WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 23Citation - Scopus: 24Determination of the Material Model and Damage Parameters of a Carbon Fiber Reinforced Laminated Epoxy Composite for High Strain Rate Planar Compression(Elsevier Ltd., 2021) Shi, C.; Guo, B.; Sarıkaya, Mustafa; Çelik, Muhammet; Chen, P.; Güden, MustafaThe progressive failure of a 0°/90° laminated carbon fiber reinforced epoxy composite was modeled in LS-DYNA using the MAT_162 material model, including the strain rate, damage progression and anisotropy effects. In addition to conventional standard and non-standard tests, double-shear and Brazilian tests were applied to determine the through-thickness shear modulus and the through-thickness tensile strength of the composite, respectively. The modulus reduction and strain softening for shear and delamination parameters were calibrated by low velocity drop-weight impact tests. The rate sensitivities of the modulus and strength of in-plane and through-thickness direction were determined by the compression tests at quasi-static and high strain rates. The fidelity of the determined model parameters was finally verified in the in-plane and through-thickness direction by the 3D numerical models of the Split Hopkinson Pressure Bar compression tests. The numerical bar stresses and damage progressions modes showed acceptable correlations with those of the experiments in both directions. The composite failed both numerically and experimentally by the fiber buckling induced fiber-matrix axial splitting in the in-plane and the matrix shear fracture in the through-thickness direction. © 2020Article Citation - WoS: 19Citation - Scopus: 21Dynamic Crushing Behavior of a Multilayer Thin-Walled Aluminum Corrugated Core: the Effect of Velocity and Imperfection(Elsevier Ltd., 2018) Sarıyaka, Mustafa; Taşdemirci, Alper; Güden, MustafaThe crushing behavior of a multilayer 1050 H14 aluminum corrugated core was investigated both experimentally and numerically (LS-Dyna) using the perfect and imperfect models between 0.0048 and 90 m s−1. The dynamic compression and direct impact tests were performed in a compression type and a modified Split Hopkinson Pressure Bar set-up, respectively. The investigated fully imperfect model of the corrugated core sample represented the homogenous distribution of imperfection, while the two-layer imperfect model the localized imperfection. The corrugated core experimentally deformed by a quasi-static homogenous mode between 0.0048 and 22 m s−1, a transition mode between 22 and 60 m s−1 and a shock mode at 90 m s−1. Numerical results have shown that the stress-time profile and the layer crushing mode of the homogeneous and transition mode were well predicted by the two-layer imperfect model, while the stress-time profile and the layer crushing mode were well approximated by the fully imperfect model. The fully imperfect model resulted in complete sequential layer crushing at 75 and 90 m s−1, respectively. The imperfect layers in the shock mode only affected the distal end stresses, while all models implemented resulted in similar impact end stresses. The distal end initial crushing stress increased with increasing velocity until about 22 m s−1; thereafter, it saturated at ~2 MPa, which was ascribed to the micro inertial effect. Both the stress-time and velocity-time history of the rigid-perfectly-plastic-locking model and the critical velocity for the shock deformation were well predicted when a dynamic plateau stress determined from the distal end stresses in the shock mode was used in the calculations.Article Citation - WoS: 28Citation - Scopus: 28Crushing Behavior and Energy Absorption Performance of a Bio-Inspired Metallic Structure: Experimental and Numerical Study(Elsevier Ltd., 2018) Taşdemirci, Alper; Akbulut, Emine Fulya; Güzel, Erkan; Tüzgel, Fırat; Yücesoy, Atacan; Şahin, Selim; Güden, MustafaA thin-walled structure inspired from a biologic creature known as balanus was investigated experimentally and numerically under quasi-static and dynamic loads for load-carrying and energy absorption properties. The structure was composed of an inner conical core with a hemispherical cap and an outer shell in frusto-conical shape and formed by deep drawing. The applied deep drawing process was modelled using nonlinear finite element code LS-DYNA to determine the residual stress/strain and the non-linear thickness distribution after the forming process. It was also shown that the load carried by the balanus structure was greater than the arithmetic sum of the load carried by the inner core and by the outer shell separately. Although the mean force increase due to interaction effect at quasi-static strain rate was approximately 5%, while it increased to roughly 26% at dynamic strain rates in drop weight experiments. The numerical models also showed that the outer shell absorbed more energy than the inner core while the difference between the energy absorbing performance of the core and shell decreased with increasing deformation rate. The effect of strain rate and inertia on the increase in crush load increased with increasing impact velocity, while the strain rate effect had greater influence than the inertia on the crush load. The increased load carrying capacity of the balanus at quasi-static and dynamic strain rates was ascribed to the interaction between the core and shell and the confinement effect of the outer shell particularly at dynamic strain rate.Article Citation - WoS: 5Citation - Scopus: 6The Varying Densification Strain in a Multi-Layer Aluminum Corrugate Structure: Direct Impact Testing and Layer-Wise Numerical Modelling(Elsevier Ltd., 2017) Odacı, İsmet Kutlay; Güden, Mustafa; Kılıçaslan, Cenk; Taşdemirci, AlperAn aluminum (1050 H14) multi-layer corrugated structure composed of brazed 16 trapezoidal zig-zig fin layers was direct impact tested above the critical velocities for shock formation using a modified Split Hopkinson Pressure Bar. The experimentally measured stress-time histories of the cylindrical test samples in the direct impact tests were verified with the simulations implemented in the explicit finite element code of LS–DYNA. The quasi-static experimental and simulation deformation of the corrugated samples proceeded with the discrete, non-contiguous bands of crushed fin layers, while the dynamic crushing started from the proximal impact end and proceeded with a sequential and in-planar manner, showing shock type deformation characteristic. The experimental and numerical crushing stresses and the numerically determined densification strains of the fin layers increased with increasing impact velocity above the critical velocities. When the numerically determined densification strain at a specific velocity above the critical velocities was incorporated, the rigid-perfectly-plastic-locking idealized model resulted in peak stresses similar to the experimental and simulation mean crushing stresses. However, the model underestimated the experimental and simulation peak stresses below 200 m s−1. It was proposed, while the micro inertial effects were responsible for the increase of the crushing stresses at and below subcritical velocities, the shock deformation became dominant above the critical velocities.Article Citation - WoS: 12Citation - Scopus: 15Effect of Heat Treatment on the Blast Loading Response of Combined Geometry Shell Core Sandwich Structures(Elsevier Ltd., 2016) Taşdemirci, Alper; Kara, Ali; Turan, Kıvanç; Şahin, Selim; Güden, MustafaThe effect of heat treatment on the dynamic crushing and energy absorption behavior of combined geometry shell cores (hemisphere and cylinder) of sandwich structures were investigated both experimentally and numerically. The applied heat treatment on the combined geometry shell cores relieved the stress caused by deep drawing, diminishing the peak transmitted forces. The verified numerical models of the as-received and heat-treated combined geometry shells were used to model blast loading of various sandwich configurations and the additional sandwich configurations of reversing the cylindrical side of the cores to the impacted side. Both the applied heat-treatment and the reversing process decreased the magnitude of the force transmitted to the protected structure. The applied heat treatment increased the arrival time of blast force wave to the protected structure, while the reversing resulted in opposite.Other Corrigendum To ‘‘the Effect of Surface Treatment on Cap Deposition of Ti6al4v Open Cell Foams in Sbf Solution.’’ [ceram. Int. 39 (2010) 1805–1816](Elsevier Ltd., 2011) Türkan, Uğur; Güden, MustafaThe authors regret that they accidentally omitted to refer to Prof. A.C. Tas, who originally found the SBF solution used in the experiments. The corrections to the affected sentences are listed below. ‘‘The SBF solution for in vitro tests was prepared by dissolving the following analytical reagents in 1 L of deionized water: 6.547 g of NaCl, 2.268 g of NaHCO3, 0.372 g of KCl, 0.124 g of Na2HPO4, 0.305 g of MgCl2 6H2O, 0.368 g of CaCl2 2H2O, 0.071 g of Na2SO4 and 6.057 g of trishydoxmethylaminomethane (A.C. Tas)’’. A.C. Tas, Synthesis of biomimetic Ca-hydroxyapatite powders at 37 8C in synthetic body fluids, Biomaterials 21 (14) (2000) 1429–1438.Article Citation - WoS: 71Citation - Scopus: 78The Strengthening Effect of Polystyrene Foam Filling in Aluminum Thin-Walled Cylindrical Tubes(Elsevier Ltd., 2005) Toksoy, Ahmet Kaan; Güden, MustafaThe strengthening effect of foam filling in thin-walled circular tubes, deforming in diamond and concertina modes, was investigated in polystyrene foam filled aluminum tubes. Empty tubes of two different diameters (16 and 25 mm) deformed in diamond mode, while foam filling changed the deformation mode into concertina in 25 mm tube due to thickening effect of foam filling. The strengthening coefficient in concertina mode was found around unity, while in diamond mode it was greater than unity. In concertina mode, foam and tube were observed to deform independently. However, in diamond mode, foam was compressed in between the folds, leading to a higher strengthening coefficient. The effects of deformation rate and the use adhesive on the average crushing loads of the filled tubes were also determined.Article Citation - WoS: 71Citation - Scopus: 81The Impact Responses and the Finite Element Modeling of Layered Trapezoidal Corrugated Aluminum Core and Aluminum Sheet Interlayer Sandwich Structures(Elsevier Ltd., 2013) Kılıçaslan, Cenk; Güden, Mustafa; Odacı, İsmet Kutlay; Taşdemirci, AlperThe impact responses of brazed and adhesively bonded layered 1050 H14 trapezoidal corrugated aluminum core and aluminum sheet interlayer sandwich panels with 3003 and 1050 H14 aluminum alloy face sheets were investigated in a drop weight tower using spherical, flat and conical end striker tips. The full geometrical models of the tests were implemented using the LS-DYNA. The panels tested with spherical and flat striker tips were not penetrated and experienced slightly higher deformation forces and energy absorptions in 0°/90° corrugated layer orientation than in 0°/0° orientation. However, the panels impacted using a conical striker tip were penetrated/perforated and showed comparably smaller deformation forces and energy absorptions, especially in 0°/90° layer orientation. The simulation and experimental force values were shown to reasonably agree with each other at the large extent of deformation and revealed the progressive fin folding of corrugated core layers and bending of interlayer sheets as the main deformation mechanisms. The experimentally and numerically determined impact velocity sensitivity of the tested panels was attributed to the micro inertial effects which increased the critical buckling loads of fin layers at increasingly high loading rates.Article Citation - WoS: 118Citation - Scopus: 144The Effect of the Interlayer on the Ballistic Performance of Ceramic/Composite Armors: Experimental and Numerical Study(Elsevier Ltd., 2012) Taşdemirci, Alper; Tunusoğlu, Gözde; Güden, MustafaThe effect of rubber, Teflon and aluminum foam interlayer material on the ballistic performance of composite armor was investigated both experimentally and numerically. Although, rubber interlayer did not cause any significant delay in the initial stress build-up in the composite layer, Teflon and aluminum foam interlayer caused a significant delay and reduction in the magnitude of the stress transmitted to the composite backing plate. Damage in the ceramic layer was found to be highly localized around the projectile impact zone for the configuration without interlayer and rubber interlayer while aluminum foam and Teflon interlayer spread the damage zone in the radial direction. Relatively large pieces of the ceramic around the impact axis in the rubber interlayer configuration were observed while the ceramic layer was efficiently fragmented in aluminum foam and Teflon interlayer configuration.Article Citation - WoS: 12Citation - Scopus: 12The Effect of Strain Rate on the Compressive Deformation Behavior of a Sintered Ti6al4v Powder Compact(Elsevier Ltd., 2008) Taşdemirci, Alper; Hızal, Alpay; Altındiş, Mustafa; Hall, Ian W.; Güden, MustafaThe high strain rate (220–550 s−1) and quasi-static (0.0016 s−1) compression deformation behavior of a sintered Ti6Al4V powder compact was investigated. The compact was prepared using atomized spherical particles (100–200 μm) and contained 38 ± 1% porosity. The deformation sequences of the tested samples were further recorded by high speed camera and analyzed as a function of strain. The failure of the compact, which was found to be similar in the studied high strain rate and quasi-static strain rate testing regimes, occurs through particle decohesion along the surface of the two cones in a ductile (dimpled) mode consisting of void initiation and growth and by void coalescence in the interparticle bond region. The effect of strain rate was to increase the flow stress and compressive strength of the compact while the critical strain corresponding to the maximum stress was shown to be strain rate independent.