The Experts below are selected from a list of 25680 Experts worldwide ranked by ideXlab platform
R Mahmudi - One of the best experts on this subject based on the ideXlab platform.
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the microstructure and impression Creep Behavior of cast mg 5sn xca alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: G Nayyeri, R MahmudiAbstract:Abstract The effects of 0.7, 1.4 and 2 wt.% Ca additions on the microstructure and Creep Behavior of a cast Mg–5Sn alloy were investigated by impression tests. Impression Creep tests were carried out in the temperature range 423–523 K and under punching stresses in the range 150–475 MPa for dwell times up to 3600 s. Analysis of the data showed that for all loads and temperatures, the Mg–5Sn–2Ca alloy had the lowest Creep rates, and thus the highest Creep resistance among all materials tested. This is attributed to the diminishing of the less stable Mg 2 Sn particles and formation of the more thermally stable CaMgSn phase which strengthens both matrix and grain boundaries during Creep deformation in the investigated system. The Creep Behavior can be divided into two stress regimes, with a change from the low-stress regime to the high-stress regime occurring, depending on the test temperature, around 0.012 σ imp / G )
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effects of sb additions on the microstructure and impression Creep Behavior of a cast mg 5sn alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: G Nayyeri, R MahmudiAbstract:Abstract The effects of 0.15, 0.4 and 0.7 wt.% Sb additions on the microstructure and impression Creep Behavior of the as-cast Mg–5 wt.% Sn alloy were investigated. The dendritic structure of the base alloy was refined after Sb additions, the effect being more pronounced in Mg–5%Sn–0.4%Sb. This alloy had the highest Creep resistance among all materials tested, mainly due to the simultaneous formation of the thermally stable Mg 3 Sb 2 and Mg 2 Sn second phase particles which strengthen both matrix and grain boundaries during Creep deformation in the investigated system. Impression Creep tests were performed in the temperature range 423–523 K and under punching stresses in the range 150–475 MPa for dwell times up to 3600 s. The Creep Behavior can be divided into two stress regimes, with a change from the low-stress regime to the high-stress regime occurring, depending on the test temperature, around 0.012 σ / G )
Yao Zhang - One of the best experts on this subject based on the ideXlab platform.
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heterogeneity effect of mechanical property on Creep Behavior of asphalt mixture based on micromechanical modeling and virtual Creep test
Mechanics of Materials, 2017Co-Authors: Hao Wang, Deyu Zhang, Yao ZhangAbstract:Abstract Based on laboratory tests and discrete element method (DEM), this study investigated the influences by mechanical property heterogeneity of different ingredients of asphalt mixture on the Creep Behavior of asphalt mixture. By considering the important material features and mechanical properties of different ingredients, such as the three-dimensional irregular shapes and elastic properties of coarse aggregates, the continuous characteristics and viscoelastic properties of asphalt mastic, and the random distribution and zero mechanical property of air voids within asphalt mastic, micromechanical modeling of asphalt mixture and virtual uniaxial static Creep test was built by using PFC3D. Weibull distribution was used to describe the heterogeneity of mechanical property for coarse aggregates and asphalt mastic within asphalt mixture. And the influences of the mechanical property heterogeneity of aggregates and asphalt mastic on the Creep Behavior of asphalt mixture were evaluated based on virtual Creep test. The results show that the built discrete element model and virtual test can well predict the Creep Behavior of asphalt mixture. Both the heterogeneity of mechanical property of aggregates and mastic have negative influences on the Creep Behavior of asphalt mixture by affecting the distribution of micromechanical forces within asphalt mixture. And heterogeneity of mechanical property of coarse aggregates causes more obvious influences. It is important to guarantee the homogeneity of mechanical property of coarse aggregates and asphalt mastic within asphalt mixture to resist Creep deformation.
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effect of air voids on the high temperature Creep Behavior of asphalt mixture based on three dimensional discrete element modeling
Materials & Design, 2016Co-Authors: Deyu Zhang, Yao Zhang, Yongli Zhao, Xiaoming HuangAbstract:Abstract This study focused on the effects of different parameters related to air voids on the Creep Behavior of asphalt mixture based on micromechanical modeling and virtual test through three-dimensional discrete element method (DEM). By using DEM software named as Particle Flow Code in three dimensions (PFC3D), user-defined micromechanical modeling was conducted for asphalt mixture. And virtual uniaxial static Creep test of asphalt mixture was conducted by PFC3D and verified by laboratory Creep test. The effects of air void content, microstructure parameters including size, elongated index and orientation of air voids, and air void distribution on the Creep Behavior of asphalt mixture were investigated based on virtual Creep test. It is proved that bigger content, size and elongated index of air voids lead to greater Creep strain of asphalt mixture. Compared to vertical orientation, horizontal orientation of air voids is more harmful to the Creep Behavior of asphalt mixture. Nonuniform distribution of air voids within asphalt mixture also has negative effects on the Creep deformation of asphalt mixture, especially for vertical nonuniform distribution of air voids. Therefore, guaranteeing and improving the content, distribution and microstructure of air voids within asphalt mixture are important to keep the high-temperature stability of asphalt mixture.
G Nayyeri - One of the best experts on this subject based on the ideXlab platform.
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the microstructure and impression Creep Behavior of cast mg 5sn xca alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: G Nayyeri, R MahmudiAbstract:Abstract The effects of 0.7, 1.4 and 2 wt.% Ca additions on the microstructure and Creep Behavior of a cast Mg–5Sn alloy were investigated by impression tests. Impression Creep tests were carried out in the temperature range 423–523 K and under punching stresses in the range 150–475 MPa for dwell times up to 3600 s. Analysis of the data showed that for all loads and temperatures, the Mg–5Sn–2Ca alloy had the lowest Creep rates, and thus the highest Creep resistance among all materials tested. This is attributed to the diminishing of the less stable Mg 2 Sn particles and formation of the more thermally stable CaMgSn phase which strengthens both matrix and grain boundaries during Creep deformation in the investigated system. The Creep Behavior can be divided into two stress regimes, with a change from the low-stress regime to the high-stress regime occurring, depending on the test temperature, around 0.012 σ imp / G )
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effects of sb additions on the microstructure and impression Creep Behavior of a cast mg 5sn alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: G Nayyeri, R MahmudiAbstract:Abstract The effects of 0.15, 0.4 and 0.7 wt.% Sb additions on the microstructure and impression Creep Behavior of the as-cast Mg–5 wt.% Sn alloy were investigated. The dendritic structure of the base alloy was refined after Sb additions, the effect being more pronounced in Mg–5%Sn–0.4%Sb. This alloy had the highest Creep resistance among all materials tested, mainly due to the simultaneous formation of the thermally stable Mg 3 Sb 2 and Mg 2 Sn second phase particles which strengthen both matrix and grain boundaries during Creep deformation in the investigated system. Impression Creep tests were performed in the temperature range 423–523 K and under punching stresses in the range 150–475 MPa for dwell times up to 3600 s. The Creep Behavior can be divided into two stress regimes, with a change from the low-stress regime to the high-stress regime occurring, depending on the test temperature, around 0.012 σ / G )
Deyu Zhang - One of the best experts on this subject based on the ideXlab platform.
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heterogeneity effect of mechanical property on Creep Behavior of asphalt mixture based on micromechanical modeling and virtual Creep test
Mechanics of Materials, 2017Co-Authors: Hao Wang, Deyu Zhang, Yao ZhangAbstract:Abstract Based on laboratory tests and discrete element method (DEM), this study investigated the influences by mechanical property heterogeneity of different ingredients of asphalt mixture on the Creep Behavior of asphalt mixture. By considering the important material features and mechanical properties of different ingredients, such as the three-dimensional irregular shapes and elastic properties of coarse aggregates, the continuous characteristics and viscoelastic properties of asphalt mastic, and the random distribution and zero mechanical property of air voids within asphalt mastic, micromechanical modeling of asphalt mixture and virtual uniaxial static Creep test was built by using PFC3D. Weibull distribution was used to describe the heterogeneity of mechanical property for coarse aggregates and asphalt mastic within asphalt mixture. And the influences of the mechanical property heterogeneity of aggregates and asphalt mastic on the Creep Behavior of asphalt mixture were evaluated based on virtual Creep test. The results show that the built discrete element model and virtual test can well predict the Creep Behavior of asphalt mixture. Both the heterogeneity of mechanical property of aggregates and mastic have negative influences on the Creep Behavior of asphalt mixture by affecting the distribution of micromechanical forces within asphalt mixture. And heterogeneity of mechanical property of coarse aggregates causes more obvious influences. It is important to guarantee the homogeneity of mechanical property of coarse aggregates and asphalt mastic within asphalt mixture to resist Creep deformation.
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effect of air voids on the high temperature Creep Behavior of asphalt mixture based on three dimensional discrete element modeling
Materials & Design, 2016Co-Authors: Deyu Zhang, Yao Zhang, Yongli Zhao, Xiaoming HuangAbstract:Abstract This study focused on the effects of different parameters related to air voids on the Creep Behavior of asphalt mixture based on micromechanical modeling and virtual test through three-dimensional discrete element method (DEM). By using DEM software named as Particle Flow Code in three dimensions (PFC3D), user-defined micromechanical modeling was conducted for asphalt mixture. And virtual uniaxial static Creep test of asphalt mixture was conducted by PFC3D and verified by laboratory Creep test. The effects of air void content, microstructure parameters including size, elongated index and orientation of air voids, and air void distribution on the Creep Behavior of asphalt mixture were investigated based on virtual Creep test. It is proved that bigger content, size and elongated index of air voids lead to greater Creep strain of asphalt mixture. Compared to vertical orientation, horizontal orientation of air voids is more harmful to the Creep Behavior of asphalt mixture. Nonuniform distribution of air voids within asphalt mixture also has negative effects on the Creep deformation of asphalt mixture, especially for vertical nonuniform distribution of air voids. Therefore, guaranteeing and improving the content, distribution and microstructure of air voids within asphalt mixture are important to keep the high-temperature stability of asphalt mixture.
Abhijit Dasgupta - One of the best experts on this subject based on the ideXlab platform.
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anisotropic steady state Creep Behavior of single crystal β sn a continuum constitutive model based on crystal viscoplasticity
International Journal of Plasticity, 2021Co-Authors: Q Jiang, Abhijit DasguptaAbstract:Abstract Body-center tetragonal (BCT) β-Sn crystals exhibit highly anisotropic properties such as stiffness and thermal expansion, which significantly affect their thermal-mechanical Behavior. The homologous temperature of β-Sn is relatively high under common applications due to its low melting point, which renders Sn and Sn-based alloys viscoplastic even at room temperature. The orientation-dependent Creep Behavior of β-Sn specimens have been previously measured by different research groups. A dislocation mechanics based crystal viscoplasticity model is applied in this study to describe this anisotropic steady-state Creep Behavior of β-Sn single crystals. The model constants are calibrated with single-crystal Creep test results available in the literature. The resulting Creep Behavior of β-Sn single-crystal is also represented with a homogenized continuum-scale finite element approach based on the use of a combined Hill-Norton approach where the Creep anisotropy is represented with Hill's anisotropic potential and the Creep flow rule is represented with Norton's power-law model. Estimation of the six Hill's constants for β-Sn requires multiple Creep tests under specific stress states, for single crystals along crystal principal directions. In this study, these physical Creep tests are replaced with ‘virtual tests’ conducted with the developed dislocation-based crystal-viscoplasticity model. To assess the ability of the Hill-Norton finite element approach to represent dislocation Creep, the finite element simulation results are compared with results of: (i) physical tests on single crystal specimens reported in the literature; and (ii) crystal-viscoplasticity modeling along many crystal orientations (beyond the fundamental calibration cases conducted along crystal principal directions). In future studies, this approach will be used for anisotropic finite element modeling of Creep in polycrystalline specimens.
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Effect of primary Creep Behavior on fatigue damage accumulation rates in accelerated thermal cycling of Sn3.0Ag0.5Cu Pb-free interconnects
EuroSimE 2008 - International Conference on Thermal Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Micro-Systems, 2008Co-Authors: Gayatri Cuddalorepatta, Abhijit DasguptaAbstract:Most studies on modeling cyclic thermo- mechanical fatigue of solder interconnects consider only the steady-state Creep Behavior of solder materials. This study explores the effect of including the primary Creep Behavior; since it may represent a significant portion of the total viscoplastic deformations in Pb-free Sn3.0Ag0.5Cu (SAC305) solder (G. Cuddalorepatta et al., 2007). The solder constitutive Behavior is modeled using partitioned elastic, plastic, and Creep models. The Creep properties are obtained from traditional constant-stress tests on a modified Iosipescu shear specimen, at different temperatures and stress levels (G. Cuddalorepatta et al., 2007). Significant scatter is observed across different specimens since the large grains in SAC305 microstructure make the specimen statistically inhomogeneous. Suitable averaging schemes are developed to deal with this scatter. In this study, constant-deformation tests are first conducted to measure the stress relaxation Behavior at different temperatures and deformation levels (G. Cuddalorepatta et al., 2007). Finite element models of the constant-deformation tests reveal that the average Behavior can be predicted with the measured average Creep properties. This prediction is improved if the primary Creep is included in the constitutive model. This exercise verifies that Creep Behavior measured under constant stress can indeed be used to predict deformations for varying stress loads. Using these verified constitutive models, the cyclic thermo-mechanical response of solder is investigated under accelerated thermal cycling conditions. The goal is to identify the difference in the fatigue damage metrics with and without primary Creep. A 3D viscoplastic finite element model of a selected BGA256 assembly is developed for this study. The model is subjected to an accelerated temperature cycle between -40degC and 125degC and the cyclic fatigue damage is assessed. These results are compared with previous studies where secondary Creep alone was used to model the viscoplastic constitutive Behavior solder. Comparisons show that the results are strongly sensitive to the inclusion or exclusion of primary Creep Behavior. These results suggest that it is very important to include primary Creep when studying thermo-mechanical fatigue damage in Pb-free SAC solders. The results of the Creep and stress relaxation tests and simulations suggest that the primary Creep model can be improved to better capture the viscoplastic response.