The impulse excitation technique (IET) is a smart and easy acoustic method to measure the Young's modulus and the shear modulus of materials. The IET method uses the sound emitted at the natural frequencies of an impacted piece of material.

In order to measure the elastic constants of your material, you must fill the following input : length, width, thickness and mass of your sample. In addition, you can choose a record duration. Note that a value between 3 and 5 seconds is a good value for duration. Finally, you can record the sound emitted by your sample by pressing the record button.

Now, you can go below to get more information about the specific setups for measuring the Young's modulus and/or the shear modulus.

Bending setup

In order to measure the Young's modulus, you need to prepare the following setup and choose the Bending option.

Your sample must have a parallelepiped shape with a small thickness. The two supports, placed in a parallel position, must be placed under the sample. You need to measure with a high precision the distance between the supports as it is shown on the figure above.

To produce the sound, you must hit the sample with a small hammer at the center of the sample. The microphone must be placed also at the center of the sample.

Torsion setup

In order to measure the shear modulus, you need to prepare the following setup and choose the Torsion option.

Your sample must have a parallelepiped shape with a small thickness. The two supports, placed in a cross position, must be placed under the sample. You need to measure with a high precision the distance between the supports as it is shown on the figure above.

To produce the sound, you must hit the sample with a small hammer at one of the corners of the sample. The microphone must be placed at the opposite corner of the sample.

Results

After recording the sound you have to wait few seconds. The results will appear below the form. These results are : the Young's modulus or the shear modulus (depending on your choice), a graph that shows the temporal signal of your sound and a graph that shows the spectral signal of your sound.

3D print your own apparatus

To get started, the supports can be simply two small cylinders. Plastic cylinders work well. If you want more elegant setup, you can 3D print these cad files. It gives the following apparatus.