Research

11 pages, 3697 KiB

Open AccessArticle

Near-Surface Mounted Reinforcement of Sawn Timber Beams-FEM Approach

by Izabela Burawska-Kupniewska and Piotr Beer

Materials 2021, 14(11), 2780; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14112780 - 24 May 2021

Cited by 2 | Viewed by 1294

The demand for timber has increased significantly in recent years. Therefore, reliable tools are needed to predict the mechanical properties of sawn timber, especially for structural applications. Very complex models require a lot of input data for analysis, which cannot always be guaranteed, [...] Read more.

The demand for timber has increased significantly in recent years. Therefore, reliable tools are needed to predict the mechanical properties of sawn timber, especially for structural applications. Very complex models require a lot of input data for analysis, which cannot always be guaranteed, especially in industrial practice. Thus, a simplified model for material description was developed and assessed with experiments (static bending tests carried out in accordance with the guidelines suggested in the European standard EN 408) and an analytical approach (gamma method according to the guidelines given in the European standard EN 1995). The effective stiffness was calculated as a major parameter, which has an influence on the elements’ behavior. The model included a near-surface mounted (NSM) local reinforcement technique, with CFRP strips of Scots pine timber beams being subjected to bending stresses. It is anticipated that the developed model can be a starting point for the repair engineering field, contributing to decision-making regarding conservation technique selection and range. Next, improvements of the model will provide more and more realistic results for numerical analysis in terms of the obtained failure mechanisms for sawn timber elements. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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11 pages, 17468 KiB

Open AccessArticle

Stochastic Thermal Properties of Laminates Filled with Long Fibers

by Jan Turant

Materials 2021, 14(10), 2511; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14102511 - 12 May 2021

Viewed by 1030

Abstract

In this paper, the stochastic parameters of the effective thermal conductivity of multilayer composites are considered. The examined specimens of composites were built with a different number of layers and each had a different saturation density of a composite matrix with fibers. For [...] Read more.

In this paper, the stochastic parameters of the effective thermal conductivity of multilayer composites are considered. The examined specimens of composites were built with a different number of layers and each had a different saturation density of a composite matrix with fibers. For each case of laminate built with a prescribed number of layers and assumed saturation density, 10,000 tests of its effective thermal conductivity were carried out using numerical experiments. It was assumed that the fibers located in each layer were rectilinear, had a circular cross-section and that they could take random positions in their repeatable volume elements (RVEs). In view of the mentioned assumptions, the heat flux passing throughout a cross-section of a composite sample, perpendicular to the fibers’ direction, was considered. The probability density functions were fitted to the obtained data and then the chosen stochastic parameters of the effective thermal conductivity coefficients were determined. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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28 pages, 37414 KiB

Open AccessArticle

Modeling Structural Dynamics Using FE-Meshfree QUAD4 Element with Radial-Polynomial Basis Functions

by Hongming Luo and Guanhua Sun

Materials 2021, 14(9), 2288; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14092288 - 28 Apr 2021

Cited by 1 | Viewed by 1521

Abstract

The PU (partition-of-unity) based FE-RPIM QUAD4 (4-node quadrilateral) element was proposed for statics problems. In this element, hybrid shape functions are constructed through multiplying QUAD4 shape function with radial point interpolation method (RPIM). In the present work, the FE-RPIM QUAD4 element is further [...] Read more.

The PU (partition-of-unity) based FE-RPIM QUAD4 (4-node quadrilateral) element was proposed for statics problems. In this element, hybrid shape functions are constructed through multiplying QUAD4 shape function with radial point interpolation method (RPIM). In the present work, the FE-RPIM QUAD4 element is further applied for structural dynamics. Numerical examples regarding to free and forced vibration analyses are presented. The numerical results show that: (1) If CMM (consistent mass matrix) is employed, the FE-RPIM QUAD4 element has better performance than QUAD4 element under both regular and distorted meshes; (2) The DLMM (diagonally lumped mass matrix) can supersede the CMM in the context of the FE-RPIM QUAD4 element even for the scheme of implicit time integration. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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10 pages, 1205 KiB

Open AccessArticle

Concurrent Lamination and Tapering Optimization of Cantilever Composite Plates under Shear

by Gokhan Serhat

Materials 2021, 14(9), 2285; https://doi.org/10.3390/ma14092285 - 28 Apr 2021

Cited by 7 | Viewed by 1554

Abstract

The operational performance of cantilever composite structures can benefit from both stiffness tailoring and geometric design, yet, this potential has not been fully utilized in existing studies. The present study addresses this problem by simultaneously optimizing layer and taper angles of cantilever laminates. [...] Read more.

The operational performance of cantilever composite structures can benefit from both stiffness tailoring and geometric design, yet, this potential has not been fully utilized in existing studies. The present study addresses this problem by simultaneously optimizing layer and taper angles of cantilever laminates. The design objective is selected as minimizing the average deflection of the tip edge subjected to shear loads while keeping the length and total volume constant. The plate stiffness properties are described by lamination parameters to eliminate the possible solution dependency on the initial assumptions regarding laminate configuration. The responses are computed via finite element analyses, while optimal design variables are determined using genetic algorithms. The results demonstrate that the plate aspect ratio significantly influences the effectiveness of stiffness tailoring and tapering as well as the optimal layer and taper angles. In addition, concurrent exploitation of the lamination characteristics and plate geometry is shown to be essential for achieving maximum performance. Moreover, individual and simultaneous optimization of layer and taper angles produce different optimal results, indicating the possible drawback of using sequential approaches in similar composite design problems. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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24 pages, 4658 KiB

Open AccessArticle

Vertex Displacement-Based Discontinuous Deformation Analysis Using Virtual Element Method

by Hongming Luo, Guanhua Sun, Lipeng Liu and Wei Jiang

Materials 2021, 14(5), 1252; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14051252 - 06 Mar 2021

Cited by 1 | Viewed by 1661

Abstract

To avoid disadvantages caused by rotational degrees of freedom in the original Discontinuous Deformation Analysis (DDA), a new block displacement mode is defined within a time step, where displacements of all the block vertices are taken as the degrees of freedom. An individual [...] Read more.

To avoid disadvantages caused by rotational degrees of freedom in the original Discontinuous Deformation Analysis (DDA), a new block displacement mode is defined within a time step, where displacements of all the block vertices are taken as the degrees of freedom. An individual virtual element space V₁(Ω) is defined for a block to illustrate displacement of the block using the Virtual Element Method (VEM). Based on VEM theory, the total potential energy of the block system in DDA is formulated and minimized to obtain the global equilibrium equations. At the end of a time step, the vertex coordinates are updated by adding their incremental displacement to their previous coordinates. In the new method, no explicit expression for the displacement u is required, and all numerical integrations can be easily computed. Four numerical examples originally designed by Shi are analyzed, verifying the effectiveness and precision of the proposed method. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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9 pages, 2385 KiB

Open AccessArticle

Homogenization of Radial Temperature by a Tungsten Sink in Sublimation Growth of 45 mm AlN Single Crystal

by Yue Yu, Botao Liu, Xia Tang, Sheng Liu and Bing Gao

Materials 2020, 13(23), 5553; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13235553 - 06 Dec 2020

Cited by 2 | Viewed by 1644

Abstract

To reduce the thermal stress during the sublimation growth of 45 mm AlN single crystal, a tungsten sink was put on the top of the crucible lid. Numerical experiments showed that the radial temperature gradient was reduced due to the homogenization effect on [...] Read more.

To reduce the thermal stress during the sublimation growth of 45 mm AlN single crystal, a tungsten sink was put on the top of the crucible lid. Numerical experiments showed that the radial temperature gradient was reduced due to the homogenization effect on temperature as a result of the sink. Therefore, this simple tungsten sink method has the potential to grow large-size AlN ingots with fewer cracks. It also reveals that enhancing the heat exchange of the crucible lid is an effective way to improve the quality of crystal growth. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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20 pages, 63495 KiB

Open AccessArticle

Numerical Optimization Simulation of Synchronous Four-Wing Rotor

by Kongshuo Wang, Haichao Liu, Tianhao Chang, Deshang Han, Yiren Pan, Chuansheng Wang and Huiguang Bian

Materials 2020, 13(23), 5353; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13235353 - 25 Nov 2020

Cited by 1 | Viewed by 1429

Abstract

The mixer is the most widely used batch mixing equipment in the rubber industry. The rotor is a core component and has a great impact on the mixing effect of the equipment. The current rotor structure design is done empirically, being tightly dependent [...] Read more.

The mixer is the most widely used batch mixing equipment in the rubber industry. The rotor is a core component and has a great impact on the mixing effect of the equipment. The current rotor structure design is done empirically, being tightly dependent on practical experience. This paper proposes a method for optimizing the rotor structure by using optimization algorithms combined with numerical simulation technology. Using MATLAB software, a parametric design program for synchronous rotors and a set of optimization programs for the particle swarm optimization (PSO) algorithm were written. The global distribution index was used as the fitness function to optimize the synchronous rotor configuration. A comparative analysis of the rotors before and after optimization shows that the optimization process is feasible, and the results are reliable. This provides new ideas for the design and development of mixer rotors. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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21 pages, 6013 KiB

Open AccessArticle

Experimental and Numerical Study on Withdrawal Strength of Different Types of Auxetic Dowels for Furniture Joints

by Ali Kasal, Tolga Kuşkun and Jerzy Smardzewski

Materials 2020, 13(19), 4252; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13194252 - 24 Sep 2020

Cited by 16 | Viewed by 2583

Abstract

Studies on the application of auxetic metamaterials and structures in furniture joints are very limited. However, they have huge potential for use in ready-to-assemble furniture. This study aimed to design and produce different types of auxetic dowels in 3D printing technology, and experimentally [...] Read more.

Studies on the application of auxetic metamaterials and structures in furniture joints are very limited. However, they have huge potential for use in ready-to-assemble furniture. This study aimed to design and produce different types of auxetic dowels in 3D printing technology, and experimentally and numerically analyze the withdrawal strength of these dowels. In the scope of the study, 24 auxetic dowels with different types and size of inclusions, different diameter of holes, and a non-auxetic reference dowel were designed and produced with appropriate muffs. Dowels were 3D printed from polyamide (PA12). Poisson’s ratios, withdrawal strength, contact pressures, and friction coefficients of dowels were determined theoretically by means of numerical analyses and real static compression tests. After the pre-production of dowels, the dowels with triangular inclusions have not been found to have sufficient strength and stiffness. Withdrawal strength of dowels decreased as the size of inclusions is decreased, or dowel hole diameter is increased. Furthermore, contact pressures and stresses in auxetic dowels were considerably lower than non-auxetic dowels under the withdrawal force. Full article

(This article belongs to the Special Issue Numerical Methods and Optimization of Structures: FEM)

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