Radial thermal expansion

J. F. Villeneuve, R. Naslain, R. Fourmeaux and J. Sevely, Longitudinal/radial thermal expansion and Poisson ratio of some ceramic fibers as measured by TEM, Composites Sci. Technology, 49,89-103 (1993). 

To prevent an ATWS (Anticipated Transient Without Scram), this separated shutdown system, low excess reactivity core and the primary flow coast down control system are adopted. Furthermore, features of the metallic fuel, thermal expansion of control rod drive line, radial thermal expansion of core and large heat capacity are expected to mitigate an ATWS. 

For the loss of flow/loss of cooling event without scram, the increased core and bulk sodium temperatures would result in negahve reachvity feedbacks from the thermal expansion of the above-core load pad (ACLP), the radial thermal expansion of the core support grid plate, and core assembly bowing, resulting in a power reduchon to near zero fission power. Decay heaf is removed by fhe passive air natural circulation heat removal... 

Internal clearance is the amount of radial play within a bearing. This clearance accommodates the effects of tight shaft and housing fits, radial thermal expansion, speed, and other operating conditions. 

The flat sealing of the calottes area around the tips compensates the radial thermal expansion of the manifold and avoids stresses by hindering thermal expansion. A minimum injection pressure applied to the surface reduces buoyancy forces. The small material volume in the calottes area facilitates the rapid change of material. Tight tolerances for the tip position and length enable exact positioning of the tip... 

The stress in a cylinder due to a thermal gradient % in the axial direction can be obtained by first subdividing the cylinder into infinitesimal rings of length dx. Hence, the radial thermal expansion due to % in each ring is given by (o ) ] )(r). This expansion can be eliminated by applying an external force P, such that... 

With disk diameters above 5.25 in., all parameters, eg, water absorption and thermal expansion, become more critical which aggravates the expansion or warp of disks. If in the future disk rotation speeds have to be increased significantly to boost data transfer rates, higher demands will be placed on warp (tilt angle) and modulus to avoid creeping (ie, irreversible elongation in radial direction). A survey of the requirement profile for the substrate material of optical disks is given in Table 5 (182,186,187,189). 

Fig. 7.14. Normalized radial residual stresses as a function of coating thickness, I/a, for varying coefficients of thermal expansion (CTE) of the coating, Oc = 10,70,130 x 10 /°C (a) Young s modulus ratio Ej/Em = 0.333 (b) Ei/En, = 1.0. After Kim and Mai (1996a, b).

For most metal-reinforced nanocomposites the thermal expansion coefficient of the metal phase will be larger than that of the matrix, reversing the expected stress fields compared to SiC-reinforced alumina. Thus while the tensile radial stresses surrounding occluded particles may induce transgranular cracking, the compressive hoop stresses may inhibit crack propagation if the particles are located at grain boundaries. Macrostresses in sub-micron Ni... 

It is worth pointing out that carbon fibre itself has anisotropic thermal expansion properties, and therefore this mismatch between the carbon fibres and the a-sialon matrix should be considered in both the radial and axial directions when carbon fibres are unidirectionally aligned in the composite. The thermal stress caused by thermal expansion differences between the carbon fibres and the matrix in the radial (cr) and axial (oa) directions can be estimated from the formulae (Chawla, 1993 Kerans and Parthasarathy, 1991) ... 

---