Materials

Research

14 pages, 4891 KiB

Open AccessArticle

Study of Effective Stress Intensity Factor through the CJP Model Using Full-Field Experimental Data

by Alonso Camacho-Reyes, Jose Manuel Vasco-Olmo, Giancarlo Luis Gómez Gonzales and Francisco Alberto Diaz

Materials 2023, 16(16), 5705; https://doi.org/10.3390/ma16165705 - 20 Aug 2023

Cited by 1 | Viewed by 1100

Abstract

In this work, the Christopher–James–Patterson crack tip field model is used to infer and assess the effective stress intensity factor ranges measured from thermoelastic and digital image correlation data. The effective stress intensity factor range obtained via the Christopher–James–Patterson model, which provides an [...] Read more.

In this work, the Christopher–James–Patterson crack tip field model is used to infer and assess the effective stress intensity factor ranges measured from thermoelastic and digital image correlation data. The effective stress intensity factor range obtained via the Christopher–James–Patterson model, which provides an effective rationalization of fatigue crack growth rates, is separated into two components representing the elastic and retardation components to assess shielding phenomena on growing fatigue cracks. For this analysis, fatigue crack growth tests were performed on Compact-Tension specimens manufactured in pure grade 2 titanium for different stress ratio levels, and digital image correlation and thermoelastic measurements were made for different crack lengths. A good agreement (~2% average deviation) was found between the results obtained via thermoelastic stress analysis and digital image correlation indicating the validity of the Christopher–James–Patterson model to investigate phenomena in fracture mechanics where plasticity plays an important role. The results show the importance of considering crack-shielding effects using the Christopher–James–Patterson model beyond considering an exclusive crack closure influence. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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12 pages, 3830 KiB

Open AccessArticle

Finite Element Simulation and Sensitivity Analysis of the Cohesive Parameters for Delamination Modeling in Power Electronics Packages

by Giuseppe Mirone, Raffaele Barbagallo, Giuseppe Bua and Guido La Rosa

Materials 2023, 16(13), 4808; https://doi.org/10.3390/ma16134808 - 4 Jul 2023

Cited by 3 | Viewed by 1384

Abstract

Delamination is a critical failure mode in power electronics packages that can significantly impact their reliability and performance, due to the large amounts of electrical power managed by the most recent devices which induce remarkable thermomechanical loads. The finite element (FE) simulation of [...] Read more.

Delamination is a critical failure mode in power electronics packages that can significantly impact their reliability and performance, due to the large amounts of electrical power managed by the most recent devices which induce remarkable thermomechanical loads. The finite element (FE) simulation of this phenomenon is very challenging for the identification of the appropriate modeling tools and their subsequent calibration. In this study, we present an advanced FE modeling approach for delamination, together with fundamental guidelines to calibrate it. Considering a reference power electronics package subjected to thermomechanical loads, FE simulations with a global–local approach are proposed, also including the implementation of a bi-linear cohesive zone model (CZM) to simulate the complex interfacial behavior between the different layers of the package. A parametric study and sensitivity analysis is presented, exploring the effects of individual CZM variables on the delamination behavior, identifying the most crucial ones and accurately describing their underlying functioning. Then, this work gives valuable insights and guidelines related to advanced and aware FE simulations of delamination in power electronics packages, useful for the design and optimization of these devices to mitigate their vulnerability to thermomechanical loads. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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19 pages, 8807 KiB

Open AccessArticle

Influence of PSD Estimation Parameters on Fatigue Life Prediction in Spectral Method

by Adam Kaľavský, Adam Niesłony and Róbert Huňady

Materials 2023, 16(3), 1007; https://doi.org/10.3390/ma16031007 - 21 Jan 2023

Cited by 5 | Viewed by 2204

Abstract

The paper analyzes in detail the influence of the Welch method on the estimation of fatigue life in the frequency domain. The aim is to examine how the setting of parameters, such as window size, weighting and overlap, affects the calculation of power [...] Read more.

The paper analyzes in detail the influence of the Welch method on the estimation of fatigue life in the frequency domain. The aim is to examine how the setting of parameters, such as window size, weighting and overlap, affects the calculation of power spectral density (PSD) and thus lifetime. The paper uses knowledge from the theory of signal processing, statistics and fatigue life estimation in the frequency domain. In order to demonstrate the general validity of the conclusions, four different reference PSD spectra are generated and examined. The spectra are converted to time histories using an inverse fast Fourier transform and then used as input (measured) data for the Welch method. The PSD thus obtained are subsequently subjected to lifetime estimation using the Dirlik and Tovo–Benasciutti models. Based on the obtained results, it was found that the best configuration of the parameters of the Welch method for fatigue calculations is the selection of the smallest possible time window (maximum 60% of the observation length) and the largest possible overlap (minimum 70% of the window size). Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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21 pages, 4562 KiB

Open AccessArticle

Complex Building Forms Roofed with Transformed Shell Units and Defined by Saddle Surfaces

by Jacek Abramczyk and Katarzyna Chrzanowska

Materials 2022, 15(24), 8942; https://doi.org/10.3390/ma15248942 - 14 Dec 2022

Cited by 3 | Viewed by 1438

Abstract

A novel method and description of creating diversified complex original building forms roofed with a number of transformed folded shell units developed on the basis of a novel reference polyhedral network and arranged according to a reference surface with the negative Gaussian curvature [...] Read more.

A novel method and description of creating diversified complex original building forms roofed with a number of transformed folded shell units developed on the basis of a novel reference polyhedral network and arranged according to a reference surface with the negative Gaussian curvature is presented. For that purpose, specific reference polyhedral networks is are defined as a complex material deliberately composed of many regular tetrahedrons that are arranged regularly to obtain original attractive complex general building forms. The proposed method is a significant extension of the previous method for shaping roof structures with the positive Gaussian curvature and fills existing gaps in current scientific knowledge. The extended method enables the designer to significantly increase the variety of the created complex shell roof forms and plane-walled folded elevation forms of buildings and to define the shapes of their rod structural systems. It allows one to overcome the existing significant geometric and material limitations related to shape transformations of nominally flat rectangular folded steel sheets into different shell forms. The developed extension is based on formation of a set of properly connected tetrahedra as a material determining different (a) inclination of elevation walls to the vertical, and (b) distribution of many individual warped roof shells in accordance with the properties of a regular surface with negative Gaussian curvature. A number of the adopted specific sets of division coefficients (parameters) is used for determining the entire network and its complete tetrahedra. The presented description makes it possible to adopt appropriate assumptions and data and then employ the innovative method to obtain the expected characteristics of the unconventional building form shaped. The presented three different special forms created with the help of the novel method and the appropriately selected diversified values of the division coefficients of pairs of the vertices of a polyhedral reference network, a polygonal eaves network and points of a reference surface confirm the innovative scientific nature of the obtained results. The method has to be computationally aided due to the complexity of mathematical operations and the need to visualize the designed forms. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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15 pages, 5315 KiB

Open AccessArticle

Comparative Manufacturing of Hybrid Composites with Waste Graphite Fillers for UAVs

by Veena Phunpeng, Karunamit Saensuriwong and Thongchart Kerdphol

Materials 2022, 15(19), 6840; https://doi.org/10.3390/ma15196840 - 1 Oct 2022

Cited by 7 | Viewed by 1681

Abstract

Materials of Unmanned Aerial Vehicles (UAVs) parts require specific techniques and processes to provide high standard quality, sufficiently strong, and lightweight materials. Composite materials with a proper technique have been considered to improve the performance of UAVs. Usually, the hybrid composite is developed [...] Read more.

Materials of Unmanned Aerial Vehicles (UAVs) parts require specific techniques and processes to provide high standard quality, sufficiently strong, and lightweight materials. Composite materials with a proper technique have been considered to improve the performance of UAVs. Usually, the hybrid composite is developed by mechanical properties with the addition of the filler component (i.e., particle) in a matrix. This research work aims to develop the effective composite materials with better mechanical properties. Considering the manufacturing of hybrid composite materials, the vacuum process is an affecting factor on mechanical properties. The comparison of the hand lay-up process (HL) and vacuum infusion process (VI) with controlled pressure and temperature are studied in this research. In addition, graphite fillers (i.e., 5 wt%, 7.5 wt%, 10 wt%, and 12.5 wt%) are added to the studied matrix. Obviously, the ply orientation is one of the factors that affects mechanical properties. Moreover, two types of ply orientation (i.e., [0°/90°]_4s and [−45°/45°]_4s) are comprehensively investigated to improve mechanical properties in the three-point bending test. The experimental results show that the vacuum infusion process of ply orientation [0°/90°]_4s with the addition of 10 wt% graphite filler exhibits remarkable flexural strength from 404 MPa (without filler) to 529 MPa (10 wt% filler). Especially, the ply orientation of [0°/90°]_4s has higher flexural strength than [−45°/45°]_4s in both processes. Considering the failure, the fracture of the specimen propagates along the trajectory of fiber fabric orientation, leading to the breakage. Subsequently, the flexural strength under the vacuum infusion process is more significant than in the hand lay-up process. Effectively, it is found that the hybrid composite in this manufacturing has a higher strength-to-weight ratio to use in the structure of UAV instead of pure aluminum. It should be noted that the proposed hybrid composite strategy used in this study is not only limited to the UAV parts. The contribution can be extended to use in other applications such as automotive, structural building, and so on. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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27 pages, 819 KiB

Open AccessArticle

A New Method for the Calculation of Characteristics of Disc Springs with Trapezoidal Cross-Sections and Rounded Edges

by Dominik Sebastian Leininger, Max Benedikt Geilen, Marcus Klein and Matthias Oechsner

Materials 2022, 15(5), 1954; https://doi.org/10.3390/ma15051954 - 6 Mar 2022

Cited by 3 | Viewed by 3193

Abstract

In the European standards specifying disc spring manufacturing, geometry, shape and characteristic, an edge rounding is prescribed. Common methods for the calculation of disc spring characteristics, even in these standards, are based on a rectangular cross-section. This discrepancy can lead to a considerable [...] Read more.

In the European standards specifying disc spring manufacturing, geometry, shape and characteristic, an edge rounding is prescribed. Common methods for the calculation of disc spring characteristics, even in these standards, are based on a rectangular cross-section. This discrepancy can lead to a considerable divergence of the computed characteristic from the characteristic determined by testing. In literature, this divergence has not yet been examined with regard to rounded edges. In this paper, a new method addressing this problem is introduced. For this purpose, the geometry of idealized disc springs is parameterized. Based on four edge radii and two angles of the inner and outer faces, equations to compute the initial cone angle and the lever arm are introduced. These equations are used to formulate an algorithm to adapt other computation methods to non-rectangular cross-sections and rounded edges. The method is applied to the formulas by Almen–Laszlo, Curti–Orlando, Zheng and those by Kobelev. FE simulations of disc springs with rounded edges and a non-rectangular cross-section were used to verify the new formulas. The results show that the introduced method can be applied to known characteristic computation methods and result in a model expansion taking cross-section variations into account. The adjusted characteristics show more accurate alignment to the FE simulation for the cross-section variations investigated. These findings not only close the geometric gap between the manufacturing guidelines and the computation on an analytical basis, they also define a new parameter space for designs of disc springs and a corresponding force computation method to optimize spring characteristics. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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20 pages, 7557 KiB

Open AccessArticle

Analysis of Experimental Results Regarding the Selection of Spring Elements in the Front Suspension of a Four-Axle Truck

by Mariusz Stańco and Marcin Kowalczyk

Materials 2022, 15(4), 1539; https://doi.org/10.3390/ma15041539 - 18 Feb 2022

Cited by 4 | Viewed by 5486

Abstract

Most special vehicles on public roads and off-road are equipped with various suspension systems. The suspensions used in trucks are designed to absorb the energy that results from overcoming uneven ground. These suspensions are divided into dependent and independent ones. Knowledge of the [...] Read more.

Most special vehicles on public roads and off-road are equipped with various suspension systems. The suspensions used in trucks are designed to absorb the energy that results from overcoming uneven ground. These suspensions are divided into dependent and independent ones. Knowledge of the loads that occur while driving a vehicle, mainly off-road, is critical from the point of view of the adhesion and fatigue life of the suspension system. In the case of four-axle cars with 2 + 2 axles, in which the first two axles are equipped with a dependent suspension based on leaf springs, only one axle may carry the load. This paper attempts to analyze the results of experimental tests carried out on a vehicle in the conditions of roads with an unstable surface such as dirt roads, gravel roads, and roadless tracks. An analysis of fatigue life estimation is presented using equivalent stress values. It was also determined how the use of front axles load equalizing elements in the tested car influences their fatigue life. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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41 pages, 35030 KiB

Open AccessArticle

Specifications for Modelling of the Phenomenon of Compression of Closed-Cell Aluminium Foams with Neural Networks

by Anna M. Stręk, Marek Dudzik and Tomasz Machniewicz

Materials 2022, 15(3), 1262; https://doi.org/10.3390/ma15031262 - 8 Feb 2022

Cited by 6 | Viewed by 2457

Abstract

The article presents a novel application of the most up-to-date computational approach, i.e., artificial intelligence, to the problem of the compression of closed-cell aluminium. The objective of the research was to investigate whether the phenomenon can be described by neural networks and to [...] Read more.

The article presents a novel application of the most up-to-date computational approach, i.e., artificial intelligence, to the problem of the compression of closed-cell aluminium. The objective of the research was to investigate whether the phenomenon can be described by neural networks and to determine the details of the network architecture so that the assumed criteria of accuracy, ability to prognose and repeatability would be complied. The methodology consisted of the following stages: experimental compression of foam specimens, choice of machine learning parameters, implementation of an algorithm for building different structures of artificial neural networks (ANNs), a two-step verification of the quality of built models and finally the choice of the most appropriate ones. The studied ANNs were two-layer feedforward networks with varying neuron numbers in the hidden layer. The following measures of evaluation were assumed: mean square error (MSE), sum of absolute errors (SAE) and mean absolute relative error (MARE). Obtained results show that networks trained with the assumed learning parameters which had 4 to 11 neurons in the hidden layer were appropriate for modelling and prognosing the compression of closed-cell aluminium in the assumed domains; however, they fulfilled accuracy and repeatability conditions differently. The network with six neurons in the hidden layer provided the best accuracy of prognosis at

M A R E \leq 2.7 %

but little robustness. On the other hand, the structure with a complexity of 11 neurons gave a similar high-quality of prognosis at

M A R E \leq 3.0 %

but with a much better robustness indication (80%). The results also allowed the determination of the minimum threshold of the accuracy of prognosis:

M A R E \geq 1.66 %

. In conclusion, the research shows that the phenomenon of the compression of aluminium foam is able to be described by neural networks within the frames of made assumptions and allowed for the determination of detailed specifications of structure and learning parameters for building models with good-quality accuracy and robustness. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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21 pages, 5285 KiB

Open AccessFeature PaperArticle

Influence of Thermal Shocks on Residual Static Strength, Impact Strength and Elasticity of Polymer-Composite Materials Used in Firefighting Helmets

by Daniel Pieniak, Agata Walczak, Marcin Oszust, Krzysztof Przystupa, Renata Kamocka-Bronisz, Robert Piec, Grzegorz Dzień, Jarosław Selech and Dariusz Ulbrich

Materials 2022, 15(1), 57; https://doi.org/10.3390/ma15010057 - 22 Dec 2021

Cited by 7 | Viewed by 3311

Abstract

The article presents results of experimental studies on mechanical properties of the polymer-composite material used in manufacturing firefighting helmets. Conducted studies included static and impact strength tests, as well as a shock absorption test of glass fiber-reinforced polyamide 66 (PA66) samples and firefighting [...] Read more.

The article presents results of experimental studies on mechanical properties of the polymer-composite material used in manufacturing firefighting helmets. Conducted studies included static and impact strength tests, as well as a shock absorption test of glass fiber-reinforced polyamide 66 (PA66) samples and firefighting helmets. Samples were subject to the impact of thermal shocks before or during being placed under a mechanical load. A significant influence of thermal shocks on mechanical properties of glass fiber-reinforced PA66 was shown. The decrease in strength and elastic properties after cyclic heat shocks ranged from a few to several dozen percent. The average bending strength and modulus during the 170 degree Celsius shock dropped to several dozen percent from the room temperature strength. Under these thermal conditions, the impact strength was lost, and the lateral deflection of the helmet shells increased by approximately 300%. Moreover, while forcing a thermal shock occurring during the heat load, it was noticed that the character of a composite damage changes from the elasto-brittle type into the elasto-plastic one. It was also proved that changes in mechanical and elastic properties of the material used in a helmet shell can affect the protective abilities of a helmet. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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14 pages, 5004 KiB

Open AccessArticle

Prediction of System Parameters of Carbon-Based Composite Structure for Different Carbon Fiber Orientations with Mode Information at Reference Angle Only

by Chan-Jung Kim

Materials 2021, 14(24), 7626; https://doi.org/10.3390/ma14247626 - 11 Dec 2021

Cited by 2 | Viewed by 1843

Abstract

The prediction of system parameters is important for understanding the dynamic behavior of composite structures or selecting the configuration of laminated carbon in carbon-based composite (CBC) structures. The dynamic nature of CBC structures allows the representation of system parameters as modal parameters in [...] Read more.

The prediction of system parameters is important for understanding the dynamic behavior of composite structures or selecting the configuration of laminated carbon in carbon-based composite (CBC) structures. The dynamic nature of CBC structures allows the representation of system parameters as modal parameters in the frequency domain, where all modal parameters depend on the carbon fiber orientations. In this study, the variation in the system parameters of a carbon fiber was derived from equivalent modal parameters, and the system parameters at a certain carbon fiber orientation were predicted using the modal information at the reference carbon fiber orientation only and a representative curve-fitted function. The target CBC structure was selected as a simple rectangular structure with five different carbon fiber orientations, and the modal parameters were formulated based on a previous study for all modes. Second-order curve-fitted polynomial functions were derived for all possible cases, and representative curve-fitting functions were derived by averaging the polynomial coefficients. The two system parameters were successfully predicted using the representative curve-fitting function and the modal information at only the reference carbon fiber orientation, and the feasibility of parameter prediction was discussed based on an analysis of the error between the measured and predicted parameters. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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17 pages, 7020 KiB

Open AccessArticle

Modeling of Curvilinear Steel Rod Structures Based on Minimal Surfaces

by Jolanta Dzwierzynska and Igor Labuda

Materials 2021, 14(22), 6826; https://doi.org/10.3390/ma14226826 - 12 Nov 2021

Cited by 3 | Viewed by 2377

Abstract

The article deals with shaping effective curvilinear steel rod roof structures using genetic algorithms by implementing them for the analysis of various case studies in order to find new and efficient structures with positive characteristics. The structures considered in this article are created [...] Read more.

The article deals with shaping effective curvilinear steel rod roof structures using genetic algorithms by implementing them for the analysis of various case studies in order to find new and efficient structures with positive characteristics. The structures considered in this article are created on the basis of the Enneper surface and minimal surfaces stretched on four arcs. On the Enneper surface, a single layer grid is used, while on the other surfaces, two-layer ones. The Enneper form structure with four supports and the division into an even number of parts along the perimeter of the covered place proved to be the most efficient, and the research showed that small modifications of the initial base surface in order to adapt the structure to the roof function did not significantly affect its effectiveness. However, the analysis and comparison of single and double-shell rod structures based on minimal surfaces stretched on four arcs have shown that a single-shell structure is much more effective than a double one. The paper considers the theoretical aspects of shaping effective structures, taking their masses as the optimization criterion. The optimization helped to choose the best solutions due to structures’ shapes and topologies. However, the obtained, optimized results can find practical applications after conducting physical tests. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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16 pages, 5198 KiB

Open AccessArticle

Thermodynamics and Analysis of Predicted Responses of a Phase Field Model for Ductile Fracture

by Aris Tsakmakis and Michael Vormwald

Materials 2021, 14(19), 5842; https://doi.org/10.3390/ma14195842 - 6 Oct 2021

Cited by 6 | Viewed by 1828

Abstract

The fundamental idea in phase field theories is to assume the presence of an additional state variable, the so-called phase field, and its gradient in the general functional used for the description of the behaviour of materials. In linear elastic fracture mechanics the [...] Read more.

The fundamental idea in phase field theories is to assume the presence of an additional state variable, the so-called phase field, and its gradient in the general functional used for the description of the behaviour of materials. In linear elastic fracture mechanics the phase field is employed to capture the surface energy of the crack, while in damage mechanics it represents the variable of isotropic damage. The present paper is concerned, in the context of plasticity and ductile fracture, with a commonly used phase field model in fracture mechanics. On the one hand, an appropriate framework for thermodynamical consistency is outlined. On the other hand, an analysis of the model responses for cyclic loading conditions and pure kinematic or pure isotropic hardening are shown. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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12 pages, 61085 KiB

Open AccessArticle

Stress-Shot-Peened Leaf Springs Material Analysis through Nano- and Micro-Indentations

by Maria Pappa, Georgios Savaidis and Nikolaos Michailidis

Materials 2021, 14(17), 4795; https://doi.org/10.3390/ma14174795 - 24 Aug 2021

Cited by 1 | Viewed by 1918

Abstract

Heat-treated and shot-peened lightweight steels with demanding requirements for durability are applied in high-performance automotive leaf springs. Due to their heat-treatment they exhibit degraded properties in the surface-near area compared to the core. This area, which may extend until 300 μm from the [...] Read more.

Heat-treated and shot-peened lightweight steels with demanding requirements for durability are applied in high-performance automotive leaf springs. Due to their heat-treatment they exhibit degraded properties in the surface-near area compared to the core. This area, which may extend until 300 μm from the surface to the core, experiences the highest bending stresses at operation. The microstructure in the surface and sub-surface layers determines the mechanical performance as well as the wear resistance. The present study refers to the material properties of a stress shot-peened 51CrV4 steel at various depths from the surface. The effect of the manufacturing process has been captured both by Vickers micro-hardness measurements and nanoindentation. The latter combined with a Fine Element Method (FEM)-based algorithm enables the determination of variations in the material’s stress–strain curves over the affected layers, which translate to internal stress changes. The nanoindentation technique has been applied here successfully for the first time ever on leaf springs. The combination of microstructural analysis, microhardness and nanoindentation captures the changes of the treated material, offering insights on the material characteristics, and yielding accurate elastoplastic material properties for local, layered-based analysis of the components’ mechanical performance at operational loading scenarios, i.e., in the framework of stress shot-peening simulation models. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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17 pages, 10878 KiB

Open AccessArticle

A Study on the Sound Insulation Performance of Cross-laminated Timber

by Jui-Yen Lin, Chieh-Ting Yang and Yaw-Shyan Tsay

Materials 2021, 14(15), 4144; https://doi.org/10.3390/ma14154144 - 25 Jul 2021

Cited by 5 | Viewed by 3159

Abstract

Cross-laminated Timber (CLT) has become an emerging board material of wood construction that is strong enough to sustain a high-rise building. However, many wooden congregate housing units overseas that utilize CLT have poor sound environments because the low mass of such wood influences [...] Read more.

Cross-laminated Timber (CLT) has become an emerging board material of wood construction that is strong enough to sustain a high-rise building. However, many wooden congregate housing units overseas that utilize CLT have poor sound environments because the low mass of such wood influences sound insulation performance. In this research, we explored the effect of different CLT walls on sound insulation performance and integrated applicable sound insulation simulation tools to simplify the process of designing a CLT wall structure. This research aimed at a double wall and CLT combined with a gypsum board as the research object. The sound insulation performance test was carried out in a laboratory, while the sound insulation performance of the structure was predicted through simulation tools and prediction models and then compared with the measured values to verify the applicability of the simulation tool. The CLT with a double wall and CLT with gypsum board (CLT + GB) achieved

R_{w}

of 50 dB. The numerical simulation had better prediction performance than INSUL at the double wall, while the double wall with cavity structure was close to the measured result via mass law calculation. The INSUL-predicted CLT with a gypsum board at 500 Hz~3150 Hz was close to the measured value. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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24 pages, 5571 KiB

Open AccessArticle

Transformed Shell Structures Determined by Regular Networks as a Complex Material for Roofing

by Jacek Abramczyk

Materials 2021, 14(13), 3582; https://doi.org/10.3390/ma14133582 - 26 Jun 2021

Cited by 6 | Viewed by 2242

Abstract

The article presents a comprehensive extension of the proprietary basic method for shaping innovative systems of corrugated shell roof structures by means of a specific complex material that comprises regular transformable shell units limited by spatial quadrangles. The units are made up of [...] Read more.

The article presents a comprehensive extension of the proprietary basic method for shaping innovative systems of corrugated shell roof structures by means of a specific complex material that comprises regular transformable shell units limited by spatial quadrangles. The units are made up of nominally plane folded sheets transformed into shell shapes. The similar shell units are regularly and effectively arranged in the three-dimensional space in an orderly manner with a universal regular reference surface, polyhedral network, and polygonal network. The extended method leads to the increase in the variety of the designed complex shell roof forms and plane-walled elevation forms of buildings. For this purpose, the rules governing the creation of the continuous roof shell structures of many shells arranged in different unconventional visually attractive patterns and their discontinuous regular modifications are sought. To obtain several novel groups of similar unconventional parametric roof forms, single division coefficients and double division coefficients are used. The easy and intuitive modifications of the positions of the vertices belonging to the polygonal network on the side edges of the polyhedral network accomplished by means of a parametric algorithm allow one to adjust the geometry of the complete shell units to the geometric and material constraints related to the orthotropic properties of the transformed sheeting by means of these coefficients. The innovative approach to the shaping of the diverse unconventional roof structures requires the solving of many interdisciplinary problems in the field of mathematics, civil engineering, construction, morphology, architecture, mechanics, computer visualization, and programming. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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18 pages, 5491 KiB

Open AccessArticle

Study of Viscoelastic Rubber Mounts on Vehicle Suspensions with In-Wheel Electric Motors

by Santiago D. Puma-Araujo, Renato Galluzzi, Xavier Sánchez-Sánchez and Ricardo A. Ramirez-Mendoza

Materials 2021, 14(12), 3356; https://doi.org/10.3390/ma14123356 - 17 Jun 2021

Cited by 4 | Viewed by 3273

Abstract

Rubber bushings and mounts are vastly used in automotive applications as support and interface elements. In suspension systems, they are commonly employed to interconnect the damping structure to the chassis. Therein, the viscoelastic nature of the material introduces a desirable filtering effect to [...] Read more.

Rubber bushings and mounts are vastly used in automotive applications as support and interface elements. In suspension systems, they are commonly employed to interconnect the damping structure to the chassis. Therein, the viscoelastic nature of the material introduces a desirable filtering effect to reduce mechanical vibrations. When designing a suspension system, available literature often deals with viscoelastic mounts by introducing a linear or nonlinear stiffness behavior. In this context, the present paper aims at representing the rubber material using a proper viscoelastic model with the selection of different in-wheels motors. Thus, the mount dynamic behavior’s influence in a suspension is studied and discussed thoroughly through numerical simulations and sensitivity analyses. Furthermore, guidelines are proposed to orient the designer when selecting these elements. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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17 pages, 4053 KiB

Open AccessArticle

Experimental Study on the Behaviour of Seismic Actions on a Flexible Glass-Reinforced Plastic Structure Used in Water Transport Pipes

by Ana Diana Ancaș, Ioan Așchilean, Mihai Profire, Florin Emilian Țurcanu and Raluca-Andreea Felseghi

Materials 2021, 14(11), 2878; https://doi.org/10.3390/ma14112878 - 27 May 2021

Cited by 2 | Viewed by 2752

Abstract

This article presents the experimental results obtained by the testing an experimental model of water distribution which is flexible and above-head mounted on a seismic platform, and their validation in a theoretical manner, but also by the Finite Element Method, using the ANSYS [...] Read more.

This article presents the experimental results obtained by the testing an experimental model of water distribution which is flexible and above-head mounted on a seismic platform, and their validation in a theoretical manner, but also by the Finite Element Method, using the ANSYS simulation program. This type of system shown by the experimental model is desired to be used in practice not only in seismic areas, but also in the areas of heavy road transport, landslides, etc. thorugh the use thereof in the most stressed points of the network (hearth entry/exit, before/after an elbow, etc.) but also on long routes, at optimal distances. The results achieved are related to glass- reinforced plastic (GRP) pipes with a nominal diameter DN = 250 mm, but conclusions may be drawn starting from these to help future research where the mass of the earth is desired to be taken into account. The present results are comprehensive for buried pipes operated dynamically or seismically at low-medium intensity, as this type of earthquake occurs more and more often in Europe. The experimental tests in this article do not have the characteristics necessary for a high intensity seismic action (above 5° Richter). Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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14 pages, 2630 KiB

Open AccessEditor’s ChoiceArticle

A FEM-Based 2D Model for Simulation and Qualitative Assessment of Shot-Peening Processes

by Georgios Maliaris, Christos Gakias, Michail Malikoutsakis and Georgios Savaidis

Materials 2021, 14(11), 2784; https://doi.org/10.3390/ma14112784 - 24 May 2021

Cited by 7 | Viewed by 2818

Abstract

Shot peening is one of the most favored surface treatment processes mostly applied on large-scale engineering components to enhance their fatigue performance. Due to the stochastic nature and the mutual interactions of process parameters and the partially contradictory effects caused on the component’s [...] Read more.

Shot peening is one of the most favored surface treatment processes mostly applied on large-scale engineering components to enhance their fatigue performance. Due to the stochastic nature and the mutual interactions of process parameters and the partially contradictory effects caused on the component’s surface (increase in residual stress, work-hardening, and increase in roughness), there is demand for capable and user-friendly simulation models to support the responsible engineers in developing optimal shot-peening processes. The present paper contains a user-friendly Finite Element Method-based 2D model covering all major process parameters. Its novelty and scientific breakthrough lie in its capability to consider various size distributions and elastoplastic material properties of the shots. Therewith, the model is capable to provide insight into the influence of every individual process parameter and their interactions. Despite certain restrictions arising from its 2D nature, the model can be accurately applied for qualitative or comparative studies and processes’ assessments to select the most promising one(s) for the further experimental investigations. The model is applied to a high-strength steel grade used for automotive leaf springs considering real shot size distributions. The results reveal that the increase in shot velocity and the impact angle increase the extent of the residual stresses but also the surface roughness. The usage of elastoplastic material properties for the shots has been proved crucial to obtain physically reasonable results regarding the component’s behavior. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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29 pages, 7635 KiB

Open AccessArticle

Transformed Corrugated Shell Units Used as a Material Determining Unconventional Forms of Complex Building Structures

by Jacek Abramczyk

Materials 2021, 14(9), 2402; https://doi.org/10.3390/ma14092402 - 5 May 2021

Cited by 4 | Viewed by 2005

Abstract

This article is an insight into interdisciplinary topics in the field of civil engineering, morphology, architecture, mechanics, and computer programming. A novel method for shaping unconventional complex roofs in which regular folded units transformed into various shells are used as a complex substitute [...] Read more.

This article is an insight into interdisciplinary topics in the field of civil engineering, morphology, architecture, mechanics, and computer programming. A novel method for shaping unconventional complex roofs in which regular folded units transformed into various shells are used as a complex substitute material is proposed. The original method’s algorithm for building systems of planes defining diversified polyhedral networks in the three-dimensional space by means of division coefficients of the subsequently determined vertices is presented. The algorithm is based on the proportions between the lengths of the edges of the reference network, the location and shape of the ruled shell units included in the designed complex roof structure, so it is intuitive. The shell units are made up of nominally flat folded sheets transformed effectively into shell forms whose static-strength properties are controlled by geometric quantities characteristic of ruled surfaces. The presented original approach to the shaping of the shell roof structures determining specific complex building forms allows us to go beyond the limitations related to the orthotropic structure of the folded roof sheeting and the shape transformations. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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9 pages, 1742 KiB

Open AccessArticle

Experimental Studies of an Asymmetric Multi-Bolted Connection under Monotonic Loads

by Rafał Grzejda, Arkadiusz Parus and Konrad Kwiatkowski

Materials 2021, 14(9), 2353; https://doi.org/10.3390/ma14092353 - 1 May 2021

Cited by 22 | Viewed by 2558

Abstract

This article describes the experimental studies of a preloaded asymmetric multi-bolted connection in the exploitation state. The construction of two stands were introduced: for bolt calibration and for evaluating the bolt forces in a multi-bolted connection. The bolts were tightened in a specific [...] Read more.

This article describes the experimental studies of a preloaded asymmetric multi-bolted connection in the exploitation state. The construction of two stands were introduced: for bolt calibration and for evaluating the bolt forces in a multi-bolted connection. The bolts were tightened in a specific optimal sequence, in three passes, monitoring the force values in the bolts using a calibrated strain gauge measuring system. The studies were conducted for the selected multi-bolted connection on an Instron 8850 testing machine. The measurement data were saved in MATLAB R2018b Simulink. The measurement results were analysed statistically and are presented via charts showing the distributions of the normalised values of the bolt forces as a function of the linearly increasing and decreasing exploitation loads. We show that the forces in individual bolts, after unloading the multi-bolted connection, change in relation to the initial values of their preload. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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25 pages, 8278 KiB

Open AccessArticle

Folded Sheets as a Universal Material for Shaping Transformed Shell Roofs

by Jacek Abramczyk

Materials 2021, 14(8), 2051; https://doi.org/10.3390/ma14082051 - 19 Apr 2021

Cited by 6 | Viewed by 2887

Abstract

This article provides a novel insight into specific properties of flat folded sheets transformed elastically into building roof shells. Elastic twist transformations of the sheets resulting from the arrangement of the sheets on two skew roof directrices cause changes in the geometric and [...] Read more.

This article provides a novel insight into specific properties of flat folded sheets transformed elastically into building roof shells. Elastic twist transformations of the sheets resulting from the arrangement of the sheets on two skew roof directrices cause changes in the geometric and mechanical sheet properties of the roof shell sheeting composed of these sheets. Regular smooth-ruled surfaces and their characteristic lines are used in the analysis of changes in the geometric properties. In the analysis of the mechanical changes, the constitutive relations and complex state of stresses are considered. The analysis is carried out on the basis of the results of the experimental tests and FEM computer simulations. They have led to the development of such a method of shaping of the effectively transformed folded covers that ensures the initial effort of each shell fold to be the smallest possible. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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11 pages, 3884 KiB

Open AccessEditor’s ChoiceArticle

Methodology for Selecting the Operating Conditions of a Vibration Generator Used in the Hot-Dip Galvanizing Process

by Wojciech Kacalak, Igor Maciejewski, Dariusz Lipiński and Błażej Bałasz

Materials 2021, 14(8), 2042; https://doi.org/10.3390/ma14082042 - 19 Apr 2021

Viewed by 2323

Abstract

A simulation model and the results of experimental tests of a vibration generator in applications for the hot-dip galvanizing process are presented. The parameters of the work of the asynchronous motor forcing the system vibrations were determined, as well as the degree of [...] Read more.

A simulation model and the results of experimental tests of a vibration generator in applications for the hot-dip galvanizing process are presented. The parameters of the work of the asynchronous motor forcing the system vibrations were determined, as well as the degree of unbalance enabling the vibrations of galvanized elements weighing up to 500 kg to be forced. Simulation and experimental tests of the designed and then constructed vibration generator were carried out at different intensities of the unbalanced rotating mass of the motor. Based on the obtained test results, the generator operating conditions were determined at which the highest values of the amplitude of vibrations transmitted through the suspension system to the galvanized elements were obtained. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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24 pages, 6739 KiB

Open AccessArticle

The Relation between Concrete, Mortar and Paste Scale Early Age Properties

by Martin Klun, Vlatko Bosiljkov and Violeta Bokan-Bosiljkov

Materials 2021, 14(6), 1569; https://doi.org/10.3390/ma14061569 - 23 Mar 2021

Cited by 6 | Viewed by 2909

Abstract

Microstructure development of concrete, mortar, and paste scale of cement-based material (CBM) during the early hydration stage has a significant impact on CBM’s physical, mechanical, and durability characteristics at the high maturity state. The research was carried out using compositions with increased autogenous [...] Read more.

Microstructure development of concrete, mortar, and paste scale of cement-based material (CBM) during the early hydration stage has a significant impact on CBM’s physical, mechanical, and durability characteristics at the high maturity state. The research was carried out using compositions with increased autogenous shrinkage and extended early age period, proposed within the RRT⁺ programme of the COST Action TU1404. The electrical conductivity method, used to follow the solidification process of CBM, is capable of determining the initial and final setting time, and the end of the solidification process acceleration stage for the paste and mortar scale. Simultaneous ultrasonic P- and S-wave transmission measurements revealed that the ratio of velocities V_P/V_S is highly dependent on the presence of aggregates—it is considerably higher for the paste scale compared to the mortar and concrete scale. The deviation from the otherwise roughly constant ratio V_P/V_S for each scale may indicate cracks in the material. The non-linear correlation between the dynamic and static elastic moduli valid over the three scales was confirmed. Additionally, it was found that the static E-modulus correlates very well with the square of the V_S and that the V_S is highly correlated to the cube compressive strength—but a separate trendline exists for each CBM scale. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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16 pages, 5678 KiB

Open AccessArticle

Estimating of Bending Force and Curvature of the Bending Plate in a Three-Roller Bending System Using Finite Element Simulation and Analytical Modeling

by Ionel Gavrilescu, Doina Boazu and Felicia Stan

Materials 2021, 14(5), 1204; https://doi.org/10.3390/ma14051204 - 4 Mar 2021

Cited by 8 | Viewed by 4639

Abstract

Many industries such as shipbuilding require steel bending plates in a wide range of radii, thus bending machines are often designed and produced on a custom basis in shipyards. From a design perspective, however, the bending force and the radius of the bending [...] Read more.

Many industries such as shipbuilding require steel bending plates in a wide range of radii, thus bending machines are often designed and produced on a custom basis in shipyards. From a design perspective, however, the bending force and the radius of the bending plate as a function of vertical displacement of the upper roller must be known. In this paper, a hybrid numerical–analytical approach is proposed to investigate the three-roller bending process for two plates of steel used in the naval industry. Firstly, the bending process is modeled using the finite element (FE) method and regression models for the bending force as a function of plate thickness and vertical displacement of the upper roller were constructed. Then, based on the findings from FE analysis, using the bent bar theory, two analytical expressions for the bending force were derived. Using geometric and deformation compatibilities, analytical expressions for the vertical displacement of the upper roller as a function of the curvature of the bending plate were also developed. The FE results suggest that the cross section of the plate is practically a plastic hinge in the tangent area of the upper roller and that the deformation compatibilities must be considered in order to estimate the curvature radius of the bending plate using analytical formulations. These results are of practical importance in designing rolling machines to estimate the setting parameters. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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14 pages, 2305 KiB

Open AccessEditor’s ChoiceArticle

Sizing and Topology Optimization of Trusses Using Genetic Algorithm

by Ingrid Delyová, Peter Frankovský, Jozef Bocko, Peter Trebuňa, Jozef Živčák, Barbara Schürger and Sára Janigová

Materials 2021, 14(4), 715; https://doi.org/10.3390/ma14040715 - 3 Feb 2021

Cited by 20 | Viewed by 2976

Abstract

Genetic algorithms are a robust method for a solution of wide variety optimization problems. It explores a big space of design variables in order to find the best solution. From the point of view of a user, the algorithm requires the encoding of [...] Read more.

Genetic algorithms are a robust method for a solution of wide variety optimization problems. It explores a big space of design variables in order to find the best solution. From the point of view of a user, the algorithm requires the encoding of design variables into the form of strings and the procedure of optimization uses them for optimization. Here, for the structural engineer, it is crucial to find the form of objective function including the constraints of the task and also to avoid critical states during the solution of structural responses. This paper presents the use of genetic algorithm for solving truss structures. The use of genetic algorithm approach is shown on three cases of truss structures. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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15 pages, 3806 KiB

Open AccessArticle

Hydroforming of Toroidal Bellows: Process Simulation and Quality Control

by Mengsi Ye, Huifang Li, Yougang Wang and Caifu Qian

Materials 2021, 14(1), 142; https://doi.org/10.3390/ma14010142 - 31 Dec 2020

Cited by 12 | Viewed by 2809

Abstract

Having higher capacity to undertake pressures and larger compensation ability compared with the U-shape bellows, toroidal or Ω-shape bellows are being more and more widely used in engineering. The wave-shape and wall thickness reduction of bellows are the most important parameters for measuring [...] Read more.

Having higher capacity to undertake pressures and larger compensation ability compared with the U-shape bellows, toroidal or Ω-shape bellows are being more and more widely used in engineering. The wave-shape and wall thickness reduction of bellows are the most important parameters for measuring the hydroforming quality of the bellows. In order to provide references for actual manufacturing, it is valuable to study the factors influencing the hydroforming process and quality of the bellows. In this paper, finite element simulations of the hydroforming process of a monolayer and single-wave toroidal bellows and a two-layer and four-wave toroidal bellows were carried out. Stress and strain distributions before and after unloading were analyzed and the wave height and wall thickness reduction were examined. The numerical results were verified by the actual hydroforming measurements. In addition, ranges of the significant structural or operating factors for producing better bellows were studied and a formula to compute the wall thickness reduction was fitted based on the sufficient numerical results of the hydroforming simulations. Full article

(This article belongs to the Special Issue Computational and Experimental Mechanics of Engineering Materials and Structures)

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