FATIGUE CRACK PROPAGATION BEHAVIOR OF 2091 T8 AND 2024 T3 UNDER CONSTANT AND VARIABLE AMPLITUDE LOADING N. OHRLOFF, A. GYSLER et G. LÜTJERING J. Phys. Colloques, 48 C3 (1987) C3-801-C3-807 DOI: 10.1051/jphyscol:1987394