A new method for fault diagnosis of rolling bearings based on the fusion of composite multiscale entropy and random forest is proposed.In view of the problem of informa-tion loss during coarse-grained analysis,a composite multiscale analysis technology is introduced,which fuses fuzzy entropy,ap-proximate entropy and sample entropy to construct a feature extraction method to ac-curately extract rolling bearing features.Sub-sequently,the feature matrix is subjected to feature selection,and the threshold is set sci-entifically and optimized by filtering method to eliminate redundant information.Then,a random forest model is constructed to deeply combine with the multiscale fault features to form a complete fault diagnosis system,which realizes accurate discrimination of rolling bearing faults.To verify the effectiveness of this method and to compare with the tradi-tional methods,rolling bearing datasets from Case Western Reserve University(CWRU)in the United States and Jiangnan University are selected for case verification.The test results show that the fault identification accuracy of this method reaches 100％and 98.8％,respec-tively,indicating that this method has signifi-cant advantages over the traditional methods in terms of fault identification accuracy and can complete rolling bearing fault diagnosis tasks with high efficiency and high accuracy.
The fuel centrifugal pump,as an impor-tant component of an aero engine,has a crucial impact on the stability and reli-ability of an aircraft.Based on the RNG k-e turbulence model and ZGB cavitation model,unsteady numerical calculation is carried out on the fuel centrifugal pump to analyze the flow characteristics of the flow field in the impeller of the fuel cen-trifugal pump under different working conditions.The research shows that the main frequency of pressure fluctuation in the impeller is the shaft frequency,and the main frequency of the cut-water and outlet extension section is the blade fre-quency,in which the pressure fluctuation amplitude at the cut-water is the larg-est.The high entropy generationzone is mainly distributed in the vicinity of the vane,and the area of high entropy gen-eration zone gradually increases with the increase of the flow rate.The distribution of vorticity is similar to that of entropy generation,mainly at the inlet and outlet of the vane,with the largest area of vor-tex core under the condition of high flow rate.The cavity appears at the leading edge of the vane at the first stage.Under the condition of the same flow rate,with the drop of cavitation number,the cav-ity continuously grows big.At the same cavitation coefficient,with the increase of the flow rate,the volume fraction of the cavity continuously increases.
Taking the 1SN16 hydraulic hose pro-duced by a company as the research object,the modelling software is used to model the rubber hosewith a layer of braided steel wire,the model is import-ed into the finite element simulation and analysis software to carry out modal analysis of the empty hose and fluid-structure interaction hose to obtain the first 8 orders of the natural frequencies of the empty hose and fluid-structure interaction hose,and the two-way fluid-structure interaction framework is built.The control variate method is applied to analyze the changes of vibration displacement of the hose wall and vibra-tion velocity of the fluid for hoses with different bending shapes(straight hose,L-shaped hose and U-shaped hose)to obtain some laws of fluid-structure interaction vibration of rubber hoses,which provide a reference for the design and selection of hydraulic hoses of wind turbines.
Taking a 260 t 8-section-jib all-terrain crane as the research object,the all-terrain crane performance calculation module is used to establish a perfor-mance calculation model of the crane and a simplified model of the extend-ing jib to study the influence of section dimensions,aspect ratio,diameter-to-thickness ratio and upper and lower cover plate thickness in the structural param-eters of the extending jib on the critical buckling load.Based on the research results and engineering design experi-ence,the design and selection method of structural parameters of the extending jib is summarized,which provides a theori-cal reference for the initial design of the extending jib structure.
在盾构掘进过程中,螺旋输送机时常发生泥沙喷涌现象.针对某工程施工过程中盾构螺旋输送机前端闸门法兰面崩开喷涌事故,依据喷涌情况,结合施工过程,对法兰面喷涌现象原因进行分析,并提出相应的处置技术,以保证盾构施工的安全进行.
In view of the problems such as large size and difficult installation of tradi-tional tailstock,an innovative design plan of tailstock for small machine tools is proposed and analyzed in terms of structure,working principle and opera-tion method.The new machine tool tail-stock is reasonably designed,structur-ally stable,and has the characteristics of easy to use.Test analysis shows that the installation efficiency,use experi-ence and operational stability of the new tailstock for small machine tools have been significantly improved.In the face of the miniaturization trend of ma-chine tools,the new tailstock for small machine tools has a broad application potential.
In view of poor accuracy and low ef-ficiency of the traditional manual tap-per,a multi-station,high-efficiency and folding-arm precision tapper is devel-oped.The equipment is equipped with a programmable logic controller and a servo system to ensure the accuracy and reliability of the tapper,the folding-arm structure allows the operator to set the parameters such as the processing speed,effective depth and pitch based on the controller,and the tapper controls the servo motor according to the design parameters to accurately process the threads.The tapper can be used in mul-tiple directions and angles along the X and Y axes,with significant advantages of high efficiency and high precision,as well as advantages of easy processing and low cost.
In order to make the lifting process simulation applicable to a wider range of lifting processes,for the cross-travelling action which is unique to the crawler crane with a structure form of front and rear crawler trucks,simulation research is carried out on the cross-travelling action of the crawler crane.With the analysis of the posture relationship be-tween the front and rear trucks as the entry point,the travelling distance of the front truck as the posture input condition of the crane at the next moment and the posture relationship as a constraint,the calculation method for automatic match-ing of the rear truck action is studied.Finally,this algorithm is applied to the lifting simulation software to improve its applicability.
Crow search algorithm(CSA)and slime mould algorithm(SMA)are two new metaheuristic optimization algorithms proposed in recent years.CSA has the characteristics of simple mechanism,not easy to fall into local optimum and good performance in engineering issues,but its local search capacity is weak and search efficiency is not high.SMA has the ad-vantages of strong scalability and strong local search capacity,but its performance is unstable in solving high-dimensional complex problems and functions with optimal solutions not at the origin,and it is easy to fall into local optimum.To overcome the shortcomings of the above algorithms,the advantages of the two algorithms are integrated by using a population classification strategy and the slime mould-crow search algorithm(SMCSA)based on time series factor is proposed.The new algorithm uses the time series factor to represent the popula-tion as a time-varying dynamic structure,enabling CSA and SMA to optimize in parallel.By varying the number of dif-ferent sub-populations,it focuses on ex-ploration at the initial stage of optimiza-tion and further development at the later stage.To verify the optimization capabil-ity and search efficiency of the proposed algorithm,SMCSA and 7 other different types of heuristic algorithms are applied to solve 15 benchmark test functions and 3 mechanical design issues.The test re-sults show that the convergence speedof SMCSAis improved compared to the original algorithms,and it has better robustness and search accuracy than the control algorithms.
During the excavation process of a shield,it was found that the frame circuit breaker in the cubical substation had frequent leakage current and tripping problems.Based on this issue,a FLUKE oscilloscope was used to analyze and inspect the lower-end equipment,and the insulation of the lower-end equipment was normal without leakage current.It was finally confirmed that the problems originated from the defects of the leak-age current detection mechanism of the frame circuit breaker in the cubical substation.It was found from the analy-sis that the sampling resistor burning caused by overcurrent led to an abnormal increase in leakage current,eventually resulting in false alarms.
In view of the current situation that the recycling efficiency of typical consum-able(PLA/ABS)scrapsfrom fused fila-ment fabrication(FFF)3D Printers is not high and the centralized recycling system is not applicable,a distributed recycling system applicable to 3D print-ing filament scraps is developed,which contains a complete process to achieve filament recycling and regeneration.The system integrates six main parts,crush-ing device,mixing device,melt extru-sion device,cooling device,automatic size control device and winding device,which conforms to the modular design scheme.The finite element analysis software ANSYS Workbench is used to carry out static analysis on the screw,a key component of the system,to cal-culate the force and deformation of the screw under working load conditions,and the results show that the strength and stiffness of the screw meet the de-sign requirements.
Coconut picking is a complex process with high labor costs that can negatively affect sales.A coconut picking robot is developed,which uses a robotic arm and a circular saw to improve the labor ef-ficiency in the coconut picking process and to some extent reduce the dangerco-efficient of manually ascending and pick-ing coconuts.The concept of the coconut picking robot is described,and the me-chanical system for the overall structure of the coconut picking robot is designed,including the conveyor track system,the picking system,etc.
The jacking operation of large heavy-du-ty structures such as offshore platforms,heavy equipment and bridge buildings is characterized by large structural dimensions,heavy jacking loads and high synchronous control accuracy.The jacking device of such large heavy-duty structures mainly adopts multigroup hy-draulic jacking cylinders for multipoint distribution arrangement and controls the motions of each group of hydraulic jacking cylinders to realize synchronous jacking operation of the whole struc-ture.An adaptive synchronous control strategy based on velocity-displacement deviation coupling is designed for the large heavy-duty distributed hydraulic jacking system,and the synchronous control strategy is tested ona distributed hydraulic jacking test platform,achiev-ing a good anti-interference synchro-nous control effect,which provides a reference for the control of various types of distributed synchronous jacking sys-tems.
The advantages,disadvantages and appli-cable occasions of using analytic method and ANSYS finite element method to optimize the design of the pipeline as-sembly sleeve are pointed out,emphasiz-ing the concept,steps and characteristics of ANSYS optimization design.The research on optimization design of the pipeline assembly sleeve by using the proposed optimization design method shows that the optimization of the pipe-line assembly sleeve based on ANSYS fi-nite element method can obtain a design result with high accuracy,and the pro-posed optimization design method has a high application and promotion value.
Model XR4660E multifunctional rotary drilling rig is a new generation of series E large tonnage product independently developed by XCMG Foundation.The structure and technical parameters of XR460E rotary drilling rig are intro-duced,as well as related technical in-novation points and construction cases.Based on the mature XR400E,this ma-chine has an increased power and sys-tem flow and an improved main hoisting force and power head torque to achieve the improvement of operating efficiency.It adopts the latest welding technology,which is,preheating before welding and heat treatment anti-deformation technol-ogy after welding of the drill pipe,to improve the weld quality and the fittin-gaccuracy of the super-long drill pipe to ensure the hole quality of the ultra-deep pile.The XR460E takes into account both stability of construction and trans-port convenience of site transfer.
The jacking system is the core equipment of the offshore jack-up jacking platform,in which the hydraulic jacking cylinder,the executive element of the jacking sys-tem,plays a role of providing the jacking power,and its reliability and environ-mental adaptability under the marine en-vironment and heavy-duty impact work-ing conditions will affect the working ability of the whole platform.The related key technologies of the offshore heavy-duty hydraulic jacking cylinder are sys-tematically elaborated from the aspects of design and process,which provides a reference for the development and design of similar products in the future.
Based on the research of domestic and in-ternational mechanical equipment main-tenance strategies and current situation of lift maintenance in China,a method for calculating the on-demand mainte-nance frequency of lifts is studied.Based on the problems found in the research of domestic and international mechanical equipment maintenance strategies,it is proposed to design a targeted mainte-nance strategy under the unique needs of a single lift.Firstly,a lift safety as-sessment model that can both determine the maintenance interval and predict the remaining service life is established.Based on the improvement and extension of each index parameter mentioned in the 2021 Document No.53 of the State Administration for Market Regulation,an evaluation model of calculating the re-gional lift performance by weighted scor-ing and evaluation method is established.The weight of each performance index parameter is comprehensively calculated by using the matrix method,dimension-less processing,standard deviation cal-culation,correlation coefficient conflict calculation and covariance calculation.Based on the weight of each performance index parameter and calculationscore of each lift performance evaluation,a formula of lift maintenance interval is designed to calculate the on-demand maintenance frequency of lifts.The fea-sibility and scientificity of the method are verified through enterprise applica-tion cases.The weighted scoring and evaluation method modified by CRITIC weighting method uses objective data and practical indexes to judge and evaluate the safety performance of each lift,and the designed formula for calculating the on-demand maintenance frequency of lifts can scientifically guide the progress of the pilot work of on-demand mainte-nance.
Hook swing is an important index forevaluating the effect of crane hook stabilization.In view of its high measure-ment cost and susceptibility to weather,an economical and practical method of gypsum powder grid point measurement is proposed to obtain crane hook swing data.Due to more subjective factors and larger errors in human eye measurement,a unary linear regression model is estab-lished for the hook swing data,and the correlation coefficients of the model are analyzed,as well as the swing change trend from it.It is concluded that only re-lying on the mechanical friction damping of the crane itself to stabilize the hook is extremely long,so the hook stabilization strategy is imperative.The data analysis results show that the unary linear regres-sion analysis method can be applied to the fitting analysis of the measurement data ofcrane hook swing,which has an important reference value for testing the effectiveness of the crane hook stabiliza-tion strategy.
With the continuous development of high-power wind turbines,the size and weight of wind turbine blades con-tinue to increase,and the existing plant configuration cannot meet the weigh-ing needs of large-scale wind turbine blades.On the basis of the analysis of the weighing method of wind turbine blades,a weighing plan of threecranes and two lifting points is proposed,and a lifting beam for weighting is designed accordingly.This plan is flexible for weighing and does not occupy the pro-duction station,which is widely appli-cable.The strength of the main body of the lifting beam is analyzed and tested.The test results show that the designed lifting beam and weighing plan can well meet the weighing needs of large-scale wind turbine blades and reduce the costs of equipment configuration and plant renovation.
The thrust grouping pressure control in the thrust system of shield is an impor-tant means for shield to dig forward and for shield posture correction.The shield thrust hydraulic cylinder generally adopts a fixed grouping mode.Taking the 8 m shield as an example,the impact of thrust hydraulic cylinder floating al-location strategies in thrust hydraulic cylinder grouping on the thrust force center and moment is compared and analyzed.It is recommended that the shield thrust system shall be designed to incorporate the 363-grouping mode on the basis of retaining the original 343-grouping to improve the correction ability of the shield in the vertical direc-tion.
