The article deals with the design of the technology of production of polyurethane foam (PU) speci... more The article deals with the design of the technology of production of polyurethane foam (PU) specimens and with their mechanical testing. A simple procedure is proposed to produce specimens with complex shapes. The procedure is tested on two different mounting foams. These specimens were subjected to several experiments. The article presents experimental results for only one mounting foam. The tests were performed on a Testometric M500-50CT testing machine. Specifically, these are a tensile/compression test, a 3-point bending test, a shear test, and a modified indentation test. For each specimen, the displacement was also measured in the selected area with Digital Image Correlation Method. These measured data are presented in the article.
Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojní. Katedra (... more Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojní. Katedra (339) pružnosti a pevnost
2018 IEEE 22nd International Conference on Intelligent Engineering Systems (INES), 2018
The Department of Robotics has been long-term involved in application of technology Rapid Prototy... more The Department of Robotics has been long-term involved in application of technology Rapid Prototyping in projects primarily implemented in the area of mobile robotics. This relates to the issue of a correctly performed design of a model in the design phase. This requires the knowledge of material properties and the possibilities of working with the designed part in 3D printer software so that the required result achieves the best possible parameters with respect to the considered use. The paper deals with the possibility of improving mechanical properties in parts produced technology Rapid Prototyping technology. Based on results measured in a different area, a proposition has been stated which anticipates that an increase of the number of contours in mechanically stressed parts can lead to better mechanical properties. The proposition has been verified in mechanical tensile tests.
In this paper, we discuss and present our progress toward a project, which is focused on fatigue ... more In this paper, we discuss and present our progress toward a project, which is focused on fatigue life prediction under multiaxial loading in the domain of low-cycle fatigue, i.e. cases, where the plasticity cannot be neglected. First, the elastic-plastic solution in the finite element analysis is enhanced and verified on own experiments. Second, the method by Jiang describing the instantaneous damage increase by analyses of load time by time, is in implementation phase. In addition, simplified routines for conversion of elastic stresses-strains to elastic-plastic ones as proposed by Firat and Ye et.al. are evaluated on the basis of data gathered from external sources. In order to produce high quality complex analyses, which could be feasible in an acceptable time, and allow the period for next analyses of results to be expanded; the core of PragTic fatigue solver used for all fatigue computations are being re-implemented to get the fully parallelized scalable solution.
Strojnícky casopis – Journal of Mechanical Engineering, 2016
The aim of this work is to find out the components of stress tensor in plane specimens. For this ... more The aim of this work is to find out the components of stress tensor in plane specimens. For this purpose the photoelasticity methodology is used. In order to make this technique more comfortable for use, there was developed an algorithm in MATLAB program. The results are compared with numerical solution. The main advantages of the developed algorithm are the speed and the capabilities to extend to analyze the plastic deformation and strain conditions in the material during forming processes.
In this paper, the authors draw attention to biomechanics connected with the possibilities of tre... more In this paper, the authors draw attention to biomechanics connected with the possibilities of treatment of complicated bone fractures. They present information about their own design, laboratory tests and numerical solutions (i.e. strength analyses and reliability assessments) of the various types of external fixators applied in traumatology and orthopaedics (i.e. intended for fractures of limbs and pelvis and its acetabulum). The new design of external fixators is based on the development of Ilizarov and other techniques and satisfies new demands of science.
This contribution presents main results of experimental tests realized on smooth specimens made o... more This contribution presents main results of experimental tests realized on smooth specimens made of ST52 steel under strain controlled uniaxial cyclic loading and compares these results with numerical simulations performed using a modified Chaboche model by finite element method. The effects of NonMasings behavior, memorization, cyclic hardening/softening and mean stress relaxation have been studied at room temperature. The experiments were realized on the reconstructed hydraulic fatigue testing machine INOVA 100 at the Laboratory of modern materials testing and defectoscopy of VŠB-TU Ostrava. Developed mixed hardening material model includes a memory surface stated in stress-space, which makes possible to significantly improve prediction of effects studied.
At the moulds and swages making happens to rise of residual stress in consequence of heat process... more At the moulds and swages making happens to rise of residual stress in consequence of heat process. These problem is very significant especially at modern technology like high – speed hard milling (HSC), when happens to extreme conditions from mechanical and heat aspects. Residual stress rise depending on cutting speed, feed, tool type and other parameters is therefore one of the most important part of optimizing of he HSC process. This paper deals with evaluation of residual stress after high – speed and conventional milling. For a measuring residual stress were select two different methods. It was method measuring by method of Barkhausen noise and hole-drilling method.Při výrobě forem a zápustek dochází ke vzniku zbytkových napětí v důsledku tepelného zpracování a obrábění. Tento problém je obzvláště významný u moderních technologií jako vysokorychlostní tvrdé frézování (HSC), kdy dochází k extrémním záběrovým podmínkám jak z mechanického, tak i z tepelného hlediska. Vznik zbytkový...
Při výrobě forem a zapustek dochazi ke vzniku zbytkových napěti v důsledku tepelneho zpracovani a... more Při výrobě forem a zapustek dochazi ke vzniku zbytkových napěti v důsledku tepelneho zpracovani a obraběni. Tento problem je obzvlastě významný u modernich technologii jako vysokorychlostni tvrde frezovani (HSC), kdy dochazi k extremnim zaběrovým podminkam jak z mechanickeho, tak i z tepelneho hlediska. Vznik zbytkových napěti v zavislosti na řezne rychlosti, posuvu, typu nastroje a dalsich parametrech je proto jednou z důležitých soucasti optimalizace procesu HSC obraběni. Tento clanek se zabýva vyhodnocenim zbytkových pnuti po vysokorychlostnim a konvencnim frezovani. Pro měřeni těchto pnuti byly zvoleny dvě různe metody. Byla to metoda měřeni pomoci Barkhausenova sumu a metoda odvrtavaci.
The article focuses on monitoring the machined surface after it has been machined with different ... more The article focuses on monitoring the machined surface after it has been machined with different milling strategies. Different milling strategies refer to milling whilst changing the tool axis relative to the surface after finishing the free form milling. The research focuses mainly on the geometric characteristics of the finished surface profile and residual stresses in the surface layer. The goal of the experimental work is to find an effective position of the tool axis, or an effective interval of the tool axis, in relation to the machined surface normal. Practical applications of the results are focused on finishing milling of complicated shape surfaces especially in the production of moulds and dies for the automotive and aerospace industries. The technology is based on the substitution of three-axis milling for multi-axis milling, i.e. mainly 5-axis simultaneous milling.
Abstract This paper attempts to describe the effect of a non-constant stress distribution on the ... more Abstract This paper attempts to describe the effect of a non-constant stress distribution on the fatigue strength of unnotched hollow specimens of various sizes and loaded by different load combinations. The chosen solution evaluates the critical volume, which decides the level of fatigue damage. It relates dimensions of these critical entities to component fatigue strengths, which replace the material parameters in multiaxial fatigue strength criteria. The output shows that the proposed critical volume method is a promising solution. The PCRN and MMP multiaxial fatigue strength methods result in the best prediction outputs from the seven methods assessed here.
The article deals with the design of the technology of production of polyurethane foam (PU) speci... more The article deals with the design of the technology of production of polyurethane foam (PU) specimens and with their mechanical testing. A simple procedure is proposed to produce specimens with complex shapes. The procedure is tested on two different mounting foams. These specimens were subjected to several experiments. The article presents experimental results for only one mounting foam. The tests were performed on a Testometric M500-50CT testing machine. Specifically, these are a tensile/compression test, a 3-point bending test, a shear test, and a modified indentation test. For each specimen, the displacement was also measured in the selected area with Digital Image Correlation Method. These measured data are presented in the article.
Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojní. Katedra (... more Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojní. Katedra (339) pružnosti a pevnost
2018 IEEE 22nd International Conference on Intelligent Engineering Systems (INES), 2018
The Department of Robotics has been long-term involved in application of technology Rapid Prototy... more The Department of Robotics has been long-term involved in application of technology Rapid Prototyping in projects primarily implemented in the area of mobile robotics. This relates to the issue of a correctly performed design of a model in the design phase. This requires the knowledge of material properties and the possibilities of working with the designed part in 3D printer software so that the required result achieves the best possible parameters with respect to the considered use. The paper deals with the possibility of improving mechanical properties in parts produced technology Rapid Prototyping technology. Based on results measured in a different area, a proposition has been stated which anticipates that an increase of the number of contours in mechanically stressed parts can lead to better mechanical properties. The proposition has been verified in mechanical tensile tests.
In this paper, we discuss and present our progress toward a project, which is focused on fatigue ... more In this paper, we discuss and present our progress toward a project, which is focused on fatigue life prediction under multiaxial loading in the domain of low-cycle fatigue, i.e. cases, where the plasticity cannot be neglected. First, the elastic-plastic solution in the finite element analysis is enhanced and verified on own experiments. Second, the method by Jiang describing the instantaneous damage increase by analyses of load time by time, is in implementation phase. In addition, simplified routines for conversion of elastic stresses-strains to elastic-plastic ones as proposed by Firat and Ye et.al. are evaluated on the basis of data gathered from external sources. In order to produce high quality complex analyses, which could be feasible in an acceptable time, and allow the period for next analyses of results to be expanded; the core of PragTic fatigue solver used for all fatigue computations are being re-implemented to get the fully parallelized scalable solution.
Strojnícky casopis – Journal of Mechanical Engineering, 2016
The aim of this work is to find out the components of stress tensor in plane specimens. For this ... more The aim of this work is to find out the components of stress tensor in plane specimens. For this purpose the photoelasticity methodology is used. In order to make this technique more comfortable for use, there was developed an algorithm in MATLAB program. The results are compared with numerical solution. The main advantages of the developed algorithm are the speed and the capabilities to extend to analyze the plastic deformation and strain conditions in the material during forming processes.
In this paper, the authors draw attention to biomechanics connected with the possibilities of tre... more In this paper, the authors draw attention to biomechanics connected with the possibilities of treatment of complicated bone fractures. They present information about their own design, laboratory tests and numerical solutions (i.e. strength analyses and reliability assessments) of the various types of external fixators applied in traumatology and orthopaedics (i.e. intended for fractures of limbs and pelvis and its acetabulum). The new design of external fixators is based on the development of Ilizarov and other techniques and satisfies new demands of science.
This contribution presents main results of experimental tests realized on smooth specimens made o... more This contribution presents main results of experimental tests realized on smooth specimens made of ST52 steel under strain controlled uniaxial cyclic loading and compares these results with numerical simulations performed using a modified Chaboche model by finite element method. The effects of NonMasings behavior, memorization, cyclic hardening/softening and mean stress relaxation have been studied at room temperature. The experiments were realized on the reconstructed hydraulic fatigue testing machine INOVA 100 at the Laboratory of modern materials testing and defectoscopy of VŠB-TU Ostrava. Developed mixed hardening material model includes a memory surface stated in stress-space, which makes possible to significantly improve prediction of effects studied.
At the moulds and swages making happens to rise of residual stress in consequence of heat process... more At the moulds and swages making happens to rise of residual stress in consequence of heat process. These problem is very significant especially at modern technology like high – speed hard milling (HSC), when happens to extreme conditions from mechanical and heat aspects. Residual stress rise depending on cutting speed, feed, tool type and other parameters is therefore one of the most important part of optimizing of he HSC process. This paper deals with evaluation of residual stress after high – speed and conventional milling. For a measuring residual stress were select two different methods. It was method measuring by method of Barkhausen noise and hole-drilling method.Při výrobě forem a zápustek dochází ke vzniku zbytkových napětí v důsledku tepelného zpracování a obrábění. Tento problém je obzvláště významný u moderních technologií jako vysokorychlostní tvrdé frézování (HSC), kdy dochází k extrémním záběrovým podmínkám jak z mechanického, tak i z tepelného hlediska. Vznik zbytkový...
Při výrobě forem a zapustek dochazi ke vzniku zbytkových napěti v důsledku tepelneho zpracovani a... more Při výrobě forem a zapustek dochazi ke vzniku zbytkových napěti v důsledku tepelneho zpracovani a obraběni. Tento problem je obzvlastě významný u modernich technologii jako vysokorychlostni tvrde frezovani (HSC), kdy dochazi k extremnim zaběrovým podminkam jak z mechanickeho, tak i z tepelneho hlediska. Vznik zbytkových napěti v zavislosti na řezne rychlosti, posuvu, typu nastroje a dalsich parametrech je proto jednou z důležitých soucasti optimalizace procesu HSC obraběni. Tento clanek se zabýva vyhodnocenim zbytkových pnuti po vysokorychlostnim a konvencnim frezovani. Pro měřeni těchto pnuti byly zvoleny dvě různe metody. Byla to metoda měřeni pomoci Barkhausenova sumu a metoda odvrtavaci.
The article focuses on monitoring the machined surface after it has been machined with different ... more The article focuses on monitoring the machined surface after it has been machined with different milling strategies. Different milling strategies refer to milling whilst changing the tool axis relative to the surface after finishing the free form milling. The research focuses mainly on the geometric characteristics of the finished surface profile and residual stresses in the surface layer. The goal of the experimental work is to find an effective position of the tool axis, or an effective interval of the tool axis, in relation to the machined surface normal. Practical applications of the results are focused on finishing milling of complicated shape surfaces especially in the production of moulds and dies for the automotive and aerospace industries. The technology is based on the substitution of three-axis milling for multi-axis milling, i.e. mainly 5-axis simultaneous milling.
Abstract This paper attempts to describe the effect of a non-constant stress distribution on the ... more Abstract This paper attempts to describe the effect of a non-constant stress distribution on the fatigue strength of unnotched hollow specimens of various sizes and loaded by different load combinations. The chosen solution evaluates the critical volume, which decides the level of fatigue damage. It relates dimensions of these critical entities to component fatigue strengths, which replace the material parameters in multiaxial fatigue strength criteria. The output shows that the proposed critical volume method is a promising solution. The PCRN and MMP multiaxial fatigue strength methods result in the best prediction outputs from the seven methods assessed here.
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Papers by František Fojtík