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Selected Papers from Experimental Stress Analysis 2020

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 30035

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Dr. Radim Kocich

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Regional Materials Technology and Science Centre (RMTSC), Faculty of Materials Science and Technology, VŠB—Technical University of Ostrava, Ostrava, Czech Republic
Interests: materials forming; severe plastic deformation; non-ferrous metals; composites; thermomechanical processing; numerical simulations
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Dr. Lenka Kunčická

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Institut of Physics of Materials, Czech Academy of Sciences, Brno, Czech Republic
Interests: thermo-mechanical treatment; non-ferrous metals; structure and stress analyses; numerical methods
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Special Issue Information

Dear Colleagues,

The Experimental Stress Analysis 2020 is organized with the support of Czech Society for Mechanics, Expert Group of Experimental Mechanics, and will be held in Sobotin, Czech Republic, 19–22 October 2020. This international conference is mainly focused on sharing professional experience and discussing new theoretical and practical findings. The objective of the conference is to identify the current situation, exchange experiences, and establish and strengthen relationships between universities, companies, and scientists from the field of experimental mechanics in mechanical and civil engineering.

The topics of the conference include experimental research on materials and structures subjected to mechanical, thermal–mechanical, or dynamic loading, including damage, fatigue, and fracture analysis. Special attention shall be paid to advances in optical methods and other nondestructive testing techniques (DIC, DIV, ESPI, photoelasticity, X-ray and neutron diffraction, etc.) and sensor technology (strain gages, optical fiber applications, accelerometers, etc.). The importance of modern experimental technique application in research and developments of nanomaterials, nanostructures, composites, smart materials, and structures and materials for additive manufacturing will be addressed during the conference.

This Special Issue will select excellent papers from Experimental Stress Analysis 2020. Original research articles, as well as review articles, are welcome in this Special Issue. Potential topics include:

Development of experimental methods in mechanics;
Development of experimental methods in biomechanics;
New methods and applications of deformation and stress analysis in mechanical structures;
New methods and applications of deformation and stress analysis in civil and other structures;
Experiment as a tool for the verification of analytical and numerical methods;
Experimental research and prediction of strength, life and operational reliability of structures and devices;
Monitoring of operational loadings and operational states of structures and devices;
Mechanics of advanced materials, composites and additive manufacturing materials.

Assoc. Prof. Radim Kocich
Dr. Lenka Kunčická
Guest Editors

Manuscript Submission Information

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

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. 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
Functional properties
Metallic systems
Mechanical processing
Structural phenomena

Published Papers (13 papers)

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Editorial

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2 pages, 197 KiB

Open AccessEditorial

Special Issue: Selected Papers from Experimental Stress Analysis 2020

by Lenka Kunčická, Radim Halama and Martin Fusek

Materials 2021, 14(5), 1136; https://doi.org/10.3390/ma14051136 - 28 Feb 2021

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(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

Research

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16 pages, 6733 KiB

Open AccessArticle

Damage Analysis of Composite CFRP Tubes Using Acoustic Emission Monitoring and Pattern Recognition Approach

by Michal Šofer, Jakub Cienciala, Martin Fusek, Pavel Pavlíček and Richard Moravec

Materials 2021, 14(4), 786; https://doi.org/10.3390/ma14040786 - 07 Feb 2021

Cited by 37 | Viewed by 2612

Abstract

The acoustic emission method has been adopted for detection of damage mechanisms in carbon-fiber-reinforced polymer composite tubes during the three-point bending test. The damage evolution process of the individual samples has been monitored using the acoustic emission method, which is one of the non-destructive methods. The obtained data were then subjected to a two-step technique, which combines the unsupervised pattern recognition approach utilizing the short-time frequency spectra with the boundary curve enabling the already clustered data to be additionally filtered. The boundary curve identification has been carried out on the basis of preliminary tensile tests of the carbon fiber sheafs, where, by overlapping the force versus time dependency by the acoustic emission activity versus time dependency, it was possible to identify the boundary which will separate the signals originating from the fiber break from unwanted secondary sources. The application of the presented two-step method resulted in the identification of the failure mechanisms such as matrix cracking, fiber break, decohesion, and debonding. Besides the comparison of the results with already published research papers, the study presents the comprehensive parametric acoustic emission signal analysis of the individual clusters. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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14 pages, 4838 KiB

Open AccessArticle

Parameters Identification of the Anand Material Model for 3D Printed Structures

by Martin Fusek, Zbyněk Paška, Jaroslav Rojíček and František Fojtík

Materials 2021, 14(3), 587; https://doi.org/10.3390/ma14030587 - 27 Jan 2021

Cited by 5 | Viewed by 1808

Abstract

Currently, there is an increasing use of machine parts manufactured using 3D printing technology. For the numerical prediction of the behavior of such printed parts, it is necessary to choose a suitable material model and the corresponding material parameters. This paper focuses on the determination of material parameters of the Anand material model for acrylonitrile butadiene styrene (ABS-M30) material. Material parameters were determined using the genetic algorithm (GA) method using finite element method (FEM) calculations. The FEM simulations were subsequently adjusted to experimental tests carried out to achieve the possible best agreement. Several experimental tensile and indentation tests were performed. The tests were set up in such a way that the relaxation and creep behaviors were at least partially captured. Experimental tests were performed at temperatures of 23 °C, 44 °C, 60 °C, and 80 °C. The results obtained suggest that the Anand material model can also be used for ABS-M30 plastic material, but only if the goal is not to detect anisotropic behavior. Future work will focus on the search for a suitable material model that would be able to capture the anisotropic behavior of printed plastic materials. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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19 pages, 11135 KiB

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Application of the Pulse Infrared Thermography Method for Nondestructive Evaluation of Composite Aircraft Adhesive Joints

by Tomáš Kostroun and Milan Dvořák

Materials 2021, 14(3), 533; https://doi.org/10.3390/ma14030533 - 22 Jan 2021

Cited by 11 | Viewed by 3412

Abstract

In this article, we examine the possibility of using active infrared thermography as a nontraditional, nondestructive evaluation method (NDE) for the testing of adhesive joints. Attention was focused on the load-bearing wing structure and related structural joints, specifically the adhesive joints of the wing spar caps and the skins on the wing demonstrator of a small sport aircraft made mainly of a carbon composite. The Pulse Thermography (PT) method, using flash lamps for optical excitation, was tested. The Modified Differential Absolute Contrast (MDAC) method was used to process the measured data to reduce the effect of the heat source’s inhomogeneity and surface emissivity. This method demonstrated a very high ability to detect defects in the adhesive joints. The achieved results are easy to interpret and use for both qualitative and quantitative evaluation of the adhesive joints of thin composite parts. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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13 pages, 3564 KiB

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Effect of the Test Procedure and Thermoplastic Composite Resin Type on the Curved Beam Strength

by Robin Hron, Martin Kadlec and Roman Růžek

Materials 2021, 14(2), 352; https://doi.org/10.3390/ma14020352 - 12 Jan 2021

Cited by 14 | Viewed by 2134

Abstract

The application of thermoplastic composites (TPCs) in aircraft construction is growing. This paper presents a study of the effect of an applied methodology (standards) on out-of-plane interlaminar strength characterization. Additionally, the mechanical behaviour of three carbon fibre-reinforced thermoplastic composites was compared using the curved beam strength test. Data evaluated using different standards gave statistically significantly different results. The study also showed that the relatively new polyaryletherketone (PAEK) composite had significantly better performance than the older and commonly used polyphenylensulfid (PPS) and polyetheretherketone (PEEK). Furthermore, considering the lower processing temperature of PAEK than PEEK, the former material has good potential to be used in serial aerospace production. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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27 pages, 11265 KiB

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Design of a Unique Device for Residual Stresses Quantification by the Drilling Method Combining the PhotoStress and Digital Image Correlation

by Miroslav Pástor, Martin Hagara, Ivan Virgala, Adam Kal’avský, Alžbeta Sapietová and Lenka Hagarová

Materials 2021, 14(2), 314; https://doi.org/10.3390/ma14020314 - 09 Jan 2021

Cited by 9 | Viewed by 2146

Abstract

This paper presents a uniquely designed device combining the hole-drilling technique with two optical systems based on the PhotoStress and digital image correlation (DIC) method, where the digital image correlation system moves with the cutting tool. The authors aimed to verify whether the accuracy of the drilled hole according to ASTM E837-13a standard and the positioning accuracy of the device were sufficient to achieve accurate results. The experimental testing was performed on a thin specimen made from strain sensitive coating PS-1D, which allowed comparison of the results obtained by both methods. Although application of the PhotoStress method allows analysis of the strains at the edge of the cut hole, it requires a lot of experimenter’s practical skills to assess the results correctly. On the other hand, the DIC method allows digital processing of the measured data. However, the problem is not only to determine the data at the edge of the hole, the results also significantly depend on the smoothing levels used. The quantitative comparison of the results obtained was performed using finite element analysis. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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19 pages, 9974 KiB

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Utilization of the Validated Windshield Material Model in Simulation of Tram to Pedestrian Collision

by Stanislav Špirk, Jan Špička, Jan Vychytil, Michal Křížek and Adam Stehlík

Materials 2021, 14(2), 265; https://doi.org/10.3390/ma14020265 - 07 Jan 2021

Cited by 6 | Viewed by 1782

Abstract

The rail industry has been significantly affected by the passive safety technology in the last few years. The tram front-end design must fulfill the new requirements for pedestrian passive safety performance in the near future. The requirements are connected with a newly prepared technical guide “Tramway front end design” prepared by Technical Agency for ropeways and Guided Transport Systems. This paper describes research connected with new tram front-end design safe for pedestrians. The brief description of collision scenario and used human-body model “Virthuman” is provided. The numerical simulations (from field of passive safety) are supported by experiments. The interesting part is the numerical model of the tram windshield experimentally validated here. The results of simulations are discussed at the end of paper. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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16 pages, 10625 KiB

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Modeling and Testing of Flexible Structures with Selected Planar Patterns Used in Biomedical Applications

by Pavel Marsalek, Martin Sotola, David Rybansky, Vojtech Repa, Radim Halama, Martin Fusek and Jiri Prokop

Materials 2021, 14(1), 140; https://doi.org/10.3390/ma14010140 - 30 Dec 2020

Cited by 19 | Viewed by 2853

Abstract

Flexible structures (FS) are thin shells with a pattern of holes. The stiffness of the structure in the normal direction is reduced by the shape of gaps rather than by the choice of the material based on mechanical properties such as Young’s modulus. This paper presents virtual prototyping of 3D printed flexible structures with selected planar patterns using laboratory testing and computer modeling. The objective of this work is to develop a non-linear computational model evaluating the structure’s stiffness and its experimental verification; in addition, we aimed to identify the best of the proposed patterns with respect to its stiffness: load-bearing capacity ratio. Following validation, the validated computational model is used for a parametric study of selected patterns. Nylon—Polyamide 12—was chosen for the purposes of this study as an appropriate flexible material suitable for 3D printing. At the end of the work, a computational model of the selected structure with modeling of load-bearing capacity is presented. The obtained results can be used in the design of external biomedical applications such as orthoses, prostheses, cranial remoulding helmets padding, or a new type of adaptive cushions. This paper is an extension of the conference paper: “Modeling and Testing of 3D Printed Flexible Structures with Three-pointed Star Pattern Used in Biomedical Applications” by authors Repa et al. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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14 pages, 5186 KiB

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On the Weldability of Thick P355NL1 Pressure Vessel Steel Plates Using Laser Welding

by Jiří Čapek, Karel Trojan, Jan Kec, Ivo Černý, Nikolaj Ganev and Stanislav Němeček

Materials 2021, 14(1), 131; https://doi.org/10.3390/ma14010131 - 30 Dec 2020

Cited by 9 | Viewed by 2168

Abstract

Pipeline transport uses millions of kilometers of pipes worldwide to transport liquid or gas over long distances to the point of consumption. High demands are placed, especially on the transport of hazardous substances under high pressure (gas, oil, etc.). Mostly seamless steel pipes of various diameters are used, but their production is expensive. The use of laser-welded pipes could significantly reduce the cost of building new pipelines. However, sufficient mechanical properties need to be ensured for welded pipes to meet stringent requirements. Therefore, laser-welded 10 mm thick pressure vessel steel plates were subjected to various mechanical tests, including high-cycle fatigue tests. Furthermore, the microstructural parameters and the state of residual stresses were determined using X-ray and neutron diffraction, which could affect fatigue life, too. The critical areas for possible crack initialization, especially in and near the heat-affected zone, were found using different tests. The presented results outline the promising application potential of laser welding for the production of pipes for high-pressure pipelines. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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19 pages, 23491 KiB

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Validation of Multiaxial Fatigue Strength Criteria on Specimens from Structural Steel in the High-Cycle Fatigue Region

by František Fojtík, Jan Papuga, Martin Fusek and Radim Halama

Materials 2021, 14(1), 116; https://doi.org/10.3390/ma14010116 - 29 Dec 2020

Cited by 5 | Viewed by 1799

Abstract

The paper describes results of fatigue strength estimates by selected multiaxial fatigue strength criteria in the region of high-cycle fatigue, and compares them with own experimental results obtained on hollow specimens made from ČSN 41 1523 structural steel. The specimens were loaded by various combinations of load channels comprising push–pull, torsion, bending and inner and outer pressures. The prediction methods were validated on fatigue strengths at seven different numbers of cycles spanning from 100,000 to 10,000,000 cycles. No substantial deviation of results based on the selected lifetime was observed. The PCRN method and the QCP method provide best results compared with other assessed methods. The results of the MMP criterion that allows users to evaluate the multiaxial fatigue loading quickly are also of interest because the method provides results only slightly worse than the two best performing solutions. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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15 pages, 7059 KiB

Open AccessArticle

Billet Straightening by Three-Point Bending and Its Automation

by Radim Halama, Jan Sikora, Martin Fusek, Jaromír Mec, Jana Bartecká and Renata Wagnerová

Materials 2021, 14(1), 90; https://doi.org/10.3390/ma14010090 - 28 Dec 2020

Cited by 5 | Viewed by 2285

Abstract

This paper presents the current results of cooperation focused on automatic billet straightening machine development. First, an experimental study of three-point bending realized on small specimens is presented to explain the basic ideas of the straightening. Then, the main regimes of straightening and the algorithm itself are described together. Subsequent finite element simulations of operational experiments show the applicability of the developed theory. The significance of material parameters estimation is depicted in this work. At least four parameters have to be properly determined for a new material in the straightening process. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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15 pages, 13017 KiB

Open AccessArticle

Monotonic Tension-Torsion Experiments and FE Modeling on Notched Specimens Produced by SLM Technology from SS316L

by Michal Kořínek, Radim Halama, František Fojtík, Marek Pagáč, Jiří Krček, David Krzikalla, Radim Kocich and Lenka Kunčická

Materials 2021, 14(1), 33; https://doi.org/10.3390/ma14010033 - 23 Dec 2020

Cited by 18 | Viewed by 2437

Abstract

The aim of this work was to monitor the mechanical behavior of 316L stainless steel produced by 3D printing in the vertical direction. The material was tested in the “as printed” state. Digital Image Correlation measurements were used for 4 types of notched specimens. The behavior of these specimens under monotonic loading was investigated in two loading paths: tension and torsion. Based on the experimental data, two yield criteria were used in the finite element analyses. Von Mises criterion and Hill criterion were applied, together with the nonlinear isotropic hardening rule of Voce. Subsequently, the load-deformation responses of simulations and experiments were compared. Results of the Hill criterion show better correlation with experimental data. The numerical study shows that taking into account the difference in yield stress in the horizontal direction of printing plays a crucial role for modeling of notched geometries loaded in the vertical direction of printing. Ductility of 3D printed specimens in the “as printed” state is also compared with 3D printed machined specimens and specimens produced by conventional methods. “As printed” specimens have 2/3 lower ductility than specimens produced by a conventional production method. Machining of “as printed” specimens does not affect the yield stress, but a significant reduction of ductility was observed due to microcracks arising from the pores as a microscopic surface study showed. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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7 pages, 3504 KiB

Open AccessArticle

High-Resolution Strain/Stress Measurements by Three-Axis Neutron Diffractometer

by Pavol Mikula, Vasyl Ryukhtin, Jan Šaroun and Pavel Strunz

Materials 2020, 13(23), 5449; https://doi.org/10.3390/ma13235449 - 30 Nov 2020

Cited by 4 | Viewed by 1650

Abstract

Resolution properties of the unconventional high-resolution neutron diffraction three-axis setup for strain/stress measurements of large bulk polycrystalline samples are presented. Contrary to the conventional two-axis setups, in this case, the strain measurement on a sample situated on the second axis is carried out by rocking the bent perfect crystal (BPC) analyzer situated on the third axis of the diffractometer. Thus, the so-called rocking curve provides the sample diffraction profile. The neutron signal coming from the analyzer is registered by a point detector. This new setup provides a considerably higher resolution (at least by a factor of 5), which however, requires a much longer measurement time. The high-resolution neutron diffraction setting can be effectively used, namely, for bulk gauge volumes up to several cubic centimeters, and for plastic deformation studies on the basis of the analysis of diffraction line profiles, thus providing average values of microstructure characteristics over the irradiated gauge volume. Full article

(This article belongs to the Special Issue Selected Papers from Experimental Stress Analysis 2020)

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