Design of T-shaped tube hydroforming using finite element and artificial neural network modeling

Fethi Abbassi,Furqan Ahmad,Sana Gulzar,Touhami Belhadj,Ali Karrech,Heung-Soap Choi 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3

Tube hydroforming (THF) is a frequently used manufacturing method in the industry, especially on automotive and aircraft industries. Compared with other manufacturing processes, THF provides parts with better quality and lower production costs. This paper proposes a design approach to estimate the T-shaped THF parameters, such as counter force, axial feed, and internal pressure, through finite element (FE) and artificial neural network (ANN) modeling. A numerical database is built through Taguchi’s L27 orthogonal array of experiments to train the ANN. The micromechanical damage model of Gurson-Tvergaard-Needleman is used with an elastoplastic approach to describe the material behavior. This study aims to find the combinations of THF parameters that maximize the bulge ratio and minimize the thinning ratio and wrinkling. The numerical results obtained by the FE model show good correlation with the results predicted by the ANN.

Investigation of thermal buckling properties of ceramic-metal FGM sandwich plates using 2D integral plate model

Fethi Salah,Belhadj Boucham,Fouad Bourada,Abdelnour Benzair,Abdelmoumen Anis Bousahla,Abdeldjebbar Tounsi 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.6

In this work, a simple four-variable integral plate theory is employed for examining the thermal buckling properties of functionally graded material (FGM) sandwich plates. The proposed kinematics considers integral terms which include the effect of transverse shear deformations. Material characteristics and thermal expansion coefficient of the ceramic-metal FGM sandwich plate faces are supposed to be graded in the thickness direction according to a "simple power-law" variation in terms of the "volume fractions" of the constituents. The central layer is always homogeneous and consists of an isotropic material. The thermal loads are supposed as uniform, linear, and nonlinear temperature rises within the thickness direction. The influences of geometric ratios, gradient index, loading type, and type sandwich plate on the buckling properties are examined and discussed in detail.

Effect of porosity on vibrational characteristics of non-homogeneous plates using hyperbolic shear deformation theory

Fethi Mouaici,Samir Benyoucef,Hassen Ait Atmane,Abdelouahed Tounsi 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.4

In this paper, a shear deformation plate theory based on neutral surface position is developed for free vibration analysis of functionally graded material (FGM) plates. The material properties of the FGM plates are assumed to vary through the thickness of the plate by a simple power-law distribution in terms of the volume fractions of the constituents. During manufacture, defects such as porosities can appear. It is therefore necessary to consider the vibration behavior of FG plates having porosities in this investigation. The proposed theory is based on assumption that the in-plane and transverse displacements consist of bending and shear components, in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. The neutral surface position for a functionally graded plate which its material properties vary in the thickness direction is determined. The equation of motion for FG rectangular plates is obtained through Hamilton`s principle. The closed form solutions are obtained by using Navier technique, and then fundamental frequencies are found by solving the results of eigenvalue problems. Numerical results are presented and the influences of the volume fraction index and porosity volume fraction on frequencies of FGM plates are clearly discussed.

CASE REPORT : Aneurysmal Bone Cyst of Sphenoid Bone and Clivus Misdiagnosed as Chordoma: A Case Report

( Fethi Emre Ustabasioglu ),( Cesur Samanci ),( Murat Asik ),( Inanc Yanik ),( Seyma Ozkanli ),( Onur Tutar ),( Zehra Isik Hasiloglu ) 대한뇌종양학회·대한신경종양학회 2015 Brain Tumor Research and Treatment Vol.3 No.2

Aneurysmal bone cysts (ABCs) are benign and rapidly expanding bone destructive lesions of any bone. They are commonly localized in the metaphysis of long bones, whereas skull base ABCs are rare. We report a case of a 21-year-old man who had been misdiagnosed as chordoma and undergone surgery. However, histopathological examination revealed it to be an ABC.

Dynamic analysis of a functionally graded tapered rotating shaft under thermal load via differential quadrature finite elements method

Fethi, Hadjoui,Ahmed, Saimi,Ismail, Bensaid,Abdelhamid, Hadjoui Techno-Press 2023 Advances in aircraft and spacecraft science Vol.10 No.1

The present study proposes a theoretical and numerical investigation on the dynamic response behaviour of a functional graded (FG) ceramic-metal tapered rotor shaft system, by the differential quadrature finite elements method (DQFEM) to identify the natural frequencies for modelling and analysis of the structure with suitable validations. The purpose of this paper is to explore the influence of heat gradients on the natural frequency of rotation of FG shafts via three-dimensional solid elements, as well as a theoretical examination using the Timoshenko beam mode, which took into account the gyroscopic effect and rotational inertia. The functionally graded material's distribution is described by two distribution laws: the power law and the exponential law. To simulate varied thermal conditions, radial temperature distributions are obtained using the nonlinear temperature distribution (NLTD) and exponential temperature distribution (ETD) approaches. This work deals with the results of the effect on the fundamental frequencies of different material's laws gradation and temperature gradients distributions. Attempts are conducted to identify adequate explanations for the behaviours based on material characteristics. The effect of taper angle and material distribution on the dynamic behaviour of the FG conical rotor system is discussed.

Investigation of the mechanical behavior of functionally graded sandwich thick beams

Fethi Mouaici,Abed Bouadi,Mohamed Bendaida,Kada Draiche,Abdelmoumen Anis Bousahla,Fouad Bourada,Abdelouahed Tounsi,Mofareh Hassan Ghazwani,Ali Alnujaie 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.5

In this paper, an accurate kinematic model has been developed to study the mechanical response of functionally graded (FG) sandwich beams, mainly covering the bending, buckling and free vibration problems. The studied structure with homogeneous hardcore and softcore is considered to be simply supported in the edges. The present model uses a new refined shear deformation beam theory (RSDBT) in which the displacement field is improved over the other existing high-order shear deformation beam theories (HSDBTs). The present model provides good accuracy and considers a nonlinear transverse shear deformation shape function, since it is constructed with only two unknown variables as the Euler-Bernoulli beam theory but complies with the shear stress-free boundary conditions on the upper and lower surfaces of the beam without employing shear correction factors. The sandwich beams are composed of two FG skins and a homogeneous core wherein the material properties of the skins are assumed to vary gradually and continuously in the thickness direction according to the power-law distribution of volume fraction of the constituents. The governing equations are drawn by implementing Hamilton’s principle and solved by means of the Navier’s technique. Numerical computations in the non-dimensional terms of transverse displacement, stresses, critical buckling load and natural frequencies obtained by using the proposed model are compared with those predicted by other beam theories to confirm the performance of the proposed theory and to verify the accuracy of the kinematic model.

The mixed finite element for quasi-static and dynamic analysis of viscoelastic circular beams

Kadioglu, Fethi,Akoz, A. Yalcin Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.15 No.6

The quasi-static and dynamic responses of a linear viscoelastic circular beam on Winkler foundation are studied numerically by using the mixed finite element method in transformed Laplace-Carson space. This element VCR12 has 12 independent variables. The solution is obtained in transformed space and Schapery, Dubner, Durbin and Maximum Degree of Precision (MDOP) transform techniques are employed for numerical inversion. The performance of the method is presented by several quasi-static and dynamic example problems.

Effect of porosity on vibrational characteristics of non-homogeneous plates using hyperbolic shear deformation theory

Mouaici, Fethi,Benyoucef, Samir,Atmane, Hassen Ait,Tounsi, Abdelouahed Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.4

In this paper, a shear deformation plate theory based on neutral surface position is developed for free vibration analysis of functionally graded material (FGM) plates. The material properties of the FGM plates are assumed to vary through the thickness of the plate by a simple power-law distribution in terms of the volume fractions of the constituents. During manufacture, defects such as porosities can appear. It is therefore necessary to consider the vibration behavior of FG plates having porosities in this investigation. The proposed theory is based on assumption that the in-plane and transverse displacements consist of bending and shear components, in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. The neutral surface position for a functionally graded plate which its material properties vary in the thickness direction is determined. The equation of motion for FG rectangular plates is obtained through Hamilton's principle. The closed form solutions are obtained by using Navier technique, and then fundamental frequencies are found by solving the results of eigenvalue problems. Numerical results are presented and the influences of the volume fraction index and porosity volume fraction on frequencies of FGM plates are clearly discussed.

Lateral torsional buckling of doubly-symmetric steel cellular I-Beams

Mehmet Fethi Ertenli,Erdal Erdal,Alper Buyukkaragoz,Ilker Kalkan,Ceyhun Aksoylu,Yasin Onuralp Özkılıç 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.5

The absence of an important portion of the web plate in steel beams with multiple circular perforations, cellular beams, causes the web plate to undergo distortions prior to and during lateral torsional buckling (LTB). The conventional LTB equations in the codes and literature underestimate the buckling moments of cellular beams due to web distortions. The present study is an attempt to develop analytical methods for estimating the elastic buckling moments of cellular beams. The proposed methods rely on the reductions in the torsional and warping rigidities of the beams due to web distortions and the reductions in the weak-axis bending and torsional rigidities due to the presence of web openings. To test the accuracy of the analytical estimates from proposed solutions, a total of 114 finite element analyses were conducted for six different standard IPEO sections and varying unbraced lengths within the elastic limits. These analyses clearly indicated that the LTB solutions in the AISC 360- 16 and AS4100:2020 codes overestimate the buckling loads of cellular beams within elastic limits, particularly at shorter span lengths. The LDB solutions in the literature and the Eurocode 3 LTB solution, on the other hand, provided conservative buckling moment estimates along the entire range of elastic buckling.

APPLICATIONS ON THE BESSEL-STRUVE-TYPE FOCK SPACE

Soltani, Fethi Korean Mathematical Society 2017 대한수학회논문집 Vol.32 No.4

In this work, we establish Heisenberg-type uncertainty principle for the Bessel-Struve Fock space ${\mathbb{F}}_{\nu}$ associated to the Airy operator $L_{\nu}$. Next, we give an application of the theory of extremal function and reproducing kernel of Hilbert space, to establish the extremal function associated to a bounded linear operator $T:{\mathbb{F}}_{\nu}{\rightarrow}H$, where H be a Hilbert space. Furthermore, we come up with some results regarding the extremal functions, when T are difference operators.