摘要:
In order to study the virtual simulation of weld morphology for V-groove multi-layer welding, the prediction of characteristic parameters for weld morphology was realized by constructing the neural network models between the characteristic parameters and process parameters of different layers. At the same time, the virtual models of different layers were established according to the characteristic parameters of weld morphology and the structure parameters of V-groove. Combined with the prediction model and the virtual model, the process parameters were associated with the weld morphology, and the virtual simulation of weld morphology was realized. In the process of establishing the virtual model, first of all, the virtual model of root weld is established. Then, the virtual model of filling layer is established based on the root layer, and the virtual model of weaving layer is established based on the filling layer. Finally, validation experiments were carried out to verify the accuracy of the model. Verification results show that the prediction model can effectively predict the characteristic parameters of each layer, and the average relative errors of melting depth and width were less than 8%. The virtual simulation morphology has a high consistency with the actual morphology, and the average relative error of cross section area was less than 10%.
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.
摘要:
The attainment of formability in ceramic welding presents an imposing quandary within the realm of the manufacturing industry. In this article, the laser welding of Al2O3 ceramics was carried out to compare and analyze the influence of laser power, welding speed, laser duty cycle, and other process parameters on the macroscopic morphology of the weld, weld cracking rate, and welded joint properties. The results show that Al2O3 ceramic welds have a greater tendency to cracking and that the laser power should be matched to the appropriate welding speed. When heat input increases, the weld cracking rate decreases and then increases. Ceramic welded joints with a weld cracking rate of less than 30 % and a bending strength of more than 4 MPa can be obtained when the heat input range is 17-20.5 J/mm for continuous laser welding or 20.5-24 J/mm for pulsed laser welding. In addition, under high heat input conditions, pulsed laser welding reduces the tendency for weld cracking compared to continuous laser.
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:
This paper presents a novel multigeneration structure powered by geothermal energy, featuring a geothermal power plant, water electrolyzer unit, methanation reactor, fuel and utility production unit, supercritical -carbon dioxide cycle, and both high -temperature and low -temperature organic Rankine cycles. Simulated in Aspen HYSYS software and analyzed from energy, exergy, economic, and environmental (4E) perspectives, the process, under base operating conditions, is capable of producing 20,940 kW of power, 620.70 kg/h of hydrogen, 4,913 kg/h of oxygen, 12.35 kg/s of domestic hot water, 5.293 kg/s of chilled water, and 2.659 kg/s of carbon dioxide with over 99% mole purity. Efficiency assessments reveal energy, exergy, and electrical efficiencies of 10.69%, 48.53%, and 3.73%, respectively, with a total unit product cost of $3.11/GJ and a net present value of $67.40 million. The water electrolyzer unit, with an 88.94% exergy efficiency and a 10% contribution to total system irreversibility, is identified as the most efficient subsystem. The geothermal power plant accounts for the highest system irreversibility at 61%, while the combustor in the fuel and utility production unit contributes 11,250 kW of irreversibility. Environmentally, the system operates with zero emissions and significantly reduces annual CO2 emissions compared to coal, oil, biomass, and natural gas power plants by 453.14 x 106, 576.80 x 106, 111.92 x 106, and 344.10 x 106 kg, respectively.
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:
High voltage ride-through (HVRT);Doubly fed induction generator (DFIG);Differentiate flatness control (DFC);Time-based virtual resistance control (TBVRC);Coefficient backpropagation droop control;(CBDC)
摘要:
With the rapid development of the wind power penetration, the suppression of wind turbine overcurrent becomes a significant challenge for high-voltage ride-through. A nonlinear hybrid flatness control (NHFC) strategy is proposed to reduce overcurrent, shorten overcurrent duration time and provide reactive power support. The control strategy consists of the following three parts: 1) a differentiate flatness control (DFC) strategy is designed for improving the duration time of the overcurrent. 2) a time-based virtual resistance control (TBVRC) strategy, where the resistance is varied with the fault voltage occurrence time, is employed to regulate and suppress the stator and rotor overcurrent. 3) a coefficient backpropagation droop control (CBDC) strategy, obtained by optimum droop coefficient calculation, is developed to provide outstanding reactive power injection for voltage support. Simulation results indicate that the proposed control strategy can effectively suppress overcurrent with less duration time while providing effective reactive power support.
作者:
Chen, Y. J.;Tang, J. X.;Pang, Z.;Yuan, C.;Yue, T. M.
期刊:
Journal of Manufacturing Processes,2024年112:263-272 ISSN:1526-6125
通讯作者:
Chen, Y
作者机构:
[Chen, Y. J.; Chen, Y; Tang, J. X.; Pang, Z.] Dongguan Univ Technol, Dept Mech Engn, Dongguan 523808, Peoples R China.;[Yuan, C.] Hunan City Univ, Coll Mech & Elect Engn, Yiyang 413000, Peoples R China.;[Yue, T. M.] Hong Kong Polytech Univ, Dept Ind & Syst Engn, Adv Mfg Technol Res Ctr, Hong Kong, Peoples R China.
通讯机构:
[Chen, Y ] D;Dongguan Univ Technol, Dept Mech Engn, Dongguan 523808, Peoples R China.
摘要:
The current challenge in laser joining polymer and ceramic heterogeneous structures lies in their relatively low mechanical strength, primarily attributed to weak interface bonding. To address this issue, this paper proposes the application of ultrasonic vibration during the laser joining process of PET with both Si3N4 and Ti-coated Si3N4 sheets to enhance the interface bonding strength. Investigating the mechanisms underlying the enhancement of interface bonding strength due to ultrasonic vibration is crucial for improving the overall mechanical strength of the joints. It is found that the physical wetting thermodynamic conditions and chemical bond thermodynamic conditions for laser joining of PET to ceramics were the surface tension of ceramics higher than that of the molten PET and the variation in the Gibbs function less than -24.3 kcal/mol, respectively. Experimental results demonstrated that the bonding interface between Si3N4 sheet and PET exhibits only physical and mechanical bonding, with no evidence of new chemical bonds. However, XPS analysis detected new Ti-C bonds at the bonding interface of Ti-coated Si3N4 and PET. Furthermore, experimental results substantiated that ultrasonic vibration could improve the spreading wetting of PET melt on the Si3N4 surface, resulting in a 17 % increase in the bonded area of the weld seam. Additionally, ultrasonic vibration enhanced the molten PET filling into the blind hole structure on the Si3N4 surface, resulting in an approximately 73 % increase in the filling depth of the blind holes. Lastly, ultrasonic vibration facilitated the chemical reaction between the molten PET and Ti atoms, resulting in an approximately 57 % increase in the thickness of the interface containing Ti-C bonds. It is evident that ultrasonic vibration can bolster the interfacial bonding strength of PET/Si3N4 and PET/Ti-coated Si3N4 in laser joining. Moreover, in comparison to physical bonding, its more pronounced impact on mechanical and chemical bonding is noteworthy.
期刊:
Advances in Civil Engineering,2023年2023 ISSN:1687-8086
通讯作者:
Wang, YK
作者机构:
[Wang, YK; Wang, Yukui; Zhang, Dan] Hunan City Univ, Hunan Engn Res Ctr Dev & Applicat Ceramsite Concre, Yiyang 413099, Peoples R China.;[Yan, Shijun] Hunan City Univ, Coll Mech & Elect Engn, Yiyang 413000, Peoples R China.;[Zhang, Dan] Hunan City Univ, Key Lab Green Bldg & Intelligent Construct Higher, Yiyang 413000, Peoples R China.;[Hu, Zhangqi] Hunan City Univ, Coll Civil Engn, Yiyang 413099, Peoples R China.
通讯机构:
[Wang, YK ] H;Hunan City Univ, Hunan Engn Res Ctr Dev & Applicat Ceramsite Concre, Yiyang 413099, Peoples R China.
关键词:
Introduction;Materials and Methods;Results;Discussion;Conclusion;Abstract;Data Availability;Additional Points;Ethical Approval;Consent;Disclosure;Conflicts of Interests;Authors’ Contributions;Funding Statement;Acknowledgements;Acknowledgments;Supplementary Materials;Reference;Dataset Description;Dataset Files;Abstract;Introduction;Introduction and Materials;Introduction and Methods;Materials;Materials and Methods;Methods;Results;Discussion;Results and Discussion;Discussion and Conclusion;Results and Conclusion;Conclusion;Conclusions;Data Availability;Additional Points;Ethical Approval;Consent;Disclosure;Conflicts of Interest;Authors’ Contributions;Funding Statement;Acknowledgements;Supplementary Materials;References;Appendix;Abbreviations;Preliminaries;Introduction and Preliminaries;Notation;Proof of Theorem;Proofs;Analysis of Results;Examples;Numerical Example;Applications;Numerical Simulation;Model;Model Formulation;Systematic Palaeontology;Nomenclatural Acts;Taxonomic Implications;Experimental;Synthesis;Overview;Characterization;Background;Experimental;Theories;Calculations;Model Verification;Model Implementation;Geographic location;Study Area;Geological setting;Data Collection;Field Testing;Data and Sampling;Dataset;Literature Review;Related Works;Related Work;System Model;Methods and Data;Experimental Results;Results and Analysis;Evaluation;Implementation;Case Presentation;Case Report;Search Terms;Case Description;Case Series;Background;Limitations;Additional Points;Case;Case 1;Case 2 etc.;Concern Details;Retraction Details;Copyright;Related Articles
摘要:
The research group utilized the estimation model of energy consumption capacity for reinforced concrete components without axial force to assess the energy consumption capacity of 92-reinforced concrete components from the PEER database, which were subjected to axial force and bending. The study also examined the impact of design parameters, including longitudinal reinforcement ratio, transverse reinforcement ratio, axial compression ratio, and shear-span ratio, on the estimation results. The research findings revealed that when applying the estimation model of energy consumption capacity for reinforced concrete components without axial force to calculate the energy consumption capacity of reinforced concrete components with axial force, there was a significant deviation rate in the estimation of cumulative energy consumption. The relationship between the deviation rate of cumulative energy consumption and longitudinal reinforcement ratio, axial compression ratio, and shear-span ratio remained unclear. However, a more apparent linear relationship was observed with the transverse reinforcement ratio. By conducting a quantitative analysis of the transverse reinforcement ratio, the researchers proposed an modified estimation model of energy consumption capacity for reinforced concrete components with axial force. Nonetheless, the accuracy of the modified estimation model was found to be high within the range of 0–250,000 kN mm of cumulative energy consumption. For cumulative energy consumption exceeding 250,000 kN mm, further experimental and theoretical research is still required to enhance the reliability of the modified estimation model.
通讯机构:
[Lixiong Li] S;School of Mechanical and Electrical Engineering, Hunan City University, Yiyang 413099, China
关键词:
Quasi -Z -source inverter;Cascaded H -bridge;Battery energy storage;State -of -charge
摘要:
Battery energy stored quasi-Z source cascaded H-bridge based photovoltaic power generation system combines advantages of quasi-z-source inverter, cascaded H-bridge, and battery energy storage system. However, the battery state of charge imbalance between the cascaded H-bridge inverter modules would reduce the system's performance and efficiency and potentially cause the system to fail. An integrated control technique of adaptive state of charge balancing based on gain scheduling and three-phase power balance of third harmonic injection based on fundamental frequency whole zero sequences is suggested for the quasi-Z source cascaded H-bridge battery storage system. Based on the mathematical relationship between the instantaneous state of charge of battery energy stored quasi-z-source cascaded H-bridge and the voltage reference value, this method updates the proportional controller gain in each sampling period. It combines the third harmonic injection method based on the fundamental frequency zero sequence to select the optimal modulation ratio Mn. Rapid state of charge balancing is accomplished without overmodulation while increasing the power balance range and decreasing DC link voltage swings. The simulation results validate the method's usefulness. The simulation results validate the proposed control method for ensuring power distribution between each phase and achieving a balanced state of charge of the battery energy stored quasi-Z source cascaded H-bridge photovoltaic system's battery energy storage.
摘要:
BACKGROUND: Respiratory mechanics monitoring provides useful information for guiding mechanical ventilation, but many measuring methods are inappropriate for awake patients. This study aimed to evaluate the accuracy of dynamic mechanics estimation using expiratory time constant (RC(exp)) calculation during noninvasivepressure support ventilation (PSV) with air leak in different lung models. METHODS: A Respironics V60 ventilator was connected to an active breathing simulator for modeling five profiles: normal adult, restrictive, mildly and severely obstructive, and mixed obstructive/restrictive. Inspiratory pressure support was adjusted to maintain tidal volumes (V(T)), achieving 5.0, 7.0, and 10.0ml/kg body weight. PEEP was set at 5 cmH(2)O, and the back-up rate was 10bpm. Measurements were conducted at system leaks of 25-28L/min. RC(exp) was estimated from the ratio at 75% exhaled V(T) and flow rate, which was then used to determine respiratory system compliance (C(rs)) and airway resistance (R(aw)). RESULTS: In non-obstructive conditions (R(aw) ≤ 10 cmH(2)O/L/s), the C(rs) was overestimated in the PSV mode. Peak inspiratory and expiratory flow and V(T) increased with PS levels, as calculated C(rs) decreased. In passive breathing, the difference of C(rs) between different V(T) was no significant. Underestimations of inspiratory resistance and expiratory resistance were observed at V(T) of 5.0ml/kg. The difference was minimal at V(T) of 7.0ml/kg. During non-invasive PSV, the estimation of airway resistance with the RC(exp) method was accurately at V(T) of 7.0ml/kg. CONCLUSIONS: The difference between the calculated C(rs) and the preset value was influenced by the volume, status and inspiratory effort in spontaneously breathing.
作者机构:
[Xu, Jun; Li, Xintao; Zheng, Kaihong; Pan, Fusheng; Kang, Yuehua; Zhou, Nan] Guangdong Acad Sci, Inst New Mat, Guangzhou 510650, Peoples R China.;[Zhao, Jun] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413002, Peoples R China.;[Yang, Hong; Jiang, Bin; Pan, Fusheng] Chongqing Univ, Coll Mat Sci & Engn, Natl Engn Res Ctr Magnesium Alloys, Chongqing 400044, Peoples R China.;[Yang, Hong; Jiang, Bin; Pan, Fusheng] Chongqing Inst Adv Light Met, Chongqing 400030, Peoples R China.;[Liu, Wenjun] Chongqing Univ Technol, Coll Mat Sci & Engn, Chongqing, Peoples R China.
通讯机构:
[Jun Xu] I;[Bin Jiang] N;Institute of New Materials, Guangdong Academy of Sciences, Guangzhou, China<&wdkj&>National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing, China<&wdkj&>Chongqing Institute for Advanced Light Metals, Chongqing, China
摘要:
Mg-3Al-1Zn (AZ31) sheets were produced by transverse gradient extrusion (TGE) process. The flow behavior and dynamic recrystallization during extrusion were systematically analyzed. The microstructures, textures, and mechanical behavior of extruded AZ31 sheet were also analyzed and compared with conventional extruded (CE) sheet. The results showed that fine grain structure and multi-type unique textures were formed in TGE sheet because of the generation of extra flow velocity along transverse direction (TD) and flow velocity gradient along extrusion direction (ED) during extrusion. The basal poles gradually deviated away normal direction (ND) from edge to center of the TGE sheet along TD, and the largest inclination angle at center region reached around 65 degrees. Furthermore, the basal poles inclined from ED to TD 40 degrees-63 degrees, except for the center region of TGE sheet. The TGE sheet presented higher ductility and strain hardening exponent (n-value), but lower yield strength and Lankford value (r-value) in comparison with the CE sheet. Both the basal <a> slip and tensile twins were easy to be activated during deformation, and the largest elongation of 41% and the lowest yield strength of 86.5 MPa were obtained for the ED-center sample in the TGE sheet.
摘要:
Super-hard abrasive grinding is considered to be the main approach to realize precision and ultra-precision machining of difficult-to-machine materials such as cemented carbide, engineering ceramics, titanium alloys and superalloy materials encountered. However, heavy grinding force, high grinding temperature and poor surface integrity are prone to be encountered in conventional negative rake angle grinding of difficult-to-machine materials. In response to these problems, a novel concept of positive rake angle grinding is first proposed and an abrasive grain regularly arranged binder-less polycrystalline diamond face grinding wheel with positive rake angle has been designed and fabricated by femtosecond laser ablation. To evaluate the grinding performance of the face grinding wheel with positive rake angle, grinding experiments of YG8 cemented carbide are conducted and compared with the traditional electroplated diamond grinding tool with equivalent abrasive grain dimension and distribution. The results show that compared with the conventional negative rake angle grinding, the normal and tangential forces in positive rake angle face grinding are reduced by 30.3 % similar to 36.4 % and 21.1 % similar to 29.3 %, respectively, and the ratio of normal to tangential force is reduced by 12.6 % similar to 20.3 %. The surface roughness and average depth of subsurface metamorphic layer are also significantly smaller. The laser fabricated polycrystalline diamond face grinding wheel also has better wear resistance in the grinding of cemented carbide. Therefore, it can be concluded that better ground surface quality is obtained by the novel grinding wheel with positive rake angle. The innovative grinding method can fill the research gap on the grinding mechanism of positive rake angle grinding and further enrich the grinding theory of difficult-to-machine materials.
摘要:
In this study, we present a novel analysis approach for lattice composite cylindrical shells reinforced with Graphene Platelets (GPL) nanoparticles. Our primary contribution lies in the investigation of these advanced structures, incorporating nanocomposite reinforcement, orthotropic inhomogeneity, and semi-analytical methods. The lattice composite comprises an anisogrid lattice laminated shell, reinforced with functionally graded GPL. We model this structure using a global continuous orthotropic deep shell approach, integrating the Halpin-Tsai and rule of mixtures homogenization strategies to estimate equivalent mechanical properties. We derive theoretical formulations utilizing Reddy's third-order shear deformation theory and nonlinear Sanders' kinematic assumptions, tailored for deep thick shells. Nonlinear equilibrium equations are obtained using Hamilton's principle and Hooke's constitutive law, leading to linearized bifurcation equations through adjacent-equilibrium and membrane pre-buckling analysis. Our stability analysis employs a semi-analytical method combining trigonometric expansion and Chebyshev collocation functions. Validation through parametric ex -amples demonstrates the accuracy and efficiency of our approach, unveiling insights into the impact of lattice composite and geometric parameters on the stability response of these innovative structures.
摘要:
In this research, the nonlinear dynamics of a clamped circular composite plate placed on a softening elastic foundation under rapid thermal loading is investigated. In this situation, based on the amount of temperature supplied to the structure and the coefficients of softening elastic foundation, two instabilities may happen one after the other. The structure will thermally buckle and deform dynamically if the applied temperature exceeds a critical level. If the softening coefficient of the elastic foundation is critical, the structure will completely lose its stability after a certain deformation range. A polymer containing graphene platelets (GPL) makes up the system. Based on various functions, the volume fraction of fillers varies along the thickness. The system's nonlinear dynamic equations are obtained by applying Hamilton's principle and the Von-Karman theory. The transient heat conduction equation is solved by the cubic B-spline collocation (CBSC) and Crank- Nicolson procedures. The CBSC and the Newmark methods are used to solve spatially and temporally dependent governing nonlinear differential equations. Also, the Newton-Raphson method is used as a powerful tool to solve nonlinear algebraic equations. The temporal evolution, phase-plane, and post-buckling-to-maximum deflection paths are demonstrated to analyze the instabilities of the plate.
作者机构:
[Zhang, Haoran] School of Mechanical and Electrical Engineering, Hunan City University, Yiyang, 413000, China;[Chen, Guoming; Zhang, Nan] Centre for Offshore Engineering and Safety Technology, China University of Petroleum, Qingdao, 266580, China;[Wang, Rongyao] School of Mechanical and Electrical Engineering, Hunan City University, Yiyang, 413000, China<&wdkj&>Centre for Offshore Engineering and Safety Technology, China University of Petroleum, Qingdao, 266580, China
通讯机构:
[Rongyao Wang] S;School of Mechanical and Electrical Engineering, Hunan City University, Yiyang, 413000, China<&wdkj&>Centre for Offshore Engineering and Safety Technology, China University of Petroleum, Qingdao, 266580, China
摘要:
Storms are a major threat to deep-sea mining activities on the high seas. Deep-sea mining takes a long time to prepare to avoid storms, and in some cases it is inevitable to evacuate to avoid storms with risers hung-off. In this work, the evacuation process with risers hung-off is studied, and mechanical properties such as stress and upper rotation of the mining riser system during the process are analyzed. Operation parameters such as speed and heading suitable for evacuation are studied. Evacuation routes of mining ship are optimized based on an improved A* algorithm, and the influencing factors of evacuation operations are analyzed. Research findings can provide guidance for decision-making related to storm avoidance in deep-sea mining and improve the safety of the mining system in the evacuation process.