Journal "MECHANIKA"
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Contents Nr.1(81)
MECHANICS OF SOLID BODIES
MECHANICS OF FLUIDS AND GASES
| S. Šinkūnas, A. Kiela. | Effect of liquid physical properties variability on film thickness (-) |
|---|---|
| A. Kellaci, R. Mazouzi, B. Khelidj, A. Bounif. | The effect of lubricant rheology on piston skirt/cylinder contact for an internal combustion engine (-) |
| F. Bode, R. Benea, V. Hodor. | Investigation on thermo-acoustical instabilities related to a confined swirling burner (-) |
| A. Bubulis, A. Bogorosh, V. Jūrėnas, S. Voronov. | Development of cavitation applications for the remediation of contaminated water (-) |
DYNAMICS OF MECHANICAL SYSTEMS
| B. Bakšys, J. Baskutienė. | Simulation of the part-to-part vibratory alignment under impact mode displacement (-) |
|---|---|
| R. Jonušas, E. Juzėnas, K. Juzėnas. | Analysis of some extreme situations in exploitation of complex rotary systems (-) |
| V. Barzdaitis, P. Mažeika. | Diagnostics practice of heavy duty high speed gear transmissions (-) |
DESIGN AND OPTIMIZATION OF MECHANICAL SYSTEMS
| Antal Tiberiu Alexandru. | Worm gears with optimized main geometrical parameters and their efficiency (-) |
|---|---|
| A. Povilionis, A. Bargelis. | Structural optimization in product design process (-) |
MECHANICAL TECHNOLOGIES
| I. Sihvo, J. Varis. | Estimation of tool wear of a gun drill using the signal curve pattern of feed force (-) |
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Articles resume
EFFECT OF EXPLOSIVE LOADING ON MECHANICAL PROPERTIES OF CONCRETE AND REINFORCING STEEL: TOWARDS DEVELOPING A PREDICTIVE MODEL
Virm. Juocevičius
Vilnius Gediminas Technical University, Saulėtekio al.11, 10223 Vilnius, Lithuania,
E-mail: virmantas.juocevicius@conserela.lt
E. R. Vaidogas
Vilnius Gediminas Technical University, Saulėtekio al.11, 10223 Vilnius, Lithuania, E-mail: erv@st.vgtu.lt
Resume
Prediction of dynamic mechanical properties of concrete and reinforcing steel is considered. The attention is focussed on dynamic loading imposed on reinforced concrete structures by large distant explosions. The prediction is made by a combined application of mathematical models describing explosive loading, straining of concrete and steel under this loading and dynamic enhancement of static mechanical properties of these materials. Problems arising at coupling these models in a combined set are discussed. The main finding is that prediction of dynamic properties is to a large extent a problem of structural analysis for explosive loading. The prediction on material level consists mainly in an application of enhancement factors relating static and dynamic properties. The intricacy of these factors lies in the input information required for their calculation. This information is obtained by a structural analysis for explosive loading. Such an analysis can be a complicated task for complex, real world structural systems.
Full article textEFFECT OF EXPLOSIVE LOADING ON MECHANICAL PROPERTIES OF CONCRETE AND REINFORCING STEEL: TOWARDS DEVELOPING A PREDICTIVE MODEL
I. Židonis
Šiauliai University, Vilniaus g. 141, 76353 Šiauliai, Lithuania, E-mail: ipolitas.zidonis@gmail.comResume
The present paper is a continuation of papers authors. The method and the formulae presented in the paper are designed for taking into account of the impact of the flanges and/or other strengthening /weakenings when making direct calculation (without the successive approximations cycles) of the stress-strain state parameters at normal sections of bar-shaped structural members according to nonlinear material stress diagrams. The formulae are applicable for members that have no cracks (e.g. for the calculation of the cracking moment) and for the sections between the cracks of the members that have cracks (for the calculation of the stress-strain state of reinforced members, for estimating the deviation of the strain of the reinforcement from the plane sections). It is also possible to ignore the stresses. When the stresses of the tensile zone of the members are ignored, the formulae are applicable even to the sections near the crack (for the calculation of the cracking moment or of the reinforcement). Direct calculation is possible when we know in advance the strain of any of the layers and when we know whether the flange and reinforcement is subject of to compression or to tension. In other cases, the calculations need to be repeated. The cases when the stress diagrams are not curvilinear and when the members have cracks will be published as separate papers.
INVESTIGATION OF FRACTURE OF INHOMOGENEOUS CAST IRON SPECIMENS
E. Stupak
Vilnius Gediminas technical university, Saulėtekio al. 11, 10223 Vilnius-40, Lithuania. E-mail: Eugenius.Stupak@fm.vgtu.lt
Resume
The proposed J-integral calculation technique in the piece-wise linear fatigue crack front has been used investigating SIF in the inhomogeneous cast iron specimens with defect and graphite voids.
The influence of crack length and front, size and position of voids on SIF have been investigated and the increase of SIF by 15% has been obtained.
Stress-strain state analysis of inhomogeneous cast iron specimens was carried out using FE code ANSYS.EFFECT OF LIQUID PHYSICAL PROPERTIES VARIABILITY ON FILM THICKNESS
S. Šinkūnas
Kaunas University of Technology, Donelaičio 20, 44239 Kaunas, Lithuania, E-mail: stasys.sinkunas@ktu.lt
A. Kiela
Kaunas University of Applied Sciences, Pramonės 22, 50387 Kaunas, Lithuania, E-mail: algimantas.kiela.@kauko.ltResume
A model for research of stabilized laminar liquid film flow on an outside surface of vertical tube based on force equilibrium equations is presented in the paper. The calculations for water, compressor oil and fuel oil films at various values of relative cross curvature of the films and ratios of heat fluxes densities were carried out. A function allowing estimating nonisothermality effect on film thickness was established. It has been determined that film thickness variation depends on the variability of liquid physical properties. Theoretical analysis of film cross curvature and external heat exchange influence on liquid film thickness variation was performed as well.THE EFFECT OF LUBRICANT RHEOLOGY ON PISTON SKIRT/CYLINDER CONTACT FOR AN INTERNAL COMBUSTION ENGINE
A. Kellaci
Khemis miliana University, Thenia road, Ain Defla, Algeria, E-mail: akellaci@yahoo.fr
R. Mazouzi
Solides Mécanique laboratory, University of Poitiers, France, E-mail: mazouzi_r@yahoo.fr
B. Khelidj
Khemis miliana University, Thenia road, Ain Defla, Algeria, E-mail: bkhelidj@orange.fr
A. Bounif
University of Science and Technology, Oran, Algeria, E-mail: bounif@univ-usto.dzResume
The sensitivity of internal combustionenginefriction tolubricant viscosity has been studied. The effect of oil viscosity on the hydrodynamic and boundary friction of the piston skirt has been discussed with various monograd lubricants. The average temperature is determined from the temperature of the liner using the Woschni correlation. The oil film viscosity is then estimated using the mean temperature of the oil film. This model takes into account the phenomenon of rupture and reformation of the oil film. The effect of viscosity on cavitation is also studied.INVESTIGATION ON THERMO-ACOUSTICAL INSTABILITIES RELATED TO A CONFINED SWIRLING BURNER
F. Bode
Technical University of Cluj-Napoca, Department of Thermotechnics, Thermal Machines and Equipments, B-dul Muncii 103-105, 400641 Cluj-Napoca, Romania, E-mail: florin.bode@termo.utcluj.ro
R. Benea
Technical University of Cluj-Napoca, Department of Mechatronics, B-dul Muncii 103-105, 400641 Cluj-Napoca, Romania, E-mail: rbenea@gmail.com
V. Hodor
Technical University of Cluj-Napoca, Department of Thermotechnics, Thermal Machines and Equipments, B-dul Muncii 103-105, 400641 Cluj-Napoca, Romania, E-mail: victor.hodor@termo.utcluj.roResume
Swirling lean nonpremixed flames are used in modern combustors. These flames are susceptible of thermo-acoustic combustion instabilities, caused by the coupling between heat release fluctuations and combustor acoustics. Thermo-acoustic instabilities are dynamic phenomena that represent a major threat for most modern combustion systems. It consists of the coupling and auto-sustenance of large amplitude and low frequency pressure and heat release oscillations. Analysis of thermo-acoustic combustion instabilities of a nonpremixed swirling flame is presented extensively in this paper. This study is concerned with the evaluation of the influences induced by the equivalence ratio on the thermo-acoustic combustion instabilities, as well with a numerical method for determining these instabilities. This analysis is made by acoustic correlation between numerical simulation using the 3D RNG k-ε model and experimental results. The dominant frequencies are located in the ranges 20-50 Hz for the nonreactive flow, and 40-300 Hz for the reactive flow. Multiple acoustic sensors are used in the experimental setup in order to account for spectral acquisition and to help eliminate the irrelevant environmental noise.DEVELOPMENT OF CAVITATION APPLICATIONS FOR THE REMEDIATION OF CONTAMINATED WATER
A. Bubulis
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania,E-mail: algimantas.bubulis@ktu.lt
A. Bogorosh
National Technical University of Ukraine, Kiev Polytechnic Institute, av. Peremogy 37, 03224 Kiev, Ukraine, E-mail: fondfti@ntu-kpi.kiev.ua
V. Jūrėnas
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania,E-mail: vytautas.jurenas@ktu.lt
S. Voronov
National Technical University of Ukraine, Kiev Polytechnic Institute, av. Peremogy 37, 03224 Kiev, Ukraine, E-mail: fondfti@ntu-kpi.kiev.uaResume
The development of cavitation applications for the remediation of contaminated water is presented. Performance data, such as scale control, corrosion and bacteria reduction, are presented. The screw propeller-type, piston-type and membrane-type cavitators were developed and investigated. Chemical qualitative and quantitative analysis of the water before and after the cavitation exposed significant reduction of dissolute hydrocarbonate and other salts. At the same time the water becomes less alkali; filtrated, becomes more transparent and freezes more quickly; melted is suitable for drinking. A quantitative energy assessment of the possibility of using the cavitation for cracking of the hydrocarbons in water feedstock is performed.SIMULATION OF THE PART-TO-PART VIBRATORY ALIGNMENT UNDER IMPACT MODE DISPLACEMENT
B. Bakšys
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania, E-mail: bronius.baksys@ktu.lt
J. Baskutienė
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania, E-mail: jbask@ktu.ltResume
Vibratory impact mode alignment of the being assembled parts is analysed in the presented paper. The dynamical model was made, which represents the interaction between movable body and supporting base during the oblique impact. Applying the model of the interaction, the influence of parameters of the dynamic system and vibratory excitation on the process of the impact mode interdependent alignment of the being assembled parts was analysed.
The movably based body has characteristic of different modes of impact displacement, which depend on the excitation frequency, part-to-part pressing force and on displacement and angular rigidity. The alignment duration dependences on system and excitation parameters were defined.
The parameters' sets area, of the part-to-part pressing force versus angular rigidity of the body, was defined, as reliable alignment by impact mode is taking place.ANALYSIS OF SOME EXTREME SITUATIONS IN EXPLOITATION OF COMPLEX ROTARY SYSTEMS
R. Jonušas
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania,E-mail:remigijus.jonusas@ktu.lt
E. Juzėnas
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania,E-mail: ejuzenas@ktu.lt
K. Juzėnas
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania, E-mail:kjuzenas@ktu.ltResume
Complex rotary systems (CRS) are widely used in energetic, chemical industry. Their reliability is one of the main tasks of plant engineering, because costs of maintenance and production loses are really significant.
Vibrodiagnostics of such systems is one of the main tools applied for the evaluation of machines condition. However complexity of those systems, probability of various defects condition that reliable determination of sources of vibrations is not always achievable. Therefore additional mean for defects determination may be applied - numerical modelling of systems dynamical condition.
This article presents data of experimental and numerical research of a CRS, where the phenomenon of rubbing occurs and subharmonic vibrations are generated. Modelling of such realistic system is also a highly complicated problem, therefore improvement of numerical model, based on experimental data is needed.DIAGNOSTICS PRACTICE OF HEAVY DUTY HIGH SPEED GEAR TRANSMISSIONS
V. Barzdaitis
Kaunas University of Technology, A. Mickevičiaus str. 37, 44244 Kaunas, Lithuania, E-mail: vytautas.barzdaitis@ktu.lt
P. Mažeika
Klaipeda University Mechatronic Science Institute, Bijūnų str. 17, 91225 Klaipėda, Lithuania,
E-mail: pranasmazeika@centras.lt
Resume
Condition monitoring of the gear power transmissions teeth meshing vibrations and bearings vibration evaluation are studied in this article. The research results were acquired in practice during long term diagnostics of energy generating machines in situ. The ordinary helical gear train has few times higher vibration acceleration level in comparison with epicyclical gear train. The gears vibration acceleration parameter was used for diagnostics and evaluation teeth meshing quality as high frequency vibration in antifriction bearing diagnostics.
WORM GEARS WITH OPTIMIZED MAIN GEOMETRICAL PARAMETERS AND THEIR EFFICIENCY
Antal Tiberiu Alexandru
The Technical University from Cluj-Napoca, C. Daicoviciu no. 15, 400020, Cluj-Napoca, Romania, E-mail: Tiberiu.Alexandru.Antal@mep.utcluj.roResume
The paper gives a method of designing worm gears with the main geometrical parameters (module mx and diameter factor q) obtained so that the overall size is low and the efficiency is high. Using the obtained expressions, a given load to be transmitted and the possible variations for addendum modification plots were generated in Matlab to help the designer to obtain maximum efficiency with minimum overall size. As shown in the plots, in order to have a high efficiency, the worm gear must be designed with high module, low diameter factor and positive addendum modification.
STRUCTURAL OPTIMIZATION IN PRODUCT DESIGN PROCESS
A. Povilionis
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania, E-mail: audrius.povilionis@ktu.lt
A. Bargelis
Kaunas University of Technology, Kęstučio 27, 44312 Kaunas, Lithuania, E-mail: algirdas.bargelis@ktu.ltResume
This paper analyzes developed methodology to apply a topology optimization of a product's first shape mode. This methodology helps to optimize the overall dimensions of a mechanical product. Starting from known loads and boundary conditions and maximum available design space, 2D topology optimization leads to the design concept of a product structure which is as light as possible. This method helps the product developer creating a mass-optimized structure proposal at the early new product design stage. The created methodology was tested by obtaining results of developing and testing a first mode shape of a grinding machine tool.ESTIMATION OF TOOL WEAR OF A GUN DRILL USING THE SIGNAL CURVE PATTERN OF FEED FORCE
I. Sihvo
Lappeenranta University of Technology, P.O. Box 20, 53851 Lappeenranta, Finland, E-mail: inga.sihvo@lut.fi
J. Varis
Lappeenranta University of Technology, P.O. Box 20, 53851 Lappeenranta, Finland, E-mail: juha.varis@lut.fi
Resume
This study concentrates on gundrilling and the related feed force signal in time domain, and possibilities of using this signal in drill wear monitoring. The behavior of the feed force was studied in a normal gundrilling procedure, and also in a situation where the feed was stopped just before guidance feed was replaced by actual drilling feed. Stopping the feed caused a new kind of behavior in the pattern of the feed force curve, which could be used in monitoring the extent of drill wear. Regression models were created in order to estimate the mean flank wear in the cutting edges, flank wear in the drill tip, and longitudinal wear based on the pattern of the feed force curve when cutting conditions remain constant. Based on the test results, it was concluded that from the pattern of the feed force curve monitored in time domain and modified by stopping the feed, it is possible to predict the extent of the wear of the gun drill.