Based on the grommet stiffness char

Based on the grommet stiffness characterization test, the radial and axial stiffnesses are of rate dependant behavior and increase when the rate of deformation increases. The grommet is stiffer in dynamic condition than in static condi- tion. When the frequency is higher, the dynamic stiffness will be correspondingly higher. It is found that the dynamic stiffness changes more significantly in crosshead peak-to- peak (p-p) displacement than its frequency. When the p-p displacement is higher, the dynamic stiffness is inversely lower. This is because the higher force induced has basically become dominant and overcomes the material resistant. Hence, the dynamic stiffness will be relatively low. The obtained 3 translational stiffnesses (ka, kr1, kr2) are applied to the FE model as compressor-piping mounting stiffnesses. Hence, this locked down the translational stiffness of the compressor-piping elastic end support, leaving translational stiffness of the chassis-piping elastic end support to be in- vestigated by fine tuning.

Based on the comparison between the numerical and experimental data, a reasonably good degree of correlation has been achieved especially on the natural frequency of the piping structures. The maximum error of approximately 4.5% and 19% occur on suction and discharge tubes respectively. Discrepancies occur between simulation and measurement results especially on natural modes. One of the reasons contributing to this problem is the measurement accuracy. Some natural frequencies appear within a very close frequency range where measurement may not able to capture the frequency response peak in a distinct form. Besides, the hit on all impact points may not be consistent and may not generate single impulse and sufficient energy to give appropriate natural mode of the structure.