Reliability of Ceramics Fracture Toughness Measurements by Indentation

Strength and Fracture Toughness of Ceramic Materials for Metal-Ceramic Prosthetic Dentistry

“…For the first type of cracks l P V = ⋅ const and l P a V = ⋅ const ( ) 2 , for the second one c l a P V = + = ⋅ const 0 67 . [28,29]. In our case, for the materials under study (see below) the exponents on P V in the l P V − relation were in the range of 0.98-1.05, in the c P V − relation they were in the range of 0.75-0.78, which is typical of Palmqvist cracks.…”

“…Microcracks, most pronounced in Duceram Plus, are observed at the boundary of crystal and amorphous phases(Fig. 2c).The properties of these materials can also be dependent on internal stresses at the phase boundary because of the difference in α values,(25)(26)(27)(28)(29)(30) …”

“…In our case, for the materials under study (see below) the exponents on P V in the l P V − relation were in the range of 0.98-1.05, in the c P V − relation they were in the range of 0.75-0.78, which is typical of Palmqvist cracks. However, the exponent on P a V in the l P a V − relation was < 2, which points to a possible formation of median cracks [29]. Therefore, in a first approximation one can speak about the formation of lateral semielliptical cracks around indenter impressions, their length on the specimen surface being comparable with their depth.…”

“…Therefore, in a first approximation one can speak about the formation of lateral semielliptical cracks around indenter impressions, their length on the specimen surface being comparable with their depth. In this case, their behavior approaches that of the median cracks [29]. Thus, to calculate K cv , a known equation by K. Niihara et al for Palmquist cracks was used [28].…”

The study of fracture toughness and failure mechanisms of cutting-tool hardmetals with plasma-modified surface

“…1). Using a general solution to an axisymmetric problem for a disk shaped crack in a infinite medium (the so called Palmqvist crack), where tensile stresses are applied to the crack edges, the adequate expressions were derived to relate the critical stress intensity factor K Ic of the specimen material to the critical load at the crack initiation stage F c and to the crack length l at the crack propagation stage [11,12]:…”