Development of Eta Factors in Elastic-Plastic Fracture Testing Using a Load Separation Technique

Abstract

A method for experimentally determining the eta (η) factor based on separation constants has been recently proposed. This method has two important implications for elastic plastic fracture toughness testing. First, the method can be used to determine the η factors for any new test specimen geometry which might be added to existing test standards. Such specimens as disk compact, arc bend, and arc tension are used in the KIc test standard. They can be added to the J based standards if the specimen calibrations are known, one being the η factor calibration. In this paper a step by step procedure is given describing η factor calibration for an arbitrary specimen geometry based on a series of blunt notched specimens. The procedure proposed in this paper was then applied to existing blunt notch data for the traditional test specimen geometries, the compact, and single edge notched bend specimens. The results of the study show different values for η from these in the existing standards both in magnitude and trend with a/W. In addition they show a slight material sensitivity. The consequences of having incorrect η factors in the test standards are explored in a sensitivity study. These results are used to evaluate the importance of having correct η factors and recommendations are made.

Non linear fracture mechanics of polymers: Load Separation and Normalization methods

“…The Load Separation Property allows the expression of the load, P, applied to a notched body as a product of two independent functions: a geometry dependant function (including crack length), and another function dependent on material deformation properties. Similarly to the developments available in literature, assuming the validity of Load Separation in the plastic displacement regime [31,77] we can speculate that the load can be represented as a product of two functions: a crack geometry function, G, and a material deformation function, H as follows:…”

The Linear Normalization Technique—an Alternative Procedure for Determining J‐r Curves From a Single Specimen Test Record Based on Landes' Normalization Method

“…where W is the specimen width. Sharobeam and Landes[l5,16] have demonstrated that the function G(a/W) can be determined from the J calibration for each geometry. When the load is divided by the crack length function a normalized load, PN, is defined which is a function only of plastic displacement:…”

“…The geometry function G(a/W) can be determined from the J calibration and for standard test Here, B is the specimen thickness, W the specimen width, and b the ligament (= Wa). According to Sharobeam et al [16], ylpl is independent of crack growth and has the following values: qpl = 2.130 for CT-specimens yip, = 1.940 for SENB-specimens vp, = 0.963 for CCT-specimens…”

A method to evaluate ductile fracture toughness based on load separation principle

“…The load separation principle was firstly proposed by Ernst et al 4 and later developed by Sharobeam and Landes, 13 Sharobeam et al, 14 Landes and Zhou, 15 Landes et al, 16 and others. 17 Bao et al 11 made further improvements on the basis of previous work considering the consistency of dimension.…”