FATIGUE LIFE OF WELDED PLATE-T JOINTS UNDER VARIABLE-AMPLITUDE LOADING

Two new PC-based systems for fatigue testing machine control and data acquisition were installed at the Metals Technology Laboratories (MTL) to facilitate tests with variable-amplitude loading using long sequences. The testing machine frames were modified for tests of welded T joints at negative load ratios (R). Results of variable-amplitude (VA) tests of eight T joints (26 and 78 mm thick) with a common-load sequence (COLOS) are presented in terms of effective, and root mean square stress ranges, and Miner's sums, and compared with data from constant-amplitude (CA) tests. Fatigue crack growth, and shape development results monitored by the AC potential drop technique, and beach marking are reported and analysed.