今日更新:International Journal of Solids and Structures 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 5 篇
Dynamic response and wave motion of a periodically supported beam under an ultra-high-speed load: wave dispersion and critical velocities
Tao Lu, Shuxuan Yuan, Tianyu Wang, Xiang Liu, Ping Wang, Rong Chen
doi:10.1016/j.ijsolstr.2024.112694
超高速载荷下周期支撑梁的动态响应和波浪运动:波的分散和临界速度
Vacuum tube transportation system is an attractive transportation mode due to the ultra-high-speed (over 1000 km/h) it can reach. Most vacuum tube transportation systems, e.g., the Hyperloop operate in elevated tube structure on periodical supports. When the speed of the vehicle reaches certain critical values, the periodical supporting structure experiences resonance-like response whose vibrational magnitude is significantly amplified. The amplification of the response has an adverse impact on the safety of the vehicle operation and severability of the supporting structures. This work aims to boost the fundamental understanding of the underlying physical mechanism of wave motions and critical velocities in the “moving load on periodical structure” problem utilizing an ultra-high-speed Hyperloop-type transportation system as an example. In this work, an ultra-high-speed moving load on a periodically supported beam is used to model the dynamic response of the supporting structure under an ultra-high-speed travelling vehicle. The steady-state response of the periodically supported beam is solved analytically and illustrated for sub- and trans-critical speeds. The dispersion relation is obtained while deriving the steady-state response. The relation between wave propagation in a periodical structure and critical speeds of the moving load on it is established. It is shown that the critical speeds could be within the operational speed range of ultra-high-speed transportation system. The number and magnitude of critical speeds are closely related to wave motions in the periodically supported structure. It is found that the primary critical speeds associated with largest beam responses may not exist, depending on the relative flexibility of the supports. The optimal structural parameters are associated with wave motion transition (between Local Resonance and Bragg Scattering) in the supporting structure. With this simplified model, wave motions in a periodical structure and critical speeds of the moving load on it is explained in a general physical sense. This work provides theoretical basis for the structural design and operation of the ultra-high-speed transportation system, as well as other engineering applications in which ultra-high-speed moving load is involved.
真空管道运输系统是一种极具吸引力的运输方式,因为它可以达到超高速(超过 1000 公里/小时)。大多数真空管道运输系统(如 Hyperloop)都是在周期性支撑的高架管结构中运行的。当车辆速度达到某些临界值时,周期性支撑结构会产生类似共振的响应,其振动幅度会显著放大。响应的放大会对车辆运行的安全性和支撑结构的可分割性产生不利影响。本研究以超高速 Hyperloop 型运输系统为例,旨在加深对 "周期结构上的移动载荷 "问题中波运动和临界速度的基本物理机制的理解。本研究利用周期支撑梁上的超高速移动载荷来模拟支撑结构在超高速行驶车辆作用下的动态响应。对周期支撑梁的稳态响应进行了分析求解,并对亚临界和跨临界速度进行了说明。在得出稳态响应的同时,还得到了频散关系。建立了周期结构中波的传播与其上移动载荷的临界速度之间的关系。研究表明,临界速度可能在超高速运输系统的运行速度范围内。临界速度的数量和大小与周期支撑结构中的波浪运动密切相关。研究发现,与最大梁响应相关的主要临界速度可能并不存在,这取决于支撑的相对柔性。最佳结构参数与支撑结构中的波浪运动转换(局部共振和布拉格散射之间)有关。利用这一简化模型,可以从一般物理意义上解释周期性结构中的波浪运动及其上移动载荷的临界速度。这项工作为超高速运输系统的结构设计和运行,以及其他涉及超高速移动载荷的工程应用提供了理论依据。
Assessment of hydrogen embrittlement behavior in Al-Zn-Mg alloy through multi-modal 3D image-based simulation
Hiro Fujihara, Hiroyuki Toda, Ken-ichi Ebihara, Masakazu Kobayashi, Tsuyoshi Mayama, Kyosuke Hirayama, Kazuyuki Shimizu, Akihisa Takeuchi, Masayuki Uesugi
doi:10.1016/j.ijplas.2024.103897
通过多模态三维图像模拟评估 Al-Zn-Mg 合金的氢脆行为
Hydrogen can strongly embrittle aluminum alloys by accumulating at precipitate interface and triggering transgranular cracking, due to stress-driven hydrogen diffusion towards crack tip and grain boundaries. However, although mechanical features near crack tip and grain boundaries, and hydrogen diffusion/trapping processes have been extensively studied separately, very few quantitative information regarding the local interactions between hydrogen distribution and stress fields with full spatial complexity has been revealed. The present study attempts to fill this gap, by using a multi-modal three-dimensional image-based simulation that combines a crystal plasticity finite element method with hydrogen diffusion analysis, to fully capture the actual stress distribution and its effect on hydrogen distribution, and more importantly on cracking probability, near a real propagating hydrogen-induced crack. Stress-diffusion-trapping coupled simulations indicate the intergranular crack transitioned to a quasi-cleavage crack in the region where the interfacial cohesive energy of semi-coherent interface of the MgZn2 precipitate was reduced by hydrogen accumulation near the crack tip. The multi-modal three-dimensional image-based simulation used in the present study successfully bridged nanoscopic debonding and macroscopic hydrogen embrittlement fracture behavior.
由于应力驱动的氢向裂纹尖端和晶界扩散,氢在析出界面积聚并引发跨晶粒裂纹,从而使铝合金发生强烈脆化。然而,尽管对裂纹尖端和晶界附近的力学特征以及氢扩散/捕集过程分别进行了广泛的研究,但很少有关于氢分布与应力场之间的局部相互作用的定量信息被揭示出来。本研究试图填补这一空白,采用基于多模态三维图像的模拟方法,结合晶体塑性有限元方法和氢扩散分析,全面捕捉实际应力分布及其对氢分布的影响,更重要的是对实际氢致裂纹附近的开裂概率的影响。应力-扩散-捕获耦合模拟表明,在 MgZn2 沉淀半相干界面的界面内聚能因裂纹尖端附近的氢积聚而降低的区域,晶间裂纹过渡到了准劈裂裂纹。本研究中使用的基于三维图像的多模态模拟成功地弥合了纳米脱粘和宏观氢脆断裂行为。
Quasi-static compressive response and energy absorption mechanism of all-CFRP honeycomb core using digital image correlation (DIC)
Yunfei Deng, Xiaoyu Hu, Xiaoyue Yang, Haoyun Yu, Yimei Zheng
doi:10.1016/j.tws.2024.111641
利用数字图像相关性(DIC)分析全-CFRP 蜂窝芯材的准静态压缩响应和能量吸收机制
In order to meet the urgent demand for the application of composite honeycomb sandwich structures, Carbon fiber reinforced polymer (CFRP) honeycomb cores were made by the hot press molding method. The mechanical behavior of the honeycomb cores under in-plane and out-of-plane compression loadings was explored, including deformation process, energy absorption mechanism, and damage modes. The research focused on the correlation between macroscopic response and local deformation, as well as the influence of loading direction on the deformation process. Digital image correlation (DIC) was used to obtain full-field strain evolution and distribution of plastic hinges during compressive loading. Especially, 2D-DIC was established to obtain the full-field strain distribution of the front and side of the cores during in-plane compression. The experimental results showed that progressive failure of the cores occurred under out-of-plane compression. The deformation was dominated by the bending deformation and the compressive deformation of cell walls when compressed in the W and L directions, corresponding to diagonal shear and layer-by-layer failure, respectively. In addition, the failure mechanism was identified by optical microscope and scanning electron microscope (SEM). This study provided a better understanding of the compressive response of the CFRP honeycomb structures.
为满足复合材料蜂窝夹层结构应用的迫切需求,研究人员采用热压成型法制造了碳纤维增强聚合物(CFRP)蜂窝芯材。研究探讨了蜂窝芯材在平面内和平面外压缩载荷作用下的力学行为,包括变形过程、能量吸收机制和损伤模式。研究重点是宏观响应与局部变形之间的相关性,以及加载方向对变形过程的影响。研究采用数字图像相关技术(DIC)获得了压缩加载过程中塑性铰链的全场应变演变和分布。特别是建立了二维数字图像相关技术(2D-DIC),以获得面内压缩过程中芯体正面和侧面的全场应变分布。实验结果表明,芯材在平面外压缩时发生了渐进破坏。在 W 向和 L 向压缩时,变形主要由细胞壁的弯曲变形和压缩变形引起,分别对应于对角剪切和逐层破坏。此外,还通过光学显微镜和扫描电子显微镜(SEM)确定了破坏机制。这项研究有助于更好地理解 CFRP 蜂窝结构的压缩响应。
Design and compressive behaviors of the gradient re-entrant origami honeycomb metamaterials
Nanfang Ma, Sihao Han, Qiang Han, Chunlei Li
doi:10.1016/j.tws.2024.111652
梯度重入折纸蜂巢超材料的设计和压缩行为
In recent years, origami honeycomb metamaterials have garnered extensive attention from researchers. Re-entrant origami honeycomb metamaterials exhibit excellent mechanical performances by virtue of lightweight, high-energy-absorbing characteristics and diverse configurations. In this study, the gradient re-entrant origami honeycomb metamaterials are designed by changing significant geometric parameters. To investigate the effects of geometric parameters variations on compressive behaviors, the theoretical analysis model of the re-entrant origami honeycomb is built to predict the compression stress under quasi-static compression and high-velocity crushing. Subsequently, the energy absorption of the uniform re-entrant origami honeycomb (UROH), the gradient-thickness re-entrant origami honeycombs (GTROHs) and the gradient-angle re-entrant origami honeycomb (GAROHs)are investigated under different compression velocities. The impact resistances of UROH, GTROHs and GAROHs are discussed systematically. By adjusting the gradient distribution of thickness, the deformation modes and Poisson’s ratio curves of the structure could be altered. Furthermore, under the high-velocity impact, the specific energy absorption (SEA) of the unidirectionally negative GTROH is increased by 36% than that of UROH at the strain of 0.29. The SEA of the unidirectionally positive GTROH is higher by 14.4% than that of UROH at the strain of 0.8. In addition, the unidirectionally positive GTROH exhibits better impact resistance performance than UROH by comparing the peak stress and SEA value under different compression velocities. This study is expected to provide the new route for designing advanced origami-inspired honeycomb structures and improving buffer protection devices.
近年来,折纸蜂窝超材料受到了研究人员的广泛关注。重入折纸蜂窝超材料凭借轻质、高能量吸收特性和多样化的结构表现出优异的力学性能。本研究通过改变重要的几何参数设计了梯度再入折纸蜂窝超材料。为了研究几何参数变化对压缩行为的影响,建立了再入折纸蜂窝的理论分析模型,以预测准静态压缩和高速挤压下的压缩应力。随后,研究了均匀再入角折纸蜂窝(UROH)、梯度厚度再入角折纸蜂窝(GTROHs)和梯度角度再入角折纸蜂窝(GAROHs)在不同压缩速度下的能量吸收情况。系统地讨论了UROH、GTROH 和 GAROH 的抗冲击性。通过调整厚度梯度分布,可以改变结构的变形模式和泊松比曲线。此外,在高速冲击下,应变为 0.29 时,单向负 GTROH 的比能量吸收(SEA)比 UROH 增加了 36%。在应变为 0.8 时,单向正 GTROH 的比能量吸收比 UROH 高 14.4%。此外,通过比较不同压缩速度下的峰值应力和 SEA 值,单向正 GTROH 比 UROH 表现出更好的抗冲击性能。这项研究有望为设计先进的折纸启发蜂窝结构和改进缓冲保护装置提供新的途径。
Dynamic characteristics of novel damping sandwich composite open cylindrical shell: from theory to simulation
Changsheng Zheng, Yunfa Zhou, Yaping Fan, Xiaotong Wang
doi:10.1016/j.tws.2024.111657
新型阻尼夹层复合材料开放式圆柱壳的动态特性:从理论到模拟
Based on the first-order shear deformation shell theory, the free vibration model of Multilayer Damping Sandwich Composite Open Cylindrical Shell (MDSCOCS) under different lay-up angles is established. The Navier double series and Rayleigh-Ritz method are used to solve the free vibration equation under four sided simply supported boundary conditions. The theoretical solutions are compared with the existing literature and finite element simulation results respectively to verify the validity of theoretical calculation model. The influences of the thickness, position, shell opening angle, composite lay-up angle and other factors on the natural frequency and loss factor of the structure under different number of core layers are investigated in detail. The analysis shows that the damping loss factor of the composite structure is greatly improved by the addition of multilayer damping sandwich, and the dynamic performance of the composite structure is optimized, compared with that of single-layer damping sandwich composite structure. It provides a theoretical basis for the design of multilayer damping sandwich composite open cylindrical shell.
基于一阶剪切变形壳理论,建立了多层阻尼夹层复合材料开式圆柱壳(MDSCOCS)在不同铺层角度下的自由振动模型。采用 Navier 双序列和 Rayleigh-Ritz 方法求解了四面简单支撑边界条件下的自由振动方程。分别将理论解与现有文献和有限元模拟结果进行比较,以验证理论计算模型的有效性。详细研究了不同芯层数量下,厚度、位置、壳体开口角、复合材料铺层角等因素对结构固有频率和损耗因子的影响。分析表明,与单层阻尼夹层复合结构相比,增加多层阻尼夹层后复合结构的阻尼损失因子得到了极大的改善,复合结构的动态性能得到了优化。它为多层阻尼夹层复合材料开口圆柱壳的设计提供了理论依据。
Experimental and theoretical investigations on out-of-plane buckling of circular aluminum arches with web openings under a central concentrated load
Nan-ting Yu, Zhao-han Deng, Bin Zhang, Wei-bin Yuan
doi:10.1016/j.tws.2024.111658
带腹板开口的圆形铝拱在中心集中荷载作用下的平面外屈曲实验和理论研究
Perforated arches with cellular openings are widely used as roof beams in various buildings due to the functional and appearance requirements of architecture. Perforated arches under a central concentrated load may suffer from out-of-plane buckling when the load reaches to a critical value. This paper presents the analytical solution based on the energy method to predict the critical load of perforated arches under a central concentrated load. Experimental tests and finite element analyses are also carried out for perforated circular aluminum arch specimens to validate the present analytical solution. Good agreement between the analytical, experimental, and numerical results is demonstrated. The present results show that the size of web openings and the slenderness of the arch could affect the out-of-plane buckling behavior of perforated arches significantly. The arch with larger web perforations or larger slenderness ratio has the lower critical load of out-of-plane buckling.
由于建筑功能和外观的要求,带蜂窝开口的穿孔拱被广泛用作各种建筑物的屋顶梁。在中心集中荷载作用下,当荷载达到临界值时,穿孔拱可能会发生平面外屈曲。本文提出了基于能量法的分析解决方案,以预测中心集中荷载下穿孔拱的临界荷载。本文还对穿孔圆铝拱试件进行了实验测试和有限元分析,以验证本分析解决方案。分析、实验和数值结果之间显示出良好的一致性。本研究结果表明,腹板开口尺寸和拱的细长度会对穿孔拱的平面外屈曲行为产生重大影响。腹板穿孔越大或细长率越大的拱的平面外屈曲临界载荷越小。
Beam-type acoustic black holes incorporating the microstructure-dependent nonlocal effect
Taoqi Lu, Weiguang Zheng, Rongjiang Tang, Li Li
doi:10.1016/j.tws.2024.111662
包含微结构非局部效应的束型声学黑洞
Acoustic black holes (ABHs) are effective passive damping structures for capturing bending waves at wedge edges. However, as the wedge shape continuously reduces in size, the intrinsic length scale of the ABH's tip gradually approaches the external length scale, such as the wavelength of wave, which causes a phenomenon known as the "scale effect" to take hold of the ABH. Despite gaining considerable attention in the past two decades, the influence of intrinsic length on the energy aggregation of ABHs has not been thoroughly investigated. This study aims to explore the significant contribution of microstructure-dependent nonlocal effects on the dynamic behavior of ABHs, which holds great scientific importance. The nonlocality arises from the inherent length of the material being studied. A nonlocal elastic theory (NET) is employed to model the dynamic behavior of one-dimensional ABH beams. Geometric acoustic method is proposed to analyze the power-law beam wave number and microstructure-related reflection coefficient. Results indicate a significant impact of nonlocality on the acoustic energy of beam-type ABHs, particularly when the nonlocal intrinsic length approaches the truncation length of the wedge. Moreover, a comparison between the present study and classical theory reveals an overestimation of the reflection coefficient in conventional works for small truncation lengths. The relationship between the reflection coefficient, truncation length, and nonlocal characteristic lengths is thoroughly examined. Additionally, the influence of the damping layer and different power-law exponents m on ABH behavior is extensively studied.
声学黑洞(ABH)是一种有效的被动阻尼结构,可捕捉楔形边缘的弯曲波。然而,随着楔形的不断缩小,ABH 顶端的内在长度尺度逐渐接近外部长度尺度,如波的波长,从而导致一种被称为 "尺度效应 "的现象对 ABH 产生影响。尽管在过去的二十年里,ABH 的内在长度对其能量聚集的影响受到了广泛关注,但人们尚未对其进行深入研究。本研究旨在探讨与微结构相关的非局部效应对 ABH 动态行为的重要贡献,这具有重要的科学意义。非局部性源于所研究材料的固有长度。本文采用非局部弹性理论(NET)来模拟一维 ABH 梁的动态行为。提出了几何声学方法来分析幂律梁波数和与微结构相关的反射系数。结果表明,非局部性对梁型 ABH 的声能有重大影响,特别是当非局部本征长度接近楔形截断长度时。此外,本研究与经典理论的比较显示,在截断长度较小时,传统理论高估了反射系数。我们深入研究了反射系数、截断长度和非局部特征长度之间的关系。此外,还广泛研究了阻尼层和不同幂律指数 m 对 ABH 行为的影响。