Impact Speed Research Articles

Foreign object damage characteristics of a thin nickel-based superalloy plate at room and high temperatures

Turbine blades with thin-walled structures usually works in harsh environments, and foreign object damage (FOD) is one of the conditions of special concern. In this paper, the FOD characteristics of thin nickel-based superalloy plates are studied by a combination of experimental, numerical and analytical methods, considering room and high temperatures, different impact conditions and plate thicknesses. An easy-to-use test system is developed to realize high speed impact of the thin nickel-based superalloy plate under elevated temperature. Crater morphologies, internal microstructure, and residual stress are analyzed after impact with different conditions. Numerical simulation of the impact process is performed by using Johnson-Cook (J-C) constitutive model. Based on Hertz theory, an analytical method for calculating the crater length and depth is proposed considering the deformation of the impact steel sphere. Results shows that the FOD characteristics at high temperature is significantly different from that at room temperature. The crater has lager dimensions under high speed and elevated temperature. Moreover, significant grain refinement is obvious and the dislocation layer is also thicker at higher speed and higher temperature. Due to the effect of high temperature softening, hardness and residual stress after impact with elevated temperature is lower than that at room temperature. Besides, non-normal impact mainly influences Goss texture and distribution of residual stress after high temperature impact. In addition, it is found that thickness have a significant effect on the FOD characteristics especially when the plate is thinner. The validity of the numerical model and analytical method is proved by comparing with the experimental results. The present study can provide data foundation and numerical analysis support for the damage assessment and maintenance of turbine blades.

Static and dynamic fracture toughness of graphite materials with varying grain sizes

Graphite materials play critical roles as moderators, reflectors, and core structural components in high-temperature gas-cooled nuclear reactors. During the reactor operation, graphite materials may experience a variety of loads, including thermal, radiation, fatigue, and dynamic loads, potentially leading to crack initiation and propagation. Therefore, it is imperative to investigate their fracture properties. Despite this, there remains a paucity of comprehensive studies on the fracture toughness of graphite materials with varying grain sizes, particularly concerning dynamic fracture toughness. This study addresses this gap by employing a digital-image-correlation-based virtual extensometer to analyze crack propagation in graphite materials of different grain sizes, enabling precise measurement of crack propagation length and fracture toughness. Findings reveal that static fracture toughness increases with larger grain sizes, while under dynamic loading, smaller grain sizes exhibit greater fracture toughness. Additionally, dynamic fracture toughness shows a near-linear increase with impact speed. Scanning electron microscopy analysis of fracture surface morphology highlights the impact of grain size and impact speed on fracture toughness. Nuclear graphite specimens with larger grain sizes have more irregular grain and pore distributions, enhancing crack deflection and propagation resistance, thereby increasing fracture toughness. The observed loading rate dependence of dynamic fracture toughness is attributed to a gradual transition from intergranular to transgranular fracture modes with increasing impact speed.

A self-regulation blades wind energy harvester system for self-powered wireless monitoring sensors

Using wind energy in the natural environment provides a promising solution for wireless sensor power supply for ecological, meteorological, environmental, and infrastructure monitoring. However, the uncertainty and disorder of natural wind restrict the further development of wind energy harvester systems and self-powered wireless sensor technology. Hence, this paper proposes a self-regulation blade wind energy harvester system (SBWEHS) for self-powered wireless monitoring sensors in remote field areas with power shortages. The system is mainly composed of three parts: wind harvesting mechanism, generator module, and energy storage module. The device can control the blade overlap ratio according to the wind speed while generating electricity to maximize the power coefficient. The system can control the blade’s closure in bad weather to protect the device. Based on the computational fluid dynamics technology of Ansys Fluent software, this study evaluated the impact of wind speed and blade overlap ratio on the two-stage blades. Experiments revealed that when the overlap ratio of the blades is fixed at 0.2 and the wind speed is set at 16 m/s, the maximum average power will reach 0.79 W, which fulfills the power requirements of wireless sensors. These results illustrate that the SBWEHS can effectively supply power for wireless monitoring sensors, especially in remote natural environments.

A multi-agent reinforcement learning approach for ART adaptive control in automated container terminals

Intelligent transportation equipment represented by Artificial Intelligence Robot of Transportation (ART) has been gradually applied to automated container terminals (ACT). ARTs have higher intelligence and distributed autonomous decision-making capability compared to AGVs. The production and operation of ACT require strict loading plans based on container types and destination ports, which puts strict requirements on the ART loading task sequence. ART travel time from the yard to the quay is highly uncertain due to special scenarios such as traffic flow convergence and turning in narrow areas, which will lead to long waits for ART due to out-of-sequence arrivals at the quay. Therefore, it is necessary to regulate the speed of ART to adjust the timing of ART arriving at the quay. However, existing scheduling systems tend to ignore the impact of ART speed and loading sequence constraints on terminal operations. To optimize the multi-ART control problem of ACT, the waiting time of ART at the quay is taken as the optimization goal, and the speed regulation of ART during each task is defined as a Markov decision process. Then, by incorporating reinforcement learning and a multi-agent approach, an adaptive decision-making method is developed to generate the optimal speed regulation strategy. This method interacts with the multi-agent simulation environment to obtain real-time status information and learns strategies online to improve the intelligence of individual agents and the collaborative capabilities of the agent group. Finally, a multi-agent simulation model embedded with a reinforcement learning agent is established on AnyLogic software. Simulation results show that this method can effectively reduce the waiting time of ART, improve the coherence and efficiency of loading operations, and exhibit good performance in online scenarios that consider emergency tasks. The results indicate that the speed of ART in ACTs with parallel layout of the yard can impact the operational efficiency of the system. Furthermore, by appropriately defining the reward function and training method, collaborative behaviour among equipment can be enhanced, ultimately optimizing the overall performance of the system.

Comparison of Electromyographic Characteristics of Volleyball Players in Stop-jumps: An Analysis at Different Speeds

The stop-jump is a crucial skill in volleyball, and analyzing its motion can greatly benefit the training of volleyball players. This paper analyzed 30 players from the volleyball team at Chongqing Normal University. To study the impact of running speed on lower limb muscle activity during stop-jumps, the players were randomly assigned the low-speed running group, the medium-speed running group, and the high-speed running group. Surface electromyography sensors were employed to collect electromyographic signals from the rectus femoris, vastus lateralis, and gastrocnemius muscles of the players during the execution of the stop-jump. The electromyographic indicators were calculated using the surface electromyography system’s built-in program, including the root-mean-square (RMS) electromyographic value and integral electromyographic (IEMG) value. The former represents the effective discharge value of motor units, which depends on the electromyographic amplitude and is related to the number of recruited motor units. The latter represents the discharge capacity of motor units involved in muscle activity per unit of time, reflecting the degree of muscle activation during exercise. Then, statistical analysis was performed on these calculated indicators using SPSS software. It was found that the stop-jump comprised three distinct stages: stop, jump, and flight. Regardless of the stage, the results indicated that the higher the speed of running, the greater the electromyographic indexes of the muscle groups. Additionally, when comparing electromyographic indexes across different stages, it was observed that the index values gradually decreased with the progression of each stage.

Assessing the Effectiveness of Speed, Agility, and Quickness (SAQ) Training on Performance among Senior and Junior Female Kho-Kho Players in Mumbai Region

Abstract: This study examines the impact of an eight-week Speed, Agility, and Quickness (SAQ) training program on senior and junior female Kho-Kho players in Mumbai. Sixty players were evenly divided into experimental and control groups. Results show significant improvements in SAQ-trained players’ performance, including enhanced speed, agility, and quickness observed through reduced completion times in Kho-Kho drills. ANOVA analysis indicates statistically significant differences in performance between experimental and control groups across various parameters. SAQ-trained groups consistently outperformed controls in sprint times, agility test scores, and reaction times. For instance, seniors in the experimental group improved from a pre-training mean sprint time of 12.5 sec to 10.8 sec post-training, while juniors improved from 13.2 sec to 11.2 sec. In contrast, control group means remained relatively unchanged. Similarly, experimental groups exhibited substantial enhancement in agility test scores and reaction times compared to controls. Seniors’ agility scores increased from a pre-training mean of 18 points to 24 points post-training, and juniors’ scores improved from 16 points to 22 points. Reaction times for both senior and junior experimental groups decreased notably post-training, whereas control groups showed minimal change. These findings emphasize the significance of integrating SAQ training into the routine of female Kho-Kho players, regardless of their age or skill level. Such training interventions hold promise for augmenting players’ physical capabilities and overall performance, thereby bolstering their competitiveness in Kho-Kho tournaments.

CONSTRUCTIONS OF THE PROTECTIVE STRUCTURES UNDER THE CONDITIONS OF HIGH-SPEED IMPACT

The stability of the building is characterized by the depth of penetration of the punch into the body of the structures, as well as their local damage due to the impact load. There was accumulated experience of mathematical modeling of the impact processes of solid bodies on various targets. The range of deformations changes of the reinforced concrete elements ("slab"), which corresponds to the high-speed interaction at the moment of punching by a solid body ("impactor") with an initial impact speed of up to 1000 m/s, as well as the determination of their dynamic nature of deformation require comprehensive justification. The analytical solution of the mathematical system of equations describing the movement of the impactor, as well as the state of the impactor and the slab during their interaction can be applied in a limited range. Therefore, the assessment of the local effect of the impact can be carried out on the basis of the results of experimental studies using empirical formulas, as well as numerical methods of modeling the work of bodies taking into account their elastic-plastic characteristics. The ANSYS software package was used in the conducted research, which implements a system of mathematical equations that describe the movement and state of the "impactor-slab" during their interaction. Based on the results of the performed numerical modeling, it was established that the tested slabs with the use of combined reinforcement - mesh and dispersed metal fiber - are not penetrated by the impactor, part of the sample remains intact. At the same time, the final speed of the impactor in these slabs is up to 35.0% less than in the slabs with the mesh reinforcement. The penetration depth decreased up to 20.0%. The experience of dispersion strengthening of the concrete indicates the inhibition of cracking in the fiber concrete elements, which makes it expedient for usage in the combined reinforced constructions of the protective structures, capable of withstanding the dynamic impacts under conditions of high-speed impact. Further development of the of technological concretes studies is needed for their possible use in barrier structures of protective structures.

Impact of Variable Speed Drive Jobsheet Integrated with Project-Based Learning Model on Electric Motor Control Skills of Vocational Students

The problem in this study is that many students in the electrical power installation engineering (EPIE) class have not mastered the skills of electric motor control (EMC). This is because the teacher still uses traditional methods in the learning process. Namely, the teacher actively explains the material according to practical experience rather than referring to EMC learning objectives. This study aims to apply a variable speed drive (VSD) jobsheet based on project-based learning (PjBL) in the EMC learning process and measure the effectiveness of the jobsheet applied. The research method used was a pre-experiment with an intact group comparison research design. The research subjects were taken from 11th-grade students of vocational schools majoring in electrical power installation engineering and were assessed using a questionnaire instrument to evaluate students' EMC performance. Data analysis techniques used were independent t-test and effect size test. Based on the independent t-test analysis results, the t-value is larger than the t-table (t = 4.936 > 1.99962), and the significance value is 0.000, which shows a significant difference in skills between the experimental and control classes. Based on the effect size analysis, the value is 1.243, which means the jobsheet can improve students' EMC skills in the large category. Based on these two results, it is known that the PjBL-based VSD jobsheet is effective in the EMC learning process. Thus, it is expected that EPIE vocational high schools can use the PjBL-based VSD Jobsheet in the EMC learning process.

Investigation on the Impact Fracture Mechanism of Rock in Microgravity Environment Using the Continuum-Discontinuum Element Method

Abstract In-depth analysis of asteroid samples will provide a key scientific basis for understanding its evolution history, resource utilization, and life origin. Obtaining rock samples from asteroids is getting more and more attention. However, successful sampling in asteroid is difficult due to extremely complex environmental conditions. In this paper, the dynamic processes of rock failure by sampling device are investigated by a continuum-discontinuum element method (CDEM) to instruct the rock sampling in asteroid. The deformation and failure of rock samples under different conditions (impact speeds, impact positions, rock cut-slot numbers, cut-slot spacings, cut-slot depths and cut-slot widths, etc.) are analyzed, and the relationships between the rock failure and hammer impact method are obtained. The results show that the cut-slot formed by grinding wheel increases the free surface of rock sample, which is beneficial to impact fracture and asteroid sampling. The relative distance between cut-slot free surface and impact position significantly affects the rock fracture under impact loading. The fracture degree of rock with single cut-slot is obviously smaller than that of rock with double cut-slots, the cut-slot scheme of double grinding wheels is more suitable for asteroid sampling. Under the impact loading, the rock fracture is negatively correlated with the cut-slot spacing formed by double grinding wheel cutting, the effective spacing of double cut-slots is 12 mm. The fracture unit number of rock varies nonlinearly with an increase of the depth from impact position, there is an optimal cut-slot depth corresponding to a certain impact velocity, and the rock crushing efficiency of asteroid sampling can be improved as the cut-slot depth matches the crack propagation depth.

Impact of Insertion Speed, Depth, and Robotic Assistance on Cochlear Implant Insertion Forces and Intracochlear Pressure: A Scoping Review.

Cochlear implants are crucial for addressing severe-to-profound hearing loss, with the success of the procedure requiring careful electrode placement. This scoping review synthesizes the findings from 125 studies examining the factors influencing insertion forces (IFs) and intracochlear pressure (IP), which are crucial for optimizing implantation techniques and enhancing patient outcomes. The review highlights the impact of variables, including insertion depth, speed, and the use of robotic assistance on IFs and IP. Results indicate that higher insertion speeds generally increase IFs and IP in artificial models, a pattern not consistently observed in cadaveric studies due to variations in methodology and sample size. The study also explores the observed minimal impact of robotic assistance on reducing IFs compared to manual methods. Importantly, this review underscores the need for a standardized approach in cochlear implant research to address inconsistencies and improve clinical practices aimed at preserving hearing during implantation.

Experimental investigation of a modified triboelectric charging device

Tribo-charging of plastic particles plays a critical role in the electrostatic separation industry, particularly for sorting millimeter-sized particles. The optimal charge/mass ratio can result in significant particle deviation in high intensity electric fields, making tribo-charging an important area of study. This work examines a modified tribo-electrostatic charging device that utilizes rotating propellers and an added air blower to increase particle charging. Through experimental analysis, the impact of air blower speed, rotating propeller speed, and sample mass was investigated using five different types of millimeter-sized particles. The results of the optimization study indicate a significant improvement in the charge/mass ratio, with the introduction of the air blower increasing the ratio by over 2.5 times.

Numerical Simulation Flow Around the Containership by using CFD Method

Predict accurately resistance of the ship and flow around ship hull form is extremely important as these are input parameters for optimizing ship hull form, designing the ship propulsion system. This paper focuses on the numerical simulation of the flow around the Container Ship Fortune Freighter in calm water condition at different ship speeds by using CFD method. The results of impact of ship speed on components of ship resistance, wave patterns, volume fraction of air, the distribution of pressure, and wall shear stress on the ship's hull surface, as well as the nominal wake field are provided and analysed in this paper.

Comparison of numerical calculations and ALOHA modeling in consequence assessment of chlorine gas emissions from ethylene dichloride reactors.

Incidents involving chemical storage tanks in the petrochemical industry are significant events with severe consequences. Within the petrochemical industry, EDC is a sector that produces ethylene dichloride through the reaction of chlorine and ethylene. The present research was conducted to evaluate the consequences of chlorine gas released from the EDC reactor in a petrochemical industry in southern Iran. Data regarding reactor specifications were obtained from the factory's technical office, while climatic data was acquired from the Meteorological Organization. The consequences of chlorine gas release from the reactor were assessed in four predefined scenarios using numerical calculation methods and modeling with the ALOHA software. The numerical calculation method involved thermodynamic fluid path analysis, discharge coefficient calculations, and wind speed impact analysis. The hazard radius was determined based on the ERPG1-2-3 index. Results showed that in the scenario of chlorine gas release from EDC reactors, according to the ALOHA model, an increase in wind speed from 3 to 7m/h led to an expanded dispersion radius. At a radius of 700m from the reactor, the maximum outdoor concentration reached 3.12ppm, decreasing to 2.27ppm at 800m and further to 1.53ppm at 1000m. The comparison of numerical calculations and modeling using the ALOHA software indicates the desirable conformity of the results with each other. The R2 coefficient for evaluating the conformity of the results was 0.9964, indicating the desired efficiency of the model in evaluating the consequences of the release of toxic gasses from the EDC tank. The results of this research can be useful in designing the site and emergency response plan.

On the Cover: High Speed Impact Testing of UHMWPE Composite Using Orthogonal Arrays

On the Cover: High Speed Impact Testing of UHMWPE Composite Using Orthogonal Arrays

Enhanced Low-Energy Chemical Oxygen Demand (COD) Removal in Aeration-Free Conditions through Pulse-Rotating Bio-Contactors Enriched with Glycogen-Accumulating Organisms

This study presents an innovative pulse-rotating biological contactor (P-RBC) designed to enrich glycogen-accumulating organisms (GAOs), thereby facilitating low-energy chemical oxygen demand (COD) removal. It then investigates the impact of rotational speed and hydraulic retention time (HRT) on GAO enrichment and COD removal efficiency. Optimized conditions at lower speeds and longer HRTs significantly enhance GAO proliferation and Polyhydroxyalkanoate (PHA) synthesis, the key to COD removal. Noteworthy findings include a maximum GAO abundance of 21.34% at a half round per hour (rph) rotating speed, which correlates with a 90.2% COD removal rate and an HRT of 6 h, yielding a 21.23% GAO abundance and 89.8% COD removal. This study also explores various carbon sources for PHA synthesis, with sodium acetate proving the most effective. Compared to other wastewater treatment methods, P-RBC demonstrates minimal energy consumption (0.09 kWh per ton of wastewater), highlighting its potential as a sustainable and effective approach for wastewater treatment.

Thermodynamic modeling and performance analysis of photovoltaic-thermal collectors integrated with phase change materials: Comprehensive energy and exergy analysis

Phase change materials (PCMs) integrated with photovoltaic-thermal (PVT) collectors can simultaneously generate and store electrical and thermal energy. However, design optimization requires accurate modeling of the complex heat transfer processes in PCMs under varying operating conditions. This study introduces an efficient simulation approach with generalized Nusselt number correlations to enable precise and rapid analysis of PCM thermal performance. A numerical model is developed to quantify heat fluxes, node temperatures, energy and exergy outputs across PCM solid, melting, and liquid states. Extensive analysis is conducted to explore the impact of irradiation, ambient temperature, PCM thickness, tilt angle, and wind speed on PVT performance. Key findings include: (1) thermal energy yield exceeds electrical output by 2.8 times owing to PV's low efficiency, while electrical exergy dominates thermal exergy by 5.3 times highlighting electric output's primacy; (2) electrical output chiefly depends on irradiation, while thermal energy and exergy are highly sensitive to ambient temperature and wind speed; (3) thermal energy escalates 4.5 times faster than electrical energy with irradiation rise, but thermal exergy drops sharply from 10.1 to 0.34 W as ambient temperature increases from 0 to 35 °C due to quality factor degradation. The study provides new generalized correlations, validated model, and extensive performance assessment to advance PCM-based PVT collector design.

Acoustic wind tunnel experimental study of aerodynamic noise distribution in high-rise buildings

Wind-induced aerodynamic disturbance has become a major noise source affecting residents in super high-rise buildings. To investigate the distribution characteristics of aerodynamic noise on high-rise building surfaces in strong wind conditions and the impact of wind speed and direction, this paper pioneers the application of the acoustic wind tunnel method based on microphone array localization to the experimental study of the surface acoustic pressure field of a high-rise building model, the far-field noise spectrum of which is obtained using the microphone array sensor. The beamforming calculation method was used to obtain the spectrum and localization cloud. By comparing the spectra and cloud diagrams under different process conditions and based on existing building wind pressure reports, it is concluded that: the noise source is always located at the height of the connecting corridor where there is large wind pressure pulsation in the two building models; the aerodynamic noise is more pronounced around building gaps where the airflow is more disturbed and also in the oncoming wind trailing direction where the wind pressure pulsation is more pronounced. An increase in wind speed increased noise source amplitude from 30 dB to 60 dB, and the location of the noise source shifted backwards to the tail of the incoming wind. This paper shows that the acoustic wind tunnel method based on microphone array localization technology can obtain the aerodynamic noise intensity on the surfaces of super high-rise buildings and reasonably predict the location of the sound source. This article puts forward suggestions to reduce noise in high-rise buildings based on experimental results.

Overvoltage Avoidance Control Strategy for Braking Process of Brushless DC Motor Drives with Small DC-Link Capacitance

Single-phase input rectifier brushless DC motor drives with a small film capacitor have many advantages, such as high power density and high reliability. However, when the motor system operates in regenerative braking mode, the dc-link capacitor with reduced capacitance may suffer from overvoltage without adding additional hardware circuits. At the same time, the braking torque control of the motor will be affected by speed variations. In order to ensure smooth and reliable operation of the motor system, an anti-overvoltage braking torque control method is proposed in this article. The relationship among the dc-link capacitance, the dc-link capacitor voltage, and the speed during regenerative braking is analyzed quantitatively, and the speed at which the regenerative braking is switched to the plug braking is obtained, which in turn consumes the capacitor energy to avoid dc-link overvoltage. Additionally, based on the relationship between the controllability of the braking torque and the speed, a reference value of the braking current that matches the speed is designed. The proposed method makes use of the capacitor’s energy storage during regenerative braking. Meanwhile, it mitigates the impact of motor speed on braking torque. Finally, the effectiveness of the proposed method is verified on a motor platform equipped with the dc-link film capacitor.

Laser-Based Mobile Visible Light Communication System.

Mobile visible light communication (VLC) is key for integrating lighting and communication applications in the 6G era, yet there exists a notable gap in experimental research on mobile VLC. In this study, we introduce a mobile VLC system and investigate the impact of mobility speed on communication performance. Leveraging a laser-based light transmitter with a wide coverage, we enable a light fidelity (LiFi) system with a mobile receiving end. The system is capable of supporting distances from 1 m to 4 m without a lens and could maintain a transmission rate of 500 Mbps. The transmission is stable at distances of 1 m and 2 m, but an increase in distance and speed introduces interference to the system, leading to a rise in the Bit Error Rate (BER). The mobile VLC experimental system provides a viable solution to the issue of mobile access in the integration of lighting and communication applications, establishing a solid practical foundation for future research.

Crashworthiness Study of Functional Gradient Lattice-Reinforced Thin-Walled Tubes under Impact Loading.

Creating lightweight and impact-resistant box structures has been an enduring pursuit among researchers. A new energy-absorbing structure consisting of a bionic gradient lattice-enhanced thin-walled tube is presented in this article. The gradient lattice and thin-walled tube were prepared using selective laser melting (SLM) and wire-cutting techniques, respectively. To analyze the effects of gradient pattern, mass ratio, diameter range and impact speed on structural crashworthiness, low-speed impact at 4 m/s and finite element simulation experiments were conducted. The study demonstrates that the design of inward radial gradient lattice-reinforced thin-walled tubes can effectively enhance structure's energy-absorption efficiency and provide a more stable mode of deformation. It also shows a 17.44% specific energy-absorption advantage over the uniformly lattice-reinforced thin-walled tubes, with no significant overall gain in peak crushing force. A complex scale evaluation method was used to determine the optimum structure and the structure type with the best crashworthiness was found to be a gradient lattice-filled tube with a thickness of 0.9 mm and a slope index of 10. The gradient lattice-reinforced thin-walled tube suggested in this investigation offers guidance for designing a more efficient thin-walled energy-absorption structure.