Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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Institution Author: search.filters.institutionAuthor.Taşdemirci, AlperPublisher: search.filters.publisher.Elsevier

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 39
    Citation - Scopus: 40
    Impact Loading of Functionally Graded Metal Syntactic Foams
    (Elsevier, 2022) Movahedi, Nima; Fiedler, Thomas; Taşdemirci, Alper; Murch, Graeme E.; Belova, Irina V.; Güden, Mustafa
    The present study addresses the impact loading of functionally graded metal syntactic foams (FG-MSF). For comparison, samples of the same material were also compression loaded at quasi-static velocities. Samples of A356 aluminium FG-MSF were produced using counter-gravity infiltration casting with combination of equal-sized layers of expanded perlite (EP) and activated carbon (AC) particles. A modified Split Hopkinson Pressure Bar test set-up was used to impact the FG-MSFs from their EP or AC layers at 55 m/s or 175 m/s impact velocities. A high-speed camera captured the deformation of the samples during testing. It was shown that increasing the loading velocity enhanced both the compressive proof strength and energy absorption of the impacted FG-MSF from both layers, confirming a dynamic strengthening effect of the foam. The samples impacted from both layers at 55 and 175 m/s showed a transition and a shock mode of deformation, respectively. The impacted samples at 55 m/s experienced lower final average strain values compared to 175 m/s.
  • Article
    Citation - WoS: 28
    Citation - Scopus: 34
    The Strain Rate Sensitive Flow Stresses and Constitutive Equations of a Selective-Laser and an Annealed-Rolled 316l Stainless Steel: a Comparative Study
    (Elsevier, 2022) Güden, Mustafa; Enser, Samed; Bayhan, Mesut; Taşdemirci, Alper; Yavaş, Hakan
    The strain rate dependent compressive flow stresses of a Selective-Laser-Melt 316L (SLM-316L) alloy and a commercial (annealed-extruded) 316L (C-316L) alloy were determined, for comparison, between 1x10-4 and ∼2500 s-1 and between 1x10-4 and ∼2800 s-1, respectively. The Johnson and Cook flow stress material model parameters of both alloys were also determined. The microstructural examinations of the deformed cross-sections of tested specimens (interrupted tests) showed a twinning-induced-plasticity in SLM-316L alloy and a martensitic transformation-induced-plasticity in C-316L alloy. Twin and martensite formations were detected microscopically higher in the dynamically tested specimens until about 0.22 strain, while the twin and martensite formations decreased at increasing strains due to adiabatic heating. The rate sensitivity of SLM-316L was determined slightly higher than that of C-316L within the quasi-static strain rate range (1x10-4 and 1x10-2 s-1), while the rate sensitivities of both alloys were similar in the quasi-static-high strain rate range (1x10-4 and ∼2500-2800 s-1) at low strains. A more rapid decrease in the rate sensitivity of C-316L at increasing strains was found in the quasi-static-high strain rate range. The similar activation volumes of both alloys, corresponding to the dislocation intersections, indicated a similar thermally activated deformation process involvement in both alloys.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 12
    Testing and Modeling Blast Loading of a Sandwich Structure Cored With a Bio-Inspired (balanus) Core
    (Elsevier, 2022) Tüzgel, Fırat; Akbulut, Emine Fulya; Güzel, Erkan; Yücesoy, Atacan; Şahin, Selim; Taşdemirci, Alper; Güden, Mustafa
    The blast loading response of a sandwich structure consisted of bio-inspired (balanus) cores/units was investigated experimentally and numerically. A Direct Pressure Pulse (DPP) set-up was used to impose a blast-like loading. The equivalent blast conditions corresponding to the used impact velocities were implemented in the models. A benchmark study was performed by using three different methods namely pure Lagrangian, Arbitrary Lagrangian Eulerian, and hybrid. Dynamic crushing behavior was analyzed and exhibited a higher specific energy absorption capacity than its constituents (core and shell). Among the core configurations, all-front configuration was found the most efficient configuration regarding the specific energy absorption.
  • Article
    Citation - WoS: 54
    Citation - Scopus: 59
    Orientation Dependent Tensile Properties of a Selective-Laser 316l Stainless Steel
    (Elsevier, 2021) Güden, Mustafa; Yavaş, Hakan; Tanrıkulu, Ahmet Alptuğ; Taşdemirci, Alper; Akın, Barış; Enser, Samed; Karakuş, Ayberk; Arslan Hamat, Burcu
    The effect of specimen inclination angle with respect to building direction on the tensile properties of a selective laser melt 316L alloy was investigated. Tensile test specimens were fabricated with the angles between 0 degrees to 90 degrees at 15 degrees intervals using a rotation scanning. In addition, 316L alloy test specimens were generated in the ANSYS 2020R1 additive module and tensile tested in LS-DYNA in order to determine the effect of residual stresses on the tensile strengths. The microscopic analysis revealed a strong < 110 > fiber texture orientation along the building direction (the loading axis of 0 degrees inclined specimens) and a weak 111 texture or nearly random distribution of directions in the normal to the building direction (tensile loading axis of 90 degrees inclined specimens). The yield and tensile strength increased and ductility decreased with increasing inclination angle. The strength variation with the inclination angle was shown well-fitted with the Tsai-Hill failure criterion. Although, the used numerical models indicated an inclination-dependent residual stress, the difference in the residual stresses was much lower than the difference in the strengths between 0 degrees and 90 degrees inclined specimens. Predictions showed a lower twinning stress in 0 degrees inclined specimens due to < 110 > fiber texture orientation in the tensile axis. The fiber texture resulted in extensive twinning; hence, higher ductility and tension-compression asymmetry in 0 degrees inclined specimens. Based on these results, the variations in the strength and ductility of tested SLM-316L specimens with the inclination angle was ascribed to the variations in the angle between the fiber texture orientation and loading axis.