IAM - Ceramic Materials and Technologies

First- and second-order approaches for the direct determination of bridging stresses from R-curve

  • Author: S. Fuenfschilling, T. Fett, S.E. Gallops, J.J. Kruzic, R. Oberacker, M.J. Hoffmann
  • Source: JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 2010, Band 30, Heft 6, S. 1229-1236

Abstract

A procedure is presented that allows the simple estimation of bridging stresses from crack growth resistance curve (R-curve) data. The first-order approximation results by taking the derivative of the R-curve. For an increased degree of accuracy a second-order solution is suggested. This step includes straight-forward integration of the first-order results. The procedure is outlined in detail and applied to fatigue threshold R-curve results for a MgO + Y2O3-doped silicon nitride (MgY-SN) and an 99.5% pure alumina obtained with compact tension specimens, and fracture toughness R-curve results for a MgO + La2O3-doped silicon nitride (MgLa-SN) obtained with notched bending bars. The approximate bridging stresses are compared with the "full solutions" computed with much more effort by solving a system of integral equations.