Understanding CDS

The 30-70-70 crack detection technique uses a single element transducer with a CDS wedge for detection and sizing of ID connected cracks. This technique uses a combination of three waves for sizing flaws of different depths.

• An OD creeping wave creates a 31.5 degree indirect shear, (red in diagram to the left), wave which mode converts to an ID creeping wave; this will produce a reflected signal on all ID connected cracks.
• A 30 degree shear wave, (yellow in diagram to the left), will reflect off the material ID at the critical angle and mode convert to a 70 degree longitudinal wave; a signal will be received by the transducer on mid-wall deep cracks.
• A 70 degree longitudinal wave, (blue in diagram to the left), will reflect off the tip of a deep wall crack.

Based on the presence or absence of these three waves, both detection and sizing of ID connected cracks is possible.

CDS Wedges

CDS Wedges are used in the "30-70-70" technique for crack detection and sizing. They are compatible with our replaceable miniature screw-in angle beam transducers, making them an economical alternative to other commercially available products.