今日更新:International Journal of Plasticity 2 篇,Thin-Walled Structures 2 篇
Crack-tip plasticity mediated grain refinement and its resisting effect on the fatigue short crack growth
Jianghua Li, Zhiyang Wang, Ningyu Zhang, Tao Shi, Elliot P. Gilbert, Gang Chen, Guian Qian
doi:10.1016/j.ijplas.2024.104102
裂纹尖端塑性介导的晶粒细化及其对疲劳短裂纹扩展的抑制作用
Fatigue short crack growth governed by the crack-tip plasticity dominates the fatigue life and strength of metallic materials or structural components. Here, for the first time, we discover a new mechanism of resisting fatigue short crack growth by grain refinement near the crack-tip driven by dynamic recrystallization in a Ni-based superalloy during high-cycle fatigue. The local cumulative plastic strain plays a determining role in the crack-tip grain refinement and concurrent dissolution of nanoprecipitation. Comprehensive microstructural analysis provides the evidence that the refined grains reduce the plastic micro-strain gradient in the vicinity of the crack-tip, which causes the crack blunting and deflection towards the interface of coarse-fine grains, hence decelerating the short crack growth. Although the grain refinement reduces the local stress threshold in the fine-grained areas (FGA), the dominant effects of FGA are identified to provide additional microstructural resistance to the propagation of short cracks.
由裂纹尖端塑性控制的疲劳短裂纹扩展决定了金属材料或结构件的疲劳寿命和强度。本文首次发现了ni基高温合金在高周疲劳过程中,通过动态再结晶驱动裂纹尖端附近的晶粒细化来抵抗疲劳短裂纹扩展的新机制。局部累积塑性应变对裂纹尖端晶粒细化和纳米沉淀的同步溶解起决定性作用。综合显微组织分析表明,细晶降低了裂纹尖端附近的塑性微应变梯度,使裂纹钝化并向粗细晶界面偏转,从而减缓了短裂纹的扩展。虽然晶粒细化降低了细晶区(FGA)的局部应力阈值,但FGA的主要作用是为短裂纹的扩展提供额外的显微组织阻力。
Enhancing Plasticity in BCC Mg-Li-Al Alloys through Controlled Precipitation at Grain Boundaries
Fan Ji, Tongzheng Xin, Yuhong Zhao, Wenkui Yang, Guoning Bai, Song Tang, Enyu Guo, Mengran Zhou, Qingyu Shi, Luqing Cui, Long-Qing Chen, Binbin He
doi:10.1016/j.ijplas.2024.104105
通过控制晶界析出提高BCC Mg-Li-Al合金塑性
This study investigates the improvement of plasticity in body-centered cubic magnesium (Mg)-lithium (Li)-aluminum (Al) alloys, crucial for lightweight structural applications. The ternary Mg-Li-Al alloys exhibits high strength but low ductility. Precipitates at grain boundaries in these alloys, linked to reduced plasticity, are examined for their crystal structure and composition. Advanced microscopic techniques reveal the transformation of precipitates and the development of specific structures at grain boundaries. Thermodynamics of element diffusion at grain boundaries are explored through first-principles calculations, and a phase-field simulation models precipitate evolution. Molecular dynamics simulations elucidate nanoscale mechanisms governing the transition from brittle to ductile fracture modes during artificial aging. The D03-Mg3Al at grain boundaries is a brittle phase, and through a 170°C aging treatment, it induces the precipitation of lamellar α-Mg phase with D03-Mg3Al as nucleation sites. The occupancy energy of Al atoms at Li sites in α-Mg is found to be lower than that in D03-Mg3Al, leading to the dissolution of D03-Mg3Al. The α-Mg, characterized by a stronger metallic nature, exhibits a better-matched modulus with the matrix and enhanced dislocation mobility. The precipitation of α-Mg plays a pivotal role in significantly improving the ductility of the alloy. This work contributes to the understanding of the complex interplay between alloy composition, grain boundary precipitates, and plasticity, as well as brings insights to guide interfacial control in the development of advanced Mg-Li-Al alloys for structural applications.
本研究探讨了体心立方镁(Mg)-锂(Li)-铝(Al)合金塑性的改善,这对轻量化结构应用至关重要。三元Mg-Li-Al合金具有高强度、低塑性的特点。这些合金的晶界析出物与塑性降低有关,研究了它们的晶体结构和组成。先进的显微技术揭示了析出相的转变和晶界处特定组织的发展。通过第一性原理计算探索了元素在晶界扩散的热力学,并采用相场模拟模型模拟了析出物的演化过程。分子动力学模拟阐明了人工时效过程中脆性断裂模式向韧性断裂模式转变的纳米级机制。晶界处的D03-Mg3Al为脆性相,经过170℃时效处理,析出以D03-Mg3Al为形核位的片层状α-Mg相。α-Mg中Li位点Al原子的占据能低于D03-Mg3Al,导致D03-Mg3Al的溶解。α-Mg具有较强的金属性质,其模量与基体匹配较好,位错迁移率增强。α-Mg的析出是显著提高合金延展性的关键因素。这项工作有助于理解合金成分、晶界沉淀和塑性之间的复杂相互作用,并为指导用于结构应用的高级Mg-Li-Al合金的界面控制提供见解。
Sound transmission loss and bending properties of sandwich structures based on triply periodic minimal surfaces
Yaozhong Wu, Xu Qi, Longfei Sun, Bo Wang, Li Hu, Peng Wang, Weijia Li
doi:10.1016/j.tws.2024.112324
基于三周期极小曲面的夹层结构的声传输损失和弯曲性能
Four types of triply periodic minimal surfaces sandwich structures (TPMS-SS), namely, G-SS, D-SS, D1-SS, and IWP-SS, have been proposed. The bending properties were evaluated by experiments and numerical simulations, and their sound insulation performance was investigated using theoretical, numerical and experimental methods. Firstly, the bending performance of four TPMS-SS was compared. Then, the acoustic vibration control equation of TPMS-SS was established and the theoretical solution for the sound transmission loss (STL) was derived based on Reissner's theory combined with the fluid-solid coupling condition. Next, experimental study was conducted on the STL performance of TPMS-SS using the impedance tube method, and the numerical model was verified using theoretical and experimental results. Finally, parametric studies were carried out to investigate the effects of parameters such as relative density (RD), panel thickness (hf), and sound incidence elevation angle (φ), as well as the type of structure, on the STL performance. The results show that TPMS-SSs can achieve more than 30 dB of STL in the frequency range of 1 Hz to 10 kHz. The STL value increases with relative density (RD), panel thickness (hf), and sound incident elevation angle (φ), while the location of the dips in the STL curves is affected by relative density and panel thickness. G-SS has the best bending performance, while D1-SS has the best acoustic performance. The results could be used for the optimization design of lightweight sandwich structures.
提出了四种三周期最小面夹层结构(TPMS-SS),即 G-SS、D-SS、D1-SS 和 IWP-SS。通过实验和数值模拟对其弯曲性能进行了评估,并采用理论、数值和实验方法对其隔音性能进行了研究。首先,比较了四种 TPMS-SS 的弯曲性能。然后,建立了 TPMS-SS 的声学振动控制方程,并根据 Reissner 理论结合流固耦合条件推导出了声音传输损失(STL)的理论解。接着,利用阻抗管方法对 TPMS-SS 的 STL 性能进行了实验研究,并利用理论和实验结果对数值模型进行了验证。最后,进行了参数研究,探讨了相对密度(RD)、面板厚度(hf)和声入射仰角(φ)等参数以及结构类型对 STL 性能的影响。结果表明,TPMS-SS 在 1 Hz 至 10 kHz 的频率范围内可达到 30 dB 以上的 STL。STL 值随相对密度 (RD)、面板厚度 (hf) 和声入射仰角 (φ) 的增加而增加,而 STL 曲线上凹点的位置则受相对密度和面板厚度的影响。G-SS 的弯曲性能最好,而 D1-SS 的声学性能最好。这些结果可用于轻质夹层结构的优化设计。
Vibration Analysis and Suppression of Axially Moving Composite Laminated Plates with Modified Energy Method and Piezoelectric Shunt Damping Circuits
Jinpeng Su, Jianhui Wei, Qiang Zhang, Duoting Wu
doi:10.1016/j.tws.2024.112340
基于改进能量法和压电并联阻尼电路的轴向运动复合材料层合板振动分析与抑制
This paper presents a modified variational modeling method and develops an electro-mechanical coupling based vibration control method for moving composite plate structures. Unlike the stationary structures, movement will introduce new challenges for both vibration analysis and control of the laminated plate. Based on the modified variational method, electromechanically coupled dynamic models for the moving plate with piezoelectric patches and control circuits are developed. To release limitations to the admissible functions, modified variational principles are derived for the interface and boundary constraints in both directions of the moving plate. On the basis of first-order shear deformation theory (FSDT), the energy functional expressions of the axially moving laminated plates are formulated and the governing equations are obtained. To suppress the vibration, a piezoelectric shunt damping circuit (PSDC) with negative capacitance is proposed and the control circuit parameters are optimized using the differential evolution (DE) algorithm. Through numerous numerical examples, the high accuracy, good efficiency, and flexibility in constructing admissible functions of the proposed modeling method are demonstrated. The developed PSDC possesses much better vibration suppression properties for the moving laminated plates than the series R-L PSDC. Effects of the moving speed and negative capacitance on the optimal circuit parameters are also examined. The appropriate values of the negative capacitance are shown to be near the capacitance of the patches.
提出了一种改进的变分建模方法,提出了一种基于机电耦合的运动复合板结构振动控制方法。与固定结构不同,运动将给层合板的振动分析和控制带来新的挑战。基于改进变分法,建立了带有压电片和控制电路的运动板的机电耦合动力学模型。为了消除可容许函数的局限性,导出了运动板两个方向的界面约束和边界约束的修正变分原理。基于一阶剪切变形理论(FSDT),建立了轴向运动层合板的能量泛函表达式,得到了控制方程。为了抑制振动,提出了一种负电容的压电并联阻尼电路,并利用差分进化算法对控制电路参数进行了优化。通过大量的数值算例表明,所提出的建模方法具有精度高、效率好、构造容许函数灵活等优点。所研制的PSDC对运动层合板具有比R-L系列PSDC更好的抑制振动性能。研究了移动速度和负电容对最优电路参数的影响。负电容的适当值显示在贴片的电容附近。