Erden Yildizdag

Istanbul Technical University · Department of Naval Architecture and Marine Engineering

Infill density used in additive manufacturing incorporates a structural response change in the structure. Infill pattern creates a microstructure that affects the mechanical performance as well. Whenever the length ratio of microstructure to geometry converges to one, metamaterials emerge and the strain-gradient theory is an adequate model to predi...

Additive manufacturing (AM) techniques, unlike traditional manufacturing methods with abrasion and shaping, are the production methods made by stacking the building material in layers on top of each other. In particular, AM techniques, which have experienced great advancements in the last 20 years, are divided into 7 main categories according to IS...

A macroscopic continuum model intended to provide predictions for the remodeling process occurring in bone tissue is proposed. Specifically, we consider a formulation in which two characteristic stiffnesses, namely the bulk and shear moduli, evolve independently to adapt the hydrostatic and deviatoric response of the bone tissue to environmental ch...

Metamaterials exhibit significantly different mechanical deformation than in classical “first-order” theory. One possible modeling approach is to use a “straingradient” theory by incorporating also higher gradients of displacements into the formulation. This procedure clearly brings in additional constitutive parameters. In this study, a numerical...

In this study, active noise cancelation (ANC) systems are developed by a computational optimization framework based on particle swarm optimization (PSO), aiming to attenuate engine noise inside smart cubic vehicle enclosures. To have rapid estimation of acoustic properties, the main PSO algorithm is coupled with an analytical solution based on modi...

In this study, an isogeometric finite element-boundary element (FE-BE) framework is proposed to investigate frequency-dependent hydrodynamic characteristics of elastic structures vibrating at free surface or in the vicinity of free surface. The overall numerical framework consists of two parts. In the first part, in vacuo dynamic characteristics ar...

In this study, a boundary integral equation method is proposed for investigating acoustic pressure radiation from a sphere pulsating near a free surface or an impedance plane. The half-space and free-space problems are investigated for the acoustic radiation of pulsating sphere. The effects of free surface and impedance boundaries are introduced in...

In this study, an isogeometric finite element-boundary element framework is presented for the hydroelastic vibration of partially or fully filled horizontal circular cylindrical thin shells. The numerical framework has two main parts, namely dry and wet analysis. In dry analysis, dry natural frequencies and mode shapes are obtained under in vacuo c...

The mechanical behavior of fibrous metamaterials is mainly determined by the interactions between the fibers composing the architecture. These interactions are usually of two different kinds: those directly depending on the positions of the fibers and those that need mediators, usually consisting of hinges, either inelastic or perfect, inducing res...

Bu çalışmada izogeometrik sonlu elemanlar metodunun serbest titreşim problemlerine uygulanışı irdelenmeye çalışılmıştır. İzogeometrik analiz ileri sürüldüğü ilk yıldan itibaren birçok araştırmacının ilgisini çekmiş ve literatürde kendine popüler bir sayısal yöntem olarak yer edinmiştir. Her ne kadar yapılan çalışmalarda bu yöntemin birçok farklı mü...

Son yıllardaki üretim ve malzeme teknolojilerindeki gelişmelere bağlı olarak değişik tipte metamalzemelerin dizaynı ve üretimi akademik ve endüstriyel araştırmalarda popüler bir konu haline gelmiştir. Bu çalışmada pantografik metamalzemelerin mekanik davranışı mikro-makro özdeşleştirme prosedürü ile geliştirilmiş bir ikinci dereceden gradyan modeli...

In this study, to estimate the acoustic field properties inside a cavity with a flexible plate, a fast analytical framework based on the modal interaction approach in frequency domain is introduced. In order to elicit such an algorithm, an in-depth investigation on self-cancellation and mode coupling phenomena is presented to show how to determine...

The design of micro mechanical devices that can facilitate large but recoverable deformations requires a mechanical behavior that embosoms hyperelasticity. While multiphoton lithography is the epitome of microscale fabrication, the employed materials demonstrate a linear elastic response accompanied by limited ductility. In this study, we investiga...

In this study, a combined finite element (FE)–boundary element (BE) method is presented to investigate the dynamic characteristics of shell and plate structures in contact with fluid. The numerical procedure consists of two parts. In the first part, the dynamic characteristics of structures are obtained under in-vacuo condition by using the finite...

The central theme of this study is to investigate a remarkable capability of a second-gradient continuum model developed for pantographic structures. The model is applied to a particular type of this metamaterial, namely the wide-knit pantograph. As this type of structure has low fiber density, the applicability of such a continuum model may be que...

In this study, a three-dimensional discontinuous Galerkin isogeometric analysis framework is presented for the analysis of composite laminates. Non-uniform rational B-splines are employed as basis functions for both geometric and computational implementations. From a practical point of view, modeling with multiple non-uniform rational B-spline patc...

In this study, the dynamic characteristics (i.e. natural frequencies and associ­ated mode shapes) of a partially filled horizontal cylindrical shell are investi­gated experimentally and by an isogeometric finite element-boundary element method. The proposed numerical procedure is divided into two parts. In the first part, the dynamic characteristic...

The equilibrium forms of pantographic blocks in a three-point bending test are investigated via both experiments and numerical simulations. In the computational part, the corresponding minimization problem is solved with a deformation energy derived by homogenization within a class of admissible solutions. To evaluate the numerical simulations, ser...

In this paper, elastic wave propagation in a one-dimensional micromorphic medium characterized by two internal variables is investigated. The evolution equations are deduced following two different approaches, namely using: (i) the balance of linear momentum and the Clausius–Duhem inequality, and (ii) an assumed Lagrangian functional (including a g...

This paper is concerned with the isogeometric analysis (IGA) of composite laminates under cylindrical bending. Non-uniform rational B-splines (NURBS) are employed as basis functions for both geometric and computational implementations. In order to account for multiple domains, each lamina is modeled as a single NURBS patch. This multipatch represen...

Currently available conductive inks present a challenge to achieving electrical performance without compromising mechanical properties, scalability, and processability. Here, we have developed blends of carbon black and the commercially available triblock copolymer, SEBS-g-MAH (FG1924G, Kraton®), that can be readily applied as a conductive coating...

Thin-walled curved shells and plates are frequently used in naval architecture and offshore engineering as structural elements. Therefore, it is important to have an accurate understanding of the dynamic characteristics (natural frequencies, mode shapes, etc.) of these structures in contact with fluid. Presence of a heavy fluid significantly alters...

In this paper, a static structural analysis of laminated composites is performed by Non-uniform rational B-splines (NURBS) based isogeometric analysis (IGA). As a concept of isogeometric analysis, NURBS are utilized as basis functions for both design and computational processes in isogeometric analysis. In the mathematical model, each layer of the...

Recent advanced manufacturing techniques such as 3D printing have prompted the need for designing new multiscale architectured materials for various industrial applications. These multiscale architectures are designed to obtain the desired macroscale behavior by activating interactions between different length scales and coupling different physical...

In this study, the hydroelastic vibration analysis of clamped rectangular plates vertically in contact with quiescent fluid is carried out. The method of analysis is divided into two parts; namely, in-vacuo and wet. Both in-vacuo and wet analyses are conducted by the novel isogeometric NURBS concept; the in-vacuo analysis is carried out by the isog...

The hydroelastic vibration analysis of clamped rectangular plates both vertically and horizontally submerged in fluid is studied by isogeometric FE/BE approach in this paper. By adopting the linear hydroelasticity theory, the computational procedure of the fluid-structure interaction problem is divided into two parts. In the first part, dynamic ana...

A novel method in numerical analysis called isogeometric analysis is applied on structural analysis of straight and free shaped slender beams as well as isotropic and composite thick beams. Relying on linearly isotropic constitutive law and geometrically non-linear structural response, stiffness matrix is generated by successive derivation of the s...