Dear Mr. Ali,
Generally mode conversion occurs for 60 deg. shear wave probe.
For other shear wave probes its occurs after 1st leg i.e. more than Half beam path distance.
To avoid mode conversion:
Try to test the butt welds from either sides of weld axis and interpret the results within a half beam path. Dont use multiple beam paths for interpretation. Also if you found any indication confirm it by other degree probes and from other side of weld axis.
IF any false echo present on screen due to mode conversion it will appear at a same point and along the complete length if geometry of weld is same. If this the case try to detect same indication by other degree shear wave probe.
To interpret between false indications due to mode conversion and discontinuity indications is done by confirming by other multiple probes. If a relevant indication it will be shown by all probes may be different amplitude.
But if Mode conversion happened in one angle probe surely there will be not a indication in another degree probe.
Hope this will help u.
On Mon, Jan 11, 2010 at 9:37 AM, ali asghari <firstname.lastname@example.org> wrote:
Dear alldoes anybody have exprience to see mode conversion & refraction of shear wave in conventional ULtrasonic testing due to wrong selection of probe?how can it detected from other reflections?& how can it prevented?regard advances
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