András Lengyel

András Lengyel
Budapest University of Technology and Economics · Department of Structural Mechanics

Doctor of Philosophy

About

32
Publications
3,447
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142
Citations
Citations since 2017
14 Research Items
94 Citations
20172018201920202021202220230510152025
20172018201920202021202220230510152025
20172018201920202021202220230510152025
20172018201920202021202220230510152025
Introduction
Skills and Expertise

Publications

Publications (32)
Article
Full-text available
The presence of knots significantly influences the mechanical behavior of timber. This research presents a parametric finite element analysis of the effect of knot characteristics on the flexural capacity of timber beams. Parameters include knot radius, longitudinal and vertical positions, length, and diving angle. The generation of the FE model is...
Article
Full-text available
The strengthening of timber beams with carbon-fibre-reinforced polymers (CFRP) has been widely used in the last decades to enhance the behaviour of historical or new timber structures, usually for bending. While considerable improvement in capacity and ductility is typically achieved, the increase in stiffness was, in many cases, well short of anal...
Article
Full-text available
This research presents a parametric three-dimensional finite element study on the effects of closely spaced knots and related fibre deviations on the flexural failure mechanism of wood. The model considers the effects of the position of the knots along the beam's longitudinal and vertical axis. The numerical models were validated by bending tests p...
Article
Full-text available
The application of fibre-reinforced polymers (FRP) for strengthening timber structures has proven its efficiency in enhancing load-bearing capacity and, in some cases, the stiffness of structural elements, thus providing cost-effective and competitive alternatives both in new design and retrofitting existing historical buildings. Over the last few...
Article
Full-text available
Fibre-reinforced polymers (FRP) are widely used to enhance the performance of structural elements of various materials, including timber. Measurements of reinforced beams mostly involve load-deflection relationships in order to experimentally verify mechanical improvements, while numerical simulations require material parameters for constitutive la...
Article
Full-text available
The primary purpose of the pursued research presented in this article is to propose a new technique to create the actual three-dimensional geometry of knots and related fibre deviations and eliminate the inconsistency between modelling the knots as openings or solids. The geometrical and mechanical characteristics of knots and related local disturb...
Article
Full-text available
This study focuses on the flexural behavior of timber beams externally reinforced using carbon fiber-reinforced polymers (CFRP). Linear and non-linear finite element analysis were proposed and validated by experimental tests carried out on 44 timber beams to inversely determine the material properties of the timber and the CFRP. All the beams have...
Article
This paper presents a study on the mechanical behaviour of thin membranes modelling the common 32-panel soccer balls. Most soccer balls are fabricated of synthetic flat panels subject to an internal pressure. Unlike most tensile structures such as tents, balls form closed surfaces, which are expected to comply strict conditions, most importantly re...
Article
Full-text available
Enhancement of structural behaviour of various construction materials using fibre reinforced plastics (FRP) is an important branch of engineering research, including the increasing application for structural timber as well. This study deals with the reinforcement of standard construction formwork timber beams with carbon fibre reinforced plastics (...
Article
In the late 1930s, an inflatable truncated icosahedral beach-ball was made such that its hexagonal faces were coloured with five different colours. This ball was an unnoticed invention. It appeared more than twenty years earlier than the first truncated icosahedral soccer ball. In connection with the colouring of this beach-ball, the present paper...
Article
Full-text available
Enhancement of timber beams with fibre reinforced materials gained momentum in the last few decades producing a wide range of materials, techniques and modelling methods. Experiments show that the potential improvement of structural behaviour is greatly affected by the type of reinforcement, wood species, etc. In this study a series of experiments...
Article
This paper deals with the consideration of loading uncertainties in topology optimization via a fundamental optimization problem setting. Variability of loading in engineering design is realized e.g. in the action of various load combinations. In this study this phenomenon is modelled by the application of two mutually excluding (i.e. alternating)...
Conference Paper
Full-text available
The volume enclosed by a membrane forming a convex polyhedron increases for inflation even if the deformation is inextensional. Here, in the case of a cube, the following problem arises: How must the surface of a cube be deformed inextensionally so that the volume of the obtained polyhedron will be as large as possible? In the paper, this problem i...
Article
Full-text available
The problem treated here is: amongst the convex polyhedra that can be circumscribed about the unit sphere and have faces, which has the minimum surface area? A new optimization method based on mechanical analogies is worked out to solve this problem. By using this method, new computer-generated solutions are presented for and . The second of these...
Article
In this paper, dimple patterns of golf balls, that can provide inspiration for design of spherical grid structures especially geodesic domes, are investigated. Several examples of golf ball designs are presented to show different symmetry groups and actual geometrical configurations.
Article
This paper is concerned with the static and kinematic behavior of two chain-like bar-and-joint assemblies which have the same topology. One is a structure which is both statically and kinematically indeterminate, and constitutes a higher-order infinitesimal mechanism. The other is a structure which is both statically and kinematically determinate,...
Conference Paper
Full-text available
Most soccer balls are made of stitched leather or synthetic panels with a bladder inside. The initial configuration of the balls can be represented by polyhedra in the three dimensional space. For the numerical evaluation of the sphericity of the ball, a method previously proposed by the first author is used in this paper. Following previous studie...
Article
Most soccer balls are made of stitched leather or synthetic flat panels with a bladder inside. The initial flat configuration is represented by polyhedra in 3-space. This paper studies polyhedra related to different symmetry groups in order to find the optimal topology and the optimal dimensions for soccer ball design. A number of polyhedra obtaine...
Article
While discussing reciprocal theorems most textbooks mention only Maxwell's reciprocal theorem as a consequence of Betti's theorem. Textbooks investigating this topic in detail mention three reciprocal theorems. In this paper we show that there exist exactly 10 reciprocal theorems and we illustrate each with an example.
Article
Full-text available
Different types of loss of stability of elastic structures are usually illustrated by simple models. This paper presents a family of structures which can demonstrate four cases of the double cusp catastrophe by the variation of a parameter. The path defined by this parameter is calculated in the diagram of the classes of the double cusp catastrophe...
Article
The compatibility paths of mechanisms with a single degree-of-freedom typically form sets of curves in the global representation space. We classify the different cases of compatibility by introducing an energy function. The result obtained also depends on which element of the mechanism is regarded as driven. The different singularity types are demo...
Article
The kinematic determinacy of a bar-and-joint mechanism is dependent on the topology and the metric properties of the structure. Special arrangements can result in singularities, such as bifurcation points on the compatibility paths. The analysis of a special four-bar linkage yields an infinitely degenerate bifurcation point. Modifications in plane...
Article
This paper deals with the singularities which occur on the compatibility paths of single degree of freedom finite mechanisms consisting of rigid bars and pin joints. We first examine the analogy between the bifurcations along the compatibility paths of mechanisms and those appeared in the equilibrium paths of elastic structures. Based on it, we pro...
Article
This article discusses singularities occurring in compatibility paths of planar bar-and-joint mechanisms with 1 degree-of-freedom. Bifurcation of branches of compatibility paths are examined and simple examples are given for several bifurcation modes. Effects of geometric imperfections on the kinematic behavior are also considered. The behavior and...
Article
Numerikus megoldásokat állítottunk elő a körpárok és körhármasok gömbön való legsűrűbb elhelyezésének problémájára, és szimmetria alapú vizsgálatokat végeztünk a gömbi körelhelyezés gráfjának Danzer-féle merevségére vonatkozóan. Egy általunk bevezetett gömbölyűségi kritérium alapján optimális, gömböt közelítő poliédereket konstruáltunk. A szakrális...
Article
Full-text available
Dr. Zhong You. Thesis (D. Phil.)--University of Oxford, 2002. Includes bibliographical references.

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