Bu makalede paralel eksenlere donme ilave ederek hypocycloid ic ve polihedral dis yuzeylerin tala... more Bu makalede paralel eksenlere donme ilave ederek hypocycloid ic ve polihedral dis yuzeylerin talasli islenmesinde kullanilan takim geometrisi sunuldu. Bu metot torna, freze ve matkap tezgahlari ve dikey isleme merkezlerinde kullanilarak bu tezgahlarin imalat kapasitesini genisletir. Metodun kinematigi takim tasarimcilarinin bakisi ve hypocycloid yuzeylerin paralel eksenlere donme ilave edilerek talasli islenmesinde temel kesme acilarinin genellestirilmis modelinin gelistirilmesi bakisi ile tanimlandi. Bu metodun uygulanabilir alanlari belirlendi.
Aluminium bronzes possess a unique combination of high strength and wear and corrosion resistance... more Aluminium bronzes possess a unique combination of high strength and wear and corrosion resistance in aggressive environments; thus, these alloys find wide application in marine, shipbuilding, aviation, railway, offshore platform applications and other fields. Iron-aluminium bronzes (IABs) are the cheapest and most widely used. When the aluminium content is above 9.4 wt%, IAB is biphasic (i.e. it undergoes -transformation) and can be subjected to all heat-treatment types depending on the desired operating behaviour of the bronze component. This article presents correlations (mathematical models) between the primary mechanical characteristics (yield limit, tensile strength, elongation, hardness and impact toughness) and the ageing temperature and time of quench at 920°C in water Cu-11Al-6Fe bronze, obtained using the centrifugal casting method. The microstructure evolution was evaluated depending on the ageing temperature and time changes. Overall, the research was conducted in three ...
This article outlines a technology for hole-finishing in short-length cylinder lines to improve w... more This article outlines a technology for hole-finishing in short-length cylinder lines to improve wear resistance. The technology is based on an optimized diamond-burnishing (DB) process. The latter was implemented on conventional and CNC lathes, milling machines, and machining centers using a simple burnishing device with an elastic beam. The material used in this study was AISI 321 austenitic stainless steel. The governing factors used were the radius of the diamond insert, burnishing force and feed rate. The objective functions relating to surface integrity characteristics were selected on the basis of their functional importance relative to the wear resistance of the processed hole surface: height and shape roughness parameters, surface microhardness, and surface residual axial and hoop stresses. The one-factor-at-a-time method (used to reduce the factor space), a planned experiment, and regression analyses were used. The multi-objective optimization tasks, which were defined for ...
Direct correlations were established between basic surface integrity (SI) characteristics (roughn... more Direct correlations were established between basic surface integrity (SI) characteristics (roughness, microhardness, residual stresses) obtained as a result of surface cold working (SCW) and bending fatigue limit of chromium-nickel austenitic stainless steels (CNASS). The results of experimental tests and optimization of the SCW process, implemented via hardening diamond burnishing (DB), are presented. When the requirement for the corresponding component is a high fatigue limit, the information obtained will help the researcher to find the inverse correlation between SI and finishing so that when the SCW process is implementing by another method, the same high fatigue limit can be achieved. Five roughness parameters that are functionally significant indicators of fatigue behavior, microhardness, and surface residual axial and hoop stresses form the vector of objective functions. The governing factors are the burnishing force and the number of passes. The fatigue limit was obtained b...
This review paper analyses and summarises the results found while studying the slide burnishing (... more This review paper analyses and summarises the results found while studying the slide burnishing (SB) of metal components refracted through a prism during the surface engineering (SE) process, over the period of January 2019 to January 2023. According to the classification of SE processes defined in the article, SB as a technique in the scope of SE that belongs to the group of static surface cold working (SCW) processes, based on severe surface plastic deformation, and is realised under the condition of sliding friction contact with the treated surface. When the deforming element is natural or artificial diamond, SB is known as diamond burnishing (DB). SB is especially suited for axes, shafts, and holes with circular cross-sections but can also be implemented on flat-face and complex surfaces. SB is eco-friendly and a very economical method for producing mirror-like surface finishes on a wide range of ferrous and non-ferrous machined surfaces, but it can also be realised as a hardeni...
The surface cold working (SCW) of austenitic stainless steel (SS) causes martensitic transformati... more The surface cold working (SCW) of austenitic stainless steel (SS) causes martensitic transformation in the surface layers, and the percentage fraction of the strain-induced martensite depends on the degree of SCW. Higher content of α′−martensite increases the surface micro-hardness and fatigue strength, but deterioration of the corrosion resistance is possible. Therefore, the desired operational behaviour of austenitic SS can be ensured by the corresponding degree of SCW and heat treatment. This article evaluates the effects of SCW performed by diamond burnishing (DB) and heat treatment on the surface integrity (SI), rotating fatigue strength, and corrosion resistance of AISI 304 austenitic SS for two initial states: as-received hot-rolled bar and initially heat-treated at 1100 °C for one hour followed by quenching in water. Then, DB was implemented as a smoothing and hardening process, both alone and in combination with heat treatment at 350 °C for three hours after DB. The electro...
The disadvantages of widely used austenitic stainless steels are their low hardness and relativel... more The disadvantages of widely used austenitic stainless steels are their low hardness and relatively low fatigue strength. Conventional chemical-thermal surface treatments are unsuitable for these steels since they create conditions for inter-granular corrosion. An effective alternative is a low-temperature surface treatment, creating an S-phase within the surface layer, but it has a high cost/quality ratio. Austenitic steels can increase their surface micro-hardness and fatigue strength via surface cold working. When the goal is to increase the rotating bending fatigue strength of austenitic chromium-nickel steels, and the requirements for significant wear resistance are not paramount, diamond burnishing (DB) has significant potential to increase the fatigue strength and, based on the cost/quality ratio, can successfully compete with low-temperature chemical-thermal treatments. The main objective of this study is to establish the effect of DB on the rotating fatigue strength of AISI ...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2021
Static mechanical surface treatment (MST) processes based on the severe plastic deformation of th... more Static mechanical surface treatment (MST) processes based on the severe plastic deformation of the surface and subsurface layers improve the surface integrity (SI) of a metal component dramatically and thus its operational properties. The finite element method (FEM) is a basic simulation method used in the numerical investigations of MST processes. Although FEM always requires experimental verification of the results so obtained and an experiment to establish an adequate material constitutive model, this method saves of the researcher significant time and resources. Based on an analysis of the published studies devoted to FE simulations of static MST processes, five basic conditions have been found to be essential in order to build an adequate FE model. The theoretical formulations are then illustrated by creating FE models of the slide diamond burnishing (SDB) process using different strategies to make a comparative analysis between them. SDB is a static MST process with a thermomechanical nature. The adequacy of each FE model, respectively, strategy, is then assessed by comparing the FE results for the residual stresses with the experimental results obtained via the X-ray diffraction technique. It has been shown that a fully coupled thermal-stress 3D FE analysis of an SDB process with nonlinear kinematic hardening should be carried out. When the burnishing velocity is relatively small, the thermal effect can be neglected.
The aim of this paper is to perform optimization of photopolymerization process of dental composi... more The aim of this paper is to perform optimization of photopolymerization process of dental composites in order to obtain maximum hardness. Samples (5 mm diameter; 2, 3 and 4 mm thickness) were made of Universal Composite (UC), Bulk fill Composite (BC) and Flowable Composite (FC). Light curing of specimens was performed with 600, 1000 and 1500 mW/cm2 light intensity and an irradiation time of 20, 40 and 60 s. Vickers microhardness on the top and bottom surfaces of samples was measured. Optimization was carried out via regression analysis using QStatLab software. Photopolymerization process parameters were calculated using a specially designed MatLab software-based algorithm. For all composites, regression models for hardness on top and bottom surfaces of composite layer were established. Layer thickness as well as hardness on top and bottom surfaces of each composite was calculated for 21 curing modes varying with light intensity and irradiation time. It was established that photopoly...
Fatigue & Fracture of Engineering Materials & Structures, 2018
One of the methods for increasing fatigue life of symmetric rotary metal components is slide diam... more One of the methods for increasing fatigue life of symmetric rotary metal components is slide diamond burnishing (SDB). This method is implemented on conventional and computer numerical control machine tools by means of simple equipment, which is its main advantage. The SDB basic parameters are diamond insert radius, burnishing force, feed rate, and burnishing velocity. The additional ones are number of passes, working scheme, and lubrication conditions. The effect of SDB additional parameters on the fatigue behaviour of 2024‐T3 Al alloy was experimentally studied. Groups of smooth and notched hourglass‐shaped specimens were slide burnished using different combinations of additional SDB parameters and then were subjected to bending fatigue tests. The residual stresses, introduced by SDB, were measured by X‐ray diffraction technique. The near‐surface microstructure of the slide‐burnished specimens was investigated. Based on the results obtained, it was established that SDB produces tw...
... Biographical notes: Jordan T. Maximov is Professor of Mechanics of Deformable Solid at the Te... more ... Biographical notes: Jordan T. Maximov is Professor of Mechanics of Deformable Solid at the Technical University of Gabrovo, Bulgaria. ... Figure 3 shows the graphs and lines of objective parameter levels and their referred values are given, respectively P*, Me*, E*, Pr* and Ra*. ...
Bu makalede paralel eksenlere donme ilave ederek hypocycloid ic ve polihedral dis yuzeylerin tala... more Bu makalede paralel eksenlere donme ilave ederek hypocycloid ic ve polihedral dis yuzeylerin talasli islenmesinde kullanilan takim geometrisi sunuldu. Bu metot torna, freze ve matkap tezgahlari ve dikey isleme merkezlerinde kullanilarak bu tezgahlarin imalat kapasitesini genisletir. Metodun kinematigi takim tasarimcilarinin bakisi ve hypocycloid yuzeylerin paralel eksenlere donme ilave edilerek talasli islenmesinde temel kesme acilarinin genellestirilmis modelinin gelistirilmesi bakisi ile tanimlandi. Bu metodun uygulanabilir alanlari belirlendi.
Aluminium bronzes possess a unique combination of high strength and wear and corrosion resistance... more Aluminium bronzes possess a unique combination of high strength and wear and corrosion resistance in aggressive environments; thus, these alloys find wide application in marine, shipbuilding, aviation, railway, offshore platform applications and other fields. Iron-aluminium bronzes (IABs) are the cheapest and most widely used. When the aluminium content is above 9.4 wt%, IAB is biphasic (i.e. it undergoes -transformation) and can be subjected to all heat-treatment types depending on the desired operating behaviour of the bronze component. This article presents correlations (mathematical models) between the primary mechanical characteristics (yield limit, tensile strength, elongation, hardness and impact toughness) and the ageing temperature and time of quench at 920°C in water Cu-11Al-6Fe bronze, obtained using the centrifugal casting method. The microstructure evolution was evaluated depending on the ageing temperature and time changes. Overall, the research was conducted in three ...
This article outlines a technology for hole-finishing in short-length cylinder lines to improve w... more This article outlines a technology for hole-finishing in short-length cylinder lines to improve wear resistance. The technology is based on an optimized diamond-burnishing (DB) process. The latter was implemented on conventional and CNC lathes, milling machines, and machining centers using a simple burnishing device with an elastic beam. The material used in this study was AISI 321 austenitic stainless steel. The governing factors used were the radius of the diamond insert, burnishing force and feed rate. The objective functions relating to surface integrity characteristics were selected on the basis of their functional importance relative to the wear resistance of the processed hole surface: height and shape roughness parameters, surface microhardness, and surface residual axial and hoop stresses. The one-factor-at-a-time method (used to reduce the factor space), a planned experiment, and regression analyses were used. The multi-objective optimization tasks, which were defined for ...
Direct correlations were established between basic surface integrity (SI) characteristics (roughn... more Direct correlations were established between basic surface integrity (SI) characteristics (roughness, microhardness, residual stresses) obtained as a result of surface cold working (SCW) and bending fatigue limit of chromium-nickel austenitic stainless steels (CNASS). The results of experimental tests and optimization of the SCW process, implemented via hardening diamond burnishing (DB), are presented. When the requirement for the corresponding component is a high fatigue limit, the information obtained will help the researcher to find the inverse correlation between SI and finishing so that when the SCW process is implementing by another method, the same high fatigue limit can be achieved. Five roughness parameters that are functionally significant indicators of fatigue behavior, microhardness, and surface residual axial and hoop stresses form the vector of objective functions. The governing factors are the burnishing force and the number of passes. The fatigue limit was obtained b...
This review paper analyses and summarises the results found while studying the slide burnishing (... more This review paper analyses and summarises the results found while studying the slide burnishing (SB) of metal components refracted through a prism during the surface engineering (SE) process, over the period of January 2019 to January 2023. According to the classification of SE processes defined in the article, SB as a technique in the scope of SE that belongs to the group of static surface cold working (SCW) processes, based on severe surface plastic deformation, and is realised under the condition of sliding friction contact with the treated surface. When the deforming element is natural or artificial diamond, SB is known as diamond burnishing (DB). SB is especially suited for axes, shafts, and holes with circular cross-sections but can also be implemented on flat-face and complex surfaces. SB is eco-friendly and a very economical method for producing mirror-like surface finishes on a wide range of ferrous and non-ferrous machined surfaces, but it can also be realised as a hardeni...
The surface cold working (SCW) of austenitic stainless steel (SS) causes martensitic transformati... more The surface cold working (SCW) of austenitic stainless steel (SS) causes martensitic transformation in the surface layers, and the percentage fraction of the strain-induced martensite depends on the degree of SCW. Higher content of α′−martensite increases the surface micro-hardness and fatigue strength, but deterioration of the corrosion resistance is possible. Therefore, the desired operational behaviour of austenitic SS can be ensured by the corresponding degree of SCW and heat treatment. This article evaluates the effects of SCW performed by diamond burnishing (DB) and heat treatment on the surface integrity (SI), rotating fatigue strength, and corrosion resistance of AISI 304 austenitic SS for two initial states: as-received hot-rolled bar and initially heat-treated at 1100 °C for one hour followed by quenching in water. Then, DB was implemented as a smoothing and hardening process, both alone and in combination with heat treatment at 350 °C for three hours after DB. The electro...
The disadvantages of widely used austenitic stainless steels are their low hardness and relativel... more The disadvantages of widely used austenitic stainless steels are their low hardness and relatively low fatigue strength. Conventional chemical-thermal surface treatments are unsuitable for these steels since they create conditions for inter-granular corrosion. An effective alternative is a low-temperature surface treatment, creating an S-phase within the surface layer, but it has a high cost/quality ratio. Austenitic steels can increase their surface micro-hardness and fatigue strength via surface cold working. When the goal is to increase the rotating bending fatigue strength of austenitic chromium-nickel steels, and the requirements for significant wear resistance are not paramount, diamond burnishing (DB) has significant potential to increase the fatigue strength and, based on the cost/quality ratio, can successfully compete with low-temperature chemical-thermal treatments. The main objective of this study is to establish the effect of DB on the rotating fatigue strength of AISI ...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2021
Static mechanical surface treatment (MST) processes based on the severe plastic deformation of th... more Static mechanical surface treatment (MST) processes based on the severe plastic deformation of the surface and subsurface layers improve the surface integrity (SI) of a metal component dramatically and thus its operational properties. The finite element method (FEM) is a basic simulation method used in the numerical investigations of MST processes. Although FEM always requires experimental verification of the results so obtained and an experiment to establish an adequate material constitutive model, this method saves of the researcher significant time and resources. Based on an analysis of the published studies devoted to FE simulations of static MST processes, five basic conditions have been found to be essential in order to build an adequate FE model. The theoretical formulations are then illustrated by creating FE models of the slide diamond burnishing (SDB) process using different strategies to make a comparative analysis between them. SDB is a static MST process with a thermomechanical nature. The adequacy of each FE model, respectively, strategy, is then assessed by comparing the FE results for the residual stresses with the experimental results obtained via the X-ray diffraction technique. It has been shown that a fully coupled thermal-stress 3D FE analysis of an SDB process with nonlinear kinematic hardening should be carried out. When the burnishing velocity is relatively small, the thermal effect can be neglected.
The aim of this paper is to perform optimization of photopolymerization process of dental composi... more The aim of this paper is to perform optimization of photopolymerization process of dental composites in order to obtain maximum hardness. Samples (5 mm diameter; 2, 3 and 4 mm thickness) were made of Universal Composite (UC), Bulk fill Composite (BC) and Flowable Composite (FC). Light curing of specimens was performed with 600, 1000 and 1500 mW/cm2 light intensity and an irradiation time of 20, 40 and 60 s. Vickers microhardness on the top and bottom surfaces of samples was measured. Optimization was carried out via regression analysis using QStatLab software. Photopolymerization process parameters were calculated using a specially designed MatLab software-based algorithm. For all composites, regression models for hardness on top and bottom surfaces of composite layer were established. Layer thickness as well as hardness on top and bottom surfaces of each composite was calculated for 21 curing modes varying with light intensity and irradiation time. It was established that photopoly...
Fatigue & Fracture of Engineering Materials & Structures, 2018
One of the methods for increasing fatigue life of symmetric rotary metal components is slide diam... more One of the methods for increasing fatigue life of symmetric rotary metal components is slide diamond burnishing (SDB). This method is implemented on conventional and computer numerical control machine tools by means of simple equipment, which is its main advantage. The SDB basic parameters are diamond insert radius, burnishing force, feed rate, and burnishing velocity. The additional ones are number of passes, working scheme, and lubrication conditions. The effect of SDB additional parameters on the fatigue behaviour of 2024‐T3 Al alloy was experimentally studied. Groups of smooth and notched hourglass‐shaped specimens were slide burnished using different combinations of additional SDB parameters and then were subjected to bending fatigue tests. The residual stresses, introduced by SDB, were measured by X‐ray diffraction technique. The near‐surface microstructure of the slide‐burnished specimens was investigated. Based on the results obtained, it was established that SDB produces tw...
... Biographical notes: Jordan T. Maximov is Professor of Mechanics of Deformable Solid at the Te... more ... Biographical notes: Jordan T. Maximov is Professor of Mechanics of Deformable Solid at the Technical University of Gabrovo, Bulgaria. ... Figure 3 shows the graphs and lines of objective parameter levels and their referred values are given, respectively P*, Me*, E*, Pr* and Ra*. ...
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