Impact localization is one of the major concerns in maintenance of aircraft structures built from composites. A lot of different techniques like acoustic emission, optimization technique based on system are nowadays investigated to identify impact location. But the method to identify impact position in complex composite structure with high accuracy in real time has not been completely established. In the present work, a new efficient method is proposed for identifying impact location in real and complex composite structure based on array signal processing and Lamb waves. There are two steps in the proposed method. The first step is to estimate the direction- of-arrival (DOA) of impact source using continuous wavelet transform (CWT) and array signal processing; the second step is to estimate the distance between impact source and the coordinate origin based on propagation characteristic of Lamb wave and CWT. The composite panel with stepped thickness of a real and complex aeronautical tank is used to verify the present methodology. The result shows that the present method may identify impact location fast and accurately.

The prediction accuracy of the simulation of cutting process is related with the description of the nonlinear behavior of material at extremely high strain, strain rate and temperature in machining. In this paper, an integral Johnson-Cook model is presented to characterize the mechanical behavior of work materials in machining, and the parameters in the model are determined by fitting the data from both quasi-static compression and cutting tests. Then the material equation of 2Cr13 stainless steel is derived with this method and used in the finite element model of orthogonal cutting with carbide tools. At last, the simulation result is verified with experimental data.

This paper discusses the feasibility of improving machining efficiency of sapphire substrate by using two-dimensional (2D) ultrasonic vibration assisted grinding. An elliptic ultrasonic vibrator is designed and produced by bonding a piezoelectric ceramic device (PZT) on a metal elastic body (stainless steel, SUS304). The sapphire substrate is fixed onto the top face of the vibrator and ultrasonically vibrates in 2D vibration mode when the PZT is excited by two alternating current voltages with a phase difference. A grinding apparatus mainly composed of the ultrasonic vibrator is constructed, and experiments are performed with lateral modulation of elliptic ultrasonic vibration vertical to the grinding direction. Both the grinding forces and the ground work surface are measured and examined. Experimental results show that the grinding force decreases significantly and the resulted surface is improved in certain degree with the ultrasonic vibration compared to those of conventional grinding without ultrasonication. This indicates that the high efficiency grinding for sapphire substrate can be performed with the two-dimensional vibration grinding technique presented in this paper.

A bio-etching method using Thiobacillus ferrooxidans (T.f.) for processing micro-gear has been developed. The principle of bio-etching method is that certain microorganisms in nature consume some metal ions to be energy during their growth. The strain of Thiobacillus ferrooxidans consume elemental ferric and cooper ions as its energy source, so T.f. is selected as bio-etching tool, Leathen culture medium is selected as culture medium of T.f., and the thin copper sheet is used as the processed material. During the micro-gear is processed, firstly, thin copper sheet of 0.05mm is cleaned in the acid liquid and some materials such as dirt and grease are cleaned away, then, the anti-erode film is applied to the surface of thin copper sheet, then the surface of thin copper sheet is irradiated by ultraviolet under the condition that the surface is covered by mask film and developed, the anti-erode film that not covered by mask film will be dissolved and cleaned away, after that, thin copper sheet is put into the T.f. liquid and agitating, after the 3h, micro-gear is obtained. The result is showed that micro-gear can be processed by bio-etching method.