I use a dual-transducer configuration (emitter and reception), and I would like to estimate the response of a steel block that contains multiple scatterers (error echoes). I would like to get an estimate of the response of the block in the absence of defects. Note: I use pseudo-chirp excitation signals (pseudo-linear FM).
You must look on response spectral analyse,on resonance frequancy shift by variations of applicate(incoming) sounding signals amplitude. Mesurement of Vp and Vs and size of object allow calculate resonance frequancy of object in the absence of defects
I agree with Nora Vilchinska. It is necessary to choose frequency, when the wave length will be bigger than the size of scatterers. And the difference between wave length and scatterer size must be not very big. Nearest to scatterer size.
I think, more better to use "C-scan presentation" transducer, which can present better view (image) of the scanning object.
Thank you for all the answers. I am currently researching the typical methods that are used in this context.
We have Ultrasonic method with conventional devices and phased array devices.
In case we use a conventional device:
the most common technique (estimation method) is Pulse Echo technique.
This technique enables the inspector to have a detail depiction of the metalic structure with one probe. If we look weldings then we need definetely probes of 45 angle, 60 angle and 70 angle. We also need a zero( or 90) angle probe to inspect the metal base.
In all other cases we use only a zero( or 90) probe. We have to be
careful with the metal because each metal has a different velocity in longitudinal and transverse wave. For instance the aluminum has approximately 3.130 m/sec velocity in transverse wave but 6.230 m/sec velocity in longitudinal wave, when the steel has 3.250 m/sec velocity in transverse wave but 5.920 m/sec velocity in longitudinal wave.
If we are able to inspect only from one side of the sample, then we choose dual probes.
An other technique is named TOFD and we need two probes which are placed in a distance between them, but with this technique we can not have an estimation about the characteristics of a possible discontinuity.
Sincerely
N. Poulakis
Tech. Educ. Inst. of W. Macedonia, Kozani, Greece.
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