Abstract:To address the dynamic characteristics of the herringbone gear compound planetary transmission system of gas turbines under high-speed and heavy-load conditions,a semi-analytical dynamic modeling method based on the coupling of bending-torsion shaft-pendulum is proposed,revealing the influence law of multi-source excitation on the dynamic behavior of the system.By establishing a concentrated mass model including the sun gear,planetary gear and internal gear ring,combined with the deformation coordination equation and the dynamic differential equation,the influences of tooth profile error,modification parameters and load torque on dynamic loads,uniform load characteristics and vibration response were analyzed.The research adopted neural networks and genetic algorithms to optimize the gear modification parameters,reducing the vibration velocity of the box by 30.5％and significantly improving the dynamic performance of the system.Experimental verification shows that the errors between the theoretical values and the measured values of the equalization coefficient and vibration velocity are 4.3％and 12.5％respectively,verifying the accuracy of the model.This research provides theoretical guidance and technical support for the design and optimization of high-speed and heavy-load herringbone gear compound planetary transmission systems.

Abstract:In the domain of mechanical manufacturing,the performance optimization of high-speed punch presses has consistently been a critical research focus.This study investigates the correlation between pressure fluctuations in the hydraulic system of high-speed punch presses and the quality of the workpiece's shear surface.Based on practical operating conditions and theoretical foundations,a meticulously designed blanking model for punch presses was established.Advanced simulation techniques were employed to conduct comprehensive analyses of the blanking process under various conditions,and an experimental platform was constructed for validation.The findings revealed that the accumulator return hydraulic system exhibited significant advantages.Regarding the reduction of the pressure variation range in the hydraulic cylinder:the pressure fluctuation in the low-pressure oil return rod chamber ranged from 7 MPa to 5.7 MPa(a variation of 1.3 MPa),whereas in the accumulator return system,the pressure fluctuated between 3 MPa and 3.8 MPa(a variation of 0.8 MPa).This demonstrates that the accumulator return method effectively stabilizes pressure variations and mitigates adverse effects caused by abrupt pressure changes.In terms of enhancing the quality of the steel plate's shear surface,after blanking various types of steel plates,it was observed that this method significantly reduces the fillet size,increases the proportion of the bright band by an average of 33％compared to the low-pressure oil return method,and eliminates the issue of tear band cracks on the shear surface present in the low-pressure oil return method.Additionally,it reduces stress concentration,substantially improving the quality of the blanked parts.These results provide essential evidence and robust support for the optimization of the hydraulic system in high-speed punch presses.

Abstract:Using a Gleeble-3800 thermal simulation experimental machine,isothermal compression tests were conducted on 2A12 aluminum alloy to study its high-temperature deformation behavior.The compression amount studied was 50％,with deformation temperatures ranging from 325 ℃ to 425℃,and strain rates from 0.001s-1 to 5 s-1.A dynamic recrystallization volume fraction prediction model for 2A12 aluminum alloy was established based on the Avrami equation.A constitutive model was developed based on a two-stage model of dynamic recovery and dynamic recrystallization.It is shown that the constructed constitutive model considering dynamic recovery and dynamic recrystallization is capable of accurately predicting the flow stress of 2A12 aluminum alloy under heat deformation conditions.The model can be embedded in finite element software,providing a theoretical basis for the numerical simulation of the aluminum alloy extrusion forming process,which is of great significance for optimizing the lightweight manufacturing process of aviation equipment.

Abstract:The creep-fatigue damage generated by turbine blades serving in the"3H"(High temperature,High pressure,High speed)environment affects the safe operation of aircraft engines.Aiming at the creep-fatigue damage failure of aircraft engine turbine blades,based on the Kachanov-Rabotnov-Lemaitre damage mechanics method,the mean stress to temperature ratio parameter is introduced to construct a creep-fatigue life prediction model for turbine blade material nickel-based superalloy DZ125.The model is verified through creep fatigue tests conducted in the laboratory.Research has shown that the constructed creep-fatigue life prediction model has high life prediction accuracy,with prediction results located within a 1.5-fold dispersion band.The above research proposes a creep-fatigue life prediction method for turbine blade materials in the"3H"environment,providing a theoretical basis for accurately predicting the structural life and having important engineering application value.

Abstract:To address the operational condition where the ladle tilting direction at Meisteel's No.2 Steelmaking Plant is opposite to the slag dumping direction,the full ladle cover technology was introduced.Based on the process layout characteristics of the plant,a"quad-chain triple-claw"cover handling system was adopted.Through rational arrangement of ladles and cover handling devices,the system achieves cover removal upon arrival and cover installation upon departure,thereby resolving the technical challenge of opposing directions between slag turnover and hot repair operations.An automatic locking device was designed to enable slag dumping and hot repair tilting with the cover attached,resolving the challenge of overturning within limited pit spacing.The system achieves over 120° rotation during hot repair operations,while allowing partial opening of the covered ladle for refractory inspection and slag removal.After implementing the full ladle cover technology,the average temperature drop during tapping was reduced by 15℃,achieving the goal of production cost reduc-tion.

Abstract:In view of the profound influence of unsteady turbulent wind loads on the dynamic response of wind turbine gearboxes,this paper presents a complex multi-degree-of-freedom dynamic model that rigorously couples nonlinear gear meshing with bearing support.Turbulent wind speed time histories are generated using the Kaimal spectrum,and the Newmark-β method is employed to obtain the system's acceleration response.Gear meshing stiffness and bearing support stiffness are treated as control variables to elucidate their effects on time-domain and frequency-domain characteristics.Model validation was performed utilizing measured vibration data acquired from a doubly-fed induction generator wind turbine.Results show that the proposed model accurately reproduces both the time-domain waveforms and the dominant frequency-domain peaks under turbulent excitation,confirming the necessity and the effectiveness of the multi-physical-field coupling approach.Furthermore,an intermediate meshing stiffness offers an optimal compromise between stability and energy transmission,while enhanced bearing stiffness markedly suppresses high-amplitude vibration and accelerates vibration decay.This study emphasises the pivotal function of turbulent wind load analysis in gearbox design and fault diagnosis,thereby establishing a substantial theoretical foundation for subsequent structural optimization.

Abstract:The static and dynamic characteristic of gearbox influences the structure strength and the transmission performance directly.The static and dynamic model of center drive gearbox is established by finite element method.The structure is analysed by I-DEAS software and the wall thickness of gearbox is optimized, making the structure of gearbox more appropriate.