Issue 33

M. Cova et alii, Frattura ed Integrità Strutturale, 33 (2015) 390-396; DOI: 10.3221/IGF-ESIS.33.43 394                             , , ,2 4 , , 1 2 1 2 1 2 1 2 1 2 1 1 max , 2 2 1 1 2 2 1 1 1 1 max , 2 2 2 2 n a eq n a n m T T V V V V T T T S V V T T V V S V V S b n n n n b n n n n n n b b b b n b n n b n                                                                      (14) And the maximum value, by changing the direction n, is:               , ,2 4 , , 1 2 1 2 max 1 1 1 1 max , 2 2 2 2 a eq n n a eq V V S V V S b b b b eigvl b eigvl b                                       (15) However, the relative amplitude between the extremes at t 2 and t 4 is only one of the possible critical amplitudes; the other possibilities are the differences between t 1 and t 2 and, finally, between t 1 and t 4 . These two combination are similar to that investigated in the single pulsating loading case. Then the relative equivalent amplitudes are:         , , ,1 2 1 1 1 1 max , 2 2 n a eq V S V S b b eigvl b eigvl b                              (16)                             S V S V eqan b b eigvl b b eigvl      2 2 41, , , 2 1 , 2 1 max (17) The researched equivalent amplitude is, finally, the maximum of each computed amplitude; hence the maximum eigenvalue of the suggested six tensors:                                                                                        ; 2 1 ; 2 1 ; 2 1 ; 2 1 ; 2 1 2 1 ; 2 1 2 1 max 2 2 1 1 2 1 2 1 , , S V S V S V S V S V V S V V eqan b b eigvl b b eigvl b b eigvl b b eigvl b b b eigvl b b b eigvl                (18) Figure 3 : Stress distribution at minimum et maximum of fatigue loading.