Self-heating Phenomenon Research Articles

Comparison of Temperature-Programmed Char Combustion in CO2−O2 and Ar−O2 Mixtures at Elevated Pressure

A pressurized thermobalance (TGA) system was built. The role of CO2 was studied in the controlled temperature combustion under pressurized conditions. Particular care was taken to employ low sample masses in thin layers, to avoid self-heating phenomena and ensure kinetic control. It was found that a CO2 partial pressure of 0.57MPa at a 0.6 MPa total pressure had no effect on the overall reaction rate of a temperature programmed combustion. KEYWORDS: High pressure thermogravimetry, char, combustion, effect of carbon dioxide

Pseudoelastic cyclic stress-strain response of over-aged single crystal Ti-50.8at%Ni

This paper concerns the High Cycle Fatigue (HCF) properties of superelastic NiTi Shape Memory Alloys (SMA). Up till today, HCF fatigue of SMAs has not been much studied and, therefore, there is a lack of tools to design the SMA pieces and structures against fatigue. In this study, it is proposed to investigate the HCF properties of NiTi SMAs by using a new approach based, on one hand, on self-heating tests under cyclic loading and, on the other hand, on a probabilistic two-scale model. The proposed model permits to establish a link between self-heating phenomena and the fatigue properties of the material. Finally, our approach is validated by comparing the model predictions to the experimental results obtained with classical HCF fatigue tests.

Progress and energy effects of weathering and degassing of solid fuels

The main phenomenon of weathering and self heating of solid fuels is the low temperature oxidation of the combustible substance. Also of importance is the degassing and low temperature devolatilization of the solid fuel and the transport of water vapour through the solid fuel bed. Energy losses and the ecological aspects of solid fuel weathering (self heating, endogenous fires, gas explosions) are the main subjects of this work. A method of the energy consumption determination in the weathering process of solid fuel, treated as a physical and chemical process, by using the kinetic relations of the main phenomena is proposed.

Identification du comportement rhéologique par analyse inverse

.The use of the inverse method principle for analysing rheological tests is presented. It is based on the finite element simulation, capable of taking into account the whole complexity of the test, especially in terms of self-heating and strain localisation phenomena. The identification of rheological parameters is then ensured by solving an inverse problem. The principle is to find the rheological coefficients which permit one to obtain the optimal comparison between the experimental measurements and the numerical resolution.

Modeling of self-heating effects in thin-film soi MOSFET's as a function of temperature

Self-heating phenomena are studied from room down to near liquid helium temperatures in fully depleted N channel thin film SIMOX MOS devices. A simple theoretical analysis of the self-heating effect is worked out. A method for the extraction of the thermal resistance and the device temperature rise directly from the static output characteristics is derived. Also direct self heating transient measurements are conducted in order to confirm our analysis.

Kinetic parameters from self-heating measurements on exothermic solid-state reactions

A method, based on the autoignition criterion, has been developed that exploits the self-heating phenomenon to determine the activation energy, E, and pseudo-zero order pre-exponential factor. A, for highly exothermic solid state reactions. Simultaneous measurement of center and wall temperatures of a cylindrical solid during programmed heating to the ignition point leads to direct calculation of the kinetic parameters. The method has been applied to the thermite reaction: 3 Cu 2O + 2 Al → 6 Cu + Al 2O 3 + 2406 J g −1. Values of E = 658 kJ mole −1 and log A = 41.1 ( A in mol m −3, sec −1) were found for the reaction.

Investigation of the self-heating phenomenon in the bulk polymerization of acrylonitrile

The temperature of the polymerizing system was measured with a thermistor during the bulk polymerization of acrylonitrile initiated by azoisobutyronitrile. The temperature of self-heating suddenly rises at a conversion of about 2%. This jump of temperature is presumably caused by the formation of a gel structure and, consequently, the outfall of thermal convection within the system.

Creep, Self Heating and Failure of Thermoplastics Under Pulsating Tensi Le Stress

Fatigue behaviour of plastics is discussed by means of creep curves and the phenomenon of self heating. Amorphous thermoplastics such as polymethyl methacrylate (PMMA) and rigid suspension polyvinyl chloride (S-PVC) and partially crystalline polypropylene (PP) are examples. In practice, the first formation of crazes and microcracks and their defor mation have to be taken as a limit for mechanical loading rather than the ultimate failure.

Origin of hysteresis in the I-V curves of point-contact junctions

Point-contact weak-link junctions often possess hysteresis in their current-voltage characteristics. We describe experimental evidence which suggests that this hysteresis is not due to the effects described by Stewart and McCumber but rather that this hysteresis is a self-heating phenomenon.

Selfheating and thermal runaway phenomena in semiconductor devices

A unitary treatment of the stationary and transient selfheating of semiconductor devices is presented which allows an analytic approach to various problems related to the thermal runaway phenomenon.

The self-heating and shrinkage phenomena during the high-temperature oxidation of porous nickel

The results of this investigation into the oxidation process of porous nickel during heating in air show the following oxidation characteristics: