Abstract:This paper presents the free vibration analysis of an edge cracked non-uniform symmetric beam made of functionally graded material. The Timoshenko beam theory is used for the finite element analysis of the multi-layered sandwich beam and the cantilever beam is modeled by 50 layers of material. The material properties vary continuously along the thickness direction according to the exponential and power laws. A MATLAB code is used to find the natural frequencies of two types of non-uniform beams, having a const… Show more
“…For this reason both the Timoshenko beam element as the bar element are incorporated into one element by the principle of superposition. The expanded Timoshenko beam element stiffness and mass matrices are given by [7]:…”
In this paper modal analysis is performed on a symmetric aluminum beam which is coated with functionally graded material containing porosities. A polynomial function is used to vary the density and elasticity through the thickness of the coating, while the effective elastic modulus and density are found with classical lamination theory. To achieve a truthful modeling the gradually changing mechanical properties of the coating are modeled as 25 layers of material, while each individual layer is isotropic and homogeneous. MATLAB is used to write a finite element code and Timoshenko beam elements are used to include shear deformation effects. To show the influences of crack location, crack depth, porosity and the polynomial function index on the natural beam frequencies a parametric study is conducted. Multiple boundary conditions were also considered and it was found that the natural frequency values were significantly affected by the studied parameters.
“…For this reason both the Timoshenko beam element as the bar element are incorporated into one element by the principle of superposition. The expanded Timoshenko beam element stiffness and mass matrices are given by [7]:…”
In this paper modal analysis is performed on a symmetric aluminum beam which is coated with functionally graded material containing porosities. A polynomial function is used to vary the density and elasticity through the thickness of the coating, while the effective elastic modulus and density are found with classical lamination theory. To achieve a truthful modeling the gradually changing mechanical properties of the coating are modeled as 25 layers of material, while each individual layer is isotropic and homogeneous. MATLAB is used to write a finite element code and Timoshenko beam elements are used to include shear deformation effects. To show the influences of crack location, crack depth, porosity and the polynomial function index on the natural beam frequencies a parametric study is conducted. Multiple boundary conditions were also considered and it was found that the natural frequency values were significantly affected by the studied parameters.
Bu çalışmada çekirdek tabakası alüminyum ve yüzeyleri porosite ihtiva eden fonksiyonel derecelendirilmiş malzeme (FDM) ile kaplı simetrik yapıda ankastre sandviç bir kirişin serbest titreşim analizi incelenmiştir. Fonksiyonel derecelendirilmiş malzemenin elastisite modülü ve yoğunluğu kirişin tabaka kalınlığı boyunca bir polinom fonksiyonla değiştiği kabul edilmiştir. FDM'yi gerçeğe yakın bir şekilde temsil etmek için kaplama kalınlığının 25 tabakadan oluştuğu ve her bir tabaka kendi içinde homojen izotrop olarak modellenmiştir. Bu yapılara ait efektif yoğunluk ve elastisite modülü tabakalı kompozit kiriş teorisi kullanılarak belirlenmiştir. Çalışmada birinci mertebe kayma deformasyonu içeren Timoshenko kiriş teorisi kullanılarak problemin çözümü sonlu elemanlar metoduyla gerçekleştirilmiştir. Kirişin doğal frekanslarının hesaplanması için MATLAB'ta sonlu elemanlar kodu yazılmıştır. Çalışmada porosite hacim oranının (a), çekirdek tabaka kalınlığının FDM kalınlık oranına (h/H), kiriş açıklığının yüksekliğine oranının (L/H) ve FDM'nin mekanik özelliklerini belirleyen polinom parametresinin (n) doğal frekansların üzerindeki etkisi incelenmiştir. İncelenen parametrelerin kirişin doğal frekanslarını önemli ölçüde etkilediği gözlemlenmiştir.
“…There are plenty of studies on free vibration behaviour and characteristics of uniform cross-section homogeneous and composite intact structures (Erdurcan and Cunedioğlu, 2020; Jiang et al, 2018; Kim and Shin, 2008; Mohanty et al, 2013; Zahedinejad, 2016; Zhang et al, 2020) and cracked structures (Cunedioglu, 2015; Ferezqi et al, 2010; Gayen and Chakraborty, 2016; Gayen et al, 2017a, 2017b, 2018; Han et al, 2020; Kisa and Brandon, 2000; Kisa et al, 1998; Liu et al, 2017; Papadopoulos, 2004; Papadopoulos and Dimarogonas, 1987; Shabani and Cunedioglu, 2019).…”
Free vibration analysis of a single edge cracked multi-layered symmetric sandwich stepped Timoshenko beams, made of functionally graded materials, is studied using finite element method and linear elastic fracture mechanic theory. The cantilever functionally graded beam consists of 50 layers, assumed that the second stage of the beam (step part) is created by machining. Thus, providing the material continuity between the two beam stages. It is assumed that material properties vary continuously, along the thickness direction according to the exponential and power laws. A developed MATLAB code is used to find the natural frequencies of three types of the stepped beam, concluding a good agreement with the known data from the literature, supported also by ANSYS software in data verification. In the study, the effects of the crack location, crack depth, power law gradient index, different material distributions, different stepped length, different cross-sectional geometries on natural frequencies and mode shapes are analysed in detail.
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