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,Thin-Walled Structures 3 篇
OXFORD-UMAT: An efficient and versatile crystal plasticity framework
Eralp Demir, Alvaro Martinez-Pechero, Chris Hardie, Edmund Tarleton
doi:10.1016/j.ijsolstr.2024.113110
牛津- umat:一种高效和通用的晶体塑性框架
The crystal plasticity-based finite element method is widely used, as it allows complex microstructures to be simulated and allows direct comparison with experiments. This paper presents the OXFORD-UMAT for Abaqus®, a novel crystal plasticity code that is publicly available online for researchers interested in using crystal plasticity. The model is able to simulate a wide range of materials and incorporates two different solvers based on the solution of slip increments and Cauchy stress with variants of state update procedures including explicit, semi-implicit, and fully-implicit for computational efficiency that can be set by the user based on the application. Constitutive laws are available for a range of materials with single or multiple phases for slip, creep, strain hardening, and back stress. The model includes geometrically necessary dislocations that can be computed using finite element interpolation functions by four alternative methods, including the total form with and without a correction for the dislocation flux, a widely used rate form, and a slip-gradient formulation. In addition, the initial strengthening and subsequent softening seen in irradiated materials can also be simulated with the model. The analysis is available in 2D (plane stress and plane strain) and 3D, including linear and quadratic elements. Here we include full derivations of the key equations used in the code and then demonstrate the capability of the code by modeling single-crystal and large-scale polycrystal cases. Comparison of OXFORD-UMAT with other available crystal plasticity codes for Abaqus® reveals the efficiency of the proposed approach, with the backup solver offering greater versatility for handling convergence issues commonly found in practical applications.
基于晶体塑性的有限元方法被广泛应用,因为它可以模拟复杂的微观结构,并可以与实验直接比较。本文介绍了Abaqus®的OXFORD-UMAT,这是一种新颖的晶体塑性代码,可供对晶体塑性感兴趣的研究人员在线公开获取。该模型能够模拟各种材料,并结合了两种不同的求解器,基于滑移增量和柯西应力的解,以及状态更新过程的变体,包括显式、半隐式和全隐式,可由用户根据应用设置计算效率。本构定律适用于滑移、蠕变、应变硬化和背应力的单相或多相材料。该模型包括几何上必要的位错,可以使用有限元插值函数通过四种替代方法计算,包括带和不带位错通量校正的总形式,广泛使用的速率形式和滑移梯度公式。此外,该模型还可以模拟辐照材料的初始强化和随后的软化过程。分析可在二维(平面应力和平面应变)和三维,包括线性和二次元。在这里,我们包括代码中使用的关键方程的完整推导,然后通过模拟单晶和大规模多晶情况来演示代码的能力。OXFORD-UMAT与Abaqus®的其他可用晶体塑性代码的比较揭示了所提出方法的效率,备用求解器为处理实际应用中常见的收敛问题提供了更大的通用性。
Cyclic and helical symmetry-informed machine learned force fields: Application to lattice vibrations in carbon nanotubes
Abhiraj Sharma, Shashikant Kumar, Phanish Suryanarayana
doi:10.1016/j.jmps.2024.105927
循环和螺旋对称的机器学习力场:在碳纳米管晶格振动中的应用
We present a formalism for developing cyclic and helical symmetry-informed machine learned force fields (MLFFs). In particular, employing the smooth overlap of atomic positions descriptors with the polynomial kernel method, we derive cyclic and helical symmetry-adapted expressions for the energy, atomic forces, and phonons, i.e., lattice vibration frequencies and modes. We use this formulation to construct a symmetry-informed MLFF for carbon nanotubes (CNTs), where the model is trained through Bayesian linear regression, with the data generated from ab initio density functional theory (DFT) calculations performed during on-the-fly symmetry-informed MLFF molecular dynamics simulations of representative CNTs. We demonstrate the accuracy of the MLFF model by comparisons with DFT calculations for the energies and forces, and density functional perturbation theory calculations for the phonons, while considering CNTs not used in the training. In particular, we obtain a root mean square error of 1.4×10^-4 Ha/atom, 4.7×10^-4 Ha/Bohr, and 4.8 cm−1 in the energy, forces, and phonon frequencies, respectively, which are well within the accuracy targeted in ab initio calculations. We apply this framework to study phonons in CNTs of various diameters and chiralities, where we identify the torsional rigid body mode that is unique to cylindrical structures and establish laws for variation of the phonon frequencies associated with the ring modes and radial breathing modes. Overall, the proposed formalism provides an avenue for studying nanostructures with cyclic and helical symmetry at ab initio accuracy, while providing orders-of-magnitude speedup relative to such methods.
我们提出了一种开发具有循环和螺旋对称的机器学习力场(MLFF)的正式化方法。具体来说,我们采用原子位置描述符的平滑重叠与多项式核方法,导出了适用于循环和螺旋对称的能量、原子力和声子(即晶格振动频率和模式)的表达式。我们使用该形式化方法构建了一个适用于碳纳米管(CNTs)的对称信息机器学习力场(MLFF),其中模型通过贝叶斯线性回归进行训练,数据来自在飞行的对称信息MLFF分子动力学模拟期间通过密度泛函理论(DFT)计算生成的代表性CNTs。通过与DFT计算的能量和力的比较以及与密度泛函扰动理论计算的声子的比较,我们展示了MLFF模型的准确性,同时考虑了未用于训练的CNTs。特别是,我们获得了1.4×10^-4 Ha/atom、4.7×10^-4 Ha/Bohr和4.8 cm^-1的均方根误差,分别用于能量、力和声子频率,这些误差均在从头算计算的精度范围内。我们将这一框架应用于研究不同直径和手性的CNTs中的声子,其中我们识别出仅存在于圆柱形结构中的扭转刚体模式,并确定了与环模和径向呼吸模相关的声子频率的变化规律。总的来说,所提出的方法为在基本精度下研究具有周期性和螺旋对称性的纳米结构提供了途径,同时相对于此类方法实现了数个数量级的加速。
Electro-mechanical-carrier coupling model of single piezoelectric semiconductor fiber pull-out
Cai Ren, Chao Liu, Kaifa Wang, Baolin Wang
doi:10.1016/j.mechmat.2024.105188
单压电半导体光纤拉拔的机电载流子耦合模型
Recently, piezoelectric semiconductor (PS) fiber composite materials are widely used in flexible and wearable optoelectronics owing to their unique properties of possessing piezoelectricity and semiconduction simultaneously. It is of great importance to investigate the interfacial characteristics of PS fiber composites in case of interfacial damages between PS fiber and elastic matrix. In this paper, a theoretical model of single piezoelectric semiconductor fiber pull-out is established to study the electro-mechanical-carrier coupling characteristics and interfacial behaviors of fiber/matrix system. Based on the shear-lag theory, the stress transfer relationship between PS fiber and elastic matrix is investigated. Closed form solutions of distributions of relevant electromechanical fields and carrier perturbation are obtained as well. The results show that the change of material parameters and structure parameters can effectively tune the mechanical, electrical and interfacial properties of composite system. In addition, the value of initial carrier concentration which reveals the semiconducting property of PS fiber has a significant influence on the distributions of electromechanical fields. The findings are valuable for adjusting the electromechanical coupling behaviors of PS fiber via specific structure design and material combination in practical applications of piezotronics.
近年来,压电半导体(PS)纤维复合材料以其同时具有压电性和半导体性的独特性能,在柔性和可穿戴光电子领域得到了广泛的应用。研究聚苯乙烯纤维与弹性基体之间的界面损伤对研究聚苯乙烯纤维复合材料的界面特性具有重要意义。本文建立了单压电半导体光纤拉拔的理论模型,研究了光纤/基体体系的机电-载流子耦合特性和界面行为。基于剪切滞后理论,研究了PS纤维与弹性基体之间的应力传递关系。得到了相关机电场分布和载流子扰动的闭形式解。结果表明,材料参数和结构参数的改变可以有效地调整复合材料体系的力学、电学和界面性能。此外,反映PS光纤半导体特性的初始载流子浓度对其机电场分布有显著影响。研究结果对于在压电实际应用中通过特殊的结构设计和材料组合来调整PS光纤的机电耦合性能具有一定的参考价值。
Research on Damage Repair and High-Velocity Impact Characteristics of Thermoplastic Composites
Feng JIN, Lulu LIU, Xinying ZHU, Zhihao XIE, Wei CHEN
doi:10.1016/j.tws.2024.112663
热塑性复合材料损伤修复及高速冲击特性研究
Low-velocity impact (LVI) can result in imperceptible damage to carbon fiber reinforced thermoplastic composites (CFRTP) laminates during service, leading to a reduction in structural strength. The thermal repair of damaged CFRTP laminates is conducted using the repairability of thermoplastic resin at high temperatures. However, the high-velocity impact characteristics of CFRTP laminates following thermal repair remain uncertain. This study examines CFRTP laminates made of two different materials (CF/PEEK and CF/PPS) with varying levels of low-velocity impact damage, and investigates the thermal repair process. A comparative experimental analysis examined the high-speed impact characteristics of CFRTP laminates under varying conditions. The results indicate that CF/PEEK laminates consistently exhibit superior compressive properties and impact resistance compared to CF/PPS laminates under similar conditions. Following damage from low-velocity impact, the compressive properties and high-velocity impact resistance of CFRTP laminates decrease, with CF/PPS laminates typically showing a lower performance retention rate. However, the thermal repair process proposed in this study significantly enhances the performance of CF/PPS laminates. Moreover, the degree of performance healing in CF/PPS laminates is consistently higher than that in CF/PEEK laminates, which is closely related to the semi-crystalline nature of PEEK resin.
低速冲击(LVI)会对碳纤维增强热塑性复合材料(CFRTP)层压板造成难以察觉的损伤,导致结构强度降低。利用热塑性树脂在高温下的可修复性,对受损CFRTP层叠板进行热修复。然而,热修复后CFRTP层压板的高速冲击特性仍然不确定。本研究考察了由两种不同材料(CF/PEEK和CF/PPS)制成的CFRTP层压板,它们具有不同程度的低速冲击损伤,并研究了热修复过程。对比实验分析了CFRTP复合材料在不同条件下的高速冲击特性。结果表明,在相同的条件下,CF/PEEK层压板始终表现出优于CF/PPS层压板的抗压性能和抗冲击性。低速冲击损伤后,CFRTP层压板的压缩性能和高速抗冲击性能下降,而CF/PPS层压板的性能保持率较低。然而,本研究提出的热修复工艺显著提高了CF/PPS层压板的性能。此外,CF/PPS复合材料的性能愈合程度始终高于CF/PEEK复合材料,这与PEEK树脂的半结晶性质密切相关。
Shear elastic buckling of corrugated steel plate shear walls with stiffeners considering torsional rigidity
Ruo-Min Wu, Chao-Qun Yu, Ling-Qi Wang, Jing-Zhong Tong
doi:10.1016/j.tws.2024.112646
考虑扭转刚度加筋波纹钢板剪力墙的剪切弹性屈曲
This paper conducted theoretical and numerical investigations on shear elastic buckling formulas of stiffened corrugated steel plate shear walls (SCSPSWs) considering torsional rigidities of stiffeners. Firstly, based on the orthotropic plate theory and the energy method, a theoretical model for the derivation of elastic buckling coefficients was established, introducing the torsional strain energy term of the stiffeners. On this basis, the variation law of the elastic buckling coefficient of the walls concerning the stiffener positions was studied, determining the optimal layout of the stiffeners. The formula for calculating the elastic buckling coefficient at any stiffener layout was provided. Furthermore, based on the stiffeners arranged in the optimal layout, the transition torsional rigidity of the stiffeners was determined, and the formulas for the elastic buckling coefficient of the SCSPSW with stiffeners considering torsional rigidity were proposed, in which the enhancement of torsional constraints provided by the stiffeners was measured by an enhancement factor. Finally, eigenvalue buckling analyses were performed based on finite element models to validate the theoretical analysis results on the optimal stiffener layout and elastic buckling coefficient.
本文对考虑加筋扭转刚度的加筋波纹钢板剪力墙剪切弹性屈曲公式进行了理论和数值研究。首先,基于正交各向异性板理论和能量法,建立了弹性屈曲系数推导的理论模型,引入了加劲筋扭转应变能项;在此基础上,研究了墙体弹性屈曲系数随加劲肋位置的变化规律,确定了加劲肋的最佳布置方式。给出了任意加劲肋布置时弹性屈曲系数的计算公式。在优化布置加劲肋的基础上,确定了加劲肋的过渡扭转刚度,提出了考虑扭转刚度的加劲肋SCSPSW弹性屈曲系数计算公式,并用增强系数来衡量加劲肋对扭转约束的增强作用。最后,基于有限元模型进行了特征值屈曲分析,验证了加强筋优化布局和弹性屈曲系数的理论分析结果。
Bending behaviors of 3D printed sandwich structures with functionally graded porous lattice cores
Meiling Fan, Tao Zeng, Rina Wu, Yuhua Cui, Guodong Xu, Xiaohong Wang, Su Cheng, Jue Zhao
doi:10.1016/j.tws.2024.112655
具有功能梯度多孔晶格芯的3D打印夹层结构的弯曲行为
A novel graded porous lattice core sandwich structure is presented to achieve a balance between lightweight and high mechanical performance for materials. An analytical model is proposed to investigate the bending responses of graded porous lattice core sandwich structures by utilizing the homogenization and dehomogenization method. A comprehensive parametric investigation on the mechanical behaviors of the graded lattice sandwich structures is conducted in order to design and optimize these materials. The precise control of porosity is implemented utilizing 3D printing techniques in this study. The theoretical results are validated by the experiments using 3D printed samples. It is found that mechanical properties can be improved through optimization of pore gradient distribution in the lattice core while maintaining a light weight of the sandwich structures. These findings offer valuable insights for designing tailored sandwich structures that are suitable for a diverse range of engineering applications.
提出了一种新型的梯度多孔晶格芯夹层结构,以实现材料轻量化和高机械性能之间的平衡。采用均匀化和去均匀化方法,建立了梯度多孔晶格芯夹层结构的弯曲响应分析模型。对梯度点阵夹层结构的力学行为进行了全面的参数化研究,从而对这些材料进行了设计和优化。在本研究中,利用3D打印技术实现了孔隙度的精确控制。通过3D打印样品的实验验证了理论结果。研究发现,在保持夹层结构轻量化的同时,通过优化晶格核孔隙梯度分布可以提高夹层结构的力学性能。这些发现为设计适合各种工程应用的定制夹层结构提供了有价值的见解。