Title: Determination of valid mode-II fracture toughnesses Kllc

Authors: W. Hiese, J.F. Kalthoff

Addresses: Experimental Mechanics, Ruhr-University Bochum, 44780 Bochum, Germany. ' Experimental Mechanics, Ruhr-University Bochum, 44780 Bochum, Germany

Abstract: From a discussion of the sizes of the plastic zones at the tip of a crack under shear (mode-II) and tensile (mode-I) conditions of loading, hypotheses on specimen size requirements are derived for determining valid values of the shear fracture toughness Kllc. The following conclusions are drawn: The minimum specimen thickness for a Kllc test can be smaller, but the minimum in-plane specimen dimensions should be larger than for a Kllc test. For verification of these hypotheses, mode-II and. additionally, mode-I fracture toughnesses are determined for the aluminium alloy 7075 and the tool steel 90 MnCrV 8. Measurements are performed with specimens of different sizes with respect to [he size of the crack lip plastic zones. The obtained data are in good agreement with the derived criteria for measuring mode-II fracture toughnesses Kllc and confirm their validily.

Keywords: crack propagation direction; crack tip plastic zones; experimental techniques; fracture toughness; mode-II loading; specimen size requirements; validity criteria; aluminium alloys; tool steel; shear; tensile.

DOI: 10.1504/IJMPT.1999.036277

International Journal of Materials and Product Technology, 1999 Vol.14 No.2/3/4, pp.355 - 368

Published online: 01 Nov 2010 *

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