Mechanical Properties and Melt Quality Relationship of Sr-modified Al-12Si Alloy

The formation of oxide film on the surface of aluminium melts, i.e. bifilms, are known to be detrimental when they are incorporated into the cast part. These defects causes premature fractures under stress, or aid porosity formation. In this work, Al-12 Si alloy was used to cast a step mould under two conditions: as-received and degassed. In addition, 10 ppi filters were used in the mould in order to prevent bifilm intrusion into the cast part. Reduced pressure test samples were collected for bifilm index measurements. Samples were machined into standard bars for tensile testing. It was found that there was a good agreement with the bifilm index and mechanical properties

Analysis and control of soft electropneumatic gripper fabricated by additive manufacturing method

Esnek elektropnömatik tutucular, yumuşak robotik cihazların geliştirilmesine ve yumuşak robotlar için farklı ve karmaşık donanım tasarımlarının etkinleştirilmesine önemli ölçüde katkıda bulunmaktadır. Birçok avantajın yanı sıra, esnek tutucuların konum geri bildiriminin olmaması, konum kontrolü için bir sorun teşkil etmektedir. Bu tez çalışması, eklemeli imalat teknolojisi kullanılarak üretilecek olan esnek elektropnömatik tutucuyla bu sorunu incelemeyi amaçlamaktadır. Esnek tutucu, 3D yazıcıda kalıplama tekniği kullanılarak iki parça halinde imal edilmiştir. Tutucunun yapısı, kalıplanmış silikon (RTV-3015) ve haznelerden oluşan polietilen tereftalat (PET) filmden oluşmaktadır. Bu bölmeler, basınçlı hava ile çalışabilen 10 adet hava geçirmez bölmeden oluşan aktif bir bölme ve PET film ile kaplanmış bir pasif bölmedir. Esnek tutucunun bükülmesi sırasında, pasif hazne içindeki PET film basınçlı hava tarafından sıkıştırılmaya başlar ve bu da tutucunun daha yüksek bir yük tutma kapasitesiyle sonuçlanır. Ayrıca esnek sensörden yapılan geri besleme modülü fabrikasyon sırasında entegre edilmiştir. Esnek tutucunun PID kontrolü için gerçek zamanlı bir kontrol deney düzeneği oluşturulmuştur. Kontrolcünün basamak ve yörünge takip performansları gözlemlenmiştir. Gerçek zamanlı deneylerin doğruluğunu karşılaştırmak için tutucunun sonlu eleman analizi COMSOL programıyla gerçekleştirildi. Deneysel çalışmaların sonuçları ile elektropnömatik tutucunun hareket özellikleri, eğilme açısı ile basınç arasındaki ilişki ve konum izleme performansı incelenmiştir. Tutucunun deneysel sonuçlarının simülasyon sonuçlarıyla iyi bir uyum içinde olduğu tespit edilmiştir. Deneysel sonuçlar, esnek tutucunun PID kontrol algoritması ile başarılı yörünge izleme performansı gösterdiğini belirlemiştir.Flexible electropneumatic grippers contribute significantly to the development of soft robotic devices and enable different and complex hardware designs for soft robots. Besides the many advantages, the lack of position feedback of flexible grippers poses a problem for position control. This thesis study aims to examine this problem with a flexible electropneumatic gripper to be produced using additive manufacturing technology. The flexible gripper is manufactured in two parts using a 3D-printed molding technique. The structure of the gripper consists of molded silicone (RTV-3015) and polyethylene terephthalate (PET) film made of chambers. These compartments are an active compartment consisting of 10 airtight compartments that can operate with compressed air, and a passive compartment covered with PET film. During the bending of the soft gripper, the PET film inside the passive chamber begins to be compressed by the compressed air, resulting in a higher load holding capacity of the gripper. In addition, the feedback module made of flexible sensor is integrated during fabrication. A real-time control experiment setup was created for the PID control of the flexible gripper. The step and trajectory tracking performances of the controller were observed. Finite element analysis of the gripper was performed with the COMSOL program to compare the accuracy of real-time experiments. The results of the experimental studies and the movement characteristics of the electropneumatic gripper, the relationship between the bending angle and the pressure, and the position tracking performance were investigated. The experimental results of the gripper were found to be in good agreement with the simulation results. Experimental results determined that the flexible gripper showed successful trajectory tracking performance with PID control algorithm

The Effect of Sr Modification and Holding Time on Si Morphology and Mechanical Properties of ETIAL 195 Alloy

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.</span