JRC2008-63044 CORRELATION OF ULTRASONIC INSPECTION OF BEARING COMPONENTS WITH BEARING FATIGUE LIFE

ABSTRACT One of the most important issues for bearing grade steels is the cleanliness of the steel. Impurities present in a cast steel can manifest as hard/brittle inclusions, which are detrimental to a bearing in service. An advanced ultrasonic measurement technique is developed to determine the inclusion size and density in bearing components. Using ultrasonic C-Scan, a map of the inclusions can be developed that pinpoints the worst areas in an entire cone or cup section nondestructively. A threshold is developed for determining good or bad locations so that specific gate settings can parse those discontinuities considered to be detrimental to rolling contact performance. In addition, multiple transducer sizes and frequencies are investigated to determine an optimized scanning configuration. This protocol can then be adapted to perform quality control specific scans capable of investigating numerous parts and determining a failure rate using the rejection criteria. NOMENCLATURE A Area of a pixel of a ultrasonic C-Scan image. AMP Amplitude image of the ultrasonic C-Scan. c w Velocity of sound in water. c L Longitudinal velocity of sound in the test material. F Focal length of the ultrasonic transducer in water. B Minimum sample thickness for fracture test

Cross-imaging system comparison of backscatter coefficient estimates from a tissue-mimicking material

A key step toward implementing quantitative ultrasound techniques in a clinical setting is demonstrating that parameters such as the ultrasonic backscatter coefficient (BSC) can be accurately estimated independent of the clinical imaging system used. In previous studies, agreement in BSC estimates for well characterized phantoms was demonstrated across different laboratory systems. The goal of this study was to compare the BSC estimates of a tissue mimicking sample measured using four clinical scanners, each providing RF echo data in the 1-15 MHz frequency range. The sample was previously described and characterized with single-element transducer systems. Using a reference phantom for analysis, excellent quantitative agreement was observed across the four array-based imaging systems for BSC estimates. Additionally, the estimates from data acquired with the clinical systems agreed with theoretical predictions and with estimates from laboratory measurements using single-element transducers

Diffuse ultrasonic scattering in heterogeneous media

Diffuse ultrasonic backscatter measurements have been especially useful for extracting microstructural information and for detecting flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Quantitative ultrasonic scattering models include components of transducer beam patterns as well as microstructural scattering information. In this dissertation, the Wigner distribution is used in conjunction with the stochastic wave equation to model this scattering problem. The Wigner distribution represents a distribution in space and time of spectral energy density as a function of wave vector and frequency. The scattered response is derived within the context of the Wigner distribution of the beam pattern of a Gaussian transducer. The source and receiver distributions are included in the analysis in a rigorous fashion. The resulting scattered response is then simplified in the single-scattering limit—the singly-scattered response (SSR)—typical of many diffuse backscatter experiments. Diffuse ultrasonic scattering experiments are usually done using a modified pulse-echo technique and utilize the variance of the signals in space as the primary measure to assess microstructure. Thus the SSR model is modified to account for normal and oblique incidence ultrasonic experiments where the wave propagates through planar or curved liquid-solid interfaces. The theoretical model is then compared with experimental results from polycrystalline materials with known microstructure. The research in this dissertation provides a fundamental approach for the multiple scattering within the material which can be exploited in the future for design of new experiments and extraction of other microstructure properties. These results are anticipated to be relevant to ultrasonic nondestructive evaluation of polycrystalline and other heterogeneous solids

Diffuse ultrasonic scattering in heterogeneous media

Diffuse ultrasonic backscatter measurements have been especially useful for extracting microstructural information and for detecting flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Quantitative ultrasonic scattering models include components of transducer beam patterns as well as microstructural scattering information. In this dissertation, the Wigner distribution is used in conjunction with the stochastic wave equation to model this scattering problem. The Wigner distribution represents a distribution in space and time of spectral energy density as a function of wave vector and frequency. The scattered response is derived within the context of the Wigner distribution of the beam pattern of a Gaussian transducer. The source and receiver distributions are included in the analysis in a rigorous fashion. The resulting scattered response is then simplified in the single-scattering limit—the singly-scattered response (SSR)—typical of many diffuse backscatter experiments. Diffuse ultrasonic scattering experiments are usually done using a modified pulse-echo technique and utilize the variance of the signals in space as the primary measure to assess microstructure. Thus the SSR model is modified to account for normal and oblique incidence ultrasonic experiments where the wave propagates through planar or curved liquid-solid interfaces. The theoretical model is then compared with experimental results from polycrystalline materials with known microstructure. The research in this dissertation provides a fundamental approach for the multiple scattering within the material which can be exploited in the future for design of new experiments and extraction of other microstructure properties. These results are anticipated to be relevant to ultrasonic nondestructive evaluation of polycrystalline and other heterogeneous solids

Use of quantitative ultrasound to detect temperature variations in biological phantoms due to heating

Abstract-High intensity focused ultrasound (HIFU) is a noninvasive technique that has great potential for improving thermal therapies. To target specified regions accurately for treatment, a robust imaging technique is required to monitor HIFU application. Therefore, the development of an ultrasonic imaging technique for monitoring HIFU treatment is highly medically significant. Quantitative ultrasound (QUS) is a novel imaging technique that may improve monitoring of HIFU treatment by quantifying tissue changes. Ultrasonic backscatter experiments were performed on two types of phantoms to understand the variations in QUS parameters with increases in temperature from 36 to 50 • C. The phantoms were biological phantoms made of agar and containing either mouse mammary carcinoma cells (4T1) or chinese hamster ovary cells (CHO) as scatterers. All scatterers were uniformly distributed spatially at random throughout the phantoms. Sound speed and attenuation were estimated in the phantoms versus temperature using insertion loss methods. Two parameters were estimated from the backscatter coefficient (effective scatterer diameter (ESD) and effective acoustic concentration (EAC)) and two parameters were estimated from the envelope statistics (k parameter and µ parameter) of the backscattered echoes versus temperature. The results of this study suggest that QUS has the potential to be used for noninvasive monitoring of temperature changes in tissues