Determination of surface mechanical properties using a hertzian contact and ultrasound sensor

Nondestructive monitoring of contact properties for biological and engineering materials is important in several engineering areas. Also, in robotics, manipulation of fragile objects requires precise determination of instantaneous contact area and forces with minimum intrusion. In this paper, a contact probe based on hertzian contact and ultrasonic energy transmission for characterization of surface properties is proposed. The probe is built from a solid semi-spherical head which is sonified from the top by an ultrasonic transducer with a center frequency of 1 MHz. Force range was 0-23N and displacements as small as 0.05 millimeters were reached with a proposed automatic control system. A quasi-static spring model to describe the interfacial properties at contact is studied. The results indicate that due to its high sensitivity, the probe could be used for measurements of surface mechanical response.