Abstract: The method of closing an open ended thermoplastic body with a thermoplastic sheet material comprises the provision of a groove in the thermoplastic body and a protrusion disposed on the output surface of a horn adapted to be resonant at an ultrasonic frequency. The protrusion of the horn is dimensioned to enter the groove and force the sheet material into contact with surfaces forming the groove for achieving, when the horn is rendered resonant, a weld between the sheet material and the body, the weld being confined to the surfaces forming the groove.

Abstract: The invention relates to an ultrasonic test instrument, in which a receiver amplifier is controlled in dependence upon time by means of a depth compensation signal or else the ultrasonic signal amplified independently of the depth is evaluated by means of a time-dependent variable threshold signal. The depth compensation signals and the time-dependent threshold signals are derived from the same digital signal values stored in a main memory. The test instrument comprises a microprocessor by means of which the digital signal values for each material requiring testing are automatically measured by the instrument itself in conjunction with whichever test probe is used provided a corresponding test block of this material is available.