Multi-field Coupling Transient Behavior Of Semi-infinite Body,micro-scale Rod And Hollow Spherical Cavity Structures In Porous Media

Classical heat transfer theory believes that the speed of heat transmission is infinite.With the continuous innovation and development of industrial technology,scholars have found that the actual heat transmission situation is contrary to the classical theory through experimental observation.Especially in some extreme heat transfer phenomenon,the traditional heat transfer theory can be unable to accurately describe the extreme heat transfer process.In order to find out the law of heat propagation in extreme environment,many scholars have proposed a series of generalized thermoelastic theories to modify the classical heat transfer theory,including L-S generalized thermoelastic theory,G-N generalized thermoelastic theory,three-phase-lag generalized thermoelastic model,etc.To base these theories,through introducing nonlocal parameters and fractional parameters,the nonlocal generalized thermoelastic theory and the fractional generalized thermoelastic theory are established.In recent years,with the innovation of material technology,porous materials have been widely used in aerospace,electronic communication,petrochemical,civil engineering,biological medicine and other fields because of their advantages such as low relative density,heat insulation and sound insulation,good air permeability.Therefore,in the environment of high temperature gradient or ultra-fast heating,revealing the mechanical behavior of porous media materials under extreme heat transfer conditions is of great significance for guiding their potential application and optimization.Moreover,in the existing literature,there are almost no studies on porous media materials under generalized thermoelastic theory.Therefore,basing on the three-phase-lag generalized thermoelastic model,L-S generalized thermoelastic theory,nonlocal effect and fractional order theory,the generalized thermoelastic coupling problem of porous media structures are analyzed by using Laplace transform and its inverse transform in this paper.Specific research contents are as follows:(1)Based on the three-phase-lag generalized thermoelastic model and the thermoelastic theory of porous media,the dynamic response of semi-infinite porous media structures subjected to ramp-type thermal shock is studied.The variation laws of dimensionless stress,temperature,displacement and volume fraction fields under different time lag factors,different times and different generalized thermoelastic theories were investigated.The results show that different time lag factors and different generalized thermoelastic theories have significant effects on the physical quantities in porous media structures.(2)Basing on the generalized thermoelastic theory of L-S and the thermoelastic theory of porous media,the governing equations of the generalized thermoelastic theory of L-S considering the nonlocal effects were derived.The dynamic response of the micro-rod with fixed ends under the shock of a moving heat source was studied.The effects of different time lag factors,moving velocity of heat source and nonlocal parameters on dimensionless stress,temperature,displacement and volume fraction fields were investigated.At the same time,based on the L-S generalized thermoelastic theory,the dynamic response of porous media structure and non-porous structure under the shock of moving heat source is compared.The results show that both the time lag factor and the change of moving heat source have obvious influence on each physical quantity.The change of non-local parameters has a certain degree of influence on other physical quantities,except temperature.There are great differences in the changes of physical quantities between pore structure and non-pore structure.(3)To base on L-S generalized thermoelastic theory and porous media thermoelastic theory,the governing equation of L-S generalized porous media thermoelastic theory considering the fractional order theory is obtained by introducing fractional order parameters into it.By using the generalized thermoelasticity of L-S type porous media,the dynamic response problem of an infinite structure of porous media with spherical cavity is solved when the interior is subjected to ramp-type thermal shock.Meanwhile,the effects of different time lag factors and fractional parameters on dimensionless stress,temperature,displacement and volume fraction field are analyzed.The results show that each physical quantity in this structure will be affected by time lag factor and fractional order parameter change.