• Composites Research
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• v.31 no.5
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• pp.238-245
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• 2018

The hydrodynamic ram (HRAM) phenomenon is one of the main types of ballistic battle damages of a military aircraft and has great importance to airframe survivability design. The HRAM effect occurs due to the interaction between the fluid and structure, and damage can be investigated by measuring the pressure of the fluid and the dynamic strains on the structure. In this paper, HRAM test of a composite T-Joint was performed using a ram simulator which can generate HRAM pressure. In addition, calibration tests of PVDF sensor were performed to determine the circuit capacitance and time constant of the measurement system. The failure behavior of the composite T-Joint due to HRAM pressure was examined using the strain gauges and a PVDF sensor which were attached to the surface of the composite T-Joint.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.910-923
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• 1992

Experimental verification of numerical results is conducted by measuring the dynamic strains of mid-points of the coupler and the lever for the 4-bar linkage mechanism with rigid bearing and flexible bearing, respectively. For the axial strain of lever mid-point, the numerical results including geometric stiffness almost agree with the experimental ones, however, the numerical results excluding geometric stiffness almost agree with the experimental ones for the axial strain of coupler mid-point. It is supposed that these phenomena should be caused by the fact that the motion of the coupler is more complicated than of the lever. The signals of dynamic strains of coupler and lever mid-points, measured by strain gages, are transformed into frequency domain by fast fourier transformer. From this experiment, the lst resonance frequencies of the coupler and the lever are obtained. It is made clear that the former almost agrees with the fundamental and the latter the 2nd mode natural frequency of the mechanism system calculated by numerical analysis.