Thermal residual stresses

Residual radiation, from nuclear power facilities, 17 553-554 Residual stress/strain measurement diffractometers in, 26 428—430 Residual thermal stresses ceramics, 5 632-633... 

Residual Thermal Stress Control of Polyimide Through the Use of Self-Assembled, Phase Separated Block Copolymers. ... 

The residual thermal stress was investigated with a Plexus stress analyzer. The residual stress, was calculated from the radii of wafer curvatures before and after polyimide film deposition by the following equation ... 

Young, R.J., Day. R.J., Zakikhani, M. and Robinson, I.M. (1989). Fiber deformation and residual thermal stresses in carbon fiber reinforced PEEK. Composites Sci. Technol. 34, 243-258. 

Previous studies of the interphase/interlayer have mainly focused on the coefficient of thermal expansion (CTE) and residual thermal stresses. The importance of residual thermal stresses cannot be overemphasized in composites technology because the combination of dissimilar materials in a composite creates inevitably an interphase across which residual stresses are generated during fabrication and in service due to the difference in thermo-mechanical characteristics. The importance of an interlayer is clearly realized through its effects in altering the residual stress fields within the composite constituents. 

Three-dimensional distributions of the micro-residual stresses are very complicated, and are affected by the elastic properties, local geometry and distribution of the composite constituents within a ply. Many analytical (Daniel and Durelli, 1962 Schapery, 1968 Harris, 1978 Chapman et ah, 1990 Bowles and Griffin, 1991a, b Sideridis, 1994) and experimental (Marloff and Daniel, 1969 Koufopoulos and Theocaris, 1969 Barnes et ah, 1991 Barnes and Byerly, 1994) studies have been performed on residual thermal stresses, A two-dimensional photoelastic study identified that the sign and level of the residual stresses are not uniform within the composite, but are largely dependent on the location (Koufopoulos and Theocaris,... 

A candidate interlayer consisting of dual coatings of Cu and Nb has been identified successfully for the SiC-Ti3Al-I-Nb composite system. The predicted residual thermal stresses resulting from a stress free temperature to room temperature (with AT = —774°C) for the composites with and without the interlayers are illustrated in Fig. 7.23. The thermo-mechanical properties of the composite constituents used for the calculation are given in Table 7.5. A number of observations can be made about the benefits gained due to the presence of the interlayer. Reductions in both the radial, and circumferential, o-p, stress components within the fiber and matrix are significant, whereas a moderate increase in the axial stress component, chemical compatibility of Cu with the fiber and matrix materials has been closely examined by Misra (1991). 

Favre J.P. (1988). Residual thermal stresses in fiber reinforced composite materials - A review. J. Mech. Behaviour of Mater. 1, 37-53. 

Gardener, S.D., Pittman, C.U. and Hackett, R.M. (1993a). Residual thermal stresses in filamentary polymer matrix composite materials incorporating an elastomeric interphase A mathematical assessment. Composites Sci. Technol. 46, 307-318. 

Jayaraman, K. and Reifsnider, K.L, (1993). The interphase in unidirectional fiber reinforced epoxies effect on residual thermal stresses. Composites. Sci. Technol. 47, 119-129. 

Vedula, M., Pangborn, R.N. and Queeney, R.A. (1988). Modifieation of residual thermal stress in a metal matrix eomposite with the use of a tailored interfacial region. Composites 19, 133-137. 

Nagy, P. B. and Adler, L. (1989). On the origin of increased backward radiation from a liquid-solid interface at the Rayleigh angle. J. Acoust. Soc. Am. 85,1355-7. [116] Narita, T., Miura, K., Ishikawa, I., and Ishikawa, T. (1990). Measurement of residual thermal stress and its distribution on silicon nitride ceramics joined to metals with scanning acoustic microscopy. /. Japan. Inst. Metals 54,1142-6. [148]... 

Numerical calculations for the residual stresses in the anode-supported cells are carried out using ABAQUS. After modeling the geometry of the cell of the electro-lyte/anode bi-layer, the residual thermal stresses at room temperature are calculated. The cell model is divided into 10 by 10 meshes in the in-plane direction and 20 submeshes in the out-plane direction. In the calculation, it is assumed that both the electrolyte and anode are constrained each other below 1400°C and that the origin of the residual stresses in the cell is only due to the mismatch of TEC between the electrolyte and anode. The model geometry is 50 mm x 50 mm x 2 mm. The mechanical properties and cell size used for the stress calculation are listed in Table 10.5. 

Kolhe, R., Wi, C.Y.I., Ustandag, E. and Sass, S.L., Residual thermal stresses and calculation of the critical metal particle size for interfacial crack extension in metal-ceramic matrix composites , Acta Mater, 1996 44(1) 279-287. 

Because nanocomposites are made from different phases with different thermal expansion coefficients and elastic moduli, they inevitably develop residual thermal stress during cooling after sintering. Assuming the dispersion phase is spherical particulate in the matrix material, residual stresses can be developed due to differences in the thermal expansion and elastic constants between the matrix and the particles [23] ... 

Blissett et al. (1997) used the concentric cylinder model of Powell et al. (1993) to obtain residual stresses, whereas Boccaccini (1998) utilised the results of a simple force balance in 1-D performed by Wang et al. (1996), which gives the residual thermal stresses in the matrix along the axial direction as ... 

Powell, K.L., Smith, P.A., Yeomans, J.A. (1993), Aspects of residual thermal stresses in continuous-fibre-reinforced ceramic matrix composites , Comp. Sci. Tech., 47, 359-367. 

In this section, an analytical solution to calculate residual stresses in an FGM disk is discussed, based on simple linear elastic plate theories of classical mechanics, and used for the calculation of residual stresses in a plane stress state. An equi-biaxial stress analysis differs from a plane stress state by simply replacing the Young s modulus A by the corresponding biaxial modulus E = E/( 1 - v). In this way, the residual thermal stress can be calculated in the centre of the FGM disk, far enough away from the free edges where a complex stress state is present. 

We propose to rationalize the observation by a phenomenon known as residual thermal stresses. Residual thermal stresses arise from the fact that carbon-fiber and epoxy have different thermal expansion coefficients and a quenching of the composite would conceivably produce residual stresses. Apparently, the quenching process may produce enough residual stresses to lower the toughness of the composite. In the absence of such residual stresses the free volume concept alone would predict a quenched glass to have larger amount of free volume and hence constitute a less brittle substance. 

In order to study the effect of physical aging on the carbon-fiber reinforced epoxy, the freshly quenched materials were then sub-Tg annealed at 140 °C. After annealing for only 10 minutes at that temperature, the toughness of the composite was restored to a level comparable to that of the postcured material (see Fig. 7). It is likely that residual thermal stresses resulted from the quenching were annealed away during this 10 minutes thermal aging at 140 °C. 

---