Study and Comparison of Test Method for Measurement of Fracture Toughness between ASTM and ISO Standards

doi:10.3901/JME.2017.06.060

Abstract

Abstract:

ASTM E1820-11 and ISO 12135-2002 are the main two testing standards of fracture toughness. There are some obvious differences between these two standards, such as blunting line, effective data andJ-Rcurve equation, which cause discrepancy of the fracture toughness results. The bases of the blunting line of the two standards are studied and the differences of the two standards are compared. The ASTM blunting line is based on elastic-perfectly plastic model of material, and the ISO blunting line is from the supposition of power law true stress strain relation. The ISO blunting line slope is more than that of the ASTM. The resistance curve of two parameter equation is used in the ASTM standard, while the curve of three parameter equation is adopted in the ISO standard. It is suggested that the test standard can be selected according to stress strain characteristics of the material. ASTM standard can be adopted for the materials with yield platform, while ISO standard can be used for the materials without yield platform. Fracture toughness tests of Q345R steel are carried out, and the ASTM and ISO standards are assessed by the test results. The results show that the stress strain curve of Q345R exist the yield platform. ASTM blunting line can better reflect crack tip bunting. The measured fracture toughness is 235.29 kJ/m² by the ASTM standard and 179.37 kJ/m² by the ISO standard, respectively, and there is difference of about 24%.

Key words: ASTM E1820-11, blunting line, ISO 12135-2002, J-Rcurve, fracture toughness

GUAN Pengtao, LI Xiangqing, ZHENG Sanlong, BAO Shiyi, GAO Zengliang. Study and Comparison of Test Method for Measurement of Fracture Toughness between ASTM and ISO Standards[J]. Journal of Mechanical Engineering, 2017, 53(6): 60-67.

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