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2021


December 30, ur paper entitled "Sacrificial Cyclic Poly(phthalaldehyde) Templates for Low-Temperature Vascularization of Polymer Matrices" is published on ACS Applied Polymer Materials! Congradulations!


November 10, we are awarded our first NSF proposal. The proposal title is "An Integrated Multiscale Reduced-Order Modeling and Experimental Framework for Lithium-ion Batteries under Mechanical Abuse Conditions". This project is in collaboration with Dr. Chen's group from University of Lousville! Congradulations!


September 11, our paper entitled "Large-deformation reduced order homogenization of polycrystalline materials" is published on Computer Methods in Applied Mechanics and Engineering! Congradulations!


August 30, our paper entitled "Multiscale reduced-order modeling of a titanium skin panel subjected to thermo-mechanical loading" is published on AIAA Journal! Congradulations!


August 16, our paper entitled "Nonlinear guided wave tomography for detection and evaluation of early-life material degradation in plates" is published on Sensors! Congradulations!


July 27, Xiang Zhang presented at the virtually in the 16th USNCCM conference. The title of his presentation is: Nonlinear Microstructure Material Design with Reduced-Order Modeling".  A copy of the abstract is attached below.

Abstract

Recent progress in multiscale modeling and sensitivity analysis, together with advancement in additive manufacturing, allow us to develop an integrated workflow to design and manufacture the microstructure geometrical features and constituent properties to deliver a desired stress-strain response. During this process, the prohibitive computational cost associated with multiple optimization iteration and costly evaluation of a single microstructure problem still limits the application of this workflow, especially for the cases that involve complex microstructure and different deformation modes. Here we present a multiscale reduced-order optimization method for efficient nonlinear microstructure material design. This method builds on the recent development on Interface-enriched Generalized Finite Element Method (IGFEM) based reduced-order model, to formulate a reduced order representation of the microstructure problem. Model order reduction is achieved by partitioning the microstructure volume and interface into a number of subdomains called parts, where a series of influence function problems based on the elastic properties of the microstrucrue are solved a priori to obtain the interaction coefficients between different parts and between each part ant the microstructure. Based on these interaction coefficients, and the assumption that the response in each part is uniform, a system of linear algebra equations is derived to replace the microstructure problem with part-wise response as unknows. In addition, the material sensitivities are further derived withing the reduced order system of equation. The reduced-order microstructure problem evaluation, and reduce-order sensitivity analysis allow us to very efficiently optimize the microstructure material properties with multiple initial states, from which we choose the best optimization results and further conduct a full IGFEM-based optimization to obtain the final optimization result. This two-step optimization process is demonstrated to deliver satisfactory results on 3D particulate composites with the presence of both volumetric and interfacial damage compare with pure IGFEM-based optimization.


May 26, Xiang Zhang presented at the virtually in the EMI 2021/PMC 2021 conference. The title of his presentation is: Multiscale Reduced-Order Modeling of a Titanium Skin Panel Subjected to Thermo-Mechanical Loading".  A copy of the abstract is attached below.

Abstract

We propose a reduced order multiscale computational approach to predict the response of a polycrystalline structure subjected to thermo-mechanical loading, in which the material microstructure (i.e., at the scale of the representative volume) and all relevant microstructural response mechanisms are directly embedded and fully coupled with a structural analysis. The proposed approach is based on the eigenstrain-based reduced order model previously developed the authors. EHM operates in a computational homogenization settings, which takes the concept of transformation field theory that pre-computes certain microscale information (e.g. localization tensors, concentration tensors) by evaluating linear elastic microscale problems and considers piece-wise constant inelastic response within partitions (e.g., grains) of the microstructure. By this approach, a significant reduction in computational cost is achieved, compared with classical computational homogenization approaches that employ crystal plasticity finite element (CPFE) simulation to describe the microscale response. While previous development considers only mechanical loading, the proposed approach further accounts for the thermal strain at the microscale, as well as temperature dependent material properties and evolution laws. To account for the thermal effects, a set of temperature influence functions, similar to the elastic and inelastic function problems are formulated, and the part-wise thermal strain is accounted for in the reduced order system. The proposed approach was calibrated and validated by a series of uniaxial tensile tests of Ti-6242S at a wide range of temperatures and strain rates. The validated model is then adopted to study the response of a generic aircraft skin panel subjected to thermo-mechanical loading associated with supersonic flight, which demonstrates the capability of the developed model for structural scale simulation that involves thermo-mechanical loading, and provides insights on understanding the plastic deformation as well as fatigue initiation of the panel structure.


May 14, our paper entitled "Rapid synchronized fabrication of vascularized thermosets and composites" is published on Nature Communications! Congradulations!


Feburary 4, our paper entitled "A GFEM-based reduced-order homogenization model for heterogeneous materials under volumetric and interfacial damage" is published on Computer Methods in Applied Mechanics and Engineering! Congradulations!


2020

November 16, Xiang Zhang presented at ASME IMECE 2020 virtually. The title of Xiang’s presentation was: “Integrating GFEM and Eigendeforamtion-based Reduced-Order Homogenization Model for Simulating Heterogeneous Materials Under Volumetric and Interfacial Damage”.


 

June 11, our paper entitled "Frontal vs. bulk polymerization of fiber-reinforced polymer-matrix composites" is accepted by Composites Science and Technology! Congradulations!


March 11, our book chapter entitled "Transverse Failure of Unidirectional Composites: Sensitivity to Interfacial Properties" is published in Integrated Computational Materials Engineering (ICME)! Congradulations!


January 27, Pengfei Shen joins CAMML as a Ph.D. student. He will be studying fatigue in additivelly manufactured Titanium alloys. Welcome Penfei!


2019

December 11, our paper entitled "Dislocation density informed eigenstrain based reduced order homogenization modeling: verification and application on a titanium alloy structure subjected to cyclic loading" is accepted by Modelling and Simulation in Materials Science and Engineering! Congradulations!


November 11, Xiang Zhang presented at ASME IMECE 2019 in Salt Lake City, UT. The title of Xiang’s presentation was: “Modeling of Process-Induced Residual Deformations in Frontal Polymerization based Manufacturing of Thermosetting Polymer Components”.

Abstract

Fontal polymerization (FP) is a rapid and energy-efficient manufacturing process for polymer and polymer composites. In FP-based manufacturing, a polymerization front is firstly initiated by a local heat stimulus to activate the catalyst present in the monomer solution, upon which the heat from the exothermic polymerization of the monomer maintains and self-propagates the reaction front, rapidly transforming the monomer into fully cured polymer. To further increase the manufacturing efficiency, a multi-point initiation approach is adopted to initiate multiple fronts and cure different regions of the manufactured part simultaneously. However, localized residual deformations is experimentally observed where fronts merge, leading to deteriorated properties at these locations. To capture the formation of residual deformations in the FP-based manufacturing process, a coupled thermo-chemo-mechanical model is developed. In this model, a fully coupled thermo-chemical model is first used to replicate the thermal and degree of cure history associated with the FP process. Key characteristics of the front, including front velocity and temperature are compared with experimental measurements. The obtained temperature and degree of cure are then fed into a static structural finite element solver that utilizes temperature- and degree-of-cure-dependent properties to solve for the displacement field. The predicted process-induced strain field is compared with Digital Image Correlation (DIC) measurements. We also explore the possibility of regulating the temperature and cure history at the front merging location to alleviate the residual deformations. 

September 19, our paper entitled "Manufacturing of unidirectional glass-fiber-reinforced composites via frontal polymerization: A numerical study" is accepted by Composite Science and Technology! Congradulations!


August 27,  Xiang Zhang officially started as a an assistant professor in the Mechanical Engineering Department at the University of Wyoming! Welcome!


July 29, Xiang Zhang presented at USNCCM 2019 in Austin, TX. The title of Xiang’s presentation was: “Modeling and Design of a New Printing Process for 3D Freeform Polymer Components based on Frontal Polymerization”.

Abstract

A rapid and energy-efficient manufacturing process for polymer and polymer composites called frontal polymerization (FP) was recently developed. In FP-based manufacturing, only an initial local heat stimulus is required to activate the polymerization, upon which the heat from the exothermic polymerization of the monomer creates a self-propagating polymerization front that transforms the monomers into fully cured polymers. A 3D printing technique that uses FP to simultaneously cure the printed material as it is deposited has also been recently introduced for free-standing polymer components. During this printing process, the polymerizing front follows the printing nozzle and rapidly transforms the viscoelastic filament into a stiff thermoset, thereby eliminating the need for support structures and post curing process and providing high printing accuracy compared to traditional direct ink writing. In this presentation, we start by introducing a coupled thermo-chemo-mechanical model specially developed to model the evolution of temperature, degree of cure, and strain fields during the FP process. The model is first validated against experimental measurements and then used to probe the front characteristics under different experimental settings. We then focus on the development of a design diagram for FP-based 3D printing to maximize the printing efficiency (i.e., maximum printing velocity) while maintaining the desired printing accuracy (i.e., limited deformation of the printed filament). The design space contains parameters that characterize the settings of the printer (e.g., ink temperature, extruding pressure, length and diameter of the nozzle), the nature of the ink (e.g., initial degree of cure and cure kinetics associated with the chosen ink composition), and the printing environment (e.g., ambient temperature and air flow rate).The constraints are associated with equilibrated printing for which the front velocity equals the printing speed, the printing accuracy achieved by limiting the deflection of the deposited filament, the capability of the printer, and non-blocking of the nozzle by a threshold depositing temperature.

July 24, our paper entitled "Experimental and numerical study of mechanical properties of multi-phase medium-Mn TWIP-TRIP steel: Influences of strain rate and phase constituents" is accepted by Acta Materialia! Congradulations!


May 15, our paper entitled "IGFEM-based shape sensitivity analysis of the transverse failure of a composite laminate" is accepted by Computationsl Mechanics. Congradulations!


April 29, Xiang Zhang accepted the offer as an assistant professor in the Mechanical Engineering Department at the University of Wyoming! Congradulations!

 

 


Contact

Xiang Zhang, Ph.D.,

Assistant Professor of Mechanical Engineering Department

Room 335B, EERB
1000 E. University
Dept. 3295
Laramie, WY 82071
EmaiL: xiang.zhang@uwyo.edu
Phone: 307-766-42381000
Fax: 307.766.2695

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