Extreme Working Conditions Research Articles

Microstructure and properties of TiC ceramic powder on a cobalt-based alloy obtained via electromagnetic-assisted laser metal deposition

The crack sensitivity of laser metal ceramic deposition is an important factor restricting its development. In this paper, a TiC-reinforced cobalt-based alloy was deposited on 300M steel using electromagnetic-assisted laser metal deposition technology. The electromagnetic composite effect on the microstructure, mechanical properties, magnetic properties, wear resistance and crack sensitivity of the laser metal deposition layer was discussed. Under the action of an electromagnetic field, the size of the TiC decreased by 54.6% compared with that of the deposited layer without an electromagnetic field. The effect of the electromagnetic composite field can reach the bottom of the molten pool, thus refining the grain size at the bottom of the coating. This resulted in a 22% increase in the hardness of the deposition layer. The electromagnetic field effect reduces the elastic modulus of the deposition layer, thus improving the mechanical properties of the coatings. In addition, compared with that of the deposition layer without an external field, the wear of the deposition layer with an electromagnetic force is obviously reduced. With increasing electromagnetic parameters, the wear resistance of the deposit increased gradually, and the thermal expansion coefficient decreased significantly, which played an important role in improving the crack resistance and comprehensive properties of the deposition layer under extreme working conditions.

Dynamic precision reliability of the aircraft landing gear retraction mechanism under coupled extreme working conditions

Dynamic precision reliability of the aircraft landing gear retraction mechanism under coupled extreme working conditions

Pedagogical support of preparation of cadets of higher educational institutions of the Ministry of the Russian Federation for Civil Defence, Emergencies and Elimination of Consequences of Natural Disastersto activity in extreme situations

The article is devoted to the study of pedagogical support for training cadets of higher education institutions of the Ministry of the Russian Federation for Civil Defence using inductive and deductive methods, Emergencies and Elimination of Consequences of Natural Disasters for activities in extreme situations, the main concepts of training cadets for work in extreme conditions, as well as the tasks facing the teaching staff are considered. The conceptual apparatus of pedagogical support for training cadets for activities in extreme situations is considered. Based on the analysis of scientific works on this topic, a number of aspects and trailers are identified that represent the basis for effective training of cadets to solve professional problems. Particular attention is paid to the formation of necessary skills, stress resistance, decision-making in dangerous conditions and the development of significant qualities.

A study of short-term wind power segmentation forecasting method considering weather on ramp segments

The short-term fluctuation of wind power can affect its prediction accuracy. Thus, a short-term segmentation prediction method of wind power based on ramp segment division is proposed. A time-series trend extraction method based on moving average iteration is proposed on the full-time period to analyze the real-time change characteristics of power time-series initially; secondly, a ramp segment extraction method based on its definition and identification technique is proposed based on the results of the trend extraction; and a segmentation prediction scheme is proposed to lean the power prediction under different time-series: the LightGBM-LSTM is proposed for the non-ramping segment using point prediction, and the CNN-BiGRU-KDE is proposed for probabilistic prediction of ramp segments. From the results, this ramp segment definition and identification technique can effectively identify the ramp process of wind power, which makes up for the misidentification and omission of the classical climbing event definition; meanwhile, the segment prediction scheme not only meets the prediction accuracy requirements of the non-ramping segment, but also provides the effective robust information for the prediction of the ramping period, which offers reliable reference information for the actual wind farms. In particular, it is well adapted to wind power prediction under extreme working conditions caused by ramping weather, which is a useful addition to short-term wind power prediction research.

Research on the potential of integrated vehicle control with closed-loop phase portrait analysis

The phase portrait is an important tool for analyzing vehicle stable region widely utilized in vehicle dynamic control systems. At handling limits, traditional open-loop vehicle stable region constraints will restrict the vehicle control ability, while the closed-loop actuator interventions can help states outside the open-loop stable region converge back to stable origin, which is more suitable for constraining vehicle states under extreme working conditions. This article systematically analyzes the potential of integrated vehicle control with closed-loop phase portrait. Firstly, a vehicle dynamic model considering actuator dynamics and tire transient characteristics is established. Then, a numerical optimal control method for calculating closed-loop controllability region is introduced. The controllability region under different friction coefficients, vehicle speeds, convergence time, vehicle steering response characteristics, actuator time constants, and tire transient characteristics are discussed and analyzed. In terms of different control inputs combinations, this article displays the controllability regions under different front steering angles, rear steering angles, direct yaw moments, and their synergistic performances. Control input laws derived from numerical optimization are summarized in two specific directions. Finally, a comparative analysis of open-loop stable regions and closed-loop controllability regions confirms the superiority of the proposed method. Potential applications of the systematic analysis are also discussed.

Improving the wettability and lubrication properties of gallium-based liquid metal through the reaction adsorption of copper and gallium

Gallium-based liquid metal (GLM) is a promising lubricant used in extreme working conditions. In this paper, a copper-containing friction pair (316L-10Cu) is prepared, and the wettability and lubrication properties of GLM are improved by the reaction adsorption of copper and gallium. Compared with 316L, the contact angle of GLM on 316L-10Cu surface decreases from 153° to 124°. At sliding speeds of 0.01m/s (boundary lubrication) and 0.05m/s (mixed lubrication), the friction coefficients of Si3N4/316L-10Cu decreases by 48.5% and 24.6% compared to Si3N4/316L, and the wear rates decreases by 86.5% and 80.7%. The improved lubrication performance is attributed to copper doping promoting the adsorption of gallium on the frictional interfaces, and better wetting enhancing the hydrodynamic pressure effect of GLM.

Research on optimization of flatness evaluation method for antenna array of a radar vehicle

Abstract Radar vehicles play an important role in providing radar services in the aviation field. The flatness of the antenna array is one of the key factors in ensuring the detection accuracy of radar vehicles for airborne targets. In this paper, the mechanical structure of a new type of radar antenna truck is designed, the stress analysis under various working conditions is carried out, the mechanical performance of the whole vehicle is checked, and the evaluation method of the flatness of the antenna array is discussed. Using ANSYS to carry out static finite element analysis and using the deformation results of each element node in ANSYS, the evaluation method based on the multiple regression function is applied to the calculation scheme of antenna array flatness. The final results show that the safety factor of the radar vehicle structure can reach more than 1.75 under extreme working conditions and more than 2.0 under other working conditions. It can work safely. Through the optimization of the shape evaluation method, the accuracy of the final shape calculation result is less than 10mm. The precision of shape error processing is improved.

Inside out: Exploring edible biocatalytic biosensors for health monitoring

Edible biosensors can measure a wide range of physiological and biochemical parameters, including temperature, pH, gases, gastrointestinal biomarkers, enzymes, hormones, glucose, and drug levels, providing real-time data. Edible biocatalytic biosensors represent a new frontier within healthcare technology available for remote medical diagnosis. The main challenges to develop edible biosensors are: i) finding edible materials (i.e. redox mediators, conductive materials, binders and biorecognition elements such as enzymes) complying with Food and Drug Administration (FDA), European Food Safety Authority (EFSA) and European Medicines Agency (EMEA) regulations; ii) developing bioelectronics able to operate in extreme working conditions such as low pH (∼pH 1.5 gastric fluids etc.), body temperature (between 37 °C and 40 °C) and highly viscous bodily fluids that may cause surface biofouling issues. Nowadays, advanced printing techniques can revolutionize the design and manufacturing of edible biocatalytic biosensors.This review outlines recent research on biomaterials suitable for creating edible biocatalytic biosensors, focusing on their electrochemical properties such as electrical conductivity and redox potential. It also examines biomaterials as substrates for printing and discusses various printing methods, highlighting challenges and perspectives for edible biocatalytic biosensors.

Research on seismic suppression performance of vertical circulation stereo garage based on friction damper and steel pipe

AbstractThe conventional vertical circulation stereo garage is susceptible to deformation and instability when subjected to extreme seismic loads and complex working conditions. The present study introduces the combination arrangement of steel pipe and friction damper to optimize vertical circulation stereo garage while also investigating their seismic suppression performance under three representative seismic waves (EL‐CNENTRO, TH1TG025(TH), and RH1TG025(RH)). The results showed that the garage structure hasbetter seismic suppression performance when the combination of steel pipes and friction dampers is applied in Scheme 4 compared to relying solely on diagonal tie rod, steel pipe or friction damper. And Scheme 4 achieves inhibition rates of up to 61.27%, 22.12%, 56.07%, and 12.84% for overall maximum deformation response, maximum Y‐direction deformation response, vertex acceleration response, and bottom shear response, respectively. This enhancement significantly improves the garage's seismic stability, providing valuable theoretical references for advancing the development and market promotion of vertical circulation stereo garages.

Mechanical properties and damage characterization of 310S steel using laser ultrasonic inspection under extreme temperature condition

Abstract To evaluate the mechanical properties of 310S stainless steel under extreme working conditions, and realize the damage characterization function, in this study, the longitudinal wave and Rayleigh wave of materials are measured by the method of coaxial inspection on reverse surface and ipsilateral ectopic inspection, respectively, and surface cracks and internal voids are detected by the scanning laser source technology and transmission scanning detection, respectively. The detection methods are designed based on the energy distribution characteristics of Rayleigh wave and longitudinal waves in laser ultrasound. The laser ultrasonic detection systems coupled with a temperature loading device (high temperature: vacuum chamber; low temperature: refrigerating chamber) developed by the laboratory enable on-site monitoring of laser ultrasonic technology in harsh environments. Experimental results demonstrate that the error in mechanical properties (elastic modulus, shear modulus, Poisson ratio) is less than 5% over a wide temperature range (-180-1000°C). At 1000°C, surface cracks wider than 0.5mm and deeper than 1.9mm as well as internal hole defects larger than 1.0mm can be detected with an error rate below 5%.

Influence of lubrication state transition on dynamic characteristics of deep groove ball bearing with localized defect in thermal environment

The accuracy of the vibration response in a defective bearing dynamics model depends on the precise representation of the lubrication friction state between the rolling element (RE) and the raceway within the model. In this study, a fault dynamic model for outer ring defect of deep groove ball bearings (DGBBs), considering the lubrication state transition in a thermal environment, is established. This model accounts for the asperity contact effect during the lubrication state transition and integrates the lubrication-friction model for temperature changes into the dynamic model when skidding occurs. The influence of lubrication state change on the fault frequency of outer ring of DGBB in thermal environment is studied. The experimental and simulation results indicate that the lubrication state of the bearing is gradually deteriorated from elastohydrodynamic lubrication to mixed lubrication with the increase of working temperature. The transformation of the lubrication state is shown to have a significant effect on friction, resulting in the fault frequency of the outer ring increasing with temperature, which exhibits substantial deviation in the thermal environment. In the temperature range of 30 °C–150 °C, the deviation of defect frequency reaches 15.5%, which affects the accuracy of bearing fault diagnosis. This study may offer recommendations for enhancing the condition monitoring of rolling bearings under extreme working conditions.

Research on Intelligent Ventilation System of Metal Mine Based on Real-Time Sensing Airflow Parameters with a Global Scheme

In ventilation systems of metal mines, the real-time measurement of the airflow field and a reduction in pollutants are necessary for clean environmental management and human health. However, the limited quantitative data and expensive detection technology hinder the accurate assessment of mine ventilation effectiveness and safety status. Therefore, we propose a new method for constructing a mine intelligent ventilation system with a global scheme, which can realize the intelligent prediction of unknown points in the mine ventilation system by measuring the airflow parameters of multiple known points. Firstly, the nodal wind pressure method combined with the Hardy–Cross iterative algorithm is used to solve the mine ventilation network, and the airflow parameters under normal operation and extreme working conditions are simulated, based on which an intelligent ventilation training database is established. Secondly, we compared the airflow parameter prediction ability of three different machine learning models with different neural network models based on the collected small-sample airflow field dataset of a mine roadway. Finally, the depth learning method is optimized to build the intelligent algorithm model of the mine ventilation system, and a large number of three-dimensional simulation data and field measurement data of the mine ventilation system are used to train the model repeatedly to realize the intelligent perception of air flow parameters of a metal mine ventilation network and the construction of an intelligent ventilation system. The results show that the maximum error of a single airflow measurement point is 1.24%, the maximum overall error is 3.25%, and the overall average error is 0.51%. The intelligent algorithm has a good model training effect and high precision and can meet the requirements of the research and application of this project. Through case analysis, this method can predict the airflow parameters of any position underground and realize the real-time control of mine safety.

A High-Temperature, High-Speed, Oil-Free Syngas Compressor for Small-Scale Combined Heat and Power

Abstract For low-emission, small-scale combined heat and power generation, integrating a biomass gasifier with a downstream solid oxide fuel cell system is very promising due to their similar operating conditions in terms of temperatures and pressures. This match avoids intermediate high-temperature heat exchangers and improves system efficiency. However, to couple both systems, a high-temperature and oil-free compressor is required to compress and push the low-density, high-temperature bio-syngas from the gasifier to the solid oxide fuel cell stack. The design and development of this high-temperature, high-speed, and gas-bearing supported compressor is presented in this work. An iterative process involving preliminary design, meanline analysis using commercial tools and in-house models is used for the design, which is then numerically analyzed using computational fluid dynamics. The goal is to achieve a design with a wide operating range and high robustness that withstands extreme working conditions. The 727 W machine is designed to run up to 210 krpm to compress 18.23kg/h of syngas at 350°C and 0.81bar. The centrifugal compressor has a tip diameter of 38 mm and consists of 9 backswept main and splitter blades. The impeller is made of Ti6Al4V and coated to prevent hydrogen embrittlement from the hot and highly reactive bio-syngas. The results obtained from the established models suggest a good concordance with the results from numerical analyses, despite the high temperatures and small scale of this design.

Numerical investigation on the impact resistance of ceramic-based composite structure with hybrid architecture

As known, ceramics possess desirable strength, hardness and low density, which have been extensively applied in engineering fields. However, the inherent brittleness makes the ceramics present poor toughness and consequently impact resistance as well. In recent decades, some ingenious architectures of biomaterials employed to improve the mechanical properties of brittle bulk materials, such as laminate and brick-mud, have become increasingly popular. Here, in order to further enhance the impact resistance of ceramics, a kind of hybrid ceramic-based composite structure is designed according to the gradient feature in dactyl club of mantis shrimp. The impact resistance performances of bulk, laminate, brick-mud and hybrid structures are investigated by finite element simulation. The results show that the hybrid structure can effectively avoid catastrophic failure, thereby having large scope of deformation area to store energy. Moreover, the damage mass of impactor for the hybrid plate is the largest due to the beginning hard collision between impactor and target plate and long cumulative damaging time of impactor. As a result, with the highest internal energy and eroding kinetic energy of impactor simultaneously, the hybrid structure dissipates the most energy of impactor. Further, under extreme working conditions of oblique and high velocity impact, the hybrid structure still exhibits optical impact resistance performance.

Torsional behaviors of motor rotor of permanent magnet semi-direct drive system for aerial passenger device

Considering the influence of motor shaft torsional damping, the torsional dynamics equations of a permanent magnet semi-direct drive rotor system in an aerial passenger device are derived. The derivation relies on the coupling between the mathematical model and the gear dynamics model of the permanent magnet motor, and the Lagrange–Maxwell equations are used for streamlined analysis. To protect the motor under extreme working conditions, the influence of supercritical Hopf bifurcation caused by different torsional dampings of the motor shaft on the torsional vibration of the motor rotor is investigated. Based on the Hurwitz criterion, the influence of the linear control gain and nonlinear gain of the washout filter on the system bifurcation point and the limit cycle amplitude of the system is analyzed. Then, from the perspective of the system instability and oscillation caused by friction damping change of the drive motor and the complex electromechanical coupling behavior in the permanent magnet semi-direct drive cutting drive system of the aerial passenger device, the system stability domain is defined. The results can be applied to effectively suppress the torsional vibration of the shaft system in the permanent magnet semi-direct drive system of the aerial passenger device, providing a theoretical guidance for stable operation of the system.

Two-stage auxiliary drifting path tracking control for distributed driving three-axle commercial vehicles

When maneuvering corners at high speeds, commercial vehicles experience significant sideslip angles and tire force saturation, which can lead to severe traffic accidents. Incorporating intelligent driving technology to develop a controllable scheme that surpasses stability constraints and maintains the vehicle in a drift state is crucial for enhancing driving safety. Therefore, based on the model characteristics of distributed drive three-axle(DDTA) commercial vehicles, a two-stage auxiliary drift controller is proposed. In the auxiliary drift stage, time-varying model predictive control (MPC) is employed to track the desired states and achieve steady-state drift path tracking under extreme working conditions. A two-stage controller switching strategy is implemented based on road information. In the yaw stability control stage, an advanced auxiliary system facilitates cooperative control to smoothly restore tire attachment and vehicle yaw. Simulation results demonstrate that the control strategy ensures consistent path tracking performance even when adhesion of the middle and rear axle saturates and peak vehicle sideslip angle reaches 32.09°. After completing the drifting, vehicle yaw successfully returns to a stable state. Subsequently, miniaturized vehicle tests qualitatively analyze relevant conclusions by elucidating transient instability evolution in vehicles subjected to steering and distributed drive. The controllable stability boundary of the vehicle is thus expanded, thereby enhancing the engineering feasibility of drift technology.

Research on erosion wear behavior of NiTi alloy coating fabricated via high-frequency induction heating technology

NiTi alloy is widely used in extreme working conditions due to its pseudoelasticity, shape memory effect and wear resistance. In this study, the NiTi alloy coating (Ni49.8Ti50.2 (at%)) was fabricated by high-frequency induction heating. The coating was well-formed on the surface of cemented carbide YG8 and converted to crystalline after aging treatment. The results of 70h erosion wear experiments carried on the rotary erosion wear test device showing that the erosion wear amount of the coating was reduced by 93 % compared with that of YG8, resulting from the deformation recovery effect. Moreover, the main erosion wear mechanism of the coating was micro-cutting and ploughing. This study can provide technical support and theoretical basis for preparing of NiTi alloy coating and erosion wear resistance.

A Study on Nurses Engagement in Extreme Work Conditions and their Perceptions of its Ethicality

A Study on Nurses Engagement in Extreme Work Conditions and their Perceptions of its Ethicality

Study on Magnetic Properties of High Performance NdFeB Magnets for NEVs under Extreme Working Conditions

Study on Magnetic Properties of High Performance NdFeB Magnets for NEVs under Extreme Working Conditions

Hosting mega sporting events in the extreme hospitality context: Why do hotel employees engage so intensively in their job duties?

Purpose This paper aims to identify why hotel employees in the Egyptian context accept the extreme job duties resulting from hosting too many mega sporting events and what outcomes they experience as a result. Design/methodology/approach The empirical data is based on semi-structured interviews with 36 hotel employees working in reservations, front desk and events management roles in four 4-star hotels located in Cairo, the capital of Egypt. Thematic analysis was subsequently used to determine the main ideas in the interview transcripts. Findings The findings show that hotel employees accept the extreme job duties resulting from hosting mega sporting events for the following four reasons: linking pay with performance, difficulty finding alternative jobs, proving their occupational identity and being subject to patriotism. Furthermore, this paper highlights that the engagement of hotel employees in extreme work conditions during such mega-sporting events might be detrimental to their mental health, resulting in increased cronyism and gender bias among them. Originality/value This paper is a pioneering study to specifically investigate how hosting mega sporting events influences the extremity of work conditions for hospitality sector employees. Prior studies (to the best of the authors’ knowledge) have not theorised and empirically analysed this specific topic, especially in under-researched settings, such as developing countries in the global south.