PSI - Issue 14

G Vamsi Krishna et al. / Procedia Structural Integrity 14 (2019) 820–829 G. Vamsi Krishna / Structural Integrity Procedia 00 (2018) 000–000

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observed at Subsystem 1 lug location. The observed maximum stress is less than material yield strength of 350 MPa and is highly localized. Since the load is static and material is ductile, these localized stress is not considered for calculation of factor of safety. The membrane and bending stresses at all other locations are much less than strength limits of material. Hence for both the face sheets and honeycomb core, sufficient factor of safety above 1.5 is ensured against the applied deceleration loads.

Fig. 8. (a): Von-Mises stress plot of honeycomb core; (b) Von-Mises stress plot of aluminium alloy face sheet

4. Experimental study 4.1. Experimental set-up for random vibration test:

Test setup consists of a 16-ton Shaker, 2-meter diameter head expander of 825 kg (for longitudinal axis test), a two-meter diameter slip table of 955kg (for Pitch & Yaw axes test) and a test fixture of 80 kg mass. Mouting bracket with two sensor packages mounted is integrated to the Fore End bulk head of the section as shown in Fig 10. Section is integrated with the fixture. Test set up of section in longitudinal and lateral axes are shown in Fig. 9 (a) and 9 (b) respectively.  Two-point control in X & Y axes (on slip table)  Four-point control in Z-Axis (on the head expander)

Fig. 9. (a): Test setup in longitudinal axis; (b) Test setup in lateral axis One critical location has been identified in test article. Tri-axial accelerometers are mounted at this location. The measurement axes of the accelerometers are aligned with the three test axes. Measurement was done in three axes simultaneously. Channel description is shown in Fig. 10. The response location R1 is located between the two subsystems (sensor packages) on the mounting plate.