Applied Mechanics and Materials Vols. 63-64

Abstract: In the engineering applications area, welding defect is a major hidden danger of structure security. the bending failure process of welded specimens is detected by using AE technique and the data samples of typical welding defect source are collected, and by using wavelet technique the typical AE datas acquired through experiment are analyzed, characteristic information of the typical acoustic emission source such as electromagnetic noise, plastic deformation, micro-crack initiation, crack unsteady expansion and fracture, etc are extracted. A serial acoustic emission source identification methods based on the energy spectrum coefficients of wavelet are established and which can realize accurately distinguishing of different acoustic emission sources, so as to provide a theoretical basis to detect equipment welding defects by acoustic emission technology dynamic in engineering practice.

Abstract: This paper based on the data of enterprise’s bench test, first set up the finite element analysis model for the front sub-frame by using the of professional finite element analysis software and fatigue life analysis software, then got the distribution information (such as the situation and the cycles) for the front sub-frame after analyzing, with these messages not only easily found out the danger area, but also provided reference for bench test improving, once more found a method that can forecast the life for mechanical products.

Abstract: This paper introduces the structural design and operation principle of rotary hydraulic cylinder. Seven spiral flows with different clearance were designed. The models were built by Pro/E. Structure meshes were generated by using Gambit. Based on laminar model and SIMPLE algorithm, the interior flow field in different clearance and the same clearance at different rotation rate were numerically simulated and analyzed with Fluent. The relationship of clearance, rotation rate and viscous force, maximum temperature, stiffness, flow rate were obtained. Simulation results show that clearance’s influence on internal leakage is greater than rotation rate, at the clearance of 0.05mm～0.10mm is relatively suitable.

Abstract: This paper takes leaning-type arch ribs system as research subject. And based on the Ritz method, the analytic solution of the lateral buckling critical load of leaning-type arch ribs system under the arch springing hinged boundary condition is derived. Compared with the result obtained from FEM, it is verified that the lateral buckling critical load analytic solution presented in this paper is accurate enough. On that basis, the effect of boundary condition on the lateral bucking critical load of leaning-type arch rib system is analyzed. It is shown that the lateral stability of the leaning-type arch rib system under arch springing clamped boundary condition is much better than the one under hinged boundary condition. And the former’s lateral bucking critical load is 2.13~2.49 times as large as the latter’s. Stable arch inclined angle growing, the leaning-type arch rib system’s lateral bucking critical load increases effectively. But its amplitude under hinged boundary condition increase larger.

Abstract: By analyzing the application of the battery, the battery voltage monitoring system, lower computer and host computer communication system, and host computer visualization VB6.0 monitoring with battery group platform are designed based on multi-channel multi-MCU and the PC-based interactive respectively. In addition, the corresponding softwares are designed to achieve optimization of static and dynamic parameters matching. Practice has proved that the design has a fairly value for further perfecting the optimization of the battery matching.

Abstract: A set of PV grid-connected controlling system basing on FPGA and MCU is designed after the study of PV grid-connected system in this paper. The function of FPGA is to control the inverter main current, and the MCU is used to realize the MPPT technology. It is very effective after testing.

Abstract: The existing moving mass control system of a nonspinning reentry warhead could not drive the system error to reach zero in finite time. In order to settle the finite time reach issue, an RBF neural network-based terminal sliding mode controller was presented to design the moving mass control system. It used a terminal sliding mode to ensure that the error reaches zero in finite time. The disturbance and coupled terms of the warhead were treated as uncertainties. An RBF neural network was used to estimate the uncertainties. A nonspinning warhead was taken in the simulation to test the performance of the presented controller. The simulation results show the presented controller has faster tracking speed and higher tracking precision than the former research result.

Abstract: The Electfoencephalogram (EEG) and electromyography (EMG) sampled from skin surface are the primary information to mirror the idea of human being. The human-machine interface based on EEG and EMG is used to control machine such as a robot. It is a new taste to apply this type of interface to some special condition such as an astronaut controlling the outside robot in a space ship. Digital signal processor (DSP) is used as sample EEG and EMG in the device. The feature of signal is extract by algorithm running in DSP to control the machine. The speech recognition based on fixed Chinese words is included in the device. Many tests proved that the developed device is capable to control the robot for key operation on a panel with high reliability.

Abstract: 3-D contours measuring method based on linear structured light is one of the most active research topics in the domain of computer vision. The process of 3-D complicated curving plane measurement based on linear structured light is composed with the camera system calibration, the extracting of light stripes center, the acquisition of 3-D contours cloud data, its pretreatment technology and 3-D reconstruction. It has broad application prospects in the fields of industrial inspection, reverse engineering, medical care, robot vision, costume design, archaeology and so on. Its key technology, current development level and the commonly used treatment methods; the research difficulties and the future development trend have been pointed out also.

Abstract: The major problem of blind source separation in frequency domain is the permutation ambiguity between different frequency bins, which is the key factor to recover the original sources correctly. A new idea is to consider the frequency components from the same source as a multivariate vector with a certain probability density function, and the vectors from different sources are independent each other. An algorithm based on this idea is proposed to solve the permutation ambiguity problem of BSS in frequency domain, and some approximate cost functions are compared with the existing algorithm in frequency domain. The computer simulations to two true speeches with strong reverberation are shown to verify the efficiency of the proposed algorithm.