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Mechanical Properties of Technical Materials
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Mechanical Properties of Technical Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Physics".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 18254

Special Issue Editor

Dr. Ján Valíček

E-Mail Website1 Website2
Guest Editor
1. Institute of Technology and Business in České Budějovice, Okružní 10, 370 01 České Budějovice, Czech Republic
2. Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia
Interests: advanced materials; mechanical properties; surface engineering; coatings; applied physics

Special Issue Information

Dear Colleagues,

Knowledge of the mechanical properties of technical materials plays an important role in designing any component, device or structure and provides very important information about their limitations of use. In particular, engineers are interested to know when the part fails (i.e., break, or otherwise change shape) under different conditions. These include loading under tension, compression, torsion, bending, repeated cyclic loading, constant loading over long time, impact, etc. The mechanical properties of materials are not constants and they often change; therefore, there is an interest in their hardness, and how these properties change with temperature. The mechanical, physical, chemical, and technological properties of materials are often interrelated. Relations are found by analyzing the nature of properties and their relationship to the structure of substances. In practice, different combinations of properties are often required, both in terms of utility properties and in terms of the specific technology of the final production. Technical practice also imposes requirements on economic, security, aesthetic, and other aspects. This will show whether the product will have the desired characteristics and whether it will also meet the other criteria. If it is found that the required properties have not been achieved, a new design must be sought and re-tested. Papers are sought that discuss the latest research in the area of identification of mechanical properties and will also introduce destructive and nondestructive mechanical testing methods. The scope of the Special Issue encompasses predicting, modifying, and describing the mechanical behavior of technical materials.

Dr. Ján Valíček
Guest Editor

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. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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

  • Mechanical properties
  • Identification of mechanical properties
  • Advances in mechanical properties of technical materials
  • Destructive and nondestructive testing
  • Strengthening and fracture mechanisms
  • Failure behavior

Published Papers (8 papers)

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Research

22 pages, 6944 KiB  
Article
Structural and Mechanical Changes of AlMgSi0.5 Alloy during Extrusion by ECAP Method
by Marta Harničárová, Jan Valíček, Milena Kušnerová, Ivan Kopal, Miloslav Lupták, Rastislav Mikuš, Zdeněk Pavelek, Martin Fabián and Vladimír Šepelák
Materials 2022, 15(6), 2020; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15062020 - 09 Mar 2022
Cited by 2 | Viewed by 1811
Abstract
SPD (several plastic deformations) methods make it possible to obtain an ultrafine-grained structure (UFG) in larger volumes of material and thus improve its mechanical properties. The presented work focuses on the structural and mechanical changes of aluminium alloy AlMgSi0.5 (EN AW 6060) during [...] Read more.
SPD (several plastic deformations) methods make it possible to obtain an ultrafine-grained structure (UFG) in larger volumes of material and thus improve its mechanical properties. The presented work focuses on the structural and mechanical changes of aluminium alloy AlMgSi0.5 (EN AW 6060) during processing by repeated extrusion through the ECAP rectangular channel. After a four-pass extrusion, the samples’ microstructures were observed using an optical microscope, where refinement of the material grains was confirmed. Tensile tests determined the extrusion forces and allowed interpretation of the changes in the mechanical properties of the stressed alloy. The grain size was refined from 28.90 μm to 4.63 μm. A significant improvement in the strength of the material (by 45%) and a significant deterioration in ductility (to 60%) immediately after the first extrusion was confirmed. The third pass through the die appeared to be optimal for the chosen deformation path, while after the fourth pass, micro-cracks appeared, significantly reducing the strength of the material. Based on the measurement results, new analytical equations were formulated to predict the magnitude or intensity of the volumetric and shape deformations of the structural grain size and, in particular, the adequate increase in the strength and yield point of the material. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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18 pages, 7448 KiB  
Article
In Situ Micro-Observation of Surface Roughness and Fracture Mechanism in Metal Microforming of Thin Copper Sheets with Newly Developed Compact Testing Apparatus
by Mandeep Singh, Shubham Sharma, Appusamy Muniappan, Danil Yurievich Pimenov, Szymon Wojciechowski, Kanishka Jha, Shashi Prakash Dwivedi, Changhe Li, Jolanta B. Królczyk, Dominik Walczak and Tien V. T. Nguyen
Materials 2022, 15(4), 1368; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15041368 - 12 Feb 2022
Cited by 21 | Viewed by 2426
Abstract
A better understanding of material deformation behaviours with changes in size is crucial to the design and operation of metal microforming processes. In order to facilitate the investigation of size effects, material deformation behaviours needed to be determined directly from material characterizations. This [...] Read more.
A better understanding of material deformation behaviours with changes in size is crucial to the design and operation of metal microforming processes. In order to facilitate the investigation of size effects, material deformation behaviours needed to be determined directly from material characterizations. This study was aimed at the design and manufacture of a compact universal testing machine (UTM) compatible with a 3D laser-confocal microscope to observe the deformation behaviour of materials in real-time. In this study, uniaxial micro tensile testing was conducted on three different thin (0.05 mm, 0.1 mm, and 0.3 mm) copper specimens with characteristic dimensions at micro scales. Micro tensile experimental runs were carried out on copper specimens with varying grain sizes on the newly developed apparatus under a 3D laser-confocal microscope. Microscale experiments under 3D laser-confocal microscope provided not only a method to observe the microstructure of materials, but also a novel way to observe the early stages of fracture mechanisms. From real-time examination using the newly developed compact testing apparatus, we discovered that fracture behaviour was mostly brought about by the concave surface formed by free surface roughening. Findings with high stability were discovered while moving with the sample grasped along the drive screw in the graphical plot of a crosshead’s displacement against time. Our results also showed very low mechanical noise (detected during the displacement of the crosshead), which indicated that there were no additional effects on the machine, such as vibrations or shifts in speed that could influence performance. The engineering stress-strain plots of the pure copper-tests with various thicknesses or samples depicted a level of stress necessary to initiate plastic flowing inside the material. From these results, we observed that strength and ductility declined with decreasing thickness. The influence of thickness on fracture-strain, observed during tensile testing, made it clear that the elongation-at-break of the pure-copper foils intensely decreased with decreases in thickness. The relative average surface-roughness Ra was evaluated, which showed us that the surface-roughness escalated with the increasing trend of plasticity deformation (plastic strain) ε. For better understanding of the effects of plastic strain on surface roughness prior to material fractures, micro tensile tests were performed on the newly developed machine under a 3D laser-confocal-microscope. We observed that homogeneous surface roughness was caused by plastic strain, which further formed the concave surface that led to the fracture points. Finally, we concluded that surface roughness was one of the crucial factors influencing the fracture behaviour of metallic sheet-strips in metal microforming. We found that this type of testing apparatus could be designed and manufactured within a manageable budget. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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20 pages, 5421 KiB  
Article
Influence of Alkali Treatment on the Microstructure and Mechanical Properties of Coir and Abaca Fibers
by Petr Valášek, Miroslav Müller, Vladimír Šleger, Viktor Kolář, Monika Hromasová, Roberto D’Amato and Alessandro Ruggiero
Materials 2021, 14(10), 2636; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14102636 - 18 May 2021
Cited by 40 | Viewed by 3056
Abstract
Composite materials with natural fillers have been increasingly used as an alternative to synthetically produced materials. This trend is visible from a representation of polymeric composites with natural cellulose fibers in the automotive industry of the European Union. This trend is entirely logical, [...] Read more.
Composite materials with natural fillers have been increasingly used as an alternative to synthetically produced materials. This trend is visible from a representation of polymeric composites with natural cellulose fibers in the automotive industry of the European Union. This trend is entirely logical, owing to a preference for renewable resources. The experimental program itself follows pronounced hypotheses and focuses on a description of the mechanical properties of untreated and alkali-treated natural vegetable fibers, coconut and abaca fibers. These fibers have great potential for use in composite materials. The results and discussion sections contribute to an introduction of an individual methodology for mechanical property assessment of cellulose fibers, and allows for a clear definition of an optimal process of alkalization dependent on the content of hemicellulose and lignin in vegetable fibers. The aim of this research was to investigate the influence of alkali treatment on the surface microstructure and tensile properties of coir and abaca fibers. These fibers were immersed into a 5% solution of NaOH at laboratory temperature for a time interval of 30 min, 1 h, 2 h, 3 h, 6 h, 12 h, 24 h, and 48 h, rinsed and dried. The fiber surface microstructures before and after the alkali treatment were evaluated by SEM (scanning electron microscopy). SEM analysis showed that the alkali treatment in the NaOH solution led to a gradual connective material removal from the fiber surface. The effect of the alkali is evident from the visible changes on the surface of the fibers. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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22 pages, 4061 KiB  
Article
A New Method of Predicting the Structural and Mechanical Change of Materials during Extrusion by the Method of Multiple Plastic Deformations
by Marta Harničárová, Jan Valíček, Milena Kušnerová, Zuzana Palková, Ivan Kopal, Cristina Borzan, Milan Kadnár and Stanislav Paulovič
Materials 2021, 14(10), 2594; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14102594 - 16 May 2021
Cited by 2 | Viewed by 1571
Abstract
The formulation of the Hall–Petch relationship in the early 1950s has raised immense interest in studying the influence of the grain size of solid materials on their properties. Grain refinement can be achieved through extreme deformation. In the presented study, Equal-Channel Angular Pressing [...] Read more.
The formulation of the Hall–Petch relationship in the early 1950s has raised immense interest in studying the influence of the grain size of solid materials on their properties. Grain refinement can be achieved through extreme deformation. In the presented study, Equal-Channel Angular Pressing (ECAP) was successfully applied to produce an ultrafine-grained microstructure in a pure commercial Cu of 99.9 wt%. Samples were processed by ECAP at 21 °C for six passes via route A. A new equation of equilibrium that allows the exact determination of the number of extrusions and other technological parameters required to achieve the desired final grain size has been developed. The presented research also deals, in a relatively detailed and comparative way, with the use of ultrasound. In this context, a very close correlation between the process functions of extrusion and the speed of longitudinal ultrasonic waves was confirmed. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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21 pages, 7222 KiB  
Article
Thermodynamics and Mechanics of Thermal Spraying of Steel EN 10060 Substrate with NiCrBSi Alloy after Milling
by Jan Valíček, Marta Harničárová, Jan Řehoř, Milena Kušnerová, Ludmila Kučerová, Miroslav Gombár, Jaroslava Fulemová, Jan Filipenský and Jan Hnátík
Materials 2020, 13(23), 5344; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13235344 - 25 Nov 2020
Cited by 1 | Viewed by 1362
Abstract
The objective of this paper is to present a new way of identifying and predicting the relationship between thermodynamic and physical-mechanical parameters in the formation of a layer after spraying on a substrate with NiCrBSi alloy and its subsequent processing by milling. The [...] Read more.
The objective of this paper is to present a new way of identifying and predicting the relationship between thermodynamic and physical-mechanical parameters in the formation of a layer after spraying on a substrate with NiCrBSi alloy and its subsequent processing by milling. The milling of the spherical surface of the EN 10060 material after spraying was performed on the DMU 40 eVolinear linear milling centre. The experimental part of the article is focused on investigating the influence of cutting parameters when machining a selected combination of materials (substrate-coating: EN 10060 steel-NiCrBSi alloy). The experiment is based on the results of direct measurements of three basic cutting parameters, namely: cutting speed vc (m∙min−1), feed per tooth fz (mm), and the depth of cut ap (mm). The new distribution functions of selected cutting parameters were derived. The analytical results of the thermodynamic calculations performed on nickel-based alloy can be used for accurate predictions of the technological parameters of milling a spherical substrate made of EN 10060 steel after HVOF spraying, and also for both sample preparation and the subsequent production of high-quality coatings. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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15 pages, 4444 KiB  
Article
Possibility of Utilization of Gate Geometry to Modify the Mechanical and Structural Properties of Castings on the Al-Si Basis
by Jan Majernik, Stefan Gaspar, Jan Kmec, Monika Karkova and Jozef Mascenik
Materials 2020, 13(16), 3539; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13163539 - 11 Aug 2020
Cited by 13 | Viewed by 2062
Abstract
The mechanical properties of die castings correlate with the inner structure of a casting, distribution of the eutectic phases, and with the content and distribution of porous cavities in the casting volume. This submitted paper deals with the issue of the possibility to [...] Read more.
The mechanical properties of die castings correlate with the inner structure of a casting, distribution of the eutectic phases, and with the content and distribution of porous cavities in the casting volume. This submitted paper deals with the issue of the possibility to influence the basic parameters affecting the quality of castings through structural modifications of the gating system. The structural parameter under assessment is the gate height. In the case of the diverse height of the gate, five sets of castings were produced. The individual sets of castings were subjected to examination of selected mechanical properties, i.e., of permanent deformation and surface hardness. At the same time, the individual sets of castings were subjected to metallographic examination of the eutectic structure of the casting. It was proved that the gate height influences the aforementioned properties of the castings and significantly affects the ratio of the eutectic phases in the volume of the casting. The conclusion describes the mutual correlation between the gate structure, the mechanical properties of the casting, and its structural composition. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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22 pages, 11775 KiB  
Article
Fracturing and Damage of 3D-Printed Materials with Two Intermittent Fissures under Compression
by Duan Zhang and Qianqian Dong
Materials 2020, 13(7), 1607; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13071607 - 01 Apr 2020
Cited by 9 | Viewed by 2143
Abstract
The crack propagation and failure of 3D-printed samples with prefabricated K–S fissures (a kinked fissure and a straight fissure) were observed under uniaxial compression, and the strain and displacement of the sample surface were quantified by the digital image correlation (DIC) method. The [...] Read more.
The crack propagation and failure of 3D-printed samples with prefabricated K–S fissures (a kinked fissure and a straight fissure) were observed under uniaxial compression, and the strain and displacement of the sample surface were quantified by the digital image correlation (DIC) method. The experimental results show that the branch inclination angle of the kinked fissure is an important factor affecting the crack initial position, and the evolution of the strain field during the failure process of the sample can better reflect the cracking law of the internal fissures. Furthermore, two coalescence modes are classified: Mode I is a tension–shear composite failure formed by the penetration of the tension–shear composite crack; Mode II is a tensile failure that penetrates the whole samples during the failure process without rock bridge damage. In addition, the numerical simulation results were well consistent with the cracking and failure modes. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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9 pages, 944 KiB  
Article
Effect of Slope Grain on Mechanical Properties of Different Wood Species
by Przemysław Mania, Filip Siuda and Edward Roszyk
Materials 2020, 13(7), 1503; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13071503 - 25 Mar 2020
Cited by 10 | Viewed by 2825
Abstract
The aim of the presented study is to determine the relationship between mechanical parameters of selected wood species (Carya sp., Fagus sylvatica L., Acer platanoides L., Fraxinus excelsior L., Ulmus minor Mill.) used for the production of hand tools and drumsticks and [...] Read more.
The aim of the presented study is to determine the relationship between mechanical parameters of selected wood species (Carya sp., Fagus sylvatica L., Acer platanoides L., Fraxinus excelsior L., Ulmus minor Mill.) used for the production of hand tools and drumsticks and the grain deviation angle from the rectilinear pattern. Modulus of rupture (MOR), modulus of elasticity (MOE), elastic strain and work to maximum load (WML) in the three-point bending test were determined. The results obtained show that the values of all the mechanical parameters measured for hickory wood are higher than those obtained for domestic species. As the grain deviation angle from parallelism increases, the mechanical properties of all analyzed wood species decrease. The greatest influence of grain deviation angle on mechanical parameters was recorded for the work to maximum load values. Full article
(This article belongs to the Special Issue Mechanical Properties of Technical Materials)
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