Digital Repository, ECF14, Cracow 2002

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Dynamic Correction Functions for K - a Numerical Approach

Last modified: 2013-02-10


It is important to determine the fracture behaviour of polymers at impact loadingand one possibility is to use a three point bend test geometry. For low and intermediate impactvelocities a load based approach can be used. There are ESIS standards both for low andintermediate impact rates. Damping is recommended at intermediate velocities in the ESISstandard. For higher impact velocities (>1m/s) these load based methods are increasinglyinaccurate due to dynamic effects. Therefore, in the case of instrumented high rate three pointbend tests with precracked specimen the time to fracture is usually measured at high rates ofloading. From the time to fracture and the compliance, a load at fracture can be computed, andsubsequently K. The values for K have to be corrected to account for dynamic effects in thespecimen due to inertia phenomena and stress waves. In this work these dynamic correctionfunction is computed numerically with a finite volume procedure for strikers with differentstiffness. The influence of the contact stiffness on the shape of the dynamic correction functionis investigated and found to be of high importance.

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