bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue of a Particle-Reinforced Cast Aluminum Matrix Composite at Room and Elevated Temperatures
Authors: Ogarevic VV , Stephens RI
Published: March 2009

Constant amplitude low-cycle fatigue, fatigue crack growth, and variable amplitude fatigue tests were performed on a 20% volume fraction SiC particle-reinforced A356 cast aluminum matrix composite at room temperature at 150°C. Data obtained were analyzed and compared with those of the unreinforced matrix material. Variable amplitude loading fatigue life calculations were performed using commercially available software.

The low-cycle fatigue results revealed that the composite material had somewhat lower fatigue resistance than the unreinforced material at room temperature and that the composite fatigue resistance decreased with increasing temperature. Room temperature fatigue crack growth rates were higher, and ΔKth values were lower in the composite compared to those of the unreinforced material. There was not much difference between the composite fatigue crack growth rates at the two temperatures. Positive R ratio increased fatigue crack growth rates of the composite, but had more effect at room temperature than at 150°C. SEM fractography revealed that pores were preferred fatigue crack initiation sites. For small ΔK, fatigue cracks grew predominantly through the matrix, while with increasing ΔK more and more particles were fractured. Micromechanisms of crack growth were of the ductile type in the matrix, while particles were cleaved. Particle/ matrix interface debonding was not observed. Both reasonable and unreasonable fatigue life predictions were obtained with this metal matrix composite using the common low-cycle fatigue and fatigue crack growth approaches.
Yield, Plastic Flow, and Fatigue of an Orthotropic Material Under Biaxial Loadings
Authors: Lin H , Nayeb-Hashemi H
Published: March 2009

Yield, plastic flow, and low-cycle fatigue damage behavior of an orthotropic Al-6061-T6 plate were investigated. Anisotropic constitutive relations and multiaxial fatigue damage models of the material were obtained to predict its yield, plastic deformation, and low-cycle fatigue life under multiaxial loading conditions. Low-cycle fatigue tests were conducted along three orientations of the plate at room temperature under three loading conditions, uniaxial tension/compression, torsion, and combined tension/torsion in-phase, to verify the theoretical predictions. The theoretical yield functions and flow relations under combined tension/torsion loading condition agreed with experimental data reasonably well. Four multiaxial fatigue damage models were evaluated and used to predict the low-cycle fatigue life along the three orientations of the plate. A damage model based on the strain vector and an anisotropic shear cracking model gave better predictions than the effective strain and the plastic work models.
Cyclic Axial-Torsional Deformation Behavior of a Cobalt-Base Superalloy
Authors: Bonacuse PJ , Kalluri S
Published: March 2009

The cyclic, high-temperature deformation behavior of a wrought cobalt-base superalloy, Haynes 188, is investigated under combined axial and torsional loads. This is accomplished through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue database has been generated on Haynes 188 at 760°C. Cyclic loading tests have been conducted on uniform gage section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. The fatigue behavior of Haynes 188 at 760°C under axial, torsional, and combined axial-torsional loads and the monotonic and cyclic deformation behaviors under axial and torsional loads have been previously reported. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress versus engineering shear strain, axial strain versus engineering shear strain, and axial stress versus shear stress spaces are presented for cyclic in-phase and out-of-phase axial-torsional tests. For in-phase tests, three different values of the proportionality constant, λ (the ratio of engineering shear strain amplitude to axial strain amplitude, γa/εa), are examined, viz., 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, ̅ (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90° with λ = 1.73. The cyclic hardening behaviors of all the tests conducted on Haynes 188 at 760°C are evaluated using the von Mises equivalent stress-strain and the maximum shear stress-maximum engineering shear strain (Tresca) curves. Comparisons are also made between the hardening behaviors of cyclic axial, torsional, and combined in-phase (λ = 1.73 and ̅ = 0°) and out-of-phase (λ = 1.73 and ̅ = 90°) axial-torsional fatigue tests. These comparisons are accomplished through simple Ramberg-Osgood type stress-strain functions for cyclic, axial stress-strain and shear stress-engineering shear strain curves.
Multiaxial Stress-Strain Creep Analysis for Notches
Authors: Moftakhar AA , Glinka G , Scarth D , Kawa D
Published: March 2009

A method for predicting time-dependent stresses and strains in the case of localized creep has been developed. This method is based on strain energy density considerations and is an extension of the method previously developed by the authors for localized time-independent plasticity problems. The solution method has been derived in a general form so that it may be applied to multiaxial notch tip stress states. This technique has been used to predict creep effects and the associated stress redistribution at the root of a notched zirconium alloy pipe and in a thin notched plate made of aluminum, both subjected to thermal creep. The predictions have been compared with the finite element data and good agreement obtained. The computational time for calculating the notch tip stresses and strains was much shorter than that required for the finite element analysis. The method can be particularly useful for the analysis of creep effects in the case of cyclic loading with hold times where the FEM calculations are very time consuming.
A Substructuring Approach to the Fatigue Modeling of Polymeric Matrix Composite Materials
Authors: Connolly MP
Published: March 2009

A fatigue model for fiber-reinforced polymeric matrix composites is proposed. This model uses a substructuring approach to predict the behavior of composite laminates based on an integration of simpler composite elements. These simpler composite elements are known as “elemental blocks” and are two-layer laminates such as [0/90] or [0/45]. These laminates are chosen in order to capture the influence of the constraint between laminae on the fatigue performance. Tension-tension fatigue tests were conducted on a number of elemental block geometries, and the modulus degradation for each of the geometries was measured and described using simple functions. The results showed that the damage accumulation and concomitant reduction in stiffness varied systematically from geometry to geometry. Using these results, a simple fatigue model is proposed to predict the behavior of more complex composites by combining the degradation functions for the individual elemental blocks. This model is based on classical lamination theory and uses the measured stiffness reduction for each elemental block, as a function of the number of cycles, to predict the overall composite stiffness matrix. In order to test the model predictions, fatigue tests were conducted on more complex composites consisting of a number of elemental blocks, and the accumulation of damage was measured again using compliance and strain gages attached to the specimen surface. These results were compared with model predictions and reasonable agreement was obtained between the measured and predicted stiffness degradation.
Effect of Pultrusion Process Variables on Cyclic Loading Damage of Graphite-Epoxy Composites
Authors: Donti RP , Vaughan JG , Mantena PR
Published: March 2009

Recent advances in pultruding composite materials have resulted in a high-performance, cost-effective manufacturing process. However, most research on pultruded products has centered on a specific application; a systematic study of the effects of various process variables on fatigue damage has not been conducted. The present study uses a fractional factorial statistical design to characterize the effects of pultrusion process variables and their interactions on the fatigue damage of pultruded graphite-epoxy. The composite material produced under the varying process conditions was subjected to tensile fatigue. The start and progress of damage mechanisms due to the loading and influenced by the processing conditions of the material are reflected by discernible changes in the loss factor (a measure of damping). The loss factor and modulus of the material were computed in real-time using computer methods. The changes shown by the loss factor are used to characterize the effects of the processing variables on the cyclic damage.
Examination of the Correlation Between NDE-Detected Manufacturing Abnormalities in MMCs and Ultimate Tensile Strength or Thermomechanical Fatigue Life
Authors: Stubbs DA , Russ SM , MacLellan PT
Published: March 2009

Titanium matrix composites containing manufacturing abnormalities were examined using ultrasonic and X-ray nondestructive evaluation techniques. The [0/90]s and [0/90]2s SCS-6/β21-S specimens were subjected to 650°C tension or thermomechanical fatigue tests to assess any degradation in strength or fatigue life due to the abnormalities. The usefulness of ultrasonic nondestructive evaluation to assess the integrity of the composites containing manufacturing abnormalities was shown through the correlation of the ultrasonic data with ultimate tensile strength and thermomechanical fatigue life. Additionally, the use of X-ray radiographic nondestructive evaluation appears to complement the ultrasonic data and is useful for analyzing fiber displacement, orientation, and nonparallelism. A simple damage parameter was developed to help quantify the ultrasonic NDE data from manufacturing abnormalities within the material. The test results on the specimens containing manufacturing abnormalities are presented with analysis of the degree of correlation between the NDE results and tensile strength and/or thermomechanical fatigue life.
Nondestructive Evaluation (NDE) of Composites Using the Acoustic Impact Technique (AIT)
Authors: Raju PK , Vaidya UK
Published: March 2009

Due to increasing use of composites as structural materials, defect characterization in composites has attracted wide attention in recent years. Several undesirable effects in composites include: fiber breakage, inclusions, voids, improper resin distribution, delaminations, and misalignment of fibers. Acoustic methods of nondestructive evaluation (NDE) are proven candidates in identifying these defects to varying levels of success. Prominence has been given to acoustic emission (AE) and ultrasonic inspection techniques in the evaluation of composites; however, the acoustic impact technique (AIT), derived from the coin-tap test, has not been explored in depth. The coin-tap test involves tapping a specific location on a structure with a “coin” or “penny” and judging the quality of the material based on the sound emanated from the localized region. In principle, a “good” region results in an intense sound as compared to a “defective” one. Although coin tapping has been used in this fashion for several years, the most significant drawback has been its operator dependency. AIT attempts to overcome this shortcoming. In AIT, the use of sophisticated electronic instrumentation provides a reliable estimate of the quality of the material. The foundation of AIT lies in sensing and analyzing localized vibrations and disturbances generated by a low-magnitude mechanical pulse input to the structure under test. In this paper, the current status of AIT is reviewed, and new developments are discussed. Results are presented relating to the application of this technique for NDE of graphite/epoxy and graphite/phenolic composites.
A Methodology to Identify Material Properties in Pavements Modeled as Layered Viscoelastic Halfspaces (Theory)
Authors: Stubbs N , Torpunuri VS , Lytton RL , Magnuson AH
Published: March 2009

An accurate, rapid, and reliable methodology for identifying material properties of pavements modeled as layered viscoelastic halfspaces subjected to dynamic excitation is developed. The methodology is based on the forward model of system identification. The Modulus of elasticity of each layer, the damping in each layer, and the slope of the creep curve for the top layer are selected as the parameters to be identified. The validity and accuracy of the proposed methodology is demonstrated by several numerical experiments involving simulated changes in the selected pavement parameters. Iterative procedures developed to solve nonlinear problems which arise in estimating the pavement parameters are presented.
Backcalculation of Pavement Layer Moduli, Thickness and Stiff Layer Depth Using a Modified Newton Method
Authors: Harichandran RS , Mahmood T , Raab AR , Baladi GY
Published: March 2009

A modified Newton method for the backcalculation of pavement layer moduli, thicknesses, and stiff layer depth from measured surface deflections is presented. The method is an iterative one and can use any mechanistic analysis program for forward calculations (presently an extended precision CHEVRON program is used for this purpose). This method has been implemented in a new backcalculation program named MICHBACK. Several examples of backcalculation based on theoretical deflection basins generated by the extended precision CHEVRON program are presented, and the effect of errors in input layer thicknesses and stiff layer depth on the backcalculated moduli are studied. Moduli backcalculated by MICHBACK are compared with results obtained by the EVERCALC 3.0 and MODULUS 4.0 programs.
Concrete Pavement Backcalculation Uing ILLI-BACK 3.0
Authors: Ioannides AM
Published: March 2009

Applications are presented of an improved closed-form backcalculation procedure for slab-on-grade concrete pavement systems. A choice is now possible from among several popular plate-sensor arrangements, involving the 300 or 450 mm dia. plate, with four or seven sensors, as well as the irregular sensor spacings arrangement used by the Strategic Highway Research Program. Based on experience from several projects, user guidelines are formulated.
Dyanamic Analysis of FWD Loading and Pavement Responce Using a Three Dimensional Dynamic Finite Element Program
Authors: Zaghloul SM , White TD , Drnevich VP , Coree B
Published: March 2009

Multi-layer analyses are commonly used to analyze falling weight deflactometer (FWD) measurements and back calculate pavement layer moduli. This type of analysis assumes static loading conditions and linear elastic material properties. The FWD loading cycle cannot be considered in any sense as a static load. It is a dynamic load with a duration in the range of 30 to 40 msec. Also, paving materials and subgrades are not linear elastic materials and their response to static loads is different than that to dynamic loads, such as FWD loading. The difference between the multi-layer analysis assumptions and actual loading and material conditions is significant.

In this paper a three-dimensional dynamic finite element program (3D-DFEM), ABAQUS, is used to conduct a non-linear dynamic analysis of FWD tests on a flexible pavement section. Verification studies have, been conducted of the 3D-DFEM to verify its static and dynamic analysis of both rigid and flexible pavements and no significant difference was found between the predicted pavement response using the 3D-DFEM and the field measured pavement response. A design of experiment was developed to study the effect of layer thicknesses and moduli on pavement surface deflections at various offset distances. Analysis of variance (ANOVA) and regression analysis were conducted to develop statistical models which can be used to predict pavement surface deflection at different offset distances as a function of layer thicknesses and moduli.
Comparing Laboratory and Backcalculated Layer Moduli on Instrumented Pavement Sections
Authors: Akram T , Scullion T , Smith RE
Published: March 2009

This paper discusses the analysis of deflection data on thick and thin asphaltic concrete pavement sections instrumented with Multidepth Deflectometers (HDD's). Surface and depth deflection data were collected under both Falling Weight Deflectometer (FWD) and truck loadings. Linear elastic analyses were performed to compare layer moduli backcalculation from; • FWD surface deflections only; and • FWD surface and depth deflections only.

Backcalculated moduli values were compared with those measured in the laboratory. The moduli calculated from FWD loads were also used to predict pavement response under known truck loads. These predictions were compared to actual measured responses. In general it was found that the FWD characterization overestimates the strength of the subgrades and underpredicts subgrade strains induced by the truck by 18%.
A Pavement Evaluation Procedure Incorporating Material Non-Linearity
Authors: de Almeida JR , Brown SF , Thom NH
Published: March 2009

Two new computer programs, LEAD and FEAD, have recently been developed at Nottingham for the back-calculation of elastic stiffnesses of pavement layers from deflections measured with the Falling Weight Deflectometer (FWD). These programs represent a significant improvement on the program PADAL, previously developed at Nottingham. A revised algorithm for the iterative back-calculation process, based on the Gauss-Newton method, has been successfully implemented. Appropriate stress-strain relationships for the granular layers and the subgrade were built into the programs, enabling the non-linear behaviour generally exhibited by these materials to be evaluated. The influence of overburden, pore pressures and “locked-in” horizontal stresses on the in situ stiffnesses is also considered. Additionally, a rigid bottom may be included in the analysis. The main difference between the two codes is in the sub-routines adopted for the computation of deflections. LEAD makes use of layered elastic analysis, while FEAD uses a finite element approach which, although more accurate for non-linear problems, is more time consuming. Data from FWD surveys have provided a means of validating the new software. Examples are presented, including comparisons with laboratory test data. The results suggest that the stress-dependent nature of the lower layers can be of significance for the overall behaviour of the pavement.
Misleading Results from Nondestructive Testing-A Case Study
Authors: Hall JW , McCaffrey PS
Published: March 2009

A new apron and taxiway at the Cape Canaveral Air Force Station skid strip. Cape Canaveral, Florida, showed depressions as a result of parking various aircraft overnight. The U. S. Army Engineer Waterways Experiment Station performed a pavement investigation which included nondestructive falling weight deflectometer (FWD) tests and test pits for California Bearing Ratio (CBR), moisture, density, and sampling. A study of the field and laboratory results showed serious inconsistencies between the test methods. FWD data indicated the new pavement to be of higher strength than the older portion. The test pit data (CBR and density) indicated the recycled base layer to be weak (due to low density), which was in direct disagreement with the FWD. A possible explanation for the failure of the FWD to correctly characterize the pavement materials is that the faster rate of loading of the FWD as compared to the static load of the parked aircraft caused the difference.
Interpretation of Dynamic Survey Measurement on Pavement with Treated Roadbase
Authors: Lepert P , Caprioli P
Published: March 2009

For over 50 years, the structural condition of a conventionnal pavements has been characterized by the bearing capacity, measured through the deflection produced by a rolling or impact load. However, modern pavements exhibit specific defects which have small or even no effect on deflection. To overcome this difficulty, two types of dynamic survey methods have been developed, the so-called “dispersive methods”, and the “impedance method”. The first group involves single-, two- and multi-station dispersive methods. Theoretical and experimental studies show that, although the multi-station dispersion method seems the most powerful! one, it requires considerable resources, and thus it is, today, inadequate for routine analysis of pavements. The two-station method provides, when pavement layers are correctly bonded, a simple but promising approach for determining the mechanical parameters of the pavements. The impedance method, which was recently developed by the french “Laboratoires des Ponts et Chaussées (LPCs)”, provides a reliable means to assess the state of pavements interlayers, and thus complete the two-station dispersive method. Therefore, the LPCs developed a new piece of equipement, the COLIBRI system, which applies both methods on a routine basis.
Radar for Pavement Thickness Evaluation
Authors: Maser KR , Scullion T , Roddis WMK , Fernando E
Published: March 2009

Pavement layer thickness data required for network and project level pavement management is often not available due to the cost, time, and traffic disruption involved in taking cores. A non-destructive, non-contact method for thickness measurement is available and can be implemented from a survey vehicle moving at highway speed. The technology incorporates horn antenna radar equipment coupled with customized processing software. The reported work represents evaluations of the method on 46 different pavement sections located in 12 different states. The processed radar data has been correlated with results from over 300 cores, showing an expected accuracy of +/-7.5% (typically +/- 0.5 inches or 12.7 mm) for asphalt thickness. Results from borings and test pits show an expected accuracy of +/- 12% (+/- 1 inch or 25.4 mm) for base thickness. The radar data has also been successfully utilized to identify changes in pavement section.
A Comparison of Laboratory and Field Sdbgrade Moduli at the Minnesota Road Research Project
Authors: Van Deusen DA , Lenngren CA , Newcomb DE
Published: March 2009

A soil sampling and testing program was conducted on the pavement embankment at the Minnesota Road Research Project. Both destructive and nondestructive approaches were taken. Nondestructive load tests were conducted both before and after base construction using a falling-weight deflectometer; both disturbed and undisturbed soil samples were retrieved. Falling-weight deflectometer tests were conducted at regular intervals along three different offsets directly on the soil embankment. A large diameter plate was used with modest load levels. Other data obtained during the testing program included jar, bag, and thin-wall soil samples, and dynamic cone penetrometer soundings. The falling-weight deflectometer load and deflection data were used to backcalculate the elastic moduli for a multi-layered system. Due to the variability in the surface conditions special backcalculation techniques had to be employed. The variability of the deflections and estimated moduli were addressed using both general statistics and geostatistical analyses. The backcalculated moduli for the near-surface layers were softer and more variable than the deeper layer. Laboratory resilient modulus tests conducted on the thin-wall samples yielded values that compared well with the backcalculated values from the deeper layer.
Detection of Multi-Course Surface Pavement Layers by the SASW Method
Authors: Gucunski N
Published: March 2009

The ability of the SASW method in detection of layer thicknesses and moduli of multi-course pavements has been examined by numerical simulation of the test. The results are represented by the response of a pavement system to a vertical circular loading in the wave number and spatial domains, from which Rayleigh wave dispersion curves were derived using procedures equivalent to those in the field. The simulation shows that for common thicknesses and material properties of pavement surface layers, and the frequency range of accelerometers, the SASW method should enable detection of individual courses. The paper also discusses the influence of receiver positioning and an applied filtering criteria on the obtained dispersion curve.
Field Testing and Structural Evaluation of Selected Concrete Pavement Sections in Florida
Authors: Wu C-L , Tia M
Published: March 2009

Twenty-four existing concrete pavement sections covering a wide range of performance levels, ages and types of subbase, surface layers and joints were selected for evaluation in order to determine the causes of the problems in the pavements with poor performance. Each section was evaluated by a condition survey, falling weight deflectometer (FWD) tests, laboratory tests on core samples, and a structural analysis. FWD tests were preformed at both midday and midnight. Loads were applied at four different positions on the slab, namely, slab center, slab corner, edge center and joint center. The measured FWD deflections at various locations were then used along with the results of the laboratory tests on the Cored samples and a finite element program, FEACONS IV, to estimate the pavement parameters. With the pavement modeled by the estimated pavement parameters, the maximum stresses caused by critical temperature-loading conditions were computed using the FEACONS IV program. The computed maximum stresses were then compared with the flexural strength of the concrete to evaluate the structural adequacy of each test section.

The critical stress analysis method, which was used in this study, was shown to give good prediction of the structural performance of the test sections. The use of a very stiff subbase is not beneficial to the performance of a concrete pavement, as indicated by the results of the critical stress analyses as well as field surveys. High elastic modulus of the concrete and long slab length were also shown to produce adverse effects to concrete pavement performance.
Backcalculation of System Parameters for Jointed Rigid Pavements
Authors: Hiltunen DR , Roque R
Published: March 2009

A procedure has been developed to backcalculate parameters required for the mechanistic evaluation of jointed rigid pavements. The two paramters are the coefficient of dowel/concrete interaction (G), and the coefficient of subgrade reaction (k) in the vicinity of the joint. The procedure involves two primary steps. First, actual FWD tests are conducted at the joints of the pavement system, and the deflection transfer efficiency and the surface deflection under the FWD load are determined. Next, a finite element model of the pavement system is used to determine the relationship between deflection transfer efficiency and surface deflection. This relationship is developed for a range of G and k values, holding all other input parameters fixed. With the two FWD measurements and the theoretical relationship between the two, the G and k parameters can be determined for the pavement system under evaluation.
Evaluation of NDT Equipment for Measuring Voids Under Concrete Pavements
Authors: Uddin W , Hudson WR
Published: March 2009

The partial loss of subgrade support associated with voids under portland cement concrete (PCC) pavements leads to increased deflections and increased load stresses. This can cause a significant reduction in the fatigue life of the pavement. This paper presents the findings of a comprehensive research study to establish the performance capabilities and limitations of the following methods and equipment for detection and measurement of voids beneath PCC pavements: (a) Proof Roller, (b) Deflection Equipment, (c) Ground Penetrating Radar Equipment, and (d) Transient Dynamic Response (TDR) Equipment. The records of grout quantity, based on field tests conducted by the highway agencies of several states during undersealing projects, were the prime source to verify the presence of voids.

All methods required extensive manual data analysis and output interpretation. Deflection methods are the least satisfactory because pavement deflections are significantly influenced by daily and seasonal variation of temperature. The TDR method is very labor intensive and relies on subjective interpretation. Radar methods hold good promise if the data interpretation and processing is enhanced.
Solar Ultraviolet Radiation: Aspects of Importance to the Weathering of Materials
Authors: Zerlaut GA
Published: March 2009

Constituents of the stratosphere and troposphere that serve to define the solar ultraviolet spectral energy distribution that is important to the outdoor deterioration of polymer-based materials are reviewed. Particular attention is devoted to the influence of ozone ⋯ both from an historical sense, and on the basis of the latest information available on the relationship between ozone depletion and the spectral energy distribution in the so-called ozone cut-off region of the solar radiation spectrum. The significance of the historically accepted solar ultraviolet spectrum, as well as that predicted on the basis of, for example, 10 and 20% decreases in total column ozone, are discussed in terms of [1] correctly measuring ultraviolet radiation in the spectral region of importance to materials, [2] assessing the effects of solar ultraviolet radiation on such materials, and [3] simulating the spectral energy distribution of solar ultraviolet radiation in indoor exposure test scenarios.
Quantitative Characterization of Photodegradation Effects of Polymeric Materials Exposed in Weathering Environments
Authors: Martin JW , Lechner JA , Varner RN
Published: March 2009

Both the experimental and mathematical analysis procedures used by the coatings and polymeric building materials communities for characterizing the photodegradation effects of UV radiation are different from those used by the medical, biological, and agricultural communities. In the building materials community, total ultraviolet radiation is monitored for characterizing the degradation effects of UV radiation. In these other disciplines, however, field and laboratory photodegradation data are related through total effective dosage, which is derived from the cumulative spectral UV irradiance to which a material is exposed along with the material's spectral absorption and guantum yield coefficients. Total effective dosage has been shown to be a good predictor of human response to solar UV radiation. The mathematical basis for determining the total effective dosage, the underlying assumptions, and supporting data and models are presented.
Effect of Light Source Emission on Durability Testing
Authors: Searle ND
Published: March 2009

Due to the wavelength specificity of the effect of light on materials, the type of light source used in durability testing significantly influences the stability ranking of materials as well as the mechanism and type of degradation. Tests of the relative stabilities of polysulfone and polyarylate show that fluorescent UVB radiation produces reversal in ranking compared with outdoor exposure while the latter is reliably simulated by borosilicate filtered xenon arc radiation. The importance of simulating the irradiance of terrestrial solar radiation over the full actinic region is illustrated by examples of the antagonistic effects of short versus long wavelength UV and data on distortion in lightfastness ranking of printing inks by either fluorescent UVB or UVA-351 lamps. The former has excessive short wavelength UV radiation and both are deficient in long wavelength UV and visible radiation. Reasons are given for dependence of stabilizer effectiveness on type of light source and illustrated with examples.
Errors Caused by Using Joules to Time Laboratory and Outdoor Exposure Tests
Authors: Grossman DM
Published: March 2009

A common practice in laboratory or outdoor weathering tests, is to time the exposure in UV Joules instead of hours or days. The assumption is that Joules of radiant UV exposure give a relatively reliable index of the degradation forces impinging on the test specimens. However, timing in Joules can be extremely misleading. Joules do not reflect variations in degradation caused by differences in exposure to moisture, temperature, or wavelength spectrum of the light source. Characterization and control of these other parameters is oftenmore important than Joules of radiant dosage. Controlled tests were conducted, varying either temperature, moisture, or wavelength spectrum while holding other conditions constant. In these tests, replicate specimens exposed to identical radiant dosage in Joules showed variations of over 500% in gloss loss and yellowing. This effect was observed in several different polymers. The conclusion is that for UV exposure tests, measuring radiant dosage may be a worthwhile control, but it is by no means sufficient as a description of the test conditions.
Surface Temperatures of Materials in Exterior Exposures and Artificial Accelerated Tests
Authors: Fischer RM , Ketola WD
Published: March 2009

Surface temperatures for a series of colored specimens were determined under typical exterior exposure and laboratory accelerated test conditions. The temperature separation of colored specimens exposed outdoors depends primarily on the total solar irradiance. Linear regression models can be used to predict surface temperature of colored specimens as a function of the temperature of a black panel. There is good temperature agreement between different types of black panels. In artificial accelerated testing, temperature separations similar to those obtained in typical exterior exposures can only be achieved by appropriate radiant heating from the device's light source. High irradiance conditions in xenon arc devices can result in slower than anticipated failure rates for lighter colored specimens when using black panel temperature control.
UV Transmission of Single Strength Window Glass
Authors: Ketola WD , Robbins JS
Published: March 2009

UV transmission of glass used for behind glass exposure tests is highly variable and is affected by the source of the glass and the spectrophotometer used for transmission measurement. The spectrophotometer is the most significant source of variability for wavelengths up to 300 nm. For wavelengths of 310 nm or longer, the source of the glass is the largest source of variability. UV transmission is related to iron and sulfur content of the glass, but the relationship is not strong enough to establish a meaningful specification. After three months exposure, UV transmission of window glass drops by 30–60% at 310 nm and by 25–50% at 320 nm. There is little change in UV transmission between three and thirty months, but the differences between glasses are still very significant. Variations in UV transmission cause tremendous differences in the short wavelength UV energy received by specimens being exposed behind different glasses. These differences can cause differences in degradation rate of 100–300%, depending on the relationship between intensity of UV radiation and rate of photochemical degradation.
Viability of High Irradiance Xenon Arc Weathering Tests
Authors: Scott KP
Published: March 2009

In the field of materials durability testing, the demand for fast answers is ever increasing. All too often though, the validity of a test is sacrificed for the sake of speed.

To obtain acceptable correlation of accelerated weathering tests with end use experience, the exposure procedure should recreate the failure mechanisms caused by natural exposure. Distortions of the critical aspects of weathering must be minimized. The most important of these is the light source.

For the purpose of acceleration there are test methods that specify light sources which are more severe qualitatively than the light present in their end use environment. Such tests often produce anomalous results.

The philosophy of high irradiance xenon arc testing is that, for best results, it is necessary first to closely match the quality of the end use light, then for acceleration, the irradiance (quantity) may be significantly increased.

A case study will be presented which compares a popular test method with a version of itself, where the quality and quantity of the xenon light were modified. The modified test method yielded better results in shorter test times.
New Accelerated Light Fastness Test with Super High Irradiance Using a Xenon Arc Lamp
Authors: Suga S , Suga S
Published: March 2009

The properly filtered xenon lamp is so similar to sunlight in spectral power distribution among various light sources, especially in UV and visible range, that its use is increasing in light exposure test. However, there is a criticism of this test mainly in automobile industry because of its lack of acceleration.

The authors developed a light fastness test system in which a xenon lamp is used, the distance between the lamp and samples is shortened to get a larger radiation effect, and a filter glass is placed in front of a specimen so as to simulate the actual environment which materials encounter in an automobile compartment. The point was how to simulate a no-air-flow condition and a temperature distribution among the surface and the backing of a material.

In this new xenon lamp testing method, a good correlation with an outdoor exposure test as well as higher acceleration has been obtained. This fading in actual outdoor exposure for one year was reproduced in about five days in the experiments where automobile interior materials, textile and plastics, were used.
Accelerated Service Life Predictions of Compact Discs
Authors: Murray WP
Published: March 2009

An Accelerated Life Expectancy test of 3M CD-ROM Media was performed on 9 sets of 16 discs. Each set was exposed to a different temperature/relative humidity combination and tested periodically for Mean Block Error Rate (BLER). By use of the Maximum Likelihood Estimate, (MLE), the rate of BLER change was determined for each disc. Within each test cell, the distribution of time for discs to reach End of-Life was fitted to a Weibull distribution and the resultant scale parameters regressed by MLE to solve an Eyring Acceleration Model. Temperature and relative humidity stresses were simultaneously modeled and relative acceleration factors were calculated for each cell. These acceleration factors were applied to the respective test cell data thereby normalizing all accelerated data to a common usage condition. From the combined normalized data an overall Weibull distribution was determined and the survival function was used to project product life-time capabilities and confidence intervals.
Utility of Immunoassay for Trace Analysis of Environmental Contaminants
Authors: Van Emon JM
Published: March 2009

Immunochemical technology is being used to solve problems in environmental chemistry. Immunoassays such as the enzyme-linked immunosorbent (ELISA) are sensitive bioanalytical procedures applicable to many classes of compounds. Immunoassays employ specific antibodies as receptor molecules for target analytes. Many different immunoassay formats have been developed to detect pesticides and other environmental contaminants. Immunoassay is an analytical technique that offers many advantages and can augment chromatographic analyses.
Assessment of the Microscreen Phage-Induction Assay for Screening Hazardous Wastes
Authors: Houk VS , DeMarini DM
Published: March 2009

The Microscreen phage-induction assay, which quantitatively measures the induction of prophage λ in Escherichia coli WP2s(λ), was used to test 14 crude (unfractionated) hazardous industrial waste samples for genotoxic activity in the presence and absence of metabolic activation. Eleven of the 14 wastes induced prophage, and induction was observed at concentrations as low as 0.4 picograms per ml. Comparisons of the mutagenic activity of these waste samples in Salmonella and their ability to induce prophage λ indicate that the phage-induction assay was a more sensitive indicator of genetic damage for this group of wastes. All but one of the wastes that were mutagenic to Salmonella were detected by the phage-induction assay, and 5 wastes not mutagenic to Salmonella were genetically active in the phage assay. The enhanced ability of the phage-induction assay to detect genotoxic activity may be related to the constituents comprising these waste samples. Partial chemical characterizations of the wastes showed high concentrations of carcinogenic metals, solvents, and chlorinated compounds, most of which are detected poorly by the Salmonella assay. However, recent studies of the induction of prophage by these chemical classes have suggested that phage induction may be a sensitive endpoint for these groups of chemicals.
Toxicological Assessment of Hazardous Waste Samples Extracted with Deionized Water or Sodium Acetate (TCLP) Leaching Media
Authors: Peterson SA , Greene JC , Miller WE
Published: March 2009

Sodium acetate and deionized water elutriates prepared from municipal and industrial waste products, and the sodium acetate leaching media per se, recommended by the EPA for the Toxicity Characteristic Leaching Procedure (TCLP), were bioassayed for their toxicity potential. The toxicity bioassay organisms included: algae, Selenastrum capricornutum; macroinvertebrates, Daphnia magna; lettuce seed root elongation, Lactuca sativa L.; and, bacteria (Microtox), Photobacterium phosphoreum. The pH 5.0 sodium acetate leaching media was highly toxic to each of the test organisms. Adjustment of the pH to 7.0 decreased toxicity approximately 2.5-fold for algae and lettuce, and 6-fold for D. magna. This reduction, while statistically significant, did not change the toxicity classification of the sodium acetate leaching media. Photobacterium phosphoreum was un-affected by pH 7 sodium acetate leaching media after 30-minutes exposure. Toxicity of the industrial waste TCLP elutriates to D. magna and S. capricornutum was similar to that obtained in the elutriates prepared with deionized water. The response of D. magna to the TCLP elutriates from sewage sludge (POTW #2), municipal ash #1 and #2, paint sludge #2, Midco volatile soil, and First Chemical Corp. indicated that these samples contained acetate soluble contaminants which were more toxic than the sodium acetate itself. Bioassays detected toxicity in either TCLP or deionized water eluted samples. Toxicity of water eluted samples can be attributed to materials leached from the waste. Toxicity of the TCLP eluted samples is problematic due to uncertainty of the amount of toxicity attributable to the leaching media itself vs. the materials leached from the wastes.
Application of a Simple Short-Term Bioassay for the Identification of Genotoxins from Hazardous Wastes
Authors: Sandhu SS , Acedo GN
Published: March 2009

The proper disposal of hazardous wastes currently generated and clean up of waste disposal sites of the past are challenges facing regulatory agencies in the industrialized nations. The estimation of levels of toxicity is an essential step in prioritizing industrial effluents and solid wastes for treatment and disposal. A number of short-term bioassays has been developed to supplement information from chemical analysis for evaluating the potential of chemical complex mixtures to induce adverse human health effects and environmental contamination. Among these bioassays, plant test systems provide simple, inexpensive, and rapid means of evaluating toxic effects of industrial wastes based on multimedia exposure. Two such assays, Tradescantia paludosa and Zea mays, have been used for monitoring the genotoxic effects of ambient air, municipal wastes, industrial effluents, solid wastes, water sediments, and pesticides. We applied the Arabidopsis embryo assay to evaluate the mutagenicity of complex environmental mixtures including industrial effluents and sludges. The industrial waste samples were tested either unextracted or as dichloromethane aqueous extracts. These samples produced positive mutagenic results in the Arabidopsis embryo assay.
Utility of

In Situ

Assays for Detecting Environmental Pollutants
Authors: Lower WR , Sandhu SS , Thomas MW
Published: March 2009

In Situ bioassays are toxicity determining techniques applied to or designed for use under real world conditions outside of the control of the laboratory. A number of plants and animals, domestic and wild, are used in situ to measure and monitor mutagenesis, carcinogenesis and other biological endpoints; for example, growth, nitrogen fixation, excretion of urinary δ-aminolevulinic acid, blood cell abnormalities, etc. The organisms include corn, soybean, spiderwort, white footed mouse, wild house mouse, mudminnow, white croaker and brown bullhead fish, sea urchin and mussel.
Evaluation and Validation of Protocols for Measurement of the Mutagenicity of Environmental Samples
Authors: Wang YY , Marsden PJ , Flessel CP , Williams LR
Published: March 2009

Protocols have been validated for the preparation of wastewater, drinking water, soil, and sediment samples for the Ames Salmonella mutagenicity assay. These protocols are proposed for use with environmental samples in “Guidelines for Preparing Environmental Waste Samples for Mutagenicity (Ames) Testing: Interim Procedures and Panel Meeting Proceedings, EPA 600/4-85-058 [1] and are validated essentially as written. Samples are extracted using EPA methods [2], concentrated, solvent exchanged, and assayed in strains TA98 and TA100 with and without S-9 activation. The performance of each method is optimized using environmental samples with variables of sample size and extraction solvent. Bias of the methods is established by using samples fortified with reference mutagens; precision is determined by testing replicate aliquots of a variety of samples. This work is an on-going effort sponsored by EMSL-LV to produce robust, reliable procedures for the measurement of mutagenicity in environmental media.
Performance of the Toxicity Characteristic Leaching Procedure
Authors: Newcomer LR , Blackburn WB , Hansen GA
Published: March 2009

The U.S. EPA has recently promulgated the use of a leaching procedure (TCLP) to be used as a criterion for disposal of hazardous wastes under the Land Disposal Restrictions Rule. The TCLP has also been included in the proposed rule for Identification and Listing of Hazardous Wastes.

Summarized are results of eight different studies designed to evaluate the TCLP method. Study results indicate that the TCLP procedure can be applied consistently by a diverse group of laboratories.
Mobilization of Volatile Toxic Components from Petroleum Product-Contaminated Soils by TCLP
Authors: Romeu AA , King C , Blevins DJ , Soutor NJ
Published: March 2009

Two different types of soil contaminated at several levels with unleaded gasoline, diesel fuel, and No. 6 fuel oil were subjected to the toxicity characteristic leaching procedure (TCLP). One soil (Kaw) was sandy-silty, with low organic carbon content (0.6%). The other (Action) was silty-clayey with a higher organic carbon content (2.3%). The TCLP leachates and neat fuels were analyzed by GC/MS for volatile organic analytes. Leaching of the volatile organic contaminants from the Action soil resembled Freundlich-type isotherms, whereas for the Kaw soil, the isotherms were almost linear. This suggests sorption from the gasoline in the Action soil and no retention in the Kaw soil. Diesel- and fuel oil-contaminated soils showed no significant differences in the concentrations of volatiles in the leachates of the two types of soil. The results indicated that there were significant differences in the leaching efficiency of TCLP which depended on soil characteristics and extent of contamination.