Search

This study analyzed the closed-die forging process of the copper alloy valve body is presented. Two variants represent the forging processes of the copper alloy valve body on conventional double-action press and multicored forging press, which differ in the initial positions of punches and the sequences of punches movement. A comparison of the two processes was made by finite element (FE) simulations, which include geometry, filling sequence, and force. However, during the experiment, it was found that when the copper alloy valve body was forged on a conventional double-action press, the central punch was easy to bend or even break, and the end surface of the central valve hole was prone to cold shut. Through further analysis of the experimental process and FE simulation results, the causes of mould failure and valve body defects were discovered. FE simulation results of force, strain, and stress all showed that the technological safety and the product quality of multicored forging press were considerably better than those of the forging on a conventional double-action press. The experimental results were in agreement with the FE simulation results.

The coupled acoustic field of fully elastic plate model is described by the modal analysis method. The acoustic potential energy resonance peaks of the fully elastic plate model are significantly more than that of the one elastic plate model due to the influence of the vibration of multi elastic plates. The acoustic field characteristics of the fully elastic plate model are analyzed when the primary excitation source is applied on the different elastic plates. The results show that the coupled acoustic field of the fully elastic plate model is dominated by the structural mode of the elastic plate with primary excitation, and the acoustic mode of the enclosure, and the structural-acoustic coupling between the plate and the enclosure; the structure modes of the other elastic plates have less effects on the acoustic field in the enclosure except the first ones of them. [ABSTRACT FROM AUTHOR]

The experimental observation of the inlet dimple of the elastohydrodynamic lubrication (EHL)film was carried out in point and elliptical contacts, respectively, and then, the numerical analysis under point contacts was conducted. The inlet dimple appears and then moves upstream toward the inlet and finally disappears with the increase of the entrainment speed. In the meantime, the dimple depth increases at the beginning and then decreases. The high load leads to a wide entrainment speed range where dimple exists. The varying range of the entrainment speed corresponding to the dimple appearance is smaller at a smaller included angle between the minor axis of elliptical contact and the entrainment direction. [ABSTRACT FROM AUTHOR]

Predicting squeeze-film damping in rare air is crucial for the design of high-Q MEMS devices. In the past, for MEMS structures with no perforations, there have been two approaches to treating the squeeze-film damping in rare air: using effective viscosity coefficient and using the molecular dynamics method. The amount of squeeze-film damping can be controlled by providing perforations in MEMS structures. To model perforation effects on squeeze-film damping, many methods have been proposed. However, the previous methods are all based on the approach using effective viscosity coefficient. The approaches treat the gas in the gap as a continuum. This paper presents an analytical molecular dynamics model for the squeeze-film damping of a perforated microplate in the free molecular regime. The quality factor is found by calculating the energy transfer from the vibrating plate to the surrounding air due to the collisions between the microplate and the molecules. This paper is an extension of the work done by Bao et al (2002 J. Micromech. Microeng. 12 341-6). Bao's work is valid only for non-perforated microplate. The accuracy of the present molecular dynamics model is verified by comparing its results with the experimental results available in the literature. The limitations of the present molecular dynamics model have been reported in this paper. [ABSTRACT FROM AUTHOR]