Lokman Gemi

Fatigue Crack Growth Behavior of Filament Wound Composite Pipes in Corrosive Environment

The stress corrosion crack growth behavior of ±45°, ±55°, and ±75° filament wound composite pipes with surface crack subjected to 0.6 M HCl acid under alternating internal pressure was investigated. E-glass/epoxy pipes consist of six layers with stacking sequences of (+45/-45) 3, (+55/-55)3, and (+75/-75)3. Dilute (0.6M) HCl acid was applied to the surface crack region by a corrosion cell mounted on the outer surface of the pipe. The specimens were tested at room temperature and exposed to open-ended fatigue tests in which the pipes can deform freely in the axial direction. The tests were performed in accordance with the ASTM D-2992 standard. The surface notches with different a/t and a/c forms were cut on the outer surface of the pipe parallel to the pipe axis. The internal pressure was generated by conventional hydraulic oil for fatigue loading. The low cycle tests were applied with 0.42 Hz frequency and R = 0.05 stress ratio. After the corrosion fatigue test, the fracture surfaces were examined and observed damage mechanisms discussed.

Comparison of stability of titanium and absorbable plate and screw fixation for mandibular angle fractures

OBJECTIVE The purpose of this experimental study was to compare the stability of titanium and absorbable plate and screw fixation systems for mandibular angle fractures. STUDY DESIGN Twenty-one sheep hemimandibles were used to evaluate 3 different plating techniques. The groups were fixated with a single titanium plate, a single absorbable plate and double absorbable plates. A cantilever bending biomechanical test model was used for the samples. Each group was tested with vertical forces by a servohydraulic testing unit. The displacement values in each group at each 10 N stage up to 100 N were compared using the 2-way analysis of variance test. RESULTS The displacement values for the 3 groups differed significantly (P < .05). The variance analyses showed that titanium plate placement had more favorable biomechanical behavior than others. In addition, the 2 absorbable plates group had more favorable biomechanical behavior than a single absorbable plate group but it was not significantly different at 10 to 40 N. CONCLUSION The study demonstrated that titanium plate and screw fixation system had greater resistance to occlusal loads than absorbable plate and screw systems. In addition, a second absorbable plate orientation provides a more favorable biomechanical behavior than a single absorbable plate placement.

The Effect of Nylon 6.6 Nanofiber Layers on Mechanical Properties of Epoxy

1 Mechanical Engineering Department, Iskenderun Technical University, Iskenderun 31200, Turkey 2 Seydisehir Vocational School, Necmettin Erbakan University, Konya 42370, Turkey 3 Ilgın Vocational School, Selcuk University, Konya, 42600, Turkey --------------------------------------------------------ABSTRACT----------------------------------------------------------In this study mechanical properties of epoxy resin reinforced with different numbers of nanofiber layers of nylon 6.6 which produced with electrospinning method was investigated. Solution of 10 wt % of Nylon 6.6/ formic acid was used for electrospinning. The special molds were prepared to produce the laminated composite plates. Static tensile tests were performed, and the specimens were evaluated with respect to tensile strength and elongation at break, which are aspects of their basic mechanical properties.

ETİAL 195 Alaşımında Sr Modifikasyonu ve Tutma Süresinin Si Morfolojisi ve Mekanik Özelliklere Etkisi

Otektik ustu Si iceren Al-Si alasimlari tipik olarak asinmaya karsi direnc arzu edilen parcalarda uygulama alani bulmaktadir. Asinma direncini arttiran en temel parametre, Si morfolojisidir. Otektik ustu alasimlarda, Si yapisi dokum sicakligindan etkin bir sekilde etkilenmektedir. Ancak, dokum sirasinda olusabilecek bifilm hatalari Si icin potansiyel heterojen cekirdek kaynagi olabilmektedirler. Bu dogrultuda bu calismada, 800 °C ergitme sicakligin farkli bekleme sureleri sonrasinda dokumler yapilarak, sivi metal icerisinde var olabilecek bifilmlerin Si morfolojisi uzerine etkisi incelenmistir. Bifilm miktari, sivi metalden alinan vakum altinda katilasma testi sonrasinda elde edilen numunelerin kesit alanindaki goruntu analizi ile tespit edilmistir. Uretilen numunelerin mikroyapilari uzerinde de goruntu analizi yapilarak Si morfolojisindeki degisim incelenmistir. Ayni zamanda her parametre icin cekme testi yapilarak Si morfolojisi ile mekanik ozellikler arasi iliski ortaya cikartilmistir Hypereutectic Al-Si alloys are typically used in applications where wear resistance is required. The primary factor that determines the wear properties is the morphology of Si in these types of alloys. Pouring temperature is one of the ways to control Si size and shape. On the other hand, bifilm defects that may be present in the liquid can significantly alter the morphology of Si acting as a heterogeneous nucleant. Therefore in this work, castings were made at 800 °C with varying holding time and the effects of bifilm on the Si morphology was studied. Bifilm content was measured by Reduced Pressure Test and image analysis was used to characterize Si morphology. In addition, tensile tests were carried out to correlate Si morphology with mechanical properties.