Speed Power Research Articles

Microstructure evolution in AlSi10Mg alloy fabricated by laser-based directed energy deposition

Investigation of the influence of processing parameters on the microstructure evolution of the melt pool is important for microstructure control in laser-based directed energy deposition (DED-LB) processes. Single-track experiments of DED-LB AlSi10Mg alloy were conducted in this work, processing with two laser powers (900 and 1800 W) at a fixed scanning speed (20 mm/s). The grain morphology was changed from columnar to equiaxed towards the center of each melt pool. Meanwhile, the morphology of the α-Al cells in the grains varied from elongated to equiaxed along the same direction due to the increase of cooling rate. A more equiaxed microstructure can be obtained in the melt pool produced at a larger laser power. The scales of the microstructures and the grain morphologies in the melt pools were in accord with the microstructure selection map and grain morphology selection map in temperature gradient (G)–growth velocity (V) space constructed by solidification models. Since G and V are directly related to laser power and scanning speed, the G–V maps can provide the guidance for processing optimization to tailor microstructures in DED-LB Al–Si alloys based on the temperature field simulations of melt pools.

Energy and exergy analysis of drying terebinth in a far infrared‐rotary dryer using response surface methodology

AbstractWater shows a strong tendency to absorb the energy of wavelengths of 3 and 6 µm, which are in the infrared (IR) range. Therefore, IR dryers are used to dry food and fruits that have a high‐water content. Thus, modeling and optimizing energy and exergy parameters of terebinth drying in an IR–rotary drum (RD) dryer were evaluated using the response surface methodology. Independent factors included IR power and rotary rotation speed, and response factors were specific energy consumption (SEC), energy efficiency (EFF), exergy efficiency (EXEFF), specific exergy loss (EXLOSS), and exergy improvement potential (EIP). According to the obtained results, the range of EFF and EXEFF was between 28.93%–9.11% and 0.88%–6.62%, respectively. As IR power and RD speed increased, SEC (123.75–39.21 MJ/kg), EXLOSS (3.97–2.97 MJ/kg), and EIP (3.62–1.009 MJ/kg) decreased, while EFF and EXEFF increased. The results obtained in this study showed that the optimal IR drying power is 616.39 W, and the optimal rotary rotation speed is 13.46 rpm.

Comparison of the Effects of Compound Training, Plyometric Exercises, and Kettlebell Exercises on Strength, Power, Dynamic Balance, and Pitched Ball Velocity in 30 Male High School Baseball Pitchers Aged 16-19 Years.

BACKGROUND The purpose of this study was to determine how the combination of plyometric training (PT), which builds strength through fast, repetitive extensions and contractions, and kettlebell training (KT), using a device that is smaller than a barbell and allows for strength and full-body work, affects the physical performance and performance of high school pitchers during the season. MATERIAL AND METHODS Participants (n=30 males; age group=16-19 years) were randomized into 3 groups: compound training group (CTG) (n=10), plyometric training group (PTG) (n=10), and kettlebell group (KTG) (n=10). All groups performed training twice weekly for 4 weeks. Pre- and post-intervention assessments were conducted on isokinetic strength to measure strength, vertical jump (VJ) to measure power, dynamic balance (Y-balance), and ball speed (BS) to measure baseball performance. RESULTS We found there was increased strength, VJ, Y-balance, and BS in the CTG, PTG, and KTG (p=.000). CTG had significantly different results than PTG and KTG (p=.000). There was a significant difference in increased strength of the right knee joint flexors between PTG and KTG (p=.000). CONCLUSIONS CTG, PTG, and KTG for pitchers during the season improved significantly. These results suggest that combination training, rather than just 1 type of training, affects pitchers' strength, VJ, Y-balance, and BS during the season.

Insight into the cracking mechanism of super-elastic NiTi alloy fabricated by laser powder bed fusion

ABSTRACT Laser powder bed fusion is considered to be an effective method for forming high-precision NiTi alloys. NiTi alloys formed from Ti-rich or low-Ni content NiTi powders as raw materials exhibit shape memory or trained to be superelastic at room temperature. To fabricate super-elastic NiTi alloys without training, it is often to increase the Ni content of the powder. However, Ni-rich NiTi powders are highly susceptible to cracking during fabrication. Therefore, this study has conducted a systematic investigation and proposed a corresponding process optimisation strategy. The results show that cracking is the result of the combined effect from residual thermal stresses and microstructure during the printing process. The melt pool morphology influenced by the thermal history as well as elemental evaporation determines the direction of crack formation and propagation. We have successfully fabricated room-temperature super-elastic NiTi samples without cracking using high laser power and high scanning speed.

Nanowatt all-optical 3D perception for mobile robotics.

Three-dimensional (3D) perception is vital to drive mobile robotics' progress toward intelligence. However, state-of-the-art 3D perception solutions require complicated postprocessing or point-by-point scanning, suffering computational burden, latency of tens of milliseconds, and additional power consumption. Here, we propose a parallel all-optical computational chipset 3D perception architecture (Aop3D) with nanowatt power and light speed. The 3D perception is executed during the light propagation over the passive chipset, and the captured light intensity distribution provides a direct reflection of the depth map, eliminating the need for extensive postprocessing. The prototype system of Aop3D is tested in various scenarios and deployed to a mobile robot, demonstrating unprecedented performance in distance detection and obstacle avoidance. Moreover, Aop3D works at a frame rate of 600 hertz and a power consumption of 33.3 nanowatts per meta-pixel experimentally. Our work is promising toward next-generation direct 3D perception techniques with light speed and high energy efficiency.

Powder Bed Fusion-Laser Beam of IN939: The Effect of Process Parameters on the Relative Density, Defect Formation, Surface Roughness and Microstructure.

This study investigates the effects of process parameters in the powder bed fusion-laser beam (PBF-LB) process on IN939 samples. The parameters examined include laser power (160, 180, and 200 W), laser scanning speed (400, 800, and 1200 mm/s), and hatch distance (50, 80, and 110 μm). The study focuses on how these parameters affect surface roughness, relative density, defect formation, and the microstructure of the samples. Surface roughness analysis revealed that the average surface roughness (Sa) values of the sample ranged from 4.6 μm to 9.5 μm, while the average height difference (Sz) varied from 78.7 μm to 176.7 μm. Furthermore, increasing the hatch distance from 50 μm to 110 μm while maintaining constant laser power and scanning speed led to a decrease in surface roughness. Relative density analysis indicated that the highest relative density was 99.35%, and the lowest was 93.56%. Additionally, the average porosity values were calculated, with the lowest being 0.06% and the highest reaching 9.18%. Although some samples had identical average porosity values, they differed in porosity/mm2 and average Feret size. Variations in relative density and average porosity were noted in samples with the same volumetric energy density (VED) due to different process parameters. High VED led to large, irregular pores in several samples. Microcracks, less than 50 μm in length, were present, indicating solidification cracks. The microstructural analysis of the XZ planes revealed arc-shaped melt pools, columnar elongated grains aligned with the build direction, and cellular structures with columnar dendrites. This study provides insights for optimizing PBF-LB process parameters to enhance the quality of IN939 components.

Phase-field ductile fracture simulations of thermal cracking in additive manufacturing

We present a multiphysics phase-field fracture model for thermo-elasto-plastic solids in the context of finite deformation and apply it to simulate the hot cracking phenomenon during metal additive manufacturing. The model is derived in a thermodynamically consistent manner, with the intercoupling mechanisms among elastoplasticity, phase-field crack and heat transfer comprehensively considered. It involves particularly coupled parameters among these materials physics, e.g. plasticity-dependent degradation function and fracture toughness, damage-dependent yield surface and thermal properties, and temperature-dependent elastoplastic properties and fracture strength. The finite element implementation of the coupled phase-field model is benchmarked with simulation results of a tensile test of an I-shape specimen, encompassing elastoplasticity, hardening, necking, crack initiation and propagation, in contrast to the related experimental results. The validated model is further employed to simulate the multiphysics hot cracking phenomenon in additive manufacturing in the context of both the effective powder-bed model and the powder-resolved model thanks to prior non-isothermal phase-field powder-bed-fusion simulations. Simulation results reveal certain key features of the hot crack and its dependency on process parameters like beam power and scan speed, which are helpful for the fundamental understanding of crack formation mechanisms and process optimization.

Effect of Laser Parameters on Surface Texture of Polyformaldehyde and Parameter Optimization

This research aimed to investigate the influence of laser process parameters on the surface texture of Polyformaldehyde (POM) and to improve its processability and process predictability. A comparative experiment and analysis involving multiple processing parameters, including laser power, scanning speed, and pulse width, were conducted on POM. Statistical prediction models of laser processing POM were established among the laser power, scanning speed, pulse width, texture depth, surface roughness at the bottom of texture, and multi-objective optimization and experimental verification of process parameters were carried out based on the grey-Taguchi analysis method. Experimental results show that the laser power and scanning speed significantly affect the texture depth. Higher laser power and lower scanning speed are conducive to forming depth. The surface roughness at the bottom of the texture increases with the increase in scanning speed and shows a tendency to rise and then fall as the laser power increases. The surface roughness and texture depth obtained under the optimal process parameters(A5B1C1) are 1.373 μm and 466.891 μm, respectively, which were reduced by 10.08 % and increased by 3.42 % compared with the minimum surface roughness and maximum depth in the orthogonal experiments. The validation experiments of the prediction model show that it can meet the reliability requirements, and the errors of the predicted values of depth and surface roughness are 1.86 % and 7.60 %, respectively. The above research provides theoretical and experimental support for the precise control of surface texture prepared by laser processing POM.

Numerical and experimental investigation of the effect of heat input on weld bead geometry and stresses in laser welding

Abstract Nowadays, laser welding is a powerful joining method. Thanks to the advantages it has, its usage area is increasing day by day. However, getting the desired result from the laser welding process is possible with the proper welding parameter selections. Otherwise, many problems may be encountered, including significantly incomplete penetration. For this reason, parameter selection has been discussed in many studies in the literature. At this point, validated numerical simulation models are precious. Since these models reduce experiment costs and save time. Especially numerical simulation of the structural steel, which is the one of most used materials, is crucial. In this study, the effects of laser power (LP) and welding speed (WS), which are among the vital parameters of laser welding, on weld width and stress were investigated numerically and statistically. Structural steel was selected as the material, and the Taguchi method was carried out for the simulation case study design. Simufact Welding software was used for simulation studies, and simulations were carried out thermomechanical. Thus, more realistic results were obtained via the thermomechanical method. One of the simulation results was verified through an experimental study. The results were evaluated with signal-to-noise (S/N) ratio and a statistical analysis of variance (ANOVA), and as a result of the study, it was seen that the welding speed was a more effective parameter, the optimal parameter combination was found to be 3500 W for laser power and 40 mm/s for welding speed to get maximum weld width and minimum equivalent stress. In addition, it was observed that correctly created simulation studies may provide very close results to experimental studies.

Co-optimization of Power Allocation and Speed Trajectory for Autonomous HEVs in Off-Road Scenarios Considering Vehicle Dynamics

Co-optimization of Power Allocation and Speed Trajectory for Autonomous HEVs in Off-Road Scenarios Considering Vehicle Dynamics

Defects, organization, and properties of TiB2–TiC Bi-ceramic phase by laser cladding in situ synthesis

An enhanced Ni50A composite coating was formed on the AISI 1045 steel surface using Ti, B4C, and Ni50A powders. The work meticulously examined the effects of various process parameters, including laser power (800, 1200, and 1600 W) and scanning speed (4, 6, and 8 mm/s), as well as different Ti/B4C powder ratios (2:1, 3:1, and 4:1, mol.%) on the defect, hardness, wear resistance, and corrosion resistance of the coating. The microstructure of the coating showed that TiB2 and TiC synthesized in situ were the key phases for coating enhancement, and there were a variety of solid solutions (FeNi3 and Cr2Ni3). TiB2 particles showed dark gray hexagons and long rectangular blocks. The TiC particles mainly appeared in light gray dendritic shapes, occasionally petal-shaped and equiaxial forms, and grew around TiB2. The research results showed that increased laser power and the Ti/B4C ratio decreased coating hardness and wear resistance. When the scanning speed increased, the hardness and wear resistance of the coating were significantly improved. The main wear mechanisms of the TiB2–TiC ceramic phase coating were oxidative wear and abrasive particle wear. Besides, the higher laser power and Ti/B4C ratio reduced the defect rate of the coating and enhanced the corrosion resistance. However, as the scanning speed increased, the defect rate increased, which decreased the corrosion resistance of the coating. The comprehensive performance evaluation showed that under the conditions of the laser power of 1200 W, a scanning speed of 8 mm/s, and a Ti/B4C ratio of 4:1, the coating exhibited optimal performance (dilution rate = 10.928±0.090%, defect rate = 8.657±0.128%, hardness = 63.300±1.159 HRC, wear volume = 0.0149±0.000100 mm3, Ecorr = −0.565±0.001 V, Icorr = 1.058E−06±1.528E−09A⋅cm2). The results provide an important basis for research on the high-quality and efficient strengthening technology and performance of refractory alloys.

Study on the influence of selective laser melting temperature on the melting bath

Abstract The high-temperature gradient and high-frequency thermal cycling during the selective laser melting process will seriously affect the melting bath morphology and dimensions, which in turn affects the quality of formed parts. In this paper, a numerical model of the SLM process is established to emulate the temperature field and investigate temperature variation of single-layer and multi-channel models, as well as the influence of disparate laser power, hatch spacing, and scanning speed on melting baths. The simulation results show that the temperature gradient at the front end of the melting bath is small due to physical phase transition, and the temperature gradient nearer to the end of the melting bath is bigger. The midpoint of the second melting channel has the highest peak temperature due to heat conduction and accumulation; the impact of each technological parameter on the melting bath is in the following order: laser power > scanning speed > hatch spacing. Therefore, it is clear that the temperature distribution will provide a theoretical foundation for regulating the stress state of molded parts and ensuring the surface quality and mechanical capacity of the processed component.

Parameter optimization and anisotropy mechanism in different build directions of the microstructures and mechanical properties for laser directed energy deposited Ti6Al4V alloy

The effects of laser power, scanning speed, and build directions (BDs) on the microstructural evolution and mechanical properties of laser directed energy deposited (LDEDed) Ti6Al4V alloy were systematically investigated in this study. All the finished LDED specimens were not heat treated and the tensile properties were not influenced by surface roughness. Particularly, the differences in grain size, grain boundary distribution, geometrically necessary dislocation (GND) density, grain orientation spread (GOS), and Schmid factor (SF) of the specimens in different BDs were investigated by scanning electron microscopy, electron backscattering diffraction, transmission electron microscopy, and tensile test. The results showed that the aspect ratio, dilution rate, and deposition angle all tended to increase with increasing laser power and scanning speed. The yield strength and the ultimate tensile strength decreased with the increase of laser power, while the elongation was the opposite. The parent grain reconstruction results indicated that the high-temperature transition phase (β phase) of the 0° LDEDed specimen was equiaxial, whereas that of the 90° LDEDed specimen was columnar. The differences in the β phase of the specimens in different BDs were directly inherited to the corresponding low-temperature sub-phase (α phase), resulting in finer grain sizes, greater GND density, larger GOS, and smaller SF in the 0° LDEDed specimen, thereby contributing to higher strength and hardness. In contrast, these values were reversed for the 90° LDEDed specimen, resulting in better plasticity and toughness. Finally, the anisotropy mechanism of the microstructures and mechanical properties of the LDEDed Ti6Al4V alloy in different BDs were revealed. This work could provide more systematic and comprehensive guidance in parameter optimization and offer valuable insights into the anisotropy mechanism of the microstructures and mechanical properties of LDEDed Ti6Al4V alloy.

Optimization of Processing Parameters for Continuous Microwave Drying of Crab Apple Slices via Response Surface Methodology.

To improve product quality and obtain suitable processing parameters for crab apple slices (CASs) produced by continuous microwave drying (CMD), the effects of processing parameters, including slice thickness, microwave power, air velocity, and conveyor belt speed, on the evaluation indexes in terms of temperature, moisture content, color (L*, a*, b*), hardness, brittleness, and total phenolic content of CASs were investigated via the response surface method. The results indicated that microwave power has the greatest effect on the evaluation indexes applied to the CASs under CMD, followed by air velocity, slice thickness, and conveyor belt speed. To produce the desired product quality, the appropriate parameters for CMD of CASs were optimized as 1.25 mm slice thickness, 14,630 W microwave power, 0.50 m·s-1 air velocity, and 0.33 m·min-1 conveyor belt speed. Following that, the moisture content under CMD was found to be 13.53%, the desired color, hardness 0.79 g, brittleness 12.97 (number of peaks), and the total phenolic content 5.48 mg·g-1. This research provides a theoretical framework for optimizing the processing parameters of CASs using the response surface method.

Зміни у фізичній підготовленості учнів ліцею спортивного профілю

The article examines the indicators of motor abilities of 10th-grade pupils of the sport’s professional college lyceum. The number of respondents was 210 people, the average age of the representatives was 15.46 years. The aim of the study is to determine the level of physical fitness of 10th-grade lyceum pupils and to investigate its dynamics over three years. Research methods and organization. The research was conducted during 2020-2022 on the basis of the Kharkiv Professional College of Sports Lyceum. In order to analyze the level of development of basic motor skills, standard tests of the school physical education program were chosen to determine indicators of speed abilities, agility, strength, power speed abilities and endurance. One-dimensional statistical analysis according to the Student’s t-test was chosen to prove the regularities discovered in the process of research and hypothesis testing. Results. The results of the study showed that the average statistical indicators of physical fitness of 10th-grade students of the Kharkiv Professional College of Sports Lyceum of the 2020-2022 sets are better than the data available in the scientific and methodological periodicals of peers who study in common schools. The average results of the sports lyceum pupils in 60 meters running range from 8.5 to 8.4 s; the results of the 4x9 m shuttle run exercise are within 9.1-9.2 s; pull-up on a high bar 8.2-8.8 times, long jump are in the range from 219 to 222 cm; running 1500 m within 5.29-5.36 min. The results of the exercises correspond to a high level of competence for representatives of this age. Statistical analysis of the obtained data showed that pupils of the 2022 control group compared to representatives of 2020 demonstrated worse results in exercises designed to determine indicators of speed, agility and endurance (p<0.05); indicators of strength and speed-power abilities do not have statistically significant differences. Conclusion. Systematic purposeful sports engagements and an increased level of physical activity allows to ensure a high level of competence in performing standard motor tests. However, during the three years of the study, the indicators of speed, agility and endurance of sports lyceum pupils statistically decreased.

Prediction of Geometric Dimensions of Deposited Layer Produced Using Laser-Arc Hybrid Additive Manufacturing.

Laser-arc hybrid additive manufacturing (LAHAM) holds substantial potential in industrial applications, yet ensuring dimensional accuracy remains a major challenge. Accurate prediction and effective control of the geometrical dimensions of the deposited layers are crucial for achieving this accuracy. The width and height of the deposited layers, key indicators of geometric dimensions, directly affect the forming precision. This study conducted experiments and in-depth analysis to investigate the influence of various process parameters on these dimensions and proposed a predictive model for accurate forecasting. It was found that the width of the deposited layers was positively correlated with laser power and arc current and negatively correlated with scanning speed, while the height was negatively correlated with laser power and scanning speed and positively with arc current. Quantitative analysis using the Taguchi method revealed that the arc current had the most significant impact on the dimensions of the deposited layers, followed by scanning speed, with laser power having the least effect. A predictive model based on extreme gradient boosting (XGBoost) was developed and optimized using particle swarm optimization (PSO) for tuning the number of leaf nodes, learning rate, and regularization coefficients, resulting in the PSO-XGBoost model. Compared to models enhanced with PSO-optimized support vector regression (SVR) and XGBoost, the PSO-XGBoost model exhibited higher accuracy, the smallest relative error, and performed better in terms of Mean Relative Error (MRE), Mean Square Error (MSE), and Coefficient of Determination R2 metrics. The high predictive accuracy and minimal error variability of the PSO-XGBoost model demonstrate its effectiveness in capturing the complex nonlinear relationships between process parameters and layer dimensions. This study provides valuable insights for controlling the geometric dimensions of the deposited layers in LAHAM.

ИССЛЕДОВАНИЕ ТЕХНИЧЕСКИХ РЕШЕНИЙ ПО РЕАЛИЗАЦИИ НАГРУЗОЧНОГО МОМЕНТА ПРИ ИСПЫТАНИИ ЭЛЕКТРИЧЕСКИХ МАШИН

The main methods of testing electrical machines are considered. It has been determined that the tradi-tional method of implementing the load moment has significant limitations. It is proposed to use an electromagnetic brake based on a hysteresis machine. This method of organizing the load torque is universal and can be used to test machines of different power and rotation speed

Microstructural Evolution and Wear Resistance of Surface Alloyed AISI 316L Stainless Steel with Equi-atomic CoCrFeMnTi by Continuous Wave Diode Laser

In this investigation, a multicomponent alloyed surface was developed on AISI 316L stainless steel (AISI 316L SS) substrate by melting it with a fiber coupled diode laser having 3.6 mm beam diameter (using argon as shrouding gas) along with simultaneous melting of equiatomic pre-mixed elemental powders of cobalt (Co), chromium (Cr), iron (Fe), manganese (Mn) and titanium (Ti) (high entropy alloy). The process parameters used in the experiment were laser power (1800–2200 W) and scan speed (6 mm/sec to 8 mm/sec). Following laser surface alloying (LSA) a detailed microstructural characterization of the surface and evaluation of surface mechanical properties (micro/nano hardness, Young’s modulus and wear resistance) were undertaken. Due to LSA there is formation of near eutectic microstructure consisting of FCC and BCC phase mixtures along with the precipitates of Fe2Ti randomly distributed in the microstructure which was confirmed by X-ray diffraction (XRD) and electron back scattered diffraction (EBSD) analysis. There is an increase in microhardness in the processed zone from 180 VHN (of as received AISI 316L SS) to 309–650 VHN. In addition, there is an increase in Young’s modulus from 208 GPa for as received AISI 316L SS to 228–301 GPa for laser surface alloyed zone. The wear resistance (against WC ball in fretting wear mode) property of AISI 316L SS substrate after LSA was superior to the substrate. The wear mechanism was established.

Deception of Heart Rate is Unable to Improve Functional Threshold Power in Cyclists

Introduction: Studies investigating the effects of deception on endurance performance have been somewhat inconclusive. The purpose of this study was to explore the use of biofeedback deception of heart rate (HR) in an attempt to improve athletic performance. Methods: Thirteen individuals (10 men, mean±SD age 29.4±10.2 years) completed two 20-minute functional threshold power (FTP) cycling tests. In the control (CON) condition, their correct HR was displayed, while in the deception (DEC) condition an incorrect HR was displayed (correct HR – 10 bpm). Paired samples t-tests were used to compare cycling variables such as power output, speed and work between conditions. Actual HR was analyzed using 2 (condition) x 10 (time; every two minutes) repeated-measures ANOVAs. Results: Mean power output in the CON condition was 226.7±69.3 W and 222.6±65.4 W in the DEC condition (p>.05). The total amount of work performed was nearly identical between conditions (CON: 709.2± J, DEC: 709.3± J; p>.05). There were no differences in actual HR between conditions (all p>.05). Conclusions: Biofeedback deception of HR was unable to improve performance. Verbal encouragement may be a moderating variable that allows successful deception to occur. Possible future studies are presented that will allow further testing of this hypothesis.

Experimental and numerical study of underwater laser transmission welding

This work demonstrates the feasibility of the underwater laser transmission welding (LTW) of polycarbonate sheets. The experiments are performed to investigate the effect of water depth, laser power, beam diameter, and scan speed on the weld strength, weld dimensions, and bond morphology. The results of mechanical properties and bond morphology of the weld joint in underwater are compared with air environment. The lap shear tests are performed to obtain the shear force–displacement of the welded joints. A three-dimensional (3-D) numerical model is developed to estimate the interface temperature in the underwater condition, which is validated by comparing the numerical weld width and weld depth with their corresponding experimental value. The bond morphology of the weldments is analyzed by the optical microscope and scanning electron microscopy (SEM). The results show that a maximum mean breaking force of 567.5 N is obtained at the 20 mm water depth which is 6 % higher than air due to lower thermal degradation and wider bubble-less region inside the welded region.