Decrease In Force Research Articles

Dynamic behavior of rack vehicle-track(rack) coupled system on super-large-slope bridges

Rack railways are mainly used in mountainous areas, where inevitably, super-large-slope bridge structures appear. The dynamic behavior of the rack vehicle-track(rack) coupled system on super-large-slope bridge is rarely studied. To address this issue, a dynamic interaction model for rack vehicle-track(rack)-bridge system is established by considering the detailed dynamic meshing behavior of gear-rack and the dynamic contact behavior of the wheel-rail. On this basis, the gear-rack meshing force and the wheel-rail contact force of rack vehicles are studied under lines with varying slopes, and the dynamic behavior of the rack vehicle and the track-bridge system with a slope of 250‰ is further analyzed. Research results show that as the slope line increases, the gear and rack meshing force increases, but the wheel-rail vertical force decreases. Concurrently, the stability index of the vehicle changed considerably, and the stability of the vehicle decreases substantially. The maximum values of the vibration acceleration of the vehicle body and bridge are 0.4 m/s2 and 0.5 m/s2, respectively, meeting the requirements of the relevant standards for the vibration acceleration of the vehicle body and bridge. Further analysis reveals that the vibration of rack is mainly affected by the meshing force, and the vibration of the bridge is mainly affected by the wheel-rail force. These research results can offer a theoretical basis for the pre-design, post-operation, and maintenance of rack railways.

Characteristic Changes of the Stance-Phase Plantar Pressure Curve When Walking Uphill and Downhill: Cross-Sectional Study.

Monitoring of gait patterns by insoles is popular to study behavior and activity in the daily life of people and throughout the rehabilitation process of patients. Live data analyses may improve personalized prevention and treatment regimens, as well as rehabilitation. The M-shaped plantar pressure curve during the stance phase is mainly defined by the loading and unloading slope, 2 maxima, 1 minimum, as well as the force during defined periods. When monitoring gait continuously, walking uphill or downhill could affect this curve in characteristic ways. For walking on a slope, typical changes in the stance phase curve measured by insoles were hypothesized. In total, 40 healthy participants of both sexes were fitted with individually calibrated insoles with 16 pressure sensors each and a recording frequency of 100 Hz. Participants walked on a treadmill at 4 km/h for 1 minute in each of the following slopes: -20%, -15%, -10%, -5%, 0%, 5%, 10%, 15%, and 20%. Raw data were exported for analyses. A custom-developed data platform was used for data processing and parameter calculation, including step detection, data transformation, and normalization for time by natural cubic spline interpolation and force (proportion of body weight). To identify the time-axis positions of the desired maxima and minimum among the available extremum candidates in each step, a Gaussian filter was applied (σ=3, kernel size 7). Inconclusive extremum candidates were further processed by screening for time plausibility, maximum or minimum pool filtering, and monotony. Several parameters that describe the curve trajectory were computed for each step. The normal distribution of data was tested by the Kolmogorov-Smirnov and Shapiro-Wilk tests. Data were normally distributed. An analysis of variance with the gait parameters as dependent and slope as independent variables revealed significant changes related to the slope for the following parameters of the stance phase curve: the mean force during loading and unloading, the 2 maxima and the minimum, as well as the loading and unloading slope (all P<.001). A simultaneous increase in the loading slope, the first maximum and the mean loading force combined with a decrease in the mean unloading force, the second maximum, and the unloading slope is characteristic for downhill walking. The opposite represents uphill walking. The minimum had its peak at horizontal walking and values dropped when walking uphill and downhill alike. It is therefore not a suitable parameter to distinguish between uphill and downhill walking. While patient-related factors, such as anthropometrics, injury, or disease shape the stance phase curve on a longer-term scale, walking on slopes leads to temporary and characteristic short-term changes in the curve trajectory.

Effect of verjuice (Vitis vinifera L.) on physicochemical and textural properties of beef M. biceps femoris.

The objective of this study was to investigate the effect of verjuice on beef M. biceps femoris (BF). BF blocks were marinated with 30%, 70%, and 100% verjuice solutions containing 2% NaCl, for different marination times (12, 24, 48, and 72 h). Verjuice marination reduced the pH values of BF samples from 6.77 in control sample to 3.66 in 100% of verjuice for 72 h. The decreased values of water holding capacity (from 54.06% to 47.46%) with increasing verjuice concentration (from 30% to 100% for 72 h) confirmed the drop of proteins isoelectric point of the muscle due to salt presence preventing fibers swelling. Less cookout was observed with increasing acid concentration. Marination time had no significant effect on L* and a* coordinates of uncooked samples while acidification made the samples lighter and less red. Enzymatic proteolysis of myosin and troponin-T concomitant with increase in myofibrillar fragmentation index contributed to the decrease of shear force in a way dependent on verjuice concentration and marination time. Sensory panelists gave the highest score to cooked samples marinated with 70% verjuice solution.

Evaluation of the influence of the material composition on the peel behavior of adhesive and cohesive peel systems using experimental fracture mechanics methods

AbstractThe study focusses on a low‐density polyethylene/isotactic polybutene‐1 peel system with low‐density polyethylene as matrix and isotactic polybutene‐1 as peel component sealed against itself (cohesive peel system), and on an ethylene vinyl acetate/linear low‐density polyethylene peel system with ethylene vinyl acetate as matrix and linear low‐density polyethylene as peel component sealed against polyethylene terephthalate (adhesive peel system). Due to a new approach to estimate the true fracture surface using 3D reconstruction, it was possible to determine the true adhesive energy release rate, especially for cohesive peel systems. This enables a direct comparison of the fracture mechanics parameters determined from both types of peel systems. The results reveal that the recipe has a distinct influence on the peel behavior. An increasing amount of the used peel component leads in any case to a decrease of the peel force as well as of the energy release rate for both, sealed adhesive and cohesive peel systems. Using application engineering examples generalizable relationships between structure and properties of peel systems could be estimated and the structure sensitivity of the fracture mechanical parameters could be proven.

Utilization of factory tea (Camellia sinensis) wastes in eco-friendly dyeing of jute packaging fabrics

Eco-friendly dyeing of jute packaging fabrics was evaluated using aqueous extraction of factory tea (Camellia sinensis) wastes. Jute and factory tea wastes are available in Bangladesh and jute bags are used for packaging of various exportable agricultural commodities. The extract of factory tea waste (FTW) is dark coffee colored and it was characterized by attenuated total reflection-fourier transform infrared (ATR-FTIR) and microbial analysis. Nontoxic, non-allergic and eco-friendly natural dyeing process of jute packaging fabrics using extract of FTW were developed and optimized. Metal mordants 10 % on the weight of fabric was used to get the fastness properties of dyed jute fabric. The methods of application of mordants were pre-mordanting, simultaneous or meta-mordanting and post-mordanting. The color fastness and tensile properties were measured for all jute packaging fabrics and it is found that the dyed jute packaging fabrics showed a slight decrease in tensile breaking force (N) than undyed jute packaging fabric. The highest color fastness obtained with the meta mordanting method with ferrous sulfate mordant in a shade of dark coffee. The results of the color fastness for light and washing showed an excellent value of grade 4–5.

Calculation model of bending deformation force of magnesium alloy integral panel

The mechanical characteristics of bending forming for magnesium alloy panel is analyzed, and mechanical model is established, stress and strain state is analyzed. A calculation model of the bending force of magnesium alloy panels is proposed firstly, which considers panel thickness, die width, and bending deformation coefficient of the panel. The theoretical calculation results of bending force for magnesium alloy panels are consistent with experimental results, in which the maximum relative error is 4.96%. The bending force is related to the curvature radius and forming temperature of the panel. As the reduction height increases, the curvature radius of the panel decreases, and the bending force increases. As the deformation temperature increases, the bending force decreases.

Numerical investigations of the restriction effects on a ship navigating in pack-ice channel

This paper adopts Computational Fluid Dynamics (CFD) method and Discrete Element Method (DEM) to simulate a ship navigating in pack-ice channel considering the effects of channel restriction. First, from the simulations of the ship sailing in open-water channel by CFD, it is found that the effects of channel width on water resistance is more pronounced than the impacts by level-ice thickness. Then, based on the stable and converged flow field obtained by CFD simulations, the CFD-DEM coupling method is applied to reveal the effects of channel width and level ice thickness on ship-ice-water interactions and ice resistances at different ship speeds. The results indicate that as the channel width decreases, the accumulation of pack ice in the areas of bow and midship intensifies. The ice resistances on the bow and midship increase notably, and the lateral ice forces exhibit pronounced asymmetric and random characteristics. In extremely narrow pack-ice channels, lower ship speed results in lager ice resistance and lateral ice force on the ship. In addition, as the level ice thickness decreases, the pack ice is more easily squeezed below the level ice, resulting in the decreases of ice resistance and lateral ice force.

VARIASI SHEAR KEY TERHADAP STABILITAS DINDING PENAHAN TANAH KANTILEVER BETON BERTULANG

Stability parameters are very important in the analysis and design of reinforced concrete cantilever retaining wall structures. One of the parameters to increase the stability of this retaining wall is to add a shear key structure. Shear keys can increase wall stability, resist shear, increase stiffness, resist lateral loads, and increase load capacity. The purpose of this research is to determine the level of stability (overturning and shearing) of reinforced concrete cantilever retaining walls by varying the shear key dimensions with the same cross-sectional area. The method used is a quantitative method using data on the properties of soil materials, reinforced concrete, and the geometry of retaining wall structures. The analysis uses the help of Geo5 software, which is geotechnical software for solving problems in the geotechnical field. In this research, four models of reinforced concrete cantilever retaining walls have been created, including model 1 (b/h = 0), namely the model without a shear key, model 2 (b/h = 1), namely square shear key, model 3 ( b/h = 1/4) is a vertical rectangular shear key and model 4 (b/h = 4/1) is a horizontal rectangular shear key. The results of the analysis produce rolling stability with an increase in rolling moment and a decrease in moment of resistance on average of 8.32% and 4.43% respectively for the model without a shear key with a maximum rolling safe factor in the horizontal rectangular shear key model of 2.24. Likewise, the shear stability of the model with a shear key results in an increase in ground shear force and a decrease in active shear force on average of 11.76% and 105.93% respectively compared to the model without a shear key with a maximum shear safe factor in the horizontal rectangular shear key model of 3.96.

Kinetic Comparison between Drop Jumps and Horizontal Drop Jumps in Elite Jumpers and Sprinters

Previous research addressed the spatiotemporal variables of the drop jump (DJ) versus the horizontal drop jump (HDJ). This study compared the kinetic variables of the DJ versus the HDJ in elite jumpers and sprinters. In a single session, sixteen elite jumpers and sprinters performed two DJ attempts with three different fall heights (0.30 m, 0.40 m, and 0.50 m), and after 2 h, performed two HDJ attempts from the same fall heights (0.30 m, 0.40 m, and 0.50 m). Kinetic variables: eccentric ground reaction forces (GRFE) and concentric ground reaction forces; eccentric impulse (PE) and concentric impulse (PC); peak power in the concentric phase; and rate of force decrease (RFDe) were measured using a research-grade force plate. The Wilcoxon test was used to compare the vertical and anteroposterior axes. GRFE was significantly higher (p ≤ 0.05) in the DJ vs the HDJ with large effect sizes. The PE (p ≤ 0.006) and PC (p = 0.002) were significantly lower in the DJ than in the HDJ. The RFDe was also significantly lower in the DJ at 0.30 m vs. the HDJ at 0.30 m (p = 0.002). In summary, elite jumpers and sprinters may benefit from incorporating both the DJ and the HDJ into their training regimens, with the DJ being particularly advantageous for enhancing power metrics and RFDe.

Improving Speed Characteristics of High-Torque-Density Motors for Physical Human–Robot Interaction Using an Independent Three-Phase Winding Structure

Recently, due to the decrease in labor force, increase in labor costs, and the desire for improved quality of life, research on robots has been actively conducted to address these issues. However, it is currently difficult to find robots that physically interact with humans. The reason is that the actuators of robots do not have a high torque density on their own. To solve this problem, high-torque-density motors, such as proprioceptive actuators, are being researched. However, the torque density is still insufficient for physical interaction with humans, so a motor with higher torque density has been developed. However, high-torque-density motors have the disadvantage of lower speed characteristics due to increased Back EMF levels. Therefore, to address the deterioration of speed characteristics in the developed motor, we applied the independent three-phase winding structure to improve the speed characteristics. Consequently, through comparison with the Y-Connection and D-Connection, we propose the most suitable winding structure for high-torque-density motors intended for physical interaction with humans.

Noise Analysis and Optimization Design of an Electric–Mechanical–Hydraulic Power Coupler for the Vehicle

This article proposes a new electric–mechanical–hydraulic power coupler (EMHPC). The EMHPC is integrated by a swash plate axial piston pump and permanent magnet synchronous motor, which can realize the conversion of electric, mechanical, and hydraulic energy. To analyze the noise characteristics of the EMHPC, the mathematical models of fluid noise and electromagnetic noise are established, respectively. An optimization model is built based on Isight, and the multi‐island genetic algorithm is used to optimize the triangular groove structure. The optimization results show that the sound pressure level of sound field monitoring points decreases at different frequencies, and the vibration displacement of the cylinder block decreases. The maximum sound pressure level of the directivity curve of the radiated sound field decreases by 9 dB. For the electrodynamic structure optimization of the EMHPC, this article establishes a combination approximation model with higher accuracy. The structure of the stator and rotor is optimized based on the combined approximate model. The optimization results show that the sinusoidal property of the radial air‐gap magnetic density curve is better after optimization, and the harmonic amplitude of the radial electromagnetic force decreases. The maximum sound pressure level in the air domain of the external sound field is reduced from 69 to 60 dB. Moreover, the superposition analysis of fluid noise and electromagnetic noise is carried out, and the main noise sources of the EMHPC in different working modes are determined.

Multi-Scale Research on the Mechanisms of Soil Arching Development and Degradation in Granular Materials with Different Relative Density

Soil arching is significantly influenced by relative density, while its mechanisms have barely been analyzed. A series of DEM numerical simulations of the classical trapdoor test were carried out to investigate the multi-scale mechanisms of arching development and degradation in granular materials with different relative density. For analysis, the granular assembly was divided into three zones according to the particle vertical displacement normalized by the trapdoor displacement δ. The results show that before the maximum arching state (corresponding to the minimum arching ratio), contact forces between particles in a specific zone (where the vertical displacement of particles is larger than 0.1δ but less than 0.9δ) increase rapidly and robust arched force chains with large particle contact forces are generated. The variation in contact forces and force chains becomes more obvious as the sample porosity decreases. As a result, soil arching generated in a denser particle assembly is stronger, and the minimum value of the arching ratio is increased with the sample porosity. After the maximum arching state, the force chains in this zone are degenerated gradually, leading to a decrease in particle contact forces in microscale and an increase in the arching ratio in macroscale. The recovery of the arching ratio after the minimum value is also more significant in simulations with a larger relative density, as the degeneration of contact force chains is more obvious in denser samples. These results indicate the importance of contact force chain stabilities in specific zones for improving soil arching in engineering practice.

In vitro study examines posterior torque impact on 3D mechanics of anterior teeth in clear aligner treatment

IntroductionThis study utilizes investigate the impact of posterior torques on the three-dimensional force exerted on the lower anterior teeth during the retraction in orthodontic clear aligners treatment.MethodsFour groups of mandibular dental arch light-cured resin models will be created, including: mandibular posterior teeth with standard torque, mandibular posterior teeth with labial torque, and mandibular posterior teeth with lingual torque. Each group will consist of 12 sets of clear aligners. The aligners will be worn, and measurements will be taken using the six-axis measurement platform to evaluate the three-dimensional force exerted on the lower anterior teeth under various initial torques applied to the mandibular posterior teeth. SPSS 26.0 used for ANOVA analysis, α = 0.05 significance level.ResultsComparing mandibular posterior teeth with standard torque to those with labial torque, no statistically significant changes were observed in buccolingual force. In the mesiodistal direction, mandibular incisors exhibited a significant decrease in distal force, while canines showed a significant increase. Both findings had a significance level of P < 0.05; Lingual torque on mandibular posterior teeth, compared to standard torque, led to a significant increase in lingual force for incisors and a significant increase in labial force for canines in the buccolingual direction (P < 0.05). Additionally, mandibular incisors exhibited a significant decrease in distal force in the mesiodistal direction (P < 0.05).ConclusionVarying initial torques on mandibular posterior teeth significantly impact force on lower anterior teeth. Labial torque reduces lingual force on incisors and increases distal force on canines. Lingual torque increases lingual force on incisors and labial force on canines.

Mechanism and deformation behavior of elliptical vibration-assisted cutting of FeNiCrCoAl high entropy alloy

The mechanical response of FeNiCrCoAl high entropy alloy (HEA) under conventional cutting and ultrasonic elliptical vibration-assisted cutting (UEVAC) was investigated using molecular dynamics (MD) methods. The effects of vibration period, axial amplitude, and normal amplitude on the material removal mechanism were studied. The results show that the average cutting temperature of the workpiece under UEVAC is significantly higher than that under conventional cutting. The high-temperature distribution area under UEVAC presents an intermittent distribution pattern, which not only facilitates the cutting process but also plays a positive role in the protection of the tool. Furthermore, as the vibration period shortens, both the average principal stress experienced by the workpiece and the triaxial cutting force decrease, while the height and quantity of chip atoms significantly increase. When the vibration period is shortened to 5 ns, the number of chip atoms is about twice that of conventional cutting, which is equivalent to doubling the removal efficiency of the material. Although an increase in axial amplitude causes an increase in the average temperature of the workpiece, it also results in larger negative principal stress. When the axial amplitude A increases to 20 Å, the peak value of the negative principal stress generated inside the base material exceeds 8000 GPa, and the triaxial cutting force tends to increase, without a significant increase in the number of chip atoms. With the increase in normal amplitude B, the average cutting temperature of the matrix also increases. But there is no significant change in the direction and magnitude of the principal stress, and the triaxial cutting force continuously increases. This study provides a theoretical basis for achieving high surface quality of HEAs.

Effect of comonomer loading on the thermal and mechanical properties of biobased copolyamides PA6/PA56

With bio-renewable and environmentally friendly nature, biobased polyamides have emerged as attractive alternatives to traditional petroleum-derived polymers. However, poor thermal and mechanical performance, high costs, and limited scalability significantly hinder their practical applications. Herein, a series of biobased copolyamides PA6/PA56 (CoPAs) were successfully synthesized from caprolactam, adipic acid, and the lysine-derived biobased monomers 1,5-pentanediamine. The copolyamides were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (1H NMR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), rheological analysis, mechanical testing, and scanning electron microscopy (SEM). The result shows the α to γ transition in the crystalline form of the copolyamides with comonomer loading. The melting temperature, crystallization temperature, and crystallinity gradually decrease due to the introduction of the odd-even structure, causing deviation in amide positions and reducing hydrogen bond formation between molecular chains. Furthermore, variable-temperature infrared (VTIR) analysis and density functional theory (DFT) calculations further confirm a decrease in intermolecular forces. Importantly, the mobility of the molecular chains in the amorphous region is significantly improved, endowing the copolyamides with sufficient degrees of freedom to cope with externally applied strains. Moreover, significant entanglement facilitates effective stress transfer during stretching. As a result, the synthesized copolyamides achieve a high strength of 51 MPa and a remarkable toughness of 199 MJ/m3, without sacrificing thermal stability and processing properties. These biobased CoPAs show great potential and prospects in the field of high-performance thermoplastic materials, films, and textiles.

Garlic oil improves small intestinal motility in experimentally induced type II diabetes mellitus in female Wistar rats.

Diabetes mellitus adversely affects the contractile ability of the small intestine. However, there is a paucity of studies investigating the impact of garlic oil on small intestinal motility. This study aimed to evaluate the potential beneficial effects of garlic oil on type 2 diabetes mellitus in rats. Thirty-six adult female Wistar rats (n = 36) were divided into four groups: control, non-diabetic rats supplemented with garlic oil, diabetic rats, and diabetic rats treated with garlic oil. The rats were anesthetized using pentobarbitone (40 mg/kg BW); various motility parameters and oxidative markers were determined in small intestinal segments. Measurements were taken for naso-anal length, waist circumference, fasting blood glucose level (FBG), and plasma insulin level. Compared to the control group, the diabetic rats exhibited a reduction in the average force of contraction and motility index in all small intestinal segments. Furthermore, the rats exhibited a reduction in the average duration of muscle contraction only in the jejunum. The rats also exhibited hyperglycemia, insulin resistance, significant oxidative stress, and obesity. This was proven by changes in motility parameters, fasting blood glucose levels, HOMA-IR values, intestinal MDA levels, and waist circumference. The non-diabetic rats supplemented with garlic oil also exhibited a decrease in the average force of contraction and motility index in all small intestinal segments, despite having consistently higher Lee index and waist circumference values. However, the diabetic rats treated with garlic oil demonstrated improved small intestinal motility in nearly all small intestinal segments and a reduction in oxidative stress. In conclusion, rats with diabetes mellitus experienced a decrease in small intestinal motility, which is primarily driven by oxidative stress. Normal rats administered with garlic oil supplements exhibited similar effects. In contrast, garlic oil treatment in diabetic rats led to enhanced small intestinal motility and a notable anti-hyperglycemic effect, which can be attributed to the potent antioxidant properties of garlic oil.

Research and Characteristic Analysis of A New Type of Dual Winding Electromagnetic Brake

Taking the electromagnetic brake as the research object, a new structure of double-winding electromagnetic brake is proposed in view of the serious temperature rise phenomenon of traditional single-winding electromagnetic brake, the high requirement of insulation level and the obvious decrease of electromagnetic force. The equivalent magnetic circuit method is used to analyze and calculate the magnetic field, and the simulation model of the new brake is constructed, and the influence of different parameters on the braking characteristics of the double-winding electromagnetic brake is analyzed by the single-variable method, and the influence curves of each parameter on the electromagnetic force and response time are obtained. At the same time, the magnetic-thermal coupling analysis of the double-winding electromagnetic brake is carried out, and the results show that the total ampere-turns and power of the double-winding electromagnetic brake decreases by 15.3% in the same proportion, the rated electromagnetic force decreases by 22.9%, the release time grows by 23.7%, and the closure time is shortened by 14.6%.

The Impact of Range of Motion on Applied Force Characteristics and Electromyographic Activity during Repeated Sets of Bench Press Exercise.

This study examined the effects of range of motion (ROM) on applied force, power output and surface electromyographic (sEMG) responses during repeated sets of bench press exercise executed as fast as possible. Ten resistance trained men performed three sets to momentary failure with two-min rest intervals under three different ROM conditions: (a) full ROM (FULL), (b) TOP, at the top half of ROM, and (c) BOTTOM, at the bottom half of ROM. Mean and peak force were higher in TOP compared to FULL and BOTTOM (mean force: 817 ± 80 vs. 657 ± 98 vs. 623 ± 122 N, respectively, p < 0.001) with no differences between FULL and BOTTOM. During repeated sets, large decreases were found in peak (by 29.4 to 45.3%) and mean power (by 55.5 to 64.7%) from the first to the last repetitions. However, the decrease in mean force was only 2% (p < 0.01) and decreases in peak force ranged from 6.7 and 8.8% to zero, indicating the velocity loss was the main contributor to fatigue in power output. Although force and power output in set 3 were unchanged in BOTTOM, mean power output decreased significantly, suggesting that lower performance and fatigue may be related to the longer muscle length. Fatigue was accompanied by an increase in sEMG activity and a decrease in median frequency in all muscles, with triceps brachialis sEMG reflecting more the force and power differences among ROMs. In conclusion, fatigue depends on velocity rather than force loss during bench press exercise at different ROMs.

Multi-objective optimization of electro-pneumatic braking process with fuzzy logic control for heavy haul railway applications

ABSTRACT This paper presents a novel approach to multi-objective optimization in heavy haul trains’ electro-pneumatic braking systems using optimizable fuzzy control. Initial findings indicate that a straightforward replacement of pneumatically controlled valves with electro-pneumatic ones, without significant control schedule modifications, fails to substantially improve the dynamics behaviour of rolling-stock. Consequently, a more sophisticated strategy based on optimizable fuzzy logic control for the electro-pneumatic valves was developed. This approach utilizes multi-objective optimization to simultaneously minimize energy dissipation during braking and reduce force peaks in freight car draft gears. The optimal solution achieved demonstrates a 13.41% reduction in kinetic energy dissipation during downhill sections, along with a concurrent decrease in draft gear peak forces by 14.22% in traction and 3.16% in buff regimes compared to standard rolling-stock with pneumatically controlled valves. This optimized fuzzy braking controller outperforms standard procedures, highlighting its potential to enhance heavy haul train efficiency while adhering to safety standards.

Nanoindentation responses of NiCoFe medium-entropy alloys from cryogenic to elevated temperatures

NiCoFe alloy, a medium-entropy alloy, shows potential for applications in extreme environments. However, there is a theoretical barrier concerning the unclear understanding of its high-temperature dislocation motion mechanism. The load response exhibits distinct signatures relevant to thermal activation, most notably a decrease in critical force (i.e., softening) from cryogenic to elevated temperatures, e.g., from 200 to 1000 K. The onset of plasticity is characterized by the nucleation of stacking faults and prismatic loops at low temperatures, whereas the surface nucleation of Shockley partial dislocations dominates plasticity at elevated temperatures. We show that thermal effects lead to non-uniform atom pile-ups and control the rate of phase transformation with increasing indentation depth. The findings in this work extend the understanding of the mechanical response of NiCoFe alloys under indentation at different temperatures, shedding light on the underlying dislocation motion mechanisms and surface deformation characteristics. The observed transformation-induced plasticity mechanism has implications for the properties of medium-entropy alloys and their potential applications in extreme environments.