, available, and future noise control technology.

The concepts of abating aircraft noise by exercising the source, path, and receiver noise control options taken together as a system and by time-phased regulations are described. Regulations proposed by the EPA designed to implement those concepts are presented as examples. Specific regulations which are time-phased in terms of current, available, and future noise control technology are examined in more detail and the economic consequences discussed.
Simulated Field Studies—Acute Hazard Assessment
Authors: Fink RJ
Published: March 2009

Acute and subacute laboratory studies are an initial assessment of pesticide toxicity and are preliminary indicators of acute environmental hazard. A carefully designed simulated field study serves to bridge the gap between laboratory indicator studies and actual hazard assessment under field conditions. A simulated field study, therefore, enables an environmental hazard assessment to be made under semi- controlled conditions that realistically mimic conditions that can be expected with full-scale field usage. The ability of a simulated field study to predict environmental hazard is no better than the degree to which it simulates actual conditions. Important factors to consider when designing a simulated field study include the selection of a nontarget species animal model indigenous to the anticipated area of use, a test site habitat that is compatible with the animal model selected, simulation of standard agricultural practices, and the generation of replicate data on the observation parameters to insure statistically reliable interpretation.
The Adenosine Triphosphate Assay: Conceptions and Misconceptions
Authors: Stevenson LH , Chrzanowski TH , Erkenbrecher CW
Published: March 2009

The present state of technology associated with the extraction and quantification of adenosine triphosphate (ATP) from aquatic samples is considered. A brief examination of the history of the method is presented, and data available from studies designed to determine the level of ATP in some aquatic environments are presented in a comparative manner. The possible interference of guanosine triphosphate in the assay procedure as well as irregularities produced by altering the luciferin concentration employed in the assay are described. Procedures currently employed for the extraction and measurement of ATP as an indication of microbial biomass are given.
Characterization of Impact Damage in Composite Laminates
Authors: Pettit DE
Published: March 2009

The potential application of the Holscan 400 as a laboratory tool to monitor characterize impact damage in graphite/epoxy composite material was evaluated. Impact damage in 16- to 32-ply-thick material was examined. A number of modifications were made to the basic Holscan system and the unit evaluated in terms of impact damage characterization ability and ease of operation in a laboratory environment. The results showed several of the modifications to be needed to provide a system with the desired capability and ease of operation.
Flaw Criticality of Graphite/Epoxy Structures
Authors: Konishi DY , Lo KH
Published: March 2009

The orderly assessment of the serviceability of graphite/epoxy structures requires a knowledge of their flaw criticality. In the Serviceability Program, industry-wide flaw likelihood/criticality surveys have been conducted and the results have been qualitatively assessed. These results were used to set nondestructive evaluation (NDE), analytic study, and experimental verification goals. The progress of this program is reported herein.

Flaws, which can result from the fabrication process, normal service utilization, and battle damage have been categorized into five types, depending on their associated stress field disturbance. Flaw detectability studies have been conducted to determine the optimal NDE process to detect these flaws. Analytic studies have been to conducted to determine the disturbance to the stress field in the vicinity of the flaws and to assess their criticality, that is, their structural integrity.

These results were used to define coupons and elements where the elements represent structures that are in a realistic stress state. Accelerated “worst expected” case environmental fatique testing has been conducted. The preliminary results show, as expected, that advanced composites are relatively damage-tolerant. Since further testing is being conducted, an up-to-date status of the program is given.

Three types of coupons are being tested. The tension coupons contain flaws such as holes, delaminations, ply separations, and scratches. The compression coupons contain delaminations, in untapered and tapered regions, and ply separations. The bolted-joint coupons contain notches at bolt holes, oversized holes, and delaminations. Static tests, both room-temperature dry and 82°C (180°F) temperature wet, are being conducted. Spectrum fatigue tests followed by residual strength tests are also being conducted. Both room-temperature dry and realistic temperature/moisture environments are used. Flaw growth specimens are also being tested. The results for the tension flaw screeing specimens are presented and assessed.
Effect of Impact Damage and Holes on the Compressive Strength of a Graphite/Epoxy Laminate
Authors: Starnes JH , Rhodes MD , Williams JG
Published: March 2009

The effect of low-velocity impact damage and circular holes on the compressive strength of a 48-ply orthotropic graphite/epoxy laminate has been studied experimentally. Unidirectional tapes made of Thornel 300 graphite fibers preimpregnated with Narmco 5208 epoxy resin were used to fabricate the [±45/02/±45/02/±45/0/90]2s laminate. Aluminum spheres 1.27 cm in diameter were used as projectiles and propelled at speeds between 52 and 101 m/s. The extent of interior laminate damage caused by impact was determined by ultrasonic inspection and, in some cases, by cross-sectioning specimens for visual inspection. Some specimens were impacted and then loaded to failure in compression to determine their residual strength. Other specimens were loaded to a prescribed compressive strain and impacted at the applied load. Some of these loaded specimens failed catastrophically on impact. Specimens that did not fail catastrophically were subsequently loaded to failure in compression to determine their residual static strength. It was found that low-velocity impact damage can seriously degrade the laminate static compressive strength. Several impact-damaged specimens were subjected to low-strain compression-compression cyclic loading, which was found to degrade further the laminate compressive strength. Specimens with circular holes with diameters up to a third of the specimen width were loaded in static compression to failure, and it was found that holes can also degrade the compressive strength of the laminate. Impact at the higher speeds reduced the compressive strength of the laminate more than largest holes studied.
A Fracture Mechanics Approach to the Analysis of Graphite/Epoxy Laminated Precracked Tension Panels
Authors: Griffith WI , Kanninen MF , Rybicki EF
Published: March 2009

A methodology for the prediction of fracture in fiber composite laminates under monotonically increasing load is presented. In the model, laminate behavior is based on damage growth in individual plies with a fracture mechanics approach being used to continually assess the damage in each ply. Within each ply, damage may occur by crack extension parallel to or perpendicular to the fiber orientation in the ply. Critical values of strain energy release rate for both modes of damage are inferred from experimental data on center-cracked, zero-degree unidirectional laminates. At present, interply interactions are neglected. Despite this severe oversimplification, a comparison of strength predictions from the laminate model shows reasonable agreement with experimental results, both quantitatively and qualitatively, for [0/90]4s, [±45]4s, and [0/±45/0]2s graphite/epoxy laminates. The features of the laminate model are contrasted with the models of a number of other researchers.
NASA Five-Ball Fatigue Tester—Over 20 Years of Research
Authors: Zaretsky EV , Parker RJ , Anderson WJ
Published: March 2009

This paper reviews, from both a technical and a historical perspective, the results of research conducted using the National Aeronautics and Space Administration five-ball fatigue tester. The test rig was conceived by W. J. Anderson in late 1958. The first data were generated in March 1959. Since then a total of approximately 500 000 test hours have been accumulated on a group of eight test rigs which are capable of running 24 h a day, 7 days a week. Studies have been conducted to determine the effect on rolling element fatigue life of contact angle, material hardness, chemistry, heat treatment and processing, lubricant type and chemistry, elastohydrodynamic film thickness, deformation and wear, vacuum, and temperature, as well as hertzian and residual stresses. A correlation was established between the results obtained using the five-ball tester and those obtained with full-scale rolling element bearings.
Development and Application of the Rolling Contact Fatigue Test Rig
Authors: Bamberger EN , Clark JC
Published: March 2009

The rolling contact (RC) fatigue test rig was developed specifically for rapid and inexpensive evaluation of materials and processes for rolling element bearing applications. The simple geometry of the test specimen, a cylindrical bar, makes it ideal for evaluating new materials where only limited quantities of the material may initially be available and also permits precise control of the mechanical and thermal processing of the test specimen.

This paper will discuss the development of the RC rig and will detail some of the major investigatory programs which have been performed in the authors' laboratory. This includes the evaluation of metallic and nonmetallic materials for bearing operation, effects of different metallurgical structures on rolling contact fatigue, and the investigation of unique processes such as ausforming and hollow rolling elements. The results of these investigations will show the relevance of the RC rig to full-scale bearing tests and to actual bearing operation in service. Last, the initial work performed on the second-generation RC rig, a high-speed version capable of surface speeds up to 25 m/s (82 ft/s), permitting operation well into the elastohydrodynamic regime, will be briefly reviewed.
Accelerated Rolling Contact Fatigue Test by a Cylinder-to-Ball Rig
Authors: Ito S , Tsushima N , Muro H
Published: March 2009

The cylinder-to-ball type of rolling contact fatigue rig is one of the most accelerated test rigs and is suitable for investigation of the influences of material and heat-treatment factors on rolling contact fatigue life. It has such merits as ease of manufacture, high precision, and easy replacement of the specimen and a high loading speed with high contact stress. The transition in the life levels of ball bearing steels and carburizing steels in relation to the year of production, beginning in 1964, is described. As examples of the test results, the influences of the fiber orientation and the forging ratio are described. The influence of the fiber orientation is great for ball bearing steel and not as great for carburizing steel. Bar forging greatly increases the rolling contact fatigue life whereas upset forging does not.
Observations of the Peeling Mode of Failure and Surface-Originated Flaking from a Ring-to-Ring Rolling Contact Fatigue Test Rig
Authors: Tokuda M , Nagafuchi M , Tsushima N , Muro H
Published: March 2009

The ring-to-ring rolling contact fatigue rig is a standard test rig for producing rolling contact fatigue. It is suitable for basic research on rolling contact phenomena. Observations of two types of surface cracks, peeling microcracks under moderate contact stress and surface cracks due to excessively high contact stress, are described in this paper. The peeling grade is related to the metallic contact ratio. The running-in property observed in metallic contact monitoring is an important factor in determining the relationship between the lubricant's characteristics and peeling failure. Rolling contact under high contact stress produces surface-originated flaking by a crack initiation mechanism, that is, crack initiation resulting from fatigue by repeated cycles of small tension and large compression.
Methods of Testing for Rolling Contact Fatigue of Bearing Steels
Authors: Galbato AT
Published: March 2009

Types of test equipment, apparatus, and the procedures employed in the evaluation of rolling contact fatigue are reviewed, covering both element and full-scale bearing tests and the significance of test results.
Rolling Bearing Life Tests and Scanning Electron Microscopy
Authors: Morrison FR , Yonushonis T , Zielinski J
Published: March 2009

Traditional techniques for the evaluation of a rolling bearing material or lubricant rely on the accelerated life testing of large lots of bearings. The rating of the bearing performance is then established on the basis of statistical estimates of the experimental Weibull parameters.

Optical evaluation of bearing surfaces has long been used to supplement life data. However, optical examination is limited to evaluating the validity of specific test points. Another surface analysis technique, scanning electron microscopy (SEM), can now be used to augment test data because of the high magnifications and depth of field available. SEM examination of tested surfaces at magnifications up to ×1000 can define alterations in surface morphology produced by wear, fatigue, and corrosive failure modes long before signs would be detectable by optical means or failure would be precipitated. These characteristics can be qualitatively evaluated to supplement collected life data, and comparisons can yield relative evaluations of bearing performance. In this manner, meaningful long-range performance projections can be obtained using small test groups.

An example of the application of this technique for the evaluation of a series of synthetic lubricants and mineral oils is presented in this paper.
Effect of Platelike Carbides Below the Rolling Surface in a Ball-Washer Thrust Rolling Contact Fatigue Tester
Authors: Tsubota K , Koyanagi A
Published: March 2009

It has been observed that platelike carbides form immediately underneath the rolling track of a specimen subjected to rolling contact fatigue tests on the ball-washer thrust type of tester. These carbides are less likely to form when the carbon concentration of the martensite matrix is low and more likely to present themselves when the carbon content is high.

Carbon is diffused in the matrix by repeated stresses in the specimen during rolling contacts. This carbon is caught by dislocations between oxide inclusions in fields right beneath the rolling track, where the density of such dislocations is high, and it precipitates as carbide.

We have assumed that flakings of the specimen from rolling contact fatigue are attributable to the development and propagation of cracks which originate at the site of the platelike carbides under the rolling track. In order to improve the rolling contact fatigue strength of bearing steel, it is necessary to lower the carbon concentration of the matrix while maintaining the hardness required for the rolling element, and also to reduce and finely disperse oxide inclusions.