Mohammad Ali Kouchakzadeh

Bio: Mohammad Ali Kouchakzadeh is an academic researcher from Sharif University of Technology. The author has contributed to research in topics: Buckling & Conical surface. The author has an hindex of 18, co-authored 53 publications receiving 784 citations. Previous affiliations of Mohammad Ali Kouchakzadeh include Tohoku University & Islamic Azad University.

Free vibration analysis of joined conical shells: Analytical and experimental study

Abstract: Natural frequencies and mode shapes of two joined isotropic conical shells are presented in this study. The joined conical shells can be considered as the general case for joined cylindrical–conical shells, joined cylinder–plates or cone–plates, conical and cylindrical shells with stepped thicknesses and also annular plates. Governing equations are obtained using thin-walled shallow shell theory of Donnell and Hamilton׳s principle. The continuity conditions at the joining section of the cones are appropriate expressions among stress resultants and deformations. The equations are solved assuming trigonometric response in circumferential and series solution in meridional directions and all combinations of boundary conditions can be assumed in this method. The results are compared and validated with the available results in other investigations and also modal testing. The effects of semi-vertex angles and meridional lengths on the natural frequency and circumferential wave number of joined shells are investigated.

Buckling analysis of elliptically delaminated composite laminates with consideration of partial closure of delamination

Abstract: By taking account of partial closure of delamination, the buckling analysis of elliptically delaminated composite laminates under in-plane compressive loads is made using a finite element method. In order to deal with the contact problem for the partial closure of delamination, a penalty function method is proposed. In the method, fictitious springs are inserted iteratively at all of the overlapped points. Stiffness of each spring is calculated by considering the overlap and stiffness of the structure at that point. Numerical calculations were carried out to clarify the effects of delamination size, shape, position through thickness and ply angle of delaminated layer on the buckling load and buckling mode. The results are shown in graphs.

Ground tyre rubber (GTR) in thermoplastics, thermosets, and rubbers

Abstract: The disposal of worn tyres and their economic recycling mean a great challenge nowadays. Material recycling is the preferred way supported by legislative actions and economical/ecological arguments. This paper surveys the recent developments devoted to the reclamation, surface treatments, and to the use of ground tyre rubber (GTR) in thermoplastics, thermosetting resins, and rubber formulations. This review discloses also the principle underlying compatibilization to improve the adhesion of GTR to the corresponding matrix. It was concluded that value-added application of GTR can especially be expected in thermoplastic elastomers, and rubber combinations.

Adaptive refinement and multiscalemodeling in 2d peridynamics

Abstract: The original peridynamics formulation uses a constant nonlocal region, the horizon, over the entire domain. We propose here adaptive refinement algorithms for the bond-based peridynamic model for solving statics problems in two dimensions that involve a variable horizon size. Adaptive refinement is an essential ingredient in concurrent multiscale modeling, and in peridynamics changing the horizon is directly related to multiscale modeling. We do not use any special conditions for the “coupling” of the large and small horizon regions, in contrast with other multiscale coupling methods like atomistic-to-continuum coupling, which require special conditions at the interface to eliminate ghost forces in equilibrium problems. We formulate, and implement in two dimensions, the peridynamic theory with a variable horizon size and we show convergence results (to the solutions of problems solved via the classical partial differential equations theories of solid mechanics in the limit of the horizon going to zero) for a number of test cases. Our refinement is triggered by the value of the nonlocal strain energy density. We apply the boundary conditions in a manner similar to the way these conditions are enforced in, for example, the finite-element method, only on the nodes on the boundary. This, in addition to the peridynamic material being effectively “softer” near the boundary (the so-called “skin effect”) leads to strain energy concentration zones on the loaded boundaries. Because of this, refinement is also triggered around the loaded boundaries, in contrast to what happens in, for example, adaptive finite-element methods.

Dynamics, vibration and control of rotating composite beams and blades: A critical review

Abstract: Rotating composite beams and blades have a wide range of applications in various engineering structures such as wind turbines, industrial fans, and steam turbines. Therefore, proper understanding of such structures is of a great importance. As a result, the behavior of rotating composite beam structures has received a lot of attention. This paper presents a comprehensive review of scholarly articles about rotating composite beams as published in the past decades. The review addresses analytical, semi-analytical and numerical studies dealing with dynamical problems involving adaptive/smart/intelligent materials (e.g. piezoelectric materials, electrorheological fluids, shape memory alloys, etc.), damping and vibration control, advanced composite materials (e.g. functionally graded materials and nanocomposites), complicating effects and loadings (e.g. added mass, tapered beams, initial curve and twist, etc.), and experimental methods. Moreover, the influence of Vlasov or restrained warping, out-of-plane warping, transverse shear, arbitrary cross-sectional geometry, trapeze phenomena, swept tip, size-dependent effect, as well as other areas that have been considered in research, are reviewed in depth. The review concludes with a presentation of the remaining challenges and future research needs.