The Present SP Tests for Determining the Transition Temperature T_(sp) on 'U' Notch Disc Specimens

摘要

The principal difference between the SP testing technique and standardized Impact testing lies in the fact that the SP tests carried out in accordance with CWA 15627 use disc-shaped test specimens without a notch. Especially in tough materials, the temperature dependence of fracture energy in the transition area is very steep and lies close to the temperature of liquid nitrogen. In this case, the determination of Tsp can lead to significant errors in its determination. Efforts to move the transition area of penetration testing closer to the transition area of standardized impact tests led to the proposal of the notched disc specimen 8 mm in diameter and 0.5 mm in thickness with a "U" shaped notch 0.2mm deep in the axis plane of the disc.The paper summarizes the results obtained to date when determining the transition temperature of Small Punch tests, Tsp, determined according to CWA 15627 for material of pipes made of P92 and P22 steels in the as delivered state and a heat treated 14MoV6-3 steel. Although the results obtained confirmed the results of other workers in that the presence of a notch in a SP disc is insufficient to increase the transition temperature significantly and certainly not to the values obtained by Charpy testing, comparison of the different behaviours of the alloys tested reveals some evidence that the notch reduces the energy for initiation. This implies that the test on a notched disc is more a test of crack growth and would be a useful instrument if included in the forthcoming EU standard for SP testing.