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CONTENTS
Volume 66, Number 3, May10 2018
 

Abstract
An experimental study has been carried out to analyze the effect of cutting parameters (cutting speed, feed and depth of cut) and tool nose radius on the surface roughness and the cutting force components during hard turning of the AISI 52100 (50 HRC) steel with a ceramic cutting tool. The tests have been conducted according to the methodology of planning experiments, based on an orthogonal plan of Taguchi (L27). By using the response surface methodology (RSM), the components of the cutting force and the roughness of the machined surface were modeled and the effects of the input parameters were analyzed statistically by ANOVA and RSM. The results show that the feed (f), the tool nose radius (r), the cutting speed (Vc), the interaction between feed and tool nose radius (fxr) as well as that of the quadratic effect (f2) all have significant effects on the surface roughness (Ra). The feed is the most influencing factor with a contribution of 47.31%. The components of the cutting force were strongly influenced by the depth of cut, followed by the advance with a lower degree. By comparing the experimental values with those predicted by the models of the cutting force components and the surface roughness, it appears that they are in very good correlation.

Key Words
hard turning; AISI 52100; cutting force; roughness; ANOVA; mixed ceramic

Address
Abderrahim Bouziane, Lakhdar Boulanouar and Ouahid Keblouti: Advanced Technologies in Mechanical Production Research Laboratory (LRTAPM), Badji Mokhtar - Annaba University, P.O Box 12, 23000 Annaba, Algeria
Mohamed Walid Azizi:
1) Advanced Technologies in Mechanical Production Research Laboratory (LRTAPM), Badji Mokhtar - Annaba University, P.O Box 12, 23000 Annaba, Algeria
2) Technical Science Department, Abdelhafid Boussouf-Mila University Center, 43000, Algeria
Salim Belhadi:
1) Advanced Technologies in Mechanical Production Research Laboratory (LRTAPM), Badji Mokhtar - Annaba University, P.O Box 12, 23000 Annaba, Algeria
2) Mechanics and Structures Research Laboratory (LMS), May 8th 1945 University, P.O. Box 401, Guelma 24000, Algeria

Abstract
The semi-analytical method to study the nonlinear dynamic behavior of simply supported spiral stiffened functionally graded (FG) cylindrical shells subjected to an axial compression is presented. The FG shell is surrounded by damping and linear/nonlinear elastic foundation. The proposed linear model is based on the two-parameter elastic foundation (Winkler and Pasternak). A three-parameter elastic foundation with hardening/softening cubic nonlinearity is used for nonlinear model. The material properties of the shell and stiffeners are assumed to be FG. Based on the classical plate theory of shells and von Kármán nonlinear equations, smeared stiffeners technique and Galerkin method, this paper solves the nonlinear vibration problem. The fourth order Runge-Kutta method is used to find the nonlinear dynamic responses. Results are given to consider effects of spiral stiffeners with various angles, elastic foundation and damping coefficients on the nonlinear dynamic response of spiral stiffened simply supported FG cylindrical shells.

Key Words
FG cylindrical shells; nonlinear dynamic analysis; spiral stiffeners; damping and elastic foundation

Address
Kamran Foroutan, Alireza Shaterzadeh and Habib Ahmadi: Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran

Abstract
Interaction of lateral loading, combined with axial force needs to be determined with care in reinforced concrete (RC) one-dimensional structural members (1D SMs) such as beam-columns (BCs) and columns. RC 1D SMs under heavy axial loading are known to fail by brittle mode and small lateral displacements. In this paper, a macro element-based algorithm is proposed to analyze the RC 1D SMs under monotonic or cyclic combined loading. The 1D SMs are discretized into macro-elements (MEs) located between the critical sections and the inflection points. The critical sections are discretized into fixed rectangular finite elements (FRFE). The nonlinear behavior of confined and unconfined concretes and steel elements are considered in the proposed algorithm. The proposed algorithm has been validated by the results of experimental tests carried out on full-scale RC structural members. The evolution of ultimate strain at extreme compression fiber of a rectangular RC section for different orientations of lateral loading shows that the ultimate strain decreases with increasing the axial force. In the examined cases, this ultimate strain ranges from 0.0024 to 0.0038. Therefore, the 0.003 value given by ACI-318 code for ultimate strain, is not conservative and valid for the combined load cases with significant values of axial force (i.e. for the axial forces heavier than 70% of the ultimate axial force).

Key Words
reinforced concrete; 1D structural members; beam-columns; columns; simulation; monotonic; cyclic; combined loading

Address
Fatemeh Nouban and Kabir Sadeghi: Department of Civil Engineering, Near East University, Near East Boulevard, ZIP: 99138, Nicosia, North Cyprus, via Mersin 10, Turkey

Abstract
In this paper, a new refined quasi-three-dimensional (3D) shear deformation theory for the bending analysis of functionally graded plate is presented. The number of unknown functions involved in this theory is only four against five or more in the case of the other shear and normal deformation theories. Due to its quasi-3D nature, the stretching effect is taken into account in the formulation of governing equations. In addition, the effect of different micromechanical models on the bending response of these plates is studied. Various micromechanical models are used to evaluate the mechanical characteristics of the FG plates whose properties vary continuously across the thickness according to a simple power law. The present theory accounts for both shear deformation and thickness stretching effects by a parabolic variation of displacements across the thickness, and the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The problem is solved for a plate simply supported on its edges and the Navier solution is used. The results of the present method are compared with others from the literature where a good agreement has been found. A detailed parametric study is presented to show the effect of different micromechanical models on the flexural response of a simply supported FG plates.

Key Words
FG plates; micromechanical models; quasi 3D shear deformation theory; stretching effect; bending

Address
Rabbab Bachir Bouiadjra: Department of Civil Engineering, University Mustapha Stambouli of Mascara, Algeria
Abdelkader Mahmoudi and Samir Benyoucef: Department of Civil Engineering, Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
Abdelouahed Tounsi:
1) Department of Civil Engineering, Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
2) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Fabrice Bernard: Laboratoire de Genie Civil et Genie Mecanique, INSA de Rennes, France

Abstract
This paper considers the smooth receding contact problem between a homogeneous half-plane and a composite laminate composed of an inhomogeneously coated elastic layer. The inhomogeneity of the elastic modulus of the coating is approximated by an exponential function along the thickness dimension. The three-component structure is pressed together by either a concentrated force or uniform pressures applied at the top surface of the composite laminate. Both semianalytical and finite element analysis are performed to solve for the extent of contact and the contact pressure. In the semianalytical formulation, Fourier integral transformation of governing equations and boundary conditions leads to a singular integral equation of Cauchy-type, which can be numerically integrated by Gauss-Chebyshev quadrature to a desired degree of accuracy. In the finite element modeling, the functionally graded coating is divided into homogeneous sublayers and the shear modulus of each sublayer is assigned at its lower boundary following the predefined exponential variation. In postprocessing, the stresses of any node belonging to sublayer interfaces are averaged over its surrounding elements. The results obtained from the semianalytical analysis are successfully validated against literature results and those of the finite element modeling. Extensive parametric studies suggest the practicability of optimizing the receding contact peak stress and the extent of contact in multilayered structures by the introduction of functionally graded coatings.

Key Words
receding contact; functionally graded coating; singular integral equation; Gauss-Chebyshev quadrature; finite element analysis

Address
Zhixin Liu, Jie Yan and Changwen Mi: Jiangsu Key Laboratory of Engineering Mechanics, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China

Abstract
Brazilian disc test is one of the most widely used experiments in the literature of geo-mechanics. In this work, the pre-holed concrete Brazilian disc specimens are numerically modelled by a two-dimensional discrete element approach. The cracks initiations, propagations and coalescences in the numerically simulated Brazilian discs (each containing a single cylindrical hole and or multiple holes) are studied. The pre-holed Brazilian discs are numerically tested under Brazilian test conditions. The single-holed Brazilian discs with different ratios of the diameter of the holes to that of the disc radius are modelled first. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured and the crack propagation mechanism around the wall of the ring is investigated. The crack propagation and coalescence mechanisms are also studied for the case of multi-holes\' concrete Brazilian discs. The numerical and experimental results show that the breaking mechanism of the pre-holed disc specimens is mainly due to the initiation of the radially induced tensile cracks which are growth from the surface of the central hole. Radially cracks propagated toward the direction of diametrical loading. It has been observed that for the case of disc specimens with multiple holes under diametrical compressive loading, the breaking process of the modelled specimens may occur due to the simultaneous cracks propagation and cracks coalescence phenomena. These results also show that as the hole diameter and the number of the holes increases both the failure stress and the crack initiation stress decreases. The experimental results already exist in the literature are quit agree with the proposed numerical simulation results which validates this simulation procedure.

Key Words
concrete rings; pre-holed Brazilian discs; crack analyses; cracks coalescence; discrete element method

Address
Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Hadi Haeri: Young Researchers and Elite Club, Bafgh Branch, Islamic Azad University, Bafgh, Iran
Alireza Bagher Shemirani: Department of Civil Engineering, Sadra Institute of Higher Education, Tehran, Iran
Maryam Firoozi Nezamabadi: Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran

Abstract
In this work, a high order hyperbolic shear deformation theory with four variables is presented to study the vibratory behavior of functionally graduated plates. The field of displacement of the theory used in this work is introduced indeterminate integral variables. In addition, the effect of porosity is studied. It is assumed that the material characteristics of the porous FGM plate, varies continuously in the direction of thickness as a function of the power law model in terms of volume fractions of constituents taken into account the homogeneous distribution of porosity. The equations of motion are obtained using the principle of virtual work. An analytical solution of the Navier type for free vibration analysis is obtained for a FGM plate for simply supported boundary conditions. A comparison of the results obtained with those of the literature is made to verify the accuracy and efficiency of the present theory. It can be concluded from his results that the current theory is not only accurate but also simple for the presentation of the response of free vibration and the effect of porosity on the latter.

Key Words
high orders hyperbolic shear deformation theory; functionally graded plate; porosity; free vibration

Address
Mahfoud Yousfi:
1) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2) Department of Civil Engineering, Faculty of Technology, University of Medea, Algeria
Hassen Ait Atmane:
1) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2) Department of Civil Engineering, Faculty of Civil Engineering and Architecture, University of Chlef, Algeria
Mustapha Meradjah: Department of Civil Engineering, Faculty of Technology, University of Sidi Bel Abbes, Algeria
Abdelouahed Tounsi:
1) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Riadh Bennai: Department of Civil Engineering, Faculty of Civil Engineering and Architecture, University of Chlef, Algeria

Abstract
In this article, buckling and free vibration of functionally graded (FG) nanobeams resting on elastic foundation are investigated by developing various higher order beam theories which capture shear deformation influences through the thickness of the beam without the need for shear correction factors. The elastic foundation is modeled as linear Winkler springs as well as Pasternak shear layer. The material properties of FG nanobeam are supposed to change gradually along the thickness through the Mori–Tanaka model. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. From Hamilton\'s principle, the nonlocal governing equations of motion are derived and then solved applying analytical solution. To verify the validity of the developed theories, the results of the present work are compared with those available in literature. The effects of shear deformation, elastic foundation, gradient index, nonlocal parameter and slenderness ratio on the buckling and free vibration behavior of FG nanobeams are studied.

Key Words
buckling; dynamic analysis; vibration; nanostructures/nanotubes; functionally graded material; nonlocal elasticity theory

Address
Farzad Ebrahimi: Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, 3414916818, Qazvin, Iran
Mohammad Reza Barati: Aerospace Engineering Department & Center of Excellence in Computational Aerospace, Amirkabir University of Technology, Tehran, Iran

Abstract
The present study addresses the direct and indirect methods of determining the mode-I fracture toughness of concrete using experimental tests and particle flow code. The direct method used is compaction tensile test and the indirect methods are notched Brazilian disc test, semi-circular bend specimen test, and hollow center cracked disc. The experiments were carried out to determine which indirect method yields the fracture toughness closer to the one obtained by the direct method. In the numerical analysis, the PFC model was first calibrated with respect to the data obtained from the Brazilian laboratory test. The crack paths observed in the simulated tests were in reasonable accordance with experimental results. The discrete element simulations demonstrated that the macro fractures in the models are caused by microscopic tensile breakages on large numbers of bonded particles. The mode-I fracture toughness in the direct tensile test was smaller than the indirect testing results. The fracture toughness obtained from the SCB test was closer to the direct test results. Hence, the semi-circular bend test is recommended as a proper experiment for determination of mode-I fracture toughness of concrete in the absence of direct tests.

Key Words
fracture toughness; CT; NBD; SCB; HCCD; bonded particle modeling

Address
Alireza Bagher Shemirani: Department of Civil Engineering, Sadra Institute of Higher Education, Tehran, Iran
Hadi Haeri: Young Researchers and Elite Club, Bafgh Branch, Islamic Azad University, Bafgh, Iran
Vahab Sarfarazi and Nima Babanouri: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Abbas Akbarpour: Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran

Abstract
In this paper, a general closed-form solution for evaluating the dynamic behavior of a Timoshenko beam on elastic foundation under a moving harmonic line load is formulated in the frequency-wavenumber domain and in a moving coordinate system. It is found that the characteristic equation is quartic with real coefficients only, and its poles can be presented explicitly. This enables the substitution of these poles into Cauchy\'s residue theorem, leading to the general closed-form solution. The solution can be reduced to seven existing closed-form solutions to different sub-problems and a new closed-form solution to the subproblem of a Timoshenko beam on an elastic foundation subjected to a moving quasi-static line load. Two examples are included to verify the solution.

Key Words
closed-form solution; beam on elastic foundation; moving load; Timoshenko beam; Cauchy\'s residue theorem

Address
Wei-Li Luo: School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China
Yong Xia: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, P.R. China
Xiao-Qing Zhou: College of Civil Engineering, Guangzhou University, Guangzhou, P.R. China

Abstract
This paper demonstrates the potential application of machine learning algorithms for approximate prediction of the load and deflection capacities of the novel type of Laced Steel Concrete-Composite1 (LSCC) beams proposed by Anandavalli et al. (Engineering Structures 2012). Initially, global and local responses measured on LSCC beam specimen in an experiment are used to validate nonlinear FE model of the LSCC beams. The data for the machine learning algorithms is then generated using validated FE model for a range of values of the identified sensitive parameters. The performance of four well-known machine learning algorithms, viz., Support Vector Regression (SVR), Minimax Probability Machine Regression (MPMR), Relevance Vector Machine (RVM) and Multigene Genetic Programing (MGGP) for the approximate estimation of the load and deflection capacities are compared in terms of well-defined error indices. Through relative comparison of the estimated values, it is demonstrated that the algorithms explored in the present study provide a good alternative to expensive experimental testing and sophisticated numerical simulation of the response of LSCC beams. The load carrying and displacement capacity of the LSCC was predicted well by MGGP and MPMR, respectively.

Key Words
composite structures; machine learning algorithms; ultimate strength; displacement

Address
Thirumalaiselvi, A., Mohit Verma, Anandavalli, N. and Rajasankar, J.: Academy of Scientific and Innovative Research, CSIR-Structural Engineering Research Centre,
CSIR Campus, Taramani, 600 113, Chennai, India

Abstract
Although a rubber isolation cushion can reduce the dynamic response of a structure itself, it has little influence on the height of a sloshing wave and even may induce magnification action. Vertical baffles are set into a base-isolated Concrete Rectangular Liquid Storage Structure (CRLSS), and baffles are opened as holes to increase the energy dissipation of the damping. Problems of liquid nonlinear motion caused by baffles are described using the Navier-Stokes equation, and the space model of CRLSS is established considering the Fluid-Solid Interaction (FSI) based on the Finite Element Method (FEM). The dynamic response of an isolated CRLSS with various baffles under an earthquake is analyzed, and the results are compared. The results show that when the baffle number is certain, the greater the number of holes in baffles, the worse the damping effects; when a single baffle with holes is set in juxtaposition and double baffles with holes are formed, although some of the dynamic response will slightly increase, the wallboard strain and the height of the sloshing wave evidently decrease. A configuration with fewer holes in the baffles and a greater number of baffles is more helpful to prevent the occurrence of two failure modes: wallboard leakage and excessive sloshing height.

Key Words
isolation; concrete; rectangular liquid storage structure; baffle; liquid-solid interaction; dynamic response

Address
Xuansheng Cheng, Bo Liu and Liangliang Cao: Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, 730050, PR China
Dongpo Yu and Huan Feng: Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education, Lanzhou University of Technology, Lanzhou, 730050, PR China


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