Week 13

Changes in conception...

Unfortunately, we made a cardinal mistake in our assumptions, so we can't compare the method of measurement of thickness using ultrasounds with classical caliper. But (thanks to our academic teacher) we fixed the procedure for measuring the attenuation factor. Now the results are satysfing. So the current list of tasks in our exercise consists a few points:

• determination of velocity of longitudinal and share waves (using different probes) in calibrating block
• determination of velocity of longitudinal wave (using different probes) in different samples
• determination of attenuation factor (using apropriate probe) in different samples

Next time we need to collect missing data (to be able to present some examples) and write the instructions.

Week 12

We determined the densities of several samples. It helped us to confirm that our results aren't similar to these taken from literature (attenuation factor, velocity of sound in material). But it doesn't prove that obtained values of eg. velocity of longitudinal wave are incorrect in general. We checked the calibration of probes using calibrating block. As it turned out, everything is set very well. As a conclusion we can say that some variances between values obtained from measurements and literature aren't similar but correct. We won't discuss this issue anymore. Now we need to focus on realizing the measurements of chosen physical quantities in different samples (thickness, velocity of sound) and checking that there's no further problems. We hope to be able to start writing instruction next week.

Week 11

Fortunately, this time everything went according to plan... but it doesn't mean that the results are satisfying. 

As it turned out, there's no difference between water and USG gel as a couplant. We supposed improved transfer of energy from the probe to the sample in case of using gel, but it doesn't happen. After testing couplants we spent most of the time trying to find the value of attenuation factor for different samples. The result are different than these published in literature (for aluminium and brass or copper). We decided to resign the measurement of mentioned physical quantity. Moreover, the problem of unidentified echoes is still open. We have assumpton that they come from the rear side of probe: the wave propagates through the probe, then it reflects, comes back and enters sample. As a result we observe fake bottom echo behind the correct one. But it's still unconfirmed.

After the consultation with academic teachers, we obtained some useful information concerning ultrasonic testing. Now we need to consider the possibility of producing additional samples with intentionally introduced flaws. It will give us a chance to expand the list of tasks for our exercise.

Week 10

Problems...
We wanted to add the measurement of sample thickness to the list of tasks in our exercise, but there are some difficulties with interpretation of data obtained from detector. For different probes and sample there are observable some unexpected echoes. They occur behind the echo from the bottom of the sample, so it's really confusing for us. We tried to figure out why they appear, but this problem is still unsolved.

Despite the facts described above, we confirmed the good correlation between sample thickness measured with caliper and ultrasonic detector (aluminium samples, normal probes, results based on bottom's echo and it's multiplicity). The plans for next week present as follows:

• considering the origin of 'strange' echos
• testing USG gel as the couplant (in compartion with water)
• measurements of attenuation factor (we need to prepare the external scale to determine the height of echoes because the original software has no this option)

Furthermore, we are invited for consultation with one of academic teachers, who will give us some advices and show samples with intentionally introduced flaws (it's possible to copy them in workshop).

Week 9

All ultrasonic probes are calibrated (except the one for surface waves). We also managed to do measurements of thickness for samples (probably) made out of aluminium. The results are encouraging. After comparing with data obtained by caliper, we found it as correct. The second measured thing was velocity of longitudinal waves. Our results are similar to the values taken from literature (only for ALU samples).

As you noticed, we got some delay according to scheme published two weeks ago. We hope to work more efficently next time.