Fatigue tests were conducted on box beams and tension panels in order to study some of the factors affecting fatigue-crack propagation. The box beams had essentially the same configuration except for the mode of connecting stringers to the tension cover. The beams with bonded stringers had the lowest rate of crack growth, and beams with riveted and integral stiffeners had successively higher rates of crack growth. Crack growth was slower in beams with close rivet spacing than in beams with greater rivet spacing. The tension panels were all of the same general configuration except that the proportions of cross-sectional areas of skin, stringers, and flanges were varied. Panels with heavy stringers and thin skin had lower rates of crack growth than did panels with heavy skin and light stringers.nStatic tests were performed on box beams, on tension panels, and on two types of wings, all of which contained fatigue cracks. The com?parison of results with predictions made by a simple theory indicates that test results were affected by a redistribution of loads among the various remaining elements and by whether cracks terminated at rivet holes。
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