Bellows is a metal pipe with stretch and flexibility. Bellows is used in various environments as expansion joints of piping equipment to absorb vibration and thermal expansion. 60% of bellows failure is caused by fatigue and low cycle fatigue failure occurs on bellows because the bellows are used in plastic region. This study intends to elucidate the mechanical properties of the bellows with elasto-plastic analysis. Then manufacturing the bellows, the shape of bellows is formed by extruding from the inside of a pipe. Therefore thickness of the bellows is not uniform and the thickness of the crown becomes thinner than the root. Analysis models considering thickness distribution are constructed in order to elucidate the influence of the thickness distribution. As a result, maximum equivalent stress is higher in U-type than n-type. Then, number of cycle to failure of U-type is about 30-40% less than fi-type, so ft-type has mechanical superiority than U-type. Also life of the bellows is reduced by considering the thickness distribution. Therefore, it is necessary to consider the thickness distribution in order to evaluate the life of bellows in safe side.
