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The tensile strength of brittle diamond lattice structure with material dispersion 材料分散的脆性金刚石晶格结构的拉伸强度
Pub Date : 2024-03-27 DOI: 10.1115/1.4065195
Xiaoyu Zhang, Zeang Zhao, Shengyu Duan, H. Lei, Daining Fang
This work investigates the effect of material dispersion on the tensile strength of brittle diamond lattice structure. In actual lattice structures fabricated by additive manufacturing, the dispersion of strength comes from microscale defect, geometric deviation and manufacture-induced anisotropy. The weakening of ultimate failure strength due to material dispersion cannot be predicted by most existing theoretical models, because they assume homogeneous and determinate mechanical properties of the lattice structure. In this paper, we employ diamond lattice structure made from brittle material as a typical example, and its tensile behavior is numerically investigated by incorporating the Gaussian distribution of strut strength. Inspired by the simulation results, a stochastic theoretical model is developed to predict the deformation and failure of diamond lattice structure with material dispersion. This model captures the fact that weaker struts break first even if the whole structure can still bear load. With the continuous increase of stress, these broken struts accumulate into continuous cracks, and ultimate failure occurs when the energy release rate of the initiated crack surpasses the intrinsic fracture toughness of the lattice structure. This research supplements stochastic feature into classical theories, and improves the understanding of potential strengthening and toughening designs for lattice structures.
这项研究探讨了材料分散对脆性金刚石晶格结构拉伸强度的影响。在增材制造的实际晶格结构中,强度的分散来自微尺度缺陷、几何偏差和制造引起的各向异性。现有的大多数理论模型都无法预测材料分散导致的极限破坏强度减弱,因为它们都假定晶格结构具有均匀且确定的力学性能。本文以脆性材料制成的金刚石晶格结构为典型实例,结合支柱强度的高斯分布对其拉伸行为进行了数值研究。受模拟结果的启发,我们建立了一个随机理论模型来预测具有材料分散性的金刚石晶格结构的变形和破坏。该模型捕捉到了这样一个事实:即使整个结构仍能承受载荷,但较弱的支柱会首先断裂。随着应力的不断增加,这些断裂的支柱会累积成连续的裂缝,当初始裂缝的能量释放率超过晶格结构的固有断裂韧性时,就会发生最终破坏。这项研究为经典理论补充了随机特征,并提高了人们对格构结构潜在加固和增韧设计的理解。
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引用次数: 0
A nonlinear mixed finite element method for the analysis of flexoelectric semiconductors 用于分析柔电半导体的非线性混合有限元法
Pub Date : 2024-03-26 DOI: 10.1115/1.4065161
Qiufeng Yang, Xudong Li, Zhaowei Liu, Feng Jin, Yilin Qu
In this paper, we develop a nonlinear mixed finite element method for flexoelectric semiconductors and analyze the mechanically-tuned redistributions of free carriers and electric currents through flexoelectric polarization in typical structures. We first present a macroscopic theory for flexoelectric semiconductors by combining flexoelectricity and nonlinear drift-diffusion theory. To use C0 continuous elements, we derive an incremental constrained weak form by introducing Langrage multipliers, in which the kinematic constraints between the displacement and its gradient are guaranteed. Based on the weak form, we established a mixed C0 continuous 9-node quadrilateral finite element as well as an iterative process for solving nonlinear boundary-value problems. The accuracy and convergence of the proposed element are validated by comparing linear finite element method results against analytical solutions for the bending of a beam. Finally, the nonlinear element method is applied to more complex problems, such as a circular ring, a plate with a hole and an isosceles trapezoid. Results indicate that mechanical loads and doping levels have distinct influences on electric properties.
本文针对挠电半导体开发了一种非线性混合有限元方法,并分析了典型结构中通过挠电极化实现的自由载流子和电流的机械调谐再分布。我们首先结合挠电性和非线性漂移扩散理论,提出了挠电半导体的宏观理论。为了使用 C0 连续元素,我们通过引入 Langrage 乘法器推导出了增量约束弱形式,其中位移及其梯度之间的运动学约束得到了保证。在弱形式的基础上,我们建立了混合 C0 连续 9 节点四边形有限元,并建立了非线性边界值问题的迭代求解过程。通过将线性有限元法的结果与梁弯曲的分析解进行比较,验证了所提出的元素的准确性和收敛性。最后,将非线性元素法应用于更复杂的问题,如圆环、带孔板和等腰梯形。结果表明,机械载荷和掺杂水平对电性能有明显的影响。
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引用次数: 0
A synergistic approach combining surface enhancement and buckling modes for improved axial crushing performance of thin-walled tubes 结合表面增强和屈曲模式的协同方法可提高薄壁管的轴向挤压性能
Pub Date : 2024-03-26 DOI: 10.1115/1.4065162
Shahrukh Alam, Mohammad Uddin, Colin Hall
In this study, thin-walled tubes were circumferentially strengthened by plasticity ball burnishing of critical locations determined from buckling mode analysis. Axial crush test results revealed that the surface treated (ST) tubes increased localized yield strength, attained superior crashworthiness performance, and triggered predictable deformation modes according to the buckling modes of the tubes. Numerical analysis was performed and successfully validated with experiment at 90% prediction accuracy. The treated tube ST-4 with 12th buckling mode outperformed a conventional tube with an increase in specific energy absorption (SEA) and crush force efficiency (CFE) by up to 70%, while sustaining a low increase in initial peak force (IPF). Furthermore, the tube demonstrated greater rate of energy dissipation compared to tubes with conventional surface treated patterns at the same level of surface treated area. The crashworthiness performance improved as the surface treated area ratio increased. A theoretical model was developed for the surface treated tube based on fundamental deformation kinematics, predicting mean crushing force and total energy absorption with an acceptable accuracy. The findings strongly suggest that the proposed surface enhanced tubes have a great potential to be used as energy absorbing structures in crashworthiness applications.
在这项研究中,通过对屈曲模式分析确定的关键位置进行塑性球烧结,对薄壁钢管进行了圆周强化。轴向挤压试验结果表明,经过表面处理(ST)的钢管提高了局部屈服强度,获得了优异的耐撞性,并根据钢管的屈曲模式引发了可预测的变形模式。我们进行了数值分析,并成功地与实验进行了验证,预测准确率达到 90%。经过第 12 种屈曲模式处理的钢管 ST-4 优于传统钢管,其比能量吸收(SEA)和挤压力效率(CFE)最高提高了 70%,而初始峰值力(IPF)的增幅较低。此外,在表面处理面积相同的情况下,与采用传统表面处理模式的钢管相比,该钢管的能量耗散率更高。随着表面处理面积比的增加,耐撞性能也有所提高。根据基本变形运动学,为表面处理管材建立了一个理论模型,以可接受的精度预测平均压溃力和总能量吸收。研究结果有力地表明,所提出的表面强化管在防撞应用中作为能量吸收结构具有巨大的潜力。
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引用次数: 0
Elliptic rigid inclusion in soft materials of harmonic type 谐波型软材料中的椭圆刚性包含物
Pub Date : 2024-03-25 DOI: 10.1115/1.4065160
Kui Miao, Ming Dai, Cun-fa Gao
We investigate finite plane deformations of an elliptic rigid inclusion embedded in a soft matrix which is made of a particular class of harmonic-type hyperelastic materials. The inclusion is assumed to be perfectly bonded to the matrix which is subjected to a constant remote in-plane loading. Utilizing the Cauchy integral techniques associated with conformal mappings, we derive closed-form solutions for the full-field deformation, Piola stress and Cauchy stress in the entire matrix. Numerical examples are presented to illustrate the current solutions in comparison with those established from linear elasticity theory. We find that in terms of the Cauchy stress around the inclusion, the maximum normal stress component always appears at the endpoints of the major axis of the inclusion irrespective of the magnitude of the remote loading, while the maximum hoop stress component occurs not exactly at the above-mentioned endpoints when the remote loading exceeds a certain value. In particular, we identify an exact explicit formula for determining the relative rotation of the inclusion during deformation induced by a remote uniaxial loading of arbitrarily-given magnitude and direction.
我们研究了嵌入软基体中的椭圆刚性包含体的有限平面变形,软基体由一类特殊的谐波型超弹性材料制成。假定包含体与矩阵完全粘合,矩阵承受恒定的远程平面内载荷。利用与共形映射相关的考奇积分技术,我们得出了整个矩阵的全场变形、皮奥拉应力和考奇应力的闭式解。我们给出了数值示例,以说明当前解法与线性弹性理论所建立的解法的比较。我们发现,就包体周围的 Cauchy 应力而言,无论远程载荷的大小如何,最大法向应力分量总是出现在包体主轴的端点处,而当远程载荷超过一定值时,最大箍应力分量并不完全出现在上述端点处。特别是,我们确定了一个精确的显式公式,用于确定任意给定大小和方向的远距离单轴载荷诱导变形过程中包含体的相对旋转。
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引用次数: 0
The mechanics of elastomeric sheet reinforced with bidirectional fiber mesh subjected to flexure on boundaries 用双向纤维网加固的弹性片材在边界上受挠曲的力学性能
Pub Date : 2024-03-18 DOI: 10.1115/1.4065108
Wenhao Yao, Tahmid Rakin Siddiqui, Chun-IL Kim
We investigate the concurrent three-dimensional deformations of fiber-reinforced composite sheets subjected to out-of-plane bending moments via a continuum model, where we invoke the Neo-Hookean strain energy model for the matrix material of fiber-reinforced composite, and assimilate the strain energy of fiber reinforcements into the matrix material model by accounting for stretching, bending, and twisting kinematics of the fibers through the computations of the first-order and second-order gradient of deformation. Emphasis is placed on deriving the Euler equation and boundary conditions of bending moment within the framework of the variational principle and configuring composite surfaces using differential geometry. Significant attention has been given to illustrating the concurrent three-dimensional deformation of fiber composite, meshwork deformation, and fiber kinematics. The simulation results reveal that for a square fiber composite subjected to the out-of-plane bending moment, the maximum in-plane deformation of matrix material occurs along the diagonal direction of the domain while the center of the domain experiences weak in-plane deformation. Notably, the matrix material performs isotropic/anisotropic properties depending on the domain size/shape. In particular, the simulated unit fiber deformations reasonably validate the overall deformation of the network, underscoring that the deformations of the embedded fiber units govern the overall mechanical performance of the fiber meshwork. More importantly, the continuum model qualitatively provides reasonable predictions on the damage patterns of construction materials by demonstrating the kinematics of matrix material and meshwork deformation.
我们通过连续模型研究了纤维增强复合材料片材在平面外弯矩作用下的三维并发变形,其中我们引用了纤维增强复合材料基体材料的新胡克应变能模型,并通过计算变形的一阶和二阶梯度,将纤维增强体的应变能纳入基体材料模型,从而考虑纤维的拉伸、弯曲和扭曲运动学。重点是在变分原理框架内推导出弯矩的欧拉方程和边界条件,并利用微分几何配置复合表面。在说明纤维复合材料的同时三维变形、网格变形和纤维运动学方面给予了极大关注。模拟结果表明,对于承受平面外弯矩的方形纤维复合材料,基体材料的最大平面内变形发生在域的对角线方向,而域的中心发生微弱的平面内变形。值得注意的是,基体材料的各向同性/各向异性取决于畴的大小/形状。特别是,模拟的单元纤维变形合理地验证了纤维网的整体变形,强调了嵌入纤维单元的变形控制着纤维网的整体机械性能。更重要的是,连续体模型通过展示基体材料和网状结构变形的运动学特性,定性地对建筑材料的损坏模式进行了合理预测。
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引用次数: 0
Determination of dynamic characteristics of lattice structure using dynamic mode decomposition 利用动态模式分解确定晶格结构的动态特性
Pub Date : 2024-03-13 DOI: 10.1115/1.4065055
Nary Savoeurn, Chettapong Janya-anurak, V. Uthaisangsuk
In this work, dynamic mode decomposition (DMD) was applied as an algorithm for determining the natural frequency and damping ratio of viscoelastic lattice structures. The algorithm has been developed based on the Hankel alternative view of Koopman and DMD (HAVOK-DMD). In general, the Hankel matrix is based on time-delay embedding, which is meant for the hidden variable in a time series data. Vibration properties of a system could be then estimated from the eigenvalues of approximated Koopman operator. Results of the proposed algorithm was firstly validated with those of the traditional discrete Fourier transform (DFT) approach and half power bandwidth (HPBW) by using analytical dataset of multi-modal spring-mass-damper system. Afterwards, the algorithm was further used to analyze dynamic responses of viscoelastic lattice structures, in which data from both experimental and numerical finite element (FE) model were considered. It was found that the DMD based algorithm could accurately estimate the natural frequencies and damping ratios of the examined structures. In particular, it is beneficial to any dataset with limited amounts of data, whereby experiments or data gathering processes are expensive.
在这项工作中,采用了动态模态分解(DMD)算法来确定粘弹性晶格结构的固有频率和阻尼比。该算法是基于 Koopman 和 DMD 的汉克尔替代观点(HAVOK-DMD)开发的。一般来说,Hankel 矩阵基于时间延迟嵌入,用于时间序列数据中的隐藏变量。根据近似库普曼算子的特征值,可以估算出系统的振动特性。首先,通过使用多模态弹簧-质量-阻尼系统的分析数据集,对所提出算法的结果与传统的离散傅里叶变换(DFT)方法和半功率带宽(HPBW)进行了验证。随后,该算法被进一步用于分析粘弹性晶格结构的动态响应,其中同时考虑了来自实验和数值有限元(FE)模型的数据。结果发现,基于 DMD 的算法可以准确估算所研究结构的固有频率和阻尼比。特别是,它对任何数据量有限的数据集都有好处,因为实验或数据收集过程都很昂贵。
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引用次数: 0
Closed-Form Solutions to Continuous-Time Algebraic Riccati Equation for Second-Order Systems 二阶系统连续时间代数里卡蒂方程的闭式解
Pub Date : 2024-03-13 DOI: 10.1115/1.4065057
Vishvendra Rustagi, Cornel Sultan
This work presents closed-form methods to solve the Continuous-Time Algebraic Riccati Equation (CARE) for second-order systems. The standard CARE solution requires the computation of certain eigenvectors, which becomes expensive and erroneous as the size of the system increases. We mitigate these issues by developing closedform solutions to CARE expressed in terms of physically meaningful mass, damping, and stiffness matrices. We present two methods – one that requires the modal transformation of mass and stiffness matrices, and another that does not require this modal transformation. We show using hundreds of high-dimensional second-order systems that the proposed methods achieve similar or better accuracy compared to the state-of-the-art, while significantly reducing the computation time. We further substantiate our methods by illustrating their advantages when applied to engineering problems such as vibration control.
本研究提出了解决二阶系统连续时间代数里卡提方程(CARE)的闭式方法。标准的 CARE 解法需要计算某些特征向量,随着系统规模的增大,这种方法变得昂贵且错误百出。我们通过开发以物理意义上的质量、阻尼和刚度矩阵表示的 CARE 闭式解来缓解这些问题。我们提出了两种方法--一种需要对质量和刚度矩阵进行模态变换,另一种则不需要这种模态变换。我们使用数百个高维二阶系统证明,与最先进的方法相比,我们提出的方法达到了相似或更高的精度,同时大大减少了计算时间。我们进一步证明了我们的方法在应用于振动控制等工程问题时的优势。
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引用次数: 0
Resolving Absorbed Work and Generalized Inertia Forces from System Energy Equation - A Hamiltonian and Phase-Space Kinematics Approach 从系统能量方程中解析吸收功和广义惯性力--哈密顿和相空间运动学方法
Pub Date : 2024-03-13 DOI: 10.1115/1.4065056
Tuhin Das
This paper develops a theoretical basis and a systematic process for resolving all inertia forces along generalized coordinates from the overall energy equation of a dynamical system. The theory is developed for natural systems with scleronomic constraints, where the potential energy is independent of generalized velocities. The process involves expansion of the energy equation, and specifically a special expansion of the kinetic energy term, from which the inertia forces emerge. The expansion uses fundamental kinematic identities of the phase space. It is also guided by insights drawn from the structure of the Hamiltonian function. The resulting equation has the structure of the D'Alembert's equation but involving generalized coordinates, from which the Lagrange's equations of motion are obtained. The expansion process elucidates how certain inertia forces manifest in the energy equation as composite terms that must be accurately resolved along different generalized coordinates. The process uses only the system energy equation, and neither the Hamiltonian nor the Lagrangian function are required. Extension of this theory to non-autonomous and nonholonomic systems is an area of future research.
本文建立了一个理论基础和系统过程,用于从动力学系统的总能量方程中解决沿广义坐标的所有惯性力。该理论是针对具有硬约束的自然系统开发的,其中势能与广义速度无关。这一过程涉及能量方程的展开,特别是动能项的特殊展开,惯性力就是从动能项中产生的。扩展使用了相空间的基本运动学特性。它还以从汉密尔顿函数结构中获得的启示为指导。由此得到的方程具有达朗贝尔方程的结构,但涉及广义坐标,由此得到拉格朗日运动方程。扩展过程阐明了某些惯性力如何在能量方程中表现为必须沿不同广义坐标精确解析的复合项。该过程只使用系统能量方程,不需要哈密顿和拉格朗日函数。将这一理论扩展到非自治和非全局系统是未来研究的一个领域。
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引用次数: 0
Size Effect of Yielding of Particle-Reinforced Composites 颗粒增强复合材料屈服的尺寸效应
Pub Date : 2024-03-07 DOI: 10.1115/1.4065007
Ruo Jing Zhang, Yan Liu
This paper illustrates how particle size affects the initial yield stress of particle-reinforced composites. A formulation in a closed form is presented to demonstrate the size effect of yielding of the composites. This paper also demonstrates that there is an upper bound and a lower bound for the size-dependent yield stress with the change of particle size. This means that decreasing particle size increases its yield stress up to an upper bound. Similarly, increasing particle size decrease its yield stress up to a lower bound. In this paper the asymptotic homogenization method is used in framework of the Cosserat elasticity. A virtual “unreinforced matrix” is introduced as a reference configuration. As a numerical example, the size effect of yielding of SiCp/Al is predicted.
本文阐述了颗粒尺寸如何影响颗粒增强复合材料的初始屈服应力。本文提出了一个封闭式公式,以证明复合材料屈服的尺寸效应。本文还证明,随着颗粒尺寸的变化,与尺寸相关的屈服应力存在上限和下限。这意味着,粒度减小会增加屈服应力,直至达到上限。同样,增大颗粒尺寸会减小其屈服应力,直至下限。本文在 Cosserat 弹性框架内使用了渐近均质化方法。引入了一个虚拟的 "未加固矩阵 "作为参考配置。以 SiCp/Al 为例,预测了其屈服的尺寸效应。
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引用次数: 0
Post-Buckling Analysis of Arch and Serpentine Structures under End-to-End Compression 端对端压缩下拱形和蛇形结构的屈曲后分析
Pub Date : 2024-02-28 DOI: 10.1115/1.4064962
Zheng Zhang, Fuhua Ye, Yuhang Dong, Fan Zhang, Zhichao Fan
Arch and serpentine structures are two fundamental structural forms with significant applications in various fields. When subjected to compressive loading at both ends, these structures undergo flexural-torsional post-buckling, resulting in complex deformation modes that are challenging to describe using basic functions, posing significant challenges in finding analytical solutions. In this study, we propose a novel approach to address this issue. By representing the lateral displacement with a trigonometric series expansion and utilizing the equilibrium equation, the angular displacement is expressed in terms of special functions known as Mathieu functions. Furthermore, the energy method is employed to obtain analytical solutions for the flexural-torsional post-buckling deformation components. The theoretical findings are validated through experiments and finite element analysis (FEA). Based on theoretical results, explicit analytical expressions for the maximum principal strain and the bending-torsion ratio of the structures are derived, offering valuable insights for the design of arch and serpentine structures in practical applications.
拱形结构和蛇形结构是两种基本的结构形式,在各个领域都有重要应用。当两端承受压缩荷载时,这些结构会发生挠曲-扭转后屈曲,从而产生复杂的变形模式,这些模式很难用基本函数来描述,这给寻找分析解决方案带来了巨大挑战。在本研究中,我们提出了一种解决这一问题的新方法。通过用三角级数展开来表示横向位移,并利用平衡方程,用称为马修函数的特殊函数来表示角位移。此外,还采用了能量法来获得屈曲扭转后屈曲变形成分的解析解。实验和有限元分析(FEA)验证了理论结论。根据理论结果,得出了结构的最大主应变和弯曲扭转比的明确分析表达式,为实际应用中拱形和蛇形结构的设计提供了宝贵的见解。
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引用次数: 0
期刊
Journal of Applied Mechanics
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