Residual stresses are the
stresses that remain after external loading has been removed. Any deformation
or annealing process can generate residual stresses. The total stresses on a
component are the sum of residual and applied stresses.
Compressive stresses (negative)
are generally desirable as they typically increase fatigue life and inhibits
stress corrosion cracking while tensile stresses (positive) adversely affect
the performance of a component.
Barkhausen Noise Analysis (BNA)
method, also referred to as the Magnetoelastic or the Micromagnetic method is
based on a concept of inductive measurement of a noise-like signal, generated
when a magnetic field is applied to a ferromagnetic sample. After a German Scientist
Professor Heinrich Barkhausen who explained the nature of this phenomenon
already in 1919, this signal is called Barkhausen noise. Learn more here.
instrumentation needed is a Rollscan CPU unit and a hand-held sensor. A fixture
for part and sensor handling will improve repeatability and simplify
measurements. Stresstech Viewscan data acquisition software allows you to
record and export the data.
Both methods are able to detect
grinding damage. However, the Barkhausen
method provides a nondestructive, repeatable and quantitative measure in
real-time while requiring no chemicals or consumables. In many cases the Barkhausen Method has
proven to be more effective than Nital Etch at detecting grinding re-temper