Abstract
It is well known that when a structure attains such a state of residual stress that no further plastic flow occurs, the structure is said to have shaken down.
But on a real material, it is often observed that an effective state of residual stress is ruined by a small load cycled many times. To apply the shake down theorems on elastic-plastic design of structures, the stability of a state of residual stress must be examined.
For this purpose, fatigue tests have been carried out on a frame structure which consists of three members of 7075-T6 aluminium alloy bending specimens. The results obtained are as follows:
(1) The state of residual stress of the structure can be computed from a static moment-curvature relation of a specimen. But a small difference was observed between the computed and experimental results. And this difference is proved to result from a cyclic creep which is relatively small on this 7075-T6 aluminium alloy.
(2) The fatigue life of the weakest member of this structure is estimated from that of single specimens. The experimental results are always a little greater than the estimated values.
