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Parameters optimization of MAG welding for enhancing the mechanical properties and buckling behaviour of welded steel

Alwan A. H., Mahmood N. Y.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

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Vol. 99, nr 1

5--13

EN

Purpose: The influence of metal active gas welding variables, including current, wire feeding speed and gas flow rate on the ultimate tensile strength and critical buckling load of steel (St.24) and the optimized welding conditions were discussed. Design/methodology/approach: The experimental steps are firstly designing the experiments, secondly conducting the mechanical tests, thirdly analysing the results through Minitab 16 and finally determining the optimum welding parameters. Confirmation tests of the optimized variables were validated. Findings: ANOVA approach manifested that the significant effect of welding variable on the tensile strength was the gas flow rate, while the current was on the critical buckling load. The results are confirmed and given the optimum values. Research limitations/implications: The influence of MAG welding variables (current, wire feeding speed and gas flow rate) on the tensile and buckling strengths of steel will be investigated in order to avoid the failure of many welded assemblies in the structures due to the buckling, in addition to reduce the requirement of long time and high cost to produce such assemblies. Therefore, it is necessary to find a solution to encounter the difficulties in their welding process. Practical implications: The major challenge was how to reduce the time and cost beside gaining the optimum properties through the designed experiments. Originality/value: The results may be helpful to design any welded joints in machine frames, structural steel connections and crane structures at the optimum condition.

2

Mechanical nature of a single walled carbon nanotube using Legendre’s polynomials

Tiwari P., Nagar P.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 4

1153--1162

EN

This paper is concerned with the mechanical response of a single-walled carbon nanotube. Euler-Bernoulli’s beam theory and Hamilton’s principle are employed to derive the set of governing differential equations. An efficient variational method is used to determine the solution of the problem and Legendre’s polynomials are used to define basis functions. Significance of using these polynomials is their orthonormal property as these shape functions convert mass and stiffness matrices either to zero or one. The impact of various parameters such as length, temperature and elastic medium on the buckling load is observed and the results are furnished in a uniform manner. The degree of accuracy of the obtained results is verified with the available literature, hence illustrates the validity of the applied method. Current findings show the usage of nanostructures in vast range of engineering applications. It is worth mentioning that completely new results are obtained that are in validation with the existing results reported in literature.

3

On the buckling and vibrational response of carbon nanotubes with spiral deformation

Yengejeh S. I., Kazemi S. A., Öchsner A.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 2

613--619

EN

Perfect and spiral models of carbon nanotubes (CNTs) have been simulated based on the finite element method and their vibrational and buckling behavior has been investigated. In order to evaluate their natural frequency and critical buckling load, computational tests have been conducted. It has been concluded that the existence of any geometrical modification in the configuration of perfect CNTs results in a remarkable reduction in the natural frequency and critical buckling load of CNTs. It has been also revealed that the analytical solutions are in good agreement with the finite element simulation results in the cases of perfect and spiral CNTs.

4

Flexural vibration and buckling analysis of single-walled carbon nanotubes using different gradient elasticity theories based on Reddy and Huu-Tai formulations

Karličić D., Kozić P., Pavlović R.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 1

217--233

EN

The aim of the present work is to analyze free flexural vibration and buckling of single-walled carbon nanotubes (SWCNT) under compressive axial loading based on different constitutive equations and beam theories. The models contain a material length scale parameter that can capture the size effect, unlike the classical Euler-Bernoulli or Reddy beam theory. The equations of motion of the Reddy and the Huu-Tai beam theories are reformulated using different gradient elasticity theories, including stress, strain and combined strain/inertia. The equations of motion are derived from Hamilton’s principle in terms of the generalized displacements. Analytical solutions of free vibration and buckling are presented to bring out the effect of the nonlocal behavior on natural frequencies and buckling loads. The presented theoretical analysis is illustrated by a numerical example, and the results are qualitatively compared by another results.

5

Buckling analysis of three-layered rectangular plate with piezoelectric layers

Yaghoobi H., Rajabi I

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 4

813--826

EN

This paper employs an analytical method to analyze the buckling of piezoelectric coupled plates with different boundary conditions on the basis of the first order shear deformation plate theory. The structure is composed of a host isotropic plate and two bonded piezo electric layers. Convergence study is performed in order to verify the numerical stability of the presented method. Also, the present analysis is validated by comparing the results with those in the literature, and then the critical buckling load of the piezoelectric coupled plates is presented in tabular and graphical forms for different plate aspect ratios, thickness of the piezoelectric, actuator voltage and boundary conditions.