Surface Abrasion ... further questions

[alexcappon]

Tank you Vanstoja for your answer..
I know now that two body abrasion wear is involved in the process I´m working on. (because of clear furrows on the surface.)

I have another questions :
- what is the influence of roughness of the surface which is abraded on the wear rate ?Is it higher for a flat surface or a rough surface or the same (no influence)?

- when I was talking on a model about wear (two body abrasive wear), I mean something that describes the geometry or shape of the cuttings that are made into the material (as a fonction of abradant asperities : shape, number, hardness, Young´S modulus.. ?) or something in this direction. Do someone know about this or have any useful references?

Would be grateful of answers..
Alex

 

[vanstoja]

Surface finish is extremely important when soft materials slide against harder surfaces. Any roughnesses on the harder material can cut or abrade the softer material. For equal hardness rubbing surfaces, the rougher surface will wear more due to surface asperity contacts. Worn away material from one surface may deposit on the opposite surface tending to "smooth" it and possibly reducing the wear rate between the two surfaces. For lubricated surface interactions, reduced surface roughnesses are desired so as not to rupture the lubricant film by protruding surface asperities. For the lubricated case, opposing surface roughnesses can be made too smooth leading to an effect called jo-blocking where surface tension in the liquid lubricant can cause lockup between the two surfaces preventing sliding or rolling action as needed in bearings, seals, etc.
According to the Wear Control Handbook cited in Thread342-116135, the factors affecting wear are environment, geometry, [wear coefficient*finish factor/hardness], film thickness, load, velocity, temperature and time. Wear coefficient,K, represents a given situation which refers to a given material-lubricant combination with a specific geometry and finish and a given environment. An expression for wear depth perpendicular to contact area is h=KPVt/H where h,P,V,t and H are depth,contact pressure, velocity, time and hardness.

 

[IRstuff]

see also: thread342-92753 and thread924-92790 for an interesting discussion about wear when one of the materials is "soft".

TTFN

 

[vanstoja]

Pages 449-457 of the Wear Control Handbook give diagrams and equations for the volume of material wear versus wear depth for circular point contacts, line contacts, spheres,circular/elliptical/rectangular/polygonal cylinders, washers, rings and bushings. Pages 499-500 give curve-fitted equations for determining wear coefficients from post-test measurements of friction coefficient and stabilized surface roughness.
Several good tutorial websites on wear of metals are:

http://www.mmat.ubc.ca/courses/mmat382/sections/cnc763.doc

http://www.alloysteel.net/english/4_wear_factors.asp

http://www.materialsengineer.com/CA-Wear.htm

http://www.machinerylubrication.com/article_detail.asp?articleid=468andrelatedbookgroup=WearDebris