Temperature affected guided wave propagation in a composite plate complementing the Open Guided Waves Platform.

The influence of temperature is regarded as particularly important for a structural health monitoring system based on ultrasonic guided waves. Since the temperature effect causes stronger signal changes than a typical defect, the former must be addressed and compensated for reliable damage assessment. Development of new temperature compensation techniques as well as the comparison of existing algorithms require high-quality benchmark measurements. This paper investigates a carbon fiber reinforced plastic (CFRP) plate that was fully characterized in previous research in terms of stiffness tensor and guided wave propagation. The same CFRP plate is used here for the analysis of the temperature effect for a wide range of ultrasound frequencies and temperatures. The measurement data are a contribution to the Open Guided Waves (OGW) platform: http://www.open-guided-waves.de . The technical validation includes initial results on the analysis of phase velocity variations with temperature and exemplary damage detection results using state-of-the-art signal processing methods that aim to suppress the temperature effect.

Combined Inspection and Data Communication Network for Lamb-Wave Structural Health Monitoring.

Guided ultrasound waves have long been studied in the context of structural health monitoring (SHM). More recently, they have also been proposed for the acoustic data communication. This paper aims at a joint approach combining guided-wave damage inspection with the acoustic data communication. In this work, a network of autonomous transceiver nodes is modeled that represents a part of an SHM system where the available bandwidth is divided into inspection and communication frequencies. The presented communication protocol is insensitive to dispersion and multipath interference that commonly hamper Lamb-wave signal processing. Experimental results include the successful detection of different damage types at several positions on a metallic plate. Moreover, the communication of the data, namely, damage indicators, across the distributed nodes to a central downstream port is shown. Finally, a numerical study regarding the dynamic behavior of autonomous sensor networks is presented.

Ultrasound Bone Fracture Sensing and Data Communication: Experimental Results in a Pig Limb Sample.

Approximately 6.3 million fractures occur each year in the United States alone. Accurately monitoring the progression of fracture healing is essential to be able to advise patients when it is safe to return to normal activity. The most common method used to confirm and monitor fracture healing is the acquisition of multiple radiographic images over the many months required for healing. This imaging method uses large expensive equipment and exposes patients to high levels of ionizing radiation. In the study described here, we tested another technology for monitoring fracture healing that could minimize the need for multiple radiographic images. We tested a piezoelectric transducer fixed to the surface of a bone that uses electromechanical impedance spectroscopy to measure simulated fractures and transmits the measurement data to an acoustic receiver located externally on the skin surface.