Due to difficult pandemic situation with COVID-19 decease, as well as due to current geopolitical... more Due to difficult pandemic situation with COVID-19 decease, as well as due to current geopolitical circumstances in the world, we are facing the shortage of steel and therefore the impossibility of delivering the contracted products within the agreed deadlines. It is thus necessary to find suitable steel for replacement. The procedure for selecting one such steel for substituting the deficit steel 25CrMo4, for the purposes of producing a responsible welded assembly, is described in this paper. After the careful analysis, the steel 42CrMo4 was taken into consideration as a possible substitute material. Prior to applying the new selected steel, it was necessary to perform the following tests: analyze its chemical composition, determine its most important mechanical properties and evaluate its weldability. Then, the optimal welding and heat treatment technologies were determined, so that the quality of the responsible welded structure would meet all the requirements, as the structure ma...
The presented work deals with an analysis of causes of the very low service life of the new versi... more The presented work deals with an analysis of causes of the very low service life of the new version of hand woodworking planing knife, which has replaced the original version of a planing knife. Based on the performed experimental works, chemical analysis, macroscopic and microscopic observation, SEM, diffractometric analysis, and Vickers hardness test it was concluded that the cause for the very low service life (practically the nonexistent one) of the new version of a planing knife are significant features of overheating. During the heating to the hardening temperature used steel was overheated, the cementite carbides dissolved, and the austenitic grains became coarse. The final microstructure of the used steel after hardening and tempering consists of brittle coarse martensitic needles, without any presence of the fine globular cementite carbides, accompanied by a very high amount of retained austenite. Thus, the chipping of the knife's cutting edge took place and the planer ...
The sandwich structures have multifold advantages with respect to other types of structures. Besi... more The sandwich structures have multifold advantages with respect to other types of structures. Besides the architectural possibilities due to their appearance, those structures can carry the same or even higher loads than some other similar structures. Optimization of the sandwich columns with the truss core, subjected to the compressive axial load, is presented in this paper. The two types of optimization were performed: the three-parameter and the four-parameter optimization - the so called full optimization. The optimization of the column geometry (face thickness, core member height and core member diameter and core height) was performed, from the aspect of the minimal weight of the structure in terms of the load index. It was performed for four types of restrictions imposed by the corresponding column failure modes: column buckling, truss macro-buckling, local buckling of the face and face wrinkling. The tree-parameter optimization resulted in somewhat larger weight of the column ...
Hard-facing as a type of the coating depositing is increasingly used today. Physical-chemical-met... more Hard-facing as a type of the coating depositing is increasingly used today. Physical-chemical-metallurgical characteristics of contact layers in tribo-mechanical systems depend on the operating conditions and the conditions under which the work surfaces were created. That is the reason the influence of the processing procedures and regime, used in the contact surfaces formation, on development of the wear process of contact elements, is being considered ever more. To determine the influence of the hard-facing technology on characteristics of the gears’ working surfaces, the experimental investigations were performed on samples hard-faced on the steel for cementation, by varying the filler metals (FM) and the hard-facing regimes. The samples tested were hard-faced by five “hard” and three “soft” filler metals. Experimental investigations included measuring the hard-faced layers’ hardness and determination of their microstructure, as well as the wear resistance in the laboratory condi...
Communications - Scientific letters of the University of Zilina
Mining machines' components, or the whole structure, are prone to frequent premature damages and ... more Mining machines' components, or the whole structure, are prone to frequent premature damages and fractures what is explained either by inadequate design and construction or by insufficient knowledge of the material's and welded joints' properties and oversights in manufacturing. Here is considered the bucket-wheel excavator, i.e. the fracture of the tooth of the girth gear, which enables the circular motion of the excavator's upper structure (which was in operation for 5000 hours). The gear was made of the cast steel GS 40 MnCrSi3 V. The reparatory hard-facing (HF) technology of the fractured tooth required specification of numerous operations including the preparation works. The reparation realized the twofold savings, in time and money-the new girth gear costs over 500 000 € and its manufacturing lasts 6 to 9 months, while the safety and quality of the repaired tooth was guaranteed.
Influence of shot peening on the wear behaviour of medium carbon, C55 steel was experimentally ve... more Influence of shot peening on the wear behaviour of medium carbon, C55 steel was experimentally verified. Experimental work included determination of the chemical composition, heat treatment, microstructure evaluation, mechanical properties measurement, shot peening treatment, the magnitude of the compressive residual stresses was evaluated, roughness profiles measurement and finally the friction tests. The results evidence the significant role played by the applied shot peening on wear behaviour of medium carbon steel. An important effect of surface roughness has been demonstrated. The coefficient of friction after shot peening compared to ground surface increased, 1.44 – 1.85 times.
The paper analyses the stability of a rectangular plate which is elastically buckled along longit... more The paper analyses the stability of a rectangular plate which is elastically buckled along longitudinal edges and pressed by equally distributed forces. A general case is analyseddifferent stiffness elastic clamping and then special simpler cases are considered. Energy method is used in order to determine critical stress. Deflection function is introduced in a convenient way so that it reflects the actual state of the plate deformation in the best manner. In this way, critical stress is determined in analytic form suitable for analysis. With help of the equation it is easy to conclude how certain parameters influence the value of critical stress. The paper indicates how the obtained solution could be utilized for determining local buckling critical stress in considerably more complex systemspressed thin-walled beams of an arbitrary length.
Two aspects of various steels’ weldability are considered in this article. The theoretical part p... more Two aspects of various steels’ weldability are considered in this article. The theoretical part presents general concepts related to steel’s weldability and the application of the most important methods for its determination. In the experimental section, results of the hard-facing application to several samples are presented, and consist of hardness measurements in the different zones of the welded samples, with the evaluation of those zones’ microstructures. The tested materials included two carbon steels and two alloyed steels, with hard-facing layers deposited by various filler metals. Experimental results were compared to results obtained by calculations; using both, authors were able to conclude which combination of filler metal, welding procedure and, if necessary, heat treatment, would achieve the optimal improvement of weldability in welding/hard-facing of each of the tested base metals.
Facta Universitatis, Series: Mechanical Engineering, 2017
Self-lubricating bearings are available in spherical, plain, flanged journal, and rod end bearing... more Self-lubricating bearings are available in spherical, plain, flanged journal, and rod end bearing configurations. They were originally developed to eliminate the need for re-lubrication, to provide lower torque and to solve application problems where the conventional metal-to-metal bearings would not perform satisfactorily, for instance, in the presence of high frequency vibrations. Among the dominant tribological parameters of the self-lubricating bearing, two could be singled out: the coefficient of friction and temperature. To determine these parameters, an experimental method was applied in this paper. By using this method, the coefficient of friction and temperature were identified and their correlation was established. The aim of this research was to determine the effect of radial force on tribological parameters in order to predict the behavior of sliding bearings with graphite in real operating conditions.
Communications - Scientific letters of the University of Zilina, 2016
The influence of the density and shape of the sandwich beam core on the beam behavior was studied... more The influence of the density and shape of the sandwich beam core on the beam behavior was studied. The two beam configurations were analyzed: the beam whose cross-section is constant along its length and the beam with periodically varying cross-section along the length. Each of the two configurations was considered for the two different core shapes-with the square and the circular holes. The diagrams of the beam deflection in terms of the number of the core unit cells are presented for the two beam configurations and the two core shapes. Based on results presented in this paper, one can conclude that in the given loading conditions, the core density, after reaching certain critical value, ceases to affect the bent sandwich beam behavior. Comparison of the two cores shapes leads to conclusion that, in the same loading conditions, the core with the square holes provides for the better sandwich beam's characteristics, i.e. such a beam has smaller deflection with respect to the beam with the core with the circular holes.
Thermal fracture characteristics – the thermal energy release rate and thermal stress intensity f... more Thermal fracture characteristics – the thermal energy release rate and thermal stress intensity factor of a semi-infinite crack at an interface between the two elastic isotropic materials, subjected to the temperature variations, are considered in this paper. Those characteristics are determined based on application of the linear elastic fracture mechanics (LEFM) concept. Expressions for obtained theoretical solutions are compared to solutions from literature and they are found to be more concise. Influence of the materials change on these two thermal fracture properties were observed, as well as the influence of the thickness ratio of the two layers constituting the interface.
The necessity of having windows on any building’s façade is not questionable. However, not every ... more The necessity of having windows on any building’s façade is not questionable. However, not every window is suitable for any building. The selection of an adequate window must include the analysis of various factors—the most important ones are the type of window (e.g., single or double glazing); filling gas in cavities (e.g., air, argon or some other gas); and placing, i.e., orientation of a window on a façade (facing north, south, or east, etc.). The research presented in this paper is dealing with the calculation of the window thermal loading for the cities of Kragujevac and Bor in Serbia and Žilina in Slovakia. These three cities were selected because they belong to different climate regions, according to the Köppen–Geiger climatic classification. The first two cities in Serbia belong to the same region Cf with difference only in the category of summer—Kragujevac Cfa and Bor Cfb—while the third city—Žilina in Slovakia—belongs to the Dfb region. The calculated thermal loading throu...
Applied Engineering Letters : Journal of Engineering and Applied Sciences, 2020
This paper presents an analysis and the test results of certain physical properties of the rock m... more This paper presents an analysis and the test results of certain physical properties of the rock materials excavated from quarries in Serbia. The four rock aggregates, considered in this analysis, are used for building the driveway constructions' layers on roads, streets, airports and base layers on railways. To that purpose, both the general and specific technical properties (petrographic, physical, mechanical and technological) of those rocks must be known to users. The four rocks, whose physical properties are analyzed, are the most important types of the building stones: limestone, dolomite marble, calcite-dolomite marble and andesite. Their physical properties tested included volumetric mass, specific mass (density), porosity and water absorption. The service life, reparation jobs and maintenance procedures of the construction machinery parts, which come into direct contact with building materials like rocks and stones, strongly depend on those stones' properties. The four tested rock materials belong into a group of the massive rocks with various porosities and tendency to absorb water.
The energy efficiency of green walls, namely, the way of saving the energy consumption by the dyn... more The energy efficiency of green walls, namely, the way of saving the energy consumption by the dynamic characteristics of the façade walls is presented in this paper. Calculation and analysis of the dynamic characteristics of walls, with and without the plant cover, were performed. Comparison of the dynamic behavior of the facade, with and without the vegetation layer, is given and advantages of the former are emphasized, as well. Three different walls with different structures, but of the same individual thicknesses of layers and the same total thickness of the wall construction, were analyzed. The difference is in the thermal mass layer in the construction of a wall made of concrete with stone aggregates, solid brick, or solid blocks of lightweight concrete. Then, the three different walls of the same composition, as in the previous case, were analyzed, with upgraded layers of the soft wood and ivy representing the living layer of the wall.
In this paper are considered the most important properties of a special class of high strength st... more In this paper are considered the most important properties of a special class of high strength steels S690QL, which can be classified into the group of special low alloyed steels. The high strength steels belong into a group of high quality steels. They possess exceptional mechanical properties, especially tensile strength and toughness. Those favorable properties are being achieved by application of special procedures of thermo-mechanical processing and simultaneous alloying with adequate elements. The advantages that the S690QL steels have with respect to other steels are being presented here. However, possibilities for application of those steels in responsible welded structures are limited due to their only relatively good weldability. The special procedures for improving it are discussed here, primarily preheating, controlled heat input during welding and additional heat treatment of the welded joint.
Conference Quality Production Improvement – CQPI, 2020
The paper-forming sieve is the most important part of the paper production machine. Reliability o... more The paper-forming sieve is the most important part of the paper production machine. Reliability of the machine as a whole depends on the sieve’s quality. An analysis of the two constructions of the paper forming sieves, which were obtained by the plasma welding of the sieve’s wires, is presented in this paper. The mechanical characteristics of the two sieves, made of wires of diameters 0.15 mm and 0.20 mm, were tested, namely the tensile strength and elongation. The tests have shown that the sieve made of the wire of the smaller diameter has the better mechanical properties. This sieve is also better from the aspect of the water removal in the press section of the paper machine.
Dimensioning of pressure vessels can be done according to various criteria, the basic one being t... more Dimensioning of pressure vessels can be done according to various criteria, the basic one being the safety against the fracture by splashing. In this paper two methods for this dimensioning procedure are presented. The first one is based on application of the classical mechanics while the second one uses the fracture mechanics principles. Both methods were applied for checking the exploitation properties and capability of a vapor distributor in a power plant. Based on the insitu measured damages and calculations by both methods, it was concluded that the vapor distributor could be further used as a part of the boiler installation in the local power plant. The second criterion, based on the application of the fracture mechanics principles, provided more reliable results than the first one, based on the classical mechanics.
Due to difficult pandemic situation with COVID-19 decease, as well as due to current geopolitical... more Due to difficult pandemic situation with COVID-19 decease, as well as due to current geopolitical circumstances in the world, we are facing the shortage of steel and therefore the impossibility of delivering the contracted products within the agreed deadlines. It is thus necessary to find suitable steel for replacement. The procedure for selecting one such steel for substituting the deficit steel 25CrMo4, for the purposes of producing a responsible welded assembly, is described in this paper. After the careful analysis, the steel 42CrMo4 was taken into consideration as a possible substitute material. Prior to applying the new selected steel, it was necessary to perform the following tests: analyze its chemical composition, determine its most important mechanical properties and evaluate its weldability. Then, the optimal welding and heat treatment technologies were determined, so that the quality of the responsible welded structure would meet all the requirements, as the structure ma...
The presented work deals with an analysis of causes of the very low service life of the new versi... more The presented work deals with an analysis of causes of the very low service life of the new version of hand woodworking planing knife, which has replaced the original version of a planing knife. Based on the performed experimental works, chemical analysis, macroscopic and microscopic observation, SEM, diffractometric analysis, and Vickers hardness test it was concluded that the cause for the very low service life (practically the nonexistent one) of the new version of a planing knife are significant features of overheating. During the heating to the hardening temperature used steel was overheated, the cementite carbides dissolved, and the austenitic grains became coarse. The final microstructure of the used steel after hardening and tempering consists of brittle coarse martensitic needles, without any presence of the fine globular cementite carbides, accompanied by a very high amount of retained austenite. Thus, the chipping of the knife's cutting edge took place and the planer ...
The sandwich structures have multifold advantages with respect to other types of structures. Besi... more The sandwich structures have multifold advantages with respect to other types of structures. Besides the architectural possibilities due to their appearance, those structures can carry the same or even higher loads than some other similar structures. Optimization of the sandwich columns with the truss core, subjected to the compressive axial load, is presented in this paper. The two types of optimization were performed: the three-parameter and the four-parameter optimization - the so called full optimization. The optimization of the column geometry (face thickness, core member height and core member diameter and core height) was performed, from the aspect of the minimal weight of the structure in terms of the load index. It was performed for four types of restrictions imposed by the corresponding column failure modes: column buckling, truss macro-buckling, local buckling of the face and face wrinkling. The tree-parameter optimization resulted in somewhat larger weight of the column ...
Hard-facing as a type of the coating depositing is increasingly used today. Physical-chemical-met... more Hard-facing as a type of the coating depositing is increasingly used today. Physical-chemical-metallurgical characteristics of contact layers in tribo-mechanical systems depend on the operating conditions and the conditions under which the work surfaces were created. That is the reason the influence of the processing procedures and regime, used in the contact surfaces formation, on development of the wear process of contact elements, is being considered ever more. To determine the influence of the hard-facing technology on characteristics of the gears’ working surfaces, the experimental investigations were performed on samples hard-faced on the steel for cementation, by varying the filler metals (FM) and the hard-facing regimes. The samples tested were hard-faced by five “hard” and three “soft” filler metals. Experimental investigations included measuring the hard-faced layers’ hardness and determination of their microstructure, as well as the wear resistance in the laboratory condi...
Communications - Scientific letters of the University of Zilina
Mining machines' components, or the whole structure, are prone to frequent premature damages and ... more Mining machines' components, or the whole structure, are prone to frequent premature damages and fractures what is explained either by inadequate design and construction or by insufficient knowledge of the material's and welded joints' properties and oversights in manufacturing. Here is considered the bucket-wheel excavator, i.e. the fracture of the tooth of the girth gear, which enables the circular motion of the excavator's upper structure (which was in operation for 5000 hours). The gear was made of the cast steel GS 40 MnCrSi3 V. The reparatory hard-facing (HF) technology of the fractured tooth required specification of numerous operations including the preparation works. The reparation realized the twofold savings, in time and money-the new girth gear costs over 500 000 € and its manufacturing lasts 6 to 9 months, while the safety and quality of the repaired tooth was guaranteed.
Influence of shot peening on the wear behaviour of medium carbon, C55 steel was experimentally ve... more Influence of shot peening on the wear behaviour of medium carbon, C55 steel was experimentally verified. Experimental work included determination of the chemical composition, heat treatment, microstructure evaluation, mechanical properties measurement, shot peening treatment, the magnitude of the compressive residual stresses was evaluated, roughness profiles measurement and finally the friction tests. The results evidence the significant role played by the applied shot peening on wear behaviour of medium carbon steel. An important effect of surface roughness has been demonstrated. The coefficient of friction after shot peening compared to ground surface increased, 1.44 – 1.85 times.
The paper analyses the stability of a rectangular plate which is elastically buckled along longit... more The paper analyses the stability of a rectangular plate which is elastically buckled along longitudinal edges and pressed by equally distributed forces. A general case is analyseddifferent stiffness elastic clamping and then special simpler cases are considered. Energy method is used in order to determine critical stress. Deflection function is introduced in a convenient way so that it reflects the actual state of the plate deformation in the best manner. In this way, critical stress is determined in analytic form suitable for analysis. With help of the equation it is easy to conclude how certain parameters influence the value of critical stress. The paper indicates how the obtained solution could be utilized for determining local buckling critical stress in considerably more complex systemspressed thin-walled beams of an arbitrary length.
Two aspects of various steels’ weldability are considered in this article. The theoretical part p... more Two aspects of various steels’ weldability are considered in this article. The theoretical part presents general concepts related to steel’s weldability and the application of the most important methods for its determination. In the experimental section, results of the hard-facing application to several samples are presented, and consist of hardness measurements in the different zones of the welded samples, with the evaluation of those zones’ microstructures. The tested materials included two carbon steels and two alloyed steels, with hard-facing layers deposited by various filler metals. Experimental results were compared to results obtained by calculations; using both, authors were able to conclude which combination of filler metal, welding procedure and, if necessary, heat treatment, would achieve the optimal improvement of weldability in welding/hard-facing of each of the tested base metals.
Facta Universitatis, Series: Mechanical Engineering, 2017
Self-lubricating bearings are available in spherical, plain, flanged journal, and rod end bearing... more Self-lubricating bearings are available in spherical, plain, flanged journal, and rod end bearing configurations. They were originally developed to eliminate the need for re-lubrication, to provide lower torque and to solve application problems where the conventional metal-to-metal bearings would not perform satisfactorily, for instance, in the presence of high frequency vibrations. Among the dominant tribological parameters of the self-lubricating bearing, two could be singled out: the coefficient of friction and temperature. To determine these parameters, an experimental method was applied in this paper. By using this method, the coefficient of friction and temperature were identified and their correlation was established. The aim of this research was to determine the effect of radial force on tribological parameters in order to predict the behavior of sliding bearings with graphite in real operating conditions.
Communications - Scientific letters of the University of Zilina, 2016
The influence of the density and shape of the sandwich beam core on the beam behavior was studied... more The influence of the density and shape of the sandwich beam core on the beam behavior was studied. The two beam configurations were analyzed: the beam whose cross-section is constant along its length and the beam with periodically varying cross-section along the length. Each of the two configurations was considered for the two different core shapes-with the square and the circular holes. The diagrams of the beam deflection in terms of the number of the core unit cells are presented for the two beam configurations and the two core shapes. Based on results presented in this paper, one can conclude that in the given loading conditions, the core density, after reaching certain critical value, ceases to affect the bent sandwich beam behavior. Comparison of the two cores shapes leads to conclusion that, in the same loading conditions, the core with the square holes provides for the better sandwich beam's characteristics, i.e. such a beam has smaller deflection with respect to the beam with the core with the circular holes.
Thermal fracture characteristics – the thermal energy release rate and thermal stress intensity f... more Thermal fracture characteristics – the thermal energy release rate and thermal stress intensity factor of a semi-infinite crack at an interface between the two elastic isotropic materials, subjected to the temperature variations, are considered in this paper. Those characteristics are determined based on application of the linear elastic fracture mechanics (LEFM) concept. Expressions for obtained theoretical solutions are compared to solutions from literature and they are found to be more concise. Influence of the materials change on these two thermal fracture properties were observed, as well as the influence of the thickness ratio of the two layers constituting the interface.
The necessity of having windows on any building’s façade is not questionable. However, not every ... more The necessity of having windows on any building’s façade is not questionable. However, not every window is suitable for any building. The selection of an adequate window must include the analysis of various factors—the most important ones are the type of window (e.g., single or double glazing); filling gas in cavities (e.g., air, argon or some other gas); and placing, i.e., orientation of a window on a façade (facing north, south, or east, etc.). The research presented in this paper is dealing with the calculation of the window thermal loading for the cities of Kragujevac and Bor in Serbia and Žilina in Slovakia. These three cities were selected because they belong to different climate regions, according to the Köppen–Geiger climatic classification. The first two cities in Serbia belong to the same region Cf with difference only in the category of summer—Kragujevac Cfa and Bor Cfb—while the third city—Žilina in Slovakia—belongs to the Dfb region. The calculated thermal loading throu...
Applied Engineering Letters : Journal of Engineering and Applied Sciences, 2020
This paper presents an analysis and the test results of certain physical properties of the rock m... more This paper presents an analysis and the test results of certain physical properties of the rock materials excavated from quarries in Serbia. The four rock aggregates, considered in this analysis, are used for building the driveway constructions' layers on roads, streets, airports and base layers on railways. To that purpose, both the general and specific technical properties (petrographic, physical, mechanical and technological) of those rocks must be known to users. The four rocks, whose physical properties are analyzed, are the most important types of the building stones: limestone, dolomite marble, calcite-dolomite marble and andesite. Their physical properties tested included volumetric mass, specific mass (density), porosity and water absorption. The service life, reparation jobs and maintenance procedures of the construction machinery parts, which come into direct contact with building materials like rocks and stones, strongly depend on those stones' properties. The four tested rock materials belong into a group of the massive rocks with various porosities and tendency to absorb water.
The energy efficiency of green walls, namely, the way of saving the energy consumption by the dyn... more The energy efficiency of green walls, namely, the way of saving the energy consumption by the dynamic characteristics of the façade walls is presented in this paper. Calculation and analysis of the dynamic characteristics of walls, with and without the plant cover, were performed. Comparison of the dynamic behavior of the facade, with and without the vegetation layer, is given and advantages of the former are emphasized, as well. Three different walls with different structures, but of the same individual thicknesses of layers and the same total thickness of the wall construction, were analyzed. The difference is in the thermal mass layer in the construction of a wall made of concrete with stone aggregates, solid brick, or solid blocks of lightweight concrete. Then, the three different walls of the same composition, as in the previous case, were analyzed, with upgraded layers of the soft wood and ivy representing the living layer of the wall.
In this paper are considered the most important properties of a special class of high strength st... more In this paper are considered the most important properties of a special class of high strength steels S690QL, which can be classified into the group of special low alloyed steels. The high strength steels belong into a group of high quality steels. They possess exceptional mechanical properties, especially tensile strength and toughness. Those favorable properties are being achieved by application of special procedures of thermo-mechanical processing and simultaneous alloying with adequate elements. The advantages that the S690QL steels have with respect to other steels are being presented here. However, possibilities for application of those steels in responsible welded structures are limited due to their only relatively good weldability. The special procedures for improving it are discussed here, primarily preheating, controlled heat input during welding and additional heat treatment of the welded joint.
Conference Quality Production Improvement – CQPI, 2020
The paper-forming sieve is the most important part of the paper production machine. Reliability o... more The paper-forming sieve is the most important part of the paper production machine. Reliability of the machine as a whole depends on the sieve’s quality. An analysis of the two constructions of the paper forming sieves, which were obtained by the plasma welding of the sieve’s wires, is presented in this paper. The mechanical characteristics of the two sieves, made of wires of diameters 0.15 mm and 0.20 mm, were tested, namely the tensile strength and elongation. The tests have shown that the sieve made of the wire of the smaller diameter has the better mechanical properties. This sieve is also better from the aspect of the water removal in the press section of the paper machine.
Dimensioning of pressure vessels can be done according to various criteria, the basic one being t... more Dimensioning of pressure vessels can be done according to various criteria, the basic one being the safety against the fracture by splashing. In this paper two methods for this dimensioning procedure are presented. The first one is based on application of the classical mechanics while the second one uses the fracture mechanics principles. Both methods were applied for checking the exploitation properties and capability of a vapor distributor in a power plant. Based on the insitu measured damages and calculations by both methods, it was concluded that the vapor distributor could be further used as a part of the boiler installation in the local power plant. The second criterion, based on the application of the fracture mechanics principles, provided more reliable results than the first one, based on the classical mechanics.
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