Academic literature on the topic 'Temperature x time exposure constants'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Temperature x time exposure constants.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Temperature x time exposure constants"
1
Blank, Vladimir D., Sergei G. Buga, Gennadi A. Dubitsky, Nadejda R. Serebryanaya, Vyatcheslav M. Prokhorov, Boris N. Mavrin, Victor N. Denisov, Leonid A. Chernozatonskii, Sofia Berezina, and Vadim M. Levin. "Synthesis of Superhard and Ultrahard Materials by 3D-polymerization of C60, C70 Fullerenes Under High Pressure (15 GPa) and Temperatures up to 1820 K." Zeitschrift für Naturforschung B 61, no. 12 (December 1, 2006): 1547–54. http://dx.doi.org/10.1515/znb-2006-1211.
Full textAbstract:
Solid fullerenes C60 and C70 have been treated at high pressure of 15 GPa and high temperatures of 520 - 1820 K for a time of exposure of 60 s and a quenching rate of 300 K s−1 using a toroid-type apparatus. X-ray diffraction and Raman spectra confirm the realization of 3D-polymerized phases in these solids at 15 GPa. The pressure/temperature maps of synthesis of metastable carbon phases on the basis of C60 and C70 have thus been extended to 15 GPa. The longitudinal and shear sound wave velocities were measured by acoustic microscopy techniques. A maximum sound wave velocity of (21±1)×105 m s−1 was observed in the sample synthesized from C60 at T = 1170 K. The elastic constants were calculated using experimental data. The acoustic microscopy images of experimental samples have been investigated.
2
Delplancke-Ogletree, M. P., M. Ye, R. Winand, J. F. de Marneffe, and R. Deltour. "Influences of thermal annealing and humidity exposure on surface structure of (100) single-crystal MgO substrate." Journal of Materials Research 14, no. 5 (May 1999): 2133–37. http://dx.doi.org/10.1557/jmr.1999.0288.
Full textAbstract:
We studied the influence of thermal annealing on the surface structure of (100) singlecrystal MgO substrates by atomic force microscopy (AFM). By annealing MgO substrates at various temperatures for 4 h in flowing oxygen, we showed that the surface reconstruction could be explained by considering surface diffusion, surface evaporation, and condensation. At an annealing temperature of 1473 K, a stepped structure was formed with screw dislocations acting as step sources. The influence of humidity on the surface morphology of MgO substrates was also studied by exposing them to a constant humidity of 40 and 80% for different times. After an exposure time of 1.5 h in 80% humidity, the substrate surface was already covered by reaction products. For the 40% humidity, the corresponding time is 10 h. The major reaction product was identified as Mg(OH)2 by x-ray diffraction.
3
Botha, Sabine, Thomas Barends, Wolfgang Kabsch, Beatrice Latz, Karol Nass, Robert Shoeman, Florian Dworkowski, et al. "Room Temperature Serial Crystallography at Synchrotrons." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C326. http://dx.doi.org/10.1107/s2053273314096739.
Full textAbstract:
Serial Femtosecond Crystallography (SFX) is the most commonly used method for the emerging structure determination at X-ray free-electron lasers (FELs). The high peak brilliance of the FEL and the possibility of using femtosecond pulses afford use of nano-to-micron sized crystals in a diffraction-before-destruction approach for the acquisition of high-resolution undamaged diffraction data [1]. The crystals are obliterated upon exposure to an FEL X-ray pulse so only a single snapshot can be collected per crystal, necessitating a constant supply of fresh crystals. The crystals are therefore injected in a liquid microjet [2], [3]. We show that this serial method of data collection and the associated data analysis can be successfully adapted to serial crystallography (SX) measurements at synchrotrons, enabling room temperature studies using the unattenuated beam. Given the continuous supply of fresh crystals, the full tolerable dose can be used for each single crystal exposure, permitting analysis of small or weakly scattering crystals. FEL X-ray pulses are much shorter than the fraction of a second exposure time at a synchrotron, so SFX injection conditions are modified in SX such as to slow down the typically fast travelling crystals. By embedding the crystals in a viscous material the crystals remain in the beam long enough to yield measurable diffraction and smearing out of the diffraction peaks due to crystal tumbling is avoided. We demonstrate the successful application of room temperature SX at the Swiss Light Source at ambient pressure. Our experimental setup allows collection of both still and rotation data. Recent progress using model systems will be presented, establishing this high throughput, high dose rate approach as a new route to structure determination of macromolecules in their native environment and at room temperature.
4
Judd, Gary J. R., Mark G. T. Gardiner, and Donald R. Thomson. "TEMPERATURE-DEPENDENT DEVELOPMENT AND PREDICTION OF HATCH OF OVERWINTERED EGGS OF THE FRUITTREE LEAFROLLER, ARCHIPS ARGYROSPILUS (WALKER) (LEPIDOPTERA: TORTRICIDAE)." Canadian Entomologist 125, no. 5 (October 1993): 945–56. http://dx.doi.org/10.4039/ent125945-5.
Full textAbstract:
AbstractThermal responses and temperature-dependent development of laboratory- and field-overwintered eggs of the fruittree leafroller, Archips argyrospilus (Walker), were described using data from constant-temperature laboratory experiments. The time required for completion of hatch of overwintering eggs declined throughout winter until the end of January, after which increasing exposure to natural or artificial cold conditions had minimal effect on median hatching time. There was little year to year variation in response to cold treatments, and thus it was concluded that diapause is terminated by 1 February. Time to hatch decreased with increasing temperature. Distributions of hatch times were near normal, with mean and median development times similar at any given temperature. Development time (days ± SD) at a mean temperature of 20 °C was similar under constant (10.7 ± 1.1) and fluctuating (9.1 ± 1.4) temperature regimes. A nonlinear, six-parameter, biophysical model, fitted (r2 = 0.99) to median hatching rates at 11 temperatures (0.5–30 °C) indicated development was nonlinear below 10 °C, increased linearly between 10 and 25 °C, was maximal at 27.5 °C, and decreased above 27.5 °C. The lower developmental threshold (± SE), estimated to be 4.95 ± 0.54 °C by linear regression (r2 = 0.98) and the x-intercept method, was used to construct a degree-day (DD) model for predicting egg hatch. Median egg development required 154 DD above 4.95 °C. Observed median egg hatch in two different field sites and years was within ± 3 days of the predicted date, using max–min air temperatures, a base temperature of 5 °C, and a starting date of 1 February for accumulating DD. This model should prove useful for scheduling management actions against fruittree leafroller on apples and pears.
5
Cavin, O. Burl, and J. S. Wolf. "X-Ray Examination of Type 310S Stainless Steel during its Oxidation in Air at 900°C*." Advances in X-ray Analysis 36 (1992): 423–31. http://dx.doi.org/10.1154/s0376030800019042.
Full textAbstract:
AbstractType 310S stainless steel was exposed in air at 900°C and simultaneously examined periodically by X-ray diffraction in an attempt to determine the structural evolution of the compounds formed on its surface. The adherent oxide product was found to be a two-layered scale composed of an inner sesquioxide and an outer spinel layer. Both of these compounds exhibited systematic changes in their unit cell sizes as a function of increasing exposure time at constant temperature. The spinel showed an increase in its lattice parameter while the sesquioxide and stainless steel substrate both had decreases in their parameters proportional to the square root of exposure time. In each of the three phases, the rate of change was constant up to approximately four hours after which the parameters approached a limiting value. Evidence also exists for the presence of at least localized stresses in the scales.
6
Wang, Pingping, Guoqin Chen, Longtao Jiang, Daguang Li, and Gaohui Wu. "Effect of thermal exposure on the microstructure of the interface in a Grf/Al composite." Science and Engineering of Composite Materials 23, no. 6 (November 1, 2016): 751–57. http://dx.doi.org/10.1515/secm-2014-0354.
Full textAbstract:
AbstractThe microstructure of the interface in a Grf/Al composite after exposure at high temperature was investigated. The graphite fiber reinforced aluminum matrix composite was prepared by the pressure infiltration method. After being heat treated at 550°C, 600°C and 640°C for different times, the microstructure of the interface in the composite was studied by using transmission electron microscopy (TEM). Furthermore, the content of Al4C3 in the interface was examined using X-ray diffraction (XRD). The results showed that not only the micro morphology but also the content of Al4C3 in the interface varied with the increase in temperature. When the composite was heat treated at 550°C and 600°C, Al4C3 with a big length-to-diameter ratio was observed in the interface, while Al4C3 with a small length-to-diameter ratio was found when the heat treatment temperature was 640°C. With the increase in the time, the content of Al4C3 in the interface increased rapidly when the composite was heat treated at 640°C. Based on the dynamic calculation, the interface reaction diffusion rate constant of the Grf/Al composite increases rapidly when the temperature is higher than 600°C.
7
Ryl, Jacek, Mateusz Cieslik, Artur Zielinski, Mateusz Ficek, Bartlomiej Dec, Kazimierz Darowicki, and Robert Bogdanowicz. "High-Temperature Oxidation of Heavy Boron-Doped Diamond Electrodes: Microstructural and Electrochemical Performance Modification." Materials 13, no. 4 (February 21, 2020): 964. http://dx.doi.org/10.3390/ma13040964.
Full textAbstract:
In this work, we reveal in detail the effects of high-temperature treatment in air at 600 °C on the microstructure as well as the physico-chemical and electrochemical properties of boron-doped diamond (BDD) electrodes. The thermal treatment of freshly grown BDD electrodes was applied, resulting in permanent structural modifications of surface depending on the exposure time. High temperature affects material corrosion, inducing crystal defects. The oxidized BDD surfaces were studied by means of cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM), revealing a significant decrease in the electrode activity and local heterogeneity of areas owing to various standard rate constants. This effect was correlated with a resultant increase of surface resistance heterogeneity by scanning spreading resistance microscopy (SSRM). The X-ray photoelectron spectroscopy (XPS) confirmed the rate and heterogeneity of the oxidation process, revealing hydroxyl species to be dominant on the electrode surface. Morphological tests using scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that prolonged durations of high-temperature treatment lead not only to surface oxidation but also to irreversible structural defects in the form of etch pits. Our results show that even subsequent electrode rehydrogenation in plasma is not sufficient to reverse this surface oxidation in terms of electrochemical and physico-chemical properties, and the nature of high-temperature corrosion of BDD electrodes should be considered irreversible.
8
Gamal, Hany, Salaheldin Elkatatny, Abdulazeez Abdulraheem, and Abdulaziz Al Majed. "Exposure Time Impact on the Geomechanical Characteristics of Sandstone Formation during Horizontal Drilling." Molecules 25, no. 11 (May 27, 2020): 2480. http://dx.doi.org/10.3390/molecules25112480.
Full textAbstract:
The rock geomechanical properties are the key parameters for designing the drilling and fracturing operations and for programing the geomechanical earth models. During drilling, the horizontal-section drilling fluids interact with the reservoir rocks in different exposure time, and to date, there is no comprehensive work performed to study the effect of the exposure time on the changes in sandstone geomechanical properties. The objective of this paper is to address the exposure time effect on sandstone failure parameters such as unconfined compressive strength, tensile strength, acoustic properties, and dynamic elastic moduli while drilling horizontal sections using barite-weighted water-based drilling fluid. To simulate the reservoir conditions, Buff Berea sandstone core samples were exposed to the drilling fluid (using filter press) under 300 psi differential pressure and 200 °F temperature for different exposure times (up to 5 days). The rock characterization and geomechanical parameters were evaluated as a function of the exposure time. Scratch test was implemented to evaluate rock strength, while ultrasonic pulse velocity was used to obtain the sonic data to estimate dynamic elastic moduli. The rock characterization was accomplished by X-ray diffraction, nuclear magnetic resonance, and scanning electron microscope. The study findings showed that the rock compression and tensile strengths reduced as a function of exposure time (18% and 19% reduction for tensile strength and unconfined compression strength, respectively, after 5 days), while the formation damage displayed an increasing trend with time. The sonic results demonstrated an increase in the compressional and shear wave velocities with increasing exposure time. All the dynamic elastic moduli showed an increasing trend when extending the exposure time except Poisson’s ratio which presented a constant behavior after 1 day. Nuclear magnetic resonance results showed 41% porosity reduction during the five days of mud interaction. Scanning electron microscope images showed that the rock internal surface topography and internal integrity changed with exposure time, which supported the observed strength reduction and sonic variation. A new set of empirical correlations were developed to estimate the dynamic elastic moduli and failure parameters as a function of the exposure time and the porosity with high accuracy.
9
Moravcikova-Gouvea, Larissa, Zuzana Kovacova, Michael Kitzmantel, Erich Neubauer, Vít Jan, and Ivo Dlouhy. "Influence of Hot Pressing Sintering Temperature on the Properties of Low-Density Al0.5NbTa0.8Ti1.5V0.2Zr Refractory High-Entropy Alloy." Materials Science Forum 1016 (January 2021): 940–45. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.940.
Full textAbstract:
In this work, the low-density Al0.5NbTa0.8Ti1.5V0.2Zr RHEA prepared by mechanical alloying combined with hot uniaxial pressing (HP) was investigated. The alloy was subjected to different sintering temperatures on the range of 1200°C up to 1600°C, while keeping a constant densification time. The influence of the increase in sintering temperatures on the RHEAs’ microstructural features, composition and basic mechanical properties was explored by means of x-ray diffraction and scanning electron microscopy, hardness testing, density determination by Archimedes’ principle and elastic moduli by ultrasonic measurements. Full density samples were obtained in all sintering temperatures. The alloy has shown a homogeneous distribution of phases, with presence of dispersed oxides inside the matrix, leading to a fine grain size distribution due to grain-boundary pinning effect, even during the exposure of the alloy at the highest sintering temperature. The mentioned effect is responsible for the achievement of high-hardness in all conditions. Powder metallurgy has been shown to be an advantageous technique for production of alloys for high-temperature applications, as the inherent in-situ formed oxides homogeneously distributed within the matrix may be beneficially used as reinforcement, thus potentially enhancing the mechanical properties of the parts.
10
Perrusquia, N. López, M. Antonio Doñu Ruiz, E. Y. Vargas Oliva, and V. Cortez Suarez. "Diffusion of Hard Coatings on Ductile Cast Iron." MRS Proceedings 1481 (2012): 105–12. http://dx.doi.org/10.1557/opl.2012.1638.
Full textAbstract:
ABSTRACTThis work estimate the growth kinetics of Fe2B coatings created on surface nodular cast iron ASTM A-536 class 80-56-06. The Fe2B coatings were formed by power packaging boriding process, considering three temperatures and exposure times different treatment. The hard coatings were evaluated through X-ray diffraction (XRD) and scanning electron microscopy (SEM). The model of diffusion employs the mass balance equation at the (Fe2B/substrate) interface to evaluate the boron diffusion coefficient in the Fe2B coating DFe2B, an expression of the parabolic growth constant, the instantaneous velocity of the Fe2B/substrate interface, and the weight gain in the boriding sample were establish as a function of the parameter ε(T) and η(T), dependents of boriding process in function of the temperature related and the time of boriding t0 (T), respectively in the Fe2B coating. Model validation was extended considering the treatment of 1273 and 1123 K for 10 h respectively, obtaining a good correlation with experimental data.
Dissertations / Theses on the topic "Temperature x time exposure constants"
1
de, Rooy S. C. "Improved efficiencies in flame weeding." Lincoln University, 1992. http://hdl.handle.net/10182/18.
Full textAbstract:
Possible areas of improving the efficiencies of the Lincoln University flame weeder are identified and investigated. The Hoffmann burner initially used in the Lincoln University flame weeder was found not to entrain sufficient air to allow complete combustion of the LPG used. A new burner, the Modified Lincoln University burner, was designed to improve the entrainment of air. Results show that the new design entrained sufficient air to theoretically allow complete combustion of the LPG, and this resulted in a 22.7% increase in heat output per Kg of LPG used over the Hoffmann burner. Temperature x time exposure constants required to kill weeds 0 - 15, 15 - 30, and 30 - 45 mm in size, were found to be respectively 750, 882, and 989 degrees Celsius.Seconds. These constants can be used to calculate the maximum speed of travel an operator can use a flame weeder at, once the temperature profile underneath its shields are established at various travel speeds, and therefore ensure that the flame weeder is used at its maximum efficiency. The constants can also be used to establish the cost efficiency of any flame weeder (in $/Ha), depending on the size of the weeds to be treated. The materials and methods used in establishing the temperature x time exposure constants can be used to establish the temperature x time exposure constant of any weed species at any size.
Books on the topic "Temperature x time exposure constants"
1
Araújo, Ana Cláudia Vaz de. Síntese de nanopartículas de óxido de ferro e nanocompósitos com polianilina. Brazil Publishing, 2021. http://dx.doi.org/10.31012/978-65-5861-120-2.
Full textAbstract:
In this work magnetic Fe3O4 nanoparticles were synthesized through the precipitation method from an aqueous ferrous sulfate solution under ultrasound. A 23 factorial design in duplicate was carried out to determine the best synthesis conditions and to obtain the smallest crystallite sizes. Selected conditions were ultrasound frequency of 593 kHz for 40 min in 1.0 mol L-1 NaOH medium. Average crystallite sizes were of the order of 25 nm. The phase obtained was identified by X-ray diffractometry (XRD) as magnetite. Scanning electron microscopy (SEM) showed polydisperse particles with dimensions around 57 nm, while transmission electron microscopy (TEM) revealed average particle diameters around 29 nm, in the same order of magnitude of the crystallite size determined with Scherrer’s equation. These magnetic nanoparticles were used to obtain nanocomposites with polyaniline (PAni). The material was prepared under exposure to ultraviolet light (UV) or under heating, from dispersions of the nanoparticles in an acidic solution of aniline. Unlike other synthetic routes reported elsewhere, this new route does not utilize any additional oxidizing agent. XRD analysis showed the appearance of a second crystalline phase in all the PAni-Fe3O4 composites, which was indexed as goethite. Furthermore, the crystallite size decreases nearly 50 % with the increase in the synthesis time. This size decrease suggests that the nanoparticles are consumed during the synthesis. Thermogravimetric analysis showed that the amount of polyaniline increases with synthesis time. The nanocomposite electric conductivity was around 10-5 S cm-1, nearly one order of magnitude higher than for pure magnetite. Conductivity varied with the amount of PAni in the system, suggesting that the electric properties of the nanocomposites can be tuned according to their composition. Under an external magnetic field the nanocomposites showed hysteresis behavior at room temperature, characteristic of ferromagnetic materials. Saturation magnetization (MS) for pure magnetite was ~ 74 emu g-1. For the PAni-Fe3O4 nanocomposites, MS ranged from ~ 2 to 70 emu g-1, depending on the synthesis conditions. This suggests that composition can also be used to control the magnetic properties of the material.
Conference papers on the topic "Temperature x time exposure constants"
1
Cheruvu, N. S., and K. T. Chiang. "Isothermal and Cyclic Oxidation Behavior of Turbine Blade Alloys." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90756.
Full textAbstract:
Oxidation behavior of two nickel-based turbine blade alloys has been investigated at three temperatures ranging from 950°C to 1066°C. Thermogravimetric analysis (TGA), isothermal exposure and cyclic oxidation tests were conducted on GTD-111 (Ni-14.1Cr-3.7W-9.2Co-1.5Mo-3.1A1-4.9Ti-0.02Cb-2.93Ta-0.11C) and IN-738 (Ni-16.0Cr-2.6W-8.1Co-1.6Mo-3.5A1-3.4Ti-0.7Cb-1.6Ta-0.10C) blade alloys. TGA results showed that the oxidation kinetics of both alloys obey parabolic rate laws. The GTD-111 material exhibited a higher parabolic rate constant than IN 738 at all temperatures investigated. Cyclic oxidation behavior of these alloys was compared by plotting the weight change results as a function of thermal cycles. Consistent with the TGA results, cyclic oxidation test results also showed that GTD-111 was less resistant to high-temperature oxidation as compared to the IN-738 alloy. To characterize the oxide scales, a series of short term isothermal oxidation tests were conducted and the spalled scale after oxidation exposure was collected and analyzed by energy-dispersive x-ray analysis (EDX) as a function of aging time. The composition of the scales varied between the alloys. The variation of oxidation behavior of these alloys is discussed with respect to the composition differences between the two alloys.
2
Lall, Pradeep, Di Zhang, Jeff Suhling, and David Locker. "Anand Viscoplasticity Model for the Effect of Aging on Mechanical Behavior of SAC305 Operating at High Strain Rate and High Temperature." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53751.
Full textAbstract:
Portable products such as smartphones and tablets stay in the powered on condition for a majority of their operational life during which time the device internals are maintained at higher than ambient temperature. Thus, it would be expected for interconnects in portable products to be at a temperature high than room temperature when subjected to accidental drop or shock. Furthermore, electronics in missile-applications may be subjected to high strain rates after prolonged period of storage often at high temperature. Electronics systems including interconnects may experience high strain rates in the neighborhood of 1–100 per sec during operation at high temperature. However, the material properties of SAC305 leadfree solders at high strain rates and high operating temperatures are scarce after long-term storage. Furthermore, the solder interconnects in simulation of product drop are often modeled using elastic-plastic properties or linear elastic properties, neither of which accommodate the effect of operating temperature on the solder interconnect deformation at high operating temperature. SAC305 solders have been shown to demonstrate the significant degradation of mechanical properties including the tensile strength and the elastic modulus after exposure to high temperature storage for moderate periods of time. Previously, Anand’s viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components under thermo-mechanical deformation. Uniaxial stress-strain curves have been plotted over a wide range of strain rates (ε̇ = 10, 35, 50, 75 /sec) and temperatures (T = 25, 50, 75, 100, 125°C). Anand viscoplasticity constants have been calculated by non-linear fitting procedures. In addition, the accuracy of the extracted Anand constants has been evaluated by comparing the model prediction and experimental data.
3
Haque, Mohammad Shafinul, and Calvin M. Stewart. "Modeling the Creep Deformation, Damage, and Rupture of Hastelloy X Using MPC Omega, Theta, and Sin-Hyperbolic Models." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63029.
Full textAbstract:
Combined cycle power plants components such as steam pipe work, pressure vessels, boilers, heat exchangers, and gas turbine disks, etc. are exposed to elevated temperature and pressure operation conditions for longer durations. Components may fail within the elastic limit due to a time dependent deformation and damage mechanism called creep. Creep prediction models are used to determine the state of these components and to schedule optimum inspection, maintenance, and replacement intervals. In this study, the deformation, damage, and life of Hastelloy X is characterized using three recently developed models; the Omega, Theta projection, and Sin-hyperbolic models. An analysis is performed to compare the models in terms of accuracy, assumptions, constant identification techniques, flexibility in use, and limitations. The influence that final creep strain has on Theta and Omega model is discussed. Sixteen tests were performed at four different configurations of stress (2.1–36.5 ksi) and temperature (1200–1800°F). In the experimental data, Hastelloy X does not exhibit the primary stage. In this study, the secondary and tertiary creep stages are modeled. Creep deformation and rupture life data is used to optimize the constants for the three models. Predictions using these models are compared with experimental data. It is found that the novel Sin-hyperbolic model better fits the experimental data, and is easier to apply. The Omega model predicts longer life than the Sinh and the Theta Projection model. The rupture life prediction of the Theta projection model is the worst due to dependence on the critical creep strain rate. It is observed that the Hastelloy X final creep strain depends on stress and temperature; this leads to a less accurate critical creep strain rate prediction resulting in inaccurate rupture life predictions for the Theta projection model. The analytical damage of the Omega model exhibits a linear evolution with time while the Sinh model show a more realistic elliptical creep damage evolution with time. A process to determine the constants of all the models is clearly described. The dependence of the trajectory of the creep curves with respect to the constants is discussed in detail. An analytical derivation of each model is provided. Predictions of these three models show that the Sinh model produces a better creep deformation curve by normalizing the experimental creep strain rate data. It is found that overall the Sinh model offers more flexibility, prediction accuracy, and is easier to apply.
4
Lall, Pradeep, Di Zhang, Jeff Suhling, and David Locker. "Anand Parameters for SAC305 Alloys After Prolonged Storage up to 1-Year." In ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2017 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ipack2017-74300.
Full textAbstract:
Electronics in automotive underhood environments may be subjected to high temperatures in the neighborhood of 175°C while subjected to high strain rate mechanical loads of vibration. Portable products such as smartphones and tablets stay in the powered on condition for a majority of their operational life during which time the device internals are maintained at higher than ambient temperature. Thus, it would be expected for interconnects in portable products to be at a temperature high than room temperature when subjected to accidental drop or shock. Furthermore, electronics in missile-applications may be subjected to high strain rates after prolonged period of storage often at high temperature. Electronics systems including interconnects may experience high strain rates in the neighborhood of 1–100 per sec during operation at high temperature. However, the material properties of SAC305 leadfree solders at high strain rates and high operating temperatures are scarce after long-term storage. Furthermore, the solder interconnects in simulation of product drop are often modeled using elastic-plastic properties or linear elastic properties, neither of which accommodate the effect of operating temperature on the solder interconnect deformation at high operating temperature. SAC305 solders have been shown to demonstrate the significant degradation of mechanical properties including the tensile strength and the elastic modulus after exposure to high temperature storage for moderate periods of time. Previously, Anand’s viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components under thermo-mechanical deformation. Uniaxial stress-strain curves have been plotted over a wide range of strain rates (ε. = 10, 35, 50, 75 /sec) and temperatures (T = 25, 50, 75, 100, 125, 150, 175, 200°C). Anand viscoplasticity constants have been calculated by non-linear fitting procedures. In addition, the accuracy of the extracted Anand constants has been evaluated by comparing the model prediction and experimental data.
5
Haque, Mohammad Shafinul, and Calvin M. Stewart. "Exploiting Functional Relationships Between MPC Omega, Theta, and Sinh-Hyperbolic Continuum Damage Mechanics Model." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63089.
Full textAbstract:
The MPC Omega and Theta models for creep deformation and life prediction have become popular in recent years. Both models offer better prediction than classical constitutive models such as Norton Power law, Bailey-Norton law, and Norton-Soderberg law to name a few. The Omega model uses a strain hardening approach and requires two material constants for creep deformation and life prediction. An analytical solution to the constants are available and it is easy to manipulate and implement numerically. However, the analytical damage of the Omega model predicts an unrealistic linear damage evolution. The Theta model uses a time-hardening approach, and requires four constant that are a function of stress and temperature. For materials under isothermal conditions, with tertiary creep dominant deformation, the Theta model constants can be determined using only two constants. Life prediction using the Theta and Omega models depends on the final creep strain. The final creep strain observed in an experiment is stochastic; dependent on the material, testing conditions, and operator. The statistics of final creep strain must be investigated before the Theta or Omega models can be applied. In literature, some authors add a nonlinear damage variable to the Theta model; however, critical damage at rupture is not unity violating the assumptions of continuum damage mechanics. There is a superior Sin-hyperbolic continuum damage model available in the literature that can be used to overcome these problems. It is hypothesized that a functional relationships exist between the three models and these relationships can be exploited to achieve more accurate and easy to implement creep deformation and life predictions. In this study, the relationships between the constants of MPC Omega, Theta, and a Sin-hyperbolic CDM models are determined analytically. The sin-hyperbolic model incorporates a continuum damage variable in the creep strain rate equation. The damage function exhibits a more realistic elliptical path and is constructed such that damage is always unity at rupture. This function facilitates conversion of one models’ constants to the constants of the other two. The relationships between the constants are identified, while maintaining dimensional homogeneity. Using the derived relationships, the three models can be easily compared and the disadvantages of each respective model can be avoided. Experimental data at four different configurations of stress (6.3 to 36.5 ksi) and temperature (1200 to 1800°F) (sixteen data sets) for Hastelloy X is used to compare the models. Creep rupture data at seven temperature levels (600 to 1000°C) and a wide stress range (5 to 500 MPa) is used to analyze life prediction. The constants for each model are determined. Using one models’ constants and the derived relationships; the predictions of the other two models are generated. It is observed that the relationship generated curves agree with experimental data. Finally, it is demonstrated that using the derived relationships, the most useful aspects of each model can combined. An elliptical damage evolution curve is obtained for the Omega model. The final creep strain rate dependency problem of the Theta model can be avoided. It is observed that the Sinh model becomes more flexible and easy to implement.
6
Slattery, Stuart R., Tamara L. Malaney, Scott J. Weber, Mark H. Anderson, Kumar Sridharan, and Todd R. Allen. "System for High Temperature Spectral Emissivity Measurement of Materials for VHTR Applications." In Fourth International Topical Meeting on High Temperature Reactor Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/htr2008-58053.
Full textAbstract:
An experimental system for in situ high temperature measurements of spectral emissivity of VHTR materials has been designed and constructed. The design consists of a cylindrical block of silicon carbide with several machined cavities for placement of test samples, as well as a black body cavity. The block is placed inside a furnace for heating to temperatures up to 1000°C. A shutter system allows for selective exposure of any given test sample for emissivity measurements. An optical periscope guides the thermal radiation from the sample to a Fourier Transform Infra Red (FTIR) spectrometer which is used for real-time measurements of spectral emissivity over a wavelength range of 0.8μm to 10μm. To specifically address the needs of VHTR applications, the system has been designed for studies with VHTR grade helium environments and air transients. Inlet and outlet gas compositions are measured using a gas chromatograph, which in conjunction with ex situ analysis of the samples by electron microscopy and x-ray diffraction will allow for the correlation of surface corrosion of the materials and their spectral emissivities under different operating and accident conditions.
7
Buschinelli, Mauricio, Xiao Huang, and Weijie Chen. "TGO Evolution and Coating Property Changes for EB-PVD TBC Coatings Under Cyclic Oxidation Condition." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22100.
Full textAbstract:
The life of a thermal barrier coating (TBC) system is governed by the microstructural evolution of the thermally grown oxide (TGO) layer between the ceramic top layer and the bond coat. While the TGO provides a barrier to the oxygen diffusion, its continuous growth imposes stresses on the TGO/bond coat and TGO/topcoat interfaces that will eventually lead to crack linkage and propagation followed by failure of the TBC system. In addition to TGO growth during thermal exposure, coating properties such as hardness, Young’s modulus and fracture toughness will also change. This study is undertaken to investigate the oxidation behaviour of an electron beam physical vapour deposition (EB-PVD) YSZ/PtAl coating system. Cyclic oxidation tests were carried out with each cycle consisting of 5 hr holding time at 1150°C followed by air cooling to room temperature. TGO evolution, coating property and maximum crack length as functions of total thermal exposure time were investigated in this study. Microstructural analyses of the coating were carried out using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Both hardness and Young’s modulus of the bond coat were measured using micro-hardness tester. The results from this study showed a parabolic TGO growth rate as a function of thermal exposure time. While no distinct mathematical relationship was found between the TGO thickness and maximum crack length, a general trend of increasing TGO thickness and maximum crack length was found with respect to exposure time. The mechanical properties of the bond coat were also found to be influenced by the thermal exposure.
8
Laurinat, James E., Matthew R. Kesterson, and Steve J. Hensel. "Pressurization Analysis for Flame Heating of a Screw Top Utility Can Loaded With Plutonium Oxide Powder." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63120.
Full textAbstract:
The documented safety analysis for the Savannah River Site (SRS) evaluates the consequences of a postulated 1000 °C (1273 K) fire in a glovebox. The radiological dose consequences for a pressurized release of plutonium oxide powder during such a fire depend on the maximum pressure that is attained inside the oxide storage containers. To enable evaluation of the dose consequences, temperature and pressure transients have been calculated for exposure of a typical set of storage containers to the fire. The oxide storage configuration selected for analysis is can/bag/can, comprised of oxide powder inside an 8.38E−6 m3 stainless steel B vial inside 0.006 kg of polyethylene bagging inside a one-quart screw top utility can of the type commonly used to package solvents or rubber cements. The analysis accounts for pressurization from gases generated by pyrolysis of the polyethylene bagging and evaporation of moisture adsorbed onto the oxide powder. Results were obtained for different can orientations and different surface fire exposures, with and without initial pressurization of the B vial by hydrogen from the radiolysis of moisture. Based on the results of hydrogen back pressure tests for plutonium oxide powders loaded with moisture, the initial gauge pressure from radiolytic hydrogen was set at a bounding value of 82 psig (5.65E5 Pa). The pressurization analysis credits venting to and from the B vial but does not credit venting or leakage from the can. Calculated maximum gauge pressures inside the utility can range from 1.98E5 Pa for an upright can exposed to fire on only one side, to 7.78E5 Pa for an upright can engulfed by fire. Maximum gauge pressures inside the B vial vary from 1.36E5 to 1.43E6 Pa. Due to the low rate of venting from the B vial into the can gas space, the can pressure is nearly independent of the B vial pressure. Calculated maximum pressures are compared to the utility can burst pressure. In lieu of an analytic structural analysis of the utility cans, burst pressures and leakage rates were measured using compressed nitrogen gas. Leakage of gas through the can lid thread and seams prevented the test apparatus from reaching the burst pressure. To achieve the burst pressure, it was necessary to seal the can lid threads and seams by brazing. The measured gauge burst pressure was 2.50E5 +/− 0.43E5 Pa. The measured burst pressures are lower than the calculated maximum pressure due to fire exposure, indicating that the utility cans could burst during exposure to a 1000 °C (1273 K) fire. Leakage rates were measured for cans initially pressurized to a gauge pressure of 1.24E5 Pa. The measured leakage rates were found to be proportional to the gauge pressure inside the can, with a time constant for leakage of 0.424 +/− 0.010 reciprocal seconds. The leakage time constants follow a threshold Weibull distribution.
9
Cho, Choonho, Tae-Yung Song, and Chungho Cho. "Corrosion Resistance of Active Coating Materials Exposed to Lead-Alloy." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89486.
Full textAbstract:
A key problem in the development of heavy liquid metal cooled reactors is a corrosion of the structural and fuel cladding materials by the coolants. Thus, the problem has been considered as an important design-factor that limits the operational temperature and flow velocity of the next generation nuclear reactors using lead-alloys. Corrosion data has been obtained on as-received and active coating materials of HT9 and 316L in a stagnant lead-alloy containing a reduced atmosphere of oxygen with an exposure time of 1500 hours at 600°C. After each test, the specimens were analyzed metallurgically by using a scanning electron microscopy (SEM) with a energy dispersive X-ray analysis (EDX) for the cross sections of the specimens. In addition, X-ray diffraction (XRD) was performed to evaluate the phase composition of the steels.
10
Stephenson, M. D., L. H. Cowell, and R. T. LeCren. "Ceramic Barrier Filters for Coal-Fueled Gas Turbine Service." In ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/91-gt-187.
Full textAbstract:
Solar Turbines is developing a coal fueled version of its 3.8 MW Centaur H gas turbine for cogeneration applications. To protect gas turbine components from erosion and corrosion due to impacting particulates, and to meet New Source Performance Standards for particulate emissions, ceramic barrier filters are being employed. The test program includes evaluation of silicon carbide candle filters. Fourteen candles are being tested for 50 h at design temperature and face velocity using the particulate-laden gas stream from a two-stage slagging combustor system. The testing includes determining collection efficiency and obtaining pressure drop versus time profiles. Additionally, exposure testing is being used to determine whether loss in strength, or changes in the chemical or mineralogical structure have occurred. This includes four-point bend testing, X-ray diffraction and scanning electron microscopy with energy dispersive X-rays.