Composite & Aero Materials (ENGF168) 

Virtual Tensile Testing Laboratory (beta)

Project leader and web-master: Dr. Fawad Inam

Specimen preparation prior to testing

By Hugh Shercliff, Joseph Robson, MATTER, released under CC BY-NC-ND 2.0 license

Before performing the test, specimens of a standard size and shape must be produced from the material to be tested. This animation shows how to prepare samples for the tensile test.

Schematics of the test

By Hugh Shercliff, Joseph Robson, MATTER, released under CC BY-NC-ND 2.0 license

The tensile test is the most commonly used method for quantifying some of the key mechanical properties of aluminium alloys. This animation shows the most important features of the tensile testing machine.

Testing of 99.5% aluminium

By MATTER, Andrew Green, released under CC BY-NC-ND 2.0 license

Commercial purity (CP) aluminium, such as EN AW-1050 has a low solute content and therefore relatively low strength when annealed. This can be increased to some extent by strain hardening. Note however that the rate of work hardening is quite low. In this animation, you can click on the white spots for TEM micrographs of the alloy at different strains.

Step by step testing of Al-5% Mg alloys

By MATTER, Andrew Green, released under CC BY-NC-ND 2.0 license

By introducing 5% Mg into solid solution, the proof stress, work hardening rate and thus Rm (UTS) can be significantly increased. From the stress-strain curve in this animation, it is clear that the effects of solid solution hardening and strain hardening are more than additive, as can be seen by comparing with the curve for 99.5% Al.

Testing of different alloys of aluminium

By Hugh Shercliff, Joseph Robson, MATTER, released under CC BY-NC-ND 2.0 license

The aim of a tensile test is to produce a plot of the stress vs strain response of the material being tested. This animation shows the stress-strain curves for different aluminium alloys.

Strain hardening during testing of aluminium materials

By MATTER, Andrew Green, released under CC BY-NC-ND 2.0 license

This interactive animation presents the basic principles of strain hardening in terms of a standard tensile test. A specimen of standard dimensions is subjected to a gardually increasing load (force) and the extension measured as a function of the force. In the animation these are converted to stress and strain and plotted graphically.

Effect of alloying in aluminium on work hardening rate

By MATTER, Andrew Green, released under CC BY-NC-ND 2.0 license

This interactive animation present stress-strain curves for both commercial purity and Mg-alloyed aluminium. In comparison with 99.5% Al, the Mg solute allows very little dynamic recovery at room temperature, thus preventing dislocation rearrangement into a cell structure. Of course, since recovery is a thermally activated process, a cell structure can be produced in Al - 5%Mg by deforming at a higher temperature, e.g. at 400 °C. In this animation you can click on the micrographs to enlarge.

Yielding across grains and dislocation pile up during tensile testing

By MATTER, Andrew Green, released under CC BY-NC-ND 2.0 license

This interactive animation shows how yielding across grains occurs under applied tensile stress s. The resolved shear stress t acts on dislocation source S1 in a favourably oriented grain 1. As s approaches the tensile yield stress sy, dislocations will pile up at grain boundaries. The pile-up in grain 1 exerts a intensified shear stress on the dislocation source S2 in grain 2. Grain 2 subsequently deforms plastically - general yielding throughout the sample then follows.

Effect of welds and holes on tensile strength of aluminium alloy

By MATTER, Frans Soetens, Torsten Höglund, released under CC BY-NC-ND 2.0 license

Local weakening like welds and bolt holes have of course influence on the strength of members in tension. For a member with a transverse but weld the strength is depending on the ultimate strength of the weld material itself but most often the ultimate strength in the heat-affected zone (HAZ) adjacent to the weld is governing. For members with holes, usually bolt holes, the ultimate strength in the section with the holes should be checked and also the tensile strength of the parent material. This example explains about the reduction of strength of members with welds and bolt holes and how to calculate the resistance.

Methods of measuring ductility

By Hugh Shercliff, Joseph Robson, MATTER, released under CC BY-NC-ND 2.0 license

Ductility is strictly defined as the ability of a material to be drawn into a wire. More generally, it is used to refer to the amount of plastic deformation a material can endure before failure. This animation presents two methods of measuring ductility.

Testing of carbon steels

By UKCME, released under CC BY-SA 2.0 license

This simulation has been designed to support the teaching of tensile testing of carbon steel. It can be used to demonstrate how tensile testing experiments are carried out to find out the effect of carbon content on the mechanical properties of steel. Stress/strain graphs have been created from real experimental data; values may be accurately taken from the graphs and be used to determine Young's Modulus. The graphs can be easily overlaid to help demonstrate the effect of the varying % carbon content.

Testing of a copper sample

By Roger White, Derrick Hurley, released under CC BY-NC-ND 2.0 license

This animation presents a tensile test on a copper sample (video).

Testing of polymers

By DoITPoMS, Dr J A Elliott, Nick Braddon, Stuart Fraser, released under CC BY-NC-SA 2.0 license

This animation presents an interactive idealised polymer stress-strain curve.

Test graph exercise

By Hugh Shercliff, Joseph Robson, MATTER, released under CC BY-NC-ND 2.0 license

And finally some questions to test what you have learnt so far...

Resources developed and funded by...