Threshold Testing


Testing for the crack growth threshold, the boundary between growth and no growth, has proven over the years to be a significant challenge to get right. Even using the latest ASTM methods, remote closure can result in false thresholds that exceed the true threshold value. FractureLab has a patented  Flat Bottom Hole (FBH) specimen which provides the following benefits:

–No preflaw typically required
–K reduces naturally as crack grows
–Small specimen size (.63 DIA x 1.75 blank)
–Uniform crack closure state across crack front (no free surface intersection)
–Crack front shape precisely known (circular & self-centering for isotropic applications)
–Stiff specimen loading set-up; enables testing at high frequency

Validation tests performed thus far suggest that this specimen gives high quality results (a low, repeatable threshold value). It may also find application in the qauntification of crack growth resistance anisotropy within the plane of the specimen.

Download more information on this test method.


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