Fracture Toughness: Evaluation of Testing Procedure To Simplify JIc Calculations

The purpose of this study is to examine the current fracture toughness test procedure and to determine if there is an easier, less complicated method to get the J_Ic value from a test record for fracture toughness specimens. The current method for constructing J_Ic is complicated and involves a detailed computer program or spreadsheet. The objective in this study is to simplify the analysis for the determination of J_Q.

This study has shown that the load and displacement record for a fracture toughness specimen can be used to directly estimate a J_Q value, a provisional value for fracture toughness, J_Ic. The maximum load point is used along with an adjustment factor for this direct estimation of the J_Q value. This J_Q value is equivalent to that obtained from the construction procedure, when a unit-sized specimen is tested, that is, a specimen with a width of 50 millimeters (2 inches) and a thickness of 25 millimeters (1 inch). Other sizes require a size adjustment factor, which is simply a function of the specimen width relative to the unit width. The adjustment factor proposed is a square root relationship between the width of the test specimen and a unit width. This shows that the effort required for the proposed new method of constructing J_Ic is less than that required for the construction method, the new method is simple in concept and requires a minimum number of calculations, and the method appears to produce values of J_Q which are comparable to those obtained from the construction procedure and may have less inherent scatter.