Strojnicky casopis - Journal of Mechanical Engineering

Strojnicky casopis - Journal of Mechanical Engineering

Basic info

  • Publisher: The Faculty of Mechanical Engineering of the Slovak University of Technology in Bratislava
  • Country of publisher: slovakia
  • Date added to EuroPub: 2019/May/26

Subject and more

  • LCC Subject Category: Engineering, Mechanical Engineering
  • Publisher's keywords: Mechanical Engineering, Biomechanics, Structural and Machine Design, Production Engineering, Fracture Mechanics and Fatigue, Power and Process Engineering, Mechatronics
  • Language of fulltext: english
  • Full-text formats available: PDF

Publication charges

  • Article Processing Charges (APCs): No
  • Submission charges: No
  • Waiver policy for charges? No

Editorial information

Open access & licensing

  • Type of License: CC BY-NC-ND
  • License terms
  • Open Access Statement: Yes
  • Year open access content began: 2015
  • Does the author retain unrestricted copyright? False
  • Does the author retain publishing rights? False

Best practice polices

  • Permanent article identifier: DOI
  • Content digitally archived in: Other
  • Deposit policy registered in: None

This journal has '111' articles

PHENOMENOLOGICAL MATERIAL MODEL OF FOAM SOLIDS

PHENOMENOLOGICAL MATERIAL MODEL OF FOAM SOLIDS

Authors: V. Goga, B. Hučko
( 0 downloads)
Abstract

n this contribution a new phenomenological model for pressure loaded foam materials is proposed. The presented relationship between compressive stresses and compressive strains is derived by using simple rheological models. The proposed model contains several parameters. The procedure of their identification and the influence of parameters on a curve shape are also explained. The accuracy of our model is tested and compared with other phenomenological models. These tests have been applied on aluminium and polyurethane foams.

Keywords: PHENOMENOLOGICAL, FOAM SOLIDS
CYCLIC PLASTIC PROPERTIES OF CLASS C STEEL EMPHASIZING ON RATCHETING: TESTING AND MODELLING

CYCLIC PLASTIC PROPERTIES OF CLASS C STEEL EMPHASIZING ON RATCHETING: TESTING AND MODELLING

Authors: R. Halama, A. Markopoulos, M. Šofer, Z. Poruba and P. Matušek
( 0 downloads)
Abstract

Cyclic plasticity modelling of metals needs individual approach. There are specific theories for various metallic materials including mainly phenomenological models, useful for practical applications [1]. However, a robust cyclic plasticity model with higher number of parameters, which should be estimated using a large amount of experimental fatigue test data, is often required for correct description of material behaviour. It is true mainly for case of stress controlled loading with non-zero mean stress value, when cyclic creep or so called ratcheting occurs. The ratcheting effect can be described as an accumulation of any component of strain tensor with increasing number of cycles. It was recognized [2 – 3], that cyclic plasticity models recently included in common commercial FE programs (namely overlay Besseling model [4] and Armstrong-Frederick type model of Chaboche [5]) cannot correctly describe ratcheting under uniaxial and non-proportional multiaxial loading simultaneously and cannot capture non-proportional hardening, non-Masing’s behavior and other important effects of cyclic plasticity. The problem can be solved by implementing a more complex cyclic plasticity model into a FE code, see publications [6] and [7]. This paper is focused on the stress-strain behaviour of the Class C steel in cyclic plastic domain and its FE simulation. An experimental study on the wheel steel specimens including uniaxial as well as multiaxial tests has been realized in the laboratory at Department of mechanics of materials of VŠB-TU Ostrava. The MAKOC model applied in simulations gives very good prediction of ratcheting in all solved cases.

Keywords: cyclic plasticity, ratcheting, FEM, low-cycle fatigue, wheel steel
ELASTOSTATIC ANALYSIS OF THE SPATIAL FGM STRUCTURES

ELASTOSTATIC ANALYSIS OF THE SPATIAL FGM STRUCTURES

Authors: J. Murín, M. Aminbaghaiو . Hrabovský
( 0 downloads)
Abstract

In this contribution, results of elastostatic analysis of spatial composite beam structmes are presented using ow- new beam finite element of double symmetric cross-section made of a Ftmctionally Graded Material (FGM). Material propett ies of the real beams vaty continuously in the longitudinal direction while variation with respect to the transversal and lateral dire.ctions is assumed to be symmetric in a continuous or discontinuous manner. Continuously longitudinal vruying spatial Winkler elastic fotmdations (except the torsional fotmdation) and the effect of axial and shear forces are considered as well. Homogenization of spatially vatying material propetties to effective quantities with a longitudinal variation is done by the multilayer method (MLM). For the homogenized beam finite element the local stiffness matrix is established by means of the transfer matrix method. By the conventional finite element procedw-e, the global element stiffness matrix and the global system of equation for the beam stmcture are established for calculation of the global displacement vector. The secondary variables (internal forces and moments) are then calculated by means of the transfer relations on the real beatns. Fwt her, the mechanical stress in the real beams are calculated. Finally, the numerical experiments are canied out concerning the elastic-static analysis of the single FGM beruns and beam structw-es in order to show the possibilities ofow- approach.

Keywords: 3D FGM beam, spatially vatying material properties, elastostatic analysis
Evaluation of Fracture Parameters for Cracks in Coupled Thermoelasticity for Functionally Graded Materials

Evaluation of Fracture Parameters for Cracks in Coupled Thermoelasticity for Functionally Graded Materials

Authors: M. Repka, J. Sládek, V. Sládek ,M. Wünsche
( 0 downloads)
Abstract

The finite element method (FEM) is developed for coupled thermoelastic crack problems if material properties are continuously varying. The weak form is utilized to derive the FEM equations. In conventional fracture theories the state of stress and strain at the crack tip vicinity is characterized by a single fracture parameter, namely the stress intensity factor or its equivalent, J-integral. In the present paper it is considered also the second fracture parameter called as the T-stress. For evaluation of both fracture parameters the quarter-point crack tip element is developed. Simple formulas for both fracture parameters are derived comparing the variation of displacements in the quarter-point element with asymptotic expression of displacement at the crack tip vicinity. The leading terms of the asymptotic expansions of fields in the crack-tip vicinity in a functionally graded material (FGM) are the same as in a homogeneous one with material coefficients taken at the crack tip.

Keywords: FGM, thermoelasticity, FEM, fracture, SIFS, T-stresses
ANALYSIS OF PIEZOELECTRIC SEMICONDUCTING SOLIDS BY MESHLESS METHOD

ANALYSIS OF PIEZOELECTRIC SEMICONDUCTING SOLIDS BY MESHLESS METHOD

Authors: P. Staňák, J. Sládek, V. Sládek
( 0 downloads)
Abstract

In this paper, a meshless local Petrov-Galerkin (MLPG) method is proposed to calculate mechanical and electrical responses of three-dimensional piezoelectric semiconductors under static load. The analyzed solid is discretized by a set of generally distributed nodal points distributed over 3D geometry. Local integral equations (LIEs) are derived from the weak form of governing equations over small local subdomains. The subdomains have a spherical shape with a nodal point located in its centre. A unit step function is used as the test functions in the local weak-form. The moving least-squares (MLS) method is adopted for the approximation of the physical quantities in the LIEs. The proposed MLPG method is verified by using the corresponding results obtained with the finite element method. Numerical examples are presented and discussed for various boundary conditions and loading scenarios to show the performance of the developed MLPG method for analysis piezoelectric semiconducting solids.

Keywords: piezoelectric semiconductors, meshless local Petrov-Galerkin (MLPG) method, MLS approximation scheme
Research of Cavitation at High Shear Stress

Research of Cavitation at High Shear Stress

Authors: Zoltán Csuka, Róbert Olšiak and Zoltán Fuszko
( 0 downloads)
Abstract

The article describes the theory of cavitation at high values of shear stress in a viscous liquid. For this purpose, a spatial model of two cylindrical shells imposed concentrically was designed. In the narrow gap between the cylinders the temperature, density and viscosity of liquid is constant. Shear stress is induced by the rotary motion of the inner cylinder, resulting in a change of velocity and pressure fields. Due to the pressure drop between the cylinders there is a precondition to the formation of cavitation bubbles at the point of the lowest static pressure. To verify the assumption was made CFD model based on simplified physical model, through which cavitation was qualitatively and quantitatively assessed. In this paper the results of the numerical solution will be presented alongside with basic form of experimental device for physical generation of cavitation at high values of shear stress.

Keywords: shear stress, cavitation, rotating cylinder, pressure drop, narrow gap, turbulence
nfluence of Induction Hardening on Wear Resistance in Case of Rolling Contact

nfluence of Induction Hardening on Wear Resistance in Case of Rolling Contact

Authors: Michal Šofer, Rostislav Fajkoš and Radim Halama
( 0 downloads)
Abstract

The main aim of the presented paper is to show how heat treatment, in our case the induction hardening, will affect the wear rates as well as the ratcheting evolution process beneath the contact surface in the field of line rolling contact. Used wear model is based on shear band cracking mechanism [1] and non-linear kinematic and isotropic hardening rule of Chaboche and Lemaitre. The entire numerical simulations have been realized in the C# programming language. Results from numerical simulations are subsequently compared with experimental data.

Keywords: Rolling Contact Fatigue, Wear, Ratcheting, R7T
Experimental Evaluation of Mechanical Properties of Friction Welded Dissimilar Steels under Varying Axial Pressures

Experimental Evaluation of Mechanical Properties of Friction Welded Dissimilar Steels under Varying Axial Pressures

Authors: Amit Handa and Vikas Chawla
( 0 downloads)
Abstract

The present study emphasizes on joints two industrially important materials AISI 304 with AISI 1021steels, produced by friction welding have been investigated. Samples were welded under different axial pressures ranging from 75MPa to 135MPa, at constant speed of 920rpm. The tensile strength, torsional strength, impact strength and micro hardness values of the weldments were determined and evaluated. Simultaneously the fractrography of the tensile tested specimens were carried out, so as to understand the failure analysis. It was observed that improved mechanical properties were noticed at higher axial pressures. Ductile failures of weldments were also observed at 120MPa and 135MPa axial pressures during fractography analysis.

Keywords: Friction Welding; Tensile Strength; Torsion Strength; Impact Strength; Micro Hardness; Scanning Electron Microscopy
Internal Combustion Engine Powered by Synthesis Gas from Pyrolysed Plastics

Internal Combustion Engine Powered by Synthesis Gas from Pyrolysed Plastics

Authors: Andrej Chríbik, Marián Polóni, Ján Lach, Ľubomír Jančošek, Peter Kunc and Josef Zbranek
( 0 downloads)
Abstract

The article discusses the application of synthesis gas from pyrolysis of plastics in petrol engine. The appropriate experimental measurements were performed on a combustion engine LGW 702 designated for micro-cogeneration unit. The power parameters, economic parameters in term of brake specific fuel consumption, and internal parameters of the engine were compared to the engine running on the reference fuel - natural gas and synthesis gas. Burning synthesis gas leads to decreased performance by about 5% and to increased mass hourly consumption by 120 %. In terms of burning, synthesis gas has similar properties as natural gas. Compared with [5] a more detailed study has been prepared on the effects of angle of spark advance on the engine torque, giving more detailed assessment of engine cycle variability and considering specification of start and end of combustion in the logarithm p-V diagram.

Keywords: natural gas, synthesis gas, spark ignition engine, cogeneration unit, cycle variability
FSW Numerical Simulation of Aluminium Plates by Sysweld - Part I

FSW Numerical Simulation of Aluminium Plates by Sysweld - Part I

Authors: Roland Jančo, Ladislav Écsi and Pavel Élesztős
( 0 downloads)
Abstract

Friction Stir Welding (FSW) is one of the most effective solid state joining processes and it has numerous potential applications in many industries. The simulation process can provide the evolution of physical quantities such as temperature, metallurgical phase proportions, stress and strain which can be easily measured during welding. The numerical modelling requires the modelling of a complex interaction between thermal, metallurgical and mechanical phenomena. The aim of this paper is to describe the thermal-fluid simulation of FSW using the finite element method. In the theoretical part of the paper heating is provided by the material flow and contact condition between the tool and the welded material. The thermal-fluid results from the numerical simulation for aluminium alloy using SYSWELD are also presented in this paper.

Keywords: Friction Stir Welding (FSW); aluminium alloy; Finite element method; thermo-fluid model
Comparison of the Viscous Liquids Spraying by the OIG and the Oil Configurations of an Effervescent Atomizer at Low Inlet Pressures

Comparison of the Viscous Liquids Spraying by the OIG and the Oil Configurations of an Effervescent Atomizer at Low Inlet Pressures

Authors: Marek Mlkvik, Róbert Olšiak and Marek Smolar
( 0 downloads)
Abstract

In this work we studied the influence of the fluid injection configuration (OIG: outside-in-gas, OIL: outside-in-liquid) on the internal flows and external sprays parameters. We sprayed the viscous aqueous maltodextrin solutions (μ = 60 mPa∙s) at a constant inlet pressure of the gas and the gas to the liquid mass flow ratio (GLR) within the range 2.5 to 20%. We found that the fluids injection has a crucial influence on the internal flows. The internal flows patterns for the OIG atomizer were the slug flows , the internal flow of the OIL device was annular which led to the significant improvement of the spray quality: Smaller droplets, faster atomization, fewer pulsations.

Keywords: effervescent atomizer, OIL atomizer, OIL atomizer, flow visualization, CFD, droplet sizing, sprays
Analysis of Pharmaceutical Excipient MCC Avicel PH102 Using Compaction Equations

Analysis of Pharmaceutical Excipient MCC Avicel PH102 Using Compaction Equations

Authors: Peter Peciar, Maroš Eckert, Roman Fekete and Viliam Hrnčiar
( 0 downloads)
Abstract

This paper focuses on the characterization of the tabletting process and analysis one of the most common pharmaceutical excipients MCC Avicel PH102 by Heckel, Kawakita, Cooper-Eaton and Adams compaction equations. Experimental material was determined by measuring its parameters as particle size distribution, angle of wall friction and flow properties and for more detailed characteristics of the material particles, microscopy images of the powder before and after compressing were created.

Keywords: Compaction equation, tabletting, angle of internal friction, angle of wall friction
Simple Planar Truss (Linear, Nonlinear and Stochastic Approach)

Simple Planar Truss (Linear, Nonlinear and Stochastic Approach)

Authors: Karel Frydrýšek and Roland Jančo
( 0 downloads)
Abstract

This article deals with a simple planar and statically determinate pin-connected truss. It demonstrates the processes and methods of derivations and solutions according to 1st and 2nd order theories. The article applies linear and nonlinear approaches and their simplifications via a Maclaurin series. Programming connected with the stochastic Simulation-Based Reliability Method (i.e. the direct Monte Carlo approach) is used to conduct a probabilistic reliability assessment (i.e. a calculation of the probability that plastic deformation will occur in members of the truss).

Keywords: planar truss, 1st and 2nd order theories, probability, reliability, nonlinearities, elasticity, plasticity, Simulation-Based Reliability Assessment (SBRA) Method, probabilistic reliability assessment
Numerical Calculation of Overhead Power Lines Dynamics

Numerical Calculation of Overhead Power Lines Dynamics

Authors: Roman Gogola, Justín Murín and Juraj Hrabovský
( 0 downloads)
Abstract

This paper contains results of transient analysis of airflow around the ACSR power line cross-section in unsymmetric multi-span. The forces applied to the power line are obtained from CFD simulations, where the wind induced vibration is studied. Effect of these forces to the maximal displacement of the power line and the maximal mechanical forces in the points of attachment are studied and evaluated.

Keywords: ACSR conductor, homogenization, CFD, FEM, transient analysis
Force Analysis of Bench Press on Stable and Unstable Base

Force Analysis of Bench Press on Stable and Unstable Base

Authors: Branislav Hučko, Michal Čekan and František Horvát
( 0 downloads)
Abstract

The contribution reviews current technologies for the measurement of performance in athletes during stationary exercise and validates the technology utilizing accelerometry. The behaviours of force during the bench press exercise on a stable and unstable base are reviewed and the results are presented. It was found that, training on an unstable base can be exploited by athletes to maximize their performance.

Keywords: Bench-press, accelerometry, impulse, performance, training

About Europub

EuroPub is a comprehensive, multipurpose database covering scholarly literature, with indexed records from active, authoritative journals, and indexes articles from journals all over the world. The result is an exhaustive database that assists research in every field. Easy access to a vast database at one place, reduces searching and data reviewing time considerably and helps authors in preparing new articles to a great extent. EuroPub aims at increasing the visibility of open access scholarly journals, thereby promoting their increased usage and impact.