今日更新：International Journal of Solids and Structures 3 篇，Journal of the Mechanics and Physics of Solids 2 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 2 篇
International Journal of Solids and Structures
Adaptive control to prevent transfer between bistable configurations of a tensegrity
Hong Hao, Deng Hua
doi:10.1016/j.ijsolstr.2023.112503
自适应控制，防止张力整体双稳态配置之间的转移
The adaptive control capability of tensegrities is investigated in terms of preventing the transfer between bistable configurations due to load-induced structural instability. In contrast to conventional structures, the structural geometry and internal force of tensegrities can be changed synchronously by member length actuation, thus achieving the adjustment of the structural elastic and geometric stiffnesses. The concept of the domain of attraction (DOA) is introduced to intuitively demonstrate the ability of a tensegrity to remain stable at the current configuration, and a method is suggested to estimate the DOA for a given load. Based on the quasistatic assumption, the analytical relationship between the eigenvalues of the structural tangent stiffness matrix and the member length actuations is derived. Further combining it with the structural equilibrium relationship, the equation that can be employed to simultaneously correct both the eigenvalues of the tangent stiffness matrix and the structural geometry is established. An adaptive control strategy is thus proposed to prevent the buckling of a loaded bistable tensegrity by specifying a threshold for the eigenvalues of the tangent stiffness matrix. A 6-bar 24-cable bistable tensegrity is employed as an illustrative example to verify the validity of the proposed adaptive control strategy by preventing mutual transfers between its bistable configurations. The results show that the load resistance of the tensegrity can be significantly improved by adaptive control without loss of the structural stability, and both the elastic stiffness and the geometrical stiffness provide comparable contributions to the adjustment of the eigenvalues of its tangent stiffness matrix.
A computational framework for the lifetime prediction of vertical-axis wind turbines: CFD simulations and high-cycle fatigue modeling
Geng F., Suiker A.S.J., Rezaeiha A., Montazeri H., Blocken B.
doi:10.1016/j.ijsolstr.2023.112504
垂直轴风力涡轮机寿命预测计算框架：CFD 模拟和高循环疲劳建模
A novel computational framework is presented for the lifetime prediction of vertical-axis wind turbines (VAWTs). The framework uses high-fidelity computational fluid dynamics (CFD) simulations for the accurate determination of the aerodynamic loading characteristics on the wind turbine, and includes these loading characteristics in a detailed 3D finite element method (FEM) model to predict fatigue cracking in the structure with a fatigue interface damage model. The fatigue interface damage model allows to simulate high-cycle fatigue cracking processes in the wind turbine in an accurate and robust fashion at manageable computational cost. The FEM analyses show that the blade-strut connection is the most critical structural part for the fatigue life of the VAWT, particularly when it is carried out as an adhesive connection (instead of a welded connection). The sensitivity of the fatigue response of the VAWT to specific static and fatigue modeling parameters and to the presence of a structural flaw is analysed. Depending on the flaw size and flaw location, the fatigue life of the VAWT can decrease by 25%. Additionally, the decrease of the fatigue resistance of the VAWT appears to be mainly characterized by the monotonic reduction of the tensile strength of the adhesive blade-strut connection, rather than by the reduction of its mode I toughness, such that fatigue cracking develops in a brittle fashion under a relatively small crack opening. It is emphasized that the present computational framework is generic; it can also be applied for analyzing the fatigue performance of other rotating machinery subjected to fluid–structure interaction, such as horizontal-axis wind turbines, steam turbine generators and multistage pumps and compressors.
本文介绍了一种新型计算框架，用于预测垂直轴风力涡轮机（VAWT）的使用寿命。该框架利用高保真计算流体动力学（CFD）模拟准确确定风力涡轮机的空气动力载荷特性，并将这些载荷特性纳入详细的三维有限元法（FEM）模型，通过疲劳界面损伤模型预测结构的疲劳开裂。疲劳界面损伤模型能够以精确、稳健的方式模拟风轮机的高循环疲劳开裂过程，且计算成本可控。有限元分析表明，叶片-支柱连接是影响风力涡轮机疲劳寿命的最关键结构部分，尤其是在采用粘合连接（而非焊接连接）的情况下。我们分析了 VAWT 的疲劳响应对特定静态和疲劳建模参数以及结构缺陷存在的敏感性。根据缺陷的大小和位置，VAWT 的疲劳寿命可缩短 25%。此外，VAWT 抗疲劳性能的降低似乎主要表现为粘合叶片-支柱连接抗拉强度的单调降低，而非其模式 I 韧性的降低，因此疲劳裂纹会在相对较小的裂纹开口下以脆性方式发展。需要强调的是，本计算框架是通用的；也可用于分析其他受流体-结构相互作用影响的旋转机械的疲劳性能，如水平轴风力涡轮机、蒸汽涡轮发电机以及多级泵和压缩机。
Thermoelastic free vibration analysis of functionally graded conical shell based on trigonometric higher-order shear deformation theory
Pal Subhendu, Rout Mrutyunjay, Karmakar Amit
doi:10.1016/j.ijsolstr.2023.112505
基于三角高阶剪切变形理论的功能分级锥壳热弹性自由振动分析
The fundamental frequency of a rotating cantilevered porous functionally graded (FG) twisted conical shell with varying thickness along the longitudinal direction is calculated using a trigonometric higher-order shear deformation theory under thermal loading. Finite element method is employed for this purpose. The shell is discretized using eight noded isoparametric shell elements with seven degrees of freedom per node. Using a simple power law across the transverse direction, the temperature-dependent material properties of the FG shell are determined. The nonlinear temperature distribution across the thickness direction is calculated using the one-dimensional Fourier heat conduction equation. The dynamic equation of motion is derived using Lagrange's equation. Finally, a parametric investigation of the effects of taper ratio, porosity, pretwist angle, temperature, and rotational speed on the fundamental frequency of the porous FG rotating conical shell is performed. It is also discussed how such characteristics affect mode shapes.
A continuous pleated birod for converting contractions into twisting through instability
Alessi Roberto, Brunetti Matteo, Paroni Roberto, Scardaoni Marco Picchi
doi:10.1016/j.jmps.2023.105451
通过不稳定性将收缩转化为扭转的连续褶皱生物棒
The mechanical behavior of a structure made by joining two flexible flanges with a deformable pleated web, simply called continuous birod, is investigated. When axially loaded, the continuous birod shows an unconventional buckling phenomenon that couples axial contractions and helical twist, with a softening-hardening postcritical force–displacement response. In this work we propose an analytical model capable to predict the critical load and displacement of a continuous birod under axial compression. Our model does not contain any heuristic term: all the parameters have a clear physical-geometrical interpretation and can be easily identified. The obtained closed-form expressions for the critical load and displacement are in good agreement with experimental evidences and finite element simulations. The model can be exploited for the design of compliance and multistable devices for advanced applications.
Stabilization against gravity and self-tuning of an elastic variable-length rod through an oscillating sliding sleeve
Koutsogiannakis P., Misseroni D., Bigoni D., Dal Corso F.
doi:10.1016/j.jmps.2023.105452
通过摆动滑动套筒实现弹性变长杆的抗重力稳定和自调整
An elastic rod, straight in its undeformed state, has a mass attached at one end and a variable length, due to a constraint at the other end by a frictionless sliding sleeve. The constraint is arranged with the sliding direction parallel to a gravity field, in a way that the rod can freely slip inside of the sleeve, when the latter is not moving. In this case, the free fall of the mass continues until the rod is completely injected into the constraint. However, when the sliding sleeve is subject to a harmonic transverse vibration, it is shown that the fall of the mass and the rod injection are hindered by the presence of a configurational force developing at the sliding sleeve and acting oppositely to gravity. During the dynamic motion, such a configurational force is varying in time because it is associated with the variable bending moment at the sleeve entrance. It is (experimentally, analytically, and numerically) demonstrated that, in addition to the states of complete injection or ejection of the elastic rod (for which the mass falls down or is thrown out), a stable sustained oscillation around a finite height can be realized. This ‘suspended motion’ is the signature of a new attractor, that arises by the constraint oscillation. This behaviour shares similarities with parametric oscillators, as for instance the Kapitza inverted pendulum. However, differently from the classical parametric oscillators, the ‘suspended’ configuration of the rod violates equilibrium and the stabilization occurs through a transverse mechanical input, instead of a longitudinal one. By varying the sliding sleeve oscillation amplitude and frequency within specific sets of values, the system spontaneously adjusts the sustained motion through a self-tuning of the rod’s external length. This self-tuning property opens the way to the design of vibration-based devices with extended frequency range.
Dual influences of deformation-induced W precipitates on dynamic recrystallization and fracture mechanism of the hot-extruded Mg-Y-Zn alloys: an experimental and phase field study
Shuai Chuan, Liu Wei, Li Huanqing, Wang Kaile, Zhang Yuntao, Xie Taoze, Chen Liwen, Hou Hua, Zhao Yuhong
doi:10.1016/j.ijplas.2023.103772
变形诱导的 W 沉淀对热挤压 Mg-Y-Zn 合金动态再结晶和断裂机制的双重影响：实验和相场研究
Understanding the relationship between nano-sized precipitates and dynamic recrystallization (DRX) during thermo-mechanical processing is vital for developing high-performance Mg-based alloys. This work uses experiment and phase field model to investigate the dynamic precipitation of W particles and DRX grains in the hot-extruded Mg98.5Y1Zn0.5 alloys at 360, 380 and 400°C and clarifies the fracture mechanisms in detail. The results reveal that under all temperatures, the hot-extruded Mg98.5Y1Zn0.5 alloys are composed of block 18R long-period stacking order (LPSO) phase, lamellar 14H-LPSO phase, W particles and a typical bimodal structure containing fine DRX grains and coarse non-DRX grains. Noted that the W particles not only promote the DRX nucleation by hindering dislocation motion to increase elastic energy, but also inhibit the growth of DRX grains by pinning grain boundaries during deformation. In addition, the strength decreases while the plasticity increases with increasing temperature for the hot-extruded Mg98.5Y1Zn0.5 alloys, but an excellent strength-plasticity balance is achieved at 400°C. More importantly, analyzing the crack extension in non-DRX, DRX and non-DRX/DRX coexistence regions shows that a ductile-brittle fracture mechanism dominates in the non-DRX regions due to the difficulty of basal slip and low fracture toughness. But a hole-joining fracture mechanism dominates in the DRX regions. The fracture mechanism in the non-DRX/DRX coexistence region is mainly determined by the DRX volume fraction. These results can provide insights and valuable references for developing high-performance Mg-based alloys.
Block shear failure of austenitic stainless steel bolted connections
Song Yuchen, Lin Xue-Mei, Yam Michael C.H., Ke Ke
doi:10.1016/j.tws.2023.111251
奥氏体不锈钢螺栓连接的块状剪切失效
Austenitic stainless steel possesses very high ductility and ultimate-to-yield strength ratio, which could possibly affect the block shear failure mechanism and the corresponding ultimate capacity of bolted connections made of this material. In response to this concern, a comprehensive experimental and numerical study on the block shear behaviour of austenitic stainless steel bolted connections (ASSBCs) is conducted and reported in this paper. Based on the results of 15 experimental tests, it is found that the governing block shear mechanism of ASSBCs (for 14 out of the 15 tests) at the ultimate load corresponds to cracking of the shear sections prior to fracture of the tensile sections. This differs significantly from the conventionally accepted block shear mechanism of mild steel bolted connections, which is net section fracture of the tension area and yielding of the shear area. This observation was further confirmed by a numerical study based on validated finite element models, where three block shear mechanisms were identified for ASSBCs. A thorough parametric study was then carried out to clarify the effects of key design parameters on the block shear behaviour of ASSBCs. Finally, the experimental and numerical results are used to evaluate the applicability of existing design equations to predicting the block shear capacity of ASSBCs. An improved block shear equation is subsequently proposed based on the available data.
Experimental study on post-fire mechanical properties and fracture behavior of Q690 steel
Cai Wenyu, Li Guo-Qiang
doi:10.1016/j.tws.2023.111253
Q690 钢着火后力学性能和断裂行为的实验研究
Fire is one of the most dangerous disasters for high-strength steel structures. After a fire event, the deterioration of mechanical properties of high-strength steel together with the complex stress state generated by external loading may lead to an unexpected failure or collapse of high-strength steel structures. Therefore, it is very critical to evaluate the post-fire behavior of high-strength steel considering stress state effects. This study conducted a series of tests on the Q690 steel specimens after being exposed to high temperatures ranging from 200 to 1000 °C with different cooling methods including air-cooling and water-cooling methods. The tested specimens including smooth round specimens, notched round specimens, and grooved plate specimens were designed to consider the failure mode in axisymmetric stress state and plane strain state. To validate the accuracy of the test results, the mechanical properties such as yield strength, ultimate strength, elastic modulus, and ultimate strain were first compared with other test results reported in the literature. The post-fire ultimate strength under different stress states was obtained directly from the test results. Then, the post-fire equivalent plastic strain at fracture of different specimens was obtained from test data together with the finite element analysis results and analyzed under different stress triaxialities and Lode angle parameters. According to this study, an increase in stress triaxiality can result in an increase in ultimate strength but a decrease in the equivalent plastic strain at fracture for Q690 steel after fire. When the exposed temperature was not higher than 800 °C, the post-fire strength of the plane strain specimen (Grooved Plane Specimen) was higher than that of the axisymmetric tension specimen (Notched Round Specimen) under a similar stress triaxiality; however, for their post-fire equivalent plastic strain at fracture, the results were opposite.
