Hello, thank you for the interesting video... Just a quick question: what about the so called "creep" or "creeping" waves? Are they surface/Rayleigh waves, or what? Thank you in advance!!
Creep waves are longitudinal waves traveling parallel to the surface. Meaning they are created at the first critical angle and they quickly lose energy in the form of indirect shear, or 'head' waves. Real surface/Rayleigh waves are created at the so-called third critical angle (see also my answer to the question of Ievgenii Kravchenko). Most likely I will do another video about the three critical angles where I will go in more detail on creep, rayleigh, and other wave forms.
Can you explain how did you get the angles values on Shear case 3 and 4? I've recalculated it, based on snell's law using water(n1.5) and steel (n2.67) indexes on shear, the critical incident angle is 41.80degrees; pass that, TIR occurs(Total Internal Reflection). I wonder how in case 4, would you get 90 degrees with an incident angle of 56.5 degrees. I guarantee you, you wouldn't get any (r) refraction with an incident angle of 56.5 degrees based on this example. (r)Refraction line would completely bend away at those angles whether using rexolite or plexiglas given they have higher n values. Lots of techs in the industry missing proper shear calibration and end up being unable to pick up any defects.
You can find on the slide that my calculations are based on Plexiglas (2670 m/s) and Steel (5920 m/s / 3200 m/s). For immersion testing, you have to recalculate with 1500 m/s.
I will try to do a video on this subject - but it might take a while. For the moment: the 3rd critical is the angle to produce a Rayleigh Wave. The speed of sound of a Rayleigh wave (~3000 m/s) is lower compared to both longitudinal (~5920 m/s) and shear wave (~3200 m/s). The first critical angle is at ~27°, the second critical angle at 56,5°and the third critical angle at ~62,9° (for coupling with a Plexiglas-Wedge). Below the first critical angle both L and S wave penetrate the component, between first and second only S Wave. Above the second: only reflection. Except for: at approximately the third critical angle the Rayleigh Wave is created. Above the third: only reflection. I hope this helps.
Dear Johannes, im starting to enjoy your channel... i would like to ask you what happend with the refracted LW when the arriving shear wave pass through steel to wedge again, the probe is able to detect that wave?
So glad i found this channel. 3 weeks in UT school, i found this channel to be super helpful and informative. subd
Very useful information.. thanks for spending time with us
one mistake in video that given second critical angle is longitudinal 90 degree inspite of shear wave 90 degree
Should the incident wave velocity be slower than the wave velocity in the other medium in order to refract ?
If your incident wave velocity is faster than the wave velocity the wave angle will be smaller than the incident angle.
Hello, thank you for the interesting video... Just a quick question: what about the so called "creep" or "creeping" waves? Are they surface/Rayleigh waves, or what? Thank you in advance!!
Creep waves are longitudinal waves traveling parallel to the surface. Meaning they are created at the first critical angle and they quickly lose energy in the form of indirect shear, or 'head' waves. Real surface/Rayleigh waves are created at the so-called third critical angle (see also my answer to the question of Ievgenii Kravchenko). Most likely I will do another video about the three critical angles where I will go in more detail on creep, rayleigh, and other wave forms.
@@NDE40 Thank you so much! Looking forward to see that video!
Can you explain how did you get the angles values on Shear case 3 and 4? I've recalculated it, based on snell's law using water(n1.5) and steel (n2.67) indexes on shear, the critical incident angle is 41.80degrees; pass that, TIR occurs(Total Internal Reflection). I wonder how in case 4, would you get 90 degrees with an incident angle of 56.5 degrees. I guarantee you, you wouldn't get any (r) refraction with an incident angle of 56.5 degrees based on this example. (r)Refraction line would completely bend away at those angles whether using rexolite or plexiglas given they have higher n values. Lots of techs in the industry missing proper shear calibration and end up being unable to pick up any defects.
You can find on the slide that my calculations are based on Plexiglas (2670 m/s) and Steel (5920 m/s / 3200 m/s). For immersion testing, you have to recalculate with 1500 m/s.
Hello, could you tell something about 3rd critical angle?
I will try to do a video on this subject - but it might take a while. For the moment: the 3rd critical is the angle to produce a Rayleigh Wave. The speed of sound of a Rayleigh wave (~3000 m/s) is lower compared to both longitudinal (~5920 m/s) and shear wave (~3200 m/s).
The first critical angle is at ~27°, the second critical angle at 56,5°and the third critical angle at ~62,9° (for coupling with a Plexiglas-Wedge). Below the first critical angle both L and S wave penetrate the component, between first and second only S Wave. Above the second: only reflection. Except for: at approximately the third critical angle the Rayleigh Wave is created. Above the third: only reflection. I hope this helps.
Dear Johannes, im starting to enjoy your channel... i would like to ask you what happend with the refracted LW when the arriving shear wave pass through steel to wedge again, the probe is able to detect that wave?