今日更新：International Journal of Solids and Structures 1 篇，Journal of the Mechanics and Physics of Solids 1 篇，International Journal of Plasticity 2 篇，Thin-Walled Structures 7 篇
International Journal of Solids and Structures
Investigation on dynamic impact behavior of bighorn sheep’s horn
Emre Palta, Howie Fang, Qian Wang, Zheng Li
doi:10.1016/j.ijsolstr.2024.113133
大角羊角的动态碰撞特性研究
The horn of the bighorn sheep is composed of keratin-based biological material that has a tubule-lamella structure, which gives it anisotropic hardening properties under impact loading. This paper aims to investigate the energy dissipation mechanisms inherent in bighorn sheep horns by developing a numerical material model that accounts for the horn’s anisotropic features and strain-rate effects. To this end, a transversely isotropic constitutive model, which includes both anisotropic hardening and strain-rate effects, was formulated to accurately predict the mechanical behavior of bighorn sheep horns. Material characterization was conducted through uniaxial compression tests that were conducted under quasi-static and dynamic conditions. The developed constitutive model was implemented into LS-Dyna via a user-defined material subroutine and was validated against empirical data. The validated numerical model was used to investigate the horn’s mechanical responses under dynamic loading conditions. The paper focused on impact energy dissipation mechanisms, including energy absorption and transition, stress distribution, and displacement wave propagation. The insights gained from this paper are expected to significantly contribute to the development of novel artificial materials with enhanced energy absorption and impact mitigation properties.
Damage-induced energy dissipation in artificial soft tissues
W.K. Sun, B.B. Yin, K.M. Liew
doi:10.1016/j.jmps.2024.105933
人造软组织损伤引起的能量耗散
A systematic understanding of the toughening and self-healing mechanisms of artificial soft tissues is crucial for advancing their robust application in biomedical engineering. However, current models predominantly possess a phenomenological nature, often devoid of micromechanical intricacies and quantitative correlation between microstructure damage and macroscopic energy dissipation. To bridge this gap, we propose a novel energy dissipation mechanism-motivated network model that incorporates three unique physical ingredients with sound theoretical basis for the first time. These innovated features include the bond percolation-mediated network density and stiffness, the damage-induced energy dissipation and stress softening, and the entropic elasticity for the highly stretchable second network. The validity of this model was examined by implementing it within a meshfree peridynamic framework for artificial soft tissues subjected to simple tension and pure shear tests. We quantitatively correlated the dissipation with the network damage to reveal the effects of network density, the breaking stretch dispersion and the stiffness ratio. Our findings highlighted that the inhomogeneity and dispersion of materials properties play significant roles in the controllable progressive damage and dissipation, thereby offering valuable guidance for designing tougher artificial soft tissues. By reactivating the failed network, we further successfully captured the self-healing behaviors of artificial soft tissues. Our work provides an inspiring modeling framework for studying toughening mechanisms of artificial soft tissues.
Navigating the strength-ductility trade-off has been a persistent challenge in Mg alloys. Here, we address this issue through a novel multiple-direction pre-deformation at room temperature that introduces a high density of <c+a> dislocations into pure Mg via dislocation transmutation. This approach achieves a remarkable enhancement in the strength-ductility synergy, increasing the yield strength from 87.6 MPa to 156.6 MPa and improving elongation to failure from 7.7% to 17.6%. In general, introducing a high-density <c+a> dislocations in Mg alloys have been difficult due to the high CRSS at room temperature. Our findings reveal that extension twinning can act as a “dislocation converter,” transforming basal dislocations in the matrix into <c+a> dislocations within twins. Intensive basal dislocations were induced in pure Mg through pre-tension and subsequently transformed into <c+a> dislocations via extension twinning during compression. This process led to a substantial number of <c+a> dislocations and I1 stacking faults, contributing to the enhanced strength. The high density of <c+a> dislocations, combined with I1 stacking faults and a reduced c/a ratio within twins, enhances the activity of pyramidal <c+a> slip, thereby significantly improving ductility. This dislocation transmutation strategy offers a promising way for producing strength-ductility synergy in Mg alloys.
Exceptional tensile ductility and strength of a BCC structure CLAM steel with lamellar grains at 77 kelvin
Jinhua Zhou, Jing Wang, Jungang Ren, Robert O. Ritchie, Zuncheng Wang, Yuchao Wu, Zhufeng He, Xin Wang, Ying Fu, Yifu Jiang, Lin Wang, Xiaowei Yin
doi:10.1016/j.ijplas.2024.104161
具有77开尔文层状晶粒的BCC结构CLAM钢的优异拉伸延展性和强度
The low-temperature tensile brittleness of body-centered cubic (BCC) metals and alloys can seriously compromise their service applications. In this study, we prepared a BCC structured China low activation martensitic steel (CLAM) steel with lamellar grains by regulating the rolling and heat-treatment processes, successfully reversing the decreasing trend of ductility in the steel with decrease in temperature. Compared with current face-centered cubic (FCC) structural steels and high-entropy alloys, the lamellar grained CLAM steel exhibits an excellent synergy of strength and ductility at 77K, but with lower raw material costs. The superior low temperature ductility of the lamellar grained steel can be attributed to an increase in grain strength at low temperatures which promotes the propagation of layered tearing cracks; this in turn leads to a significant increase in the necking area of the steel, thereby compensating for the decrease in ductility. We conclude that our lamellar grain structures can be utilized to significantly enhance the low-temperature tensile ductility of BCC metals and alloys, thereby expanding their service range to cryogenic temperatures.
Web Shear Buckling of Steel-Concrete Composite Girders – Advanced Numerical Analysis
Mehmed Numanović, Markus Knobloch
doi:10.1016/j.tws.2024.112671
钢-混凝土组合梁腹板剪切屈曲的高级数值分析
Load-bearing capacity of plate girders, often used in design of bridges and high-rise buildings, is limited by the shear capacity of connected slender plate elements subjected to shear buckling. To quantify this, experimental investigations on five large-scale steel and steel-concrete composite plate girders loaded solely in shear, with a minimal influence of bending moments, have been conducted and evaluated. In this paper, the phenomenon of web shear buckling is investigated within the numerical analysis using the ABAQUS Software. An advanced numerical model has been developed and results validated against existing experimental findings. One of the focal points of this study represents the methodology of developing such a comprehensive numerical model, implementation of suitable analysis procedures, material models, boundary conditions, finite elements and interactions, in order to correctly replicate the observed response in the tests. In addition, case studies tackling the influence of web slenderness, aspect ratio, initial imperfections, shear connection and concrete classes on the structural-mechanical behavior of steel-concrete composite girders in shear as well as the applicability and suitability of the existing analytical model are also presented and analyzed.
Copper foam/paraffin phase change reinforced composites (CPPC) were fabricated using vacuum immersion technology to address the pressing need for phase change reinforced composite applications. Experiments were conducted to explore the influence of strain rate and relative density of the matrix material on the mechanical properties of the CPPC under both quasi-static and dynamic conditions. A 3D-Voronoi model of the CPPC was developed with randomly varying relative density, based on real porous metal foam and utilizing graphical parametric design tools. The mechanical behavior of the CPPC under impact loading was studied, focusing on deformation, energy absorption, and damage mechanisms. Comparison and analysis of stress-strain curves and deformation modes were performed using experimental and modeling data. The shear failure modes of CPPC under quasi-static compression include 'X-shaped fracture,' 'blocky spalling,' or '45° parallel fracture,' depending on the relative density of the copper foam matrix. The addition of paraffin effectively improved the energy-absorbing properties of copper foam. As the relative density of the copper foam matrix increased, the enhancement in energy absorption became more pronounced, while the improvement in modulus and yield strength decreased. The composite exhibited an 83% increase in specific energy absorption compared to copper foam alone, with the paraffin filler absorbing 69% of the total energy during impact loading. The CPPC acted as a mechanical filter through stress wave reflection and transmission attenuation. The investigation into the shock mitigation and failure mechanisms of CPPC could offer valuable insights for the design of functional composites. Furthermore, it could inspire the creation of impact-resistant and heat dissipation structures for electronic devices.
A comprehensive study of beam modal functions in the free vibration analysis of cylindrical shells: critical examination on the applicability to the clamped-free boundary condition
Ganghui Xu, Changsheng Zhu
doi:10.1016/j.tws.2024.112674
圆柱壳自由振动分析中梁模态函数的综合研究：对无夹紧边界条件适用性的关键检验
Over the past few decades, approximate methods that can provide solutions of sufficient accuracy have received considerable attention in the free vibration analysis of cylindrical shells, where a great deal of studies adopted the beam modal functions as the trial functions for the axial mode shapes of cylindrical shells. Nevertheless, most studies were restricted to the application of single term beam modal function and failed to simulate elastic boundary conditions of cylindrical shells, while the accuracy of the corresponding methods has recently sparked significant controversy, especially for cylindrical shells under the clamped-free boundary condition. This paper presents a comparative study of three forms of beam modal functions in the free vibration analysis of cylindrical shells, one of which is proposed for the first time to simulate elastic boundary conditions of cylindrical shells. A unified model is developed using the general Rayleigh-Ritz method, incorporating the breathing modes with circumferential orders being zero, and four types of commonly used thin shell theories, namely the Donnell, Reissner, Love, and Sanders theories. From both perspectives of natural frequencies and mode shapes, numerical results are validated by comparison with those existing in the literature and those calculated from the finite element method (FEM). The results not only clarify the distinction of different forms of beam modal functions used in the Rayleigh-Ritz method, but also provide explanations for the controversy raised in recent studies. Furthermore, the unified formulations can be extended to vibration analysis of various forms of shell structures, and can also be helpful to the vibration analysis of beams and plates with elastic boundary conditions.
Physics-informed radial basis networks for force finding of cable domes
Mingliang Zhu, Jin Wang, Jiamin Guo
doi:10.1016/j.tws.2024.112675
用于索穹顶受力测量的物理信息径向基网络
The stiffness of cable dome structures is entirely derived from the prestress in their cables and struts, making force-finding a critical step in their design. However, traditional force-finding methods are often complex to implement and have limited applicability. To address these challenges, this paper establishes a general force-finding framework for cable domes based on physics-informed radial basis networks (PIRBN), utilizing neural network techniques to achieve an efficient and reliable force-finding process. Additionally, a loss function is derived that incorporates the physical characteristics of cable domes from the perspective of structural stiffness. Case studies on three types of cable domes were conducted, and the hyperparameter tuning of the network model was simplified using the Optuna hyperparameter optimization method. The results show that PIRBN is suitable for force-finding analysis in both single and multiple prestress mode cable domes, considering the effects of external loads, and provides high computational efficiency and broad applicability.
Self-healing effect on the impact-resistance of hybrid stitch toughening CFRP composites: Experimental and numerical study
Zhenzhen Zhang, Yutong Liu, Ying Tie, Yuliang Hou, Cheng Li
doi:10.1016/j.tws.2024.112635
复合缝增韧CFRP复合材料抗冲击性能的自愈效应：实验与数值研究
The self-healing effect on the impact-resistance has been investigated for hybrid stitch toughening CFRP composites using multiscale modeling. The stitches made of the healing agent, poly ethylene-co-methacrylic acid (EMAA), facilitate the repair of delamination damages via a self-healing process. The other stitches, fabricated from carbon fiber, contribute to the enhancement of interlaminar toughness. Considering the local structural features adjacent to the stitches, an equivalent fiber-embedded laminate (EFEL) cell is established to characterize the mesoscale behavior. A modified constitutive model is developed to accurately describe the deformation modes of the EFEL cell. Subsequently, a macroscale model is constructed by directly extending the EFEL cells. The self-healing of the impact-resistance is numerically explored through multiple low-velocity impact (LVI) tests. The proposed modeling approach enables a prediction error less than 8.4% and the computation time of approximately 17.3 h (1036 min), demonstrating the high accuracy and efficiency. After the self-healing process, the peak impact forces of the LVI specimens increase, while decreases in absorbed energy are observed. Moreover, the healed specimens exhibit fewer damaged elements and a smoother damaged surface compared with the unhealed ones. It demonstrates that the EMAA healing agent possesses the capability to improve the impact-resistance of hybrid stitch toughening CFRP composites.
采用多尺度模型研究了复合针状增韧CFRP复合材料的自愈效应。由愈合剂——聚乙烯-甲基丙烯酸（EMAA）制成的缝线，通过自愈过程促进分层损伤的修复。其他缝线由碳纤维制成，有助于增强层间韧性。考虑到缝线附近的局部结构特征，建立了等效的纤维嵌入层压（EFEL）单元来表征缝线的中尺度行为。提出了一种修正的本构模型，以准确地描述电光放电单元的变形模式。然后，通过直接扩展EFEL单元，构建了宏观尺度模型。通过多次低速冲击（LVI）试验，数值探讨了抗冲击的自愈性。该建模方法预测误差小于8.4%，计算时间约为17.3 h (1036 min)，具有较高的精度和效率。自愈过程后，LVI试样的峰值冲击力增大，而吸收能量减小。与未愈合的试件相比，愈合后试件的损伤元素较少，损伤表面更光滑。结果表明，EMAA愈合剂具有提高复合针状增韧CFRP复合材料抗冲击性能的能力。
Shear performance prediction for corrugated steel web girders based on machine-learning algorithms
Yong Liu, Wei Ji, Jieqi Li, ShiBo Liu, Wenjuan Yang
doi:10.1016/j.tws.2024.112668
基于机器学习算法的波纹钢腹板梁抗剪性能预测
This study aimed to predict the shear strength of corrugated steel web girders (CSWGs) by developing a new method based on four machine-learning (ML) algorithms, namely the support vector machine, artificial neural network, random forest, and XGBoost. Based on the acquired experimental and numerical data, a database containing 552 samples was constructed to train and test the ML models. A five-fold cross-validation approach was adopted during training to prevent model overfitting. A RandomizedSearchCV was used to optimize the hyperparameters of each model. The performance of the trained models was evaluated using four performance metrics, and the results revealed that the coefficients of determination (R2) of all ML models exceeded 0.97 when used on both training and validation sets, demonstrating the excellent performance of the ML models in predicting the shear strength of CSWGs. Additionally, the implemented ML models outperformed existing design codes and empirical formulae. The XGBoost model yielded the best prediction results with an R2 of 0.999, mean absolute error of 44.98 kN, root-mean-square error of 66.67 kN, and mean absolute percentage error of 2.1 %. By using the Shapley additive explanation to derive a visual, quantitative explanation of the XGBoost model, the yield strength, web thickness, and web height were identified as the most critical factors affecting the shear strength of CSWGs, and their average absolute Shapley values accounted for approximately 91.45 % of the total value. The ML models implemented in this study provide a promising new approach for pre-designing and verifying the stability of CSWGs.
Weak form quadrature shell elements based on absolute nodal coordinate formulation
Zixuan He, Huayi Li, Hongzhi Zhong
doi:10.1016/j.tws.2024.112670
基于绝对节点坐标公式的弱形式正交壳单元
Weak form quadrature elements for moderately thick shells with arbitrary initial configurations are developed under the framework of continuum mechanics and the absolute nodal coordinate formulation (ANCF). Locking problems of shell analysis are discussed. Nonlinear analysis of various shell structures is conducted. The joint constraint equations for shells with discontinuous slopes are established. Five examples encompassing static and dynamic shell analysis, post-buckling analysis of shells, as well as analysis of shells with discontinuous mid-surface slopes are examined to assess the performance of the proposed elements. Satisfactory results are obtained, validating the efficacy of the proposed elements.
