| 摘要 |
This process consists in applying an excitation voltage, in subjecting the material to a deformation, in generating ultrasonic oscillations in the latter and in determining their amplitude. The period of the oscillations and the amplitude of the return signal are measured and the amplitude of the mechanical oscillations is maintained in a range of critical values by modulation of the excitation voltage using impulses of variable width. After the amplitude of the return signal has reached its upper value, the delivery of the excitation voltage is interrupted and after it has decreased to its lower value the excitation voltage is applied again. The device comprises a tool (1), a source (2) of supply, an automatic tuning unit (3). This set additionally comprises a controller (8), a unit (4) for measuring the amplitude of the return signal, a comparator (7), an arithmetic and logical device (5) and a memory unit (6). <IMAGE>
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