The Experts below are selected from a list of 18 Experts worldwide ranked by ideXlab platform

Philip John Hogg - One of the best experts on this subject based on the ideXlab platform.

  • Impact damage detection and degradation monitoring of wet GFRP composites using Noncontact Ultrasonics
    Polymer Composites, 2009
    Co-Authors: K. Berketis, Dimitrios Tzetzis, Philip John Hogg
    Abstract:

    Two different non-crimp glass fabrics with a polyester resin were used to produce laminated plates that were subjected to low velocity impact testing using three impact energy levels. The plates were immersed in water at 65°C for up to 24 months. The effectiveness of a traditional water coupled and an air-coupled ultrasonic C-Scan system was assessed in terms of damage size evaluation at various time intervals. The conditioned impacted plates were retested statically in compression to determine the residual strength for evaluation of damage tolerance. Weight change measurements revealed an initial increase due to water diffusion, followed by an extended decrease due to matrix dissolution at long-term immersion times. The use of water coupled pulse-echo Ultrasonics proved ineffective after long-term water immersion as damaged areas became ultrasound-invisible. The contrast between impact damaged areas and water diffused areas was restored with the air-coupled C-scan. The macroscopic damage size was not affected by the long-term water immersion and the overall weight change while the residual compression strength was seemed to be dependent on the time of immersion and the size of the pre-existing impact damage. Calibrating the aircoupled system to a dry condition specimen, a good qualitative and quantitative indication of the degraded state of water immersed plates was obtained. This monitoring system for the degradation process seems to be very promising. POLYM. COMPOS., 30:1043-1049, 2009.© 2008 Society of Plastics Engineers.

  • Noncontact Ultrasonics used for impact damage detection on long-term water-immersed GFRP composites
    International Journal of Microstructure and Materials Properties, 2009
    Co-Authors: K. Berketis, Dimitrios Tzetzis, Philip John Hogg
    Abstract:

    Traditional water immersion and Noncontact ultrasonic C-Scan systems were used for damage detection and quantification on wet Glass Fibre Reinforced Polymer (GFRP) composite plates. Long-term immersion for up to 24 months of low-velocity impact-damaged GFRP plates in hot water at 65°C and 93°C caused serious matrix and interface degradation. The water diffusion profile was followed by water uptake measurements. The use of water-immersion, single-probe pulse-echo Ultrasonics proved ineffective after long-term water immersion as damaged areas became ultrasound-invisible. The impact-damaged part was filled with water, thus acting in a similar way to the rest of the undamaged material. The use of a pair of 400 kHz air-coupled through thickness ultrasonic probes was investigated for damage detection and evaluation. The contrast between impact-damaged areas and water-diffused areas was restored and damage size detection was possible. Calibrating the system for the group wave velocity of a dry-condition specimen, a good qualitative and quantitative indication of the degraded state of specimens can be obtained. This system proved to be very promising for both the impact damage sizing and for the monitoring of the degradation process.

K. Berketis - One of the best experts on this subject based on the ideXlab platform.

  • Impact damage detection and degradation monitoring of wet GFRP composites using Noncontact Ultrasonics
    Polymer Composites, 2009
    Co-Authors: K. Berketis, Dimitrios Tzetzis, Philip John Hogg
    Abstract:

    Two different non-crimp glass fabrics with a polyester resin were used to produce laminated plates that were subjected to low velocity impact testing using three impact energy levels. The plates were immersed in water at 65°C for up to 24 months. The effectiveness of a traditional water coupled and an air-coupled ultrasonic C-Scan system was assessed in terms of damage size evaluation at various time intervals. The conditioned impacted plates were retested statically in compression to determine the residual strength for evaluation of damage tolerance. Weight change measurements revealed an initial increase due to water diffusion, followed by an extended decrease due to matrix dissolution at long-term immersion times. The use of water coupled pulse-echo Ultrasonics proved ineffective after long-term water immersion as damaged areas became ultrasound-invisible. The contrast between impact damaged areas and water diffused areas was restored with the air-coupled C-scan. The macroscopic damage size was not affected by the long-term water immersion and the overall weight change while the residual compression strength was seemed to be dependent on the time of immersion and the size of the pre-existing impact damage. Calibrating the aircoupled system to a dry condition specimen, a good qualitative and quantitative indication of the degraded state of water immersed plates was obtained. This monitoring system for the degradation process seems to be very promising. POLYM. COMPOS., 30:1043-1049, 2009.© 2008 Society of Plastics Engineers.

  • Noncontact Ultrasonics used for impact damage detection on long-term water-immersed GFRP composites
    International Journal of Microstructure and Materials Properties, 2009
    Co-Authors: K. Berketis, Dimitrios Tzetzis, Philip John Hogg
    Abstract:

    Traditional water immersion and Noncontact ultrasonic C-Scan systems were used for damage detection and quantification on wet Glass Fibre Reinforced Polymer (GFRP) composite plates. Long-term immersion for up to 24 months of low-velocity impact-damaged GFRP plates in hot water at 65°C and 93°C caused serious matrix and interface degradation. The water diffusion profile was followed by water uptake measurements. The use of water-immersion, single-probe pulse-echo Ultrasonics proved ineffective after long-term water immersion as damaged areas became ultrasound-invisible. The impact-damaged part was filled with water, thus acting in a similar way to the rest of the undamaged material. The use of a pair of 400 kHz air-coupled through thickness ultrasonic probes was investigated for damage detection and evaluation. The contrast between impact-damaged areas and water-diffused areas was restored and damage size detection was possible. Calibrating the system for the group wave velocity of a dry-condition specimen, a good qualitative and quantitative indication of the degraded state of specimens can be obtained. This system proved to be very promising for both the impact damage sizing and for the monitoring of the degradation process.

Dimitrios Tzetzis - One of the best experts on this subject based on the ideXlab platform.

  • Impact damage detection and degradation monitoring of wet GFRP composites using Noncontact Ultrasonics
    Polymer Composites, 2009
    Co-Authors: K. Berketis, Dimitrios Tzetzis, Philip John Hogg
    Abstract:

    Two different non-crimp glass fabrics with a polyester resin were used to produce laminated plates that were subjected to low velocity impact testing using three impact energy levels. The plates were immersed in water at 65°C for up to 24 months. The effectiveness of a traditional water coupled and an air-coupled ultrasonic C-Scan system was assessed in terms of damage size evaluation at various time intervals. The conditioned impacted plates were retested statically in compression to determine the residual strength for evaluation of damage tolerance. Weight change measurements revealed an initial increase due to water diffusion, followed by an extended decrease due to matrix dissolution at long-term immersion times. The use of water coupled pulse-echo Ultrasonics proved ineffective after long-term water immersion as damaged areas became ultrasound-invisible. The contrast between impact damaged areas and water diffused areas was restored with the air-coupled C-scan. The macroscopic damage size was not affected by the long-term water immersion and the overall weight change while the residual compression strength was seemed to be dependent on the time of immersion and the size of the pre-existing impact damage. Calibrating the aircoupled system to a dry condition specimen, a good qualitative and quantitative indication of the degraded state of water immersed plates was obtained. This monitoring system for the degradation process seems to be very promising. POLYM. COMPOS., 30:1043-1049, 2009.© 2008 Society of Plastics Engineers.

  • Noncontact Ultrasonics used for impact damage detection on long-term water-immersed GFRP composites
    International Journal of Microstructure and Materials Properties, 2009
    Co-Authors: K. Berketis, Dimitrios Tzetzis, Philip John Hogg
    Abstract:

    Traditional water immersion and Noncontact ultrasonic C-Scan systems were used for damage detection and quantification on wet Glass Fibre Reinforced Polymer (GFRP) composite plates. Long-term immersion for up to 24 months of low-velocity impact-damaged GFRP plates in hot water at 65°C and 93°C caused serious matrix and interface degradation. The water diffusion profile was followed by water uptake measurements. The use of water-immersion, single-probe pulse-echo Ultrasonics proved ineffective after long-term water immersion as damaged areas became ultrasound-invisible. The impact-damaged part was filled with water, thus acting in a similar way to the rest of the undamaged material. The use of a pair of 400 kHz air-coupled through thickness ultrasonic probes was investigated for damage detection and evaluation. The contrast between impact-damaged areas and water-diffused areas was restored and damage size detection was possible. Calibrating the system for the group wave velocity of a dry-condition specimen, a good qualitative and quantitative indication of the degraded state of specimens can be obtained. This system proved to be very promising for both the impact damage sizing and for the monitoring of the degradation process.

David A. Hutchins - One of the best experts on this subject based on the ideXlab platform.

  • Industrial Applications of Noncontact Ultrasonics Techniques
    Ultrasonic Nondestructive Evaluation Systems, 2014
    Co-Authors: Luigi Battaglini, Sergio Callegari, Salvatore Caporale, L.a.j. Davis, Stefano Laureti, Luca Senni, David A. Hutchins
    Abstract:

    In many application environments, it is not possible to practice nondestructive evaluation (NDE) by physically contacting the material under test with probes. Examples include the evaluation of objects that are moving (e.g., on an assembly line), hot materials, materials that cannot risk contamination, and more. Lack of contact means that, typically, the coupling material is air. This poses specific requirements, due to the acoustic impedance mismatch that an air layer can provoke and the consequent energy losses. In this chapter, some examples of setups, transducer arrangements, and signal processing strategies capable of addressing such requirements are illustrated, showing how concepts presented in the previous chapters can be deployed in this particular context. Furthermore, some typical achievable results are illustrated, with respect to a few different testing scenarios, such as the testing of composite materials, the inspection of concrete, imaging of surfaces or thin materials, and food inspection.

Ernesto Indacochea - One of the best experts on this subject based on the ideXlab platform.

  • The Detection of Burn-Through Weld Defects Using Noncontact Ultrasonics.
    Materials (Basel Switzerland), 2018
    Co-Authors: Zeynab Abbasi, Donald Yuhas, Lu Zhang, Alexandra-del-carmen Basantes, Niloofar Tehrani, Didem Ozevin, Ernesto Indacochea
    Abstract:

    Nearly all manufactured products in the metal industry involve welding. The detection and correction of defects during welding improve the product reliability and quality, and prevent unexpected failures. Nonintrusive process control is critical for avoiding these defects. This paper investigates the detection of burn-through damage using Noncontact, air-coupled Ultrasonics, which can be adapted to the immediate and in-situ inspection of welded samples. The burn-through leads to a larger volume of degraded weld zone, providing a resistance path for the wave to travel which results in lower velocity, energy ratio, and amplitude. Wave energy dispersion occurs due to the increase of weld burn-through resulting in higher wave attenuation. Weld sample micrographs are used to validate the ultrasonic results.