Geometry of Deformation Equation  
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The figure shows the brass link labeled 1 and the steel rod labeled 2. The reference datum is a vertical line passing through the left inside edge of the brass link. The brass link and the steel rod are elongated by delta subscript 2.

The link must be elongated a little bit more to fit the rod into the opening. This extra elongation is equal to the 0.2-mm misfit length of the rod.