The figure shows an aluminum bar of dimensions 30 millimeters by 24 millimeters  sandwiched between copper bars of dimensions 30 millimeters by 12 millimeters above and below it. The bars are held in place by pins on either end.

Next, consider the overall geometry of the assembly and how that geometry dictates the deformations that can occur.

Since the copper and aluminum bars are connected by pins, they must deform exactly the same amount. In terms of the deformations, this relationship can be stated as .

This equation is called the geometry of deformation equation.

Even though there are two copper bars, the deformation of each copper bar 1) must be exactly the same as deformation δ2 of the aluminum bar because of the presence of the pins.