研究目的
To confirm the reliability of the indentation fracture (IF) method using powerful optical microscopy for measuring the indentation fracture resistance (KIFR) of alumina ceramics.
研究成果
The grand averages of KIFR for the two samples reported by the participants were 4.28±0.32 and 3.63±0.24 MPa·m1/2, respectively, which demonstrates a significant improvement in the reproducibility of the test results compared with those of the previous round-robin tests conducted approximately two decades ago.
研究不足
The slight deviation of the averages received from each lab from that re-measured at AIST was attributable to misreading of the crack length by the participants, suggesting there still remains room for a little improvement of the accuracy.
1：Experimental Design and Method Selection:
A round robin test was conducted by thirteen laboratories in Japan to measure the indentation fracture resistance (KIFR) of two types of alumina ceramics using a new approach that employs both an objective lens of 40x or 50x and a traveling stage to reduce the measuring error of crack lengths.
2：Sample Selection and Data Sources:
Two types of alumina ceramics with different purity levels were used as common samples for the round-robin indentation tests.
3：List of Experimental Equipment and Materials:
Vickers hardness tester, powerful optical microscope with an objective lens of 40× or 50×, traveling stage, and measuring microscope.
4：Experimental Procedures and Operational Workflow:
Each laboratory made more than eight Vickers indentations with a hardness tester at an indentation load of 98 N and a contact time of 15 s. The lengths of the impression diagonals and surface cracks were measured within 10 min after unloading.
5：Data Analysis Methods:
KIFR was calculated using Niihara’s equation for the median crack system.
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