Geometry Change During Analysis

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Dear All,

I am trying simulate (in ABAQUS) a fracture toughness test (CT). During loading, the crack tip 'jumped' before ductile tearing initiated.

This 'jump' needs to be incorporated into the modelling process as it affects the values of J. I'm trying to incorporate this by changing the geometry of the model part way through the test.

Does anybody know if changing the model part way through the test possible?

Does anybody know of a better way to model this effect?

thanks!

Will