Article
Engineering, Mechanical
S. H. Sajjadi, A. R. Khorshidvand, M. Jabbari, M. Javadi
Summary: A new brittle fracture criterion was proposed for sharp V-shaped notches, taking into account the effect of shear stress and showing strong correlation with experimental results. This criterion has broad applicability and is capable of predicting fracture in various loading conditions.
FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES
(2021)
Article
Engineering, Geological
J. Justo, J. Castro, S. Cicero
Summary: This study evaluates the fracture of U-notched limestone samples under mixed mode I + II loading conditions at varying temperatures. The Theory of Critical Distances is applied successfully to analyze the experimental results, providing accurate assessments for both pure mode I and mixed mode fracture conditions. The results show a certain influence of notch radius on the critical distance, with relatively constant values observed for different mode mixities.
ROCK MECHANICS AND ROCK ENGINEERING
(2021)
Article
Mechanics
F. Hatami, M. R. Ayatollahi, A. R. Torabi
Summary: The study developed fracture limit curves for key-hole notched components made of brittle materials, and conducted fracture tests to evaluate the influence of notch tip radius on fracture toughness. The results showed good consistency between the experimental data and fracture limit curves, indicating reliable estimation of notch fracture toughness under different loading conditions.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2021)
Article
Mechanics
Wei Liu, Yulong Li, Zhiqian Zhang, Liyun Yang, Yi Luo, Zhongwen Yue
Summary: This study investigates the mixed-mode I+II fracture characteristics of V-notched rock specimens under impact loads, considering the effects of loading rate, notch angle, and loading angle. Experimental and numerical analysis results show that loading rate has a significant positive effect on the fracture toughness value, but has a negative effect on the crack initiation angle.
ENGINEERING FRACTURE MECHANICS
(2023)
Article
Engineering, Mechanical
Zelin Liu, Chunde Ma, Xin'ao Wei
Summary: Fracture characteristics of layered rocks under mixed mode I/III loading are significantly influenced by bedding angle alpha and loading mode. The equivalent fracture toughness and fracture energy exhibit different trends under different loading modes and bedding angles. The acoustic emission characteristics and fracture trajectory are also significantly influenced by bedding angle, loading mode, and bedding strength. The results provide new insights into the mixed mode I/III fracture mechanism of layered rocks.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2023)
Article
Engineering, Mechanical
Quanqi Zhu, Diyuan Li, Jinyin Ma, Zhenyu Han, Xibing Li
Summary: The dynamic mixed mode I/II fracture properties of hard rock were investigated through split-Hopkinson pressure bar tests on cracked straight through Brazilian disc (CSTBD) diorite specimens. The fracture load and toughness for different crack angles or mode mixities were determined. The dynamic fracture process and crack mouth opening displacement (CMOD) were monitored, and the fractal and morphology characteristics of fracture surfaces were analyzed. The study found that the CMOD behavior is closely related to the force acting on the crack surface, and the allowable CMOD decreases with increasing crack angle. Stress-based and strain-based fracture criteria were introduced, and the GMTS criterion and EMTSN criterion showed the best prediction effect for fracture toughness and crack initiation angle respectively. Observation results showed that the macro fracture trajectories were controlled by the prefabricated crack angle, while the mode mixity had little impact on the meso-roughness and micro-morphology of the fracture surface. The fracture surface of CSTBD diorite specimen exhibited mixed tensile-shear cracks under dynamic load.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2023)
Article
Engineering, Mechanical
Pedram Bagheri, A. R. Torabi
Summary: This research investigates the fracture toughness of U-notched Russian pine specimens with highly orthotropic nonlinear behavior under mixed mode I/II loading conditions theoretically and experimentally. The notch strength of orthotropic specimens is successfully predicted by introducing a novel two-step model of material simplification. The two-step model proposed can be successfully applied for mixed mode I/II fracture estimation of notched orthotropic specimens with nonlinear behavior.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2022)
Article
Engineering, Mechanical
Reza Jalayer, Behnam Saboori, Majid Reza Ayatollahi
Summary: A new test specimen is proposed for investigating mixed mode I/II/III fracture of materials. This test specimen creates mixed mode I/III loading conditions by displacing the position of an inclined crack from the middle of the rectangular specimen, in addition to mode II loading under anti-symmetric four-point bending. The experimental fracture loads of PMMA specimens are compared with theoretical predictions, showing satisfactory consistency.
FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES
(2023)
Article
Engineering, Mechanical
Jian Liu, Lan Qiao, Yuan Li, Qingwen Li, Dongjue Fan
Summary: This study investigates the effect of quasi-static loading rate on the mixed-mode I/II fractures of rock materials. The results show that fracture toughness increases with increasing quasi-static loading rate, while crack initiation angle and fracture geometry remain relatively stable. A generalized maximum tangential strain energy density (GMTSED) criterion is proposed to analyze the development of fracture toughness and crack initiation angle. The experimental and analytical results support the validity of the GMTSED criterion.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2022)
Article
Energy & Fuels
Peiwang Cao, Tao Zhou, Yang Ju, Jianbo Zhu
Summary: It is still unclear how different loading angles (beta) affect the mixed mode I/II fracture behavior of rock. To investigate this, cracked straight through Brazilian disc tests were performed on sandstone under various beta. The results show that the effect of beta on peak load and crack propagation velocity is slight, but there is a linear increase in mixed mode I/II fracture toughness with increasing beta.
GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
(2023)
Article
Engineering, Mechanical
Xinting Miao, Haisheng Hong, Jian Peng, Tao Ping, Fengfeng Bie, Chenyang Jiang
Summary: The mixed mode fracture behaviors of TC4 titanium alloy were systematically studied by finite element method, testing, and theoretical analysis. It was found that there is II-III coupling effect ahead of the crack tip for mixed mode crack, and three-dimensional stress intensity factors were defined and calculated based on this. Under I-II mixed mode loading, the crack exhibited a planar propagation state, and the deflection angle increased with the mode II component. The I-II mixed mode fracture of TC4 showed a brittle fracture mechanism, and the brittle fracture criteria were in agreement with test results with some conservatism. However, under I-III mixed mode loading, the crack exhibited a spatial propagation state, and the deflection angle firstly increased then decreased with the mode III component. This is because the fracture mechanism shifted from brittle to brittle-ductile mixed fracture mode as the mode III component increased. The brittle criterion had a good prediction on I-III mixed mode brittle fracture behavior, with a low enough mode III component. The conclusions in this paper are of great significance to the mixed mode fracture evaluation of TC4 titanium alloys.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2023)
Article
Chemistry, Multidisciplinary
Takashi Sumigawa, Takahiro Shimada, Kai Huang, Yuki Mizuno, Yohei Hagiwara, Naoki Ozaki, Takayuki Kitamura
Summary: Crystal defects, specifically dislocations, play a crucial role in brittle fracture of materials. This study investigates the fracture mechanism of dislocations in SrTiO3 through atomic-level observations and theoretical evaluations, revealing a lower fracture strength and quantitatively evaluating the fracture toughness of dislocation-induced cracks.
Article
Engineering, Multidisciplinary
Fan Fei, Jinhyun Choo
Summary: The proposed double-phase-field formulation combines two different phase fields to describe cohesive tensile fracture and frictional shear fracture in rocks. It allows for direct use of material strengths measured from experiments and can naturally distinguish between different fracture modes. The validation results demonstrate the effectiveness of the model in simulating mixed-mode fractures in rocks.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2021)
Article
Engineering, Mechanical
Robab Bahadori, Majid R. Ayatollahi, Nima Razavi, Filippo Berto
Summary: The study found that in geometrically symmetric U-notched specimens under pure mode I loading, high geometrical constraints can lead to the occurrence of maximum tangential stress at two symmetric points on both sides of the notch bisector line, and the fracture does not always occur along the notch bisector line. The generalized MTS criterion shows good predictions for experimentally obtained values of crack initiation angle and notch fracture resistance, suggesting its effectiveness in predicting fracture behavior in U-notched specimens.
FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES
(2021)
Article
Materials Science, Multidisciplinary
Kazuma Shimizu, Mitsuru Ohata, Hiroto Shoji, Hiroyasu Tanigawa, Taichiro Kato
Summary: This study evaluates the applicability of Weibull stress in assessing the crack-tip plastic constraint effect and the mixed loading modes on the brittle fracture resistance of ferritic steel. It was found that the mixed loading modes provide different stress fields around the crack-tip, affecting the fracture resistance differently.
MECHANICS OF MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Seyed Karen Alavi, Majid R. Ayatollahi, Bahador Bahrami, Morteza Nejati
Summary: This study presents an analytical stress solution for bi-material V-notches with an end hole. The stress field is derived as an asymptotic series solution using the Kolosov-Muskhelishvili approach, with the constant coefficients computed using the least square method. The accuracy of the solution is verified through benchmarking with finite element method results.
MATHEMATICS AND MECHANICS OF SOLIDS
(2023)
Article
Engineering, Mechanical
M. Bakhshizadeh, S. Pirmohammad, M. R. Ayatollahi
Summary: This paper investigates the impact of supports on fracture mode of loading using semicircular bending specimen through finite element analysis and experiments. The results show that parameters like support type and crack angle can influence the values of geometry factors, and the friction coefficient can significantly change the loading mode at the crack tip.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2022)
Article
Engineering, Mechanical
Saeid Ghouli, Majid R. Ayatollahi, Bahador Bahrami, Jamaloddin Jamali
Summary: This article promotes the usage of digital image correlation (DIC) technique for determining in-situ stress and predicting fracture in cracked dental biomaterial samples. The elastic and fracture properties of the dental material are measured using DIC method, and a modified single edge notched bend (SENB) specimen with varying crack length is utilized for mixed mode fracture experiments. A stress-based fracture criterion is implemented and combined with two different critical distance models. In-situ stress is calculated using DIC analysis data and supervised learning algorithm, and the crack growth angle and fracture load for the tested biomaterial specimens are estimated, showing good correlation with experimental measurements.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2022)
Article
Materials Science, Multidisciplinary
S. M. Javad Razavi, Amir Nabavi-Kivi, Majid R. Ayatollahi
Summary: Fused deposition modeling is an additive manufacturing technique used for rapid manufacturing and prototyping. However, the layer-wise fabrication process often leads to anisotropic behavior in the final products. This research aims to determine whether the isotropic assumption of material using maximum tangential stress and mean stress criteria can predict the mixed-mode fracture resistance of 3D-printed parts. The results show that both criteria can accurately predict the fracture loads of the fused deposition modeling parts.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART L-JOURNAL OF MATERIALS-DESIGN AND APPLICATIONS
(2023)
Article
Engineering, Mechanical
Majid R. R. Ayatollahi, Parham Rezaeian, Amir Nabavi-Kivi, Mohammad Reza Khosravani
Summary: This study investigates the effect of heat treatment on the tensile, flexural, and fracture strength of PLA specimens made by the FDM technique. Annealing at different temperatures (80℃, 100℃, 120℃) was conducted on dog bone and ECT specimens to evaluate the mechanical and fracture performance of the FDM-PLA parts. Fracture behavior was assessed using EMC, J-integral, ASED, and MTS criteria, and compared with experimental results. Heat treatment significantly improved the structural integrity of FDM specimens, with a 57% increase in fracture resistance.
FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES
(2023)
Article
Chemistry, Physical
Alireza Akhavan-Safar, Ghasem Eisaabadi Bozchaloei, Shahin Jalali, Reza Beygi, Majid R. Ayatollahi, Lucas F. M. da Silva
Summary: Repeated impact is a common loading condition for bonded joints. However, the behavior of metal-composite bonded joints under repeated impact loads has not been widely studied. This study proposes the use of bi-adhesive technique to improve the durability of composite-metal joints under impact fatigue. Experimental and numerical analyses reveal that the double adhesives technique significantly enhances the impact fatigue life of the joints.
Article
Mechanics
A. Nabavi-Kivi, Majid R. Ayatollahi, Nima Razavi
Summary: This study investigates the fracture behavior of FDM specimens made of ABS under mixed-mode I/III loading conditions. Four different raster configurations and five loading angles were used, and the failure loads were predicted using the Equivalent Material Concept coupled with J-integral and Maximum Tangential Stress criteria. Both criteria were able to accurately predict the experimental failure loads, and SEM analysis confirmed the presence of three failure features.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2023)
Article
Engineering, Mechanical
Pedram Bagheri, Ali Reza Torabi, Bahador Bahrami
Summary: This research focuses on the numerical investigation of fracture loads of U-notched specimens made of Al-6061-T6 and Al-5083 under pure opening mode and mixed mode I/II loading conditions. A new methodology is introduced to assess the notch fracture loads and crack growth path using the combination of the equivalent material concept (EMC) and extended finite element method (XFEM). The results are compared with a conventional elastic-plastic damage model, and the EMC-XFEM model is found to be more efficient and accurate in predicting fracture of ductile aluminum notches.
FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES
(2023)
Article
Engineering, Mechanical
Reza Jalayer, Behnam Saboori, Majid Reza Ayatollahi
Summary: A new test specimen is proposed for investigating mixed mode I/II/III fracture of materials. This test specimen creates mixed mode I/III loading conditions by displacing the position of an inclined crack from the middle of the rectangular specimen, in addition to mode II loading under anti-symmetric four-point bending. The experimental fracture loads of PMMA specimens are compared with theoretical predictions, showing satisfactory consistency.
FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES
(2023)
Article
Engineering, Mechanical
Bahador Bahrami, Hossein Talebi, Majid R. Ayatollahi, Mohammad Reza Khosravani
Summary: This research demonstrates the application of artificial neural network (ANN) in predicting fracture under mixed-mode I/II loadings. By analyzing the importance of different input factors, crack parameters and material properties are selected as input data. Multiple ANN models are trained and optimized using different algorithms. The optimized models show low errors and high accuracy in predicting fracture, indicating the effectiveness and potential wide range application of data-driven fracture predictions compared to traditional physics-based criteria.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Materials Science, Composites
Mostafa Moazzami, M. R. Ayatollahi, Alireza Akhavan-Safar, Sofia Teixeira de Freitas, Lucas F. M. da Silva
Summary: Moisture diffusion occurs in composite laminates when exposed to humidity, leading to a reduction in their mechanical properties, especially flexural stiffness, which is important in design. This research investigates the mechanical properties of CFRP and GFRP composites as a substrate in adhesive joints under cyclic wet/dry aging conditions for long-term structural applications. The results show that the reduction in flexural stiffness is more severe in CFRP laminates compared to GFRP laminates, indicating the suitability of GFRP laminates for ocean applications.
JOURNAL OF COMPOSITE MATERIALS
(2023)
Article
Engineering, Civil
S. Karen Alavi, Majid R. Ayatollahi, Mohd Yazid Yahya, S. S. R. Koloor
Summary: This work presents an analytical investigation of the damped forced vibration behavior of viscoelastic annular sector plates made of porous polymer foam. The motion equations are derived using the first-order shear deformation theory (FSDT) in conjunction with the energy method and calculus of variations. Three types of pore distribution in the plate thickness are explored, and the obtained relations are extended to constitutive equations using the standard linear solid (SLS) viscoelastic model. The system of equations with variable coefficients is solved using perturbation technique and Fourier series, and the asymmetrically dynamic response is computed analytically in a closed-form solution. Transient dynamic behavior of viscoelastic functionally graded porous (VFGP) annular sector plates is then analyzed for various loadings, and a user-defined field code is developed for reliability evaluation.
THIN-WALLED STRUCTURES
(2023)
Article
Chemistry, Physical
Ali Reza Torabi, Moslem Mirzavand, Behnam Saboori, Sergio Cicero
Summary: The purpose of this study is to predict the load-bearing capacity of fracture specimens containing V-notched friction-stir welded joints. Elastic-plastic fracture criteria are complex and time-consuming for the fracture analysis of FSWed alloys. In this study, the equivalent material concept (EMC) is applied, and two brittle fracture criteria are utilized to accurately predict the load-bearing capacity.
Article
Polymer Science
Hossein Talebi, Mohsen Askari, Majid Reza Ayatollahi, Sergio Cicero
Summary: The research investigates the fracture behavior of brittle specimens weakened by V-shaped notches with end holes (VO-notches). Experimental investigation is conducted, and it is found that the size of the notch end-hole has an effect on the fracture resistance. Two stress-based criteria, the maximum tangential stress (MTS) criterion and the mean stress (MS) criterion, are developed for VO-shaped notches under mixed-mode I/III loading, and they accurately predict the fracture resistance of VO-notched samples with about 92% and 90% accuracy, respectively.
Article
Engineering, Chemical
A. Akhavan-Safar, Sh. Jalali, L. F. M. da Silva, M. R. Ayatollahi
Summary: Cyclic loading significantly affects the durability of adhesively bonded joints, especially under cyclic impact loads. Low-energy cyclic impacts decrease the fracture energy of the joints, challenging the assumption of infinite life under cyclic impacts. The stress concentration caused by cyclic impact stress waves leads to a higher density of cracks at the specimen edges. Comprehensive inspections for bonded structures exposed to low-energy cyclic impacts are important to maintain joint strength and safe design and inspection practices.
INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES
(2023)
Article
Mechanics
Xiaolong Liu, Kelian Luo, Pengcheng Gao, Tao Cong, Xi Wang, Wenjing Wang
Summary: This paper investigates the formation mechanisms of the zig-zag crack region on the shattered rim of railway wheels. The zig-zag crack region, identified as a typical region for crack propagation in rolling contact fatigue behavior, was observed using scanning electron microscopy and transmission electron microscopy. The formation of the zig-zag morphology is attributed to the periodic deflection of the propagation path relative to the initial propagation plane, caused by the limited plastic deformation zone at the crack tip. Grain refinement and secondary cracks in the zig-zag crack region are a result of the large compressive and shear stresses induced by rolling contact loading.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Anastasia Iziumova, Aleksei Vshivkov, Ivan Panteleev, Virginia Mubassarova, Oleg Plekhov, Denis Davydov
Summary: The aim of this study was to investigate the correlation between structural, acoustic emission, and thermal characteristics of fatigue crack growth in titanium alloys. Cluster analysis of the acoustic emission signals revealed two different types of signals observed during the fatigue crack development. It was experimentally demonstrated that the stored energy tends to reach an asymptotic value at the final stage of fatigue crack growth and this is correlated with the twinning process intensification in titanium alloy Ti Grade 2. A correlation was assumed between the stages of change in heat flux, the cumulative energy of the first cluster of acoustic emission signals, and the crack length.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
M. Vieira de Carvalho, I. A. Rodrigues Lopes, F. M. Andrade Pires
Summary: This study investigates the numerical challenges of fracture mechanics models within implicit quasi-static frameworks and proposes an instability criterion. The ratio of cohesive to internal power is identified as a crucial factor. Two strategies for handling fracture problems with instabilities are discussed and a comparative assessment is performed. The study also examines more complex material responses, including transformation-induced plasticity effects.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Thomas Duminy, Aurelien Doitrand, Sylvain Meille
Summary: This study conducted in situ wedge splitting tests on millimeter-size PMMA samples and proposed a method to determine the material tensile strength and critical energy release rate using digital image correlation and a full finite element implementation of the coupled criterion.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Xin Chang, Xingyi Wang, Chunhe Yang, Yintong Guo, Yanghui Wan
Summary: The influence of cyclic thermal shock and high-temperature acid etching on the Mode I fracture of shale was investigated in this study. It was found that cyclic thermal shock severely degrades the strength and fracture toughness of shale, while high-temperature acid etching treatment improves the fracture toughness. These findings are valuable for optimizing process parameters to reduce initiation pressure in deep shale formations.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Liaojun Yao, Mingyue Chuai, Zhangming Lyu, Xiangming Chen, Licheng Guo, R. C. Alderliesten
Summary: Methods based on fracture mechanics have been widely used in fatigue delamination growth (FDG) characterization of composite laminates. This study proposes appropriate similitude parameters to represent FDG behavior with different R-ratios.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Zesheng Zang, Zhonghui Li, Yue Niu, Shan Yin
Summary: This study conducted experiments and recorded signals to investigate the fracture behavior and damage evolution characteristics of coal samples. The results showed that as loading proceeds, the stress, electric potential (EP), and acoustic emission (AE) values increase, and EP and AE signals are excited when stress drops. The fracture behavior of coal samples is altered by flaw inclination, and the destruction mode becomes increasingly complicated. The damage evolution characteristics of coal samples can be evaluated and analyzed by defining the coefficient of variation (CV value) of EP and the b value of AE.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Clotilde Berdin, Nathalie Prud'homme
Summary: In this study, zirconia layers with different fractions of tetragonal phase and thicknesses were tested for multi-cracking behavior. Cracks perpendicular to the tensile direction were observed, showing a blunting effect into the substrate. The ratio of crack spacing at saturation to layer thickness decreased as the layer thickness increased. Unit cell modeling was used to establish a relationship between crack spacing and layer strength, which fell within the bounds of Hu and Evans model and was found to be insensitive to the tetragonal zirconia fraction.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Huadong Zhang, Weichen Kong, Y. H. Liu, Yuh J. Chao
Summary: Williams' series expansion crack tip solution in linear elasticity is modified to include a uniform crack face pressure. Practical methods to calculate T-stress from near crack tip stresses are outlined. The analytical results are consistent with numerical results.
ENGINEERING FRACTURE MECHANICS
(2024)
Article
Mechanics
Jiahao Kong, Haoyue Han, Tao Wang, Guangyan Huang, Zhuo Zhuang
Summary: This paper introduces a phase-field model for polymer foam materials by combining the phase-field method with the crushable foam model. The model is calibrated using experimental data and successfully simulates the fracture processes of polyurethane under different loading conditions. The study is important for the engineering applications of polymer foam materials.
ENGINEERING FRACTURE MECHANICS
(2024)
