Papers by Keyword: Ultrasonic Evaluation

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Authors: In Young Yang, Yong Jun Yang, Jun Woo Park, Kil Sung Lee, Young Tae Cho, Je Woong Park, David K. Hsu, Kwang Hee Im
Abstract: Carbon/carbon(C/C) composite materials have obvious advantages over conventional materials, which consist of carbon fibers embedded in a carbon matrix. It’s low density, high thermal conductivity and excellent mechanical properties at elevated temperatures make it an ideal material for aerospace applications especially aircraft brake disks. Because of permeation of coupling medium such as water, it is desirable to perform contact-less nondestructive evaluation to assess material properties and part homogeneity. In this work, a C/C composite material was characterized with non-contact and contact ultrasonic methods using automated acquisition scanner. . Due to the acoustic impedance mismatch found between most materials and air, a major limitation for air-coupled transducers, through-transmission mode was performed. Especially ultrasonic images and velocities for C/C composite disk brake were measured and found to be consistent to some degree with the non-contact and contact ultrasonic measurement methods. 400 kHz frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the inhomogeneity in material property. Non-contact measured results were compared with those obtained by the motorized system using contact drycoupling ultrasonics and through transmission method in immersion. Results using a proposed peak-delay measurement non-contact method corresponded well to the ultrasonic velocities of the contact pulse overlap method.
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Authors: M. Dubuget, R. El Guerjouma, Sylvain Dubois, J.C. Baboux, Alain Vincent
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Authors: Jae Ki Sim, Kwang Hee Im, David K. Hsu, Sung Jin Song, Hyeon Cho, Hak Joon Kim, Young Hwan Seo, In Young Yang
Abstract: Carbon/phenolic composite (CPC) materials have obvious advantages over conventional materials, which are consisting of carbon fibers embedded in a carbon matrix. The CPCs have become to be utilized as parts of aerospace applications and its low density, high thermal conductivity and excellent mechanical properties at elevated temperatures make it an ideal material for aircraft brake disks. Because of permeation of coupling medium such as water, it is desirable to perform contact-less nondestructive evaluation to assess material properties and part homogeneity. In this work, a C/P(Carbon/phenolic) composite material was characterized with non-contact and contact ultrasonic methods using automated acquisition scanner. Also through transmission mode was performed because of the main limitation for air-coupled transducers, which is the acoustic impedance mismatch between most materials and air. Especially ultrasonic images and velocities for C/C(Carbon/Carbon) composite disk brake was measured and found to be consistent to some degree with the non-contact and contact ultrasonic measurement methods. Low frequency throughtransmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity. Measured results were compared with those obtained by the motorized system with using dry-coupling ultrasonics and through transmission method in immersion. Finally, results using a proposed peak-delay measurement method well corresponded to ultrasonic velocities of the pulse overlap method.
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Authors: Jae Ki Sim, Kwang Hee Im, David K. Hsu, Ji Hoon Kim, Hyun Lee, Jae Jung Hwang, Kyung-Youn Bak
Abstract: In order to assess material properties and part homogeneity in carbon matrix composite (CMC) brake disks we have performed nondestructive evaluation, which are originally developed for aerospace applications. In this paper we have adopted several ultrasonic techniques to evaluate carbon matrix composites for the material properties that are attributable to the manufacturing process. In a carbon matrix composite manufactured by chemical vapor infiltration (CVI) method, the spatial variation of ultrasonic velocity was measured and found to be consistent with the densification behavior in CVI process in order to increase the density of the CMC composites. Ultrasonic velocity and attenuation depend on a density variation of materials. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity. Optical micrograph had been examined on the surface of the CMCs using a destructive way. Also a motorized system was adopted to measure ultrasonic velocity on the point of the CMC materials under the same coupling conditions. Manual results were compared with those obtained by the motorized system with using dry-coupling ultrasonics and through transmission method in immersion.
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Authors: Woo Chan Ethan Kim, Seung Yong Yang, Noh Yu Kim
Abstract: A quantitative ultrasound (QUS) method is developed for estimation of volume fraction of porous Kelvin structure to understand acoustic characteristics of trabecular bone. A Kelvin cellular specimen composed of isotropic tetra-kaidecahedron was produced by 3D printer with ABS plastic material to simulate artificial trabecular bone. The unit cell of Kelvin specimen has a size of 3.4mm and 81% of porosity. The specimen was completely filled with paraffin wax as a substitute of bone marrow. The speed of sound (SOS) of the wax-filled Kelvin specimen was measured using the time-of-flight (TOF) of ultrasound. Based on micro-structural model, shape parameters of Kelvin specimen is correlated with SOS and elastic constant to evaluate volume fraction of the specimen quantitatively. 25.8% of volume fraction was estimated for the Kelvin specimen which has actual volume fraction of 19%. It is concluded from experiment that the ultrasonic method developed in this study is effective and can be applied to diagnose and monitor osteoporosis.
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Authors: In Young Yang, Kwang Hee Im, David K. Hsu, Sung Jin Song, Hyeon Cho, Sun Kyu Kim, Young Hwan Seo, Je Woong Park
Abstract: Carbon/phenolic composite (CPC) materials are unique which consist of carbon fibers embedded in a carbon matrix. The CPCs are originally developed for aerospace applications and its low density, high thermal conductivity and excellent mechanical properties at elevated temperatures make it an ideal material for aircraft brake disks. The properties of the CPC are dependent on the manufacturing methods used for production and fiber arrangement. It is desirable to perform nondestructive evaluation to assess material properties and part homogeneity in order to ensure product quality and structural integrity of CPC brake disks. In this work, a CPC material was nondestructively characterized and a technique was developed to measure ultrasonic velocity in C/P composites using automated data acquisition software. Also a motorized system was adopted to measure ultrasonic velocity on the point of CPC materials under the same coupling conditions. Manual results were compared with those obtained by the motorized system with using drycoupling ultrasonics and through transmission method in immersion. A peak-delay measurement method well corresponded to ultrasonic velocities of the pulse overlap method and throughtransmission mode and C-scan image signal based on peak-to-peak amplitude.
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Authors: J. Alfredo López, Francisco J. Carrión, Juan A. Quintana, Didier Samayoa-Ochoa, María G. Lomelí, Pablo R. Orozco
Abstract: Failure of one upper anchorage element in a cable-stayed bridge and its consequent analysis concluded that the main cause of the failure was a deficient heat treatment that resulted in large micro structural grain size and low fracture toughness, vulnerable to fatigue damage. Previous research studies demonstrated that ultrasonic evaluation could provide some insight of the microstructural integrity by correlating the ultrasonic response to the grain size. Thus, this technique was used to inspect the 112 elements in service in the bridge and 16 were qualified as structurally deficient, without direct verification of the grain size, since these elements were partially embedded in the concrete structure. Late rehabilitation of the bridge considered the replacement of the 16 structural deficient anchorage elements, plus 4 elements qualified in good condition, to complete a reliability analysis for the remaining 92 elements from the statistical mechanical properties of the removed pieces. Rehabilitation made possible the confirmation of the initial diagnosis made by ultrasonic inspection and fatigue cracks were identified in some elements. This study demonstrated that the ultrasonic non destructive evaluation is highly reliable for structural integrity qualification of steel structural elements partially embedded in concrete.
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