Abstract
ABSTRACTThis article examines the validity of a test method to determine the torsion strength of bioceramics under in-vivo-mimicking circumstances. The torsion test setup consisted of upper and lower grip jigs, designed to grip dog bone-type bioceramic specimens, and an opening torque tester for PET bottles. A specimen was set on the torque tester through the lower grip jig at the bottom, and the upper grip jig was then mounted on the top end of the specimen. The upper grip jig was rotated by hand to apply torque until the specimen was fractured by the torsion. The torsion strength was calculated using the maximum torque at fracture and the gage diameter. Five calcium phosphate bioceramics were employed for the torsion test. The torsion strength data obtained by this method agreed closely with data measured using a material testing machine with a convertor from the linear crosshead motion into the rotation. Round-robin tests among four different organizations in Japan revealed that the torsion strength data showed good agreement for each sample immersed for 24 hr under phosphate-buffered solution as in-vivo-mimicking circumstances. These results verified the ability of the easy-to-use torsion method to give appropriate strength data with a simple experimental setup.
Highlights
Bioceramics are regarded as key materials among advanced technologies because they play a role in many promising applications designed to improve people’s quality of life in our aging society [1]
We focused on an opening torque tester for PET bottles incorporating simple grip jigs
Within the experimental data in this study, the easy-to-use torsion test method is useful for obtaining reasonable torsion strength data, which is in good agreement among different organizations and which clearly shows the differences in the samples
Summary
Bioceramics are regarded as key materials among advanced technologies because they play a role in many promising applications designed to improve people’s quality of life in our aging society [1]. In 1981, Petrovic and Stout [19,20] reported tension/ torsion tests of α-Al2O3 rod specimens, in which the principal stress ratio σ2/σ1 was changed from 0 (pure tension) to −1 (pure torsion) and found that the tensile fracture strength σ1f increased with increases in the principal compressive stress σ2 In their following articles [21,22], they conducted axial tension, hoop tension, balanced biaxial tension, balanced tensioncompression, and pure torsion tests for α-Al2O3 tube specimens. In a previous article [30], the present authors optimized this torsion test method by changing the specimen geometry and improving the jig mechanism to prevent bending moments and axial loading during torsion testing, and showed reasonable torsion strength data for blackboard chalk and five types of hydroxyapatite ceramics with different porosities. These samples had been used in the previous study [30]
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