科创中国

在洪水计算中,河道糙率是一个重要参数.通过对河道糙率影响因素分析,利用李营水文试验站的实测资料,阐述了河道糙率的计算方法.糙率确定时影响因素较多,不同的水深、植被、河床等因素,都会对糙率值产生影响.在实际计算中,大部分设计河段没有实测糙率资料,在实际应用中要借助相似河道的参数代替,对计算精度影响较大.收集了国内外不同情况下的河道糙率实验资料,可供河道糙率计算参考.

As the two most important indexes of bearing raceway,surface roughness and roundness have significant influence on bearing noise.Some researchers have carried out studies in this field,however,reason and extent of the influence of raceway surface geometric characteristics on bearing running noise are not perfectly clear up to now.In this paper,the raceway of 6309 type bearing's inner and outer ring is machined by floating abrasive polishing adopting soft abrasive pad.Surface roughness parameters,arithmetical mean deviation of the profile Ra,the point height of irregularities Rz,maximum height of the profile Rmax and roundness f of raceways,are measured before and after machining,and the change rules of the measured results are studied.The study results show that the floating abrasive polishing can reduce the surface geometric errors of bearing raceway evidently.The roundness error is reduced by 25%,Rmax value is reduced by 35.5%,Rz value is reduced by 22%and Ra value is reduced by 5%.By analyzing the change of the geometrical parameters and the shape difference of the raceway before and after machining,it is found that the floating abrasive polishing method can affect the roundness error mainly by modifying the local deviation of the raceway's surface profile.Bearings with different raceway surface geometrical parameter value are assembled and the running noise is tested.The test results show that Ra has a little,Rmax and Rz have a measurable,and the roundness error has a significant influence on the running noise.From the viewpoint of controlling bearings'running noise,raceway roundness error should be strictly controlled,and for the surface roughness parameters,Rmax and Rz should be mainly controlled.This paper proposes an effective method to obtain the low noise bearing by machining the raceway with floating abrasive polishing after super finishing.

Iterative methods based on finite element simulation are effective approaches to design mold shape to compensate springback in sheet metal forming.However,convergence rate of iterative methods is difficult to improve greatly.To increase the springback compensate speed of designing age forming mold,process of calculating springback for a certain mold with finite element method is analyzed.Springback compensation is abstracted as finding a solution for a set of nonlinear functions and a springback compensation algorithm is presented on the basis of quasi Newton method.The accuracy of algorithm is verified by developing an ABAQUS secondary development program with MATLAB.Three rectangular integrated panels of dimensions 710 mm′750 mm integrated panels with intersected ribs of 10 mm are selected to perform case studies.The algorithm is used to compute mold contours for the panels with cylinder,sphere and saddle contours respectively and it takes 57%,22%and 33%iterations as compared to that of displacement adjustment(DA)method.At the end of iterations,maximum deviations on the three panels are 0.618 4 mm,0.624 1 mm and 0.342 0 mm that are smaller than the deviations determined by DA method(0.740 8 mm,0.740 8 mm and 0.713 7 mm respectively).In following experimental verification,mold contour for another integrated panel with 400 mm*380 mm size is designed by the algorithm.Then the panel is age formed in an autoclave and measured by a three dimensional digital measurement devise.Deviation between measuring results and the panel's design contour is less than 1 mm.Finally,the iterations with different mesh sizes(40 mm,35mm,30 mm,25 mm,20 mm)in finite element models are compared and found no considerable difference.Another possible compensation method,Broyden-Fletcher-Shanmo method,is also presented based on the solving nonlinear functions idea.The Broyden-Fletcher-Shanmo method is employed to compute mold contour for the second panel.It only takes 50%iterations compared to that of DA.The proposed method can serve a faster mold contour compensation method for sheet metal forming.

多年调节水库调节性能较高,其兴利库容对整个工程规模的确定至关重要.以贵州省麻江县上寨水库多年调节水库为例,通过对水库的径流系列进行分析,采用时历法和数理统计法对水库的兴利库容进行计算,对该水库的兴利库容计算结果进行了评价,并对多年调节水库兴利调节中采用的基础资料及计算方法进行了简要分析.

Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely.A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented,and an optimization method with two processes for determining the orientation of a pre-applied universal magnetic spin vector is proposed.To realize quick and non-contact steering swimming,a fuzzy comprehensive evaluation method for optimizing the steering driving angle is presented based on two evaluation indexes including the average steering speed and the average steering trajectory deviation,achieving the initial optimal orientation of a universal magnetic spin vector.To further reduce robotic magnetic vibration,a main target method for optimizing its final orientation,which is used for fine adjustment,is employed under the constrains of the magnetic moments.Swimming experimental results in curve pipe verified the effectiveness of the optimization method,which can be effectively used to realize non-contact steering swimming of the petal-shaped robot and reduce its vibration.

Common compliant joints generally have limited range of motion,reduced fatigue life and high stress concentration.To overcome these shortcomings,periodically corrugated cantilever beam is applied to design compliant joints.Basic corrugated beam unit is modeled by using pseudo-rigid-body method.The trajectory and deformation behavior of periodically corrugated cantilever beam are estimated by the transformation of coordinate and superposition of the deformation of corrugated beam units.Finite element analysis(FEA)is carried out on corrugated cantilever beam to estimate the accuracy of the pseudo-rigid-body model.Results show that the kinetostatic behaviors obtained by this method,which has a relative error less than 6%,has good applicability and corrugated cantilever beam has the characteristics of a large range of motion and high mechanical strength.The corrugated cantilever beam is then applied to design a flexible rotational joint to obtain a larger angle output.The paper proposes a pseudo-rigid-body model for corrugated cantilever beam and designed a flexible rotational joint with large angle output.

南水北调中线天津干线采用全箱涵无压接有压自流输水方案,调节池是实现无压流和有压流平稳过渡的重要控制性建筑物.经多方案比选,斜坡式调节池结构安全稳定,水力条件好,实现了上下游流态的平稳衔接.

Traditional model for calculating performance parameters of a fix-pad journal bearing leads to heavy workload,complicated and changeable formulae as it requires deriving various geometric formulae with different bearing types such as circular journal bearing,dislocated bearing and elliptic bearing.Considering different pad preload ratios for non-standard bearing,traditional model not only becomes more complicated but also reduces scalability and promotion of the calculation programs.For the complexly case of traditional model while dealing with various fix-pad journal bearings,unified coordinate system model for performance calculation of fix-pad journal bearing is presented in the paper.A unified coordinate system with the bearing center at the origin is established,and the eccentricity ratio and attitude angle of axis relative to each pad are calculated through the coordinates of journal center and each pad center.Geometric description of fix-pad journal bearing is unified in this model,which can be used for both various standard bearing and non-standard bearing with different pad preload ratios.Validity of this model is verified with an elliptical bearing.Performance of a non-standard four-leaf bearing with different pad preload ratios is calculated based on this model.The calculation result shows that increasing preload ratio of the pad 1 and keeping that of the left three pads constant improves bearing capacity,stiffness and damping coefficients.This research presents a unified coordinate system model unifies performance calculation of fix-pad journal bearings and studied a non-standard four-leaf bearing with different pad preload ratios,the research conclusions provides new methods for performance calculation of fix-pad journal bearings.

The existing researches of the evaluation method of ride comfort of vehicle mainly focus on the level of human feelings to vibration. The level of human feelings to vibration is influenced by many factors, however, the ride comfort according to the common principle of probability and statistics and simple binary logic is unable to reflect these uncertainties. The random fuzzy evaluation model from people subjective response to vibration is adopted in the paper, these uncertainties are analyzed from the angle of psychological physics. Discussing the traditional evaluation of ride comfort during vehicle vibration, a fuzzily random evaluation model on the basis of annoyance rate is proposed for the human body's subjective response to vibration, with relevant fuzzy membership function and probability distribution given. A half-car four degrees of freedom suspension vibration model is described, subject to irregular excitations from the road surface, with the aid of software Matlab/Simulink. A new kind of evaluation method for ride comfort of vehicles is proposed in the paper, i.e., the annoyance rate evaluation method. The genetic algorithm and neural network control theory are used to control the system. Simulation results are obtained, such as the comparison of comfort reaction to vibration environments between before and after control, relationship of annoyance rate to vibration frequency and weighted acceleration, based on ISO2631/1(1982), ISO 2631–1(1997) and annoyance rate evaluation method, respectively. Simulated assessment results indicate that the proposed active suspension systems prove to be effective in the vibration isolation of the suspension system, and the subjective response of human being can be promoted from very uncomfortable to a little uncomfortable. Furthermore, the novel evaluation method based on annoyance rate can further estimate quantitatively the number of passengers who feel discomfort due to vibration. A new analysis method of vehicle comfort is presented.

Vehicle mass is an important parameter in vehicle dynamics control systems.Although many algorithms have been developed for the estimation of mass,none of them have yet taken into account the different types of resistance that occur under different conditions.This paper proposes a vehicle mass estimator.The estimator incorporates road gradient information in the longitudinal accelerometer signal,and it removes the road grade from the longitudinal dynamics of the vehicle.Then,two different recursive least square method(RLSM)schemes are proposed to estimate the driving resistance and the mass independently based on the acceleration partition under different conditions.A 6 DOF dynamic model of four In-wheel Motor Vehicle is built to assist in the design of the algorithm and in the setting of the parameters.The acceleration limits are determined to not only reduce the estimated error but also ensure enough data for the resistance estimation and mass estimation in some critical situations.The modification of the algorithm is also discussed to improve the result of the mass estimation.Experiment data on a sphalt road,plastic runway,and gravel road and on sloping roads are used to validate the estimation algorithm.The adaptability of the algorithm is improved by using data collected under several critical operating conditions.The experimental results show the error of the estimation process to be within 2.6%,which indicates that the algorithm can estimate mass with great accuracy regardless of the road surface and gradient changes and that it may be valuable in engineering applications.This paper proposes a recursive least square vehicle mass estimation method based on acceleration partition.