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The purpose of this paper is to measure the non-linear dynamic properties of O-rings in wide frequency ranges including in the ultra-high-speed rotational regions and to calculate the stability threshold of herringbone grooved aerodynamic journal bearings with O-rings support. First, the Voigt model was used as a rheological model of the O-rings, and the spring and the damping coefficients were evaluated in a wide frequency range from 0.5 to 4 kHz. Then, the stability threshold of the herringbone grooved aerodynamic journal bearings supported by O-rings was calculated. In this calculation, the compressible Reynolds equation based on the Narrow Groove Theory was solved by the perturbation method. Finally, the theoretical results were compared with the experimental results. The calculated results had a good agreement with the experimental ones.

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A miniature mechanical seal with cooling water circulating system has been developed as a shaft seal for rotary blood pumps. The present paper describes the establishment of the experimental methods under blood sealing and the estimation of the effect of the surface roughness on the shaft seal problems, especially in the increase of the friction and the leakage. Micro-leakage rates of the blood and the cooling water were measured by an ion chromatography. In this method, the ion concentration was converted into the leakage rate. The frictional loss torque was measured by a torque meter. Results are provided with three types of surface roughness, Ra = 0.009 μm, Ra = 0.088 μm and Ra = 0.170 μm. It is shown that as the surface roughness increases the leakage decreases while the frictional loss torque increases under blood sealing. The best surface roughness in the torque and the leakage characteristics were different.

A miniature mechanical seal with the cooling water circulating system has been developed as a solution of the shaft seal problems in rotary blood pumps. The present paper describes the effect of the surface roughness in the sealing gap on the shaft seal problems under blood sealing. The sealing surface roughness of tested three seat rings were designed to be Ra=0.009, 0.088 and 0.170µm. The frictional loss torque in the sealing gap and the leakage of the blood and the cooling water were measured in this work. Results show that the maximum frictional loss torque measured in the seat ring of Ra=0.009µm, and the frictional loss torque decreased as the surface roughness increased. The leakage rate of the cooling water is larger than that of the blood in all seat rings, even though the blood chamber has higher pressure. The sealing characteristics between under the blood and water sealing were different. Moreover, the best surface roughness in the torque and the leakage characteristics were also different. Thus, it is important to study under blood sealing in the design of the surface roughness of the mechanical seals for rotary blood pumps.