Additive manufacturing (AM) has been envisioned by many as a driving factor of the next industrial revolution. Potential benefits of AM adoption include the production of low-volume, customized, complicated parts/products, supply chain efficiencies, shortened time-to-market, and environmental sustainability. Work remains, however, for AM to reach the status of a full production-ready technology. Whereas the ability to create unique 3D geometries has been generally proven, production challenges remain, including lack of (1) data manageability through information management systems, (2) traceability to promote product producibility, process repeatability, and part-to-part reproducibility, and (3) accountability through mature certification and qualification methodologies. To address these challenges in part, this paper discusses the building of data models to support the development of validation and conformance methodologies in AM. We present an AM information map that leverages informatics to facilitate part producibility, process repeatability, and part-to-part reproducibility in an AM process. We present three separate case studies to demonstrate the importance of establishing baseline data structures and part provenance through an AM digital thread.
Results and analyses of a sensitivity study of six controlled variables on the response of the National Institute of Standards and Technology (NIST) 500mm guarded-hot-plate apparatus are presented. The effects of four factors held constant as well as three uncontrolled environmental variables were also examined. The goal of the study is to derive a sensitivity analysis ranking of the relative importance of factors and interactions affecting the apparatus. Sixty-six thermal conductivity measurements were conducted across three experiments at a mean temperature of 310 K for a pair of fibrous-glass specimens (120 kg.m(-3)) having nominal dimensions 500mm in diameter and 26mm in thickness. The apparatus response was studied using an orthogonal fractional factorial design, a one-factor-at-a-time design, and a full factorial design for a subset of factors from the fractionated design. The results indicate that most important factor affecting the thermal conductivity measurement was the temperature difference across the air space separating the central meter plate and the surrounding guard plate, described here as the gap temperature difference (Delta T-g). The study also revealed an interaction between the gap temperature difference and the temperature difference across the specimen (Delta T-avg). An empirical model for the results of the sensitivity study is presented. Results of the gap temperature difference (Delta T-g) are similar to published results from another guarded-hot-plate apparatus. Improvements for equipment operation, as well as insights to the sources of experimental uncertainty, are presented.
Internal curing uses pre-wetted fine lightweight aggregate (LWA) to supply cementitious systems with water. This increases the hydration of cement and reduces the influence of self-desiccation resulting in concrete with increased compressive strength, reduced permeability, and reduced shrinkage potential. Whereas these mixtures have shown great potential, there has been considerable debate on how internally cured samples should be conditioned during laboratory testing. This paper explores the influence of sample storage on the properties of mixtures prepared with and without internal curing. Samples were prepared and cured in different exposure conditions including environments in which: (1) moisture is supplied either via soaking or misting, (2) moisture is neutral, and (3) moisture loss is allowed. Experimental results show that when adequate external curing water is supplied, only limited benefits are seen from internal curing. The benefits of internal curing are more evident in systems that do not receive additional external curing water (sealed) and even more so when systems are exposed to external drying. Conditions where inadequate external curing water is supplied may be more representative of what would be experienced in the field.
Rheometers for measuring the properties of fluids are usually calibrated using a standard reference oil. However, a rheometer used for concrete cannot be calibrated using an oil, because of the unusual geometry and size. It would be advantageous to have a granular reference material. A material that can simulate a Bingham fluid, such as cement paste, was developed in this study as a mixture of corn syrup, water, and fine limestone. This reference material will form the basis of future mortar and concrete reference materials containing fine and coarse aggregates. This paper illustrates the various aspects of the development and shows data obtained using various geometries of rheometers.
The use of the oxygen storing capacity (OSC) of CeO2 to enhance the conditioning of engine exhaust is being explored as a means to reduce the harmful products of emission. A doping agent, Zr, is used to further improve ceria’s OSC and thermal stability. In this study, a high OSC endowed cerium-zirconium mixed-oxide (Ce0.6Zr0.4O2) three-way catalyst (TWC) was synthesized using a surfactant assisted co-precipitation method, and a stable suspension of the mixed oxide in diesel was prepared. The characterization of the mixed oxide and nanofuel was done using different analytical techniques, and the formation of a solid solution of the mixed oxide was confirmed. A stable dispersion of mixed oxide nanoparticles in diesel was achieved with the use of a mixed alkyl chain length surfactant. The thermal conductivity of the nanofuel did not show any significant increase with an increase in TWC concentration, and the calorific value of the nanofuel decreased. It is concluded that the cerium-zirconium mixed-oxide has a much higher OSC than pure ceria and could be potentially be used for better combustion of fuel in engines.
This paper is a continuation of the authors' previous work on the nucleate pool boiling heat transfer of nanofluids [Suriyawong, A. and Wongwises, S., “Nucleate pool boiling heat transfer characteristics of TiO2-water nanofluids at very low concentrations,” Exp. Therm. Fluid Sci., Vol. 34, No. 8, 2010, pp. 992–999.] This study presents new correlation for predicting heat transfer coefficient for nucleate pool boiling of TiO2-water nanofluids at several low concentrations. Unlike most previous studies, the proposed correlation consists of various relevant factors. Two horizontal circular plates made from copper and aluminum with different surface roughness values are used as heating surfaces. Because the calculation concerns with properties of nanofluids, this research uses various correlations from previous studies to find the properties of nanofluids and the best one is selected for the presentation. Compared with measured data of nucleate pool boiling of water and nanofluids from present and previous studies, it was found that the developed correlation could be used for prediction at a certain level.
Specimens for the Sizewell B reactor pressure vessel (RPV) in-service steels surveillance program are irradiated inside eight capsules located within the reactor pressure vessel and loaded prior to commissioning. The periodic removal of these capsules and testing of their contents provides material properties data at intervals during the lifetime of the plant. Neutron activation measurements and radiation transport calculations play an essential role in assessing the neutron exposure of the specimens and RPV. Following the most recent withdrawal, seven capsules have now been removed covering nine cycles of reactor operation. This paper summarizes the dosimetry results of the Sizewell B surveillance program obtained to date. In addition to an overview of the calculational methodology it includes a review of the measurements. Finally, it describes an extension of the methodology to provide dosimetry recommendations for the core barrel and briefly discusses the results that were obtained.
The current American Association of State Highway and Transportation Officials standard on crushed concrete in base applications (M 319-02) allows up to 5 % brick by mass, and more with the approval of the engineer; however, in some regions the brick content may be greater than 10 %. More than 41 states allow the use of crushed concrete in highway applications, but only a handful allow the use of building derived concrete (BDC) or mixed stream crushed concrete. Barriers to increasing the appropriate use of BDC in highway applications include a lack of data comparing BDC properties and performance to natural aggregates, as well as data that pavement engineers can use for design. This research has focused on characterizing BDC that was screened to meet New Hampshire Department of Transportation specifications. The gradation, optimum water content, unit weight, and resilient modulus were measured for the BDC and for the control materials, which were a crushed stone and a sand. The resilient modulus was measured using both a laboratory triaxial cell, and a light falling weight deflectometer (LWD) in a test pit. The resilient modulus of the BDC exceeded that of the control materials as measured in the laboratory and using the LWD. In addition, the laboratory resilient modulus showed good correlation with the LWD stiffness. These results suggest that BDC would perform as well as natural aggregates in base course applications.
Abstract To estimate the temperature distribution, stress distribution, and stress direction in a blade in service, the morphology of γ′ precipitates in Ni-based superalloy serviced in the first stage low pressure turbine (1st LPT) blade of a jet engine was investigated before and after aging. Using a field emission scanning electron microscope, microstructures were observed in forty portions of the blade. Most of the γ′ precipitates remained cuboidal in the serviced blade. Many secondary γ′ precipitates were observed in the γ matrix at the root part. In contrast, there were no secondary γ′ precipitates at the leading edge of the tip part. After simple aging, low-completion rafted γ/γ′ structures appeared on the suction side of the 70 mm part, while in other portions, coarsening of the γ′ precipitates was observed. Therefore, the leading edge of the 1st LPT blade tip was exposed to the highest temperatures in service. However, the stresses were extremely low in all portions of the blade.
The activities of nuclides produced via the neutron irradiation of reactor pressure vessel (RPV) steel are used to validate respective fluence calculations. Niobium, nickel, and technetium isotopes from RPV trepans of the decommissioned NPP Greifswald (VVER-440) have been analyzed. The activities were determined by TRAMO (Monte-Carlo) fluence calculations, newly applying 640 neutron-energy groups and ENDF/B7 data. Relative to earlier results, fluences up to 20 % higher have been computed, leading to somewhat better agreement between measurement and calculation, particularly in the case of Tc-99.
An adhesion testing device was built, based on the ASTM C 633-79 standard, to study the deposition of metallic coatings produced by the HVOF (high velocity oxygen fuel) thermal spray process with the materials 1342 VM, 1350 VM, and 8812, and by the arc spray (AS) process with the materials STELLIT 6 PM SD 38 EF, 97 MXC, and 140 MXC. This type of test is widely used as a tool to determine the influence of the conditions of the thermal spray technique, substrate surface and abrasive blasting on the strength, and adhesion of the sprayed layer on the substrate. The sprayed coatings were characterized based on their hardness, metallographic characteristics, and roughness measurements. They also underwent adhesion tests, and the fracture surfaces of each material were analyzed, revealing mixed results, i.e., different types of fractures involving cohesive fracture, adhesive failure, and adhesive fracture, according to the type of coating produced.
Abstract Eccentrically-loaded single-edge crack tension, ESE(T), specimens made of A36 structural steel were tested over a wide range in stress ratios (R=0.1 and 0.7) in laboratory air. Two test methods were used: (1) ASTM Standard E647 load-reduction method and (2) compression precracking. After compression precracking (CP), three different loading sequences were used: (1) constant amplitude (CPCA), (2) load reduction (CPLR), and (3) constant stress-intensity factor (CPCK). The crack-compliance method was used to determine that the specimens had no residual stresses; and that the effects of tensile residual stresses from compression precracking dissipated in about 2 compressive plastic-zone sizes. Agreement was found between the A36 and TC-128B steel ΔK-rate data tested at both low and high stress ratio (R) conditions. At R=0.1 loading, the CPCA and CPLR tests generated lower thresholds and faster rates than using the standard ASTM load-reduction method. All load-reduction tests exhibited an accumulation of debris at the crack front near threshold conditions. A crack-closure analysis was preformed to calculate the effective stress-intensity factor range (ΔKeff) against rate using measured 1 % offset (OP1) values for all R=0.1 tests. The ΔKeff-rate data correlated well with the high-R results.
In the present work, the effect of the addition of aluminum nanoparticles in concentrations varying from 0.001 to 0.5 vol. % on the cooling performance and quench severity of water during immersion quenching is investigated. The results of cooling curve analyses show that an increase in nanoparticle concentration increased the cooling rates at critical temperatures up to 0.05 vol. % and decreased them thereafter. The transition from the vapor blanket stage to the nucleate boiling stage was also altered by quenching in nanofluids. A finite difference heat transfer program was employed to generate cooling curves at different values of heat transfer coefficient from thermo-physical properties of the quench probe material. A Grossmann H quench severity versus cooling rate curve was established, and from this curve, the H factors of prepared nanofluids were estimated. An increase in nanoparticle concentration up to 0.05 vol. % resulted in an increase of the H value of water from 63 m−1 to 93 m−1, and any further increase in the concentration of nanoparticles resulted in a decrease in H. The results suggest both the enhancement and the deterioration of the cooling performance of water by the addition of aluminum nanoparticles.
The shielding integral benchmark archive and database (SINBAD) collection of experiments descriptions was initiated in the early 1990s. SINBAD is an international collaboration between the Organization for Economic Cooperation and Development's Nuclear Energy Agency Data Bank (OECD/NEADB) and the Radiation Safety Information Computational Center (RSICC) at Oak Ridge National Laboratory (ORNL). SINBAD was designed to compile experiments and corresponding computational models with the goal of preserving institutional knowledge and expertise that need to be handed down to future scientists. SINBAD can serve as a learning tool for university students and scientists who need to design experiments or gain expertise in modeling and simulation. The SINBAD database is currently divided into three categories—fission, fusion, and accelerator experiments. Many experiments are described and analyzed using deterministic or stochastic (Monte Carlo) radiation transport software. The nuclear cross sections also play an important role as they are necessary in performing computational analysis.
Abstract Al-alloy (Al-5 wt. %Zn and Al-5 wt. %Si) nanoparticle dispersed (0.01 − 2.00 vol. %) ethylene glycol based nanofluids are prepared by a two-step process. Prior to dispersing in ethylene glycol by magnetic stirring and ultrasonication the Al-alloy nanoparticles synthesized by mechanical alloying are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area diffraction (SAD), and energy dispersive spectroscopy (EDS) to analyze the identity, size, shape, and purity of the powder. A maximum thermal conductivity enhancement of 16 % for Al-5 wt. %Zn and 13 % for Al-5 wt. %Si dispersed nanofluids are observed at 0.1 vol. % of nanoparticle concentrations. Rheological studies of nanofluids show interesting findings as the viscosity of both types of nanofluids are observed to exhibit values lower than that of base fluid at lower concentrations and higher at higher concentrations. Maximum enhancement of viscosity up to 180 % for Al-5 wt. %Si and 120 % for Al-5 wt. %Zn dispersed nanofluids are observed at 2.0 vol. % concentration.
Oil sands are natural deposits of bituminous sand materials that are mined and processed for crude oil. They are routinely used in oil sand fields for building temporary and sometimes permanent roads serving mining and hauling activities. Although the principal application of these materials for road building has been in the unbound layers of the pavement structure, the full benefits of oil sands, particularly their sustainability and environmental friendliness, are yet to be realized. In their natural state, oil sands have similarities to cold mix asphalt mixtures which are often comprised of uniformly graded fine to medium sands and used for pavement repair and patching applications. Yet, they may exhibit complex stress dependent characteristics and viscoelastic and plastic behavior under dynamic loading of mining and off-road construction equipment. This paper presents findings from a comprehensive laboratory research program conducted on three types of oil sand materials with the main goal to characterize their engineering behavior. The research efforts focused on establishing a suite of tests to determine strength, modulus, and deformation characteristics under realistic traffic loading and climatic conditions. The developed suite of tests established essential trends in oil sand behavior for developing laboratory guidelines and test protocols and typical material characterization models for their sustainable use in geotechnical and road building applications.
There are several methods available to measure residual stress fields present within a structural component. Recently a new so called on-line crack compliance technique has been proposed, which is based on linear elastic fracture mechanics. This experimental method uses incremental crack mouth opening displacements measured during fatigue crack growth testing to generate information on the existing residual stresses along the crack line. The present study employs two dimensional (2D) plane stress finite element simulations of fatigue crack growth from a cold worked hole to investigate the performance of this technique. Using the simulation results, the stress intensity factors due to the residual stress field normalized by the maximum applied stress intensity factor KIrs/KImax were obtained from the on-line crack compliance method. For validation, the J-integral approach was used to calculate KIrs/KImax values from fatigue crack growth simulations in an elastic material. The two methods generated nearly identical results. Fatigue crack growth was also simulated in an elastic-plastic material. Even though the stress intensity factor is not the appropriate crack tip characterizing technique for elastic-plastic material conditions, it is still investigated here to approximate the actual testing conditions, where plastic deformation near the crack tip is unavoidable. The KIrs/KImax solutions are presented for different cold work levels and applied loadings. Results indicate that the agreement between the elastic and elastic-plastic crack growth solutions is dependent on the maximum applied loading level, as might be expected.
This paper provides an overview of the development of standardized methodology to evaluate joint seal continuity, encompassed in the newly published ASTM C 1736-11, “Standard Practice for Non-Destructive Evaluation of Adhesion of Installed Weatherproofing Sealant Joints Using a Rolling Device.” This standard practice was created under the jurisdiction of ASTM Committee C 24 on Building Seals and Sealants and is the direct responsibility of Subcommittee 30 on Adhesion; it was approved July 1, 2011. Fundamental details contributing to the successful usage of this practice are examined by answering the following questions: Where exactly do the stresses produced by this procedure have an effect upon the sealant-to-substrate bond-line? How does joint geometry impact this bond-line stress? What level of stress on a bond-line provides usable information without damaging the seal?
Accurate prediction of radiation fields generated by heavy ion interactions is important in medical applications, space missions, and in design and operation of rare isotope research facilities. In recent years, several well-established computer codes in widespread use for particle and radiation transport calculations have been equipped with the capability to simulate heavy ion transport and interactions. To assess and validate these capabilities, we performed simulations of a series of benchmark-quality heavy ion experiments with the computer codes FLUKA, MARS15, MCNPX, and PHITS. We focus on the comparisons of secondary neutron production. Results are encouraging; however, further improvements in models and codes and additional benchmarking are required.
