WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
Browse
3 results
Search Results
Article Citation - WoS: 10Citation - Scopus: 11Finite Element Analysis of Low-Speed Oblique Impact Behavior of Adhesively Bonded Composite Single-Lap Joints(Springer, 2023-04-14) Atahan, M. Gokhan; Apalak, M. KemalThe development of a realistic numerical model that predicts the impact behavior of adhesively bonded composite joints is important for many industrial sectors such as automotive, aerospace, and marine. In this study, it was aimed to develop a numerical model that can predict the low-velocity oblique impact behavior of composite single-lap joints close to the experimental results. The validation of the proposed numerical model was carried out with the results of the previously experimentally tested joints. In explicit finite element analysis, the orthotropic material model and Hashin's damage criterion were used in the numerical model of composite adherends. The adhesive region was divided into three different regions. The cohesive zone model (CZM) was used to determine the damage initiation and propagation in the upper and lower interface regions of adhesive. The middle region of the adhesive between the two cohesive interfaces was modeled with an elastic-plastic material model to reflect the plastic material behavior of the adhesive in the analysis. The effects of impact angle, fiber orientation, and overlap length on adhesive damage initiation and propagation were investigated in detail. There is a good agreement between the numerical and experimental results, considering the contact force-time variations and composite and adhesive damage. The impact angle and fiber angle had a significant effect on the impact behavior of the composite joints and the adhesive damage initiation and propagation. The increase in impact angle and fiber angle caused a decrease in the maximum contact force value. Adhesive damage propagation patterns varied according to the composite fiber orientation. In addition, since the shear toughness of the adhesive is higher than its tensile toughness, the amount of adhesive damage and damage propagation rate decreased as the impact angle increased.Article Citation - WoS: 3Citation - Scopus: 5Elliptical Quantum Rings With Variable Heights and Under Spin-Orbit Interactions(MDPI, 2023-09-11) Mora-Ramos, Miguel E.; Vinasco, Juan A.; Radu, A.; Restrepo, Ricardo L.; Morales, Alvaro L.; Sahin, Mehmet; Duque, Carlos A.We investigate the electronic properties of a semiconductor quantum ring with an elliptical shape and non-uniform height, allowing for distributed quantum-dot-like bulges along its perimeter. The adiabatic approximation and the finite element method are combined to calculate the allowed electron states in the structure under the effective mass approximation, considering the contributions from Rashba and Dresselahaus spin-orbit interactions and the Zeeman effect in the presence of an applied magnetic field. We discuss the features of the calculated spectra for two different ring geometries: a symmetric one with four dot-like bulges, and an asymmetric one with three hilled protuberances. The information about those states allows us to evaluate the linear optical absorption response associated with interlevel transitions between the ground and lowest excited states. This phenomenon takes place at resonant energies of only a few milielectronvolts. It is observed that spin-orbit interactions tend to quench this response under zero-field conditions in the case of symmetric confinement.Article Citation - WoS: 23Citation - Scopus: 25Comprehensive Analysis of Experimental and Numerical Results of Bond Strength and Mechanical Properties of Fly Ash Based GPC and OPC Concrete(Elsevier Sci Ltd, 2024-02) Aslanbay, Yuksel Gul; Aslanbay, Huseyin Hilmi; Ozbayrak, Ahmet; Kucukgoncu, Hurmet; Atas, OguzhanNowadays, materials in the more environmentally friendly waste product class, which can be an alternative to standard Portland cement (OPC), are frequently used by researchers in concrete production. One of these, namely fly ash-based geopolymer concrete (GPC), should demonstrate its superiority over OPC in terms of chemical and mechanical properties to enhance its utilization. One of the mechanical properties of GPC is the bond strength between reinforcement and concrete. In this study, it was aimed to obtain bond strengths by performing tensile tests on GPC samples with varying sodium silicate/sodium hydroxide (SS/SH) and alkaline activator/fly ash (AA/FA) ratios. A pull-out experimental setup was prepared in accordance with RILEM Standard. Experimental results were compared with numerical results obtained from finite element models designed in ABAQUS software and were found to be compatible. When evaluated in terms of peak load and max bond stress values, GPC is superior to OPC. Compared to OPC an increase in the SS/SH ratio enhances mechanical properties such as compressive strength and bond load, whereas an increase in the AA/FA ratio with a value of 0.7 in the series has the opposite effect. In the finite element models, stress values are higher in samples with an AA/FA ratio of 0.5 compared to other ratios. An increase in the AA/FA ratio leads to a decrease in stress values. The analytical results are demonstrated that the proposed model can be utilized to assess the bond strength performance between traditional reinforced concrete and fly ash-based geopolymer concrete. Additionally, as a result of experimental studies, a formula that can be used to estimate bond strength based on GPC compressive strength and shows the superiority of GPC compared to studies in the literature has been proposed.