Engineering Fracture Mechanics最新文献_第5页

Investigating rock particle breakage using 3D coupled peridynamics-discrete element method: Emphasis on local surface features 利用三维围岩动力学-离散元耦合方法研究岩石颗粒破裂：强调局部表面特征

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110585

N.S.S.P. Kalyan , Yutaka Fukumoto , Ramesh Kannan Kandasami

Individual particle breakage within rock-based granular medium profoundly influences the overall macro-scale behavior of the assembly, with the strength being notably impacted by particle morphology and surficial features. However, the widely used numerical methods often oversimplify the realistic morphology, resulting in unrealistic particle breakage simulations. The current study addresses the limitation by specifically investigating the influence of local surface geometry on particle strength and breakage patterns. X-ray Computed Tomography (CT) images of particles were used to obtain the realistic geometry and Voronoi Parallel Linear Enumeration (VPLE), a morphology-preserving surface generation strategy was introduced to capture the complex surficial features. A coupled peridynamics-discrete element framework was proposed to simulate the breakage of individual rock based aggregates. The numerical framework was validated with Brazilian tests on basalt rock cores, and a rigorous comparison was made against other finite-discrete element methods. The study explores different extremes of particle morphology, considering the presence and absence of concavities in the breakage simulations. Robust computational geometry pipeline was employed to measure contact area and local radius of curvature during the breakage. The findings highlight that the concave features, along with the contact curvature significantly reduce the particle strength (

\approx 40 %

) as opposed to the convex particle variants exhibiting higher strength. The presence of sharp surficial features led to multiple failure mechanisms, including initial asperity crushing and subsequent splitting failure. The present work strongly emphasizes the importance of considering realistic particle geometry in numerical simulations of granular materials undergoing crushing.

岩基颗粒介质中的单个颗粒破碎会深刻影响组合体的整体宏观尺度行为，颗粒形态和表面特征对强度有显著影响。然而，广泛使用的数值方法往往会过度简化现实形态，从而导致不切实际的颗粒破碎模拟。本研究通过专门研究局部表面几何形状对颗粒强度和断裂模式的影响，解决了这一局限性。研究使用粒子的 X 射线计算机断层扫描（CT）图像来获取真实的几何形状，并引入了 Voronoi 平行线枚举（VPLE）这一形态保留表面生成策略来捕捉复杂的表面特征。提出了一种周动力学-离散元耦合框架，用于模拟基于岩石的单个聚集体的破碎。该数值框架通过巴西玄武岩岩心测试进行了验证，并与其他有限离散元方法进行了严格比较。研究探讨了颗粒形态的不同极端，考虑了破碎模拟中凹面的存在和不存在。在断裂过程中，采用了强大的计算几何管道来测量接触面积和局部曲率半径。研究结果表明，凹面特征以及接触曲率大大降低了颗粒强度（≈40%），而凸面颗粒则表现出更高的强度。尖锐表面特征的存在导致了多种失效机制，包括最初的表面破碎和随后的分裂失效。本研究成果有力地强调了在对发生破碎的颗粒材料进行数值模拟时考虑现实颗粒几何形状的重要性。

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引用次数: 0

Fatigue analysis of novel hole hemmed joints for hybrid busbars in electric vehicle batteries 用于电动汽车电池混合母线的新型孔折边接头的疲劳分析

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110590

B.F.A. da Silva , M.M. Kasaei , A. Akhavan-Safar , R.J.C. Carbas , E.A.S. Marques , L.F.M. da Silva

This study investigates the fatigue behavior and failure modes of novel hole-hemmed joints, assessing their suitability as hybrid aluminum-copper busbars for electric vehicle batteries. The hole-hemmed joining process, which avoids the need for additional elements, heat, or welding, presents a sustainable solution for hybrid busbar manufacturing. The joints undergo quasi-static shear tests to determine failure mechanisms, strength, and failure displacements. A finite element model of the hole-hemmed process and shear test is developed to evaluate the impact of mechanical interlock on joint performance and to predict regions prone to crack initiation during fatigue testing. Shear fatigue tests and quasi-static shear post-fatigue tests reveal two primary failure modes: cracking at the edge of the aluminum outer sheet branch and bending of the copper inner sheet. The study also examines stiffness degradation and damage evolution during fatigue tests. A normalized load-cycle curve, plotting normalized fatigue load against fatigue life, is created to better predict joint fatigue life. Through comprehensive testing and modeling, the research provides a deep understanding of the mechanical performance of these novel hole-hemmed joints, underscoring their potential for use in hybrid busbars.

本研究调查了新型孔铰接接头的疲劳行为和失效模式，评估了其作为电动汽车电池铝铜混合母线的适用性。孔铰接连接工艺避免了附加元件、加热或焊接的需要，为混合动力母线的制造提供了一种可持续的解决方案。接头经过准静态剪切测试，以确定失效机理、强度和失效位移。为评估机械互锁对接头性能的影响，并预测疲劳试验中容易产生裂纹的区域，开发了孔铰工艺和剪切试验的有限元模型。剪切疲劳试验和准静态剪切疲劳后试验揭示了两种主要失效模式：铝外板分支边缘开裂和铜内板弯曲。研究还考察了疲劳试验过程中的刚度退化和损伤演变。通过绘制归一化疲劳载荷与疲劳寿命的归一化载荷循环曲线，可以更好地预测接头的疲劳寿命。通过综合测试和建模，研究人员深入了解了这些新型孔铰接接头的机械性能，并强调了它们在混合母线中的应用潜力。

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引用次数: 0

Simulation of progressive failure process in solid rocket propellants using a phase-field model 利用相场模型模拟固体火箭推进剂的渐进失效过程

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110577

Tong Wang , Zhi Sun , Xiaofei Hu , Huiqian Xu , Peng Zhang , Weian Yao

Dense interface cracks and their transformation into matrix cracks of propellants are complicated and pose challenges to existing numerical methods for fracture analysis. However, understanding fracture behavior of solid propellants is a key aspect for the development of high-performance solid rocket motors. We proposed a fracture phase field method in this study accounting for material interfaces to accurately capture the complicated failure processes of solid rocket propellant while a precise computational model is adopted. The widely concerned challenges such as the extremely thin actual interface width, strong material heterogeneity, material viscoelasticity, crack interaction, computational efficiency are all solved or at least eased with the new method. The proposed method has provided a reliable tool for the design and evaluation of propellants which has long been desired in engineering. In addition, we propose an easy implementation way of the proposed method which may be interesting both engineering and academic practices. A few numerical examples with comparison with experimental results are provided for the verification and validation of the proposed method, and the comparison results show excellent agreements.

推进剂的致密界面裂纹及其向基体裂纹的转化非常复杂，对现有的断裂分析数值方法提出了挑战。然而，了解固体推进剂的断裂行为是开发高性能固体火箭发动机的一个关键方面。我们在本研究中提出了一种考虑材料界面的断裂相场方法，以准确捕捉固体火箭推进剂的复杂失效过程，同时采用精确的计算模型。新方法解决或至少缓解了实际界面宽度极薄、材料异质性强、材料粘弹性、裂纹相互作用、计算效率等广泛关注的难题。所提出的方法为推进剂的设计和评估提供了一种可靠的工具，而这正是工程界长期以来所期望的。此外，我们还提出了一种易于实施的方法，这可能对工程和学术实践都很有意义。为了验证和确认所提出的方法，我们提供了一些与实验结果对比的数值示例，对比结果表明两者非常吻合。

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引用次数: 0

Investigation on fatigue performance and microstructure of split sleeve cold expansion of TC4 holes TC4 孔分体式套筒冷膨胀疲劳性能和微观结构研究

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110587

Lei Huang , Shoucai Wang , Haikun Ma , Ru Su , Changzhou Xu , Wenzhong Liu , Dayong Wu , Jie Kang

The exceptional performance of pivotal structural components serves to enhance the aircraft’s efficient and secure operational profile. The structural components are connected and assembled primarily through fastener holes. However, discontinuities in structural components can lead to stress concentrations around holes, resulting in fatigue failure of the structural components. This is significant in enhancing the fatigue performance of the hole structure. In this study, TC4 titanium alloy was strengthened by split sleeve cold expansion (SCE) technique and its effect on residual stress, microstructure and fatigue fracture was investigated. The results indicate that SCE induces residual compressive stress at the hole edges, thereby inhibiting fatigue crack propagation. Geometrically necessary dislocations are formed at the interface between the α phase and β phase to accommodate the strain gradient. Low angle grain boundaries (LAGBs) impede dislocation movement and accumulate dislocation density, leading to an increase in LAGB misorientation and subsequent transition to high angle grain boundaries. The SCE process led to the formation of subgrain boundaries and refined the grains in the material. The fatigue life of the material was extended by 6.2 times, with peak compressive residual stresses up to 244 MPa at the inlet side. The combined effects of residual compressive stresses, back stress and grain refinement contribute to improving the fatigue life of the hole structure.

枢轴结构部件的优异性能有助于提高飞机的运行效率和安全性。结构部件主要通过紧固件孔进行连接和组装。然而，结构部件的不连续性会导致孔周围的应力集中，从而导致结构部件的疲劳失效。这对提高孔结构的疲劳性能意义重大。在这项研究中，采用分体套筒冷膨胀（SCE）技术强化了 TC4 钛合金，并研究了其对残余应力、微观结构和疲劳断裂的影响。结果表明，SCE 会在孔边缘产生残余压应力，从而抑制疲劳裂纹的扩展。为了适应应变梯度，在 α 相与 β 相的界面上形成了几何上必要的位错。低角度晶界（LAGB）会阻碍位错运动并积累位错密度，从而导致 LAGB 错向增加，随后过渡到高角度晶界。SCE 过程导致亚晶界的形成，并细化了材料中的晶粒。材料的疲劳寿命延长了 6.2 倍，入口侧的残余压应力峰值高达 244 兆帕。残余压应力、背应力和晶粒细化的综合效应有助于提高孔结构的疲劳寿命。

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引用次数: 0

Experimental study on the Mode l fracture toughness of frozen silty clay incorporating Digital image correlation 结合数字图像相关性对冻结淤泥质粘土的模式 l 断裂韧性进行实验研究

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110597

Weihang Hua , Huimei Zhang , Yongtao Wang , Haojun Xia

To investigate the effects of initial moisture content and temperature on the Mode I fracture toughness (K_Ic) of frozen silty clay, a series of three-point bending tests were conducted. Rectangular specimens with prefabricated cracks were tested, and digital image correlation (DIC) technology was employed to analyze the microscopic characteristics at the crack tip. The results indicate that the Mode I fracture toughness of frozen silty clay increases with decreasing temperature and increasing initial moisture content. Temperature governs the failure mode, with plastic failure predominantly occurring at high temperatures and brittle failure at low temperatures. Based on the load–displacement curves and DIC recordings, the macroscopic fracture process of the specimens can be categorized into three stages: elastic deformation, formation of the failure surface, and specimen failure. Additionally, the crack propagation process can be further divided into three stages: initiation and development of microcracks, transition from microcracks to macroscopic cracks, and rapid development of macroscopic cracks. These findings provide critical insights for slope stability research in cold regions and offer new perspectives for engineering design and construction in similar environments.

为了研究初始含水量和温度对冻结淤泥质粘土的模式 I 断裂韧性（KIc）的影响，进行了一系列三点弯曲试验。试验采用了预制裂缝的矩形试样，并利用数字图像相关（DIC）技术分析了裂缝尖端的微观特征。结果表明，冷冻淤泥质粘土的模式 I 断裂韧性随着温度的降低和初始含水量的增加而增加。破坏模式受温度影响，塑性破坏主要发生在高温下，而脆性破坏则发生在低温下。根据荷载-位移曲线和 DIC 记录，试样的宏观断裂过程可分为三个阶段：弹性变形、形成破坏面和试样破坏。此外，裂纹扩展过程还可进一步分为三个阶段：微裂纹的产生和发展、微裂纹向宏观裂纹的过渡以及宏观裂纹的快速发展。这些发现为寒冷地区的边坡稳定性研究提供了重要启示，并为类似环境下的工程设计和施工提供了新的视角。

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引用次数: 0

Excavation-induced cracking of clastic rock: A true triaxial instantaneous unloading study with varied levels of initial damage 开挖诱发的碎屑岩开裂：不同初始损伤程度的真正三轴瞬时卸载研究

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-28 DOI: 10.1016/j.engfracmech.2024.110595

Feiyan Wang , Yangyi Zhou , Xiaojun Yu , Bentong Sun , Yangyang Cui , Tianxiang Song

The cracking and squeezing problem in deep engineering significantly constrains project construction. To reveal the cracking mechanism of rock under instantaneous unloading, a self-designed rigid true triaxial experimental apparatus, equipped with groundbreaking electromagnetic unloading and high-speed camera functions, was utilized to conduct instantaneous unloading tests on clastic rock with varied levels of initial damage. The results indicate that samples undergo severe and irreversible lateral dilation during instantaneous unloading, with dilational strain rapidly increasing at higher initial damage levels. Instantaneous unloading induces the generation of numerous tensile microcracks, which propagate and coalesce rapidly. The crack propagation speed, as well as the length and width of the cracks at failure, increase with the rise of the initial damage level. The samples eventually exhibit two distinct macroscopic fracture zones: a tensile fracture zone and a tensile-shear mixed fracture zone. Analysis of acoustic emission hits and energy indicates that higher initial damage levels correspond to greater unloading damage, with a higher overall proportion of tensile cracks throughout the experiment. Under the induction of blasting excavation, radial stress is rapidly unloaded, and dense tensile cracks emerge in the immediate surrounding rock, leading to cracking and squeezing towards the free face. Importantly, higher initial damage levels intensify the squeezing effect. The self-developed equipment serves as a crucial technical tool for researching excavation unloading, and the insights derived from this study provide valuable guidance for understanding cracking mechanisms and informing the construction of deep engineering projects.

深部工程中的开裂和挤压问题严重制约着工程建设。为揭示岩石在瞬时卸载作用下的开裂机理，利用自行设计的刚性真三轴试验装置，配备了开创性的电磁卸载和高速摄像功能，对不同初始损伤程度的碎屑岩进行了瞬时卸载试验。结果表明，样品在瞬时卸载过程中会发生严重且不可逆的横向扩张，在初始损伤程度较高时，扩张应变会迅速增加。瞬时卸载诱导产生大量拉伸微裂缝，这些裂缝迅速扩展和凝聚。裂纹的扩展速度以及破坏时裂纹的长度和宽度随着初始损伤程度的增加而增加。样品最终呈现出两个明显的宏观断裂带：拉伸断裂带和拉伸剪切混合断裂带。声发射命中率和能量分析表明，较高的初始损伤水平对应较大的卸载损伤，整个实验过程中拉伸裂纹的总体比例较高。在爆破开挖的诱导下，径向应力迅速卸载，紧邻的围岩中出现密集的拉伸裂缝，导致开裂并向自由面挤压。重要的是，较高的初始损伤程度会加剧挤压效应。自主研发的设备是研究开挖卸荷的重要技术工具，该研究得出的见解为了解开裂机理和指导深层工程项目施工提供了宝贵的指导。

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引用次数: 0

Development of Johnson-Cook-Distinct Lattice Spring Model and its application in projectile penetration into metal targets 约翰逊-库克-分格弹簧模型的开发及其在射弹穿透金属目标中的应用

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-26 DOI: 10.1016/j.engfracmech.2024.110571

Jianjun Ma , Jiajun Wang , Yuexiang Lin , Jinxin Zhao , Zhenyu Yin , Linchong Huang

Projectile penetration into metal targets plays an important role in modern protective structure engineering, damage assessmentin terrorist attacks, and car clash accident analysis, etc. The penetration process of metal target has been characterized by large deformation, high temperature, high pressure, and dynamic damage, which can be classified as a continuous-discontinuous dynamical process. To capture the dynamic responses of metal materials subjected to high-speed penetration, Johnson-Cook model has been implemented in a continuum-discrete model, namely, Distinct Lattice Spring Model (DLSM). This is achieved by redefining the constitutive model in DLSM, with plasticity hardening (plastic strain effects), strain rate, temperature, damage evolution, equation of state, etc., being taken into account, thus developing a new numerical model called JC-DLSM model. This model is validated through studying Taylor rod high-speed impact experiments, thin metal plate penetration experiments, and projectile impact experiments on titanium alloy targets. Good agreement between numerical modelling and experimental data has been achieved for all cases considered, thereby demonstrating the capability of JC-DLSM to reproduce the damage characteristics and ballistic limits of metals under high-speed impact/penetration. Then, the impacts of projectile shape, metal target surface configuration on the characteristics of penetration damage patterns have been investigated. This contributes to a better understanding of the damage mechanisms of metal targets upon penetration or impact, facilitating the computational means for analysing and optimizing the penetration resistance of protective engineering structures.

射弹穿透金属目标在现代防护结构工程、恐怖袭击中的损伤评估、汽车碰撞事故分析等方面发挥着重要作用。金属目标的穿透过程具有大变形、高温、高压和动态损伤的特点，可归类为一个连续-非连续的动力学过程。为了捕捉金属材料在高速穿透过程中的动态响应，Johnson-Cook 模型被应用到连续-离散模型中，即分格弹簧模型（DLSM）。这是通过重新定义 DLSM 中的构成模型来实现的，其中考虑了塑性硬化（塑性应变效应）、应变速率、温度、损伤演变、状态方程等因素，从而建立了一个名为 JC-DLSM 模型的新数值模型。通过研究泰勒杆高速冲击实验、薄金属板穿透实验和钛合金靶弹丸冲击实验，对该模型进行了验证。在所考虑的所有情况下，数值建模与实验数据之间都取得了良好的一致性，从而证明了 JC-DLSM 能够再现高速冲击/穿透下金属的损伤特征和弹道极限。然后，研究了弹丸形状、金属靶表面构造对穿透损伤模式特征的影响。这有助于更好地理解金属目标在穿透或撞击时的损伤机制，为分析和优化防护工程结构的抗穿透性提供了计算手段。

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引用次数: 0

Effect of isotropy and anisotropy: toward understanding the fracture behavior of magnetoactive elastomers 各向同性和各向异性的影响：了解磁活性弹性体的断裂行为

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-24 DOI: 10.1016/j.engfracmech.2024.110553

Nusrat Jahan Salim, Ignacio Arretche, Connor D. Pierce, Elizabeth J. Smith, Kathryn H. Matlack

Magnetoactive elastomers (MAEs) exhibit magneto-mechanical coupling and typically contain micron-sized spherical ferromagnetic particles embedded in an elastomeric matrix. Anisotropic particle arrangement in MAEs, achieved by curing the material in a magnetic field, offers tailored and enhanced magneto-mechanical coupling compared to isotropic configurations. While tunable MAE properties such as the effective modulus and vibrational response have been relatively well studied, a thorough understanding of their fracture mechanisms, particularly in MAEs with microstructural anisotropy or composites with similar structures remains almost completely unexplored. Here, we characterize the fracture mechanisms of anisotropic and isotropic unmagnetized MAEs using experiments and simulations, focusing on the effects of spherical particles in anisotropic chain-like configurations. Specifically, we experimentally measure the fracture toughness of MAEs containing different volume fractions of particles, and with particles arranged both randomly and aligned at 0°, 45°, and 90° to the loading direction. Results show that anisotropic MAEs with particle chains aligned with the load direction can improve fracture toughness by up to almost 600%, whereas isotropic MAEs increase the fracture toughness by only 420%, compared to the pure elastomer. Scanning electron microscopy of the post-fractured surface reveals toughening mechanisms at micro-scale, such as chain waviness, particle agglomeration, and particle distribution. Simulations using a finite element method-based decoupled phase field-cohesive zone model on simplified geometries qualitatively support imaging interpretations. Overall, this work explains how internal geometry, including waviness in particle chains, chain alignment, and particle agglomerations affects fracture of MAEs and generally soft composites with chain-like geometries of spherical particles. These results have engineering applications in improving fracture properties of smart soft composites relevant to soft robotics, tunable vibration absorbers, and noise attenuators.

磁活性弹性体（MAE）具有磁-机械耦合性，通常包含嵌入弹性体基质中的微米级球形铁磁性颗粒。通过在磁场中固化 MAE 材料，MAE 中的各向异性颗粒排列可提供定制的、比各向同性配置更强的磁机械耦合。虽然对有效模量和振动响应等可调 MAE 特性的研究相对较多，但对其断裂机制的透彻了解，尤其是对具有微结构各向异性的 MAE 或具有类似结构的复合材料的了解，仍几乎完全空白。在此，我们利用实验和模拟来描述各向异性和各向同性非磁化 MAE 的断裂机制，重点关注各向异性链状结构中球形颗粒的影响。具体来说，我们通过实验测量了含有不同体积分数颗粒的 MAE 的断裂韧性，这些颗粒既有随机排列的，也有与加载方向成 0°、45° 和 90° 排列的。结果表明，与纯弹性体相比，各向异性 MAE 的断裂韧性可提高近 600%，而各向同性 MAE 的断裂韧性仅提高 420%。对断裂后的表面进行扫描电子显微镜观察，可发现微观尺度的增韧机制，如链状波纹、颗粒聚集和颗粒分布。使用基于有限元法的去耦合相场-粘合区模型对简化几何形状进行模拟，定性地支持了成像解释。总之，这项工作解释了内部几何形状（包括颗粒链的波浪状、链排列和颗粒团聚）如何影响 MAE 和一般具有球形颗粒链状几何形状的软复合材料的断裂。这些结果在工程应用中可用于改善智能软复合材料的断裂性能，如软机器人、可调减震器和噪音衰减器。

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引用次数: 0

Impact of elevated loading rates on the shape of the Master Curve (ASTM E1921) for a German RPV steel 加载速率升高对德国 RPV 钢主曲线（ASTM E1921）形状的影响

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-24 DOI: 10.1016/j.engfracmech.2024.110588

Johannes Tlatlik , Uwe Mayer

The Master Curve Methodology (ASTM E1921) experimentally assesses a materials temperature-dependent fracture toughness, predominantly for quasi-static testing conditions. The treatment of elevated loading rates is described by the annex A1 of ASTM E1921 and A14 of ASTM E1820. This paper presents results of the evaluation of a large and standard-conforming database in order to verify the procedures recommended by the standard for elevated loading rates. Testing involved C(T)- and SEN(B)-specimens of the RPV-steel 22NiMoCr3-7 (A508 Grade 2) for loading rates of 10⁰ MPa√m/s ≤

\dot{K}

≤ 10⁴ MPa√m/s in the ductile to brittle transition region. While valid T₀-values were found, single-temperature T₀-values were observed to differ more than expected from multi-temperature T₀-values, which cannot be explained by the Master Curve uncertainty. The shape and underlying distribution of the Master Curve show deviations with increased loading rate. The shape factor p is optimized with respect to the individual data, and it increases with

\dot{K}

, but deviations are not completely overcome. This can be linked to a change in distribution, which was demonstrated by an optimization of minimum fracture toughness K_min, which increases with temperature. It is argued that the cause for the observations is linked to both heating processes and local crack arrest that severely influence macroscopic fracture behavior. Also, an individual adjustment of p or K_min is not helpful due to the material-dependency in practice. It is recommended that fracture mechanics testing at elevated loading rates is performed close to or below T₀ in order to minimize the influence of dynamic loading conditions on the assessment.

主曲线法（ASTM E1921）主要针对准静态测试条件，通过实验评估材料随温度变化的断裂韧性。ASTM E1921 附件 A1 和 ASTM E1820 附件 A14 对加载速率升高的处理进行了说明。本文介绍了对符合标准的大型数据库进行评估的结果，以验证标准推荐的加载速率升高的程序。测试涉及 RPV 钢 22NiMoCr3-7 的 C(T)-和 SEN(B)-试样（A508 2 级），加载速率为 100 MPa√m/s ≤ K̇ ≤ 104 MPa√m/s，处于韧性到脆性的过渡区域。虽然发现了有效的 T0 值，但观察到单温 T0 值与多温 T0 值的差异比预期的要大，这不能用主曲线的不确定性来解释。主曲线的形状和基本分布随着加载速率的增加而出现偏差。形状系数 p 根据单个数据进行了优化，并随 K̇ 值的增加而增加，但偏差并未完全消除。这可能与分布的变化有关，最小断裂韧性 Kmin 的优化证明了这一点，它随温度的升高而增大。有观点认为，观察结果的原因与加热过程和局部裂纹捕获有关，这严重影响了宏观断裂行为。此外，在实际应用中，由于材料的依赖性，单独调整 p 或 Kmin 也无济于事。建议在接近或低于 T0 的条件下进行高加载速率下的断裂力学测试，以尽量减少动态加载条件对评估的影响。

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引用次数: 0

Finite element modeling for cohesive/adhesive failure of adhesive structures with a thermosetting resin 热固性树脂粘合结构内聚/粘合失效的有限元建模

IF 4.7 2区工程技术 Q1 MECHANICS

Engineering Fracture Mechanics

Pub Date : 2024-10-24 DOI: 10.1016/j.engfracmech.2024.110552

Yamato Hoshikawa , Yoshiaki Kawagoe , Kazuki Ryuzono , Tomonaga Okabe

In this study, we established a novel method based on the finite element method (FEM) for predicting the strength of adhesive structures. Viscoplasticity, void growth, and cohesive zone model were introduced into the FEM to create a nonlinear damage growth (NDG) model. This model was used to comprehensively analyze the process zones within the adhesive layer. Furthermore, the embedded process zone approach was used to develop an interface constitutive law that averages the mechanical response of the adhesive layer. This modified Ma–Kishimoto (MMK) model can accurately represent the adhesive layer as an interface element and is computationally efficient. Furthermore, the study obtained the necessary interface properties for the MMK model from the NDG model, creating a numerical material test that can approximate the effect of the process zone. To validate the proposed method, single-lap shear tests were performed, and the accuracy of the predicted strength and deformation field was evaluated. The damage evolution in the NDG model and the MMK model were compared, and the scope of application of the MMK model was discussed. The results of this study can be used as a reference for the failure mechanism of thermosetting adhesives and establishment of design indices for adhesive structural strength.

在这项研究中，我们建立了一种基于有限元法（FEM）的新方法，用于预测粘合剂结构的强度。在有限元法中引入了粘弹性、空隙增长和内聚区模型，从而建立了非线性损伤增长（NDG）模型。该模型用于全面分析粘合剂层内的加工区。此外，嵌入式加工区方法还被用于开发界面构成定律，以平均粘合剂层的机械响应。这种改良的 Ma-Kishimoto (MMK) 模型可以将粘合剂层作为界面元素进行精确表示，并且计算效率高。此外，该研究还从 NDG 模型中获得了 MMK 模型所需的界面属性，从而创建了一个可近似反映加工区影响的数值材料测试。为了验证所提出的方法，进行了单圈剪切试验，并评估了预测强度和变形场的准确性。比较了 NDG 模型和 MMK 模型的损伤演变，并讨论了 MMK 模型的应用范围。研究结果可作为热固性粘合剂失效机理和建立粘合剂结构强度设计指数的参考。

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