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Application

Automated Precracking to international Standards using a choice of compliance, potential drop or manual techniques for automatic crack measurement

The purpose of precracking is to introduce a defect into a specimen for subsequent fracture toughness testing or crack growth investigation. In materials testing, the defect takes the form of a small crack. Ideally, the crack should have a sharp crack tip with minimal plastic zone surrounding the crack front because any plasticity in front of the crack face will increase resistance to crack growth. The ideal precrack can be achieved by:

         initiating the crack at a high stress intensity factor (Kmax).

         growing the crack whilst automatically reducing the stress intensity factor (Kmax) by following a user programmed negative K gradient. (This technique is also known as load shedding)

  • finishing the crack growth at a constant delta K until the desired crack length is achieved

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