Thermal expansion instantaneous

The parameter R is applicable for the case of instantaneous change in surface temperature (infinite h) for conditions of rapid heat transfer R is for a relatively low Biot modulus ( jl< 2) for conditions of slow heat transfer R" is for a constant heating or cooling rate.88 defines the minimum temperature difference to produce fracture under conditions of infinite heat-transfer coefficient, i.e. A = 1. The parameter Ris inversely proportional to a. Alow value of a is therefore essential for good thermal stress resistance. The coefficient of thermal expansion normally increases with increasing temperature however, thermal conductivity decreases. 

After a temperature quench from T0 to T with AT = T, T0 > 0 an almost instantaneous volume decrease from V0 to V1 occurs, determined by the thermal expansion coefficient ag. Subsequently the volume gradually decreases (volume retardation) to UlDO as determined by the Aa = [Pg.429]

Background At elevated temperatures the rapid application of a sustained creep load to a fiber-reinforced ceramic typically produces an instantaneous elastic strain, followed by time-dependent creep deformation. Because the elastic constants, creep rates and stress-relaxation behavior of the fibers and matrix typically differ, a time-dependent redistribution in stress between the fibers and matrix will occur during creep. Even in the absence of an applied load, stress redistribution can occur if differences in the thermal expansion coefficients of the fibers and matrix generate residual stresses when a component is heated. For temperatures sufficient to cause the creep deformation of either constituent, this mismatch in creep resistance causes a progres-... 

PAS is a technique based on the so-called optoacoustic effect When a short pulse of electromagnetic radiation interacts with condensed matter, the absorbed energy is converted into heat by fast nonradiative relaxation processes. Subsequently, the thermal expansion of the instantaneously heated medium causes an acoustic pulse, which is detected. 

The thermal expansion coefficient of a material is a measure of the rate of change in volume, and therefore density, with temperature. The true (sometimes called instantaneous) thermal expansion coefficient is defined as the slope of the volume versus temperature curve, at a specified temperature and constant pressure (usually 1 atmosphere) ... 

Thermal property evaluation took place with respect to thermal expansion, diffusivity, specific heat, and ultimately thermal conductivity. Instantaneous CTE data at 20°C is presented in Figure III. The thermal expansion of these materials is an important consideration to take account of, as many applications require matching CTE s to help reduce thermal mismatch stresses during cycling. Results are plotted with a rule of mixture model as well as the Turner and Kemer models for CTE. These are shown in Equations 5, 6, and 7 respectively. These predictions were also based on the SiCrSi system, with the property inputs provided in Table II. 

The early Universe can be reasonably described as a dilute gas of particles and radiation in thermal equilibrium, uniquely characterised by its instantaneous density and temperature. The expansion of space causes further dilution and coohng of this gas. 

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