bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coarse Aggregate Shape and Size Properties Using a New Image Analyzer
Authors: Rao C , Tutumluer E , Stefanski JA 
Published: February 2009

Abstract
Automation of coarse aggregate shape and size determination using image analysis techniques is described in this paper as an alternative approach to current manual and time-consuming test procedures. A new image analyzer system, referred to as the University of Illinois Aggregate Image Analyzer (UI-AIA), uses a three-camera setup to view each aggregate particle from three orthogonal directions. Both volume (and therefore weight) and shape factors can be determined precisely for each particle based on sound image analysis and geometric principles. In addition, the grain size distribution of an aggregate sample can be determined. Tests conducted on ten aggregate samples were used to evaluate the perfor mance of the laboratory prototype UI-AIA in automating the standard ASTM D 4791-99, Standard Test Method for Flat Particles, Elongated Particles, or Flat and Elongated Particles in Coarse Aggregate and ASTM C 136-96a, Standard Method of Test for Sieve Analysis of Fine and Coarse Aggregates. The accuracy and repeatability of the imaging technique were evaluated for the computed aggregate volumes, percent by weight flat and elongated ratios, and gradation curves. Results from the new UI-AIA were in very good agreement with the manual measurements performed in two separate laboratories to ensure their exactness. The UI-AIA has scope for further modifications and improvements.
Homogeneous Unit Delineation for Interpreting Dynamic Cone Penetrometer Measurements
Authors: Divinsky M , Livneh M 
Published: February 2009

AbstractThe current investigation is concerned with the homogeneous unit delineation procedure for pavements and subgrade soils using dynamic cone penetrometer (DCP) data as widely employed in the evaluation of the pavement structure components. For the purposes of highlighting statistically homogeneous groups of the measurements along the registered DCP data profile, the conventional (AASHTO) cumulative difference approach procedure has been applied to the profile of DCP characteristic values. The delineating procedure shows significant sensitivity to the existing change in the mean value levels of the DCP measurements. Analysis of the procedure application to the profile of the DCP characteristic values (Penetration Index) and to the original number-of-blows values recorded during the DCP test has been done. The approach simplifies application of the AASHTO delineating procedure when using the original number-of-blows data during the DCP test. The approach produces the boundary position indication for the specific DCP characteristic profiles. Penetration characteristics for the delineated units have been used for predicting the California Bearing Ratio (CBR) parameter. The approach has been supported by Microsoft Excel spreadsheets for the semi-automated analysis of the DCP data and application of the delineation procedure.
Synthesis of Methane Hydrate in an Unconsolidated Medium
Authors: Siriwardane HJ , Smith DH 
Published: February 2009

Abstract
Under certain conditions of low temperature and high pressure, mixtures of small gas molecules and water form crystalline, ice-like compounds called clathrate hydrates. It is believed that large quantities of natural deposits of methane hydrate are formed in unconsolidated media from natural gas and water. Development of recovery techniques for this potential natural gas resource requires comprehensive laboratory investigations of engineering properties, which in turn require a capability for reproducibly synthesizing methane hydrate in unconsolidated matrix materials. This paper presents a procedure for synthesizing methane hydrate in an unconsolidated sand matrix. Results of dissociation experiments indicate that the samples prepared according to this procedure are relatively homogeneous and suitable for use in investigations of mechanical and other properties. The methane hydrate content and porosity of the samples can be controlled in the procedure developed.
Simulation of Irradiation Effects in Reactor Pressure Vessel Steels: the Reactor for Virtual Experiments (REVE) Project
Authors: Jumel S , Domain C , Ruste J , Van Duysen J-C , Becquart C , Legris A , Pareige P , Barbu A , Van Walle E , Chaouadi R , Hou M , Odette GR , Stoller RE , Wirth BD 
Published: February 2009

Abstract
Components of commercial nuclear reactors are subjected to neutron bombardments that can modify their mechanical properties. Prediction of in-service and post-service behaviors generally requires irradiation in so-called “test reactors” as well as subsequent mechanical testing in specialized hot cell facilities. However, the use of these research facilities is becoming more problematic, in particular due to increasing costs and decreasing availability. One way of partially mitigating these problems is to complement the empirical approach by developing tools for numerical simulation of irradiation effects in materials. The development of such tools is clearly an ambitious task that will require a long-term international collaborative effort.
In this paper, we present an outline of the Reactor for Virtual Experiments (REVE) project, a collaborative European and American effort aimed at developing quantitative simulations of irradiation effects in materials. The first demonstration phase of REVE will target embrittlement of reactor pressure vessel (RPV) steels, since the effects and mechanisms of irradiation damage in this material are relatively well understood and many modeling tools have been developed or are under development in this field. As for any experiment, the input variables of the REVE simulation will be the neutron spectrum, time and temperature of irradiation, the alloy composition (e.g., Cu, Ni, Mn, and C contents) and microstructure and the unirradiated mechanical properties. The simulations will predict the irradiation-induced increases of yield stress and Charpy transition temperature as well as the decrease of toughness due to the concomitant evolution of the microstructure.
Model-Fitting the Master Curves of the Dynamic Shear Rheometer Data to Extract a Rut-controlling Term for Asphalt Pavements
Authors: Shenoy A 
Published: February 2009

Abstract
The dynamic shear rheometer is currently being used by the asphalt community for determination of the viscoelastic properties of asphalts following the recommendations of the Strategic Highway Research Program. The Superpave specification parameter |G*|/sinδ was identified as the term to be used for high temperature performance grading of paving asphalts in rating the binders for their rutting resistance. However, this term was found to be inadequate in describing the rutting performance of certain binders, particularly, the polymer-modified ones. A refinement of the Superpave specification parameter for performance grading of asphalt led to the evolution of the term |G*|/(1 − (1/tanδ sinδ)). This performance-based specification term was shown to be more sensitive to the variations in the phase angle δ than the Superpave specification parameter and thus was found to describe the unrecovered strain in the binders more accurately, especially in the case of polymer-modified asphalts.
The high specification temperature THS (°C) is specified as the temperature at which the term |G*|/(1 − (1/tanδ sinδ)) takes a value of 1 kPa for the original unaged binder and a value of 2.2 kPa for the RTFOT aged binder. Though this refinement of the Superpave specification parameter has led to a better discrimination between the rutting resistances of various asphalts, it is found that not all asphalts that have been performance-graded as being the same behave identically in their rutting performance. Thus, there is a need to create a rut-controlling term that will distinguish between asphalts that are graded the same but prepared by different modification routes. Such a rut-controlling term can then be used as a performance-related specification.
The present work extracts the rut-controlling term by model-fitting the master curve formed from the |G*|/(1 − (1/tanδ sinδ)) or |G*|/(sinδ)9 versus frequency data at various temperatures for each binder. Each master curve is fitted with a constitutive equation from which model parameters are evaluated. The slope B1 in the low frequency region of the master curve is normalized with the term (T/THS), resulting in the rut-controlling term that relates to the permanent strain after 5000 cycles in the repeated shear at constant height experiment on the Superpave shear tester at temperature T.
Influence of Suction Dissipation on Compression of Compacted Rock Aggregates Due to Immersion
Authors: Yoshida N , Nishi M 
Published: February 2009

Abstract
This paper focuses on the influence of suction dissipation upon the development of compressive settling in compacted rock aggregates due to immersion. The influence of disintegration of the material upon the development of compressive settling is also addressed. For this, a staged compression-immersion test is carried out on compacted quartz porphyry as well as mudstone aggregates. The results show that for the quartz porphyry aggregates, the influence of suction is slight. For the mudstone aggregates, a relatively high suction exists initially, probably due to the inherent nature of this type of rock, and the influence of the dissipation of mere suction upon compressive settling could be smaller than that of disintegration or degradation of the aggregates.
Evaluation of the Uniaxiality of the Stress State in O-Ring Fracture Strength Specimens
Authors: Sipics MJ , Segall AE , Conway JC 
Published: February 2009

AbstractTo investigate the experimental implications of using O-ring specimens for evaluating the fracture strength of ceramics in tubular form, a statistically designed series of finite element analysis (FEA) calculations was performed. These calculations focused on the ranges of specimen dimensions and loading distributions required to maintain a uniaxial stress state within the O-ring specimen under diametral loading. Results of the FEA calculations indicated that the degree of uniaxiality of the O-ring stress state could be described completely by a combination of the depth-to-thickness ratio (b/t) and the inner radius-to-outer radius ratio (ri/rc). It was also found that a relatively wide range of geometries can be accurately used to extract fracture strength design data, provided b/t does not get too large nor ri/ro too close to zero. However, there is cause for concern when b/t→0 or ri/ro→1, as this implies a small sample of material (and flaws) in the critical tensile stress region. Results also indicated that the uniaxiality of the O-ring stress state followed the expected 1/v dependence so that the behaviors of different materials can be easily surmised from the current results. On the other hand, load magnitude did not seem to have any effect on the stress-state despite the Boussinesq-type loading, while the distribution of the load over a finite contact area section could.
Test Method to Determine Flammability of Aerospace Materials
Authors: Hirsch DB , Beeson HD 
Published: February 2009

AbstractQualitative correlations between ground upward flammability tests and flammability testing in microgravity indicate that the NASA STD 6001 Test 1 provides conservative results by sustaining flaming combustion in less severe environments than those in which extinguishment occurs in quiescent microgravity environments. The upward flammability test is conducted in the most severe flaming combustion environment expected in the spacecraft. Its pass/fail test logic does not allow a precise quantitative comparison with other ground or microgravity materials flammability test results. Thus, although reasonable from a flammability safety point of view, the test is likely to eliminate materials that may be safe for use on spacecraft. A different test logic that will determine materials self-extinguishment limits is suggested to address these impediments. Data to support this approach are presented, including self-extinguishment limits in concurrent and countercurrent flows and under quiescent conditions. The proposed method will allow continued use of existing NASA flammability data and make possible quantitative correlations between ground testing and microgravity test results. Quantitative correlations between ground test results and microgravity combustion data will improve the aerospace materials selection process and allow realistic estimates of spacecraft fire extinguishment requirements. Theoretical analyses of flaming combustion will be possible, leading to a better understanding of materials combustion. This will benefit not only the aerospace community, but also the combustion community at large.
Sensitivity Evaluation of a Disk-type Torque Transducer Used as a Transfer Device
Authors: Ohgushi K , Ueda K , Ota T , Katase Y 
Published: February 2009

Abstract
A torque transfer device is used for international comparison between torque standard machines or for comparison verification between a torque standard machine and torque calibration machine. This experimental study revealed a problem in the case of using a high-precision torque transducer as the transfer device. For a disk-type torque transducer, it was found that a considerable deviation in the torque output sensitivity occurred depending on the dimensions of the adapter flange and the fastening torque of the screw bolts directly connecting the torque transducer to the adapter flanges. A solution is proposed to overcome this difficulty.
The Influence of Laboratory Aging Method on the Rheological Properties of Asphalt Binders
Authors: Abbas A , Choi BC , Masad E , Papagiannakis T 
Published: February 2009

Abstract
Asphalt binders used in asphalt concrete roadway pavements experience aging during construction and subsequently during their service lives. Aging is the combined effect of the evaporation of volatile compounds and the chemical reaction of residual compounds with oxygen. This aging affects the rheological properties of asphalt binders. The SuperpaveTM testing and specification system uses two laboratory procedures for aging of binders prior to measuring their rheological properties, namely the rolling thin film oven (RTFO) and the pressure aging vessel (PAV). These two procedures are used to simulate the aging that takes place during construction and during service, respectively. This paper examines whether the SuperpaveTM prescribed sequence of binder aging procedures (i.e., the RTFO followed by the PAV) is necessary, or whether similar binder rheological properties are obtained using the PAV procedure only. For this purpose, three binders were tested, namely an unmodified PG 64-28, an SBS polymer-modified binder of the same grade, and an SBS polymer-modified PG 76-28. The low temperature and fatigue rheological properties were measured by a bending beam rheometer (BBR) and a dynamic shear rheometer (DSR), respectively. The findings of the study suggest that, with a few exceptions, the rheological properties measured after aging with the RTFO followed by PAV are significantly different than those obtained after PAV aging only.
Plastic Instability and Mechanical Anisotropy of Textured Zinc
Authors: Samba Siva Rao G , Godavarti PS , Mahmood ST , Linga Murty K 
Published: February 2009

Abstract
The influence of the material parameters, strain hardening, and strain-rate hardening on the plastic instability of textured zinc sheets tested in uniaxial tension was investigated. The experimental instability strains are observed to be in accord with those evaluated from the analytical expressions involving the material parameters. The crystallite orientation distribution function obtained from the pole figure data is used in conjunction with a plasticity model to predict the anisotropy parameters (R and P) and subsequently the width strains in longitudinal and transverse zinc sheets. While the experimental R and P values matched well with those predicted for basal slip, the predicted width strains beyond uniform deformation are observed to be higher than the experimental values.
Dynamic Loading Fracture Tests of Ferritic Steel Using the Direct Current Potential Drop Method
Authors: Oh YJ , Kim JH , Hwang IS 
Published: February 2009

Abstract
To apply the leak-before-break concept to nuclear piping, the dynamic strain aging of low alloy steel materials has to be considered. For this goal, J-R tests are needed over a range of temperatures and loading rates, including rapid dynamic loading conditions. In dynamic J-R tests, the unloading compliance method cannot be applied and usually the direct current potential drop (DCPD) method is used. But, the DCPD method is known to have a problem in defining the crack initiation point due to a potential peak that arises in the early part of loading of ferromagnetic materials. In this study, the characteristics of measured DC potential peaks were investigated for SA106 Gr. C piping steels, and the definition of crack initiation point was determined by backtracking from the physically-measured final crack length. It is proposed that this technique could be applied as an improved DCPD method applicable for the dynamic loading J-R test.
Instrumental Method to Evaluate Leather Compressive Properties
Authors: Chen Y 
Published: February 2009

Abstract
An instrumental attachment and testing method was developed on a QTest™ tensile tester to evaluate leather compressibility. Six types of leather including pig, deer, cow, emu, goat, and alligator, were tested in terms of compressive modulus, linearity, energy, resilience, and thickness. A linear function was proposed to characterize the relationship between logarithmic stress and strain. This enabled calculation of all initial compressive moduli for these leather samples. The instrumental obtained data helped comparison of the compressive properties among the leather samples.
Simulation and Prediction of Hardness Performance of Rockwell Diamond Indenters Using Finite-Element Analysis
Authors: Ma L , Low S , Zhou J , Song J , deWit R 
Published: February 2009

Abstract
The difficulty in manufacturing Rockwell diamond indenters to the required geometric specifications has resulted in most commercially manufactured indenters to vary in shape from one to another. This difference in shape is thought to be a major contributor to the Rockwell C scale hardness measurement uncertainty. In this paper, a finite-element analysis (FEA) is used to simulate the Rockwell hardness measurement process. The influences of the indenter's geometry, including tip radius, cone angle, and form error on Rockwell hardness tests are analyzed by the FEA model, and further verified by experimental results. A new method is developed to directly input the Rockwell indenters' profiles into the FEA model for hardness performance prediction. The prediction results show good agreement with NIST experimental results.
Investigation of Stress-Strain Relationship of Confined Concrete in Hollow Bridge Columns Using Neural Networks
Authors: Mo YL , Hung HY , Zhong J 
Published: February 2009

Abstract
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 a computation and knowledge representation paradigm, called a network, to model material behavior. The main benefits in using a neural network is that the network is built directly from experimental data using the self-organizing capabilities of the neural network, i.e., 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 stress-strain relationship of confined concrete in hollow bridge columns is modeled with a back-propagation neural network. The results of using networks to study the behavior of confined concrete look very promising.
Analytical Model for Fatigue Crack Propagation in Concrete
Authors: Ramsamooj DV 
Published: February 2009

AbstractA new approximate analytical model is presented for the fatigue crack propagation rate in concrete. The model considers fatigue cracking at all stress levels up to the modulus of rupture. As the bending stress increases, the size of the inelastic zone compared to the crack length increases, and the stress intensity factor no longer controls the stresses in the vicinity of the crack tip, necessitating the use of the path-independent J-integral. At high stress levels fatigue crack propagation becomes nonlinear, and fracture may occur by ultimate strength collapse. Recently Kharlab postulated a hypothesis that enables the prediction of fracture of concrete by a single criterion that considers failure at any stress level for any size beam.An approximate analytical method for fatigue crack propagation in concrete at any stress level is presented. It incorporates the size effect and uses the crack tip opening displacement as the primary criterion upon which the rate of crack propagation is dependent. The model is validated by the published experimental data on concrete fatigue.
Evaluation of Bearing Capacity Improvement Using Composite Grids
Authors: Sivakumar Babu GL , Srinivasa Rao BM , Sridharan A 
Published: February 2009

Abstract
Recently, composite reinforcements in which combinations of materials and material forms such as strips, grids, and strips and anchors, depending on requirements, have proven to be effective in various ground improvement applications. Composite geogrids studied in this paper belong to the category of composite reinforcements and are useful for bearing capacity improvement. The paper presents evaluation of results of bearing capacity tests conducted on a composite geogrid, made of composite reinforcement consisting of steel and cement mortar. The study shows that the behavior of composite reinforcements follows the general trends observed in the case of conventional geogrids, with reference to the depth of first layer below the footing, number of layers of reinforcement, and vertical spacing of the reinforcement. Results show that the performance is comparable to that of a conventional polymer geogrid.
Stress Concentration Factor Formulas Useful for All Notch Shapes in a Flat Test Specimen Under Tension and Bending
Authors: Noda NA , Takase Y 
Published: February 2009

Abstract
In this work, stress concentration factors Kt for a flat bar with circular-arc or V-shaped notches are considered based on the exact solutions for special cases and accurate numerical results. Then, a set of Kt formulas useful for any notch shape is proposed. The conclusions can be summarized as follows. For the limiting cases of deep (d) and shallow (s) notches, the body force method is used to calculate the Kt values. Then, the formulas are obtained as Ktd and Kts. Next, the notch shape is classified into several groups according to the notch radius and notch depth. Then, the least squares method is applied for calculation of Kt/Ktd and Kt/Kts. Finally, convenient formulas are proposed that are useful for any notch shape in a flat test specimen. The formulas yield stress concentration factors with less than 1% error for any notch shape in a flat test specimen.