PSI - Issue 14

K. Vijayan et al. / Procedia Structural Integrity 14 (2019) 642–648 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

647

6

built-up system. The first two frequencies of the assembly were close the bending natural frequency of the pillar fixed at one end like a cantilever. The third frequency was close to the torsion mode.

Fig. 8. Model in ANSYS APDL with dimensions.

Table 2. Natural frequency of the built-up system with spring constant

Mode number

Frequency(Hz)

Type

1 2 3

50.3

Bending Bending Torsion

75

80.25

A BK shaker of 100 N capacity was used to excite the shaker. An impulse input was provided to emulate an impulse hammer. The purpose of using the shaker rather than an impulse hammer was because the available impulse hammer was not able to excite the modes of the welded aluminum plates. The stinger of the shaker and the accelerometer were placed at the tip of the welded section. The welded section was clamped to the built-up system. The transfer function plot generated from the impulse is shown in Fig.9. It can be observed from the figure even though the welded plate forms a small portion of the built-up system it has significantly influenced the vibration amplitude. The Q factor values obtained using circle fitting for the second mode was found to be 6,1.5 and 0.9 for good, intermediate and bad tensile strength welds respectively.

Fig. 9. Damping behavior variation for different samples.