作者：
Sha Ni;Jianhui Yan*;Tong Wei;Jiwen Wu;Hongyu Yang
期刊：
Surface and Coatings Technology,2025年511:132279 ISSN：0257-8972
通讯作者：
Jianhui Yan
作者机构：
[Jiwen Wu] School of Mechanical Engineering, Hunan University of Science and Technology, Xiangtan 411201, PR China;College of Mechanical and Electrical Engineering, Hunan City University, Yiyang 413000, PR China;[Jianhui Yan; Tong Wei; Hongyu Yang] School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, PR China;[Sha Ni] School of Mechanical Engineering, Hunan University of Science and Technology, Xiangtan 411201, PR China<&wdkj&>College of Mechanical and Electrical Engineering, Hunan City University, Yiyang 413000, PR China
通讯机构：
[Jianhui Yan] S;School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, PR China
摘要：
The inadequate wear durability of CoCrFeNiMo high-entropy alloy coatings poses great challenges to achieving reliable surface protection for engineering components. This study strategically addresses this limitation by incorporating ceramic carbide particles. The pure CoCrFeNiMo (P0), CoCrFeNiMo-10wt%Cr 3 C 2 (CrC10), and CoCrFeNiMo-10wt%B 4 C (BC10) composite coatings were deposited onto Q235 substrate utilizing laser cladding. Those coatings' structural characteristics, mechanical properties, tribological behavior, and wear mechanisms were analyzed and compared. The P0 coating was composed of FCC and σ phases with a herringbone-like hierarchical eutectic structure, showing good fracture toughness (10.7–24.61 MPa·m 1/2 ). The Cr 3 C 2 -added coating had a typical dendrite structure, and the primary phase from FCC gradually transformed upward into the σ phase. Adding B 4 C particles induced plenty of carbides and borides precipitation such as MoC, M 7 C 3 , and Fe 3 (B, C) in BC10 coating. Adding carbide particles promoted the solid solution strengthening of C and B atoms and in-situ precipitation of reinforcement phases, significantly enhancing the hardness. The hardnesses of P0, CrC10, and BC10 coatings were 652.8, 744.3, and 1162.1 HV 0.2 , respectively. Benefiting from the synergistic effect of the Mo-rich hardening phase and lubricating oxide layer, the BC10 coating achieved the lowest wear rate (9.8 × 10 −6 mm 3 ·N −1 ·m −1 ), showing an order-of-magnitude improvement over the P0 and CrC10 coatings. The P0 and CrC10 coatings predominantly exhibited abrasive wear modes. Surprisingly, the worn surface of the BC10 coating was very slight without detectable scratches or delamination, which was dominated by oxidative wear.
The inadequate wear durability of CoCrFeNiMo high-entropy alloy coatings poses great challenges to achieving reliable surface protection for engineering components. This study strategically addresses this limitation by incorporating ceramic carbide particles. The pure CoCrFeNiMo (P0), CoCrFeNiMo-10wt%Cr 3 C 2 (CrC10), and CoCrFeNiMo-10wt%B 4 C (BC10) composite coatings were deposited onto Q235 substrate utilizing laser cladding. Those coatings' structural characteristics, mechanical properties, tribological behavior, and wear mechanisms were analyzed and compared. The P0 coating was composed of FCC and σ phases with a herringbone-like hierarchical eutectic structure, showing good fracture toughness (10.7–24.61 MPa·m 1/2 ). The Cr 3 C 2 -added coating had a typical dendrite structure, and the primary phase from FCC gradually transformed upward into the σ phase. Adding B 4 C particles induced plenty of carbides and borides precipitation such as MoC, M 7 C 3 , and Fe 3 (B, C) in BC10 coating. Adding carbide particles promoted the solid solution strengthening of C and B atoms and in-situ precipitation of reinforcement phases, significantly enhancing the hardness. The hardnesses of P0, CrC10, and BC10 coatings were 652.8, 744.3, and 1162.1 HV 0.2 , respectively. Benefiting from the synergistic effect of the Mo-rich hardening phase and lubricating oxide layer, the BC10 coating achieved the lowest wear rate (9.8 × 10 −6 mm 3 ·N −1 ·m −1 ), showing an order-of-magnitude improvement over the P0 and CrC10 coatings. The P0 and CrC10 coatings predominantly exhibited abrasive wear modes. Surprisingly, the worn surface of the BC10 coating was very slight without detectable scratches or delamination, which was dominated by oxidative wear.
摘要：
Fatigue failure of joints is a critical factor affecting structural safety design. This study investigates the failure mechanism of aluminum (Al)-steel tubular joints fabricated via magnetic pulse crimping (MPC) using multiscale characterization techniques. Shear effects caused the thinning of the Al tube, which induced the formation of a notch on the inner surface. The mechanical interlocking of the material and the notch effect led to stress concentration, thereby promoting fatigue crack initiation (FCI) at the notch. Fracture morphology indicated that FCI was a mixture of intergranular and transgranular fracture. Interestingly, under higher stress conditions (58.5 MPa), the fatigue crack propagation (FCP) rate was extremely fast. The crack propagation process lacked a steady-state stage, with no distinct fatigue striations forming before fracture occurred. The features of the dimples were the main characteristic of final fracture (FF). Electron backscattered diffraction (EBSD) results showed that the differences in plastic deformation degree, dislocation density, and grain Schmid factor (SF) value were the main causes of intergranular and transgranular fracture in FCI.
Fatigue failure of joints is a critical factor affecting structural safety design. This study investigates the failure mechanism of aluminum (Al)-steel tubular joints fabricated via magnetic pulse crimping (MPC) using multiscale characterization techniques. Shear effects caused the thinning of the Al tube, which induced the formation of a notch on the inner surface. The mechanical interlocking of the material and the notch effect led to stress concentration, thereby promoting fatigue crack initiation (FCI) at the notch. Fracture morphology indicated that FCI was a mixture of intergranular and transgranular fracture. Interestingly, under higher stress conditions (58.5 MPa), the fatigue crack propagation (FCP) rate was extremely fast. The crack propagation process lacked a steady-state stage, with no distinct fatigue striations forming before fracture occurred. The features of the dimples were the main characteristic of final fracture (FF). Electron backscattered diffraction (EBSD) results showed that the differences in plastic deformation degree, dislocation density, and grain Schmid factor (SF) value were the main causes of intergranular and transgranular fracture in FCI.
关键词：
Mg-Sn-Zn alloy;Ce and Gd addition;Strength-ductility synergy;VPSC simulation;Deformation mechanisms
摘要：
The effects of incorporating dilute Gd and Ce on the microstructure and mechanical properties of Mg-0.5Sn-0.3Zn (TZ00, wt%) alloys are systematically revealed. The results indicate that the co-addition of 0.3 wt% Gd and 0.3 wt% Ce can significantly reduce the grain size from 40.8 μm to 12.0 μm, enhance dynamic recrystallization, and attenuate the intensity of basal texture. Furthermore, plenty of micron- and nano-scale (Gd, Ce)MgSn phases are precipitated. In comparison with the TZ00 alloy, the Mg-0.5Sn-0.3Zn-0.3Gd-0.3Ce alloy (TZGE0000, wt%) displays synergistic improvements in strength and ductility. The corresponding tensile yield strength (TYS), ultimate tensile strength (UTS), and elongation (EL) are 214.1 MPa, 297.4 MPa, and 23.5 %, respectively. The primary reason for this strength improvement is the combined effects of grain refinement and (Gd, Ce)MgSn nano-phase strengthening, while the ductility enhancement is mainly due to the refined grain size, weakened basal texture, increased activation of prismatic slip and {10−12} tensile twinning. Additionally, relative Visco-Plastic Self-Consistent (VPSC) simulations confirm that the combined addition of Gd and Ce can promote the activation of non-basal slip and {10−12} tensile twinning during the deformation process. In more detail, basal and prismatic slips are the primary deformation mechanisms during tensile loading, together with a minor occurrence of {10−12} tensile twinning and pyramidal slip coordination deformations. Conversely, {10−12} tensile twinning predominates during the compression deformation.
The effects of incorporating dilute Gd and Ce on the microstructure and mechanical properties of Mg-0.5Sn-0.3Zn (TZ00, wt%) alloys are systematically revealed. The results indicate that the co-addition of 0.3 wt% Gd and 0.3 wt% Ce can significantly reduce the grain size from 40.8 μm to 12.0 μm, enhance dynamic recrystallization, and attenuate the intensity of basal texture. Furthermore, plenty of micron- and nano-scale (Gd, Ce)MgSn phases are precipitated. In comparison with the TZ00 alloy, the Mg-0.5Sn-0.3Zn-0.3Gd-0.3Ce alloy (TZGE0000, wt%) displays synergistic improvements in strength and ductility. The corresponding tensile yield strength (TYS), ultimate tensile strength (UTS), and elongation (EL) are 214.1 MPa, 297.4 MPa, and 23.5 %, respectively. The primary reason for this strength improvement is the combined effects of grain refinement and (Gd, Ce)MgSn nano-phase strengthening, while the ductility enhancement is mainly due to the refined grain size, weakened basal texture, increased activation of prismatic slip and {10−12} tensile twinning. Additionally, relative Visco-Plastic Self-Consistent (VPSC) simulations confirm that the combined addition of Gd and Ce can promote the activation of non-basal slip and {10−12} tensile twinning during the deformation process. In more detail, basal and prismatic slips are the primary deformation mechanisms during tensile loading, together with a minor occurrence of {10−12} tensile twinning and pyramidal slip coordination deformations. Conversely, {10−12} tensile twinning predominates during the compression deformation.
摘要：
Previous studies have indicated an association between neutrophil extracellular traps (NETs) and acute respiratory distress syndrome (ARDS). This study aimed to investigate the potential causal effects of NETs and NETs-related biomarkers on ARDS or vice-versa. A two-sample Mendelian randomization (MR) utilizing genome-wide association studies (GWAS) data was employed to analyze the causality. The primary analysis was conducted using inverse-variance weighted (IVW) methods; weighted median, MR-Egger, and weighted model methods were used to validate the results. Horizontal pleiotropy and outlier detection were assessed via MR-Egger and MR pleiotropy residual sum and outlier (MR-PRESSO), respectively; Cochran's Q test evaluated heterogeneity, while Leave-one-out analyses were used to evaluate the presence of predominant instrumental variables (IVs). IVW method suggested causal associations between genetically predicted IL-13 and a higher risk of ARDS [OR (95%CI) = 1.52 (1.03-2.23), P = 0.047], while there was no causal effect of other factors on ARDS (all P > 0.05). Also, ARDS had no effect on NETs and NETs-related biomarkers (all P > 0.05). Cochran's Q confirmed no significant heterogeneity. MR-Egger regression ruled out horizontal pleiotropy's influence, and MR-PRESSO analysis identified no outliers, reinforcing the study's findings. This MR study established a causal relationship between IL-13 and ARDS, suggesting its potential role as a therapeutic target and biomarker of ARDS. Future work should delve into the underlying mechanisms and clinical applications.
摘要：
Purpose: To assess the accuracies of airway resistance (R-aw) and compliance (C-rs) calculations using the expiratory time constant (RCexp) method as well as the accuracy of P-mus estimation in obstructive lung models. Methods: A Respironics V60 ventilator was connected to an active lung simulator. The driving pressure was maintained at 5-10 cmH(2)O and positive end-expiration pressure (PEEP) was 5 cmH(2)O. Maximal P-mus, estimated based on equations of motion and respiratory mechanical properties, was calculated by the RCexp method to derive respiratory system compliance (C-rs) and inspiratory (R-insp) and expiratory (R-exp) resistance. Results: During PAV, the assist proportion was adjusted to 55% and 40% with P-mus of 5 and 10 cmH(2)O, respectively. P-mus measurement errors were <20% of the preset values in most lung conditions. In the active lung model with PAV, an overestimation of Raw was found in the normal resistance condition, and R-insp was underestimated in the severe obstructive model (P < 0.01). Crs was overestimated significantly except in the severe obstructive model at a P-mus of 10 cmH(2)O (all P < 0.01). Using the RCexp method, the target of <= 20% between the calculated and preset values in airway resistance was achieved in most obstructive models at a P-mus of 5 cmH(2)O. Conclusions: The RCexp method might provide real-time assessments of respiratory mechanics (elastance and resistance) in the PAV mode. With low inspiratory effort, the estimation error was acceptable (<20%) in most obstructive lung models.
期刊：
International Communications in Heat and Mass Transfer,2025年164:108861 ISSN：0735-1933
通讯作者：
Xiong, ZH
作者机构：
[Xiong, Zhihong] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413000, Hunan, Peoples R China.;[Chen, Nanzhong; Xiong, Zhihong] Cent South Univ, Coll Mech & Elect Engn, Changsha 410083, Hunan, Peoples R China.
通讯机构：
[Xiong, ZH ] H;Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413000, Hunan, Peoples R China.
关键词：
The main bearing of TBM;CFD simulation;Oil-air two-phase flow;Slewing bearing lubrication test bench
摘要：
The main bearing of a TBM is a large-scale, low-speed, heavy-load slewing bearing, which is crucial for effective lubrication and heat dissipation. In this paper, CFD simulations were conducted to analyze the oil-air two-phase flow under different oil supply rates, inner ring speeds, and oil immersion heights. The simulations were validated with a slewing bearing lubrication test bench. The results demonstrate that the main bearing exhibits a layered oil-air two-phase flow. When the oil supply rate is increased, the oil volume fraction in the main air phase rises, and the auxiliary thrust roller chamber is more significantly affected. Moreover, increasing the rotation speed and immersion height leads to an increase in the interface height and an expansion of the main oil phase region, while having a negligible impact on the oil volume fraction of the main air phase.
The main bearing of a TBM is a large-scale, low-speed, heavy-load slewing bearing, which is crucial for effective lubrication and heat dissipation. In this paper, CFD simulations were conducted to analyze the oil-air two-phase flow under different oil supply rates, inner ring speeds, and oil immersion heights. The simulations were validated with a slewing bearing lubrication test bench. The results demonstrate that the main bearing exhibits a layered oil-air two-phase flow. When the oil supply rate is increased, the oil volume fraction in the main air phase rises, and the auxiliary thrust roller chamber is more significantly affected. Moreover, increasing the rotation speed and immersion height leads to an increase in the interface height and an expansion of the main oil phase region, while having a negligible impact on the oil volume fraction of the main air phase.
期刊：
Materials Science and Engineering: A,2024年913:147089 ISSN：0921-5093
通讯作者：
Bin Jiang
作者机构：
[Zhao, Jun; Wu, Shiqin; Yuan, Yueyang] School of Mechanical and Electrical Engineering, Hunan City University, Yiyang, 413002, China;[Xu, Jun] Guangdong Provincial Key Laboratory of Metal Toughening and Application, Institute of New Materials, Guangdong Academy of Sciences, Guangzhou, 510650, China;[Jiang, Bin] National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing, 400044, China;[Chai, Yanfu] School of Mechanical and Electrical Engineering, Shaoxing University, Shaoxing, 312000, China;[Wang, Qinghang] School of Mechanical Engineering, Yangzhou University, Yangzhou, 225127, China
通讯机构：
[Bin Jiang] N;National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing, 400044, China
摘要：
Effects of Sn, Mn, and their combined additions on microstructural characteristic and tensile properties of extruded Mg-1Gd (G1) alloy are explored. Compared to the sole Sn or Mn addition, an excellent grain refining is happened with the Sn and Mn combined addition. The average grain size of G1, Mg-1Gd-0.8Sn (GS10), Mg-1Gd-0.7Mn (GM10) and Mg-1Gd-0.8Sn-0.7Mn (GSM100) alloys is ∼21.3, 10.1, ∼12.8 and ∼6.8 μm, respectively. The sole Mn addition enhances the strength and ductility of G1 alloy. The forming the fine α-Mn particles and grain refining are attributed to the improved properties of GM10 alloy. The sole Sn addition increases the yield strength of G1 alloy along extrusion direction (ED), but it decreases along transverse direction (TD), The inhomogeneous distribution of coarse GdMgSn particles and formation of TD-split texture should play an important role. The combined effects of Sn and Mn additions guarantee high strength-ductility synergy of GSM100 alloy. The GSM100 alloy exhibits the ultimate strength, yield strength and ductility of ∼276, ∼158 MPa and 24.7 % along ED, and ∼253, ∼157 MPa and 17.5 % along TD, respectively. The jointly effect of the fine grains, a lot of fine GdMgSn and α-Mn particles, the texture weakening and Sn solute atom contributes to the enhancement of properties of GSM100 alloy.
作者机构：
[Zhou, Li; Zhou, L] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413001, Peoples R China.;[Liu, Yan] Hunan City Univ, Coll Informat & Elect Engn, Yiyang 413001, Peoples R China.
通讯机构：
[Zhou, L ] H;Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413001, Peoples R China.
关键词：
Object detection;generic object tracking using regression networks;tracking learning detection;intelligent robots;Laplace probability density
摘要：
The development of intelligent robot has always been an important research direction in the field of artificial intelligence, and the object detection of robot is the basis of intelligent perception and autonomous action. This study proposes an improved object detection algorithm which integrates two kinds of intelligent robot object detection techniques. In this process, the relationship between the center position of the target in the frame used for object detection and tracking is analyzed. It uses Laplace probability density as the parameter to calculate the center position relationship, and joins the correction network to correct the feature point positioning. The object re-capture function is added to solve the problem of object loss in the long-term object detection task, and the classifier is used to realize the object recognition. The results show that when the number of targets in the image reaches 20, the capture accuracy of the two data sets remains above 98.7%. In the intersection to union ratio test, when the real rectangular box contained 2M pixels, the intersection to union ratio of the method proposed in this study remains at or above 0.989. When conducting actual application memory usage tests, the proposed method maintains a memory usage of less than 2000Mb at runtime. It is shown that this method has better target detection efficiency and quality, and the requirement of hardware is lower.
摘要：
Depletion of fossil fuel resources at a high speed and increasing demand for energy supply for various purposes in today's life integrated with industry has led to collective contemplation for the optimal and maximum utilization of fossil fuels through the implementation of multigeneration systems. In the presented study, a multigeneration system for cooling, power, freshwater, and Hydrogen production is proposed and investigated from exergy, energy, and economic viewpoints through a specific scenario. A case study is performed, revealing that the system can deliver a net output power of 16,251.8 kW, a cooling load of 15,905.0 kW, produce freshwater at a rate of 3.891 kg/s, and generate hydrogen at 0.284 kg/h. The energy and exergy efficiencies of the system are 60.48 % and 32.55 %, respectively. An economic analysis shows a payback period of 0.474 years. A parametric evaluation is performed to perceive the system operation in various conditions. Subsequently, a multi-objective optimization using the MOPSO-LINMAP method is conducted to identify the optimal operating conditions for the system. The optimization results are compared with the case study findings, demonstrating further improvements in performance metrics. The optimized system achieves a slightly higher energy efficiency of 61.62 % and a lower payback period of 0.40 years, underscoring the benefits of the optimization process. This study highlights the potential of the proposed system to efficiently and economically meet the demands for power, hydrogen, cooling, and freshwater in various applications.
作者机构：
[Chen, Changqing; Chen, Chang] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413000, Peoples R China.;[Xia, Yunqing; Chen, Changqing; Chen, Chang] Xiangtan Motor Co Ltd, Xiangtan 411201, Peoples R China.;[Tang, Weihua] Hunan Elect Power Design Inst Co LTD, China Energy Engn Grp, Changsha 410007, Peoples R China.
通讯机构：
[Chen, CQ ] H;Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413000, Peoples R China.;Xiangtan Motor Co Ltd, Xiangtan 411201, Peoples R China.
摘要：
In order to solve the problem of frequency modulation power deviation caused by the randomness and fluctuation of wind power outputs, a method of auxiliary wind power frequency modulation capacity allocation based on the data decomposition of a "flywheel + lithium battery" hybrid-energy storage system was proposed. Firstly, the frequency modulation power deviation caused by the uncertainty of wind power is decomposed by the successive variational mode decomposition (SVMD) method, and the mode function is segmented and reconstructed by high and low frequencies. Secondly, a mathematical model is established to maximize the economic benefit of energy storage considering the frequency modulation mileage, and quantum particle swarm optimization is used to solve the target model considering the charging and discharging power of energy storage and the charging state constraints to obtain the optimal hybrid-energy storage configuration. Finally, the simulation results show that, in the step disturbance, the Delta fmax of the hybrid-energy storage mode is reduced by 37.9% and 15.3%, respectively, compared with single-energy storage. Under continuous disturbance conditions, compared with the single-energy storage mode, the Delta fp_v is reduced by 52.73%, 43.72%, 60.71%, and 47.62%, respectively. The frequency fluctuation range is obviously reduced, and the frequency stability is greatly improved.
摘要：
Our aim with this paper is to model and investigate the vibration and damping of a new hybrid composite shell. The considered composite cylindrical shell includes an FGM anisogrid lattice shell perfectly filled with viscoelastic foams. The modeling of the lattice part composed of spiral and hoop ribs is accomplished according to a global continuous standard based on orthotropic deep shells. The distribution pattern of the metal and ceramic constituents along the lattice ribs is specified by a power law. The homogenizations between ceramic and metal phases within the ribs, as well as between the FGM lattice structure and foam, are governed by the rule of mixtures. Based on the transferred Kelvin–Voigt viscoelastic scheme, the dynamic moduli of the foam portion are acquired. Because viscoelastic foam is a soft material, the higher-order shear deformation shell theory is used to estimate the system's displacement components. After emanating the dynamic equations by Hamilton's principle, the Chebyshev collocation-based semi-numerical method is implemented to detect the system's frequencies and loss factors. The comprehensive results show the role of each composite characteristic in the vibration and damping behavior of the defined structure.
Our aim with this paper is to model and investigate the vibration and damping of a new hybrid composite shell. The considered composite cylindrical shell includes an FGM anisogrid lattice shell perfectly filled with viscoelastic foams. The modeling of the lattice part composed of spiral and hoop ribs is accomplished according to a global continuous standard based on orthotropic deep shells. The distribution pattern of the metal and ceramic constituents along the lattice ribs is specified by a power law. The homogenizations between ceramic and metal phases within the ribs, as well as between the FGM lattice structure and foam, are governed by the rule of mixtures. Based on the transferred Kelvin–Voigt viscoelastic scheme, the dynamic moduli of the foam portion are acquired. Because viscoelastic foam is a soft material, the higher-order shear deformation shell theory is used to estimate the system's displacement components. After emanating the dynamic equations by Hamilton's principle, the Chebyshev collocation-based semi-numerical method is implemented to detect the system's frequencies and loss factors. The comprehensive results show the role of each composite characteristic in the vibration and damping behavior of the defined structure.
作者机构：
[Chen, Cong; Zhang, Yi; Chen, C; Yin, Xuni] Hunan Univ, State Key Lab Adv Design & Mfg Vehicle, Changsha 410082, Peoples R China.;[Yin, Xuni] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413000, Peoples R China.
通讯机构：
[Chen, C ] H;Hunan Univ, State Key Lab Adv Design & Mfg Vehicle, Changsha 410082, Peoples R China.
关键词：
Al 2 O 3 ceramic;Laser welding;Cracking rate;Heat input;Preheating
摘要：
Crack defects in ceramic welding are a significant challenge in electronic packaging that requires urgent resolution. In this study, fiber laser-based welding was employed to join 1 mm thick Al2O3 ceramic plates. The investigation focused on weld surface formation, crack defects, and performance attributes across varying heat input and preheating temperatures. The findings indicate a propensity for crack initiation at the weld center or within the base material during Al2O3 ceramic laser welding. Nonetheless, the susceptibility to cracking in Al2O3 welded joints can be mitigated, and joint flexural strength enhanced by adjusting heat input or by introducing a preheating treatment. The flexural strength peaked at a preheating temperature of 100 °C, exhibiting a 112 % increase compared to non-preheated welded joints. In addition, the best matching relationship between heat input and the preheating temperature was obtained through numerical calculations. The relationship between heat input and preheating temperature determines the cracking tendency region, and based on their interrelation, the cracking tendency region is partitioned into three distinctive regions. Subsequently, the three regions were experimentally validated, with results exhibiting a high degree of congruence, thereby offering significant guidance in the selection of laser welding parameters for Al2O3 ceramics.
Crack defects in ceramic welding are a significant challenge in electronic packaging that requires urgent resolution. In this study, fiber laser-based welding was employed to join 1 mm thick Al2O3 ceramic plates. The investigation focused on weld surface formation, crack defects, and performance attributes across varying heat input and preheating temperatures. The findings indicate a propensity for crack initiation at the weld center or within the base material during Al2O3 ceramic laser welding. Nonetheless, the susceptibility to cracking in Al2O3 welded joints can be mitigated, and joint flexural strength enhanced by adjusting heat input or by introducing a preheating treatment. The flexural strength peaked at a preheating temperature of 100 °C, exhibiting a 112 % increase compared to non-preheated welded joints. In addition, the best matching relationship between heat input and the preheating temperature was obtained through numerical calculations. The relationship between heat input and preheating temperature determines the cracking tendency region, and based on their interrelation, the cracking tendency region is partitioned into three distinctive regions. Subsequently, the three regions were experimentally validated, with results exhibiting a high degree of congruence, thereby offering significant guidance in the selection of laser welding parameters for Al2O3 ceramics.
摘要：
The role of a shock generator in the fuel distribution of a scramjet engine is highly significant. In this article, the usage of the erected 3-lobe nozzle in the existence of a shock generator for fuel injection inside a supersonic combustion chamber is fully studied. A three-dimensional model of the extruded 3-lobe nozzle with two altitudes of 4 mm and 2 mm is produced to disclose the importance of the produced vortex upstream/downstream by the usage of the extruded injector. Comprehensive computational analysis is done to investigate the mixing efficiency and fuel diffusion of the proposed jet configuration. Impacts of the coaxial inward air jet on the hydrogen dispersion of the annual extruded 3-lobe injector are also revealed in the present research. The results of the flow structure indicate that the produced vortex upstream of the erected nozzle improves the fuel dispersion behind the hydrogen jet. Our findings show that the effects of injector height are more considerable than the use of an inner air jet for advance of the fuel mixing within the combustor of a scramjet engine.
摘要：
Traditional grinding, which is predominantly performed with a negative rake angle (NRA), can be transformed into grinding with a positive rake angle (PRA) by employing femtosecond pulsed laser technology to modify the apex angle of the grains to be less than 90°. This innovative approach aims to reduce grinding forces and grinding temperatures while improving the surface quality of typical hard-to-machine materials. To assess the performance of PRA single grain grinding and to investigate the underlying mechanisms, the finite element simulation software ABAQUS 6.14 was employed to model the grinding of Ti6Al4V titanium alloy with a single diamond abrasive grain. The dependence of grinding force and temperature in single grain grinding with a PRA or an NRA under different grinding parameters was studied and compared. PRA and NRA single diamond grain grinding experiments on Ti6Al4V alloy were carried out, with grinding forces measured using a dynamometer and compared with the simulation results. The grinding surface morphology and surface roughness were observed and measured, and a comparison was made between PRA and NRA grinding. The results indicated that in single diamond grain grinding, transforming to a PRA significantly enhances grinding performance, as evidenced by reduced grinding forces, lower temperatures, improved surface morphology, and decreased surface roughness. These findings suggest that PRA single diamond grain grinding offers substantial benefits for the precision machining of hard-to-machine materials, marking a step forward in optimizing surface finishes.
摘要：
Microstructures and mechanical properties of the extruded Mg-1Nd-1Mn-xZn (NMZ11x, x = 0, 1 and 2 wt.%) alloys were explored. The NMZ110 alloy exhibits a partial dynamically recrystallized (DRXed) microstructure containing fine DRXed grains and coarse unDRXed grains. 1 wt.% Zn addition leads to more uneven distribution microstructure and then becomes uniform microstructure after 2 wt.% Zn addition. This phenomenon is attributed to the altered Mg12Nd particle size and distribution. The volume fractions of Mg12Nd particles were raised with the increase of Zn addition and the distribution of coarse Mg12Nd particles becomes uneven firstly and then evolves uniform. In addition, the texture was continuously strengthened with increasing Zn addition (the basal panel of most grains tilting 40 +/- 5 degrees along the extrusion direction, ED, changed to the basal panel of most grains paralleling to ED, typical strong basal texture). The change of texture characteristics was mainly affinitive with the decreasing concentration of Nd solute in matrix influenced by increasing Mg12Nd particles. The tensile test showed that Zn addition gradually enhanced the tensile strengths of extruded NMZ11x alloy bars, obtaining the highest yield strength of 212 MPa and ultimate tensile strength of 267 MPa (NMZ112). The increasement of strengths was mainly ascribed to Zn solution strengthening, Mg12Nd particle strengthening and texture strengthening. Besides, adding Zn element can reduce the elongation of the NMZ11x alloy bars. This decrease was mainly associated with increasing coarse Mg12Nd particles and the strong basal texture.
通讯机构：
[Cai, ZH ] H;Hunan City Univ, Coll Mech & Elect Engn, Yiyang 413000, Peoples R China.;Hunan Univ, Coll Elect & Informat Engn, Changsha 410082, Peoples R China.
关键词：
Frequency regulation;SOC segmented feedback inertia control (SSFIC);Maximum frequency differential inertia control (MFDIC);Exponential inertia droop control (EIDC);DC voltage compensation control (DVCC)
摘要：
When DC-side energy storage batteries participate in frequency regulation, inconsistent inertia requirements exist for frequency deterioration and recovery stages. In addition, the frequency regulation power can lead to the DC overvoltage of the DFIG. To address these issues, this paper proposes a voltage suppression strategy (VSS) during multi-stage frequency regulation with the DC-side energy storage batteries. In the frequency deterioration stage, a SOC segmented feedback inertia control (SSFIC) is developed to reduce the frequency change rate. In the frequency recovery stage, to mitigate transient maximum frequency deviation, a maximum frequency differential inertia control (MFDIC) is constructed by incorporating the transient maximum frequency deviation into inertia control coefficient. In the frequency regulation stage, to decrease the steady state frequency deviation and avoid the secondary frequency drop, an exponential inertia droop control (EIDC) is created by considering the droop coefficient as an exponential function of the frequency change rate. To suppress the DC voltage fluctuation, a DC voltage compensation control (DVCC) is presented to transform the active power of SSFIC, MFDIC and EIDC to the d-axis current compensation increment of GSC. Extensive simulation results have proved that the proposed strategy can successfully enhance the frequency regulation and voltage suppression ability.
When DC-side energy storage batteries participate in frequency regulation, inconsistent inertia requirements exist for frequency deterioration and recovery stages. In addition, the frequency regulation power can lead to the DC overvoltage of the DFIG. To address these issues, this paper proposes a voltage suppression strategy (VSS) during multi-stage frequency regulation with the DC-side energy storage batteries. In the frequency deterioration stage, a SOC segmented feedback inertia control (SSFIC) is developed to reduce the frequency change rate. In the frequency recovery stage, to mitigate transient maximum frequency deviation, a maximum frequency differential inertia control (MFDIC) is constructed by incorporating the transient maximum frequency deviation into inertia control coefficient. In the frequency regulation stage, to decrease the steady state frequency deviation and avoid the secondary frequency drop, an exponential inertia droop control (EIDC) is created by considering the droop coefficient as an exponential function of the frequency change rate. To suppress the DC voltage fluctuation, a DC voltage compensation control (DVCC) is presented to transform the active power of SSFIC, MFDIC and EIDC to the d-axis current compensation increment of GSC. Extensive simulation results have proved that the proposed strategy can successfully enhance the frequency regulation and voltage suppression ability.
