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Structural evaluation provides valuable information about the expected behavior of pavements and can be very useful at the network level of pavement management for project prioritization purposes. However, due to the expense involved in data collection and analysis, structural capacity is usually not determined at the network level. In Kansas, due to limited resources and the large size of the network (10 971 miles), annual network-level structural data collection at the same rate (five to ten tests per mile) as the project level is not realistic. This study was initiated to determine the sample size (% mileage) at the network level as well as the test intervals and frequency that can be used as guides for network-level deflection testing and structural evaluation of pavements. Falling-weight deflectometer (FWD) data, collected on 571 km (357 miles) of non-interstate asphalt pavements of the Kansas Department of Transportation from 1993 to 1996, were used in the analysis. Three response variables were studied: (1) normalized and temperature-corrected first sensor deflection, (2) backcalculated subgrade resilient modulus (Mr), and (3) effective pavement modulus (Ep). Statistical analysis of these variables showed that the FWD tests up to a three-year interval at the network level yield statistically similar pavement responses and layer properties. At the network level, FWD tests on 20% mileage appear to be a valid statistical choice, and three tests per mile is the minimum test frequency required. An analysis procedure for assessing structural deterioration of pavements at the network level is also demonstrated.

The determination of the optimum lime content of fly ash is very important to enhance its use. Recently, methods have been established to obtain the optimum lime content of fly ashes. Strength obtained at different ages becomes important for different applications. The effect of the curing period on the optimum lime content of fly ashes is not established, nor are methods available for obtaining the same. Based on detailed strength tests on different fly ashes with various lime contents after curing for different periods, it has been established that the effect of the curing period becomes important for optimum lime content of certain fly ashes depending upon their chemical composition. The optimum lime content corresponds to the production of a maximum amount of calcium silicate hydrate compounds of Type I. In addition to the strength test, the sediment volume test has also been used to study the effect of the curing period on the optimum lime content of the fly ashes. Both methods compared well and hence the simpler free swell sediment volume test may be adopted.

This paper documents the process used the United States Environmental Protection Agency (USEPA) to estimate the mean and standard deviation of data reported by in-control wastewater laboratories during Water Pollution (WP) studies. This process is then applied to the data reported for each specific sample, analyte, and method in ten WP studies and linear relationships between the mean response and true analyte concentration, and between the interlaboratory standard deviation of responses and true analyte concentration, are presented. Such relationships can be invaluable as background information for anyone who must conduct an interlaboratory study using the same methods to analyze similar interference-free samples, or who must evaluate the analytical quality of such data.

The electrolytic processes in the ASTM C 1202 chloride penetration test method have been reexamined both theoretically and experimentally. The analyses show that hydroxyl (OH−) ion generated at the cathode during testing carries a substantial part of the current and that chloride (Cl−) ion is not the sole current carrier. Attention has also been drawn to the implication of the experimental results on the determination of the Cl− ion diffusivity by the ASTM C 1202 experimental setup.

The transition temperatures of Cr-0.5Mo, Cr-Mo, and Cr-Mo-V steels were determined using the Charpy V-notch (CVN) and the small punch (SP) tests. It was confirmed that there was a linear correlation between the transition temperature of ductile-brittle behavior determined by the Charpy V-notch test and that obtained from the small punch test. However, the estimation of CVN transition temperature by means of this linear equation is not completely reliable because of the large experimental scatter of data. In order to improve the reliability of the transition temperature estimation, a multiple linear regression (MLR) analysis was conducted to evaluate the effect of different variables of the manufacturing process and service conditions. This analysis permitted the determination of the following regression equation: CVNDBTT = 1.35 SPDBTT − 0.84 × 10 3 d − 1 ∕ 2 + 326 . This equation enables one to assess more accurately the transition temperature corresponding to the Charpy V-notch test using that of the small punch test and the austenitic grain size, expressed by d − 1 ∕ 2 .

A novel instrument is presented capable of measuring the principal strains at a point on a photoelastic coating. The oblique incidence method of principal strain separation is employed, using three fringe order measurements, which are made by the automated method known as spectral contents analysis. The oblique incidence measurements are made after rotation of the polariscope about any two orthogonal axes. Three polariscopes are built into the instrument, as is a CCD camera, to facilitate accurate positioning of the instrument. The instrument was used to analyze the principal strain distributions in a disk under diametrical compression, a plate with a central hole under tension, and a stepped plate in tension. The strains in the disk and the plate with a hole were compared with theoretical results, and the strains in the stepped plate were compared with a finite element analysis of the problem. The correlation between the experimental and theoretical or numerical strains was better than 0.95 in most cases.

A common method of disposing of ash generated from coal-fired thermal power plants is wet disposal, where the ash is mixed with water to make a slurry and is disposed of in ash ponds or lagoons. Such a disposal system allows for ash-water interaction, and alkalis present in the ash react with water, leading to the formation of ash zeolites. Formation of zeolites alters the overall properties of the ash. Controlled laboratory experiments have been conducted on a lagoon ash to determine the effects of zeolitization on its physico-chemico-mineralogical properties. Further investigations have been carried out to demonstrate the effect of zeolitization of the ash on its geotechnical properties such as its compaction, consolidation, and permeation characteristics. Such a study is required for bulk utilization of the ash (as a fill material) where compaction, consolidation, and permeation properties are most important.

A new criterion is proposed for testing for outliers when the population standard deviation a is known. The advantage of this criterion is that no table is required and a fixed significance level can be selected. Compared with the current ASTM E 178 criterion for outlier rejection, under the same chance of making a Type I error, the U test has less chance of making a Type II error and therefore is a more powerful test.

In this paper, an estimation method is proposed for the size distribution of particles in materials. The configuration of particles is assumed to be spheroidal and all observed information is gathered from cutting planes. The apparent size distribution measured from 2D is corrected to the 3D true size distribution, then the expected size distribution can be estimated from a small size up to an extreme size. This estimation method is most versatile, and involves Saltycov's method and extreme statistics at the same time. The procedure is applied to an artificial material with a given particle size distribution in computer simulation in order to examine its validity. The estimated results are compared with the given distribution, and the validity of the method is confirmed.

The authors present an application of the Solartron 1200 Real Time Signal Processor to correcting the on-line random loading in a fatigue test system. By inputting a power spectrum described by a data file to a computer, its corresponding random process may be simulated. Since the processor is connected with a computer, results of signal processing done by the processor are sent to the computer periodically during the test. The computer performs pattern matching using the correlation coefficient value (CCV) between a loading spectrum and its predetermined target. If a CCV exceeds its threshold, the old data file will be replaced with a new one and the random loading exerted on a specimen will be updated. When the new data file is obtained based on optimal control strategy, the updated loading spectrum will approach its target. Therefore, an electrohydraulic fatigue test system equipped with a real-time signal processor can realize an on-line correction of a random loading based on the target spectrum desired. Since this updating does not change the original software package and hardware of the system, the performance of the system and testing quality are safely improved.

One of the important areas of application of commercial thermal imagers is nondestructive thermal testing. An analysis of two standards published by the American Society for Testing and Materials describing measurement procedures of the minimum resolvable temperature difference (MRTD) and the minimum detectable temperature difference (MDTD) was made in this paper. It was shown that in the case of modern thermal imagers, the measurement results of these parameters carried out according to the ASTM recommendations may be unreliable. Proposals to update the standards and to enable accurate measurement of the parameters mentioned above are presented. A laboratory setup for measurement of the MRTD and the MDTD that fulfills requirements of the proposals is described. Measurement results of the parameters for a modern commercial imager according to updated procedures are presented. Erratum to this paper appears in 28(6).

Thermal power stations use pulverized coal as fuel, producing enormous quantities of ash as a waste product of combustion. Nearly 800 million metric tons of ash is produced each year all over the world. In India, presently 97 million metric tons of ash is produced annually by power stations. The problem of ash disposal is a difficult one due to the limited availability of vacant space around the power plants. In view of the large quantities of ash, its bulk utilization is essential, which is possible only through geotechnical applications such as embankments, back-fill material, subbase material, and the like. For the above applications, one of the important engineering properties is the angle of internal friction, which is determined either by box shear or triaxial shear tests. This paper examines the angle of repose of pond ashes and its relation with the angle of internal friction, using direct shear tests. Determination of the angle of repose is an easy and quick procedure for cohesionless materials. The angles of repose of sand and of quarry dust also are examined for comparison purposes. A relationship between angle of internal friction for materials in the loose, dry condition and the angle of repose is established. Further, a simpler method of measurement of the angle of repose is proposed.

In order to gain detailed insight into the processes taking place during rolling contact fatigue (RCF) and rolling contact wear, the test machine used must be closely controllable and offer comprehensive data collection facilities. This paper describes a machine that has been developed to offer these facilities over a wide range of test conditions, and that has the facility for the early detection of cracks by an eddy current method., An existing twin-disk contact simulation machine has been comprehensively updated to enhance the range of tests possible and, most importantly, to offer close control over very short numbers of machine cycles, allowing the very early stages of the development of fatigue cracks and wear damage to be examined. Results of tests to examine the capabilities of the rebuilt machine and a study of the repeatability of results under two particular test conditions are presented.

During our field observations and water tests of wood-framed houses in North Carolina that are clad with EIFS, we noted common features in their exterior wall construction that caused significant deterioration to the sheathing and stud wall framing. For several reasons, these problems would be less severe or absent if the houses were clad with traditional residential wall systems (i.e., wood shingles or clapboards, brick veneer, or traditional stucco). To define the design “problem” we review issues relevant to the performance of surface-sealed barrier EIFS including common sources of moisture intrusion, the potential for moisture entrapment within the wall system, i.e., the lack of drying capacity of the wall, and the moisture sensitivity of various substrates. We focus on presenting suggestions for resolving the problems and designing a functional EIF system for use on moisture-sensitive substrates such as wood-framed construction, with particular attention to structures in climates with heavy rainfall and high humidity.

The understanding of the mechanisms of fatigue-crack propagation in advanced ceramics at elevated temperatures (>800 degrees C) has in part been hampered by the experimental difficulty in directly measuring crack lengths, and hence crack-growth rates, at such high temperatures.

To be able to determine the accuracy in the extrapolation of creep rupture data, expressions for estimating the error are presented. One expression is based on the statistical uncertainty in the least square fit to the data. This estimate can be considered as the minimum possible error that is present in extrapolated values. Expressions for the upper limit of the error based on linear as well as higher-order polynomials are derived. It is demonstrated that the expression based on linear extrapolation has a general applicability and covers most cases of technical interest. Comparison to previously performed extrapolation analyses shows that the actual variation between extrapolation methods lies in general between the least square error and the upper limit estimate. It is proposed that design values derived from extrapolated creep rupture data should be reduced, with an additional data factor if the estimated error in the extrapolation is larger than what is typical in the materials codes and standards. Values for these data factors are given.

A modified version of ASTM Test Method F167195, Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Blood-Borne Pathogens Using Phi-X174 Bacteriophage Penetration as a Test System, was characterized using as test material pieces of condom latex with laser-drilled holes of known size. The modified test included the initial 5-min, no-pressure period together with the 1-min, 2-psi period, but eliminated the final 54-min, no-pressure period. Virus penetration was detected for all holes with diameters above 1.0 µm. The quantitative results were in good agreement with calculated fluid flow through a cylinder (Poiseuille equation) for holes above 2 µm. A brief argument is presented suggesting that the final 54-min period at no pressure be eliminated from the test protocol.

Double-stacked empty corrugated fiber-board boxes were conditioned in normal and tropical climates and then compression tested in aligned, laterally offset, and diagonally offset configurations to determine the effect on compression strength. The results showed that offsets caused a greater reduction in strength than humidity effects. In a separate experiment, three-high pallet loads of infant formula in two-piece plastic cans were stacked in various staggered positions to evaluate the effect of pallet offset on stack stability. It was found that factors other than the amount of offset, such as pallet strength, uneven floors, and stretch wrapping were most influential.

The Center for Devices and Radiological Health, Food and Drug Administration, evaluated a prototype device using novel technology to detect pinholes in male latex condoms. This device uses multiple electrodes, maintained at high positive voltage, which interrogate a latex condom placed on a conducting mandrel. An electric discharge occurs only when a small hole is present in the condom and is sensed by the device. The mandrel is rotated to map out the entire surface of the condom. Using latex condoms with laser-drilled holes ranging from approximately 1 to 30 µm in diameter, we examined the sensitivity of this device. The smallest holes were detected, and the overall false negative rate was 2%.

In this paper, a simple method is proposed for estimating with a few strain gages stress fields near a notch root in plates under in-plane loading. In the present method, the stress fields are estimated by solving the boundary value problems. Concretely, we use the Airy's stress function for an arbitrary plate with a free circular hole, considering an edge near a notch root as a part of a free circular hole. The unknown coefficients of the Airy's stress function are determined from stress values with strain gages along a certain closed curve so that the Airy's stress function satisfies the boundary conditions at the curve. The strain values are measured only at four points on a circular arc whose radius is 1.5 times as large as the notch root radius. The method of least squares is used for determining the unknown coefficients. We demonstrate the present method using eight types of notched plates. We obtained accurate estimation results except for a few cases.

Anisotropic constitutive relations with respect to the principal axes of an orthotropic solid are formulated using the macroscopic continuum plasticity theory of Shih and Lee. The general anisotropic constitutive relations are derived for predicting the plastic deformation behavior of a new material orientation. Straincontrolled cyclic tests were conducted along the 45° direction in the plane of the plate to verify the general anisotropic constitutive relations. The predictions agree very well with the experimental yield and plastic flow behavior. The axial-torsional coupling terms in the general constitutive relations are also determined and explained. The constitutive equations were used to predict the low-cycle fatigue life of this material under both proportional and non-proportional loadings. An anisotropic shear cracking model, developed earlier, provided a good prediction of the fatigue life of this material under both proportional and non-proportional loadings.

An experimental program has been implemented to determine small offset yield loci for the nickel-base superalloy In conel 718 (IN718) under axial-torsional loading at elevated temperatures. Initial and subsequent yield loci were determined for solutioned IN718 at 23 and 454°C and for aged (precipitation-hardened) IN718 at 23 and 649°C. The shape of the initial yield loci for solutioned and aged IN718 agrees well with the von Mises prediction. However, in general, the centers of initial yield loci are eccentric to the origin due to a strength-differential (S-D) effect that increases with temperature. Subsequent yield loci exhibit kinematic and distortional hardening, and solutioned IN718 shows a weak cross effect. This work demonstrates that it is possible to determine yield surfaces for metallic materials at temperatures up to at least 649°C using multiple probes of a single specimen. The experimental data are first of their kind for a superalloy at these temperatures and will enable a better understanding of multiaxial material response.

Data are presented to support modification to a provisional American Society for Testing and Materials (ASTM) sampling and analytical technique for metalworking fluids (ASTM P-42-97). The method, tentatively recommended by ASTM Subcommittee D-22.04, involves collection of the aerosolized fluid on a filter and separation of the fluid from co-sampled particulate matter via solvent extraction of that fluid from the filter. The solubilities of nine metalworking fluids were tested in seven solvents: acetone, dichloromethane, ethyl acetate, isopropanol, methanol, toluene, water, and three solvent blends: dichloromethane: methanol, dichloromethane:methanol:toluene, and dichloromethane:methanol:hexane. A ternary blend of dichloromethane: methanol:toluene (1:1:1) was found to dissolve samples of the four classes of metalworking fluids within about I min.

It has been the author's experience that researchers will routinely use linear models to describe the relationships between correlated variables when that approach to modeling may not be the most rational. This article illustrates some of the circumstances when linear modeling is and is not the most viable alternative in characterizing the relationship between correlated variables. In this study, several data sets are examined to illustrate how amenable they are to linear modeling. One data set selected shows a nearly ideal example of when linear least-squares regression is a realistic descriptor of the relationship between correlated variables. A second data set shows how material idiosyncrasies, such as species, size, or grade effects, can result in misleading models for parameter prediction. A third data set illustrates a more subtle inhomogeneity that is frequently found in experimental data involving tests of clear wood. When the relationship between correlated variables changes due to a shifting failure mechanism, a presumed linear relationship may misrepresent the relationship between variables in a large portion of the domain. It is the intent of this paper to remind or make researchers aware of the subtle characteristics of data sets that can influence modeling results. One possible mechanism for modeling nonlinearly related variables (the univariate S B and the bivariate S BB distribution) is offered for consideration. This model has the unique feature of quantifying, in an analytic, closed-form fashion, the probability of a predicted variable for any value of the domain. In addition, when certain input values used to calculate S BB bivariate distribution parameters are defined correctly, convergence to the clear wood strength of a material or product is achieved.

A catapult arrangement capable of propelling small granite chippings at velocities of between 4 and 20 ms-1 at laminated glass structures similar to those used in car windscreens has been designed and manufactured. The results from a series of studies utilizing this equipment are presented, with the overall aim of reducing the weight of these constructions with no loss in impact resistance. The impact resistance of the laminates has been shown to depend strongly on the thickness of the outer glass layer, while the inner glass layer is of secondary, and in most cases, minor relevance. Tests in which the composition and thickness of the interlayer have been varied have revealed that this layer is of no consequence in terms of the impact resistance of the structure as a whole. Chemical strengthening of the outer glass layer has been carried out, and no improvement in performance is observed due to the nature of the stone geometry. Finally, tests on bilayer systems have been carried out, and these results indicate a potential weight saving for no loss in impact performance.

The successful performance of exterior insulation and finish systems (EIFS) is related directly to the sealants used to weatherseal the EIFS and adjacent materials to EIFS. With millions of square feet of EIFS installed, proper restoration of EIFS joints can help ensure long-tern watertight performance of the EIFS wall. A new test method that closely parallels ASTM C 1135-Test Method for Determining Tensile Adhesion Properties of Structural Sealants, is currently under consideration by ASTM Task Group C 24.20.12. This new test method allows sealant joints to be evaluated in many conditions to more closely simulate actual field conditions. This paper will focus on types of EIFS joint failure and possible causes for failure. Different restoration methods will be discussed with particular attention to the use of sealants to overlay failed sealant joints. A modification to the test method under review by ASTM Task Group C 24.20.12 will be used to evaluate various joint conditions with EIFS, including standard square joints, hourglass-shaped joints, overlay joints with wet sealants, and overlay joints with performed sealants.

To investigate the hypothesis that Superpave Volumetric mix design yields superior performing mixes overall, the Portuguese Road Directorate (JAE) compared the performance of Superpave mixes with the peformance of other mixes. The comparisons were made with gradations, that pass through, above, and below the restricted zone. Performance was evaluated using the Marshall test, the Hveem test, the Repetitive Simple Shear Test at Constant Height, the Four Point Bending Fatigue Test, and the French Wheel Tracking Device. These research efforts led to consideration as to what extent the binder and gradation selections are dependent on the mix design tool. The results indicate that some Superpave mixed yield the lowest laboratory performance in some of the tests.

A numerically generated expression to determine crack length in a compact tension specimen from back face strain compliance is presented. The numerically generated back face strain expression is bounded by two experimentally determined expressions previously published in the literature. Additionally, stress intensity factor and crack mouth opening expressions are determined. These expressions agree well with previously published results.

The five-point bending test is configured as a continuous two-span beam having point loads at each midspan. It was proposed by others as an approach to evaluating the shear capacity of structural size lumber and engineered wood products because earlier tests with wood-based structural panels yielded shear failure modes. In the tests with structural panels, the thickness/depth ratio was large relative to that in structural lumber, although the length/depth ratios were the same. In addition, the density of the structural panels was greater than that of structural lumber. At the load-bearing positions, rounded bearing surfaces were used for the tests of structural panels, but flat bearing plates have been the practice in tests of structural size lumber. In this study, finite-element analyses of the bearing plates and the resulting stress distributions on structural lumber were conducted, first on an orthotropic half-plane and then in the five-point test geometry for structural lumber. The analyses used linear elastic and nonlinear compressive stiffness perpendicular to the grain and nonlinear shear modulus. Our testing showed that elementary beam theory failed to accurately predict the stresses in the critical region of the specimens. In addition, it appears unlikely that sufficient bearing can be developed in smaller lumber sizes to make the five-point bending method reflective of the true shear capacity.

We observed using the in-plane moire method the propagation of plastic strain in a uniform tension specimen made of HSLA 80 steel loaded quasi-statically. The steel shows a localized, heterogeneous type of transition from elastic to plastic deformation. Plastic strain generally initiates at one end of the specimen and gradually propagates toward the other end. The magnitude of plastic strain, once initiated and propagation begun, is about seven times the elastic strain. An interface band of the order of a few millimeters separates the elastic and plastic zones. Since it is a nonuniform deformation, local strain measurement methods such as strain gage, clip gage, etc. are not suitable to characterize the mechanical properties of this material.

This study provides a comparison of paper and plastic corrugated materials that are used for packaging. The test containers were mail trays used by the United States Postal Service. The test methods consist of performing an accelerated test in a warehouse facility that closely simulates the everyday handling characteristics encountered by these trays in postal facilities. The results also compared differences in material-recycled content and fabrication processes. The results show that the reusable plastic corrugated trays performed 2.5 to 3 times better than similar types of reusable paper corrugated trays.

Fracture testing on compact tension (CT) and threepoint bend (3PB) specimens is preceded by fatigue precracking. Fatigue cracks have curved crack fronts. Nevertheless, crack front curvature is not taken into account in numerical modeling of fracture toughness testing procedures. In this paper we analyze actual fatigue cracks in CT specimens and show that the difference between crack depth at the center plane and at the surface of specimens is typically 0.01 to 0.03 of the specimen width. Three-dimensional elastic-plastic finite element analyses were performed for CT and 3PB specimens with crack fronts of different curvatures, and the CTOD δ5 and the J-integral were determined. It is found that the ratio δ 5 C ∕ δ 5 is sensitive to the crack front curvature and strongly affected by side grooves. It is also shown that crack front curvature variations that are within the limits given by the test standards affect to a certain extent the η factor employed for the determination of the experimental value of the J-integral using the area under the force versus load-point displacement record. These facts should be kept in mind when toughness is measured.

This paper is an overview of what we know about occurrence of wood decay above ground within buildings. It presents information concerning under what conditions decay may become established. In laboratory tests involving optimum moisture and temperature conditions for decay fungi, and direct contact with large quantities of specific well-developed decay fungi, substantial decay in small specimens of untreated wood of nondurable species can occur in a few weeks. The simultaneous occurrence of optimum conditions for decay and high degree of inoculation with mature decay fungi is probably very rare in buildings. However, spore germination also proceeds rapidly at optimum moisture and temperature conditions. For most decay fungi, optimum moisture conditions mean moisture contents above fiber saturation (usually around 25 to 30% mc,) but well below the waterlogged condition. Optimal temperatures for most decay fungi are in the range of 21 to 32°C. Untreated wood and wood-based products will not decay if intermittently wetted for short periods to moisture contents above fiber saturation or if wetted to such levels for periods of a few months when temperature is low. However, little is known in quantitative terms about decay development under fluctuating conditions. Moisture and temperature conditions are not expected to fluctuate appreciably behind external insulation and finish system (EIFS) claddings. Given this, we can find nothing in the research literature that would contradict the 20% wood moisture content rule for this application.

Statistical design of experiments was employed to study the effect of austenitizing temperature, austempering temperature, and austempering time on the quasi-static and dynamic fracture toughness of austempered ductile iron of a standard composition. Regression equations were developed to determine the relative significance of the variables in affecting the quasi-static and dynamic fracture toughness of the austempered iron studied.

The stretch zone width ( SZW = 1 ∕ 2 CTOD , the crack tip opening displacement) method for determining JIC involves fewer specimens and lesser size restrictions compared to the con ventional J-R curve method. However, the accuracy of the SZW-based procedure depends on each term of the J-CTOD relationship, i.e., J IC = m ∙ σ ∙ CTOD C . This paper presents a numerical investigation of the J-CTOD relationship, which has been carried out using a large-deformation finite element method (FEM). The slope of the blunting line (m) is computed for various combinations of yield strength-to-elastic modulus ratio ( σ o ∕ E ), power law strain-hardening exponent (n), and different measures of stress (σ in the J-CTOD relationship). This work brings out the importance of the correct choice of the stress measure, and the one suggested here is the integral average of the flow stress [ σ * = ∫ 0 e * σ d e / ∫ 0 e * d e ] . Also, an effective CTOD approach is numerically validated where a sharp fatigue precrack of fracture specimens can be substituted by one with a finite notch root radius without loss of accuracy in JIC.

The transition point of fatigue crack growth (FCG) between the near-ΔKth and the Paris regions is an important value to study fatigue behavior. This study introduces a curve-fitting technique to identify this point for nickel-based superalloy U720 with stress ratio of R = 0.1 at room temperature. The value of ΔKth under these conditions is also determined.

Baseline fatigue data are presented through a series of strain-controlled tension-compression-type fatigue tests on smooth specimens of a Type S1214 mild steel under various combinations of strain amplitudes and nonzero mean strains. The strain magnitudes were chosen in the upper limit of the elastic range, in the plastic range, or in the transition area between the elastic and the plastic range. Experimental results show that for strain amplitudes in the upper limit of the elastic range, positive mean strains prolong fatigue life and negative mean strains shorten fatigue life. The observations are explained by the analysis of the basic material properties associated with the material concerned. The cyclic response behavior of the materials, namely the Bauschinger effect, the cyclic softening, and the mean stress relaxation processes have been studied also to reveal the underlying fatigue mechanism. Several modified models have been proposed for life prediction under nonzero mean strain and/or mean stress based on experimental observations. The comparison of the experimental results with the predictions made from the proposed models and from an existing model are also presented.

The stress-strain behavior of a Fe-Ni-Cr alloy during in-phase and out-of-phase tests under conditions synchronizing thermal cycling with mechanical cycling has been studied by using a specially designed thermal cycling unit. The curves of cycling stress, strain, and temperature versus time indicate that the thermomechanical cycling softening phenomenon occurring in the higher-temperature region, close to the maximum thermal cycling temperature, is a common characteristic under thermomechanical cycling in-phase and out-of-phase superposition tests. However, a difference in behavior between in-phase and out-of-phase is evident. The tests show that the thermomechanical cycling softening occurred in the tensile strain range for in-phase testing and occurred in the compressive strain range for out-of-phase.

This paper deals with the influence of material structure parameters (fiber treatment and content of micropores) on the impact behavior of composite materials. Furthermore, an impact falling-weight testing device and the characteristic impact values are introduced. The role of the fiber/matrix interphase was investigated by using glass and natural (jute) fibers with different treatments. To study the influence of the content of micropores, epoxy foam reinforced with glass fiber mats were prepared. All materials were impacted on an instrumented low-velocity non-penetration falling-weight impact tester. By integrating the measured force/deflection curves, all characteristic values were determined. Finally, the fatigue behavior of epoxy foam reinforced with pre-treated woven fabrics and the jute/PP laminates under repeated impact were investigated. In all impact experiments, the damping index responded more sensitively to changes in the material structure than did the loss energy. Furthermore, it was found that the damping index is an excellent measurement for characterizing the extent of damage.

A knowledge of permeability and consolidation is essential in a number of engineering problems such as settlement, seepage, and stability of the structures. Since fly ash is used very widely for several geotechnical applications, there is a need to understand its permeability and consolidation behavior. This paper presents a detailed study conducted on two Indian fly ashes. It brings out the role of chemical composition (free lime) on the permeability and consolidation behavior of fly ashes. It is found that the permeability values computed based on grain-size distribution agree well with those obtained based on test data.

The suitability of dense-graded hot-mix asphalt concrete mixtures for fatigue-resistant flexible pavements is investigated. The fatigue lives of several mixes including those with additives of latex, rubber, and sulfur are predicted by a theory derived from fracture mechanics. There is good agreement between the model predictions for the fatigue lives and the experimental results for the laboratory tests. The material properties are then used to predict the fatigue performance of two of these mixes in a simulated full-depth flexible pavement and a three-layer flexible pavement. There is poor agreement between the model predictions for the performance of the simulated pavements and the laboratory tests. Several reasons are postulated for the differences in the fatigue lives for the laboratory beam tests and the simulated pavements.

Failure analysis is an essential element of all engineered products. The goal of failure analysis is the understanding of the root causes of any undesirable effects. Microfocus X-ray imaging (radioscopy and computed tomography) offers detailed information on the internal assembly and material condition of objects under failure analysis investigation. Using advanced systems for the acquisition of radioscopic and computed tomography (CT) images, failure analysis investigations are improved in technical accuracy at a reduced flow time and cost over alternative approaches. A versatile microfocus radioscopic system with CT capability has been implemented successfully as a standard tool in the Boeing Phantom Works Failure Analysis Laboratory. Using this tool, studies of electronic, electromechanical, and composite material items have been performed. Such a system can pay for itself within two years through higher productivity of the laboratory, increased laboratory value to the company, and resolution of critical problems whose worth far exceeds the value of the equipment.

New theoretical developments are presented to predict the permanent deformation in asphalt concrete caused by constant-load creep and by cyclic loads. The constitutive model utilizes multi-yield surfaces and isotropic hardening. A new hardening law for the changes in the values of the plastic moduli during monotonic or cyclic loading is derived from Rowe's stress-dilatancy theory. A complete description of the permanent deformation of asphalt concrete under constant load creep and cyclic loading is given, including the elastic, viscoelastic, plastic, and microcracking components, to predict the permanent deformation under cyclic loading. The model parameters have clearly defined physical meanings and can be determined from simple conventional laboratory tests. A computer program called RUT determines the permanent deformation. There is good agreement between the model predictions and the experimental data.

The flash point of a liquid material is used to classify whether the material is flammable or combustible. 1,4-dimethylbenzene (p-xylene) has been used historically to verify the proper operation of different flash point test equipment. Because of the toxicity and low flash point value of 1,4-dimethylbenzene, an interlaboratory study was conducted to determine alternate flash point reference standards. This study reports the flash points of n-decane, n-undecane, n-tetradecane, and n-hexadecane using various flash point test methods. The flash points of these materials were found to be testmethod dependent because of the inherent differences in the various flash point test methods. The reported reference flash point values of these materials are now used to verify the proper operation of flash point test equipment in place of 1,4-dimethylbenzene.

Falls resulting from slips on walkway surfaces are a significant source of injury in society. To measure friction between the floor and the shoe, various types of tribometers and ASTM standards have been developed to assess walkway slip-resistance with the goal of improving pedestrian safety. The purpose of this study was to determine the repeatability and bias of the PIAST and VIT tribometers under both dry and wet conditions. Both devices were tested on an AMTI force platform over a wide range of angles. Bias was assessed by comparing the tribometer slip resistance reading to the actual Fx/Fz ratio measured by the force plate, while reliability was established by evaluating the ability of the tribometers to reproduce Fx, Fz, and the Fx/Fz ratio. Both tribometers demonstrated high degrees of bias and repeatability under both wet and dry conditions; however, each measured different slip-resistance values for the same surface. Further study should be directed at establishing which tribometer best simulates initial foot contact during gait with respect to measuring slip resistance.

This paper describes ultrasonic transmission techniques for sensor signals transmitted through water-filled pilot pipes for underground microtunneling systems. Underwater ultrasonic waves are used for transmitting the orientation and location signals of a remote-controlled machine. We have investigated the relationship between ultrasonic transmission loss and frequency with propagation distance in water-filled pipes. Digital signals can be transmitted at 100 bps for more than 50 m in 80-mm-diameter steel pipes by using underwater ultrasonic pulse waves above 300 kHz. A compact prototype ultrasonic transmitter and receiver were developed, making it possible to transmit and receive 8-bit signals through flowing water in the pilot pipes by processing their signal waveforms. Field trials demonstrated a range of signal transmission of pitching angle data over a 40-m distance for an actual compact microtunneling system.

In North America, at present, no test procedure exists for certifying roofing systems under dynamic wind loads. To develop such a dynamic test procedure, the National Research Council of Canada (NRC) formed an industry-based consortium during 1994. The consortium is known as the Special Interest Group for Dynamic Evaluation of Roofing Systems (SIGDERS). This paper reports SIGDERS' progress on dynamicload cycle development. Wind tunnel investigations were carried out using two flexible roofing membranes: poly(vinyl chloride) (PVC) and ethylene propylene diene monomer (EPDM). Using the wind tunnel pressure records as source data and comparing the membrane responses of PVC with EPDM, SIGDERS developed a dynamic load cycle. With input from industries, building owners, and roofing associations, the developed load cycle has been generalized and extended to evaluate the ultimate strength of flexible membrane roofs. To validate the newly developed load cycle, several membrane roofing systems were investigated and then reported separately. The SIGDERS load cycle in a laboratory mimics failure modes similar to those observed in the field.

To reduce slips and falls there is a need for repeatable and reproducible measurement, under both field and laboratory conditions, of the slip resistance between pedestrian shoe bottoms and the surfaces involved in human locomotion. Improvement of repeatability (within laboratory) and reproducibility (between laboratories) of portable tribometer test results should be a goal of tribometer designers., This paper reviews the background of advances in friction-related knowledge applicable to improving the repeatability and reproducibility in walkway-safety tribometry. It explores the use of the scanning electron microscope and the coherent-light profilometer to define morphological differences between Neolite® Test Liner and Standard Leather test feet sanded with two different abrasive-paper grits and worn shoe-bottom surfaces composed of the same materials. The experimental method and results are discussed, as is the significance of the findings. Also discussed is the issue of abrasive-paper grit size and its effect on tribometric test results. The paper suggests directions for further research.

A technique using displacement field data to qualify mechanical tests for in-plane deformation is proposed. Contour lines of the displacement fields that result from applied forces in mechanical tests are used for quantitative analysis and graphical representation of quality of the mechanical testing system in the tests. This method can visually, directly, and sensitively detect loading problems, such as misalignment, existing in the tests. A theoretical analysis using a displacement contour map to describe quantitatively the effect of the misalignment in a uniaxial tension test is described in detail. A technique to obtain the displacement contour map from the displacement field data and on-line inspection of some test system misalignment is presented. Several examples, including an eccentric tension test, a tension test with inhomogeneous fixing of a specimen in the grips, and an Iosipescu composite shear test with various degrees and sources of misalignment are analyzed with this contour method.