bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of Fatigue Propagation Life in Resistance Spot Welds
Authors: Sheppard SD 
Published: March 2009

The main objective of this research is to develop a model of fatigue crack propagation in resistance spot welded joints. An important feature of this development is that the model should be usable by designers considering fatigue response of structures containing multiple welds. This objective is achieved by examining the stress state around a load bearing resistance spot weld. A general expression for the structural stress around the weld is formulated that is dependent only upon the loading immediately surrounding the weld and is therefore independent of specimen design.
In previous work [1], it was found that structural stress could be successfully used to estimate life for crack initiation and growth to a length of 0.25 mm in resistance spot welds (RSW), and that this period represents less than 30% of the total life in as-welded joints. It is important to note that estimation of this period is highly dependent on fatigue related material properties.
In the current work, structural stress is related to crack propagation life through linear elastic fracture mechanics. Life estimates are made using the resulting relationship between structural stress and life. These estimates are compared with experimentally measured lives of welds in HSLA steel. A variety of specimen configurations are considered (e.g., tensile-shear, coach peel) in a number of conditions (e.g., as-welded, pre-stressed). Estimations are all within a factor of three of measured lives.
This approach to life estimation uses simple finite element representations of the weld connection to calculate structural stress. It is therefore appropriate for use by designers/analysts making life estimations based on finite element representations of structures containing multiple spot welds.
A Reverse Plasticity Criterion for Specifying Optimal Proof Load Levels
Authors: Tipton SM , Sorem JR 
Published: March 2009

It is well known that the fatigue strength of certain engineering components can be enhanced by the application of overloads. Extended fatigue life can occur when components with stress gradients at critical locations (e.g., bending or the presence of a stress concentration, or both) are service loaded positively in one direction following an overload in the same direction. Localized plasticity can result in residual compressive stresses that combine with the applied service stress history to enhance fatigue life.
For a component with a stress concentration (notch), guidelines are presented for specifying an “optimal” overload level based on the elastically calculated severity of the notch and the axial stress-strain behavior of the material, characterized by a Ramberg-Osgood relation. An algorithm is presented based on standard notch strain analysis techniques (Neuber's Rule and the strain energy density approach) and the concept of a reverse plasticity criterion. Use of the algorithm is demonstrated by generating examples of design curves for engineering steels. One version of the algorithm, based on a Neuber analysis, suggests that the optimal overload level is a function of only the yield strength of the material and independent of the strain hardening exponent. The results presented in this paper approximate situations where notch root constraint is small or negligible. However, the approach can be extended to account for multiaxial constraint on notch root deformation. Although the algorithm and criterion attempt to maximize the local compressive stress, supplemental analyses are required to assure that fracture or gross plastic deformation, or both, are avoided. Limitations to the approach are discussed and modifications are suggested with regards to the Bauschinger effect. The approach does not attempt to address the maintainability of the residual stress during subsequent fatigue loading and experimental data for direct comparison to the approach do not currently exist.
Fabrication of Zr-2.5Nb Pressure Tubes to Minimize the Harmful Effects of Trace Elements
Authors: Theaker JR , Choubey R , Moan GD , Aldridge SA , Davis L , Graham RA , Coleman CE 
Published: March 2009

Trace elements can reduce the fracture resistance of Zr-2.5Nb pressure tubes. The effects of hydrogen as hydrides and oxygen as an alloy-strengthening agent are well known, but the contributions of carbon, phosphorus, chlorine, and segregated oxygen have only recently been recognized. Carbides and phosphides are brittle particles, while chlorine segregates to form planes of weakness that produce fissures on the fracture face of test specimens. A high density of fissures is associated with low toughness. With long hold times in the (α + β) region, oxygen partitions into the α-grains; such grains are hard and, if they survive fabrication, may reduce the toughness of the finished tube. Through a cooperative program involving AECL and the manufacturers, a series of manufacturing innovations and controls has been introduced that minimizes these harmful effects.
Hydrogen is present in the zirconium sponge as water, can be absorbed at each stage of tube fabrication, and needs to be carefully controlled, particularly during ingot breakdown and subsequent forging. Hydrogen concentrations in finished tubes have been reduced by a factor of three through the optimization of manufacturing processes and the implementation of new technology. Multiple vacuum arc melting, use of selected raw materials, and intermediate ingot surface conditioning have resulted in much improved fracture toughness through the reduction of chlorine and phosphorus concentrations. Optimum distribution of oxygen may be achieved through changes to the extrusion process cycle. An understanding of the Zr-2.5Nb-C phase diagram, particularly the solubility of carbon at low concentrations, has resulted in the specification of a lower carbon concentration.
Corrosion Behavior of Zircaloy-4 Cladding with Varying Tin Content in High-Temperature Pressurized Water Reactors
Authors: Garde AM , Pati SR , Krammen MA , Smith GP , Endter RK 
Published: March 2009

Fuel rods clad with Zircaloy-4 with varying tin contents (1.33 to 1.58% Sn) and annealing parameters (1.0 to 4.1 × 1017 h with Q/R = 40 000°K) were irradiated in demonstration fuel assemblies in a high-temperature pressurized water reactor (PWR) to burnups in excess of 35 giga watt days per metric ton of uranium (GWd/MTU). The same cladding variants were subjected to long-term static water autoclave tests at 633°K of duration greater than 1100 days. Production fuel rods fabricated with low-tin (1.33 Sn) and high-tin (1.55 Sn) Zircaloy-4 cladding were also irradiated in regular fuel assemblies in two high-temperature PWRs to burnups up to 48 GWd/MTU. Poolside cladding oxide thickness measurements were conducted on 167 high-tin rods and 67 low-tin rods during refueling outages. The measured, circumferentially averaged, peak cladding oxide thickness values ranged from 3 to 113 μm. At high burnups, the oxide thickness on low-tin cladding was 30 to 40% lower than that on high-tin cladding. The long-term autoclave results also showed the beneficial effect of lower tin level on the corrosion rate, although to a lower degree than in PWRs. The 633 K water autoclave test appears to rank the corrosion resistance of the investigated Zircaloy-4 variants in the same order as in PWRs. Hydrogen analysis results indicate that tin level does not influence the hydrogen uptake of autoclave-tested samples. The observed in-PWR influence of tin level on the Zircaloy-4 cladding corrosion rate was incorporated in the ESCORE clad corrosion model by adjusting the pre-exponential term in the post-transition corrosion rate equation.
A corrosion rate acceleration at high burnups may be related to either hydride precipitation at the metal oxide interface or to degradation of the oxide thermal conductivity. The observed effect of tin on the uniform corrosion resistance of Zircaloy-4 in high temperature water is consistent with the corrosion mechanism that assumes the migration of 02- anion vacancies through the oxygen deficient zirconia to be the rate-controlling process. It is postulated that lower tin level in Zircaloy-4 decreases the vacancy concentration in the oxide and, thereby, increases the corrosion resistance. It may be possible to further improve the corrosion resistance of low-tin Zircaloy-4 by optimizing the nitrogen and tin concentrations in Zircaloy.
Clay Soil Heave Caused by Lime-Sulfate Reactions
Authors: Mitchell JK , Dermatas D 
Published: March 2009

Reactions between lime, alumina released from clay during pozzolanic reactions, and sulfates present in some soils (causing the formation of the highly expansive crystalline mineral ettringite) have been responsible for the deterioration and ultimate failure, by expansion, of several lime stabilization projects.
The mechanisms for these reactions were hypothesized, and a laboratory research program using lime-treated artificial soil samples of compacted kaolinite-sand and montmorillonite-sand mixtures, incorporating known amounts of sulfates, was designed and undertaken. The strength, swelling, compositional, and micromorphological characteristics of the treated samples were determined following different curing times and soaking conditions.
Ettringite formation was evidenced in all lime-treated samples, whenever sulfates were present. A non-expansive monosulfate calcium-aluminum-hydrate forms first in the high alumina content lime-treated kaolinite-sand mixes. The monosulfate converts to an expansive trisulfate form (ettringite), after a period of a few months. Conversely, ettringite starts to form at the early curing stages (after a few days) in the low alumina lime-treated montmorillonite-sand mixes.
It was found that the amount of heave following ettringite hydration and growth is a function of the amount and rate of release of alumina into solution. The amount and type of sulfates present is also a factor influencing the quantity and crystal morphology of ettringite formed. Moreover, temperature and humidity fluctuations were also found to play an important role in the overall ettringite-related heave mechanism, as they affect reaction rates, solubilities of species, and the overall stability fields of a soil system's components.
Continuing research will extend the results reported here to a more quantitative specification of conditions leading to deleterious reactions in lime stabilization applications. Concurrently, treatment methods that may prevent such adverse reactions are being explored.
Some Results from Ongoing Research on Road Roughness
Authors: Hegmon RR 
Published: March 2009

Road roughness can be described by two dimensional profiles in the direction of travel. These profiles are used for driving actuators for vehicle testing and dynamic computer simulations. Road roughness affects primarily ride quality and dynamic wheel loads. The effects of dynamic wheel loads on the stresses in the pavement and subsequent effect on pavement life is the subject of current research at the FHWA (Federal Highway Administration).
This paper presents a review of the extensive work done over the years in the Pavement Division of the Office of Research of FHWA and some recent results on road roughness profiling and on pavement response to dynamic loads. Current and planned work is described in some detail. The current interest is on the interactions between rough pavements and heavy trucks. Field and laboratory measurements, and computer simulations to predict the interaction forces are discussed. Distribution of strains and deflections under passing truck wheels are shown for different test conditions.
Thermal Performance of HCFC-22 Blown Extruded Polystyrene Insulation
Authors: Yarbrough DW , Graves RS , Christian JE 
Published: March 2009

A closed-cell foamboard insulation containing chlorodifluoromethane (HCFC-22) has been monitored in the laboratory and in the field for about three years. Experimental data for this developmental extruded polystyrene insulation has been obtained in two laboratories using three apparatuses. A correlation of apparent thermal conductivity with time gives the thermal resistivity of the two-inch-thick unfaced foamboards to within 3% with 95% confidence. A thermal resistivity of 30.2 m∙K/W (4.36 ft2∙h∙°F/Btu∙in) was calculated from the correlation for time equal 180 days after manufacture. Based on three years of data, the predicted thermal resistivity is 27.6 m∙K/W (3.98 ft2∙h∙°F/Btu∙in) as time since manufacture becomes large. Field measurements confirm the decrease with time of the thermal resistivity that was observed in the laboratory.
A three-dimensional model for heat transfer through foamboard was used to predict thermal resistivity as a function of time. A comparison of the experimental results with the model shows a radiative contribution to the total heat flux of about 30%. A one-dimensional model was used to show the effect of initial foamgas pressure and thickness on thermal performance.
Experimental Test Results of Interior Vs. Exterior Insulation in Extremely Hot Climates
Authors: Al-Mofeez I , Woods PK 
Published: March 2009

Three room-sized building modules were constructed in Elhasa, Saudi Arabia during the summer of 1988. These test modules were identical except for the manner in which they were insulated. One had no insulation, another had insulation on the exterior surface of the exterior walls, and a third had insulation on the inside surface of the exterior walls. Hypotheses were developed and tested based upon an equation expressing the anticipated relationship of lifecycle costs among these three test modules. The equation is: Lifecycle cost (E) &lt; Lifecycle cost (I) &lt; Lifecycle cost (U); where (E) is exterior insulated condition, (I) is interior insulated condition, and (U) is uninsulated condition.
To estimate present worth and equipment size, MRT field measurements were used to fine tune an hour-by-hour energy simulation program called ENERCALC. The thermal characteristics of the buildings were entered along with the annual weather data for the site of the experiment. The buildings' annual heat gains and losses, peak heat gains and losses, summer hourly air-conditioning demand profile, and the present worth of each building were then compared. The comparison indicated that the life-cycle cost of the externally insulated building was the lowest among the three buildings.
Low-Frequency Shear Wave Logging in Unconsolidated Formations for Geotechnical Applications
Authors: Kaneko F , Kanemori T , Tonouchi K 
Published: March 2009

There are four kinds of methods used in low-frequency shear wave logging. They are the downhole method, uphole method, cross-hole method, and suspension PS logging. Among these methods, the downhole method is commonly used in Japan. Hundreds of shear wave measurements using the downhole method have been carried out since it was established in the 1970s.
Suspension PS logging is a recently developed method in which a nonsymmetric seismic source and two receivers are built into a single probe. Source-to-receiver spacing is 2 and 3 m and the logging frequency ranges from 100 to 1000 Hz. Shear waves generated by the seismic source in the probe are detected with the receivers installed 1 m apart, and the shear wave velocity is calculated from the difference of the arrival time between the two receivers. Because the distance between the two receivers is fixed in the probe and the shear wave source produces a repeatable signal, velocity values obtained by suspension PS logging have less errorsxompared with the other methods.
Shear wave velocity measurements have important applications in earthquake engineering. In this paper, shear wave velocity measurements are shown to give a useful indication of soil liquefaction potential and shear moduli that can be used to predict the amplitude of surface soil motions during earthquakes.
Flexibility of the Human Knee as a Result of Varus/Valgus and Axial Moments in Vivo: Experiments and Results
Authors: Mills OS , Hull ML 
Published: March 2009

Knee ligamentous injuries persist in the sport of Alpine skiing. To better understand the load mechanisms that lead to injury, pure varus/valgus and pure axial moments were applied both singly and in combination to the right knees of six human test subjects. The corresponding relative knee rotations in three degrees of freedom were measured. Knee flexion angles for each test subject were 15 and 60° for the individual moments and 60° for the combination moments. For both knee flexion angles, hip flexion angle was 0°. Leg muscles were quiescent and axial force was minimal during all tests. Tables of data include sample statistics for each of four flexibility parameters in each loading direction.
Data were analyzed statistically to test for significant differences in flexibility parameters between the test conditions. In flexing the knee from 15 to 60°, the resulting knee rotations under single moments depended on flexion angle with varus, valgus, and internal rotations increasing significantly. Also, rotations were different depending on load direction; varus rotation was significantly different and greater than valgus rotation at both flexion angles. Also external rotation was significantly different and greater than internal at 15° flexion but not 60° flexion. Coupled rotations under single moments were also observed. Applying pure varus/valgus moments resulted in coupled external/internal rotations that were inconsistent and hence not significant. Applying pure axial moments resulted in consistent and hence significant varus/valgus rotations; an external axial moment induced varus rotation and an internal axial moment induced valgus rotation. For combination moments, varus/valgus rotations decreased significantly from those rotations at similar load levels in the single moment studies. Also, a varus moment significantly increased external rotation and a valgus moment significantly decreased internal rotation. These differences indicate significant interaction between corresponding load combinations. These results suggest that load interaction is a potentially important phenomenon in knee injury mechanics.
The Benefits and Economic Consequences of Materials Property Databases
Authors: Barrett AJ 
Published: March 2009

Computerized materials property databases and networks are at the leading edge of the introduction of machine readable, numeric data systems in technology. Managers of such systems are faced with pioneering the acceptance both of a new product, namely, high quality data, and a novel means for its delivery. They are well able to catalog the features of their systems, but some of them are less articulate on the benefits which are on offer and which need to be put forward to funding bodies and to potential users.
A CODATA project is currently drawing up structured lists of benefits classified under functional headings. This is a first step in constructing a practical package of assistance to materials database managers in the promotion of their systems, in the evaluation of actual user needs, and, eventually, in preparing a basis for the realistic demonstration of favorable national and international economic consequences.
Materials Property Database Requirements for Gas-Fueled Ceramic Heat Exchangers
Authors: Munro RG , Begley EF 
Published: March 2009

The Structural Ceramics Database (SCD) system is being developed at the National Institute of Standards and Technology to provide a critical link between the development of new materials in research laboratories and the application of those materials in industry. To achieve this goal, considerable effort is being devoted to establishing the SCD materials property database in a highly user-friendly computerized format for use on personal computers. The system is designed to provide a consistent and attractive mechanism for communicating critical data to design engineers involved in product development.
The development of the SCD is being guided by focusing attention on specific applications. Such focusing provides a more cost effective approach to database construction because the materials and the properties included in the system are determined and constrained by the needs of the application. The utility of the resulting data, however, extends well beyond the guiding application.
The first phase of the development of the SCD is focused on the material, property, and information requirements that derive from the specific application of a materials property database to ceramic heat exchangers.
Matrix Cracking in Composite Laminates with Resin-Rich Interlaminar Layers
Authors: Ilcewicz LB , Dost EF , McCool JW , Grande DH 
Published: March 2009

The critical stress or strain causing the onset of matrix cracking in composite laminates has been referred to as in situ transverse lamina strength. A majority of past studies have considered relatively brittle composites exposed to room temperature environments and static load conditions. In the current work, fracture mechanics analysis and test data for a toughened composite material that has a resin-rich interlaminar layer (RIL) were used to investigate in situ strength. Exposure to a range of environmental conditions was considered.
A parametric analysis study was performed to judge the effects of laminate and material variables. A finite thickness effect, indicating an interaction between ply group thickness and effective flaw size, was found dominant. The magnitude of the effect was directly related to RIL stiffness. In situ strength was found to decrease with decreasing RIL stiffness. Experiments with five different laminate layups and six different environmental conditions confirmed the analysis. This work indicates the need to use a fracture mechanics model of actual lamina microstructure and heterogeneous properties to predict in situ strength in materials with RIL.
20 Years Experience in the Paver Pavement Management System: Development and Implementation
Authors: Shahin MY 
Published: March 2009

The development of a pavement management system for the US Army began in 1968. Since that time there have been many successes, but the road to development and implementation has been full of obstacles and can generally be described as “rough. This paper discusses the Army's PAVER pavement management system in terms of its history, development challenges, implementation obstacles, and solutions.
The Development issues that proved to be significant included: * Engineering technology as it relates to pavement mechanistic behavior, pavement distress, condition prediction modeling, and optimization. * A sponsor who understands the importance of pavement management and is willing to defend its development. * A user group that is progressive and willing to give constructive direction and feedback. * A research team that is not discouraged by tough challenges or initially disappointing results.
The Implementation issues that proved to be significant included: * Availability of manpower and monetary resources. * The pavement management system's ability to provide for field needs such as annual planning, long-range work planning, and project justification. * Availability of credential training. * Endorsement by nationally respected organizations such as APWA, FAA, and FHWA. * Obtaining system approval by the head organization. * Finding the right branch and the right responsible person within the implementing agency.
This paper discusses all the above issues and includes a description of PAVER'S evolution from 1968 to 1990, from both a development and an implementation point of view.