Article
Materials Science, Multidisciplinary
Zhiping Liu, Zongchen Li, Chuanhai Huang, Xiaoli Jiang
Summary: In this study, the combined method of drilling stop hole and FRP reinforcement was used to repair cracked steel plates under cyclic tension. Through experimental investigation and FEM evaluation, it was found that the combined method significantly extended the residual fatigue life compared to using stop hole alone, mainly due to the increase in crack initiation life at the stop hole.
MECHANICS OF ADVANCED MATERIALS AND STRUCTURES
(2021)
Article
Mechanics
R. Sachse, A. K. Pickett, P. Middendorf
Summary: In this paper, a systematic study was conducted on the effect of mechanical design features on fatigue crack growth in adhesive joints. A material model and methodology for fatigue crack growth analysis were presented. The results suggest that a combination of local reinforcement, through-thickness reinforcement, and compression preload are necessary for efficient crack growth arrest, while simply reducing peel stresses is not sufficient. Increasing the effective crack front length and introducing through-thickness stresses can significantly reduce local fatigue crack growth rates.
COMPOSITE STRUCTURES
(2021)
Article
Materials Science, Multidisciplinary
Lin Zhang, Xiaohui Wei
Summary: In this study, we improved the ability of a back-propagation neural network to predict fatigue crack growth life by using Lagrange interpolation. The method combines the trend of the entire data set to handle the retardation interval and interpolates multiple data points in this interval when local data is lacking. The proposed method has been proven to significantly improve the predictive ability on the entire range of experiment data.
MECHANICS OF MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Hao Gong, Feng-Peng Yang, Te Chen
Summary: This study proposes an improved model for predicting fatigue crack growth under variable amplitude loads. The model combines the effects of crack closure and residual stress, and achieves overload acceleration and delayed retardation phenomena by introducing a damping threshold factor and considering the change of crack opening stress. The predicted fatigue crack growth rates are validated using experimental data and Monte Carlo simulation.
JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE
(2022)
Article
Engineering, Aerospace
Kai Liu, Fangli Wang, Wei Pan, Le Yang, Shuwei Bai, Qiang Zhu, Mingbo Tong
Summary: This paper uses a probabilistic method to analyze the average behavior time of widespread fatigue damage (WFD) in an aircraft multi-site damage (MSD) structure and simulates the entire process from crack initiation to structural failure. By statistically analyzing the test data, the probability distribution of crack initiation life and growth rate is obtained and expressed through the randomization of variables. Through the Monte Carlo method, the initiation, propagation, and connection of multiple cracks in the MSD structure to the occurrence of WFD are realized. The calculation results are in good agreement with experimental data and can accurately predict the life of MSD structures under a certain reliability.
Article
Engineering, Mechanical
Hao Gong, Zeng-gui Jin, Feng-peng Yang, Wen-tao Mao
Summary: To investigate the effects of the stop-hole on fatigue crack path and life under mixed I-II cyclic loads, a series of tests were conducted using compact tension-shear specimens with different stop-hole diameters and various loading angles. The results showed that fatigue life increased with loading angle and hole diameter. Numerical simulation was used to enhance the experimental database, and a variable-length recurrent neural network was proposed based on the database to remember crack segment information. The results were encouraging and provided inspiration for evaluating component safety.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2023)
Article
Engineering, Mechanical
Hao Gong, Feng-peng Yang, Te Chen, Zeng-gui Jin
Summary: This paper investigates the fatigue crack growth retardation mechanisms of Q420 steel under mixed I-II mode overloads at different loading angles. It is found that the retardation level and fatigue life decrease with increasing loading angle. A combined model is proposed to predict the fatigue crack growth rate and fatigue life, which agrees well with experimental results.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2022)
Article
Engineering, Mechanical
Lin-qi Xie, Chang-yu Zhou, Peng Zhang, Xiao-hua He
Summary: This study investigated the mixed mode I-II fatigue crack growth behavior of commercial pure titanium (CP-Ti) under tensile overload at negative load ratios using experiments and finite element method (FEM). The effects of loading angle, load ratio, and overload on crack growth were discussed, and the mechanism of crack growth under overload was revealed. The experimentally compared fatigue crack growth path and rate with/without overload, and investigated the overload retardation effect. The variation of plastic zone and the distribution of stress and strain were simulated through FEM. The microscopic perspective, crack closure, residual compressive stress at crack tip, mode II shear component, and compressive load effect on overload retardation effect were demonstrated.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2022)
Article
Materials Science, Multidisciplinary
Grzegorz Lesiuk, Hryhoriy Nykyforchyn, Olha Zvirko, Rafal Mech, Bartosz Babiarczuk, Szymon Duda, Joao Maria De Arrabida Farelo, Jose A. F. O. Correia
Summary: The paper compares the effectiveness of three different strategies - using raw rail steel, steel reinforced with composite material CFRP, and applying an anti-crack growth fluid - in decelerating the fatigue crack growth rate. The study found that cracks grew fastest in the case of raw material and slowest when anti-crack growth fluid was applied, demonstrating the significant impact of fluid activity on reducing crack growth. Additionally, the analysis of fatigue fracture surfaces using microscopy revealed the mechanism behind crack growth.
Article
Mechanics
Iman Shakeri, Amir Reza Shahani, Calvin David Rans
Summary: This study focused on the fatigue crack growth behavior of welded joints under various loading scenarios, finding that the crack growth retardation behavior is sensitive to post-welding heat treatments. A modification to the Wheeler model was proposed to improve the accuracy of retardation prediction after applying a mixed mode overload.
ENGINEERING FRACTURE MECHANICS
(2021)
Article
Engineering, Civil
Yixin Chen, Joseph Saunders, Ian Hodgson, Richard Sause
Summary: This paper presents research on distortion-induced fatigue cracking in steel bridge girders at a connection plate-to-girder web weld toe after retrofit of an original fatigue crack using a crack-arrest hole. Three-dimensional finite-element analyses were conducted to evaluate fatigue stresses before and after the original fatigue crack develops and before and after a crack-arrest hole retrofit. The study also included fatigue tests to validate the results obtained from the finite-element analyses.
JOURNAL OF BRIDGE ENGINEERING
(2023)
Article
Engineering, Mechanical
Han Cheng, Yongxiang Hu
Summary: The study investigates the generation and effect of crack face closure under laser shock, aiming to understand the reason for the high-level crack closure induced by laser peening on initial fatigue cracks. It is found that crack face closure results in a firm compression on the crack face, causing significant elongation in the crack wake during the crack opening process to prevent crack face separation under high-level external load. The contribution of crack face closure to crack retardation is comparable to laser peening-induced residual stress.
INTERNATIONAL JOURNAL OF FATIGUE
(2023)
Article
Materials Science, Multidisciplinary
Jesus Toribio, Juan-Carlos Matos, Beatriz Gonzalez
Summary: This article investigates the retardation effect in plasticity-induced fatigue crack growth rate for low-medium strength steel, finding that the retardation effect increases with an increase in the initial kinked crack tip angle and length, as well as with a decrease in the stress intensity factor (SIF) range.
Article
Nanoscience & Nanotechnology
Esmaeil Sadeghi, Gbenga Asala, Paria Karimi, Dunyong Deng, Johan Moverare, Thomas Hansson
Summary: A unique melting strategy was implemented in EB-PBF of Alloy 718, resulting in the formation of a bimodal grain morphology consisting of fine equiaxed and columnar grains. The microstructure was preserved following various thermal post-treatments. Clustered inclusions acted as the crack initiation site, reducing the specimens' total fatigue life. Intergranular fracture mode was favored in the plastic zone ahead of the crack tip.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Engineering, Mechanical
Wandong Wang, Lingzhen Li, Ardalan Hosseini, Elyas Ghafoori
Summary: The study proposes an innovative fatigue strengthening solution for metallic structures using iron-based shape memory alloy and bonding technique. Experimental results demonstrate that bonded prestressed Fe-SMA strips are much more effective than traditional CFRP strips in retarding fatigue crack growth, extending the fatigue crack growth life by a factor of 3.51.
INTERNATIONAL JOURNAL OF FATIGUE
(2021)
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, Textiles
Alireza Akhavan-Safar, Fatemeh Delzendehrooy, Majidreza Ayatollahi, Lucas Filipe Martins da Silva
Summary: This study investigates the influence of date palm fibers on the fracture energy of adhesives. The results show the outstanding potential of date palm fibers in enhancing the tensile fracture energy of adhesives. In particular, the Rachis fibers can improve the fracture energy of the enhanced adhesive to 7.6 times that of the neat adhesive.
JOURNAL OF NATURAL FIBERS
(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
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
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
Materials Science, Characterization & Testing
A. R. Torabi, M. R. Ayatollahi, F. Berto, S. M. J. Razavi
Summary: The present study aims to experimentally verify the effectiveness of the Averaged Strain Energy Density (ASED) criterion for brittle fracture in blunt V-notches under pure compression.
STRENGTH OF MATERIALS
(2022)
