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Jinxiong Zhou's blog

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Optimizing deployment dynamics of composite tape-spring hinges

The composite tape-spring hinge (CTSH) is a lightweight structural connector widely employed in space structures, including spacecraft and satellites, due to its high specific strength and stiffness. Introducing cutouts enables CTSH to possess folding and deployment capability, while optimizing the cutouts finely to optimize the performance of CTSH. However, the interaction between cutout size and the dynamic deployment of CTSH is a novel topic.

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A mesoscale computational approach to predict ABD matrix of thin woven composites

The ABD matrix is a fundamental method to characterize the overall stiffness behavior of laminated composite structures. Although classical laminate theory has been widely used, it has limitations in predicting the ABD matrix for woven composites. To address this issue, this paper presents a mesoscale homogenization approach aimed at computing the ABD matrix for thin woven composites accurately. The mesoscale representative volume element (RVE) of the woven composite is generated using TexGen and imposed with periodic boundary conditions to enforce the Kirchhoff thin plate assumption.

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A hybrid proper orthogonal decomposition and next generation reservoir computing approach for high-dimensional chaotic prediction: Application to flow-induced vibration of tube bundles

To address the significant challenges in predicting high-dimensional chaotic systems, this paper introduces a novel hybrid strategy that combines proper orthogonal decomposition (POD), which serves as reduced order modeling (ROM), with next generation reservoir computing (NGRC), a data-driven prediction model.

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Folding, stowage, and deployment of composite thin-walled lenticular tubes

This paper presents an integrated experimental and numerical investigation of the dynamic deployment behavior of Composite thin-walled lenticular tube (CTLT) that wraps around a central hub, with emphasis on the effect of long-term storage. The deployment experiments were performed on the CTLT prototype both before and after it had been stowed for extended storage periods. The results indicate that after being stowed for 6 and 10.5 months the CTLT is deployed slower and the deployment time increases by 8.2% and 15.0%, respectively.

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Implementation of ABAQUS User Subroutines for Viscoplasticity of 316 Stainless Steel and Zircaloy-4

This paper describes the formulations for the viscoplasticity of metals based on the Chaboche and Delobelle model. The implementations of the viscoplastic models were detailed herein and then implemented via user subroutines for material models (UMAT) in ABAQUS. Two typical metals, i.e., 316 Stainless Steel and Zircaloy-4, were chosen as examples and their viscoplastic behaviors were captured. Numerical simulations are compared to reported experiments in order to validate the models and the UMAT codes.

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Modal analysis of lead-bismuth eutectic flow in a single wire-wrapped rod channel

The thermal-hydraulics as well as flow-induced vibration of wire-wrapped rod bundles calls for accurate and efficient liquid metal flow simulation and prediction, yet it remains a challenge due to the complex geometries and high Reynolds number flow in wire-wrapped rod channel. Previous efforts towards this goal exclusively adopts full-order modeling (FOM), which is prohibitively computation-intensive.

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Maximizing buckling load of metabeams via combinatorial optimization of microstructures

Design of mechanical metamaterials is typically realized by repeating microstructured building blocks or unit cells. Microstructures of these unit cells can be identical, whereas individual design of each cell and various combinations of unit cells definitely offer more freedoms and possibilities for combinatorial design of metamaterials. Unfortunately, this combinatorial design problem is prohibitively challenging, if not impossible, due mainly to its huge number of combinatorial cases.

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Modeling SEBM Process of Tantalum Lattices

Selective electron beam melting (SEBM) is one of the popular powder-bed additive manufacturing (AM) technologies, of which there have been extensive studies employing numerical simulations to investigate the thermo-physical phenomena. A procedure for deducing thermo-physical properties of powders from bulk properties of tantalum is presented.

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Surrogate Modeling Accelerated Shape Optimization of Deployable Composite Tape-Spring Hinges

Composite tape-spring hinge (CTSH) is a simple yet elegant mechanical component for various deployable space structures. This paper formulates and addresses cut-out shape optimization of a CTSH, which is seldom touched upon in literature. Both the maximum strain energy stored during the folding process as well as the maximum bending moment during deployment were maximized in a concurrent way, and the multi-objective optimization problem was realized by merging data-driven surrogate modeling and shape optimization.

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Multiscale modeling of viscoelastic behavior of unidirectional composite laminates and deployable structures

Due to the inherent viscoelasticity of constituent matrix and the possibility of long-term storage, space deployable structures made of composites are likely to exhibit relaxation in the stored strain energy, which may degrade their deployment performance. This paper presents a bottom-up finite element based multiscale computational strategy that bridges the experimentally measurable properties of constituent fibers and matrix to numerical predictions of viscoelastic behavior of composite laminates and general shell structures.

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Implementation of Abaqus user subroutines and plugin for thermal analysis of powder-bed electron-beam-melting additive manufacturing process

Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that is widely used for making three-dimensional (3D) objects by adding materials layer by layer. EBM is a very complex thermal process which involves several physical phenomena such as moving heat source, material state change, and material deposition. Conventionally, these phenomena are implemented using in-house codes or embedding some user subroutines in commonly used commercial software packages, like Abaqus, which generally requires considerable expertise.

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Achieving selective snapping-back and enhanced hysteresis in soft mechanical metamaterials via fibre reinforcement

When a soft mechanical metamaterial, consisting of a regular array of representative volume elements (RVE), is stressed up to a large strain, the delicately tailored behavior of the RVE does not prevail in the metamaterial due to boundary effect and manufacturing imperfections.

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A predictive deep-learning approach for homogenization of auxetic kirigami metamaterials with randomly oriented cuts

This paper describes a data-driven approach to predict mechanical properties of auxetic kirigami metamaterials with randomly oriented cuts. The finite element method (FEM)was used to generate datasets, the convolutional neural network (CNN) was introduced to train these data, and an implicit mapping between the input orientations of cuts and the output Young’s modulus and Poisson’s ratio of the kirigami sheets was established. With this input–output relationship in hand, a quick estimation of auxetic behavior of kirigami metamaterials is straightforward.

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Modeling SMA-enabled soft deployable structures for kirigami/origami reflectors

The synergic combination of smart soft composites with kirigami/origami principles leads to self-deployable systems. To date, the development of soft deployable structures has largely been an empirical process. Focusing on the recently developed shape memory alloy (SMA)-based soft deployable structures, this paper describes an analytical model and a finite element (FE) numerical scheme to investigate deformation and deployment performance of this system.

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Snap-back induced hysteresis in an elastic mechanical metamaterial under tension

We combine experiment and finite element simulation and come up with a design of a mechanical metamaterial which demonstrates snap-back induced hysteresis and energy dissipation. The resultant is an elastic system that can be used reversibly for many times. The underlying mechanism of existence of hysteresis and the physics of snap-back induced elastic instability is unveiled. Our results open an avenue for design and implementation of recoverable energy dissipation devices by harnessing mechanical instability.

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Shooting and arc-length continuation method for periodic solution and bifurcation of nonlinear oscillation of viscoelastic dielectric elastomers

A majority of dielectric elastomers (DE) developed so far have more or less viscoelastic properties. Understanding the dynamic behaviors of DE is crucial for devices where inertial effects can not be neglected. Through construction of a dissipation function, we applied the Lagrange’s method and theory of non-equilibrium thermodynamics of DE and formulated a physics-based approach for dynamics of viscoelastic DE.

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Shooting and Arc-Length Continuation Method for Periodic Solution and Bifurcation of Nonlinear Oscillation of Viscoelastic Dielectric Elastomers



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Predicting origami-inspired programmable self-folding of hydrogel trilayers

Imitating origami principles in active or programmable materials opens the door for development
of origami-inspired self-folding structures for not only aesthetic but also functional purposes. A
variety of programmable materials enabled self-folding structures have been demonstrated across
various fields and scales. These folding structures have finite thickness and the mechanical
properties of the active materials dictate the folding process. Yet formalizing the use of origami

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Soft mobile robots driven by foldable dielectric elastomer actuators

A cantilever beam with elastic hinge pulled antagonistically by two dielectric elastomer (DE) membranes in tension forms a foldable actuator if one DE membrane is subject to a voltage and releases part of tension. Simply placing parallel rigid bars on the prestressed DE membranes results in enhanced actuators working in pure shear state. We report design, analysis, fabrication and experiment of soft mobile robots that are moved by such foldable DE actuators.

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Modeling programmable deformation of self-folding all-polymer structures with temperature-sensitive hydrogels

soft active hydrogels with hard passive polymers gives rise to all-polymer
composites. The hydrogel is sensitive to external stimuli while the passive
polymer is inert. Utilizing the different behaviors of two materials subject to
environmental variation, for example temperature, results in self-folding soft
machines. We report our efforts to model the programmable deformation of
self-folding structures with temperature-sensitive hydrogels. The self-folding
structures are realized either by constructing a bilayer structure or by
incorporating hydrogels as hinges. The methodology and the results may aid the

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Propagation of instability in dielectric elastomers

When an electric voltage is applied across the thickness of a thin layer of an dielectric elastomer, the layer reduces its thickness and expands its area. This electrically induced deformation can be rapid and large, and is potentially useful as soft actuators in diverse technologies. Recent experimental and theoretical studies have shown that, when the voltage exceeds some critical value, the homogenous deformation of the layer becomes unstable, and the layer deforms into a mixture of thin and thick regions.

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A subdomain collocation method based on Voronoi domain partition and reproducing kernel approximation

A subdomain collocation method based on Voronoi diagrams and reproducing kernel approximation is presented. The unkonwn field variables are approximated via reproducing kernel approximation. The body integration arising from the numerical evaluation of Galerkin weak form is converted into much cheaper contour integration along the boundary of each Voronoi cell. The Voronoi cells also provide an natural structure to perform h-adaptivity.

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