Answer to: "Is there a material that actually stops the hammer from swinging back up?" Yes, there is, in any case for our test machine. And quite interestingly, it is not only a "strong" material in the sense of strength (or stress), but a material of very good ductility. Among the best in the Charpy impact test are fine-grained very low carbon steels, and they may absorb much more than 300 Joules. But a more powerful impact test machine will do for any material. Sorry for the late reply.
And in the case where such a sample stops the hammer you can shortly after hear the technician curse it (at least the ones that really care and value their machines)
hey i have a question, even though its 8 years later ahah. how do you decide how deep the notch must be? is this decided by standardisation? sorry not english so i maybe misunderstood. thank you for the video!
Answer to "hey i have a question, even though its 8 years later ahah. how do you decide how deep the notch must be? is this decided by standardisation? sorry not english so i maybe misunderstood. thank you for the video!": Yes, it is specified by standardisation. Many decades ago, various types and depths of notches were extensively tested, and the type of notch shown (V-notch, 2 mm depth) has proven to be the best for typical ferritic steels.
Funny story. So our "old decrepet" instructor (ha, he was probably 50!) is showing us this and we wanted to try different materials. We asked about Lead. So he put a Lead sample in it, and the dial barely got moved! So someone asks what if we heated it up? One guy had a lighter, and we heated it up to probably well over 200F. Everybody wanted to get a close look, so we all crowded around it, some on our knees. The hammer swung down and . . . it stopped!!! BUT the whole test unit moved violently about six inches!!! We all jumped back and our eyes were all soooo wide open!!! And we came in the next evening and . . . the maintenance guys had bolted it to the floor!!! Funny as heck, but wow did we learn a LOT about experimental variables and unexpected results!
Apart from the function of the "counter bearing" not being fully explained (something had to happen for the hammer to continue its swing) the presentation was well done.
If there's a lecturer or a teacher here, please try the human experiment of this test. I can assure you that it would really leave an impact on the students, especially on male students, even more so if you let them do the test on their own by using their own bodies. They won't ever forget the lesson they've learned. Why? Because "no pain, no gain"
Viewing this very informative article several years after posting...I hope some improvements have been made for PPE for testing staff in the ensuing years. Otherwise very well made and described.
Answer to "Viewing this very informative article several years after posting...I hope some improvements have been made for PPE for testing staff in the ensuing years. Otherwise very well made and described.": As regards PPE, a lot has changed in recent years. New machines all have their own transparent housing as a standard for industrial use. Nevertheless, in laboratories (such as our own), under certain conditions, the procedure shown in the video is still allowed.
The explanation on Wikipedia: "The test is similar to the Charpy impact test but uses a different arrangement of the specimen under test. The Izod impact test differs from the Charpy impact test in that the sample is held in a cantilevered beam configuration as opposed to a three-point bending configuration."
The difference is that the pendulum is different, the sample bar size is the same, and the way of placement is also different, the opening direction of the notch is different, so the fracture mode is different too, the energy loss is different, the Charpy impact tester's flying power is small, it is suitable for the products with low impact strength.The fly - out power of Izod impact tester is large and suitable for ductile materials. And the samples are placed in different ways, izod places vertically and Charpy places horizontally.
By your Replaying the question "Q: Is there a material that actually stops the hammer from swinging back up? " Does that mean very low carbon steel is the toughest metal ?if it's not .what's the toughest metal and his absorbed energy ?
Great video. Very well put together and nice, concise and clear explanations of the science. Would you be able to do a similar video for the drop weight tear test (which is also used to provide fracture appearance results)? Vielen Dank :)
+tanmay thakkar You put the iPhone in place of the specimen (don't forget to notch it properly), and proceed as usual. The kinetic energy is transferred directly into the battery (and some into the rest of the phone, too).
Hi, nice educating video. If we were to test a S275J0H 100x100x5.00mm Square Tube for impact test at 0C and if the impact test result was 22-23Joules. According to your experience, what would be the very same Square Tubes' impact test result if we tested same tube at room temperature rather than 0C . Can you comment on this ?
It seems to me that with ever increasing specification and increasingly finer tolerances being embodied in even more ambitious design and construction this test, with its significant human input in calibration, is crude and no longer fit for purpose. Case in point : in the step 1 initial drag indicator setting, the needle isn't quite set at the mark. Later, the needle is not to be found at the zero mark, as expected but is a fraction greater. This might be caused by the operator looking at the gauge from a side angle instead of looking at it face on. What then is the size of the discrepancy? And is this discrepancy enough to influence the accuracy of the test results?
Answer to "It seems to me ... accuracy of the test results?": In a few words: The general principle of testing is perfectly OK, and the test is being applied more than ever. As regards the calibration: The initial setting of the indicator (before the test) is without consequences, but the indicator must reach mark zero in a test without specimen. This was not done quite perfectly in the video; the video wants to show the principle of testing.
@@MaterialsScience2000 A fair enough comment. Those involved in the making of the video SHOULD have had the experiment carried out as required in the detail. Images speak louder than words. Not to have done so would inevitably give rise to speculation that sloppy actual testing might have played a part in subsequent events.
Answer to "This is ancient technology." Similar comments sometimes come from my students. To admit, this looks like ancient technology. However, it is used very often, and I myself am astonished to see, how many new testing machines are manufactured at the moment ...
Answer to "For some reason, I always thought that it is pronounced sharpy and only written Charpy. In any case, that is what they taught us.": Thanks, yes, "sharpy" is the correct (French) pronunciation, because Charpy was a French engineer and scientist. In English it is often pronounced in the way we have done it.
The test specimen is prepared according to which standard? If we want to carry out impact test, how many such test specimens we need, is it a single value reading test or multiple value avg should be taken? At what temp the test should be carried out? (In some cases -30 deg Celsius or room temp is maintained)
Answer to "The test specimen is prepared according to which standard? If we want to carry out impact test, how many such test specimens we need, is it a single value reading test or multiple value avg should be taken? At what temp the test should be carried out? (In some cases -30 deg Celsius or room temp is maintained)": The standard is ISO 148, the number of the specimens may vary according to circumstances and accuracy requirements, 1 to 3 at a given temperature are typical. The specimen temperature can (and must) be varied depending on the temperature, at which the material will be used in practise, a typical range is -200 °C to +100 °C.
Answer to "if required by the client, should the test be done on each 6/12m raw material before fabrication?" In the extreme case, yes. When the safety requirements are very high, this is actually done, sometimes even with several test specimens from one single piece of raw material. Of course, this is very expensive. There are a number of reasonable compromises between not testing at all and testing each single piece of raw material. A very interesting question …
Answer to "It's 2020 and I find this useful. Is the Video clip open source, in case I want to use for a presentation?": The video runs under the standard TH-cam license. So no download allowed. However, you can always set up a direct online link to the video during your presentation. Good luck for your presentation!
Answer to "Why is there two methods for impact testing- charpy and Izod impact test. Which is preferred?" Both methods test very similar properties. When testing metallic materials, especially steels, the Charpy notched bar impact test is much more common, which can also be seen in the corresponding industry standards. But why are both test methods still used in parallel .... good question.
Answer to "The guy puts the sample with the weight up... he is not afraid of losing his fingers": It looks dangerous, but the pendulum of our machine is securely fastened and can only be released with two different actions of both hands at the same time.
There are normalised measurements for this. If you type "minimum thickness of v notch charpy" in to google and go to images you will find a detailed overview. Please note that de V-notch should be made with the proper tools because it is normalised as well.
What are impact test results usually measure in, when I google I see J/m3, J/m2 & J/m. I assume this maybe relates to some distance, cross sectional area or volume of the deformed specimen ???
+Richard Walker Answer to "What are impact test results usually measure in, when I google I see J/m3, J/m2 & J/m. I assume this maybe relates to some distance, cross sectional area or volume of the deformed specimen ???" Typically only the energy is measured, so the result is given in Joule. Formerly the result was also given in J/cm^2; the energy was divided by the (smallest) cross sectional area.
Answer to "what about hcp?": Some people state, that materials with hcp structure also show an S-shaped KV vs T curve with upper and lower shelf region. Interestingly, I could not find any reliable data on typical materials with hcp structure, such as magnesium or titanium.
Why don't people use shipping container modified tanks to store solar energy? For example, automating concentrated solar thermal power to pump water from the low tank to the high tank during sunny day and release water to drive electric generator and back to the low tank during the night. You can search "Burning Stuff With 2000ºF Solar Power!!" "shipping container pool diy" and GREENPOWERSCIENCE for a lot of examples. Actually, potential energy of the tank themselves can also be used for generating electricity already. Of course, you need to use a lot pulleys or hydraulic jacks for that.
Answer to "What is the more failur in impact tesy :specimen with a V notch or specimen with a U notch ??? Plz I need answer": The V-notch is the "more severe" notch, resulting in lower absorbed energies and a higher transition temperature. In comparison, the U-notch is milder, resulting in higher impact energies and lower transition temperatures.
Do you know how can I make one? I need to make one for my school and we need a bit of help. It could really help us if you could help us, such as giving as the blueprints... Thank you
Answer to "Do you know how can I make one? I need to make one for my school and we need a bit of help. It could really help us if you could help us, such as giving as the blueprints...Thank you" Sorry, we have no blueprints, this actually is a comparatively old machine, refurbished. If I were you, I would try to buy a used one on the second hand market - they are good value for the money. If this does not work, please buy the appropriate technical standard ISO 148. There you can find all relevant data to build one on your own.
Answer to "Safety glasses ??": Principally always a good idea! Yet, the main problems are "flying samples" and personal injuries. Therefore, all modern machines for industrial use all have their own transparent housing. Nevertheless, in laboratories the procedure shown in the video is (under certain conditions) still allowed. We have never had a problem, but safety is always top priority.
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...
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!
Well to provide for a localised stress concentration. While no doubt the material will fail under test conditions, the notch is provided primarily for two reasons. 1, to provide for accuracy, and 2, to ensure that the material fails at an exact point. Hope this answers your question
Answer to "Why noch is necessary while performing the test??" The main reason (when testing steels) is the creation of a three-dimensional stress state below the notch. This hinders the plastic deformation. Materials that are not very tough (like some polymers) are tested with a non-notched sample.
This is the best charpy testing demonstration and narration that I have seen so far. Thanks for producing this video.
Fresse
Answer to: "Is there a material that actually stops the hammer from swinging back up?"
Yes, there is, in any case for our test machine. And quite interestingly, it is not only a "strong" material in the sense of strength (or stress), but a material of very good ductility. Among the best in the Charpy impact test are fine-grained very low carbon steels, and they may absorb much more than 300 Joules. But a more powerful impact test machine will do for any material. Sorry for the late reply.
And in the case where such a sample stops the hammer you can shortly after hear the technician curse it (at least the ones that really care and value their machines)
hey i have a question, even though its 8 years later ahah. how do you decide how deep the notch must be? is this decided by standardisation? sorry not english so i maybe misunderstood. thank you for the video!
Answer to "hey i have a question, even though its 8 years later ahah. how do you decide how deep the notch must be? is this decided by standardisation? sorry not english so i maybe misunderstood. thank you for the video!": Yes, it is specified by standardisation. Many decades ago, various types and depths of notches were extensively tested, and the type of notch shown (V-notch, 2 mm depth) has proven to be the best for typical ferritic steels.
@@MaterialsScience2000 thanks for the awnser! Good video
@@MaterialsScience2000 cheers, used this video for my school engineering assignment as reference
thanks for the informative video. our lecturer never gave us a real life demonstration of the Charpy test, and this helps alot
Did your lecturer do it in Grand Blue Style?
Best explanation and demonstration of the Destructive testing, V-notch Charpy Impact test.
Grand blue?
we did this expt today itself....took only 3 minutes ..loved it..simple concept...and nyc demo...keep it up
Grand Blue manga brought me here. Thank you.
You're not the only one.
ke kosa
I'm here because of it as well
Me2 no balls crushed here
Same
Funny story. So our "old decrepet" instructor (ha, he was probably 50!) is showing us this and we wanted to try different materials. We asked about Lead. So he put a Lead sample in it, and the dial barely got moved! So someone asks what if we heated it up? One guy had a lighter, and we heated it up to probably well over 200F. Everybody wanted to get a close look, so we all crowded around it, some on our knees. The hammer swung down and . . . it stopped!!! BUT the whole test unit moved violently about six inches!!! We all jumped back and our eyes were all soooo wide open!!! And we came in the next evening and . . . the maintenance guys had bolted it to the floor!!! Funny as heck, but wow did we learn a LOT about experimental variables and unexpected results!
Grandblue brought me here
Excellent video. Great brief tutorial on what Charpy Impact Testing is.
Very useful for the technical translation I am working on, concerning a failure that occurred in a gas pipeline. Thank you!
Wow. I've heard stories of metal tools shattering in Antarctica like glass... Now I know why. Thank you.
Only the man with the crotch of steel can pull this test, Grand Blue style, without flinching
I see you are a man culture as well
Man of culture
Let me guess, you have done this? I am only learning about it in a textbook for my welding ticket
Apart from the function of the "counter bearing" not being fully explained (something had to happen for the hammer to continue its swing) the presentation was well done.
An incredibly detailed and helpful video. Thank you so much!
soo simple, but whoever thought of this test is just brilliant
Best learning one for Charpy Impact Testing. Thank you!
then you should read the grand blue manga. It is better there than here
A certain Diving Manga brought me here 🤣
Very helpful video. Filled with detailed information. Thanks a lot for sharing this.
If there's a lecturer or a teacher here, please try the human experiment of this test. I can assure you that it would really leave an impact on the students, especially on male students, even more so if you let them do the test on their own by using their own bodies. They won't ever forget the lesson they've learned.
Why? Because "no pain, no gain"
I just love your videos. They help me a lot to have better understanding of some processes I've just read about.
Thank you for the video. The picture in my textbook is not really clear, this video really helps to clarify it.
Viewing this very informative article several years after posting...I hope some improvements have been made for PPE for testing staff in the ensuing years. Otherwise very well made and described.
Answer to "Viewing this very informative article several years after posting...I hope some improvements have been made for PPE for testing staff in the ensuing years. Otherwise very well made and described.": As regards PPE, a lot has changed in recent years. New machines all have their own transparent housing as a standard for industrial use. Nevertheless, in laboratories (such as our own), under certain conditions, the procedure shown in the video is still allowed.
This needs more likes! Very nice video.
Fun fact: the angle, the velocity and the impact force of the pendulum can be alterated depends on the weight of the pendulum’s material
El video del ensayo es muy ilustrativo lo usaré en mis clases
Lo vi en el manga de Grand Blue y me pareció interesante xdd
This organization spread the knowledge in simple, but well thought. Thanks for contribution to the society...
Great demonstration and explanation!
Hi i really interesting with your vedio, i put your vedio with ss in my assingment collage 👍… It really nice
great work....fully explained in a decent way...........
u guys are awesome science warriors ty for your efforts
Well done. Great explanation.
Amazing explanation
Can you please tell how the setup of izod test is different from charpy test?
The explanation on Wikipedia: "The test is similar to the Charpy impact test but uses a different arrangement of the specimen under test. The Izod impact test differs from the Charpy impact test in that the sample is held in a cantilevered beam configuration as opposed to a three-point bending configuration."
The difference is that the pendulum is different, the sample bar size is the same, and the way of placement is also different, the opening direction of the notch is different, so the fracture mode is different too, the energy loss is different, the Charpy impact tester's flying power is small, it is suitable for the products with low impact strength.The fly - out power of Izod impact tester is large and suitable for ductile materials. And the samples are placed in different ways, izod places vertically and Charpy places horizontally.
By your Replaying the question "Q: Is there a material that actually stops the hammer from swinging back up? " Does that mean very low carbon steel is the toughest metal ?if it's not .what's the toughest metal and his absorbed energy ?
sick sweater bro
Thanks for Unloading.. U have given brief info ..nice ..
Keep going, What a fabulous!
Answer is 101 degrees
Nice video, thanks for the explanation.
very informative and precise
Great video. Very well put together and nice, concise and clear explanations of the science.
Would you be able to do a similar video for the drop weight tear test (which is also used to provide fracture appearance results)?
Vielen Dank :)
Sorry, we do not own a drop weight tear testing machine, and the video production is a lot of work, so we concentrate on the most popular topics.
Excelente explicación. Gracias y Saludos
Very impressive
This video is excellent. Thank you.
Really informative.. Thanks
dankeschön das video ist echt hammer!
That is so cool thank you for sharing this information
One crazy weird trick - this machine can also be used to charge your iPhone.
They call it CharpyCharging.
+Godfrey Poon how?
+tanmay thakkar You put the iPhone in place of the specimen (don't forget to notch it properly), and proceed as usual. The kinetic energy is transferred directly into the battery (and some into the rest of the phone, too).
+Godfrey Poon He's joking everyone... don't do this to your phone
+Godfrey Poon I tried it, it works! Thank man
The saddest thing of all is that you had to warn people that he was joking.
Thank you very much. It was really useful and helped me alot.
perfectly explained
Muito top o vídeo pois faz todo o sentido.
Great video!
Very good
Thanks Mam ,,,, keep the written title on the screen
Excellent video! Thank you!
Appreciated. Helpful, thank you.
Hi, nice educating video.
If we were to test a S275J0H 100x100x5.00mm Square Tube for impact test at 0C and if the impact test result was 22-23Joules.
According to your experience, what would be the very same Square Tubes' impact test result if we tested same tube at room temperature rather than 0C .
Can you comment on this ?
nice and clear. thanks
Amazing
well done
It seems to me that with ever increasing specification and increasingly finer tolerances being embodied in even more ambitious design and construction this test, with its significant human input in calibration, is crude and no longer fit for purpose. Case in point : in the step 1 initial drag indicator setting, the needle isn't quite set at the mark. Later, the needle is not to be found at the zero mark, as expected but is a fraction greater. This might be caused by the operator looking at the gauge from a side angle instead of looking at it face on. What then is the size of the discrepancy? And is this discrepancy enough to influence the accuracy of the test results?
Answer to "It seems to me ... accuracy of the test results?": In a few words: The general principle of testing is perfectly OK, and the test is being applied more than ever. As regards the calibration: The initial setting of the indicator (before the test) is without consequences, but the indicator must reach mark zero in a test without specimen. This was not done quite perfectly in the video; the video wants to show the principle of testing.
@@MaterialsScience2000 A fair enough comment. Those involved in the making of the video SHOULD have had the experiment carried out as required in the detail. Images speak louder than words. Not to have done so would inevitably give rise to speculation that sloppy actual testing might have played a part in subsequent events.
This is ancient technology.
Answer to "This is ancient technology." Similar comments sometimes come from my students. To admit, this looks like ancient technology. However, it is used very often, and I myself am astonished to see, how many new testing machines are manufactured at the moment ...
Grasias cosme exelente video
Hi, does MaterialScience2000 have a similar video for and Izod impact test.
Answer to "Hi, does MaterialScience2000 have a similar video for and Izod impact test.": Sorry, no, we have concentrated on the Charpy impact test.
Good video
very nice
Thanks so much for Impact test
For some reason, I always thought that it is pronounced sharpy and only written Charpy. In any case, that is what they taught us.
Answer to "For some reason, I always thought that it is pronounced sharpy and only written Charpy. In any case, that is what they taught us.": Thanks, yes, "sharpy" is the correct (French) pronunciation, because Charpy was a French engineer and scientist. In English it is often pronounced in the way we have done it.
I come here after reading grand blue
The test specimen is prepared according to which standard? If we want to carry out impact test, how many such test specimens we need, is it a single value reading test or multiple value avg should be taken? At what temp the test should be carried out? (In some cases -30 deg Celsius or room temp is maintained)
Answer to "The test specimen is prepared according to which standard? If we want to carry out impact test, how many such test specimens we need, is it a single value reading test or multiple value avg should be taken? At what temp the test should be carried out? (In some cases -30 deg Celsius or room temp is maintained)": The standard is ISO 148, the number of the specimens may vary according to circumstances and accuracy requirements, 1 to 3 at a given temperature are typical. The specimen temperature can (and must) be varied depending on the temperature, at which the material will be used in practise, a typical range is -200 °C to +100 °C.
Could u provide cyclic testing of beam column joints
Amazing vid
Can I test small beam specimen with this impact tester? Is it possible to place the small beam somewhere after the position of specimen position?
if required by the client, should the test be done on each 6/12m raw material before fabrication?
Answer to "if required by the client, should the test be done on each 6/12m raw material before fabrication?" In the extreme case, yes. When the safety requirements are very high, this is actually done, sometimes even with several test specimens from one single piece of raw material. Of course, this is very expensive. There are a number of reasonable compromises between not testing at all and testing each single piece of raw material. A very interesting question …
Thank you for this video!
It's 2020 and I find this useful.
Is the Video clip open source, in case I want to use for a presentation?
Answer to "It's 2020 and I find this useful. Is the Video clip open source, in case I want to use for a presentation?": The video runs under the standard TH-cam license. So no download allowed. However, you can always set up a direct online link to the video during your presentation. Good luck for your presentation!
@@MaterialsScience2000 Thank you so much, I appreciate it.
THANKS FOR VIDEO
well done,
Why is there two methods for impact testing- charpy and Izod impact test. Which is preferred?
Answer to "Why is there two methods for impact testing- charpy and Izod impact test. Which is preferred?" Both methods test very similar properties. When testing metallic materials, especially steels, the Charpy notched bar impact test is much more common, which can also be seen in the corresponding industry standards. But why are both test methods still used in parallel .... good question.
@@MaterialsScience2000 is it possible that test specimen will pass in one method and fail in the other.
Thanks very much
i wonder how much my finger would absorb
The guy puts the sample with the weight up... he is not afraid of losing his fingers
Answer to "The guy puts the sample with the weight up... he is not afraid of losing his fingers": It looks dangerous, but the pendulum of our machine is securely fastened and can only be released with two different actions of both hands at the same time.
What is the minimum thickness of test specimen required for V notch test.
There are normalised measurements for this. If you type "minimum thickness of v notch charpy" in to google and go to images you will find a detailed overview. Please note that de V-notch should be made with the proper tools because it is normalised as well.
How is the V-Notch produced in specimen? And V-Notch only?
it is made by notch cutter. Both V-notch and U notch can be made.
excuse me sir i want to ask Does the indicator of the impact test kit sell? If there is, please let me know
What are impact test results usually measure in, when I google I see J/m3, J/m2 & J/m. I assume this maybe relates to some distance, cross sectional area or volume of the deformed specimen ???
+Richard Walker Answer to "What are impact test results usually measure in, when I google I see J/m3, J/m2 & J/m. I assume this maybe relates to some distance, cross sectional area or volume of the deformed specimen ???" Typically only the energy is measured, so the result is given in Joule. Formerly the result was also given in J/cm^2; the energy was divided by the (smallest) cross sectional area.
Bro also make a video on izod test
Great
what about hcp?
Answer to "what about hcp?": Some people state, that materials with hcp structure also show an S-shaped KV vs T curve with upper and lower shelf region. Interestingly, I could not find any reliable data on typical materials with hcp structure, such as magnesium or titanium.
Pac-man knows it all!
Why don't people use shipping container modified tanks to store solar energy? For example, automating concentrated solar thermal power to pump water from the low tank to the high tank during sunny day and release water to drive electric generator and back to the low tank during the night.
You can search "Burning Stuff With 2000ºF Solar Power!!" "shipping container pool diy" and GREENPOWERSCIENCE for a lot of examples.
Actually, potential energy of the tank themselves can also be used for generating electricity already. Of course, you need to use a lot pulleys or hydraulic jacks for that.
What is the more failur in impact tesy :specimen with a V notch or specimen with a U notch ??? Plz I need answer
Answer to "What is the more failur in impact tesy :specimen with a V notch or specimen with a U notch ??? Plz I need answer": The V-notch is the "more severe" notch, resulting in lower absorbed energies and a higher transition temperature. In comparison, the U-notch is milder, resulting in higher impact energies and lower transition temperatures.
what's the name of this machine ,where can i found information about its specification
It is a Charpy impact testing machine, there are several manufacturers; an internet search will find them.
شكرا
Do you know how can I make one? I need to make one for my school and we need a bit of help. It could really help us if you could help us, such as giving as the blueprints...
Thank you
Answer to "Do you know how can I make one? I need to make one for my school and we need a bit of help. It could really help us if you could help us, such as giving as the blueprints...Thank you" Sorry, we have no blueprints, this actually is a comparatively old machine, refurbished. If I were you, I would try to buy a used one on the second hand market - they are good value for the money. If this does not work, please buy the appropriate technical standard ISO 148. There you can find all relevant data to build one on your own.
Safety glasses ??
Answer to "Safety glasses ??": Principally always a good idea! Yet, the main problems are "flying samples" and personal injuries. Therefore, all modern machines for industrial use all have their own transparent housing. Nevertheless, in laboratories the procedure shown in the video is (under certain conditions) still allowed. We have never had a problem, but safety is always top priority.
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...
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!
Why noch is necessary while performing the test??
Well to provide for a localised stress concentration. While no doubt the material will fail under test conditions, the notch is provided primarily for two reasons. 1, to provide for accuracy, and 2, to ensure that the material fails at an exact point. Hope this answers your question
Answer to "Why noch is necessary while performing the test??" The main reason (when testing steels) is the creation of a three-dimensional stress state below the notch. This hinders the plastic deformation. Materials that are not very tough (like some polymers) are tested with a non-notched sample.