μ\mu2mech: a Software Package Combining Microstructure Modeling and Mechanical Property Prediction

We have developed a graphical user interface (GUI) based package $\mu$2mech to perform phase-field simulation for predicting microstructure evolution. The package can take inputs from ab initio calculations and CALPHAD (Calculation of Phase Diagrams) tools for quantitative microstructure prediction. The package also provides a seamless connection to transfer output from the mesoscale phase field method to the microscale finite element analysis for mechanical property prediction. Such a multiscale simulation package can facilitate microstructure-property correlation, one of the cornerstones in accelerated materials development within the integrated computational materials engineering (ICME) framework

Comparative FEA Analysis of Composite Materials Virtual Microstructures

A 3D virtual composite material microstructure finite element model was developed to simulate the effects of mesh size and material input on the mechanical behavior of isotropic composite materials. Finite element theory and statistically generated Representative Volume Elements (RVEs) were used as the main strategy for the constitutive modeling...Se desarrolló un modelo de elementos finitos de microestructura de material compuesto virtual en 3D para simular los efectos del tamaño de malla y la entrada de material en el comportamiento mecánico de los materiales compuestos isotrópicos..

Finite Element Modeling of the Effect of Reflow Porosity on the Mechanical Behavior of Pb-free Solder Joints

abstract: Pb-free solders are used as interconnects in various levels of micro-electronic packaging. Reliability of these interconnects is very critical for the performance of the package. One of the main factors affecting the reliability of solder joints is the presence of porosity which is introduced during processing of the joints. In this thesis, the effect of such porosity on the deformation behavior and eventual failure of the joints is studied using Finite Element (FE) modeling technique. A 3D model obtained by reconstruction of x-ray tomographic image data is used as input for FE analysis to simulate shear deformation and eventual failure of the joint using ductile damage model. The modeling was done in ABAQUS (v 6.10). The FE model predictions are validated with experimental results by comparing the deformation of the pores and the crack path as predicted by the model with the experimentally observed deformation and failure pattern. To understand the influence of size, shape, and distribution of pores on the mechanical behavior of the joint four different solder joints with varying degrees of porosity are modeled using the validated FE model. The validation technique mentioned above enables comparison of the simulated and actual deformation only. A more robust way of validating the FE model would be to compare the strain distribution in the joint as predicted by the model and as observed experimentally. In this study, to enable visualization of the experimental strain for the 3D microstructure obtained from tomography, a three dimensional digital image correlation (3D DIC) code has been implemented in MATLAB (MathWorks Inc). This developed 3D DIC code can be used as another tool to verify the numerical model predictions. The capability of the developed code in measuring local displacement and strain is demonstrated by considering a test case.Dissertation/ThesisM.S. Mechanical Engineering 201

The effect of initial texture on multiple necking formation in polycrystalline thin rings subjected to dynamic expansion

In this paper, we have investigated, using finite element calculations, the effect of initial texture on the formation of multiple necking patterns in ductile metallic rings subjected to rapid radial expansion. The mechanical behavior of the material has been modeled with the elasto-viscoplastic single crystal constitutive model developed by Marin (2006). The polycrystalline microstructure of the ring has been generated using random Voronoi seeds. Both 5000 grain and 15000 grain aggregates have been investigated, and for each polycrystalline aggregate three different spatial distributions of grains have been considered. The calculations have been performed within a wide range of strain rates varying from to , and the rings have been modeled with four different initial textures: isotropic texture, Goss texture, R Goss texture and Z fiber texture. The finite element results show that: (i) the spatial distribution of grains affects the location of the necks, (ii) the decrease of the grain size delays the formation of the necking pattern and increases the number of necks, (iii) the initial texture affects the number of necks, the location of the necks, and the necking time, (iv) the development of the necks is accompanied by a local increase of the slip activity. This work provides new insights into the effect of crystallographic microstructure on dynamic plastic localization and guidelines to tailor the initial texture in order to delay dynamic necking formation and, thus, to improve the energy absorption capacity of ductile metallic materials at high strain rates.This work has received funding from the European Union's Horizon 2020 Programme (Excellent Science, Marie-Skłodowska-Curie Actions) under REA grant agreement 777896 (Project QUANTIFY). The support of National Science Centre, Poland , through the project 2021/41/B/ST8/03345 is acknowledged.Publicad

Simulation analysis of graphene addition on polymeric composite

Natural fibres in composite materials, such as kenaf fibres, are used to reinforce polypropylene (PP) due to their light weight and high mechanical performance required in various applications, such as automotive. Although natural fibres seem to be the most promising material, manufacturing parameters and material composition are crucial to determining balanced output performance. Therefore, this study provides essential knowledge on defining the parameters and the effect of addition of graphene content to kenaf fibres composites using computer simulation via Abaqus CAE software. Detailed analyses were compared with the experimental data of Young’s modulus and tensile strength. General static and dynamic explicit analyses were conducted using Abaqus CAE simulations, and set at 40 wt. % kenaf fibres, 0, 1, 3, and 5 wt. % graphene. Short kenaf fibres were utilised together with graphene nanoplatelets and prepared using a hot-pressing technique with the temperature set at 190 °C and pressure of 5 MPa for 5 min. The findings indicated that the simulation and experimental data from previous studies data congruent which is Young’s modulus and tensile strength increased with addition of graphene content. Thus, the simulated data could predict the experimental mechanical performance, in which 24 MPa of tensile strength was recorded for 3 wt. % of graphene additions

Methods in Modelling of Composite Materials with Microstructure

Composite material properties are dependent on their microstructure. To adequately model these materials, a revised formulation of elasticity that accounts for microstructural effects must be considered. Size dependent behaviour is an inherent property of such materials, resulting in a need for non-classical continuum theories for adequate characterization. The modelling of bi-material composites is investigated, with emphasis on how material microstructure impacts the overall behaviour of continua. The work aims to provide mathematical models capable of predicting the homogenized material response under specified loads given known constituent properties, for eventual use in creating design provisions, integration into numerical simulations, and further applications in materials research. Specifically, this thesis considers Cosserat (micropolar) elasticity to model microstructural effects. Fiber reinforced composites with unidirectional fibers are modelled as transversely isotropic materials under the framework of Cosserat elasticity. The model assumes a periodic microstructure and develops a boundary condition to account for the periodicity. The governing equations for plane strain are developed, with the conditions for existence and uniqueness of the solution established. A three-dimensional model for an exponentially graded composite with microstructural effects is developed under the framework of Cosserat elasticity. The mixed boundary value problem is formulated and existence and uniqueness of a weak solution is established for use in accordance with the finite element method. The finite element formulation is developed and integrated into the commercial software Abaqus through a user developed element, with an associated post processing code for output visualization. Given a lack of elastic constants from experiments, validation is partially obtained through recovery of the classical limit. Following this, a conceptual extension to demonstrate a proof of concept is applied, with conclusions drawn based on the results. Recommendations for future extensions of the model are provided

Geometric prior of multi-resolution yielding manifolds and the local closest point projection for nearly non-smooth plasticity

Elastoplasticity models often introduce a scalar-valued yield function to implicitly represent the boundary between elastic and plastic material states. This paper introduces a new alternative where the yield envelope is represented by a manifold of which the topology and the geometry are learned from a set of data points in a parametric space (e.g. principal stress space, -plane). Here, deep geometric learning enables us to reconstruct a highly complex yield envelope by breaking it down into multiple coordinate charts. The global atlas that consists of these coordinate charts in return allows us to represent the yield surface via multiple overlapping patches, each with a specific local parametrization. This setup provides several advantages over the classical implicit function representation approach. For instance, the availability of coordinate charts enables us to introduce an alternative stress integration algorithm where the trial stress may project directly on a local patch and hence circumvent the issues related to non-smoothness and the lack of convexity of yield surfaces. Meanwhile, the local parametric approach also enables us to predict hardening/softening locally in the parametric space, even without complete knowledge of the yield surface. Comparisons between the classical yield function approach on the non-smooth plasticity and anisotropic cam-clay plasticity model are provided to demonstrate the capacity of the models for highly precise yield surface and the feasibility of the implementation of the learned model in the local stress integration algorithm

Integrated computational materials engineering workflows for microstructure-sensitive fatigue of advanced alloys

The high cost and data scatter of physical fatigue experiments, particularly in the High Cycle Fatigue (HCF) regime, requires a paradigm shift to efficiently assess the fatigue criticality of metallic components. Integrated Computational Materials Engineering (ICME) presents an attractive additional pathway that employs microstructure-sensitive simulations given accessible process paths and resulting microstructures to assist and augment decision-support from experiments. In this research, multilevel scripted workflows are implemented into the open-source Python programming language to study the effects of intrinsic (e.g., crystallographic orientation distribution, grain shape, and grain size distribution) microstructure attributes, boundary conditions (e.g., fully periodic vs. traction free), strain states (e.g., uniaxial, shear, biaxial), and model sample sizes. Digital microstructure instantiations of Duplex Ti-6Al-4V and Al 7075-T6 are generated for simulation with Crystal Plasticity Finite Element Method constitutive models using the open-source Dream.3D software, with extreme value fatigue response as the primary performance requirement. Fatigue Indicator Parameters (FIPs) are used as surrogate measures of the driving force for fatigue crack formation and are volume averaged over regions within grains representative of fatigue damage process zones. These FIPs are fit to known extreme value distributions so that the effects of different microstructure attributes and boundary/strain states may be assessed. Other extreme FIP characteristics (e.g., proximity to free surface, elastic strain normal to slip plane) are examined. A major contribution of this thesis to the research community is the open-source PRISMS-Fatigue framework pursued in collaboration with researchers at the University of Michigan, which is a highly efficient, scalable, flexible, and easy-to-use community ICME platform.Ph.D