Intrinsic Errors on Sheet Strain Measurements Based on a Printed Square Grid

The paper studies the intrinsic errors on strain measurements induced by the application of an electrochemical etched square grid through serigraphy. Systematic periodic strains are observed when the etched grid is directly measured before any mechanical deformation. These apparent, non-zero strains are the errors induced by the imperfection of the applied grid. They determine the limiting precision of the measuring process. The errors are due to interference between the periodic square grid and an underlying periodic structure, the dot structure of the printer used for the original drawing of the grid or the periodic pitch of the serigraphic tissue and even both. Although they are small, they can suggest an unstable deformation, even at large strains. [S1087-1357(00)02004-9]