Severe Working Conditions Research Articles

Laser cladding Ni60-SiC/Ti3SiC2 self-lubricating composite coatings on IN718 alloy: Wear mechanisms and oxidation behaviors

To enhance the service performance of IN718 alloy under severe working conditions, the self-lubricating composite coating of Ni60-SiC/Ti3SiC2 was fabricated on its surface using laser cladding. By systematically analyzing the microstructure and properties of composite coatings, the wear mechanism at different temperatures and the oxidation behavior at 800°C of coatings were discussed in depth. The results demonstrate that an increase in coatings’ microhardness by a factor of 1.9 to 3.1 over IN718 was achieved, benefiting from the fine-grained and solid-solution strengthening actions, and the hard phases such as C23C6, Ni3Si, TiC distributed diffusely inside the coatings. The tribological performance of coatings was also significantly improved, in which the coating with 10 wt.% Ti3SiC2 added had the lowest wear rates of 2.13 and 3.57×10-5 mm3/N·m at RT and 600°C, respectively, which were reduced by 82.74% and 87.43% compared to the substrate. When the test temperature changes from RT to 600°C, the main wear form of coatings changes from adhesive and abrasive wear to oxidative wear. With the Ti3SiC2 content increasing, the oxide film is gradually dense and uniform, and the oxidation resistance is significantly improved.

Thermodynamic analysis of a modified two-stage transcritical CO2 refrigeration cycle with an ejector and a subcooler

In the application scope of large-scale supermarkets, the practicality of transcritical CO2 refrigeration device has been confirmed to be quite satisfying. A modified two-stage transcritical CO2 refrigeration cycle with an ejector and a subcooler (MTC) is proposed in this paper. In the modified cycle, the ejector recovers expansion works and reduces irreversible losses in the throttling process. The subcooler provides subcooling degree for the CO2 entering the low-temperature (LT) evaporator, thus increasing the refrigeration capacity and improving the COP of the modified cycle. Thermodynamic analysis has shown that the exergy efficiency (ηex) and COP of MTC under given operating condition has been enhanced by 13.7 % and 14.2 % compared to BTC. The discharge temperature at the outlet of high-pressure compressor in MTC is decreased by 8.3℃. Under typical operating condition, the optimal discharge pressure of MTC is 9.07 MPa, which is lower than that of BTC. The correlation to calculate optimal discharge pressure for single-stage CO2 refrigeration cycle is also suitable for MTC under given operating conditions. The MTC has also shown better performance under variable operating conditions. For MTC, when the temperature at the outlet of gas cooler increases from 35 – 45℃, the COP and ηex are enhanced by 14.1 % - 16.1 % and 12.8 % - 14.2 % compared to BTC, respectively. When gas cooler outlet pressure decreases from 11.0 to 7.5 MPa, the COP and ηex are enhanced by 14.0 % - 22.8 % and 13.4 % - 18.7 %. As the evaporating temperature at the cold side of subcooler increases from -25 to -15℃, the COP and ηex increase from 1.82 to 1.98 and 27.4 % to 29.7 %. With the ratio of refrigeration capacity (Rec) between medium-temperature evaporator and low-temperature evaporator varies from 0.7 to 1.2, the COP and ηex are improved by 10.7 % - 16.3 % and 10.7 % - 15.4 % compared to BTC. There is the maximum exergy loss at gas cooler in the MTC, whereas that of BTC is located in the expansion valve before LT evaporator. The economic analysis shows the cost per unit of exergy of MTC is decreased by 11.5 % under typical operation condition. According to simulation results, the modified cycle has better performance in severe working conditions such as high gas cooler outlet temperature and low gas cooler outlet pressure in the given range of working conditions compared to BTC.

Support Vector Machine-Based Fault Diagnosis under Data Imbalance with Application to High-Speed Train Electric Traction Systems

The safety and reliability of high-speed train electric traction systems are crucial. However, the operating environment for China Railway High-speed (CRH) trains is challenging, with severe working conditions. Dataset imbalance further complicates fault diagnosis. Therefore, conducting fault diagnosis for high-speed train electric traction systems under data imbalance is not only theoretically important but also crucial for ensuring vehicle safety. Firstly, when addressing the data imbalance issue, the fault diagnosis mechanism based on support vector machines tends to prioritize the majority class when constructing the classification hyperplane. This frequently leads to a reduction in the recognition rate of minority-class samples. To tackle this problem, a self-tuning support vector machine is proposed in this paper by setting distinct penalty factors for each class based on sample information. This approach aims to ensure equal misclassification costs for both classes and achieve the objective of suppressing the deviation of the classification hyperplane. Finally, simulation experiments are conducted on the Traction Drive Control System-Fault Injection Benchmark (TDCS-FIB) platform using three different imbalance ratios to address the data imbalance issue. The experimental results demonstrate consistent misclassification costs for both the minority- and majority-class samples. Additionally, the proposed self-tuning support vector machine effectively mitigates hyperplane deviation, further confirming the effectiveness of this fault diagnosis mechanism for high-speed train electric traction systems.

Low-Cost Magnesium-Based Thermoelectric Materials: Progress, Challenges, and Enhancements.

Magnesium-based thermoelectric (TE) materials have attracted considerable interest due to their high ZT values, coupled with their low cost, widespread availability, nontoxicity, and low density. In this review, we provide a succinct overview of the advances and strategies pertaining to the development of Mg-based materials aimed at enhancing their performance. Following this, we delve into the major challenges posed by the severe working conditions, such as high temperature and thermal cycling, which adversely impact the behavior and long-term stability of the TE modules. Challenges include issues like the lack of mechanical strength, chemical instability, and unreliable contact. Subsequently, we focus on the key methodologies aimed at addressing these challenges to facilitate the broader application of the TE modules. These include boosting the mechanical strength, especially the toughness, through grain refining and additions of second phases. Furthermore, strategies targeted at enhancing the chemical stability through coatings and modifying the microstructure, as well as improving the contact design and materials, are discussed. In the end, we highlight the perspectives for boosting the practical applications of Mg-based TE materials in the future.

A cross exploratory analysis between nursing working conditions and the occurrence of errors in the northeast region of Brazil

ObjectivesAnalyze and verify the association between working conditions and the occurrence of errors in nursing work. BackgroundMany of the known errors in nursing are based on the structural failure of the complex health service system. Our study addresses the question “Is there an association between errors made by nursing workers and working conditions?” MethodsThe study was carried out through a cross-sectional exploratory analysis of 19 ethical-disciplinary processes focused on errors made by nursing workers. The articles were processed, judged, and archived at the Regional Nursing Councils of the Northeast Region of Brazil from 2000 to 2018. The chi-square test or Fisher's exact test was used to verify the relationship between the variables through multivariate analysis. ResultsThe analyzes show that working conditions can interfere at occurrence in error. This increases the chance of an “inconsequential” error occurring for the patient in poor/very poor working conditions. The most serious errors, “with consequences irreversible” for the patient, only occur from more severe working conditions. Adversely, it was found that there is no statistically significant difference in the frequency of errors in hospitals (33.33 %) compared to “other places” (28.58 %) when these occurred in poor working conditions. When conducting the incident in poor working conditions, there was a minimum of 52 % protection OR = 0.48 % [0.16; 11.80]; (1–0.48)) against these errors in general in the nursing area. ConclusionThe strong association was exposed in working conditions classified as bad/very bad/very bad, resulting in the most serious errors and with irreversible consequences for patients. However, a level of protection for different types of workers was noticed in the field, which shows that there is hope that if the work environment changes with more organization, management, and standards of care, we can prevent future errors.

Enhancing flame and electrical surface discharge resistance in silicone rubber composite insulation through aluminium hydroxide, clay, and glass fibre additives

Silicone rubber (SR) is a leading polymer used in electrical outdoor insulation applications due to its superior hydrophobic characteristics. However, the low flame and electrical surface discharge resistance of SR limit its broad viability and challenge its integrity in severe outdoor working conditions. This work attempts to explore the flame retardancy and surface discharge characteristics of SR co-filled with aluminium hydroxide (ATH), nanoclay montmorillonite (MMT), and chopped glass fibre (GF). Results indicate that the incorporation of ATH/MMT/GF could assist in improving the fire and surface discharge resistance of the SR material. It is noted that the maximum average rate of heat emission (MARHE) and total smoke production (TSP) are measured at 24.93 kW/m2 and 0.48 m2 in SRE, relative to 61.29 kW/m2 and 6.02 m2 in SRB. Using finite element analysis (FEA), the maximum electric field strength is computed at 4.66 × 106 V/m in the air gap coupled with a high-voltage (HV) plate and sample. SRE exhibits a higher partial discharge inception voltage (PDIV) value of 2.32 kVrms than its counterparts, while the maximum discharge magnitude (Qmax) is computed at 7095 pC, relative to 7746 pC in SRB. SRE emerges as a preferable SR composite to be used in electrical insulation applications with excellent flame and surface discharge resistance characteristics.

Asymmetric two-dimensional poroelastic analysis of heterogeneous smart discs considering hygrothermal loading

The objective of this study is to examine through the finite element method the impacts of employing two-dimensional (2D) properties grading on the behaviors of piezoelectric sensors/actuators due to their significance. These structures are modeled as variable thickness discs and are assumed to be exposed to simultaneous asymmetric loading conditions (thermal, hygral, electrical, and mechanical loads). Results demonstrate that the 2D grading is superior compared to the conventional one-dimensional grading for reducing the von Mises stress. The reduction reached, for instance, 8.3% allowing further increase of loading and/or safety. Also, the change of the displacement is varied between −4.5% and 31% depending on the considered grading pattern, and thus can be controlled to a desired value which helps to improve the sensing and actuating functionality for certain requirements. The study also examines the effects of porosity, and the results are compared to nonporous discs. Reductions of the maximum compressive tangential stress and von Mises stress reached 79.75% and 33.6%, respectively at specific porosity distribution patterns and volume fractions. These findings have significant implications for the manufacturing of smart structures, enabling them to operate in severe working conditions with better sensing and actuating capabilities than previously possible.

Reconfiguration of stability and control strategy for some unmanned deformable vehicles

An unmanned deformable vehicle can switch between wheeled driving and legged walking through reconfiguration. The system is prone to tipping instability when reconstructing from a vehicle state in wheeled motion to a humanoid state in legged motion. To improve reconfiguration stability, a center-of-mass position-adjusting mechanism was designed based on structure optimization design for the unmanned deformable vehicle. The zero moment point was adjusted by controlling a center-of-mass position-adjusting mechanism, thereby further improving the reconfiguration stability of the system. In this study, the structure of the unmanned deformable vehicle was designed and a reconfiguration kinematic model was established based on spinor theory. A reconfiguration dynamic model was established based on Newton-Euler equation, and the zero moment point was used as the stability criterion for the reconfiguration motion. To improve the reconfiguration stability of the system, simulated annealing algorithm was used to optimize the main parameters of the system under both basic and severe working condition reconfiguration processes. To further improve the reconfiguration stability, a variable universe-fuzzy control strategy was designed to control the stability of the reconfiguration process of the whole vehicle. The results showed that the reconfiguration stability could be significantly improved under various working conditions by using the stability control after the system was optimally designed.

Analysis of Water-Lubricated Journal Bearings Assisted by a Small Quantity of Secondary Lubricating Medium with Navier–Stokes Equation and VOF Model

Due to the low viscosity of water, water-lubricated bearings are susceptible to significant wear and noise in demanding operating conditions. It has been demonstrated that a small quantity of secondary lubricating medium can improve the lubrication performance of water-lubricated contact surfaces and achieve the purpose of temporary risk aversion. As a further step, the feasibility of the proposed idea is experimentally validated on a water-lubricated bearing test bench. A numerical model that couples the N–S equation and the VOF model is then developed to investigate the behavior of the flow field lubricated by pure water and water with a small quantity of the secondary lubricating medium. This model provides the predictions of important quantities such as the load-carrying capacity, the secondary lubricating medium volume fraction and the contact pressure under different lubricated conditions. The results show that the secondary lubricating medium can enter into the contact region and improve the lubrication performance of water-lubricated bearings, especially at lower shaft rotational speeds. Therefore, the feasibility of our proposed idea is verified, which provides a promising approach to reduce the wear and friction of water-lubricated bearings when they encounter short-time severe working conditions.

A Comparative Azeotropic Research on Combustion of Common Ternary Systems

Methyl Tertiary Butyl Ether (MTBE) and Methanol are effective fuel oxygenate that boost octane number, improve fuel performance, combustion behavior and minimize environmental pollutant emissions. In the petroleum business, however, their high-water solubility restricts their use in terms of fuel homogeneity loss. This work presents a full investigation map for the status of the phase diagram for the tertiary system of MTBE-methanol-water at different temperatures; 0, 40, and 70oC, and different pressures; 1.0 and 3.0 atm, based on different compositions. Furthermore, the thermodynamic coefficient, UNIFAC-LL, was linked to the Aspen plus Version 9. After validation of the software by the real experimental data, the software was used to complete the full map at all missing conditions. Pressure does not influence the occurrence of phase transitions, but the temperature has a minor effect on the LLE. The methanol concentration at which phase separation occurred dropped from 43% to 31.2% when the temperature was lowered from 70 to 40°C. With the use of simulation, the compositions at which phase separation occurs were also discovered. Last but not least, it was observed that the thermodynamic model (UNIFAC-LL) properly predicted the behavior of the methanol-water–MTBE ternary system with less than 3% inaccuracy in the binodal curve points. Consequently, a validated phase diagram is developed to accurately predict the physical state of the MTBE-methanol-water system at ant temperature, pressure, and mole fraction of each component. Hence, it guarantees the feasibility of using this tertiary system, as an effective octane booster additive, under severe working conditions.

A new method to establish coupled multi-physics model of lubricated pin-hole oscillating pair

Under severe working conditions, about 10 % of the total engine friction loss originates from the piston pin-hole oscillating pair, significantly impacting the engine's reliability. Nevertheless, a systematic analysis encompassing the multi-physics environment (including lubrication, dynamics, and heat transfer) and their coupled behaviors is still lacking. A new coupled modeling method is proposed to achieve this, which can account for thermal deformation and frictional heat generation. All key components in this study are represented as three-dimensional flexible bodies, enabling a thorough characterization of the intricate secondary motions influencing lubrication. The method is applied to a lubricated oscillating pair test system, and a 1:1 simulation model is established. Experimental results also affirm its high accuracy. The model calculation results demonstrate that thermal deformation constrains pin secondary motions and increases axial load inhomogeneity. After factoring in fluid and asperity friction heat, the average friction coefficients at the small end hole (SEH) and pin base hole (PBH) increase by 1.8 % and 11.3 %, respectively. Furthermore, a parametric analysis is conducted, and the instantaneous friction coefficient curves under different loads/temperatures/frequencies are given. These findings can offer valuable insights into the tribological design of oscillating pairs.

Caputo-Fabrizio fractional order derivative stochastic resonance enhanced by ADOF and its application in fault diagnosis of wind turbine drivetrain

Fault diagnosis of wind turbine drivetrains is vital to maintain the reliability of wind turbines and stochastic resonance (SR) is regarded as a powerful method to amplify the fault-induced weak characteristics of vibration signals. However, without considering the high dependence between current and previous values of vibration signals, integer-order SR may not be effective enough to amplify the weak characteristics. Moreover, non-Gaussian noise originating from severe working condition generally reduce the efficiency of amplification. To address these issues, a Caputo-Fabrizio fractional order derivative (CF) SR improved by ascending density outlier factor (ADOF) for fault diagnosis of wind turbine drivetrains is proposed in this paper. First, ADOF is constructed to remove the large impulsive noise of vibration signals. Second, CF is discretized into the second-order SR model, then the weak characteristics of vibration signal are amplified by the established CF second-order SR model (CF-SR). The effectiveness is validated by a simulation and two experimentations based on two real vibration signals collected from the key components of wind turbines. Compared with traditional diagnosis methods such as deconvolution and Kurtogram, the proposed method is superior for fault diagnosis of wind turbines working in severe environments.

Effect of solubilization heat treatment on microstructure and corrosion resistance of joints welded with the autogenous TIG process duplex stainless steel

Duplex stainless steels (DSSs), are used commonly under severe working conditions, subject to high stresses associated with corrosion. A typical DSS is composed of the combination involving two types of microstructures, ferritic and austenitic, which characterizes it as a material with corrosion resistance in aggressive media, due to its ability to passivate. The use of DSS has been increasingly exploited in the oil industry, and its use has occurred in numerous areas, standing out in the production of flexible pipelines, which in most applications, is associated with a welding process. They require special care when welded by the tungsten inert gas (TIG) welding process. Temperature variations in this process, along with heat treatment, promote the formation of precipitates in the matrix and change the phase balance. This significantly influences the mechanical and corrosion properties of DSSs. The objective of this work is to study the influence of two different parameters of solubilization heat treatment after welding on the microstructure and corrosion resistance of a DSSs welded joints. After the autogenous TIG welding process, the welds were subjected to thermal solubilization treatments for 10 and 25 s at 1050 °C. The conditions subjected to the solubilization heat treatment were compared with the as TIG welded control condition. The microstructure was analyzed by confocal microscopy and the corrosion resistance was evaluated by the "A" method of the ASTM G48 standard.

Study on tribological properties of high entropy alloy composite coatings with different tungsten carbide contents in laser cladding

AbstractThe severe working conditions of mining machinery make the wear of its parts extremely serious, thus reducing its service life, increasing the probability of accidents, and may cause huge economic wastage. So promoting the improvement of mining machinery is imperative, and the melting of wear‐resistant layer on the surface of wear‐prone equipment is a more effective improvement method. The study was performed by laser fusing a composite coating of CoCrFeNiMn high‐entropy alloy with different WC contents, and a second phase was generated in the coating by an additive method to achieve the strengthening of the coating. The experiments revealed that all the coatings had FCC phase as the main phase by analyzing the phase conformation, structure, stiffness, and abrasiveness. When the WC dosage exceeded 20 wt.%, Fe3W3 (M6C) carbide reinforced phases with different morphologies were produced in the coatings. Forty wt.% of the coatings showed the highest hardness, which was 3.1 times better than that of the coatings without WC particles, and 30 wt.% of the coatings showed the best abrasiveness. HT0 coatings showed the least friction factor of 0.27. HT600 and HT800 corresponded to friction factors of 0.37 and 0.35, respectively. The coefficient of friction of the coating was most stable after about 3 min at room temperature, and the wear phase took longer after annealing. During the break‐in phase, the precipitated phase has a supportive effect and prolongs the break‐in period. The coating using the studied method improves the wear resistance of mechanical parts and extends their service life, which has some economic and practical value.

Correlation between cargo properties and train overturning safety for a high-speed freight train under strong winds

The high-speed railway has become an important passenger transport mode. Relying on the abundant passenger transport experience and expansive railway network, the high-speed freight train (HSFT) is feasible to be developed and has great application potential. As a critical component of HSFT, the cargo plays an important role in the overturning safety of HSFT under strong wind conditions. Previous studies about the aerodynamic performance of the high-speed train usually regarded the loaded carbody as an individual rigid body. Limited attention was paid to the variability inside the vehicle. In order to improve the running safety of HSFT under strong wind conditions, the multibody dynamics simulation is adopted to demonstrate the effect of cargo property on the overturning risk of HSFT under the aerodynamic loads obtained through the computational fluid dynamics (CFD) simulations. It is demonstrated that the inner side crosswind is more dangerous than the outer side crosswind. The speed of HSFT should be limited according to the cargo quantity, and the maximum speed for a fully loaded HSFT can be 305 km/h when the crosswind velocity is 20 m/s. The larger cargo density should be encouraged because it is good for train overturning safety in severe working conditions.

Inhibition properties of Vang tea-water extract for carbon steel corrosion in acidic environments

BackgroundMetallic corrosion saps the economy, pollutes the environment, and affects human health and life due to the related toxic chemicals, unwanted reactions, and project collapse, as well as contaminative products. The use of corrosion inhibitors could be a great help to reduce corrosion of metallic materials in severe working conditions. In recent years, natural products have been used for protecting against the corrosion of carbon steel. MethodsVang tea leaves - water extract (VTLWE) was recommended as a corrosion inhibitor with low-cost and a safe class of material for carbon steel in 1.0 M HCl, 0.5 M H2SO4, and their mixed acidic solutions. VTLWE raw materials were characterized by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and liquid chromatography-mass spectrometry (LC-MS). Electrochemical properties have been characterized by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PD). Post-immersion surface analyses were also evaluated using scanning electron microscopy (SEM), ATR-FTIR, and X-ray photoelectron spectroscopy (XPS). Significant FindingsThe electrochemical data showed that VTLWE posed as a mixed-type inhibitor with more cathodic characteristics and the inhibition effectiveness significantly depended on the VTLWE concentration that increased with an increase of VTLWE in 1.0 M HCl and 0.5 M H2SO4 solutions due to lower corrosion current density and higher polarization resistance. In addition, the results also indicated that 0.5 M H2SO4 solution was more aggressive than 1.0 M HCl solution and was subjected to a higher level of steel corrosion inhibition by VTLWE. Surface analysis results confirmed the occurrence of the organic film layer on the steel surface, assigning to the bonding of functional groups and heteroelements in VTLWE species that were available in investigated solutions. Therefore, the work could add VTLWE as new materials to inhibition systems, giving rise to the durable protection against steel corrosion and supplying inspiration in related applications.

Research on pendulum-type tunable vibration energy harvesting

Sensors, as the most common electronic devices in electromechanical systems, are often scattered in huge numbers in the environment to be monitored. When the power of the sensor comes from batteries, the long-term continuous power supply and the replacement of the battery under severe working conditions are the main problems. Compared with other energy sources, vibration energy is more universal and stable, so it is often harvested and utilized by specific devices. Most of the traditional vibration energy harvesting devices have the disadvantage that the natural frequency cannot be tuned, which will lead to significant decline of energy harvesting efficiency when the environmental frequency changes. Although some energy harvesting devices are with tunable nature frequency, the linearity is relatively poor when tuning. In order to solve the problems above, a structural model of an electromagnetic energy harvesting device using motion of a pendulum rod is constructed. Natural frequency characteristics and electromagnetic field finite element simulation analysis of the model are carried out. An experimental platform of the device and a corresponding electric energy storage circuit are designed and built. Simulation and experimental results show that the natural frequency of the device can be tuned linearly in the range of 7 Hz–13.5 Hz. The maximum induced electromotive force that the device can output is 1.37 V and the maximum power is 521 mW. When the device is connected to the electric energy storage circuit, the device can output 3.4 V DC voltage. Compared with the traditional devices that can only harvest energy efficiently from a single vibration frequency, the advantage of this model is that its natural frequency can be adjusted to adapt to different ambient vibration frequencies and the linearity of tuning has been verified, which makes its energy harvesting efficiency relatively higher. The device model proposed in this paper would have potential application value in the field of vibration energy harvesting and wireless micro sensors power supply.

Minimum entropy deconvolution enhanced by KLOF and phase editing for fault diagnosis of rotating machinery

Repetitive impulses are critical characteristics in vibration signals of fault rotating machinery and minimum entropy deconvolution (MED) is an effective tool to extract these characteristics for fault diagnosis. However, early fault-induced impulses are usually weak and submerged in heavy background noise when rotating machinery operate in severe environment. Under this circumstance, MED generally fails to isolate useful impulses from contaminated signals. To overcome the shortcoming, this paper proposed a kernel local outlier factor MED enhanced by phase editing method (KPMED) for fault diagnosis of rotating machinery. First, non-Gaussian noise components in fault signals are removed by kernel-based local outlier factor (KLOF) in data cleaning way. Second, the residual Gaussian noise components are eliminated by phase editing (PE) in complex domain with phase perspective. Finally, the fault-induced repetitive periodic impulses are extracted by selecting MED filtered signal with large value of kurtosis for diagnosis. The effectiveness of KPMED is validated by a simulated bearing fault signal and two vibration signals collected from a pinion of a wind turbine and a rolling element bearing, respectively. Compared with original MED and its corresponding variants, KPMED is more accurate and suitable for fault diagnosis of rotating machinery under severe working conditions.

Application of a coarse-to-fine minimum entropy deconvolution method for rotating machines fault detection

Due to the severe working condition and long-term service, the key rotating parts including the bearing and gearbox, are susceptible to damage. Blind deconvolution which can eliminate the influence of the transfer path and enhance the fault-related feature is widely used for machinery fault diagnosis. Not only the objective function but the initial filter can influence the convergence properties of the deconvolution algorithm. For example, in practical application, the classical MED trends to converge to fault-unrelated outliers if the initial filter coefficients are not appropriate. Motivated by this, the effect of initialization on the convergence of MED is firstly investigated. Subsequently, a coarse-to-fine MED (CFMED) is designed to highlight the fault-induced repetitive impulses. Specifically, the procedure of pre-iterating is used to search for the convergence direction and coarsely update the initial filter. Then, the dropout step is introduced to drop out the redundant candidates and reserve the expected solution by quantitatively measuring the sparsity of all possible solutions in the frequency domain. Meanwhile, CFMED is more robust to filter size than MED. Finally, the simulation and experimental data with bearing and planetary gearbox fault verify CFMED is more suitable for the fault diagnosis of rotating machines compared with original MED.

Friction assessment of ultralow viscosity lubricant formulations based on a validated elastohydrodynamic simulation

High-performance engines are highly optimized machines; therefore, any identification of potential improvement requires a detailed study to assess different performance scenarios, working fluids and engine configurations. Simulation tools are among the best ways to study all possible options. In this framework, a validated elastohydrodynamic (EHD) simulation model of the connecting rod journal bearing is used to assess the performance of different lubricant formulations in mixed lubrication scenarios. To simulate a realistic scenario, a finite element analysis (FEA) is performed, where the assembly of connecting rod and shaft supports are modelled with finite element models (FEM) to account for elastic deformations on journal bearings. Furthermore, a set of oil properties is measured and collected to import into GT-Suite commercial software. This set enables us to consider the dependence of variables such as viscosity, density, specific heat transfer, and coefficient of friction on the shear rate, pressure, temperature, and air solution. Moreover, a friction assessment methodology is presented to choose the best lubricating oil for severe working conditions. This test method accounts for several factors: tribology, rheology, wear, and lubrication regime. The results are presented for three ultralow viscosity lubricants and the reference oil from validation. This assessment gives a complete comparison of lubricants performance, where lubrication regime and tribological losses are key factors to select the best candidate.