We start with the compressible Oldroyd–B model derived in[2](J.W.Barrett,Y.Lu,and E.Suli,Existence of large-data finite-energy global weak solutions to a compressible Oldroyd–B model,Commun.Math.Sci.,15(2017),1265–...We start with the compressible Oldroyd–B model derived in[2](J.W.Barrett,Y.Lu,and E.Suli,Existence of large-data finite-energy global weak solutions to a compressible Oldroyd–B model,Commun.Math.Sci.,15(2017),1265–1323),where the existence of global-in-time finite-energy weak solutions was shown in two dimensional setting with stress diffusion.In the paper,we investigate the case without stress diffusion.We first restrict ourselves to the corotational setting as in[28](P.L.Lions,and N.Masmoudi,Global solutions for some Oldroyd models of non-Newtonian flows,Chin.Ann.Math.,Ser.B,21(2)(2000),131–146)We further assume the extra stress tensor is a scalar matrix and we derive a simplified model which takes a similar form as the multi-component compressible Navier–Stokes equations,where,however,the pressure term related to the scalar extra stress tensor has the opposite sign.By employing the techniques developed in[30,35],we can still prove the global-in-time existence of finite energy weak solutions in two or three dimensions,without the presence of stress diffusion.展开更多
From existing knowledge about high-temperature cavitation mechanisms, necessary conditions were discussed for the suppression of cavitation failure during superplastic deformation in ceramic materials. The discussion,...From existing knowledge about high-temperature cavitation mechanisms, necessary conditions were discussed for the suppression of cavitation failure during superplastic deformation in ceramic materials. The discussion, where special attention was placed on the relaxation of stress concentrations during grain-boundary sliding and cavity nucleation and growth, leaded to a conclusion that cavitation failure could be retarded by the simultaneous controlling of the initial grain size, the number of residual defects, diffusivity, dynamic grain growth and the homogeneity of microstructure. On the basis of this conclusion, high-strain-rate superplasticity （defined as superplasticity at a strain rate higher than 0.01 s^-1） could be intentionally attained in some oxide ceramic materials. This was shown in tetragonal zirconia and composites consisting of zirconia, a-alumina and a spinel phase.展开更多
基金The work of Y.Lu has been supported by the Recruitment Program of Global Experts of China.The work of M.Pokorny was supported by the grant of the Czech Science Foundation No.19-04243S.
文摘We start with the compressible Oldroyd–B model derived in[2](J.W.Barrett,Y.Lu,and E.Suli,Existence of large-data finite-energy global weak solutions to a compressible Oldroyd–B model,Commun.Math.Sci.,15(2017),1265–1323),where the existence of global-in-time finite-energy weak solutions was shown in two dimensional setting with stress diffusion.In the paper,we investigate the case without stress diffusion.We first restrict ourselves to the corotational setting as in[28](P.L.Lions,and N.Masmoudi,Global solutions for some Oldroyd models of non-Newtonian flows,Chin.Ann.Math.,Ser.B,21(2)(2000),131–146)We further assume the extra stress tensor is a scalar matrix and we derive a simplified model which takes a similar form as the multi-component compressible Navier–Stokes equations,where,however,the pressure term related to the scalar extra stress tensor has the opposite sign.By employing the techniques developed in[30,35],we can still prove the global-in-time existence of finite energy weak solutions in two or three dimensions,without the presence of stress diffusion.
基金supported by a Grant-in-Aid for Scientific Research B21360328 from JSPSGrant-in-Aid for Scientific Research on Priority Areas 474-19053008 from MEXT,Japan
文摘From existing knowledge about high-temperature cavitation mechanisms, necessary conditions were discussed for the suppression of cavitation failure during superplastic deformation in ceramic materials. The discussion, where special attention was placed on the relaxation of stress concentrations during grain-boundary sliding and cavity nucleation and growth, leaded to a conclusion that cavitation failure could be retarded by the simultaneous controlling of the initial grain size, the number of residual defects, diffusivity, dynamic grain growth and the homogeneity of microstructure. On the basis of this conclusion, high-strain-rate superplasticity （defined as superplasticity at a strain rate higher than 0.01 s^-1） could be intentionally attained in some oxide ceramic materials. This was shown in tetragonal zirconia and composites consisting of zirconia, a-alumina and a spinel phase.
