Residual stress thermal mismatch

Fig. 9. Residual stresses owing to thermal expansion mismatch between a particle with radius a and thermal expansion coefficient and a matrix with thermal expansion coefficient The stresses illustrated here are for and P is the interfacial pressure.

Kuntz, M., Meier, B. and Grathwohl, G. (1993). Residual stresses in fiber-reinforced ceramics due to thermal expansion mismatch. J. Am. Ceram. Soc. 76, 2607-2612. 

A thermally induced residual stress. The origin of the residual stresses is a mismatch of thermal expansion behaviors among the components. Rigid connection of each component with different thermal expansion coefficients causes residual stresses. For example, the electrolyte and electrodes are fabricated and connected at a high temperature. If the thermal expansion behaviors are not identical among the components, residual stresses will occur in the cell at room temperature. For stacks, similar residual stresses will occur by a mismatch of thermal expansion behavior among cells and other stack components. 

In addition to the occurrence of the residual stress, cells warp toward the cathode side because of the mismatch of the thermal expansion behavior between the electrolyte and anode. Thus, the deformations of cells at room temperature are also... 

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. 

Niihara [1] considered the improved toughness was mainly attributed to the residual stress that results from differential thermal expansion coefficients of two phases. In Al203/SiC systems, the tensile hoop stress, thought to be over 1000 MPa around the nanoparticles within the matrix grains, was generated from the large thermal expansion mismatch. Thus, the material may be... 

Particular interest has been paid to the analytical prediction of the A Tc for the onset of matrix cracking. Blissett et al. (1997) and Boccaccini (1998) considered the residual stresses present in the composite due to thermal expansion mismatch between fibre and matrix which, when superimposed to... 

Residual stress resulting from the thermal expansion mismatch between the fiber and matrix is another factor which will affect the interfacial properties, matrix cracking stress and the mechanical properties of ceramic... 

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-... 

The polyimide and Cu powders were put in the die, and joined without graded layers. The thickness of the polyimide and Cu layers was 5 mm. A cross section is shown in Fig. 3. The interface of polyimide and Cu was cracked by the residual stress coming from the thermal expansion mismatch of polyimide and Cu. A graded layer (0.5 mm) of 50 vol% polyimide and 50 vol% Cu was inserted between the polyimide layer ( 3.5 mm) and the Cu layer (3.5 mm). The photograph of a FGM with... 

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