SEDL / STP / STP527-EB / STP34706S

Measuring K^R-Curves for Thin Sheets

Ripling, EJ
Director of research and research engineer, respectively, Materials Research Laboratory, Inc., Glenwood, Ill.

Falkenstein, E
Director of research and research engineer, respectively, Materials Research Laboratory, Inc., Glenwood, Ill.

Pages: 12    Published: Jan 1973

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Abstract

A modification of the tapered double cantilever beam specimen for measuring K^R-curves of thin sheets is described. The modification consists of adhering properly contoured cover plates to the sheet to form a composite zero K-gradient (ZKG) specimen.

This testing procedure has a number of advantages over those presently used for plane stress testing:

1. K is proportional to the applied load and independent of crack length. Consequently, the specimen is stable, allowing for the collection of the complete K^R-curve.

2. The testing procedure is simplified, and the instrumentation required to collect data, even at high rates, is relatively simple, since only load need be monitored.

3. Buckling is eliminated without the need of constraining members near the crack.

4. Cracking rate is related linearly to displacement rate.