Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Keywords on Rough Surface:
1. The degree of scattering is based on the ratio of roughness to
wavelength. When roughness is less than about 1/10 a wavelength,
scatter will be negligible.
2. Consequences of Surface Roughness:
• Signal reduction
• Redirect and mode convert some energy which when returned to the
probe can be the source of spurious signals.
3. The False Indications: In contact testing false indications from standing
waves resulting from scatter on rough surfaces will normally have short
sound paths. They can be eliminated as true flaws by failing to locate any
trace of indication from the full skip or from the opposite side