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As a key component of the integrated transmission device of tracked armored vehicles, the confluence planetary row has the advantages of high transmission efficiency, high load capacity and compact space structure, but its working condition is very complex and variable, and the vibration characteristics under the extreme high and low temperature environment directly affect the service performance of the integrated transmission device. In this study, a comprehensive test rig for the vibration of the confluence planetary row is designed and built, and the dynamic characteristics tests of the confluence planetary row gear system are carried out under normal temperature conditions and temperature rise conditions. The results show that under normal temperature conditions, the rotational speed and load power have a greater influence on the system vibration amplitude; and under temperature rise conditions, when the temperature is constant, the load power has a greater influence on the system vibration amplitude in the low frequency band, and the rotational speed plays a dominant role in the high frequency band. When the speed and load power are certain, the influence of temperature on the low frequency region is more obvious, and the higher the temperature, the more obvious the influence will be. The research results have theoretical and application values for condition monitoring and health maintenance of the confluence planetary row under complex working conditions.

In order to understand the effect of low - frequency vibration stimulation on the behavior and physiology of Larimichthys crocea,this study simulated the vibration of breeding cabin by self-made steel sink and actuator,and used the main frequency of underwater noise of traditional knocking operation to catch large yellow croaker. The frequency of 125 Hz (150 dB) and 200 Hz (150 dB) were used to conduct vibration stimulation experiments on 250 g and 500 g groups of large yellow croaker to determine the behavioral response and physiological and biochemical changes of large yellow croaker ( cortisol, epinephrine, thyroxine). The results showed that:(1) In the early stage of acoustic stimulation,the behavioral responses of the two groups of test fish were characterized by random movement,cruising away after slow approach,free or around cruising. After adaptation,the test fish were basically in a regular or free cruising around the wall,cruising away after slow approach,or stagnant,and there was no obvious disturbance response. (2) In 250 g test group,the change of adrenaline at 125 Hz frequency (about 40. 93% increase) was the most significant (P<0. 05). Under the condition of 200 Hz frequency,the change of thyroxine (increased by about 41. 08%) was the most significant (P< 0. 05). Except for increase of other blood indexes except epinephrine was higher than that of 125 Hz frequency group. Therefore,250 g large yellow croaker was more sensitive to 200 Hz. In the 500 g test group, the change of thyroxine ( increased by about 28. 68%) at 125 Hz frequency was the most significant ( P < 0. 05),and other blood indexes decreased. Under the condition of 200 Hz frequency,the change of thyroxine (increased by about 41. 79%) was the most significant (P<0. 05) and higher than that of 125 Hz frequency group,while other blood indexes increased in different degrees in 200 Hz frequency group. Therefore,the 250 g and 500 g groups were more sensitive to 200 Hz vibration stimulation. In this study, the effects of low - frequency vibration stimulation on the behavioral response and physiological and biochemical indexes of large yellow croaker were analyzed. The aim was to improve the growth rate,survival rate and quality of large yellow croaker during the breeding process of large yellow croaker,and to provide data support and reference [ABSTRACT FROM AUTHOR]

In order to prolong the service life of wireless vibration sensors when collecting a large number of high-frequency vibration data, this paper studied the existing vibration data compression algorithms, put forward and analyzed the existing problems, and on this basis, proposed an effective mechanism of K-means clustering-discrete cosine transform (DCT) dual data compression. According to the characteristics of predictive maintenance data, K-means clustering-DCT dual compression algorithm firstly used K-means algorithm to aggregate and classify vibration data, and then carried out DCT compression according to the frequency domain characteristics of vibration signals. The verification results showed that the algorithm significantly improved the data compression efficiency and reduced the transmission of redundant data by aggregating vibration data. In addition, under the condition of the same amount of data, the algorithm had better application performance after improving the peak signal-to-noise ratio compared with other algorithms.

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Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the problem that the unclear removal mechanism of CFRP could not ensure machining quality of Al and CFRP at the same time during low-frequency vibration-assisted drilling process of Al/CFRP laminated structure, the tool path during vibration-assisted drilling was analyzed by theoretic method. Based on this, the effect of low frequency vibration on material removal and processing quality at Al entrance, CFRP exit and hole wall of the laminated structure was revealed. The influence of low-frequency vibration parameters was further studied, a drilling platform including low-frequency vibration tool holder was built, based on which low-frequency vibration-assisted drilling experiments with special designed tools for CFRP at different amplitudes were conducted. The results indicate that low-frequency vibration can effectively achieve aluminum alloy chip breaking, avoiding scratching of long chips and improving the processing quality of Al part. The introduction of low-frequency vibration can increase the maximum axial force and excessive amplitude can exacerbate tear damage of CFRP at the exit and reduce the quality of drilled hole wall. [ABSTRACT FROM AUTHOR]

This paper is aims to study the influence mechanism of low frequency vibration on coal seepage in mining process. By adding vibrating device to triaxial seepage test and combining with Meso-scomic test, the evolution law of coal rock permeability and internal Meso-structure disturbed by vibration under effective volume stress is analyzed. The results show that vibration can increase the permeability of coal and rock. When the vibration frequency is 10 Hz, the resonance effect of coal and rock is produced, and the permeability of coal and rock reaches the maximum. The permeability of coal and rock decreases with the increase of effective volume stress. The porosity and gray value are used to describe the permeability change of coal and rock specimens, that is, the permeability increases with the increase of porosity and decreases with the increase of gray value. The research conclusion has a new understanding of coal and gas outburst induced by low frequency vibration, which is conducive to reduce the occurrence of coal mining safety accidents. [ABSTRACT FROM AUTHOR]

In order to study the influence mechanism of vibration on the safety of coal mining in the process of excavation, the vibration disturbance system is added on the basis of triaxial seepage test, and the evolution law of permeability of coal petrography under low frequency vibration and different effective stress is analyzed. And the process of internal fracture of coal petrography during loading is analyzed by combining with microscopic test. The test result shows that the greater the effective stress applied, the smaller the permeability under the load condition, and decrease in the form of negative exponential; under the effect of low frequency vibration, the higher the frequency of disturbance, the greater the permeability and rise exponentially. The CT image processing can clearly observe the expansion law of the original fracture after vibration and loading, and analyze quantitatively the evolution law of coal-rock fracture by using the porosity. The conclusions obtained will be used to guide the engineering practice and so as to effectively prevent the occurrence of coal mining safety accidents. [ABSTRACT FROM AUTHOR]

CFRP/Ti stacks have been widely used in aviation industry. Mechanical characteristics of Carbon fiber reinforced plastic(CFRP) is greatly different from that of the titanium alloy. The low thermal coefficient and elastic modulus of Titanium alloy lead to long spiral chips with high temperature during drilling which may cause surface scratches of machined hole and damages to the CFRP layer. In the paper three types of drilling methods:conventional drilling,rotary ultrasonic assisted drilling and low-frequency vibration assisted drilling are compared and analyzed from the following points of view: Cutting temperate,drilling quality and chip morphology. It is shown that compared with conventional drilling,both the ultrasonic vibration and low frequency vibration assisted drilling could reduce the temperature and improve the drilling quality. The low frequency vibration assisted drilling method could break the cutting chips belts of titanium alloy material to small chips. Due to the reason,the cutting temperature could be reduced by 45%. As a result,the CFRP damages caused by over heated cutting chips belts of titanium alloy could be avoided,and the drilling quality could be improved to a great deal. [ABSTRACT FROM AUTHOR]

To study the influence of low-frequency disturbance load on gas porosity，the authors developed a porosity formula under coal porosity pressure，absorption strength and decreasing vibration stress. The authors adopted the change law of porosity and uniaxial compressive strength，and tested the uniaxial compressive strength changes of a sample under different frequencies and different vibrating time models. The test reveals that uniaxial compressive strength decreases and porosity increases when vibrating time extends under the low frequency and same frequency. When frequency decreases，uniaxial compressive strength increases and porosity declines. At the frequencies of 30 Hz and 20 Hz，the D-value of uniaxial compressive strength porosity is smaller than that at the frequencies of 20 Hz and 10 Hz. The test also demonstrates that vibration increases porosity and then decreases uniaxial compressive strength. Moreover，at the increasing frequencies of 10 Hz，20 Hz and 30 Hz，porosity gradually increases and uniaxial compressive strength decreases respectively. The calculated porosity reflects the variation of uniaxial compressive strength under vibration. The authors compared the relationship between calculation porosity and uniaxial compressive strength，and then obtained the class exponential change law of the former. The formula best reveals the different frequencies and time ranges imposed on the porosity changes under low frequency. [ABSTRACT FROM AUTHOR]

To solve the instability problem of the magnetic suspension rotor caused by the low frequency vibration during high speed operation, the improved disturbance observer is utilized to observe the low frequency vibration of the magnetic suspension rotor, making a provision for the suppression of the vibration in the controller. The improved disturbance observer can not only correctly observe the low frequency vibration of the magnetic suspension rotor in high speed, but also effectively overcome the effect of the deformation of the magnetic suspension rotor in high speed. Related experiments were performed at 24 000 r/min for a 100kW magnetic suspension motor. The results of the experiments show that the low-frequency gain of the magnetic suspension motor decreased by 20 dB, and the vibration is reduced by 36. 8 μm. The control precision increases by 63. 89% after adding the improved disturbance observer into the active magnetic bearing system, compared with the original system. The results show that adding the improved disturbance observer into the system can effectively suppress the low frequency vibration and improve the stability of the magnetic suspension motor in high speed. [ABSTRACT FROM AUTHOR]