Journal of the Acoustical Society of America, Oct 1, 2003
A common occurrence of cavitation damage is the waterside pitting of a wet sleeve liner in a dies... more A common occurrence of cavitation damage is the waterside pitting of a wet sleeve liner in a diesel engine. The automotive industry utilizes an ultrasonic test of 20 kHz according to ASTM standards to quantify the effectiveness of engine coolant additives to prevent damage. However, recent tests indicate a mismatch between the ultrasonic test results and actual engine test runs. The focus of this study is to generate numerical models of bubble dynamics using already published literature. In most of the published papers higher-range frequencies (ultrasonic >15 kHz) are used. It is useful to explore the results of lower excitation frequencies as the vibrating frequencies of a diesel engine liner are between 500–9000 Hz. A Rayleigh–Plesset equation, nonlinear in nature, is used to plot the relation between bubble radius and time. Plots of the numerical solution from MATLAB are compared with plots published in the literature. Results from when the frequency of excitation is changed to the liner wall frequency and the fluid properties are changed to approximate engine conditions will be presented. Future work will examine the energy released by the bubble collapse and its correlation with erosion measured as mass change in a standard test button.
A ruggedized field measurement system for determining wood pile lengths of existing bridges is pr... more A ruggedized field measurement system for determining wood pile lengths of existing bridges is presented. The development of the measuring system was the goal of a two year funded research project sponsored by the Tennessee Department of Transportation. The measurement technique is based on longitudinal vibration theory. Determination of the wave speed in the wood and the resonant frequencies of a pile will yield the length estimation. The equipment package uses piezoelectric actuators, random excitation, and force and accelerometer transducer responses to generate the required data for length assessment. The data acquisition and processing occur in the field and are controlled by a LabWindows/CVI custom program. An electronic pulse and special signal conditioning are used for determining accurate delay time between accelerometer locations for the wave speed calculation. Random excitation is used to generate the power spectral densities and frequency response functions of the transducers attached to the pile. Typical field data will be discussed along with the results from preliminary field tests.
30th Aerospace Sciences Meeting and Exhibit, Jan 6, 1992
ABSTRACT Turbulence measurements in a five-inch diameter circular duct were performed before and ... more ABSTRACT Turbulence measurements in a five-inch diameter circular duct were performed before and after screen and perforated plate inserts. The effects on turbulence of two different screens, a perforated plate, a slotted plate, and a combination of the two screens were investigated. Hot-wire anemometry using X-wire probes was employed along with a digital data acquisition system to acquire the turbulence data. Spectral analysis was conducted employing the correlogram technique to obtain the energy spectra of the turbulence fluctuations. The Reynolds number range used for the tests was 37,500 to 150,000.
A method for field measurement of timber pile length in bridge foundations is possible by determi... more A method for field measurement of timber pile length in bridge foundations is possible by determining the natural frequency spacing between consecutive resonant peaks in the longitudinal frequency response function (FRF) as well as experimental determination of the longitudinal wave speed. The measurement procedure relies on vibration modes excited through the attachment of small actuators driven with random input and the recorded response of attached accelerometers. The identification of natural frequencies in timber piles is complicated by the inhomogeneous nature of wood and the location of measurement points at possible longitudinal nodes along the pile. Missing peaks and corrupted spectrums are common in the experimental data collected during the testing of timber piles. A form of cepstral analysis using the FRF shows promise towards overcoming some of the inherent difficulties in identifying the natural frequency spacing between resonant peaks in the spectrum. The details of t...
– This paper describes a research experience for undergraduates (REU) program that focuses on mul... more – This paper describes a research experience for undergraduates (REU) program that focuses on multidisciplinary high-tech opportunities in the metalcasting industry, resulting in a set of multidisciplinary research projects. Undergraduate students and mentors from electrical, mechanical, and chemical engineering and industrial technology are involved. We discuss the lessons learned and the challenges that we have faced in the recruitment and operation of the program during the first two years. We also discuss in detail the benefits and drawbacks of the unique model, Student as the Principal Investigator (SPI), utilized in our program. In this model, undergraduate students define their own research question within a given framework instead of following a plan defined for him/her by the mentor. Mentors were involved to a limited extent in defining and updating the research question while the students maintained ownership of the research. Although the model is generally positive, some ...
Fusion level of expanded polystyrene (EPS) foam is a prominent factor in the quality of lost foam... more Fusion level of expanded polystyrene (EPS) foam is a prominent factor in the quality of lost foam metal castings. Foam plates of different fusions based on percentage void volume are used in research regarding lost foam castings. Quick identification and quantification of higher fused samples from lower fused samples is required. A non-destructive evaluation (NDE) based on vibration testing can be used to differentiate the fusion levels of the EPS foam. To demonstrate the viability of the technique, the natural ...
An autocorrelation method on FRFs has been successfully used for detecting flaws in simple beam s... more An autocorrelation method on FRFs has been successfully used for detecting flaws in simple beam structures made of aluminum or carbon fiber composites. The method relies on using the βl eigenvalues of the transverse bending modes to calculate a signature plot that is representative of the flaw. It also uses the fact that difference between the βl eigenvalues for higher consecutive modes is a constant, π. The βl usage restricts this method exclusively to beams. Application of this method to more complicated structure ...
Journal of the Acoustical Society of America, Oct 1, 2003
A common occurrence of cavitation damage is the waterside pitting of a wet sleeve liner in a dies... more A common occurrence of cavitation damage is the waterside pitting of a wet sleeve liner in a diesel engine. The automotive industry utilizes an ultrasonic test of 20 kHz according to ASTM standards to quantify the effectiveness of engine coolant additives to prevent damage. However, recent tests indicate a mismatch between the ultrasonic test results and actual engine test runs. The focus of this study is to generate numerical models of bubble dynamics using already published literature. In most of the published papers higher-range frequencies (ultrasonic >15 kHz) are used. It is useful to explore the results of lower excitation frequencies as the vibrating frequencies of a diesel engine liner are between 500–9000 Hz. A Rayleigh–Plesset equation, nonlinear in nature, is used to plot the relation between bubble radius and time. Plots of the numerical solution from MATLAB are compared with plots published in the literature. Results from when the frequency of excitation is changed to the liner wall frequency and the fluid properties are changed to approximate engine conditions will be presented. Future work will examine the energy released by the bubble collapse and its correlation with erosion measured as mass change in a standard test button.
A ruggedized field measurement system for determining wood pile lengths of existing bridges is pr... more A ruggedized field measurement system for determining wood pile lengths of existing bridges is presented. The development of the measuring system was the goal of a two year funded research project sponsored by the Tennessee Department of Transportation. The measurement technique is based on longitudinal vibration theory. Determination of the wave speed in the wood and the resonant frequencies of a pile will yield the length estimation. The equipment package uses piezoelectric actuators, random excitation, and force and accelerometer transducer responses to generate the required data for length assessment. The data acquisition and processing occur in the field and are controlled by a LabWindows/CVI custom program. An electronic pulse and special signal conditioning are used for determining accurate delay time between accelerometer locations for the wave speed calculation. Random excitation is used to generate the power spectral densities and frequency response functions of the transducers attached to the pile. Typical field data will be discussed along with the results from preliminary field tests.
30th Aerospace Sciences Meeting and Exhibit, Jan 6, 1992
ABSTRACT Turbulence measurements in a five-inch diameter circular duct were performed before and ... more ABSTRACT Turbulence measurements in a five-inch diameter circular duct were performed before and after screen and perforated plate inserts. The effects on turbulence of two different screens, a perforated plate, a slotted plate, and a combination of the two screens were investigated. Hot-wire anemometry using X-wire probes was employed along with a digital data acquisition system to acquire the turbulence data. Spectral analysis was conducted employing the correlogram technique to obtain the energy spectra of the turbulence fluctuations. The Reynolds number range used for the tests was 37,500 to 150,000.
A method for field measurement of timber pile length in bridge foundations is possible by determi... more A method for field measurement of timber pile length in bridge foundations is possible by determining the natural frequency spacing between consecutive resonant peaks in the longitudinal frequency response function (FRF) as well as experimental determination of the longitudinal wave speed. The measurement procedure relies on vibration modes excited through the attachment of small actuators driven with random input and the recorded response of attached accelerometers. The identification of natural frequencies in timber piles is complicated by the inhomogeneous nature of wood and the location of measurement points at possible longitudinal nodes along the pile. Missing peaks and corrupted spectrums are common in the experimental data collected during the testing of timber piles. A form of cepstral analysis using the FRF shows promise towards overcoming some of the inherent difficulties in identifying the natural frequency spacing between resonant peaks in the spectrum. The details of t...
– This paper describes a research experience for undergraduates (REU) program that focuses on mul... more – This paper describes a research experience for undergraduates (REU) program that focuses on multidisciplinary high-tech opportunities in the metalcasting industry, resulting in a set of multidisciplinary research projects. Undergraduate students and mentors from electrical, mechanical, and chemical engineering and industrial technology are involved. We discuss the lessons learned and the challenges that we have faced in the recruitment and operation of the program during the first two years. We also discuss in detail the benefits and drawbacks of the unique model, Student as the Principal Investigator (SPI), utilized in our program. In this model, undergraduate students define their own research question within a given framework instead of following a plan defined for him/her by the mentor. Mentors were involved to a limited extent in defining and updating the research question while the students maintained ownership of the research. Although the model is generally positive, some ...
Fusion level of expanded polystyrene (EPS) foam is a prominent factor in the quality of lost foam... more Fusion level of expanded polystyrene (EPS) foam is a prominent factor in the quality of lost foam metal castings. Foam plates of different fusions based on percentage void volume are used in research regarding lost foam castings. Quick identification and quantification of higher fused samples from lower fused samples is required. A non-destructive evaluation (NDE) based on vibration testing can be used to differentiate the fusion levels of the EPS foam. To demonstrate the viability of the technique, the natural ...
An autocorrelation method on FRFs has been successfully used for detecting flaws in simple beam s... more An autocorrelation method on FRFs has been successfully used for detecting flaws in simple beam structures made of aluminum or carbon fiber composites. The method relies on using the βl eigenvalues of the transverse bending modes to calculate a signature plot that is representative of the flaw. It also uses the fact that difference between the βl eigenvalues for higher consecutive modes is a constant, π. The βl usage restricts this method exclusively to beams. Application of this method to more complicated structure ...
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