1. The influence of the ratio of circumference to cross-sectional area of tensile bars on the fatigue life of additive manufactured AISI 316L steelLuka Ferlič, Filip Jerenec, Mario Šercer, Igor Drstvenšek, Nenad Gubeljak, 2024, original scientific article Abstract: The static and dynamic loading capacities of components depend on the stress level to which the material is exposed. The fatigue behavior of materials manufactured using additive technology is accompanied by a pronounced scatter between the number of cycles at the same stress level, which is significantly greater than the scatter from a material with the same chemical composition, e.g., AISI 316L, but produced by rolling or forging. An important reason lies in the fact that fatigue cracks are initiated almost always below the material surface of the loaded specimen. Thus, in the article, assuming that a crack will always initiate below the surface, we analyzed the fatigue behavior of specimens with the same bearing cross section but with a different number of bearing rods. With a larger number of rods, the circumference around the supporting part of the rods was 1.73 times larger. Thus, experimental fatigue of specimens with different sizes showed that the dynamic loading capacity of components with a smaller number of bars is significantly greater and can be monitored by individual stress levels. Although there are no significant differences in loading capacity under static and low-cycle loading of materials manufactured with additive technologies, in high-cycle fatigue it has been shown that the ratio between the circumference and the loading cross section of tensile-loaded rods plays an important role in the lifetime. This finding is important for setting a strategy for manufacturing components with additive technologies. It shows that a better dynamic loading capacity can be obtained with a larger loading cross section.
Keywords: AISI 316L stainless steel, additive manufacturing, FEM, high-cycle fatigue, fractography analysis
Published in DKUM: 25.11.2024; Views: 0; Downloads: 7
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2. Behaviour of cellular metamaterials under impact loading conditions : doctoral disertationYunus Emre Yilmaz, 2024, doctoral dissertation Abstract: This doctoral thesis investigates cell-size-graded metallic and non-metallic Triply Periodic
Minimal Surface (TPMS) structures' behavior under varying loading rates. Using experimental
tests, analytical calculations, and advanced computer simulations, the research explores the
interplay between material properties, cell size grading, and deformation mechanisms under
different strain rates. The study focuses on enhancing the Direct Impact Hopkinson Bar (DIHB)
setup for accurate force and displacement measurements and pioneering a method for
quantifying inertial forces, critical at high strain rates.
Key findings show that cell-size grading significantly affects deformation patterns, with initial
deformation occurring in regions with smaller and lower stiffness cells across different loading
rates and TPMS geometries. The research also highlights topology's influence on mechanical
response, with photopolymer-based diamond structures showing superior energy absorption
and gas-atomized steel structures favoring gyroid configurations. This underscores the
importance of considering both topology and base material selection during TPMS design. The
study demonstrates the increasing prominence of inertial forces as deformation rates rise,
impacting structural response and failure likelihood in TPMS structures.
These insights inform the design of optimized cellular metamaterials for high-performance
applications requiring superior energy absorption and structural integrity under high loading
rates. The research advances material characterization techniques and computational
modelling capabilities, contributing to the development of next-generation cellular
metamaterials for broader engineering applications.
Keywords: Triply Periodic Minimal Surfaces, TPMS, Cell-size-grading, Impact, High-strainrate, Digital Image Correlation
Published in DKUM: 17.10.2024; Views: 0; Downloads: 16
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3. Motor unit discharge rate modulation during isometric contractions to failure is intensity- and modality-dependentTamara Valenčič, Paul Ansdell, Callum G. Brownstein, Padraig M. Spillane, Aleš Holobar, Jakob Škarabot, 2024, original scientific article Abstract: The physiological mechanisms determining the progressive decline in the maximal muscle torque production capacity during isometric contractions to task failure are known to depend on task demands. Task-specificity of the associated adjustments in motor unit discharge rate (MUDR), however, remains unclear. This study examined MUDR adjustments during different submaximal isometric knee extension tasks to failure. Participants performed a sustained and an intermittent task at 20% and 50% of maximal voluntary torque (MVT), respectively (Experiment 1). High-density surface EMG signals were recorded from vastus lateralis (VL) and medialis (VM) and decomposed into individual MU discharge timings, with the identified MUs tracked from recruitment to task failure. MUDR was quantified and normalised to intervals of 10% of contraction time (CT). MUDR of both muscles exhibited distinct modulation patterns in each task. During the 20% MVT sustained task, MUDR decreased until ∼50% CT, after which it gradually returned to baseline. Conversely, during the 50% MVT intermittent task, MUDR remained stable until ∼40–50% CT, after which it started to continually increase until task failure. To explore the effect of contraction intensity on the observed patterns, VL and VM MUDR was quantified during sustained contractions at 30% and 50% MVT (Experiment 2). During the 30% MVT sustained task, MUDR remained stable until ∼80–90% CT in both muscles, after which it continually increased until task failure. During the 50% MVT sustained task the increase in MUDR occurred earlier, after ∼70–80% CT. Our results suggest that adjustments in MUDR during submaximal isometric contractions to failure are contraction modality- and intensity-dependent.
Keywords: muscle contractions, high-density EMG signals, electromyiograms
Published in DKUM: 23.08.2024; Views: 117; Downloads: 9
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4. Parallel self-avoiding walks for a low-autocorrelation binary sequences problemBorko Bošković, Jana Herzog, Janez Brest, 2024, original scientific article Abstract: A low-autocorrelation binary sequences problem with a high figure of merit factor represents a formidable computational challenge. An efficient parallel computing algorithm is required to reach the new best-known solutions for this problem. Therefore, we developed the sokol solver for the skew-symmetric search space. The developed solver takes the advantage of parallel computing on graphics processing units. The solver organized the search process as a sequence of parallel and contiguous self-avoiding walks and achieved a speedup factor of 387 compared with lssOrel, its predecessor. The sokol solver belongs to stochastic solvers and cannot guarantee the optimality of solutions. To mitigate this problem, we established the predictive model of stopping conditions according to the small instances for which the optimal skew-symmetric solutions are known. With its help and 99% probability, the sokol solver found all the known and seven new best-known skew-symmetric sequences for odd instances from to . For larger instances, the solver cannot reach 99% probability within our limitations, but it still found several new best-known binary sequences. We also analyzed the trend of the best merit factor values, and it shows that as sequence size increases, the value of the merit factor also increases, and this trend is flatter for larger instances.
Keywords: low-autocorrelation binary sequences, self-avoiding walk, graphic processor units, high performance computing
Published in DKUM: 22.08.2024; Views: 45; Downloads: 2
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5. The importance of autonomy of European Union member states with regard to the use of genetically modified organisms on the right to healthcare : an analysis of judgements of the Court of Justice of the European UnionKatja Meško Kuralt, 2022, original scientific article Abstract: The European Union Member States (hereinafter: EU MS) have the possibility of restricting or banning the cultivation of GMOs under the Directive 2015/412 but under certain conditions. EU MS must also pay attention to the provisions of the Treaty on the Functioning of the Euro-pean Union or Treaty Establishing the European Community (hereinafter: TFEU), the provi-sions relating to the free movement of goods, which is one of the key objectives of the func-tioning of the European Union. This contribution is based on the data obtained from an analy-sis of Court of Justice of the European Union (hereinafter: CJEU) cases concerning the use of genetically modified organisms (hereinafter: GMO(s)). The analysis highlights the link between environmental risk assessment and the right to healthcare. The purpose of this paper is to make the individual aware of the possibilities they have regarding the use of GMOs.
Keywords: Directive 2001/18, Directive 2015/4120, Directive 2018/350, high level of protection of human life and health, possibility of restricting or prohibiting the production of GMOs, free movement of goods, environmental risk assessment
Published in DKUM: 26.06.2024; Views: 144; Downloads: 19
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6. Motor unit identification in the M waves recorded by high-density electromyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, original scientific article Keywords: M wave, high-density surface EMG, firing identification, motor unit
Published in DKUM: 13.06.2024; Views: 144; Downloads: 10
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7. Identification of motor unit firings in H-reflex of soleus muscle recorded by high-density surface electromyographyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, original scientific article Keywords: motor units identification, high-density surface EMG, decomposition, H-reflex
Published in DKUM: 13.06.2024; Views: 133; Downloads: 11
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8. Materials for HybridNeuro webinar titled "Validation of results: statistical models and MU identification accuracy"Aleš Holobar, Nina Murks, 2024, complete scientific database of research data Abstract: This dataset contains a collection of teaching materials that were used in the HybridNeuro project webinar titled "Validation of results: statistical models and MU identification accuracy". The webinar was presented by Aleš Holobar and covered the complexities of motor unit (MU) identification accuracy, regression analysis and Bayesian models. The primary aim of the webinar was to spark a robust discussion within the scientific community, particularly focusing on the application and implications of linear mixed models and Bayesian regression in the realm of MU identification. The teaching materials include Matlab and R source code for statistical analysis of the included data, as well as three examples of MU identification results in CSV format (from both synthetic and experimental HDEMG signals). The presentation slides in PDF format are also included. The dataset is approximately 9 MB in size.
Keywords: HybridNeuro, webinar, teaching materials, statistical models, regression analysis, motor unit identification, matlab, rstudio, statistics, surface high density electromyogram (HDEMG), tibialis anterior, dataset
Published in DKUM: 30.05.2024; Views: 221; Downloads: 19
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9. Simulated and experimental HDEMG signals of biceps brachii muscle for analysis of motor unit mergingAleš Holobar, Jakob Škarabot, Dario Farina, 2024, complete scientific database of research data Abstract: This dataset contains a collection of simulated and experimental surface HDEMG recordings of the biceps brachii muscle during the isometric elbow flexion. Simulated data contains 50 recordings: 5 subjects and 5 excitation levels, each with and without added noise. Experimental data contains 16 recordings: 2 subjects with 4 excitation levels and 2 repetitions of each level. Synthetic data was simulated using the cylindrical volume conductor model [1] and the motor unit recruitment and firing modulation model proposed in [2]. Each recording is 20 seconds in length with 90 HDEMG channels sampled at 2048 Hz and is stored as a 2D matrix of raw EMG values in Matlab’s MAT format. Experimental surface EMG data was recorded on two volunteers during isometric contractions at constant force level. Each recording is 25 seconds in length with 64 HDEMG channels sampled at 2048 Hz and is also stored as a 2D matrix of raw EMG values in Matlab’s MAT format. The dataset is approximately 1.5 GB in size.
Keywords: surface high density electromyogram (HDEMG), motor unit, spike train, motor unit merging, simulated data, experimental data, biceps brachii, dataset
Published in DKUM: 30.05.2024; Views: 172; Downloads: 14
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