Research

19 pages, 6762 KiB

Open AccessArticle

Research on the Influence of Compression and Offset of Cushion Blocks on the Axial Strength of Transformers

by Lu Sun, Shuguo Gao, Tianran Li, Jiaxin Yao, Ping Wang and Jianhao Zhu

Appl. Sci. 2023, 13(24), 13289; https://doi.org/10.3390/app132413289 - 15 Dec 2023

Viewed by 588

The instability of the winding-cushion structure is one of the primary causes of transformer failures. Insulation cushion compression and offset are the predominant forms leading to structural instability. Therefore, this paper, using the SFSZ7-31500/110 transformer as an example, first derives the theoretical formula [...] Read more.

The instability of the winding-cushion structure is one of the primary causes of transformer failures. Insulation cushion compression and offset are the predominant forms leading to structural instability. Therefore, this paper, using the SFSZ7-31500/110 transformer as an example, first derives the theoretical formula for mechanical stress calculation. It clarifies the key influencing parameters of the winding-cushion block structure on the axial bending stress of the winding. Subsequently, an electromagnetic force finite element calculation model is established to obtain the axial force distribution in the winding and the distribution of unbalanced displacement during short-circuit processes. Based on the force and offset distribution, a specific cushion block compression and offset test platform is constructed. By setting different cushion block variables, the effects of cushion block unbalanced height and cushion block offset on the winding’s bending elastic modulus are determined. Finally, a simulation model for stress calculation of the winding-cushion block structure is established, revealing the influence pattern of cushion block compression and offset instability on the axial strength of the winding. The results of this study indicate that the greater the uneven cushion block height, the lower the axial strength of the winding. Under the same cushion block offset angle, winding structures with non-uniform cushion block offsets exhibit the worst axial stability. When the offset angles are 30°, 45°, and 60°, the maximum axial bending stress of the winding increases by 1.73%, 3.46%, and 7.82%, respectively. Increasing the offset angle exacerbates the decrease in the axial strength of the winding up to a certain extent. The findings in this study have significant implications for enhancing a transformer’s short-circuit resistance. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

17 pages, 4966 KiB

Open AccessArticle

Effect of Laser Treatment on Intrinsic Mechanical Stresses in Titanium and Some of Its Alloys

by Magdalena Jażdżewska, Michał Bartmański, Andrzej Zieliński and Dominika Beata Kwidzińska

Appl. Sci. 2023, 13(10), 6276; https://doi.org/10.3390/app13106276 - 20 May 2023

Cited by 4 | Viewed by 1479

Abstract

Laser surface treatment conducted at different power levels is an option to modify titanium bone implants to produce nano- and microtopography. However, such processing can lead to excess mechanical stress within the surface layer. This research aims to calculate the level of such [...] Read more.

Laser surface treatment conducted at different power levels is an option to modify titanium bone implants to produce nano- and microtopography. However, such processing can lead to excess mechanical stress within the surface layer. This research aims to calculate the level of such residual stresses after the surface processing of Ti grade IV, Ti15Mo, and Ti6Al7Nb alloys with an Nd:YAG laser. Light and scanning electron microscopies (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), optical profilography, and nano-indentation tests were applied to characterize the surface zone. The laser processing resulted in a distinct surface pattern and the formation of remelted zones 66–126 µm thick, with roughness values ranging between 0.22 and 1.68 µm. The mechanical properties were weakly dependent on the material composition. The residual stresses caused by the laser treatment were moderate, always tensile, increasing with loading, and was the highest for the Ti15Mo alloy. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

12 pages, 4701 KiB

Open AccessArticle

Prediction of Deflection Due to Multistage Loading of a Corrugated Package

by Jong-Min Park, Tae-Yun Park and Hyun-Mo Jung

Appl. Sci. 2023, 13(7), 4236; https://doi.org/10.3390/app13074236 - 27 Mar 2023

Cited by 2 | Viewed by 1013

Abstract

With the expansion of overseas markets, transportation distance, storage periods in warehouses, and traffic volume of goods are increasing. In this distribution environment, the safety problem due to the decrease in the strength of the multistacked corrugated package is becoming very important. This [...] Read more.

With the expansion of overseas markets, transportation distance, storage periods in warehouses, and traffic volume of goods are increasing. In this distribution environment, the safety problem due to the decrease in the strength of the multistacked corrugated package is becoming very important. This study aims to develop a CAE prediction technology for the height change of multistacked corrugated packages, and for this study, the FEA simulation method for existing corrugated packages has been investigated and supplemented. The four-point bending FE model and the box compression test FE model were also constructed based on the simplified and homogenized composite model for the target corrugated fiberboard (double wall of EB-flute) itself. Four-point bending, box compression, and creep tests were performed to obtain the material constant required for FEA simulation. Through the comparison of the F–D curve area between the test and the FEA simulation, parameter optimization that minimizes the area difference was performed using HyperStudy. The FEA simulation and stacking test for the multistacked target corrugated package were performed simultaneously on four actual stacking scenarios with different package weights and package sizes. A comparison of height changes after 72 h of stacking for each of the four scenarios showed that the concordance between the test and FEA simulation was more than 80% in all cases. To further expand the scope of this application, it is necessary to secure additional reliability through continuous comparative monitoring using the test data and physical properties of various corrugated fiberboards. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

20 pages, 6046 KiB

Open AccessArticle

Prediction of Pre- and Post-Breakage Behavior of Laminated Glass Using a Phase-Field Damage Model

by Jaroslav Schmidt, Tomáš Janda and Michal Šejnoha

Appl. Sci. 2023, 13(3), 1708; https://doi.org/10.3390/app13031708 - 29 Jan 2023

Cited by 2 | Viewed by 1191

Abstract

Laminated glass composed of several layers of glass plies bonded to a polymer interlayer enjoys ever growing interest in modern architecture. Being often used in impact protection designs requires understanding of both pre- and post-breakage behavior of these structures. This paper contributes to [...] Read more.

Laminated glass composed of several layers of glass plies bonded to a polymer interlayer enjoys ever growing interest in modern architecture. Being often used in impact protection designs requires understanding of both pre- and post-breakage behavior of these structures. This paper contributes to this subject by examining an application of an explicit phase field dynamic model to the description of fracture in a laminated glass subjected to a low velocity impact. The achieved results indicate the ability of the proposed model to successfully describe the onset of damage and subsequent crack propagation. It has, however, been observed that a relatively fine mesh is needed to interpolate a sharp discontinuity accurately, which makes this approach computationally demanding. The model is first validated against experimental results obtained for a single-layer float glass. Next, the usability of the phase-field damage model as a crack predictor in individual layers of the composite is investigated. The dependence of the results on residual stiffness, element type, and initial tensile strength is examined and discussed. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

16 pages, 4809 KiB

Open AccessArticle

Numerical and Experimental Investigation of Flexural Properties and Damage Behavior of CFRTP/Al Laminates with Different Stacking Sequence

by Shiyi Gao, Wenbin Hou, Jianing Xing and Lin Sang

Appl. Sci. 2023, 13(3), 1667; https://doi.org/10.3390/app13031667 - 28 Jan 2023

Cited by 4 | Viewed by 1645

Abstract

Fiber Metal Laminates (FMLs) are hybrid materials that combine metal components with fiber-reinforced composites. The properties and failure modes of CArbon fiber Reinforced composites/Aluminum Laminates (CARALLs) composed of T700/PA6 unidirectional prepreg and 6061 aluminum alloy were studied using experimental and numerical simulation analysis. [...] Read more.

Fiber Metal Laminates (FMLs) are hybrid materials that combine metal components with fiber-reinforced composites. The properties and failure modes of CArbon fiber Reinforced composites/Aluminum Laminates (CARALLs) composed of T700/PA6 unidirectional prepreg and 6061 aluminum alloy were studied using experimental and numerical simulation analysis. Through three-point bending experiments, the bending behavior of CARALLs with different composite/metal layer methods was examined. It was found that FMLs in the 2/1 patch form (one layer of aluminum and two layers of T700/PA6 unidirectional prepreg) show the highest bending modulus and strength compared with other stacking sequences. With the metal volume fraction increased, the bending properties of CARALLs decreased, suggesting the important role of the carbon fiber composite layer in the load-bearing capacity. Lastly, the Linde and Hashin failure criteria were employed to analyze the bending behavior and damage mechanism of CARALLs with different stacking sequences. The simulation results were in good agreement with the experimental results, which provides more insight into the prediction of the bending behavior of CARALLs hybrids. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

30 pages, 4922 KiB

Open AccessArticle

Torsional Capacity Prediction of Reinforced Concrete Beams Using Machine Learning Techniques Based on Ensembles of Trees

by Diana S. O. Bernardo, Luís F. A. Bernardo, Hamza Imran and Tiago P. Ribeiro

Appl. Sci. 2023, 13(3), 1385; https://doi.org/10.3390/app13031385 - 20 Jan 2023

Viewed by 1601

Abstract

For the design or assessment of framed concrete structures under high eccentric loadings, the accurate prediction of the torsional capacity of reinforced concrete (RC) beams can be critical. Unfortunately, traditional semi-empirical equations still fail to accurately estimate the torsional capacity of RC beams, [...] Read more.

For the design or assessment of framed concrete structures under high eccentric loadings, the accurate prediction of the torsional capacity of reinforced concrete (RC) beams can be critical. Unfortunately, traditional semi-empirical equations still fail to accurately estimate the torsional capacity of RC beams, namely for over-reinforced and high-strength RC beams. This drawback can be solved by developing accurate Machine Learning (ML) based models as an alternative to other more complex and computationally demanding models. This goal has been herein addressed by employing several ML techniques and by validating their predictions. The novelty of the present article lies in the successful implementation of ML methods based on Ensembles of Trees (ET) for the prediction of the torsional capacity of RC beams. A dataset incorporating 202 reference RC beams with varying design attributes was divided into testing and training sets. Only three input features were considered, namely the concrete area (area enclosed within the outer perimeter of the cross-section), the concrete compressive strength and the reinforcement factor (which accounts for the ratio between the yielding forces of both the longitudinal and transverse reinforcements). The predictions from the used models were statistically compared to the experimental data to evaluate their performances. The results showed that ET reach higher accuracies than a simple Decision Tree (DT). In particular, The Bagging Meta-Estimator (BME), the Forests of Randomized Trees (FRT), the AdaBoost (AB) and the Gradient Tree Boosting (GTB) reached good performances. For instance, they reached values of R² (coefficient of determination) in the range between 0.982 and 0.990, and values of cvRMSE (coefficient of variation of the root mean squared error) in the range between 10.04% and 13.92%. From the obtained results, it is shown that these ML techniques provide a high capability for the prediction of the torsional capacity of RC beams, at the same level of other more complicated ML techniques and with much fewer input features. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

18 pages, 18433 KiB

Open AccessArticle

Investigation of Mechanical Properties of Al/CNT Nanocomposites Produced by Powder Metallurgy

by Íris Carneiro and Sónia Simões

Appl. Sci. 2023, 13(1), 54; https://doi.org/10.3390/app13010054 - 21 Dec 2022

Cited by 2 | Viewed by 1470

Abstract

Demanding requirements in automotive and aerospace applications promote the growing need to obtain materials and advanced technology capable of combining low weight with high mechanical properties. Aluminum matrix nanocomposites could be great candidates to respond to such needs. In this sense, this investigation [...] Read more.

Demanding requirements in automotive and aerospace applications promote the growing need to obtain materials and advanced technology capable of combining low weight with high mechanical properties. Aluminum matrix nanocomposites could be great candidates to respond to such needs. In this sense, this investigation aims to study the mechanical properties of nanocomposites of aluminum matrices reinforced with carbon nanotubes (CNTs). The nanocomposites were produced by powder metallurgy with 1.00 vol.% of reinforcement and ultrasonication as the dispersion method. Tensile, Vickers microhardness and nanoindentation tests were carried out in different sections. Microstructural characterizations were conducted in scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) to understand and relate to the mechanical properties. An increase in the yield strength of 185% was observed for the nanocomposites, which can be attributed to the load transfer mechanism. However, the CNTs observed at the grain boundaries promote a decrease in the ductility of the nanocomposites. The mechanical behavior of the nanocomposites was further investigated by EBSD observation. The results revealed that the nanocomposites have a less extensive area of plastic deformation than the Al matrix, which is consistent with the tensile results. The presence of reinforcement affects the lattice rotation during the tensile test and the active slip systems, thus affecting their deformation behavior. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

19 pages, 36135 KiB

Open AccessArticle

A New Approach to Identifying an Arbitrary Number of Inclusions, Their Geometry and Location in the Structure Using Topological Optimization

by A. V. Krysko, Anton Makseev, Anton Smirnov, M. V. Zhigalov and V. A. Krysko

Appl. Sci. 2023, 13(1), 49; https://doi.org/10.3390/app13010049 - 21 Dec 2022

Cited by 1 | Viewed by 979

Abstract

In the present paper, a new approach to identifying an arbitrary number of inclusions, their geometry and their location in 2D and 3D structures using topological optimization was proposed. The new approach was based on the lack of initial information about the geometry [...] Read more.

In the present paper, a new approach to identifying an arbitrary number of inclusions, their geometry and their location in 2D and 3D structures using topological optimization was proposed. The new approach was based on the lack of initial information about the geometry of the inclusions and their location in the structure. The numerical solutions were obtained by the finite element method in combination with the method of moving asymptotes. The convergence of the finite element method at the coincidence of functions and their derivatives was analyzed. Results with an error of no more than 0.5%, i.e., almost exact solutions, were obtained. Identification at impact on the plate temperature and heat flux by solving the inverse problem of heat conduction was produced. Topological optimization for identifying an arbitrary number of inclusions, their geometry and their location in 2D problems was investigated. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

22 pages, 7833 KiB

Open AccessArticle

Crack Extension Analysis of Atmospheric Stress Corrosion Based on Peridynamics

by Can Tan, Songrong Qian and Jian Zhang

Appl. Sci. 2022, 12(19), 10008; https://doi.org/10.3390/app121910008 - 05 Oct 2022

Cited by 1 | Viewed by 1386

Abstract

Based on peridynamics, an atmospheric stress corrosion model was proposed. In this model, the role of hydrogen and stress in anodic-dissolution-dominated stress corrosion cracking was considered, and atmospheric corrosion was characterized by the change in liquid film thickness on the metal surface in [...] Read more.

Based on peridynamics, an atmospheric stress corrosion model was proposed. In this model, the role of hydrogen and stress in anodic-dissolution-dominated stress corrosion cracking was considered, and atmospheric corrosion was characterized by the change in liquid film thickness on the metal surface in the atmospheric environment. The near-field kinetic anodic dissolution model and the atmospheric corrosion model were coupled by varying the liquid film thickness. The thickness of the liquid film depended on factors such as the temperature, relative humidity, and hygroscopic salts. We validated the model using stress corrosion behavior from the literature for 304 stainless steel in a simulated atmospheric environment. The results of the model captured the crack expansion process. The obtained crack expansion direction and branching behavior agreed well with the experimental results in the literature. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

14 pages, 2791 KiB

Open AccessArticle

Numerical Homogenization of Single-Walled Corrugated Board with Imperfections

by Damian Mrówczyński, Anna Knitter-Piątkowska and Tomasz Garbowski

Appl. Sci. 2022, 12(19), 9632; https://doi.org/10.3390/app12199632 - 25 Sep 2022

Cited by 7 | Viewed by 1265

Abstract

Numerical homogenization is an excellent tool for the quick simplification of complex structures with a model that is much simpler and, at the same time, accurately reflects the mechanical behavior of the original model. Corrugated cardboard modeling, with all geometrical nuances preserved, is [...] Read more.

Numerical homogenization is an excellent tool for the quick simplification of complex structures with a model that is much simpler and, at the same time, accurately reflects the mechanical behavior of the original model. Corrugated cardboard modeling, with all geometrical nuances preserved, is a complicated and time-consuming process. The transfer of a full 3D model of corrugated board composed of two flat layers and a corrugated middle layer to one layer only, with substitute elastic parameters, greatly simplifies this process. Because the individual layers of corrugated cardboard are made of paper with a grammage in the range of 80–200 g/m², i.e., very thin plates, they are slightly buckled even in the initial configuration. These imperfections affect the equivalent parameters that are obtained in the homogenization process. This paper presents an approach of taking into account these imperfections when creating a simplified model. The numerical homogenization method based on the equivalence of elastic energy between a representative volumetric element (i.e., a part of a full 3D model) and an equivalent plate were applied. Different shapes of imperfections were analyzed in order to account for the buckling modes, notably for a specific unit deformation and curvature. Finally, one form of initial imperfections was proposed, which most accurately reflects the decrease in all plate stiffnesses. Full article

(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Numerical Modeling and Mechanical Properties Analysis for Metallic and Composite Materials and Structures

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (10 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI