Balázs Pere

36171931300

Publications - 14

An effective reduction method with Caughey damping for spurious oscillations in dynamic problems

Balázs Pere Daniel Serfozo

Publication Name: Meccanica

Publication Date: 2025-09-01

Volume: 60

Issue: 9

Page Range: 2927-2946

Description:

The numerical solution of dynamic problems often results spurious oscillations. In order to eliminate them, a damping effect must be included in the numerical scheme. However, the concrete shape of the damping characteristics has a great importance in the efficiency of oscillation reduction. In this article, a novel approach has been introduced with adjustable damping character. The damping effect is exerted as viscous damping according to the formulation of Caughey damping. Using the proposed method, a wide range of damping curves can be approximated with high accuracy. The newly developed method is mainly useful for contact-impact and wave propagation problems.

Open Access: Yes

DOI: 10.1007/s11012-025-02036-9

Numerical investigation of composite metal foams using substructure techniques

Imre Norbert Orbulov Balázs Pere Márió Kovács

Publication Name: Composite Structures

Publication Date: 2025-01-01

Volume: 353

Issue: Unknown

Page Range: Unknown

Description:

An accurate description of the mechanical behaviour of inhomogeneous, anisotropic composite materials, such as metal matrix syntactic foams (MMSFs), is a challenging task. This paper is based on the so-called substructure technique, which has never been used for the mechanical modelling of metal foams or MMSFs. Using this method, a finite element model with low computational requirements but still modelling inhomogeneous properties can be constructed that reproduces the results of laboratory measurements with high accuracy. In all cases, the tests presented in this paper are limited to the linearly elastic phase. As the most common investigation of MMSFs is the compression test, this study considers only this loading case. A more detailed discussion of the stress analysis of MMSFs is given at the end of this work. A potential cause of 45° crack planes during compression tests and the evolution of stresses as a function of space-filling are also investigated.

Open Access: Yes

DOI: 10.1016/j.compstruct.2024.118731

Application Analysis of a Novel Reduction Method for Spurious Oscillations in 2D Impact Problems

Balázs Pere Daniel Serfozo

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 231-239

Description:

The numerical solution of impact problems are oftentimes problematic due to the presence of spurious oscillations in the resulting functions. Eliminating these oscillations is complicated and requires a damping effect to be exerted in the solution. In the proposed method, viscous damping has been applied with a special damping character. Using this scheme, the numerical solution of 2D impact problems contains significantly less oscillations compared to other widely applied methods. In quantitative terms, an improvement of 2.42% and 9.29% or more can be achieved in the time evolution of the velocity and the pressure, respectively.

Open Access: Yes

DOI: 10.3233/ATDE240550

Wave Propagation in Composite Metal Foams Investigated by Finite Element Methods in Two Dimensional Case

Balázs Pere Márió Kovács

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 224-230

Description:

The presented work is based on the wave propagation properties of composite metal foams in a two-dimensional model with a focus on the energy absorption. The energy flux method was used for the study and it was shown that composite metal foams have a significant energy absorption capacity. Hence, they can be used with high efficiency, for example, as a sound insulation layer. A pair of materials commonly used in syntactic metal foams, iron shell and aluminium matrix material, was used in the finite element model. Damping is included in the calculations to avoid oscillations.

Open Access: Yes

DOI: 10.3233/ATDE240549

An Improved Bulk Viscosity Method for Contact-Impact Problems

Balázs Pere Daniel Serfozo

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2024-01-01

Volume: 21

Issue: 8

Page Range: 243-262

Description:

Dynamic contact and impact problems are widely applicable. An accurate solution for these kinds of problems could be used in many fields of mechanical engineering (e.g., cutting metalwork, cogwheel drives, etc.). However, the proper handling of the contact is problematic, as there emerges a substantial amount of nonlinearity in the displacement field. Therefore, a spurious high frequency oscillation is present in the solution. These oscillations must be avoided, as divergence can easily occur in the contact algorithm due to them. In order to eliminate this effect, the applied numerical method must be chosen and set properly. In this study, we focused on the best possible elimination of these oscillations by which the choice of the proper numerical method has a great importance.

Open Access: Yes

DOI: 10.12700/APH.21.8.2024.8.13

A method to accurately define arbitrary algorithmic damping character as viscous damping

Balázs Pere Daniel Serfozo

Publication Name: Archive of Applied Mechanics

Publication Date: 2023-09-01

Volume: 93

Issue: 9

Page Range: 3581-3595

Description:

Undesired oscillations often emerge in numerical solutions, especially in the case of dynamic problems. These are mainly spurious oscillations which must be eliminated or reduced at least to provide accurate results. Numerical methods with damping effect are especially useful to achieve this goal. However, the concrete shape of the damping characteristics has a great impact on the effectiveness. Dissipative numerical methods mostly have a specific damping character with very limited alteration possibility. In this article, a novel numerical method has been introduced where the dissipative effect is exerted via viscous damping. Using the proposed method, a great variety of damping curves can be defined accurately, straight through the determination of the algorithmic damping ratio. The newly developed technique is mainly useful for applications where the shape of the damping characteristics significantly affects the accuracy.

Open Access: Yes

DOI: 10.1007/s00419-023-02454-9

Approximation of the stiffness of laminate stacks of electric motors subjected to cyclic loads

Dániel Feszty Balázs Pere Viktor Szabó

Publication Name: Materialpruefung Materials Testing

Publication Date: 2023-08-01

Volume: 65

Issue: 8

Page Range: 1202-1208

Description:

Electric motors in automotive applications are subjected to high thermal and structural loads, while having strict requirements regarding dimensions, mass, and costs. The design of such motors requires sophisticated simulation models. The laminate stack in the rotor of such a motor is made of steel sheets and behaves transversally isotropic: the radial stiffness is equivalent to steel, and in the axial direction, it has a highly progressive nonlinear stiffness characteristic. The loading and unloading stiffness curves change from cycle to cycle when subjected to repetitive loads. In this paper, the usage of a single approximating curve to describe the longitudinal stiffness of the laminate stack is proposed. This approximation can be used in FEM models to reproduce the structural nonlinear behavior of such a laminate stack using a simpler approach than implementing the full loading and unloading curves in a material model, at a price of negligible loss of precision.

Open Access: Yes

DOI: 10.1515/mt-2022-0382

Application of Substructure Techniques to Syntactic Metal Foams in a Finite Element Environment

Imre Norbert Orbulov Balázs Pere Márió Kovács

Publication Name: Periodica Polytechnica Mechanical Engineering

Publication Date: 2023-01-01

Volume: 67

Issue: 4

Page Range: 276-284

Description:

The presented work focuses on the development of a novel method that can numerically describe the properties of metal matrix syntactic foam (MMSF) with low memory requirements and short computational times without losing the properties of the interior structure. In this paper, we propose a novel method that avoids using the homogenization technique and instead rearranges stiffness matrices and constructs specific substructures to perform the overall construction. The two-dimensional cases are discussed in order to focus on the methodology itself. First, the reductions and structural design with solid mesh structures were performed, and then the model was applied on structures filled with iron hollow spheres. So far, the method has been used to evaluate small deformations to see how suitable the subspace technique is for describing metal foams. Aluminum was used as the matrix material, as it is one of the most common materials for MMSFs. The optimal parameters were searched that resulted in the shortest running time for the given construction. Since in the proposed substructure technique only the displacement values at the boundary points are computed, a back-calculation step for each selected substructure was performed to see the interior deformations in the vicinity of an iron hollow sphere.

Open Access: Yes

DOI: 10.3311/PPme.22313

Application analysis of time stepping methods for impact problems

Balázs Pere Daniel Serfozo

Publication Name: Pollack Periodica

Publication Date: 2022-12-31

Volume: 17

Issue: 3

Page Range: 30-35

Description:

Dynamic contact and impact problems are widely applicable. An accurate solution method for these kinds of problems can be used in many fields of mechanical engineering (e.g., cutting metalwork, cogwheel drives, etc.). However, the proper handling of the contact is problematic, as there emerges a substantial amount of nonlinearity in the displacement field. Therefore, a spurious high frequency oscillation is present in the solution. These oscillations must be avoided, as divergence can easily occur in the contact algorithm due to them. In order to eliminate this effect, the applied numerical method must be chosen and set properly. In this study, a comprehensive guide is provided for the appropriate selection of the proper numerical method and its parameters.

Open Access: Yes

DOI: 10.1556/606.2022.00599

Experimental analysis and numerical modelling of contact damping

Balázs Pere B. Magyar R. Wohlfart R. Zana G. Stépán G. Csernák

Publication Name: Journal of Sound and Vibration

Publication Date: 2020-10-13

Volume: 484

Issue: Unknown

Page Range: Unknown

Description:

The energy dissipation in assembled metal structures is mainly related to various physical phenomena – usually modelled as dry friction – on the contact surfaces. However, the reliable numerical modelling of assemblies is a challenging task due to the complexity of the contact mechanisms. To fit the models to experimental results, it is beneficial if the material damping can be separated from the contact damping. The paper presents measurement results aiming to distinguish material damping from the damping related to the contact between the conforming surfaces of assembled machine parts. To evaluate the role of contact in damping and to find a connection between the contact-related increase of modal damping and the mode shapes, the modal damping ratios of a monolithic body and a shrink-fitted assembly are compared. It is demonstrated that the contact damping is linear in the examined case. Based on the experiments, a finite element (FE) model was developed that does not apply computationally expensive contact algorithms. The FE model was able to reproduce the measured modal damping values of the assembled structure at all the natural frequencies that fell in the frequency range of the measurement. This result is achieved by fitting only a single damping parameter. The research work is motivated by metal cutting, where the damping of the machine-tool-workpiece loop plays a key role in the stability of the process, particularly in case of high speed machining.

Open Access: Yes

DOI: 10.1016/j.jsv.2020.115544

Modelling of heat generation in vehicle components made of rubber caused by finite deformations

Balázs Pere Veronika Szüle

Publication Name: Lecture Notes in Mechanical Engineering

Publication Date: 2018-01-01

Volume: 0

Issue: 9783319756769

Page Range: 142-154

Description:

Generally, the most frequently used structural materials are metals which have high strength and stiffness. However, there are many cases, when other important properties come to the fore as well as high deformation by elastic behavior, high viscosity namely good damping effect. The metals do not have these above mentioned properties, but the rubber does. The rubber - thanks to its elastic behavior - is able to establish an elastic connection between hard and brittle structural elements, however, has high load carrying capacity. Vehicle components made of rubber usually exhibit large deformations. Cyclic finite deformations may induce increasing temperature in hyperelastic materials. This case - where changes in deformation and in temperature occur simultaneously - is called coupled thermomechanical problem. Both the mechanical and thermal processes have their own governing equations, that is why special techniques are needed for the computation. A special technique will be presented for solving coupled problems, this is operator split method. The goal of this paper is to show how to solve the coupled thermomechanical problem by the principle of virtual power and the principle of virtual temperature, and how to apply them together.

Open Access: Yes

DOI: 10.1007/978-3-319-75677-6_12

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

A Method for Measuring Normal and Shear Stiffness of Laminate Stacks of Electric Motors

Dániel Feszty Balázs Pere Dániel Harrach Viktor Szabó

Publication Name: Periodica Polytechnica Mechanical Engineering

Publication Date: 2023-01-01

Volume: 67

Issue: 2

Page Range: 110-117

Description:

Structural simulations of electric motors require precise material models. Laminate stacks that are made of several identical steel sheets are particularly challenging to simulate using FEA. The structural stiffness of laminate stacks usually follows transversal isotropic behavior. Measuring a complete laminate stack used in passenger cars is challenging due to its size and the high testing load needed to reach real loads experienced while in operation. A new method capable of performing such measurements is presented in this article, with the help of equipment normally used for testing structures used in civil engineering. Two sets of exemplary results are presented utilizing this measurement procedure, that were performed on a real automotive rotor laminate stack: axial compression stiffness from a cyclic test, and shear stiffness at various axial preload levels. In the axial compression load case, the loading and unloading curves form a hysteresis, that changes in every test cycle. Shear stiffness shows high dependance on the axial compression preload. After loading and unloading the stack with shear loads, significant plastic deformations remain.

Open Access: Yes

DOI: 10.3311/PPme.20505