bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Methods for Census Taking of Commensal Rodents in Rodenticide Evaluations
Authors: Kaukeinen DE
Published: March 2009

Various population assessment methods usable for commensal rodent populations, namely, catch-mark-release trapping, food or poison consumption, tracking determinations, and counting systems or devices are reviewed. The last three methods were chosen for further evaluation and modification in the course of over 30 field evaluations of rodenticides. Two new methods for censusing commensal rodent populations are presented: a convenient method for the production of tracking tiles and a passive electronic device for registering and counting rodent activity, based on the detection of naturally emitted body heat. Suggestions on the use of these new methods and food consumption in censusing, as well as representative data, are included.
Procedure for Visually Estimating Bird Damage to Grapes
Authors: DeHaven RW , Hothem RL
Published: March 2009

Bird damage was assessed in 48 plots of wine grapes located in two regions of California during 1977. In each plot, five randomly selected grape bunches on each of 40 randomly selected vines were visually assessed, using an eight-value rating scale based on the arc-sine transformation. A hoop sampler and a rope device aided random selection of the bunches in untrellised and trellised vineyards, respectively. The mean damage ratings, calculated for use in analysis of variance, were backtransformed to estimate the percentage loss in the plots. Independent observers using this system were reasonably accurate in estimating known levels of bird damage. Because of the relative variation among the plots between the among-vine and the within-vine variances, the optimum plot sampling rates for the number of vines and bunches per vine varied greatly. The procedure tested is probably most useful for comparing bird damage levels on experimental plots of grapes, but could be adapted for estimating percentage bird losses in vineyards.
1977 Screening Survey for Measurement of Organic Priority Pollutants in Petroleum Refinery Wastewaters
Authors: Pfeffer FM
Published: March 2009

The U.S. Environmental Protection Agency (EPA), Robert S. Kerr Environmental Research Laboratory (RSKERL), Ada, Okla., provided technical assistance to the EPA, Effluent Guidelines Division (EGD), in screening wastewaters from the petroleum refining industry for the priority pollutants. This paper will describe RSKERL's involvement in the measurement of specific organics: sampling, sample handling, sample preparation, and quality control. Limited comparative data from split sampling are presented. Also discussed are the problems encountered and solved while strictly adhering to the EPA's sampling and analysis procedures of March 1977.
Development of Basic Material(s) Data for Evaluating Crack Growth Life
Authors: Bucci RJ
Published: March 2009

Fracture toughness, fatigue crack growth rate, and sustained load crack growth data comprise a basic package of materials property information used in predicting growth of cracks by fracture mechanics methods. Accurate analysis requires carefully developed laboratory results using various simple specimen configurations to describe these properties. A contributing factor to variability in life prediction is the lack of consistent procedures for obtaining and reporting this information for use in design. Though a standard does exist for direct fracture toughness determinations (ASTM Method E 399), standards for subcritical crack growth measurement are in various stages of development. Accuracy of life prediction is further confounded by judgment required of the analyst in selecting the most appropriate test and interpreting material property data for use in the computational methodology.

This paper reviews the status on standardization of test practices for characterizing basic material properties used in crack growth analysis. Emphasis is given to aspects of fatigue crack growth because of the relative importance of its characterization to life prediction by damage integration techniques. Other criteria are outlined to provide helpful guidelines to the design engineer seeking to recognize problems and minimize variability in life prediction.
Part-Through Crack Growth Predictions Using Compact Tension Crack Growth Rate Data
Authors: Rudd JL
Published: March 2009

The validity of using compact tension fatigue crack growth rate data to predict constant amplitude fatigue crack growth of part-through crack specimens was assessed. The assessment reported herein is one of six such assessments made by various members of the ASTM Task Group E24.06.01 on Application of Fracture Data in Life Prediction. Each of six members of this task group predicted the crack growth behavior for ten part-through crack specimens using compact tension crack growth rate data, with only one member having prior knowledge of the part-through crack test results. This author's assessment is presented in detail together with a comparison of the ratio of the analytical/experimental cycles to “breakthrough” and “failure” as determined by each of the six members of the task group.
Acoustic Emission—Some Examples of Increasing Industrial Maturity
Authors: Spanner JC
Published: March 2009

During the past 15 years, acoustic emission (AE) has been applied throughout the world to a variety of engineering structures in the aerospace, chemical, petroleum, nuclear, transportation, manufacturing, and utility industries. In addition, many reports and articles have described the merits of AE as a method for characterizing the metallurgical processes that occur during tests to measure the mechanical and physical properties of solid materials.

Documented applications of AE have been numerous and imaginative, and may generally be categorized as: (1) monitoring of components and systems during proof testing for the purposes of qualification or requalification; (2) on-line surveillance of systems and components; (3) detection and location of leaks; (4) in-process weld monitoring; (5) characterization or measurement of mechanical properties; and (6) monitoring of geologic structures. On-line surveillance may take several forms including continuous monitoring, intermittent monitoring, limited-zone monitoring, and acoustic signature analysis (loose parts, vibration, fluid flow, etc.).

This paper reviews a cross section of industrial applications to develop the theme that AE is an emerging nondestructive testing (NDT) method. The technology is exhibiting definite signs of increasing industrial maturity, and several related factors will be discussed to illustrate this point. Surveys of defects that have been found in the pressure boundaries of components manufactured in the United States, United Kingdom and West Germany will be reviewed since they add perspective to the current level of industrial interest in AE. Selected examples of typical AE applications are also described to provide an assessment of acoustic emission as a complementary NDT method, rather than as a recently discovered panacea.
Some Examples of Evaluating Structural Integrity by Acoustic Emission Monitoring during Pressure Testing
Authors: Keledy FC , Hartman WF
Published: March 2009

Several examples of acoustic emission (AE) testing of piping and vessels are presented. For each case, the procedure, results, and comparison of the results with independent test methods are discussed. Also, consideration is given to the economics of using AE monitoring, especially in relation to alternative methods of inspection.

A convection coil assembly, consisting of 432 m of Incoloy tubing, was monitored during hydrotesting. The AE results indicated four critically active sources and then the coil was selectively disassembled for additional examinations of the suspected thermally induced cracks. In a second field application, thirteen autoclaves were individually monitored during hydrotesting. The AE records indicated a number of sources in five autoclaves. Four of these were scheduled for reexamination in two years. On the basis of the AE results, one autoclave was taken out of service and a major crack in the vessel's jacket was confirmed.

A chemical processing vessel, having a surface area of 170 m2, was AE tested during filling with water. Eight regions, having significantly active AE sources, were identified and evaluated. The unit was subsequently removed from service and replaced. A metals processing vessel, having a surface area of 158 m2, was monitored during pressurization. Eight regions of regular AE activity were documented. None of these were considered to indicate critical flaw size. Several of the defects were confirmed by other types of inspection.
Acoustic Emission Inspection of Buried Pipelines
Authors: McElroy JW
Published: March 2009

This paper describes the results of a five year testing program utilizing acoustic emission (AE) techniques to locate defects in buried gas distribution pipelines. Several weld failures on these lines emphasized the need to develop inspection techniques in order to locate weld flaws in high stress regions to permit prompt repair and assure system integrity. Acoustic emission testing was found to be a feasible technique to locate the flaws. To date over 40 000 m of oxyacetylene welded buried steel pipelines have been tested on the Philadelphia Electric gas system.

This paper discusses some of the procedural and calibration problems encountered in applying the AE technique. The manner in which the emitters were ranked is developed. The contributions of mechanical and electrical error involved in locating the flaw is discussed in the paper. Correlation of AE results with visual examination and other methods of nondestructive evaluation (NDE) is accomplished through comparing the AE emitter ranking with the flaw criticality.
Acoustic Emission Monitoring of Intermediate Pressure Vessels Tested under the ORNL Heavy Section Steel Technology Program
Authors: Naus DJ
Published: March 2009

Acoustic emission (AE) as a technique for detecting and locating flaws in thick-walled steel pressure vessels is being investigated as a part of the Heavy-Section Steel Technology Program at Oak Ridge National Laboratory (ORNL). A detailed description of the acoustic emission monitoring of the most recently completed vessel test, V-7B, and the fatigue crack sharpening of the flaw for test vessel V-8 is presented. Results obtained during these tests indicate that AE is capable of locating flaws, detecting the onset of flaw growth, and providing an indication of the rate of crack extension (immediacy of fracture).
Inspection of Nuclear Reactors by Means of Acoustic Emission during Hydrostatic Test
Authors: Votava E , Jax P
Published: March 2009

The paper presents the state of the art for the surveillance of nuclear reactor components by acoustic emission (AE) during hydrostatic tests, as obtained during several inspections made by the Kraftwerk Union (KWU) and Battelle.

The necessary preconditions, wave propagation, calibration method, location accuracy, attenuation of AE signals due to geometrical configurations (nozzles), and the correlation between AE sources and defects as detected by other nondestructive testing methods (NDT) are presented and discussed.

The present results indicate the following:

∎ AE has a high sensitivity for detecting small leakages.

∎ AE signals from inside and outside of a thick reactor component can be located with approximately the same degree of sensitivity and accuracy.

∎ AE is a very sensitive NDT method, able to detect even very small flaws.

∎ AE indications lie preferentially in areas of seam welds, nozzles, welded-on attachments (auxiliary welds), closure studs, or other prominent areas.
Collaborative Study of a Tentative Standard Method for the Determination of Uranium in Water
Authors: Casella VR , Bishop CT , Glosby AA
Published: March 2009

A procedure for the determination of uranium isotopes in water has been developed at Mound Facility. The procedure consists of coprecipitation of uranium with ferrous hydroxide, a nitric-hydrofluoric acid dissolution if the sample contains sediment, separation of the uranium by anion exchange in hydrochloric acid, electrodeposition, and alpha pulse height analysis. After a single-laboratory evaluation at Mound, the present procedure was collaboratively tested by seven other laboratories. A copy of the procedure and four water samples, ranging from 1 to 2000 disintegrations per minute (dpm) of uranium per litre of water, were sent to the participating laboratories. Two of these samples were taken from actual effluents discharged to the environment and the third was a spiked “substitute ocean water” sample. The fourth sample contained “diluted pitchblende ore” of a known uranium concentration added to a litre of deionized water. Data from the seven collaborating laboratories have been evaluated. The average uranium concentrations determined by these laboratories agreed with the reference values to within 5 percent, and the average tracer recovery was 70 percent. The precision of the results approached counting statistics error for the three water samples which did not contain sediment.
The Status and Quality of Radiation Measurements in Water—1977
Authors: Shawver JM
Published: March 2009

This paper is a summary of the data returned to the Quality Assurance Branch, Environmental Monitoring and Support Laboratory—Las Vegas (EMSL-LV), U.S. Environmental Protection Agency (EPA), by participants in the Environmental Radioactivity Laboratory Intercomparison Studies Program. Some 150 state, Federal, private, and international laboratories analyzed samples of unknown concentration at or near environmental levels for various radionuclides as part of the Intercomparison Studies Program for Water. In all, 24 water studies were conducted in 1977, requiring participating laboratories to measure the following radionuclides: gross alpha, gross beta, tritium, chromium-51, zinc-65, cobalt-60, ruthenium-106, cesium-134, cesium-137, strontium-89, strontium-90, radium-226, radium-228, and plutonium-239. This paper examines the precision and accuracy of the cumulative reported intercomparison data for the 1977 water analyses.
Standards for the Assay of Radionuclides in Solid Environmental Samples
Authors: Noyce JR
Published: March 2009

This paper discusses radioactivity standards in the form of naturally occurring solid materials for use in the assay of solid environmental samples for radioactivity. Topics include the selection and preparation of materials for these standards, “spiking” with radionuclides (if desired), induced segregation of particles, availability and proper use of these standards, and their application to both radio-chemical and nondestructive types of assay. The role these standards have in quality-assurance programs is also considered.
The Standardization of Alpha-Particle Sources
Authors: Lucas LL
Published: March 2009

The calibration of alpha-particle sources at the National Bureau of Standards (NBS) began about 1950 with the measurement of 2π alpha-particle-emission rates using a hemispherical gas-flow proportional counter. Today activities are also determined using defined-geometry counters with scintillation detectors and 4πα-γ coincidence counters. As the measurement techniques have evolved, the overall uncertainty associated with the determination of the activity of an alpha-particle source has decreased by about an order of magnitude, from several percent to several tenths of one percent. The factors contributing to the overall uncertainty fall into two general categories: those associated with the detection system (such as uncertainties in geometry, scintillation efficiency, and deadtime) and those associated with the source (such as uncertainties in self-absorption and scattering). These factors are discussed, along with suggestions for minimizing the overall uncertainty.
Control of Lifetime in Silicon by Implantation of Iron
Authors: Mamine T , Hayashi H , Matsushita T , Yanada T , Kumagai O , Nishiyama K , Kaneko K
Published: March 2009

The hole lifetime in n-type silicon could be reduced by the implantation of iron in a well-controlled manner. By choosing a suitable dose and annealing temperature, a nearly temperature-independent hole lifetime was obtained. The temperature dependence of the hole lifetime was analyzed by the Shockley-Read-Hall theory, and we found that two types of recombination centers,—that is, a process-induced center and an iron-implanted center,—were responsible for the recombination. The energy level, the capture cross section, and the charge state of these centers were determined by deep-level transient spectroscopy (DLTS) and by compensation effect. We applied the method of iron implantation to fast-switching diodes and gate-controlled switches (GCSs) and demonstrated that iron offered improved high-temperature properties when applied to switching devices.
Mechanisms of the Erosion of Metals by Solid Particles
Authors: Hutchings IM
Published: March 2009

The behavior of spherical and angular particles on oblique impact with a metal surface is illustrated by experiments using macroscopic projectiles. Three classes of behavior are identified: plowing and two types of cutting. Results of energy loss and crater volume determinations are given which agree with theoretical predictions. The strain rates occurring in erosion are estimated and shown to be extremely high (105–107 s-1). This may explain the failure of quasi-static strength measurements to predict erosion resistance. The possibility of erosion being caused by melting is discussed and it is concluded that the process is primarily mechanical, with thermal effects playing only a subsidiary part.
Erosion-Corrosion of Coatings and Superalloys in High-Velocity Hot Gases
Authors: Barklow RH , Goebel JA , Pettit FS
Published: March 2009

Degradation of nickel- and cobalt-base superalloys in corrosive, particleladen gas streams is being investigated by injecting salt and abrasive particles into a high-velocity combustor. The test conditions being used are intended to simulate the mechanism of materials degradation expected in coal-fired gas turbines where components will be subjected to hot corrosion from impurities in the coal and high-velocity impingement of fly ash particles. Oxidation-erosion experiments (with abrasive particles but no salt), considered a prerequisite for understanding the more complex case of erosion-hot corrosion, defined regimes of particle size and flux where the following situations were observed: (1) material loss predominantly by mechanical erosion, (2) material loss by an oxidation-erosion interaction, and (3) deposition of the solid particles on the leading edge of the cylindrical test specimens. A preliminary erosionhot corrosion experiment showed a marked interaction between sulfate-induced hot corrosion and particulate erosion; the rate of metal consumption was much greater than that attributable to the sum of erosion and hot corrosion processes acting alone.
Analysis of Brittle Target Fracture from a Subsonic Water Drop Impact
Authors: Rosenblatt M , Ito YM , Eggum GE
Published: March 2009

The erosive damage of an infrared transparent material by a subsonic water drop impact has been numerically simulated. The important early-time pressure loading characteristics from a water drop impact are discussed, and the predicted target damage (in terms of fracture patterns) is presented for variations in material flaw size, material gain size, and impact velocity.
Adaptation of Jet Accumulation Techniques for Enhanced Rock Cutting
Authors: Mazurkiewicz M , Barker CR , Summers DA
Published: March 2009

The velocity of a waterjet can be increased when the jet impacts a target material or another waterjet. A theory describing such augmentation in terms of velocity, mass, and energy change is considered. The phenomenon is sensitive to jet structure and the jet velocity profile. Jet velocity profiles do not remain constant over great distances from the nozzle, and ultimately disrupt into droplets. Within the droplet the profile is more regular and the velocity constant. The theory is extended to cover the case of droplet collisions, and experimental evidence of jet augmentation and its effects is presented.
Cavitating Jet Apparatus for Cavitation Erosion Testing
Authors: Lichtarowicz A
Published: March 2009

A submerged cavitating jet is used to erode a specimen placed in its path. The erosion depends primarily on the jet velocity, the downstream pressure, and the standoff distance of the specimen. An apparatus for erosion testing based on this principle is described. Results are presented showing the effect of these parameters on erosion. They indicate that scaling should be carried out on the basis of constant cavitation number. The results show that the method is suitable for cavitation erosion testing and that testing time and jet velocity (and hence the upstream pressure) can be traded one against the other provided that the cavitation number remains constant. In this method, all of the variables can be controlled independently. The method offers the advantages associated with flow-induced cavitation together with the short testing time offered by magnetostriction devices.
Marine Applications of High-Pressure Waterjets
Authors: Hilaris JA , Labus TJ
Published: March 2009

High-pressure waterjets were investigated for hull cleaning, metal cutting, and concrete weight coating removal from submarine pipelines. All testing was performed in the submerged condition and a selective material removal capability was observed for the hull cleaning operation. This selective material removal capability was a sensitive function of jet pressure and jet angle at fixed cleaning rates. Results for the metal cutting indicated that positive jet angles and low concentrations of polymers could increase depth of cut significantly. Projected concrete weight coating removal rates were five times that achieved by conventional methods.
The Theory of Instability of the Tearing Mode of Elastic-Plastic Crack Growth
Authors: Paris PC , Tada H , Zahoor A , Ernst H
Published: March 2009

This paper presents a new approach to the subject of crack instability based on the J-integral R-curve approach to characterizing a material's resistance to fracture. The results are presented in the chronological order of their development (including Appendices I and II).

First, a new nondimensional material parameter, T, the “tearing modulus,” is defined. For fully plastic (nonhardening) conditions, instability relationships are developed for various configurations, including some common test piece configurations, the surface flaw, and microflaws. Appendix I generalizes these results for the fully plastic case and Appendix II treats confined yielding cases.

The results are presented for plane-strain crack-tip and slip field conditions, but may be modified for plane-stress slip fields in most cases by merely adjusting constants. Moreover, an accounted-for compliance of loading system is included in the analysis.

Finally, Appendix III is a compilation of tearing modulus, T, properties of materials from the literature for convenience in comparing the other results with experience.
Elastic-Plastic Fracture Mechanics for Two-Dimensional Stable Crack Growth and Instability Problems
Authors: Kanninen MF , Rybicki EF , Stonesifer RB , Broek D , Rosenfield AR , Marschall CW , Hahn GT
Published: March 2009

An elastic-plastic fracture mechanics methodology for treating two-dimensional stable crack growth and instability problems is described. The paper draws on “generation-phase” analyses in which the experimentally observed applied-load (or displacement) stable crack growth behavior is reproduced in a finite-element model. In these calculations a number of candidate stable crack growth parameters are calculated for the material tested. The quality of the predictions that can be made with these parameters is tested with “application-phase” analyses. Here, the finite-element model is used to predict stable crack growth and instability for a different geometry, with a previously evaluated parameter serving as the criterion for stable growth. These analyses are applied to and compared with measurements of crack growth and instability in center-cracked panels and compact tension specimens of the 2219-T87 aluminum alloy and the A533-B grade of steel.

The work shows that the crack growth parameters (COA)c, Jc, dJc/da, and the linear elastic fracture mechanics (LEFM)-R, which sample large portions of the elastic-plastic strain field, vary monotonically with stable crack extension. However, the parameters (CTOA)c, R, Go, and Fc, which reflect the state of the crack tip process zone, are essentially independent of the amount of stable growth when the mode of fracture does not change. Useful, stable growth criteria can therefore be evaluated from the crack tip state at the onset of crack extension and do not have to be continuously measured during stable crack growth. The possibility of making accurate predictions for the extent of stable crack growth and the load level at instability is demonstrated using only the value of J c at the onset of crack extension.
On Criteria for J-Dominance of Crack-Tip Fields In Large-Scale Yielding
Authors: McMeeking RM , Parks DM
Published: March 2009

Very detailed finite-strain/finite-element analyses of deeply cracked plane-strain center-notch panel and single-edge crack bend specimens were generated using nonhardening and power-law-hardening constitutive laws. The deformation was followed from small-scale yielding into the fully plastic range. The objective was to provide insight as to the minimum specimen size limitations, relative to the characteristic crack-tip opening dimension J/σo, necessary to assure a J-based dominance of the crack-tip region. The criterion used to judge the degree of dominance was the extent of agreement of the present stress and deformation fields at the blunted crack tips with those calculated by McMeeking for small-scale yielding. For deeply cracked bend specimens, we find very close agreement of the near-tip fields with those of small-scale yielding up to J values of σoL/25, where L represents the remaining uncracked ligament (and in the deeply cracked case, the only pertinent specimen dimension). This value is consistent with previously proposed J testing size limitations. However, we find that quite detectable deviation from the small-scale yielding fields occurs in both hardening and nonhardening center-crack specimens at considerably smaller J values relative to ligament dimension. This suggests that minimum specimen size requirements necessary to ensure a J-based characterization of the crack tip region may well be more stringent for center-crack or other low plastic constraint configurations than in bend-type specimens. A perhaps overly conservative value of 200 is proposed as the minimum ligament-to-J/σo ratio which ensures a sensible J-based characterization of the crack-tip region in center-crack specimens of materials exhibiting moderate to low strain hardening.
Numerical Study of Initiation, Stable Crack Growth, and Maximum Load, with a Ductile Fracture Criterion Based on the Growth of Holes
Authors: d'Escatha Y , Devaux JC
Published: March 2009

Considering a material at the ductile plateau, fracture tests on small specimens in generalized yielding conditions are common. We need to extract from them adequate information to characterize the fracture resistance properties of the material. We also need to predict initiation, crack growth, and maximum load for a crack found in a ductile structure. But the real problems are three-dimensional; for instance, semi-elliptical surface cracks or through-cracks in “small” thicknesses (tunneling and mixed-mode fracture). Moreover, they are not only in the symmetrical Mode I case (angled crack extension).

The common denominator of all these phenomena is the ductile fracture processes in the material at the crack border; these micromechanisms extend over some characteristic length which needs to be introduced at a crack tip because of the very intense strain gradient. We thus need a ductile fracture damage function belonging to the continuum mechanics frame and related to the history of stresses and strains averaged over such a characteristic volume. In this numerical feasibility study, using elastic-plastic finite-element computations and guided by a ductile fracture model in three stages—void nucleation, void growth, and coalescence—we tried such a differential damage history, in a most simplified form. We integrated this during the whole stress and strain history in each finite element along the crack path, and we studied the influence of the mechanical and numerical parameters playing a role in this methodology. We describe herein the evolution, which results from this criterion, of some parameters used in the literature as initiation and crack growth criteria.
Size Effects on the Fatigue Crack Growth Rate of Type 304 Stainless Steel
Authors: Brose WR , Dowling NE
Published: March 2009

Planar size effects on the fatigue crack growth rate of AISI Type 304 stainless steel characterized by linear-elastic fracture mechanics were experimentally investigated. Constant-load amplitude tests were conducted on precracked compact specimens ranging in width from 2.54 to 40.64 cm (1 to 16 in.). The da/dN versus ΔK data are compared on the basis of several size criteria which are intended to limit plasticity and thus enable linear-elastic analysis of the data. Also, the cyclic J-integral method of testing and analysis was employed in the fatigue tests of several specimens undergoing gross plasticity. The cyclic J crack growth rate data agree well with that from the linear-elastic tests. It is argued that an appropriate size criterion for linear-elastic tests must limit the size of the monotonic plastic zone and thus be based on Kmax, the maximum stress intensity. While the size criteria considered vary widely in the amount of plasticity they allow, they provide comparable correlations of crack growth rate. Thus the use of the most liberal criterion is justified.
Methods of Gust Spectra Prediction for Fatigue Damage
Authors: Wilson WW , Garrett JE
Published: March 2009

The prediction of aircraft responses to atmospheric turbulence using a general exponential gust exceedance equation is based on the assumption that altitude dependent spectra curve fit parameters contained in the exceedance equation are representative of the atmosphere and thus equally applicable to accelerations, loads, stresses, etc. Using vertical acceleration gust data recorded during fleet operations of the USAF C-5A transport aircraft, altitude dependent curve fit parameters were developed; these parameters were then shown to accurately predict the recorded wing stress gust experience at three wing locations, thus supporting the assumption of their uniformity between response parameters. This gust analysis then was substantiated with a second, independent analysis in which the recorded vertical acceleration gust data were converted directly to stress spectra by means of analytical stress to acceleration ratios.
Test Simulation of Fighter Aircraft Maneuver Load Spectra
Authors: Jeans LL , Tribble WL
Published: March 2009

This paper studies the use of power spectral density (PSD) and related random data analysis techniques in the test laboratory to characterize low frequency loading spectra output response, measured from a specimen, for the purpose of comparing test machine responses. In recent years digital techniques have been developed that simulate aircraft maneuver spectrum loading in the time domain. In this study one of these techniques is used to generate the input load spectrum signal to an electrohydraulic closed-loop test machine for fatigue testing of graphite/epoxy to titanium step lap bonded joints at various frequencies and PSD shapes. The output signal was measured directly from the specimen by recording on tape the dynamic strain gage signal. This signal then was processed to determine the PSD response and root mean square (RMS) time history. These data were compared with the recorded strain amplitude time history and the input load amplitude, frequency, and PSD information. A qualitative correlation was found between variations in specimen fatigue life, output signal waveform and amplitude, and variations in PSD. PSD is a measure of loading energy in the time domain and can be influenced both by load amplitude and waveform variations. Thus, the way a fatigue test machine processes an input load and frequency signal can affect the measured fatigue life of certain materials.
Dislocation Structures Around the Crack Tips in the Early Stage in Fatigue of Iron
Authors: Katagiri K , Awatani J , Omura A , Koyanagi K , Shiraishi T
Published: March 2009

Dislocation structures around the early stage fatigue cracks up to 170 µm in length formed in polycrystalline iron specimens were directly observed through an ultrahigh-voltage electron microscope operating at 2 MV. For this purpose, thin foils perpendicular to the surface were prepared from bulk specimens cycled up to 60 percent of the fatigue life of 2.5 × 105 cycles, by means of electroplating and jet electropolishing technique.

There were found some small straight cracks penetrating the cells (size: 2 to 5 µm), formed beneath the specimen surface as well as in the interior. Some straight screw dislocation lines parallel to the direction of the crack growth, one of the projections of the 〈111〉 directions, were observed in the cells just ahead of the crack. No marked entanglement of dislocations was observed within these cells.

On the other hand, some tangled dislocations were observed in the cells formed just around the cracks growing along grain boundaries.

The results just described are compared with those of the early stage fatigue crack formed in two kinds of face-centered-cubic (fcc) metals with different stacking fault energy (copper and α-brass) obtained previously, and the mechanisms of fatigue crack initiation and growth in the early stages are discussed.
Fatigue Behavior of Polymers
Authors: Beardmore P
Published: March 2009

The overall cyclic response of ductile polymers is independent of the micromechanistic deformation phenomena and is always manifest as cyclic softening. Cyclic hardening does not occur irrespective of temperature and strain rate. Varying the deformation mechanisms by microstructural modification—amorphous versus crystalline versus composite—does not affect the response in kind, only in degree. In a similar manner, changing testing variables such as strain rate and temperature only results in a change in the magnitude of the softening. At sufficiently high strain rates, self-heating of the specimen can occur, resulting in failure due to thermal softening rather than true cyclic fatigue failure. The interaction of creep and fatigue in polymers is complex and although, in general, damage accumulation is accelerated, under certain conditions the combination is not deleterious.
Statistical Aspects of Fatigue at Microscopic, Specimen, and Component Levels
Authors: Fong JT
Published: March 2009

The study of fatigue mechanisms at the microscopic level is examined. The complexity of the microstructure and the availability of quantitative microscopy concepts created a need to introduce statistical tools to the fundamental aspects of fatigue research. Examples of the corrosion fatigue of high-strength steel, the bending fatigue of currency paper, and the swelling of nuclear fuel elements are used to illustrate this new viewpoint. The statistical concept of stress in a medium with distributed voids or other geometric imperfections is introduced to permit the use of models different from the conventional continuum viewpoint. The concept of a nested model and the incorporation of a size effect in the study of fatigue at three microscopic levels and three macroscopic (specimen, component, structure) levels are discussed.
Toxicology of Degradation Products of Plastics
Authors: Autian J
Published: March 2009

A successful implant must meet two important criteria: (1) the ability to function in a living organism and (2) biocompatibility. If an implant has a tendency to degrade, both of these characteristics can be altered, leading to a failure of the implant and possible harm to the patient. This paper will deal with a brief discussion of the subject of toxicology, followed by selected examples of problems which have occurred in the use of a plastic for a biomedical application, and, finally. suggestions will be made as to in-vivo and in-vitro tests which may be appropriate for ascertaining whether a new plastic will degrade, releasing biologically active constituents.
Wear and Degradation of Retrieved Ultrahigh Molecular Weight Polyethylene and Other Polymeric Implants
Authors: Gibbons DF , Anderson JM , Martin RL , Nelson T
Published: March 2009

The statistics regarding the number of autopsies containing associated implants on the pathology service at the University Hospitals of Case Western Reserve University are presented. The objectives of the Pathology Department's retrieval and analysis program are presented, and the special methods used for analyzing the tissue and implant responses are described. Examples of wear and degradation of the polymeric components which have been analyzed are presented. Silicone rubber poppet occluders which demonstrate abrasive wear are discussed, and the tissue response to wear particles incorporated in the liver is documented. Silicone fluid in the fibrous capsule from a gelfilled breast prosthesis is analyzed. Analyses of degraded and worn ultrahigh molecular weight polyethylene (UHMWPE) joint components by thin-section optical microscopy, scanning electron microscopy, and xylene extraction techniques are presented. The principal wear mechanisms are abrasive wear and cracking between the incompletely sintered UHMWPE powder.
Localized Corrosion Susceptibility of Work-Hardened Stainless Steels in a Physiological Saline Solution
Authors: Cigada A , Mazza B , Mondora GA , Pedeferri P , Re G , Sinigaglia D
Published: March 2009

This paper describes: (1) an electrochemical technique for crevice corrosion testing and (2) the results of a study concerning the susceptibility to crevice and pitting corrosion of work-hardened AISI 316L and 304L stainless steels in a sodium chloride buffered solution simulating the aggressiveness of the human body. In particular, the importance of the deformation degree and the orientation of the specimen surface under study with respect to the deformation direction is shown and discussed in relation to characteristic structural aspects.
Titanium Release from Implants: A Proposed Mechanism
Authors: Solar RJ , Pollack SR , Korostoff E
Published: March 2009

The excellent corrosion resistance of titanium surgical implant alloys is well documented. However, titanium compounds have been occasionally found in tissues adjacent to titanium implants, and these findings were reported to be unrelated to wear processes. The purpose of this study was to determine a mechanism by which titanium is released from an implant.

The corrosion behavior of commercially pure titanium and Ti-6Al-4V was studied by electrochemical means, namely, anodic polarization and differential capacitance techniques. Tests were performed in Ringer's solution at 37°C. Solution pO2, pH, and surface finish of the specimen were varied to include all probable in vivo conditions.

The corrosion resistance of commercially pure titanium and Ti-6Al-4V was not significantly altered by variations in pH, pO2, or surface finish. The electrochemical reaction which occurred was growth of the metal's protective passive film. The data indicated that the effective area of a specimen was less than its apparent surface area and was dependent on pH and surface finish. These findings suggest a model of the implant surface in which the natural air oxide that initially forms is comprised of microscopic oxide needles at surface irregularities plus a smooth planar oxide. It is proposed that the oxide needles can be broken off or dissolved in vivo, providing the source of the titanium sometimes found in tissue adjacent to an implant. Use of certain pretreatments may remove the needles prior to surgery, resulting in the more common case in which titanium is not found in the tissue.
Clinical Experience with Prosthetic Materials: Historical Perspectives, Current Problems, and Future Directions
Authors: Laing PG
Published: March 2009

This paper describes a surgeon's clinical experience with the use of prosthetic materials over the course of his 30-year career in orthopedic surgery. In the beginning, a historical review is given detailing the progressive improvement in techniques and in selection of materials for the manufacture of implants, beginning with the use of iron wire in the 18th century and proceeding systematically through the development of an appreciation of the significance of the composition of the metal used, and later, of the nonmetallic material used. A discussion of the progressively more acute appreciation of the two-way-street nature of the problem of compatibility is presented. A development of the cobalt-chrome-molybdenum alloys is briefly reviewed. A development of the austenitic stainless steels and their increasing refinement over the years is also reviewed. The development of the use of titanium and its alloys, beginning in the United Kingdom and proceeding to other countries, is reviewed. The place of thermoplastic and thermosetting resins is then described, beginning with the wide use of the Judet prosthesis following the Second World War and proceeding to the development of the total joint replacement era with the use of polymethyl methacrylate to serve as a grouting compound in the fixation of both metallic and ultrahigh molecular weight polyethylene components. The tissue reaction to wear particles is described and illustrated, demonstrating a new dimension in tissue reaction to implant materials. In conclusion, it is suggested that several of the new biomaterials being developed in various laboratories and universities in the world will find their way into use in surgery. Hopefully a substitute for polymethyl methacrylate will be found, with less mechanical and biological problems. A fundamental understanding of the processes involved in interaction between implant and host is needed for the development of more suitable implant materials in the future.
Corrosion Resistance of Titanium Surgical Implant Alloys: A Review
Authors: Solar RJ
Published: March 2009

The performance of titanium and its alloys in surgical implant applications is examined with respect to the materials' biocompatibility and ability to withstand the corrosive fluids of the human body. Both in-vitro and in-vivo experimentation is reviewed, as well as the reported clinical results. For comparative purposes, other commonly used implant alloys are discussed. Since the corrosion resistance of titanium and its alloys is due to a passive film which covers the metal, a portion of the paper is devoted to the nature of the passive film. Studies dealing with formation, compositions, and structures of titanium passive films, as well as environmental effects on these films are examined. In-vitro studies have been carried out in numerous physiological solutions using various electrochemical techniques. Among the parameters studied were pH, pO2, surface finish, surface treatments, crevice corrosion, galvanic coupling, stress, fatigue, and fretting corrosion. In every study titanium and its alloys compared favorably with the other materials tested. In-vivo studies as early as 1940 showed that titanium is as well tolerated biologically as is stainless steel and Vitallium. More recent animal studies confirmed the early conclusions, and, in fact, it appears that titanium and some of its alloys may be actually better tolerated than stainless steel and the cobalt-chromium alloys. Clinical findings have been consistent with the results of in-vitro and in-vivo studies; not a single corrosion-related failure of a titanium or titanium-alloy implant could be found in the clinical literature. In summary, the available information indicates that titanium and some of its alloys may be the most biocompatible and corrosion-resistant metallic implant materials in present use.
Corrosion Studies on Nickel-Based Casting Alloys
Authors: Meyer JM , Wirthner JM , Barraud R , Susz CP , Nally JN
Published: March 2009

Three different methods—electrochemical measurements (polarization curves, polarization resistance curves, and open-circuit potentials), immersion tests, and in-vivo evaluation—have been used to investigate the corrosion resistance of commercial nickel-chromium dental casting alloys and of the newly developed nickel-vanadium and nickel-vanadium-chromium alloys.

Nickel-chromium alloys can be assigned to five different classes, according to their composition. All of the three methods of investigation used in this study have demonstrated that the electrochemical behavior of these alloys differs markedly among classes, and even within a given class. The molybdenum and manganese contents do play a significant role in corrosion resistance: alloys with high molybdenum and manganese content exhibit a much wider passivation range and a better resistance to pitting in chloride-containing solutions than those without. Alloys without any molybdenum are constantly active and corroding. The addition of cobalt or gallium as a ternary constituent also enhances corrosion resistance.

The nickel-vanadium-chromium system offers good promise for the development of a new type of alloy for possible use in dentistry. The alloy 57Ni-25V-18Cr, for example, compares favorably with existing nickel-chromium alloys and even outclasses them for yield strength and polarization resistance.

A thorough evaluation of the biocompatibility of all nickel-based alloys, according to the newest recommended practices, is still needed.
Legal and Regulatory Aspects of Implant Performance and Failure
Authors: Piehler HR
Published: March 2009

The present and future influences of products liability litigation and federal regulation in reducing risks stemming from the use of surgical implants are analyzed by focusing on the determination of the sources or causes of implant failure in addition to the mechanisms of failure. Where risk levels can be shown to be currently low, monitoring sources of failure rather than regulating by standards or premarket approval is recommended. Current trends in products liability litigation and federal regulation are reviewed and shown to reveal a tendency toward requiring a more open disclosure of source-of-failure information and also a tendency toward the development of performance standards for informational, as well as level-setting, purposes. A seriated trial format is proposed for use in products liability cases involving medical devices, both to increase the quality of litigation and to eliminate nonmeritorious negligence per se actions as well. The use of litigation results and field-failure experience in developing performance tests for hip nails is presented and shown to be useful in providing information to surgeons and in stimulating device improvements.
The Plate Count in Aquatic Microbiology
Authors: Buck JD
Published: March 2009

The application and inherent difficulties of the traditional plate count the technique and its variations are presented. While the plate count has been, and continues to be, used for enumeration of microorganisms in natural waters, recent criticisms of the technique appear increasingly in the literature. Accordingly, the quantitative nature of the plate count in discussed in relation to limitations of the procedure and current alternatives for microbial enumeration. Constant evaluation of newly evolving quantitative procedures for the denomination of microbial numbers, biomass, and activity is recommended to prevent the “standardization” of techniques which, like the plate count, subsequently become subject to debate as to their appropriateness in ecological studies. The plate count is still seen as a valuable tool for its originally intended purpose and should be supplemented and reevaluated in conjunction with contemporary quantitative methods.