PSI - Issue 19

Hiroyuki Oguma et al. / Procedia Structural Integrity 19 (2019) 224–230 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Test results

3.1. Tensile test

Tensile test results are summarized in Table 1. Breaking load of the as-received and sandblasted specimens was 3590 N and 2649 N, respectively. The as-received specimens show higher static strength than the sandblasted specimens. Variation of the strength value is smaller in sandblasted specimens than in as-received specimens. From the point of view of mechanical design, smaller variation is one advantage of the surface treatment.

Table 1. Static strength.

Failure load [N]

Nominal shear stress [MPa]

Surface treatment

Ave. 3590 2649

SD 331 163

Ave. 11.5

SD 1.1 0.5

As-received Sandblasted

8.5

3.2. Fatigue test

The number of cycles to failure ( N f ) as a function of the load amplitude ( P a ) is shown in Fig. 5. Regardless of the stress ratios, fatigue life monotonically increases with decreasing load amplitude. Meanwhile, fatigue life depends more strongly on load amplitude when the stress ratio is larger, or with higher mean load. For the as-received specimens, as shown in Fig. 5. (a), the distribution range of the test data obtained under R = − 1, − 0.5 and 0.1 is small, and the effect of mean load was not observed. However, when R becomes more than 0.5, the data distribute in a shorter life regime with higher stress ratio. Regarding the sandblasted specimens (see Fig. 5 (b)), a similar trend is observed. Fatigue strengths of the as-received specimens are higher than those of the sandblasted specimens in short life regime; however, the difference becomes smaller in long life regime around 10 7 cycles.

a

b

Fig. 5. Fatigue test results under several stress ratios (a) as-received; (b) sandblasted.