Hi,
The precise mechanism of friction is still incompletely understood. There is some evidence to suggest that molecular attraction plays an important part, and that the independence of the contact area is only apparent. If the contact surfaces were greatly magnified, one would see that contact really only occurred over relatively few small areas, giving rise to local interference or even possibly small pressure welds.
Above is an extract on friction from a text book. Hence one can understand why there are large fluctuations in the value of the friction coefficient.
I have piping text books which give different coefficients on steel on steel, depending on type of contact.
point contact (pipe on steel round bar) 0.2
edge contact (pipe shoe on steel round bar) 0.3
line contact (pipe on steel beam) 0.25
face to face contact (pipe shoe on steel beam) 0.4
Ajith Suriyaaratchie
> ** High Priority **
>
> As you have mentioned Mr Raj, I am asking about the 20mm rod which we weld
on the plate (casted on the top of sleeper) or rack. As you have mentioned
about the frictional force - Frictional force is nothing but the
multiplication of frictional coefficient of metal and the reaction which is
getting from the fixed body. so, i don't think that there will be any
measure difference in the frictional force (resistance which will act on
pipe while expansion of pipe metal takes place) when the contact is either
point contact, line contact or surface contact.
> One of the reasons which i heard about the provision of Rod is to reduce
corrossion. during rainy season, rain water may get collected on the top of
sleeper plate - which can corrode the pipe also. To avoid this collecion of
water between bottom of pipe and top of sleeper, rod is provided.
> Please suggest whether it is true or any other reason is there.
>
> regards,
> rakesh
>
> >>> RaviRaj_Rastogi@ril.com 05/02/02 02:45PM >>>
>
>
>
>
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Received on Sat May 04 09:35:00 2002
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