今日更新：International Journal of Solids and Structures 1 篇，Journal of the Mechanics and Physics of Solids 2 篇，Thin-Walled Structures 8 篇
International Journal of Solids and Structures
Large deformation response of a novel triply periodic minimal surface skeletal-based lattice metamaterial with high stiffness and energy absorption
Lijun Xiao, Gaoquan Shi, Genzhu Feng, Shi Li, Song Liu, Weidong Song
doi:10.1016/j.ijsolstr.2024.112830
具有高刚度和吸能性能的新型三周期极小表面骨架晶格超材料的大变形响应
Triply periodic minimal surface (TPMS) lattice metamaterial presents superior mechanical performance over traditional strut-based lattice metamaterials due to their unique structural characteristics. However, the high stiffness–stable plastic response trade-off dilemma is still the major challenge for skeletal-based metamaterials. Herein, a novel TPMS skeletal lattice metamaterial is proposed. Finite element simulations are conducted to reveal its elastic properties and plastic response under compression. Afterwards, validation experiments are performed on the lattice specimens fabricated by the most common Fused Deposition Modeling (FDM) process. The nominal stress–strain curves and collapse mode of the lattice materials are obtained accordingly. Both the numerical simulations and experiments demonstrate that the proposed TPMS lattice metamaterial exhibits high specific modulus, strength and energy absorption, together with a smooth and elongated stress plateau, thereby overcoming the strength-efficiency trade-off. Different from the rigid nodal region in traditional strut-based lattices, the strut connection parts in the novel TPMS lattices experience shear and twisting, which avoids the catastrophic failure of the struts and enhances the loading efficiency of the structure under compression. Meanwhile, the numerical results indicate that the stable plastic response of the designed architecture is insensitive to the plastic flow behavior of the bulk material, which is also supported by the experimental results. It is also demonstrated that the novel TPMS lattice metamaterial presents several times higher stiffness as well as energy absorption simultaneously than the current strut-based lattice materials, which can be potentially applied as load-bearing components and impact energy absorbers.
Asymptotic, second-order homogenization of linear elastic beam networks
Yang Ye, B. Audoly, C. Lestringant
doi:10.1016/j.jmps.2024.105637
线性弹性梁网络的渐近二阶均匀化
We propose a general approach to the higher-order homogenization of discrete elastic networks made up of linear elastic beams or springs in dimension 2 or 3. The network may be nearly (rather than exactly) periodic: its elastic and geometric properties are allowed to vary slowly in space, in addition to being periodic at the scale of the unit cell. The reference configuration may be prestressed. A homogenized strain energy depending on both the macroscopic strain ɛ and its gradient ∇ ɛ is obtained by means of a two-scale expansion. The homogenized energy is asymptotically exact two orders beyond that obtained by classical homogenization. The homogenization method is implemented in a symbolic calculation language and applied to various types of networks, such as a 2D honeycomb, a 2D Kagome lattice, a 3D truss and a 1D pantograph. It is validated by comparing the predictions of the microscopic displacement to that obtained by full, discrete simulations. This second-order method remains highly accurate even when the strain gradient effects are significant, such as near the lips of a crack tip or in regions where a gradient of pre-strain is imposed.
Scaling-law variance and invariance of cell plasticity
Jiu-Tao Hang, Huan Wang, Guang-Kui Xu
doi:10.1016/j.jmps.2024.105642
细胞塑性的尺度律变异与不变性
Scaling-laws are ubiquitous as universal physical principles in physics, biological systems, and human behavior. The scaling-law rheological responses of viscoelastic and plastic deformations and rate-dependent softening and stiffening during dynamic loading are remarkable characteristics of living cells and cell-like materials; however, the underlying mechanisms remain poorly understood. Here, we first propose a cellular structural model with 3-dimensional anisotropic discrete and plastic cytoskeletal networks to study the scaling-law rheological responses of cells. Besides the scaling-law invariance observed in cellular plastic deformation and viscoelastic deformation under large force ranges, there is evidence of scaling-law variance under relatively small force ranges. We develop a minimal mechanical model to elucidate the origins of scaling-law variance and invariance of cellular viscoelastic and plastic deformations. Interestingly, we find that cell materials can transition from fluid to solid over time and from elasticity to plasticity with increasing force. Furthermore, it is shown that the heterogeneity of three-dimensional cytoskeletal network dominates the anisotropic viscoplastic behavior of cells. We show that the stress-strain curves of cells with plastic cytoskeletons can be collapsed onto a single master curve of cells with elastic cytoskeletons. Moreover, we discover and derive a novel scaling-law ΔF∼v0α wherein the extent of force relaxation on cells during cyclical mechanical stimuli follows the same power-law dependence on the loading rate, as creep compliance on time. Our findings provide evidence that structure-based simulation and theoretical models can naturally capture the scaling-law invariance and variance of cellular deformations, in agreement with many experimental findings.
Bearing–curling interaction of austenitic stainless steel thin sheet bolted connections
Ke Jiang, Shuai Li, Yukai Zhong, Ou Zhao
doi:10.1016/j.tws.2024.111912
奥氏体不锈钢薄板螺栓连接的轴承-卷曲相互作用
The bearing–curling interactive behaviour and capacities of austenitic stainless steel thin sheet bolted connections are studied in this paper, underpinned by testing and numerical modelling. Experiments were firstly conducted on 26 austenitic stainless steel thin sheet bolted connection specimens, including 19 specimens designed with curling and 7 specimens designed without curling. The test failure loads, failure modes, load–in-plane elongation curves and load–out-of-plane deformation curves were fully reported. The experimental programme was followed by a numerical modelling programme, where finite element models were firstly developed to repeat the experimental results and then used to carry out parametric studies to generate a numerical data pool. Based on the obtained numerical data, the influences of end distance, edge distance, longitudinal spacing, transverse spacing and sheet thickness on failure loads of austenitic stainless steel thin sheet bolted connections were discussed. The test and numerical data were used to assess the existing design provisions, as given in the European code and American specification. The assessment results revealed that the European code led to overall accurate but scattered failure load predictions, while the American specification was shown to result in overly unsafe and scattered failure load predictions.
Multi-objective shape-section optimization of free-form latticed shells using the RBF-NSGA-II algorithm
Ying Xu, Yufeng Gai, Hongtao Li, Qinghua Han
doi:10.1016/j.tws.2024.111918
基于RBF-NSGA-II算法的自由形式格壳形状截面多目标优化
In this study, a novel RBF-NSGA-II optimization framework based on the response surface methodology (RSM) and the constrained NSGA-II algorithm is proposed to simultaneously improve the static, nonlinear stability and economic performance of free-form latticed shells. The bending stiffness of joints is innovatively considered one of the design variables for shape-member section coupled optimization. The augmented radius basis functions (RBFs) are adopted to develop the metamodels of both the objectives and constraints. The improved minimum distance selection method (TMDSM) is used to select the optimal solution from the Pareto optimal solution set. Moreover, three alternative solutions are presented as supplements to meet various engineering requirements. The proposed RBF-NSGA-II algorithm is validated to have high accuracy for multi-objective optimization problems with high nonlinearity. Compared with those of the initial structures, the strain energy and steel consumption of the optimal structure decreased by 82.23% and 17.97%, respectively, while the buckling load considering both the geometric nonlinearity and material nonlinearity increased by 1.2 times. The involvement of the joint stiffness is demonstrated to have a great influence on the multi-objective optimization results. It is necessary to consider the joint stiffness as one of the design variables during shape-member section coupled optimization.
Direct Spot Joining of Thin Gauge Aluminum Alloy to Stainless Steel and Joint Performance in A Corrosion Environment
Abdul Sayeed Khan, Pingsha Dong, Kai Sun, Doug Larsen
doi:10.1016/j.tws.2024.111919
薄板铝合金与不锈钢的直接点焊及其在腐蚀环境下的接头性能
Direct joining of aluminum alloy and steel sheets offers a great potential for achieving effective structural lightweighting for transportation systems. The major challenge is how to avoid the formation of brittle intermetallic compounds (IMCs), which can be detrimental to joint load capacity and corrosion resistance. This paper presents a friction-based direct solid-state joining method for welding thin aluminum alloy (AA6061-T6) to stainless steel (316). Using a flat head friction stir tool, a strongly bonded interface was achieved under a steady-state dwell time of 20-sec and 1000 rpm by avoiding excessive heating via keeping the friction tool pin away from the steel surface, eliminating introducing detrimental IMCs. The effects of an automotive-relevant corrosion environment condition on joint strengths are considered. Mechanical test results show that aluminum and stainless-steel spot joints produced by the proposed method exhibit no corrosion-induced damage or cracking nor any noticeable reduction in strengths, resulting in dominantly ductile failure mode.
A combined experimental and numerical study was carried out to explore the dynamic response of Q235 thin-walled cylindrical shells under lateral shock loading. The machined Q235 specimens were clamped on both sides and subjected to centered lateral simulated shock loading via foam projectile impact tests, with their dynamic deformation evolution, mid-point deflections, and final deformation modes experimentally measured. The mid-point deflections of the impact side are all positive (the direction of deformation is the same as the impact direction) while those of the rear side all exhibit negative values (the direction of deformation is opposite to the impact direction). To further explore this phenomenon, the method of finite element (FE) was employed to simulate the foam projectile impact, with good agreement against experimental measurements achieved. Using the validated numerical model, the effects of impact velocity, length-to-diameter ratio, and thickness-to-diameter ratio on the dynamic response of the thin-walled cylindrical shell were further analyzed. The direction of both side deflections and deformation modes are significantly affected by the impact level and the shell geometries. For the rear side, within the given range of impact momentum, the numerically predicted deflection varies from -1.775 mm to 2.45 mm. Thereupon, the coupling of indentation and bulge deformation patterns are indicated, and their corresponding contribution changes are considered the main mechanism for determining the final deformation of the thin-walled cylindrical shell's rear side.
Experimental and Numerical Investigation on Out-of-Plane Ultimate Strength of High-Strength Steel Arches
Zhenyu Pan, Hanwen Lu, Airong Liu, Jialin Wang, Mark A. Bradford
doi:10.1016/j.tws.2024.111898
高强钢拱面外极限强度的试验与数值研究
This study presents an experimental investigation on the out-of-plane ultimate strength of high-strength-steel (HSS) I-section arches, which has not been reported previously. Fourteen I-section HSS arches having different yield strengths, cross-sectional dimensions, slendernesses, and rise to span ratios were tested under three-point symmetrical vertical loading. The corresponding out-of-plane deformation modes and strengths are identified. Subsequently, in order to predict the out-of-plane capacities of HSS arches, a finite element analyses is carried out, which takes into consideration residual stresses and initial geometrical imperfections. This analysis demonstrates a strong alignment with the experimental results, confirming the accuracy of finite element model and experimental results. Furthermore, the study comprehensively analyzes the influence of yield strength of steel, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. Through a parametric analysis, design formulas for the out-of-plane bearing capacity of HSS arches subjected to arbitrary compression forces combined with arbitrary bending moments are formulated. It is found that the out-of-plane ultimate strength of HSS arches is significantly influenced by the yield strength of the steel. Compared to a low strength steel (LSS) arch, the out-of-plane ultimate bearing capacity of the HSS arch increases with an increase in yield strength in the plastic stage, and the ultimate lateral displacement of the HSS arch decreases with an increase in yield steel strength due to the lower ductility of HSS. In addition, after reaching the out-of-plane ultimate bearing load of arch, the load-displacement curve of the HSS arch drops faster than the LSS arch. It is also found that the proposed design formulas can effectively predict the out-of-plane bearing capacity of HSS arches.
Analytical Modelling and Critical Temperature of Circular CFST Column Exposed to Standard Fire
Wei Li, Jie Hu
doi:10.1016/j.tws.2024.111900
CFST圆形柱在标准火灾下的解析模型和临界温度
This paper establishes a finite element (FE) model for the fire resistance analysis of concrete-filled steel tubular (CFST) columns with circular cross section with comparison of different modelling methods. This model is then validated by experimental results from a database consisted of 123 circular CFST columns fire tests. The critical temperature is clarified for the circular CFST column exposed to standard fire. The performance of circular CFST columns is discussed and extensive parametric study is performed by the FE model. The equation for the critical temperature of circular CFST columns to axial compression is proposed and compared with FE and test results. The results show that the established FE model well captures the CFST column behaviour exposed to standard fire, and the proposed critical temperature method can provide more accurate fire resistance predictions than current codes of practice.
A new model for calculating the ultimate shear resistance of steel I-section girders
Luke Lapira, Leroy Gardner, M. Ahmer Wadee
doi:10.1016/j.tws.2024.111908
一种计算工字型钢梁极限抗剪承载力的新模型
The design resistance in shear of thin-walled I-sections has elicited numerous theories over the past decades. While there is a consensus on the post-buckling tension-field action that increases the ultimate resistance of thin webs in shear, the mechanism governing this tension-field action still remains debated. Presently, four constituent components for the shear resistance of I-sections are identified: (1) the resistance of the isolated web subject to a pure shear stress; (2) an increase in the web buckling stress due to flexural restraints provided by the flanges; (3) an increased web post-buckling resistance due to membrane restraint provided by the flanges; and (4) a direct contribution from the flanges to the shear resistance of the I-section. Each of these components is examined through parametric studies using finite element (FE) models analysed within Abaqus that are validated against published experimental results. A new design methodology for the resistance of I-sections in shear is presented, with closed-form expressions developed for each of the four component contributions. When compared with the current approach within EN 1993-1-5, the proposed formulae predict the shear resistance of the cross-section with greater accuracy and consistency.
Buckling analysis of a helical extension spring under combined loading
José González-Cabrero, Hugo Font, Francisco Cavas, Manuel Paredes
doi:10.1016/j.tws.2024.111914
螺旋伸缩弹簧在复合载荷作用下的屈曲分析
A new formula is introduced to analytically determine the critical torsional load or angle of rotation that confers instability in a tension spring under combined tension and torsion load using the theoretical framework of Greenhill's problem applied to an elastic bar as a starting point. The formula's effectiveness is evaluated with experimental torsion tests and finite element method simulations in Abaqus. The results demonstrate the formula's accuracy in predicting instability within specific stretched operating ranges, and achieving a relative error in correlation below 10% for most operating points. The study underscores the significance of preload and pre-stretching in enhancing the spring's resistance to buckling.
