机械专业毕业论文外文翻译Word下载.docx

1、英文原文：Experimental investigation of laser surface textured parallel thrust bearingsPerformance enhancements by laser surface texturing （LST） of parallel-thrust bearings is experimentally investigated. Testresults are compared with a theoretical model and good correlation is found over the relevant op

2、erating conditions. A compari-son of the performance of unidirectional and bi-directional partial-LST bearings with that of a baseline, untextured bearing ispresented showing the benets of LST in terms of increased clearance and reduced friction.KEY WORDS: uid lm bearings, slider bearings, surface t

3、exturing1. IntroductionThe classical theory of hydrodynamic lubrication yields linear （Couette） velocity distribution with zero pressure gradients between smooth parallel surfaces under steady-state sliding. This results in an unstable hydrodynamic lm that would collapse under any external force act

4、ing normal to the surfaces. However, experience shows that stable lubricating lms can develop between parallel sliding surfaces, generallybecause of some mechanism that relaxes one or more of the assumptions of the classical theory.A stable uid lm with sucient load-carrying capacity in parallel slid

5、ing surfaces can be obtained, for example, with macro or micro surface structure of dierent types. These include waviness 1 and protruding microasperities 24. A good literature review on the subject can be found in Ref. 5. More recently, laser surface texturing （LST） 68, as well as inlet roughening

6、by longitudinal or transverse grooves 9 were suggested to provide load capacity in parallel sliding. The inlet roughness concept of Tonder 9 is based on eective clearance reduction in the slidingdirection and in this respect it is identical to the par- tial-LST concept described in ref. 10 for gener

7、ating hydrostatic eect in high-pressure mechanical seals.Very recently Wang et al. 11 demonstrated experimentally a doubling of the load-carrying capacity for the surface- texture design by reactive ion etching of SiC parallel-thrust bearings sliding in water. These simple parallel thrust bearings a

8、re usually found in seal-less pumps where the pumped uid is used as the lubricant for the bearings. Due to the parallel sliding their performance is poorer than more sophisticated tapered or stepped bearings. Brizmer et al. 12 demon-strated the potential of laser surface texturing in the form of reg

9、ular micro-dimples for providing load-carrying capacity with parallel-thrust bearings. A model of a textured parallel slider was developed and the eect of surface texturing on load-carrying capacitywas analyzed. The optimum parameters of the dimples were found in order to obtain maximum load-carryin

10、g capacity. A micro-dimple collective eect was identi-ed that is capable of generating substantial load-carrying capacity, approaching that of optimumconventional thrust bearings. The purpose of the present paper is to investigate experimentally the validity of the model described in Ref. 12 by test

11、ing practical thrust bearings and comparing the performance of LST bearings with that of the theoretical predictions and with the performance of standard non-texturedbearings2. BackgroundA cross section of the basic model that was analyzed in Ref. 12 is shown in figure 1. A slider having a width B i

12、s partially textured over a portion Bp =B of its width. The textured surface consists of multiple dimples with a diameter，depthand area density Sp. As a result of the hydrodynamic pressure generated by the dimples the sliding surfaces will be separated by a clearancedepending on the sliding velocity

13、 U, the uid viscosity l and the external loadIt was found in Ref. 12 that an optimum ratio exists for the parameter that provides maximum dimensionless load-carrying capacity where L isthe bearing length, and this optimum value is hp=1.25. It was further found in Ref. 12 that an optimum value exists

14、 for the textured portion a depending onthe bearing aspect ratio L/B. This behavior is shown in gure 2 for a bearing with L/B = 0.75 at various values of the area density Sp. As can be seen in the range of Sp values from 0.18 to 0.72 the optimum a value varies from 0.7 to 0.55, respectively. It can

15、also be seen from gure 2 that for a 0.85 no optimum value exists for Sp and the maximum load W increases with increasing Sp. Hence, the largest area density that can be practically obtained with the laser texturing is desired. It is also interesting to note from gure 2 the advantage of partial-LST （

16、a 1） over the full LST （a = 1） for bearing applications. At Sp= 0.5, for example, the load W at a = 0.6 is about three times higher than its value at a = 1. A full account of this behavior is given in Ref. 12.3. ExperimentalThe tested bearings consist of sintered SiC disks 10 mm thick, having 85 mm outer diameter and 40 mm inner diameter. Each bearing （see gure 3