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Effects of the composite stacking sequence on the failure load of the single lap bonded joint

Mokhtari M., Madani A., Benzaama H., Malarino S.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 4

1257--1268

EN

Composite materials are widely used in aircraft structures, their relative rigidity/weight confers their advantage over metal structures, and the stacking sequence plays an important role for their use. The objective of this work is to analyze by the finite element method the mechanical behavior of a single lap joint of composite/composite type under a tensile load. In order to see the effects on the failure load, two basic parameters are taken into consideration; the stacking sequence of composite and thickness of each layer constituting the composite. Calculation of the failure load is made numerically with the ABAQUS code using the developed technique of VCCT (Virtual Crack Closure Technique) based on fracture mechanics. Finally, the influence of the bonding defect on the failure load is analyzed. The results clearly show the importance of optimizing fiber orientation and hence the stacking sequence for proper use of composite in bonded assemblies.

2

A new automated stretching finite element method for 2D crack propagation

Bentahar M., Benzaama H., Bentoumi M., Mokhtari M.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 3

869--881

EN

This work presents a study of crack propagation with a new 2D finite element method with the stretching of the mesh. This method affects at each propagation step new coordinates of each element node of the mesh. The structure is divided to areas and each area has its own coordinate formulas. A program in FORTRAN allows us to create a parametric mesh, which keeps the same number of nodes and elements during different steps of crack propagation. The nodes are stretched using the criterion of maximum circumferential stress (MCS). The fracture parameters such as stress intensity factors in modes I and II and the orientation angles are calculated by solving the problem by the finite element code ABAQUS.

3

A critical review on soil ionisation modelling for grounding electrodes

Mokhtari M., Abdul-Malek Z., Gharehpetian G.B.

Archives of Electrical Engineering

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2016

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Vol. 65, nr 3

449--461

EN

Grounding electrode resistance non-linearly changes under impulse conditions due to soil ionisation phenomenon. Several models have been proposed to model soil ionisation for grounding electrodes applications. However, to date, there is yet an attempt made to compile all these works into a comprehensive review article. Therefore, this paper is written with the objective of summarizing all related works in this field as a one– stop reference. With reference to the literature, this paper is written to summarize the working principles of the soil ionisation models as well as the accuracy and performance analysis of the models. This paper, particularly highlights the deficiencies of the available models in terms of accuracy and performance. This knowledge will contribute to the development of a new accurate and efficient soil ionisation model.

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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

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2015

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Vol. 15, no. 3

668--679

EN

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.