Issue 61

M. S. Baharin et alii, Frattura ed Integrità Strutturale, 61 (2022) 230-243; DOI: 10.3221/IGF-ESIS.61.15

a pre-stress state before loading, the fatigue life becomes more severe, which agrees to a study made by Elmushyaki [29] on a structure that exhibits greater damage when preloaded force is given.

SP-1

SP-2

SP-3

Lineare (SP-1)

Lineare (SP-2)

Lineare (SP-3)

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R² = 1,00 R² = 0,79 R² = 0,94

Average fatigue life (s)

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Load applied (N) with R = 1.25

Figure 8: Average fatigue life against given load for all three metal sandwich panels at stress ratio, R = 1.25

(a)

(b) Figure 9: Fatigue life distribution modelled using finite element to determine the critical region based on; (a) front view of sandwich panel geometrical body, (b) bonding area for SP-1 at stress ratio, R = 1.25 with a load of 37422N. At the greatest stress ratio with R = 5, Fig. 10 shows a comparison of average fatigue life values for all sandwich panels with three different core surface designs. Comparisons were made between SP-3 and SP-1 followed by SP-3 and SP-2. At a load of 32076 N, 0.166% was the difference and increased to 4.97% for the final load of 48114 N. As for the comparison between SP-3 and SP-2, it was 0.16% at the starting load of 32076 N and the differences grew to a value of 3.29% with the final load of 48114 N. It was found that SP-1 had the highest fatigue life value with an average value of 1821.7 when comparison was made between all three core design sandwich panels at the highest stress ratio of R = 5. SP-2 had the second highest value of 1783.3 seconds, and SP-3 obtained the lowest fatigue life value of 1733.3 seconds. Based on Fig. 10, the simulation results

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