Question

Explain why barreling occurs in compression testing and what the remedy is for barreling

Answer 1

Barreling in the compression test occurs in specimen  as follow see the figure.

Notice here more thicker at centres and less thicknes at top and bottom.

This shape is simillar to barrel hence known as barreling effect.

See below figure.

Figure 1 is before compression.

Figure 2 is after compression,

we can clearly observe the barreling effect in figure 2.

Now

the main reason behind this effect is the frictional between dies and specimen.

The centres portions are almost free to expand due to fenite poision ratio of specimen with compression force .

But the top and bottom portions experiences friction and can not move or expand freely in lateral direction hence results in barreling of the specimen.

Now the Remedies for it is to use proper lubricant between specimen and dies of the testing machine.

So that edges can move freely in lateral direction.

Also having more smoother surface of the specimen touching the dies will help in reducing friction between specimen and dies hence barreling effect will get reduced.