Gordan Jelenić - Academia.edu (original) (raw)

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Papers by Gordan Jelenić

Sažetak: Predstavljen je geometrijski točan prostorni gredni konačni element proizvoljnog reda te... more Sažetak: Predstavljen je geometrijski točan prostorni gredni konačni element proizvoljnog reda temeljen na teoriji nepomičnog pola. Za razliku od originalne formulacije koju su predstavili Bottasso i Borri, ova koristi uobičajene kinematičke nepoznanice pa se stoga može kombinirati sa standardnim konačnim elementima. Preliminarni rezultati pokazuju da, ukoliko pomake i rotacije popravljamo u Gaussovim integracijskim točkama, ova formualcija može dati točnije rezultate. Ovaj rad je planiran za objavu u zborniku radova druge ECCOMAS konferencije mladih istraživača (2 ECCOMAS Young Investigators Conference) koja će se održati u Bordeauxu u Francuskoj u rujnu ove godine [3]. Ključne riječi: 3D grede, nelinearna analiza, interpolacija ovisna o konfiguraciji, fixed-pole pristup

International Journal for Numerical Methods in Engineering

Multibody System Dynamics

This paper presents a formulation for frictionless beam-to-beam contact using the mortar method. ... more This paper presents a formulation for frictionless beam-to-beam contact using the mortar method. The beams are modelled using the geometrically exact theory. A similar approach has been proposed very recently, with respect to which we offer a formulation based on a Lagrange-multiplier method and a simpler algorithm to cover the static interaction within the contact zone and analyse the performance of the method for different orders of interpolation for the Lagrange multiplier and in the presence of self-contact. Appropriate contact kinematics is developed from which the residual vector and the tangent stiffness matrix are obtained from a suitable contact potential and its variation and consistent linearisation for implementation in the finite element method. The algorithm describing the fulfilment of the contact kinematics is described in detail. The mortar method is found out to be suitable for modelling beam-to-beam contact and self-contact. The geometrically exact beam theory ass...

U radu je ukratko predstavljena nelinearna geometrijski točna teorija greda. Izveden i implementi... more U radu je ukratko predstavljena nelinearna geometrijski točna teorija greda. Izveden i implementiran je konačni element na temelju te teorije. Također je opisana Newton-Raphsonova iteracijska metoda, koja uključuje ažuriranje vrijednosti s posebnim naglaskom na neograničeno velike 3D rotacije. Ovaj algoritam je bitan za samo programiranje metode konačnih elemenata. Na kraju je element testiran preko standardnih numeričkih primjera iz literature

Zbornik radova jedanaestog susreta Hrvatskog društva za mehaniku, Sep 16, 2021

Sažetak U ovome radu je kratko predstavljena geometrijski točna teorija greda, zapisana u Liejevi... more Sažetak U ovome radu je kratko predstavljena geometrijski točna teorija greda, zapisana u Liejevi grupi pomaka krutog tijela (3). Zapisane su jednadžbe za statičku ravnotežu i provedena je diskretizacija zapisa u konačni element. Na kraju je element testiran preko standardnog numeričkog primjera iz literature.

$Research paper thumbnail of On characterising fracture resistance in mode-I delamination$

9th International Congress of Croatian Society of Mechanics, 2018

In this work we focus on the mode-I quasi-static crack propagation in adhesive joints or composit... more In this work we focus on the mode-I quasi-static crack propagation in adhesive joints or composite laminates. For this problems a number of different standards have been approved. The most widely used are based on the double cantilever beam (DCB) test and on linear elastic fracture mechanics (LEFM) but differ in some aspects of the testing procedure and the recommended data-reduction schemes. The applicability of these methods is still a matter of debate in the scientific community, particularly in the case of ductile interfaces. We revisit the accuracy of the most used standards and compare it with other methods based on either LEFM or J-integral theory. All the methods analysed in our work are based on either Euler-Bernoulli or Timoshenko beam theories. We present a number of numerical examples where we compare different expressions for fracture resistance obtained with different methods. The input for the analysis, which includes applied load, cross-head displacement and rotation, crack length and cohesive zone length, is obtained from the numerical model which simulates real experiments. In these simulations, we use a Timoshenko beam model with a bi-linear CZM, which allows us accurate comparison with analytical formulas for fracture resistance based on Euler-Bernoulli and Timoshenko beam theory.

KSCE Journal of Civil Engineering, 2022

Zbornik radova, 2021

Ovaj rad razmatra deformacije pri čistom savijanju homogenih i heterogenih nosača. Deformacije su... more Ovaj rad razmatra deformacije pri čistom savijanju homogenih i heterogenih nosača. Deformacije su određene analitičkim putem, eksperimentalno, metodom tenzometrije te metodom konačnih elemenata. Definirana je geometrija uzoraka koja čini nosače heterogenima i izvedena formula momenta površine drugog reda oslabljenog nosača. Cilj rada je provjera primjenjivosti gredne teorije za analizu heterogenih izotropnih i ortotropnih nosača. Uspoređeni su rezultati tri pristupa, pri čemu su eksperimentalni rezultati korišteni kao referentni.

We present a new three-node Timoshenko curved-beam finite element for in-plane actions constructe... more We present a new three-node Timoshenko curved-beam finite element for in-plane actions constructed on expanded linked interpolation for a straight beam. Only the displacements and the rotation of the cross-section are interpolated and the element is formulated in a pure displacement-based fashion. At first the displacement fields are enriched in polynomial order to the quartic form associated to two pairs of internal bubble parameters. Then the shear strain constraints are enforced on the displacement interpolations and this parameters are expressed in terms of the rotation degrees of freedom resulting in a new linked interpolation for a curved beam element. At the same time the geometry is approximated using Lagrangean interpolation, so that the element-stiffness assembly is very simple and can easily be implemented in a computer code. The beam kinematics is defined using the global displacement variables in contrast to the commonly used displacement unknowns in the local coordinat...

Acta Geotechnica Slovenica, 2013

In this paper deformation of a Bernoulli beam resting on Winkler's soil is reviewed in light ... more In this paper deformation of a Bernoulli beam resting on Winkler's soil is reviewed in light of the mixed finite-element methodology. While the stiffness matrix of the Bernoulli beam problem utilising the standard displacement-based approach, in which only the displacement field is interpolated, may be alternatively obtained using a mixed-type approach to the absolutely shear-stiff second-order Timoshenko beam (in which the rotation and shear-stress resultant fields are additionally interpolated), the two approaches lead to different Winkler-type soil-stiffness contributions. Furthermore, extending the mixed-type formalism into both of these elements by additionally interpolating the distributed soil-reaction field, the soil-stiffness contributions differ additionally. In this way four different elements are obtained, with one, two, three or four independently interpolated fields, in which the beam stiffness matrix is equal, but the soil stiffness matrices are different. It is d...

Dynamic sensitivity of a one-dimensional stack of four rigid blocks with controlled initial gaps,... more Dynamic sensitivity of a one-dimensional stack of four rigid blocks with controlled initial gaps, undergoing external harmonic vibrations is investigated. Time variation of the mass inertia and the relative kinetic energy are considered as dynamic block stack attributes. Numerical simulation is based on the Non Smooth Contact Dynamics (NSCD) time integration framework Solfec (http://code.google.com/p/solfec/). Sensitivity space parameters include a range of excitation frequencies and velocity amplitudes.

Zbornik radova, 2018

Provedeno je eksperimentalno ispitivanje dinamičkog odziva modela slobodno oslonjene grede s doda... more Provedeno je eksperimentalno ispitivanje dinamičkog odziva modela slobodno oslonjene grede s dodatnim koncentriranim masama. Određene su amplitude pobude unutar kojih je odgovor grede linearan. Prikazani su eksperimentalno dobiveni rezultati za pomake grede prilikom harmonijske jednolike i nejednolike pobude te prilikom simulacije Northridge potresnog zapisa, koji se mogu koristiti kao eksperimentalni benchmark primjerci za nejednoliku pobudu oslonaca.

Finite Elements in Analysis and Design, 2015

The 6D representation of the configuration tensor was used to develop a geometrically non-linear ... more The 6D representation of the configuration tensor was used to develop a geometrically non-linear beam finite element of an arbitrary order with Lagrangian (additive) interpolation of the configurational parameters. Analogously to the 3D case, where additive interpolation of the rotational parameters results in non-objective formulation, as shown by Crisfield and Jelenić, the proposed elements exhibit even worse non-objective behaviour, evident even in planar cases! A remedy for this problem was to develop and implement the so-called generalised shape functions (given by Jelenić and Crisfield for a 3D case) for the configurational parameter (which is a 6D vector). This successfully solved the problem of objectivity, but decreased formulation robustness significantly. We assume that the cause of this are not the shape functions themselves, but the significant numerical instability of the transformational matrices they contain. In this paper we pinpoint the terms in those matrices which we assume to be responsible for loss of robustness and analyse them with respect to computational precision and propose a remedy.

Finite-element implementation of mechanical problems defined on non-linar manifolds requires part... more Finite-element implementation of mechanical problems defined on non-linar manifolds requires particular attention, since some of the important physical properties of equilibrium or motion are not necessarily automatically inherited from the underlying continuous governing equations. Here we review some of the features of the so-called objective, helicoidal and fixed-pole approaches and show that there exist interesting similarities between them even though their development has been motivated by clearly different demands. More detail is presented for the configuration space formed by a product of a three-dimensional vector space and a three-parametric orthogonal differential manifold as well as the non-linear non-orthogonal six-parametric differential manifold of complete motion.

U ovome radu provedena je numericka analiza problema deformiranja linearno elasticnih plocastih n... more U ovome radu provedena je numericka analiza problema deformiranja linearno elasticnih plocastih nosaca. Numericka analiza provedena je primjenom metode konacnih elemenata. Upotrijebljen je trokutni konacni element s vezanom interpolacijom za polje pomaka koji se temelji na Mindlinovoj teoriji srednje debelih ploca. Ponasanje spomenutog elementa testirano je na tri tipska problema te na debelim i tankim plocama.