https://www.fracturae.com/index.php/fis/issue/feed Frattura ed Integrità Strutturale 2020-09-18T07:56:26+00:00 Francesco Iacoviello iacoviello@unicas.it Open Journal Systems <p>Frattura ed Integrità Strutturale (Fracture and Structural Integrity) is the International Journal of the Italian Group of Fracture (ISSN 1971-8993). It is an open-access journal published online every three months (January, April, July, October).&nbsp;<br>Frattura ed Integrità Strutturale encompasses the broad topic of structural integrity, which is based on the mechanics of fatigue and fracture and is concerned with the reliability and effectiveness of structural components. The aim of the Journal is to promote works and researches on fracture phenomena, as well as the development of new materials and new standards for structural integrity assessment. The Journal is interdisciplinary and accepts contributions from engineers, metallurgists, materials scientists, physicists, chemists, and mathematicians.</p> <p><strong>More details:</strong></p> <p>- The Journal is financially supported by the <a href="https://www.gruppofrattura.it/">Italian Group of Fracture (IGF)</a> and by crowdfunding. It is completely free of charge both for readers and for authors. Neither processing charges nor submission charges are required.</p> <p>- Papers can be published only after a preliminary plagiarism/autoplagiarism check and a blind peer-review process (two reviewers, at least). More than one reviewing rounds are possible.</p> <p>- The Journal is well indexed (e.g., Scopus, since 2012, and WoS, since 2015).</p> <p>- All the papers are published with their Visual Abstracts (2 minutes max videos with the "cores" of the papers). All the Visual Abstracts are also available in a dedicated <a href="https://www.youtube.com/channel/UC3Ob2GNW8i0phNiiKjEVv0A">YouTube channel</a>.&nbsp; All the issues are also published in a browsable version. All the issue in browsable version are also published in a dedicated website (<a href="https://sites.google.com/view/fisbrowasable">LINK</a>).</p> https://www.fracturae.com/index.php/fis/article/view/2925 An innovative fixture for testing the crashworthiness of composite materials 2020-09-18T07:56:26+00:00 Lorenzo Vigna lorenzo_vigna@polito.it Iman Babaei iman.babaei@polito.it Ravin Garg ravin.garg@polito.it Giovanni Belingardi giovanni.belingardi@polito.it Davide Salvatore Paolino davide.paolino@polito.it Andrea Calzolari andrea_calzolari@instron.com Giuseppe Galizia giuseppe_galizia@instron.com <p>Despite the growing diffusion of composite materials in automotive and aerospace sectors, a standard procedure for testing their crashworthiness has not been developed yet. At present, the international standards for testing composite materials under impact conditions are not adequate to test their crush behavior.</p> <p>In this paper, a procedure for measuring the energy absorption due to the compressive crushing of a composite flat specimen, along its mid plane, is proposed. The experimental setup requires a fixture to hold the specimen and to avoid its buckling and an instrumented drop weight tower to obtain the force-displacement curves with the aim of calculating the Specific Energy Absorption.</p> <p>The paper will describe the adopted test procedure and some of the features of the newly developed experimental setup. The effectiveness of the procedure is demonstrated by testing several glass fiber-epoxy specimens under different impact energies.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2924 Analytical solution for statif bending analyses of functionally grades plates with porosities 2020-09-12T17:13:01+00:00 Slimane MERDACI slimanem2016@gmail.com <p><span style="text-decoration: underline;">The paper examines a static bending of porous functional plates (FGP) and rectangular plate solutions, based on an underlying high-order shear deformation theory. The proposed high-order shear deformation theory, as opposed to other theories, includes four unknowns. For this reason, a new shear strain function is considered. The technique of Navier is used in closed-form FGP solutions. Results of deflections and stresses are presented for simply supported border conditions. Current figures are contrasted with the non-poreous plate deflecting solutions and the literature's stresses. Effects of different parameters, including thickness, gradient index and porosity of FGM plates, are discussed.</span></p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2921 Evaluation of the survivability of CFRP honeycomb-cored panels in compression after impact tests 2020-09-10T09:28:15+00:00 Oleg Staroverov cem_staroverov@mail.ru Elena Strungar cem.spaskova@mail.ru Valery Wildemann wildemann@pstu.ru <p>This paper is oriented to the experimental research of the mechanics of the CFRP sandwich plates, glass and carbon fiber sample panels with a large-cell honeycomb core. The method for testing polymer composite sample plates in compression after impact (CAI) tests with joint use of a testing machine and a video system for deformation field registration was tested. Analysis of the experimental data obtained highlighted the impactive sensitivity zone for the test specimens. A quantitative assessment of the load-bearing capacity of glass and carbon fiber sample panels in CAI tests with the different levels of the drop weight impact energy was performed. Photos of samples after impact have been provided.</p> <p>Vic-3D non-contact three-dimensional digital optical system was used to register the displacement and deformation fields on the surface of the samples. The video system was used to evaluate various damage mechanisms, including matrix cracking, delaminations, and rupture of the damaged fibers. The paper studied the evolution of non-homogeneous deformation fields on the surface of the composite samples during the post-impact compression tests and analyzed the configuration of non-homogeneous deformation fields.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2919 Development of mesh turbine prototype equipped with the jet control system 2020-09-09T14:40:36+00:00 Yu.A. Sazonov mikhal.mokhov@mail.ru Mikhail Mokhov mikhal.mokhov@mail.ru I.V. Gryaznova mikhal.mokhov@mail.ru V.V. Voronova mikhal.mokhov@mail.ru Kh.A. Tumanyan mikhal.mokhov@mail.ru M.A. Frankov mikhal.mokhov@mail.ru V.A. Mun mikhal.mokhov@mail.ru N.N. Balaka mikhal.mokhov@mail.ru <p>In the conditions of instability on the oil and gas market, it is necessary to intensify the exploratory scientific research for the development of advanced and inexpensive pumping and compressor equipment intended for more efficient hydrocarbon production. A new gas compression technology has been developed and patented using a jet compressor unit when the ejector is switched on in a cyclic mode. On-off cycling of the ejector instead of its continuous operation makes it possible to increase the gas compression ratio multiply. To increase the energy efficiency of the jet compressor unit, the technology of energy recovery with the application of a special turbine having the mesh structure of the flow part has been proposed and patented. Research and development works, on the way to the development of intelligent turbines and intelligent compressor units, have been carried out.3D-models with the application of the SOLIDWORKS 3D CAD-system have been developed. The development of efficient and cheaper compressor units will make it possible to solve current production problems when extracting hydrocarbons in complicated conditions, as well as at the late stage of oil and gas fields’ development. Certain results of scientific research performed can be used in other production branches, including energy, transport and robotics.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2918 Fatigue Loading Characteristic for the Composite Steel-Concrete Beams 2020-09-10T03:36:36+00:00 Ahmed I.Hassanin ahmed_eng8028@yahoo.com Hesham M. Fawzy hmshaban@eng.zu.edu.eg Ahmed I. Elsheikh ahmed.elsheikh@liverpool.ac.uk <p>During the past few decades, composite beams (steel I beam and concrete slab) have had a wide range of uses, particularly in bridge construction. This is due to its relatively low economic cost compared to individual steel structures or reinforced concrete structures. This type of bridges in particular and many similar industrial structures in general are repeatedly subjected to fatigue loads, and that is frequently, as a result of the vehicles passing on these bridges or the vibrations caused by the machines in the industrial facilities. It has been observed during the successive studies that they have been interested in studying this problem that it is concerned with the external structural behavior of these beams &nbsp;such as a load –deflection relation, observing the cracks appearing during the failure stage and the strain in the steel and concrete flanges. Hence, in this study we have focused on several factors affecting mode of failure of these beams under the fatigue loads, and the common element in all stages of failure was the shear stud, specifically the welding collar at the base of this stud as it is a structurally weak region.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2917 Investigation of the effect of impact load on concrete-filled steel tube columns under fire 2020-09-08T18:50:01+00:00 Ali Golsoorat Pahlaviani Ali.golsoorat_pahlaviani@iauctb.ac.ir Ali Mohammad Rousta arousta@yu.ac.ir Peyman Beiranvand peyman51471366@gmail.com <p>Concrete-filled steel tube (CFST) columns are increasingly used in the construction of high-rise buildings which require high strength and large working space especially at lower stories. As compared to reinforced concrete columns, existence of the exterior steel tube not only bears a portion of axial load but also most importantly provides confinement to the infill concrete.with the confinement provided by the steel tube, axial strength of the infill concrete can be largely enhanced.this paper presents the investigation effect of impact load on concrete-filled steel tube columns under fire by numerical simulations using ABAQUS software.the results indicate that the CFST sections with larger confinement factor ξ=1.23 behaved in a very ductile manner under lateral impact. And the sections with smaller confinement factor ξ=0.44&nbsp; generally behaved in a brittle mechanism.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2915 Assessment of the strength reliability of high-temperature heat exchangers with long service life at the design stage 2020-09-08T12:48:03+00:00 Vyacheslav Popov quazzar.89@mail.ru <p>The article describes a method for assessing the strength reliability of high-temperature heat exchangers with service life of several tens of thousands of hours at the design stage, when there is not enough statistical data on the operating time of elements and material properties. The method shows, how to determine the missing coefficients of variation for calculating reliability and build the function of the probability of failure-free operation, considering the change of the properties of the structural material over time. The method of visualizing the distribution of zones, both satisfying and not satisfying reliability criteria at the nodes of any finite element model, is also described.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2914 Experimental and numerical study of heat transfer in friction stir spot welded aluminium alloys 2020-09-07T01:18:48+00:00 Saadat Ali Rizvi alisaadat@rediffmail.com <p>In this work, die steel tool is used to join the two aluminum sheet together on a drilling machine. For this, a cylindrical shaped tool was manufactured. This tool is then clamped into the drilling machine tool post. This rotating tool is then inserted into the workpiece thus generating heat due to friction. The plastic deformation of the aluminum starts near the vicinity of tool impression. The tool transferred the soften material from tip to plunger. The plunger is in contact with the Aluminum sheet. Soften material is forged on the sheet with the help of plunger and thus creating a solid phase joint between the Aluminum sheets.Three-dimensional numerical modelings were performed on Ansys software. A three-dimensional heat transfer model is used to solve the problem of friction stir welding. This model is solved by using the energy conservation equation. This model involves the heat generated at the interface of the workpiece and the rotating tool. The steady-state heat transfer equation was used to study the problem. The numerically computed and the measured value is compared to validate the results</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2913 Experimental Characterization of a New Sustainable Sand Concrete of Oued El-Ratm (Algeria) in Aggressive areas 2020-09-07T04:44:35+00:00 Meriem Fakhreddine Bouali m.bouali@univ-soukahras.dz Mohammed Mani m.mani39@gmail.com Abdelouahed Kriker a_kriker@yahoo.fr Abdelkader Hima Abdelkader-hima@univ-eloued.dz <p>The scarcity of building materials and the shortage of coarse aggregates which represents the main component of concrete is a problem in the most third world countries, especially in the vast desert areas in Algeria. &nbsp;In desert conditions where the environment suffers from the phenomenon of rising water and aggressive soil; the evaluation of existing abundant Sand Dune and its compensation for naturel Sand could be a very good economic solution. Several researches at the local and the global levels confirm that Sand Dune can be exploited in concrete after a granular correction. In this paper, a new Sand resource (Oued El-Ratm, El Oued-Algeria) is proposed as an alternative of natural Sand to perform a Sand Concrete. The findings of this experimental study show that the Sand Concrete based on this new resource of sand dune of the Algerian desert has a good resistance when used in the ambient Saharan aggressive conditions.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2912 Controlling of Strip Footing Failures Rested on Swelling Soil by Geofoam 2020-09-06T15:36:19+00:00 Adel Diab a_fd2561@yahoo.com <p>Swelling soils are considered a highly problematic soil due to the volume change actions. The cyclic heave and settlement of expansive soils could be the main reason for considerable damages to the structures, roads, and highways. Many available methodologies are followed to combat these problems of the swelling soils. This paper presents the results of experimental research which performed to show the efficiency of the (EPS) geofoam layers system as a new technique for controlling the upward movement of structures over swelling soils. The performance of the geofoam layer under the footing at different positions is studied. Geofoam layer has twoconfigurations; flat and ribbed cross-section. Different densities and thicknesses of geofoam are considered in the study. Sand with different thicknesses is placed above swelling soil as a partial replacement under the footing. &nbsp;Their effectiveness of the performance is analyzed and discussed. Test results show a noticeable reduction in heave as a result of using the ribbed geofoam layer and partial replacement by sand above the swelling soil.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2911 Proposed Design Criteria for column strengthened using ‎steel angles and strips 2020-09-06T10:12:35+00:00 Ahmed Ismail a.es.gabr@gmail.com <p>This paper presents an analytical model to construct the interaction diagrams (normal force and moment) for the RC column strengthened using steel jacket technique. The proposed model is defined using strain distribution block by determining the location of the neutral axis in the concrete section block. The proposed design formula is verified using experimental results performed by previous researches and numerical models using nonlinear commercial program ANSYS. The factors affecting the capacity of the strengthened column are taken into consideration such as the amount of loads resisted by the steel cage, steel strips spacing, and the effect of concrete confinement. The results of the proposed model are in good agreement with the results from the experimental and numerical work used in verification. A practical design formula is conducted for strengthened columns subjected to eccentric loads.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2910 Delamination buckling of FRP strips in strengthened structural RC beams and masonry walls 2020-09-05T14:57:05+00:00 Samir Khatir Samir.khatir@ugent.be <p>This paper deals with delamination buckling of fiber reinforced polymer (FRP) strips glued to reinforced concrete (RC) beams or to heterogeneous material as masonry.</p> <p>In the field of rehabilitation of existing civil structures, the strengthening using composite materials is becoming a frequent technique although many points have not yet been clarified. The delamination of FRP strips’ layer can be often the cause of loss of the strength capacity in strengthened elements. In general, the delamination is due to loss of adhesion of FRP on the adherent material under tensile loading. This type of delamination foresees a slip of FRP strip and development of fracture energy until the detachment.</p> <p>Delamination buckling of FRP strips is instead due to compression loading. Although the FRP is usually adopted to improve the tensile capacity, in civil structural elements subjected to cycle loading, as RC frames in seismic areas or masonry cross walls, the loading is cyclic and the strengthening of FRP strips may be subjected to compressive stresses with separation of the layer from the adherent element. This type of delamination may significantly influence the strength, stiffness and stability. In this paper experiments on the strengthening of RC beams and masonry walls with GlassFRP strips are shown; further, analytical and numerical analysis have been developed to study this mechanism of delamination which too often has been missed in the design of strengthening with FRP strips.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2909 Numerical analysis of the influence of maximum residual thermal stresses on the intensity factor between the matrix and particle interfaces in metal matrix composite 2020-09-02T21:50:06+00:00 Taieb Nehari nehari1976@gmail.com Kaddour Bahram Kadero_7@hotmail.com Driss Nehari nehari_dr@yahoo.fr Abdelfatah Marni Sandid abdelfatahsandid@hotmail.com <p>A critical problem in the application of metal matrix composites is the presence of high residual thermal stresses induced during the development process. These thermally induced stresses are generally detrimental to the service life of this type of composite. This article discusses the influence of maximum residual stresses on the intensity factor. The results interpreted in terms of damage, allowed us to identify the risk zones; characterized by a significant level of maximum residual stresses (S<sub>11Max</sub>, S<sub>22Max</sub>, S<sub>33Max</sub>), namely the particle/Matrix interface.</p> <p>The results also show that the loading conditions and the inter-distance between matrix and particle with two interfacial cracks have an important effect on max residual stresses and stress intensity factors.</p> <div id="kpm-root" class="kpm_LTR notranslate" translate="no">&nbsp;</div> Copyright (c) 2020 Taieb Nehari, Kaddour Bahram, Driss Nehari, Abdelfatah Marni Sandid https://www.fracturae.com/index.php/fis/article/view/2908 Mechanical properties of the most common European woods: a literature review 2020-08-28T09:30:06+00:00 Beatrice Bartolucci bartolucci.1710376@studenti.uniroma1.it Andrea De Rosa andrea.derosa8@studenti.unina.it Chiara Bertolin chiara.bertolin@ntnu.no Filippo Berto filippo.berto@ntnu.no Francesco Penta penta@unina.it Anna Maria Siani annamaria.siani@uniroma1.it <p>Wood is an orthotropic material used since ancient time. A literature research about the mechanical properties of density, fracture toughness, modulus of elasticity, and Poisson’s ratio has been done to have a broader view on the subject. The publications relating to the topic were found through the two search engines Scopus and Google Scholar that have yielded several papers, including articles and book sections. In general, there is no standardization on the method of analysis carried out on wood, underlining the great difficulty in studying this complex material. The parameter of density has a great variability and needs a deeper investigation; fracture toughness is not always available in literature, not even in the different directions of the wood sample. Interesting is the modulus of elasticity, which provides a correlation with density, especially in longitudinal section but, again, it needs to be studied in detail. The parameter of Poisson’s ratio is provided as single values in three different directions, but mainly for softwood. All the parameters require a more in-depth study for both softwood and hardwood. Furthermore, the type of analysis, whether experimental or modelling, needs to be standardized to have more comparable results.</p> Copyright (c) 2020 Beatrice Bartolucci , Andrea De Rosa , Chiara Bertolin, Filippo Berto, Francesco Penta, Anna Maria Siani https://www.fracturae.com/index.php/fis/article/view/2907 On the effect of stiffness/softness and morphology of interphase phase on the effective elastic properties of three-phase composite material 2020-08-28T02:35:05+00:00 fedaoui kamel kamel.fedaoui@umc.edu.dz Lazhar Baroura barouralaz@yahoo.fr Karim Arar arar_karim@yahoo.fr Hichem Amrani amranihichem78@hotmail.fr Mohamed said boutaani poutasfr@yahoo.fr <p>In the present study, Composite material consisting of an elastic homogeneous isotropic matrix in which are embedded coated elastic isotropic inclusions, widely used in many applications is investigate by homogenization approach coupled to the finite elements method. A finite element model is proposed to predict the Young and Shear modulus of the three-phase composite containing spherical inclusions surrounded by a spherical or ellipsoid interphase layer. Three cases of particles volume fractions and interphase was considered with addition of two interphase morphology. Young modulus of interphase region was varied from soft to hard than the matrix properties. We note that interphase morphology and properties plays an important role in the elastic properties of composite with increasing the volume fraction of inclusions and interphase. The results were compared to the first order bounds Voigt and Reuss, and the mean field homogenization techniques. A sensitive study of the effect of mesh density on the results of the von Mises stresses and elastic properties has been made.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2906 Biochar-based cement pastes and mortars with enhanced mechanical properties 2020-08-28T07:40:11+00:00 Alice Sirico alice.sirico@unipr.it Patrizia Bernardi patrizia.bernardi@unipr.it Beatrice Belletti beatrice.belletti@unipr.it Alessio Malcevschi alessio.malcevschi@unipr.it Luciana Restuccia luciana.restuccia@polito.it Giuseppe Andrea Ferro ferro@polito.it Daniel Suarez-Riera daniel.suarez@polito.it <p>Nowadays, the environmental impact of cementitious material industry and more generally of building activities is matter of concern, especially in terms of their effects on climate change and consumption of natural resources. Within this context, the aim of this paper is the investigation of the role of biochar, a solid carbonaceous by-product material resulting from biomass pyrolysis/gasification of residual biomass, as a sustainable ingredient for the production of cementitious materials, combining carbon sink properties with enhanced mechanical properties. Although biochar is mainly investigated as agricultural amendment, there is also evidence that biochar may be a eco-friendly material to enhance the sustainable performance of cementitious materials. As outlined in literature, biochar can be used as filler to modify the nanogranular nature of cement matrix, or as substitute of clinker to reduce the emissions of greenhouse gases related to cement production. In this work, biochar is added as micro-nano particles in different cementitious composites, i.e. cement pastes and mortars, as a function of filler or partial substitute of cement. The main mechanical properties of biochar-based materials are then investigated to determine the optimal percentage of biochar addition.</p> Copyright (c) 2020 Alice Sirico, Patrizia Bernardi, Beatrice Belletti, Alessio Malcevschi, Luciana Restuccia, Giuseppe Andrea Ferro, Daniel Suarez-Riera https://www.fracturae.com/index.php/fis/article/view/2905 A Parametric Study Of Friction Stir Spot Welding (FSSW) For Polymer Materials Case Of High Density Polyethylene Sheets: Experimental And Numerical Study 2020-09-05T12:13:00+00:00 Djilali Benyerou djilali.benyerou@univ-mascara.dz El Bahri Ould Chikh b.ouldchikh@univ-mascara.dz Hadj Miloud Meddah hm.meddah@univ-mascara.dz Ali Benhamena ali.benhamena@univ-mascara.dz Habib Khellafi khellafi29@univ-mascara.dz Kaddour Hachelaf kaddour.hachellaf@univ-mascara.dz Abdellah Lounis lounis.abdallah@univ-mascara.dz <p>Friction stir spot welding (FSSW) is a very important part of conventional friction stir welding (FSW) which can be a replacement for riveted assemblies and resistance spot welding. This technique provides high quality joints compared to conventional welding processes. Friction stir spot welding (FSSW) is a new technology adopted to join various types of metals such as titanium, aluminum, magnesium. It is also used for welding polymer materials which are difficult to weld by the conventional welding process. In various industrial applications, high density polyethylene (HDPE) becomes the most used material. The parameters and mechanical properties of the welds are the major problems in the welding processes. In this paper, we have presented a contribution in finite element modeling of the friction stir spot welding process (FSSW) using Abaqus as a finite element solver. The objective of this paper is to study the HDPE plates resistance of stir spot welding joints (FSSW). First, we show the experimental tests results of high-density polyethylene (HDPE) plates assembled by friction stir spot welding (FSSW). Three-dimensional numerical modeling by the finite element method makes it possible to determine the best representation of the weld joint for a good prediction of its behavior. Comparison of the results shows that there is a good agreement between the numerical modeling predictions and the experimental results.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2904 Evaluation of rutting and fatigue behavior of modified asphalt binders with combinations of Nano-CuO, carbon nanotubes and Styrene-Butadiene-Styrene 2020-08-30T07:08:36+00:00 Hassan Latifi hassanlatifi3270@gmail.com Nahid Amini nahid.amini@srbiau.ac.ir <p>In this study, the changes in aging and rheological properties of pure and modified asphalt binder and mixture with Nano-CuO, carbon nanotubes (CNT) and Styrene-Butadiene-Styrene (SBS) in order to evaluate rutting and fatigue behavior were investigated. First, rotating thin-film oven and pressurized aging vessel tests were conducted. Then, some tests including rotational viscosity (RV), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), loaded-wheel tracking (LWT) and linear amplitude sweep (LAS) were carried out. Results of RV and DSR tests showed that the modified asphalt binders had more viscosity and aging resistance than pure asphalt binder. Fatigue life in LAS test for Nano-CuO-CNT-SBS modified was more than 1.7 times the PC-value (Control sample). It was found from MSCR test results that best improvement according to values of Jnr was for Nano-CuO-modified asphalt binder especially at higher temperatures because of its high specific heat capacity (Cp) as a PCM material. In addition, Nano-CuO-modified asphalt binder almost met the limitation of Jnr for very heavy traffic and heavy traffic loading at 64 °C and 70 °C, respectively. In summary, aging index (AI) and G*×sin(δ) confirmed each other, while G*×sin(δ) and fatigue life from LAS test were not accurately correlated.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2903 Fatigue Behavior of Metallic Components Obtained by Topology Optimization for Additive Manufacturing 2020-08-25T10:30:14+00:00 Felipe Fiorentin ffiorentin@inegi.up.pt Bernardo Oliveira bernardogarrett12@gmail.com João Pereira jcpereira@inegi.up.pt José Correia jacorreia@fe.up.pt Abilio M.P. de Jesus ajesus@fe.up.pt Filippo Berto filippo.berto@ntnu.no <p>The main goal of the present research is to propose an integrated methodology to address the fatigue performance of topology optimized components, produced by additive manufacturing. The main steps of the component design will be presented, specially the methods and parameters applied to the topology optimization and the post-smoothing process. The SIMP method was applied in order to obtain a lighter component and a suitable stiffness for the desired application. In addition, since residual stresses are intrinsic to every metallic additive manufacturing process, the influence of those stresses will be also analyzed. The Laser Powder Bed Fusion was numerically simulated aiming at evaluating the residual stresses the workpiece during the manufacturing process and to investigate how they could influence the fatigue behavior of the optimized component. The effect of the built orientation of the workpiece on the residual stresses at some selected potential critical points are evaluated. The final design solution presented a stiffness/volume ratio nearly 6 times higher when compared to the initial geometry. By choosing the built orientation, it is possible impact favorably in the fatigue life of the component.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2901 Strain-gradient effect on the crack tip dislocations density 2020-08-24T08:56:45+00:00 Valery Shlyannikov shlyannikov@mail.ru Andrey Tumanov tymanoff@rambler.ru Ruslan Khamidullin ruslankhamidullin94@mail.cru <p>In this study, the influence of a material’s plastic properties on the crack tip fields and dislocation density behavior is analytically and numerically analyzed using the conventional mechanism-based strain-gradient plasticity (CMSGP) theory established using the Taylor model. The material constitutive equation is implemented in a commercial finite element code by a user subroutine, and the crack tip fields are evaluated with novel parameters in the form of the intrinsic material length, characterizing the scale over which gradient effects become significant. As a consequence of the strain-gradient contribution, FE results show a significant increase in the magnitude of the stress fields of CMSGP when the material length parameter is considered. It is found that the density of geometrically necessary dislocations (GND) is large around the crack tip, but it rapidly decreases away from the crack tip. On the contrary, the density of statistically stored dislocations (SSD) is not as large as geometrically necessary dislocations around the crack tip, but it decreases much slower than GND away from the crack tip. A couple effect of material work hardening and the crack tip distance is identified.</p> Copyright (c) 2020 Valery Shlyannikov; Andrey Tumanov; Ruslan Khamidullin https://www.fracturae.com/index.php/fis/article/view/2899 Experimental Study of EMG 8-electrode Active Circuit Placement on Forearm for Gesture Detection 2020-08-21T07:58:54+00:00 Ivan Vladimirovich Krechetov amolajou@gmail.com Arkady Alekseevich Skvortsov amolajou@gmail.com Ivan Aleksandrovich Poselsky amolajou@gmail.com <p>This paper presents the results of experimental studies of developed active digital electrodes for surface electromyogram. Two layouts of 8 electrodes on the forearms of the test subjects have been investigated. Factors affecting the quality of the gesture recognition system by electromyogram have been considered. It has been demonstrated that the ring layout of electrodes around the forearm can be used in the manufacture of universal prosthetic sockets of upper-limb prostheses and makes it possible to achieve high accuracy of gesture detection. Recommendations on the use of specific motor gestures (up to 8 pcs.) to control different operation modes of the bionic prosthesis have been provided. The developed three-pin active electrodes operate according to the bipolar circuit and make it possible to use them without the necessity of the skin cover pre-treatment.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2898 Experimental study of 7-DOF bionic forearm prosthesis 2020-08-21T07:49:17+00:00 Ivan Vladimirovich Krechetov amolajou@gmail.com Arkady Alekseevich Skvortsov amolajou@gmail.com Ivan Aleksandrovich Poselsky amolajou@gmail.com <p>In this work, an experimental study on the grip of complex shape objects by the developed hand module of the bionic prosthesis has been conducted. A description of the seven-degree-of-freedom (7-DOF) control system of the hand module has been presented. The hand module is designed for the use in forearm and shoulder prostheses; finger modules can be used separately in the manufacture of hand prostheses. Developed programming units can be used in the building control systems of the gripping anthropomorphic manipulator, which has a kinematic structure similar to the human hand but a different number of controlled and dependent degrees of freedom. The project aims at the development of a bionic forearm prosthesis which has reliability and performance close to a healthy human hand.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2897 Analysis of means and methods of stress-strain state control of structures during operation 2020-08-21T07:40:19+00:00 Ivan V. Devyatov amolajou@gmail.com Sergei A. Iurgenson amolajou@gmail.com Ivan A. Zharenov amolajou@gmail.com Andrei A. Trutnenko amolajou@gmail.com Dmitrii V. Tuev amolajou@gmail.com <p>This article defines the basic set of means and methods of the structural health monitoring of metal structures and structures from polymer composite materials (PCMs) used in the construction and aviation industry. The analysis of means and methods of strain-stress state control of a structure during operation (detection of defects and crack growth) and their comparison is provided.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2896 Evaluation of the contact surface parameters at knurling finned heat-exchanging surface by knurls at ring blanks 2020-08-21T07:35:11+00:00 Aslan Adal`bievich Tatarkanov amolajou@gmail.com Islam Alexandrovich Alexandrov amolajou@gmail.com Andrej Vladimirovich Olejnik amolajou@gmail.com <p>Tubular parts with an external finned heat-exchanging surface are usually produced by the laborious method of cutting on lathes. In addition, there is a method for the high-performance manufacturing of fins by cold knurling with ring-cut knurls, which, compared with cutting, reduces labor intensity by two to six times. Obtaining finned surfaces on ring blanks with high surface quality during knurling requires for accurate calculation of the ratio of longitudinal and transverse strains. The most important factors determining the ratio of longitudinal and transverse strains (rolling-out and rolling-off) are the length and width of the contact surface. The need for a quantitative assessment of the parameters of longitudinal and transverse strains determined the purpose of this manuscript. The aim is to develop a methodology for calculating the contact surface of a knurl with a ring blank (pipe) when knurling with ring-cut knurls. The proposed methodology for calculating the knurl's contact surface with a pipe when knurling with ring-cut knurls allows for estimating the recommended range of pipe sizes for knurling. Based on the dependencies mentioned in the manuscript, the limiting sizes for blank pipes were calculated to ensure high-quality finning.</p> Copyright (c) https://www.fracturae.com/index.php/fis/article/view/2895 Development of mesh turbine prototype equipped with the jet control system 2020-08-21T07:31:43+00:00 Yu.A. Sazonov amolajou@gmail.com M.A. Mokhov amolajou@gmail.com I.V. Gryaznova amolajou@gmail.com V.V. Voronova amolajou@gmail.com Kh.A. Tumanyan amolajou@gmail.com M.A. Frankov amolajou@gmail.com V.A. Mun amolajou@gmail.com N.N. Balaka amolajou@gmail.com <p>In the conditions of instability on the oil and gas market, it is necessary to intensify the exploratory scientific research for the development of advanced and inexpensive pumping and compressor equipment intended for more efficient hydrocarbon production. The ongoing research work is being undertaken with a view to search and study new technical opportunities for the development of advanced pumping and compressor equipment adapted to the complicated conditions of oil and gas production in the presence of solid abrasive particles in the flow of the pumped medium. A new gas compression technology has been developed and patented using a jet compressor unit when the ejector is switched on in a cyclic mode. On-off cycling of the ejector instead of its continuous operation makes it possible to increase the gas compression ratio multiply. To increase the energy efficiency of the jet compressor unit, the technology of energy recovery with the application of a special turbine having the mesh structure of the flow part has been proposed and patented. Research and development works, on the way to the development of intelligent turbines and intelligent compressor units, have been carried out.</p> Copyright (c)