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Search Results (466)

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Keywords = hole-crack

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15 pages, 6090 KiB  
Article
Vacuum Brazing of 6061 Aluminum Using Al-Si-Ge Filler Metals with Different Si Contents
by Sen Huang, Jiguo Shan, Jian Qin, Yuanxun Shen, Chao Jiang and Peiyao Jing
Metals 2025, 15(8), 857; https://doi.org/10.3390/met15080857 (registering DOI) - 31 Jul 2025
Viewed by 201
Abstract
Al-xSi-35Ge (x = 4, 6, 8, 10, 12, wt.%) filler metals were prepared to vacuum braze 6061 aluminum alloy. The wettability of filler metals was studied. A thermodynamics model of the Al-Si-Ge ternary alloy was established to analyze the mechanism and impact of [...] Read more.
Al-xSi-35Ge (x = 4, 6, 8, 10, 12, wt.%) filler metals were prepared to vacuum braze 6061 aluminum alloy. The wettability of filler metals was studied. A thermodynamics model of the Al-Si-Ge ternary alloy was established to analyze the mechanism and impact of Si in the microstructure of the brazed joint. The findings indicated that Si addition had a slight effect on the melting point of Al-xSi-35Ge filler metals. Great molten temperature region of fillers was responsible for the loss of Ge during the wetting process, making residual filler metal difficult to melt. The microstructure of the joint was characterized by a multilayer structure that was primarily composed of three zones: two transition regions (Zone I) and a filler residual region (Zone II). There was liquidation of filler metal for Al-Si-35Ge filler metals during brazing, resulting in holes and cracks in joints. Increasing the Si content in fillers could alleviate the liquidation of filler metal, owing to diminishing difference of chemical potential of Ge (μGe) in fillers and 6061 substrates, hindering the diffusion of Ge from filler metal to substrates. Full article
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29 pages, 4633 KiB  
Article
Failure Detection of Laser Welding Seam for Electric Automotive Brake Joints Based on Image Feature Extraction
by Diqing Fan, Chenjiang Yu, Ling Sha, Haifeng Zhang and Xintian Liu
Machines 2025, 13(7), 616; https://doi.org/10.3390/machines13070616 - 17 Jul 2025
Viewed by 261
Abstract
As a key component in the hydraulic brake system of automobiles, the brake joint directly affects the braking performance and driving safety of the vehicle. Therefore, improving the quality of brake joints is crucial. During the processing, due to the complexity of the [...] Read more.
As a key component in the hydraulic brake system of automobiles, the brake joint directly affects the braking performance and driving safety of the vehicle. Therefore, improving the quality of brake joints is crucial. During the processing, due to the complexity of the welding material and welding process, the weld seam is prone to various defects such as cracks, pores, undercutting, and incomplete fusion, which can weaken the joint and even lead to product failure. Traditional weld seam detection methods include destructive testing and non-destructive testing; however, destructive testing has high costs and long cycles, and non-destructive testing, such as radiographic testing and ultrasonic testing, also have problems such as high consumable costs, slow detection speed, or high requirements for operator experience. In response to these challenges, this article proposes a defect detection and classification method for laser welding seams of automotive brake joints based on machine vision inspection technology. Laser-welded automotive brake joints are subjected to weld defect detection and classification, and image processing algorithms are optimized to improve the accuracy of detection and failure analysis by utilizing the high efficiency, low cost, flexibility, and automation advantages of machine vision technology. This article first analyzes the common types of weld defects in laser welding of automotive brake joints, including craters, holes, and nibbling, and explores the causes and characteristics of these defects. Then, an image processing algorithm suitable for laser welding of automotive brake joints was studied, including pre-processing steps such as image smoothing, image enhancement, threshold segmentation, and morphological processing, to extract feature parameters of weld defects. On this basis, a welding seam defect detection and classification system based on the cascade classifier and AdaBoost algorithm was designed, and efficient recognition and classification of welding seam defects were achieved by training the cascade classifier. The results show that the system can accurately identify and distinguish pits, holes, and undercutting defects in welds, with an average classification accuracy of over 90%. The detection and recognition rate of pit defects reaches 100%, and the detection accuracy of undercutting defects is 92.6%. And the overall missed detection rate is less than 3%, with both the missed detection rate and false detection rate for pit defects being 0%. The average detection time for each image is 0.24 s, meeting the real-time requirements of industrial automation. Compared with infrared and ultrasonic detection methods, the proposed machine-vision-based detection system has significant advantages in detection speed, surface defect recognition accuracy, and industrial adaptability. This provides an efficient and accurate solution for laser welding defect detection of automotive brake joints. Full article
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16 pages, 5222 KiB  
Article
Rock Physics Characteristics and Modeling of Deep Fracture–Cavity Carbonate Reservoirs
by Qifei Fang, Juntao Ge, Xiaoqiong Wang, Junfeng Zhou, Huizhen Li, Yuhao Zhao, Tuanyu Teng, Guoliang Yan and Mengen Wang
Energies 2025, 18(14), 3710; https://doi.org/10.3390/en18143710 - 14 Jul 2025
Viewed by 303
Abstract
The deep carbonate reservoirs in the Tarim Basin, Xinjiang, China, are widely developed with multi-scale complex reservoir spaces such as fractures, pores, and karst caves under the coupling of abnormal high pressure, diagenesis, karst, and tectonics and have strong heterogeneity. Among them, fracture–cavity [...] Read more.
The deep carbonate reservoirs in the Tarim Basin, Xinjiang, China, are widely developed with multi-scale complex reservoir spaces such as fractures, pores, and karst caves under the coupling of abnormal high pressure, diagenesis, karst, and tectonics and have strong heterogeneity. Among them, fracture–cavity carbonate reservoirs are one of the main reservoir types. Revealing the petrophysical characteristics of fracture–cavity carbonate reservoirs can provide a theoretical basis for the log interpretation and geophysical prediction of deep reservoirs, which holds significant implications for deep hydrocarbon exploration and production. In this study, based on the mineral composition and complex pore structure of carbonate rocks in the Tarim Basin, we comprehensively applied classical petrophysical models, including Voigt–Reuss–Hill, DEM (Differential Effective Medium), Hudson, Wood, and Gassmann, to establish a fracture–cavity petrophysical model tailored to the target block. This model effectively characterizes the complex pore structure of deep carbonate rocks and addresses the applicability limitations of conventional models in heterogeneous reservoirs. The discrepancies between the model-predicted elastic moduli, longitudinal and shear wave velocities (Vp and Vs), and laboratory measurements are within 4%, validating the model’s reliability. Petrophysical template analysis demonstrates that P-wave impedance (Ip) and the Vp/Vs ratio increase with water saturation but decrease with fracture density. A higher fracture density amplifies the fluid effect on the elastic properties of reservoir samples. The Vp/Vs ratio is more sensitive to pore fluids than to fractures, whereas Ip is more sensitive to fracture density. Regions with higher fracture and pore development exhibit greater hydrocarbon storage potential. Therefore, this petrophysical model and its quantitative templates can provide theoretical and technical support for predicting geological sweet spots in deep carbonate reservoirs. Full article
(This article belongs to the Special Issue New Progress in Unconventional Oil and Gas Development: 2nd Edition)
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16 pages, 3262 KiB  
Article
Comparison of Acoustic Tomography and Drilling Resistance for the Internal Assessment of Urban Trees in Madrid
by Miguel Esteban, Guadalupe Olvera-Licona, Gabriel Humberto Virgen-Cobos and Ignacio Bobadilla
Forests 2025, 16(7), 1125; https://doi.org/10.3390/f16071125 - 8 Jul 2025
Viewed by 225
Abstract
Acoustic tomography is a non-destructive technique used in the internal assessment of standing trees. Various researchers have focused on developing analytical tools using this technique, demonstrating that they can detect internal biodeterioration in cross-sections with good accuracy. This study evaluates the use of [...] Read more.
Acoustic tomography is a non-destructive technique used in the internal assessment of standing trees. Various researchers have focused on developing analytical tools using this technique, demonstrating that they can detect internal biodeterioration in cross-sections with good accuracy. This study evaluates the use of two ultrasonic wave devices with different frequencies (USLab and Sylvatest Duo) and a stress wave device (Microsecond Timer) to generate acoustic tomography using ImageWood VC1 software. The tests were carried out on 12 cross-sections of urban trees in the city of Madrid of the species Robinia pseudoacacia L., Platanus × hybrida Brot., Ulmus pumila L., and Populus alba L. Velocity measurements were made, forming a diffraction mesh in both standing trees and logs after cutting them down. An inspection was carried out with a perforation resistance drill (IML RESI F-400S) in the radial direction in each section, which allowed for more precise identification of defects and differentiating between holes and cracks. The various defects were determined with greater accuracy in the tomographic images taken with the higher-frequency equipment (45 kHz), and the combination of ultrasonic tomography and the use of the inspection drill can provide a more accurate representation of the defects. Full article
(This article belongs to the Special Issue Wood Properties: Measurement, Modeling, and Future Needs)
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17 pages, 5076 KiB  
Article
Enhancing Fatigue Life Prediction Accuracy: A Parametric Study of Stress Ratios and Hole Position Using SMART Crack Growth Technology
by Yahya Ali Fageehi and Abdulnaser M. Alshoaibi
Crystals 2025, 15(7), 596; https://doi.org/10.3390/cryst15070596 - 24 Jun 2025
Viewed by 535
Abstract
This study presents a unique and comprehensive application of ANSYS Mechanical R19.2’s SMART crack growth feature, leveraging its capabilities to conduct an unprecedented parametric investigation into fatigue crack propagation behavior under a wide range of positive and negative stress ratios, and to provide [...] Read more.
This study presents a unique and comprehensive application of ANSYS Mechanical R19.2’s SMART crack growth feature, leveraging its capabilities to conduct an unprecedented parametric investigation into fatigue crack propagation behavior under a wide range of positive and negative stress ratios, and to provide detailed insights into the influence of hole positioning on crack trajectory. By uniquely employing an unstructured mesh method that significantly reduces computational overhead and automates mesh updates, this research overcomes traditional fracture simulation limitations. The investigation breaks new ground by comprehensively examining an unprecedented range of both positive (R = 0.1 to 0.5) and negative (R = −0.1 to −0.5) stress ratios, revealing previously unexplored relationships in fracture mechanics. Through rigorous and extensive numerical simulations on two distinct specimen configurations, i.e., a notched plate with a strategically positioned hole under fatigue loading and a cracked rectangular plate with dual holes under static loading, this work establishes groundbreaking correlations between stress parameters and fatigue behavior. The research reveals a novel inverse relationship between the equivalent stress intensity factor and stress ratio, alongside a previously uncharacterized inverse correlation between stress ratio and von Mises stress. Notably, a direct, accelerating relationship between stress ratio and fatigue life is demonstrated, where higher R-values non-linearly increase fatigue resistance by mitigating stress concentration, challenging conventional linear approximations. This investigation makes a substantial contribution to fracture mechanics by elucidating the fundamental role of hole positioning in controlling crack propagation paths. The research uniquely demonstrates that depending on precise hole location, cracks will either deviate toward the hole or maintain their original trajectory, a phenomenon attributed to the asymmetric stress distribution at the crack tip induced by the hole’s presence. These novel findings, validated against existing literature, represent a significant advancement in predictive modeling for fatigue life assessment, offering critical new insights for engineering design and maintenance strategies in high-stakes industries. Full article
(This article belongs to the Special Issue Fatigue and Fracture of Crystalline Metal Structures)
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27 pages, 7946 KiB  
Article
Double-Borehole Superimposed Effect of a New Non-Explosive Directional Rock-Breaking Method
by Quan Zhang, Manchao He, Kai Chen, Shan Guo, Chun Yang, Rongzhou Yang, Yun Wu, Jiong Wang and Chao Wang
Appl. Sci. 2025, 15(12), 6805; https://doi.org/10.3390/app15126805 - 17 Jun 2025
Viewed by 284
Abstract
Due to the difficulty of creating directional fractures efficiently and accurately with existing non-explosive rock-breaking methods, a directional fracturing technique utilizing a coal-based solid waste expansive agent, termed the instantaneous expansion with a single fracture (IESF), has been developed. IESF can generate high-pressure [...] Read more.
Due to the difficulty of creating directional fractures efficiently and accurately with existing non-explosive rock-breaking methods, a directional fracturing technique utilizing a coal-based solid waste expansive agent, termed the instantaneous expansion with a single fracture (IESF), has been developed. IESF can generate high-pressure gases within 0.05–0.5 s and utilize gas pressure to achieve directional rock fragmentation. The rock-breaking mechanisms under double-borehole conditions of conventional blasting (CB), shaped charge blasting (SCB), and IESF were studied by theoretical analysis, numerical simulation, and in situ test. The gas pressure distribution within directional fractures of IESF was determined, and the crack propagation criterion between double-borehole was established. Numerical simulation results indicated that the stress distribution in CB was random. SCB exhibited tensile stress of −10.89 MPa in the inter-borehole region and −8.33 MPa on the outer-borehole region, while IESF generated −14.47 MPa and −12.62 MPa in the corresponding regions, demonstrating that stresses generated between adjacent boreholes can be superimposed in the inter-hole region. In CB, strain was concentrated along main fractures. SCB exhibited strains of 7 mm and 8 mm in the shaped charge direction, while non-shaped charge directions showed a strain of 1.5 mm. For IESF, strain in the shaped charge direction measured 6 mm, compared to 1 mm in non-shaped charge directions, resulting in superior directional fracture control. In situ test results from Donglin Coal Mine demonstrated that IESF can form superior directional rock-breaking efficacy compared to both CB and SCB, with the average crack rates of 95.5% by IESF higher than 85.0% by SCB. This technique provides a non-explosive method that realizes precise control of the direction of cracks while avoiding the high-risk and high-disturbance problems of explosives blasting. Full article
(This article belongs to the Special Issue Advanced Technology in Geotechnical Engineering)
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17 pages, 5320 KiB  
Article
Compressive Failure and Dual-Defect Coupling Effects of Open-Hole Composite Laminates with Drilling-Induced Delamination
by Rui Zhu, Yonghui Liu, Xingyue Nie, Qingqing Xiao, Jingpu Liang and Dongfeng Cao
Materials 2025, 18(12), 2790; https://doi.org/10.3390/ma18122790 - 13 Jun 2025
Viewed by 310
Abstract
This study investigates the influence of drilling-induced delamination damage on the compressive mechanical behavior of open-hole carbon fiber-reinforced composite laminates and explores the failure mechanisms under dual-defect coupling effects. Specimens with circular delamination defects of varying sizes were fabricated by embedding polytetrafluoroethylene (PTFE) [...] Read more.
This study investigates the influence of drilling-induced delamination damage on the compressive mechanical behavior of open-hole carbon fiber-reinforced composite laminates and explores the failure mechanisms under dual-defect coupling effects. Specimens with circular delamination defects of varying sizes were fabricated by embedding polytetrafluoroethylene (PTFE) films during the layup process. Ultrasonic C-scan and digital image correlation (DIC) techniques were used to monitor delamination propagation and deformation behavior. A cohesive zone-based numerical model was developed and validated against experimental results to reveal the three-stage failure process in single-defect cases. The validated model was then used to analyze the coupling effects of dual defects (same side and opposite side). The results show that dual delamination defects significantly reduce the compressive load-bearing capacity of open-hole composite laminates. Specifically, same-side defects exhibit a failure mode similar to single-defect structures, while opposite-side defects display a unique failure behavior characterized by dual-crack propagation, further reducing the compressive load-bearing capacity. Full article
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21 pages, 8892 KiB  
Article
Study on the Influence of Delay Time on the Propagation Law of Adjacent Blast Hole Cracks
by Yu Wang, Yang Yang, Xiang Zhang, Ziyi Fan, Fangqiang Hu, Jianqiang He and Jianbin Zhao
Buildings 2025, 15(12), 2030; https://doi.org/10.3390/buildings15122030 - 12 Jun 2025
Viewed by 1039
Abstract
In open-pit bench pre-splitting blasting, the interaction of explosion-induced stress waves between blast holes is essential for safeguarding the rear rock mass. This study utilizes the caustic method to examine the propagation velocity of explosion-induced cracks, the stress intensity factor at the crack [...] Read more.
In open-pit bench pre-splitting blasting, the interaction of explosion-induced stress waves between blast holes is essential for safeguarding the rear rock mass. This study utilizes the caustic method to examine the propagation velocity of explosion-induced cracks, the stress intensity factor at the crack tip, and the final morphology of cracks between adjacent blast holes with varying delay times. Field pre-splitting blasting experiments were carried out to validate these effects. The experimental results reveal that, for short inter-hole delay times (0–12 μs), a “hook-like” crack intersection zone emerges between blast holes. Changes in delay time influence the patterns of crack propagation, leading to deviations in the propagation direction of cracks in subsequent blast holes due to the combined effects of stress waves and cracks from preceding holes. The fracture mechanism evolves from pure Mode I (tensile) to a mixed Mode I-II (tensile-shear). Vibration signals from the field blasting tests were analyzed using the variational mode decomposition (VMD) method. The findings indicate that optimized inter-hole delay times can reduce peak particle velocity (PPV) by 18.7–23.4% compared to simultaneous initiation, thereby significantly minimizing damage to the rear rock mass, a crucial factor for maintaining slope stability. Full article
(This article belongs to the Section Building Structures)
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19 pages, 5574 KiB  
Article
Low-Damage Grasp Method for Plug Seedlings Based on Machine Vision and Deep Learning
by Fengwei Yuan, Gengzhen Ren, Zhang Xiao, Erjie Sun, Guoning Ma, Shuaiyin Chen, Zhenlong Li, Zhenhong Zou and Xiangjiang Wang
Agronomy 2025, 15(6), 1376; https://doi.org/10.3390/agronomy15061376 - 4 Jun 2025
Viewed by 399
Abstract
In the process of plug seedling transplantation, the cracking and dropping of seedling substrate or the damage of seedling stems and leaves will affect the survival rate of seedlings after transplantation. Currently, most research focuses on the reduction of substrate loss, while ignoring [...] Read more.
In the process of plug seedling transplantation, the cracking and dropping of seedling substrate or the damage of seedling stems and leaves will affect the survival rate of seedlings after transplantation. Currently, most research focuses on the reduction of substrate loss, while ignoring damage to the hole tray seedling itself. Targeting the problem of high damage rate during transplantation of plug seedlings, we have proposed an adaptive grasp method based on machine vision and deep learning, and designed a lightweight real-time grasp detection network (LRGN). The lightweight network Mobilenet is used as the feature extraction network to reduce the number of parameters of the network. Meanwhile, a dilated refinement module (DRM) is designed to increase the receptive field effectively and capture more contextual information. Further, a pixel-attention-guided fusion module (PAG) and a depth-guided fusion module (DGFM) are proposed to effectively fuse deep and shallow features to extract multi-scale information. Lastly, a mixed attention module (MAM) is proposed to enhance the network’s attention to important grasp features. The experimental results show that the proposed network can reach 98.96% and 98.30% accuracy of grasp detection for the image splitting and object splitting subsets of the Cornell dataset, respectively. The accuracy of grasp detection for the plug seedling grasp dataset is up to 98.83%, and the speed of image detection is up to 113 images/sec, with the number of parameters only 12.67 M. Compared with the comparison network, the proposed network not only has a smaller computational volume and number of parameters, but also significantly improves the accuracy and speed of grasp detection, and the generated grasp results can effectively avoid seedlings, reduce the damage rate in the grasp phase of the plug seedlings, and realize a low-damage grasp, which provides the theoretical basis and method for low-damage transplantation mechanical equipment. Full article
(This article belongs to the Section Precision and Digital Agriculture)
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22 pages, 14111 KiB  
Article
High-Speed Bearing Reliability: Analysis of Tapered Roller Bearing Performance and Cage Fracture Mechanisms
by Qingsong Li, Jiaao Ning, Hang Liang and Muzhen Yang
Metals 2025, 15(6), 592; https://doi.org/10.3390/met15060592 - 26 May 2025
Viewed by 543
Abstract
This investigation examines the fracture mechanisms of 31,311 tapered roller bearing cages using finite element analysis (FEA) and the Gurson–Tvergaard–Needleman (GTN) damage model. Static, dynamic, modal, and harmonic response analyses identify critical stress concentrations at the contact interface between the rolling elements and [...] Read more.
This investigation examines the fracture mechanisms of 31,311 tapered roller bearing cages using finite element analysis (FEA) and the Gurson–Tvergaard–Needleman (GTN) damage model. Static, dynamic, modal, and harmonic response analyses identify critical stress concentrations at the contact interface between the rolling elements and the outer ring, with maximum deformation occurring in the inner ring. Modal analysis excludes resonance as a potential failure cause. Crack initiation and propagation studies reveal that cracks predominantly form at the pocket bridge corners, propagating circumferentially. The propagation angle increases under circumferential and coupled loading conditions while remaining constant under longitudinal loading. Based on the GTN model, this study is the first to examine the crack propagation and fracture toughness of the cage under various loading conditions. The results indicate that longitudinal loading (Load II) yields the highest fracture toughness, significantly surpassing those under circumferential (Load I) and coupled loading (Load III). Load II exhibits the strongest crack growth resistance, with a peak CTODc of 0.598 mm, attributed to plastic strain accumulation. Fracture toughness decreases with crack depth, as CTODc declines by 66.5%, 20.1%, and 58.4% for Loads I, II, and III, respectively. Crack deflection angles show the greatest variation under Load I (35% increase), while Loads II and III demonstrate minimal sensitivity (<10% change). The optimization of the bearing cage pocket hole fillet radius from 0 mm to 0.75 mm demonstrates a maximum stress concentration reduction of 38.2% across different load conditions. This work introduces a novel methodology for predicting cage fracture behavior and optimizing design, offering valuable insights to enhance the reliability and longevity of systems in high-speed, high-load applications. Full article
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14 pages, 4100 KiB  
Article
The Influence of Mineral Powder Dosage on the Mechanical Properties and Microstructure of Self-Compacting Concrete
by Li Duan, Guihong Xu, Wenbo Deng, Li He and Yi Hu
J. Compos. Sci. 2025, 9(6), 258; https://doi.org/10.3390/jcs9060258 - 23 May 2025
Viewed by 459
Abstract
The dosage of mineral powder has a complex influence on the compressive strength of self-compacting concrete, among which the pore structure is a key determining factor. This study investigated the effects of different dosages of mineral powder (0%, 5%, 10%, 20%, and 30%) [...] Read more.
The dosage of mineral powder has a complex influence on the compressive strength of self-compacting concrete, among which the pore structure is a key determining factor. This study investigated the effects of different dosages of mineral powder (0%, 5%, 10%, 20%, and 30%) on the workability, mechanical properties, and pore distribution in C80 self-compacting concrete. The research results show that an appropriate dosage of mineral powder (0–20%) can significantly improve the spreadability and fluidity of C80 self-compacting concrete. This phenomenon is mainly attributed to the shape effect and micro-aggregate effect of mineral powder, which improve the fluidity of concrete, reduce the viscosity of the paste, and thereby increase the spreadability and gap-passing rate. By testing the BSD-PS1/2 series fully automatic specific surface area and pore size analyzer, we found that there are columnar pores and ink bottle-shaped pores in C80 self-compacting concrete, as well as a small amount of plate-like slit structures. Our observations with an SEM scanning electron microscope revealed that the width of micro-cracks and micro-holes is between 1 and 5 μm and the diameter is between 3 and 10 μm. These microstructures may have an impact on the mechanical properties of the structure. By applying fractal theory and low-temperature liquid nitrogen adsorption tests, this study revealed the relationship between the fractal characteristics of internal pores in C80 self-compacting concrete and the dosage of mineral powder. The results show that with the increase in mineral powder dosage, the fractal dimension first decreases and then increases, reflecting the change rule of the complexity of pore structure first decreasing and then increasing. When the dosage of mineral powder is about 20%, the compressive strength of SCC reaches the maximum value, and this dosage range should be considered in engineering design. Full article
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16 pages, 8572 KiB  
Article
Fracture Behavior and Cracking Mechanism of Rock Materials Containing Fissure-Holes Under Brazilian Splitting Tests
by Hengjie Luan, Kun Liu, Decheng Ge, Wei Han, Yiran Zhou, Lujie Wang and Sunhao Zhang
Appl. Sci. 2025, 15(10), 5592; https://doi.org/10.3390/app15105592 - 16 May 2025
Viewed by 366
Abstract
Fractures and voids are widely distributed in slope rock masses. These defects promote crack initiation and propagation, ultimately leading to rock mass failure. Investigating their damage evolution mechanisms and strength characteristics is of significant importance for slope hazard prevention. A numerical simulation study [...] Read more.
Fractures and voids are widely distributed in slope rock masses. These defects promote crack initiation and propagation, ultimately leading to rock mass failure. Investigating their damage evolution mechanisms and strength characteristics is of significant importance for slope hazard prevention. A numerical simulation study of Brazilian splitting tests on disk samples containing prefabricated holes and fractures was conducted using the Finite Element Method with Cohesive Zone Modeling (FEM-CZM) in ABAQUS by embedding zero-thickness cohesive elements within the finite element model. This 2021 study analyzed the effects of fracture angle and length on tensile strength and crack propagation characteristics. The results revealed that when the fracture angle is small, cracks initiate near the fracture and propagate and intersect radially as the load increases, ultimately leading to specimen failure, with the crack coalescence pattern exhibiting local closure. As the fracture angle increases, the initiation location of the crack shifts. With an increase in fracture length, the crack initiation position may transfer to other parts of the fracture or near the hole, and longer fractures may result in more complex coalescence patterns and local closure phenomena. During the tensile and stable failure stages, the load–displacement curves of samples with different fracture angles and lengths exhibit similar trends. However, the fracture angle has a notable impact on the curve during the shear failure stage, while the fracture length significantly affects the peak value of the curve. Furthermore, as displacement increases, the proportion of tensile failure undergoes a process of rapid decline, slow rise, and then rapid decline again before stabilizing, with the fracture angle having a significant influence on the proportion of tensile failure. Lastly, as the fracture angle and length increase, the number of damaged cohesive elements shows an upward trend. This study provides novel perspectives on the tensile behavior of fractured rock masses through the FEM-CZM approach, contributing to a fundamental understanding of the strength characteristics and crack initiation mechanism of rocks under tensile loading conditions. Full article
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9 pages, 2959 KiB  
Proceeding Paper
Prediction of Random Crack Propagation Life of Thin Porous Plate with Multiple Site Damage
by Hanbin Sun, Xianmin Chen and Jun Yang
Eng. Proc. 2024, 80(1), 47; https://doi.org/10.3390/engproc2024080047 - 10 May 2025
Viewed by 186
Abstract
Based on the crack propagation rate test of LY12CZ aluminum alloy flat plate, the distribution characteristics of Paris formula parameters were characterized by the three-parameter logarithmic normal distribution, and a LY12CZ random crack propagation analysis method was established. By using the Monte-Carlo method [...] Read more.
Based on the crack propagation rate test of LY12CZ aluminum alloy flat plate, the distribution characteristics of Paris formula parameters were characterized by the three-parameter logarithmic normal distribution, and a LY12CZ random crack propagation analysis method was established. By using the Monte-Carlo method to simulate the randomness of crack growth, a prediction model of the random crack propagation life of a thin porous plate with multiple site damage (MSD) was established and programmed. The model can accurately predict the crack growth life and failure probability of thin porous plates with MSD, which provides an effective engineering analysis method for the MSD evaluation of the thin plate structure with multiple holes. Full article
(This article belongs to the Proceedings of 2nd International Conference on Green Aviation (ICGA 2024))
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17 pages, 5108 KiB  
Article
Biodegradation Efficacy of Aspergillus niger and Trichoderma harzianum on Low-Density Polyethylene
by Momina Ahmed, Shazia Iram, Noshabah Tabassum, Mahnoor Sajid, Kingkham Paseutsakoun, László Aleksza and András Székács
Polymers 2025, 17(10), 1303; https://doi.org/10.3390/polym17101303 - 10 May 2025
Viewed by 1398
Abstract
This study investigates the biodegradation potential of two fungal strains, Aspergillus niger and Trichoderma harzianum, on polyethylene plastic bags, addressing the environmental challenges posed by the resistance of the plastic material to degradation. The fungi were cultivated, and their spore suspensions were [...] Read more.
This study investigates the biodegradation potential of two fungal strains, Aspergillus niger and Trichoderma harzianum, on polyethylene plastic bags, addressing the environmental challenges posed by the resistance of the plastic material to degradation. The fungi were cultivated, and their spore suspensions were tested for polyethylene degradation in both the soil and liquid salt media. Degradation was assessed using weight loss measurements, thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). After one month in liquid medium, A. niger induced a 45.62 ± 0.21% weight loss of polyethylene, while T. harzianum achieved a 36.0 ± 0.21% weight reduction. In soil, weight losses of 9.09 ± 0.08% and 10.00 ± 0.18% were observed after two months, respectively. TGA confirmed that the fungus-treated polyethylene samples were less thermally stable than untreated controls, indicating successful biodegradation. FTIR analysis revealed structural changes in the degraded polyethylene, while SEM images demonstrated significant surface alterations, including pitting, roughening, cracks, holes, and fungal colonization. These findings confirm the enzymatic action of fungi in degrading polyethylene into monomeric forms. The study highlights the potential for fungal biodegradation as an environmentally friendly strategy to mitigate plastic pollution. Future studies should characterize the specific enzymes involved and explore genetic engineering to enhance degradation rates. Full article
(This article belongs to the Special Issue Degradation and Stability of Polymer-Based Systems: 2nd Edition)
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22 pages, 10554 KiB  
Article
Effect of Starch Variety and Environmental Conditions on the Aerobic Biodegradation of Citric Acid-Compatibilized Thermoplastic Starch/Polylactic Acid Blends
by Elizabeth Moreno-Bohorquez, Mary Judith Arias-Tapia, Keydis Martínez-Villadiego, Jesús D. Rhenals-Julio and Andrés F. Jaramillo
Polymers 2025, 17(10), 1295; https://doi.org/10.3390/polym17101295 - 8 May 2025
Viewed by 723
Abstract
In this study, the aerobic degradation of sweet potato (Ipomoea batatas; SP) and diamond yam (Dioscorea rotundata; DY) thermoplastic starch (TPS) blends, combined with polylactic acid (PLA) and varying ratios of citric acid (CA) as a crosslinker, [...] Read more.
In this study, the aerobic degradation of sweet potato (Ipomoea batatas; SP) and diamond yam (Dioscorea rotundata; DY) thermoplastic starch (TPS) blends, combined with polylactic acid (PLA) and varying ratios of citric acid (CA) as a crosslinker, was investigated in compost and seawater environments. After 50 d of composting, weight losses in the SP-TPS/CA/PLA blends were 56.9%, 52.3%, and 77.5%, while those of DY-TPS/CA/PLA were 55.8%, 52.2%, and 62.2% for 0%, 1%, and 5% CA, respectively. In seawater, the SP-TPS/CA/PLA blends showed weight losses of 52.9%, 46.8%, and 61.5%, and the DY-TPS/CA/PLA blends lost 35.2%, 32.1%, and 43.9% for the same CA ratios, respectively. In both media, SEM revealed structural damage, holes, cracks, and changes in coloration, reflecting microbial activity. Additionally, in compost and seawater, TGA results showed that PLA remained the predominant component after 50 d, as most of the degradation occurred on TPS due to its amorphous structure and higher hydrophilicity. In both media, the SP-TPS/CA5/PLA and DY-TPS/CA5/PLA blends exhibited faster degradation, whereas SP-TPS/CA1/PLA and DY-TPS/CA1/PLA displayed higher stability and lower disintegration. Additionally, all blends required over 50 d to degrade completely, as evidenced by the absence of a plateau phase in the biodegradability curves. Statistical analysis showed that, in seawater, the degradation behavior of the blends was similar to cellulose. However, the CA ratio had a greater impact on the compost degradation of the blends with SP-TPS than on DY-TPS. Therefore, the critical factors influencing the degradation of these blends are the starch source and the CA ratio. Full article
(This article belongs to the Special Issue Synthesis and Applications of Biodegradable Polymer Composites)
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