Koichi Funabashi

Mechanism and optimum shape of knife edge for metal sealing

Abstract The contacting state of knife-edge seals was investigated and a new type of knife edge was developed. The contacting state of knife-edge seals was divided into three types according to the apex width of the knife edge: (a) penetration type, (b) indentation type, and (c) intermediate type. The developed knife edge had a contacting state of penetration type (a). Because of the narrow apex width of the knife edge, the values of Pc/l for the compressive forces per unit length required for sealing were lower than those of other types of knife-edge seals. The contact pressure required for sealing was nearly equal to the Meyers hardness in the sealing surface layer, regardless of the surface roughness in turning. The optimum shape of the knife edge was of type (a) and had a ridge in a V-shaped cross-section with a plane inclined 30° off normal and the flat area of its apex finished by lapping was about 35 μm wide. The knife edge made of hard material with optimum shape could be utilized in the cases where the sealing materials were copper, carbon steel and stainless steel, and the values of Pc/l were approximately 15–40, 45–110 and 80–190 kN m−1, respectively.

Microscopic normal displacement of contacting bodies with tangential load

Abstract Normal microdisplacements of contacting bodies caused by applying a tangential load are investigated in this study. A new method to calculate the normal microdisplacement of an actual contacting surface was introduced and the calculated results were compared with the experimental results obtained for sand-blasted surfaces. Experiments and calculations were carried out for the following three cases: 1. (1) rigid surface asperities penetrating a mating plastic material; 2. (2) surface asperities plastically compressed by a flat anvil; 3. (3) asperities made of the same plastic material as the mating flat surface.

Sealing Characteristics of an Annular Wedge-Shaped Gasket.

The authors have investigated the sealing characteristics between the surface of an annular wedge-shaped plastic gasket and a smooth seal face of a rigid ball in static contact. The following results were obtained from gas leak tests, calculation of the deformation of a wedge-shaped gasket and a compression test. ( 1 ) In order to seal tightly, a contacting width of a wedge resulting from the plastic deformation of a gasket was required because of the work hardening of the surface irregularities on the gasket. ( 2 ) The contacting width of a wedge increased with a decrease in the conical half-angle of the seal face, θ. Therefore, the linear sealing load, Pc/l, decreased with a decrease in the θ-values. For example, the value of Pc/l at θ=15°was about 0.5 times that at θ=90°. ( 3 ) The recommended values of θ were in the range from 10°to 35°, and it was possible to forecast the Pc/l-values corresponding to that range.

Evaluation of Three-Dimensional Shape of Steel Ball by Spherical Harmonic Function.

In the previous report, it was shown that harmonic analysis results on the three-dimensional shape of a steel ball obtained by use of spherical functions gave good evaluations of characteristics of steel balls used in a bearing assembly. However, this type of analysis is inadequate for evaluating the shape of the ball geometrically. In this paper, first, the possibility of three-dimensional geometrical evaluation by spherical harmonic analysis is described. The reference direction is defined as the index for directivity of each order of the spherical component and has no relationship with the coordinates for measurement. This reference direction or the value of each spherical component for which this direction is obtained, is utilized to illustrate and evaluate the spherical shape of the steel ball. Second, the method for estimating the three-dimensional shape of the steel ball by two-dimensional measurement is explained (e. g., a roundness meter). Mean Fourier coefficients of cross-sectional forms of the steel ball are theoretically calculated, and the correlation between this value and the harmonic analysis result obtained through the use of the spherical functions is obtained.