So now back again.

Before Christmas we made a lecture on basic breaking mechanics.

Linear breaking mechanics, that was the last thing we did.

We did a little calculation on the topic.

We did a little calculation on where we could use something like this.

I think the most important takeaway message for linear breaking mechanics is that we have two main energy contributions.

One is the resistance R.

This is constant

or the energy we have to put in to create a length R.

This is linear with the length R, which means the resistance R is constant.

Or rather the amount of elastic energy we get by extending the break.

We have recorded this a few times.

This is the break.

It is a semi-circular, relatively good approach.

This means the volume we get by extending the break is delta A.

The break length was somewhere A.

This is linear.

This means the energy is square with the length.

This is square with the length.

This means that the break length A

C

is always critical.

From critical break length A

C

there will always be more and more progress.

This can be a very brittle material

a very small break length.

We can be in the micrometer area or even smaller.

With very ductile materials, this can be a very long break length.

It can be a meter.

And somewhere in between

this is usually the case for most materials.

This can also be tested if you come to Stuttgart.

There are actually test machines that can do up to 6 meganewtons.

6 million newtons.

The test machine is about 6x6 meters in size.

They built this machine and built a fracture mechanism for the core technology.

They had to do a sample with the meter diameter so that you could check critical break lengths.

We have moved a little further.

We can use the Griffith variant or the tension fields.

As shown here

there is always a value of the tension intensity K1

2 or 3.

Depending on whether the fracture opens like this, or like this.

In this case, it does not open, but moves.

This tension intensity factor K is basically what describes the state of the fracture.

We can calculate this only based on the tension

the length of the fracture and a geometry factor.

The geometry factor is dependent on the component geometry.

This means that there is typically a function from fracture length to component size.