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 1 篇,Thin-Walled Structures 5 篇
Post-Necking full-field FEMU identification of anisotropic plasticity from flat notched tension experiments
Emmanouil Sakaridis, Christian C. Roth, Benoit Jordan, Dirk Mohr
doi:10.1016/j.ijsolstr.2024.113076
基于平缺口拉伸实验的后颈场FEMU各向异性塑性识别
This work introduces a finite element model updating (FEMU) identification scheme to determine the material parameters of an anisotropic metal plasticity model. Surround digital image correlation (DIC) data is collected from tensile tests on mildly notched flat specimens and it is used to minimize specimen alignment errors when comparing simulations and experiments. The front surface displacement fields and resultant force history are leveraged to calibrate a Whip-Bezier based material model in a computationally-efficient procedure, which treats the pre- and post-necking regimes separately. Experimental data from specimens with a larger notch radius (NT20) serve as the training set, while data from specimens with a smaller notch radius (NT6) are used for validation. Analysis of identification methods using datasets from virtual experiments highlights the improved generalization ability of the full-field approach compared to solely using force–displacement curves. However, this work also demonstrates that through-thickness necking in real notched tensile experiments is asymmetric. This can hinder the identification of the large strain segment of hardening laws, especially when a FEMU approach incorporates full-field information from one specimen surface only. Consequently, it is recommended to use advanced finite element models that capture asymmetric localized strain fields or to base the identification of large strain hardening responses on experiments that achieve large strains without asymmetric through-thickness strain localization, such as in-plane torsion tests.
本文介绍了一种有限元模型更新(FEMU)识别方案,用于确定各向异性金属塑性模型的材料参数。环绕数字图像相关(DIC)数据是从轻度缺口平面试样的拉伸试验中收集的,并用于在比较模拟和实验时最小化试样对准误差。利用前表面位移场和合力历史,在计算效率高的程序中校准基于Whip-Bezier的材料模型,该程序分别处理颈缩前和颈缩后状态。缺口半径较大的标本(NT20)的实验数据作为训练集,缺口半径较小的标本(NT6)的数据用于验证。利用虚拟实验数据集的识别方法分析表明,与仅使用力-位移曲线相比,全场方法具有更好的泛化能力。然而,这项工作也表明,在实际缺口拉伸实验中,全厚度颈缩是不对称的。这可能会阻碍对硬化规律的大应变段的识别,特别是当FEMU方法仅包含来自一个试样表面的全场信息时。因此,建议使用捕捉非对称局部应变场的先进有限元模型,或者基于在没有非对称全厚度应变局部化的情况下获得大应变的实验(如面内扭转试验)来识别大应变硬化响应。
Intrinsic tensile brittleness of tilted grain boundaries and its shear toughening
Jia Meng, Shenyou Peng, Qihong Fang, Jia Li, Yujie Wei
doi:10.1016/j.jmps.2024.105869
倾斜晶界的内在拉伸脆性及其剪切增韧
In the endeavors of working with microstructures in polycrystalline metals for better strength and ductility, grain boundaries (GBs) are placed at the front burner for their pivotal roles in plastic deformation. Often the mechanical properties of polycrystalline metals are governed by mutual interactions among GBs and dislocations. A thorough comprehension of GB deformation is therefore critical for the design of metals of superb performance. In this research, we investigated the mechanical behavior of symmetric tilt grain boundaries in face-centred cubic (F.C.C.) nickel, which may be subject to tension, shearing, and mixing-mode load using molecular dynamics simulations. We observed that (1) there exist four types of micro deformation mechanisms in GBs, and illustrate at the atomistic scale their distinctions and their dependence on the activation of lattice slip in the crystal; (2) GBs are intrinsically brittle under tension but exhibit ductile behavior during shearing. Shifting from pure tension with increasing shear component during mixing-mode load leads to GB toughening; and (3) there lacks conceivable dependence of GB tensile strength on tilted GBs, in contrast to a relatively rough trend of greater shear strength in GBs of large misorientation. GB energy shows no direct connection with GB strength, as broadly reported in existing literature. This research enhances our mechanistic understanding of GB plasticity in crystalline metals, and points to a potential way of making strong-yet-tough polycrystalline metals through GB engineering: in addition to GB structure manipulation, tuning the loading mode of GBs may open another avenue for their better performance.
在研究多晶金属的显微组织以获得更好的强度和延展性的过程中,晶界(GBs)因其在塑性变形中的关键作用而受到重视。多晶金属的力学性能通常是由位错和gb之间的相互作用决定的。因此,对GB变形的透彻理解对于设计具有卓越性能的金属至关重要。在这项研究中,我们利用分子动力学模拟研究了面心立方镍中对称倾斜晶界的力学行为,这种晶界可能受到张力、剪切和混合模式载荷的影响。结果表明:(1)晶体中存在四种微变形机制,并在原子尺度上说明了四种微变形机制的区别及其对晶格滑移激活的依赖;(2) GBs在拉伸作用下具有脆性,但在剪切作用下具有延性。混合模式下,随着剪切分量的增加,由纯拉伸转变为GB增韧;(3)相对于取向偏差较大的GB, GB抗拉强度对倾斜GB的依赖程度较低,而相对粗糙的趋势是GB的抗剪强度增大。如现有文献广泛报道的那样,国标能量与国标强度没有直接关系。本研究增强了我们对结晶金属中GB塑性的机理理解,并指出了通过GB工程制造强韧多晶金属的潜在途径:除了对GB结构进行操纵外,调整GB的加载模式可能为其更好的性能开辟另一条途径。
Crack-tip cleavage/dislocation emission competition behaviors/mechanisms in magnesium:ALEFM prediction and atomic simulation
Jia-ping Ma, Lin Yuan, Ying-ying Zong, Ming-yi Zheng, De-bin Shan, Bin Guo
doi:10.1016/j.ijplas.2024.104134
镁中裂纹尖端解理/位错发射竞争行为/机制:ALEFM预测和原子模拟
Structural properties and reliability of materials can be improved by increasing fracture toughness. At the atomic scale, the fracture is a material separation process, and the fracture toughness of materials is associated with the atomic-scale crack-tip behaviors/mechanisms. The crack-tip behaviors are relevant to the energy state of atoms in the system. Atomic thermal oscillation increases with increasing temperature, which may affect/alter the crack tip behaviors. This work is the first to investigate the temperature-dependent crack-tip cleavage/dislocation emitting competition in magnesium (Mg) using anisotropic linear elastic fracture mechanics theory, Density Functional Theory (DFT), and atomic simulation. Crack-tip behaviors are examined using a specially designed ‘K-field’ loads model. DFT calculations show that a single crystal system with lower entropy and higher Gibbs free energy implies stronger interatomic bonding that favors a higher KIc. Changes in the stress distribution initiate a brittle-ductile transition in crack-tip behavior. The ductile crack tip can be blunted by continuous crack-tip dislocations nucleation/slip, and the evolution of the ductile crack-tip geometry from sharp to semicircular structure significantly decreases the stress concentration at the crack tip. A new criterion of the crack-tip force vector is established, which reasonably explains the geometrical evolution of ductile crack tip where the angle θ between the crack plane and the slip plane is 0°<θ<90° and θ=90°. This work expands the atomic-scale brittle/ductile crack-tip behaviors/mechanisms of Mg, which provides a reference for crack-tip behavior analysis in engineering research.
通过提高断裂韧性可以改善材料的结构特性和可靠性。在原子尺度上,断裂是一种材料分离过程,材料的断裂韧性与原子尺度的裂纹尖端行为/机制有关。裂纹尖端行为与系统中原子的能量状态有关。原子热振荡随温度升高而增加,这可能会影响/改变裂纹尖端行为。本研究首次使用各向异性线性弹性断裂力学理论、密度泛函理论(DFT)和原子模拟研究了镁 (Mg) 中与温度相关的裂纹尖端裂解/位错发射竞争。利用专门设计的 “K-场 ”载荷模型对裂纹尖端行为进行了研究。密度泛函理论计算表明,单晶体系统具有较低的熵和较高的吉布斯自由能,这意味着较强的原子间键合有利于较高的 KIc。应力分布的变化引发了裂纹尖端行为的脆性-韧性转变。韧性裂纹尖端可通过连续的裂纹尖端位错成核/滑移而变钝,韧性裂纹尖端的几何形状从尖锐结构演变为半圆形结构可显著降低裂纹尖端的应力集中。建立了一个新的裂纹尖端力矢量准则,该准则合理地解释了裂纹平面与滑移平面之间的夹角θ为0°<θ<90°和θ=90°时韧性裂纹尖端的几何演变。这项工作拓展了镁的原子尺度脆性/韧性裂纹尖端行为/机理,为工程研究中的裂纹尖端行为分析提供了参考。
A Meshfree Formulation for Size-dependent Thermal Buckling and Post-Buckling Behaviour of Porous Microplates on Elastic Foundation Subjected to Localized Heating
Varun Jain, Rajesh Kumar, Tanish Dey, S.N. Patel, Gaurav Watts
doi:10.1016/j.tws.2024.112451
局部加热作用下弹性地基上多孔微板尺寸相关热屈曲和后屈曲行为的无网格计算公式
The semi-analytical framework is developed for in-plane thermal stresses within the microplates under localized heating. Localized heating is modelled using Fourier Series expansions over the complete domain of the plate. These stresses within the plate are estimated after solving the in-plane thermoelasticity problem using Airy's stress approach. Utilizing these stresses, present work also studies the buckling and post-buckling behaviour of a porous metal foam microplate resting on Winkler and Pasternak elastic foundations. The plate is modelled using Reddy's third-order shear deformation theory (TSDT) and von Kármán geometric nonlinearity, and the size-dependent effects are included using the modified strain gradient theory (MSGT). Galerkin's weighted residual method converts the partial differential equations (PDEs) into algebraic equations. The post-buckling equilibrium path is obtained using the modified Newton-Raphson method. The mode shapes of the microplate for the various configurations of the plate with different boundary conditions due to localized thermal loading are plotted. Also, these mode shapes are compared with the mode shapes of the microplate due to in-plane mechanical loading. The parametric effect of porosity, elastic foundation parameters, thickness of plate, size of plate, boundary conditions and loading concentrations on the buckling and post-buckling behaviour of the plate is studied.
建立了微板局部加热条件下面内热应力的半解析框架。局部加热是用傅立叶级数在整个板域上展开来模拟的。在用艾里应力法求解面内热弹性问题后,对板内应力进行了估计。利用这些应力,本工作还研究了基于温克勒和帕斯捷尔纳克弹性地基的多孔金属泡沫微板的屈曲和后屈曲行为。采用Reddy的三阶剪切变形理论(TSDT)和von Kármán几何非线性对板进行了建模,并采用修正应变梯度理论(MSGT)考虑了尺寸相关效应。伽辽金加权残差法将偏微分方程转化为代数方程。采用改进的牛顿-拉夫逊法得到了后屈曲平衡路径。绘制了微孔板在不同边界条件下的模态振型图。同时,将这些模态振型与微孔板在平面内机械载荷作用下的模态振型进行了比较。研究了孔隙率、弹性基础参数、板厚、板尺寸、边界条件和加载浓度等参数对板屈曲和后屈曲行为的影响。
A quasi-3D SinZZ model-driven multi-field Chebyshev FEM for nonlinear vibration control in multilayer multiferroic composite plates
Duy-Khuong Ly, Bao-Anh Hoang Tran, Trung-Hau Dang, Chanachai Thongchom, Trung Nguyen-Thoi
doi:10.1016/j.tws.2024.112457
准三维SinZZ模型驱动的多场Chebyshev有限元法用于多层多铁复合材料板的非线性振动控制
This paper presents an advanced numerical method for modeling and mitigating nonlinear vibrations in thin multilayered fiber-reinforced multiferroic composite plates, addressing complex multi-physical interactions. The proposed methodology leverages a multi-physical coupling Chebyshev finite element formulation, utilizing high-order shape functions derived from Chebyshev polynomials. By integrating the strengths of spectral element methods and Legendre spectral finite element methods, this approach effectively overcomes challenges such as shear locking and spurious zero energy modes while ensuring high convergence rates in multi-physical problems. A quasi-3D refined model, incorporating the Murakami zig-zag model and sinusoidal shear deformation theory, is employed to accurately capture the nonlinear Von Kármán strain–displacement relationship and the magneto-electro-elastic coupling in multilayer structures with thickness-dependent material properties. To suppress nonlinear vibrations, the study utilizes a closed-loop multiphysical Chebyshev finite element model for time-domain analysis of viscoelastically damped systems, employing the Golla-Hughes-McTavish model. The results underscore the significant influence of multiferroic properties and the strategic distribution of ferroelectric fibers within the substrate on the dynamic behavior of the plate. The numerical validation, supported by rigorous verification, demonstrates the robustness of the proposed method in effectively simulating and controlling multilayer fiber-reinforced multiferroic composite plates. Additionally, this research highlights the potential for significant vibration reduction through semi-active damping mechanisms, offering valuable insights for practical applications in industries where precision and stability are critical.
本文提出了一种先进的数值方法来模拟和减轻薄多层纤维增强多铁复合材料板的非线性振动,处理复杂的多物理相互作用。提出的方法利用多物理耦合切比雪夫有限元公式,利用由切比雪夫多项式衍生的高阶形状函数。该方法结合了谱元方法和勒让德谱有限元方法的优点,在保证多物理问题的高收敛速度的同时,有效克服了剪切锁定和伪零能模式等难题。结合村上之锯齿模型和正弦剪切变形理论,建立准三维精细模型,精确捕捉材料厚度相关多层结构中的非线性Von Kármán应变-位移关系和磁-电弹性耦合。为了抑制非线性振动,该研究利用闭环多物理Chebyshev有限元模型对粘弹性阻尼系统进行时域分析,采用了Golla-Hughes-McTavish模型。结果强调了多铁性和铁电纤维在衬底内的策略性分布对板的动态行为的显著影响。数值验证得到了严格的验证,证明了该方法对多层纤维增强多铁复合材料板的有效模拟和控制具有鲁棒性。此外,这项研究强调了通过半主动阻尼机制显著减少振动的潜力,为精度和稳定性至关重要的行业的实际应用提供了有价值的见解。
Superior strength and energy absorption capability of LPBF metallic functionally graded lattice structures
Saad Waqar, Sajjad Hussain, Chuanxi Ren, Meng Wang, Aamer Nazir, Xingdong Dan, Chunjin Wang, Zibin Chen
doi:10.1016/j.tws.2024.112471
LPBF金属功能梯度晶格结构具有优异的强度和吸能性能
Lightweight structures exhibiting superior mechanical response are highly desirable and find widespread applications in aerospace, biomedical, and automotive industries. Lattice structures are among the promising lightweight mechanical metamaterials with excellent specific strength and energy absorption capabilities. To further enhance the behavior of stretching dominant lattice structures for high-strength applications without compromising their lightweight nature, volume fraction-based functional gradience has been proposed and evaluated in detail in this study. Laser powder bed fusion fabricated Ti6Al4V octet lattice structures with uniform volume fractions and functionally graded lattice structures were fabricated and investigated. Experimental and numerical investigations focused on various functional gradient lattice structures, including Uni-Graded, Bi-Graded Horizontal, and Bi-Graded Vertical, encompassing a wide range of volume fraction variations. The incorporation of functional gradience resulted in a substantial enhancement in both strength and energy absorption capabilities. Uni-Graded and Bi-Graded Vertical functionally graded lattice structures with significant volume fraction variations (referred to as UG3 & BGV3) exhibited an approximate 25% enhancement in compressive strength, rising from 160 MPa for uniform lattice structure to 200 MPa. Furthermore, these functionally graded lattice structures also demonstrated a remarkable enhancement in energy absorption capacity per unit volume (91% for UG3 and 101% for BGV3), underscoring the significant role of functional grading patterns and volume fraction variations in shaping the behavior of lattice structures.
具有优异机械响应的轻质结构是非常可取的,并在航空航天,生物医学和汽车工业中得到广泛应用。晶格结构具有优异的比强度和能量吸收能力,是一种很有前途的轻型机械超材料。为了进一步增强在高强度应用中拉伸主导晶格结构而不影响其轻量化特性的行为,本研究提出了基于体积分数的功能梯度,并对其进行了详细评估。制备并研究了均匀体积分数的Ti6Al4V八元晶格结构和功能梯度晶格结构。实验和数值研究集中于各种功能梯度晶格结构,包括单梯度、双梯度水平和双梯度垂直,涵盖了广泛的体积分数变化。功能梯度的结合导致了强度和能量吸收能力的实质性增强。体积分数变化较大的单梯度和双梯度垂直功能梯度晶格结构(称为UG3和BGV3)的抗压强度提高了约25%,从均匀晶格结构的160 MPa提高到200 MPa。此外,这些功能梯度晶格结构也显示出单位体积能量吸收能力的显著增强(UG3为91%,BGV3为101%),强调了功能梯度模式和体积分数变化在塑造晶格结构行为方面的重要作用。
Vibration of composite open shell of hydrogen-electric fuselage with rectangular cutout in hygrothermal circumstances: theoretical and experimental research
Xu-Yuan Song, Hao-Ran Li, Zhen Zhang, Jian Zang, Ye-Wei Zhang, Li-Qun Chen
doi:10.1016/j.tws.2024.112473
热湿环境下矩形开壳复合材料氢电机身振动的理论与实验研究
An effective formulation is performed to approximate calculate the vibration of the typical composite fuselage battery compartment structures of the hydrogen-electric aircraft, which are highly sensitive to hygrothermal circumstances. The strain energy, kinetic energy and hygrothermal potential energy of CLOCSRC are deduced in frame of Donnell's shell assumption and a series of hypothetical elastic springs operating on the edges of divided components are introduced to simulate coupling connection and the elastic supports of the open shell, which contribute to total system energy in the form of elastic spring potential energy. The equations of motion for CLOCSRC subjected to distinct hygrothermal circumstances and arbitrary boundaries are eventually obtained in frame of the Rayleigh-Ritz method by means of the modified orthogonal polynomial as the displacement admissible function. After confirming the convergence and accuracy of the presented formulation by experiment and finite element method, several numerical examples are presented to investigative the effects of geometric parameters, elastic boundaries and hygrothermal circumstances on the vibration of CLOCSRC. Differ from traditional investigation, the present paper offers an effective approach to insight the hygrothermal mechanism of open shell with rectangular cutouts creatively. The relevant investigation demonstrated that the current strategy is beneficial for further research on the vibration characteristics of CLOCSRC.
对典型的对湿热环境高度敏感的氢动力飞机复合材料机身电池舱结构的振动进行了有效的近似计算。在Donnell壳体假设框架下推导了CLOCSRC的应变能、动能和湿热势能,并引入一系列假设的弹性弹簧作用于分离构件的边缘,模拟了耦合连接和开壳的弹性支撑,以弹性弹簧势能的形式贡献了系统总能量。最后以修正正交多项式作为位移容许函数,在Rayleigh-Ritz法的框架下得到了不同热湿环境和任意边界下CLOCSRC的运动方程。在通过实验和有限元方法验证了该公式的收敛性和准确性的基础上,通过数值算例研究了几何参数、弹性边界和湿热环境对CLOCSRC振动的影响。与传统的研究不同,本文创造性地提供了一种有效的方法来了解矩形开壳的热湿机理。相关研究表明,目前的策略有利于进一步研究CLOCSRC的振动特性。
Experimental study on seismic performance of assembled buckling-restrained brace with low yield point steel
Meng Wang, Yunshan Tong
doi:10.1016/j.tws.2024.112474
低屈服点钢组合抗屈曲支撑抗震性能试验研究
Based on the design concept of seismic resilience, which aims to achieve controllable damage during earthquakes and rapid post-earthquake functional recovery within the structure, an assembled buckling-restrained brace with low yield point steel (ALYBRB) was proposed. To evaluate its seismic performance, quasi-static cyclic loading tests were conducted on five ALYBRB specimens. The influence of core steel material, bolt spacing of the external restraint system, and the gap between the core and the external restraint system on the seismic performance of ALYBRBs were investigated. The results indicated that the ALYBRBs exhibited superior plastic deformation capacity, stable energy dissipation capacity, and exceptional fatigue performance, as well as significant cyclic hardening characteristics and hysteretic properties with good symmetry. The cumulative plastic deformation coefficient (CPD) of ALYBRBs with LYP100 and LYP160 steel were 2.33 times and 1.51 times greater than that with Q235 steel, respectively. The maximum equivalent viscous damping coefficients of all specimens can achieve a range of 73.0% to 86.2% of the theoretically maximum value. The strain hardening adjustment factors of all specimens ranged between 1.34 and 1.90. The average compression strength adjustment factor for the properly designed ALYBRB specimens was 1.12. Reducing the bolt spacing can effectively inhibit the multi-wave buckling of the core, which is conducive to the improvement of energy dissipation efficiency in ALYBRBs. ALYBRB specimen with excessive gap exhibited decreased ductility, energy dissipation efficiency, and fatigue performance, and its out-of-plane deformation mode was a combination of bending deformation in the constrained yield segment and the transition segment deformation.
基于抗震弹性设计理念,提出了一种低屈服点钢组合抗屈曲支撑(ALYBRB),旨在实现地震时结构损伤可控和震后结构功能快速恢复。为评价其抗震性能,对5个ALYBRB试件进行了准静力循环加载试验。研究了芯钢材料、外约束系统螺栓间距、芯与外约束系统间距对alybrb抗震性能的影响。结果表明:alybrb具有优异的塑性变形能力、稳定的耗能能力和优异的疲劳性能,具有显著的循环硬化特性和良好的对称性滞回性能。使用LYP100和LYP160的alybrb的累积塑性变形系数(CPD)分别是使用Q235的2.33倍和1.51倍。各试件的最大等效粘性阻尼系数可达到理论最大值的73.0% ~ 86.2%。各试样应变硬化调整系数在1.34 ~ 1.90之间。合理设计的ALYBRB试件的平均抗压强度调整系数为1.12。减小锚杆间距可以有效抑制锚杆芯的多波屈曲,有利于提高alybrb的耗能效率。间隙过大的ALYBRB试件延性、耗能效率和疲劳性能下降,其面外变形模式为约束屈服段弯曲变形和过渡段变形的结合。