今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 2 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇
Data-driven analysis of structural instabilities in electroactive polymer bilayers based on a variational saddle-point principle
Siddharth Sriram, Elten Polukhov, Marc-André Keip
doi:10.1016/j.ijsolstr.2024.112663
基于变分鞍点原理的电活性聚合物双层结构不稳定性数据驱动分析
In this work, we use a data-driven approach to model the onset of wrinkling in composite dielectric elastomer (DE) bilayer structures that are subjected to combined electro-mechanical loading conditions. Specifically, the critical surface-charge density required to activate wrinkling and the resulting number of half-waves are determined as functions of the tunable geometrical and material features of the DE bilayer using supervised machine learning (ML) models. The required data for the ML surrogates is generated using a finite-element-based framework for structural stability analysis of the DE bilayer, which is rooted in a variational saddle-point formulation for non-linear electro-elastostatics. Within the considered broad design space for the DE bilayer, the data points are sampled according to a Latin-hypercube-type design, following which training and test datasets containing the values of the target variables for the sampled input-feature vectors are generated using the adopted finite-element framework. Subsequently, we implement and compare the capabilities of different ML models to capture accurately the non-linear dependence of the wrinkling characteristics on the tunable features of the DE bilayer.
在这项工作中,我们使用数据驱动的方法来模拟复合介质弹性体(DE)双层结构在复合机电载荷条件下起皱的开始。具体来说,激活起皱所需的临界表面电荷密度和产生的半波数是使用监督机器学习(ML)模型确定的,作为DE双层可调几何和材料特征的函数。ML替代品所需的数据是使用基于有限元的框架生成的,用于DE双层结构稳定性分析,该框架植根于非线性电弹性静力学的变分鞍点公式。在考虑DE双层的广泛设计空间内,根据拉丁超立方体类型的设计对数据点进行采样,然后使用所采用的有限元框架生成包含采样输入特征向量的目标变量值的训练和测试数据集。随后,我们实现并比较了不同机器学习模型的能力,以准确捕获皱褶特征对DE双层可调特征的非线性依赖。
Nonlinear constitutive model of CFRP composites under constant direct current: combined effects of thermal damage and dielectric degradation
Haoran Song, Zheng Zhong
doi:10.1016/j.jmps.2024.105547
恒直流电作用下CFRP复合材料的非线性本构模型:热损伤和介电退化的联合效应
Prolonged exposure to low-density direct current (DC) can lead to mechanical degradation of carbon fiber-reinforced polymer (CFRP) composites, posing significant risks to material safety and reliability. This paper presents a nonlinear constitutive model to elucidate the mechanical degradation of CFRP composites when subjected to DC influences. Grounded in the principles of non-equilibrium thermodynamics, this model introduces two internal variables to account for the impact of thermal damage and dielectric degradation on the Helmholtz free energy. Furthermore, specialized dissipation functions are employed to derive the evolution equations governing these internal variables. Utilizing the model, we analyze the damage progression in carbon fiber–epoxy laminates subjected to constant DC loading. The theoretically projected resistivity and elastic modulus align closely with available experimental data in literature, thus confirming the rationality and accuracy of the proposed model. This model holds the potential to forecast the long-term evolution of mechanical properties in unidirectionally reinforced composite materials with varying carbon fiber contents under the influence of DC, thereby furnishing a theoretical foundation for enhancing the reliability design of CFRP composites in electrically-charged environments.
长时间暴露在低密度直流电(DC)下会导致碳纤维增强聚合物(CFRP)复合材料的机械降解,对材料的安全性和可靠性构成重大风险。本文提出了一种非线性本构模型来解释CFRP复合材料在直流作用下的力学退化。该模型以非平衡态热力学原理为基础,引入了两个内部变量来解释热损伤和介电退化对亥姆霍兹自由能的影响。此外,利用专门的耗散函数推导出控制这些内部变量的演化方程。利用该模型分析了碳纤维环氧复合材料在恒定直流载荷作用下的损伤过程。理论推算的电阻率和弹性模量与文献实验数据吻合较好,证实了模型的合理性和准确性。该模型具有预测不同碳纤维含量的单向增强复合材料在直流影响下力学性能长期演变的潜力,从而为提高CFRP复合材料在带电环境下的可靠性设计提供理论依据。
Temperature-Dependent, Multi-Mechanism Crystal Plasticity Reveals the Deformation and Failure Behaviour of Multi-Principal Element Alloys
Yilun Xu, Xiaochong Lu, Xinyu Yang, Wanghui Li, Zachary Aitken, Guglielmo Vastola, Huajian Gao, Yong-Wei Zhang
doi:10.1016/j.jmps.2024.105549
温度相关的多机制晶体塑性揭示了多主元素合金的变形和破坏行为
In this work, we have developed a temperature-dependent, multi-mechanism crystal plasticity (CP) model aimed at unravelling the deformation and failure resistance of Cantor alloy-like multi-principal element alloys (MPEA) under both uniaxial tensile and cyclic loading conditions. Three deformation mechanisms: dislocation slip, deformation twinning, and phase transformation are considered under a unified stress-driven, thermally activated law. In addition, the effect of short-range ordering (SRO) is introduced by accounting for the inhomogeneous distributions of material properties within individual grains. Our work yields the following key findings: (1) The rate- and temperature-sensitivity of the materials, such as the occurrence and sequence of dislocation slip, deformation twinning, and martensitic phase transformation observed in experiments, can be captured through the calibrated material properties. (2) The enhancement of the mechanical response of the Cantor alloy-like MPEAs due to the SRO effect is intrinsically linked to the generation of geometrically necessary dislocations resulting from localized variations in material properties. (3) The excellent fatigue and fracture resistance exhibited by Cantor alloy-like MPEAs at low temperatures can be attributed to the homogenization of stored energy density within the microstructure. This homogenization arises from the development of deformation twinning and martensitic phase transformation. Our newly developed CP model and the key findings provide a valuable guide for the design of MPEAs to achieve superior fatigue and fracture resistance without compromising their inherent strength.
在这项工作中,我们开发了一个温度依赖的多机制晶体塑性(CP)模型,旨在揭示Cantor合金类多主元素合金(MPEA)在单轴拉伸和循环加载条件下的变形和抗破坏能力。在统一的应力驱动、热激活规律下,考虑了位错滑移、变形孪晶和相变三种变形机制。此外,通过考虑单个晶粒内材料性能的不均匀分布,引入了短程有序(SRO)的影响。我们的工作产生了以下关键发现:(1)材料的速率和温度敏感性,例如在实验中观察到的位错滑移、变形孪晶和马氏体相变的发生和顺序,可以通过校准的材料特性来捕获。(2) SRO效应对类康托合金MPEAs力学响应的增强与材料性能局部变化引起的几何必要位错的产生有着内在的联系。(3) Cantor类合金mpea在低温下表现出优异的抗疲劳性和抗断裂性,这可归因于微观组织内存储能量密度的均匀化。这种均质化是由形变孪晶和马氏体相变的发展引起的。我们新开发的CP模型和关键发现为mpea的设计提供了有价值的指导,从而在不影响其固有强度的情况下实现卓越的抗疲劳和断裂性能。
Anisotropic and heterogeneous acoustoplasticity of α-Ti during ultrasonic vibration assisted compression: modeling and experiments
Haidong Zhang, Lei Deng, Yi Hao, Cheng Li, Xuefeng Tang, Pan Gong, Mao Zhang, Junsong Jin, Xinyun Wang
doi:10.1016/j.ijplas.2024.103886
超声振动辅助压缩过程中α-Ti的各向异性和非均质声塑性:模型和实验
Introducing ultrasonic vibration (UV) into the plastic deformation process is a promising and efficient way to improve the formability of metallic materials. However, the acoustoplasticity of α-Ti with pronounced anisotropic behavior during UV-assisted deformation is still not well understood, and the underlying mechanisms associated with the ultrasonic effect on multiple slip/twinning systems remain ambiguous. In this research, the anisotropic and heterogeneous acoustoplasticity of α-Ti was investigated through modeling and experiments. A novel acoustic crystal plasticity model considering the anisotropic ultrasonic response of multiple slip/twinning systems was proposed, in which the ultrasonic softening is determined by the coupling effect of crystal orientation, mechanical threshold, and ultrasonic energy density. The proposed model was validated through the mechanical response of the UV-assisted compression and the twin volume fraction of α-Ti specimens along RD, TD, and ND directions. Full-field crystal plasticity simulations regarding UV-assisted compression were carried out. Then the mechanism of the acoustoplasticity of α-Ti was explored via the analysis of ultrasonic activation on multiple slip/twinning systems and the grain scale deformation behavior. A considerable anisotropic and heterogeneous ultrasonic softening effect of α-Ti was found, and the anisotropy as well as the magnitude of ultrasonic softening increase with the ultrasonic energy density. The ultrasonically activated deformation modes gradually change from prismatic slip and tensile twinning to basal slip and compressive twinning from RD, TD to ND specimens, which results in a higher average CRSS decrease and more pronounced ultrasonic softening macroscopically. The grain scale stress inhomogeneity of α-Ti is relieved under UV, and the local deformation and grain rotation are both enhanced. The dislocation motion and twinning behavior are both promoted by UV. The facilitated twinning behavior can be attributed to the enhanced dislocation assisted nucleation and propagation of deformation twins under UV. These findings provide a fundamental understanding of the anisotropic and heterogeneous acoustoplasticity of α-Ti during the UV-assisted deformation process.
在塑性变形过程中引入超声振动是提高金属材料成形性的一种有效途径。然而,具有明显各向异性行为的α-Ti在紫外辅助变形中的声塑性仍未得到很好的理解,并且超声效应在多滑移/孪晶体系中的潜在机制仍不清楚。本研究通过模型和实验研究了α-Ti的各向异性和非均质声塑性。提出了一种考虑多滑移/孪晶系统各向异性超声响应的声学晶体塑性模型,该模型中超声软化由晶体取向、力学阈值和超声能量密度的耦合效应决定。通过紫外辅助压缩的力学响应和α-Ti试样沿RD、TD和ND方向的双体积分数验证了该模型的有效性。进行了紫外辅助压缩下的全场晶体塑性模拟。然后通过超声对多滑移/孪晶体系的激活和晶粒尺度变形行为分析,探讨α-Ti的声塑性机理。α-Ti具有明显的各向异性和非均质超声软化效应,且各向异性和超声软化幅度随超声能量密度的增大而增大。从RD、TD到ND试样,超声激活变形模式由棱柱滑移和拉伸孪晶逐渐转变为基底滑移和压缩孪晶,导致宏观上CRSS平均降幅较大,超声软化更为明显。UV作用下α-Ti的晶粒尺度应力不均匀性得到缓解,局部变形和晶粒旋转均增强。紫外光促进了位错运动和孪晶行为。紫外光作用下,位错辅助变形孪晶形核和扩展的增强是促进孪晶行为的主要原因。这些发现为α-Ti在紫外辅助变形过程中的各向异性和非均质声塑性提供了基本的认识。
Nonlinear Electromechanical Responses in Multi-layered Fiber-reinforced Dielectric Elastomer Composites
Marzie Majidi, Masoud Asgari
doi:10.1016/j.tws.2024.111599
多层纤维增强介电弹性体复合材料的非线性机电响应
The capabilities of dielectric elastomer actuators (DEAs) across various applications of soft smart materials constantly expands. However, the electromechanical behavior of multi-layer anisotropic dielectric elastomer composites (DECs), has not been studied accurately despite of its great potentials. Hence, this paper proposes a comprehensive coupled electromechanical model to address this issue and effectively capture various attributes of such an actuator including the number of layers and layers’ configuration. Using a coupled nonlinear model enables it to analyze multi-layer DECs with an unlimited number of layers, and reinforcing fiber families. A new user defined material subroutine is developed to explore the actuation performance of different multi-layer DECs such as binder, diaphragm, and tubular actuators. It provides a unique insight into effects of the number and arrangement of layers on the electromechanical performance of these actuators. Experimental results have been used for validation of developed model and numerical implementation. The results propose a practical tool for designing and optimizing fiber-reinforced multi-layer DECs based on objective purposes, contributing to developing more efficient and reliable electromechanical models for these materials.
介电弹性体致动器(dea)在各种软智能材料应用中的能力不断扩大。然而,多层各向异性介电弹性体复合材料(DECs)的机电性能虽然具有很大的潜力,但尚未得到准确的研究。因此,本文提出了一个综合的耦合机电模型来解决这一问题,并有效地捕获了该执行器的各种属性,包括层数和层的配置。采用耦合非线性模型可以分析无限层数的多层DECs和增强纤维族。开发了一种新的用户自定义材料子程序,用于探索不同多层DECs(粘结器、膜片和管状执行器)的驱动性能。它提供了一个独特的见解,对这些执行器的机电性能层的数量和安排的影响。实验结果用于验证所建立的模型和数值实现。研究结果为基于客观目的设计和优化纤维增强多层DECs提供了实用工具,有助于开发更有效和可靠的这些材料的机电模型。