Studying of Volumetric Expansion and Uniaxial Stress-Strain Using Speckle

摘要

The paper presents a speckle photographic technique for studying the effect of both temperature and mechanical stress on a sheet of acrylic ( Poly Methyl Methacrylate ) . A temperature control system was used to heat the acrylic sheet with a homogeneous d istribution of temperature on the acrylic surface. Standard masses calibrated at NIS laboratory of mass were used to produce uniaxial stress on the acrylic sheet. The object sides were illuminated by diode laser and the speckle was recorded under both effe cts and then analyzed by the Fourier transformation. The correlated speckle patterns produce d Young's interference fringes which differ ed in numbers, separation, and orientation according to the applied effect. Both volumetric thermal expansion and modulu s of elasticity could be measured and were found to be in good agreement with the corresponding reference values of the object material . Theoretical analysis, method, and results are also presented. The results proved the reliability of the used technique for studying thermal and mechanical expansions of the acrylic material