Modeling and Simulation of Hydraulic Hammer for Sleeve Valve

Hydraulic hammer is commonly used hydraulic equipment in engineering work. The characteristics, high acceleration, high frequency and inertial working pressure, make it greatly different from the working conditions of conventional hydraulic equipment, while hydraulic hammer for sleeve type is also not the same as other hydraulic hammers in structure, efficiency and working performance. Based on the principle of hydraulic hammer for sleeve type, the mathematical model of hydraulic hammer for sleeve type was set with various conditions in the reciprocating movement of piston. In addition, more detailed sketch model can be easily built with the mathematical model in multi-domain system analysis software, AMESim. The simulation system of breaker built based on the principle of power bond graph structures in AMESim system is considered comprehensively to achieve its functions and characteristics, which can quickly realize the calculation of main simulation parameters for impactor. The calculated parameters can be proved to be biased with the test prototype. So these parameters must be optimized by Design Exploration to find the appropriate parameters.

Quiet Zone Design in Diffuse Fields Using Ultrasonic Transducers

This paper presents quiet zone design using ultrasonic transducers for local active control in pure tone diffuse fields. Most of researches in local active noise control used conventional loudspeakers for the secondary sources to produce quiet zones. Recently ultrasonic transducers have been used for the secondary sources to control the plane wave in active noise control. However there is no research related to active noise control in diffuse fields using ultrasonic transducers. Therefore this study uses ultrasonic transducers for the secondary sources to control the diffuse fields. The quiet zone produced using ultrasonic transducers in single tone diffuse fields has been analyzed through simulations in this work. The results showed that quiet zones created using ultrasonic transducers were larger than those created using conventional loudspeakers. This is due to the fact that the audible sound pressure produced by the ultrasonic transducers decays slowly with the distance. Therefore the secondary field created by an ultrasonic transducer could fit the primary field better and the larger zone of quiet could be obtained using the ultrasonic transducer. Also the audible sound produced by the ultrasonic transducers is directional;therefore the sound pressure amplification outside the quiet zones was lower.

Improving the high frequency response of a loudspeaker using hydrogen-free diamond-like carbon film coating at low temperature

Hydrogen-free diamond-like carbon(DLC) thin films were deposited at low temperature(less than 100°C) by an RF magnetron sputtering facility.DLC films have the ability to change the sound velocity(E/) in loudspeakers for applications of hard coating.The hydrogen-free DLC films were coated onto PEI diaphragm substrates.The I D /I G ratio and the surface roughness are 2.09 and less than 0.86 nm(Ra) with a scanning area of 50 m×50 m,respectively.Frequency response analysis of the DLC films on the diaphragm shows that the high frequency response increases by 0.2 dB-5.1 dB(6 kHz-11.2 kHz),0.4 dB-1.8 dB(11.8 kHz-20 kHz) on average.On the basis of the results of this study,we validated that it was feasible to sputter hydrogen-free DLC films on polymer substrates for mass production.These results also provided useful parameters for future applications of electro-acoustic devices.