Papers by Author: Mineo Mizuno

Abstract: The calf serum solution was defined as the international standard lubricant for wear characterization of artificial hip joints. It is, however, known that its composition varies according to age, manufacturing processes or production areas of bovine cattle, and that the difference in composition has large effect on the wear characterization. It was difficult to compare the results obtained by different laboratories. Therefore, it is desirable to develop an artificial lubricant whose composition can be always set to a specified value as an alternative to bovine serum. In the present study, the effect of each major constituent in bovine serum on wear property was studied by hip simulator. As a result, transparent and stable lubricant solutions were prepared. It showed quite similar wear property to bovine serum by controlling the composition. These results serve as a guide to propose the new lubricant suitable for the wear characterization of hip joint.

Abstract: Bioactive bone cement with mechanical properties higher than that of commercial polymethylmethacrylate (PMMA) bone cement are strongly desired to be developed. In the present study, PMMA-based cement incorporated with nano-sized rutile particles was prepared. The PMMA-based cement (rutile content was 50 wt%) shows the compressive strength (136 MPa) higher than that of commercial PMMA bone cement (88 MPa). The hardened cement formed apatite on the surface in a simulated body fluid within 3 days. Therefore, this PMMA-based cement incorporated with rutile particles might be useful as cement for fixation of prostheses as well as self-setting bone substitutes, because of its high apatite forming ability and mechanical strength.

Abstract: The present study describes the effect of indenter materials on Hertzian cracking behavior of alumina ceramics in sphere indentation. Numerical analysis (FEM) was carried out to investigate the influence of the frictional resistance at the interface due to the elastic mismatch between the indenter and the flat specimen on the stress distribution near the contact area. Two kinds of alumina ceramics with different mechanical properties were used for the flat specimen. Materials of the sphere indenter were cemented carbide, silicon nitride, alumina and hardened steel. The indenter was penetrated into the specimen with an electro-mechanical testing apparatus at a constant cross-head-speed in air. The indentation fracture was monitored with the acoustic emission signal. The numerical analysis revealed that the frictional resistance had influenced on the stress distribution. The experimental data showed that the ring crack radius, the crack pass below the contact zone and the indentation strength were different depending on the indenter material. From the comparison between the numerical analysis and the experimental data, it was found that the minimum value of the ring crack radius of the low density alumina flat specimen corresponds to the position of the maximum tensile stress.