This part of ISO 4386 specifies an ultrasonic testing method for determining bond defects between the bearing metal and the backing. The test can be performed on metallic multilayer plain bearings consisting of steel- or copper-based material backings lined with bearing metal based on lead and tin, with layer thicknesses greater than or equal to 0,5 mm. For cast iron backings, this part of ISO 4386 is applicable with restrictions. The ultrasonic signal reflected by the bond interface between the bearing metal and the backing is used to determine bonding defects. Ultrasonic testing is not possible on edge zones of sliding surface, flange sides, joint areas, oil holes, grooves, etc. in a range of less than half the diameter of the ultrasonic probe because of undefined reflections. The same applies to bearings with dovetail keying grooves at the bond. Ultrasonic testing of bond does not apply along the edges of the dovetails. Evaluation of the bond on the visible transition from the backing to the bearing metal (on end faces or joint faces) is only practicable by the penetrant testing method specified in ISO 4386-3. This part of ISO 4386 only describes in detail the pulse-echo method. Within the meaning of this part of ISO 4386, the ultrasonic method only permits a qualitative evaluation of the bonding and not a quantitative determination of the bond strength. The ultrasonic bond test differs only between bond and bond defect.