Volume 29, Issue 3 (May 2001)
Direct Measurement of Displacement in Instrumented Charpy Impact Testing for Structural Integrity Assessment
The present research aims to develop a method for the direct measurement of load-line displacement during instrumented Charpy impact tests. The method involves direct measurement of the load-line displacement using a laser interferometer in addition to the load-line displacement derived from the load signal by double integration according to standard procedures. The ISO striker edge is instrumented with a piezoelectric sensor and the system is calibrated in situ in the impact tester as recommended by ISO 14556:2000 Steel Charpy V-notch Pendulum Impact Test—Instrumented Test Method, using a 0.5% accuracy reference load cell and a hydraulic jack system.
Introductory tests were conducted using fatigue precracked and V-notched specimens in the temperature range + 23 to −80°C on a conventional ship grade steel NVE36 for application in floating production, storage, and off-loading (FPSO) vessels. The results were promising and good correlation was obtained with results from conventional instrumented impact testing where the load-line displacement was calculated by double integration of the force versus time plot.