Interference Torque of a Gas-Dynamic Bearing Gyroscope Subject to a Uniform Change of the Specific Force and the Carrier Angular Velocity.

The work is devoted to an analysis of interference torque of a gas-dynamic bearing gyroscope, while a condition with uniformly changed specific force and carrier angular velocity are taken into account. A five-degrees-of-freedom (5-DOF) model is established considering the translation and tilt of the rotor, which solves dynamic rotor equations and the Reynolds equation simultaneously. The model makes it possible to obtain the rotor trajectory under time-transient specific force and carrier angular velocity. The interference torque of the gyroscope is analyzed based on the rotor trajectory. Results indicate that the gas-dynamic bearings show a significant hysteresis effect with a perturbation of bearing force or bearing moment, which indicates the necessity of transient research. Interference torque is large when the carrier angular velocity starts to change or stops to change, and when the specific force stops to change. When the specific force change rate is less than 8.4 km/s3 with no change of the carrier angular velocity, the condition could be simplified as a steady state, which is consistent with the previous study.

Measurement of position synchronization of high-precision dual parallel motion stages by digital image correlation technique.

In this paper, a method for measuring the synchronization error of high-precision dual parallel motion stages is presented. The method is based on a full-field measurement using two-dimensional digital image correlation (DIC) technology. Its outstanding advantage is that it allows users to take measurements in a reliable plane-to-plane manner. Combined with a digital microscope, the resolution of the measurement can reach micrometer level. The method also provides a measure of parallelism error between the stages, used to compensate for the initially measured synchronization error results. In order to demonstrate the method's capabilities, a test case was carried out. In addition, the results obtained through DIC were statistically analyzed to improve their reliability. The final results indicated that this method is successful in the characterization of the position synchronization error.

In-plane deformation monitoring of a cylindriscal specimen using a simple approximate method combined with two-dimensional digital image correlation.

This paper presents a quick-to-implement and simple approximate method that uses a single camera system to measure the relatively small surface deformation of a cylindrical specimen in the context of triaxial tests in geotechnical engineering. Digital images of a speckled cylindrical specimen before and after loading were obtained from only one perspective view. For each acquired image, there are geometric distortions and speckle losses, which are mainly caused by both perspective projection and column shape. Based on particular prior knowledge, we attempted to back-project the raw perspective images onto a cylindrical curved surface to reconstruct the speckle feature scene. These back-projected images were subsequently analyzed by the two-dimensional digital image correlation method to reveal the surface deformation information of the region of interest on the surface of the test specimen. Finally, a test case and a finite element study were, respectively, given to validate the effectiveness of the method. This feasibility study demonstrates the potential of extending this method to handle a wide range of regular cylindrical specimens with a relatively small deformation which are analyzed without taking out-of-plane motion into consideration.

Microstructure and mechanical property of Ruditapes philippinarum shell.

In order to provide reference for the development of relevant dredging and processing machinery of the manila clam (Ruditapes philippinarum), the clam shell´s microstructure, phase composition, microhardness, nanoindentation hardness and elastic modulus were investigated, the quasi static compression and orthogonal compression tests of live clams were carried out as well. The shell consists of the outer, middle, and inner layer, which correspond with the composite prismatic structure, crossed-lamellar structure, and homogeneous structure, respectively. X-ray diffraction (XRD) results indicated that all the three layers are made up of pure aragonite phase, the outer layer of the shell displays greater intensity and more diffraction peaks than the middle and inner layer. The microhardness of the inner layer, ~ 3.00 GPa, is harder than the middle and outer layer. Both in the middle and outer layers, the microhardnesses of the vertical section perpendicular to the growth lines are obviously higher than that of the cross section parallel to the growth lines. The similar trend was observed in nanoindentation hardness (H) and elastic modulus (E), but the H/E ratios between three layers and two sections are close to 0.05. The quasi static compressive strengths of live clams with loading along the X (beak horizontal), Y (beak upward and umbo downward), and Z (beak vertical) orientations were tested, and the differences were identified. The lowest strength was found with loading orientation Z, the Weibull strength at 50% probabilities of fracture force is just 153 N. The results of the orthogonal compression tests demonstrated that the fracture force of clams varies from approximately 100 N to 400 N, the effect of the clams´â€¯age on fracture force is more significant (p < 0.01) than loading orientation and loading speed. Therefore, the clams´â€¯age and ultimate load of fracture should be taken into account during clam production mechanization, for the purpose of maintaining the clams´ integrity and survival prior to sale.