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CONTENTS
Volume 10, Number 1, March 2021
 


Abstract
In this paper, the dynamic analysis of single-layer rectangular armchair graphene nanoplates has been considered. The theory of nonlocal elasticity for small scale effects and the Kirchhoff's theory for plates have been used to obtain the dynamic equation of graphene nanoplates. Discrete Least Squares Meshless (DLSM) method has been used to examine the response of single-layer graphene nanoplates with various boundary conditions. The validation of the results has also been carried out using dynamic analysis of single-layer rectangular armchair graphene nanoplates under stationary loads. Results revealed that DLSM method is an efficient mean to solve the problems of structural mechanics in nano-dimensions. In addition, in nanostructures, the small scale effects have considerable impacts that should be considered as well. An increase in nonlocal coefficient increases the deflection. Higher nonlocal coefficient leads to higher deflection intensity and vibration amplitude.

Key Words
dynamic analysis; graphene nanoplate; nonlocal elasticity theory; Discrete Least Squares Meshless (DLSM) method

Address
Faculty of Civil Engineering, Babol Noshirvani University of Technology, Shariati Av., Babol, Mazandaran, Iran.


Abstract
A recently popular method for retrofitting reinforced structure beams is to bond composite plates to their tensile faces. An important failure mode of such plated beams is the debonding of the composite plates from the base material of the beam due to high level of stress concentration in the adhesive at the ends of the composite plate. This paper, shows and presents in more detail a closed-form rigorous solution for interfacial stress in cantilever aluminum beams strengthened with bonded composite (sika wrap) plates and subjected to a uniformly distributed load. The results show that there exists a high concentration of both shear and normal stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the thickness of the laminate; the effect on plate length of the strengthened cantilever beam region, the effect of adhesive (modules, thickness) and the effect of loading and geometry for the cantilever beam; where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. The theoretical predictions are compared with other existing solutions. Finally, this research is helpful for the understanding on mechanical behaviour of the interface and design of the composite-aluminum hybrid structures.

Key Words
strengthening; shear lag effect; sika wrap composite plate; interfacial stresses; aluminum cantilever beam

Address
(1) Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria;
(2) Department of Civil Engineering, Ibn Khaldoun University of Tiaret, Algeria.

Abstract
The Cu-Al-Mn shape memory alloy (SMA) with a new different composition was fabricated by arc melting method. The characteristic shape memory effect (SME) property of Cu-Al based SMA was revealed by performing thermostructural measurements. The differential scanning calorimetry (DSC) tests were taken to observe the reversible martensitic phase transformation peaks of the alloy as evidence of SME property of the alloy. To determine the basic thermodynamical parameters of the alloy, these endothermic and exothermic transformation peaks were analyzed by the tangent differentiation method that was performed automatically by the DSC analyzing program over a manually selected part on the DSC curve and by these analyses the characteristic martensitic transformation temperatures (working temperatures) that found below 100°C and the enthalpy change values of the alloy were directly obtained. The other kinetic transformation parameters of the alloy - the entropy change, hysteresis, and equilibrium temperature - were also determined. The common high-temperature behavior of the Cu-Al based Heusler alloys was detected by differential thermal analysis (DTA) measurement. The XRD and metallography tests that were conducted at room temperature showed the presence of M18R and the dominant 2H martensite structures that formed in the alloy and this dual martensitic structure was also prescribed by determining the theoretical e/a ratio of the alloy. Furthermore, the microhardness tests on the alloy demonstrated the high ductility feature of the alloy. All results demonstrated that the CuAlMn alloy exhibiting a shape memory effect property can be useful in smart alloy applications.

Key Words
shape memory alloy; CuAlMn Heusler alloy; ductility; entropy; shape memory effect; martensite; DSC; DTA; XRD; optical metallography shape memory alloy; CuAlMn Heusler alloy; ductility; entropy; shape memory effect; martensite; DSC; DTA; XRD; optical metallography

Address
(1) Canan Aksu Canbay, Oktay Karaduman, Pshdar A. Ibrahim:
Department of Physics, Firat University, 23119 Elazig Center, Elazig, Turkey;
(2) İskender Őzkul:
Department of Mechanical Engineering, Mersin University, 3334 Yenişehir, Mersin, Turkey.

Abstract
In this study, forced vibration analysis of a fiber reinforced composite cantilever beam is investigated under a harmonic load. In the beam model, the Timoshenko beam theory is used. The governing equations of problem are derived by using the Lagrange procedure. In the solution of the problem the Ritz method is used and algebraic polynomials are used with the trivial functions for the Ritz method. In the solution of the forced vibration problem, the Newmark average acceleration method is used in the time history. In the numerical examples, the effects of fibre orientation angles, the volume fraction and dynamic parameters on the forced vibration response of fiber reinforced composite beam are presented and discussed.

Key Words
fiber reinforced composite materials; forced vibration analysis; Timoshenko Beams; Ritz Method

Address
Department of Civil Engineering, Bursa Technical University, 16330, Bursa, Turkey.


Abstract
This study aimed an experimental data about the effect of physical properties of samples on the mechanical characteristics of high-density polyethylene (HDPE) used for the manufacture of preinsulated pipes for heating networks. The main waterproofing insulation material in the construction of preinsulated pipelines for heating networks is polyethylene. Outer outer casing of preinsulated pipes made of high density polyethylene (HDPE) are used as a waterproofing insulation of polyurethane foam of steel pipes manufactured in the factory. The sufficient resistances to cracking and mechanical stress, resistance to ultraviolet radiation, high density, high strength, low aging are main properties of HDPE. The study of HDPE of different manufacturers is relevant because of the aging of preinsulated pipelines with HDPE outer casing. In this study are tested physical characteristics of HDPE as a melt flow rate, density at 23°C, water content of PE80, PE100 pipe polyethylene of different world manufacturers. The best samples of HDPE and the effects of various aging factors on the properties of polyethylene are presented.

Key Words
building materials; polyethylene; HDPE; heating networks; material properties

Address
Department of Building Materials and Technologies, Karaganda Technical University, N. Nazarbayeva 56, 100000 Karaganda, Kazakhstan.



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