János Égert

8115877300

Publications - 4

Numerical determination of orthotropic material properties of textile composite layers and their validation by measurement

Béla M. Csizmadia Gergely Bojtár János Égert

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2017-01-01

Volume: 14

Issue: 2

Page Range: 47-67

Description:

The knowledge of orthotropic material properties of composite layers is very important for mechanical design of machine structures from composite material. This information cannot be found in related professional literature therefore it is necessary to determine by measurement, by basic experiments of mechanics of materials. The paper presents a new 3D finite element layer model-cell based on the meso-structure of a textile composite layer, with which one shall be able to determine the material constants of an orthotropic layer. The applicability of the numerical layer model-cell and the accuracy of the numerical results are confirmed by experimental results. The numerically determined material properties of the layers are used at mechanical modeling and computation of complex, layered composite structures.

Open Access: Yes

DOI: 10.12700/APH.14.2.2017.2.3

Numerical estimation method of orthotropic material properties of a roving for reinforcement of composite materials

Béla M. Csizmadia Gergely Bojtár János Égert

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2016-01-01

Volume: 13

Issue: 6

Page Range: 163-182

Description:

Knowledge of the material properties is important at machine design from composite materials. This information cannot be found in related literature and is not standard, therefore, it was necessary to determine, by measurements and by basic experiments of the mechanics of materials. This paper presents a new 3D finite element (FE) model-cell for the modeling of the material properties of a roving. By this numerical modeling method, one can determine the orthotropic and macroscopic material properties of a roving. This model-cell, models numerically, a roving, which consists of multiples of thousands of fibers that are embedded in a matrix material, as a homogenized orthotropic material. The numerical results of the material properties of the roving, can be applied to the definition of the macroscopic material properties of fiber reinforced composite laminates.

Open Access: Yes

DOI: DOI not available

Experimental and numerical investigation of internally reinforced damaged pipelines

Balázs Pere János Lukács Gyula Nagy János Égert Imre Török

Publication Name: 18th European Conference on Fracture Fracture of Materials and Structures from Micro to Macro Scale

Publication Date: 2010-12-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

The purpose of the paper is to present the role of the internal reinforcing on the structural integrity of steel pipes, based on numerical and experimental investigations. For FE analysis of unreinforced case three mechanical models were applied: multilayered elastic shell, 3D elastic solid and 3D elastic-plastic solid FE models. The aim of the numerical analysis was to clarify deformations, stresses and strains in the surrounding area of defects both in the steel pipe and on the composite reinforcement. A further task is to determine numerically the width of reinforcement and the number of layers needed for the repair. For experimental investiga-Tions internal reinforcement was developed using glass fibre polymer matrix composite. Fa-Tigue and burst tests were performed on pipe sections containing artificial metal loss defects. Both unreinforced and reinforced pipeline sections were examined. The applicability of the hybrid structure was demonstrated by means of the numerical and the experimental results.

Open Access: Yes

DOI: DOI not available

Experimental and numerical investigations of external reinforced damaged pipelines

Balázs Pere János Lukács Gyula Nagy János Égert Imre Török

Publication Name: Procedia Engineering

Publication Date: 2010-04-01

Volume: 2

Issue: 1

Page Range: 1191-1200

Description:

The lifetime management of different engineering structures and structural elements is one of the important technical-economic problems nowadays. The purpose of the paper is to present the role of the external reinforcing on the structural integrity of industrial and transporting steel pipelines, based on experimental and numerical investigations. External reinforcement was developed using carbon fibre polymer matrix composite (PMC). Fatigue and burst tests were performed on pipeline sections containing natural and artificial metal loss defects, and girth welds including weld defects (passed and not passed quality). Both unreinforced and reinforced pipeline sections were examined. For the FEM investigation of the problem three groups of mechanical models are applied: multilayered elastic shell, 3D elastic solid and 3D elastic-plastic solid FEM models. The aim of this numerical analysis is to clarify the deformation, stresses and strains in the surrounding area of defects both in the steel pipe and in the composite reinforcement. A further task is to determine numerically the width of the reinforcement and the number of layers needed for reinforcement or repair. The applicability of the hybrid structure (steel + PMC) was demonstrated by means of the experimental and the numerical results. © 2010 Published by Elsevier Ltd.

Open Access: Yes

DOI: 10.1016/j.proeng.2010.03.129