Bo Li

Case Western Reserve University | CWRU · Department of Mechanical and Aerospace Engineering

Over the last two decades, meshfree Galerkin methods have become increasingly popular in solid and fluid mechanics applications. A variety of these methods have been developed, each incorporating unique meshfree approximation schemes to enhance their performance. In this study, we examine the application of the Moving Least Squares and Local Maximu...

Plain Language Summary Many mission concepts exploring planets, moons and other bodies include flying directly through material such as gas, ice particles, or dust grains for collection and/or analysis. In particular, Saturn's moon Enceladus has a plume of water ice particles that appear to be sourced from its subsurface ocean, making them valuable...

Printed electronics are widely used in wearable tech, IoT, and medical devices, and reliable sintering methods are essential for achieving optimal electrode conductivity. However, existing sintering models are often based on trial-and-error or past experience, highlighting the need for a reliable numerical model to improve the process. Traditional...

Fibronectin (Fn) has been observed to assemble in the extracellular matrix (ECM) of cell culture and stretch in response to the external force. The alteration of molecule domain functions generally follows the extension of Fn. Several researchers have investigated fibronectin extensively in molecular architecture and conformation structure. However...

The Laser Metal Deposition (LMD) involves extremely complex multi-scale multi-physics and multiple thermal cycles issues, making it difficult to accurately predict the resultant mechanical properties of fabricated components from given process parameters. This research, by proposing a cladding stacking model that uses the structural evolution histo...

本文提出了一种带相变的热流固强耦合问题的数值求解方法，即热耦合最优输运无网格（HOTM）方法。该方法结合了最优输运无网格方法（OTM）和热流固变分本构模型，能够解决多介质耦合问题中常见的极大变形、大温度梯度、高加热/冷却速率、包括熔化、气化和固化在内的多相变和多相混合等问题。该方法用节点和物质点进行空间离散，同时求解动量和能量守恒方程来获得材料的变形、温度和局部状态。HOTM方法已被用于金属粉末床激光选区熔融工艺（SLM）和超高速激光熔覆技术（EHLA）的直接数值模拟，量化了SLM中粉末颗粒尺寸分布对成型材料孔隙度的影响，以及计算了EHLA中金属涂层的近似孔隙率，模拟与实验结果高度吻合。该方法能够加深我们对金属增材制造工艺中控制成品质量的理解。

Shape‐morphing capabilities of metamaterials can be expanded by developing approaches that enable the integration of different types of cellular structures. Herein, a rational material design process is presented that fits together auxetic (anti‐tetrachiral) and non‐auxetic (the novel nodal honeycomb) lattice structures with a shared grid of nodes...

A phase-aware constitutive model is developed and integrated with the meshfree simulations to study the failure mechanisms of space structural materials under the oblique hypervelocity impact of ice. The proposed constitutive model covers material’s dynamic behavior in a wide range of temperature, pressure, and strain rates. The numerical analysis...

A fully coupled thermomechanical computational framework based on the Hot Optimal Transportation Meshfree (HOTM) method is presented to derive the process-microstructure-properties correlation for resin-based friction composites manufactured by hot pressing technique. The raw material is considered as reinforcing fibers and strengthening particles...

Laser Powder Bed Fusion (LPBF) is an additive manufacturing method that manufactures high density and quality metal products. We present a coupled grain growth and heat transfer modeling technique to understand the materials microstructure evolution in metals during the cooling process of LPBF. The phase-field model is combined with a transient hea...

We present a computational model based on the Hot Optimal Transportation Meshfree (HOTM) method and a thermo-visco-elasto-plastic constitutive model for the high-fidelity simulation of high and hypervelocity impact of small ice particles. The competition and combination among various energy dissipation mechanisms in the high energy density event, i...

A turbine disk design based on uncertainty quantifies the risks and improves the structural reliability. An optimized design issue related to turbine disk fatigue life reliability with subjective and objective multi-source uncertainties is a three-layer nested analysis process, where each iterative step requires a double-layer nested analysis conta...

We present a dynamic adaptive eigenfracture algorithm for the study of crack propagation in brittle materials. The original eigenfracture method is an variational approximation of the Griffith-type fracture with convergence as the element size vanishes. To improve its convergence rate, we extend the eigenfracture approach by using the effective ene...

We present a powder‐scale computational framework to predict the microstructure evolution of metals in powder bed fusion additive manufacturing (PBF AM) processes based on the hot optimal transportation meshfree (HOTM) method. The powder bed is modeled as discrete and deformable three‐dimensional bodies by integrating statistic information from exp...

We present a monolithic incremental Lagrangian framework based on meshfree methods, the Hot Optimal Transportation Meshfree (HOTM) method, for a robust and efficient solution of the dynamic response of materials under extreme thermomechanical conditions, possibly involving extremely large deformation, phase transition and multiphase mixing. The HOT...

The above referenced paper has been removed from publication. (April 21, 2020) Copyright © 2020 by ASME

We present a powder-scale meshfree direct numerical simulation (DNS) capability for the powder bed fusion (PBF) based additive manufacturing (AM) processes using the novel Hot Optimal Transportation Meshfree (HOTM) method. The HOTM method is an incremental Lagrangian meshfree computational framework for materials behaviors under extreme thermomecha...

We present a fully coupled thermomechanical simulation of the hot forming process of composite materials. The raw material is a mixture of resin powders, strengthening particles and reinforcing fibers. Complex material responses in the process, such as phase change (melting and polymerization) and reorientation of the fibers, determine the microstr...

We present a meshfree direct numerical simulation (DNS) capability for the additive manufacturing (AM) process of metals based on the hot optimal transportation meshfree (HOTM) method. The HOTM method is a meshfree thermomechanical Lagrangian computational framework for material behaviors under extreme thermomechanical loading conditions. It combin...

We present a three-dimensional micromechanical computational framework for the direct mesoscale simulation of compressive failure mechanisms in ceramic materials at high strain rates based on the Optimal Transportation Meshfree (OTM) method and the microstructure-informed Eigen-fracture approach. A statistically equivalent polycrystal structure of...

We propose a novel computational model for the high fidelity prediction of failure mechanisms in brittle polycrystalline materials. A three-dimensional finite element model of the polycrystalline structure is reconstructed to explicitly account for the micro-features such as grain sizes, grain orientations, and grain boundary misorientations. Grain...

High purity polycrystalline tantalum (Ta) was shocked through 1 to 3.5 Mbar pressures creating Richtmyer-Meshkov unstable interfaces that were used to determine the dynamic material strength. The experiments were performed on the Omega laser at the University of Rochester Laboratory for Laser Energetics. Prior to shock, the driven surfaces of the t...

We present a monolithic Lagrangian meshfree solution for Fluid–Structure Interaction (FSI) problems within the Optimal Transportation Meshfree (OTM) framework. The governing equations of the fluid and structure are formulated in the Lagrangian configuration and solved simultaneously in a monolithic way. Mainly, the fully discretized equations are c...

A novel surrogate model based on the Local Maximum-Entropy (LME) approximation is proposed in this paper. By varying the degrees of locality, the LME-based surrogate model is constructed according to the local behavior of the response function at the prediction points. The proposed method combines the advantages of both local and global approximati...

The objective of this work is twofold. First, we develop an eigensoftening algorithm to capture the gradual process of failure in materials with a softening behavior as an extension of the eigenerosion approach. Both methods are validated against the physical measurements in three-point bending tests of concrete with a drop- weight device, includin...

Periodic boundary condition for the representative volume element (RVE) model of the 3D braided composite is required to predict the braided composite properties in the framework of mean field homogenization. Meanwhile, generating periodic mesh is quite challenging due to complicated mesoscopic features for 3D braided composites. This paper present...

A meshfree numerical model, based on the principle of Local Maximum Entropy, with a B-Bar based algorithm to avoid instabilities, is applied to solve consolidation problems in saturated soils. This numerical scheme has been previously validated for purely elasticity problems without water (mono phase), as well as for steady seepage in elastic porou...

A meshfree numerical model, based on the principle of Local Maximum Entropy (LME), including a B-bar algorithm to avoid instabilities, is applied to solve axisymmetric consolidation problems in elastic saturated soils. This numerical scheme has been previously validated for purely elastic problems without water (mono phase), as well as for steady s...

Ceramic and composite resin blocks for CAD/CAM machining of dental restorations are becoming more common. The sample sizes affordable by these blocks are smaller than ideal for stress intensity factor (SIF) based tests. The J-integral measurement calls for full field strain measurement, making it challenging to conduct. Accordingly, the J-integral...

The object of this work is to establish a meshfree framework for solving coupled, steady and transient problems for unconfined seepage through porous media. The Biot's equations are formulated in displacements (or u − w) assuming an elastic solid skeleton. The free surface location and its evolution in time are obtained by interpolation of pore wat...

We present an Optimal Uncertainty Quantification (OUQ) protocol for systems that are characterized by an existing physics-based model and for which only legacy data is available, i. e., no additional experimental testing of the system is possible. Specifically, the OUQ strategy developed in this work consists of using the legacy data to establish,...

We formulate a simple one-parameter macroscopic model of distributed damage and fracture of polymers that is amenable to a straightforward and efficient numerical implementation. We show that the macroscopic model can be rigorously derived, in the sense of optimal scaling, from a micromechanical model of chain elasticity and failure regularized by...

Presented is a massively parallel implementation of the Optimal Transportation Meshfree (pOTM) method Li et al., 2010 for explicit solid dynamics. Its implementation is based on a two-level scheme using Message Passing Interface between compute servers and threaded parallelism on the multi-core processors within each server. Both layers dynamically...

The present work is concerned with the verification and validation of an implementation of the eigenfracture scheme of Schmidt et al. (SIAM J Multi-scale Model Simul 7:1237–1266, 2009) based on material-point erosion, which we refer to as eigenerosion. Eigenerosion is derived from the general eigenfracture scheme by restricting the eigendeformation...

We present a validation assessment of the eigenerosion scheme applied in conjunction with the Optimal Transportation Meshfree (OTM) method. The assessment is based on the detonation-driven 304L steel spherical-cap fragmentation experiments of Campbell et al. Campbell et al., 2007. Metrics used for purposes of validation include the velocity history...

We describe through static and dynamic applications the implementation of the eigenerosion scheme within a material point discretization method. Eigenerosion is derived from the general eigenfracture scheme (Schmidt et al. 2009) by restricting the eigendeformations to be either zero, in which case the local behavior is elastic, or equal to the loca...

Large scale three-dimensional numerical simulations of hypervelocity impact of Aluminum alloy 6061-T6 plates by Nylon 6/6 cylindrical projectile have been performed using the Optimal Transportation Meshfree (OTM) method of Li et al.[7] along with the seizing contact and variational material point failure algorithm [17] and [18]. The dynamic respons...

SUMMARY We develop a multiscale model of ductile damage by void growth in general materials undergoing arbitrary deformations. The model is formulated in the spirit of multiscale finite element methods (FE 2), that is, the macroscopic behavior of the material is obtained by a simultaneous numerical evaluation of the response of a representative vol...

The present work is concerned with the verification and validation of an implementation of the eigenfracture scheme of Schmidt et al. (SIAM J Multiscale Model Simul 7:1237–1266, 2009) based on material-point erosion, which we refer to as eigenerosion. Eigenerosion is derived from the general eigenfracture scheme by restricting the eigendeformations...

This work is concerned with establishing the feasibility of a data-on-demand (DoD) uncertainty quantification (UQ) protocol based on concentration-of-measure inequalities. Specific aims are to establish the feasibility of the protocol and its basic properties, including the tightness of the predictions afforded by the protocol. The assessment is ba...

This Part II of this series is concerned with establishing the feasibility of an extended data-on-demand (XDoD) uncertainty quantification (UQ) protocol based on concentration-of-measure inequalities and martingale theory. Specific aims are to establish the feasibility of the protocol and its basic properties, including the tightness of the predict...

We develop an optimal transportation meshfree (OTM) method for simulating general solid and fluid flows, including fluid–structure interaction. The method combines concepts from optimal transportation theory with material-point sampling and max-ent meshfree interpolation. The proposed OTM method generalizes the Benamou–Brenier differential formulat...

This dissertation is concerned with the development of a robust and efficient meshless method, the Optimal Transportation Method (OTM), for general solid flows involving extremely large deformation, fast, transient loading and hydrodynamic phenomena. This method is a Lagrangian particle method through an integration of optimal transportation theory...