Applied Mechanics and Materials Vols. 401-403

Abstract: This paper presents a polymer diaphragm based Fabry-Perot (F-P) sensor system for aeroacoustic measurement in air. The diaphragm of a novel polymer material poly phthalazinone ether sulfone ketone (PPESK) is used as the sensing element. The effective dimension of the diaphragm is 1.0mm in diameter and 6μm in thickness. Thanks to the good mechanical feature of the material and the interferometric-intensity demodulation mechanism, the sensor diaphragm shift sensitivity of 0.72 nm/Pa, correspond to an acoustic pressure to voltage sensitivity of 5.56mV/Pa has been achieved. Experimental results showed that the characteristics of the sensor system is comparable with traditional electrical microphone in frequency range 100Hz to 1kHz and the sensor has the potential to be used as an optical microphone.

Abstract: Based on the mechanical analysis of hydraulic excavator working device, the mechanical relationships between the work load (digging resistance) on the bucket teeth and forces on bucket hydraulic cylinder and boom hydraulic cylinder has been established. Utilizing the geometric relationships among each parts of working device, the formulae of the normal component and the tangential component of excavating resistance have been deduced. A hydraulic excavator load force-time process measurement method was provided, which has such advantages as less measuring points, simpler measuring procedure and lower cost. And the load force-time process could make the load force spectrum for structure optimization design and fatigue life evaluation without the limit of cross section shape change.

Abstract: A composite bistatic radars system is put forward to availably enhance the performance of anti-stealthy ,anti-reconnaissance, anti-jamming and anti-destruction for monostatic radar. The process modeling and technical project is introduced in this paper, and the detection area and measurement accuracy of the composite bistatic radars system is analyzed on the T/R-R process modeling. Lastly, a set of simulated experiments for the detection performance of composite bistatic radars system is carried out. The result of the simulation can provide the basis for structure multi-input and multi-output scouting early-warning detection system in the complex electromagnetic environment.

Abstract: To realize the closed-cycle control of the giant magnetostricitive accurate driver sensorless, it must make the effective identification and precise extraction to the self-sensing signal of the driver. Based on the characteristic of self-permeability change of the magnetostricitive material under the effect of the external loading, establishing the electromagnetic model which can reflect the dynamic feature of the driver and the bridge circuit analysis model of GMM self-sensing driver. According to the established eletromagnetic and mechanical models, it proposes a kind of new self-sensing signal extraction technology, to make the driving function and self-sensing function to be realized by using a coil. Besides, it presents the schematic circuit diagram and analyzes the working principle of the circuit. The research of the experiment indicates that the circuit designed can successfully detect the variation of the displacement of the driver.

Abstract: In the field of natural gas pipeline leak detection, based on infrasonic wave method of gas pipeline leak detection technology gradually be taken seriously. This paper introduces the basic features of pipeline leak signals and basic principles of infrasonic wave leak detection technology. It analyzes the key factors, which affect accurate positioning. According to the characteristics of leak signal and performance requirements of leakage monitoring system, the infrasonic wave speed algorithm in gas pipeline is modified. Using correlation analysis and wavelet transform method on the leakage signals, the dynamic response time diversity between sensors installed in first and last stop will be more precise. As a result, it improves the positioning precision of leak detection effectively.

Abstract: The lower limit of the existing vortex mass flow meter based on differential pressure is high. So the application of the existing vortex mass flow meter is limited in the measurement for low flow rate. This paper proposes a method using vortex mass flow meter of dual bluff body based on differential pressure principle. The differential pressure signal between the upstream and downstream can be amplified by the vortex overlap caused by the dual bluff body structure. The results of the simulation by Fluent show that this method can reduce the lower limit of measurement, and improve the measurement sensitivity effectively.

Abstract: This paper puts forward the overall scheme of CNC System Reliability Testing base on the SCADA(Supervisory Control And Data Acquisition) system,introduces to the principle and sets up the physical system According to the selected hardware and software of data acquisition system and data storage system.It selects the mechanical load set load simulation method according to the characteristics of the test sample size is bigger. Using UG software to design and install to loading plate ,and tested.At present,The system of test has run with the safe operation of the normal,and obtain actual measured data about the reliability of CNC system.

Abstract: The elm wood samples were tested by the technique of stress wave, and the testing results were analyzed by using the statistic software of SPSS. The results showed that the moister content of wood, wood crack, the sizes of holes and numbers of holes have significant influence on propagation parameters and dynamic modulus of elasticity. Under the same specifications, the propagation time of the stress wave was longer in the wood with holes or cracks than the perfect wood samples, and the time become longer with the increasing the sizes and numbers of holes or cracks. The studying results of the thesis will provide a sound background for the application of stress-wave technique in detecting the inner defects of wood products and other wooden structures.

Abstract: The elm wood samples were tested by the technique of ultrasonic, and the testing results were analyzed by using the statistic software of SPSS. The results showed that the moister content of wood, wood crack, the sizes of holes and numbers of holes have significant influence on propagation parameters and dynamic modulus of elasticity. If there are holes or cracks in the propagation path, the propagation time will be longer, and the propagation velocity and wood modulus will decrease accordingly. The studying results of this paper will provide a sound background for the application of ultrasonic technique in detecting the inner defects of wood products and other wooden structures, and also offer important reference for testing the inner defects of old trees and ancient buildings.

Abstract: In order to detect lubricating oil moisture content quickly, and replace lubricating oil of equipment in time , impedance type moisture content of lubricating oil detecting system based on AD5933 and cylindrical coaxial capacitive sensor are explored. The paper selected the excitation voltage amplitude and frequency reasonably, and studied the relationship between water content of lubricating oil and impedance value. The result suggests that when the excitation voltage amplitude is 2V, the frequency ranges from 4 kHz to 6 kHz, moisture content of lubricating oil is closely related to impedance value and lubricating oil resistance value decreases with the increase of its moisture content. In addition, the mathematical model between moisture content of lubricating oil and the impedance value is established, moisture content of lubricating oil can be calculated according to the impedance value.