Focusing on the loading capacity and applications in power transmission of plastic gears, the failure modes and loading capacity under the current materials and technology levels were introduced. The strengthening measures for improving loading capacity of plastic gears were elaborated from the application of new materials, lubrication improvement, collaborative design, and so on. The applications and potential of plastic gears scenarios in power transmissions such as automobile engines, vehicle reducers, and aeroengine accessory gearboxes were introduced, which has important reference significance for promoting the development of high load plastic gear technology and applications.

To accurately predict and optimize the aerodynamic noise of the self-ventilated permanent magnet synchronous motors(SVPMSM) at high speed, a method combined with CFD approach and Lighthill acoustic analogy was applied to simulate the aerodynamic noise of the motors. RNG k-ε model and large eddy simulation were used to simulate the flow field in the motors. Then, Lighthill acoustic analogy method was used to solve the acoustic problems, which were verified by experiments. A simplified model without air duct was established to study the effects of different fan structures on aerodynamic noise. The effects of duct expansion chamber structures on aerodynamic noise was studied by the motor simulation model. The results show that the difference between the sound power levels calculated by the motor simulation and the test at 4250 r/min is as 0.6 dB(A), which prove that the aerodynamic noise simulation model may effectively predict the aerodynamic noise of the motors. Through motor optimization, it is found that the changes of fan inner radius and blade curvature have little effect on the flow field, so there is little difference in aerodynamic noise. More blades and equidistant arrangement have better acoustic characteristics than less blades and non-equidistant arrangement. The expansion cavities added to the air ducts of the motors have a better noise reduction effectiveness at the low frequencies. The sound power level of the motors with the expansion chamber length of 94.4 mm is lower than that with the expansion cavity length of 134.4 mm. Setting two expansion cavities in the air ducts have a better noise reduction effectiveness than that only setting one expansion cavity.

To elucidate the effects of thread rolling parameters and end configurations on the formation of folding defects, an experimental investigation was conducted on the thread end rolling processes and fatigue behavior, and the folds with different processing parameters were analyzed. The results show that for the folding in the end region, higher thread rolling speed and lower feed rate significantly mitigate the occurrence of folds. For the tooth base folding, increases in thread rolling speed and feed rate will initially reduce the number of folds. In terms of fatigue characteristics, increases in thread rolling speed and decreases in feed rate leads to a gradual reduction in fatigue cracks originating from folding defects. Consequently, the optimization of thread rolling process parameters and end groove configurations is essential for reducing the incidence of folding defects in short end bolts.

 In order to solve the problems such as low positioning accuracy, large structural dimensions, and difficulty in applying pre-pressure, which were commonly found in M-DOF ultrasonic motors, a novel bonded-type disc stator M-DOF ultrasonic motor was proposed. Firstly, finite element simulations were carried out to verify the working principles of the disc stator and determine the geometry. Then, the disk stator was fabricated and tested for the impedance characteristics and vibration characteristics. Finally, the prototype of the M-DOF ultrasonic motor was assembled, and the mechanics performance characteristics were evaluated experimentally. The experimental results show that both of the start/stop response time of the prototype are less than 20 ms, and the angular displacement resolutions are less than 30 μrad respectively. The prototype has the advantages such as rapid response and high positioning accuracy.

To address the insufficient climbing and obstacle-surmounting performance of traditional closed-chain leg mechanisms, a scaled reconfigurable design of component elements was developed based on the Watt-type closed kinematic chain. An intermittent mechanism was adopted to couple walking power with reconfigurable power, and an integrated reconfigurable closed-chain leg mechanism was proposed. The sensitivity of linkage reconfiguration and the interval of parament adjustment were analyzed, and the optimal solutions for the reconfigurable linkages and their parameters were determined. A four-biped walking platform was built to analyze the platforms reconfigurable strategies and obstacle-surmounting strategies. A prototype was developed, and walking and obstacle-surmounting experiments were conducted for validation. The results indicate that the walking platform constructed on the basis of the integrated reconfigurable closed-chain leg mechanisms, enhances obstacle-surmounting performance while ensuring overall rigidity.

Based on the improved W-M fractal function, the surface morphology of helical gear teeth was characterized from tooth height and tooth width. A time-varying contact stiffness model for helical gears was established by adopting a conical asperity and considering the time-varying contact radius of curvature of helical gears during the meshing processes. The time-varying mesh stiffness calculated based on the conical asperity model was found to be close to that obtained from the calculation of the ISO6336-1—2006 standard. The results show that the time-varying contact load and time-varying contact stiffness of helical gears exhibit different trends with changes in fractal dimension, characteristic scale coefficient, dimensional contact area, and material plasticity index.

The internal stiffener layout and support location of housing structure played an important role in improving of structural performance and lightweight. A design method for hybrid distribution optimization of stiffener and support locations of housing structures was proposed. Independent support elements and stiffener base structures were introduced to establish a mathematical model for the hybrid optimization of stiffener distribution and support location of the housing structure. The optimal design for stiffener distribution of the housing structure was performed by an adaptive growth method. The support location was optimized based on the bi-directional evolutionary structural optimization method. The results show that the support locations and distribution of stiffeners obtained from the hybrid optimization have better mechanics properties than the optimized results of the housing structure with known support locations.

Aiming at the challenges of internal power supply and electrical signal transmission in rolling bearings, the intelligent sensing technology for bearings was studied based on acoustic emission. Firstly, based on the rotational vibration characteristics of the faulty bearings, a temporal phase difference vortex transmission model of acoustic signals was constructed. Then, a circular hollow acoustic metasurface structure was designed, and the acoustic vortex focusing mechanism and metasurface transmission performance were studied. The correlation between fault types and acoustic vortex topological charges was simulated and analyzed. Finally, the vortex focusing transmission method of bearing fault acoustic emission signals was verified through simulation and experimental setup of faulty bearings.

In order to improve the dynamics characteristics of multi-link mechanisms with lubrication clearances of revolute joints, a 2-degree of freedom seven link mechanism was taken as research object, a lubrication clearance model for the revolute joints was established, the dynamics equation of the mechanisms with lubrication clearances was derived by Lagrangian multiplier method, and the correctness of the dynamics equation was verified through experiments. A dynamics optimization model of the mechanisms with lubrication clearance was established and solved using genetic algorithm to optimize the variables. The results show that dynamics optimization may reduce the acceleration of the slider by 25%, and the forces between the motion elements at clearances A and B of the rotating pair are reduced by 14.8% and 18.2% respectively, which effectively improve the dynamics characteristics of the mechanisms with lubrication clearances of revolute joints.

To investigate the factors restricting the high-speed applications of single sealing land slippers, a flow-solid-thermal coupling dynamic model was established, considering the sealing land wear profile. The effects of rotational speed and seal width on oil film thickness, operational posture, bearing stiffness and leakage were analyzed. Results show that at high speed, the increases of centrifugal moment of the slipper lead to a larger tilt angle and a reduced minimum bottom clearances. Simultaneously, the enhanced dynamic pressure effect increases the suction-side clearances, reduces oil film stiffness, and elevates the risk of partial wear. Increasing the width of the sealing lands may improve the supporting stiffness of the slipper, but the outer-to-inner diameter ratio exceeding 1.6 will result in thicker oil films and increased leakage. It is concluded that leakage and partial wear are the main factors restricting the high-speed applications of single sealing land slippers. Introducing microstructures on wide sealing lands to limit wedge-shaped dynamic pressure effects may effectively expand the allowable speed ranges of slippers.

By analyzing the relationship between dual quaternions and rigid body motion, and the relationship between dual quaternions and screw motion, a transformation operator of the end-effector pose was obtained based on dual quaternions with the combination of PoE formula. Based on the Newton-Raphson method, the dual quaternions were applied to solve the numerical solution of the inverse kinematics of redundant robots. Based on the linear interpolation characteristics of dual quaternions, a trajectory planning method was proposed based on screw linear interpolation. Taking two types of redundant robots as examples, the proposed trajectory planning method that achieved smooth motion and controllable velocity in Cartesian space was verified. Dual quaternions have better stability and higher solving speed than homogeneous matrices in solving kinematics numerical solutions.

 The multimanned two-sided disassembly with walking workers was an ideal choice for processing large products with multiple attributes in disassembly line. So, a multimanned two-sided disassembly of walking workers line balancing problem was proposed. A mathematical model was built with the goal of minimizing the number of multimanned workstations, senior workers, idle time, and fatigue index. In addition, a salp swarm-differential evolution algorithm with incentive strategy was proposed to solve the disassembly line balancing problem. The algorithm performance was validated by using large-scale cases. The proposed model and algorithm were applied to a used car dismantling case, and multiple allocation schemes were obtained for enterprises to flexibly choose from.

Assembly information modeling was the foundation of digital assembly and intelligent assembly. However, the manual interactive modeling was inefficient and prone to errors in assembly feature recognition and assembly feature fitting, which was difficult to meet the precise modeling needs of complex mechanical systems. Based on the assembly process information implied by a 3D assembly model, this paper used STEP model files as inputs to study the algorithms for automatic extraction of assembly features and recognition of fitting relationships focused on geometric information. Furthermore, an information reasoning algorithm was proposed for constructing an integrated assembly information model from the perspectives of assembly accuracy modeling and assembly sequence planning. Finally, the effectiveness of the proposed algorithms was demonstrated through the construction of assembly instance information models based on the developed system.

To improve the success rate and efficiency of robotic grasping for occluded target objects in cluttered scenes, a collaborative push-grasp strategy was proposed based on deep reinforcement learning. The strategy employed 2 deep Q networks and used RGB-D images as inputs to determine push or grasp actions, which optimized object arrangement for better grasping conditions. A “grab-push-grab” three-stage training method was introduced in the model to enhance grasping capabilities significantly. An image morphology-based assessment method effectively identified and filtered low-quality grasp actions to increase successful rates and efficiency. Experimental results confirm that this method significantly enhances the successful rate and efficiency of grasping target objects.

Taking the self-piercing riveting of 6082 aluminum alloy as the research object, the fatigue crack propagation mechanism and fretting wear behavior of the joints were studied by tensile tests, fatigue tests and scanning electron microscopy. The results show that compared to the 0° and 45°, the joint has the best static mechanics properties under the loading angle of 90°. Under the same load level, the fatigue life of the joints increases with the increase of the loading angles. Under high-cycle fatigue, the joints fail by cracking of the lower plate, while under low-cycle fatigue, the joints fail by cracking of the upper plate and rivet fracture. Fretting wear affects the location and propagation path of the fatigue crack initiation in the joints, and the loading angles of the joints affect the fretting wear in different areas of the joints. Under the loading angle of 90°, the fretting wear in the contact areas between rivet head and upper plate is the most serious. Under the loading angle of 0°, the fretting wear in the contact areas between lower plate and surface of the rivet leg is the most serious.

The impacts of 5 embeddings on tensile-shear properties of the secondary bonding joints were analyzed. The experimental results indicate that to improve the quality of the joints, the embedded metal mesh might undergo surface treatment. Tensile-shear strength of the joints by resistance heating technology is better than that by autoclave technology. The additions of embedded material enhanced the tensile shear properties of the joints, and the joints with prepreg embedding demonstrate the best tensile-shear strength. Nickel mesh embeddings exhibit higher densities, and have better bonding quality than that of copper mesh. End regions of the overlap joint experience severe stress concentration. Metal mesh embeddings enhance joint tensile stiffness. The joints with embeddings exhibit cohesive failure, adhesive failure, fiber tearing fracture of bonded parts and embedding failure, and the peeling stress is a major factor in failure. The more irregular distribution of failure modes is in the failure section, the poorer bonding quality is.

 In order to suppress the swaying of carbody caused by abnormal wheel-rail matching relationships in EMU operation, a semi-active rotary arm joint was proposed to replace the passive rotary arm joint. The semi-active rotary arm joint with two-level stiffness characteristics was designed, and a mechanics model of the semi-active rotary arm joint was established. The complex stiffness expression of semi-active rotary arm joint with variable inertia channel was derived. The accuracy of the model was verified by bench test comparisons. Based on the control strategy of semi-active rotary arm joint, the co-simulation model of semi-active rotary arm joint and vehicle dynamics was established, and the influences of semi-active rotary arm joint on vehicle dynamics performance under different wheel-rail matching relationships was analyzed. The results show that the semi-active rotary arm joint may effectively reduce the high-amplitude and low-frequency swaying of the carbody in speed interval corresponding to primary hunting, and obviously reduce the amplitude at main frequency of lateral acceleration of the carbody under the condition of low-conicity wheel-rail matching. Compared with the vehicle equipped with traditional passive rotary arm joint, the vehicle equipped with semi-active rotary arm joint has better curve passing capacity and higher critical speed under the conditions of normal wheel-rail matching.

Aiming at the issues of drivers fatigue caused by working environment of monorail cranes in underground transportation, an analysis method of drivers operating comfort was presented based on biomechanics simulation and surface electromyography experiments. A driver-operating system biomechanics coupling model was constructed by Anybody, and the fatigue characteristics of the drivers during operation were quantitatively analyzed. The results show that the average muscle activation of biceps brachii is as 0.171, with the maximum muscle force of 106.9 N, while the muscle activation of gastrocnemius is as 0.288, with the maximum muscle force of 235.6 N； the overall fatigue level of the driver's lower limbs is greater than that of the upper limbs. The accuracy of the simulation results was verified by EMG experiments. The relative error is less than 15%, and the correlation coefficients all are more than 0.966(P < 0.05).

Aiming at the problems of weak timeliness of experience feedback in the process of nuclear power equipment constructions, inconsistent perception of experience knowledge by each participant, and low reuse rate of experience feedback knowledge, the experience knowledge was intellectualized, and a unified experience feedback mapping was constructed. The characteristics of experience feedback information were analyzed, and the structure of key knowledge domains and mapping framework of experience feedback were constructed. The proposed multi-dimensional information perception model and improved PCNN relationship extraction model achieved good results on nuclear power enterprise dataset, and the experience feedback mapping was generated based on Neo4j graph database. The results show that the method may complete the deep-level retrieval of tacit knowledge of nuclear power products, assist the nuclear power professional technology and management personnels to quickly parse and transfer the experience feedback knowledge, and realize the transformation of the application mode of nuclear power construction experience feedback precipitation from document-centered to knowledge-centered.