PSI - Issue 19

Jan Presse et al. / Procedia Structural Integrity 19 (2019) 423–432 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

427

5

400

HYB(D5) k= 4.75 HYB(D5) HYB(D3) k= 5.33 HYB(D3) ADH k= 7.11 ADH SPR(D5) k= 3.17 SPR(D5)

R=0.1 f=10Hz

Load amplitude F a [N]

40

1,0E+04

1,0E+05

1,0E+06

1,0E+07

Cycles to failure N [-]

Fig 3. Fatigue test results for hybrid joined CP connections.

Since the fatigue performance of the hybrid joined lap shear specimens is driven by the ability of the adhesive to bear shear loads an estimation of fatigue life for adhesively bonded connections should lead to an accurate estimation for hybrid joined connection as well. The fact that the SPR rather bears higher load ranges for the CP specimens while the adhesive shows better fatigue performance for lower load ranges, an estimation of fatigue life of riveted connections is necessary for this load case. Especially because hybrid joined components usually endure a mix of the mentioned load cases the estimation for riveted connections is essential. The results and insights of the experiments under quasi-static and cyclic load build a database for numerical approaches for fatigue life estimation. The investigations show the parameters with the highest impact and their contributions to the fatigue strength of each joining technology. In further studies within this project, an approach for fatigue life estimation of thin sheet connections joined with self-piercing rivets has been developed. It is based on the structural stress approach, developed by Rupp et al. [2] for resistance spot welds (RSW). Rupp used analytical solutions from shell and plate theory to calculate local radial stresses from internal cross-sectional forces and moments derived from an FE-simulation on the spot weld. The structural stress is calculated by combination and superposition of the axial, shear and bending radial stress contributions around the nugget (Eq. 1-3). ( , ) = , (1) 4. Approach to estimate fatigue life of thin sheet connections joined by Self-Piercing Rivets