A CALIBRATION FUNCTION FOR NOTCHED CYLINDRICAL TENSION SPECIMENS, BASED ON THE COMMON FORMAT EQUATION - NUMERICAL AND EXPERIMENTAL-DATA ANALYSIS

Calibration functions for two-dimensional fracture test specimens, rep resenting the relation between load, plastic displacement and uncracke d ligament length, have been recently developed through the use of the Common Format Equation (CFE) proposed by Donoso and Landes. In the CF E, the behavior of the fracture test specimen is expressed as the prod uct of three terms: a constraint factor, Omega(.); a geometry and liga ment size-dependent function, G, and a hardening function H. One of th e main assumptions of the CFE approach is that, for any given two-dime nsional fracture test specimen geometry, the behavior may be predicted from the material stress-strain behavior, by using the appropriate G function. In other words, the material tensile properties, normally ob tained with smooth cylindrical specimens, are transferred to the notch ed two-dimensional fracture specimens by means of the hardening functi on H. In another work by Donoso and Landes it has been further shown t hat calibration curves for planar, two-dimensional fracture specimens, may also be obtained directly from cylindrical specimen tensile data, using a model based on the CFE. In this model, the normalized load is directly related to true stress, and the normalized displacement to t rue strain,as obtained from a conventional tensile test performed with cylindrical specimens. In this context, one can expect that the same approach may be applied to the transfer of material properties from sm ooth cylindrical specimens to notched cylindrical specimens. The latte r is a type of geometry that is deserving a lot of attention presently , because of some advantages when compared to planar specimens. In thi s work, both numerical and experimental data for a ferritic steel and a weld metal, are obtained and analysed in order to develop the calibr ation function for notched cylindrical specimens under tension load, b ased on the CFE approach. It is shown that the geometry function obtai ned, which depends on the ratio of the diameter d of the notched secto r (the ligament of the specimen), to the diameter D of the cylindrical portion of the specimen, normalizes the load-plastic displacement dat a to a common format that depends solely on the material properties. C opyright (C) 1996 Elsevier Science Ltd