Re: [MV] why don't engine blocks crack too?

From: wwd@netheaven.com
Date: Sun Oct 14 2001 - 06:36:48 PDT


In <list-1330568@skylee.com>, on 10/14/01
   at 09:36 AM, "J. Forster" <jfor@onemain.com> said:

>Cavitation is when the pressure in a fluid

         edit_out [bubble] edit_out

>goes down and a bubble
>spontaneously forms and then collapses. It is typically found in pumps,
>ultrasonic cleaners, and near propellers in water. The conditions in the
>cavitation region are extreme and can erode nearby materials. In fact,
>there was a Scientific American article about these bubbles emitting
>light.

>Electrolytic action is electro-chemical material removal or deposition
>(like plating). An electrolytic cell can be formed by dissimilar metals.

>-John

When the bubble forms on the metal surface, molecules of the metal are
'sucked' off since the bubble is actually a vacuum. The bubbles travel off
somewhere and more are formed, usually at a pit or protrusion in the metal
surface. The erosion is therefore continuous for a given set of
conditions. Better prop shape and material, polished and painted surfaces
as well as reduced rpm's will help minimize this

Bill

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