Numerical Simulation Research On Thermal Protection Coating During Service Process

Thermal protection coating is a kind of insulating coating to protect substrate material.Thermal protection coating can protect substrate material from oxidation and corrosion,meanwhile,it can make substrate material service in higher temperature so that the service life of substrate material can be extended.So it has been applied widely in many fields,such as aerospace.With the development of research program of hypersonic vehicle,preparation and application of thermal protection coating has become one of the main research objectives,and lots of researchers all around the world have done masses of work.Thermal protection coating has to bear large temperature gradient under high temperature,and there is thermal stress in the whole coating structure under the effect of high temperature,which can affect its performance.Therefore,research on temperature and stress response of thermal protection coating servicing under high temperature is the emphasis of this thesis.Taking the nozzle as target location,a two-dimensional axisymmetric finite element(FE)model based on SiC/SiC composite which has excellent performance under high temperature was constructed,and research on the temperature field,stress and strain field of thermal protection coating servicing under typical high temperature was conducted.Main contents and conclusions are as follows:Firstly,with the aid of heat transfer and thermal stress finite element theory,thermal protection coating model based on SiC/SiC composite was established to simulate the temperature field,stress and strain field using software MSC.Marc.The results indicate that thermal protection coating reduces the substrate temperature markedly,which shows its excellent heat insulation effect.There is large stress gradient near the ceramic coating and bond coating interface,bond coating and substrate interface owing to mismatching of material properties.And there is large total equivalent plastic strain in bond coating area.Then,in view of the instability of the thermal protection coating structure during reuse,numerical simulation of temperature field,stress and strain field was conducted,ignoring the creep behavior at elevated temperature.And the evolution of temperature and stress were analyzed.The results indicate that with the increase of cycle,temperature does not change at all,but stress varies with position,and total equivalent plastic strain accumulates in the plastic deformation area.In the end,based on the FE results of service process,temperature and stress sensitivity analysis of thermal protection coating was carried out using local sensitivity method.The results indicate that temperature field is sensitive to heat conductivity and thickness of ceramic coating,but insensitive to specific heat.And stress field is sensitive to heat conductivity,elastic module,coefficient of thermal expansion,poison’s ratio and thickness of ceramic coating,but insensitive to specific heat.