This program is brought to you by the Oga-ma Seiki, a company that is familiar with the world's OS engines.
In 1911, the first small engine was released in Japan and it was exported to the United States. In 1913, the engine was developed.
In the next 40 years, they have been looking at the small engines and are walking on this road. The OS engine, which always leads the world of small engines.
The road of science, today we are in the research room of the Koube University Engineering Department.
Today, I would like to ask Professor Takao Nakagawa, the Production and Engineering Engineering major at Koube University.
Professor, I have heard that there is a fatigue in metals.
When you say fatigue, humans run, play, and work, and fatigue occurs.
There is fatigue in metals.
What does fatigue mean?
When a car is used for a long time, the metal starts to get tired and breaks.
When it is used for a long time, it is used to make a permanent deformation that does not return to its original state.
When it gets worse, it becomes a very small crack.
Then, it will break. Is there an accident?
There are many cases where the metal is broken by fatigue.
When you go to a big factory, you may find that there is a lot of fatigue.
When did you start to study the fatigue in metals?
It has been said that it started in 1840.
Who started it?
There is a man named Wehler in the railway department.
He was the designer of the train's suspension in 1852.
At that time, the shaft broke a lot.
He wanted to do a test.
He invented a rotating bending test machine.
Rotating bending test machine?
What is it?
This is a test where you rotate the test product, fix one side, and add force to the other side.
It is a test where you put weight on it.
That's why you studied it more and more.
What kind of force is fatigue?
Sometimes it breaks when you pull it at once.
What kind of fatigue is fatigue?
It is not that fatigue breaks in one go.
It is the power and time in this diagram.
When the power repeats and acts repeatedly, fatigue is destroyed after a long time.
In some cases, the cracks are connected and a large crack is formed.
As the crack becomes bigger, the remaining cross-section becomes smaller.
Finally, the last one, the only one, is not able to withstand the load.
What does it mean to pull it at once and then break it?
It is called a single-load pull.
What does it mean to pull it at once and then break it?
The vertical axis is the force.
The horizontal axis is the force.
The force and the length are directly related.
This is called the Foucault's law.
There is a limit to this. The limit is the force.
The force and the length are directly related.
However, this is a one-time process.
When the force repeats and acts repeatedly,
the force and the length are directly related.
The force and the length are directly related.
This area is the cause of the load.
This is what you mean by pulling at once.
If you pull at once, you get this cross-section.
This is what we have seen.
This is the test version of the test.
The test version will be disassembled here.
This is what we have seen.
The whole surface is very rough.
Another feature is that the area near the disassembly surface is very uneven.
The hole is visible.
So this is the test version.
This is the test version of the test.
This is the test version to disassemble the machine.
This is the test version of the test.
How many times will this be disassembled?
Depending on the size of the machine,
it will be necessary to repeat the process 10 million times.
I would like you to repeat this process.
We have done this for a short time.
This is the result of the test.
What else is there?
This is the twist and bending.
This is the result of the test.
This is the test version of the test.
These three are the test version of the test.
This is the twist and bending.
The disassembled surface is here and here.
This is the twist and bending.
The parts that are rough and smooth are here.
This is a very strong force.
The cracks are clearly visible near the broken surface.
This is the crack.
This crack is caused by the force of the force.
If the force is weak, the crack will break.
It will break in one place.
The surface is rough and smooth.
It is dangerous because there is fatigue in the machine.
What should we do to prevent fatigue?
There are two main reasons.
One is that fatigue is easy to cause by concentrating.
The part that is hard to concentrate on, the part that has a crack, or the part that has a hole, is the first reason.
The other reason is that...
We should not make such a thing from the beginning.
The other reason is that when designing, we have to decide the shape.
We have to make it in a way that is easy to concentrate on.
We have to make a hole.
When we do this kind of research, when designing a machine,
we can say that this part is the part that can withstand such a big force.
We have to test it over and over again to see if we need something bigger for fatigue.
If we make a mistake, an accident will occur.
We have to test it over and over again to see if we can withstand such a big force.
If we use the material to design, we can say that we can handle it.
Today we talked about fatigue in metals.
Thank you very much.
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