Dual hologram interferometry

This report describes dual hologram interferometry, a new electro-optic technique used to calculate two-dimensional density distributions from measurable changes in index of refraction. Using this technique, two scenes recorded at different times are stored in separate holograms. One hologram contains reference data depicting the subject in an undisturbed state and the other hologram describes the same subject in a test or disturbed condition. Desired interference patterns are obtained by super-imposing the two separate scenes which are simultaneously reconstructed from each hologram. Specific interferograms, infinite fringe and various finite fringe patterns, are obtained by carefully regulating the optical attitude between the holograms and the reference beam during reconstruction of the scenes. In this project, dual hologram interferometry is used to describe quantitatively free convection from a uniformly heated right circular cylinder. Temperature distributions through the boundary layer and local heat transfer coefficients are determined at different azimuth positions. The results are compared both to experimental data obtained from another holographic technique and to a theoretical prediction of this specific test. This investigation shows that dual hologram interferometry accurately records changes in index of refraction which means the technique can be used to accurately measure experimental fluid flow data.     

Kaffee und Tee

Ohne Zusammenfassung     

Uniaxial deformation behavior of different polypropylene cast films at temperatures near the melting point

A new apparatus for stretching polypropylenes at elevated temperatures below the melting point at high deformation speeds (up to 750 mm/s) is described. In the temperature range of 140-160 °C the tensile behavior of polypropylene undergoes a shift from the ductile to the quasi-rubber-like deformation behavior. Furthermore, the deformation behavior is strongly affected by the strain rate. The homogeneity of sample deformation increases with the deformation rate. Furthermore, the influence of the cast film morphology on the uniaxial deformation behavior is investigated and discussed in terms of the degree of crystallinity and crystallite size. The degree of the residual crystallinity plays a decisive role for the deformation behavior. At similar degree of crystallinity, the yield stress is significantly influenced by the crystallite size in a way that the larger the crystallite size the higher the yield stress.     

Wein

Ohne Zusammenfassung     

Wein

Ohne Zusammenfassung