Special Issue "Applications of Finite Element Modeling for Mechanical and Mechatronic Systems"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editors

Prof. Dr. Marek Krawczuk
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Guest Editor
Faculty of Electrical and Control Engineering, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland
Interests: finite element modeling; numerical modeling; signal processing; numerical analysis; structural analysis; finite element analysis
Special Issues and Collections in MDPI journals
Prof. Dr. Magdalena Palacz
E-Mail
Guest Editor
Faculty of Organization and Management, Silesian University of Technology, Roosevelta 26, 41-800 Zabrze, Poland
Interests: finite element modelling; finite element analysis; mechanical properties; mechanics of materials; mechanical behaviour of materials; solid mechanics
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Numerical modeling is very important in today's engineering because, among other things, it reduces the costs associated with prototyping or predicting the occurrence of potentially dangerous situations during operation in certain defined conditions. Different methods have so far been used to implement the real structure into the numerical version. The most popular have been variations of the finite element method (FEM). The aim of the proposed Special Issue is to familiarize the reader with the latest applications of the finite element method for the modeling and analysis of diverse mechanical problems.

It is our pleasure to invite you to submit a manuscript for this Special Issue covering the latest and most interesting aspects of the numerical point of view applications of the FEM. The aim of this issue is to provide readers with a better understanding of the various applications of the FEM via the experiences of the many active research communities and their current engineering needs.

Prof. Marek Krawczuk
Prof. Magdalena Palacz
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • finite element method
  • numerical modeling
  • mechanical parameters
  • damage detection

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Editorial

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Editorial
Special Issue “Applications of Finite Element Modeling for Mechanical and Mechatronic Systems”
Appl. Sci. 2021, 11(11), 5170; https://doi.org/10.3390/app11115170 - 02 Jun 2021
Viewed by 318
Abstract
Modern engineering practice requires advanced numerical modeling because, among other things, it reduces the costs associated with prototyping or predicting the occurrence of potentially dangerous situations during operation in certain defined conditions. Different methods have so far been used to implement the real [...] Read more.
Modern engineering practice requires advanced numerical modeling because, among other things, it reduces the costs associated with prototyping or predicting the occurrence of potentially dangerous situations during operation in certain defined conditions. Different methods have so far been used to implement the real structure into the numerical version. The most popular have been variations of the finite element method (FEM). The aim of this Special Issue has been to familiarize the reader with the latest applications of the FEM for the modeling and analysis of diverse mechanical problems. Authors are encouraged to provide a concise description of the specific application or a potential application of the Special Issue. Full article

Research

Jump to: Editorial

Article
3D-Based Transition hpq/hp-Adaptive Finite Elements for Analysis of Piezoelectrics
Appl. Sci. 2021, 11(9), 4062; https://doi.org/10.3390/app11094062 - 29 Apr 2021
Cited by 1 | Viewed by 218
Abstract
This paper concerns the algorithm of transition piezoelectric elements for adaptive analysis of electro-mechanical systems. In addition, effectivity of the proposed elements in such an analysis is presented. The elements under consideration are assigned for joining basic elements which correspond to the mechanical [...] Read more.
This paper concerns the algorithm of transition piezoelectric elements for adaptive analysis of electro-mechanical systems. In addition, effectivity of the proposed elements in such an analysis is presented. The elements under consideration are assigned for joining basic elements which correspond to the mechanical models of either the first or higher order, while the electric model is of arbitrary order. In this work, three variants of the transition models are applied. The first one assures continuity of displacements between the basic models and continuity of electric potential between these models, as well. The second transition piezoelectric model guarantees additional continuity of the stress field between the basic models. The third transition model additionally enables continuous change of the strain state between the basic models. Based on the mentioned models, three types of the corresponding transition finite elements are introduced. The applied finite element approximations are hpq/hp-adaptive ones, which allows element-wise changes of the element size parameter h, and the element longitudinal and transverse orders of approximation, respectively, p and q, depending on the error level. Numerical effectiveness of the models and their approximations is investigated in the contexts of: ability to remove high stress gradients between the basic and transition models, and convergence of the numerical solutions for the model problems of piezoelectrics with and without the proposed transition elements. Full article
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Article
Automation of a Thin-Layer Load-Bearing Structure Design on the Example of High Altitude Long Endurance Unmanned Aerial Vehicle (HALE UAV)
Appl. Sci. 2021, 11(6), 2645; https://doi.org/10.3390/app11062645 - 16 Mar 2021
Cited by 1 | Viewed by 335
Abstract
In the aerospace industry, thin-layer composites are increasingly used for load-bearing structures. When designing such composite structures, particular attention must be paid to the development of an appropriate geometric form of the structure to increase the structure’s load capacity and reduce the possibility [...] Read more.
In the aerospace industry, thin-layer composites are increasingly used for load-bearing structures. When designing such composite structures, particular attention must be paid to the development of an appropriate geometric form of the structure to increase the structure’s load capacity and reduce the possibility of a loss of stability and harmful aeroelastic phenomena. For this reason, the use of knowledge-based engineering support methods is complicated. Software was developed to propose and quickly evaluate a thin-layer load-bearing structure using generative modeling methods to facilitate development of the initial concept of an aerospace load-bearing structure. Finite Element Method (FEM) analysis verifies and improves such structures. The most important contributions of the paper are a methodology for automating the design of ultralight and highly flexible aircraft structures with the use of generative modelling, proposing and verifying the form of generative models for selected fragments of the structure, especially wings, and integration of the use of generative models for iterative improvement of structures using low- and middle-fidelity methods of numerical verification. Full article
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Article
Impact of Disabled Driver’s Mass Center Location on Biomechanical Parameters during Crash
Appl. Sci. 2021, 11(4), 1427; https://doi.org/10.3390/app11041427 - 04 Feb 2021
Cited by 2 | Viewed by 481
Abstract
Adapting a car for a disable person involves adding additional equipment to compensate for the driver’s disability. During this process, the change in the driver’s position and kinematics and their impact on safety levels during crash is not considered. There is also a [...] Read more.
Adapting a car for a disable person involves adding additional equipment to compensate for the driver’s disability. During this process, the change in the driver’s position and kinematics and their impact on safety levels during crash is not considered. There is also a lack of studies in the literature on this problem. This paper describes a methodology for conducting a study of the behavior of a disabled driver during a crash using the finite element method, based on an explicit time integration method. A validated car model and a commercial dummy model were used. The results show that the use of a handle on the steering wheel and a hand control unit causes dangerous lateral displacements relative to the seat. Amputation of the left leg or right arm causes significant shoulder rotations, amputation of the left leg causes increased thoracic loads. Amputation or additional equipment have no significant impact on head injuries. Full article
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Article
Reverse Engineering and Topology Optimization for Weight-Reduction of a Bell-Crank
Appl. Sci. 2020, 10(23), 8568; https://doi.org/10.3390/app10238568 - 30 Nov 2020
Cited by 1 | Viewed by 554
Abstract
This paper describes a new design method that was developed to achieve an optimal design method for weight reduction of a bell crank, sourced from a Louis Christen Road Racing F1 Sidecar. The method involved reverse engineering to produce a 3D model of [...] Read more.
This paper describes a new design method that was developed to achieve an optimal design method for weight reduction of a bell crank, sourced from a Louis Christen Road Racing F1 Sidecar. The method involved reverse engineering to produce a 3D model of the mechanical part. The 3D bell crank model was converted to a finite element (FE) model to characterize the eigenvalues of vibration and responses to excitation using the Lanczos iteration method in Abaqus software. The bell crank part was also tested using a laser vibrometer to capture its natural frequencies and corresponding vibration mode shapes. The test results were used to validate the FE model, which was then analysed through a topology optimization process. The objective function was the weight and the optimization constraints were the stiffness and the strain energy of the structure. The optimized design was converted back to a 3D model and then fabricated to produce a physical prototype for design verification and validation by means of FE analysis and laboratory experiments and then compared with the original part. Results indicated that weight reduction was achieved while also increasing the natural frequency by 2%, reducing the maximum principal strain and maximum von Mises stress by 4% and 16.5%, respectively, for the optimized design when compared with the original design. The results showed that the proposed method is applicable and effective in topology optimization to obtain a lightweight (~3% weight saving) and structurally strong design. Full article
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Article
A Posteriori Detection of Numerical Locking in hpq-Adaptive Finite Element Analysis
Appl. Sci. 2020, 10(22), 8247; https://doi.org/10.3390/app10228247 - 20 Nov 2020
Cited by 1 | Viewed by 502
Abstract
The proposed detection algorithms are assigned for the hpq-adaptive finite element analysis of the solid mechanics problems affected by the locking phenomena. The algorithms are combined with the M- and hpq-adaptive finite element method, where M is the element model, h denotes the element size parameter, and p and q stand for the longitudinal and transverse approximation orders within an element. The applied adaptive scheme is extended with the additional step where the locking phenomena are a posteriori detected, assessed and resolved. The detection can be applied to shear, membrane, or shear–membrane locking phenomena. The removal of the undesired influence of the numerical locking on the problem solution is based on p-enrichment of the mesh. The detection algorithm is also enriched with the locking assessment algorithm which is capable of determination of the optimized value of p which is sufficient for the phenomena removal. The detection and assessment algorithms are based on a simple sensitivity analysis performed locally for the finite elements of the thin-walled domain. The sensitivity analysis lies in comparison of the element solutions corresponding to two values of the order p, namely current and potentially eliminating the locking. The local solutions are obtained from the element residual method. The elaborated algorithms are original, relatively simple, extremely reliable, and highly effective. Full article
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Article
Optimizing Roller Design to Improve Web Strain Uniformity in Roll-to-Roll Process
Appl. Sci. 2020, 10(21), 7564; https://doi.org/10.3390/app10217564 - 27 Oct 2020
Cited by 2 | Viewed by 433
Abstract
In this work, we investigated the compensation of strain deviation in the machine direction of a web in the roll-to-roll process. As flexible devices have become popular, many researchers have begun to study roll-to-roll processes for the mass-production of flexible devices at low [...] Read more.
In this work, we investigated the compensation of strain deviation in the machine direction of a web in the roll-to-roll process. As flexible devices have become popular, many researchers have begun to study roll-to-roll processes for the mass-production of flexible devices at low cost. In the continuous roll-to-roll process, an electronic circuit pattern is printed on the web while the web is transferring. Due to tension and Poisson’s ratio, a non-uniform strain distribution can occur in the web. This strain distribution occurs mainly at the center of the web and causes a register error in the machine direction. In this work, we designed a roller to minimize the strain deviation. The design of the compensation roller was optimized using the design of experiments (DOE) methodology and analysis of variance (ANOVA), and the compensation performance was verified through experiments and simulations. According to the results of a comparative experiment conducted to confirm the correcting performance of the optimized roller, the strain deviation in the machine direction decreased by approximately 48% with the proposed roller compared to that of the conventional roller. Full article
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Article
Modeling Head-On Collisions: The Problem of Identifying Collision Parameters
Appl. Sci. 2020, 10(18), 6212; https://doi.org/10.3390/app10186212 - 07 Sep 2020
Cited by 1 | Viewed by 487
Abstract
The analyses performed by the experts are crucial for the settlement of court disputes, and they have legal consequences for the parties to legal proceedings. The reliability of the simulation result is crucial. First, in article, an impact simulation was performed with the [...] Read more.
The analyses performed by the experts are crucial for the settlement of court disputes, and they have legal consequences for the parties to legal proceedings. The reliability of the simulation result is crucial. First, in article, an impact simulation was performed with the use of the program default data. Next, the impact parameters were identified from a crash test, and a simulation was presented. Due to the difficulties in obtaining the data identified, the experts usually take advantage of simplifications using only default data provided by the simulation program. This article includes the original conclusions on specific reasons of simplified collision modeling in Multi Body Systems (MBS) programs and provides specific directions of development of the V-SIM4 program used in the study to enhance the models applied. This manuscript indicates a direction for crash model development in MBS programs to consider a varied 3D body space zones stiffness related to the structure of the car body and the internal car elements instead of modeling the car body as a solid with an average stiffness. Such an approach would provide an alternative to Finite Element Method (FEM) convention modeling. Full article
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Article
Design and Structural Analysis of a Front Single-Sided Swingarm for an Electric Three-Wheel Motorcycle
Appl. Sci. 2020, 10(17), 6063; https://doi.org/10.3390/app10176063 - 01 Sep 2020
Cited by 1 | Viewed by 924
Abstract
This study focuses on the structural analysis of the front single-sided swingarm of a new three-wheel electric motorcycle, recently designed to meet the challenges of the vehicle electrification era. The primary target is to develop a swingarm capable of withstanding the forces applied [...] Read more.
This study focuses on the structural analysis of the front single-sided swingarm of a new three-wheel electric motorcycle, recently designed to meet the challenges of the vehicle electrification era. The primary target is to develop a swingarm capable of withstanding the forces applied during motorcycle’s operation and, at the same time, to be as lightweight as possible. Different scenarios of force loadings are considered and emphasis is given to braking forces in emergency braking conditions where higher loads are applied to the front wheels of the vehicle. A dedicated Computer Aided Engineering (CAE) software is used for the structural evaluation of different swingarm designs, through a series of finite element analysis simulations. A topology optimization procedure is also implemented to assist the redesign effort and reduce the weight of the final design. Simulation results in the worst-case loading conditions, indicate strongly that the proposed structure is effective and promising for actual prototyping. A direct comparison of results for the initial and final swingarm design revealed that a 23.2% weight reduction was achieved. Full article
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Article
Finite Element Study of the Effect of Internal Cracks on Surface Profile Change due to Low Loading of Turbine Blade
Appl. Sci. 2020, 10(14), 4883; https://doi.org/10.3390/app10144883 - 16 Jul 2020
Cited by 2 | Viewed by 654
Abstract
Turbine blades for thermal power plants are exposed to severe environments, making it necessary to ensure safety against damage, such as crack formation. A previous method detected internal cracks by applying a small load to a target member. Changes in the surface properties [...] Read more.
Turbine blades for thermal power plants are exposed to severe environments, making it necessary to ensure safety against damage, such as crack formation. A previous method detected internal cracks by applying a small load to a target member. Changes in the surface properties of the material were detected before and after the load using a digital holographic microscope and a digital height correlation method. In this study, this technique was applied in combination with finite element analysis using a 2D and 3D model simulating the turbine blades. Analysis clarified that the change in the surface properties under a small load varied according to the presence or absence of a crack, and elucidated the strain distribution that caused the difference in the change. In addition, analyses of the 2D model considering the material anisotropy and thermal barrier coating were conducted. The difference in the change in the surface properties and strain distribution according to the presence or absence of cracks was elucidated. The difference in the change in the top surface height distribution of the materials with and without a crack was directly proportional to the crack length. As the value was large with respect to the vertical resolution of 0.2 nm of the digital holographic microscope, the change could be detected by the microscope. Full article
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Article
Bias Truck Tire Deformation Analysis with Finite Element Modeling
Appl. Sci. 2020, 10(12), 4326; https://doi.org/10.3390/app10124326 - 24 Jun 2020
Cited by 1 | Viewed by 496
Abstract
This paper presents a method for modeling of pneumatic bias tire axisymmetric deformation. A previously developed model of all-steel radial tire was expanded to include the non-linear stress–strain relationship for textile cord and its thermal shrinkage. Variable cord density and cord angle in [...] Read more.
This paper presents a method for modeling of pneumatic bias tire axisymmetric deformation. A previously developed model of all-steel radial tire was expanded to include the non-linear stress–strain relationship for textile cord and its thermal shrinkage. Variable cord density and cord angle in the cord-rubber bias tire composite are the major challenges in pneumatic tire modeling. The variabilities result from the tire formation process, and they were taken into account in the model. Mechanical properties of the composite were described using a technique of orthotropic reinforcement overlaying onto isotropic rubber elements, treated as a hyperelastic incompressible material. Due to large displacements, the non-linear problem was solved using total Lagrangian formulation. The model uses MSC.Marc code with implemented user subroutines, allowing for the description of the tire specific properties. The efficiency of the model was verified in the simulation of mounting and inflation of an actual bias truck tire. The shrinkage negligence effect on cord forces and on displacements was examined. A method of investigating the influence of variation of cord angle in green body plies on tire apparent lateral stiffness was proposed. The created model is stabile, ensuring convergent solutions even with large deformations. Inflated tire sizes predicted by the model are consistent with the actual tire sizes. The distinguishing feature of the developed model from other ones is the exact determination of the cord angles in a vulcanized tire and the possibility of simulation with the tire mounting on the rim and with cord thermal shrinkage taken into account. The model may be an effective tool in bias tire design. Full article
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Article
Design Optimization for the Thin-Walled Joint Thread of a Coring Tool Used for Deep Boreholes
Appl. Sci. 2020, 10(8), 2669; https://doi.org/10.3390/app10082669 - 13 Apr 2020
Cited by 3 | Viewed by 552
Abstract
Threaded joints are key components of core drilling tools. Currently, core drilling tools generally adopt the thread structure designed by the API Spec 7-1 standard. However, fractures easily occur in this thread structure due to high stress concentrations, resulting in downhole accidents. In [...] Read more.
Threaded joints are key components of core drilling tools. Currently, core drilling tools generally adopt the thread structure designed by the API Spec 7-1 standard. However, fractures easily occur in this thread structure due to high stress concentrations, resulting in downhole accidents. In this paper, according to the needs of large-diameter core drilling, a core barrel joint was designed with an outer diameter of Φ135 mm and a trapezoidal thread profile. Subsequently, a three-dimensional simulation model of the joint was established. The influence of the external load, connection state and thread structure on the stress distribution in the joint was analyzed through simulations, from which the optimal thread structure was determined. Finally, a connection test was carried out on the threaded joint. The stress distribution in the joint thread was indirectly studied by analyzing gas leaks (i.e., the sealing effect) under axial tension. According to the test data and the simulation results, the final joint thread structure was optimized, which lays a good foundation for the design of a core barrel. Full article
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Article
Numerical and Experimental Analysis of Torsion Springs Using NURBS Curves
Appl. Sci. 2020, 10(7), 2629; https://doi.org/10.3390/app10072629 - 10 Apr 2020
Cited by 1 | Viewed by 720
Abstract
Torsion springs, which transfer power through the twisting of their coil, provide advantages such as module simplification and efficient use of space. The design of a torsion spring has been formulated, but it is difficult to determine the local behaviors of torsion springs [...] Read more.
Torsion springs, which transfer power through the twisting of their coil, provide advantages such as module simplification and efficient use of space. The design of a torsion spring has been formulated, but it is difficult to determine the local behaviors of torsion springs according to actual load conditions. This study proposes a torsion-spring design method through finite element analysis (FEA) using nonuniform-rational-basis-spline (NURBS) curves. Through experimentation, the angle and displacement values for the actual spring load were converted into useable data. Torsion-spring displacement values were obtained via experimentation and converted into coordinates that may be expressed using NURBS curves. The results of these experiments were then compared to those obtained via FEA, and the validity of this method was thereby verified. Full article
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Article
Mechanical Integrity Analysis of a Printed Circuit Heat Exchanger with Channel Misalignment
Appl. Sci. 2020, 10(6), 2169; https://doi.org/10.3390/app10062169 - 22 Mar 2020
Cited by 2 | Viewed by 838
Abstract
Printed circuit heat exchangers (PCHEs), which are used for thermal heat storage and power generation, are often subject to severe pressure and temperature differences between primary and secondary channels, which causes mechanical integrity problems. PCHE operation may result in discontinuity, such as channel [...] Read more.
Printed circuit heat exchangers (PCHEs), which are used for thermal heat storage and power generation, are often subject to severe pressure and temperature differences between primary and secondary channels, which causes mechanical integrity problems. PCHE operation may result in discontinuity, such as channel misalignment, due to non-uniform thermal fields in the diffusion bonding process. The present paper analyzes the mechanical integrity, including the utilization factors of stress and deformation under various channel misalignment conditions. The pressure difference of the target PCHE is 19.5 MPa due to the high pressure (19.7 MPa) of the steam channel in the Rankine cycle and the low pressure (0.5 MPa) of molten salt or liquid metal in the primary channel. Additionally, the temperature difference between channels is around 25 °C, however the average temperature is around 500 °C. The PCHE has a relatively large primary channel measuring approximately 3 x 3 mm, and a steam channel measuring 2 x 1.5 mm. The finite element method (FEM) is applied to determine the stress by changing the misalignment to below 30% of the primary channel width. It was found that the current PCHE is operable up to 700 °C in terms of the ASME code under these design conditions. Additionally, the change of utilization factor due to the misalignment increases, but is still under the ASME acceptance criteria of 700 °C; however, it violates the criteria at 725 °C, which is the allowable temperature condition. Therefore, the mechanical integrity of the PCHE with low-pressure molten salt or liquid metal and a high-pressure steam channel is acceptable in terms of utilization factor. Full article
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Article
Finite Element Approaches to Model Electromechanical, Periodic Beams
Appl. Sci. 2020, 10(6), 1992; https://doi.org/10.3390/app10061992 - 14 Mar 2020
Cited by 1 | Viewed by 650
Abstract
Periodic structures have some interesting properties, of which the most evident is the presence of band gaps in their frequency spectra. Nowadays, modern technology allows to design dedicated structures of specific features. From the literature arises that it is possible to construct active [...] Read more.
Periodic structures have some interesting properties, of which the most evident is the presence of band gaps in their frequency spectra. Nowadays, modern technology allows to design dedicated structures of specific features. From the literature arises that it is possible to construct active periodic structures of desired dynamic properties. It can be considered that this may extend the scope of application of such structures. Therefore, numerical research on a beam element built of periodically arranged elementary cells, with active piezoelectric elements, has been performed. The control of parameters of this structure enables one for active damping of vibrations in a specific band in the beam spectrum. For this analysis the authors propose numerical models based on the finite element method (FEM) and the spectral finite element methods defined in the frequency domain (FDSFEM) and the time domain (TDSFEM). Full article
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Article
Finite Element Modeling and Stress Analysis of a Six-Splitting Mid-Phase Jumper
Appl. Sci. 2020, 10(2), 644; https://doi.org/10.3390/app10020644 - 16 Jan 2020
Cited by 2 | Viewed by 693
Abstract
In this study, a finite element, fully three-dimensional solid modeling method was used to study the mechanical response of a steel-cored aluminum strand (ACSR) with a mid-phase jumper under wind load. A whole model (simplifying an ACSR into a solid cylinder) and a [...] Read more.
In this study, a finite element, fully three-dimensional solid modeling method was used to study the mechanical response of a steel-cored aluminum strand (ACSR) with a mid-phase jumper under wind load. A whole model (simplifying an ACSR into a solid cylinder) and a local model (modeling according to the actual structure of an ACSR) of the mid-phase jumper were established. First, the movement of the mid-phase jumper of the tension tower under wind load was studied based on the whole finite element model, and the equivalent Young’s modulus of the whole model was adjusted based on the local model. The results of the whole model were then imported into the local model and the stress distribution of each strand of the ACSR was analyzed in detail to provide guidance for the treatment measures. Therefore, the whole model and the local model complemented each other, which could reduce the number of model operations and ensure the accuracy of the results. Through the follow-up test to verify the results of the finite element simulation and the comparison of the simulation and fatigue test results, the causes of the broken strand of the ACSR were discussed. Although this modeling method was applied to the stress and deformation analysis of a mid-phase jumper in this study, it can be used to study the bending deformation of rope structures with a complex geometry and the main bending deformation. In addition, the effect of the friction coefficient on the bending of the mid-phase jumper was studied. Full article
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Article
Finite Element Method and Cut Bar Method-Based Comparison Under 150°, 175° and 310 °C for an Aluminium Bar
Appl. Sci. 2020, 10(1), 296; https://doi.org/10.3390/app10010296 - 31 Dec 2019
Cited by 1 | Viewed by 816
Abstract
Analyses were developed using a finite element method of the experimental measurement system for thermal conductivity of solid materials, used by the Centro Nacional de Metrología (CENAM), which operates under a condition of permanent heat flow. The CENAM implemented a thermal conductivity measurement [...] Read more.
Analyses were developed using a finite element method of the experimental measurement system for thermal conductivity of solid materials, used by the Centro Nacional de Metrología (CENAM), which operates under a condition of permanent heat flow. The CENAM implemented a thermal conductivity measurement system for solid materials limited in its operating intervals to measurements of maximum 300 ° C for solid conductive materials. However, the development of new materials should be characterised and studied to know their thermophysical properties and ensure their applications to any temperature conditions. These task demand improvements in the measurement system, which are proposed in the present work. Improvements are sought to achieve high-temperature measurements in metallic materials and conductive solids, and this system may also cover not only metallic materials. Simulations were performed to compare the distribution of temperatures developed in the measurement system as well as the radial heat leaks, which affect the measurement parameters for an aluminium bar, and uses copper bars as reference material. The simulations were made for measurements of an aluminium bar at a temperature of 150 ° C, in the plane and 3D, another at 175 ° C and one more known maximum temperature reached by a sample of the aluminium bar with a new heater acquired at 310 ° C. Full article
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Article
Experimental and Numerical Investigation of Striker Shape Influence on the Destruction Image in Multilayered Composite after Low Velocity Impact
Appl. Sci. 2020, 10(1), 288; https://doi.org/10.3390/app10010288 - 31 Dec 2019
Cited by 10 | Viewed by 1106
Abstract
The paper presents results obtained by experimental and numerical research focusing on the influence of the strikers’ geometry at the images of the destruction created in hybrid composite panels after applying impact load. In the research, the authors used four strikers with different [...] Read more.
The paper presents results obtained by experimental and numerical research focusing on the influence of the strikers’ geometry at the images of the destruction created in hybrid composite panels after applying impact load. In the research, the authors used four strikers with different geometry. The geometries were designed to keep the same weight for each of them. The composite panels used in the experiment were reinforced with aramid and carbon fabrics. An epoxy resin was used as a matrix. The experiments were carried with an impact kinetic energy of 23.5 J. The performed microscopy tests allowed for determination of destruction mechanisms of the panels depending on the geometry of the striker. The numerical calculations were performed using the finite element method. Each reinforcement layer of the composite was modeled as a different part. The bonded connection between the reinforcement layers was modeled using bilateral constraints. That approach enabled engineers to observe the delamination process during the impact. The results obtained from experimental and numerical investigations were compared. The authors present the impact of the striker geometry on damage formed in a composite panel. Formed damage was discussed. On the basis of the results from numerical research, energy absorption of the composite during impact depending on the striker geometry was discussed. It was noted that the size of the delamination area depends on the striker geometry. It was also noted that the diameter of the delamination area is related to the amount of damage in the reinforcing layers. Full article
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Article
Analysis of the Influence of High Peening Coverage on Almen Intensity and Residual Compressive Stress
Appl. Sci. 2020, 10(1), 105; https://doi.org/10.3390/app10010105 - 21 Dec 2019
Cited by 1 | Viewed by 659
Abstract
The effectiveness of shot peening is mainly determined by the peening coverage. The peening coverage is required to be 100% for current technical standards of shot peening. With the increase of material strength, higher peening coverage is required in shot peening process. However, [...] Read more.
The effectiveness of shot peening is mainly determined by the peening coverage. The peening coverage is required to be 100% for current technical standards of shot peening. With the increase of material strength, higher peening coverage is required in shot peening process. However, the influence of high peening coverage on Almen intensity and residual compressive stress is unclear, the difficulty mainly lies in the lack of quantitative description of peening coverage in finite element analysis. To analyze the influence of high peening coverage on Almen intensity and residual compressive stress, firstly an approximate quantitative description of peening coverage based on dent size, the distance of shots and shot numbers is proposed in this study. Based on this quantitative description of peening coverage, the arc height and residual stress of the Almen test are simulated with the finite element method. The simulation results of arc height and saturation curve agree well with that of the Almen test, by which the effectiveness of the quantitative description and FE simulation are proved. The further study indicates that in shot peening processes, the excessive peening coverage doesn’t improve Almen intensity and residual compressive stress. Full article
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Article
The Impact of the Strength of Roof Rocks on the Extent of the Zone with a High Risk of Spontaneous Coal Combustion for Fully Powered Longwalls Ventilated with the Y-Type System—A Case Study
Appl. Sci. 2019, 9(24), 5315; https://doi.org/10.3390/app9245315 - 05 Dec 2019
Cited by 21 | Viewed by 949
Abstract
During the ventilation of longwalls in hard coal mines, part of the air stream migrates to the goaves with caving. These goaves constitute a space (void) filled with rocks following coal extraction. In the case where these goaves contain coal susceptible to spontaneous [...] Read more.
During the ventilation of longwalls in hard coal mines, part of the air stream migrates to the goaves with caving. These goaves constitute a space (void) filled with rocks following coal extraction. In the case where these goaves contain coal susceptible to spontaneous combustion, the flow of such an air stream through the goaves may lead to the formation of favourable conditions for coal oxidation, self-heating and spontaneous combustion. Such an area is referred to as the zone with a particularly high risk of spontaneous coal combustion (endogenous fires). The location and extent of this zone depend on many factors, with one of the most important being the permeability of the goaves which determines the tensile strength of the roof rocks forming the caving. This strength determines the propensity of these rocks to transform into the state of caving and the degree of tightness of the cave-in rubble (treated as a porous medium). The purpose of the present paper is to determine how the tensile strength of roof rocks influences the extent of the zone with a particularly high risk of spontaneous coal combustion (endogenous fires) in caving goaves of the longwalls ventilated with the Y-type system. To achieve this goal, model-based tests were conducted for a region of the longwall mined with caving and ventilated with the Y-type system. Critical air speed and oxygen concentration values in the caving goaves of this longwall were determined for the actual conditions of exploitation. These parameters define the risk zone of spontaneous coal combustion. The tests also helped to determine the extent of this zone, depending on the strength of the rocks forming the caving. The results obtained unequivocally indicate that the type of rocks forming the caving affects its permeability and the extent of the risk zone for spontaneous coal combustion. At the same time, the distribution of this zone is substantially different than in the case of other ventilation systems. The results obtained are of real practical significance for preventive measures to reduce fire risks. The effectiveness of these measures significantly improves the safety of mining exploitation. Full article
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