Research

17 pages, 15241 KiB

Open AccessArticle

Experimental Study on the Localized Deformation and Damage Behavior of Polymer-Bonded Explosive Simulant under Cyclic Compression

by Dong Jia, Zhiming Hao, Yunqiang Peng, Shunping Yan and Wenjun Hu

Materials 2024, 17(4), 919; https://doi.org/10.3390/ma17040919 - 16 Feb 2024

Viewed by 480

Abstract

Uniaxial cyclic compression tests were performed to investigate the compression deformation and damage of polymer-bonded explosive (PBX) simulant, particularly shear localization. The macroscopic mechanical behavior and mesoscale failure mechanisms of the PBX simulant were analyzed by optical observation and SEM scanning methods. After [...] Read more.

Uniaxial cyclic compression tests were performed to investigate the compression deformation and damage of polymer-bonded explosive (PBX) simulant, particularly shear localization. The macroscopic mechanical behavior and mesoscale failure mechanisms of the PBX simulant were analyzed by optical observation and SEM scanning methods. After each cyclic compression, the specimen was scanned by X-ray computed tomography (CT), and the internal 3D deformation of the specimen was calculated using the digital volume correlation (DVC) method. The results show that the stress–strain curve of the PBX simulant exhibits five stages and coincides with the morphological changes on the surface of the specimen. The mesoscale failure mechanism is dominated by particle interface debonding and binder tearing, accompanied by a small amount of particle breakage. There are three bifurcation points (T₁, T₂, and T₃) in the curves of the normal and shear strain components with compression strain. It was found that these bifurcation points can reflect the full progression of the specimen from inconspicuous damage to uniformly distributed damage, shear localization, and eventual macroscopic fracture. The strain invariant I₁ can quantitatively and completely characterize the deformation and damage processes of the PBX simulant under cyclic compression. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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12 pages, 3909 KiB

Open AccessArticle

The Influence of Hard Coatings on Fatigue Properties of Pure Titanium by a Novel Testing Method

by Cai Hu, Lei Zhao, Yong Zhang, Zhinan Du and Yunlai Deng

Materials 2024, 17(4), 835; https://doi.org/10.3390/ma17040835 - 09 Feb 2024

Viewed by 547

Abstract

This study investigates the impact of hard coatings on the fatigue properties of pure titanium. A specialized fatigue test which ensured machine equivalence was conducted to compare the fatigue behavior of coated and uncoated metals. The findings reveal that the application of coatings [...] Read more.

This study investigates the impact of hard coatings on the fatigue properties of pure titanium. A specialized fatigue test which ensured machine equivalence was conducted to compare the fatigue behavior of coated and uncoated metals. The findings reveal that the application of coatings adversely affects the fatigue properties of pure titanium due to stress concentration from the coating, which accelerates fatigue crack propagation within the substrate material. Notably, zigzag fatigue cracks at the interface between the coating and substrate and multiple micro-cracks initiated within the coating are found. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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18 pages, 15196 KiB

Open AccessArticle

Deformation and Force Chain of Two-Dimensional Granular Systems under Continuous Loading

by Fanxiu Chen, Yuxin Liu, Yuan Wang, Yanji Gu, Yang Yu and Jie Sun

Materials 2023, 16(15), 5441; https://doi.org/10.3390/ma16155441 - 03 Aug 2023

Cited by 1 | Viewed by 743

Abstract

A continuous loading experiment of a two-dimensional granular system was carried out and the experimental data were obtained by digital image correlation (DIC). The deformation field of the granular system and the changing laws of the deflection angle and coordination number of the [...] Read more.

A continuous loading experiment of a two-dimensional granular system was carried out and the experimental data were obtained by digital image correlation (DIC). The deformation field of the granular system and the changing laws of the deflection angle and coordination number of the granules on force chains with time were obtained. Based on the granule element method, the quantitative calculation of contact force was realized, and the internal force chains of the granular system were identified. The effects of contact force between granules and mechanical parameters on the evolution of force chains in a two-dimensional granular system under line loads were analyzed. The formation, evolution, and reconstruction of force chains in a granular system during loading, as well as the influence of the force chain network evolution on the macroscopic mechanical properties of granules were discussed. The experimental results indicated that the evolution of force chains was directly related to the number, geometric properties, and permutation distribution of granules in direct contact with the external load. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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24 pages, 5284 KiB

Open AccessArticle

Experimental Study on the Effect of an Organic Matrix on Improving the Strength of Tailings Strengthened by MICP

by Lin Hu, Huaimiao Zheng, Lingling Wu, Zhijun Zhang, Qing Yu, Yakun Tian and Guicheng He

Materials 2023, 16(15), 5337; https://doi.org/10.3390/ma16155337 - 29 Jul 2023

Cited by 1 | Viewed by 687

Abstract

In order to improve the effect of microbial-induced calcium carbonate precipitation (MICP) in tailings reinforcement, sodium citrate, an organic matrix with good water solubility, was selected as the crystal form adjustment template for inducing calcium carbonate crystallization, and the reinforcements of tailings by [...] Read more.

In order to improve the effect of microbial-induced calcium carbonate precipitation (MICP) in tailings reinforcement, sodium citrate, an organic matrix with good water solubility, was selected as the crystal form adjustment template for inducing calcium carbonate crystallization, and the reinforcements of tailings by MICP were conducted in several experiments. The effects of sodium citrate on the yield, crystal form, crystal appearance, and distribution of calcium carbonate were analyzed by MICP solution test; thus, the related results were obtained. These showed that the addition of a proper amount of organic matrix sodium citrate could result in an increment in the yield of calcium carbonate. The growth rate of calcium carbonate reached 22.6% under the optimum amount of sodium citrate, and the crystals of calcium carbonate were diverse and closely arranged. Based on this, the MICP reinforcement test of tailings was carried out under the action of the optimum amount of sodium citrate. The microscopic analysis using CT and other means showed that the calcium carbonate is distributed more uniformly in tailings, and the porosity of samples is significantly reduced by layered scanning analysis. The results of triaxial shear tests showed that adding organic matrix sodium citrate effectively increased the cohesion, internal friction angle, and peak stress of the reinforced tailings. It aims to provide a novel idea, a creative approach, and a method to enhance the reinforcement effect of tailings and green solidification technology in the mining environment. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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20 pages, 10184 KiB

Open AccessArticle

Efficient Evaluation of Concrete Fracture Surface Roughness Using Fringe Projection Technology

by Meiling Dai, Xirui Wang, Cheng Cheng, Zhuoli Chen and Jiyu Deng

Materials 2023, 16(12), 4430; https://doi.org/10.3390/ma16124430 - 16 Jun 2023

Cited by 1 | Viewed by 1705

Abstract

The evaluation of concrete surface roughness is crucial in the field of civil engineering. The purpose of this study is to propose a no-contact and efficient method for the measurement of the roughness of concrete fracture surfaces based on fringe-projection technology. A simple [...] Read more.

The evaluation of concrete surface roughness is crucial in the field of civil engineering. The purpose of this study is to propose a no-contact and efficient method for the measurement of the roughness of concrete fracture surfaces based on fringe-projection technology. A simple phase-correction method using one additional strip image is presented for the phase unwrapping to improve the measurement efficiency and accuracy. The experimental results indicate that the measuring error for plane height is less than 0.1mm, and the relative accuracy for measuring a cylindrical object is about 0.1%, meeting the requirements for concrete fracture-surface measurement. On this basis, three-dimensional reconstructions were carried out on various concrete fracture surfaces to evaluate the roughness. The results reveal that the surface roughness (R) and fractal dimension (D) decrease as the concrete strength increases or the water-to-cement ratio decreases, consistent with previous studies. In addition, compared with the surface roughness, the fractal dimension is more sensitive to the change in concrete surface shape. The proposed method is effective for detecting concrete fracture-surface features. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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14 pages, 5168 KiB

Open AccessEditor’s ChoiceArticle

Study on the Compressive Properties of an Elastomeric Porous Cylinder Using 360° Three-Dimensional Digital Image Correlation System

by Wei Sun, Jie Zhao, Xin Li, Zhongda Xu and Zhenning Chen

Materials 2023, 16(12), 4301; https://doi.org/10.3390/ma16124301 - 10 Jun 2023

Cited by 1 | Viewed by 800

Abstract

To study the compressive properties of an elastomeric porous cylinder, a 360° 3D digital image correlation (DIC) system is proposed. This compact vibration isolation table system captures different segments of the object from four different angles and fields of view, enabling a comprehensive [...] Read more.

To study the compressive properties of an elastomeric porous cylinder, a 360° 3D digital image correlation (DIC) system is proposed. This compact vibration isolation table system captures different segments of the object from four different angles and fields of view, enabling a comprehensive measurement of the full surface of the object. To increase the stitching quality, a coarse–fine coordinate matching method is presented. First, a three-dimensional rigid body calibration auxiliary block is employed to track motion trajectory, which enables preliminary matching of four 3D DIC sub-systems. Subsequently, scattered speckle information characteristics guide fine matching. The accuracy of the 360° 3D DIC system is verified through a three-dimensional shape measurement conducted on a cylindrical shell, and the maximum relative error of the shell’s diameter is 0.52%. A thorough investigation of the 3D compressive displacements and strains exerted on the full surface of an elastomeric porous cylinder are investigated. The results demonstrate the robustness of the proposed 360° measuring system on calculating images with voids and indicate a negative Poisson’s ratio of periodically cylindrical porous structures. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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12 pages, 4871 KiB

Open AccessArticle

Influence of Manufacturing Defects on Mechanical Behavior of the Laser Powder Bed Fused Invar 36 Alloy: In-Situ X-ray Computed Tomography Studies

by Shuo Yang, Qidong Yang, Zhaoliang Qu and Kai Wei

Materials 2023, 16(8), 2956; https://doi.org/10.3390/ma16082956 - 07 Apr 2023

Cited by 2 | Viewed by 1525

Abstract

The mechanical properties of laser powder bed fused (LPBFed) Invar 36 alloy have been limited by the presence of manufacturing defects. It is imperative to investigate the influence of these defects on the mechanical behavior of LPBFed Invar 36 alloy. In this study, [...] Read more.

The mechanical properties of laser powder bed fused (LPBFed) Invar 36 alloy have been limited by the presence of manufacturing defects. It is imperative to investigate the influence of these defects on the mechanical behavior of LPBFed Invar 36 alloy. In this study, in-situ X-ray computed tomography (XCT) tests were conducted on LPBFed Invar 36 alloy fabricated at different scanning speeds to examine the relationship between manufacturing defects and mechanical behavior. For LPBFed Invar 36 alloy fabricated at a scanning speed of 400 mm/s, the manufacturing defects were randomly distributed and tended to be elliptical in shape. Plastic deformation behavior was observed, and failure initiated from defects inside the material resulting in ductile failure. Conversely, for LPBFed Invar 36 alloy fabricated at a scanning speed of 1000 mm/s, numerous lamellar defects were observed mainly located between deposition layers, and their quantity was significantly increased. Little plastic deformation behavior was observed, and failure initiated from defects on the shallow surface of the material resulting in brittle failure. The differences in manufacturing defects and mechanical behavior are attributed to changes in input energy during the laser powder bed fusion process. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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15 pages, 10458 KiB

Open AccessArticle

Single-Camera Three-Dimensional Digital Image Correlation with Enhanced Accuracy Based on Four-View Imaging

by Xinxing Shao, Jingye Qu and Wenwu Chen

Materials 2023, 16(7), 2726; https://doi.org/10.3390/ma16072726 - 29 Mar 2023

Cited by 1 | Viewed by 1270

Abstract

Owing to the advantages of cost-effectiveness, compactness, and the avoidance of complicated camera synchronization, single-camera three-dimensional (3D) digital image correlation (DIC) techniques have gained increasing attention for deformation measurement of materials and structures. In the traditional single-camera 3D-DIC system, the left and right [...] Read more.

Owing to the advantages of cost-effectiveness, compactness, and the avoidance of complicated camera synchronization, single-camera three-dimensional (3D) digital image correlation (DIC) techniques have gained increasing attention for deformation measurement of materials and structures. In the traditional single-camera 3D-DIC system, the left and right view images can be recorded by a single camera using diffraction grating, a bi-prism, or a set of planar mirrors. To further improve the measurement accuracy of single-camera 3D-DIC, this paper introduces a single-camera four-view imaging technique by installing a pyramidal prism in front of the camera. The 3D reconstruction of the measured points before and after deformation is realized with eight governing equations induced by four views, and the strong geometric constraints of four views can help to improve the measurement accuracy. A static experiment, a rigid body translation experiment, and a four-point bending experiment show that the proposed single-camera 3D-DIC method can achieve higher measurement accuracy than the dual-view single-camera 3D-DIC techniques and that the single-camera 3D-DIC method has advantages in reducing both random error and systematic error. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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12 pages, 2819 KiB

Open AccessArticle

Defect Detection of Pipeline Inner Surface Based on Coaxial Digital Image Correlation with Hypercentric Lens

by Jiankang Qi, Mengqiao Xu, Weiling Zhang, Yubo Liu and Xiangjun Dai

Materials 2022, 15(21), 7543; https://doi.org/10.3390/ma15217543 - 27 Oct 2022

Cited by 4 | Viewed by 1374

Abstract

A coaxial dual-camera digital image correlation system using a hypercentric lens was proposed to determine the defect position in the inner wall of a pipeline under loads. Compared with the traditional dual-camera system, this system ensures that both cameras can capture a 360-degree [...] Read more.

A coaxial dual-camera digital image correlation system using a hypercentric lens was proposed to determine the defect position in the inner wall of a pipeline under loads. Compared with the traditional dual-camera system, this system ensures that both cameras can capture a 360-degree panoramic image in the same position. Herein, the imaging principle of the system was introduced in detail. In addition, the effectiveness and accuracy of the proposed method were verified through verification and application experiments. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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18 pages, 8242 KiB

Open AccessArticle

Multi-Camera Digital Image Correlation in Deformation Measurement of Civil Components with Large Slenderness Ratio and Large Curvature

by Yuntong Dai and Hongmin Li

Materials 2022, 15(18), 6281; https://doi.org/10.3390/ma15186281 - 09 Sep 2022

Cited by 4 | Viewed by 1583

Abstract

To address the limitations of conventional stereo-digital image correlation (DIC) on measuring complex objects, a continuous-view multi-camera DIC (MC-DIC) system and its two forms of camera arrangement are introduced. Multiple cameras with certain overlapping field of view are calibrated simultaneously to form an [...] Read more.

To address the limitations of conventional stereo-digital image correlation (DIC) on measuring complex objects, a continuous-view multi-camera DIC (MC-DIC) system and its two forms of camera arrangement are introduced. Multiple cameras with certain overlapping field of view are calibrated simultaneously to form an overall system for measuring the continuous full-surface deformation. The bending experiment of coral aggregate concrete beam and the axial compression experiment of timber column are conducted to verify the capability of continuous-view MC-DIC in deformation measurement of civil components with large slenderness ratio and large curvature, respectively. The obtained deformation data maintain good consistency with the displacement transducer and strain gauge. Results indicate that the continuous-view MC-DIC is a reliable 3D full-field measurement approach in civil measurements. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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15 pages, 4068 KiB

Open AccessArticle

Modal Analysis Using Digital Image Correlation Technique

by Peter Frankovský, Ingrid Delyová, Peter Sivák, Jozef Bocko, Jozef Živčák and Michal Kicko

Materials 2022, 15(16), 5658; https://doi.org/10.3390/ma15165658 - 17 Aug 2022

Cited by 6 | Viewed by 1725

Abstract

The present paper discusses a new approach for the experimental determination of modal parameters (resonant frequencies, modal shapes and damping coefficients) based on measured displacement values, using the non-contact optical method of digital image correlation (DIC). The output is a newly developed application [...] Read more.

The present paper discusses a new approach for the experimental determination of modal parameters (resonant frequencies, modal shapes and damping coefficients) based on measured displacement values, using the non-contact optical method of digital image correlation (DIC). The output is a newly developed application module that, based on a three-dimensional displacement matrix from the experimental measurement results, can construct a frequency response function (FRF) for the purpose of experimental and operational modal analysis. From this frequency response function, the modal parameters of interest are able to be determined. The application module has been designed for practical use in Scilab 6.1.0, and its code interfaces directly with the ISTRA4D high-speed camera software. The module was built on measurements of a steel plate excited by an impact hammer to simulate experimental modal analysis. Verification of the correctness of the computational algorithm or the obtained modal parameters of the excited sheet metal plate was performed by simulation in the numerical software Abaqus, whose modal shapes and resonant frequencies showed high agreement with the results of the newly developed application. Full article

(This article belongs to the Special Issue Modern Experimental and Measurement Methods for Mechanics of Materials)

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