Abstract
The Charpy V-notch (CVN) impact test has been widely used by operators and pipe mills to measure steel pipe resistance to fracture propagation. The tests are generally conducted at multiple temperatures to capture the transition from low impact energy nonductile regime to the high impact energy ductile regime. Due to the limitation of wall thickness and curvature of the pipe cross section, the CVN test for thin-walled line pipe generally can only be conducted with reduced size CVN coupons. The reduced size CVN coupon both decreases the measured impact energy and lowers the apparent transition temperature. Prior work (1996) developed a procedure to interpret the CVN data from various size of coupons. The procedure is also able to estimate the entire transition curve even based on a single test data point. This procedure has been widely used since then and been adopted in Section 9F.2.2 of ASME FFS-1/API 579 (2016). In this procedure, the difference between SATT from a given size CVN and the SATT of full pipe wall thickness drop weight tearing test (DWTT) was described by an equation derived from data fitting. Since the SATT of DWTT is fixed, the relationship between SATT from two different sizes of CVN coupons can be correlated through this equation. However, the wall thickness of the pipe is left in this correlation, which implies an artificial impact of pipe dimensions to the changes of SATT among CVN coupons sizes. In this paper, the equation between SATT of CVN and DWTT is updated, which both removes the pipe wall thickness from the correlation among different CVN sizes and achieves better data fitting. This update maintains all the capability of the prior procedure while improving the accuracy and clarity. Worked examples are provided at the end the paper to demonstrate the application of the updated procedure.
