Posted by Gordon England on January 08, 2004 at 04:15:03:
In Reply to: Surface Impact Resistance posted by Richard on January 05, 2004 at 19:12:11:
: I am building a simple ball-impact tester to test the surface impact resistance/hardness of various wood finishes, based on one I used at university. It consists of a 5ft length of drain-pipe and a 2" diameter hardened steel ball to drop down the pipe onto my sample peices.
: However I can't remember how to calculate the hardness using this method and don't have a text readily at hand. Can I use the Brinell formula directly, or do I need another? What if I want to convert these values to Janka Hardness values (as used in a table of wood species I have), how do you do this?
: Any suggestions will be greatly appreciated.
: ~Richard, Winnipeg Canada.
Hi Richard
Sounds like a good test. I assume you intend to measure the diameter of the impression left after testing. You could simply just use the diameter measurement as your hardness number or apply a formula such as impact load divided by impression surface area similar to Brinell or Vickers hardness scales. At the end of the day it will not matter as long as you have a good scale that indicates the relative differences in hardness for your particular method.
To compare the hardness scale you chose for your method to that of another hardness testing method will require direct practical comparison and extrapolation between results as used for most other conversion tables.
You may also consider measuring the rebound height of the ball as well!
Hope this is helpful.
Regards Gordon
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