Thermal decohesion model validity for polycrystalline advanced ceramics

Dynamic fracture toughness determination of polycrystalline advanced ceramics using the crack closure integral method

“…Moreover, dynamic fracture toughness has more pronounced decrement rate above 1 m/s for FG and 0.3 m/s for CG material. Dynamic effects are therefore more pronounced in coarse grain material, which is in line with a thermal decohesion model validity observed in Petrovic and Kljuno (2017).…”

“…where, α = a/h, Pin is the breaking load and f(α) is a fitting function of α as outlined in Petrovic et al (2011). Results obtained by experimental testing were earlier presented in Petrovic and Kljuno (2017).…”

Fracture mechanisms of polycrystalline advanced ceramics

“…At dynamic rates the fracture toughness drops consistently, most likely due to a temperature increase at the crack tip. Because of the tremendously short time scales available for fracture to initiate and propagate, heat originated in very small field ahead of the crack tip remains captured and adiabatic environment takes place, which is suggested by the fact that material satisfies an adiabatic thermal decohesion model as found in [3]. This results in the temperature and temperature gradients in observed field becoming elevated, leading to the deterioration and damage of the cobalt phase due to differences in the coefficients of thermal expansion of ceramics grains and cobalt binder, and a corresponding decrease in fracture toughness.…”

“…Two grades of polycrystalline advanced ceramics have been used for investigation [3] containing different mean WC grain sizes and amounts of cobalt utilized as a binder in the obtained composite. These material grades will be referred to as grade A and grade B and contain average WC grains of 6 and 30 μm, respectively.…”