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In this work, vibration analysis of rolling element bearings (REBs) defects is studied. The REBs are the most widely used mechanical parts in rotating machinery under high load and high rotational speeds. When the defect in a rolling element comes into contact with another element surface, an impact force is generated which is resulting in an impulsive response of the bearing. A defect at any element of the REB transmits to all other elements such as outer race, inner race, ball and, train cage of the bearing. The defect in rolling elements may lead to serious catastrophic consequences resulting in costly downtime. For this purpose, the vibration analysis technique which is a reliable and accurately detecting defect in the bearing elements is used. The vibration data captured and used for determination and validation is composed from four different defects states of the REB -outer raceway defect, inner raceway defect, ball defect, and combination of the bearing elements defect-and one representing normal state of the bearing for four different running speeds with two load levels. The results obtained from the experiments have illustrated and explained.

Additive Manufacturing (AM), widely known as three-dimensional (3D) printing, is the process that a product is fabricated layer by layer in Cartesian coordinate system. Fused Deposition Modelling (FDM) is the most used AM process for functional rapid prototyping and products reduces the time and material involved in manufacturing. The purpose of this study is to investigate the effects of 3D printer system vibrations on the surface roughness of fabricated products. Polyethyletherphthalate Glycol (PET-G) is used as material for fabrication. Six different filling structures -Rectilinear, Grid, Triangular, Wiggle, Fast Honeycomb, and Full Honeycomb -were used and for each structure two different top -two and three -layers implemented. A total of 12 samples specimens were fabricated. The results showed that using Full Honeycomb filling structure with three top layers is more suitable for surface roughness compare to the others filling structure used. It can be concluded that the vibration of 3D printer system considering type of filling structure and number of top layers have a significant effect on surface quality of product. ÖZETYaygın olarak üç boyutlu (3D) baskı olarak bilinen Eklemeli Üretim (Additive Manufacturing -AM), bir ürünün Kartezyen koordinat sisteminde katmanla üretildiği süreçtir. Erişim Birikim Modelleme (Fused Deposition Modeling -FDM), fonksiyonel hızlı prototipleme ve ürün için en çok kullanılan AM sürecidir, üretimle ilgili zamanı ve malzemeyi azaltır. Bu çalışmanın amacı, 3D yazıcı sistem titreşimlerinin, imal edilen ürünlerin yüzey pürüzlülüğü üzerindeki etkilerini araştırmaktır. Üretim için malzeme olarak Polietileterftalat Glikol (PET-G) kullanılmıştır. Altı farklı dolgu şekli -Rectilinear, Grid, Triangular, Wiggle, Fast Honeycomb ve Full Honeycomb -kullanılmış ve her yapı için iki farklı üst katmaniki ve üç katmanuygulanarak toplam 12 test numunesi basılmıştır. Basılan ürünlerin yüzey pürüzlülüğü ölçümleri yapılarak elde edilen veriler üzerinden karşılaştırma yapılmış ve sonuçlar analiz edilmiştir. Sonuçlar, üç üst katmanlı ızgara (Grid) doldurma yapısının kullanılması, yüzey pürüzlülüğü için diğer doldurma yapılarına kıyasla daha uygun olduğunu göstermiştir. Dolgu Düzce Üniversitesi Bilim ve Teknoloji Dergisi, 7 (2019) 147-157 şekli türüne ve üst katmanların sayısına bağlı olarak 3D yazıcı sisteminin titreşiminin ürünün yüzey kalitesi üzerinde önemli bir etkisi olduğu görülmüştür.

The purpose of this study is to utilize Taguchi method, which can prove to be a handy and effective tool for determining minimum vibration response of rotor-bearing system set to avoid running at critical speed. In the study, three test cases considering different coupling type (elastic, jaw, and solid) and disc location (disc location A, B, and C) were conducted to observe behavioral changes of the shaft system considering vibration signatures. Each test case was conducted for three different shaft running speeds of 12, 18, and 24 Hz. To find the minimum peak amplitude values by experimenting different combinations of the rotor-bearing system set needs a lot of experiments for reaching solution. Moreover, the solution proves costly because of the time consumed in doing many experiments. This fact depicts the importance of an efficient optimization method to be used. Taguchi method can determine the design parameters, which have the greatest influence on the solution through a very limited number of experiments, for finding optimum set of rotor-bearing system. The method is performed using an iterative procedure to gain an optimum design.

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