Radiation effects dimensional changes

Wood is an anisotropic material that undergoes uneven dimensional changes and, under extreme variations of environmental conditions, becomes distorted and warped (see Chapter 10). Exposed to the atmosphere, wood is also susceptible to the mechanical forces of wind and rain, and the effects of solar radiation the latter, in particular, causes discoloration initially, and then photochemical degradation, which often results in the wood s total decomposition. Wood is also prone to consumption by bacteria, fungi, insects, and rodent animals (Unger et al. 2001). 

Assumptions 1 Heat transfer is steady since there is no indication of any change with time. 2 Heat transfer is one-dimensional since there is thermal symmetry about the centerline and no variation in the axial direction. 3 Thermal conductivities are constant. 4 The thermal contact resistance at the interface is negligible. 5 Heat transfer coefficient incorporates the radiation effects, if any.. . . .. 

A one-dimensional thermal response model was developed to predict the temperature of FRP structural members subjected to fire. Complex boundary conditions can be considered in this model, including prescribed temperature or heat flow, as well as heat convection and/or radiation. The progressive changes of thermophysical properties including decomposition degree, density, thermal conductivity, and specific heat capacity can be obtained in space and time domains using this model. Complex processes such as endothermic decomposition, mass loss, and delatnina-tion effects can be described on the basis of an effective material properties over the whole fire duration. 

Large dimensional changes can be induced by radiation which distorts the object and changes the image permanently. This is a serious effect in polymer microscopy because it can be accidentally overlooked. Loss of mass is difficult to miss and the transient crystallographic contrast details require the operator to be concerned about radiation damage. But the distortion may be instantaneous under the viewing conditions normally used and the result is a stable and maybe mislead-... 

By far the greater proportion of incident X-radiation is transmitted by a crystalline sample. However, a small fraction is scattered (effectively reflected) in all directions by every motif in the material, without change in wavelength. The motif is the repeating unit of pattern in a crystal it is the TAG molecule in the case of a fat crystal. Motifs can be considered to be located at or near the intersections of an imaginary 3-dimensional grid called the crystal lattice and the intersections are called lattice points (Hammond, 1997). 

Mapes et al (Refs 83,151 152) continued their studies on the effect of gamma Co radiation on ten plastic-bonded HMX and DATB compns. Exposures up to 3.5 x 10 R at three rates, 4.3 x 10 , 2.1 x 10 and 7.4 x 10 R/hr, were obtained. Physical changes were determined by measurements of diameter, length and weight and by calcns of volume and density. DATB/EXON displayed the most resistance to dimensional and weight changes. DATB/EXON had practically no changes while HMX/NC at... 

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