A theoretical model of stress distribution and contact width is established by Hertz contact theory. The reaction of roller under specific load is analyzed. The results shows that linear profile have significant edge contact stress concentration, which increases with the increase of load. The roller with logarithmic profile can solve the stress concentration, but it can't completely eliminate it. Under the same load, with the increase of the bias factor, the maximum contact stress of the roller decreases sharply at first and then increases slowly. The position where the maximum contact stress occurs shifts from both ends of the roller to the middle of the roller. The profile design of roller with logarithmic type can take a value between 1.0 and 2.5 for the bias factor based on working conditions, roller size and load conditions. The value of bias factor is adaptive to tilt error and the impact of tilt error on contact stress can be reduced by setting a reasonable value.

For the nut connection problems of narrow and deep cavity, invisibility, no access to traditional operating tools of aero-engine rotor, a new automation assembly method is advocated based on the image recognition and laser assisted positioning technology. The automated blind assembly torque device is developed with the functions of automatic folding of wrench head, accurate positioning, rapid nut recognizing, and electric loading, which can enter the narrow and deep operation space that is invisible to naked eye, to solve the low-level errors caused by artificial missing and wrong nuts, avoiding collision and damage on the inner wall of the shaft cavity. The device can carry out the compound tightening strategy with torque and angle to achieve the accurate automatic connection of engine rotor nut all the time, and the %GageR&R and %P/T of system precision are %22.21, %3.78 respectively through the test of automatic blind nut assembly, which will increase the accuracy and consistency on the large degree, which will lay the important foundation of the working stability and reliability of aero-engine farther.

By predicting the wear trend of aeroengine, the wear state of aeroengine can be monitored effectively. Among the effective observation data reflecting the engine wear state, the oil analysis data can indirectly reflect the overall wear trend of aeroengine. Therefore, by establishing a trend prediction model based on oil sample analysis data, so as to realize the wear trend prediction of engine. However, the current models used in aeroengine trend prediction are mainly single prediction models, and the combined prediction models are only general linear combinations, with poor prediction effect. Therefore, a nonlinear variable weight combination prediction model based on support vector machine is proposed, and realizes the parameter optimization through particle swarm optimization algorithm. The oil sample analysis data is obtained through the bearing fatigue test of the whole life oil system, and the oil samples are collected at fixed intervals for performance analysis. Through the combination prediction analysis of the spectral analysis data, by comparing the prediction results of the combination prediction and the prediction results of the single prediction model, the prediction accuracy exceeds the prediction accuracy of the single prediction model, which fully verifies the superiority and effectiveness of the combination prediction model proposed in this paper.

In order to explore the safety threat of slope deformation to transmission lines, taking the transmission tower-line system as the research object, the overall finite element model of the tower-line system considering soil-structure interaction (SSI) effect is established, and the rationality of the numerical analysis model is verified based on the field measured data. On this basis, considering the relationship between the slope deformation area and the spatial position of the tower and the influence of the slope deformation angle, the response law of the stress characteristics of the tower-line system to the slope deformation is explored. The results show that when the towers are located above, below and inside the slope deformation body respectively, the failure mode and deformation resistance of the upper tower line system are significantly different. And with the increase of slope deformation angle, compared with horizontal slope deformation, the anti-deformation ability of tower-line system will decrease by 25%-50%. When the tower is located outside the slope deformation body, the anti-deformation ability of tower-line system will decrease most seriously, with the decrease range of 33%-50%.

Aiming at the problem of motor failure caused by complex factors interacting and interfering during the operation of pure electric mining trucks, a method based on principal component analysis (PCA) and random forest (RF) is proposed for predictive diagnosis. A dataset is constructed based on the actual collected motor failures of electric mining trucks, and the eigenvalue extraction and dimensionality reduction of the failure data are carried out using principal component analysis to reduce the dimensional redundancy of the data; the random forest prediction model is used to train and test the dimensionality-reduced data, and to predict the motor failure categories. The results show that the accuracy of motor fault type diagnosis using PCA-RF method reaches more than 97%, which is significantly improved compared with the accuracy of the method without dimensionality reduction processing. The accuracy of the above method for motor fault diagnosis of electric mining trucks is confirmed.

In order to explore the effects of maintenance difficulty degree of component on the maintenance cost and availability of the model. Taking a mechanical component of electric multiple unit (EMU) as the research object, and a component reliability threshold as the decision variable, the two-parameter Weibull distribution is adopted to describe the evolution law of component failure rate, combined with the existing fixed period multi-level imperfect maintenance rule of EMU in China, a preventive maintenance strategy for single component of EMU with bi-objective optimization is established. Bi-level imperfect maintenance is implemented in the maintenance mode and the concept of efficiency-cost ratio is introduced to discriminate the selection of each maintenance method of the component. Considering four factors, the difficulty of detecting parts, the location of parts, the difficulty of disassembling parts and the complexity of parts. Analytic hierarchy process (AHP) is adopted to quantify the maintenance difficulty degree and to study impact on the cost and availability of maintenance. The analysis shows that the maintenance model considering the maintenance difficulty can effectively reduce the maintenance cost and improve the availability, which provides a theoretical reference for the development of the maintenance strategy of EMU.

The fuel consumption meter measurement method and bench test are generally used to analyze the economy and power performance of vehicles, but the two measurement methods have high costs and complex structures. In response to this problem, back propagation (BP) neural network and regression model were selected to calculate and predict the economy and power performance of explosion-proof rubber tire vehicle diesel engines. Through comparison with experiments, the accuracy of BP neural network and regression model prediction was studied. The results show that the error between BP neural network and regression model is less than 5% when predicting fuel consumption rate and evaluating power performance, and both can be used to predict the economy and power performance of rubber tire vehicles.

In order to explore the factors influencing the slip rate between tracked combine harvester and paddy soil, a coupled simulation model of tracked combine harvester and paddy soil is established by the RecurDyn software. Selecting the mass, driving speed, steering angular speed of the tracked combine harvester and the moisture content, positive slope, and oblique slope of the paddy soil as test factors, simulations under different conditions are implemented. Through a six-factor two-level PB (Plackett-Burman) test was conducted to screen out the slip rate significant factors that is soil moisture content, positive slope, and steering angle velocity. Then, a three-factor three-level BB (Box-Behnken) test was conducted on the three selected factors. The results show that soil moisture content, positive slope, and steering angle velocity have a very significant impact on slip rate, and the order of significance is steering angle velocity>soil moisture content>positive slope. As the positive slope and steering angle velocity increase, the slip rate increases significantly, while as the soil moisture content increases, the slip rate slowly decreases. The soil moisture content has a certain interaction with the positive slope and steering angular velocity. However, there is basically no interaction between positive slope and steering angular velocity. This study has important reference value and scientific significance for improving the path tracking accuracy and stability of tracked combine harvester for autonomous harvesting operation in paddy soil.

In order to solve the problems of incomplete balance equation, inaccurate balance equation and large error of cam contour caused by the influence of piston deflection on cam dynamic moment in existing cam construction of pedal brake unit, the structure of pedal brake cam and output force stability were studied. Firstly, the concept of optimum compensation angle is introduced, and the rotating moment of the thrust caused by piston deflection in two directions to the cam articulation point is included in the new balance equation, which makes the balance equation more complete, accurate and has less error. Based on this, a new cam mechanism is designed and constructed. Then, on the pedal brake unit routine tester, a comparative experiment is carried out on the stability of output force value between the original cam mechanism and the newly constructed cam mechanism with optimized compensation angle. Finally, the above data and the curves of action travel and output force are comprehensively compared and analyzed. The results show that the output force value stability of cam with compensation angle is better than that of cam without compensation angle. In actual operating stroke, the maximum difference of output force between two times is (-0.8, +0.6) kN with compensation angle cam error, and (-1.2, +1.2) kN without compensation angle cam error. The error with compensation angle cam is also less than that without compensation angle cam error.

Middle outrigger is the main support leg of tunnel erecting machine, and hydraulic system plays an important role in the erection process of prefabricated utility tunnel sections. To solve the problems of slow action and low positioning accuracy of hydraulic cylinder of middle outrigger, the hydraulic system of tunnel erecting machine is optimized through on-site experiments and AMESim simulation analysis. According to the erection process and hydraulic system principle of tunnel erecting machine, a preliminary analysis and on-site measurements of original middle outrigger hydraulic system are conducted, and an optimized system scheme applying high-frequency response proportional valve and accumulator is proposed. Then, the reasonable accumulator working parameters of optimized hydraulic system are explored, and the high-frequency response proportional valve control strategy based on feedforward compensation is studied. Finally, the optimized hydraulic system is simulated and compared with measurement data. The results show that the combination of high-frequency response proportional valve and accumulator can significantly improve the response characteristics and position control accuracy of hydraulic system. The hydraulic cylinder displacement of optimized system is increased by 82.2% within 0.5 s of system startup, and the maximum hoisting positioning error is ±2.0 mm, which can meet the erection and installation requirements of utility tunnels.