INVESTIGATION OF THE RATCHETING PHENOMENON FOR DOMINATING BENDING LOADS

For components subjected to strong mechanical and cyclically thermal l oads, proof of a limitation of permanent strain is of great significan ce due to the danger of deformation progressing from cycle to cycle (r atcheting). Within the framework of investigations concerning the load situation of the first wall of a fusion reactor, experimental and the oretical studies on ratcheting were carried out. Progressive deflectio ns were identified under suitable conditions on internally cooled beam -shaped components subjected to cyclic heating and a bending load. A s imple beam model can be used for systematic theoretical analysis in th is case. Its treatment leads to the development of so-called Bree diag rams with which the structural behaviour can be characterized as a fun ction of the applied primary and secondary stresses. The peculiarities arising under predominant bending loads will be discussed. (C) 1997 E lsevier Science S.A.