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Volume 6, Number 3, September 2017

This paper describes an investigation on the effect of using three different filler metals on fatigue behavior of mechanical structures welded. The welding is carried out on the steel A510AP used for the manufacture of gas cisterns and pipes. The welding process used is manual welding with coated electrodes and automatic arc welding. Compact tension CT50 specimen has been used. The three zones of welded joint; filler metal FM, heat affected zone HAZ and base metal BM have been investigated. The results show that the crack growth rate CGR is decreasing respectively in BM, FM and HAZ; however, this variation decreases when stress intensity factor SIF increases. For low values of SIF, the CGR is inferior in the over-matched filler metal of which the value of mismatch M is near unity, but for high values of M the CGR is superior, and the effect of the over-matching on CGR becomes negative. No deviation of the crack growth path has been noticed.

Key Words
yield stress; fatigue crack growth; stress intensity factor; crack growth path; overmatch; undermatch

(1) Abdelkader Alioua, Benattou Bouchouicha, Mokhtar Zemri:
Department of Mechanical Engineering, Laboratory LMSR, University Djilali Liabes Sidi Bel Abbes, PB 89 ITMA Sidi Bel Abbes, Algeria;
(2) Abdellatif IMAD:
Laboratory of Mechanics of Lille, CNRS UMR 8107, Ecole Polytech\'Lille, University of Lille 1, France.

High energy ball milling is employed to produce iron matrix- multiwall carbon nanotube (MWCNT) reinforced composite. The damage caused to MWCNT due to harsh ball milling condition and its influence on interfacial bonding is studied. Different amount of MWCNT is used to find the optimal percentage of MWCNT for avoidance of the formation of chemical reaction product at the matrix - reinforcement interface. Effect of process control agent is assessed by the use of different materials for the purpose. It is observed that ethanol as a process control agent (PCA) causes degradation of MWCNT reinforcements after milling for two hours whereas solid stearic acid used as process control agent, allows satisfactory conservation of MWCNT structure. It is further noted that at a high MWCNT content (~ 2wt.%), high energy ball milling leads to reaction of iron and carbon and forms iron carbide (cementite) at the iron-MWCNT interface. At low percentage of MWCNT, dissolution of carbon in iron takes place and the amount of reinforcement in iron matrix composite becomes negligibly small. However, under the present ball milling condition (ball to metal ratio~ 6:1 and 200 rpm vial speed) iron-1wt.% MWCNT composite of good interfacial bonding can retain the tubular structure of reinforcing MWCNT.

Key Words
Multi Wall Carbon Nanotube (MWCNT); composite; Mechanical Alloying (MA); X-ray diffraction; transmission electron microscopy; interfacial bonding

Department of Metallurgical and Materials Engineering, Malaviya National Institute of Technology, Jaipur, India.

A simple closed-form solution to calculate the interfacial shear and normal stresses of retrofitted concrete beam strengthened with thin composite plate under mechanical loads including the creep and shrinkage effect has been presented in this paper. In such plated beams, tensile forces develop in the bonded plate, and these have to be transferred to the original beam via interfacial shear and normal stresses. Consequently, debonding failure may occur at the plate ends due to a combination of high shear and normal interfacial stresses. These stresses between a beam and a soffit plate, within the linear elastic range, have been addressed by numerous analytical investigations. Surprisingly, none of these investigations has examined interfacial stresses while taking the creep and shrinkage effect into account. In the present theoretical analysis for the interfacial stresses between reinforced concrete beam and a thin composite plate bonded to its soffit, the influence of creep and shrinkage effect relative to the time of the casting, and the time of the loading of the beams is taken into account. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of interfacial stress distributions.

Key Words
interfacial stresses; strengthening; creep; shrinkage; concrete beam; FRP composite

(1) Rabahi Abderezak, Tahar Hassaine Daouadji, Benferhat Rabia:
Département de génie civil , Université Ibn Khaldoun Tiaret; BP 78 Zaaroura, Tiaret, Algérie;
(2) Rabahi Abderezak, Tahar Hassaine Daouadji, Benferhat Rabia, Adim Belkacem:
Laboratoire de Géomatique et Développement Durable, Université de Tiaret, Algérie;
(3) Boussad Abbes, Fazilay Abbes:
Laboratoire GRESPI—Campus du Moulin de la Housse, Reims Cedex 2, France;
(4) Adim Belkacem:
Département des sciences et technologies, Centre Universitaire Tissemsilt, Algérie.

Thermo-mechanical vibration characteristics of in homogeneousporous functionally graded (FG) micro/nanobeam subjected to various types of thermal loadings are investigated in the present paper based on modified couple stress theory with consideration of the exact position of neutral axis. The FG micro/nanobeam is modeled via a refined hyperbolic beam theory in which shear deformation effect is verified needless of shear correction factor. A modified power-law distribution which contains porosity volume fraction is used to describe the graded material properties of FG micro/nanobeam. Temperature field has uniform, linear and nonlinear distributions across the thickness. The governing equations and the related boundary conditions are derived by Extended Hamilton\'s principle and they are solved applying an analytical solution which satisfies various boundary conditions. A comparison study is performed to verify the present formulation with the known data in the literature and a good agreement is observed. The parametric study covered in this paper includes several parameters such as thermal loadings, porosity volume fraction, power-law exponents, slenderness ratio, scale parameter and various boundary conditions on natural frequencies of porous FG micro/nanobeams in detail.

Key Words
free vibration; thermal effect; porosity; FG microbeam; modified couple stress theory

Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran.

In this article, novel olefin polymerization catalyst with lower cost and simple synthetic process were developed, ArOTiCl3 complexes [(2-OMeC6H4O)TiCl3(C1), (2,4-Me2C6H3O)TiCl3(C2), TiCl3(1,4-OC6H4O)TiCl3 (C3), TiCl3(1,4-OC6H2O-Me2-2,5) TiCl3(C4)] and corresponding (ArO)2TiCl2 complexes [TiCl2(OC6H4-OMe-2)2(C5) and TiCl2(OC6H3-Me2-2,6)2(C6)] have been synthesized by the reaction of TiCl4 with phenol, all these complexes were well characterized with 1H NMR,13C NMR, MASS and EA. When combined with methylaluminoxane (MAO), the ArOTiCl3 / MAO system shows high activity for ethylene copolymerization with 1-octene and copolymer was obtained with broaden molecular weight distribution (MWD). The 13C NMR result of polymer indicates that the 1-octene incorporation in polymer reached up to 8.29 mol%. The effects of polymerization temperature, concentration of polymerization monomer and polymerization time on the catalytic activity have been investigated.

Key Words
ArOTiCl3 complex; catalyst; ethylene/1-octene; copolymerization

(1) Jianwei Wang, Sheng Xu, Puke Mi:
School of Materical Science and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P.R. China;
(2) Yingchun Ren, Sheng Xu:
School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P.R. China.

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