Optometric Methods for Testing Sections of Buckling

The article presents a study aimed to experimentally identify the correlation between the deflection arrow of a buckled flat bar and the magnitude of applied force P as well as to determine the value of critical force necessary for maintaining the equilibrium of the flat bar in its bent form. The study-related tests involved the use of a Gleeble 3800 metallurgical process simulator. Based on the data obtained in the tests and using Euler’s equation, it was possible to determine the transverse modulus of elasticity. An inductance-type extensometer (usually used in the Gleeble simulator) and a digital image correlation system (used in both the visible and ultraviolet light configuration) were applied to record changes in the length of the flat bar in time. The study also included the investigation of methods used when marking the surface of materials subjected to measurements involving the use of digital image correlation, i.e.:

• covering the surface with light-coloured paint and depositing the “speckled pattern”,
• deposition of the “speckled pattern” in the form of an impression using a microhardness tester,
• deposition of the “speckled pattern” in the form of a pattern burnt out by the laser beam on the specimen surface.