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Prediction of the bending and out-of-plane loading effects on formability response of the steel sheets

Peng Deping, Chen Shun, Darabi Roya, Ghabussi Aria, Habibi Mostafa

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

563--575

EN

Failure in sheet metal forming can occur by necking, fracture or wrinkling. By using a forming limit diagram (FLD) as a powerful tool to prevent sheets metal failures in the forming process, provides parameters controlling throughout forming. There are different developed methods for predicting FLDs, which estimate sheet metal forming strains limits. Assessment of FLD estimation reveals that there is a dependency between the effect of several factors containing normal stress, shear stress, sheet thickness, mechanical properties, metallurgical properties, yield function, strain path, and bending with formability. In this research, the effects of bending via two finite element models are investigated. In the first method, the out-of-plane deformation is applied by increasing punch displacement to study the effects of bending. In the second method, the effect of bending is investigated via changing punch diameter (25, 50, 70 and, 100 mm). The Marciniak–Kuczynski (M–K) theory is used to predict the time of localized necking in finite element simulations. Furthermore, a novel method for the determination of the inhomogeneity coefficient is presented in M–K model to simulate the groove width for M–K model. To verify finite element simulation results, Nakazima tests with 50 and 100 mm punch diameters were done as experimental studies. The comparison of experimental results and finite element analysis illustrates that the increasing bending or the out-of-plane loading can improve formability. At the end, the effect of bending on FLD is reported as an equation based on minor and major strains.

2

On the nonlinear dynamics of the multi-scale hybrid nanocomposite-reinforced annular plate under hygro-thermal environment

Al-Furjan M. S. H., Dehini Reza, Paknahad Masoud, Habibi Mostafa, Safarpour Hamed

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

51--75

EN

In this article, the nonlinear free and forced vibration analysis of multi-scale hybrid nano-composites (multi-scale HNC) annular plate (multi-scale HNCAP) under hygro-thermal environment and subjected to mechanical loading is presented. The material of matrix composite is enhanced by either carbon fibers (CF) or carbon nanotubes (CNTs) at the small or macro-scale. The multi-scale laminated annular plate’s displacement fields are determined using third-order shear deformation theory (third-order SDT) and nonlinearity of vibration behavior of this structure is taken into account considering Von Karman nonlinear shell model. Energy method known as Hamilton principle is applied to create the motion equations governed to the multi-scale HNCAP, while they are solved using generalized differential quadrature method (GDQM) as well as multiple scale method. The results created from finite-element simulation illustrates a close agreement with the semi-numerical method results. Ultimately, the research’s outcomes reveal that increasing value of the moisture change (ΔH) and orientation angle parameter (θ), and the rigidity of the boundary conditions lead to an increase in the structure’s frequency. Besides, whenever the values of the nonlinear parameter (γ) are positive or negative, the dynamic behavior of the plate tends to have hardening or softening behaviors, respectively. Also, there are not any effects from γ parameter on the maximum amplitudes of resonant vibration of the multi-scale HNCAP. Last but not least, by decreasing the structure’s flexibility, the plate can be susceptible to have unstable responses.

3

Energy absorption of the strengthened viscoelastic multi-curved composite panel under friction force

Shao Yunhong, Zhao Yang, Gao Jun, Habibi Mostafa

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

71--99

EN

This study investigated FG carbon nanotubes filled composites, which are promising metamaterials that can be useful in the energy absorption field. This structure can absorb energy through elastic deformation. For this issue, absorbed energy and dynamic stability analysis of the FG-CNTRC curved panel surrounded by a non-polynomial viscoelastic substrate using three-dimensional poroelasticity theory is investigated. For stability of the structure after vibrating, the viscoelastic substrate as the non-polynomial viscoelastic model is presented. The curved panel comprises multilayer carbon nanotubes (CNT) which are uniformly distributed in all layers of facing sheets; however, the system’s weight fraction alters for each layer through the thickness orientation. The influences of several parameters, such as Winkler–Pasternak parameters, span angle CNTs’ volume fraction, length to radius ratio, compressibility coefficient, friction coefficient, torsional parameter, initial axial stress, and damping factor on the dynamic responses of the FG-CNTRC curved panel surrounded by a non-polynomial viscoelastic substrate are investigated. The golden result of this paper is that the effect of radial stress on the energy absorption is hardly dependent on the value of the foundation parameters. As an applicable outcome in pertained applications, by increasing the compressibility, and friction coefficients, the composite shell's energy absorption decreases.