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O形密封件摩擦性能英文文献和翻译(5)

时间:2017-01-02 15:04来源:毕业论文
tently higher than at 9%. Repeated tests were carried out but is was found that the scatter of results is con- siderable and therefore it is rather difficult to suggest any governing law. This is beli


tently  higher  than at 9%.
Repeated tests were carried out but is was found  that the scatter of  results is con-
siderable and  therefore it  is rather  difficult to  suggest any governing law. This  is
believed to  be  linked to  the  lack  of dimensional accuracy  of the O-rings  tested.
Analysis of  experimental  error is given  in a later section.
3.2. EFFECT OF O-RING MATERIAL
The performance of a  PTFE-encapsulated O-ring was  compared to  that  of an Fig. 6. Friction force against gauge pressure for teflon-encapsulated  seal at 9% and 16% squeeze.
ordinary rubber O-ring as shown  in fig.  7.  It can be seen that the PTFE-encapsu-
lated O-ring  shows significantly  lower friction  than the conventional  single-mate-
rial O-ring type seal. The seals of ordinary design could only be tested over a limited
pressure range. The force required to overcome  the friction exceeded the limits of
the test rig. However, it can be seen from fig. 7 that the rubber-only O-ring seals per-
form  differently  from  the  teflon-encapsulated  O-ring  seal.  The  gradient  of  the
curves representing frictional performance  of the rubber se~tls  is greater than that
of  the  PTFE-encapsulated  seal  with  the  force  increasing  far more  quickly with
increasing pressure. This could well reflect the difference in hardness of materials tested. The PTFE-encapsulated silicone O-ring had a hardness of 90 as measured
on Shore A scale, while  the  hardness of  the natural rubber O-ring was 60.
This friction behaviour can be explained  in the following way. The exclusively
rubber seals are all much more compliant  than the teflon-encapsulated  seals. This
means that, when pressurised, the exclusively rubber seals have more tendency  to
be deformed  and extruded  between  the shaft and the seal gland. As a result of such
extrusion  there  is  a  greatly  increased resistance  to motion and hence frictional
force.
As mentioned previously, a  shaft with its  surface ground to 0.2  #m was used
throughout  the studies  and, therefore,  the  results presented  are pertinent  to this  spe-
cific roughness. However, the effect of roughness on the performance of O-ring
type seal considered  in  this paper could  be significant.
3.3. EFFECT OF LUBRICATION
A series of  tests were  carried out on  teflon-encapsulated  O-rings  by adding  differ-
ent  lubricating  fluids  to the shaft/seal  interface. The  results of  these  tests are shown
in fig. 8. The friction  forces measured  under lubrication conditions  were, as antici-
pated, significantly  less than those recorded under dry conditions. The differences
in  the magnitude of  frictional  force between  oil and grease used  are not very signifi-
cant. The high-melting-point  grease gave the lowest values. The results demon-
strate that if any lubricant was to enter the shaft/seal interface  the frictional force
would vary greatly and in an unpredictable manner. If consistent values are to be
found it  is clearly important  to  ensure that  lubricating liquids cannot enter  the
shaft/seal  interface  during operation.
Since all the friction measurements were carried out at  the commencement  of对O型环式密封件的摩擦和直线运动开始时轴的表压之间关系调查结果进行提出和讨论。多个不同的O形圈的材料进行了研究,与最低的摩擦在干燥条件下被发现是由聚四氟乙烯包覆硅胶密封条生产。大量的润滑流体摩擦密封进行了研究与效果结果包括。 O形密封件摩擦性能英文文献和翻译(5):http://www.youerw.com/fanyi/lunwen_1699.html
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