bluuebunny/crossref_metadata_2025 huggingface dataset:
Charpy Transition Studies of an Embrittled AISI 8640 Lower Bainitic Steel
Authors: Rinnovatore JV , Lukens KF , Reinhold J , Mahon W
Published: May 2009

A study was performed of the effects of phosphorus and arsenic as embrittling agents on the Charpy impact behavior of resulfurized AISI 8640 steel. The steel was heat-treated to several bainitic and one martensitic condition with a wide range of strength levels. Charpy transition temperature curves were developed for each condition. SEM fractography was used to analyze the fracture behavior of the various heat-treated structures. The results show that AISI 8640 steel with high phosphorus and high arsenic was embrittled in the low-strength bainitic condition as well as in the high-strength martensitic condition. Embrittlement was evidenced by low Charpy impact energies, increased transition temperatures, and an intergranular fracture mode.
Numerical Analysis of Plasticity Effects in the Hole-Drilling Residual Stress Measurement
Authors: Beghini M , Bertini L , Raffaelli P
Published: May 2009

The aim of this work was to analyze the effect of plasticity on residual stress measurement when the through thickness center-hole technique is used. The study investigated the effect of the most important loading, measuring, and material parameters, i.e., the residual stress intensity, the ratio between the principal residual stresses, the orientation of the strain-gage rusette with reference to the residual stress principal directions, the yield strength, and the strain hardening characteristics of the material.

By means of a finite element simulation of the measurements, the errors that are usually produced by the direct use of ASTM E 837 (Test Method for Determining Residual Stresses by the Hole-Drilling Strain Gage Method) for the elaboration of the rosette strain gage readings was firstly determined by considering large enough ranges of the above-mentioned parameters to represent many conditions of practical concern. Afterwards it was shown that, at least within the limit of validity of the model, a considerable reduction of those errors can be obtained by using the proposed analytical procedure for elaborating the readings of a classical these elements strain-gage rosette.

Moreover, the use of a new type of rosette with four radially oriented strain gages was proposed which could lead to further improvement of the measurement accuracy in any considered condition.
Determination of Softening Kinetics in a Material by Measuring the Evolution of Hot Flow Stress
Authors: Field DP , Sample VM , Rader RS
Published: May 2009

A new technique for estimating the time and temperature-dependent softening response of a deformed material is proposed. The hot flow stress is measured at various intervals in a quasistatic softening experiment to determinse the kinetics of softening. A major advantage of the proposed technique is that a single specimen can be used to estimate the evolution of softening without having to cool and reheat the specimen for each measurement. High resolution strain measurement apparatus is used in the experiments, as minimizing strain is a critical requirement in property performing the measurement. Test control requires optimal performance from the servohydraulic system which must operate near its threshold for reliable information to be obtained. Experimental results indicate that age hardening response as well as recovery and recrystallization kinetics can be measured using this method.
Electrochemical Impedance Spectroscopy for Monitoring Coating Performance in Condensing Environments
Authors: Rosenberg HS , Syrett BC
Published: May 2009

A novel method is described for monitoring coating performance in the thin liquid films found in condensing environments, such as in the corrosive condensate found in flue gas desulfurization (FGD) systems. The method involves exposing coated metal panels to controlled environments, created by atomizing solutions of appropriate composition, in fog chambers. The fog deposits on the coated surface as a thin film that simulates the condensate formed in actual service. The performance of the coatings is monitored in situ by electrochemical impedance spectroscopy (EIS) during periods when the exposed coated surfaces are temporarily flooded with bulk solution having the same composition as the condensate. The method has been used to evaluate the effects of sixteen environmental factors on the performance of eight coatings currently used in FGD outlet ducts.
Proposed Test Method for Dynamic, Properties of Connections Assembled with Mechanical Fasteners
Authors: Dolan JD
Published: May 2009

A new test procedure for connections assembled with mechanical fasteners is presented. The procedure provides information on cyclic and dynamic characteristies that will allow the relative performance of connections manufactured with different materials to be directly compared. An equivalent energy elastic-perfectly plastic system is defined that allows comparison of initial stiffness, yield load, and ductility on an equivalent basis. The hysteretic and equivalent viscous damping are also determined to provide information on the energy dissipation characteristics of the connection. Adoption of this test procedure will provide information that will allow engineers and architects to evaluate the performance of competing materials with direct comparisons. It will also provide uniform data from which revisions to the model building codes and design specifications for each material can be made on an equivalent basis.
An Analysis of Creep and Shrinkage in Mortars
Authors: Taves LBS
Published: May 2009

This paper examines the subject of creep and shrinkage in mortars. Previous research has revolved around brickwork or blockwork piers. An experimental program was devised to measure the shrinkage and creep in mortarts alone, using a range of seven mortar mixes. Some of the findings confirm earlier research, but considerable additional information concerning creep and shrinkage in mortars has been obtained. Results indicate that the quantity of line in a mortar is related to shrinkage and creep: the richer the mortar is in lime, the higher the values for creep and the lower the values for shrinkage. The laboratory data add to existing knowledge of mortars and their properties.
Solvent-Free, Nuclear-Free Determination of Asphalt Content and Gradation of Hot-Mix Asphalt Concrete
Authors: Todres HA , Bhattacharja S
Published: May 2009

A new method of analyzing hot-mix asphalt concrete has been developed that involves the pyrolysis or burn-off of the asphalt cement in a furnace. The method is simple and rapid, providing both asphalt content and aggregate gradation within about 1 to 1½ h (substantial reductions in this time appear achievable). The method will permit elimination of solvent and nuclear techniques currently in use that have specific disadvantages and hazards. It can also be used, if desired, to supplement the nuclear gage, in which case burn-off will be used for gradation and the nuclear gage for asphalt content.

Methods of performing the test, taking and analyzing data, etc., are described. Results based on aggregates and an asphalt cement widely used in the Chicago area are presented in detail. Further research is under way, and the questions that remain to be answered for the method to be standardized for widespread use are listed.
Temperature Dependence of Dynamic Young's Modulus and Mechanical Damping in a Nextel Fiber-Reinforced Glass Composite
Authors: Wolfenden A , Gill JE , Chawla KK , Vaidya RU , Venkatesh R
Published: May 2009

The piezoelectric ultrasonic composite oscillator technique (PUCOT), was used to measure the temperature dependence of dynamic Young's modulus and damping for a ceramic matrix composite (CMC) consisting of N51A glass as the matrix and Nextel 480 continuous fibers (volume fraction 0.29) as the reinforcement. The temperature range covered was 20 to 462°C. It was found that the Young's modulus decreased linearly with temperature, at a relatively low rate, and that the damping followed the form exp(-H/kT), where the value of the effective activation energy H was 0.07 ± 0.02 eV/atom, k is Boltzmann's constant, and T is temperature in Kelvin. Possible interpretations for this value of H are discussed. The glass transition temperature of the glass was found to be about 500°C.
Comparison of Selected Properties of Barrier Textile Materials Used in Durable, Moisture Repellent Protective Clothing
Authors: Slaten BL , Shanley LA , Bellingar T
Published: May 2009

The needs of workers in hazardous environments are extremely varied. The choice of textile materials must be made on the basis of end use and critical characteristics needed for protection, comfort, and performance of the workers. The purpose of this study was to conduct a series of experiments in order to provide scientific data on the qualities and characteristics of several barrier textile massenals. These materials would be suitable for garments for off-shore oil riggers, pesticide applicators, forestry personnel, hazardous waste disposal workers, military personnel, skiers, hikers, and pilots. The following properties were evaluated: stiffness, drape, abrasion resistance, air permeability, water resistance, tear resistance, breaking force and elongation, oil repellency, and soil release. These data provide a range of information on various properties that users of fabrics for prosective clothing need to be aware of in the selection of fabrics for garments.
Compressibility Relations for Peat and Organic Soil
Authors: Gunaratne M , Stinnette P , Mullins AG , Kuo CL , Echelberger WF
Published: May 2009

A new technique is formulated to predict the ultimate settlement (primary and secondary) of normally consolidated organic soils on the basis of the organic content. Data from a large number of oedometer tests on samples collected from organic soil deposits in Central Florida exhibit a definitive relationship of ultimate settlement versus organic content. These laboratory test results are analyzed using the Gibson and Lo rheological model to develop expressions for primary and secondary compressibilities in terms of organic content and consolidation pressure. It is shown how the compressibility relations predicted by the authors' approach concur with extensive data collected by other researchers. The usefulness of the authors' analytical relations is displayed by showing how the expected ultimate settlement of an organic soil subjected to a given pressure increase can be computed readily by using them.
The Shape of Mechanical Hysteresis Loops for Metals Under Harmonic Loading
Authors: Bovsunovsky AP , Kratko AG
Published: May 2009

Previous experimental investigations (direct and indirect) on the shape of hysteresis loops have been carried out at stress amplitudes that exceeded the fatigue limit, that is, under conditions of active fatigue damage.

The experimental procedure used in the present research provides higher resolution than the earlier work and permits investigations at stress amplitudes below the fatigue limit. For the objective estimation of the shape of a hysteresis loop several criteria were proposed and the most effective criterion was chosen.

Metals with distinctly different levels of damping were tested. The tests were carried out at resonance bending frequencies. As a result of both analytical and experimental investigations it was shown that hysteresis loops for metals with a high level (Cu-Al alloy, maximum decrement 1.4 × 10−1) and a moderate level (EI-961 alloy steel, maximum decrement 8.7 × 10−3) of damping are close to elliptic in shape. The error of the experimental procedure was too great for testing an alloy with a low level of damping (PT-5 titanium alloy, maximum decrement 1.5 × 10−3). The tests on the PT-5 alloy allowed the investigators to ascertain only that the loop's shape in this case is more elliptic than crescent-shaped or parabolic.
Design and Performance of an Automated Test Facility for Hot-Compression Testing
Authors: Cheng YW , Filla BJ , Tobler RL
Published: May 2009

The design of an apparatus for hot-deformation testing of materials is described, and experimental results demonstrating successful performance are presented. The apparatus is used to uniaxially compress small steel cylinders between two ceramic platens in an evacuated test chamber at high temperatures. Components of the system include a 100 kN servohydraulic test machine, a compact radiant furnace and programmable temperature controller, a microcomputer for executing mechanical strikes, and a digital storage oscilloscope for high-speed data acquisition. In the initial experiments described here, steel specimens 10 mm in diameter and 15 mm high are compressed at strain rates up to 50/s and maximum test temperatures up to 1200°C. Attractive features of the apparatus include its relatively low cost, compact size, and capability for high strain rates.
A Note on One-Point-Bend Impact Fracture Experiments with Curved Specimens
Authors: Giovanola JH , Klopp RW , Kirkpatrick SW
Published: May 2009

We describe an extension of the one-point-bend impact test for measuring dynamic initiation fracture toughnesses with curved specimens cut from the wall of tubes. We present the impact response curve for a specific geometry of curved specimen. We validate the extension of the test procedure and data reduction method by comparing (1) the measured dynamic initiation toughness with data obtained with rectangular specimens cut from the wall of the same 300M tube and (2) the stress-intensity history measured in the experiment with that calculated in a dynamic finite element simulation of the test. For both comparisons, the agreement is excellent.
Interlaboratory Comparison of the ASTM Standard Test Methods for Water Vapor Transmission of Materials (E 96-95)
Authors: Kumaran MK
Published: May 2009

An interlaboratory comparison was initiated by the ASTM C16 Committee on Thermal Insulation to determine the precision of the test method prescribed by ASTM Standard Test Methods for Water Vapor Transmission of Materials (E 96-95). Expanded polystyrene board was chosen as the test material. Nine laboratories completed the measurements according to the dry cup and the wet cup procedures prescribed by the standard. Statistical analyses of the data resulted in the following precision statement for the water vapor permeability:

Dry cup method:

Permeability of material = 3.1E-12 kg m−1 s−1 Pa−1

Repeatability standard deviation (within a laboratory) = 1.6E-1.3 kg m−1 s−1 Pa−1

Reproducibility standard deviation (between laboratories) = 4.7E-13 kg m−1 s−1 Pa−1

Wet cup method:

Permeability of material = 3.4E-12 kg m−1 s−1 Pa−1

Repeatability standard deviation (within a laboratory) = 1.7E-13 kg m−1 s−1 Pa−1

Reproducibility standard deviation (between laboratories) = 4.1E-13 kg m−1 s−1 Pa−1

A specific procedure was uniformly used to analyze the data and to calculate the permeability of the test material from the raw data provided by the participating laboratories. Corrections were made for the resistances offered by the still air layer inside the cup and by the specimen surfaces and for the edge masking details.
Cumulative Fatigue Damage Mechanisms and Quantifying Parameters: A Literature Review
Authors: Yang L , Fatemi A
Published: May 2009

Cumulative fatigue damage analysis plays an important role in fatigue life prediction of components and structures which are subjected to field loading histories. Understanding of cumulative damage mechanisms is essential since it provides the necessary physical bases for modeling the cumulative damage process. A damage measure that can reflect and quantify the real damage state the material undergoes is also a key issue for successful modeling of cumulative fatigue damage. This review paper provides a comprehensive overview of research activities highlighting the recent findings and progress on phenomenological observations and mechanisms, as well as quantification measures of cumulative fatigue damage. Depending on the definition of failure or the characteristics of failure experienced in a material, the effectiveness of a damage parameter could vary from case to case. Many damage parameters have been proposed and many of them are in use. Those to be reviewed are sorted into categories of metallurgical parameters, surface crack quantifications, mechanical measures, and physical parameters. Early studies on cumulative damage mechanisms and quantifying measures are reviewed only briefly, since they have been covered in the existing literature.
Bearing Strength of White Oak Pegs in Red Oak and Douglas Fir Timbers
Authors: Church JR , Tew BW
Published: May 2009

The safe and consistent design of connections in modern timber-framed structures requires an understanding of the structural properties of the timbers as well as the bearing and bending strength limitations of the where oak pegs used in construction. This paper addresses the bearing strength of white oak dowels in both red oak and Douglas fir timbers. The effects of peg grain orientation, peg diameter, peg-hole clearance, specimen grain orientation, and specimen wood species were studied. A modified bearing strength test was developed to eliminate localized crushing of the white oak dowel by the test machine. Bearing strength tests were performed on 183 wood specimens. The bearing strength of pegged connections was found to be relatively insensitive to the factors investigated and lower than bearing strengths using similar steel fasteners for all test configurations.
A Statistical Evaluation of the Staircase and the ArcSin√P Methods for Determining the Fatigue Limit
Authors: Braam JJ , van der Zwaag S
Published: May 2009

A critical evaluation of the statistics of the fatigue limit as determined by the staircase method and the ArcSin√P transformation is presented. The effects of the testing conditions on the accuracy of results obtained are examined. A modified analysis of the data obtained via the staircase method is presented which yields a reliable estimate of the standard deviation of the fatigue limit, even for small sample sets.
A Probabilistic Study of the Influence of Hanger Alignment on the Reliability of Refractory Furnace Roof Anchors
Authors: Segall AE , Shelleman DL , Pan MJ , Landy RA , Nelson BR
Published: May 2009

A probabilistic fracture methodology was applied to an analysis of refractory anchors used for furnace roof construction. Initially, strength date were obtained from modulus of rupture (MOR) specimens machined from refractory anchors composed of three different materials. For all of the fracture strength tests, the tension side of the MOR specimens was always taken from the as-pressed/fired surface of a sectioned anchor to ensure that the resulting data accurately reflected the strength of the as-used materials. The resulting Weibull data were then used in conjunction with a finite-element stress analysis and probabilistic reliability assessment to determine the influence of the alignment of the metal hangers used to secure the anchors. While all three materials exhibited a vulnerability to brittle fracture under the applied loads, the risk was clearly the highest when the metal hanger was not properly aligned and loads therefore not properly distributed over the entire contact region.
Evaluation of Modified Weibull Distribution for Describing the Strength of Ceramic Fibers and Whiskers with Varying Diameters
Authors: Zhu YT , Butt DP , Taylor ST , Lowe TC
Published: May 2009

A modified Weibull distribution is evaluated for characterizing the statistical strength of ceramic fibers and whiskers with varying diameters from filament to filament. Many commercial ceramic fibers and whiskers have a significant range of diameters. A single-modal Weibull distribution is found inadequate to describe the statistical strength of these fibers and whiskers because of the effect of fiber diameter variation on strength. Procedures for extracting distribution parameters for the modified Weibull distribution from experimental data are presented. Comparison of the modified Weibull distribution with the single-modal Weibull distribution is made for the strength data from Nicalon fibers, Nextel (Al2O3) fibers, hydridopolysilzazlane (HPZ) Si-N-C-O fibers, Al2O3 whiskers, Si3N4 whiskers, and SiC whiskers. Due to its ability to account for the diameter effect on strength, the modified Weibull distribution can yield a more accurate β value than the single-modal Weibull distribution. The Modified Weibull distribution is shown to fit experimental data well and is recommended for characterizing the strength of ceramic fibers and whiskers, the diameters of which vary from filament to filament.
Impact Force Comparison of Polymers: Molded-Notch Versus Cut-Notch Using the ASTM D 256 Izod Impact Test Method
Authors: Schaeffer SL , Johnson RL , Lewis WB
Published: May 2009

This study was conducted to compare the Izod impact values of injection molded polymer specimens with molded- versus machined-notch specimens. The ASTM D 256 notched Izod impact test was used to measure the impact values of both specimen types. The impact values were compared to determine if differences exist between specimens that had the molded notch and specimens that had the cut notch. Post-molding machining of the notch is the procedure required by ASTM D 256-93a, Standard Test Methods for Determining the Pendulum Impact Resistance of Notched Specimens of Plastics.

Specimens from six different polymer families were produced using the reciprocating-screw injection molding process and a two-cavity mold. The polymers tested were poly(acrylonitrile-butadiene-styrene) (ABS), high-impact polystyrene (HIPS), poly(methyl methacrylate) (PMMA), polyamide (PA), polypropylene (PP), and polycarbonate (PC).

It was found that five of the six polymers had significantly higher impact values in the molded-notch condition. Impact values for polypropylene were as much as 300% greater in the molded-notch condition. Testing of polycarbonate resulted in a bimodal distribution among cut-notch specimens; however, the molded-notch specimens fractured as significantly higher values. Although the mean impact value for molded-notch specimens of ABS was slightly higher than that of the cut-notch specimens, it was found that there was no statistically significant difference for ABS.

It was found that the geometries of the molded notches were not uniform among the different materials, even though they were produced from the same mold, Molding of the materials resulted in slightly different notch geometries when inspected at × 50 magnification.
A Method of Finding the Effective Length of the Specimen Used in the Hot Torsion Test and Recommendations on Geometry of the Test Specimen
Authors: Khoddam S , Lam YC , Thomson PF
Published: May 2009

The length of the specimen in the hot torsion test is an important geometrical parameter and affects all calculations based on the results of the hot torsion test. To lessen the error in the analysis of the specimen due to deformation outside the gage length, an effective length may be used. Improvement in the accuracy of analyses of the hot torsion test is also important to inverse numerical solutions because the initial guess needed to start an inverse numerical solution may be obtained using an analytical solution. Determination of the effective length of a specimen is explained and illustrated for two different constitutive relationships. Recommendations on the choice of the hot torsion test specimen are given. It is shown that neglect of deformation outside the gage section may result in the flow curve obtained by using the hot torsion test results being lower than the flow curve achieved by other tests.
Studies of the Specific Gravity of Some Indian Coal Ashes
Authors: Pandian NS , Rajasekhar C , Sridharan A
Published: May 2009

One of the major problems faced by coal based thermal power stations is handling and disposal of ash. Among the various uses of fly ash, the major quantity of ash produced is used in geotechnical engineering applications such as construction of embankments, as a backfill material, etc. The generally low specific gravity of fly ash resulting in low unit weight as compared to soils is an attractive property for its use in geotechnical applications. In general, specific gravity of coal ash lies around 2.0 but can vary to a large extent (1.6 to 3.1). The variation of specific gravity of coal ash is due to the combination of various factors like gradation, particle shape, and chemical composition. Since specific gravity is an important physical property, it has been studied in depth for three Indian coal ashes and reported in this paper.
Measurement of Crack Arrest Fracture Toughness of a Ship Steel Plate
Authors: Pussegoda LN , Malik L , Morrison J
Published: May 2009

Two types of full thickness compact crack arrest (CCA) specimens have been used to characterize the crack arrest toughness of a 15.5-mm-thick ship plate steel in both the L-T and T-L orientations. One was a modified version of that used in ASTM Standard E 1221, and the other was based on the proposed procedure of Crosley and Ripling [1] for non-plane strain testing. The latter specimens employed a strain age embrittled chevron notch as the crack starter. The testing was performed over the temperature range from −40° (the nil-ductility transition temperature (NDTT) of the steel) up to −5°C. None of the results from the ASTM E 1221 type specimens met the validity requirements of the ASTM procedure. Even though they had the largest dimensions allowed in the test specification, the limited thickness of these specimens meant that they were too small for valid plane strain testing. In the non-plane strain test procedure, the in-plane dimensions are scaled to the expected crack arrest toughness at the test temperature, and the main qualifying requirement is for the crack to be arrested at a point in the specimen lying within certain defined limits. Although difficulties were encountered with variability in run/arrest behavior, this specimen gave some useful crack arrest toughness data for this steel, particularly with regard to the relatively high values obtained when testing near the top of the test temperature range. The effectiveness of the crack starter technique used in both type of specimens is also discussed, as well as possible modifications for future tests.
Adapting Superpave Technology to Design of Hot Recycled Mixes
Authors: Foo KY , Kandhal PS
Published: May 2009

Mix design procedures for recycled asphalt pavements require the selection of virgin asphalt or recycling agent and recycled hot mix asphalt (HMA) mix design. This research project was undertaken (a) to develop a procedure for selecting the performance grade (PG) of virgin asphalt binder based on the Superpave PG grading system and (b) to design hot recycled mix using Superpave technology. Blending charts were constructed and used to select the PG grade of virgin asphalt binder for mixes with 0, 20, 30, and 40 percent of recycled asphalt pavement material (RAP). Superpave volumetric mix design were conducted on mixes with 0, 20, 30, and 40 percent RAP. Evaluation of the volumetric properties of these mixes has indicated that the Superpave volumetric mix design procedures can be adapted to design recycled HMA mixtures with minimal modification.
Ultimate Strength of Resistance Spot Welds Subjected to Combined Tension and Shear
Authors: Lee YL , Wehner TJ , Lu M-W , Morrissett TW , Pakalnins E
Published: May 2009

A new test setup and data concerning the ultimate strength behavior of resistance spot welds in a mild strength steel subjected to combined tension and shear loads are presented. A test plan based on a design of experiments (DOE) with three design factors (coupon width, coupon length, and nugget diameter) was conducted to investigate the influence of the factors on the ultimate strength of the resistance spot welds under different loading angles. In this program, test loads were monotonically applied to the resistance spot weld at a specific angle until the load carrying capacity of the resistance spot weld was exceeded. It was found that the nugget diameter contributes the most (more than 70%) to the total variation of the recorded ultimate strength and that the coupon length has little effect. A deterministic ultimate strength model was proposed to take into account the interaction of in-plane shear and 90° out-of-plane tensile loading in the resistance spot weld. A reliability model was also demonstrated to evaluate the ultimate strength of a single resistance spot weld.
Fatigue Crack Propagation Threshold: What Is It and How Is It Measured?
Authors: Marci G
Published: May 2009

The present understanding of a “fatigue crack propagation threshold” implies a nonpropagation condition of a fatigue crack and in addition some property usable for design (similar to the “fatigue strength” in Wöhler-type fatigue). The first task is the definition of a nonpropagation condition, to be denoted as ΔKth. In the next step, a “property usable for FCP design” is defined which is a nonpropagation condition characterized as the largest amplitude ΔK which does not produce fatigue crack propagation rates larger than 10−7 mm/cycle under any cyclic loading condition. The parameter so defined is termed the threshold and denoted as ΔKT. Every ΔKT is a nonpropagation condition, but not every nonpropagation is a threshold value ΔKT. The existence of such a parameter ΔKT has to be proven by special, extensive tests, which are presented with the respective results. Once the proof related to ΔKT has been furnished, measurement of ΔKT is done by the simplest technique available. Nonpropagation conditions ΔKT and threshold ΔKT data for Al- and Ti-alloys are presented. Furthermore, test procedures and specimen preparations are outlined.
A Method of Fatigue Testing of Concrete Highway Joint Sealants in Shear
Authors: Rogers AD , Lee-Sullivan P , Bremner T
Published: May 2009

A simple test method has been developed to simulate the movement of a typical transverse contraction joint used in joining concrete highway pavement sections constructed without dowels. The test apparatus enables the effects of temperature, joint size, and pavement deflection on the performance of the sealant to be evaluated in joints subjected to large differential movements. Testing at temperatures below and above ambient is possible by incorporating an environmental chamber. A detailed description of the fatigue test apparatus and specimen preparation is provided. Typical results of tests conducted at room temperature, −40°C, and +40°C are presented as well as the results of thermal cycling.
Ultrasonic Wave Measurements of Elastic Moduli E, G, and μ for Product Development and Design Calculations
Authors: Papadakis EP
Published: May 2009

A technique is presented to measure the isotropic elastic constants of small specimens using instrumentation designed for the ultrasonic measurement of thickness. Specimens as small as 5 mm × 5 mm × 0.5 mm can be measured. Shape is not critical as long as the major faces are plane and parallel. Young's modulus E, the shear (stiffness) modulus G, and Poisson's ratio μ are calculated from measurements of density and ultrasonic shear and longitudinal wave velocities. Samples of automotive valve train materials and of brake drum materials were machined from components, measured, and analyzed. Specimens included gray cast iron during stages of a development process, chill cast iron, hardened cast iron, low alloy steel, tool steel, stainless steel, a nickel-based superalloy, and a powder metal alloy. The magnitudes of the measured values of the elastic constants are reasonable when compared with published values available for some materials. The measurement error for each of the constants is estimated to be less than 1%.

Moduli determined by this method can be used in finite element analysis to improve design. When material properties are different near the surface, elastic constants characteristic of the surface layer can be measured. The development of new fabrication, alloying, or treatment processes can be monitored to assure the production of the desired material properties if modulus or some property correlated with modulus is desired. When the material properties are a function of the fabrication process, e.g., small castings or powder metal components, reliable elastic constants can be found. “Small” is relative to the practicality of cutting tension bars and torsion rings from parts, so “Small” may seem rather large in some cases. Metal stampings can be analyzed in a through-thickness direction. The elastic properties of nonmetallics—ceramics, glasses, and plastics—can also be measured.
On the Determination of Fracture Energy Using the Peel Test
Authors: Moidu AK , Sinclair AN , Spelt JK
Published: May 2009

This paper presents an improved model for the prediction of the adherend plastic dissipation in the peel test, thereby allowing the determination of the critical fracture eaergy. The model, which is based on earlier work, takes into account the effects of adhesive shear stresses, and a bilinear stress-strain response for the flexible adherend. Treating the flexible adherend as a beam-on-elastic foundation, expressions for the normal and shear foundation constants due to the compliance at the root of the adherend under elastic-plastic loading are derived using the deformation theory of plasticity. Application of the model to experimental peel data shows that it gives an improved estimate of the critical fracture energy.
Piezo-Actuated Microtensile Test Apparatus
Authors: Read DT
Published: May 2009

The design and performance of a microtensile test device designed for measuring the mechanical properties of thin films are reported. The moving grip is cantilevered to avoid friction. Piezoelectric actuation allows precise control of the applied tension. Force is measured indirectly using an eddy-current sensor near a flexible measuring beam, and grip displacement is measured using two similar displacement sensors. The apparatus is constructed for use with specially designed specimen assemblies in which the thin film to be tested is suspended across a silicon frame. The apparatus is rigid enough that the frames can be cut without applying tension to the thin-film tensile specimen. The tester is run in closed-loop control through a laboratory computer, which records force, displacement, and other parameters 5 times per second. Key capabilities are: stroke, 50 μm; maximum force, 1 N; minimum cycle time, 2 s; displacement resolution, ± 20 nm; and force resolution, ± 200 μN.
Influence of Corrosion on the Fatigue Properties of Al 7075-T6
Authors: Du ML , Chiang FP , Kagwade SV , Clayton CR
Published: May 2009

Chloride ion attack on Al 7075-T6 in aqueous hydrochloric acid leads to localized corrosion and subsequent initiation of fatigue cracks on the surface. Pitting is observed when the specimen is exposed to a corrosive environment. Microcracks, voids, extrusions, and intrusions are then formed during the fatigue process. From a global viewpoint, all of the corrosion and fatigue damage appears to be randomly oriented, resulting in a change in the surface roughness. The Laser Speckle Sensor technique is used to detect the minute surface texture change, associated with the damage caused by corrosion and fatigue. Nonuniform surface roughness is observed due to corrosion. The corrosion pits tend to coalesce along the rolling direction. The change in surface roughness is significant around the crack tip during the fatigue process. As a result there are synergistic activities; the surface roughness caused by corrosion and fatigue leads to crack initiation, and the crack growth further increases surface roughness.
Investigation of Welding Effect on Rebars Using Neural Networks
Authors: Mo YL , Koan KJ
Published: May 2009

Typically material modeling has involved the development of mathematical models of material behavior derived from human observation of experimental data. An alternative procedure, discussed in this paper, is to use of computation and knowledge representation paradigm, called a neural network, to model material behavior. The main benefits in using a neural network approach are that all behavior can be represented within the unified environment of a neural network and that the network is built directly from experimental data using the self-organizing capabilities of the neural network, meaning that the network is presented with the experimental data and learns the relationships between stresses and Strains. Such a modeling strategy has important implications for modeling the behavior of complex materials. In this paper, the mechanical behavior of rebars affected by welds is modeled with a back-propagation neural network. The results of using networks to study the effect of welds on rebars look very promising.
Establishing Mechanical Property Allowables for Metals
Authors: McLellan DL , McLellan MM
Published: May 2009

Allowable mechanical property development for structural design of metallic aerospace vehicles requires an approved method for statistically analyzing empirical test data. When sufficient test data have been analyzed, the resulting allowables are presented to members of the metal-producing industry, airframers, and regulatory agencies for approval. Upon approval, these properties are published by the government for unrestricted use. However, even though sufficient data are made available, the analysis process is not always straightforward. When data do not conform to acceptable distributions, the process cannot be completed: The purpose of this paper is to promote a better understanding of this type of problem, and a possible rationale to overcome such events without increasing the amount of test data.
Design and Development of a High-Speed Bearing Test Apparatus
Authors: Kim K
Published: May 2009

A bearing test apparatus was developed to test high-speed rolling element bearings such as the main-shaft bearings of gas turbine engines. The apparatus design was focused on the evaluation of the lubrication characteristics of bearings in an environment similar to that of gas turbine engines, such as the same bearing support structure, the lubrication method, the squeeze film damper, and the operating conditions. Using the module design of the system, both ball and roller bearings can be tested, and the bearings can be tested up to 42 000 rpm and 19 600 N axial and 1960 N radial load. The testing was successively carried out with the bearings up to 30 000 rpm.
Eddy Current Decay and Resistivity Measurements on Longitudinally Grooved High-Purity Aluminum Bars
Authors: Gillenwater MW , Hartwig KT , Hua CY
Published: May 2009

The eddy current decay (ECD) method for determining electrical resistivity uses a relationship between the time constant of magnetic flux diffusion and resistivity. This method is shown to be valid for determining the resistivity of solid high-purity aluminum cylinders with eight equally spaced longitudinal grooves machined into the surface. The effects of changes in groove dimensions for a 25.4-mm-diameter, superconducting magnetic energy storage (SMES) conductor stabilizer are reported. Observations of machining, heat treatment, and material inhomogeneity effects are discussed. It is found that the ECD time constant is dependent primarily on groove depth and that groove width has only a minor influence. An empirical equation relating groove dimensions with the time constant and with resistivity is presented.
Variation of Resilient Modulus of Aggregate Base and Its Influence on Pavement Performance
Authors: Tian P , Zaman MM , Laguros JG
Published: May 2009

Resilient modulus (MR), which properly characterizes the load-deformation response of pavement materials under traffic loading, is evaluated. The MR variations due to three different gradations and three different moisture contents were investigated for Richard Spur (RS) aggregate, which is commonly used in Oklahoma as the base material of roadway pavements. The three gradations selected are finer limit, median, and coarser limit, as specified by the Oklahoma Department of Transportation (ODOT) for Type A aggregate. The three moisture contents selected are optimum moisture content (OMC), 2% below and 2% above the OMC. Six duplicate MR tests under identical conditions were conducted for each case by using the AASHTO designation T 294-94. The variabilities of MR values due to the three different gradations and three different moisture contents were found to be within 10 to 50% and 10 to 20%, respectively. Furthermore, the material model coefficients K1 and K2 were calculated, and a multiple linear regression model for predicting the MR values of the aggregate was established in this study. Finally, the effect of MR variation on pavement performance was demonstrated by using one pavement design example.
Pin-on-Disk Corrosion-Wear Test
Authors: Friedersdorf FJ , Holcomb GR
Published: May 2009

An electrochemical pin-on-disk corrosion-wear apparatus was developed at the Albany Research Center of the U.S. Department of Energy. The instrument was qualified on a low-alloy T1 tool steel [ASTM A 514] and a 304 stainless steel (Type 304). The apparatus incorporates simple specimen and counterface geometry and is instrumented for simultaneous corrosion and wear testing. The electrochemical and wear parameters of potential, current, charge, sliding speed, frictional force, and normal acceleration can be continuously displayed and recorded. After a break-in period, the electrochemical pin-on-disk produced constant wear rates independent of path length for both ASTM A 514 steel and 304 stainless steel. Results for 304 stainless steel in sulfate solutions show that abrasive wear causes the corrosion potential to shift by 0.4 V in the active direction and the passive current density to increase by three orders of magnitude, compound with the condition of no wear. Current density was a linear function of the sliding speed at a constant applied anodic potential. The open circuit corrosion potential exhibits a decay function behavior with respect to the sliding speed. Volume loss and corrosion measurements showed that mechanical removal of material was responsible for 95% of the corrosion-wear losses for 304 stainless steel. Continual corrosion exposure, however, increased the mechanical removal of material by 35 to 48%.
Stress-State Permeability Relationships for Clays with Coarse Fraction
Authors: Pandian NS , Narasimha Raju PSR , Nagaraj TS
Published: May 2009

In standard laboratory consolidation tests, only the fraction of soil passing through a particular size of the sieve, called the matrix material, is used. This size is usually restricted to 110 of the height of the consolidation ring. Particles larger than this size that are removed before the test may consist of gravel, fragments of sock, or other coarse materials. Hence, it is not possible to estimate the compressibility and permeability of the total material based on the compressibility and permeability behavior obtained from laboratory consolidation tests on the matrix material. In the present investigation an attempt has been made to estimate the compressibility and permeability behavior of the total material based on the compressibility and permeability behavior of the matrix material. The results indicate that the presence of coarse particles will reduce the compressibility of the soil in proportion to the coarse fraction present in the whole soil and will not affect the permeability of the soil for the range investigated. If the coarse fraction exceeds the limiting percentage, the void ratiovertical effective stress path will also start to deviate from the predicted path. An expression has been developed to estimate approximately the deviating pressure, and it is found to depend on the soil type as well as the percent clay fraction.
Adhesively Bonded Strain Gages for Extended Use at 315°C on Polymers
Authors: Rabzak C , Pereira JM , Roberts GD
Published: May 2009

A unique strain gage and adhesive system was developed for mechanical property measurement of polymers and polymer composites at elevated temperatures. This system overcomes some of the problems encountered in using commercial strain gages and adhesives. An important limitation with typical commercial strain gage adhesives is that they require a post-cure at temperatures substantially higher than the maximum test temperature. The exposure of the specimen to this temperature may affect subsequent results, and in some cases may be higher than the glass transition temperature of the polymer. In addition, while typical commercial strain gages can be used for short times at temperatures up to 370°C, their long-term use is limited to 230°C. This precludes their use for testing some high-temperature polyimides near their maximum-temperature capability. The system that was developed consists of a nonencapsulated, unbacked gage grid that is bonded directly to the polymer using a specially formulated adhesive. The gage is applied after the specimen has been cured, but prior to the normal post-cure cycle. The adhesive was formulated to cure under the specimen post-cure conditions. Special handling, mounting, and electrical connection procedures were developed, and a fixture was designed to calibrate each strain gage after application on the specimen. A variety of tests was conducted to determine the performance characteristics of the gages at elevated temperatures on PMR-15 neat resin and titanium specimens. These tests included static tension, thermal exposure, and creep tests. The gage and adhesive system performed within normal strain gage specifications at 315°C under these conditions.
A Procedure for Fracture Toughness Testing Using a Chevron-Notched Crack-Arrest Specimen
Authors: Bonenberger RJ , Dally JW , Fourney WL
Published: May 2009

A new chevron-notched crack-arrest (CNCA) specimen has been developed for determining the fracture toughness of metals in a more cost-effective manner. The specimen is a hybrid design that incorporates features from the standard KIc and KIc specimens. Details of the specimen geometry and associated test procedures are described. Strain gages record the stress state in the specimen, and a clip gage measures the crack mouth opening displacement. The method for extracting arrest and initiation toughness from the measured data is presented. Fracture experiments using the CNCA specimen ware conducted to determine Ka and Kc for A533-B reactor grade steel at 23°C. The Ka and Kc results from this study were consistent with similar data established for the same material by other-researchers. A fractographic analysis identified cleavage as the dominant failure mode during crack propagation, with a conversion to ductile tearing just before arrest.
A Strategy for Mimicking Voids in Historic Masonry
Authors: Sickels-Taves LB , Sheehan MS
Published: May 2009

This paper examines the issue of voids in historic masonry. Tabby, an historic, concrete-like substance composed of lime, sand, oyster shell, and water, was selected as the masonry to examine. This study had a two-fold purpose: to develop a strategy for mimicking voids using tabby as a test bed for employment in other masonry contexts, and to replicate the appearance of historic tabby while eliminating the liabilities associated with opea voids in the Masonry matrix. To this end, glass beads were introduced into the tabby mix. The desired result was a product that appeared to have voids, but in fact did not. Test results indicated that the visual appearance of original tabby is mimicked due to the translucent quality of glass, and the structural instability factor is reduced by effectively filling the voids without altering the physical characteristics or producing additional liabilities.