The Ultrasonic NDT Technique Utilizing the Longitudinal or Transverse Waves Induced by Lamb Wave in Thin Plates

This paper presents a new ultrasonic NDT technique for measuring the thicknessof a nonmetal material(called the ciadding material)with low sound velocity which iscladded on the one side of a thin metal plate(called the base)with high sound velocity such as tubes,tins and other closed containers,testing and inspecting the unglued area betweenthem,detecting the inner defect of the compesite from the side of the base in case that themeasurement and inspection has to be carried out on the side of the base.The principle ofthe technique is that a longitudinal or transverse wave induced by the pulse Lamb wave inthe base is transmited in certam direction into the compounded material,then reflected bythe upper and lower boundary of the compounded material.The same mode pulse Lambwave is formed while the longitudinal or transverse wave in the compounded material returnthe base.

This paper presents a new ultrasonic NDT technique for measuring the thickness of a nonmetal material (called the cladding material) with low sound velocity which is cladded on the one side of a thin metal plate (called the base) with high sound velocity such as tubes, tins and other closed containers, testing and inspecting the unglued area between them, detecting the inner defect of the composite from the side of the base in case that the measurement and inspection has to be carried out on the side of the base. The principle of the technique is that a longitudinal or transverse wave induced by the pulse Lamb wave in the base is transmited in certain direction into the compounded material, then reflected by the upper and lower boundary of the compounded material. The same mode pulse Lamb wave is formed while the longitudinal or transverse wave in the compounded material return the base.