Simple Formulas for Dynamic Fracture Mechanics Parameters of Elastic and ViscoElastic Three-Point Bend Specimens Based on Timoshenko's Beam Theory

Abstract

Simple formulas for the dynamic fracture mechanics paramerters of a three-point elastic or viscoelastic bend specimen are derived by means of the Timoshenko's beam theory. Numerical analysis is performed for a specimen of steel or PMMA impacted by a falling steel cylinder or sphere. The contact force between the specimen and impactor is estimated by applying the Hertz's theory to the local deformation near the contact point, and the fracture mechanics parameters are evaluated by the simple formulas. For the purpose of comparison, computations are also performed by using the formula which has been obtained previously using the Euler-Bernoulli's beam theory. A fracture test of PMMA beam was conducted and the dynamic strain intensity factor was measured by a strain gauge mounted near the crack-tip. It is found that the fracture mechanics parameters are overestimated if the effects of rotary inertia and transverse-shear deformation of specimen are neglected. © 1984, The Japan Society of Mechanical Engineers. All rights reserved.