Hello Dr. Vrana, could you do video/blog on nonlinear UT methods for early damage detection vs how they compare with the linear methods. I'm really new to NDE methods, and trying to do my masters thesis on identification & sizing of fatigue cracks. All the recent papers seems to favor nonlinear methods (e.g. frequency modulation, wave mixing, non-linear coefficient) for detecting early damage. I feel like, as someone like you who has been in this industry a long time can shed some light on the feasibility of these non-linear methods.
Unfortunately, I do not have any experience in nonlinear UT. For crack detection and wall thickness measurements I would always use linear methods to do their ease of use. However, in the detection of early damage, we are most likely speaking about damages that are #1 clearly smaller than the wavelength and #2 still quite "integrated" into the material and therefore create weak signals. And this is where nonlinear UT or even nonlinear reconstruction could help. Also, take a look into some medical applications.
again thank you for your videos. I've watched most of them to get a grasp on UT methods. Specially, integrating NDE and AI seems really promising, and I'm planning on looking into that field more.
Is not it dangerous sometimes to evaluate FBH size purely on an amplitude based technique? Like DGS or DAC basically. The reflector may be "equivalent" to a disk shape, but it might be much bigger than it appears! Because the indication could be irregular, and would scatter the sound rather than a specular reflector. I know, yes... the amplitude based technique is a core assessment method but sometimes I doubt its reliability.
Yes, you are right. Amplitude-based techniques can be misleading. #1 The calibration needs to be performed accurately. #2 The check of the equipment needs to be done accurately (for example if the probe frequency is not the frequency stipulated by the manufacturer DGS can be off drastically). #3 Larger, angled, indications have a quite directed reflection. Therefore, if they are not perpendicular to the ultrasonic beam only a fraction of the beam is collected by the probe. However, once we get to indications that are in the order of magnitude of the wavelength this angle dependency is quite minimal - also the structure of such small defects is quite insignificant (as this structure is way smaller than the wavelength it is not "seen" by UT. Meaning those indications can be sized quite accurately. And if all the other factors are also controlled you can achieve a surprisingly good sizing accuracy. And in case you wanna do better: th-cam.com/video/-dPkgov5E-M/w-d-xo.html
Hello Dr. Vrana, could you do video/blog on nonlinear UT methods for early damage detection vs how they compare with the linear methods. I'm really new to NDE methods, and trying to do my masters thesis on identification & sizing of fatigue cracks. All the recent papers seems to favor nonlinear methods (e.g. frequency modulation, wave mixing, non-linear coefficient) for detecting early damage. I feel like, as someone like you who has been in this industry a long time can shed some light on the feasibility of these non-linear methods.
Unfortunately, I do not have any experience in nonlinear UT. For crack detection and wall thickness measurements I would always use linear methods to do their ease of use. However, in the detection of early damage, we are most likely speaking about damages that are #1 clearly smaller than the wavelength and #2 still quite "integrated" into the material and therefore create weak signals. And this is where nonlinear UT or even nonlinear reconstruction could help. Also, take a look into some medical applications.
Thank you so much for the suggestion. And yes, by early damage I meant defects smaller than the wave length & producing weak signals.
again thank you for your videos. I've watched most of them to get a grasp on UT methods. Specially, integrating NDE and AI seems really promising, and I'm planning on looking into that field more.
@@abrarsalekinraiyan3170 COmbination of nonlinear UT, reconstruction, and some AI could really be a fascinating topic ....
Thanks for sharing
You are very welcome
Very informative. Thanks for the detailed explanation. Much appreciated
Just what I was looking for, at a convenient time 😁
Great !!!
Is not it dangerous sometimes to evaluate FBH size purely on an amplitude based technique? Like DGS or DAC basically. The reflector may be "equivalent" to a disk shape, but it might be much bigger than it appears! Because the indication could be irregular, and would scatter the sound rather than a specular reflector. I know, yes... the amplitude based technique is a core assessment method but sometimes I doubt its reliability.
Yes, you are right. Amplitude-based techniques can be misleading. #1 The calibration needs to be performed accurately. #2 The check of the equipment needs to be done accurately (for example if the probe frequency is not the frequency stipulated by the manufacturer DGS can be off drastically). #3 Larger, angled, indications have a quite directed reflection. Therefore, if they are not perpendicular to the ultrasonic beam only a fraction of the beam is collected by the probe.
However, once we get to indications that are in the order of magnitude of the wavelength this angle dependency is quite minimal - also the structure of such small defects is quite insignificant (as this structure is way smaller than the wavelength it is not "seen" by UT. Meaning those indications can be sized quite accurately. And if all the other factors are also controlled you can achieve a surprisingly good sizing accuracy. And in case you wanna do better: th-cam.com/video/-dPkgov5E-M/w-d-xo.html
Dear Mr.Vrana, many thanks for this lesson. There are a lot of variables that affect DGS correct sizing. This is one Iwas not aware of.
You are very welcome
So you lectured about ultrasonic testing?
Not really - I am a consultant on UT and NDE 4.0