Comparison of fracture resistance as measured by the indentation fracture method and fracture toughness determined by the single-edge-precracked beam technique using silicon nitrides with different microstructures

Crack profiles under a Vickers indent in silicon nitride ceramics with various microstructures

“…The amounts of the sintering additives of the first two sets of samples were fixed at 2.5 wt% Al 2 O 3 and 2.5 wt% Y 2 O 3 (A group) and 5 wt% Al 2 O 3 and 5 wt% Y 2 O 3 (B group) as listed in Table 1. The sintering temperature and soaking time of these samples were varied as follows: 1750 8C for 1 h, 1850 8C for 1 h, 1950 8C for 2 h and 1950 8C for 8 h. By contrast, the amount of the additives of the last set of samples was changed from 1 wt% Al 2 O 3 and 1 wt% Y 2 O 3 to 10 wt% Al 2 O 3 and 10 wt% Y 2 O 3 while the sintering condition was set constant at 1950 8C for 2 h. The detailed fabrication procedure was described in our previous papers [17,18]. Silicon nitrides from commercial sources were also used as test materials.…”

“…The fracture resistance of the former samples showed relatively higher value than those of the latter samples except the OP3 sample, as well. Quantitative analysis of microstructures for some selected samples together with its relation to the mechanical properties can be found in our previous studies [17][18][19].…”

Determination of fracture toughness using the area of micro-crack tracks left in brittle materials by Vickers indentation test

“…The specimens have been fabricated and tested with the a/w ratio of about 0.5 (where a is the groove depth and w is the width of the sample). The calculation procedure and accuracy of fracture toughness values obtained from these methods have been thoroughly covered in [1][2][3][4][5][6] and [36]. Fracture toughness values have been measured for four times in SEVNB and SENB methods, and three times in CNB method.…”

“…Chevron notch bar (CNB) [1][2][3], single-edge notch beam (SENB) [2][3][4][5][6], single-edge V-notched beam (SEVNB), single-edge pre-cracked beam (SEPB) [4,5], edge-loaded split (ELS) [7,8] and the double cantilever beam (DCB) are some of these methods, most of which have limited usage because of the difficulty in preparing the ceramic samples and high expenses associated with implementation. To solve this problem, a new method has emerged in the last few decades, which relies on the evaluation of indenter's effect left in the materials [9].…”

Investigation of the effect of ZrO2 and ZrO2/Al2O3 additions on the hot-pressing and properties of equimolecular mixtures of α- and β-Si3N4

“…Macrohardness and fracture toughness values have been determined, at room temperature, on the polished surface considering an average of five indentation using Vickers indentation method [51][52][53][54][55][56][57][58][59][60][61] with 20 kg load for 15 s. The crack paths, introduced by Vickers indentation with 20 kg load, were investigated in order to evaluate toughening mechanisms. Calculation of the fracture toughness ''K IC '' was carried out based on the nature of cracks observed.…”