The joints in machine tools influence greatly the static, dynamic and thermal characteristics of the machines. Then the many researches on them have been carried out. Under these conditions, the authors have established the quantitative measurement method of contact stiffness of the joint with same material combination considering the real contact area, since the real contact area is far smaller than the nominal contact area. In this research, we propose the new measurement method of contact stiffness of the joint with different material combination expanding the former method we developed and its validity is considered. In consequence, the following results are obtained. 1) The measurement method applicable to the joint with various material combinations is established using inserted specimens. 2) The real contact area of the joint with different material combination can be accurately measured considering the reflected level of ultrasonic wave at the real contact area of the joint.3) The contact stiffness of the joint with different material combination can be treated as the series coupling of the each contact stiffness constructing the joint. 4) The contact stiffness of the joint and each contact stiffness of the contact springs constructing the joint can be measured by the proposed method.

A generalized infinite element is presented by combining following aspects: (1) The geometry mapping in the Cartesian system is chosen so as to facilitate the generation of infinite element mesh; (2) The decay variable is defined as the in situ major axis of the confocal ellipse where the field point is located, so it is dependent not only on the infinite-directional coordinate but on the finite-directional one(s); (3) The shape function is constructed so that it exactly satisfies the multipole expansion along the edges of the infinite element; (4) The conjugated weighting function is adopted to eliminate the harmonic terms from the integrands; and (5) the more proper form of phase factor and weighting factor is recommended. Compared with the Bettess element and the Astley element, the present element greatly reduces the element number within the finite element zone for problems with a large aspect ratio. Compared with the Burnett element and the modified Burnett element, the present element permits the free orientation of the infinite element, and thereby is suitable for more general exterior problems, either of a closed surface (source) or of an opening surface (source). Several typical examples are given and their results show that the generalized infinite element is robust and flexible.

No abstract

The effects of the coolant activated by ultrasonic waves, which are in the order of MHz frequency, on performances of cylindrical grinding were examined experimentally. The coolant is also termed as megasonic coolant. From the experiments, the following results are obtained. The activation of the coolant by ultrasonic waves increases the spouting strength of the coolant. The ultrasonic vibration is maintained to have a spouted distance of 160 mm. This makes the coolant to twine around the wheel and the workpiece surface, and ensures that the coolant infiltrates into the grinding point. In the grinding for hardened steels, the megasonic coolant suppresses dulling and wheel wear. On the other hand, in the grinding for hard to grind materials, such as stainless steels and aluminum alloys, the megasonic coolant suppresses depositing and welding of chips on working surface, which would improve surface finish.

No abstract