Study of Rubber Blends by Electronic Speckle Pattern Interferometry

Nowadays, the optical methods for deformation measurement are gaining more and more applications from the aspect of solution of problems relating to elasticity and strength. The advantage of such methods is based on the measurement of non-destructive way without assembly of measuring elements regarding to the critical areas of structures. One of these contactless measuring methods is Electronic Speckle Pattern Interferometry ESPI that is based on the discovery of so-called speckle patterns. Electronic Speckle Pattern Interferometry is an optical full-field measurement method for determination of deformations of object surfaces with sensitivity below fractions of the wavelength of light. A back scattered object beam of an object surface and a reference beam, originating from the same laser light source, are superimposed on a video camera and interfere to a speckle pattern. Speckle pattern is based on the record before and after deformation of the object yield to a non-unique fringe pattern. Using a phase shifting method, this non-uniqueness can be solved and the fringe pattern can be evaluated using a computer algorithm. In this study, experimental investigation of vibration behaviour of square rubber blends plates by electronic speckle pattern interferometry (ESPI) is employed. Resonant frequencies and corresponding mode shape are obtained experimentally using the introduced method. Frequencies of resonant vibrational modes depend on elastic properties of material, especially on Young modulus E, Poisson ratio μ and density of material ρ. This fact gives us, in principle, the possibility to estimate the elastic constant of materials from the vibrational measurement. The numerical calculations by the finite element method (Cosmos) are performed and the results are compared to the experimental measurements.