Stress and strain state of tube hydroforming and it's influence on destabilization

Aiming at the mechanics of tube hydroforming, the plasticity method was adopted in analyzing the stress character and it's variation during the different stage of tube hydroforming. And the strain state and it's calculating formula was given and derived through incremental theory. At the same time, combining with the strain calculating formula, that the thickness strain was the key of tube hydroforming was pointed out. Base on the stress and strain character discussed above, the reason of different destabilization format was discussed carefully in the end.