EVALUATION OF RESIDUAL STRESS IN A THICK-WALLED TUBE FOR FUNCTIONALLY GRADIENT MATERIAL

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A study has been done for examining the residual stress in a thick-walled tube of a functionally gradient material manufactured by a centrifugal method. Duralcan F3D.20S composites that were AL/20vol%SiC were adopted as a master composites. The effectiveness of the curved beam theory considering the gradation of properties was first to eamine by a ring compression test. The circumferential strain generated by residual stress were measured based on the cutting test and the observed strain were in the range of - 750mu strain to 500mu strain. Based on this results, the distribution of residual stress were analyzed as an inverse problem and a numerical analysis was also adopted to solve the thermal deformation of axial symmetry. When the test pieces were cooled uniformly, the yielded stress and strain were changed from compression to tension toward the outside of the tube accompanied with a decrease in a coefficient of thermal expansion., It was concluded that the residual stress were generated by a cooling from a reference temperature of half the melting point to ambient temperature that was about 140K.The residual stress were found to enlarged corresponding to the increase of thermal epansion mismatch and radial thickness.