Browsing by Author "Sun, Zhen"

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    Assessment of O-ring Seal Performance by Measurement of Acoustic Emission Signals
    (2011-04-13) Sun, Zhen
    O-rings are commonly installed in fluid systems for sealing purpose. There is ongoing research towards improving O-rings’ sealing performances by using adaptive elastomeric materials at the Department of Mechanical Engineering at University of Minnesota. As part of seal development the performance of the seal has to be assessed. In this research a test stand for measuring leakage was constructed and leakage measurement was demonstrated as the seal leakage was measured by Monitoring Acoustic Emission (AE) signals. The test stand was constructed in which a specified load or a specified displacement can be applied to an O-ring held between flat plates, high pressure air introduced to the inside of the seal and AE due to leakage measured. The scope of this research was to try to quantify leakage rate of in use O-ring as a function of AE signals. The AE signals were measured as a function of volumetric air flow rate Q, working fluid pressure P, O-ring counterface force F and seal AE sensor distance d. Results showed that the Root Mean Square (RMS) values of AE signals increased with Q, P and F but decrease with d. Results also showed that the frequency spectrums of AE signals were wideband with multiple peaks at different frequencies. The physical interpretation of frequency spectrum was discussed but was not fully explained.
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    Study of Behaviors of Single Large Intruders in Bulk Flow
    (2009-04-08) Sun, Zhen
    Understanding the fundamentals of granular flow is crucial to industrial applications. Good examples are found in processing pharmaceutical pills and ceramic powders. Mixing granular materials is a major concern for engineers who process granular materials. Developing sensor particles to track the flow of granular materials is a good way to understand the characteristics of granular flow. In order to facilitate the development of sensor particles, it is crucial to understand how the sensor particles behave in bulk granular flow. This research was to study how a single intruder's (sensor) movement might be different than that of the bulk particles. In other words, this research is to understand the segregation process, so that details of this disparate movement could be used to predict the bulk behavior. Most of the segregation occurs in the vertical direction so that most parts of this research is focused on exploring the vertical segregation between intruders and matrix particles.
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    Ultra Reliable Detection of Imminent Collision for Enhanced Occupant Safety
    (Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2012-05) Taghvaeeyan, Saber; Sun, Zhen; Mott, Michael; Rajamani, Rajesh
    This project focuses on the use of anisotropic magnetoresisitve (AMR) sensors for detection of an imminent unavoidable collision. An analytical formulation is developed for the variation of the magnetic field around a car as a function of position. Based on magnetic field measurements using AMR sensors, the position and velocity of any other car can be estimated and an imminent collision detected just prior to collision. The developed AMR sensor system has very high refresh rates, works at very small distances down to zero meters and is highly inexpensive. A variety of experimental results are presented to demonstrate the performance of the system for both one-dimensional and two-dimensional relative motion between cars. The second part of the project conducts simulations to show the benefits of detecting an imminent collision using the developed AMR sensors. An occupant model is developed to analyze occupant motion inside a car during a frontal collision. Analytical formulations and simulations are used to show how occupant safety can be enhanced when knowledge of an imminent collision is available.