PSI - Issue 5

Tomasz Tomaszewski et al. / Procedia Structural Integrity 5 (2017) 840–847 Tomasz Tomaszewski et al. / StructuralIntegrity Procedia 00 (2017) 000 – 000

4

843

Table 1. Compilation of values of K coefficient within the material variability range, load type (Tomaszewski et al. (2014, 2016)). Material Type of load S o [mm 2 ] K S = S u o / S u s K HC = σ (-1) o / σ (-1) s

3.5 7.5

1.150 1.135

1.131 1.108

Axial load, R = 0.1 Axial load, R = 0.1

Aluminium alloy

AW-6063 T6

28

1

1

3.5

1.006

1.002

Copper

CW004AR240

28

1

1

3.1

- -

0.974

Rotary bending

19.6

1

S355J2+C

3.1

1.014

0.976

Axial load, R = -1 Axial load, R = -1 Axial load, R = -1

19.6

1

1

Steel

3.5

1.008

1.012

S235JR

28

1

1

3.5

1.043

1.075

1.4301

14

1

1

Table 3. Mechanical properties of the 1.4301 steel. Type of geometry S u , MPa S y , MPa A , %

Table 2. Chemical composition of the 1.4301 steel. C [%] Si [%] Mn [%] P [%] S [%] Cr [%]

Ni [%] 8.1

N [%]

Z , %

0.02

0.41

1.54

0.028 0.001

18.1

0.051

Standard spec. Minispecimen

623 666

269 322

69.5 73.8

77.1 72.1

3.2. High-cycle fatigue tests Carrying out tests of experimental nature for small specimens necessitates referring the results to the standard specimens and describing the reasons for the potential divergences of results. The specimens used in the tests are presented in Fig. 2, and the dimensions in Table 4. The specimens are of uniform shape and fixed value of theoretical stress concentration factor α k equal to 1.05. The test specimen size was changed by reducing only the geometrical dimensions relative to the standard specimen. The specimens were collected from a metal sheet of 4 mm thickness. Fixed parameters of the technological process were maintained.

Table 4. Specimen dimensions. Type of geometry t [mm] w 1 [mm]

w 2 [mm]

R [mm]

l [mm]

S o [mm 2 ]

Standard spec. Minispecimen

4

7

14

25 18

100

28

1.4

2.5

5

35

3.5

Fig. 2. Geometry of the flat smooth specimen for fatigue testing made of steel 1.4301

Fatigue tests were performed with a sinusoidal, symmetrical cycle ( R = -1). The purpose was to determine fatigue characteristics σ a -N for a stress-controlled test. The scope of tests included high-cycle fatigue. The criterion ending the fatigue test was macro-crack on the specimen. The proposed test conditions aimed at determining the impact of