PSI - Issue 53

Andrea Zanichelli et al. / Procedia Structural Integrity 53 (2024) 3–11 Author name / Structural Integrity Procedia 00 (2019) 000–000

8 6

4.1. Plain specimens As far as the plain specimens are concerned, the procedure described in sub-Section 2.1 is applied. The comparison between the calculated and the experimental number of loading cycles to failure, N cal and N exp , respectively, is shown in Figure 2(a) for each test examined, where the dashed lines represent the scatter band with factor 2 and the dot-dashed lines represent the scatter band with factor 3. The data in red are related to the pure axial and pure torsional fatigue tests, whereas the biaxial (that is, combined axial-torsional) fatigue tests are in black. The results are also grouped by loading ratio R and phase angle β (in the case of biaxial loading). It can be highlighted that all the results fall within the scatter band 2 in case of axial loading (with both loading ratio R =-1 and R =0) and torsional loading (with loading ratio R =-1). Moreover, the estimations related to the case of biaxial loading are mainly within the scatter band 3, except for the case characterised by R =-1 and 90 β = ° , which is at least on the conservative side.

10 7

CONSERVATIVE

(a)

CONSERVATIVE

(b)

10 6

10 5

N exp [cycles] 10 4

R=-1, β =0° R=0, β =0° R=-1, β =90° R=0, β =90° AXIAL, R=-1

R=-1, β =0° R=-1, β =90° R=0, β =0° R=0, β =90°

TORS. R=-1 AXIAL R=0 AXIAL R=-1

10 3 10 7

3

4

5

6

7

3

4

5

6

7

7

CONSERVATIVE

(d)

CONSERVATIVE

(c)

6

10 6

5

N exp [cycles] 10 5

R=-1, β =0° R=-1, β =90° R=0, β =0° R=0, β =90°

R=-1, β =0° R=-1, β =90° R=0, β =0° R=0, β =90°

4

3

10 4

10 3

10 4

10 5

10 6

10 7

10 4

10 5

10 6

10 7

N cal [cycles]

N cal [cycles]

Fig. 2. Experimental, N exp , vs estimated, N cal , fatigue life for: (a) plain specimens; (b) specimens with a sharp notch (root radius r=0.07 mm); (c) specimens with a circular notch (root radius r=2 mm); and (d) specimens with a blunt notch (root radius r=5 mm).