Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
2 results
Search Results
Master Thesis The Investigation of the Dynamic Compression Characteristics of a Layered Glass System(01. Izmir Institute of Technology, 2023) Ağırdıcı, Burak; Taşdemirci, AlperLayered glass structures are one of the most common material types used in air, land, and sea vehicles. Since these structures are exposed to external impact loads, it is important to determine their dynamic mechanical behavior. In this study, dynamic compression characteristics of the layered glass system were investigated numerically using the LS-DYNA finite element program. The Johnson Holmquist Ceramics material model was used for the glass layer, the Ogden Rubber material model, which is used in material models with high elastic structural behavior was used for the polyvinyl butyral (PVB) interlayer, and the SAMP-1 material model was used for the polycarbonate interlayer. Numerical studies were carried out to investigate the stress wave propagation, the amount of energy released, and the deceleration rate of the penetration velocity. Split Hopkinson Pressure Bar setup was used to numerically load the layered glass systems at high strain rates for a reliably easy controlled wave generation. The layered glass structure consisting of two interlayer types with different thicknesses was loaded in the SHPB system, and the effect of the interlayer material type and thickness on the stress wave propagation was investigated. Then, the projectile impact test was modeled at different impact velocities for a square plate of PVB-layered glass structure. The thickness of the PVB interlayer was kept constant, while the thickness and location of the glass layer varied. From the results, the slowing rate of the projectile, the amount of erosion energy, and the energy balance were determined.Master Thesis The Effect of Strain Rate on the Dynamic Mechanical Behaviour of Concrete(Izmir Institute of Technology, 2018) Uysal, Çetin Erkam; Taşdemirci, Alper; Güden, MustafaThe fast-growing population of mankind has brought out household needs and working structures that might be subjected to static and dynamic loads. Impact loads and repetitive dynamic loads can produce an overload on the structures in a very short period that causes relentless casualties and unfortunate property losses. The response of the concrete material on strain rate increase is critical. The dynamic characterization of concrete, lack of adequate and consistent study causes disagreement about strain rate sensitivity of concrete, so a consensus has not been reached. In this study, quasi-static (3.55x10-5, 3.23x10-4, and 2.97x10-3 s-1) and high strain rate (140-250 s-1) tests were conducted and the effect of strain rate on the mechanical behavior of concrete was investigated both experimental and numerical. A modified Split Hopkinson Pressure Bar test setup was used, by using an EPDM (Ethylene Propylene Diene Monomers) rubber pulse shaper, non-oscillatory results and nearly constant strain rate were reached, and premature failure was prevented. Modeling the test setup was conducted in Ls-Dyna and the Holmquist-Johnson Cook material model parameters were found. A good agreement between experimental and numerical results was reached. The strength enhancements of concrete material, while increasing strain rate was noticed. Using both experimental and numerical studies, the total strength increase is due to inertia effect and strain rate sensitivity effects were observed.