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Strain Energy Density (SED)

Based on the “Theory of Ductile Fracture” by GE Bockrath and JE Glasco, the method measures the strain energy under the full range stressstrain curve. 

Two portions of the curve are evaluated separately, the uniform plastic region (that portion of the curve before necking occurs) and the damage zone (that portion of the curve after necking starts).  The strain energy density for each portion of the curve is then related to the stressstrain field at the crack tip to estimate the fracture toughness of the material.

The method is most effective at predicting Critical Fracture Stress under uniform tensile conditions (such as cylindrical pressure vessels) typically modeled as center cracked panels although it can be used to estimate KIc.  The method has the advantage of predicting fracture stress when global stresses greater than the material’s yield stress as well as under elastic conditions.

Engineering Stress Strain curve showing the two regions evaluated by the NanoSolutions SED model.

Method for estimating KIC from full range stress strain curve

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