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,International Journal of Plasticity 1 篇,Thin-Walled Structures 2 篇
M-Voronoi and other random open and closed-cell elasto-plastic cellular materials: Geometry generation and numerical study at small and large strains
Z. Hooshmand-Ahoor, Haoming Luo, K. Danas
doi:10.1016/j.ijsolstr.2024.112680
M-Voronoi和其他随机开闭孔弹塑性细胞材料:小应变和大应变的几何生成和数值研究
The present study deals with a numerical design strategy of a novel class of three-dimensional random Voronoi-type geometries, called M-Voronoi. These materials comprise random, non-quadratic convex void shapes and non-uniform intervoid ligament thicknesses, and can span high-to-low relative densities. The starting point for their generation is a random adsorption algorithm (RSA) construction with spherical voids embedded in an incompressible, nonlinear elastic matrix phase. The initial RSA geometry is subjected to large elastic volume changes by prescribing Dirichlet boundary conditions. Due to the incompressibility of the matrix phase, the externally imposed volume changes lead to significant void growth. The numerical growth process may be stopped at any desired porosity. The proposed M-Voronoi process is general and allows the formation of isotropic (or anisotropic) designs. As a byproduct of the developed approach, we also present a novel remeshing technique allowing to read arbitrary geometries of one or multiple phases. The elasto-plastic properties of the M-Voronoi porous materials are numerically investigated at small strains as well as large compressive and shear loads. Their response is assessed by comparison with other well-known random and periodic porous geometries such as polydisperse porous materials with spherical voids (RSA), classical TPMS Gyroid geometries and random Spinodoid topologies. The results show that M-Voronoi and RSA (with spherical voids) geometries exhibit the stiffest elastic and highest flow stress response compared to the other two geometries. This study shows unambiguously that randomness may or may not lead to enhanced mechanical response such as higher stiffness or flow stress.
本研究涉及一种新型三维随机voronoi型几何图形的数值设计策略,称为M-Voronoi。这些材料包括随机的,非二次凸空隙形状和非均匀空隙间韧带厚度,并且可以跨越高到低的相对密度。其生成的起点是随机吸附算法(RSA)的构造,其中球形空隙嵌入在不可压缩的非线性弹性矩阵相中。通过规定狄利克雷边界条件,使初始RSA几何结构受到较大弹性体积变化的影响。由于基体相的不可压缩性,外部施加的体积变化导致显著的空隙生长。数值生长过程可以在任何期望的孔隙率处停止。提出的M-Voronoi过程是通用的,允许形成各向同性(或各向异性)设计。作为开发方法的副产品,我们还提出了一种新的重网格技术,允许读取一个或多个相位的任意几何形状。对M-Voronoi多孔材料在小应变和大压缩、剪切载荷下的弹塑性特性进行了数值研究。通过与其他已知的随机和周期性多孔几何结构(如具有球形孔洞的多分散多孔材料(RSA),经典TPMS Gyroid几何结构和随机Spinodoid拓扑结构)进行比较,评估了它们的响应。结果表明,与其他两种几何形状相比,M-Voronoi和RSA(带球面孔洞)几何形状具有最硬的弹性和最大的流动应力响应。这项研究明确地表明,随机性可能会也可能不会导致机械响应的增强,如更高的刚度或流动应力。
On the role of plastic relaxation in stress assisted grain boundary oxidation
Y. Piao, D.S. Balint
doi:10.1016/j.jmps.2024.105552
应力辅助晶界氧化中塑性松弛的作用
The influence of plasticity on the high-temperature stress-assisted grain boundary oxidation of nickel-based superalloys used in applications such as turbine rotor discs is investigated using the method of discrete dislocation plasticity (DDP). The misfit stress fields of nib-shaped intrusions are captured by a continuous distribution of edge dislocations whose extra half planes represent the volumetric misfit of the oxide, which is implemented in a planar formulation of DDP by invoking the linear superposition principle. DDP simulations show that stresses generated by an intrusion several microns or more in size are large enough to generate dislocation pileups with associated stresses at the intrusion interface on the order of 1 GPa, which in turn lead to localised growth and morphology change of the intrusion by stress-assisted diffusion. This morphology change relaxes the compression stress inside the intrusion near the base, and therefore increases the fracture resistances of the intrusion. The effects of applied loading and background plasticity on the growth rate of the intrusion in defect-free and prestrained samples are predicted. It is found that applied tensile stress generally increases grain boundary oxidation, while in prestrained samples the enhancement of the intrusion growth rate by the applied load is insignificant due to dislocation pile-ups ahead of the oxidation process.
采用离散位错塑性(DDP)方法研究了塑性对涡轮转子盘等镍基高温合金高温应力辅助晶界氧化的影响。尖状侵入体的错配应力场由边缘位错的连续分布捕获,其额外的半平面表示氧化物的体积错配,这是通过调用线性叠加原理在DDP的平面公式中实现的。DDP模拟结果表明,几微米或更大尺寸的侵入所产生的应力足以在侵入界面产生1 GPa量级的位错堆积和相关应力,从而导致应力辅助扩散侵入的局部生长和形态变化。这种形态变化使侵入体内部靠近基部的压应力松弛,从而提高了侵入体的抗破裂能力。预测了外加载荷和本底塑性对无缺陷和预应变试样中侵入体生长速率的影响。结果表明,施加拉伸应力通常会增加晶界氧化,而在预应变样品中,由于在氧化过程之前存在位错堆积,施加载荷对侵入生长速率的提高不显著。
Enhanced mechanical and thermal properties in 3D printed Al2O3 lattice/ epoxy interpenetrating phase composites
Yida Zhao, Xiu Yun Yap, Pengcheng Ye, Ian P. Seetoh, Huilu Guo, Changquan Lai, Du Zehui, Chee Lip Gan
doi:10.1016/j.mechmat.2024.104930
3D打印Al2O3晶格/环氧互渗相复合材料的力学和热性能增强
Interpenetrating phase composites (IPCs) with 3D printed alumina microlattices infiltrated with epoxy have been fabricated. Mechanical analysis shows that the IPCs under quasi-static compression generally exhibit fracture behaviour similar to that of their ceramic-lattice constituent but in a gradual manner. The IPCs with Simple Cubic lattices initiate the fractures at the struts in the outer lattice planes, while IPCs with Octet Truss and Kelvin Cell lattices tend to fracture at their (110) or (111) planes. The compressive strength and energy absorption of IPCs follow the order of Simple Cubic > Kelvin Cells > Octet Truss when the ceramic volume fraction is 0.3. The IPCs display compressive strengths up to 120% higher and energy absorption 100% greater than the iso-strain combined properties of the lattice and epoxy up to the lattice's point of failure. The factors governing the fracture behaviour and the strengthening and energy absorption mechanisms were thoroughly discussed. Furthermore, the IPCs show much better retention of mechanical strength and dimensional stability at elevated temperatures compared with many commonly used particle or fiber-reinforced epoxy matrix composites.
制备了3D打印氧化铝微晶格的互穿相复合材料(IPCs)。力学分析表明,IPCs在准静态压缩下的断裂行为与它们的陶瓷晶格成分相似,但断裂是渐进的。具有简单立方晶格的IPCs首先在外晶格面的支撑处断裂,而具有八元桁架和开尔文晶格的IPCs则倾向于在(110)或(111)面断裂。当陶瓷体积分数为0.3时,IPCs的抗压强度和吸能大小依次为:Simple Cubic > Kelvin Cells > Octet Truss。在晶格失效点之前,IPCs的抗压强度比晶格和环氧树脂的等应变组合性能高出120%,能量吸收高出100%。对影响断裂行为的因素、强化和吸能机理进行了深入探讨。此外,与许多常用的颗粒或纤维增强环氧基复合材料相比,IPCs在高温下具有更好的机械强度和尺寸稳定性。
Tensile properties and microstructural evolution of 17-4 PH stainless steel fabricated by laser hybrid additive manufacturing technology
Nan Li, Qiang Wang, Michael Bermingham, Wenjuan Niu, Peng Han, Nan Guo, Shenao Li
doi:10.1016/j.ijplas.2024.103885
激光复合增材制造技术制备17-4 PH不锈钢拉伸性能及显微组织演变
Wire-based laser directed energy deposition (LDED) technology is an attractive and efficient additive manufacturing technology, which shows great potential in the process of manufacturing high-value engineering components. However, the thermal effect will lead to a large amount of residual tensile stress in the components, and the large crystal structures after solidification seriously affects the tensile performance. The pursuit of high mechanical properties in additive manufacturing components have prompted researchers to seek new strengthening process to produce high-strength components. Therefore, in this paper, laser shock peening (LSP) composite wire-based LDED were used for the additive manufacturing of 17-4 PH stainless steel under the specified experimental conditions, and the effects of LSP on microstructure evolution, microhardness, and tensile properties of wire-based LDED components were systematically studied. Results showed that uniform grains with an average size of 2.31 μm were generated on the top surface of specimen due to the ultra-high plastic strain induced by LSP shock wave. The size of hierarchical martensitic units shows varying degrees of reduction after LSP treatment, which is shown by the width decrease of packet, block and lath. Dynamic recrystallization caused by rearrangement and annihilation of high-density dislocations promoted the grain refinement. Meanwhile, the residual stress was completely converted from tensile state into compressive state with a maximum value of 425 MPa, and the microhardness was also enhanced to a peak value of 432 HV. In addition, we observed that the high-density dislocation environment created by LSP treatment promoted the further precipitation, and the aggregation phenomenon of precipitates was observed in the dense dislocation area. Furthermore, the tensile strength and elongation of LSP treated specimen were improved significantly, which was attributed to the combined effects of grain refinement, introduction of dislocation structures, precipitation strengthening and gradient residual compressive stress. In summary, laser hybrid additive manufacturing technology provides a new idea and method for the production of high-performance precipitation hardening stainless steel components.
线基激光定向能沉积(LDED)技术是一种极具吸引力的高效增材制造技术,在制造高价值工程部件的过程中显示出巨大的潜力。但热效应会导致构件中存在大量残余拉伸应力,凝固后的大晶体结构严重影响拉伸性能。增材制造部件对高机械性能的追求促使研究人员寻求新的强化工艺来生产高强度部件。因此,本文在规定的实验条件下,采用激光冲击强化(LSP)复合丝基LDED对17-4 PH不锈钢进行增材制造,系统研究了LSP对丝基LDED构件的微观组织演变、显微硬度和拉伸性能的影响。结果表明:由于LSP激波引起的超高塑性应变,试样上表面形成了平均尺寸为2.31 μm的均匀晶粒;LSP处理后,分层马氏体单元的大小有不同程度的减小,表现为分组、块和条的宽度减小。高密度位错的重排和湮灭引起的动态再结晶促进了晶粒的细化。同时,残余应力完全由拉伸状态转化为压缩状态,最大值为425 MPa,显微硬度也有所提高,峰值为432 HV。此外,我们观察到LSP处理造成的高密度位错环境促进了进一步的析出,并且在密集位错区域观察到析出物的聚集现象。此外,LSP处理试样的抗拉强度和伸长率显著提高,这是晶粒细化、位错组织引入、沉淀强化和梯度残余压应力共同作用的结果。综上所述,激光混合增材制造技术为生产高性能沉淀硬化不锈钢构件提供了新的思路和方法。
Axial compressive behavior of pre-damaged concrete-filled square steel tube columns repaired with section circularization and CFRP composites
Kang Zhao, Zhongjun Hu, Boxin Wang, Weicheng Liao, Yan Xu
doi:10.1016/j.tws.2024.111606
预损伤方钢管混凝土柱经截面圆化和CFRP复合材料修复后的轴压性能
This study focused on repair treatments for the effective reuse of damaged concrete-filled square steel tube (CFSST) columns with carbon fiber-reinforced polymer (CFRP) composites. Forty specimens were designed to investigate the effects of pre-damage levels, section circularization, and the number of CFRP layers on the compressive behavior of the repaired CFSST columns. Test results indicated that the method of section circularization and CFRP wrapping effectively restored the degraded initial axial stiffness of the pre-damaged CFSST columns and increased the ultimate bearing capacity of the pre-damaged CFSST columns by 49-180% compared to their undamaged condition. Considering the influence of the pre-damage level and the contribution of section circularization, the ultimate bearing capacity calculation model was suggested for predicting the compressive behavior of the repaired CFSST columns. The experimental results and collected test data have well verified the accuracy and applicability of the calculation model.
本文主要研究了用碳纤维增强聚合物(CFRP)复合材料修复受损方钢管混凝土(CFSST)柱的有效再利用。设计了40个试件,研究了预损伤水平、截面圆度和CFRP层数对修复后CFSST柱抗压性能的影响。试验结果表明,截面圆化和CFRP包覆能有效恢复预损伤CFSST柱初始轴向刚度的退化,使预损伤CFSST柱的极限承载力比未损伤状态提高49 ~ 180%。考虑预损伤程度的影响和截面圆弧化的贡献,提出了预测修复后CFSST柱抗压性能的极限承载力计算模型。实验结果和收集的测试数据很好地验证了计算模型的准确性和适用性。
Behaviour and design of CFS stud walls under both sides fire exposure
Son Tung Vy, Anthony Ariyanayagam, Mahen Mahendran
doi:10.1016/j.tws.2024.111619
两侧受火作用下CFS钉墙的性能与设计
Cold-formed steel (CFS) stud wall systems fabricated using CFS channel studs, tracks and fire-rated sheathing materials are increasingly used in Australia, New Zealand, Europe and North America. Although a large number of research studies has focused on the behaviour of load-bearing CFS stud wall systems at ambient temperature and in fire, the knowledge related to the behaviour as well as suitable design methods of these wall systems exposed to fire on both sides is very limited. Recently, the safety of CFS stud walls under both sides fire exposure has become a concern to fire engineers. In this study, detailed investigations of load-bearing CFS stud walls under both sides fire exposure were undertaken using thermal and sequentially coupled structural finite element (FE) models. These models were validated against the standard fire test results of CFS stud walls under one side fire exposure available in the literature. Using the thermal and sequentially coupled structural FE analysis results, the effects of cavity insulation, thickness of gypsum plasterboards and both sides fire exposure on the behaviour and fire resistance level (FRL) of CFS stud walls were investigated and the results were compared with those for CFS stud walls under one side fire exposure. These results highlighted the major differences between the CFS stud walls under one side and both sides fire exposures in terms of their thermal and structural behaviour and FRL. Finally, appropriate design guidelines using the direct strength method in the CFS design standards are proposed.
在澳大利亚、新西兰、欧洲和北美,使用冷弯型钢(CFS)螺柱、轨道和防火护套材料制成的冷弯型钢(CFS)螺柱墙系统的应用越来越广泛。虽然大量的研究都集中在承重CFS螺柱墙系统在环境温度和火灾下的性能,但有关这些墙系统在两侧火灾下的性能以及合适的设计方法的知识非常有限。近年来,混凝土柱墙两侧受火情况下的安全问题一直是消防工程师关注的问题。在这项研究中,采用热耦合结构有限元(FE)模型对两侧火灾暴露下的承重CFS钉墙进行了详细的研究。这些模型与文献中可用的单侧火灾暴露下CFS螺柱墙的标准防火测试结果进行了验证。利用热学和序列耦合结构有限元分析结果,研究了空腔保温、石膏板厚度和两侧受火对CFS柱墙性能和耐火水平的影响,并与单侧受火下CFS柱墙的结果进行了比较。这些结果突出了在一侧和两侧火灾暴露下的CFS钉墙在其热学和结构行为以及FRL方面的主要差异。最后,提出了适用于CFS设计标准中直接强度法的设计准则。