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CONTENTS
Volume 60, Number 3, November10 2016
 

Abstract
This paper describes a systematic numerical investigation into the nonlinear elastic behavior of conical shells, with various types of initial imperfections, subject to a uniformly distributed axial compression. Three different patterns of imperfections, including first axisymmetric linear bifurcation mode, first non-axisymmetric linear bifurcation mode, and weld depression are studied using geometrically nonlinear finite element analysis. Effects of each imperfection shape and tapering angle on imperfection sensitivity curves are investigated and the lower bound curve is determined. Finally, an empirical lower bound relation is proposed for hand calculation in the buckling design of conical shells.

Key Words
buckling; conical shell; imperfection sensitivity; weld depression

Address
Meisam Shakouri: Department of Aerospace Engineering, Semnan University, Semnan, Iran
Andrea Spagnoli: DICATeA, University of Parma, Parco Area delle Scienze 181/A, 43124 Parma, Italy
M.A. Kouchakzadeh: Department of Aerospace Engineering and Center of Excellence in Aerospace Systems, Sharif University of Technology, P.O. Box 11155-8639, Tehran, Iran

Abstract
In this paper, the response and failure of sharp-notched 6061-T6 aluminum alloy circular tubes with five different notch depths of 0.4, 0.8, 1.2, 1.6 and 2.0 mm subjected to cyclic bending were experimentally and theoretically investigated. The experimental moment-curvature relationship exhibits an almost steady loop from the beginning of the first cycle. And, the notch depth has almost no influence on its relationship. However, the ovalization-curvature relationship exhibits a symmetrical, increasing, and ratcheting behavior as the number of cycles increases. In addition, a higher notch depth of a tube leads to a more severe unsymmetrical trend of the ovalization-curvature relationship. Focusing on the aforementioned relationships, the finite element software ANSYS was used to continue the related theoretical simulation. Furthermore, the five groups of tubes tested have different notch depths, from which five unparallel straight lines can be observed from the relationship between the controlled curvature and the number of cycles required to produce failure in the log-log scale. Finally, a failure model was proposed to simulate the aforementioned relationship. Through comparison with the experimental data, the proposed model can properly simulate the experimental data.

Key Words
failure life estimation; sharp-notched circular tubes; cyclic bending; moment; curvature; ovalization; finite element ANSYS analysis

Address
Kuo-Long Lee: Department of Innovative Design and Entrepreneurship Management, Far East University, No. 49, Chung Hua Rd., Hsin-Shih Dist., Tainan 744,Taiwan
Kao-Hua Chang: Department of Mold and Die Engineering, National Kaohsiung University of Applied Sciences, No. 415, Chien Kung Rd., Kaohsiung 807,Taiwan
Wen-Fung Pan: Department of Engineering Science, National Cheng Kung University, No. 1, University Rd., Tainan 701, Taiwan

Abstract
Bone is a living material with a complex hierarchical structure that gives it remarkable mechanical properties. Bone constantly undergoes mechanical. Its quality and resistance to fracture is constantly changing over time through the process of bone remodeling. Numerical modeling allows the study of the bone mechanical behavior and the prediction of different trauma caused by accidents without expose humans to real tests. The aim of this work is the modeling of the femur fracture under static solicitation to create a numerical model to simulate this element fracture. This modeling will contribute to improve the design of the indoor environment to be better safe for the passengers\' transportation means. Results show that vertical loading leads to the femur neck fracture and horizontal loading leads to the fracture of the femur diaphysis. The isotropic consideration of the bone leads to bone fracture by crack propagation but the orthotropic consideration leads to the fragmentation of the bone.

Key Words
extended finite element method (X-FEM); crack/damage detection/identification; structural design; simulation

Address
Zagane Mohammed El Sallah, Benbarek Smail, Sahli Abderahmane, B. Bachir Bouiadjra and Serier Boualem: Laboratory Mechanics Physics of materials (LMPM), University Djillali Liabes of Sidi bel abbes, BP89 city Larbi Ben M

Abstract
A sensitivity analysis estimates the effect of the change in the uncertain variable parameter on the probability of the structural failure. A novel fuzzy random reliability sensitivity measure of the failure probability is proposed to consider the effect of the epistemic and aleatory uncertainties. The uncertainties of the engineering variables are modeled as fuzzy random variables. Fuzzy quantities are treated using the y-cut approach. In fact, the fuzzy variables are transformed into the interval variables using the y-cut approach. Genetic approach considers different possible combinations within the search domain (y-cut) and calculates the parameter sensitivities for each of the combinations.

Key Words
reliability; fuzzy random variables; sensitivity analysis; y-cut approach

Address
Parinaz Jafari and Ehsan Jahani: Department of Engineering and Technology, University of Mazandaran, babolsar, Mazandaran, Iran

Abstract
During earthquake, the motion of ground is affected significantly by source characteristics, source-to-site path properties and local site conditions. Due to the influence of local soil conditions different places experience distinctive amplitude of surface ground motion. Ground response analysis of a specific site utilizing the borehole information at different locations is done in present study. The ground motion with the highest peak ground acceleration for this site obtained from the ground response analysis is used in finite element soil-structure interaction analysis of multi-storey shear wall buildings with various positions of shear walls. The variation in seismic response of buildings and advantageous position of shear wall are determined. The study reveals that providing shear wall at the core of buildings at the specific site is advantageous among all shear wall configurations considered.

Key Words
ground response analysis; soil-structure interaction; shear wall

Address
B.R. Jayalekshmi: Department of Civil Engineering, National Institute of Technology Karnataka, Surathkal 575-025, India
H.K. Chinmayi: Department of Civil Engineering, Nagarjuna College of Engineering and Technology, Bangalore 562-164, India

Abstract
In this paper, we investigate the free vibration of axially loaded non-uniform Rayleigh cantilever beams. The Rayleigh beams account for the rotary inertia effect which is ignored in Euler-Bernoulli beam theory. Using an inverse problem approach we show, that for certain polynomial variations of the mass per unit length and the flexural stiffness, there exists a fundamental closed form solution to the fourth order governing differential equation for Rayleigh beams. The derived property variation can serve as test functions for numerical methods. For the rotating beam case, the results have been compared with those derived using the Euler-Bernoulli beam theory.

Key Words
Rayleigh beam; free vibration; inverse problem; closed-form solution; test functions

Address
Korak Sarkar, Ranjan Ganguli: Department of Aerospace Engineering, Indian Institute of Science, Bangalore-560012, India
Isaac Elishakoff: Department of Mechanical Engineering, Florida Atlantic University, Boca Raton, FL 33431-0991, USA

Abstract
This study predicts the strength of rotary brace damper by analyzing a new set of probabilistic models using the usual method of multiple linear regressions (MLR) and advanced machine-learning methods of multivariate adaptive regression splines (MARS), Rotary brace damper can be easily assembled with high energy-dissipation capability. To investigate the behavior of this damper in structures, a steel frame is modeled with this device subjected to monotonic and cyclic loading. Several response parameters are considered, and the performance of damper in reducing each response is evaluated. MLR and MARS methods were used to predict the strength of this damper. Displacement was determined to be the most effective parameter of damper strength, whereas the thickness did not exhibit any effect. Adding thickness parameter as inputs to MARS and MLR models did not increase the accuracies of the models in predicting the strength of this damper. The MARS model with a root mean square error (RMSE) of 0.127 and mean absolute error (MAE) of 0.090 performed better than the MLR model with an RMSE of 0.221 and MAE of 0.181.

Key Words
rotary brace damper; passive energy dissipation; nonlinear response; MLR; MARS; damper strength

Address
I. Mansouri: Deptartment of Civil Engineering, Birjand University of Technology, Birjand, Iran
M. Safa, Z. Ibrahim: Deptartment of Civil Engineering, University of Malaya, Kuala Lumpur, Malaysia
O. Kisi: Center for Interdisciplinary Research, International Black Sea University, Tbilisi, Georgia
M.M. Tahir: UTM CRC, Institute for Smart Infrastructure and Innovative Construction, UTM, Johor Bahru, Malaysia
S. Baharom: Department of Civil and Structural Engineering, National University of Malaysia, Malaysia
M. Azimi: Department of Quantity Surveying, Universiti Teknologi Malaysia, Johor Bahru, Malaysia

Abstract
Sinusoidal shear deformation theory (SSDT) is developed here for dynamic buckling of functionally graded (FG) nano-plates. The material properties of plate are assumed to vary according to power law distribution of the volume fraction of the constituents. In order to present a realistic model, the structural damping of nano-structure is considered using Kelvin-Voigt model. The surrounding elastic medium is modeled with a novel foundation namely as orthotropic visco-Pasternak medium. Size effects are incorporated based on Eringen\'n nonlocal theory. Equations of motion are derived from the Hamilton\'s principle. The differential quadrature method (DQM) in conjunction with Bolotin method is applied for obtaining the dynamic instability region (DIR). The detailed parametric study is conducted, focusing on the combined effects of the nonlocal parameter, orthotropic visco-Pasternak foundation, power index of FG plate, structural damping and boundary conditions on the dynamic instability of system. The results are compared with those of first order shear deformation theory and higher-order shear deformation theory. It can be concluded that the proposed theory is accurate and efficient in predicting the dynamic buckling responses of system.

Key Words
dynamic buckling; FG nano-plate; SSDT; viscoelastic; orthotropic visco-Pasternak medium

Address
A. Ghorbanpour Arani: Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran; Institude of Nanoscience and Nanotechnology, University of Kashan, Kashan, Iran
A. Cheraghbak and R. Kolahchi: Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran

Abstract
The use of shape memory alloys (SMAs) has been seriously considered in seismic engineering due to their capabilities, such as the ability to tolerate cyclic deformations and dissipate energy. Five 3-D extended end-plate connection models have been created, including one conventional connection and four connections with Nitinol bolts of four different prestress forces. Their cyclic behaviors have been investigated using the finite element method software ANSYS. Subsequently, the moment-rotation responses of the connections have been derived by subjecting them to cyclic loading based on SAC protocol. The results obtained in this research indicate that the conventional connections show residual deformations despite their high ductility and very good energy dissipation; therefore, they cannot be repaired after loading. However, while having good energy dissipation and high ductility, the connections equipped with Nitinol bolts have good recentering capability. Moreover, a connection with the mentioned specifications has been modeled, except that only the external bolts replaced with SMA bolts and assessed for seismic loading. The suggested connection shows high ductility, medium energy dissipation and very good recentering. The main objective of this research is to concentrate the deformations caused by cyclic loading on the connection in order to form super-elastic hinge in the connection by the deformations of the shape memory alloy bolts.

Key Words
end-plate connection; shape memory alloy; super-elastic behavior; cyclic performance; recentering

Address
Nader Fanaie and Morteza N. Monfared: Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

Abstract
In this article, the generalized coupled non-Fickian diffusion-thermoelasticity analysis is carried out using an analytical method. The transient behaviors of field variables, including mass concentration, temperature and displacement are studied in a strip, which is subjected to shock loading. The governing equations are derived using generalized coupled non-Fickian diffusion-thermoelasticity theory, which is based on Lord-Shulman theory of coupled thermoelasticity. The governing equations are transferred to the frequency domain using Laplace transform technique and then the field variables are obtained in analytical forms using the presented method. The field variables are eventually determined in time domain by employing the Talbot technique. The dynamic behaviors of mass concentration, temperature and displacement are studied in details. It is concluded that the presented analytical method has a high capability for simulating the wave propagation with finite speed in mass concentration field as well as for tracking thermoelastic waves. Furthermore, the obtained results are more realistic than that of others.

Key Words
non-Fickian diffusion; wave propagation; mass concentration; thermoelasticity; analytical method; coupled problems

Address
Seyed Amin Hosseini: Mechanical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, PO Box: 91775-1111, Mashhad, Iran
Mohammad Hossein Abolbashari: Department of Mechanical Engineering, Lean Production Engineering Research Center, Ferdowsi University of Mashhad, PO Box: 91775-1111, Mashhad, Iran
Seyed Mahmoud Hosseini: Industrial Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, PO Box: 91775-1111, Mashhad, Iran


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