The ultrasonic wave velocities of Japanese cedar columns were measured using a non-contact method. An air-coupled ultrasonic wave was propagated through the axial and lateral directions of wood. The velocities in the ...The ultrasonic wave velocities of Japanese cedar columns were measured using a non-contact method. An air-coupled ultrasonic wave was propagated through the axial and lateral directions of wood. The velocities in the axial direction (V<sub>L</sub>) showed the minimum values around the pith. The averaged V<sub>L</sub> increased from 3600 m/s towards the outside of measurement area and attained the maximum values (=4010 m/s). The velocities in the lateral direction (V<sub>RT </sub>) showed no tendency among measurement points. The averaged V<sub>RT </sub> was 1450 m/s. The velocities obtained using the non-contact method showed a significant positive relationship with those obtained using the contact method. The averaged ratio of V<sub>L</sub> to V<sub>RT </sub> was measured to be approximately 2.2 to 2.8. These ratios were in agreement with those from a contact method. These findings suggest that it is possible to measure the velocity in Japanese cedar columns with the non-contact method by using air-coupled ultrasonics.展开更多
By means of ultrasonic attenuation apparatus, the ultrasonic velocity and attenuation ofanhydride-cured epoxy resins (EP)/poly (ethylene oxide) (PEO) blends were measured on thebasis of pulse-echo method. It was found...By means of ultrasonic attenuation apparatus, the ultrasonic velocity and attenuation ofanhydride-cured epoxy resins (EP)/poly (ethylene oxide) (PEO) blends were measured on thebasis of pulse-echo method. It was found that the sonic velocity of the blends decreased as thetemperature increased, but attenuation coefficient increased and possessed a peak value. Largervelocity and smaller attenuation coefficient(α)can be obtained from perfect crosslinking networkstructures of pure DGEBA cured with phthalic anhydride(PA). As for cured DGEBA/PEO blendsystems,sonic velocity decreased as a function of PEO concentration,but attenuation coefficient(α) increased.展开更多
Roller bearings support heavy loads by riding on an ultra-thin oil film(between the roller and raceway),the thickness of which is critical as it reflects the lubrication performance.Ultrasonic interfacial reflection,w...Roller bearings support heavy loads by riding on an ultra-thin oil film(between the roller and raceway),the thickness of which is critical as it reflects the lubrication performance.Ultrasonic interfacial reflection,which facilitates the non-destructive measurement of oil-film thickness,has been widely studied.However,insufficient spatial resolution around the rolling line contact zone remains a barrier despite the use of miniature piezoelectric transducers.In this study,a finite-element-aided method is utilized to simulate wave propagation through a three-layered structure of roller-oil-raceway under elastohydrodynamic lubrication(EHL)with nonlinear characteristics of the i)deformed curvature of the cylindrical roller and ii)nonuniform distribution of the fluid bulk modulus along the circumference of the oil layer being considered.A load and speed-dependent look-up table is then developed to establish an accurate relationship between the overall reflection coefficient(directly measured by an embedded ultrasonic transducer)and objective variable of the central oil-film thickness.The proposed finite-element-aided method is verified experimentally in a rollerraceway test rig with the ultrasonically measured oil-flm thickness corresponding to the values calculated using the EHLtheory.展开更多
文摘The ultrasonic wave velocities of Japanese cedar columns were measured using a non-contact method. An air-coupled ultrasonic wave was propagated through the axial and lateral directions of wood. The velocities in the axial direction (V<sub>L</sub>) showed the minimum values around the pith. The averaged V<sub>L</sub> increased from 3600 m/s towards the outside of measurement area and attained the maximum values (=4010 m/s). The velocities in the lateral direction (V<sub>RT </sub>) showed no tendency among measurement points. The averaged V<sub>RT </sub> was 1450 m/s. The velocities obtained using the non-contact method showed a significant positive relationship with those obtained using the contact method. The averaged ratio of V<sub>L</sub> to V<sub>RT </sub> was measured to be approximately 2.2 to 2.8. These ratios were in agreement with those from a contact method. These findings suggest that it is possible to measure the velocity in Japanese cedar columns with the non-contact method by using air-coupled ultrasonics.
文摘By means of ultrasonic attenuation apparatus, the ultrasonic velocity and attenuation ofanhydride-cured epoxy resins (EP)/poly (ethylene oxide) (PEO) blends were measured on thebasis of pulse-echo method. It was found that the sonic velocity of the blends decreased as thetemperature increased, but attenuation coefficient increased and possessed a peak value. Largervelocity and smaller attenuation coefficient(α)can be obtained from perfect crosslinking networkstructures of pure DGEBA cured with phthalic anhydride(PA). As for cured DGEBA/PEO blendsystems,sonic velocity decreased as a function of PEO concentration,but attenuation coefficient(α) increased.
文摘Roller bearings support heavy loads by riding on an ultra-thin oil film(between the roller and raceway),the thickness of which is critical as it reflects the lubrication performance.Ultrasonic interfacial reflection,which facilitates the non-destructive measurement of oil-film thickness,has been widely studied.However,insufficient spatial resolution around the rolling line contact zone remains a barrier despite the use of miniature piezoelectric transducers.In this study,a finite-element-aided method is utilized to simulate wave propagation through a three-layered structure of roller-oil-raceway under elastohydrodynamic lubrication(EHL)with nonlinear characteristics of the i)deformed curvature of the cylindrical roller and ii)nonuniform distribution of the fluid bulk modulus along the circumference of the oil layer being considered.A load and speed-dependent look-up table is then developed to establish an accurate relationship between the overall reflection coefficient(directly measured by an embedded ultrasonic transducer)and objective variable of the central oil-film thickness.The proposed finite-element-aided method is verified experimentally in a rollerraceway test rig with the ultrasonically measured oil-flm thickness corresponding to the values calculated using the EHLtheory.
