今日更新:International Journal of Solids and Structures 3 篇,Journal of the Mechanics and Physics of Solids 3 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 5 篇
Emergence of tension-compression asymmetry from a complete phase-field approach to brittle fracture
Chang Liu, Aditya Kumar
doi:10.1016/j.ijsolstr.2024.113170
从完全相场分析脆性断裂的拉压不对称性的出现
The classical variational approach to brittle fracture propagation does not distinguish between strain energy accumulation in tension versus compression and consequently results in physically unrealistic cracking under compression. A variety of energy splits have been proposed as a possible remedy. However, a unique energy split that can describe this asymmetry for general loading conditions has not been found. The main objective of this paper is to show that a complete phase-field theory of brittle fracture nucleation and propagation, one that accounts for the material strength at large, can naturally capture the tension-compression asymmetry without an energy split. One such theory has been recently proposed by Kumar et al. (2018). Over the past few years, several studies have shown that this theory is capable of accurately describing fracture nucleation and propagation for materials soft and hard under arbitrary monotonic loading conditions. However, a systematic study of the tension-compression asymmetry that emerges from this theory has not yet been reported. This paper does precisely that. In particular, this paper reports a comprehensive study of crack propagation in two problems, one involving a symmetric tension-compression state and the other involving larger compressive stresses at the crack tip. The results are compared with popular energy splits used in literature. The results show that, remarkably, for the second problem, only the complete theory is able to produce experimentally consistent results.
脆性断裂扩展的经典变分方法没有区分拉伸和压缩下的应变能积累,从而导致物理上不现实的压缩开裂。作为一种可能的补救措施,已经提出了各种各样的能源拆分。然而,一个独特的能量分裂,可以描述这种不对称的一般加载条件尚未发现。本文的主要目的是表明,一个完整的脆性断裂成核和扩展的相场理论,一个解释材料强度的理论,可以自然地捕捉拉压不对称而没有能量分裂。Kumar等人(2018)最近提出了一个这样的理论。近年来的一些研究表明,该理论能够准确地描述任意单调加载条件下软、硬材料的断裂形核和扩展。然而,从这一理论中产生的拉压不对称性的系统研究尚未被报道。本文正是这样做的。特别地,本文报道了两个问题中裂纹扩展的全面研究,一个涉及对称的拉压缩状态,另一个涉及裂纹尖端较大的压应力。结果与文献中常用的能量分割进行了比较。结果表明,值得注意的是,对于第二个问题,只有完整的理论才能产生与实验一致的结果。
Unified characterization of failure surfaces and golden-ratio ductile-to-brittle classification for isotropic materials
Sontipee Aimmanee, Pijak Tiraviriyaporn
doi:10.1016/j.ijsolstr.2024.113184
各向同性材料破坏面统一表征及黄金比例延脆分级
The failure surface, often referred to as the failure angle, defines the specific planar orientation within a material that reaches its load-carrying capacity, represented by material strengths. Analyzing this critical surface is elemental for material characterization, providing profound insights into ductility and brittleness. Despite the diversity of methodologies employed for determining the failure plane from various criteria, a universally accepted theory that systematically governs this characteristic across a broad spectrum of isotropic materials remains elusive. Therefore, this paper aims to develop a unified framework for predicting the failure surface for all homogeneous isotropic solids by considering the convergence of three key material constitutive models: elasticity, failure, and plasticity. A universal energy-based failure criterion is utilized to determine failure angles under fundamental loading scenarios, including uniaxial tension, uniaxial compression, pure shear, and biaxial tension–compression. The sliding, splitting, and crushing behaviors are obtained from the direct and shear strain increments, while the ratio of the two strain increments elucidates the dominant roles in ductile and brittle failure modes. For the first time, the developed theory links the failure angle to Poisson’s ratio, and uniaxial strength properties, unveiling a connection between intrinsic material parameters and extrinsic ductility and brittleness induced by external loadings. The failure angle representing ductile-to-brittle transition under the applied stresses in the principal stress coordinates is shown to be directly related to the golden ratio and independent of loading types. This research addresses longstanding mysteries by providing a deeper understanding of the physics of solids and suggesting potential applications with a phase-field model for predicting the evolving fracture direction.
破坏面,通常称为破坏角,定义了材料内部达到其承载能力的特定平面方向,用材料强度表示。分析这一关键表面是材料表征的基本要素,提供了对延展性和脆性的深刻见解。尽管从各种标准中确定破坏面所采用的方法多种多样,但在广泛的各向同性材料中系统地控制这一特性的普遍接受的理论仍然难以捉摸。因此,本文旨在通过考虑三个关键材料本构模型:弹性、破坏和塑性的收敛性,建立一个统一的框架来预测所有均质各向同性固体的破坏面。采用通用的基于能量的破坏准则来确定基本加载场景下的破坏角度,包括单轴拉伸、单轴压缩、纯剪切和双轴拉压缩。直接应变增量和剪切应变增量分别获得了岩石的滑动、劈裂和破碎行为,而两种应变增量的比值说明了在韧性破坏模式和脆性破坏模式中起主导作用。该理论首次将破坏角与泊松比和单轴强度特性联系起来,揭示了材料的内在参数与外部载荷引起的外在延性和脆性之间的联系。在主应力坐标下,表示韧性-脆性转变的破坏角与黄金比例直接相关,与加载类型无关。该研究通过提供对固体物理的更深入理解,并提出了相场模型预测裂缝方向演变的潜在应用,解决了长期存在的谜团。
A response surface function method to characterize residual stress and cumulative plastic strain through indentation
Hui Chen, Pascale Kanoute, Manuel François
doi:10.1016/j.ijsolstr.2024.113176
一种表征压痕残余应力和累积塑性应变的响应面函数法
Shot peening is a mechanical surface treatment used to improve the material fatigue performance by introducing compressive residual stress and work hardening. In order to characterize the residual stress (RS) and cumulative plastic strain (PS) of the treated surface simultaneously using the instrumented indentation technique, a Response Surface Function method is proposed in this work using a calibration by finite element simulations. The method is first verified numerically, and the results indicate that the determined values can accurately represent the input values, which shows the possibility of experimental application. The proposed method is then applied experimentally on a nickel-based alloy, Inconel 625. For validation, the solved profiles are compared with the profiles measured by X-ray diffraction (XRD). Although there is a difference between the profiles obtained by these two measurement techniques, the proposed method makes an advance on the characterization of residual stress and cumulative plastic strain simultaneously. It has demonstrated its feasibility, indicating its potential for practical application.
喷丸强化是一种机械表面处理,通过引入压缩残余应力和加工硬化来改善材料的疲劳性能。为了利用仪器压痕技术同时表征处理表面的残余应力(RS)和累积塑性应变(PS),本文提出了一种响应面函数法,采用有限元模拟校准。首先对该方法进行了数值验证,结果表明,所确定的数值能够准确地表示输入值,显示了实验应用的可能性。然后将该方法应用于镍基合金Inconel 625的实验中。为了验证,将解出的轮廓与x射线衍射(XRD)测量的轮廓进行了比较。虽然这两种测量方法得到的剖面存在差异,但所提出的方法在同时表征残余应力和累积塑性应变方面取得了进步。实验证明了该方法的可行性,表明了其实际应用的潜力。
Phase field fracture in elastoplastic solids: a stress-state, strain-rate, and orientation dependent model in explicit dynamics and its applications to additively manufactured metals
Cunyi Li, Jian Liu, Le Dong, Chi Wu, Grant Steven, Qing Li, Jianguang Fang
doi:10.1016/j.jmps.2024.105978
弹塑性固体的相场断裂:显式动力学中的应力状态、应变速率和取向依赖模型及其在增材制造金属中的应用
Phase field models have gained growing popularity in analysing fracture behaviour of materials. However, few have been explored to simulate dynamic ductile fracture to date. This study aims to develop a phase field framework considering strain rate, stress state, and orientation dependent ductile fracture under dynamic loading. Firstly, governing equations of displacement and phase fields are formulated in an explicit finite element framework. Secondly, constitutive relations are established with a hypoelastic-plasticity framework, encompassing the influence of material orientation and strain rate on both plasticity and fracture initiation. Stress states dependent fracture initiation is also considered. Thirdly, finite element implementation and corotational formulation for constitutive equations are derived. To validate the proposed model, finally, additively manufactured samples, involving material-level and crack propagation specimens are tested under dynamic loading conditions. Overall, the proposed phase field model can properly reproduce the experimental force-displacement curves and crack paths. Uniaxial tension tests reveal that a higher strain rate can lead to a higher hardening curve and lower ductility. Other material specimens further demonstrate the capability to predict stress state and orientation dependent dynamic fracture. To simulate dynamic crack paths accurately, it is necessary to consider anisotropic fracture initiation. Lastly, the phase field model was applied for the first time to predict the dynamic response of triply periodic minimal surface (TPMS) structures. Dynamic crack patterns were effectively captured, and the fracture mechanisms were thoroughly analysed. This study provides an explicit phase field framework for dynamic ductile fracture, with applications to additively manufactured materials and structures.
相场模型在分析材料断裂行为方面得到了越来越广泛的应用。然而,迄今为止,模拟动态韧性断裂的方法还很少。本研究旨在建立考虑应变速率、应力状态和取向依赖的动态加载韧性断裂相场框架。首先,在显式有限元框架中建立了位移场和相场的控制方程。其次,在低弹塑性框架下建立本构关系,考虑材料取向和应变速率对塑性和断裂起裂的影响;还考虑了应力状态相关的破裂起裂。第三,推导了本构方程的有限元实现和坐标表达式。为了验证该模型的有效性,最后在动加载条件下对增材制造的材料级和裂纹扩展试件进行了试验。总体而言,所提出的相场模型能够较好地再现试验力-位移曲线和裂纹路径。单轴拉伸试验表明,较高的应变率会导致较高的硬化曲线和较低的塑性。其他材料样品进一步证明了预测应力状态和取向依赖的动态断裂的能力。为了准确地模拟动态裂纹路径,必须考虑各向异性起裂。最后,首次将相场模型应用于三周期最小表面(TPMS)结构的动态响应预测。有效捕获了动态裂纹模式,并对断裂机理进行了深入分析。该研究为动态韧性断裂提供了明确的相场框架,并应用于增材制造材料和结构。
A visco-hyperelastic constitutive model of hydrogel considering the coupling effect between segment motion and interchain slippage
Xinyu Liu, Qingsheng Yang, Xia Liu, Ran Tao, Wei Rao
doi:10.1016/j.jmps.2024.105996
考虑节段运动和链间滑移耦合效应的水凝胶粘-超弹性本构模型
Segment motion induces interchain slippage, leading to a complex coupling between hyperelastic and viscoelastic behaviors in hydrogels. Traditional models, which treat these behaviors separately and introduce a coupling free energy, struggle to capture this visco-hyperelastic coupling mechanism accurately. In this work, we develop a visco-hyperelastic constitutive model incorporating viscoelastic contributions into the general hyperelastic free energy to capture the coupling mechanism. The model introduces both the end-to-end distance and the envelope radius to describe the three-dimensional chain conformation. A joint probability distribution of these two parameters is used to capture the relationship between the chain conformation and the chain distribution. We also propose a two-level macro-micro transition framework to link the evolution of end-to-end distance and envelope radius to macroscopic deformations. In the first level of such macro-micro transition, the elongation of individual chains in various directions within the network is mapped to the overall chain elongation. In the second level, both interchain slippage and total chain elongation are incorporated into the overall deformation of the polymer network. A comparison between our predicted results with our experimental data demonstrates the predictability of the new model. Finally, the modeling results show that the interchain slippage always involves two sequential stages, i.e., orientation and relative slippage; and the increasing strain rate enhances the asynchronous responses between segment motion and relative slippage due to multichain interactions, making the viscoelastic responses of hydrogel more obvious.
片段运动引起链间滑移,导致水凝胶中超弹性和粘弹性行为之间的复杂耦合。传统模型分别处理这些行为并引入耦合自由能,难以准确地捕捉这种粘-超弹性耦合机制。在这项工作中,我们建立了一个粘-超弹性本构模型,将粘弹性贡献纳入一般超弹性自由能,以捕获耦合机制。该模型引入了端到端距离和包络半径来描述三维链的构象。这两个参数的联合概率分布用于捕获链构象和链分布之间的关系。我们还提出了一个两级宏观-微观过渡框架,将端到端距离和包络半径的演变与宏观变形联系起来。在这种宏观-微观过渡的第一级,网络内各个方向上单个链的延伸率被映射为整体链的延伸率。在第二级,链间滑移和总链伸长都被纳入聚合物网络的整体变形中。将我们的预测结果与实验数据进行比较,证明了新模型的可预测性。最后,仿真结果表明:链间滑移始终包含定向滑移和相对滑移两个连续阶段;随着应变速率的增大,由于多链相互作用,段运动与相对滑移之间的非同步响应增强,使得水凝胶的粘弹性响应更加明显。
Fracture process zone and fracture energy of heterogeneous soft materials
Xiang Wu, Xiao Li, Shuo Sun, Yilin Yu, Zhengjin Wang
doi:10.1016/j.jmps.2024.105997
非均质软材料断裂过程区与断裂能
Bio-inspired heterogeneous soft materials are under rapid development due to their superior fracture and fatigue resistance. In the last few years, several kinds of fibrous soft composites in different length scales have been fabricated. However, the fracture behavior and toughening mechanism of this class of materials are still elusive. Here we develop a theoretical model for the crack tip field of fiber reinforced soft composites. The distribution of deformation around the crack tip and released elastic energy during crack propagation are obtained. The fracture process zone and fracture energy are quantified. There is a critical sample height, below which the fracture process zone size and fracture energy are size-dependent, above which they approach material-specific constants: steady-state fracture process zone size and steady-state fracture energy. A formula is derived to relate the steady-state fracture process zone size and parameters of the composite. It is found that both the steady-state fracture process zone size and the critical sample height scale with the fractocohesive length of the composite. The steady-state fracture energy of the composite can be enhanced either by enlarging the fracture process zone size through tuning fiber geometry or by increasing the work to rupture of the fiber through chemical treatment. This work reveals the toughening mechanism of heterogeneous soft materials and paves the way to design soft materials of high fracture energy, high fatigue threshold, and low hysteresis. It also provides a practical guideline for determining the sample size to measure the steady-state fracture energy of heterogeneous soft materials.
仿生非均质软材料因其优异的抗断裂和抗疲劳性能而得到迅速发展。近年来,制备了几种不同长度尺度的纤维软复合材料。然而,这类材料的断裂行为和增韧机理尚不清楚。本文建立了纤维增强软质复合材料裂纹尖端场的理论模型。得到了裂纹扩展过程中裂纹尖端周围的变形分布和释放的弹性能。对断裂过程区和断裂能进行了量化。有一个临界样品高度,在此高度以下,断裂过程区尺寸和断裂能与尺寸相关,在此高度以上,它们接近于特定于材料的常数:稳态断裂过程区尺寸和稳态断裂能。导出了复合材料稳态断裂过程区尺寸与断裂参数的关系式。结果表明,复合材料的稳态断裂过程区尺寸和临界试样高度尺度均与断裂黏合长度有关。通过调整纤维几何形状,增大断裂过程区尺寸,或通过化学处理,增大纤维的断裂功,可以提高复合材料的稳态断裂能。本研究揭示了非均质软材料的增韧机理,为设计高断裂能、高疲劳阈值、低迟滞的软材料铺平了道路。为测量非均质软质材料稳态断裂能的试样尺寸确定提供了实用的指导。
An FFT based chemo-mechanical framework with fracture: Application to mesoscopic electrode degradation
Gabriel Zarzoso, Eduardo Roque, Francisco Montero-Chacón, Javier Segurado
doi:10.1016/j.mechmat.2024.105211
基于FFT的断裂化学力学框架:介观电极降解的应用
An FFT based method is proposed to simulate chemo-mechanical problems at the microscale including fracture, specially suited to predict crack formation during the intercalation process in batteries. The method involves three fields fully coupled, concentration, deformation gradient and damage. The mechanical problem is set in a finite strain framework and solved using Fourier Galerkin for non-linear problems in finite strains. The damage is modeled with Phase Field Fracture using a stress driving force. This problem is solved in Fourier space using conjugate gradient with an ad-hoc preconditioner. The chemical problem is modeled with the second Fick’s law and physically based chemical potentials, is integrated using backward Euler and is solved by Newton–Raphson combined with a conjugate gradient solver. Buffer layers are introduced to break the periodicity and emulate Neumann boundary conditions for incoming mass flux. The framework is validated against Finite Elements the results of both methods are very close in all the cases. Finally, the framework is used to simulate the fracture of active particles of graphite during ion intercalation. The method is able to solve large problems at a reduced computational cost and reproduces the shape of the cracks observed in real particles.
提出了一种基于FFT的微尺度化学力学问题(包括断裂)模拟方法,特别适用于电池嵌入过程中裂纹形成的预测。该方法涉及三个完全耦合的场:浓度场、变形梯度场和损伤场。将力学问题设置在有限应变框架中,并采用傅里叶伽辽金法求解有限应变非线性问题。损伤模型采用应力驱动相场断裂。在傅里叶空间中,利用共轭梯度和特别预条件解决了这一问题。化学问题用第二菲克定律和基于物理的化学势建模,用后向欧拉积分,用牛顿-拉夫森结合共轭梯度求解器求解。引入缓冲层来打破周期性并模拟入射质量通量的诺伊曼边界条件。对框架进行了有限元验证,两种方法的结果在所有情况下都非常接近。最后,利用该框架模拟了石墨活性粒子在离子插入过程中的断裂。该方法能够以较低的计算成本解决大问题,并能再现真实颗粒中观察到的裂纹形状。
Effect of 0°-layers ratio on the dynamic fracture toughness of longitudinal compression failure of CFRP laminates
Zhuo Zhang, Kai Zhang, Gang Zhang, Bailin Zheng
doi:10.1016/j.tws.2024.112766
0°层数比对CFRP复合材料纵向压缩破坏动态断裂韧性的影响
The influence of layups on longitudinal compressive fracture toughness of CFRP laminates under quasi-static and high-rate loading conditions was studied in this paper. Three kind layups of laminates were compressed at speeds of 0.001 m/s, 5.7 m/s and 13.7 m/s with a universal test machine and electromagnetic Hopkinson bars. Surface displacement and strain of the specimen are recorded by digital image correlation systems and dynamic J integral was determined with the equivalent integral region method. The J-integral for longitudinal compression at crack initiation increases with an increasing proportion of the 0°-layer, attributed to enhanced interaction between fibers and the matrix. However, the fiber compressive fracture toughness exhibits negligible variation with loading rate when the proportion of the 0°-layer is small. In contrast, it decreases with increasing loading rate when the proportion is high.
研究了在准静态和高速率加载条件下,铺层对CFRP复合材料纵向压缩断裂韧性的影响。利用万能试验机和电磁霍普金森棒,分别以0.001 m/s、5.7 m/s和13.7 m/s的速度对三种层压板进行压缩。采用数字图像相关系统记录试样的表面位移和应变,采用等效积分区域法确定动态J积分。裂纹起裂时纵向压缩的j积分随着0°层比例的增加而增加,这是由于纤维与基体之间的相互作用增强。而当0°层掺量较小时,纤维的压缩断裂韧性随加载速率的变化可以忽略不计。当比例较大时,随着加载速率的增加,其减小。
Large amplitude vibration of rotating graphene reinforced titanium alloy dovetailed blades with general boundary conditions
Ming Yang Fan, Jie Chen
doi:10.1016/j.tws.2024.112801
石墨烯增强钛合金燕尾叶片在一般边界条件下的大振幅振动
Engine blades are generally installed on disks via dovetail joints, which can alleviate stress concentrations at the blade root and prevent heat transfer. As a result, the connection stiffness is strongly affected by the clearance between the blade and disk as well as the rotation speed of the blade. This paper first proposes a functionally graded graphene-reinforced titanium alloy trapezoid plate with elastic boundary conditions to investigate the large amplitude vibration of rotating dovetailed blades. The elastic boundaries are modelled by applying a series of artificial springs, and the related admissible displacement functions are constructed by orthogonal polynomials through the Gram–Schmidt process. The governing equations of the functionally graded graphene platelet reinforced composite (FG-GPLRC) trapezoid plate are derived by the first-order shear deformation theory (FSDT) and Lagrange equation. The numerical results of the large amplitude vibration of the plate are obtained by the weighted residual method combined with a direct iterative algorithm and verified through analytical solutions of the harmonic balance method. The effects of the stiffness of the constraint springs, rotation speed and structural parameters on the linear and nonlinear free vibrations of the FG-GPLRC trapezoid plate are thoroughly studied.
发动机叶片一般通过燕尾接头安装在圆盘上,这样可以缓解叶根处的应力集中,防止热传递。因此,连接刚度受到叶片与圆盘间隙以及叶片转速的强烈影响。本文首先提出了一种具有弹性边界条件的功能梯度石墨烯增强钛合金梯形板,用于研究旋转燕尾叶片的大振幅振动。采用一系列人工弹簧对弹性边界进行建模,并通过Gram-Schmidt过程用正交多项式构造相应的容许位移函数。利用一阶剪切变形理论(FSDT)和拉格朗日方程推导了功能梯度石墨烯血小板增强复合材料(FG-GPLRC)梯形板的控制方程。采用加权残差法与直接迭代法相结合的方法,得到了平板大振幅振动的数值计算结果,并通过谐波平衡法的解析解进行了验证。研究了约束弹簧刚度、转速和结构参数对FG-GPLRC梯形板线性和非线性自由振动的影响。
Analytical study on the flexural wave band gaps of arbitrary periodic stiffened plates by using beam-plate coupling theory
Xunyu Li, Yinggang Li, Yong Hu, Weilin Zhao, Junwei Bai, Xiaobin Li
doi:10.1016/j.tws.2024.112802
用梁-板耦合理论分析任意周期加筋板的弯曲带隙
In this paper, the flexural wave band gap characteristics of periodic stiffened plates are studied by using beam-plate coupling theory. A theoretical model of arbitrary periodic stiffened plate is established considering the coupling effect of Timoshenko beam and Kirchhoff plate. The flexural wave band structures of periodic stiffened plate are calculated by using plane wave expansion method and Bloch theorem. Numerical calculation and experimental tests were conducted to verify the proposed theoretical model. In addition, the parametric studies were performed to examine the effects of geometric parameters on both bandgap and vibration reduction characteristics of periodic stiffened plate. Results show that periodic stiffened plate can yield significant flexural wave band gaps and vibration isolation performance in a specific frequency range, which shows a good agreement with numerical simulation and experimental results. The geometrical parameters of stiffened plates have a significant influence on adjusting low-frequency flexural wave band gaps. These research findings offer a new technical approach for low frequency vibration and sound optimization of stiffened structures.
本文利用梁-板耦合理论研究了周期加筋板的弯曲带隙特性。考虑Timoshenko梁与Kirchhoff板的耦合效应,建立了任意周期加筋板的理论模型。采用平面波展开法和布洛赫定理计算了周期加筋板的弯曲带结构。通过数值计算和实验验证了所提出的理论模型。此外,还进行了参数化研究,考察几何参数对周期性加筋板带隙和减振特性的影响。结果表明:周期加筋板在特定频率范围内具有显著的弯曲带隙和隔振性能,与数值模拟和实验结果吻合较好;加筋板的几何参数对低频弯曲带隙的调节有显著影响。这些研究成果为加强结构的低频振动和声优化提供了新的技术途径。
Experimental and numerical investigations on the mechanical behavior of composite pre-tightened tooth connection under impact loading
Ming-Zhao Chen, Fei Li, Qi-Lin Zhao, Dong-Dong Zhang, Shu-Ting Ye, Wei-Bo Yang
doi:10.1016/j.tws.2024.112803
冲击载荷作用下复合材料预紧齿连接力学性能的实验与数值研究
The composite Pre-Tightened Tooth Connection (PTTC) is characterized by high connection efficiency and large bearing capacity, specifically designed for use in fiber-reinforced polymer (FRP)-metal protective structures that are inherently subjected to impact loads. In this study, impact tests were performed on single- and double-tooth specimens under high-velocity impact loads using the Split Hopkinson Pressure Bar (SHPB) apparatus to investigate their impact behavior. Additionally, a progressive damage model was numerically developed and validated against the experimental results to examine the failure patterns and mechanisms of the PTTC. The effects of tooth depth, tooth length, number of teeth, and impact velocity on the impact behavior were also analyzed parametrically. The results indicated that the primary failure modes of the PTTC are ductile compression-shear failure and brittle shear failure. In cases of compression-shear failure, the bearing capacity is lower than that of shear failure; however, it exhibits superior energy absorption characteristics. Therefore, it is recommended that the PTTC be designed to facilitate compression-shear failure when subjected to high-velocity impact. The length, depth, and number of teeth significantly influence the failure mode, bearing capacity, and energy absorption of the PTTC. Adequate design attention should be given to these factors for applications involving impact loads.
复合材料预紧齿连接(PTTC)具有连接效率高、承载能力大的特点,专门用于承受冲击载荷的纤维增强聚合物(FRP)-金属保护结构。在本研究中,使用分离式霍普金森压力杆(SHPB)装置对高速冲击载荷下的单齿和双齿试件进行了冲击试验,以研究它们的冲击行为。此外,还建立了一个渐进损伤模型,并与实验结果进行了验证,以检验PTTC的破坏模式和机制。参数化分析了齿深、齿长、齿数和冲击速度对冲击性能的影响。结果表明:PTTC的主要破坏模式为延性压剪破坏和脆性剪切破坏;压剪破坏时,承载力低于剪切破坏;然而,它表现出优越的能量吸收特性。因此,建议将PTTC设计为易于在高速冲击下发生压剪破坏。齿的长度、深度和数量对PTTC的失效模式、承载能力和能量吸收有显著影响。对于涉及冲击载荷的应用,在设计时应充分注意这些因素。
Achieving Broadband RCS Reduction on Curved Surfaces through Gradient Unit Design and Partition Layout Strategy
Mengzhou Chen, Liuying Wang, Gu Liu, Chaoqun Ge, Long Wang, Tonghao Liu, Dichen Li, Qingxuan Liang, Yixing Huang
doi:10.1016/j.tws.2024.112804
通过梯度单元设计和分区布局策略实现曲面宽带RCS缩减
Novel metastructure designs can efficiently manipulate electromagnetic responses. However, achieving exceptional electromagnetic manipulation capabilities in conformal states remains challenging. Herein, we proposed an innovative method that integrates gradient units with the partition layout strategy to facilitate broadband radar cross section (RCS) reduction under different curvatures. The proposed metastructure demonstrates broadband impedance matching characteristics through a gradient multi-layer design and exhibits strong adaptability to complex structures owing to the application of additive manufacturing technology. It demonstrates a remarkable -10 dB RCS reduction across a wide frequency bandwidth of 5.4–18 GHz in its planar state by integrating the micro-material composition and macro-geometry design while maintaining RCS reduction within the central angle range up to 90°. This paper presents a straightforward and innovative approach for constructing conformal metastructures, highlighting their potential applications in both military and civilian domains.
新的元结构设计可以有效地控制电磁响应。然而,在保形状态下实现特殊的电磁操纵能力仍然具有挑战性。为此,我们提出了一种将梯度单元与分区布局策略相结合的创新方法,以促进不同曲率下宽带雷达截面(RCS)的减小。该元结构通过梯度多层设计具有宽带阻抗匹配特性,并由于增材制造技术的应用而对复杂结构具有较强的适应性。通过集成微材料成分和宏观几何设计,在平面状态下,在5.4-18 GHz的宽频带上,RCS显著降低-10 dB,同时保持RCS降低在高达90°的中心角范围内。本文提出了一种简单而创新的构造保形元结构的方法,并强调了其在军事和民用领域的潜在应用。