To 
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To receive exact results when
performing a tensile test at first
you need a perfect prepared tensile
specimen. This specimen has to meet the standard (ASTM,
GHOST, EN, ISO, DIN, AFNOR, BS, JIS …) as well as the mechanical
requirements. If the specimen has a bad quality the results of your test
are wrong and not reliable. What for you invest in a HQ tensile test
machine when your specimens do not allow correct results?
Tensile specimens
those do not have a perfect edge / flank never will give you the high
elongation the material is able to do. Often you loose 1/8 – 1/3 of the
possible total elongation
At a
tensile specimen that is blanked only (sheet metal tensile
specimens from 0,05 – 8.0 mm thickness; imperial thickness 0.002 - 0.3
inch) the results of elongation, yield point, Rp0.2, Rto.5 are mostly
wrong and total elongation is missing.
Even at weak material the
edges will be deformed by deep drawing effect (see the side of matrix.
If you don’t remove this damage of the edge your results of Rp0.2 / Rt
0.5 / yield point will be higher (up to 20 %) because this cold
deforming process at blanking will effect a cold hardening effect into
the edges and material.
Additional this cold hardened zone will
content micro cracks and this will finally bring the effect that this
cracks will be the initial marks of rupture. This will influence the
total elongation up to 1/8 – 1/3.
With each coil you process
wrong (and wasting) you loose money for the investment for a HQ specimen
preparation system.
And also every national and international
standard say: A cold hardened edge / damaged edge from punching /
blanking has to be removed…
… not to influence the mechanic /
technologic results of the performed tensile tests.
But at least:
This biggest problem is to loose a customer
because of wrong quality … | |
