Darren Lee Hallman

Dynamic Characteristics of Shape Memory Alloy Metal Mesh Dampers

*† ‡ The study presented in this paper involved characterizing the amplitude and frequency dependent stiffness and damping coefficients for oil-free metal mesh dampers weaved from several different types of materials. The material test matrix consisted of stainless steel 304, Inconel 600, copper, and nickel-titanium (NiTi) shape memory alloy. The research specifically focuses on NiTi alloy damper and how the stiffness and damping performance compares with the other metal mesh damper materials. Steady state forced vibration and transient vibration tests were used to characterize the stiffness and damping as functions of frequency and vibration amplitude. The results show that vibration amplitude has the opposite influence on the NiTi material damping when compared to the other materials, whereas the influence of vibration amplitude on NiTi stiffness was the same as the other materials. While the conventional metal samples give decreasing damping as vibration amplitude increases, the NiTi samples generated increasing damping as vibration levels increased. In addition to comparisons of stiffness and damping between different materials with the same mesh density, a lower mesh density for NiTi was tested and compared to the higher mesh density damper.

An Off-Resonance Synchronous Vibration Based Method for Rotor System Damage Detections

This paper presents a methodology of detecting rotor imbalances, such as mass imbalance and crack-induced imbalance, using shaft synchronous vibrations. A vibration detection algorithm is derived based on the first order nonresonant synchronous vibration response. A detection system is integrated by using state-of-the-art commercial analysis equipment. A laboratory rotor test rig with controlled mass imbalances was used to verify the integrated system. The system is then deployed to an engine sub-assembly test setup. Four specimens were used in the subassembly test and the test results are reported in the final section.Copyright

A Resonant Synchronous Vibration Based Approach for Rotor Imbalance Detection

This paper presents a methodology of detecting rotor imbalances, such as mass imbalance and crack-induced imbalance, using shaft synchronous vibrations. An iterative scheme is developed to identify parameters from measured synchronous vibration data. A detection system is integrated by using state-of-the-art commercial analysis equipment. A laboratory rotor test rig is used to verify the system integration and algorithm validation. A real engine test has been carried out and the results are reported.