Speaker
Description
We use the Moiré fringe patterns to measure the stress and strain values of rubber in tension, and analyze the stress-strain relationship. With the printed straight-line pattern on a standard dog-bone specimen, the Moiré patterns can be constructed when the rubber specimen is stretched. The geometrical relationship of bright and dark fringes is used to calculate the strain values both in the axial and transverse directions. Together with optical images for cross-section measurement, we can measure true stress and strain values, and determine the homogeneity of such values simultaneously. This true stress-strain relationship is different from the typical engineering stress-strain relationship in the sense that the latter is calculated from the fixed initial cross-section area of the specimen. When compared with the standard engineering measurement, the results from the Moiré method exhibit the same trends in the stress and strain values, and the stress-strain relationship is in good agreement in the linear elastic regime. More importantly, the Moiré method can provide direct measurement results of the true stress-strain relationship.
