13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- In this paper, theoretical prediction thermal shock residual strength with the temperature-dependent material properties of UHTCs is presented. The theoretical model is capable of predicting qualitatively thermal shock residual strength behavior of UHTCs observed in experiments, i.e., when the thermal shock temperature difference ∆T is less than the critical thermal shock temperature difference ∆Tc, crack propagation didn’t occur and the strength remains unchanged. At ∆T =∆Tc, the strength drops precipitously, then decreases gradually and tends to be a constant as the increase of thermal shock temperature difference ∆T. The results of the theoretical model applying to the diborides of zirconium based UHTCs are compared to the results which haven’t take the effect of temperature on material properties into consideration. It shows that the thermal shock residual strength and thermal shock resistance is very sensitive to their temperature-dependent material properties. If the temperature dependence of material is ignored, the critical thermal shock temperature difference ∆Tc will be underestimated. And the thermal shock residual strength with temperature-dependent material properties is higher than the one without the consideration of temperature-dependent material properties if the ∆T is less than a certain value, but the results are reversed as the ∆T is larger than the certain value. Therefore, when determined the thermal shock residual strength, it must take the temperature-dependent material properties into fully account. Acknowledgements This work was supported by the National Science Foundation of China (Project ID: 90916009 and 11172336). References [1] F. Monteverde, A. Bellosi, Microstruture and properties of an HfB2-SiC composite for ultra high temperature applications. Advan Eng Mater, 6 (2004) 331–336. [2] C. Wang, J. Yang, W.P. Hoffman, Thermal stability of refractory carbide/boride composites. Mater Chem Phys, 74 (2002) 272–281. [3] M. Gasch, D. Ellerby, E. Irby, S. Beckman, M. Gusman, S. Johnson, Processing properties and arc jet oxidation of hafnium diboride-silicon carbide ultra high temperature ceramics. J Mater Sci, 39 (2004) 5925–5937. [4] M.M. Opeka, I.G. Talmy, E.J. Wuchina, J.A. Zaykoski, S.J. Causey, Mechanical, Thermal, and oxidation properties of refractory hafnium and zirconium compounds. J Eur Ceram Soc, 19 (1999) 2405–2414. [5] S.H. Meng, G.Q. Liu, S.L. Sun, Prediction of crack depth during quenching test for an ultra high temperature ceramic. Mater Des, 31 (2010) 556–559. [6] W.D. Kingery, Factors affecting thermal stress resistance of ceramic materials. J Am Ceram Soc, 38 (1955) 3–15. [7] J.C. Han, B.L. Wang, Thermal shock resistance of ceramics with temperature-dependent material properties at elevated temperature. Acta Mater, 59 (2011) 1373–1382. [8] S.H. Meng, G.Q. Liu, Y. Guo, X.H. Xu, F. Song, Mechanisms of thermal shock failure for ultra-high temperature ceramic. Mater Des, 30 (2009) 2108–2112. [9] S.H. Meng, H. Jin, J. An, G.H. Bai, W.H. Xie, Mechanism analysis of thermal shock properties for ZrB2-20%SiCp-10%AlN ultra-high temperature ceramic with the surface defects. Solid State Sci, 12 (2010) 1667–1671. [10] J.C. Han, B.L. Wang, Thermal shock resistance enhancement of functionally graded material by multiple cracking. Acta Mater 54 (2006) 963–973. [11] Z.H. Jin, R.C. Batra, Thermal shock cracking in a metal-particle-reinforced ceramic matrix composite. Eng Fract Mech, 62 (1999) 339–350. [12] X.H. Zhang, L. Xu, S.Y. Du, W.B. Han, J.C. Han, C.Y. Liu, Thermal shock behavior of
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