Crack growth and closure behavior of short cracks are investigated for random loading using in-plane bending specimens of 2024-T351 aluminum alloy. In this study, we use an artificial prepared two-dimensional short crack through-thickness cracks and road ratio, R which is -0.5, testing frequency is 20Hz. We use a random loading block of history length at 500 cycle and 1000 cycles in each narrow and wide band random loading. We wish to know the effect of band-width and growth in short crack. The crack opening loading under random loading is different from that under constant amplitude loading, indicating that the crack closure behavior under random loading can not be estimated from constant amplitude loading test. The cracks opening load under random loading is nearly constant and corresponds to that at maximum range-pair cycle in a block. Also, it is hard to find that the effect of history length and band-width characteristics have clear effects on short crack opening load level and the crack opening stress intensity factor is inclined to increase from the lower to the higher value, and it shows a tendency to decrease when the value of maximum intensity factor reaches 13MPa√m. But predictions based upon measured opening data appear to be non-conservative in wide band random loading test and slightly non-conservative in narrow band random loading test.
