### STP627: Crack Propagation with Crack-Tip Critical Bending Moments in Double-Cantilever-Beam Specimens

Burns, SJ

*Associate professor and research assistant, University of Rochester, Rochester, N.Y.*

Chow, CL

*Associate professor and research assistant, University of Rochester, Rochester, N.Y.*

Pages: 13 Published: Jan 1977

**Abstract**

Rapidly wedged, double-cantilever-beam (DCB) specimens have a critical bending moment as a propagating fracture criterion in the limit of the Bernoulli-Euler beam theory. The magnitude of the critical bending moment is calculated from a fully dynamic analysis of crack propagation. The shear force in the beam at the constant displacement rate end of the DCB specimen, multiplied by the square root of the loading time, is related to the critical bending moment. Experimental measurements of the time dependence of the shear force have been used to calculate the specific fracture surface energy versus crack velocity. The crack velocity in a single specimen decreases with increasing time, it varies by a factor of five and is typically 0.01 of √*E/ρ*. Details of the experimental measurements for brittle and ductile fractures, including stress intensity values versus crack velocity, are described.

**Keywords:**

cantilever beams, crack propagation, fracture properties, stress intensity, shear force, bending, crack velocity

**Paper ID:** STP27390S

**Committee/Subcommittee:** E08.06

**DOI:** 10.1520/STP27390S

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