Effect of temperature on damage mechanism and fracture behavior of LiH ceramic under 3-point bending at different loading rates

The damage mechanism and fracture behavior of lithium hydride (LiH) ceramic are key to its design and application at elevated temperature in nuclear engineering. LiH ceramic is tested in a loading rate range of 0.001-2 mm/min from room temperature (RT) to 600 degrees C using digital image correlation (DIC) method combined with high-speed photography. At low temperature (up to 300 degrees C), LiH ceramic undergoes brittle fracture. At high temperature (up to 600 degrees C), LiH ceramic undergoes creep fracture at low loading rate and ductile fracture at high loading rate. The main crack growth rate of LiH ceramic with ductile fracture is higher than that of LiH ceramic with creep fracture, and is lower than that of LiH ceramic with brittle fracture. With the change of temperature and loading rate, three damage mechanisms, fatigue damage corresponding to SCG of inherent flaws, creep damage represented by creep microcracks and ductile damage symbolled by dimples, occur simultaneously and show competitive characteristics, one of which dominates the failure. At low loading rate, there is a transition of the dominant damage mechanism from fatigue to creep damage with increasing temperature. At high temperature, the dominant damage mechanism changes from creep to ductile damage with the increase of loading rate.