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A parametric study of the mechanical behavior of nested multi tube structures under quasi-static loading

Chahardoli S., Alavi Nia A., Asadi Mehrdad

Archives of Civil and Mechanical Engineering

2019

Vol. 19, no. 4

943--957

Mechanical behavior of nested aluminum structures under lateral and quasi-static loadings has been investigated in current paper. These structures consist of two nested tubes in which the inner tube is located vertically in the horizontal outer tube. The research has been done numerically and experimentally. In the numerical section, the LS-DYNA software has been used while experimental results are implemented to validate the FE outcome. The well correlated numerical results show that increasing the diameter of the inner tube leads to a decrease in the maximum force and the specific energy absorption. Later, employing the optimization by response surface method in Minitab software, the energy absorber's characteristics has been optimized and introduced as new set of specifications. High crush force efficiency is the main criterion in current research.

A parametric study on the mechanical performance of buried X65 steel pipelines under subsurface detonation

Mokhtari M., Alavi Nia A.

Archives of Civil and Mechanical Engineering

2015

Vol. 15, no. 3

668--679

Existing studies on the response of buried steel pipelines to explosion generally concern finding safe distance of explosion where pipeline does not undergo plastic deformation while intentional explosions impose intense deformations on steel pipelines. In order to address this gap, the present investigation is carried out numerically dealing with the response of buried API 5L grade X65 pipelines to a nearby sever explosion due to sabotage or war. Furthermore, the effects of the pipeline diameter-to-thickness ratio and internal pressure on this response were investigated numerically. A combined Eulerian–Lagrangian (CEL) method was adopted to develop a full-coupled 3D finite element model. Employing simplified Johnson-Cook material model to simulate mechanical behavior of steel pipelines and considering air in the model increased the simulation accuracy. The results from present study were compared with those of recent investigations and good agreements were observed. The results show that, the amount of deformation and consequently the value of maximum equivalent strain of pipelines decrease with either increase in operating pressure or decrease in diameter-to-thickness ratio; however, the effect of pipeline internal pressure was far more than diameter-to-thickness ratio. The results obtained from the present study can be used for improvement in protective design of steel pipelines.