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Number of results: 66
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Abstract

This paper presents an experimental analysis of flexural capacity and deformability of structural concrete slabs prepared as composite members consisting of two concrete layers made of reinforced ordinary concrete (N) and fiber reinforced concrete (SFRC). The reinforced concrete composite slabs used in the tests were prepared in the dimensions of 600 x 1200 x 80 mm. The basis was composed of two layers consisting of SFRC, one as the top layer, and one as ordinary concrete. The results of the analysis confirm a significant improvement of structural properties of the composite slab in comparison to the slabs prepared wholly of ordinary concrete.

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Authors and Affiliations

B. Sadowska-Buraczewska
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Abstract

An automated method for crack identification and quantitative description of crack systems in concrete was developed in order to aid a service life assessment of concrete elements in structures. Flat polished specimens for crack analysis were impregnated with epoxy resin containing fluorescent dye. The examination of the crack system was performed in ultraviolet light using a stereomicroscope and an Image Pro Plus image analysis system on specimens cored out of several concrete structures. The laboratory tests were performed on cast specimens to establish correlations between water penetration and chloride diffusion and crack system parameters. The analysis of cracks in concrete cores taken from structures resulted in interesting conclusions based on the crack width distribution and crack localization with respect to steel reinforcement. The method was found very effective to support standard concrete diagnostics methods.

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Authors and Affiliations

M.A. Glinicki
A. Litorowicz
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Abstract

Inconel 713C precision castings are used as aircraft engine components exposed to high temperatures and the aggressive exhaust gas

environment. Industrial experience has shown that precision-cast components of such complexity contain casting defects like

microshrinkage, porosity, and cracks. This necessitates the development of repair technologies for castings of this type. This paper

presents the results of metallographic examinations of melted areas and clad welds on the Inconel 713C nickel-based superalloy, made by

TIG, plasma arc, and laser. The cladding process was carried out on model test plates in order to determine the technological and materialrelated

problems connected with the weldability of Inconel 713C. The studies included analyses of the macro- and microstructure of the

clad welds, the base materials, and the heat-affected zones. The results of the structural analyses of the clad welds indicate that Inconel

713C should be classified as a low-weldability material. In the clad welds made by laser, cracks were identified mainly in the heat-affected

zone and at the melted zone interface, crystals were formed on partially-melted grains. Cracks of this type were not identified in the clad

welds made using the plasma-arc method. It has been concluded that due to the possibility of manual cladding and the absence of welding

imperfections, the technology having the greatest potential for application is plasma-arc cladding.

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Authors and Affiliations

J. Adamiec
K. Łyczkowska
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Abstract

The paper presents the results of research on the microstructure of GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoCuN25-6-3 cast steels with

a varying carbon content. The cause for undertaking the research were technological problems with hot cracking in bulk castings of duplex

cast steel with a carbon content of approx. 0.06% and with 23% Cr, 8.5% Ni, 3% Mo and 2.4% Cu. The research has shown

a significant effect of increased carbon content on the ferrite and austenite microstructure morphology, while exceeding the carbon content

of 0.06% results in a change of the shape of primary grains from equiaxial to columnar.

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Authors and Affiliations

G. Stradomski
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Abstract

The usefulness of elastic compliance measurements to estimate crack closure in structural steel and the validity of the assumption of a constant compliance value for the fully open crack is examined. Based on considering different issues related to the experimental technique and compliance data processing, local compliance measurements and the compliance offset method recommended by the ASTM standard are selected to be most suitable for structural steel. The compliance data generated in fatigue tests on I 8G2A steel conducted under a variety of loading conditions enabled to choose an optimal strain gauge positioning and appropriate offset criterion values for the original compliance offset method and its modified (normalized) version. The adequacy of the closure measurements is assessed through checking the ability of the resulting effective stress intensity factors to account for the observed effects of the loading conditions on fatigue crack growth rates.
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Authors and Affiliations

Małgorzata Skorupa
Andrzej Skorupa
Tomasz Machniewicz
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Abstract

Effects of specimen thickness and stress ratio on fatigue crack growth and crack closure levels under constant amplitude loading and after a single overload have been studied experimentally for a structural steel ( I 8G2A). The corresponding crack growth data from the fatigue tests have been presented and evaluated. The experimental trends have been compared to those reported in the literature for various steels. The ability of the effective stress intensity factor range based on crack closure measurements to correlate the observed crack growth response has been investigated.
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Authors and Affiliations

Małgorzata Skorupa
Andrzej Skorupa
Jaap Schijve
Tomasz Machniewicz
Paweł Korbut
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Abstract

In this paper, the different mechanical behaviors of layered rocks with different bedding angles during uniaxial compression tests are studied. Numerical simulation models of layered rock are validated based on laboratory tests, and uniaxial compression tests are conducted by using Particle Flow Code (PFC). Using these simulations, the uniaxial compressive strength, failure patterns, development of micro-cracks, and displacement of meso particles are analyzed. When the bedding angle is similar to the failure angle, the macro failure planes develop directly along the beddings, the bedding behavior dictates the behavior of the layered rock, reducing the compressive strength.

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Authors and Affiliations

Nan Yao
Yi-Cheng Ye
Bin Hu
Wei-Qi Wang
Qi-Hu Wang
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Abstract

The numerical solutions of stress and strain components on the critical plane of tungsten carbide coating were solved based on the critical plane method in three-dimensional coordinate system, and accordingly three strain energy density parameters (Smith-Watson-Topper, Nita-Ogatta-Kuwabara and Chen parameters) were determined to reveal the fretting fatigue characteristics of tungsten carbide coating. In order to predict the fretting fatigue life based on the strain energy density criterion, the expressions between the strain energy density parameter and the fretting fatigue life was obtained experimentally. After the comparison of the three strain energy parameters, it was found that all three parameters could accurately predict the crack initiation position, but only the Smith-Watson-Topper parameters could accurately predict the crack initiation angle. The effects of cyclic load, normal load and friction coefficient on fretting fatigue damage behaviors were discussed by using the Smith-Watson-Topper criterion. The results show that the fretting fatigue life decreases with the increase of cyclic load; an increase in the normal contact load will cause the Smith-Watson-Topper damage parameters more concentrated at the outer edge of the bridge foot; a decrease in the friction coefficient will increase the Smith-Watson-Topper damage parameters in the middle of the contact surface.
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Authors and Affiliations

Xin Zeng
1 2
Xiaoxiao Wang
1 2
Xuecheng Ping
1 2
Renjie Wang
1 2
Tao Hu
3

  1. Tianjin University of Science and Technology, School of Mechanical Engineering, Tianjin 300222, China
  2. Tianjin University of Science and Technology, Tianjin Key Laboratory of Integrated Design and Online Monitoring of Light Industry and Food Engineering Machinery and Equipment, Tianjin 300222, China
  3. Shanghai Xifa Business Consult ing Co., Ltd., Shanghai 200232, China
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Abstract

Adetailed tie model of cracking is proposed. The model is dedicated to both semi-massive RC (reinforcement concrete) members subjected to early-age imposed strains and non-massive members in which imposed strains occur after concrete hardening. As distinct from the currently applied European guidelines, the proposed model enables an analysis of crack width changes. These are a function of progressive imposed strain, material and geometry data, but also depend on the scale of cracking which determines the strain conditions of a member. Consequently, the new model takes account of not only the factors determining the cracking development but also the member relaxation effect that results from cracking. For this reason a new definition of restraint factor is proposed, which takes into account the range of cracking of a structural member, i.e. the number and width of cracks. Parametric analyses were performed of both the changes of the degree of restraint after cracking as well as the changes of crack width depending on the adopted type of aggregate, class of concrete and the coefficient of thermal expansion of concrete. These analyses indicate the potential benefits of the application of the presented model for both a more accurate interpretation of research and economical design of engineering structures.
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Authors and Affiliations

Mariusz Zych
1
ORCID: ORCID

  1. Cracow University of Technology, Faculty of Civil Engineering, St. Warszawska 24, 31-155 Cracow, Poland
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Abstract

One of the worst accidents that can take place in industrial presses is related to the risk of generating cracks in the columns. In order to avoid press columns from being subjected to tensile stress in the loading phase, the columns are sometimes assembled precompressed, so that nominal stress maintains negative values throughout the work cycle. Previous researches have considered cracks propagating under cyclic compressive loads in notched specimens. In these cases, the fatigue cracks are initiated at the notch root due to residual tensile stresses and grew at a progressively decreasing speed before arresting. The subject of the present paper is to give a paradigmatic example of crack initiation and propagation also in a general compressive field.
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Authors and Affiliations

Giorgio Olrni
Alessandro Freddi
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Abstract

New approach using direct crack width calculations of the minimum reinforcement in tensile RC elements is presented. Verification involves checking whether the provided reinforcement ensures that the crack width that may result from the thermal-shrinkage effects does not exceed the limit value. The Eurocode provisions were enriched with addendums derived from the German national annex. Three levels of accuracy of the analysis were defined - the higher the level applied, the more significant reduction in the amount of reinforcement required can be achieved. A methodology of determining the minimum reinforcement for crack width control on the example of a RC retaining wall is presented. In the analysis the influence of residual and restraint stresses caused by hydration heat release and shrinkage was considered.

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Authors and Affiliations

M. Knauff
B. Grzeszykowski
A. Golubińska
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Abstract

The paper presents the results of tests on dynamic stability of Bernoulli-Euler beam with damages. Damages (cracks) were modeled using three rotational springs. An analysis of the influence of crack depth and their position relative to the beam ends on dynamic stability of the beam was carried out. The problem of dynamic stability was solved by applying the mode summation method. Applying an orthogonal condition of eigenfunctions, the dynamic of the system was described with the use of the Mathieu equation. The obtained equation allowed the dynamic stability of the tested system to be analyzed. Stable and unstable solutions were analyzed using the Strutt card.
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Authors and Affiliations

W. Sochacki
1
ORCID: ORCID
S. Garus
1
ORCID: ORCID
J. Garus
1
ORCID: ORCID

  1. Czestochowa University of Technology, Department of Mechanics and Fundamentals of Machinery Design, Faculty of Mechanical Engineering and Computer Science, 73 Dąbrowskiego Str., 42-201 Częstochowa, Poland
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Abstract

Slender systems are mostly studied when Euler’s load or follower load is considered. The use of those types of external loads results in well-known divergence or flutter shape of the characteristic curve. In this study, one takes into account the specific load which allows one to obtain an interesting divergence – pseudo flutter shape of characteristic curves on the external load–vibration frequency plane. The curves can change inclination angle as well as one can observe the change in vibration modes along them. The shape of those curves depends not only on the parameters of the slender system but also on loading heads that induce the specific load. In this study, one considers the slender multimember system in which cracks are present and weaken the host structure. The results of theoretical as well as numerical simulations are focused on the influence of the parameters of the loading heads on vibrations, stability, and loading capacity of the investigated system as well as on the possibility of partial reduction of unwanted crack effect.
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Authors and Affiliations

Krzysztof Sokół
1
ORCID: ORCID
Krzysztof Kuliński
2

  1. Department of Mechanics and Machine Design Foundations, Czestochowa University of Technology, Czestochowa, Poland
  2. Department of Civil Engineering, Czestochowa University of Technology, Czestochowa, Poland
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Abstract

Prediction of propagation time of corrosion is a key element in evaluating the service life of corroded reinforced concrete (RC) structures. Corroded steel products often expand in volume and thus generate tensile stress in the concrete cover. When this tensile stress exceeds the tensile strength of the concrete, cracking occurs. The tensile stresses in concrete due to corrosion are usually perpendicular to the longitudinal axis of the reinforcement. In the reinforced concrete beams, tensile stresses in concrete due to bending is perpendicular to the longitudinal direction of stirrups. In the reinforced concrete slabs, the tensile stresses in concrete due to bending is also perpendicular to the axis of longitudinal reinforcement subjected to bending in the other direction. In such cases, the tensile stresses in concrete due to corrosion of reinforcement has the same direction as the tensile stress caused by bending. When the load-induced stress in the concrete has the same direction as that of the corrosion-induced stress, cracks will likely appear more quickly and vice versa. The main objective of this paper is to build a predictive model of corrosion propagation time taking into account: (1) the effect of stresses due to load; (2) the change of corrosion current density. The model was implemented on Matlab software. The results show the influence of the load, and other parameters on the corrosion propagation stage, when considering the end of this corrosion propagation stage is cracking of concrete cover.
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Authors and Affiliations

Dao Van Dinh
1
ORCID: ORCID
Tran Viet Hung
1
ORCID: ORCID

  1. Structural Engineering Section – University of Transport and Communications Add: No.3 Cau Giay Street, Lang Thuong ward, Dong Da District, Hanoi, Vietnam
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Abstract

The strip yield model from the NASGRO computer software has been applied to predict fatigue crack growth in two different aircraft aluminium alloys under constant amplitude loading and programmed and random variable amplitude load histories. The computation options realized included either of the two different strip yield model implementations available in NASGRO and two types of the input material data description. The model performance has been evaluated based on comparisons between the predicted and observed results. It is concluded that altogether unsatisfactory prediction quality stems from an inadequate constraint factor conception incorporated in the NASGRO models.
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Authors and Affiliations

Małgorzata Skorupa
Tomasz Machniewicz
Andrzej Skorupa
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Abstract

Experimental evaluations on interlaminar and intralaminar fracture of multilayered and sandwich epoxy and polyester fabrics show an interesting behaviour at delamination initiation and crack propagation. Mode I and Mode Il tests were done on layered specimens with same type of ani ficial delamination to investigate the material influence on interlaminar fracture toughness and crack propagation. In sandwich specimens with a rigid foam core, the intralaminar damage failure and propagation are monitored.
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Authors and Affiliations

D.M. Constantinescu
N. Constantin
T. Goss
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Abstract

Rock masses, especially those with different pre-existing cracks, are prone to instability and failure under tensile loading, resulting in different degrees of engineering disasters. Therefore, to better understand the effect of pre-existing cracks with different dip angles on the tensile instability failure behaviour of rocks, the mechanism of crack initiation, propagation and coalescence in precracked sandstone under radial compression loading is investigated through numerical simulations. The temporal and spatial evolution of acoustic emission (AE) events is investigated by the moment tensor (MT), and the fracture mode of micro-cracks is determined. The results show that the pre-existing cracks weaken the specimens. The strength, crack initiation points and macro-failure modes of the specimens differ significantly depending on the dip angle of the pre-existing crack. For different dip angles of the pre-existing cracks, all the micro-cracks at the crack initiation point are tensile cracks, which are dominant during the whole loading process, and mixed cracks are mainly generated near the upper and lower loading ends after the peak stress. Of the total number of events, more than 75% are tensile cracks; approximately 15% are shear mode cracks; and the remainder consist of mixed mode cracks. The study reveals the instability and failure mechanism of pre-cracked rock, which is of great significance to ensure the long-term stability of rock mass engineering.
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Authors and Affiliations

Guozhu Wang
1
ORCID: ORCID
Xulin Luo
2
ORCID: ORCID
Lei Song
3
ORCID: ORCID
Yu Wang
3
ORCID: ORCID
Mouwang Han
3
ORCID: ORCID
Zhaocun Song
3
ORCID: ORCID
Linjun Wu
3
ORCID: ORCID
Zukun Wang
3
ORCID: ORCID

  1. China University of Mining and Technology (CUMT), State Key Laboratory for Geomechanics and Deep Underground Engineering, Xuzhou 221116, China
  2. Zhengzhou University of Industrial Technology, School of Architectural Engineering, Zhengzhou 451150, China
  3. CUMT, Xuzhou 221116, China
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Abstract

Fissures are an important factor to induce slope instability of expansive soil channel, which destroys the integrity of soil mass and deteriorates soil mass. Currently, the research is limited to the fissures in the plane direction, and it is very important to reveal the development mechanism of fissures in expansive soils along the depth direction by studying the development law of fissures in expansive soils with different thicknesses. In this study, taking expansive soil on channel slope of the Middle Route Project of South-to-North Water Transfer as an example, crack expansion tests with thickness of 10 mm, 20 mm, 30 mm and 40 mm are carried out based on self-designed crack expansion test device. An innovative test method for volumetric fracturing rate is proposed and the following conclusions are drawn: (1) the later the cracking time of soil body is, the lower the water content of cracking and the higher the water content after stabilization when the soil body is thicker; (2) When the fissures develop in soils of different thicknesses, their plane fissure rate changes with time in accordance with the logistic law; (3) Volumetric fracturing increases significantly with thickness; (4) The development of fissures is the form of stress release of soil mass, and the release along depth direction is the main form for soil mass with large thickness. (5) It is of great significance to study the law of fracture development in depth direction for further exploring the mechanism of fracture propagation.
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Authors and Affiliations

Jianhua Guo
1
Gang Ding
1
ORCID: ORCID
Hanhui Wang
1
ORCID: ORCID
Shichang Li
2
ORCID: ORCID
Zhangjun Dai
2
ORCID: ORCID

  1. Changjiang Institute of Survey, Planning, Design and Research Corporation, Wuhan 430010, China
  2. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, Hubei Province, China
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Abstract

Due to the large amount of binder and low water-cement ratio, high-performance cement composites have high compressive strength and a dense hardened cement paste microstructure. External curing is insufficient, as it cannot reach the interior parts of the structure, which allows autogenous shrinkage to occur in the inside. Lack of prevention of autogenous shrinkage and high restraint causes structural microcracks around rigid components (aggregate, rebars). Consequently, this phenomenon leads to the propagation of internal microcracks to the surface and reduced concrete durability. One way to minimize autogenous shrinkage is internal curing. The use of soaked lightweight aggregate to minimize the risk of cracking is not always sufficient. Sorption and desorption kinetics of fine and coarse fly ash aggregate were tested and evaluated. The correlation between the development of linear autogenous shrinkage and the tensile stresses in the restrained ring test is assessed in this paper. A series of linear specimens, with cross-section and length custom designed to match the geometry of the concrete ring, were tested and analyzed. Determination of the maximum tensile stresses caused by the restrained autogenous shrinkage in the restrained ring test, together with the approximation of the tensile strength development of the cement composites were used to evaluate the cracking risk development versus time. The high-performance concretes and mortars produced with mineral aggregates and lightweight aggregates soaked with water were tested. The use of soaked granulated fly ash coarse lightweight aggregate in cementitious composites minimized both the autogenous shrinkage and cracking risk.
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Authors and Affiliations

Adam Zieliński
1
ORCID: ORCID
Anton K. Schindler
2
ORCID: ORCID
Maria Kaszyńska
1
ORCID: ORCID

  1. West Pomeranian University of Technology, Faculty of Civil Engineering and Environmental, al. Piastów 50a, 70-311 Szczecin, Poland
  2. Department of Civil and Environmental Engineering, Auburn University, 237 Harbert Center, Alabama 36849, Auburn, USA
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Abstract

The authors present the part of research devoted to the "squat" -type crack development in the heads of railway rails. This paper contains description of the results of investigations of the influence of the dynamic interaction, between the railway bogie running along the track on the "squat't-type crack development. The studies are performed by the use of computer simulation technique. The study is divided into two parts. The first part explains, how the vertical displacement of the wheel varies during the quasi-static rolling of the bo gie wheel along the cracked rail. In the second part of the paper, this displacements fluctuation is introduced to dynamic analysis. The histories of the wheel-rail force fluctuation during passage along the rail with the "squat'l-type crack were obtained as the result of dynamic analysis.
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Authors and Affiliations

Mirosław Olzak
Tomasz Szolc
ORCID: ORCID
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Abstract

The mutual influence of fatigue processes, abrasive wear and corrosion of chain links on the functional properties of mining round link chains has been presented in this paper. Selected results of experimental investigations in the field of synergic impact of these destructive processes on the operational durability of mining chains have also been presented. The emphasis was given to the necessity of a comprehensive consideration of destructive processes that occur in various conditions of use of round link chains applied in mining machines.
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Bibliography

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[3] S. Mikuła, Trwałość zmęczeniowa cięgien łańcuchowych górniczych maszyn urabiających i transportowych. Prace Badawcze CMG Komag, Gliwice (1978).
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[8] J. Hankus, M. Szot, A. Pytlik, K. Paradowski, Badania łańcuchów ogniwowych górniczych. Materiały Sympozjum Szkoleniowego Europejskiego Studium Menedżerskiego, Jastrzębie Zdrój (2006).
[9] H . Kania, Kształtowanie struktury oraz odporność korozyjna powłoki Zn-Al otrzymanych metodą metalizacji zanurzeniowej. Wydawnictwo Politechniki Śląskiej, Gliwice (2017).
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[18] E . Remiorz, S. Mikuła, Eksploatacyjna diagnostyka ogniwowych łańcuchów górniczych stosowanych w pociągowych układach łańcuchowych maszyn ścianowych. Maszyny Górnicze 36 (1), (2018).
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Authors and Affiliations

Eryk Remiorz
1
ORCID: ORCID
Stanisław Mikuła
1
ORCID: ORCID

  1. Silesian University of Technology, Faculty of Mining, Safety Engineering and Industrial Automation, Department of Mining Mechanization and Robotisation, 2 Akademicka Str., 44-100 Gliwice, Poland
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Abstract

A general model of the equations of generalized thermo-microstretch for an infinite space weakened by a finite linear opening mode-I crack is solved. Considered material is the homogeneous isotropic elastic half space. The crack is subjected to a prescribed temperature and stress distribution. The formulation is applied to generalized thermoelasticity theories, using mathematical analysis with the purview of the Lord-Şhulman (involving one relaxation time) and Green-Lindsay (includes two relaxation times) theories with respect to the classical dynamical coupled theory (CD). The harmonic wave method has been used to obtain the exact expression for normal displacement, normal stress force, coupled stresses, microstress and temperature distribution. Variations of the considered fields with the horizontal distance are explained graphically. A comparison is also made between the three theories and for different depths for the case of copper crystal.

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Authors and Affiliations

Khaled Lotfy
Alaa Abd El-Bary
Mohamed Allan
Marwa H. Ahmed
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Abstract

This study proposes a method that combines Histogram of Oriented Gradients (HOG) feature extraction and Extreme Gradient Boosting (XGBoost) classification to resolve the challenges of concrete crack monitoring. The purpose of the study is to address the common issue of overfitting in machine learning models. The research uses a dataset of 40,000 images of concrete cracks and HOG feature extraction to identify relevant patterns. Classification is performed using the ensemble method XGBoost, with a focus on optimizing its hyperparameters. This study evaluates the efficacy of XGBoost in comparison to other ensemble methods, such as Random Forest and AdaBoost. XGBoost outperforms the other algorithms in terms of accuracy, precision, recall, and F1-score, as demonstrated by the results. The proposed method obtains an accuracy of 96.95% with optimized hyperparameters, a recall of 96.10%, a precision of 97.90%, and an F1-score of 97%. By optimizing the number of trees hyperparameter, 1200 trees yield the greatest performance. The results demonstrate the efficacy of HOG-based feature extraction and XGBoost for accurate and dependable classification of concrete fractures, overcoming the overfitting issues that are typically encountered in such tasks.
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Authors and Affiliations

Ida Barkiah
1
Yuslena Sari
2

  1. Department of Civil Engineering, Universitas Lambung, Mangkurat, Indonesia
  2. Department of Information Technology, Universitas Lambung Mangkurat, Indonesia
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Abstract

The paper presents the susceptibility of AE44 magnesium alloy to electrochemical corrosion and stress corrosion cracking (SCC). The evaluation of the intensity of the interaction of the corrosive environment was carried out using the corrosion tests and the Slow Strain Rate Test (SSRT). Corrosion tests performed in 0.1 M Na2SO4 solution (immersion in solution and under cathodic polarization conditions) revealed that the layer of corrosion products was much thicker after immersion test. The results of SSRT showed that the AE44 alloy deformed in the solution was characterized by higher plasticity compared to the alloy deformed in the air after immersion in solution. Moreover, the fractures were characterized by different morphology. In the case of an alloy deformed in the solution under cathodic polarization many microcracks on the fracture were observed, which were not observed in the case of the alloy deformed in the air.

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Authors and Affiliations

M. Sozańska
A. Mościcki
B. Chmiela

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