Sıcaklık etkisindeki metal matrisli kompozit dönen diskteki ısıl gerilmelerin analizi

Abstract

Bu çalışmada, ortasında dairesel delik bulunan bir kompozit disk modellenmiştir. Kompozit malzeme, alüminyum matrise sahiptir ve çelik fiberlerle takviye edilmiştir. Çözüm için sonlu elemanlar metodu (FEM) tercih edilmiştir. Sonlu elemanlar metodu son zamanlarda çeşitli alanlardaki birçok mühendislik probleminin çözümünde tercih edilen bir yöntemdir. Bu amaçla, modelleme ve analizler için ANSYS yazılımı kullanılmıştır. Kompozit disk önceki çalışmalardan farklı olarak, üç boyutlu olarak oluşturulmuştur. Üç boyutlu kompozit disk modeli üzerine çeşitli sınır şartları, uniform sıcaklıklar (60, 90, 120, 150, 180, 210, 240 ve 270 °C) ve açısal dönmeler (10, 20, 30, 40 rad/sn) uygulamıştır. Daha önceki çalışmalarda genel olarak, tek bir yük nedeniyle oluşan gerilmeler ve dolayısıyla tek bir yükün yapı üzerine etkisi incelenmiştir. Bu çalışmada ise sıcaklık ve açısal hız birlikte uygulanmak suretiyle, kompozit disk üzerinde oluşan gerilmelere, iki yükün birden etkisi incelenmiştir. Meydana gelen ısıl gerilmelerin miktarları hesaplanmış ve disk üzerindeki dağılımları elde edilmiştir. Radyal, teğetsel ve z-yönlerinin hepsi için gerilmelerin değerleri ve dağılımları elde edilmiştir. Farklı yükleme durumlarına göre elde edilen sonuçlar, birbiriyle karşılaştırılmıştır. Elde edilen sonuçlara göre, ısıl gerilmelerin değerleri ve dağılımlarının, uygulanan uniform sıcaklık ve açısal hız değişimine bağlı olarak değişim gösterdiği anlaşılmıştır.

The goal of this study analysis of thermal stresses in a metal matrix composite rotating disc that was exposed temperature. The composite material was aluminum matrix and it was reinforced by steel fibers, curvilinearly. The material properties provided from earlier studies (Çallıoğlu vd., 2006; Altan ve Topçu, 2010). These researchers have produced this composite material and they measured mechanical properties of it via experimental techniques. The finite element method (FEM) was preferred for solution. Since, it is known that FEM is a powerful tool for solving of many engineering problems recently. A lot of previous studies pointed out that the FEM results were in a good agreement with experimental results and analytical results. ANSYS software was used for both modeling and analyses of rotating composite disc. Because, many researchers and designers have preferred this program for thermal stress problems and etc. The metal matrix composite disc was created as three dimensional as a difference from previous studies. This was an innovation for solving the composite disc problem. Since modeling and solving of this problem were very difficult for researchers using analytical methods, especially. FEM and ANSYS were supplied to solve this problem as three dimensional easily. The ¼ part of the composite disc was modeled because of the symmetry condition. It is an advantage of FEM solution. Therefore, symmetry boundary conditions were applied on three dimensional composite disc. A circular hole was also created in center of disc. Mapped mesh was created on three dimensional disc. It is known that the designing of a structure with mapped mesh is very difficult if structure have a circular hole and circular dimensions. When the structure is three dimensional, creating of mapped mesh is also very hard. Various boundary conditions were performed on three dimensional composite disc. Firstly, some uniform temperatures were applied on it as 60, 90, 120, 150, 180, 210, 240 ve 270 °C. And then angular velocities were carried out as 10, 20, 30, 40 rad/s. It is mean that ecah uniform temperature were applied on disc when one of the angular velocity was also peformed. Briefly, stresses of the three dimensional composite disc were determined for both temperature effect and rotation in the same time. Analyses were done for all uniform temperatures and angular velocities. It is said that only one loading condition was applied on the disc in many previous studies. Because, appliying of two loading condition were difficult. The magnitudes of thermal stresses were calculated and its distributions were obtained on the disc. The obtained results were compared with each other. According to different loading conditions mentioned as uniform temperature effect and rotation, values and distributions of thermal stresses were changed by changing magnitudes of uniform temperatures and angular velocities. The highest values of stresses were calculated when 270 °C uniform temperature applying and 40 rad/s angular velocity. The lowest values of stresses were calculated when 60 °C uniform temperature applying and 10 rad/s angular velocity. The magnitudes of stresses for tangential and radial directions were higher than z-direction. The distributions of stresses on the disc were seen as similar for radial and tangential directions, whereas distributions of stresses were very different for zdirection. Both tensile and compressive stresses were occurred on the three dimensional disc. It was understood that the anisotropic material properties of composite disc caused this case. Different thermal expansion coefficients related to directions of composite were important occurring, magnitudes and distributions of stresses.