Answer to "I guess it's not necessary to put the drag-indicator at 0, only below the expected final position? At another video where many tests were executed the testerperson just give it a swing back for each test...": Correct!

Answer to "Hi, could I use part of this video for my next video? It deals with the engineering of aircraft Panavia Tornado and I would give a short description of fatigue aspect. Thanks": Sorry, that's not allowed; we've had bad experiences. Good luck with your videos!

Answer to "I just started doing this at my job. Still fairly new to it. How would i know the difference between a legit deep crack and one that is more of a surface defect? Not sure if you guys will understand what im trying to say lol": This one of the problems of MPI, the depth of a crack cannot be measured reasonably.

Answer to "at 01:10, don’t forget that applying an alternating voltage is what creates an alternating current which will create an alternating magnetic field.": Perfectly explained, thanks!

Answer to "How to break a small sample out of a resin? if you have to perform hardness and you don't want the resin to effect the measurements, how shall I proceed to take out a sample from resin?": You do not need to remove the sample from the resin. Select a suitable test force for the Vickers hardness test (e.g. 1 or 0.1 kp) and carry out the test. Only clamp the resin properly, it should not move horizontally or tilt. A slight elastic yielding has no consequences, as the Vickers test is force-controlled. Good luck!

Answer to "I've been a metallurgist for over 40 years - 2% Nital would have been better than 10% . Also why not refer to the steels as 1054, 1080 etc.": Thank you! You are right about using 2% Nital. The etching time is longer, rinsing is easier, etc.. We used 10% Nital to speed up the etching time for the video. And we used the standardised European designations for the steels, simply because we live in Europe. Unfortunately, there are no international (ISO) steel designations yet.

Answer to "Surface area of the indentation surface, which is spherical, or the surface area of the indentation projected as a circle?" The Brinell hardness is defined as the test force (in kiloponds!) divided by the spherical indentation area (in square millimetres). The spatial area is therefore taken, not the projected area.

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Answer to "I have a sample to test. How can I connect with you?": This machine is intended to illustrate the principle of fatigue testing. We do not use it for commercial tests, sorry.

Answer to "Why are the surfaces in the tests you presented different? For example, in diamond the surface was small, but here it is large.": The diamond indenter for the Vickers hardness test is comparatively small. Consequently, the material to be tested must be fairly homogeneous and the surface roughness must be low. The ball indenter for the Brinell hardness test is comparatively large and the tested material may (to a certain extent) have a certain inhomogeneity and higher roughness. This is reflected in the surface quality of the test samples.

@@MaterialsScience2000 Thank you.

Answer to "Plz tell the precise time of etching": The etching time can vary greatly, from 2 seconds to several minutes, depending on the etchant and the material. In most cases, you have to try it out.

Answer to "Hello i saw there it shown both vertical and longitudinal defect . My question does ure machine can produce 2 type curent flow and magnetic/coil flow in 1 shot so u can found 2 direction of those defect? Thks from Indonesia": We have only used one magnetisation direction at a time in the video. Nevertheless, you can often see defects that extend almost in the direction of the magnetic field, because in most cases the magnetic field does not run exactly along the defects and therefore has a component perpendicular to the defects. A trick to show all defects is to use both types of magnetisation in quick succession.

Answer to "Can you have written practical notes": The idea of our videos is to show the practical procedure of some material testing methods. Sorry, no written notes are available. There are many textbooks on the market.

Answer to "How did the wave not spread and disperse?": The beam actually widens, diverges and disperses. The video is simplified and does not show this effect. However, there are probes on the market that can focus the ultrasonic wave to a certain degree. This results in less divergence of the wave and/or focusing.