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Abstract: In this work, Laser Powder Bed Fusion (LPBF), an additive manufacturing (AM) process, was optimised to produce pure magnesium components. The focus of the presented work is on the prediction of the relative product density using the machine learning model XGBoost to improve the production process and thus the usability of the material for practical use. Experimental tests with different parameters, laser power, scanning speed and layer thickness, and fixed parameters, track overlapping and hatching distance, were analysed and resulted in relative material densities between 89.29% and 99.975%. The XGBoost model showed high predictive power, achieving an R2 test result of 0.835, a mean absolute error (MAE) of 0.728 and a root mean square error (RMSE) of 0.982. Feature importance analysis showed that the interaction of laser power and scanning speed had the largest influence on the predictions at 35.9%, followed by laser power × layer thickness at 29.0%. The individual contributions were laser power (11.8%), scanning speed (10.7%), scanning speed × layer thickness (9.0%) and layer thickness (3.6%). These results provide a data-based method for LPBF parameter settings that improve manufacturing efficiency and component performance in the aerospace, automotive and biomedical industries and identify optimal parameter regions for a high density, serving as a pre-optimisation stage.
Keywords: additive manufacturing, machine learning, XG Boost, magnesium, relative density
Published in DKUM: 03.11.2025; Views: 0; Downloads: 6
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Abstract: This paper presents a wear simulation-based performance evaluation of the conveyor belt transfer chute using the DEM (Discrete Element Method). Compared to known analytical and empirical wear models, DEM simulation can significantly increase the performance of wear analysis by enabling the analysis and optimization of highly complex geometries of material handling systems such as conveyor belt transfer chutes. Only the correct design of the conveyor belt transfer chute has the potential to significantly extend its service life, resulting in considerable cost savings. Based on the parametric analysis of different angles and radius in the upper head and lower section of the transfer chute, a new geometry of the transfer chute was proposed. The wear depth of the new conveyor belt transfer chute is compared with the wear resistant and low-carbon steel of the transfer chute along with the moderate and relatively high values of the solid granules mass flow. The results show that the wear depth of the transfer chute can be significantly reduced by using the wear-resistant steel compared to the low-carbon steel, which is significantly evident in high throughput rates of the solid granules mass flow.
Keywords: bulk material flow, Discrete Element Method (DEM), transfer chute wear simulation, archard and relative wear, performance analysis
Published in DKUM: 10.03.2025; Views: 0; Downloads: 18
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Abstract: Athletes are often subjected to a great physical strain during training and competition. Sport activities performed in hot and humid conditions may result in different heat illnesses with mild or fatal consequences. Against this background it is important to know the thermal state of athletes during physical activity. This article presents the development of a smart T-shirt for monitoring the thermal status of an athlete. The smart T-shirt was created by embedding an electronic system with temperature and humidity sensors that allows the measurement of temperature and the relative humidity of the microclimate. A smart T-shirt is comfortable, and integrated sensors and electronics do not affect wearing comfort. A good concurrence between the temperature and humidity results from using the smart T-shirt, and thus the medical device was achieved. Data obtained can be of great importance to the sports staff who will be able to monitor the athletes' thermal state during matches and competitions.
Keywords: smart T-shirt, microclimate temperature, relative humidity of the microclimate
Published in DKUM: 26.03.2024; Views: 190; Downloads: 36
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Abstract: This paper presents the results of 120 determinations of the shear modulus (G) of a saturated granular soil (20–40 Ottawa sand) in different conditions of relative density (Dr), effective consolidation pressure (σ’ c) and level of torsional excitation (Te). The equipment used was a resonant-column apparatus manufactured by Wykeham Farrance and the tests were performed with relative density values of 20, 40, 60 and 80%, effective consolidation pressures of 50, 100, 150, 200, 250 and 300 kPa, and torsional excitations of 0.025, 0.05, 0.1, 0.2 and 0.4 volts (V), leading to shear strains (γ) between 0.002% and 0.023%. The results led to very simple empirical expressions for the shear modulus as a function of the angular strain for different effective consolidation pressures and void-ratio values.
Keywords: resonant column, resonant frequency, shear modulus, relative density, effective consolidation pressure, dynamic shear modulus
Published in DKUM: 18.06.2018; Views: 1315; Downloads: 101
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Abstract: Salt is an important ingredient in the production of meat product. Any reduction of salt requires a special treatment. This study was conducted to evaluate the effect of salt reduction on the growth of microorganisms in Kranjska sausages during their shell-life and to carry out a sensory assessment. The 18 lots of sausages were prepared under salt-reduced (1.6%) and control (2.3%) salt concentrations, directly on the production line. A total of 85 sausages were analysed and the data were used for the comparisons of groups (ANOVA) and to detect the significant variables (polynomial models) influenced on the total number of microorganisms (TNMs). The significant differences were determined between the lots (representing the microbiological status of the stuffing), between the salt-reduced samples and control samples, and between the different humidity levels. The correlations and significant relationships were determined between the TNMs and the lots, the salt concentrations, and the relative humidity. The polynomial models were to general to be used for the prediction. For sensory analysis implemented on 40th day 18 sausages were assessed. The reduction of salt resulted in lower scores in the sensory evaluation. The less-salted sausages contained more microorganisms.
Keywords: Kranjska sausage, reduction of salt, sensory evaluation, models, relative humidity
Published in DKUM: 14.11.2017; Views: 1566; Downloads: 415
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