Research Paper

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(Abstract)
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==<b>Abstract</b>==
 
==<b>Abstract</b>==
  
The finite element method is used to study the e€ffects of particle cluster morphology on the fracture and debonding of silicon particles embedded in an Al-1%Si matrix subjected to tensile-compressive cyclic loading conditions. Representative of an actual cast Al-Si alloy, clusters of silicon inclusions (4-8 particles) are considered. The silicon particles are modeled with a linear-elastic constitutive relationship and the matrix material is modeled using an internal state variable cyclic plasticity model fitted to experimental data on matrix material. A total of seven parameters are varied to create 16 idealized microstructures: relative particle size, shape, spacing, configuration, alignment, grouping and matrix microporosity. A two-level design of experiment (DOE) methodology is used to screen the relative importance of the seven parameters on the fracture and debonding of the silicon particles. The results of the study demonstrate that particle shape and alignment are undoubtedly the most dominant parameters influencing initial particle fracture and debonding. Particle debonding results in a local intensification of stresses in the Al-1%Si matrix that is significantly larger than that due to particle fracture. The local stress fields after particle fracture are primarily concentrated within the broken particle halves. After the fracture of several particles within a cluster, the spacing between adjacent particles enters as a second-order effect. When several particles within a cluster debond, the spacing between adjacent particles enters as a dominant effect due to the large local stress intensification in the surrounding Al-1%Si matrix.
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The objective of this research is to study the influence of morphology on fracture and debonding of silicon particles embedded in an Al-1%Si matrix. The fracture and deboning is caused by applied tensile and compressive cyclic loading conditions. Finite element method is used to study these effects to accurately represent particle geometry, particle interactions, and the stress-strain behavior of the aluminum matrix. A cluster of 4 to 8 silicon particle inclusion is chosen for the study over infinite array of inclusion or single isolated inclusion. Silicon particles are modeled with linear elastic constitutive relationship and matrix material using internal state variable cyclic plasticity model. A two level design of experiments method is used to test 16 sets of combination made with 7 variables; relative particle size, shape, spacing, configuration, alignment, grouping and matrix microporosity. Results of the study proves the dominance of shape and alignment during initial fracturing and debonding and spacing during later. Local intensification of stresses in induced by particle debonding in Al-1%Si matrix. This intensification of stresses is higher than that of particle fracture. Enhancement is spacing due to consecutive fracturing in the cluster turns out to be another dominant factor due to large local intensification of stresses.  
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==Methodology==
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Two level design of experiments method is used to study the effects of seven parameters at their chosen range of conditions is shown in Fig.1. A total of 16 significant combinations of the 7 morphological parameters at their extreme allowed conditions are chosen for the study, shown in the following design matrix in Table 1. The extremes for these parameters are based on micro-graphical observations from an A365 aluminum alloy study which constitutes silicon particles.Finite element cases were created for all 16 combinations with following assumptions; 1) Traces of other element are not considered in the model though that are generally present in the alloy to promote hardening and other casting properties. 2) The silicon particles are assumed to behave in an isotropic linear elastic. The Al matrix material is described using an internal state variable plasticity model with coupled micro void growth. 3) Temperature and strain rate dependence on the plasticity of the model were not considered. Experimental data regression is thoroughly used to generate constants for the model. In Fig 2, stress-strain model output is compared to experimental output for cycles 1, 2, and 10. A point of saturation is attained at the end of 10 cycles in both cases. Maximum tensile principal stress is an important study parameter which is the proposed cause of fracture in Si particles. Debonding is studied on the basis of hydrostatic stresses on particle matrix interface. The screening of the two significant parameters is listed under table 2
  
 
==<b>Introducation</b>==
 
==<b>Introducation</b>==

Revision as of 12:22, 5 May 2015

Abstract

The objective of this research is to study the influence of morphology on fracture and debonding of silicon particles embedded in an Al-1%Si matrix. The fracture and deboning is caused by applied tensile and compressive cyclic loading conditions. Finite element method is used to study these effects to accurately represent particle geometry, particle interactions, and the stress-strain behavior of the aluminum matrix. A cluster of 4 to 8 silicon particle inclusion is chosen for the study over infinite array of inclusion or single isolated inclusion. Silicon particles are modeled with linear elastic constitutive relationship and matrix material using internal state variable cyclic plasticity model. A two level design of experiments method is used to test 16 sets of combination made with 7 variables; relative particle size, shape, spacing, configuration, alignment, grouping and matrix microporosity. Results of the study proves the dominance of shape and alignment during initial fracturing and debonding and spacing during later. Local intensification of stresses in induced by particle debonding in Al-1%Si matrix. This intensification of stresses is higher than that of particle fracture. Enhancement is spacing due to consecutive fracturing in the cluster turns out to be another dominant factor due to large local intensification of stresses.

Methodology

Two level design of experiments method is used to study the effects of seven parameters at their chosen range of conditions is shown in Fig.1. A total of 16 significant combinations of the 7 morphological parameters at their extreme allowed conditions are chosen for the study, shown in the following design matrix in Table 1. The extremes for these parameters are based on micro-graphical observations from an A365 aluminum alloy study which constitutes silicon particles.Finite element cases were created for all 16 combinations with following assumptions; 1) Traces of other element are not considered in the model though that are generally present in the alloy to promote hardening and other casting properties. 2) The silicon particles are assumed to behave in an isotropic linear elastic. The Al matrix material is described using an internal state variable plasticity model with coupled micro void growth. 3) Temperature and strain rate dependence on the plasticity of the model were not considered. Experimental data regression is thoroughly used to generate constants for the model. In Fig 2, stress-strain model output is compared to experimental output for cycles 1, 2, and 10. A point of saturation is attained at the end of 10 cycles in both cases. Maximum tensile principal stress is an important study parameter which is the proposed cause of fracture in Si particles. Debonding is studied on the basis of hydrostatic stresses on particle matrix interface. The screening of the two significant parameters is listed under table 2

Introducation

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