Development of a Virtual Instrument for Immersion Type Ultrasonic Inspection with a Computer Controlled Multi-Axis Motion Controller
The Pulse Echo (PE) technique is a widely used ultrasonic non destructive testing technique to test materials by analyzing ultrasound echoes reflected from flaws and discontinuities. In conventional PE technique, called contact type PE, an ultrasonic transducer is in constant contact with a test piece, transmitting and receiving ultrasonic signals from the test specimen. The inherent shortcomings of PE are the need for; uniform couplant conditions, the ultrasonic transducer to remain in contact with the test object throughout the scan and a limitation to scan regular surfaced objects only. This paper provides for extending a system initially developed for contact type PE, to perform Immersion Testing (IT) which is a contactless pulse-echo inspection method with the probe and test piece separated by a predetermined volume of water of certain thickness. A computer controlled 3-axis transducer position manipulator (motion frame) is constructed for assistance in conducting automated tests. The efficacy of immersion testing relies on the precise control of the motion of transducer. The existing immersion type motion controllers along with dedicated data acquisition and analysis system are quite expensive and are beyond the affordability of smaller ultrasonic labs. Hence the proposed system including the motion frame and Data Acquisition Unit (DAQ) can serve as a competent, low-cost and reliable IT system benefitting several small scale industries and labs.
Modified treatment of ultrasonic pulse-echo immersion technique
Abstract A modified treatment of ultrasonic pulse-echo immersion technique is formulated to permit experimental determination of the amplitude reflection coefficient and the ultrasonic attenuation coefficient α especially when the acoustic impedance of the measured specimen is far from that of the immersion liquid. The modified treatment is tested experimentally on blends of styrene–butadiene rubber (SBR 1502) and natural rubber (SMR 20) containing different concentrations of high abrasion furnace black. The effect of changing the immersion liquid on the obtained values of α is studied by using distilled water and ethyl alcohol as immersion liquids. The effect of changing the specimen thickness is also investigated. It is found that neither the immersion liquid nor the specimen thickness has any effect of the obtained values of α if the present modification is adopted.
Comparison between prediction and measurement of viscoelastic moduli in composite materials versus temperature using ultrasonic immersion technique with oil
An oil immersion ultrasonic method used for measuring elastic and viscoelastic properties of materials versus temperature is presented. From velocity and amplitude measurements, the complex viscoelastic tensor can be entirely determined from room temperature to temperatures near the glass transition temperature of the material. This tensor permits the computation of velocities and attenuations of heterogeneous or homogeneous modes in any direction of wave propagation. A micromechanics model is used to compare experimental results with theoretical ones and to analyze anisotropic elastic and viscoelastic behavior of composite materials.