In the aim of valid assessment of components integrity built-in industrial plants it was necessar... more In the aim of valid assessment of components integrity built-in industrial plants it was necessary to apply methodological approach, which includes: plant service history data acquisition, assortment and analysis, defining a programme for non-destructive and destructive inspection of material, and formulating of acceptance criteria. This paper present an example of integrity assessment of hot-water boiler tubing system exposed to corrosion based on boiler service history, previous test results and comparison of new results to adopted acceptance criteria. Integrity assessment of critical components represent background for defining of boiler tube partial replacement proposal, and also for defining of corrective and preventive maintenance measures. .
Characterization of HSS steels is necessary in order to meet all design and service requirements ... more Characterization of HSS steels is necessary in order to meet all design and service requirements for different industrial steel structures. Number of factors must be considered due to the HSS steal relatively low ductility. These factors should include at least a reduced deformability, weldability and demanding toughness, as well as fracture behaviour under the different loads. This paper compares data provided by two microscope imaging techniques. Following tests were performed: impact testing at different temperatures, tensile tests at room temperature and dynamic-cyclic loading test and characterization of fracture surfaces by scanning electron microscope and 3D digital optical microscope. 3D digital optical microscope in this study was used as non-contact technique witch provides fracture surface roughness information as a background for the determination of geometrical parameters for ductility characterization of materials obtained on fracture surfaces of mechanical testing spe...
Reliability and availability are the basic technical indicators of service quality in the broades... more Reliability and availability are the basic technical indicators of service quality in the broadest sense, and therefore the concurrency of thermal power plants in the terms of deregulated electricity market. Service history of the condensation type thermal power plant with coal powder combustion was analyzed in this article in the manner convenient for reliability calculations. Reliability calculations was made in first approximation without analyzing physical causation of reliability exchanges.
The introduction of resin-based cements and an adhesive-bonding system in daily dental practice h... more The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on s...
Lecture notes in mechanical engineering, Sep 14, 2016
The heat resistant tempered martensite ferritic steel X20CrMoV121 (DIN) has been extensively used... more The heat resistant tempered martensite ferritic steel X20CrMoV121 (DIN) has been extensively used within the last few decades as a material for boiler tubing systems and pipelines in thermal power plants (TPP). Long-term behavior of this steel is vastly researched and very well known, but main disadvantage is its poor weldability. In situ welding of martensitic steels is always challenging task and is usually quite difficult to implement properly in a short time, during forced outages of TPP. In this paper, characterization and mechanical properties of undermatch welded joint made during partial replacement of boiler outlet superheater (SH) in TPP by austenitic filler material, after 10 years of service are presented. Due to “cold” technique of welding, which does not required post weld heat treatment, this procedure were regular and widely used repair welding technique in two TPP (620 MW) units. In the purpose of comparison, two other type of matching welding joints of the same SH were also characterized: shop welded joint made by electrical resistance flash butt welding, as well as field welded joint made by gas tungsten arc welding during assembling of SH, which were both in service approximately 150,000 h.
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Transactions of the Indian Institute of Metals, Oct 31, 2019
In this study, two erosion protection MMC coatings with WC particles were deposited by the plasma... more In this study, two erosion protection MMC coatings with WC particles were deposited by the plasma transferred arc (PTA) welding. One of the coatings with tungsten carbide WC in the NiBSi matrix (WC/NiBSi), and the second coating WC in NiCrBSi matrix (WC/NiCrBSi) was deposited by the flame spray process on the same substrate material S235JR steel. Experiments were performed using a gas blast sand erosion test facility with high-velocity erodent particles impact (approximately 100 m/s) at different particle impact angles (20°-45°), with an objective to study erosion wear characteristics and mass loss of two MMC coatings. Microstructural characterization of MMC coatings was done by scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, whereas X-ray diffraction analysis was used for identification of present phases. The hardness of coatings was determined by Vickers hardness measurements. WC/ NiBSi obtained by the PTA process shows superior hardness and erosion properties.
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
This paper presents the technological process for obtaining basalt-stainless steel composite mate... more This paper presents the technological process for obtaining basalt-stainless steel composite materials and testing their physical and mechanical properties. The phases of the technological process consist of: milling, homogenization, pressing, and sintering to obtain composite materials with improved fracture toughness. Andesite basalt from the deposit site "Donje Jarinje", Serbia, was used as a matrix in the composites, while commercial austenitic stainless steel 316L in the amount of 0-30 wt.% was used as a reinforcement. Although the increase of 316L amount caused a continuous decrease in the relative density of sintered samples, the relative density of sample containing 30 wt.% of 316L was above 94%. The 316L grains, which possess a larger coefficient of thermal expansion than the basalt matrix, shrinking faster during cooling from sintering temperature resulting in the formation of compressive residual stress in the basalt matrix surrounding the spherical steel grains. The presence of this stress activated toughening mechanisms such as crack deflection and toughening due to compressive residual stress. The addition of 20 wt.% of reinforcing 316L particles increased the fracture toughness of basalt by more than 30%. The relative density of these samples was measured to be 97%, whereas macrohardness was found to be 6.2 GPa.
Vertical cylindrical vessel-chambers as a part of coal — drying plants, whose purpose is to colle... more Vertical cylindrical vessel-chambers as a part of coal — drying plants, whose purpose is to collect wastewater, are supported at 3 points in upper dish head area and are made of fine-grained Mn steel plates, joined by welding. Significant thinning and leaking in upper dish head area of the vessel occurred due to original design provoking an intensive abrasion, cracking
Martensitic steel X20CrMo12.1 has been extensively used within the last few decades as a material... more Martensitic steel X20CrMo12.1 has been extensively used within the last few decades as a material for tubing systems and pipelines in thermal power plants (TPP). Long term behavior of this steel is very well known and understood and because of that was found to be reliable material for prolonged service at elevated temperatures. It is well known that during operation TPP components are subject to microstructural changes that inevitably reflect decrease in their mechanical properties that lead to the loss of structural integrity and serviceability of component. This paper deals with the comprehensive investigation carried out on the main steam gate valve parent material of welded joint, as a part of main steam pipeline, after 170.000 h of service (545°C and 19MPa). The obtained results showed that the microstructural degradation caused by long term operation had little effects on the hardness and strength of material, while the changes in impact toughness were observed. Comprehensive microstructural analysis included the examination of the microstructure on the surface and trough the wall thickness.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
In the aim of valid assessment of components integrity built-in industrial plants it was necessar... more In the aim of valid assessment of components integrity built-in industrial plants it was necessary to apply methodological approach, which includes: plant service history data acquisition, assortment and analysis, defining a programme for non-destructive and destructive inspection of material, and formulating of acceptance criteria. This paper present an example of integrity assessment of hot-water boiler tubing system exposed to corrosion based on boiler service history, previous test results and comparison of new results to adopted acceptance criteria. Integrity assessment of critical components represent background for defining of boiler tube partial replacement proposal, and also for defining of corrective and preventive maintenance measures. .
Characterization of HSS steels is necessary in order to meet all design and service requirements ... more Characterization of HSS steels is necessary in order to meet all design and service requirements for different industrial steel structures. Number of factors must be considered due to the HSS steal relatively low ductility. These factors should include at least a reduced deformability, weldability and demanding toughness, as well as fracture behaviour under the different loads. This paper compares data provided by two microscope imaging techniques. Following tests were performed: impact testing at different temperatures, tensile tests at room temperature and dynamic-cyclic loading test and characterization of fracture surfaces by scanning electron microscope and 3D digital optical microscope. 3D digital optical microscope in this study was used as non-contact technique witch provides fracture surface roughness information as a background for the determination of geometrical parameters for ductility characterization of materials obtained on fracture surfaces of mechanical testing spe...
Reliability and availability are the basic technical indicators of service quality in the broades... more Reliability and availability are the basic technical indicators of service quality in the broadest sense, and therefore the concurrency of thermal power plants in the terms of deregulated electricity market. Service history of the condensation type thermal power plant with coal powder combustion was analyzed in this article in the manner convenient for reliability calculations. Reliability calculations was made in first approximation without analyzing physical causation of reliability exchanges.
The introduction of resin-based cements and an adhesive-bonding system in daily dental practice h... more The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on s...
Lecture notes in mechanical engineering, Sep 14, 2016
The heat resistant tempered martensite ferritic steel X20CrMoV121 (DIN) has been extensively used... more The heat resistant tempered martensite ferritic steel X20CrMoV121 (DIN) has been extensively used within the last few decades as a material for boiler tubing systems and pipelines in thermal power plants (TPP). Long-term behavior of this steel is vastly researched and very well known, but main disadvantage is its poor weldability. In situ welding of martensitic steels is always challenging task and is usually quite difficult to implement properly in a short time, during forced outages of TPP. In this paper, characterization and mechanical properties of undermatch welded joint made during partial replacement of boiler outlet superheater (SH) in TPP by austenitic filler material, after 10 years of service are presented. Due to “cold” technique of welding, which does not required post weld heat treatment, this procedure were regular and widely used repair welding technique in two TPP (620 MW) units. In the purpose of comparison, two other type of matching welding joints of the same SH were also characterized: shop welded joint made by electrical resistance flash butt welding, as well as field welded joint made by gas tungsten arc welding during assembling of SH, which were both in service approximately 150,000 h.
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Transactions of the Indian Institute of Metals, Oct 31, 2019
In this study, two erosion protection MMC coatings with WC particles were deposited by the plasma... more In this study, two erosion protection MMC coatings with WC particles were deposited by the plasma transferred arc (PTA) welding. One of the coatings with tungsten carbide WC in the NiBSi matrix (WC/NiBSi), and the second coating WC in NiCrBSi matrix (WC/NiCrBSi) was deposited by the flame spray process on the same substrate material S235JR steel. Experiments were performed using a gas blast sand erosion test facility with high-velocity erodent particles impact (approximately 100 m/s) at different particle impact angles (20°-45°), with an objective to study erosion wear characteristics and mass loss of two MMC coatings. Microstructural characterization of MMC coatings was done by scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, whereas X-ray diffraction analysis was used for identification of present phases. The hardness of coatings was determined by Vickers hardness measurements. WC/ NiBSi obtained by the PTA process shows superior hardness and erosion properties.
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
This paper presents the technological process for obtaining basalt-stainless steel composite mate... more This paper presents the technological process for obtaining basalt-stainless steel composite materials and testing their physical and mechanical properties. The phases of the technological process consist of: milling, homogenization, pressing, and sintering to obtain composite materials with improved fracture toughness. Andesite basalt from the deposit site "Donje Jarinje", Serbia, was used as a matrix in the composites, while commercial austenitic stainless steel 316L in the amount of 0-30 wt.% was used as a reinforcement. Although the increase of 316L amount caused a continuous decrease in the relative density of sintered samples, the relative density of sample containing 30 wt.% of 316L was above 94%. The 316L grains, which possess a larger coefficient of thermal expansion than the basalt matrix, shrinking faster during cooling from sintering temperature resulting in the formation of compressive residual stress in the basalt matrix surrounding the spherical steel grains. The presence of this stress activated toughening mechanisms such as crack deflection and toughening due to compressive residual stress. The addition of 20 wt.% of reinforcing 316L particles increased the fracture toughness of basalt by more than 30%. The relative density of these samples was measured to be 97%, whereas macrohardness was found to be 6.2 GPa.
Vertical cylindrical vessel-chambers as a part of coal — drying plants, whose purpose is to colle... more Vertical cylindrical vessel-chambers as a part of coal — drying plants, whose purpose is to collect wastewater, are supported at 3 points in upper dish head area and are made of fine-grained Mn steel plates, joined by welding. Significant thinning and leaking in upper dish head area of the vessel occurred due to original design provoking an intensive abrasion, cracking
Martensitic steel X20CrMo12.1 has been extensively used within the last few decades as a material... more Martensitic steel X20CrMo12.1 has been extensively used within the last few decades as a material for tubing systems and pipelines in thermal power plants (TPP). Long term behavior of this steel is very well known and understood and because of that was found to be reliable material for prolonged service at elevated temperatures. It is well known that during operation TPP components are subject to microstructural changes that inevitably reflect decrease in their mechanical properties that lead to the loss of structural integrity and serviceability of component. This paper deals with the comprehensive investigation carried out on the main steam gate valve parent material of welded joint, as a part of main steam pipeline, after 170.000 h of service (545°C and 19MPa). The obtained results showed that the microstructural degradation caused by long term operation had little effects on the hardness and strength of material, while the changes in impact toughness were observed. Comprehensive microstructural analysis included the examination of the microstructure on the surface and trough the wall thickness.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
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