When plates are tested ultrasonically this rarely concerns fatigue cracks. These testing problems, therefore, will be discussed briefly first. Where in-service defects are not the result of manufacturing defects, they always occur as incipient cracks normal to the surface. This applies for instance to corrosion- fatigue cracks in the case of caustic embrittlement, cracks at rivet holes, or fatigue cracks in flanges, rims, etc. If the direction of propagation of the cracks is known approximately, they can be easily found by means of zigzag transverse waves, and if the surface is good, also by means of surface waves. Regarding cracks at rivet holes, see also Chapter 27, and regarding corrosion and thickness determinations on plate, see 32.1.
KeywordsFatigue Welding Attenuation Manganese Titanate
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