今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 5 篇
International Journal of Solids and Structures
Stability discussion and application study of pseudo-corner models
Tianyin Zhang, Xianhong Han
doi:10.1016/j.ijsolstr.2024.113136
伪角模型的稳定性讨论及应用研究
Accurate plastic flow modelling under complex working conditions is crucial for metal deformation simulations. Recently, some advanced pseudo-corner models have been developed to describe corner effects and analyze strain localization problems. The present work consists of three parts. The first part discusses the intrinsic stability of the pseudo-corner model class, which forms the premise of application analysis. The second part applies the pseudo-corner models and the associated flow rule (AFR) to buckling onset estimation, plastic post-buckling analysis and shear band analysis. The experimental conditions are strictly reproduced and the optimal model parameters are determined. The results reveal that the pseudo-corner models and AFR are indistinguishable in the buckling onset estimation. AFR overestimates the post-buckling strength of circular tubes under axial compression, and cannot reproduce the shear band development during sheet bending; while the pseudo-corner models have better prediction performance in both scenarios. The results also suggest that the parameter values of pseudo-corner models are apparently inconsistent in the above two types of problems. Then in the third part, two representative influencing factors including strain gradient plasticity and initial imperfections are discussed, and this inconsistency is finally attributed to the shortwave surface defect which however is usually neglected by previous studies.
Thermodynamic potentials for viscoelastic composites
Martín I. Idiart
doi:10.1016/j.jmps.2024.105936
粘弹性复合材料的热力学势
Explicit expressions for the free-energy and dissipation densities of viscoelastic composites at fixed temperature are proposed. The composites are comprised of an arbitrary number of distinct constituents exhibiting linear Maxwellian rheologies and distributed randomly at a length scale that is much smaller than that over which applied loads vary significantly. Central to their derivation is the recognition that any viscous deformation field can be additively decomposed into an irrotational field and a solenoidal field in such a way that variational approximations available for elastic potentials become applicative to viscoelastic potentials. The thermodynamic potentials conform to a generalized standard model with a finite number of effective internal variables with explicit physical meaning. Specific approximations of the Hashin–Shtrikman and the Self-Consistent types are worked out in detail. Under particular circumstances, these approximations may turn out exact. Macroscopic stress–strain relations and intraphase statistics of the stress field up to second order are also provided.
O-ring durability is a key issue for engineering structures that require sealing over a long service life. Rubber-like materials are used for this type of component because of the assumption of incompressibility, i.e. a high bulk modulus K . However, this assumption has been called into question in the literature, particularly for elastomers under high hydrostatic pressures. This work examines the compressibility of rubber-like materials, with a particular focus on fluorosilicone elastomers (FVMQ). A method of confined compression using a transparent crucible is presented, which allows local measurement of the displacement field. This technique provides a better understanding of the analysis of oedometric compression data and a reliable way to determine the K value. Furthermore, this approach allows following the evolution of K over time with accelerated ageing. Three ageing temperatures - 200, 220 and 250 °C - were tested up to 34, 15 and 1 weeks respectively. For the three ageing temperatures, the FVMQ results show a decrease in K values with ageing. In particular, at 250 °C, a turning point was observed after 72 h of ageing. These results highlight the influence of ageing on the compressibility of the FVMQ and the presence of two different ageing mechanisms affecting the K evolution.
Significantly enhanced mechanical properties of NiCoV medium-entropy alloy via precipitation engineering
Junyang He, Weijin Cai, Na Li, Li Wang, Zhangwei Wang, Shuai Dai, Zhifeng Lei, Zhenggang Wu, Min Song, Zhaoping Lu
doi:10.1016/j.ijplas.2024.104180
通过沉淀工程使NiCoV中熵合金的力学性能得到显著提高
Precipitation engineering is one of the most effective means to enhance the strength of an alloy, which essentially requires precipitates with certain deformability, fine size, and uniform distribution. However, for multicomponent alloy systems, the chemical complexity poses significant difficulties in applying this strengthening method due to the diversity and brittleness of the potential precipitate phases. In this work, we demonstrated the precipitation engineering in a chemically complex prototype alloy NiCoV. Specifically, formation of detrimental σ, μ and Heusler phases was avoided by reducing the V content, and a two-step short-term annealing was designed to trigger homogeneous κ nucleation while inhibiting its rapid coarsening. It is found that both grain and phase boundaries can trap V atoms, which not only pins these interfaces but also hinders the V partitioning needed for κ growth. Consequently, we achieved an ultrafine κ/γ architecture in the NiCoV0.9 alloy, which surprisingly exhibited an ultrahigh yield strength of 1.6 GPa and a total work-hardening amount of 219 MPa. Our analysis indicates that the hetero-deformation induced (HDI) stress is mainly responsible for the high strength, while the coherent nature of phase boundaries and decent deformability of κ alleviate stress concentration, giving rise to the pronounced work-hardening. Our work highlights the importance of suitable phase selection and delicate substructure tailoring in precipitation engineering, with key findings also useful for enhancing overall mechanical properties in other multicomponent alloys.
A Crashworthiness Design Framework based on Temporal-Spatial Feature Extraction and Multi-Target Sequential Modeling
Hechen Wei, HaiHua Wang, Ziming Wen, Yong Peng, Hu Wang, Fengchun Sun
doi:10.1016/j.tws.2024.112694
基于时空特征提取和多目标序列建模的飞机耐撞设计框架
Temporal-spatial crashworthiness design remains a challenging issue in engineering applications. Metamodeling techniques have been widely used to improve design efficiency by reducing the need for extensive experiments or simulations. However, these methods often fail to capture the essential information of temporal and spatial during the dynamical procedure. In this study, a novel multi-target modeling and optimization framework is introduced to overcome these limitations. This framework utilizes autocorrelation functions to identify key temporal-spatial segments, ensuring that the most influential factors are captured, and then builds a metamodel using multi-target regression techniques and partial autocorrelation functions, effectively capturing the complex relationships among different time steps. An adaptive sampling strategy is also employed to generate additional training data according to the objective functions, thereby enhancing the accuracy and robustness of the metamodels. These improvements enable a more accurate and interpretable integration of temporal-spatial information compared to popular methods. The effectiveness of the proposed framework is demonstrated through its successful implementation in optimizing crashworthiness across diverse scenarios: a cylindrical tube, a multi-cell energy-absorbing structure, and a B-pillar designed to withstand side impacts. The results show that the proposed method provides reliable predictions for subsequent optimization tasks and has the potential to address complex crashworthiness design challenges by comprehensively considering temporal-spatial information.
Microstructure and mechanical properties of WE43 magnesium alloy fabricated by wire-arc additive manufacturing
Fukang Chen, Xiaoyu Cai, Bolun Dong, Sanbao Lin
doi:10.1016/j.tws.2024.112699
线弧增材制造WE43镁合金的组织与力学性能
Wire-arc additive manufacturing (WAAM) is emerging as a revolutionary method for fabricating heat-resistant WE43 magnesium alloy (WE43-Mg) components and multiple other Mg alloys. In this study, we successfully utilized cold metal transfer WAAM technology to fabricate high quality single-pass thin-walled WE43-Mg structures. The results show that the microstructure is mainly composed of equiaxed grains, and Mg14Nd2(Y,Gd) is the main second phase distributed along the grain boundaries. The relative density of the sample reaches 99.96%, and the main defects are oxide inclusions. The room temperature yield strength, ultimate tensile strength and elongation are 147.0 MPa, 221.9 MPa and 7.2%, respectively, with anisotropy rates of 1.9%, 2.2% and 3.7%. High-temperature tensile tests conducted at 250°C showed a slight increase in ultimate tensile strength and a significant increase in elongation from 7.2% to 16.8%, representing a 133% improvement. Under these conditions, the proportion of substructure increased significantly, and the proportion of low-angle grain boundaries rose from 3.2% to 69%. The stress-strain curves exhibited pronounced serrated flow behavior, which can be attributed to the interaction between solute atoms and dislocations.
The metastructures actuated by rotational motion with quasi-zero stiffness, negative stiffness, and bistability
Diankun Pan, Shuangfen Tan, Zhimin Zhang, Wenbing Li
doi:10.1016/j.tws.2024.112700
转动驱动的元结构具有准零刚度、负刚度和双稳性
In this paper, a mechanical metastructure actuated by rotational motion is proposed, which consists of several cosine beams and two supporting frames, with its mechanical properties tuned by the remaining shape of the beam concerning the size of the inner frame. The finite element method combining the experiments is adopted to explore the effect of geometric parameters and identify the variation of mechanical properties with the size of the inner frame, exhibiting different features including positive stiffness, quasi-zero stiffness, negative stiffness, and bistability. An angle difference describing the geometric relationship between the beam and the inner frame is employed to relate the mechanical properties. For the maximized angle difference, the quasi-zero stiffness is obtained and the bistability is easy to capture when the angle difference is around zero. Next, the quasi-zero stiffness feature and bistability are investigated in parametric analysis concerning the shape of the beam and offset distance, respectively, and the double-layer structures with two-step quasi-zero stiffness feature or multistability are designed to expand the design space of the proposed structure. The metastructure in this work provides a new option for designing multistable structures with rotational deformation freedom and developing torsional vibration isolators.
Impact Resistance Performance of 3D Woven TZ800H Plates with Different Textile Architecture
Qingbo Guo, Yachen Xie, Mengqi Yuan, Hong Zhang, Tao Wang, Guangyan Huang
doi:10.1016/j.tws.2024.112701
不同纺织结构的三维编织TZ800H板的抗冲击性能
Two typical methods commonly used to improve the mechanical properties and impact resistance properties of 3D woven composites are studied, namely weave pattern and layered architectures. The mechanical property and impact resistance performance were studied by utilizing the quasi-static compressive test, split Hopkinson pressure bar (SHPB) test and ballistic impact test. The compressive responses in warp and weft directions with different strain rates 0.001, 500 and 1300 s-1 were presented and analysed, providing strain rate influence on the material strength of different 3D woven composites. The impact resistance performance including damage mode, ballistic limit and specific energy absorption of three structures were discussed through impact tests. The results reveal that as the strain rate increases, the compressive strength and Young's modulus in both directions of 3D woven composites exhibit a significant increase. The compressive strength and modulus in the warp direction of the composites can be enhanced by using shallow interlocking of the warp tow or layered architectures. However, the two methods degrade the failure strain and weaken the strain rate strengthening effect of compressive strength in the weft direction, resulting in a significant decrease in the average strain energy density. For the ballistic impact case, the crimp of warp tows would decrease its load-bearing capacity, while resisting matrix crack growth under the ballistic impact. The significant reduction in the average strain energy density in the weft direction leads to a decrease in ballistic limit and specific energy absorption capacity under ballistic impact.
Nonlinear deflection and thermal post-buckling analysis of sector annular poroelastic composite nanodisks using mathematical simulation and machine learning algorithm
Zhijun Xu, Yang Han, Mohammed El-Meligy, Khalil El Hindi, Hamed Safarpour
doi:10.1016/j.tws.2024.112702
基于数学模拟和机器学习算法的扇形环形孔弹性复合材料纳米盘非线性挠曲和热后屈曲分析
Poroelastic nanodisks offer mechanical engineers enhanced control over material properties, enabling precise tuning of mechanical responses for advanced applications in sensors, actuators, and nano-mechanical systems. This study presents a comprehensive analysis of thermally-affected multi-directional functionally graded sector annular nanodisks, focusing on their thermal-post buckling and nonlinear deflection behaviors. Utilizing a refined quasi-3D logarithmic theory (RQLT), the study incorporates the effects of Von-Karman nonlinearity to accurately capture the large deflection responses of these advanced nanostructures under thermal loading. The material properties of the nanodisks are graded in multiple directions, enhancing their ability to withstand thermal stresses and maintain structural integrity. To solve the complex governing equations derived from the RQLT, a nonlinear discrete-singular convolution (DSC) solution procedure is employed. This novel numerical technique allows for precise computation of the nonlinear deformation and stability characteristics of the nanodisks, providing insights into their behavior under various thermal conditions. The nonlinear DSC method's ability to handle singularities and discontinuities makes it particularly suitable for this type of advanced analysis. After obtaining the mathematics simulation data, a machine learning algorithm is used to test, train, and validate the results for future analysis of the mentioned problem with low computational cost. The results demonstrate the critical influence of thermal gradients and material gradation on the post-buckling and nonlinear deflection responses of sector annular nanodisks. The interplay between thermal effects and material properties highlights the necessity for incorporating multi-directional functionally graded materials in the design of high-performance nanostructures. This study's findings are pivotal for the development of next-generation nanodisks used in thermal environments, offering a robust analytical and computational framework for their assessment and optimization.