PSI - Issue 75

Kalle Lipiäinen et al. / Procedia Structural Integrity 75 (2025) 19–28 Lipiainen et al./ Structural Integrity Procedia (2025)

23 5

ends at the backside of the component can be seen in Fig. 4. The same boundary condition (T1=T2=T3= 0) were used on all bolted connections. Load is applied to the centre bolt end-node at both load cases separately. The strain gauges (SGs) are installed to the direction of the max principal strains, as shown in Fig. 4. SG1 was positioned in location with non-linear behaviour. Thus, it was not used to validate FE-model. Furthermore, SG2 measured strain were around 15% higher in the test than FEA. The component ultimate load capacity was found when rupture occurred with 26kN compressive load after withstanding 40kN tensile load. Fatigue test load was scaled down for the test series. Differences in displacements between the FE-model and physical test suggests to differences in boundary conditions, which e.g. does not replicate correctly the possible bearing yield of the fastener holes in the FE-analysis.

Strain gauge locations

a

T1 = T2 = T3 = 0 Bolted connections

b

c

Load 20 kN up

SG 1

SG 2

SG 2 1560 µ ε

SG 2 -1590 µ ε

SG 1 1600 µ ε

SG 1 -1650 µ ε

Non linear behaviour observed in SG1 area

Load 20 kN down

0

e

40

d

-4000

-2000

0

a -1290 -1900

µstr MPa

-5

30

SG1 SG2

Non-linear -210

-10

E = 110 GPa

20

Load 20 kN load (Up) MPa

a 1160 1800 µstr

-15

SG1 SG2

Non-linear

Force [kN]

Load [kN]

10

20 kN load (down)

200 E = 110 GPa

-20

0

-25

0

2000

4000

Strain [microstrain, 10^-6]

Strain [microstrain, 10^-6]

Fig. 4. Patran/Nastran FE-model for comparison of the test results.

The FE-model with elastoplastic material model was estimated with Ramberg-Osgood equations: = +0.002( ) 1⁄ , = +0.002 , = + where E =110 GPa, = 0.02, =860 MPa, = 930 MPa, = 10 %. Fig. 5 presents FE-analysis results are from non-linear Nastran SOL400 analysis solution. the stress tensor plots for max principal stresses at 20 kN upwards force are shown. Highest stresses close to crack initiation sites (from 280 MPa to 395 MPa) are highlighted to Figures on front side.

Fig. 5. FEA result for the component with major principal stresses with 20 kN load both directions.