机械毕业设计外文翻译岩土材料的摩擦声波.docx

1、机械毕业设计外文翻译岩土材料的摩擦声波中文3280字 毕业设计（论文）外文资料翻译 学院： 机械工程学院 专业： 机械设计制造及其自动化 班级： 姓名： 学号： 外文出处： Tyler T J, Hill R, Lai E. Friction generated ultrasound from geotechnical materialsJ. Ultrasonics, 2004, 42(1): 169-172. 附 件：1、外文原文；2、外文资料翻译译文。指导教师评语：签字： 年 月 日附件1：Friction generated ultrasound from geotechnical ma

2、terialsTJ Tyler, R Hill, E LaiAbstractDrilling is a process involved with product manufacturing and for civil engineers, site preparation. The usual requirement is for efficient material removal. In this study, the friction pair interaction generated by a drilling process provides ultrasound informa

3、tion related to parameters for the geotechnical material being drilled, where the drill bit has non-degrading ultrasonic characteristics and no essential requirement for material removal. This study has considered monitoring the ultrasonic signal generated by drilling process, with a view to charact

4、erising the parameters of the geotechnical material being drilled and provides a novel method to identify or characterise ground structures. Drilling of geotechnical material systems, typically involve the interaction of a rotating probe and a granular composite medium. The applied load and angular

5、velocity are measured to determine their relevance to the ultrasonic signal. Samples of granular materials have been graded into controlled grain size ranges. Attention has been focused on determining the effects on the ultrasound signal of grain size, bulk density and the water content of the granu

6、lar material. A comparison between the various granular samples of the different grain sizes, density, water content and the associated ultrasonic signal has been done. The effect of each variable, and existing theory for these effects is commented upon. The broad aim of this research is to evaluate

7、 ultrasonic monitoring of drilling and assess its potential for real-time geotechnical ground condition monitoring applications and offer it as an alternative to existing methods. _ 2004 Published by Elsevier B.V.1. Introduction The ultrasound generated from a solidsolid friction pair has been the m

8、ain focus of research concerning friction-generated ultrasound, mainly associated with rotating and reciprocating machines. A frictional process developed during relative movement between contacting materials has an inherent level of wear that eventually would result in failure. Monitoring the ultra

9、sonic signal generated from machinery has become an alternative condition-monitoring tool, as the generated signal contains information related to the microcondition of the friction pair. It is possible to detect when components of a machine are becoming worn and a thus reduce the risk of catastroph

10、ic failure leading to production down time. Holroyd and Randall 1 discussed the sensitivity of using acoustic emission (AE) for detecting changes in lubrication, overloading, wear and review a number of different techniques used to analysethe acoustic signature. Further methodologies for analysing t

11、he friction generated acoustic signatures were discussed by Bukkapatnam et al. 2 and provide a novel analysis technique based on chaos theory, wavelets and neural networks. Much of the research concerning condition monitoring focuses on the changes in the signal due to wear, but some research have a

12、lso focused on the parameters associated with the generated acoustic signal.Work by Diei 3 monitored the acoustic emission generated by tool wear during face milling and proposed a power function relationship between the AERMS voltage and the rate of frictional energy dissipationgiven by AERMS ekgss

13、AaV Tm=2 e1T where k and m are constants that depend on the AE measuring system and the material properties of the friction pair, g is a function of surface roughness and elastic properties of the friction pair, ss is the shear strength of the interfacial material, Aa is the visible area of contact

14、and V is the sliding velocity. The parameters g and Aa essentially define the real area of contact andtherefore, the AERMS is a function of the real area of contact, the shear strength and the sliding velocity. Results obtained by Dieis work also indicated a linearrelationship between the AERMS and

15、the sliding velocity. Jiaa and Dornfield 4 monitored the AE generated by a pin on disk experiment, highlighting that the AE is caused by impulsive shock due to asperity collisions and micro-vibrations excited by stickslip phenomena. The research shows that the AERMS increases with load while a linea

16、r relationship exists between the relative surface velocity and the AERMS. Sarychev and Shchavelin 5 describe the frictional process and the generated acoustic emission associated with it. Two general rules were established relating the rate of counting the acoustic pulses (count rate) to the slidin

17、g speed of the friction pair and the applied load. The general rule for the dependence of the count rate N_ on the sliding velocity is in the form: N_ A t BvX e2T where A and B are constants and X P1. A similar relationship also applies for the dependence of the load on the count rate, but the expon

18、ent X 61. A further relationship was expressed relating the AE activity to the regime of friction in elastic contact: N_ a k N0:71h0:71A0:71 c r0:90R1:60 a V e3T where N is the normal load, h the generalised elastic modulus, Ac the counter area of contact, r the surface asperity tip radius, Ra is th

19、e surface roughness and k is a coefficient of proportionality. Further work by Baranov 6 produced two models relating the frictional parameters of the friction pair to the acoustic parameters; count rate and acoustic energy. The model for the count rate is based on the assumption that the rate of co

20、unting acoustic pulses is directly proportional to the number of contact points formed per unit time. Work by Henrique et al. 7 studied particle collisions down an inclined slope and the number of acoustic events were used to monitor the number of collisions (contacts) generated when a ball was roll

21、ed down the slope. The model for the acoustic energy relates the mechanical potential energy generated during the elastic deformation of a contacting asperity to the amplitude distribution of the acoustic signal. The energy model does not take into consideration the effects of wear and is based on t

22、he AE generated due to elastic contact.Current studies in friction-generated acoustics have shown that the acoustic signals contain information relating to the material parameters of the friction pair. The work in this study uses the acoustic signal as a tool to characterise the material properties

23、of the friction pair. The idea for this study originates from a study by Hill 8 for Scientifics, when it became apparent that monitoring the ultrasound generated by a drilling process process had potential for ground condition monitoring. The overall aim of this work is to develop a method of charac

24、terising geotechnical materials using a typical drilling process and monitoring the ultrasound generated due to the interaction between the drill tip and the geotechnical material.2. Experimental designA simplified drilling arrangement has been constructed where a rotating probe is used to maximise

25、the friction at the probe-tipgranular contact. The probe string is designed, using a suitable coupling device, so that the ultrasonic signal is transmitted from the probe tip to a stationary piezoelectric sensor. The signal is amplified by 60 dB and filtered between 250 and 500 kHz. The captured sig

26、nal is therefore in the mid-ultrasonic range and relates to the transducer monitoring frequency used. A schematic diagram of the experimental arrangement can be seen in Fig. 1. The probe rotates, while being submerged in a granular medium of controlled particle size, initial density and water conten

27、t. The feed rate and angular velocity were set to a constant value and the applied load, count rate and ultrasonic energy were simultaneously monitored. The effects of the particle size, density and water content on two ultrasonic parameters (count rate and energy) have been investigated and the sys

28、tem aims to be a future option for ground condition monitoring.3. ResultsThe effect of load on the count rate can be seen in Fig. 2a. The signal values on the left of the figure correspond to the probe tip not being in contact with the granular medium. When the probe is pushed into the granular mate

29、rial the load increases. The data highlights a stabilizatio(reduction) in the count rate and is referred to as the characteristic count rate for a particular friction pair. The stabilisation of the count rate means that no more oscillations are being produced due to an increase in the load and there

30、fore the signal amplitude is only subject to amplitude increase. Different grades of particulate material have been used and the characteristic count rate monitored. The results indicate that a lower characteristic count rate occurs as the average particle size is increased. Eight samples of sand we

31、re used and the characteristic count rate is compared with the particle size in Fig. 2b. Larger particle sizes produce fewer contacts and therefore the results agree with the assumption stated by Baranov et al. 6 that, the rate of counting is proportional to the number of contacts formed per unit ti

32、me. The results in Fig. 2c reveal that the water content has little effect on the characteristic count rate. Four ranges of grain size have been used and the count rate is plotted against the mass percentage water content. There is a small variation in the count rate but the separation in the signals generated by thedifferent particle sizes still exist. Results have revealed that the count rate value does not significantly change due to the addition of water and that the count ratesignal is mainly dependent on the number of contacts formed. Therefore, regardless of the water content of