Advanced Materials, Structures, Symmetrical Design and Mechanism in Mechanical Engineering

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Engineering and Materials".

Deadline for manuscript submissions: 30 November 2024 | Viewed by 24651

Special Issue Editors


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Guest Editor
School of Traffic and Transportation Engineering, Central South University, Changsha 410075, China
Interests: bionic structure design; traffic and vehicle crash safety; simulation; optimization
Special Issues, Collections and Topics in MDPI journals
Institute of Systems Engineering, Macau University of Science and Technology, Avenida Wai Long, Taipa, Macao
Interests: petri net theory and application; supervisory control of discrete event systems; workflow analysis; system reconfiguration; game theory; production scheduling and planning; data and process mining
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
School of Mechanical Engineering, Shandong University, Jinan, China
Interests: bionic structure design; biomaterials; numerical simulation; multidisciplinary optimization
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Mechanical engineering is a field of basic research, which covers quite a lot of areas, such as materials science, machine design, physics, and of course mechanics. With the rapid development of computer technology, many advanced technologies have been applied to the field of mechanical engineering, such as rapid prototyping, numerical simulation, data-driven, evolutionary computation, and deep learning. Symmetry is a critical element in mechanical engineering, e.g., vehicle devices, heavy machinery, and engineering machinery, and has been exploited in the design and optimization process of materials, structures, and equipment. In the opinion of the Guest Editors, there are many theories and applications of advanced technologies in mechanical engineering that also need the theory of symmetry.

This Special Issue on “Advanced Materials, Structures, and Design Methods in Mechanical Engineering” aims to incorporate the latest research progress in the field of mechanical engineering that includes advanced materials, structures, and design methods. Topics include but are not limited to the following:

  • Rapid prototyping, analytical and numerical simulation technologies of materials with novel mechanical properties;
  • Multiscale composite material selection technology;
  • Interdisciplinary application in intelligent and green manufacturing;
  • Performance analysis techniques for different key indicators of mechanical structures;
  • Multidisciplinary optimization methods of advanced mechanical structures;
  • Other related research topics.

Prof. Dr. Guangdong Tian
Prof. Dr. Yong Peng
Dr. Zhiwu Li
Dr. Amir M. Fathollahi-Fard
Dr. Honghao Zhang
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 submissions that pass pre-check are 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. Symmetry is an international peer-reviewed open access monthly 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 2400 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

  • Symmetrical Design and Mechanism

Published Papers (15 papers)

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Research

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15 pages, 4988 KiB  
Article
Symmetrical Modeling of Physical Properties of Flexible Structure of Silicone Materials for Control of Pneumatic Soft Actuators
by Eduard Muratbakeev, Yuriy Kozhubaev, Yao Yiming and Shehzad Umar
Symmetry 2024, 16(6), 750; https://doi.org/10.3390/sym16060750 - 16 Jun 2024
Viewed by 428
Abstract
With the ongoing advancements in material technology, the domain of soft robotics has garnered increasing attention. Soft robots, in contrast to their rigid counterparts, offer superior adaptability to the environment, enhanced flexibility, and improved safety, rendering them highly suitable for complex application scenarios [...] Read more.
With the ongoing advancements in material technology, the domain of soft robotics has garnered increasing attention. Soft robots, in contrast to their rigid counterparts, offer superior adaptability to the environment, enhanced flexibility, and improved safety, rendering them highly suitable for complex application scenarios such as rescue operations and medical interventions. In this paper, a new type of pneumatic software actuator is proposed. The actuator adopts a combination of a soft structure and pneumatic control, which is highly flexible and versatile. By using the flow of gas inside the soft structure, high-precision and flexible motion control is realized. In the design process, the extensibility and adaptability of the structure are considered, so that the actuator can adapt to different working environments and task requirements. The experimental results show that the pneumatic soft actuator exhibits excellent performance in terms of accuracy, response speed, and controllability. This research provides new ideas and methods for the development of the field of pneumatic actuators and has wide application prospects. The main research content of this paper is as follows: first, the soft pneumatic actuator is modeled and simulated, the structure is optimized on the basis of simulation, and finally, the performance of the actuator is tested. Full article
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23 pages, 7326 KiB  
Article
Theoretical Modeling and Experimental Verification of Elliptical Hyperbolic Hybrid Flexure Hinges
by Yan Wang, Lizhong Zhang, Lixin Meng, Hongjie Lu and Yongheng Ma
Symmetry 2024, 16(3), 345; https://doi.org/10.3390/sym16030345 - 13 Mar 2024
Viewed by 778
Abstract
A flexure hinge composed of elliptical and hyperbolic hybrid configurations is developed and analyzed in this paper. The analytical models of compliance, rotation accuracy, and maximum stress of the flexure hinge are established, and the correctness of the models is validated by finite [...] Read more.
A flexure hinge composed of elliptical and hyperbolic hybrid configurations is developed and analyzed in this paper. The analytical models of compliance, rotation accuracy, and maximum stress of the flexure hinge are established, and the correctness of the models is validated by finite element analysis and experiments. The influence of structural parameters on compliance and rotation accuracy is discussed. The concept of compliance stress ratio is proposed to assess the deformation capacity of flexure hinges when subjected to the same stress, which provides a basis for quantitatively comparing the comprehensive performance of flexure hinges. The performance of the hybrid flexure hinge is compared with that of elliptical, hyperbolic, and circular flexure hinges by taking the compliance accuracy ratio and the compliance stress ratio as the performance evaluation indexes. The results show that the hybrid flexure hinge combines the advantages of hyperbolic and elliptical hinges and has a balanced performance in compliance, rotation accuracy, and low stress. The designed hybrid flexure hinge is suitable for the support structure of fast steering mirrors, which provides a valuable reference for the engineering optimization design of flexure hinges. Full article
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24 pages, 21477 KiB  
Article
A General Framework for Material Properties Calculation and the Free Vibration Analysis of New Three-Phase Composite Cylindrical Shell Structures
by Wei Zhang, Jinqiu Duan, Tao Liu, Yan Zheng and Yingjing Qian
Symmetry 2024, 16(1), 20; https://doi.org/10.3390/sym16010020 - 22 Dec 2023
Cited by 1 | Viewed by 923
Abstract
New three-phase composite structures reinforced synergistically by nano-fillers and macroscopic fibers have great application potential. This paper presents a general framework for material properties calculation and the free vibration analysis of three-phase composite shell structures. Based on this methodological system, the free vibration [...] Read more.
New three-phase composite structures reinforced synergistically by nano-fillers and macroscopic fibers have great application potential. This paper presents a general framework for material properties calculation and the free vibration analysis of three-phase composite shell structures. Based on this methodological system, the free vibration characteristics of three types of nano-enhanced functionally graded three-phase composite cylindrical shells are investigated. First, the equivalent mechanical properties of these three three-phase composites were evaluated using the Halpin–Tsai and Mori–Tanaka models. The governing equations for the cylindrical shells were derived based on the first-order shear deformation theory (FSDT) and Hamilton’s principle. The equations were discretized using Galerkin’s method and solved to obtain the natural frequencies and mode shapes. The finite element simulation results and existing literature verified the accuracy and reliability of the method in this paper. The synergistic effects of nano-reinforced fillers and macroscopic fibers on the free vibrations of these structures were also analyzed. Among them, the natural frequency of the three-phase composite cylindrical shells was the highest when graphene platelets (GPLs) were used as the nano-reinforced fillers, which was 150.32% higher than that of fiber-reinforced epoxy composite cylindrical shells. These studies provide theoretical guidance for the design and manufacture of such symmetric or antisymmetric structures in the future. Full article
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19 pages, 11196 KiB  
Article
Design and Biomechanical Properties of Symmetrical Lumbar Fusion Cage Based on Lightweight Titanium Alloy Flexible Microporous Metal Rubber
by Juan Xiao, Tianqi Zhu, Linlin Li, Liangliang Shen, Zhiying Ren and Jian Xu
Symmetry 2023, 15(10), 1938; https://doi.org/10.3390/sym15101938 - 19 Oct 2023
Viewed by 1202
Abstract
In recent years, the incidence rate of lumbar diseases has been progressively increasing. The conventional lumbar fusion cages used in existing lumbar interbody fusion surgery are not able to take into account the multiple characteristics of cushioning, vibration reduction, support, cell adhesion, and [...] Read more.
In recent years, the incidence rate of lumbar diseases has been progressively increasing. The conventional lumbar fusion cages used in existing lumbar interbody fusion surgery are not able to take into account the multiple characteristics of cushioning, vibration reduction, support, cell adhesion, and bone tissue growth. Therefore, in this work, based on the CT data of a lumbar intervertebral disc plain scan, a combined symmetric lumbar fusion cage structure was innovatively designed. The core was made of lightweight TC4 medical titanium alloy flexible microporous metal rubber (LTA-FMP MR), and the outer frame was made of cobalt–chromium–molybdenum alloy. Its comprehensive biomechanical performance was comprehensively evaluated through finite element simulation, static and dynamic mechanics, and impact resistance tests. The three-dimensional model of the L3/L4 lumbar segment was established by reverse engineering, and a Mises stress analysis was conducted on the lumbar fusion cage by importing it into Ansys to understand its structural advantages compared to the traditional lumbar fusion cage. Through static experiments, the influence of the internal nucleus of a symmetrical lumbar fusion cage with different material parameters on its static performance was explored. At the same time, to further explore the superior characteristics of this symmetrical structure in complex human environments, a biomechanical test platform was established to analyze its biomechanical performance under sinusoidal excitation of different amplitudes and frequencies, as well as impact loads of different amplitudes and pulse widths. The results show that under different amplitudes and frequencies, the lumbar fusion cage with a symmetrical structure has a small loss factor, a high impact isolation coefficient, and a maximum energy consumption of 422.8 N·mm, with a maximum kinetic energy attenuation rate of 0.43. Compared to existing traditional lumbar fusion cages in clinical practice, it not only has sufficient stiffness, but also has good vibration damping, support, and impact resistance performance, and has a lower probability of postoperative settlement, which has broad application prospects. Full article
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14 pages, 5501 KiB  
Article
Automatic Trajectory Determination in Automated Robotic Welding Considering Weld Joint Symmetry
by David Curiel, Fernando Veiga, Alfredo Suarez, Pedro Villanueva and Eider Aldalur
Symmetry 2023, 15(9), 1776; https://doi.org/10.3390/sym15091776 - 16 Sep 2023
Viewed by 1135
Abstract
The field of inspection for welded structures is currently in a state of rapid transformation driven by a convergence of global technological, regulatory, and economic factors. This evolution is propelled by several key drivers, including the introduction of novel materials and welding processes, [...] Read more.
The field of inspection for welded structures is currently in a state of rapid transformation driven by a convergence of global technological, regulatory, and economic factors. This evolution is propelled by several key drivers, including the introduction of novel materials and welding processes, continuous advancements in inspection technologies, innovative approaches to weld acceptance code philosophy and certification procedures, growing demands for cost-effectiveness and production quality, and the imperative to extend the lifespan of aging structures. Foremost among the challenges faced by producers today is the imperative to meet customer demands, which entails addressing both their explicit and implicit needs. Furthermore, the integration of emerging materials and technologies necessitates the exploration of fresh solutions. These solutions aim to enhance inspection process efficiency while providing precise quantitative insights into defect identification and location. To this end, our project proposes cutting-edge technologies, some of which have yet to gain approval within the sector. Noteworthy among these innovations is the integration of vision systems into welding robots, among other solutions. This paper introduces a groundbreaking algorithm for tool path selection, leveraging profile scanning and the concept of joint symmetry. The application of symmetry principles for trajectory determination represents a pioneering approach within this expansive field. Full article
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20 pages, 16699 KiB  
Article
A Coupling Optimization Method of Vehicle Structure and Restraint System for Occupant Injury Protection in Traffic Accidents
by Danqi Wang, Junyuan Zhang, Tianqi Zhang, Honghao Zhang and Yong Peng
Symmetry 2023, 15(2), 558; https://doi.org/10.3390/sym15020558 - 20 Feb 2023
Cited by 3 | Viewed by 1449
Abstract
Vehicle front-end structure has the characteristic of symmetry. The damage of occupants in the crash process is determined by the combined effect of the front-end structure and the restraint system of the vehicle. In this paper, the coupling relationship and an optimized method [...] Read more.
Vehicle front-end structure has the characteristic of symmetry. The damage of occupants in the crash process is determined by the combined effect of the front-end structure and the restraint system of the vehicle. In this paper, the coupling relationship and an optimized method for the vehicle front-end structure and restraint system are studied based on vehicle crash dynamics, to reduce occupant injury. A fast solution algorithm for occupant motion response was established using a crash analytical model. Then, an occupant response database was established using the algorithm, to analyze the coupling relationship between the crash pulse and the restraint specific stiffness, with respect to the curve shape and parameters. The results showed that the combination of the concave crash pulse and upward restraint stiffness curve was the best coupling. Subsequently, a coupled optimization method of a concave pulse and upward restraint stiffness was proposed and combined with a crash analytical model and genetic algorithm (GA). The crash pulse and restraint stiffness of vehicle crash data from the NHTSA databases were optimized, as an example, to verify the effectiveness of the method. The optimal occupant acceleration was reduced by 44%. In addition, the feasibility of the optimal result is discussed, to provide a reference for occupant injury protection in traffic accidents. Full article
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17 pages, 6115 KiB  
Article
Methodology for the Path Definition in Multi-Layer Gas Metal Arc Welding (GMAW)
by David Curiel, Fernando Veiga, Alfredo Suarez and Pedro Villanueva
Symmetry 2023, 15(2), 268; https://doi.org/10.3390/sym15020268 - 18 Jan 2023
Cited by 2 | Viewed by 1642
Abstract
The reconstruction of the geometry of weld-deposited materials plays an important role in the control of the torch path in GMAW. This technique, which is classified as a direct energy deposition technology, is experiencing a new emergence due to its use in welding [...] Read more.
The reconstruction of the geometry of weld-deposited materials plays an important role in the control of the torch path in GMAW. This technique, which is classified as a direct energy deposition technology, is experiencing a new emergence due to its use in welding and additive manufacturing. Usually, the torch path is determined by computerised fabrication tools, but these software tools do not consider the geometrical changes along the case during the process. The aim of this work is to adaptively define the trajectories between layers by analysing the geometry and symmetry of previously deposited layers. The novelty of this work is the integration of a profiling laser coupled to the production system, which scans the deposited layers. Once the layer is scanned, the geometry of the deposited bead can be reconstructed and the symmetry in the geometry and a continuous trajectory can be determined. A wall was fabricated under demanding deposition conditions, and a surface quality of around 100 microns and mechanical properties in line with those previously reported in the literature are observed. Full article
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13 pages, 18418 KiB  
Article
Response Evolution of a Tetrachiral Metamaterial Unit Cell under Architectural Transformations
by Linar Akhmetshin, Kristina Iokhim, Ekaterina Kazantseva and Igor Smolin
Symmetry 2023, 15(1), 14; https://doi.org/10.3390/sym15010014 - 21 Dec 2022
Cited by 2 | Viewed by 1514
Abstract
This paper studies a mechanical metamaterial with tetrachiral topology by mathematical modeling. Chirality is the property of an object that makes the object distinguishable from its mirror image; chirality can be left- or right-handed. The mechanical response of two metamaterial unit cells with [...] Read more.
This paper studies a mechanical metamaterial with tetrachiral topology by mathematical modeling. Chirality is the property of an object that makes the object distinguishable from its mirror image; chirality can be left- or right-handed. The mechanical response of two metamaterial unit cells with different configurations (patterns A and B) is investigated. It is found that the cubic cell with a regular pattern A exhibits orthotropic mechanical behavior under loading along three coordinate axes. An irregular pattern B differs from pattern A in that the upper face of the unit cell has an opposite chirality. This architectural transformation is considered as a topological defect, which enhances the twisting effect in the loaded metamaterial. Analysis of displacements and stresses shows that the mechanical behavior of the pattern B cell is described by the model of a transversely isotropic material. The orthotropic and transversely isotropic behavior of the cells of given configurations is also confirmed by the values of the effective elastic constants. Microstructural geometry and mechanical deformation of metamaterials are shown to be closely related. It is shown that a topological defect in a unit cell of a tetrachiral metamaterial strongly determines its twisting behavior. Full article
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32 pages, 14010 KiB  
Article
Asymmetrical Damage Aspects Based Investigations on the Disc Brake of Long-Range UAVs through Verified Computational Coupled Approaches
by Vijayanandh Raja, Raj Kumar Gnanasekaran, Parvathy Rajendran, Aiffah Mohd Ali, Raffik Rasheed, Hussein A. Z. AL-bonsrulah and Mohammed Al-Bahrani
Symmetry 2022, 14(10), 2035; https://doi.org/10.3390/sym14102035 - 29 Sep 2022
Cited by 11 | Viewed by 1825
Abstract
In recent years, the use of unmanned aerial vehicles (UAVs) has increased significantly. Asymmetrical factors, or frictional studies on the disc brake of UAVs, are one of the safety considerations taken into consideration during the design process because UAVs and their components have [...] Read more.
In recent years, the use of unmanned aerial vehicles (UAVs) has increased significantly. Asymmetrical factors, or frictional studies on the disc brake of UAVs, are one of the safety considerations taken into consideration during the design process because UAVs and their components have been built with the best safety in mind. This study focuses on choosing the optimal material for a UAV’s disc brake by using transient structural and thermal models. In order to compare the asymmetry-based frictional force produced by the two ways; the processes used in the transient simulation are validated using pin-on-disc (POD) testing. The foundation for this validation investigation is a metal matrix composite made of an aluminum alloy, and the basis tool is an ASTM G99-based computational test specimen. Steel-EN24 and carbon ceramic matrix composites testing are expanded using the same POD tests. A range of 3 percent to 8 percent error rates is found. As a result, the calculation techniques are applied to the UAV’s disc brake after they have proven to be trustworthy. This fixed-wing UAV’s extensions have a 5 kg payload capacity. The weight, avionics components, tire dimensions, and disc brake dimensions of the other UAV design parts are calculated using analytical formulas. The final designs are made using CATIA as a result. The grid convergence experiment is organized using a traditional finite element analysis tool. Finally, at its maximum rotational speed, a UAV’s disc brake is put through asymmetrical friction testing based on structural and thermal consequences. The correct materials for critical applications, such as carbon fiber-woven-wet-based reinforced polymer and Kevlar unidirectional-49-based reinforced polymer composites for changing rotating speeds, have now been made possible by fixed-wing UAVs. Full article
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14 pages, 4786 KiB  
Article
Study of Low-Frequency Sound Absorption Based on Negative Stiffness Membrane Structure
by Xiaoyuan Zheng, Chenxu Fu, Hongbai Bai, Zhu Lin and Xingxing Liu
Symmetry 2022, 14(9), 1858; https://doi.org/10.3390/sym14091858 - 6 Sep 2022
Cited by 2 | Viewed by 1612
Abstract
The system stiffness of a negative stiffness membrane structure is widely investigated in metamaterial research, and some special performances have been achieved. While for acoustics, low-frequency absorption still remains a big issue, so in this work, a negative stiffness membrane structure with its [...] Read more.
The system stiffness of a negative stiffness membrane structure is widely investigated in metamaterial research, and some special performances have been achieved. While for acoustics, low-frequency absorption still remains a big issue, so in this work, a negative stiffness membrane structure with its theoretical calculation model and experimental verification of sound absorption is established. Moreover, the nonlinear stiffness changes of the thin film under different deformation conditions and different spacing between two permanent magnets are systematically analyzed, obtaining the theoretical stiffness analytical equation of the negative stiffness thin-film structure system. Combined with finite element simulation analysis, the stiffness variation rule and influencing factors of the negative stiffness membrane system are discussed. Specifically, the impact of the mass radius, mass thickness, and film thickness on the magnetic force and system stiffness is analyzed. Based on the acquired testing results, the proper addition of the magnetic suction structure will induce a shift of the absorption peak to a lower frequency region. This work provides useful insights for the further development of the low-frequency sound absorption theory and testing prototype with a negative stiffness membrane structure. Full article
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45 pages, 33688 KiB  
Article
Multi-Disciplinary Computational Investigations on Asymmetrical Failure Factors of Disc Brakes for Various CFRP Materials: A Validated Approach
by Vijayanandh Raja, Raj Kumar Gnanasekaran, Abdul Razak Kaladgi, Parvathy Rajendran, Sher Afghan Khan and Mohammad Asif
Symmetry 2022, 14(8), 1616; https://doi.org/10.3390/sym14081616 - 5 Aug 2022
Cited by 2 | Viewed by 2121
Abstract
Finite element analyses (FEA) are flexible and advanced approaches, which are utilized to address difficult problems of aerospace materials that exhibit both structural symmetrical and structural asymmetrical characteristics. Frictional behavior effects are used as a crucial element in this multidisciplinary study, and other [...] Read more.
Finite element analyses (FEA) are flexible and advanced approaches, which are utilized to address difficult problems of aerospace materials that exhibit both structural symmetrical and structural asymmetrical characteristics. Frictional behavior effects are used as a crucial element in this multidisciplinary study, and other structural, thermal properties are computed using FEA. Primary lightweight materials such as glass fiber reinforced polymer (GFRP), carbon fiber reinforced polymer (CFRP), kevlar fiber reinforced polymer (KFRP), titanium alloy, tungsten carbide, steel alloys, and advanced lightweight materials, such as silicon carbide (SiC) mixer, based on aforesaid materials underwent comprehensive investigations on aircraft disc brake, two-wheeler disc brake, and ASTM general rotating test specimen (G-99). Standard boundary conditions, computational sensitivity tests, and theoretical validations were conducted because the working nature of FEA may impair output dependability. First, FEA calculations were performed on a standard rotating disc component with two separate material families at various rotational velocities such as 400 RPM, 500 RPM, 600 RPM, 800 RPM, and 10 N of external frictional force. Via tribological experiments, frictional force and deformation of FEA outcomes were validated; the experimental outcomes serve as important boundary conditions for real-time simulations. Second, verified FEA was extended to complicated real-time applications such as aircraft disc brakes and automobile disc brakes. This work confirms that composite materials possess superior properties to conventional alloys for aircraft and vehicle disc brakes. Full article
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29 pages, 550 KiB  
Article
Supervisory Control of Automated Manufacturing Systems Based on State-Tree Structures
by Chan Gu, Junbo Zhao and Zhou He
Symmetry 2022, 14(7), 1470; https://doi.org/10.3390/sym14071470 - 18 Jul 2022
Viewed by 1310
Abstract
The automated manufacturing systems (AMS) can be regarded as a resource allocation system which can be abstracted as discrete event systems (DES) for analysis. Once an effective computational method is put forward to the DES, the corresponding real AMS, connected by networks or [...] Read more.
The automated manufacturing systems (AMS) can be regarded as a resource allocation system which can be abstracted as discrete event systems (DES) for analysis. Once an effective computational method is put forward to the DES, the corresponding real AMS, connected by networks or sensors, can be indirectly controlled. Supervisory control theory (SCT) of DES is developed with the intention of discovering the maximally permissible supervisor of AMS. The state-tree structure (STS) is an extension of SCT, whose application is mainly to solve the SCT state explosion of complicated AMS. The nonblocking supervisory control is investigated on the foundation of predicates in STS, of which the synthesis focuses on the states of the system but ignores the transition between events. In order to effectively solve the above problems, this paper puts forward a novel method based on state feedback control (SFBC) in the STS framework, by which the relation among events is discussed. First, following the definition of the SFBC for predicates, the algorithms to compute the SFBC under reachability, coreachability, and weak controllability are introduced. Second, it is proved that the nonblocking SFBC obtained by the proposed algorithm is equivalent to the one by computing predicates first, which ensures the satisfactory controllers for the supervisory control problems. To demonstrate the contribution of the proposed approach, which is designed considering the symmetry of the system behavior between the real system and its STS model, three examples are illustrated. Full article
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12 pages, 378 KiB  
Article
Petri-Net-Based Scheduling of Flexible Manufacturing Systems Using an Estimate Function
by Gongdan Xu and Yufeng Chen
Symmetry 2022, 14(5), 1052; https://doi.org/10.3390/sym14051052 - 20 May 2022
Cited by 5 | Viewed by 1650
Abstract
In this paper, a novel admissible estimate function is proposed to schedule flexible manufacturing systems (FMSs) by using heuristic search. The FMSs to be scheduled are modeled by P-timed Petri nets. The problem is to make the system evolve from the initial marking [...] Read more.
In this paper, a novel admissible estimate function is proposed to schedule flexible manufacturing systems (FMSs) by using heuristic search. The FMSs to be scheduled are modeled by P-timed Petri nets. The problem is to make the system evolve from the initial marking to a given final marking by firing a sequence of transitions. The structure of jobs in an FMS is always symmetrical to utilize the shared resources, but the processing time of each job is asymmetrical to reduce the global process time. By utilizing the structural symmetry of a Petri net model of an FMS, a partial reachability graph is generated such that the notorious state explosion problem is mitigated. For each generated marking, the proposed estimate function is used to provide an estimated cost for firing the transition sequence. Then, we can select the marking with the smallest cost from the generated markings and compute its successors. This process is continued until the system reaches the final marking. With the proposed method, the performance is evaluated in terms of the cost of the obtained transition firing sequence and the number of the expanded markings. The cost provided by the proposed estimate function is closer to the optimal cost than the previous work, i.e., the proposed method can find a transition firing sequence with less expanded markings and minimal process time from a marking to the final marking. Experimental results are used to demonstrate and evaluate the proposed approach. Full article
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12 pages, 6129 KiB  
Article
Three-Dimensional Finite Element Modelling of Sheet Metal Forming for the Manufacture of Pipe Components: Symmetry Considerations
by Trunal Bhujangrao, Fernando Veiga, Mariluz Penalva, Adriana Costas and Cristina Ruiz
Symmetry 2022, 14(2), 228; https://doi.org/10.3390/sym14020228 - 25 Jan 2022
Cited by 7 | Viewed by 2921
Abstract
The manufacture of parts by metal forming is a widespread technique in sectors such as oil and gas and automotives. It is therefore important to make a research effort to know the correct set of parameters that allow the manufacture of correct parts. [...] Read more.
The manufacture of parts by metal forming is a widespread technique in sectors such as oil and gas and automotives. It is therefore important to make a research effort to know the correct set of parameters that allow the manufacture of correct parts. This paper presents a process analysis by means of the finite element model. The use case presented in this paper is that of a 3-m diameter pipe component with a thickness of 22 mm. In this type of application, poor selection of process conditions can result in parts that are out of tolerance, both in dimensions and shape. A 3D finite element model is made, and the symmetry of the tube section generated in 2D is analysed. As a novelty, an analysis of the process correction as a function of the symmetrical deformation of the material in this case in the form of a pipe is carried out. The results show a correct fitting of the model and give guidelines for manufacturing. Full article
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Review

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23 pages, 4304 KiB  
Review
Symmetry and Its Application in Metal Additive Manufacturing (MAM)
by Virginia Uralde, Fernando Veiga, Eider Aldalur, Alfredo Suarez and Tomas Ballesteros
Symmetry 2022, 14(9), 1810; https://doi.org/10.3390/sym14091810 - 1 Sep 2022
Cited by 8 | Viewed by 2320
Abstract
Additive manufacturing (AM) is proving to be a promising new and economical technique for the manufacture of metal parts. This technique basically consists of depositing material in a more or less precise way until a solid is built. This stage of material deposition [...] Read more.
Additive manufacturing (AM) is proving to be a promising new and economical technique for the manufacture of metal parts. This technique basically consists of depositing material in a more or less precise way until a solid is built. This stage of material deposition allows the acquisition of a part with a quasi-final geometry (considered a Near Net Shape process) with a very high raw material utilization rate. There is a wide variety of different manufacturing techniques for the production of components in metallic materials. Although significant research work has been carried out in recent years, resulting in the wide dissemination of results and presentation of reviews on the subject, this paper seeks to cover the applications of symmetry, and its techniques and principles, to the additive manufacturing of metals. Full article
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