Numerical Simulation Of Erosion Failure Of Thermal Barrier Coatings Based On Material Point Method

Thermal barrier coatings are widely used in aero engines due to their excellent thermal insulation properties,which face destruction and failure problems caused by many factors when used at extremely high temperatures.As erosion damage is one of the main reasons for the failure of the coatings,the study has a great guiding significance for the coatings’ application in the paper.However,the research of the erosion is limited by the high cost of the erosion experiments and the dissimilar service environment of thermal barrier coatings.Numerical simulation methods are necessary to use for the research.To study the large deformation problems of the erosion damage of the thermal barrier coatings and to solve the problem of mesh distortion,finite element method(FEM)is used in these cases.The numerical simulations of erosive destruction were performed based on the material point method(MPM)and the influence laws of various parameters on the damage of thermal barrier coatings were discussed.The specific research contents are as follows:The control equation and the solution algorithm flow chart of the MPM were deduced and given.The self-written program in FORTRAN language was used for the numerical simulation on erosion damage of the thermal barrier coatings caused by external particles.The results of the erosion deformation laws and the depth of the coatings were in good agreement with the results that gained from FEM in the existing literature,which proved that the self-edit program of MPM for the simulation of the erosion destruction was effective and feasible.The erosion damage process of thermal barrier coatings was simulated based on MPM.The effect of erosion particle parameters(erosion angle α,erosion velocity v,particle size,shape and forward inclination angel γ etc.)and coatings’ structural parameters(columnar crystal width D,inter-granular gap d)on erosion damage were analyzed.It was found that the erosion mechanism of EB-PVD coatings caused by particles is to form kink bands,and the kink bands are symmetrically distributed when α=90°α≠90°,the kink bands are consistent with the horizontal component of the velocity instead of distributing symmetrically,and the secondary damage of coatings is easier to occur with the decrease of α.The erosion depth(increases with the increase of the particle size and velocity v.And the erosion damage caused by prismatic particles was far greater than circular particles.With the increase of γ of the prismatic particles,the damage to the coatings is more serious.When the width of the columnar crystal(D)decreases,the erosion depthd will be larger,and the kink bands are easier to crack.When D becomes larger,the undeformed area absorbs the energy generated by erosion and collision,and the bottom of the columnar crystal may crack and fail.The erosion depthd increases with the increase of inter-granular gap d.When d is large,it is not conducive to the expansion of the kink bands.And on the contrary,when d is too small,the strain tolerance of the coatings will decrease.The research in this paper provides a new method for simulating the erosion damage of thermal barrier coatings,and has provided some guidance for the design and engineering application of them.