Experience with low-cycle fatigue of pressure vessel steels

Attention was focused on reducing the danger of the occurrence of low-cycle fatigue of reactor vessel welded necks exposed to constant pressure at variable load. It is shown that on the basis of the results obtained so far neck behaviour in service may be predicted. In neck production or in the occurrence of welded joint defects critical points may arise subject to low-cycle fatigue. In the given configuration the load size resulting in fatigue depends on the operating conditions. In addition to strict observance of operating conditions, the danger of failure due to fatigue may also be reduced by a careful choice of material. (J.B.)