Constant and variable amplitude loading of 6261 aluminium alloy I-beams with welded cover plates-Influence of weld quality and stress relief

摘要

A study of the constant amplitude and variable amplitude (VA) fatigue performance of 6261-T6 aluminium I-beams with a welded rectangular cover plate is reported. The test programme involved >100 specimens and considered the effects of weld 'quality' (in terms of weld toe angle, leg length and heat input), and thermal and vibratory stress relief on stress-life curves under simple repeated two- level block loading. The number of high-to-low amplitude cycles in a single VA block was varied from 1/20, through 10/20 to 1/1000 and 1/50,000. Load amplitude increase percentages of 25/100, 75/100 and 150/100 were considered. Observed fatigue lives were compared with the predictions of Miners rule and explanations are proposed for situations where Miners rule is non-conservative.