Gökmen Atlihan

In this study, the influence of the cryogenic cooling on the natural frequency and wear behaviors of the three different aluminum alloys of AA2024, AA6061 and AA7075 were examined. In addition, hardness and microstructural observations were also performed to reveal the effect of cryogenic cooling on the wear performance of the Al alloys. Pin on disc test equipment was utilized to observe the wear performance of the Al alloys and field emission scanning electron microscope was used to go in depth about microstructural evaluations. For the determination of the natural frequency of the Al alloys designed with different tapered angles from 0? to 1?, vibration test equipment was used. As a result of this work, it has been observed in experimental and analytical analysis that the natural frequency values decrease with the increase of the tapered angle of the fixed beam attached from the short (b) side. The highest frequency values were obtained when the tapered angle was 0? in the experimental and analytical analysis of the fixed beam attached from the short (b) side. Again, the highest frequency values were obtained when the tapered angle of the fixed beam, which was attached from the short (b) side, was 1? in the experimental and analytical analysis. In addition, when the worn surfaces and wear data are examined in general, it is seen that the amount of oxide on the surface increases as a result of the applied cryo-cooling, and because of the increased oxide layer, metal-to-metal contact occurs during wear, and it acts as a solid lubricant by protecting the surface under the metal. In this way, it has been observed that the wear loss is reduced and the worn surface images are directly affected. The results of the analytical and experimental analyses of fixed-support beams indicate that the natural frequency values of the beam can be altered by modifying the tapered angle of the beam and the location of the support. Lastly, no significant change was observed in natural frequency values with cryogenic effect.

Purpose: This study aims to reveal the influences of three-dimensional (3D) printing parameters such as layer heights (0.1 mm, 0.2 mm and 0.4 mm), infill rates (40, 70 and 100%) and geometrical property as tapered angle (0, 0.25 and 0.50) on vibrational behavior of 3D-printed polyethylene terephthalate glycol (PET-G) tapered beams with fused filament fabrication (FFF) method.Design/methodology/approach: In this performance, all test specimens were modeled in AutoCAD 2020 software and then 3D-printed by FFF. The effects of printing parameters on the natural frequencies of 3D-printed PET-G beams with different tapered angles were also analyzed experimentally, and numerically (finite element analysis) via Ansys APDL 16 program. In addition to vibrational properties, tensile strength, elasticity modulus, hardness, and surface roughness of the 3D-printed PET-G parts were examined.Findings: It can be stated that average surface roughness values ranged between 1.63 and 6.91 µm. In addition, the highest and lowest hardness values were found as 68.6 and 58.4 Shore D. Tensile strength and elasticity modulus increased with the increase of infill rate and decrease of the layer height. In conclusion, natural frequency of the 3D-printed PET-G beams went up with higher infill rate values though no critical change was observed for layer height and a change in tapered angle fluctuated the natural frequency values significantly.Research limitations/implications: The influence of printing parameters on the vibrational properties of 3D-printed PET-G beams with different tapered angles was carried out and the determination of these effects is quite important. On the other hand, with the addition of glass or carbon fiber reinforcements to the PET-G filaments, the material and vibrational properties of the parts can be examined in future works.Practical implications: As a result of this study, it was shown that natural frequencies of the 3D-printed tapered beams from PET-G material can be predicted via finite element analysis after obtaining material data with the help of mechanical/physical tests. In addition, the outcome of this study can be used as a reference during the design of parts that are subjected to vibration such as turbine blades, drone arms, propellers, orthopedic implants, scaffolds and gears.Social implications: It is believed that determination of the effect of the most used 3D printing parameters (layer height and infill rate) and geometrical property of tapered angle on natural frequencies of the 3D-printed parts will be very useful for researchers and engineers; especially when the importance of resonance is known well.Originality/value: When the literature efforts are scanned in depth, it can be seen that there are many studies about mechanical or wear properties of the 3D-printed parts. However, this is the first study which focuses on the influences of the both 3D printing parameters and tapered angles on the vibrational behaviors of the tapered PET-G beams produced with material extrusion based FFF method. In addition, obtained experimental results were also supported with the performed finite element analysis.

Alüminyum alaşımlarının döküm yoluyla üretilmesindeki önemli kusurlardan birisi sıcak yırtılmadır. Bu çalışmada, farklı özelliklere sahip 1050 ve 5083 döküm alaşımlarının sıcak yırtılmaları araştırılmış ve sıcak yırtılmaya neden olan tasarım parametreleri ile döküm koşulları belirlenmiştir. Ayrıca sıcak yırtılmanın metalografik ve mekanik özellikler üzerindeki etkileri de araştırılmıştır. Bununla birlikte, Vakum Altında Katılaşma Testi (VAKT) ile bifilm indeks ölçümleri gerçekleştirilerek sıcak yırtılmanın metal kalitesi üzerindeki etkileri, döküm alaşımlarının yapısındaki porozitelerin varlığına bağlı olarak incelenmiştir. Son olarak, döküm alaşımlarının doğal frekans analizleri ve titreşim testleri yapılmış, serbest titreşim ve burkulma karakteristikleri farklı sınır koşulları altında ayrı ayrı incelenmiştir.

Today, fused deposition modeling (EMM), which is one of the additive manufacturing methods, can transform the highlighted ideas into three-dimensional products after their designs. For this reason, it is frequently preferred in many platforms, from applications in aerospace and aviation to the construction of houses in the construction industry and the production of parts as a hobby. In this study, the influence of the taper angle (ϴ=0, ϴ=0.25 ve ϴ=0.50) and boundary conditions (narrow or wide side is fixed) on the natural frequency values of the tapered Polyethylene terephthalate glycol (PET-G) beams that are manufactured with fused deposition modeling (FDM) was determined by both experimental and Ansys APDL finite element analysis program and compared between each other. In addition, in order to experimentally determine the elasticity modulus values that should be assigned as material data in the finite element analysis program, tensile test samples were produced with the same FDM parameters, in accordance with the ASTM D638 standard, and the relevant samples were subjected to the tensile test. In addition to these, hardness and surface roughness measurements were also carried out from the produced samples. As a result, it has been determined that the natural frequency values increase with the increase of the taper angle from 0.25 to 0.50 in the tapered beams produced by FDM and when the fixing is applied from the wide edge compared to the narrow edge. The finite element analysis results and the experimental results are in good agreement.

Bu çalışmada, otomotiv sanayisinde kullanılabilecek PLA (Poli-Laktik Asit) malzemesinin yapısı hücresel hibrit malzeme olan bal petekli yapılardan üretilmiş kirişlerin doğal frekans değerleri üzerindeki etkisi incelenmiştir. Yapılan çalışmada dörtgen, beşgen, altıgen ve yuvarlak gibi farklı çekirdek yapısındaki petekler ile bunların kombinasyonu olan altıgen-dörtgen(kare)-daire ve beşgen-altıgen-daire gibi çeşitli bal petekli kirişlerin tasarımı ve üretimi gerçekleştirilmiştir. Üretimi gerçekleştirilen kirişin nümerik (Ansys) ve deneysel titreşim analizleri yapılıp oluşan doğal frekans değerleri karşılaştırılması yapılarak titreşim mod değerlerinin birbirine yakın olduğu görülmüştür. Oluşturulan ankastre mesnetli kirişlerde, bal peteği yapılarının şekillerine göre aynı hacim ve yapıda olanların doğal frekans değerlerinin değiştirilebileceği gösterilmiştir.

In this study, the effects of location, size and number of delaminations, boundary conditions, orientation angles and stacking sequences on the natural frequency of laminated composite beams are in...