The Experts below are selected from a list of 5937 Experts worldwide ranked by ideXlab platform
W Eichlseder - One of the best experts on this subject based on the ideXlab platform.
-
Fatigue Lifetime of az91 magnesium alloy subjected to cyclic thermal and mechanical loadings
Materials & Design, 2014Co-Authors: Mohammad Azadi, G H Farrahi, Gerhard Winter, W EichlsederAbstract:Abstract In the present paper, thermo-mechanical Fatigue (TMF) and low cycle Fatigue (LCF) or isothermal Fatigue (IF) Lifetimes of a cast magnesium alloy (the AZ91 alloy) were studied. In addition to a heat treatment process (T6), several rare elements were added to the alloy to improve the material strength in the first step. Then, the cyclic behavior of the AZ91 was investigated. For this objective, strain-controlled tension–compression Fatigue tests were carried out. The temperature varied between 50 and 200 °C in the out-of-phase (OP) TMF tests. The constraint factor which was defined as the ratio of the mechanical strain to the thermal strain, was set to 75%, 100% and 125%. For LCF tests, mechanical strain amplitudes of 0.20%, 0.25% and 0.30% were considered at constant temperatures of 25 and 200 °C. Experimental Fatigue results showed that the cyclic hardening behavior occurred at the room temperature in the AZ91 alloy. At higher temperatures, this alloy had a brittle fracture. But also, it was not significantly clear that the cyclic hardening or the cyclic softening behavior would be occurred in the material. Then, the high temperature LCF Lifetime was more than that at the room temperature. The OP-TMF Lifetime was the least value in comparison to that of LCF tests. At the end of this article, two energy-based models were applied to predict the Fatigue Lifetime of this magnesium alloy.
-
a new energy based isothermal and thermo mechanical Fatigue Lifetime prediction model for aluminium silicon magnesium alloy
Fatigue & Fracture of Engineering Materials & Structures, 2013Co-Authors: G H Farrahi, Mohammad Azadi, Gerhard Winter, W EichlsederAbstract:In this paper, a new Fatigue Lifetime prediction model is presented for the aluminium–silicon–magnesium alloy, A356.0. This model is based on the plastic strain energy density per cycle including two correction factors in order to consider the effect of the mean stress and the maximum temperature. The thermal term considers creep and oxidation damages in A356.0 alloy. To calibrate the model, isothermal Fatigue and out-of-phase thermo-mechanical Fatigue (TMF) tests were conducted on the A356.0 alloy. Results showed an improvement in predicting Fatigue Lifetimes by the present model in comparison with classical theories and also the plastic strain energy density (without any correction factors). Therefore, this model is applicable for TMF, low cycle Fatigue (LCF) and both TMF/LCF Lifetimes of the A356.0 alloy. Furthermore, this model can be easily used for the estimation of thermo-mechanical conditions in components such as cylinder heads.
-
A new energy-based isothermal and thermo-mechanical Fatigue Lifetime prediction model for aluminium–silicon–magnesium alloy
Fatigue & Fracture of Engineering Materials & Structures, 2013Co-Authors: G H Farrahi, Mohammad Azadi, Gerhard Winter, W EichlsederAbstract:In this paper, a new Fatigue Lifetime prediction model is presented for the aluminium–silicon–magnesium alloy, A356.0. This model is based on the plastic strain energy density per cycle including two correction factors in order to consider the effect of the mean stress and the maximum temperature. The thermal term considers creep and oxidation damages in A356.0 alloy. To calibrate the model, isothermal Fatigue and out-of-phase thermo-mechanical Fatigue (TMF) tests were conducted on the A356.0 alloy. Results showed an improvement in predicting Fatigue Lifetimes by the present model in comparison with classical theories and also the plastic strain energy density (without any correction factors). Therefore, this model is applicable for TMF, low cycle Fatigue (LCF) and both TMF/LCF Lifetimes of the A356.0 alloy. Furthermore, this model can be easily used for the estimation of thermo-mechanical conditions in components such as cylinder heads.
Pavel Hutař - One of the best experts on this subject based on the ideXlab platform.
-
Fatigue Lifetime estimation of railway axles
Engineering Failure Analysis, 2017Co-Authors: Pavel Pokorný, Lubos Nahlik, Rostislav Fajkos, Martin Sevcik, Petr Matusek, Pavel HutařAbstract:Abstract The railway axles are subjected to cyclic loading during their operation. Their load is of long-term nature, therefore a real risk of Fatigue failure exists. This failure could lead to derailment of the whole train with serious consequences. To prevent such scenario, the railway axles have to be safely removed from operation before their final failure occurs. This paper presents methodology for the residual Fatigue Lifetime prediction of the railway axle based on the linear elastic fracture mechanics concept. The methodology contains estimation of the critical position of initial crack, prediction of the Fatigue crack front shape development during crack propagation, separation of the bending and press-fitting contributions to the axle load, experimental measurement of the crack growth kinetics of EA4T steel and subsequent estimation of the residual Fatigue Lifetime of railway axle. Part of the presented study is also devoted to the probability aspects of determination of material characteristics describing Fatigue crack propagation and retardation effects caused by existence of plastic zone ahead of propagating Fatigue crack. Described methodology is already applied in the design process of new railway axles in Bonatrans company.
-
effect of residual stresses on the Fatigue Lifetime of railway axle
Procedia structural integrity, 2017Co-Authors: Pavel Hutař, Pavel Pokorný, Jan Poduska, Rostislav Fajkos, Lubos NahlikAbstract:Abstract The operation of railway axles should fulfill at least two main demands: safety and low operation costs. A significant part of operation costs is given by the length of regular inspection intervals which should reveal potential Fatigue cracks in railway axle. The detection of cracks is of a probabilistic nature, therefore their detection is not ensured in all cases. For the safe operation of trains, an existence of potential initial crack should be considered on the axle surface and residual Fatigue Lifetime should be conservatively determined for this case. Reliable procedure of residual Fatigue Lifetime estimation should take into account real axle geometry, material characteristics and loading of the railway axle. This paper shows methodology for determination of residual Fatigue Lifetime (RFL) based on the fracture mechanics approach, taking into account real spectrum of the loading cycles, existence of press-fitted wheels and surface residual stresses given by the thermo-mechanical surface treatment of the railway axle. It is demonstrated that the effect of the residual stresses is significant and should not be neglected in the numerical estimation of residual Fatigue Lifetime of the axle.
-
Influence of Initial Inclined Surface Crack on Estimated Residual Fatigue Lifetime of Railway Axle
Journal of Multiscale Modelling, 2016Co-Authors: Lubos Nahlik, Pavel Pokorný, Martin Sevcik, Pavel HutařAbstract:Railway axles are subjected to cyclic loading which can lead to Fatigue failure. For safe operation of railway axles a damage tolerance approach taking into account a possible defect on railway axle surface is often required. The contribution deals with an estimation of residual Fatigue Lifetime of railway axle with initial inclined surface crack. 3D numerical model of inclined semi-elliptical surface crack in railway axle was developed and its curved propagation through the axle was simulated by finite element method. Presence of press-fitted wheel in the vicinity of initial crack was taken into account. A typical loading spectrum of railway axle was considered and residual Fatigue Lifetime was estimated by NASGRO approach. Material properties of typical axle steel EA4T were considered in numerical calculations and Lifetime estimation.
-
residual Fatigue Lifetime estimation of railway axles for various loading spectra
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: Pavel Pokorný, Pavel Hutař, Lubos NahlikAbstract:Abstract The knowledge of the residual Fatigue Lifetime of railway axles is very important for the safe operation of trains. The railway axles could include some defects like cracks, scratches or inhomogeneities which could contribute to the Fatigue crack initiation and in the final stage to axle failure. The non-destructive testing methods are not reliable for detection of relatively short (circa 1–2 mm), but even dangerous cracks. For conservative estimation of residual Fatigue Lifetime the railway axle containing initial crack should be considered. The residual Fatigue Lifetime is given by the number of load cycles for Fatigue crack growth from the initial size of the crack up to the critical size with consequent Fatigue failure of railway axle. Railway axles are used in different types of trains which are used under different conditions (regional trains, urban trains, high speed trains, freight trains, etc.). This work is focused on numerical estimation of residual Fatigue Lifetime of railway axle while several different load spectra taken from the literature are considered in the performed estimations. This paper also shows the influence of the discretization level of the continuous load spectrum and effect of magnification or diminution of load spectrum on the calculated residual Fatigue Lifetime of the railway axle.
-
Influence of variable stress ratio during train operation on residual Fatigue Lifetime of railway axles
Procedia structural integrity, 2016Co-Authors: Pavel Pokorný, Lubos Nahlik, Pavel HutařAbstract:Abstract Railway axles are subjected to cyclic loading, which could lead to Fatigue failure. Therefore, it is desired to know residual Fatigue Lifetime of railway axles to ensure safe operation of trains. Because of detection of relatively small Fatigue cracks is not guaranteed an estimation of residual Fatigue Lifetime is based on damage tolerance approach. The acting stress ratio is variable due to variable amplitude loading and load caused by existence of press-fitted wheel in the vicinity of assumed crack. The contribution is focused on influence of variable stress ratio in EA4T steel on residual Fatigue Lifetime of railway axles. The influence of stress intensity factor on Fatigue crack propagation rate was experimentally evaluated for three different stress ratios, which correspond to operation conditions. Two different expressions of Fatigue crack propagation rate were used and mutually compared to show influence of the stress ratio on residual Fatigue Lifetime of structure made of EA4T steel. The first expression considers stress intensity factor range (respecting stress ratio R ) and the second one uses maximal value of the stress intensity factor. The paper shows ability of both expressions to describe experimental data obtained under different stress ratios and their influence on estimated residual Fatigue Lifetime values. The results obtained contribute to the better estimation of residual Fatigue Lifetime of railway axles and generally to the safer rail transportation.
Pavel Pokorný - One of the best experts on this subject based on the ideXlab platform.
-
Fatigue Lifetime estimation of railway axles
Engineering Failure Analysis, 2017Co-Authors: Pavel Pokorný, Lubos Nahlik, Rostislav Fajkos, Martin Sevcik, Petr Matusek, Pavel HutařAbstract:Abstract The railway axles are subjected to cyclic loading during their operation. Their load is of long-term nature, therefore a real risk of Fatigue failure exists. This failure could lead to derailment of the whole train with serious consequences. To prevent such scenario, the railway axles have to be safely removed from operation before their final failure occurs. This paper presents methodology for the residual Fatigue Lifetime prediction of the railway axle based on the linear elastic fracture mechanics concept. The methodology contains estimation of the critical position of initial crack, prediction of the Fatigue crack front shape development during crack propagation, separation of the bending and press-fitting contributions to the axle load, experimental measurement of the crack growth kinetics of EA4T steel and subsequent estimation of the residual Fatigue Lifetime of railway axle. Part of the presented study is also devoted to the probability aspects of determination of material characteristics describing Fatigue crack propagation and retardation effects caused by existence of plastic zone ahead of propagating Fatigue crack. Described methodology is already applied in the design process of new railway axles in Bonatrans company.
-
effect of residual stresses on the Fatigue Lifetime of railway axle
Procedia structural integrity, 2017Co-Authors: Pavel Hutař, Pavel Pokorný, Jan Poduska, Rostislav Fajkos, Lubos NahlikAbstract:Abstract The operation of railway axles should fulfill at least two main demands: safety and low operation costs. A significant part of operation costs is given by the length of regular inspection intervals which should reveal potential Fatigue cracks in railway axle. The detection of cracks is of a probabilistic nature, therefore their detection is not ensured in all cases. For the safe operation of trains, an existence of potential initial crack should be considered on the axle surface and residual Fatigue Lifetime should be conservatively determined for this case. Reliable procedure of residual Fatigue Lifetime estimation should take into account real axle geometry, material characteristics and loading of the railway axle. This paper shows methodology for determination of residual Fatigue Lifetime (RFL) based on the fracture mechanics approach, taking into account real spectrum of the loading cycles, existence of press-fitted wheels and surface residual stresses given by the thermo-mechanical surface treatment of the railway axle. It is demonstrated that the effect of the residual stresses is significant and should not be neglected in the numerical estimation of residual Fatigue Lifetime of the axle.
-
Influence of Initial Inclined Surface Crack on Estimated Residual Fatigue Lifetime of Railway Axle
Journal of Multiscale Modelling, 2016Co-Authors: Lubos Nahlik, Pavel Pokorný, Martin Sevcik, Pavel HutařAbstract:Railway axles are subjected to cyclic loading which can lead to Fatigue failure. For safe operation of railway axles a damage tolerance approach taking into account a possible defect on railway axle surface is often required. The contribution deals with an estimation of residual Fatigue Lifetime of railway axle with initial inclined surface crack. 3D numerical model of inclined semi-elliptical surface crack in railway axle was developed and its curved propagation through the axle was simulated by finite element method. Presence of press-fitted wheel in the vicinity of initial crack was taken into account. A typical loading spectrum of railway axle was considered and residual Fatigue Lifetime was estimated by NASGRO approach. Material properties of typical axle steel EA4T were considered in numerical calculations and Lifetime estimation.
-
residual Fatigue Lifetime estimation of railway axles for various loading spectra
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: Pavel Pokorný, Pavel Hutař, Lubos NahlikAbstract:Abstract The knowledge of the residual Fatigue Lifetime of railway axles is very important for the safe operation of trains. The railway axles could include some defects like cracks, scratches or inhomogeneities which could contribute to the Fatigue crack initiation and in the final stage to axle failure. The non-destructive testing methods are not reliable for detection of relatively short (circa 1–2 mm), but even dangerous cracks. For conservative estimation of residual Fatigue Lifetime the railway axle containing initial crack should be considered. The residual Fatigue Lifetime is given by the number of load cycles for Fatigue crack growth from the initial size of the crack up to the critical size with consequent Fatigue failure of railway axle. Railway axles are used in different types of trains which are used under different conditions (regional trains, urban trains, high speed trains, freight trains, etc.). This work is focused on numerical estimation of residual Fatigue Lifetime of railway axle while several different load spectra taken from the literature are considered in the performed estimations. This paper also shows the influence of the discretization level of the continuous load spectrum and effect of magnification or diminution of load spectrum on the calculated residual Fatigue Lifetime of the railway axle.
-
Influence of variable stress ratio during train operation on residual Fatigue Lifetime of railway axles
Procedia structural integrity, 2016Co-Authors: Pavel Pokorný, Lubos Nahlik, Pavel HutařAbstract:Abstract Railway axles are subjected to cyclic loading, which could lead to Fatigue failure. Therefore, it is desired to know residual Fatigue Lifetime of railway axles to ensure safe operation of trains. Because of detection of relatively small Fatigue cracks is not guaranteed an estimation of residual Fatigue Lifetime is based on damage tolerance approach. The acting stress ratio is variable due to variable amplitude loading and load caused by existence of press-fitted wheel in the vicinity of assumed crack. The contribution is focused on influence of variable stress ratio in EA4T steel on residual Fatigue Lifetime of railway axles. The influence of stress intensity factor on Fatigue crack propagation rate was experimentally evaluated for three different stress ratios, which correspond to operation conditions. Two different expressions of Fatigue crack propagation rate were used and mutually compared to show influence of the stress ratio on residual Fatigue Lifetime of structure made of EA4T steel. The first expression considers stress intensity factor range (respecting stress ratio R ) and the second one uses maximal value of the stress intensity factor. The paper shows ability of both expressions to describe experimental data obtained under different stress ratios and their influence on estimated residual Fatigue Lifetime values. The results obtained contribute to the better estimation of residual Fatigue Lifetime of railway axles and generally to the safer rail transportation.
Lubos Nahlik - One of the best experts on this subject based on the ideXlab platform.
-
Fatigue Lifetime estimation of railway axles
Engineering Failure Analysis, 2017Co-Authors: Pavel Pokorný, Lubos Nahlik, Rostislav Fajkos, Martin Sevcik, Petr Matusek, Pavel HutařAbstract:Abstract The railway axles are subjected to cyclic loading during their operation. Their load is of long-term nature, therefore a real risk of Fatigue failure exists. This failure could lead to derailment of the whole train with serious consequences. To prevent such scenario, the railway axles have to be safely removed from operation before their final failure occurs. This paper presents methodology for the residual Fatigue Lifetime prediction of the railway axle based on the linear elastic fracture mechanics concept. The methodology contains estimation of the critical position of initial crack, prediction of the Fatigue crack front shape development during crack propagation, separation of the bending and press-fitting contributions to the axle load, experimental measurement of the crack growth kinetics of EA4T steel and subsequent estimation of the residual Fatigue Lifetime of railway axle. Part of the presented study is also devoted to the probability aspects of determination of material characteristics describing Fatigue crack propagation and retardation effects caused by existence of plastic zone ahead of propagating Fatigue crack. Described methodology is already applied in the design process of new railway axles in Bonatrans company.
-
effect of residual stresses on the Fatigue Lifetime of railway axle
Procedia structural integrity, 2017Co-Authors: Pavel Hutař, Pavel Pokorný, Jan Poduska, Rostislav Fajkos, Lubos NahlikAbstract:Abstract The operation of railway axles should fulfill at least two main demands: safety and low operation costs. A significant part of operation costs is given by the length of regular inspection intervals which should reveal potential Fatigue cracks in railway axle. The detection of cracks is of a probabilistic nature, therefore their detection is not ensured in all cases. For the safe operation of trains, an existence of potential initial crack should be considered on the axle surface and residual Fatigue Lifetime should be conservatively determined for this case. Reliable procedure of residual Fatigue Lifetime estimation should take into account real axle geometry, material characteristics and loading of the railway axle. This paper shows methodology for determination of residual Fatigue Lifetime (RFL) based on the fracture mechanics approach, taking into account real spectrum of the loading cycles, existence of press-fitted wheels and surface residual stresses given by the thermo-mechanical surface treatment of the railway axle. It is demonstrated that the effect of the residual stresses is significant and should not be neglected in the numerical estimation of residual Fatigue Lifetime of the axle.
-
Influence of Initial Inclined Surface Crack on Estimated Residual Fatigue Lifetime of Railway Axle
Journal of Multiscale Modelling, 2016Co-Authors: Lubos Nahlik, Pavel Pokorný, Martin Sevcik, Pavel HutařAbstract:Railway axles are subjected to cyclic loading which can lead to Fatigue failure. For safe operation of railway axles a damage tolerance approach taking into account a possible defect on railway axle surface is often required. The contribution deals with an estimation of residual Fatigue Lifetime of railway axle with initial inclined surface crack. 3D numerical model of inclined semi-elliptical surface crack in railway axle was developed and its curved propagation through the axle was simulated by finite element method. Presence of press-fitted wheel in the vicinity of initial crack was taken into account. A typical loading spectrum of railway axle was considered and residual Fatigue Lifetime was estimated by NASGRO approach. Material properties of typical axle steel EA4T were considered in numerical calculations and Lifetime estimation.
-
residual Fatigue Lifetime estimation of railway axles for various loading spectra
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: Pavel Pokorný, Pavel Hutař, Lubos NahlikAbstract:Abstract The knowledge of the residual Fatigue Lifetime of railway axles is very important for the safe operation of trains. The railway axles could include some defects like cracks, scratches or inhomogeneities which could contribute to the Fatigue crack initiation and in the final stage to axle failure. The non-destructive testing methods are not reliable for detection of relatively short (circa 1–2 mm), but even dangerous cracks. For conservative estimation of residual Fatigue Lifetime the railway axle containing initial crack should be considered. The residual Fatigue Lifetime is given by the number of load cycles for Fatigue crack growth from the initial size of the crack up to the critical size with consequent Fatigue failure of railway axle. Railway axles are used in different types of trains which are used under different conditions (regional trains, urban trains, high speed trains, freight trains, etc.). This work is focused on numerical estimation of residual Fatigue Lifetime of railway axle while several different load spectra taken from the literature are considered in the performed estimations. This paper also shows the influence of the discretization level of the continuous load spectrum and effect of magnification or diminution of load spectrum on the calculated residual Fatigue Lifetime of the railway axle.
-
Influence of variable stress ratio during train operation on residual Fatigue Lifetime of railway axles
Procedia structural integrity, 2016Co-Authors: Pavel Pokorný, Lubos Nahlik, Pavel HutařAbstract:Abstract Railway axles are subjected to cyclic loading, which could lead to Fatigue failure. Therefore, it is desired to know residual Fatigue Lifetime of railway axles to ensure safe operation of trains. Because of detection of relatively small Fatigue cracks is not guaranteed an estimation of residual Fatigue Lifetime is based on damage tolerance approach. The acting stress ratio is variable due to variable amplitude loading and load caused by existence of press-fitted wheel in the vicinity of assumed crack. The contribution is focused on influence of variable stress ratio in EA4T steel on residual Fatigue Lifetime of railway axles. The influence of stress intensity factor on Fatigue crack propagation rate was experimentally evaluated for three different stress ratios, which correspond to operation conditions. Two different expressions of Fatigue crack propagation rate were used and mutually compared to show influence of the stress ratio on residual Fatigue Lifetime of structure made of EA4T steel. The first expression considers stress intensity factor range (respecting stress ratio R ) and the second one uses maximal value of the stress intensity factor. The paper shows ability of both expressions to describe experimental data obtained under different stress ratios and their influence on estimated residual Fatigue Lifetime values. The results obtained contribute to the better estimation of residual Fatigue Lifetime of railway axles and generally to the safer rail transportation.
Mohammad Azadi - One of the best experts on this subject based on the ideXlab platform.
-
Sensitivity analysis for effects of displacement amplitude and loading frequency on low-cycle Fatigue Lifetime in carbon/epoxy laminated composites
MATEC Web of Conferences, 2018Co-Authors: Mohammad Azadi, Mohsen Alizadeh, Hassan SayarAbstract:In the present article, the low-cycle Fatigue Lifetime of carbon/epoxy laminated composites has been investigated. The sensitivity analysis has been also performed to study effects of the displacement amplitude and the loading frequency on the low-cycle Fatigue Lifetimes in composites. For such objective, displacement-control low-cycle Fatigue testing has been done on the open-hole standard specimen. Fatigue tests included 4 different displacement amplitudes at 200 mm/min of the loading frequency and 4 different loading frequencies under 7 mm of the displacement amplitude. The sensitivity analysis was carried out by the MINITAB software, considering a linear function for fitting experimental data by the predicting model. Experimental results showed that by increasing the displacement amplitude, the low-cycle Fatigue Lifetime decreased, as expected. In addition, when the loading frequency enhanced, the low-cycle Fatigue Lifetime of composites decreased. Besides, the maximum stress had a reverse behavior, compared to the Fatigue Lifetime. The sensitivity analysis depicted that the displacement amplitude was sensitive on both the Fatigue Lifetime and the maximum stress. The loading frequency was sensitive on the maximum stress and was not sensitive on the Fatigue Lifetime.
-
Cyclic thermo-mechanical stress, strain and continuum damage behaviors in light alloys during Fatigue Lifetime considering heat treatment effect
International Journal of Fatigue, 2017Co-Authors: Mohammad AzadiAbstract:Abstract In this article, thermo-mechanical Fatigue behaviors in light alloys have been investigated to find the effect of heat treatments. For this objective, thermo-mechanical Fatigue tests were performed on the A356.0 aluminum alloy and the AZE911 magnesium alloy, with and without typical T6 heat treatments. Obtained results demonstrated no significant difference in thermo-mechanical Fatigue Lifetime of the A356.0 alloy between non-heat-treated and heat-treated test specimens at 250 °C of the maximum temperature, which was attributed to the over-ageing phenomenon. As a consequence, this low effect showed that the heat treatment could be eliminated for cylinder heads. However, the thermo-mechanical Fatigue Lifetime of the AZE911 alloy was significantly affected by the heat treatment. The explanation for the mentioned behavior could be found in the material micro-structure, which was affected by dissolving the brittle intermetallic phase in the matrix of the AZE911 alloy. However, the magnesium alloy still requires more improvements in the Fatigue Lifetime for a possible substitution in cylinder heads. Continuum damage behaviors showed that higher damage values occurred in the aluminum alloy, in comparison to the magnesium alloy, both for heat-treated and non-heat-treated specimens.
-
Fatigue Lifetime of az91 magnesium alloy subjected to cyclic thermal and mechanical loadings
Materials & Design, 2014Co-Authors: Mohammad Azadi, G H Farrahi, Gerhard Winter, W EichlsederAbstract:Abstract In the present paper, thermo-mechanical Fatigue (TMF) and low cycle Fatigue (LCF) or isothermal Fatigue (IF) Lifetimes of a cast magnesium alloy (the AZ91 alloy) were studied. In addition to a heat treatment process (T6), several rare elements were added to the alloy to improve the material strength in the first step. Then, the cyclic behavior of the AZ91 was investigated. For this objective, strain-controlled tension–compression Fatigue tests were carried out. The temperature varied between 50 and 200 °C in the out-of-phase (OP) TMF tests. The constraint factor which was defined as the ratio of the mechanical strain to the thermal strain, was set to 75%, 100% and 125%. For LCF tests, mechanical strain amplitudes of 0.20%, 0.25% and 0.30% were considered at constant temperatures of 25 and 200 °C. Experimental Fatigue results showed that the cyclic hardening behavior occurred at the room temperature in the AZ91 alloy. At higher temperatures, this alloy had a brittle fracture. But also, it was not significantly clear that the cyclic hardening or the cyclic softening behavior would be occurred in the material. Then, the high temperature LCF Lifetime was more than that at the room temperature. The OP-TMF Lifetime was the least value in comparison to that of LCF tests. At the end of this article, two energy-based models were applied to predict the Fatigue Lifetime of this magnesium alloy.
-
a new energy based isothermal and thermo mechanical Fatigue Lifetime prediction model for aluminium silicon magnesium alloy
Fatigue & Fracture of Engineering Materials & Structures, 2013Co-Authors: G H Farrahi, Mohammad Azadi, Gerhard Winter, W EichlsederAbstract:In this paper, a new Fatigue Lifetime prediction model is presented for the aluminium–silicon–magnesium alloy, A356.0. This model is based on the plastic strain energy density per cycle including two correction factors in order to consider the effect of the mean stress and the maximum temperature. The thermal term considers creep and oxidation damages in A356.0 alloy. To calibrate the model, isothermal Fatigue and out-of-phase thermo-mechanical Fatigue (TMF) tests were conducted on the A356.0 alloy. Results showed an improvement in predicting Fatigue Lifetimes by the present model in comparison with classical theories and also the plastic strain energy density (without any correction factors). Therefore, this model is applicable for TMF, low cycle Fatigue (LCF) and both TMF/LCF Lifetimes of the A356.0 alloy. Furthermore, this model can be easily used for the estimation of thermo-mechanical conditions in components such as cylinder heads.
-
A new energy-based isothermal and thermo-mechanical Fatigue Lifetime prediction model for aluminium–silicon–magnesium alloy
Fatigue & Fracture of Engineering Materials & Structures, 2013Co-Authors: G H Farrahi, Mohammad Azadi, Gerhard Winter, W EichlsederAbstract:In this paper, a new Fatigue Lifetime prediction model is presented for the aluminium–silicon–magnesium alloy, A356.0. This model is based on the plastic strain energy density per cycle including two correction factors in order to consider the effect of the mean stress and the maximum temperature. The thermal term considers creep and oxidation damages in A356.0 alloy. To calibrate the model, isothermal Fatigue and out-of-phase thermo-mechanical Fatigue (TMF) tests were conducted on the A356.0 alloy. Results showed an improvement in predicting Fatigue Lifetimes by the present model in comparison with classical theories and also the plastic strain energy density (without any correction factors). Therefore, this model is applicable for TMF, low cycle Fatigue (LCF) and both TMF/LCF Lifetimes of the A356.0 alloy. Furthermore, this model can be easily used for the estimation of thermo-mechanical conditions in components such as cylinder heads.
