Crack length calculation for bend specimens under static and dynamic loading Fengchun Jiang, Aashish Rohatgi, Kenneth S. Vecchio * , Raghavendra R. Adharapurapu Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, EBUII, Room #260, La Jolla, CA 92093-0411, USA Received 17 June 2003; accepted 26 October 2003 Abstract Crack length calculations in bend specimens have been derived by analyzing the sampleÕs load-line compliance. This compliance equation is based upon calculating stiffness that incorporates the effects of shear deformation, rotary inertia and crack length in a dynamic test. Three-point bend tests for a high-strength steel and an aluminum alloy were conducted under static and dynamic loading to investigate the validity of the equation derived. The present static test results show good agreement with those predicted from ASTM E399. Dynamic crack lengths determined by the for- mula proposed in this work are also in good agreement with other models in the literature, and with the experimental results presented here. The applicability of the present approach to effective crack length determination under small- scale yielding conditions is discussed. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Crack length; Load-line compliance; Three-point bend specimen; Static and dynamic loading; Model 1. Introduction The calculation and measurement of crack length is very important in the study of fracture mechanics. For instance, the crack length needs to be known in the determination of resistance curves (R-curve), crack propagation velocity, crack propagation toughness and crack arrest toughness. The most popular experimental methods used in static fracture testing to measure the crack length are the compliance method and the potential drop method. These two methods are used in ASTM E399 [1] and ASTM E647 [2]. Various researchers have tried to determine the crack length indirectly. For example, in their aim to determine J –R curves, researchers have performed load-displacement tests on pre-cracked specimens and determined the crack length indirectly via mathematical analysis. Such techniques include * Corresponding author. Tel.: +1-858-534-6076; fax: +1-858-534-5698. E-mail address: kvecchio@ucsd.edu (K.S. Vecchio). 0013-7944/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.engfracmech.2003.10.004 Engineering Fracture Mechanics 71 (2004) 1971–1985 www.elsevier.com/locate/engfracmech