Characterization of Polymer Material in Dependence of High Strain Rate

V magistrskem delu smo s pomočjo vzvratnega inženiringa določali lastnosti polimera v odvisnosti od visokih hitrosti specifičnih deformacij. Vzorce smo izdelali s pomočjo injekcijskega brizganja, jih testirali z enoosnim nateznim preizkusom ter pnevmatskim streljanjem. Pri tem smo ugotovili, da se mehanske lastnosti med obremenitvijo spremenijo, tako smo potrdili domnevo o odvisnosti materiala od hitrosti specifične deformacije. Med simulacijskim delom smo s pomočjo parametrov Cowper-Symondsovega reološkega modela določili napetostno in deformacijsko stanje med obremenitvijo. Ugotovili smo, da je polipropilen pri konvencionalnih obremenitvenih stanjih mehak in žilav, medtem ko je pri visokih in hipnih obremenitvah kazal visoko trdoto in krhkost. Z uporabo Cowper-Symondsovega modela smo simulacijsko stanje uspešno približali preizkusom s pnevmatskim streljanjem, zaradi česar lahko zaupamo rezultatom napetostnega stanja iz simulacij. Pokazali smo obnašanje materiala v odvisnosti od hitrosti specifične deformacije v območju med 0,012 in 60 s-1.Using the method of reverse engineering the objective of this thesis was to analyse dependence of polymer material from high strain rate. The samples were made by injection moulding method and tested by uniaxial tensile tests and pneumatic steel ball shooting. It was found out that mechanical properties of material were changed due to load and this proved dependency from high strain rates. Cowper-Symonds material model was used for numerical investigation to determine stress and strain in material during used load. It was found out that using conventional methods, polypropylene shows soft and tenacious nature, but using high speed and high load material shows high toughness and fragility. Using Cowper-Symonds material model for the simulations the result between simulations and pneumatic tests were compared. It can be concluded that the stress-strain results obtained from simulation are reliable. Our method showed strain rate dependency in range from 0,012 to 60 s-1