Metal Technology: Testing mechanical properties of metals by stretching (1969)

The freight train travels by rail.

The rails on which the train goes.

Oil pump.

A crane in the shop.

Machine parts.

The behavior of metals during loads.

Metal structure.

A bursting machine.

Checking the part for a break.

Under the microscope, it can be seen that the grains in the metal structure are deformed in the direction of the tensile force.

At a certain amount of load, the part breaks.

To determine the mechanical properties of metal, special laboratories equipped with various bursting machines have been created at factories.

A cartoon explaining the operation of a bursting machine.

With the help of bursting machines, you can learn such important mechanical properties of metals as strength, elasticity, plasticity.

Samples of parts provided to the laboratory from production for testing.

For a specific test, a sample with a diameter of 8mm, a length of 40mm, a cross-sectional area of 50.2 mm2 is taken.

Testing of this part for rupture.

Part stretching diagram.

The vertical axis is the magnitude of the load.

On the horizontal axis - lengthening of the part.

The concept of ultimate strength.

The first part of the diagram shows the linear dependence of elongation on load.

We will remove the load, the size has been reduced to the previous size.

With a further increase in the load, the sample received a residual elongation.

The formula of the elastic limit.

In the first part of the test, the part received elastic changes.

The area of fluidity.

After going beyond the yield point, the material begins to resist deformation again.

When the strength limit is reached, local constrictions of the part - the neck - begin to form.

A cartoon explaining the plasticity of metal.

The formula of relative elongation.

During the test, the sample not only lengthened, but also became noticeably thinner.

The formula of relative narrowing.

The part was made of low-carbon steel.

Grey cast iron parts usually collapse suddenly.

The results of stretching tests are made available to designers, technologists or researchers.

The results of the study show the suitability of metal for creating new durable structures.