PSI - Issue 5

Raffaella Sesana et al. / Procedia Structural Integrity 5 (2017) 531–538 Delprete, Sesana/ Structural Integrity Procedia 00 (2017) 000–000

537

Fig. 4. Layer 10 (left) and 7 (right) data fitting: experimental calibration data (blue), W ALSE fitting curve (black).

To perform the ALSE model validation, the following procedure was followed. According to the parameters of Table 2 and Eq. (3), the empirical parameter W ALSE can be estimated for any layer and any plastic strain value. Reversing Eq. (5), taking into account of Eq. (3), and knowing the value of the equivalent stress for each specimen sample, an estimation of the number of cycle to failure is obtained:

W ALSE σ max

N f =

(6)

Specimens adopted for validation and the corresponding estimated parameters are reported in Table 3 along with results; the estimated numbers of cycles are reported with the percent difference with the experimental results. In Figures 5 and 6 the same results are plotted.

Table 3. ALSE and MC models validation results. Specimens Experimental N f ALSE N f

BMC N f

ALSE Difference [%]

BMC Difference [%]

1_1 2_1 3_5 7_6 8_5 9_6

3088 20516

3248 11004 1049 3607 1032 4568

5.2

1726 9949 1080 1995

− 44.1 − 51.5 58.6 − 50.1 − 29.2 − 82.9

− 46.4

681 4000 1102 7853

54

− 9.8 − 6.4

780

1345

− 41.8

Fig. 5. Comparison of life estimations for ALSE and BMC models.

Fig. 6: Experimental TMF life versus predicted fatigue life.

6. Discussion and conclusions

In the present analysis two LCF models were calibrated and implemented with specimens obtained from different layer of a commercial Aluminium alloy cylinder head. The comparison between the estimated life cycle shows that, in isothermal conditions, the estimation obtained by means of a new energetic model are closer to the actual specimens duration than BMC estimations. The BMC model, according to Standard, follows the experimental