SEDL / STP / STP803V1-EB / STP37308S

Effects of Thickness on J-Integral in Structures

Sakata, M
Professor, associate professor, and research associate, Department of Physical Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo,

Aoki, S
Professor, associate professor, and research associate, Department of Physical Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo,

Kishimoto, K
Professor, associate professor, and research associate, Department of Physical Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo,

Kanzawa, M
Research engineers, Research Laboratory, Ebara Corp., Fujisawa, Kanagawa,

Ogure, N
Research engineers, Research Laboratory, Ebara Corp., Fujisawa, Kanagawa,

Pages: 19    Published: Jan 1983

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Abstract

The distribution of the Ĵ-integral, an extension of the J-integral, is calculated along the crack front of compact specimens of varying thicknesses by a three-dimensional elastic-plastic finite-element method. The Ĵ-integral takes the maximum value at the midthickness and smaller values near the plate surfaces, and the Ĵ-value at the midthickness coincides with the J-value determined from the computed load versus load-line displacement curve by using the Merkle-Corten formula. These results explain why the plane-strain fracture toughness value J^Ic can be experimentally determined by using specimens of moderate thickness.

To avoid the expense of three-dimensional computations, an empirical formula based on a two-dimensional finite-element method is proposed to determine the J-value which coincides with the Ĵ-value at midthickness in a cracked structure. Experimental results on compact specimens of 304 and 4340 steels and also on rotating disks of 4340 steel indicate that the onset of crack growth in a structure with finite thickness can be estimated by using the empirical formula and the J^Ic-value of the compact specimen.