I met you a few years ago at a NSRP meeting I attended with Steve Cogswell. It was my pleasure as I found you quite informative.
I wanted to thank you for your article in the January 2010 JPCL. I found it very educational and greatly appreciated the ability to accept your synosis or to get more indepth.
Of particular interest was the section on increased surface area per unit of suface. Could you further characterize the nature of the, for lack of a better term, microprofile as to angularity or lack of. I envision the optimum character to be a microprofile on the macroprofile achieved with abrasive blasting.
Lee- The way that a solid abrasive hitting the surface moves the metal around to make the profile is different from the liquid drop at high velocity. This is studied in universities doing high velocity research of liquids.
In very general terms, the solid abrasive, as it hits the metal, heats the metal, tears it, mashes it around (metal is mallable), and makes “large” indentions. Also, abrasives can cause hackles of steel (spikes of steel standing up), and/or become embedded in the steel. This type of profile is what the “paint people” measure.
First it is easy to see that a stream of water can remove the embedded solid particles, or wash off the hackles. If the original profile was measured with the embedded particles, then the removal can change the profile.
But when water itself is used to create the profile, it removes little bits of the metal on a granular scale. So the profile is much finer that the larger profile caused by the abrasive. It is a combination of cavitation, and hydraulics actions, so that an “undercut” can form.
I observed a fine micro-profile on top of the existing macro profile when I first looked at WJ about 1983. Scientists have been studying this profile formation for years because of the effect of erosion on the leading wings of air-craft, rockets, and yes- cavitation of propellors.
The two references that I like to use are : Tom Taylor, “Surface roughening of metallic substrates by high pressure pure waterjet”, Surface and Coatings Technology, Vol 76-77, 1995, p 95-100. He has some excellent pictures on profiles on steel, and discusses that the profile is fractal.
And a patent-by Van Kuiken for aluminium, US patent 5,380, 564 or 5,626,674(and others) You can pick up this patent from the U.S. patent web site.
Dr. Frenzel,
I met you a few years ago at a NSRP meeting I attended with Steve Cogswell. It was my pleasure as I found you quite informative.
I wanted to thank you for your article in the January 2010 JPCL. I found it very educational and greatly appreciated the ability to accept your synosis or to get more indepth.
Of particular interest was the section on increased surface area per unit of suface. Could you further characterize the nature of the, for lack of a better term, microprofile as to angularity or lack of. I envision the optimum character to be a microprofile on the macroprofile achieved with abrasive blasting.
Lee Norton
Lee- The way that a solid abrasive hitting the surface moves the metal around to make the profile is different from the liquid drop at high velocity. This is studied in universities doing high velocity research of liquids.
In very general terms, the solid abrasive, as it hits the metal, heats the metal, tears it, mashes it around (metal is mallable), and makes “large” indentions. Also, abrasives can cause hackles of steel (spikes of steel standing up), and/or become embedded in the steel. This type of profile is what the “paint people” measure.
First it is easy to see that a stream of water can remove the embedded solid particles, or wash off the hackles. If the original profile was measured with the embedded particles, then the removal can change the profile.
But when water itself is used to create the profile, it removes little bits of the metal on a granular scale. So the profile is much finer that the larger profile caused by the abrasive. It is a combination of cavitation, and hydraulics actions, so that an “undercut” can form.
I observed a fine micro-profile on top of the existing macro profile when I first looked at WJ about 1983. Scientists have been studying this profile formation for years because of the effect of erosion on the leading wings of air-craft, rockets, and yes- cavitation of propellors.
The two references that I like to use are : Tom Taylor, “Surface roughening of metallic substrates by high pressure pure waterjet”, Surface and Coatings Technology, Vol 76-77, 1995, p 95-100. He has some excellent pictures on profiles on steel, and discusses that the profile is fractal.
And a patent-by Van Kuiken for aluminium, US patent 5,380, 564 or 5,626,674(and others) You can pick up this patent from the U.S. patent web site.