When using direct ink writing technology to prepare FGMs (functionally graded materials) parts, there is a delay in the change of material ratio, which leads to poor consistency between the material ratio of the prepared parts and the design goals, and increases the uncertainty of material properties, resulting in potential use risks. In order to accurately learn the delay information of material ratio under different process parameters, a neural network prediction model based on computational fluid dynamics was constructed. Based on RNG k-\epsilon model, an optimized Bayesian regularized neural network model was used to predict the delay information corresponding to different process parameters, namely, the delivery delay time and global delay time were predicted under different initial ratio and target ratio of materials, screw rotation speed, sum of double extruded plunger feed rates. The prediction accuracy could reach 94.87% and 92.74%, respectively. Using digital image processing methods to process FGMs samples printed under different process parameters, the results showed that the material gradient change curve of the actual printed samples had a high degree of coincidence with the simulation results, verifying the accuracy of the simulation results based on computational fluid dynamics as the analysis framework, as well as the feasibility and reliability of the constructed optimized neural network model for predicting delay information. The research results provide a reference for integrating digital prediction methods into FGMs part body preparation processes in the future, and can promote the transformation of traditional manufacturing models to digital manufacturing models, ultimately achieving the accurate manufacturing of FGMs parts.

Fatigue failure of metal components is a common form of failure in industry. In order to improve the prediction accuracy of fatigue life of components, aiming at the influence of average strain on fatigue life under low cycle fatigue load, a low cycle fatigue life prediction model considering average strain was established based on the continuum damage mechanics and its irreversible thermodynamic framework, by introducing the Ramberg-Osgood cyclic constitutive model and using equivalent intrinsic damage dissipation work as an equal life condition. In order to compare and verify the effectiveness and progressiveness of the new model, the new model, modified Ohji model, Sandor model and Wei-Wong model were used to predict the low cycle fatigue life of 45 steel and 2124-T851 aluminum alloy with superimposed average strain, and compared with the corresponding test results. The results showed that the prediction results of the new model were in good agreement with the experimental results, and its prediction effect was better than the existing models. The fatigue life prediction method based on the intrinsic damage dissipation theory provides a new idea for the fatigue life prediction of metal materials.

Storage tanks are prone to structural failure under occasional explosive loads, resulting in the outflow of liquid inside the tank and causing huge economic losses. However, storage tanks designed with weak roofs can reduce losses in such accidents. Therefore, taking the vertical vault storage tank as the research object, taking into account factors such as internal pressure, stress and crack propagation during the tank failure process, a method for evaluating the implosion weak roof performance of storage tank based on multiple discriminant conditions was established. Meanwhile, by means of numerical simulation, a three-dimensional finite element model of storage tank implosion was established using the CEL (coupled Euler-Lagrange) fluid-structure coupling algorithm. The failure process of storage tank under implosion load and the weak roof performance of storage tank under different influencing factors were studied. The calculation results showed that in the evaluation of weak roof performance based on pressure and stress, the peak pressure ratios of the storage tank at positions of 90°, 135° and 180° were greater than 1, meeting the requirements of weak roof; in the evaluation of weak roof performance based on structural fracture, due to the extension of cracks below the liquid level, two cracks passed through the liquid level of 1.99 m and 5.21 m, respectively, and the storage tank did not have weak roof performance. As the volume and liquid level of the storage tank increased, the weak roof performance of storage tank increased. Based on the calculated results, the method of setting a protective ring above the liquid level was adopted to optimize the storage tank, so that the non-weak roof storage tank met the design requirements of the weak roof structure. The established evaluation conditions for the weak roof performance of storage tanks can provide reference for the design and analysis of the weak roof of storage tanks.

The existing hexapod robots have shortcomings in single foot structure design, body layout and compliant motion control, resulting in weak terrain adaptability and low motion compliant performance. Therefore, observation experiment was conducted on a typical hexapod organism-ant. Based on the analysis of the physiological structure characteristic and driving mode of ant, basic principles applicable to the structure design of hexapod robot were proposed; based on the design of a low inertia single foot structure, an overall biomimetic structure of a hexapod robot driven by joint motors was proposed by optimizing the body layout of the robot; based on the gait of the straight and turning movements of the hexapod robot, a foot end trajectory combining trigonometric function curve and straight line was planned, and a compliant motion control method for the hexapod robot based on hierarchical control was proposed. The prototype experimental results showed that the hexapod robot had a reasonable structure design and could achieve relatively compliant straight and turning movements. The research results can provide important references for the design of robot biomimetic structure and compliant motion control.

Aiming at the requirements of teleoperation robots grasping soft or fragile objects in unknown environments such as the deep sea, a master-slave soft hand position tracking method for human-computer interactive teleoperation robot was proposed. Firstly, the structure and working principle of the master-slave soft hand control system were introduced. The system mainly included the master control loop, acommunication link and slave control loop, which was used to control the grasping action of the soft hand. Then, the modeling process and controller design of the soft finger were described. The hypothetical modal method was used to model the soft finger, and the model predictive control algorithm was introduced into the position tracking control of the soft finger to solve the problem of poor performance of the soft slave hand tracking soft master hand. Finally, the soft master hand, soft slave hand and their control systems were designed and developed, in which the soft slave hand was made of silicone and embedded with solid materials to increase the stiffness. Meanwhile, the experiment of soft slave hand tracking soft master hand to grasp the target object was conducted. The simulation results showed that the designed model predictive controller could effectively solve the problem of control accuracy degradation caused by model mismatch for soft fingers; the experimental results showed that the developed soft slave hand could effectively track the soft master hand to grasp the target objects, and the entire control system ran well. The research results provide a reference for the tracking control application of soft hands of human-computer interactive teleoperation robot.

The higher performance requirements for the drive motor are put forward because of the complex operating environment of the electric drive vibroseis. Aiming at the power requirements of the vibroseis under driving and excitation conditions, the matching design of the drive motor's power parameters was carried out, and the main design parameters of the drive motor were determined; a 2D finite element model of the drive motor was established, the magnetic flux density characteristics and harmonic amplitude of the motor under no-load and rated operating conditions were studied using the subdomain method, and the law of harmonic distortion of the motor's magnetic flux was analyzed; the optimal design of the air gap length of the motor and the orthogonal optimization test of the motor rotor structure were carried out, and the optimal structural parameters of the rotor were obtained. Therefore, a motor prototype was developed. The results showed that the magnetic flux density waveform in the motor magnetic isolation bridge and the region between the the permanent magnet and the rotor edge was severely distorted; the high-order harmonics in the region between the permanent magnet and the rotor edge had a significant impact on the motor, the proportion of the third harmonic in the fundamental wave was as high as 83%; the efficiency of the optimized motor reached 96.8%. The research results provide a reference for the optimization of electric drive vibroseis.

In order to realize the customization, reusability and economy of atomization assisted CVD (chemical vapor deposition) cavity, and meet the actual requirements of high-quality single crystal Ga₂O₃ thin film preparation, a new atomization assisted CVD cavity was designed and developed. The cavity was mainly composed of reaction chamber module, cooling module and buffer chamber module. Ga₂O₃ thin films were prepared by using a new cavity and a conventional cavity, and then the X-ray diffraction (XRD) patterns analysis and its surface morphology observation by atomic force microscope (AFM) were carried out. The experimental results showed that the new cavity could produce better performance α-Ga₂O₃ and β-Ga₂O₃ thin film; the half-peak widths of (006) crystal plane of the α-Ga₂O₃ thin films prepared by the new cavity and the conventional cavity were 0.172° and 0.272°, respectively, and the surface roughness was 25.6 nm and 26.8 nm, respectively. It could be seen that the α-Ga₂O₃ thin film made with the new cavity had better crystallinity, surface smoothness and density. Through the design of the new cavity, a stable environment conducive to the growth of single crystal Ga₂O₃ thin film was constructed, which provided a reliable path for the optimization of the preparation process of Ga₂O₃ thin film. The research results provide a reference for the preparation of high-quality metal oxide semiconductor films.

In order to improve the ability of parallel robots to adapt to multiple complex terrain environments, a variable-direction multi-terrain mobile full R pair parallel robot was proposed by combining the advantages of reconfigurable parallel robots and multi-motion mode mobile robots. Based on the spatial axis relation of adjacent kinematic pairs, a closed chain mechanism with three-direction rotation ability was constructed by taking the planar single-ring 4R mechanism as the body. Based on the orthogonal spatial geometric relation, two closed chains with full R pairs were formed into an omni-directional mobile parallel mechanism which could realize multiple rolling modes through geometric deformation and self-reconstruction. Then, the degree of freedom analysis and verification, gait planning simulation and motion control design for the designed parallel robot were carried out. Finally, the robot prototype was made to verify the feasibility of the robot design scheme and its motion mode through experiments. The results showed that using geometric deformation and self-reconstruction could improve the ability of parallel robots to adapt to multiple complex terrain environments. The research results can provide a new idea for the design of multi-mode parallel mobile robots.

The phenomenon of error averaging in the linear feed system of precision machine tools is a key concern in machine tool accuracy design. Taking a typical linear feed system with double guide rails and four sliders in precision horizontal machining center as the research object, the averaging mechanism between the geometric error of rolling guide rail pair and the motion error of workbench was emphatically studied. Firstly, the equivalent stiffness method based on transfer function was used to establish the mapping relationship between the geometric error of guide rail and the motion error of workbench, and the error averaging mechanism was revealed by taking the normal straightness error as an example. Then, the finite element model of the linear feed system with double guide rails and four sliders was established, and the averaging coefficients of the geometric error of guide rail and the motion error of workbench were analyzed. Finally, an error averaging mechanism analysis experiment was conducted to verify the correctness of the theoretical analysis and simulation analysis by measuring the geometric error of guide rail and the motion error of workbench and calculating the error averaging coefficient. The research results provide a theoretical basis for the accuracy design of machine tools.

Aiming at the complexity of rock crushing process and the limitations of traditional simulation models, which reflects the little information about the replacement particle groups and can not locate a particle in the replacement particle groups, resulting in the simulated particles can not be broken continuously and the simulation accuracy is low, an improved crushing model developed by the discrete element application program interface is proposed, which is the bonded particle model (BPM) with multiple replacements. This method realizes the multiple continuous replacements of particles during the crushing process, which is closer to the actual crushing process and can improve the simulation accuracy. Based on the three-dimensional model of dual-roller crusher and the W-ore particle groups after parameter calibration, the visual simulation analysis of laminated crushing of W-ore particle groups in crusher was carried out, and the laminated crushing characteristics of the dual-roller crusher were studied through indoor tests to verify the effectiveness of numerical simulation. The results showed that: the relationship between the force on W-ore particles and the crushing rate obtained through simulation indicated that the dual-roller crusher could achieve laminated crushing; the error of particle size distribution after crushing was 0.889?1.940 mm, and the particle size distribution after crushing met the normal distribution, which verified the simulation analysis was accurate and effective. The laminating crushing test results of W-ore with different particle size ratios showed that the influence of particle interaction on crushing efficiency was greater than that of particle low porosity. The research results provide a basis for improving the production efficiency of dual-roller crusher, and the proposed improved crushing model also provides a new method for the study of material crushing.

Aerostatic bearings have the characteristics of high precision, low friction and long life, which are widely used in aerospace and other fields. The bearing area and thickness of gas film of different aerostatic bearings are very different, resulting in extremely complex flow field inside the gas film. However, the traditional N-S (Navier-Stokes) equation based on the laminar flow hypothesis can not accurately predict the working characteristics of the bearing. Therefore, taking the disk-shaped center air supply orifice throttle aerostatic bearing as the research object, a mathematical model of its gas film flow field was established based on the gas lubrication and turbulence theory, and the development motion of turbulent spots in the gas film flow field after forming vortices and the transition process to smooth laminar flow were analyzed. Under the same operating conditions, the k-? model was adopted for the characteristic flow field when the gas film thicknss was smaller (<10 μm), the large eddy simulation (LES) model was adopted for the characteristic flow field when the gas film thickness was medium (10?20 μm), and the k-? model and the laminar flow model were adopted for the characteristic flow field when the gas film thicknss was larger (20?30 μm). Then, the static characteristics test platform of aerostatic bearing was designed and built to verify the accuracy of the calculation model. The results showed that selecting appropriate calculation model according to different operating conditions could improve the calculation accuracy of gas film flow field of aerostatic bearings. When the gas film thickness was less than 10 μm, the turbulence in the gas cavity was relatively large, and it was appropriate to describe it using the k-? model. When the gas film thickness increased to 10?20 μm, the large vortices in the gas cavity diffused and transported energy along the radius at a certain speed, which should be described by the LES model. When the gas film thickness increased to 20?30 μm, the capacitance effect of the gas film increased, which made the rear half of the gas cavity present laminar flow characteristics, and the hybrid calculation model should be used to describe it. The research results provide reference data for the design of aerostatic bearings under different operating conditions, and the accurate selection of calculation model is conducive to shortening the development cycle.

The wear of the sealing surface has a significant impact on the sealing performance of V-shaped combined sealing ring. A finite element model of the V-shaped combined sealing ring was established. Based on the characteristics of rapid wear in areas with high contact pressure and the movement of the area with greater wear towards the air side, the contact pressure distribution of the sealing ring under different wear states was studied by modifying the contour of the V-shaped ring in the finite element simulation process to represent the different wear states of the V-shaped combined seal. Considering the coupling effect between deformation of V-shaped combined sealing ring and lubricating oil film, based on the elastohydrodynamic lubrication theory, an elastohydrodynamic lubrication mathematical model for V-shaped combined sealing ring was established. Based on the small deformation theory, the elastic deformation of the sealing ring under high pressure was obtained by the deformation influence coefficient matrix method. The oil film pressure distribution and thickness distribution in the working process of the sealing ring were solved by the finite difference method, and the influence of the wear and roughness of the sealing surface on the lubrication performance of the combined sealing ring was analyzed. A V-shaped combined sealing ring performance test bench was built to obtain the friction torque and leakage rate of the sealing ring under mild and moderate wear conditions at different motor speeds, and the test results were compared with the simulation results. The results showed that as wear intensified, the pressure and thickness of the oil film near the lubricating oil side increased; for seals that had already undergone wear, an increase in roughness would increase the oil film pressure; an increase in motor speed would increase the frictional torque and leakage rate of the sealing ring. The research results provide a reference for improving the performance of V-shaped combined sealing ring.

Wind resistance braking is an effective braking measure for high-speed trains running at speeds exceeding 350 km/h during high-speed stage of auxiliary braking or emergency braking. Developing a wind resistance braking device with superior comprehensive aerodynamic performance and wide applicability is one of the key technical issues that urgently need to be solved in the development of the next generation high-speed trains with running speeds of 400+ km/h. On the basis of summarizing and analyzing the feasibility and practicality of existing technologies, the design concept and method of a new wind resistance braking device was proposed, with a focus on meeting the requirements of multi-level collaborative braking, optimizing aerodynamic performance, reducing aerodynamic noise and weakening structural vibration. Therefore, a window-shaped wind resistance braking device and its improved design scheme were completed. The results showed that the multi-mode selective braking was achieved by rotationally opening the two-row wind resistance braking plates set forward and backward along the front and rear edges of the installation base, which effectively overcame the problems of severe aerodynamic noise, flutter and low braking efficiency of the rear wind resistance braking plate caused by traditional wind resistance braking plates opening from front to back; at the same time, the secondary aerodynamic performance of the wind-resistance braking device was optimized by using two braking compensation methods, self-feeding compensation and plate diversion, which further improved the peripheral flow field structure of the device during braking, and avoided the formation of additional aerodynamic resistance in non-braking state to the greatest extent. Aiming at the transmission control of wind resistance braking device, the circuit simulation control and hydraulic drive control schemes were innovatively designed. Taking the CR400AF platform electrical multiple unit with a running speed of 400 km/h and equipped with a single improved window-shaped wind resistance braking device as the calculation model, the simulation results showed that the device contributed 4.70 kN of aerodynamic resistance and generated 1.13 kN of aerodynamic lift during emergency braking, exhibiting good resistance increasing characteristics in high-speed stage. The window-shaped wind resistance braking device and its improved design scheme have strong advantages in braking efficiency, braking plate utilization, aerodynamic performance and aerodynamic noise. The design and application of future high-speed train wind resistance braking devices require further experimental research from the aspects of line conditions, operating wind environment, instantaneous start-stop performance, electronic control system, structural vibration and strength design.

In order to solve the problems of inconvenience in experimental operation, difficulty in monitoring equipment operation status and poor interactivity caused by concealed installation position and difficulty in installing auxiliary devices on the self-built laser parallel processing experimental platform, taking a single optical displacement stage in the experimental platform as an example, an interactive control system based on digital twin technology was designed by using Unity engine. This interactive control system used MQTT (message queuing telemetry transport) communication protocol protocol to complete the cross-software information interaction by using the server to transfer data. The Kinesis control software of optical displacement stage and the virtual control panel in Unity engine served as clients in MQTT communication, acting as subscribers and publishers. The digital twin model of the optical displacement stage performed real-time mapping of the motion state of its physical entity based on data information. Users completed synchronous interactive control of the physical entity and the digital twin model through the Kinesis control software or virtual control panel. The secondary development of Kinesis control software was carried out by referencing.dll file, and the motion control class of Kinesis control software was called to complete the motion control of the optical displacement stage. The motion data variables were set to high-precision float type and decimal type to ensure that the data precision was not lost. Ten groups of actual processing data were selected to test the operation latency and synchronization of the interactive control system. The results showed that the data publishing time on the Kinesis control software and the data subscription time on the Unity engine were controlled within 20 ms and 10 ms, respectively. The designed system can better ensure the consistency of synchronous control and real-time action mapping between the digital twin model and the physical entity, which achieves the visual monitoring function of the motion state of the optical displacement stage. In addition, the motion data type can meet the micron level information transmission, ensuring the accuracy requirements of the optical displacement stage. At the same time, the functions of virtual control panel run normally, which improves the convenience of the optical displacement stage control.

Compliant actuators can achieve safe interaction between robots and humans due to their inherent flexibility, and have strong environmental adaptability. To meet the requirements of exoskeleton robots for joint flexibility and variable stiffness characteristics, a reconfigurable variable stiffness compliant actuator was designed, which could achieve reconstruction by changing the geometric parameters, materials and quantity of elastic components, and achieve variable stiffness within an adjustable range by adjusting the radial preload. Firstly, based on the transmission principle of a zero-length frame four-bar mechanism, a stiffness mathematical model of the variable stiffness compliant actuator was established, and the influence of the number of flexible branches and the stiffness and preload of elastic components on the output torque and stiffness of the actuator was analyzed. Then, an ADAMS virtual prototype model of the actuator was established, and the statics performance simulation analysis was carried out to verify the correctness of the stiffness mathematical model. Finally, the dynamics model of the actuator was established and the transfer function of the dynamics system was obtained through Laplace transform. The frequency characteristics analysis results indicated that the stability of the compliant actuator was good. The designed compliant actuator had a small volume and small mass, which could be applied in the driving mechanism of wearable exoskeleton robots. The research results provide theoretical and technical references for the design of compliant driving joints in robots.