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Heating Tests (heating + test)
Selected AbstractsA double structure generalized plasticity model for expansive materialsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2005Marcelo Sánchez Abstract The constitutive model presented in this work is built on a conceptual approach for unsaturated expansive soils in which the fundamental characteristic is the explicit consideration of two pore levels. The distinction between the macro- and microstructure provides the opportunity to take into account the dominant phenomena that affect the behaviour of each structural level and the main interactions between them. The microstructure is associated with the active clay minerals, while the macrostructure accounts for the larger-scale structure of the material. The model has been formulated considering concepts of classical and generalized plasticity theories. The generalized stress,strain rate equations are derived within a framework of multidissipative materials, which provides a consistent and formal approach when there are several sources of energy dissipation. The model is formulated in the space of stresses, suction and temperature; and has been implemented in a finite element code. The approach has been applied to explaining and reproducing the behaviour of expansive soils in a variety of problems for which experimental data are available. Three application cases are presented in this paper. Of particular interest is the modelling of an accidental overheating, that took place in a large-scale heating test. This test allows the capabilities of the model to be checked when a complex thermo-hydro-mechanical (THM) path is followed. Copyright © 2005 John Wiley & Sons, Ltd. [source] A study on the behavior of a cylindrical type Li-Ion secondary battery under abnormal conditions. Über das Verhalten eines zylindrischen Li-Ionen Akkumulators unter abnormalen BedingungenMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 5 2010S. Kim zylindrische Li-Ionen Akkumulatoren; mechanisches Verhalten; abnormale Bedingungen; Separator Abstract Li-ion (lithium ion) secondary batteries are rechargeable batteries in which lithium ions move between the cathode and the anode. Lithium is not as safe as nickel cadmium (NiCd), and the Li-ion battery can under some conditions increase in temperature and ignite abnormal conditions which includes overcharging, being subjected to an impact, or being hit by a projectile. Before studying causes of Li-ion battery explosions, the term "abnormal condition" was defined. Next, to check the mechanical conditions, an impact test by a free falling object of 9.1 kg weight made of steel was carried out. After the impact test, the damage of the separator around the hollow of the jelly roll in the cell was observed. Following this, the same cell's electrochemical conditions were assessed through a heating test to determine the potential thermal runaway. Finally, to analyze the mechanical damage to the Li-ion batteries during the charging and the impact test, a finite element analysis was performed using LS-DYNA and ABAQUS software. A cylindrical type Li-ion secondary battery was selected for the impact test, heating test, and simulation. The test and simulation results provided insights into the extent to which cylindrical cells can endure abnormal conditions. [source] Ignition studies of cerium nitrate treated towelsFIRE AND MATERIALS, Issue 3 2006C. L. Beyler Abstract This study evaluated the ignitability of cotton towel material saturated with an oxidizer solution of 0.5 N cerium nitrate in 2 N nitric acid. Four types of ignition testing were performed in this work: self-heating oven tests, hot object ignition tests, radiative smoldering ignition tests, and piloted flaming ignition/burning rate tests. Results indicate that cerium nitrate significantly enhances the ignitability of the towels. Self-heating properties of cerium nitrate treated towels were measured using the standard constant temperature oven method described by Bowes. Based upon these self-heating properties, self-heating is not a hazard for storage scenarios other than bulk storage (depths of several meters) of cerium nitrate treated towels at room temperature. Surface ignition of hot objects was observed for object temperatures as low as 250°C placed upon room temperature cerium nitrate treated towels. Ignition for hot objects buried within a pile of towels occurred for object temperatures as low as 230°C. Radiant heating tests of cerium nitrate treated towels showed initiation of smolder at heat fluxes as low as 3 kW/m2 at surface temperatures as low as 175°C. This compares with ordinary cellulosic materials that require 7,8 kW/m2 heat fluxes and temperatures of 250°C. All four scenarios demonstrate enhanced ignitability and burning rates of cerium nitrate treated towels. Copyright © 2005 John Wiley & Sons, Ltd. [source] Oxidation behaviour of Fe-Cr-Al alloys during resistance and furnace heatingMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2006H. Echsler Abstract The behaviour of thin Fe-Cr-Al heating element strips was investigated with respect to the oxidation limited life times and geometrical changes during resistance and furnace heating. For this purpose, isothermal and cyclic oxidation tests varying in their total exposure time and cycle duration were performed in the temperature range 1050,1200 °C. Specimens subjected to rapid cyclic, resistance heating revealed shorter life times than calculated for specimens subjected to isothermal exposure. The life times were found to increase with increasing cycle duration and hence decreasing number of cycles for a given time at temperature. This life time decrease is related to an "hour glass" waviness of the specimens, which develops during prolonged thermal cycling. The development of this plastic deformation also occurred during furnace heated, thermal cycling tests. A two-step mechanism is introduced combining an oxidation kinetics related time to the onset of significant waviness with an enhancement of this waviness as a result of a ratcheting effect. The latter seems to strongly depend on the number of cycles and on the plastic deformation generated during each cycle rather than on the total time at temperature. The development of an "hour glass" waviness leads to an enhanced aluminium depletion due to an increase of the specimen surface area. Additional deformation phenomena like "hot tube" or "corkscrew" behaviour occur during the resistance heating tests. These are related to a temperature gradient that develops over the specimen width due to the poor aspect ratio of the specimens. [source] Measurement and prediction of thermal conductivity for hemp fiber reinforced compositesPOLYMER ENGINEERING & SCIENCE, Issue 7 2007T. Behzad The thermal conductivity of hemp fiber reinforced polymer composites were studied from the steady state temperature drop across samples exposed to a known heat flux. The transverse and in-plane thermal conductivities for oriented and randomly oriented composites for different volume fractions of fiber were investigated. Experimental results showed that the orientation of fibers has a significant effect on the thermal conductivity of composites. To validate the experimental results, the heating tests for the thermal conductivity measurements were simulated by a finite element model using the thermal conductivity values obtained from the experiments. Predicted temperatures show close agreement with measured temperatures. Moreover, the experimental results of thermal conductivities of composites at different directions were compared with two theoretical models and illustrated good agreement between the obtained results and models. POLYM. ENG. SCI. 47:977,983, 2007. © 2007 Society of Plastics Engineers [source] Heat transfer to a moving packed bed of nickel pelletsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2008M. H. I. Baird Abstract Heat transfer between a bed of nickel pellets and a vertical section of electrically heated steel pipe has been measured, with the pellet bed inside the vertical pipe. Most of the data are for a 20.27 cm diameter pipe but some data were also obtained for a 10.23 cm diameter pipe. The effective thermal conductivity of the stationary pellet bed has been estimated approximately from the results of unsteady heating tests. Tests have been carried out with a downwardly moving bed, including the effect of air flowing upwards through the bed. Average values of the pellet-side heat transfer coefficient are between 72 and 135 W/(m2°C) depending on the mass fluxes of air and pellets, and have been expressed as an empirical correlation. Le transfert de chaleur entre un lit de pastilles de nickel et une section verticale d'une conduite d'acier chauffée électriquement a été mesuré, le lit de pastilles se trouvant à l'intérieur de la conduite verticale. La plupart des données ont été obtenues pour une conduite de 20,27 cm de diamètre, mais certaines données ont également été obtenues pour une conduite de 10,23 cm de diamètre. La conductivité thermique effective d'un lit de pastilles stationnaire a été estimée de manière approximative à partir des résultats de tests de chauffe en régime non stationnaire. Les tests ont été menés avec un lit en mouvement descendant, incluant l'effet de l'air circulant dans le sens ascendant dans le lit. Les valeurs moyennes du coefficient de transfert de chaleur du côté des pastilles sont comprises entre 72 et 135 W/(m2°C) selon les flux massiques de l'air et des pastilles, et sont exprimées en tant que corrélation empirique. [source] | |||||||||||||