Temperature effect on dynamic characteristics and power flow of thin structures

Abstract

Thin plates are being used in many engineering applications. However, thin plate-like structures face vibration problems and are exposed to high temperature in the different operational conditions. These conditions can cause degradation, and seriously affect the structural integrity, safety, and stability of the structure. Hence, it is extremely important to identify the dynamic characteristics and vibration power flow of the thin structure at different temperatures that indicates the transmission path, position of vibration sources, and sinks. This study examined the potential changes in the dynamic characteristics and vibration power flow of the thin structure at different temperatures. In the first step, experimental and numerical studies of dynamic characteristics and vibration power flow for thin plate were conducted. The thin plate was modelled in Patran software, and modal analysis was performed using MSC Nastran software. Then the experimental modal analysis was conducted to validate the results of the numerical analysis. In the second step, the effects of temperature changes on the dynamic characteristics and vibrational power flow were investigated. A climate chamber room was used to investigate the temperature effect on the dynamic characteristics and power flow. Finally, vehicle exhaust system, actual complex structure, was used for actual life application of vibration power flow at different temperatures. Based on the results, the visualization of vibration power flow and transmission paths were generated at its first four natural frequencies. The changes of vibration power flow of the plate and the exhaust system at different temperatures were generated. The data from both experiment and simulation show a good agreement. The high temperature shifts the natural frequencies to lower frequencies. At 90℃, the first and second modes shifted about 3 Hz, and the third and fourth modes shifted about 5 Hz, lower than those at the normal temperature. The finding indicates the higher the temperature, the lower the frequency shifted. At higher mode, the power flow pattern changed at a certain temperature. In addition, the temperature effect on the dynamic characteristics of the exhaust system is not significant at the lower modes. At the higher mode, the natural frequency is shifted to about 2 Hz when the temperature reaches 270℃. Due to the hanger isolators, the vibration power of the exhaust system reduced overall 19%. The maximum total powers were at 180℃ of the exhaust system (without hanger) and 150℃ of the exhaust system (with hanger). The results showed that the boundary conditions of the exhaust system could lower the temperature at which the maximum power flow occurs. In sum, the findings on the effect of temperature on dynamic characteristics and vibration power flow are useful to those concerned with minimizing vibration level in engineering components to consider for their design criteria or maintenance process.