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In order to study the strength performance of the airship envelope and the influence of overpressure bearing on its residual strength, the sample forms and experiments plans for the uniaxial and biaxial tensile of the envelope material were designed, and the tearing situation of the airship was analyzed with the help of a high-speed camera. Based on the experimental data, fitted the uniaxial tensile strength curve when the airship bears air pressure, and the longitudinal and latitudinal strength envelope line of the material when it was biaxially stretched. The experimental results demonstrate that there is a negative correlation between the residual strength of the envelope and the airship bearing air pressure when uniaxially stretched, the bearing strength of the envelope is comprehensively affected by the longitudinal and latitudinal strengths when biaxially stretched. This experiment also analyzes the failure situation of the airship envelope, which can provide an experimental guidance for its strength prediction.

In order to explore the influence of the size effect on the fracture strength of unidirectional continuous glass fiber reinforced polypropylene composites（unidirectional GF/PP composites）, the Zwick/Roell Z005 universal material testing machine was used to test different gauge lengths through orthogonal test methods.（60 mm, 100 mm, 200 mm）, unidirectional GF/PP composites with different widths（10 mm, 15 mm, 20 mm） are subjected to tensile test. The test results show that as the test size increases, the breaking strength of unidirectional GF/PP composites gradually decreases. Because the fracture strength of unidirectional GF/PP composites has a large dispersion, the distribution law of the strength of unidirectional GF/PP composites under different size conditions is obtained through the classic two-parameter Weibull strength statistical model, and the improved generalized The two-parameter weakest chain strength statistical model introduces the exponential parameterβto modify the influence of the spatial distribution of defects. The fracture strength data under different sizes are processed in a unified manner. The resulting failure function comprehensively reflects the size effect on the unidirectional GF/PP composite The effect of material breaking strength.

Electrochemically producing formate by oxidizing methanol is a promising way to add value to methanol. Noble metal-based electrocatalysts, which have been extensively studied for the methanol oxidation reaction, can catalyze the complete oxidation of methanol to carbon dioxide, but not the mild oxidation to formate. As a result, exploring efficient and earth-abundant electrocatalysts for formate production from methanol is of interest. Herein, we present the electro-oxidation of methanol to formate, catalyzed by iron-substituted lanthanum cobaltite (LaCo1−xFexO3). The Fe/Co ratio in the oxides greatly influences the activity and selectivity. This effect is attributed to the higher affinity of Fe and Co to the two reactants: CH3OH and OH−, respectively. Because a balance between these affinities is favored, LaCo0.5Fe0.5O3 shows the highest formate production rate, at 24.5 mmol ​h−1 goxide−1, and a relatively high Faradaic efficiency of 44.4% in a series of (LaCo1−xFexO3) samples (x ​= ​0.00, 0.25, 0.50, 0.75, 1.00) at 1.6 ​V versus a reversible hydrogen electrode.

In order to verify the bending effect of quartz wafer,a special elastic ring clamping structure was designed to install and position the sensitive element. According to elastic mechanics and piezoelectricity,the calculation formula of bending stress and polarization of quartz wafer were deduced and the stress analysis of the elastic ring wafer clamping structure was carried out. In order to reduce the influence of structural deformation on sensor application performance,using the energy principle of elastic mechanics the static stiffness formula of the elastic ring wafer clamping structure under load was calculated. Using the finite element method the strength and stiffness of the elastic ring wafer clamping structure was verified. The theoretical calculation,finite element analysis and experimental measurement results show that the rigidity of the elastic ring wafer clamping structure is more than 10 kgf/um,which meets the requirements of sensor design. The research can provide technical support for the structural design of the new cantilever force sensor and micro actuator.

According to the structure orthogonal anisotropic periodic raised structure plate,the equivalent stiffness of the arc periodic raised structure plate is investigated. Based on the classical theory of elastic thin plate and the homogeneous distribution characteristics of the plate,the analytic equation of the equivalent stiffness of the arc periodic raised structure plate is derived.The finite element method is used to simulate the numerical results of arc periodic raised structure plate with simply supported on Four Sides under the concentrated load. The rationality and accuracy of equivalent stiffness is verified. Then the natural frequency of the arc periodic raised structure plate under simply supported on four sides is calculated by using the analytic method. The calculation results are in agreement with the finite element simulation results,and the correctness of the analytical equation of the equivalent stiffness is verified again. The present new method can be used to calculate the equivalent stiffness of the periodic raised structure plate accurately. Moreover,the calculation is directly performed with the geometric parameters of the typical unit.This method is intuitive and concise,and improves the efficiency of solution. The results have important guiding significance for studying the static and dynamic characteristics of the periodic raised structure plate and engineering applications.

The main drive system of rolling mill is a complicated electromechanical system,as the main device of transmitting motion and torque. The factor of electromechanical coupling is one of the important reasons for the abnormal variation of torsional vibration. The paper mainly researched that the dynamic analyses of the torsional vibration of main drive system of rolling mill. Comparative analysis the torsional vibration of main drive system is obtained between considering electromechanical coupling and not considering electromechanical coupling. Then,the mechanical and mathematical models of the main drive torsional vibration system are established. Based on Matlab/Simulink simulation,the unstable state of the main drive torsional vibration system is used to be studied,and then the influences of the uncertain parameters on the torsional vibration of main drive system are analyzed. The results could be revealed the oscillation law for the torsional vibration of main drive system of rolling mill and provided a theoretical foundation for the formulation of control strategy.

Strip steel vibrations is inevitable in the rolling process of tandem mill, and the coupled model between elastoplastic body of strip steel and main drive system directly affects the overall dynamic performance of rolling mill. According to the movement mechanism of strip steel and main drive system, the main drive system was simplified to a two-degree-of-freedom discrete model and the strip steel was simplified to an axially moving Euler beam, the coupled vibration mechanical model of transverse and longitudinal vibrations of strip steel and torsional vibration of main drive system was established. Then, the nonlinear vibration differential equations of the coupled model were derived with Hamilton’s principle. The modified iteration method and the Kantorovich averaging method were used to solve the differential equations. Finally, by using the Matlab simulation, the influence of torsional vibration fundamental frequency of main drive system on strip steel vibration characteristics was discussed. The results can enrich the theoretical achievements on vibration of rolling mill, and it is valuable for transforming theoretical results into engineering applications.

The surface roughness data of test-pieces with transverse profiles were firstly measured by a roughness profile measuring analyzer. With the help of the Fourier nonlinear approximation the measured data was used to form a roughness function which was superimposed to film thickness equation and a mixed thermal elastohydrodynamic lubrication model for the rolling bearing was then established. Based on the model,45 sets of numerical calculations were carried out by changing the roughness values under other conditions of the rolling bearing were fixed. Then the two quantitative relationships between the average oil film at the contact point and the roughness as well as the maximum subsurface principal stress and the roughness are respectively established through the regression analysis of the calculation results.

The surface roughness data of test-piece with transverse roughness profiles are measured.With the help of the Fourier approximation,the measured data are used to form a roughness function which is then added to the oil film thickness equation and a model of mixed elastohydrodynamic lubrication for an involute spur gear transmission is established. Based on this model,nearly 130 groups numerical calculations are carried out through changing the pinion speeds for medium and heavy-duty gear transmissions respectively.The computing results show increasing the pinion speed can effectively improve the gearing lubrication state and reduce the contact stress on rough surface. However,decreasing of the contact stress is very slowly with the addition of the pinion speed when the speed exceeds a certain value.

A kind of CVT mountain bike is designed innovatively,the working principle and structure of the continuously variable transmission（ CVT） and booster are analyzed in detail. The driving force when CVT mountain bike started is calculated,all show that the bike started lightly with the reasonable transmission structure. The finite element analysis（ FEA） of frame and handlebar is carried out,the displacement contour and stress distribution figures of the frame as well as the displacement maps of the handlebar indicate that the structure could meet the requirements with a higher safety factor.

Taking a type of transmission as the research object,the axis gear system dynamics model is set up,and the dynamic time history and load spectrum of the transmission shell under the working condition are obtained. Based on dynamic load incentive,the finite element simulation model of the boundary element is established,the vibration acceleration and near sound field radiated noise of the shell surface are calculated. The gearbox shell vibration and radiated noise test platform is built,the shell surface vibration acceleration value and the acoustic noise spectrum of nearly one meter position under the same condition are test,and compared with the simulation results,the validity of the finite element model and the boundary element model is verified. Finally,the different local gearbox shell is optimized,through the simulation calculation,the results show that the optimized gearbox shell vibration amplitude and radiated noise is better inhibition.

In order to enhance heat transfer performance of plate-fin radiator,multi-objective optimization was carried out to the structural parameters of the serrated fin based on the genetic algorithm. According to the result of optimization,threedimensional physical model of the channel was built. The temperature field was investigated by the method of CFD. The heat transfer factor,friction factor and comprehensive performance evaluation factor of fin were obtained. The simulation results show that the heat transfer performance of the optimized fin was improved. Heat transfer performance of copper fin is better than that of aluminum fin. The validity of the simulation result is verified by wind tunnel test.

The fatigue life scatter factor is an important reliability index of the assessment of aircraft fatigue life. At present,the safe-life of a fleet is gotten by using the total test hours and the fatigue scatter factor. Usually,the environment scatter factor caused by the different service environments is not considered,and the fatigue scatter factor mainly includes two parts,one is the load scatter factor caused by the load spectrum difference of fleets; the other is the structure scatter factor caused by the difference of material and manufacturing quality. The expressions of scatter factor of fatigue life obeying the log-normal distribution and Weibull distribution are introduced and analyzed. To the situation that the structure fatigue life of the same aircraft model under different load spectrums obeys the log-normal distribution,the condition that the fatigue scatter factor is the product of the load scatter factor and the structure scatter factor is deduced. To the situation that the structure fatigue life obeys the different distributions,the service flying hours can be converted into the equivalent flying hours under the same test load spectrum based on the equal damage principle,the structure scatter factor under this spectrum can be calculated and can be taken as the fatigue life scatter factor,the safe-life calculated by this scatter factor can be seen as the reference value for the management of individual aircraft life.

The surface roughness data of test-pieces with transverse profiles were firstly measured by a roughness profile measuring analyzer. With the help of the Fourier nonlinear approximation the measured data were used to form a roughness function which was superimposed to film thickness equation and a mixed thermal elastohydrodynamic lubrication model was then established. Based on the model,280 sets of numerical calculations were carried for both medium and heavy duty transmissions through changing the roughness values. The results show that the contact stress τmax,rfor rough teeth surfaces is increased by 5%compared with the contact stress τmax,sfor smooth teeth surfaces when the root mean square roughness of tooth surface σ≤0. 3μm; While the τmax,ris increased by 15- 20% compared with the τmax,swhen σ ≥ 0. 5 μm. At the end,several theoretical formulas for determining the roughness factors are created based on the multiple regression analysis of the above calculated results.

As the wind turbine gearbox mounted on a flexible support tower,the wind turbine tower will be bent and wiggled under the complex working conditions,and it will serious influence on the dynamic characteristic of the wind turbine gear transmission system. Considering the coupling effect of wind turbine tower swing and planetary wheel drive torsional vibration,by using the lumped parameter method,the dynamics analysis model of the flexible support of wind turbine planetary gear transmission system is established,and then the numerically solution is carried out with Matlab. By taking the instance analysis of the mainstream 1. 5MW wind turbine,the displacement progress of each part of planetary gear system under 16 seconds random time series wind load is got. The result shows that,in the process of wind turbine operation tower generates excessive vibration,and the vibration of the tower exacerbates the vibration of the components of wind turbine planetary gear system. Then,the impact of the flexible of the wind turbine tower must be considered in the wind turbine planetary gear design.

The shore bridge reducer in the lifting mechanism often emit heat because of continuous operation and high load,if improper heat dissipation will greatly reduce its life. To achieve the real-time online condition assessment of the reduction gearbox of the hoisting mechanism,the influence parameters of heat dissipation should be known for determining the heat dissipation condition. In order to obtain the influence parameters,from the simplest condition,the stopped state in the work,by using the lumped heat capacity method,the reduction gearbox heat dissipation model is studied,the curve fitting theoretic support and the factors that can affect the heat dissipation are got. In order to verify the actual influence of these factors on the reducer heat dissipation,by using the control variable method,the actual temperature data is computed and analyzed. Then,by means of the function mapping software Origin,the temperature data of the reduction gearbox is fitted,a quadratic exponential function model is fitted and the function parameter is obtained. Combining with the influence factors,the regularity analysis is carried out,the foundation for future work of heat dissipation factor parametric is provided.

In order to discuss theoretically the effects of surface roughness on gearing contact fatigue stress,a mixed Elastohydrodynamic Lubrication（ EHL） model for heavy-duty gear transmission was established based on the transverse roughness features simulated by the fractal function,which were superimposed to the film equation. Applied the multi-grid method,40 groups of numerical calculations were completed. The results show that the average film thickness is almost linearly increased with an increment of the roughness value. But it is not simply the case that the less the roughness value,the better. When the roughness is less than a critical value,however,increasing roughness value is found to reduce the maximum principal shear stress on pinion subsurface. At the end,the quantitative relation between the maximum principal shear stress and the roughness is acquired based on the regression analysis of the calculation results.

A three-dimensional sliding model of micro-scale was established between two rough surfaces exhibiting fractal behavior,and the thermo-mechanical coupling factor in the process of contact was considered. The surface temperature in sliding processes was analysed using the finite element analysis taking into account Ti-6Al-4V elastic-plastic properties with material failure. The transient surface temperature distribution of the rough surface was presented. The numerical results showed that the surface temperature in initial time rise sharply and then tend to be temporarily stable until a new contacted asperity coming into interaction. With the increase of friction slide distance the surface temperature was to present the state of fluctuating. The values of highest temperature at contact zones were different,while the highest temperature at contact zone was higher relative to the greater interface shear strength. Compared with the experimental data of the literatures,it was concluded that the rationality of the simulation,these results also deepened understanding the reason of the friction and wear.

The surface roughness data of a disc with longitudinal roughness texture is measured by a roughness profile measuring analyzer firstly. With the help of the nonlinear Fourier transform,the measured data is used to form a roughness function which is then added to the oil film thickness equation and a model of mixed Elastohydrodynamic lubrication for a pair of mechanical parts in higher pair contact is established. Based on this model,45 groups numerical calculations are carried through changing lubricant viscosities. The computing results show that the average oil film thickness for rough surfaces is smaller than the corresponding value for smooth surface. But the two tend to consistent when the film ratio exceeds a specific value. As the viscosity increases,the maximum value of contact stress on rough surface decreases gradually,but it is always greater than the corresponding value for smooth surface contact. However,the both are less than the corresponding Hertz stress regardless of rough or smooth surface contact,which indicates once again that a scientific lubrication is very helpful for increasing the contact fatigue life of mechanical parts.