08-08-2014, 07:16 PM
How I think it works is, (I can't be sure it's the exact same type as the ones we used to have at the steelworks)
You slide the unit over a bar and clamp the thumb wheels, the pointy screws bite into the bar at a distance called the gauge length,
Then you externally load the bar in tension or compression but not in bending like you test belt or saw blade tension, if for example the bar has a cross section of 100 square millimetres and the load is a hundred newtons, the reading will be a direct strain reading when 1 Pascal of pressure is acting on the sample bar,
FYI it's more likely to be many thousands of newtons for example the yield strength for a particular steel might be 400MPa in this example the force on that bar would have to be 400,000,000N or 400 Mega Newtons to reach yield, so at 200 Mega Newtons there would be an expected stretch (called strain) when testing materials in a production environment the user would know what this number should be and if the sample test is out of spec it all goes in the scrap tub.
Or more likely after you get beaten up by the boss for finding an out of spec batch and costing the company thousands you leave the tricky little strain tester in it's box for good until it is sold to Bob at a Car Boot sale.
Regards
Rick
You slide the unit over a bar and clamp the thumb wheels, the pointy screws bite into the bar at a distance called the gauge length,
Then you externally load the bar in tension or compression but not in bending like you test belt or saw blade tension, if for example the bar has a cross section of 100 square millimetres and the load is a hundred newtons, the reading will be a direct strain reading when 1 Pascal of pressure is acting on the sample bar,
FYI it's more likely to be many thousands of newtons for example the yield strength for a particular steel might be 400MPa in this example the force on that bar would have to be 400,000,000N or 400 Mega Newtons to reach yield, so at 200 Mega Newtons there would be an expected stretch (called strain) when testing materials in a production environment the user would know what this number should be and if the sample test is out of spec it all goes in the scrap tub.
Or more likely after you get beaten up by the boss for finding an out of spec batch and costing the company thousands you leave the tricky little strain tester in it's box for good until it is sold to Bob at a Car Boot sale.
Regards
Rick
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