Abstract: An internal condition of a concrete structure is objectively evaluated irrespective of surrounding noise or the shape of a hammer, by placing a vibration sensor in direct contact with a measuring surface so as to directly convert a vibration generated on the measuring surface into a corresponding voltage without the intervention of a medium such as air thereby to quantify the vibration generated on the measuring surface concerned. A structure diagnosis apparatus of the present invention includes a vibration unit for generating an elastic wave in a measuring object of a concrete structure, a vibration detector adapted to be placed in contact with a surface of the measuring object for detecting a component in a predetermined frequency range of an elastic vibration generated on the surface of the measuring object by the vibration unit; and a display device for displaying a maximum amplitude of an output signal of the vibration detector.

Abstract: An elastic wave generator includes an excitation coil, a magnetostriction oscillator around which the excitation coil is wound and an oscillator support. The excitation coil is wound around the oscillator, which is made of laminated magnetostriction sheets having a positive strain characteristic, in which length varies directionally upon magnetic excitation. The oscillator support has a first support surface bearing against a first end surface of the magnetostriction oscillator, intersecting the direction along which the length of the magnetostriction oscillator changes and a second support surface shrink-fit against a second end surface of the magnetostriction oscillator, intersecting the direction along which the length of the magnetostriction oscillator changes. Thus, the changes in the length of the magnetostriction oscillator due to the magnetic excitation of the excitation coil appearing at the first and second end surfaces is directly supported by the first and second support surfaces.

Abstract: A nondestructive testing apparatus is provided with a wave transmitter by a metal-based magnetostrictive vibrator, a magnetically excited current feeding device for feeding the magnetically excited current to the magnetostrictive vibrator, a wave receiver for detecting an acoustic elastic wave propagating through the measurement object, a filter for extracting a signal in a target frequency band to be measured, and an automatically amplifying rate controlling function-equipped amplifier for automatically controlling the amplifying rate so as to obtain a given magnitude amplitude regardless of the magnitude of the reflection wave or the transmission wave detected by the wave receiver, which constitute a feedback loop.