Theoretical and Applied Fracture Mechanics最新文献

Study and mechanism analysis on fracture mechanical properties of steel fiber reinforced recycled concrete (SF-R-RC)

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-28 DOI: 10.1016/j.tafmec.2024.104780

Zhenpeng Yu , Tianqian Wu , Xinjian Sun , Lei Xie , Kequan Yu

Recycled concrete has deficiencies in its overall performance due to the deteriorated properties of the recycled aggregate (RA) used. Based on the RA characteristics and fiber reinforcement mechanism, designing recycled concrete by adding steel fiber (SF) and enhancing RAs in a coordinated manner can effectively improve the overall performance of recycled concrete. Therefore, this paper considers the SF content and RA enhancement to study the fracture mechanical properties of steel fiber reinforced recycled concrete (SF-R-RC), and the main conclusions are as follows: the fracture mechanical properties of SF-R-RC are significantly affected by aggregate enhancement and SF content. Without the SFs, the strengthened coated recycled aggregate concrete (CRAC) was better than unreinforced recycled aggregate concrete (RAC) in terms of the unstable fracture load, fracture energy, initial fracture toughness and unstable fracture toughness, but weaker than normal aggregate concrete (NAC). The increase in the unstable fracture load, fracture energy, initial fracture toughness and unstable fracture toughness of NAC, RAC and CRAC with the increase in SF content was observed, with CRAC showing the most significant increase in these fracture parameters. Applying digital image correlation (DIC) and acoustic emission (AE) techniques, the effect of SF content and RA enhancement method on the crack evolution process and damage distribution law of SF-R-RC was studied. Meanwhile, the microscopic testing technique was used to reveal the mechanism of the influence of SF and RA enhancement on the fracture mechanical properties of SF-R-RC. The research results of this paper provide a theoretical basis for the application of RA enhancement and SF reinforcement methods of recycled concrete in practical engineering.

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引用次数: 0

Simulation of mixed mode I-II fatigue crack propagation in concrete with different strengths

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-26 DOI: 10.1016/j.tafmec.2024.104779

Hong Chen , Zhimin Wu , Rena C. Yu

The mode-I fatigue crack propagation in concrete has been extensively studied. However, many concrete structure failures occur subjected to mixed-mode fatigue loads in practice. The accurate predictions for the mixed mode I-II fatigue crack propagation and fatigue life are crucial for evaluating the structural safety of concrete constructions. In this paper, the mixed mode I-II fatigue crack propagation process on concrete with different strengths is simulated using the fatigue tension-softening constitutive model and the crack propagation criterion of the initial fracture toughness as a parameter (SIF-based criterion). The numerical results indicated that the fatigue crack length decreases with increasing the concrete strength for a given fatigue load level, but the fatigue life significantly increases with concrete strength. Further, a modified Paris law is presented on the basis of the numerical results for concrete with different strengths. With the known tensile strength of concrete, the mixed mode I-II fatigue crack propagation rate of concrete with different strengths can be presented. The proposed model in this study is useful in further predicting the fatigue life of concrete structures under mixed-mode fatigue loads.

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引用次数: 0

Effect of the surface morphology of 3D printed titanium substrates on the mode I fracture toughness of metal-metal and metal-composite bonded joints

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-26 DOI: 10.1016/j.tafmec.2024.104778

Michele Gulino , Rosemere de Araujo Alves Lima , Fabrizio Moroni , Alessandro Pirondi , Sofia Teixeira de Freitas

Parts manufactured with Laser Powder Bed Fusion (LPBF) are drawing interest in the adhesive joints research because of their high surface roughness, which is usually associated with good adhesion. This work aims to assess the adhesion strength of the inherent surface morphology of LPBF manufactured titanium.

Double Cantilever Beam (DCB) tests were carried out to determine the mode I fracture toughness of joints comprising as-printed titanium (Ti6Al4V) adherends, namely titanium-titanium secondary bonded and titanium-Carbon Fibre Reinforced Polymer (CFRP) co-bonded joints. The effect of high-temperature oxidation on the fracture toughness was also evaluated by testing a batch of joints in which the titanium underwent a post-printing thermal treatment. The as-printed specimens were compared to the same type of joints but with sandblasted titanium adherends to evaluate the effect of this surface pre-treatment on the value of fracture toughness.

The results indicate that non-oxidised titanium joints with untreated adherends had an average of 11% higher fracture toughness than their sandblasted counterparts. On the other hand, sandblasting proved beneficial for oxidised joints, increasing the fracture toughness by 64% on average over the untreated samples.

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引用次数: 0

Fatigue characterisation of structural steel by means of the small punch test: Development of a methodology 通过小冲压试验确定结构钢的疲劳特性：方法的开发

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-24 DOI: 10.1016/j.tafmec.2024.104772

S. Otero, G. Álvarez, M.M. Llera, C. Rodríguez

Knowledge of the fatigue behaviour of materials is fundamental to the safe design of structures. Standardised tests are used for this purpose, but their application requires a considerable amount of material, which in many cases is not available. To overcome this problem, the use of miniature tests would be the optimal solution. This work analyses the application of the Small Punch Test (SPT) to characterise the fatigue behaviour of structural steels. To this end, an experimental methodology has been developed to analyse not only where SPT-fatigue damage initiates and how it propagates, but also its relationship with changes in specimen compliance. Based on this methodology, different S_PT-N iso-damage curves and the SPT-fatigue limit have been obtained for two structural steels. By comparing these results with those obtained from rotating beam fatigue tests, a simple correlation has been proposed between the fatigue limits obtained from SPT and rotating beam fatigue tests.

了解材料的疲劳特性是安全设计结构的基础。标准化测试可用于此目的，但其应用需要大量材料，而在许多情况下，这些材料是不可用的。为了解决这个问题，使用微型试验是最佳解决方案。这项研究分析了小冲压试验（SPT）在表征结构钢疲劳行为方面的应用。为此，我们开发了一种实验方法，不仅可以分析 SPT 疲劳损伤的起始位置和扩展方式，还可以分析其与试样顺应性变化之间的关系。基于这种方法，我们获得了两种结构钢的不同 SPT-N 等损伤曲线和 SPT 疲劳极限。通过将这些结果与旋转梁疲劳试验得出的结果进行比较，提出了 SPT 和旋转梁疲劳试验得出的疲劳极限之间的简单关联。

引用次数: 0

Non-Proportional mixed mode plastic zones via finite elements and artificial neural networks 通过有限元和人工神经网络实现非比例混合模式塑性区

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-23 DOI: 10.1016/j.tafmec.2024.104777

V. Infante , R. Baptista

The plastic zone developed around a fatigue crack tip can affect both fatigue and fracture material behaviour. Predicting the plastic zone shape and size under cyclic conditions can, therefore, enhance fatigue crack propagation analysis. While there are theoretical solutions for the elastic stress and strain fields under pure or mixed mode conditions around the crack tip, solutions for plastic fields must be determined using experimental or numerical approaches. The Compact Tension Shear (CTS) specimen has been extensively used to analyse plastic zones under proportional conditions, but when non-proportional conditions are applied the number of necessary analyses for a reasonable understanding of the plastic zone shape and size around the crack tip can increase exponentially. To address this problem, a combined approach was used to reduce the number of required plastic zone simulations. First, a hand selected number of loading configurations were simulated using the Finite Element Method (FEM), predicting the plastic zone shape and size. Then, an Artificial Neural Network (ANN) was trained to predict the plastic zone under different conditions. Using only 18 configurations for 3 different loading conditions, the trained ANN was able to accurately predict the plastic zone shape and size for both tensile and shear propagation modes. The network can now be used to predict the plastic zone influence on fatigue and fracture behaviour, without the need for further numerical analysis. The paper results also show that crack propagation direction can be correlated and predicted using the applied loads and the resulting plastic zone.

疲劳裂纹尖端周围形成的塑性区会影响材料的疲劳和断裂行为。因此，预测循环条件下塑性区的形状和大小可以加强疲劳裂纹扩展分析。虽然裂纹尖端周围纯模式或混合模式条件下的弹性应力场和应变场有理论解决方案，但塑性场的解决方案必须通过实验或数值方法来确定。紧凑拉伸剪切（CTS）试样已被广泛用于分析比例条件下的塑性区，但当应用非比例条件时，要合理了解裂纹尖端周围塑性区的形状和大小，所需的分析次数可能会呈指数增长。为了解决这个问题，我们采用了一种综合方法来减少所需的塑性区模拟次数。首先，使用有限元法（FEM）对人工选择的加载配置进行模拟，预测塑性区的形状和大小。然后，对人工神经网络（ANN）进行训练，以预测不同条件下的塑性区。只使用了 3 种不同加载条件下的 18 种配置，经过训练的人工神经网络就能准确预测拉伸和剪切两种传播模式下的塑性区形状和大小。现在，该网络可用于预测塑性区对疲劳和断裂行为的影响，而无需进一步的数值分析。论文结果还表明，裂纹扩展方向可以通过施加的载荷和产生的塑性区进行关联和预测。

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引用次数: 0

Assessment of measurement uncertainty associated with fracture toughness calculation based on energy release rate in spherical indentation tests 基于球形压痕试验能量释放率计算断裂韧性的测量不确定性评估

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-23 DOI: 10.1016/j.tafmec.2024.104775

Cláudio Costa Souza , Regina Paula Garcia Moura , Waldek Wladimir Bose Filho , Rosenda Valdés Arencibia

This work aims to evaluate the uncertainty associated with the fracture toughness of 4130 M steel obtained via instrumented indentation tests and the methodology proposed by Zhang, Wang and Wang (2019). These authors take the energy release rate as a basis to determine fracture toughness. In this study, the uncertainty was assessed using the Guide to the Expression of Uncertainty of Measurement (GUM) and Monte Carlo methods. For uncertainty assessment, all measurands and input variables were identified based on the equations proposed by these authors. Then, the standard uncertainty associated with each input variable was calculated by applying the GUM method. To determine the uncertainty associated with the energy release rate J_SIT the Monte Carlo method was applied. The results obtained showed that the expanded uncertainty associated with J_SIT considering three tests was 1.486 N.mm⁻¹. This uncertainty represents 7.25 % of the average J_SIT value (20.490 N.mm⁻¹). The expanded uncertainty associated with K_IC was 7.520 MPa.m^0.5. These represent 3.82 % of the average K_IC (196.562 MPa.m^0.5) value obtained. This paper demonstrates that despite the complexity of the mathematical equation proposed by Zhang, Wang and Wang (2019), to obtain fracture toughness via instrumented indentation tests, the uncertainty associated can be successfully accessed by combining the GUM and Monte Carlo methods. This work showed that the application of the instrumented indentation technique with the methodology proposed by Zhang, Wang and Wang (2019) provided fracture toughness values with excellent quality under the experimental conditions used in this study.

这项工作旨在评估通过仪器压痕测试获得的 4130 M 钢断裂韧性的不确定性，以及 Zhang、Wang 和 Wang（2019 年）提出的方法。这些作者将能量释放率作为确定断裂韧性的基础。本研究采用《测量不确定度表达指南》（GUM）和蒙特卡罗方法评估不确定度。在进行不确定性评估时，根据这些作者提出的公式确定了所有测量值和输入变量。然后，采用 GUM 方法计算与每个输入变量相关的标准不确定度。为了确定与能量释放率 JSIT 相关的不确定性，采用了蒙特卡罗法。结果显示，考虑到三次试验，与 JSIT 相关的扩展不确定性为 1.486 N.mm-1。该不确定性占 JSIT 平均值（20.490 N.mm-1）的 7.25%。与 KIC 相关的扩展不确定性为 7.520 MPa.m0.5。这占所获得的 KIC 平均值（196.562 MPa.m0.5）的 3.82%。本文表明，尽管 Zhang、Wang 和 Wang（2019 年）提出的通过仪器压痕测试获得断裂韧性的数学方程很复杂，但通过结合 GUM 和蒙特卡罗方法，可以成功地获得相关的不确定性。这项工作表明，在本研究使用的实验条件下，仪器压痕技术与 Zhang、Wang 和 Wang（2019）提出的方法的应用提供了质量上乘的断裂韧性值。

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引用次数: 0

An analytical model based on cross-sectional geometric characteristics for calculating crack opening displacement in reinforced concrete beams 基于截面几何特征的钢筋混凝土梁裂缝张开位移计算分析模型

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-22 DOI: 10.1016/j.tafmec.2024.104770

Chunyu Fu , Yunpeng Liu , Yongsheng Lao , Jianming Wang

To accurately calculate crack opening displacement (COD) in reinforced concrete beams, this study establishes a relationship between COD, cross-sectional rotation, and strain distribution by utilizing the geometric relationships of deformation in the cracked region. Based on the varying bond characteristics between the reinforcement and concrete, a method is developed to calculate COD by analyzing the nonlinear strain distribution in both materials and determining the sectional rotation of the cracked beam. This proposed method was validated through experimental tests on a cracked reinforced concrete beam model. The results indicate that, as the load increases, the bond stiffness between the reinforcement and concrete diminishes, leading to nonlinear changes in the tensile strain of the reinforcement. This results in an increasing slope of the crack opening displacement with increasing load, showing a clear nonlinear trend, even under small loads. However, a linear relationship is observed between crack opening displacement and structural deflection. The proposed method, based on the geometric relationship of sectional deformation, accurately predicts these nonlinear deformations, offering a novel approach for calculating crack opening displacements.

为了准确计算钢筋混凝土梁的裂缝张开位移（COD），本研究利用裂缝区域变形的几何关系，建立了裂缝张开位移、截面旋转和应变分布之间的关系。根据钢筋和混凝土之间不同的粘结特性，通过分析两种材料中的非线性应变分布和确定开裂梁的截面旋转，开发了一种计算 COD 的方法。通过对开裂钢筋混凝土梁模型进行实验测试，验证了所提出的方法。结果表明，随着荷载的增加，钢筋和混凝土之间的粘结刚度减小，导致钢筋拉应变的非线性变化。这导致裂缝张开位移的斜率随荷载增加而增大，即使在小荷载下也显示出明显的非线性趋势。不过，裂缝张开位移与结构挠度之间呈线性关系。所提出的方法基于截面变形的几何关系，能准确预测这些非线性变形，为计算裂缝张开位移提供了一种新方法。

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引用次数: 0

Influence of freeze–thaw cycles on fracture behaviors of Nano-SiO2 modified high-strength high- ductility alkali-activated material 冻融循环对纳米二氧化硅改性高强度高延展性碱活性材料断裂行为的影响

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-21 DOI: 10.1016/j.tafmec.2024.104774

Li Li , Peng Jin , Kun Zhang , Chenyu Yan , Ning Zhang , Yang Li , Qi Feng

Nano-SiO₂ (NS) can effectively improve the mechanical properties of cement-based materials and alkali-activated materials, but its effect on the durability and fracture properties of high-ductility concrete has not been revealed. The influences of freeze–thaw cycles on the bending fracture behaviors of NS modified high-strength high-ductility alkali-activated material (HSHDAM) were studied herein. There were 4 wt content of NS (0 %, 4 %, 8 % and 12 %) and 4 numbers of freeze–thaw cycles (25, 50, 75 and 100) assessed. The results indicated that with the increase of freeze–thaw cycles number, the compressive strength, dynamic modulus of elasticity, fracture toughness of initiation and instability and fracture energy of HSHDAM were all decreased continually and significantly, but the ductility index was increased. With the increase of the NS weight content, the compressive strength, dynamic modulus of elasticity, fracture toughness of initiation and instability, and fracture energy and ductility index of HSHDAM were all increased continually, while the bending strength seems to be optimal at 4 % NS content. 75 freeze–thaw cycle was the threshold value for the strengthening effect of NS on bending strength and ductility index. With the addition of NS, the better bonding properties of polyethylene fiber, more fully cracking behaviors, and compact alkali-activated matrix contributed to these good fracture and anti-freeze–thaw behaviors. The addition of NS can alleviate the deterioration of HSHDAM mechanics and fracture properties caused by freeze–thaw cycle.

纳米二氧化硅（NS）能有效改善水泥基材料和碱活性材料的力学性能，但其对高导混凝土耐久性和断裂性能的影响尚未被揭示。本文研究了冻融循环对 NS 改性高强高导碱活性材料（HSHDAM）弯曲断裂行为的影响。共评估了 4 种 NS 重量含量（0%、4%、8% 和 12%）和 4 种冻融循环次数（25、50、75 和 100）。结果表明，随着冻融循环次数的增加，HSHDAM 的抗压强度、动态弹性模量、起始断裂韧性、不稳定性断裂韧性和断裂能均持续显著下降，但延性指数有所上升。随着NS重量含量的增加，HSHDAM的抗压强度、动态弹性模量、起始和不稳定断裂韧性、断裂能和延性指数均持续上升，而弯曲强度似乎在NS含量为4%时达到最佳。75 次冻融循环是 NS 对弯曲强度和延展性指数产生强化作用的临界值。添加 NS 后，聚乙烯纤维更好的粘结性能、更充分的开裂行为以及碱激活基体的致密性都有助于实现这些良好的断裂和抗冻融行为。添加 NS 可以缓解冻融循环对 HSHDAM 力学性能和断裂性能的影响。

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引用次数: 0

Progressive failure characteristics and damage constitutive model of fissured rocks under water–rock coupling 水岩耦合作用下裂隙岩的渐进破坏特征和损伤构成模型

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-20 DOI: 10.1016/j.tafmec.2024.104765

Jiyuan Hu , Dongfa Sheng , Feifei Qin , Yingchao Zhu , Ziheng Li , Taicong Chen , Hongquan Yu

An in-depth study of the damage characteristics of rocks under water–rock coupling (WRC) and the weakening mechanism of their mechanical properties is of great guiding significance for practical engineering. This paper studies the influence of WRC on the mechanical properties, energy dissipation characteristics and damage evolution law of fractured limestone during long-term immersion damage, revealing the mechanical behavior of fractured rock mass in a water environment. To explore the influence of the nonlinear process of macroscopic and mesoscopic damage evolution on the mechanical behavior of fractured rock mass, based on the evolution law of dissipated energy of rock specimens, this paper proposes a critical point of pore compaction and constructs a strain difference function between the compaction stage and the linear elastic stage. On this basis, a segmented damage constitutive model consisting of an empirical pore compaction model and a macro-meso coupled damage constitutive model was established. The model was compared with the calculation results of the model that did not consider the pore compaction stage. It was found that the strength characteristics and damage evolution law of the fractured rock mass revealed by this model were more in line with the experimental results, thus verifying the rationality of the model. Finally, damage evolution and the physical significance of the model parameters proposed in this paper were systematically discussed.

深入研究岩石在水岩耦合（WRC）作用下的损伤特征及其力学性能的削弱机理，对实际工程具有重要的指导意义。本文研究了水岩耦合对断裂石灰岩长期浸泡破坏过程中力学性质、耗能特征和损伤演化规律的影响，揭示了断裂岩体在水环境中的力学行为。为探讨宏观和中观损伤演化的非线性过程对断裂岩体力学行为的影响，本文基于岩石试件耗能演化规律，提出了孔隙压实临界点，并构建了压实阶段与线弹性阶段的应变差函数。在此基础上，建立了由经验孔隙压实模型和宏观-介质耦合损伤构成模型组成的分段损伤构成模型。该模型与未考虑孔隙压实阶段的模型计算结果进行了比较。结果发现，该模型揭示的断裂岩体强度特征和损伤演化规律与实验结果更加吻合，从而验证了模型的合理性。最后，系统讨论了本文提出的模型参数的损伤演化和物理意义。

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引用次数: 0

Modelling unstable crack propagation in concrete by finite element method with continuous nodal stress

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics

Pub Date : 2024-11-20 DOI: 10.1016/j.tafmec.2024.104767

Wang Zhang , Zhimin Wu , Rena C. Yu , Jianjun Zheng

Cracks in concrete will propagate unstably due to excessive shear stress, interactions at the rock-concrete interface, or sudden energy release, significantly compromising structural bearing capacity. To investigate this phenomenon, a nonlinear numerical method for modelling mixed-mode I-II crack propagation has been developed. This approach integrates dynamic equilibrium with a fictitious crack model and an initiation fracture toughness criterion. Key innovations include the incorporation of a finite element method with continuous nodal stress to enhance calculation accuracy, the utilization of kinetic energy to compensate for abrupt losses of strain energy during crack propagation, and the consideration of the deformation of the distributive beam and its interactions with specimens and supports. It was validated by modelling classic benchmarks for the dynamic initiation and propagation of brittle materials under mode I and mixed-mode I-II loading, and applied to analyse unstable crack propagation in concrete for four-point shear (FPS) beam specimens under various ratios of mode I and II stress intensity factors (K_I/K_II = 0 to 5.32) and loading rates (2 × 10^-7 m/s to 2 × 10^-3 m/s). Results indicated that the method effectively captures unstable crack propagation, with load-crack mouth shear displacement (CMSD) curves and crack propagation trajectories closely matching the experimental data. Furthermore, it was observed that when the elastic strain energy within the concrete beam exceeds the residual energy stored in the extended cracks, the crack transitions from stability to instability; conversely, if the elastic strain energy is less than or approximately equal to the residual energy, the crack decelerates and returns to stability. Additionally, parametric analyses reveal that lower distributive beam stiffness, shorter preset crack lengths, reduced concrete fracture energy, and a less robust cohesive force–displacement curve increase the likelihood of unstable crack propagation in concrete.

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引用次数: 0