| Metal honeycomb materials and ceramic matrix composite materials possess excellent thermal/mechanical properties,and have been widely used in the field of aviation,nuclear energy,navigation,transportation and national defense.During their service,they are often faced with complex temperature environments.This puts makes a strict request on the service safety of these materials.Mechanical properties,as an important index to evaluate the service safety of materials,will evolve with temperature.Therefore,it is of great scientific significance and engineering application value to understand the key controlling factors of the mechanical properties of metal honeycomb and ceramic matrix composites as well as their evolution law with temperature during service,and to reasonably and effectively characterize their mechanical properties.Based on the force-heat equivalence principle,the following researches were carried out for metal honeycomb materials,thermal barrier coatings and ceramic materials:1)A temperature-dependent numerical model of metal honeycomb materials was established.The effect of temperature on the mechanical properties of honeycomb material under out-of-plane compression was studied.The crush load efficiency(CLE)and deformation pattern are temperature insensitive in the temperature range of this study.Then,based on super folding element theory,the temperature dependent theoretical models without fitting parameters for the plateau stress and specific energy absorption(SEA)of metallic honeycomb materials were developed.These theoretical models are successfully verified by numerical simulations and experiment results.Furthermore,the effects of parent material properties on the plateau stress and SEA at different temperatures were discussed.The results in this study can provide useful guidelines in optimizing the choice of parent materials to fabricate metallic honeycombs with better energy absorption efficiency at different temperatures.2)Considering the effect of plastic deformation energy on the damage and failure,a damage failure criterion for thermal barrier coating(TBC)under thermal cycling load was proposed Based on the damage failure criterion,the failure energy density distribution in each layer of TBC after a thermal cycle load was simulated and analyzed,and the reason why the cracks first appear in the upper left of TC/TGO interface trough is given.With the thermal cycle loading,it was found that the cracks propagate to the interior of the ceramic layer,but not always along the TC/TGO interface.Moreover,it was not easy to occur on the top of the wave peak of the thermal growth oxide layer,which is consistent with the experimental results reported.The results can provide technical reserve for damage failure behavior and performance evaluation of thermal barrier coatings under thermal cycling load.3)A thermal shock failure criterion applied to the temperature dependence of ultrahigh temperature ceramic materials under three-dimensional stress state was established.Combining with the finite element method,the thermal shock behavior of zirconium boride ultra-high temperature ceramic matrix composites with the leading edge shape and different geometric dimensions was numerically analyzed.The simulation results were compared with the experimental results,and a good agreement was obtained,which verifies the rationality of the temperature dependent failure criterion.Further,based on the numerical simulation model,the effect of geometry on the thermal shock resistance of ceramic materials at 800? was studied.It is found that the specimen with smaller leading edge radius,larger wedge angle and thinner thickness will have stronger thermal shock resistance.These results can provide a support for the study of thermal shock resistance of ceramic materials with different geometrical morphology. |
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