PSI - Issue 38

Matthias Hecht et al. / Procedia Structural Integrity 38 (2022) 251–259

254 4

Matthias Hecht et al. / Structural Integrity Procedia 00 (2021) 000–000

a

b

c

d

specimen clamping

specimen clamping

= 54 mm

adhesive layer

a = 0.3 mm

load

load

= 60 mm

Fig. 1 (a) Test rig at Fraunhofer LBF; (b) drafting of the adhesively butt-bonded double hollow cylinder specimens; (c) test rig at LWF of Paderborn University; (d) typical failure of a specimen

Prior to the execution of the test series, a specimen with strain gauges was applied to verify that the loads are applied correctly and that the specimens can be inserted into the test rig almost load-free. The specimens are fixed in the test rig by different kind of clamps, Figure 1 (a) and (c). 2.3. Applied loads and resulting nominal stresses The specimens are tested under pure tensile and torsional loading and under combined loading without phase shift and with a phase shift of = 90°. The nominal normal stress = 4∙ ( 2 − 2 ) (6) under axial load is calculated from the inner diameter , the outer diameter and the axial load . The nominal shear stress = 16∙ ∙ ( 4 − 4 ) (7) under torsional loading can be calculated from with the applied moment . All multiaxial tests were carried with a constant ratio between normal and shear stress amplitudes by a factor two: , = 2 , . 2.4. Load sequence under variable amplitudes The load sequence used for the tests under variable amplitudes is a Gaussian spectrum with a sequence length =50,000 cycles used for the axial and torsional load channel, Figure 2.