今日更新:International Journal of Solids and Structures 4 篇,Journal of the Mechanics and Physics of Solids 4 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 8 篇
International Journal of Solids and Structures
Propagation mechanism of low-frequency elastic waves and vibrations in a new tetragonal hybrid metamaterial
Yang Hong-yun, Cheng Shu-liang, Li Xiao-feng, Yan Qun, Wang Bin, Xin Ya-jun, Sun Yong-tao, Ding Qian, Yan Hao, Zhao Qing-xin
doi:10.1016/j.ijsolstr.2023.112536
新型四方混合超材料中低频弹性波和振动的传播机理
In order to achieve low-frequency vibration and noise reduction, artificial metamaterial with great potential in this field have been widely found. Based on previous studies, a new tetragonal hybrid metamaterial structure is proposed in this paper. It is exciting that the combination of inclusions with different material properties and sizes can affect the generation of band gaps. Then, based on the selected frequency, the propagation characteristics of waves in the structure were qualitatively analyzed using group velocity and phase velocity, and the potential for vibration reduction and noise reduction of the proposed structure was verified through finite element simulation of vibration in finite period structures. The results show that the proposed structure can open multiple broadband gaps, and the frequency range of the band gap can be flexibly adjusted according to needs. This study provides a new way for the design of low-frequency phononic metamaterial systems.
A graph-based probabilistic geometric deep learning framework with online enforcement of physical constraints to predict the criticality of defects in porous materials
Krokos Vasilis, Bordas Stéphane P.A., Kerfriden Pierre
doi:10.1016/j.ijsolstr.2023.112545
基于图的概率几何深度学习框架,在线执行物理约束,预测多孔材料缺陷的临界度
Stress prediction in porous materials and structures is challenging due to the high computational cost associated with direct numerical simulations. Convolutional Neural Network (CNN) based architectures have recently been proposed as surrogates to approximate and extrapolate the solution of such multiscale simulations. These methodologies are usually limited to 2D problems due to the high computational cost of 3D voxel based CNNs. We propose a novel geometric learning approach based on a Graph Neural Network (GNN) that efficiently deals with three-dimensional problems by performing convolutions over 2D surfaces only. Following our previous developments using pixel-based CNN, we train the GNN to automatically add local fine-scale stress corrections to an inexpensively computed coarse stress prediction in the porous structure of interest. Our method is Bayesian and generates densities of stress fields, from which credible intervals may be extracted. As a second scientific contribution, we propose to improve the extrapolation ability of our network by deploying a strategy of online physics-based corrections. Specifically, we condition the posterior predictions of our probabilistic predictions to satisfy partial equilibrium at the microscale, at the inference stage. This is done using an Ensemble Kalman algorithm, to ensure tractability of the Bayesian conditioning operation. We show that this innovative methodology allows us to alleviate the effect of undesirable biases observed in the outputs of the uncorrected GNN, and improves the accuracy of the predictions in general.
Experimental and FEM investigation of bending behaviors of S-core sandwich panel composites
Öztemiz Hasan Murat, Temiz Şemsettin
doi:10.1016/j.ijsolstr.2023.112546
S 型芯夹芯板复合材料弯曲行为的实验和有限元研究
Sandwich panel composites have numerous applications in material technology. The sandwich panel composite structure’s mechanical behavior and performance are determined by the material properties and geometry of the relevant components. The top and bottom sheets of the designed sandwich panel composite material are made of stainless steel-316, the core material is aluminum 1050A-0, and the binding element is DP-8405 acrylic adhesive. Three-point bending tests and finite element models were utilized to investigate the bending behavior of S-core composite sandwich panels. Finite element models have been developed to characterize the effect of composite element bending behavior on variations. The specific flexural modulus and strength of composite S-core sandwich structures can be compared to core structures in the literature in general. As a consequence, the minimum weight design was used as a guideline to produce weight and density-efficient hybrid composite sandwich panels. The load-carrying capacity of the composite panel increased as the wall thickness of the S-shaped core increased when the damage loads were examined in the variations. It has been ascertained that as the core height increases, the load-carrying capacity of the composite panel decreases.
夹芯板复合材料在材料技术领域应用广泛。夹芯板复合材料结构的机械行为和性能由相关部件的材料特性和几何形状决定。所设计的夹芯板复合材料的顶板和底板由不锈钢-316 制成,芯材为铝 1050A-0,粘合元件为 DP-8405 丙烯酸粘合剂。利用三点弯曲试验和有限元模型研究了 S 型芯复合夹芯板的弯曲行为。开发的有限元模型用于描述复合材料弯曲行为对变化的影响。复合 S 型芯材夹层结构的特定弯曲模量和强度可与一般文献中的芯材结构进行比较。因此,最小重量设计被用作生产重量和密度效率高的混合复合夹层板的指导原则。在对破坏载荷的变化进行研究时,复合材料板的承载能力随着 S 形夹芯壁厚的增加而增加。可以确定的是,随着夹芯高度的增加,复合板的承载能力会降低。
Facilitating polymer property prediction with machine learning and Group Interaction Modelling methods
Kazemi-Khasragh Elaheh, Fernández Blázquez Juan P., Garoz David, González Carlos, Haranczyk Maciej
doi:10.1016/j.ijsolstr.2023.112547
利用机器学习和群体相互作用建模方法促进聚合物性能预测
Identification of a suitable polymer material for a given applications requires information about the properties and behavior of the material, which is time-consuming and costly to measure experimentally. In this study, we explore two computational alternatives; namely, Group Interaction Modelling (GIM) and Machine Learning (ML) approaches, as two avenues for predicting six different thermal and mechanical properties of polymers. Random Forest (RF) was employed as ML algorithm. Molecular descriptors for ML and physical input parameters for GIM method were obtained directly from the chemical structure information of polymers. The ML models developed in this study exhibited strong predictive performance, achieving R2 values ranging from 0.83 to 0.955 across the evaluated properties. The accuracy of the ML and GIM method has been compared with each other, and the evaluation is demonstrated that ML approach offers more reliable predictions over the GIM method. Furthermore, we found that the accuracy of the GIM predictions was highly dependent on the accuracy of the Debye temperature values used as an input parameter, particularly for predicting the glass transition temperature. Therefore, for better prediction in GIM procedure, it is essential to use accurate techniques to find the Debye temperature values.
为特定应用确定合适的聚合物材料需要了解材料的特性和行为,而实验测量耗时且成本高昂。在本研究中,我们探索了两种计算方法,即群体交互建模(GIM)和机器学习(ML)方法,作为预测聚合物六种不同热性能和机械性能的两种途径。随机森林(RF)被用作 ML 算法。ML 方法的分子描述符和 GIM 方法的物理输入参数直接从聚合物的化学结构信息中获取。本研究中开发的 ML 模型表现出很强的预测性能,在所评估的各种特性中,R2 值从 0.83 到 0.955 不等。我们比较了 ML 方法和 GIM 方法的准确性,结果表明 ML 方法比 GIM 方法提供了更可靠的预测。此外,我们还发现 GIM 预测的准确性在很大程度上取决于作为输入参数的德拜温度值的准确性,尤其是在预测玻璃化转变温度时。因此,要在 GIM 程序中进行更好的预测,必须使用精确的技术来找到德拜温度值。
Journal of the Mechanics and Physics of Solids
Non-Hermitian wave dynamics of odd plates: Microstructure design and theoretical modelling
Wang Yanzheng, Wu Qian, Tian Yiran, Huang Guoliang
doi:10.1016/j.jmps.2023.105462
奇数板的非赫米梯波动力学:微结构设计和理论建模
The concept of odd elasticity was recently introduced to characterize the elastic behavior of solids that consist of active components, exhibiting an asymmetric elastic modulus tensor. In this paper, we propose, for the first time, the microstructure design of an odd plate, which is composed of a lattice plate with a piezoelectric-patch-based sensor-actuator feed-forward system. By leveraging the nonreciprocal coupling between shear forces and bending curvatures, the odd plate constitutive relation is formulated in the low frequency region, which features as four asymmetric coupling parameters known as “odd parameters”. We reveal that the two-dimensional (2D) odd plates can perform directional wave energy amplification and the amplification angle can be determined analytically through the rotation of coordinate system. We also numerically demonstrate the directional wave amplification phenomena that arise from the optimal combination of odd parameters. In addition, we analytically uncover the presence of Stoneley-like interfacial waves between two plates with two odd parameters in opposite signs, which is further characterized by the numerical simulation. Unlike interfacial waves between topological structures, the interfacial waves between odd plates can exist for any working frequency, enabling the design of some novel waveguides. This research on the control of flexural waves in odd plates could shed lights on 2D non-Hermitian systems in elasticity.
Topology optimization of flexoelectric metamaterials with apparent piezoelectricity
Greco F., Codony D., Mohammadi H., Fernández-Méndez S., Arias I.
doi:10.1016/j.jmps.2023.105477
具有表观压电性的柔电超材料拓扑优化
The flexoelectric effect, coupling polarization and strain gradient as well as strain and electric field gradients, is universal to dielectrics, but, as compared to piezoelectricity, it is more difficult to harness as it requires field gradients and it is a small-scale effect. This drawback can be overcome by suitably designing multiscale metamaterials made of a non-piezoelectric base material but exhibiting apparent piezoelectricity. We develop a theoretical and computational framework to perform topology optimization of the representative volume element of such metamaterials by accurately modeling the governing equations of flexoelectricity using a Cartesian B-spline method, describing geometry with a level set, and resorting to genetic algorithms for optimization. We consider a multi-objective optimization problem where area fraction competes with each one of the four fundamental piezoelectric functionalities (stress/strain sensor/actuator). We computationally obtain Pareto fronts, and discuss the different geometries depending on the apparent piezoelectric coefficient being optimized. Our results show that optimal material architectures strongly depend on the specific functional property being optimized, and that, except for stress actuators, optimal structures are low-area-fraction lattices. In general, we find competitive estimations of apparent piezoelectricity as compared to reference materials such as quartz and PZT ceramics. This opens the possibility to design devices for sensing, actuation and energy harvesting from a much wider, cheaper and effective class of materials.
Mechanics and topology of twisted hyperelastic filaments under prescribed elongations: Experiment, theory, and simulation
Liu Lei, Liu Hao, He Yuming, Liu Dabiao
doi:10.1016/j.jmps.2023.105478
规定伸长率下扭曲超弹性细丝的力学和拓扑学:实验、理论和模拟
Soft filaments can be stretched, bent, and twisted, exhibiting complex configurations. When a filament undergoes large torsional deformation, it can display instabilities, and its post-buckling behavior and configuration evolution differs significantly from that observed under small deformation. We study the mechanics and topologically complex morphologies of twisted rubber filaments under prescribed elongation by combining experiment and finite strain theory. Based on the Mooney-Rivlin model, a finite strain theory of the hyperelastic filament under combined tension, bending, and torsion has been established, accounting for both geometrical and material nonlinearities. An experimental and theoretical morphological phase diagram is constructed as a function of the twist density and the initial elongation. The buckling and post-buckling behaviors of the twisted rubber filaments under prescribed elongation are well captured by the theory that considers geometrical nonlinearity and self-contact. By tracking the interconversion of link, twist, and writhe, we accurately determine the configuration and the critical points of phase transitions. The theoretical predictions agree closely with the measurements. This work sheds light on understanding the morphological complexity of the loaded hyperelastic rod.
Asymptotically matched extrapolation of fishnet failure probability to continuum scale
Xu Houlin, Vievering Joshua, Nguyen Hoang T., Zhang Yupeng, Le Jia-Liang, Bažant Zdeněk P.
doi:10.1016/j.jmps.2023.105479
鱼网失效概率渐近匹配外推至连续尺度
Motivated by the extraordinary strength of nacre, which exceeds the strength of its fragile constituents by an order of magnitude, the fishnet statistics became in 2017 the only analytically solvable probabilistic model of structural strength other than the weakest-link and fiber-bundle models. These two models lead, respectively, to the Weibull and Gaussian (or normal) distributions at the large-size limit, which are hardly distinguishable in the central range of failure probability. But they differ enormously at the failure probability level of 10^-6, considered as the maximum tolerable for engineering structures. Under the assumption that no more than three fishnet links fail prior to the peak load, the preceding studies led to exact solutions intermediate between Weibull and Gaussian distributions. Here massive Monte Carlo simulations are used to show that these exact solutions do not apply for fishnets with more than about 500 links. The simulations show that, as the number of links becomes larger, the likelihood of having more than three failed links up to the peak load is no longer negligible and becomes large for fishnets with thousands of links. A differential equation is derived for the probability distribution of not-too-large fishnets, characterized by the size effect, the mean and the coefficient of variation. Although the large-size asymptotic distribution is beyond the reach of the Monte Carlo simulations, it can by illuminated by approximating the large-scale fishnet as a continuum with a crack or a circular hole. For the former, instability is proven via complex variables, and for the latter via a known elasticity solution for a hole in a continuum under shear. The fact that rows or enclaves of link failures acting as cracks or holes can form in the large-scale continuum at many random locations necessarily leads to the Weibull distribution of the large fishnet, given that these cracks or holes become unstable as soon they reach a certain critical size. The Weibull modulus of this continuum is estimated to be about the triple of that for the central range of small fishnets. The new model is expected to allow spin-offs for printed materials with octet architecture maximizing the strength–weight ratio.
A shear-lag model for laminated beams with extreme modulus mismatch between layers
Wang Zheliang, Sheng Hao, Lin Xinyi, Rao Yifan, Liu Jia, Lu Nanshu
doi:10.1016/j.mechmat.2023.104844
层间模量极度不匹配的层压梁剪力滞后模型
Multilayer laminated beams, comprised of alternating stiff and soft layers, are widely used in flexible electronics and photonics. These structures exhibit complex mechanical behaviors that deviate from the Euler–Bernoulli beam theory under conditions of extreme inter-layer modulus mismatch. Extending beyond prior studies on trilayer beams, we present an analytical framework for laminated beams with arbitrary number of layers subjected to various bending conditions, and validate our theory with finite element analysis. We define an equivalent flexural rigidity, exploring its dependence on position and deformation, and systematically examine the impact of the number of layers, applied deformation, layer properties, and the layer aspect ratio.
Investigations on austenite stability and martensitic transformation kinetics of a medium Mn steel under different strain states
Zou Yuming, Gao Qihan, Ding Hua, Zhang Yu, Tang Zhengyou
doi:10.1016/j.ijplas.2023.103788
不同应变状态下中锰钢的奥氏体稳定性和马氏体转变动力学研究
Martensitic transformation has received wide attention due to its significant role in improving mechanical properties of medium Mn steels. In this paper, three typical strain states in sheet metal forming, uniaxial tension, biaxial tension and plane strain states, were selected to investigate the effect of the strain state on martensitic transformation of a medium Mn steel at room temperature. The experimental results show that the austenite stability of the medium Mn steel is seriously strain state dependent. The sample deformed under the plane strain state exhibits the lowest austenite stability, while it progressively increases for biaxial tension and uniaxial tension states. The microstructural evolution and the strain partitioning behavior of the material are characterized. It is indicated that the strains in austenite under different deformation modes are quite different even though the overall deformation conditions are similar, which leads to different transformation rates of γ → α’ transformation. Besides, the ε-martensitic transformation that only generates under the plane strain state further decreases the austenite stability. A strain state dependent α’-martensitic transformation kinetics law is proposed that incorporates the effect of the stress triaxiality and Lode angle parameter, which provides a reasonable prediction of γ → α’ transformation in the medium Mn steel over a wide range of strain states.
Experimental Investigation on Seismic Performance of Cold-Formed Steel Strap-Braced Stud Walls Under Lateral Cyclic and Vertical Loading
Rad Pouya Lotfi, Clifton Charles, Lim James, Hajirasouliha Iman
doi:10.1016/j.tws.2023.111312
冷弯钢带支撑龙骨墙在侧向循环和垂直荷载作用下的抗震性能实验研究
Cold-formed steel (CFS) construction offers several benefits over traditional construction, including being lightweight, sustainable, recyclable, quick to build, insect and rot-resistant, and suitable for computer-aided design and manufacture. Despite extensive research on CFS elements, there are still gaps in our understanding of the behaviour of CFS structural systems, particularly their response to severe earthquake events. This experimental program aims to provide a better understanding on the seismic behaviour of strap-braced stud-walls as a lateral force resisting system for residential medium-rise buildings. An innovative test rig is developed that is capable of applying a constant vertical load during lateral cyclic testing, replicating the loading conditions expected during an earthquake event in such cases. For the first time, seven full-scale tests are conducted on CFS walls under vertical and horizontal loading using standard sections in New Zealand. The vertical capacity, lateral stiffness, ultimate strength, ductility, and failure mechanisms of the specimens are investigated. Subsequently, a modified detailing is suggested, which allows CFS walls to exhibit considerably better seismic behaviour compared to the systems with conventional detailing. It is shown that by adopting the modified detailing, CFS walls exhibit an ideal elastic-plastic curve with negligible degradation in successive cycles and a high ductility factor exceeding 5. The results of this study should prove useful for more efficient design of CFS strap-braced stud walls for mid-rise buildings.
Forming characteristics of thin-walled tubes manufactured by free bending process-based nontangential rotation bending die
Hu Shenghan, Cheng Cheng, El-Aty Ali Abd, Zheng Shuo, Wu Cong, Luo Haoran, Guo Xunzhong, Tao Jie
doi:10.1016/j.tws.2023.111313
基于自由弯曲工艺的非切线旋转弯曲模具制造的薄壁管的成型特性
The free-bending process of a metal tube involves a geometric relationship between the eccentricity, the rotation angle of the bending die, the deformation zone length, and the bending radius. Ideally, during the forming process, the contact position between the bending die, and the outer bend of the tube remains tangent. However, due to factors such as the clearance of the bending die and material properties, the rotation angle can be adjusted within a specific range while still ensuring smooth tube formation. The tangential state is disrupted when the rotation angle changes, resulting in overbending or underbending. Thus, in this study, a new theoretical analysis of the free bending process, accounting for clearance, was developed to analyse the material flow and changes in the bending radius during the nontangential contact between the bending die and the tube. In addition, the reasons for achieving smooth tube bending even after adjusting the rotation angle were explained, and the deformation mechanism of the tube under the combined effects of additional tangential force from the bending die and axial propulsive force was analysed. Furthermore, the impact of the rotation angle on the bending radius and the displacement of the strain neutral layer (strain NL) was determined. Afterwards, finite element (FE) modeling and forming experiments were conducted to verify the proposed theoretical analysis under different deformation zone lengths and eccentricities conditions. Besides, the distribution of the inner and outer wall thicknesses of the tube under the nontangential rotation of the bending die was further analysed. The simulation and experimental results fit well with that obtained from theoretical analysis.
Experimental and numerical investigation on cold-formed steel zed section beams with complex edge stiffeners
Li Qiu-Yun, Young Ben
doi:10.1016/j.tws.2023.111315
带复杂边缘加劲件的冷弯型钢 zed 截面梁的实验和数值研究
This paper describes the experimental and numerical investigation on the flexural performance of cold-formed steel (CFS) zed section members bent about the neutral axis parallel to the flanges. In the test program, twelve pairs of zed section specimens fabricated from steel sheets of grades G450, G500 and G550 were loaded under four-point bending. Three series of sectional shapes, namely the zed sections with plain flanges as well as complex edge stiffeners consisting of double-fold inward and outward return lips, were devised for the test specimens. In the numerical investigation, the finite element model of four-point bending members, which was developed using ABAQUS and calibrated against the experimental results, was adopted to predict the behaviour of CFS unstiffened and edge-stiffened zed section beams over wide ranges of flange-to-web width ratio, lip-to-flange width ratio, return lip-to-lip width ratio and cross-sectional compactness. Furthermore, underpinned by the bending capacities acquired from the 12 experiments and 222 FE analyses in this study as well as 22 tests available in the literature, it was demonstrated that the current direct strength method (DSM) codified in the AISI S100 generally provided conservative flexural strength predictions for the unstiffened zed section members, while led to overall slightly unconservative design for the edge-stiffened zed section beams. In addition, based upon the DSM-based approaches that were addressed in the previous studies to account for the effect of local-distortional interaction, the nominal flexural strengths of the CFS zed section members with simple and complex edge stiffeners were found to be underestimated by 17% to 21% on average. Accordingly, the modified DSM formulae were recommended in this study for the CFS unstiffened and edge-stiffened zed section beams bent about the neutral axis parallel to the flanges.
In this paper, an analytical method is proposed for the analysis of the effects of the strain gradients on the frequency band structures and band-gaps of the elastic waves propagating in one-dimensional (1D) nano-sized phononic crystals (PCs). The considered 1D nano-sized PCs are made of periodic unit-cells containing a metal section and an epoxy section. The strain gradients are taken into account to obtain the governing equations by using the strain energy, the kinetic energy and the Hamilton's principle. An analytical solution based on the transfer matrix method is derived to compute the frequency dispersion curves or band structures of the elastic waves. The continuity conditions on the interface between the neighboring sections and the periodic boundary conditions for the unit-cell are satisfied using the proposed analytical method. Two band-gap characteristics, namely the starting frequency and the width of each band-gap, are defined and investigated. The effects of the small-scale parameters in the strain-gradient theory on the band structures and the band-gap characteristics are analyzed and discussed in detail. It is demonstrated that the strain gradients may significantly influence the frequency band structures and the band-gap characteristics of the elastic waves propagating in 1D nano-sized PCs.
本文提出了一种分析方法,用于分析应变梯度对在一维(1D)纳米声子晶体(PC)中传播的弹性波的频带结构和带隙的影响。所考虑的一维纳米级声波晶体由包含金属部分和环氧树脂部分的周期性单元单元组成。考虑到应变梯度,利用应变能、动能和汉密尔顿原理获得了控制方程。基于传递矩阵法得出的解析解可以计算出弹性波的频散曲线或频带结构。利用所提出的分析方法,可以满足相邻部分之间界面的连续性条件和单元单元的周期性边界条件。定义并研究了两个带隙特征,即起始频率和每个带隙的宽度。详细分析和讨论了应变梯度理论中的小尺度参数对带状结构和带隙特性的影响。结果表明,应变梯度会显著影响在一维纳米 PC 中传播的弹性波的频带结构和带隙特性。
Fatigue resistance of rib-to-bimetallic steel deck welded joints in orthotropic steel bridge decks
Liao Xiaowei, Wei Hanlin, Pan Hongyang, Li Hai-Ting, Sun Bo, Xin Haohui
doi:10.1016/j.tws.2023.111318
正交异性钢桥面中肋条与双金属钢桥面焊接接头的抗疲劳性能
The stainless-cladding techniques have been applied in the top plate of the orthotropic steel decks in the high-speed railway steel bridges to improve the corrosion and wear resistance. The rib-to-deck (RD) welded joint with the stainless-clad bimetallic steel deck plate becomes a new critical fatigue detail. This study firstly examines the fatigue performance of this full-scale new RD joint through six high-cycle constant-amplitude fatigue tests and two beach-mark tests under eccentric over-rib loading. The structural hot-spot stress at the weld toe on the deck plate is obtained by strain gauges and the linear extrapolation method for each RD specimen before the cyclic loading. Experimental results indicate that five RD specimens suffer from the toe-deck failure modes, while the rests encounter root-deck cracking. The fatigue strength of these new RD joints satisfies the FAT100 hot-spot stress S-N curve based on the IIW design recommendation. Numerical simulation is further conducted to investigate the effect of different cracking modes and welding technologies on the fatigue crack propagation behavior of this new RD joint. Root-deck cracking mode shows weakly higher fatigue resistance than the toe-deck failure case. Using the double-side welds between the U-rib and deck plate, and the thickened-edge U-rib technology can slightly enhance the fatigue life in terms of toe-deck cracking mode in contrast with the traditional single-side groove welds. Experimental and numerical validation quantify the excellent fatigue performance of this new RD joint in comparison with the other types of RD welded joints.
This study investigates the plastic deformation and hardening behavior of the direct-quenched ultra-high strength steel S960MC at various temperatures ranging from room temperature to 900 ℃. In this regard, the Hollomon and Voce equations are used to model the hardening behavior of the material at different temperatures. The suitability of each equation to predict the plastic flow of S960MC is evaluated based on the best resulted fit for the material. In addition, microstructural investigations are carried out to indicate the correlations between the microstructural changes, occurring in the range of room temperature to 900 ℃, and hardening behavior and governing parameters. The Hollomon approach showed deviations from the experimental results for room to intermediate temperatures; however, the Voce equation modeled the material's strain hardening and flow behavior more successfully for the entire temperature range of room temperature–900 ℃. Additionally, there was a significant consistency between the Kocks-Mecking and Voce parameters. Dislocation interactions, dynamic strain aging, dynamic recrystallization, dynamic recovery, tempering (martensite decomposition), and austenite formation were the most influential microstructural features on the hardening behavior at various temperatures. The correlations between these microstructural features and hardening parameters were established satisfactorily for both the Hollomon and Voce approaches.
Characterization of Multiple Debris Cloud Impacts-induced Pitting Damage Evolution in Spacecraft Structures Using Temperature-dependent Ultrasonic Nonlinearity
Chi Runqiang, Gao Jiaxin, Hu Diqi, Zhang Weigui, Pang Baojun, Cao Wuxiong
doi:10.1016/j.tws.2023.111322
利用随温度变化的超声波非线性表征多次碎片云撞击诱发的航天器结构点状损伤演变
Facing the harsh cryogenic-elevated temperature condition, evaluation of the debris cloud-induced pervasive but highly complex pitting damage in manned spacecraft structures, featuring multitudinous small-scale craters and cracks disorderedly scattered over a wide region, accompanied by a diversity of micro-damages, is hitherto still a challenging task. In line with the fact that the use of ultrasonic nonlinearity is restricted by its intrinsic vulnerability to measurement contamination, in particular temperature fluctuations. With this motivation, an insight into the modulation mechanism of typical elastic parameters of material at macroscopic under varying temperatures, as well as microscopic interatomic potential, is achieved via theoretical analysis. Based on this, temperature sensitivity coefficients (TSCs) of these elastic parameters are obtained, and a nonlinear temperature sensitivity index (TSI) is established. On this basis, an active TSI-based evaluation method is proposed to improve the accuracy and reliability of pitting damage evaluation by controlling detection temperature (i.e., exploitation of the benign aspects of the temperature sensitivity of ultrasonic nonlinearity), rather than eliminating or compensating for its adverse effect, when other nonlinear sources interference. This method is experimentally corroborated, in which the multiple debris cloud impacts-induced accumulated pitting damage are accurately and intuitively characterized through temperature control, in terms of its severity and distribution characteristics, which is consistent with the theoretical prediction. These findings provide an active structural health monitoring (SHM) strategy for promoting the practical application of this proposed approach for characterizing pitting damage evolution in manned spacecraft in qualitative and semi-quantitative manners.
在严酷的低温条件下,评估载人航天器结构中由碎片云引起的普遍但高度复杂的点状损伤(其特征是在广泛区域内无序分布着许多小尺度的凹坑和裂纹,并伴有多种微损伤),迄今为止仍是一项具有挑战性的任务。由于超声波非线性本身易受测量污染,特别是温度波动的影响,因此其使用受到限制。基于这一动机,我们通过理论分析深入了解了材料在不同温度下的宏观典型弹性参数以及微观原子间势能的调制机制。在此基础上,获得了这些弹性参数的温度敏感系数(TSCs),并建立了非线性温度敏感指数(TSI)。在此基础上,提出了一种基于 TSI 的主动评估方法,当其他非线性源干扰时,通过控制检测温度(即利用超声非线性温度敏感性的良性方面),而不是消除或补偿其不利影响,来提高点蚀损伤评估的准确性和可靠性。实验证实了这种方法,通过温度控制,可以准确、直观地描述多个碎片云撞击引起的累积点蚀损伤的严重程度和分布特征,这与理论预测是一致的。这些发现提供了一种积极的结构健康监测(SHM)策略,可促进实际应用这种拟议方法,以定性和半定量的方式确定载人航天器点蚀损伤演变的特征。
Frequency veering and nonlinear coupled vibration analysis of variable stiffness composite plates with curvilinear fiber paths
Liu Xiaofeng, Sun Wei, Liu Honghao, Du Dongxu, Ma Hongwei
doi:10.1016/j.tws.2023.111323
具有曲线纤维路径的变刚度复合板的频率偏移和非线性耦合振动分析
The coupling forced vibration behaviors of a variable stiffness plate with curvilinear fiber paths at mode veering regions caused by variations of fiber angle have been rarely found in previous papers, especially in the presence of considering the complex material nonlinearity of composite materials. In this paper, the variable stiffness plate of carbon fiber reinforced composites (CFRC) with curvilinear fiber paths is taken as the research object, and the influence of curvilinear fiber paths on its natural characteristics and vibration responses are studied in detail on the basis of considering the material nonlinearity of CFRC. Firstly, it is found that the variations of curvilinear fiber paths can cause complex frequency veering behavior of the variable stiffness plate, and lead to the appearance of irregular modal shapes formed by modal interaction. Then, the forced vibration response of the variable stiffness plate in the frequency veering region is analyzed methodically, and the variation rules of the vibration response under modal interaction is obtained. After analyzing the nonlinear vibration response of the variable stiffness plate under the combined influence of modal interaction and CFRC material nonlinearity, the mechanism of complex nonlinear dynamic behavior of variable stiffness plate in frequency veering region is further investigated.