Method, light extensometer and test item for defining transversal contraction without contact uses changes in gaps between reflective strips in a stress direction to calculate lengthwise expansion and transversal contraction.

摘要

A test item (6) with many reflective strips (8) set at a diagonal angle (7) to a surface of stress is scanned by a light extensometer (1) with two or more bundles of light rays (5). A computer analyses their reflective response (9). From changes in gaps between strips measured in a stress direction (4), local lengthwise expansion can be calculated with local transversal contraction from angle changes in the strips detected by displacement in parallel light bundles.