A New Method for the Determination of the Rotational Factor rat Low Temperatures Using the P-△ and Vg-△ Curves

This paper presents a new and simpler method for determining the rotational factor at low temperatures of three-point bend specimens. Its basic principle, calculating equations and some test results are discussed in detail.
When evaluating the ductile fracture toughness J_1c of two kinds of low alloy structure steel 15MnVN and 16Mn using J-R curve, we recorded the Vg-△ curve(clip gauge displacement versus loadpoint displacement) and P-△ curve simultaneously with the same recorder. From the recorded P-△ and Vg-△ curves, the rotational factor r for each of the final loads in the process of loading of the three-point bend test specimens could be calculated.
The results thus obtained are in good agreement with the theoretical values and are consistent with those measured with other means.