PSI - Issue 57

Francis Blanc et al. / Procedia Structural Integrity 57 (2024) 343–354 Francis BLANC / Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 8 Figure 7 Figure 9 and Figure 10 shows different curves obtained for 4 Life factor with several D/d ratio. These curves show the 3 or 4 points measured and the arithmetic average of these points for the same number of cycles. For LF75 curve (Figure 7), it can be seen that the 50% duration stage is at 73% residual tensile force for ratio D/d = 12.5 instead of 83% for ratio D/d = 25. There is therefore a 10% difference between the two stage, in favor of ratio D/d = 12.5.

Figure 7: Fatigue curve for 75

For LF100 curve (Figure 7), a complete Lf100 curve has already been plotted with a D/d ratio = 25 (pulley size 300 mm) and an Sf = 4. Two additional Lf100 fatigue curves have been partially plotted with a stage point in duration, in order to compare the appearance of different Lf curves with each other. The two partial curves were plotted with ratios D/d = 33 (  400 mm pulley) and D/d = 12.5 (  150 mm pulley). The comparison below shows a certain similarity for D/d = 33 and D/d = 25. The fatigue life is shorter on the D/d = 33 curve, as the force is greater (Sf = 3). On the other hand, for the D/d = 12.5 curve, fatigue life is much lower at Sf = 8. Comparing the graphs as a percentage of the number of cycles, we note the following differences for stages at 50% of service life: - ratio D/d = 33 at residual stress at 80% of static failure compared with ratio D/d = 25, i.e. 9% higher, - ratio D/d = 12.5 with residual stress at 60% of static failure, compared with ratio D/d = 25, i.e. 11% lower. For LF150 curve (Figure 9), a complete Lf150 curve has already been drawn with a D/d ratio = 25 (pulley size  300 mm) and an Sf = 6. An additional Lf150 fatigue curve has been partially plotted with a stage point in duration, in order to compare the appearance of different Lf curves with each other. The partial curve was plotted with D/d ratios = 33 (pulley size  400 mm). The comparison shows a rather different service life for the two curves, as the D/d = 33 curve is obtained with a higher effort (Sf = 4.5).