As a critical component of pressure equipment, ellipsoidal head is widely used in the fields of petrochemical industry and nuclear plant. The design of ellipsoidal head is so important to guarantee the safety and economy of the pressure equipment. Based on the Chinese standards GB/T 150 and JB 4732, ASME BPVC Section Ⅲ. division 1-Subsection NE, Code Case N-284, Section Ⅷ division 1 and division 2, and the European Standard EN 13445, the design methods for internally pressurized ellipsoidal head were discussed and compared in detail. ASME Codes and EN 13445 adopt the design methods based on various failure modes of internally pressurized ellipsoidal head. However, the Chinese standards GB/T 150 and JB 4732 adopt the strength design methods based on maximum stress and limit pressure, respectively. The design equation for preventing local buckling failure was not presented in the Chinese standards, which was disadvantageous for the design of large-scale thin-walled ellipsoidal head. The design results of JB 4732 were too conservative, which was not economical. Moreover, it concluded that there was a defect in these design methods that the effect of both strain hardening and large deflection was ignored. Therefore, it will be a good suggestion to improve the design methods of internally pressurized ellipsoidal head for Chinese standards.

In order to solve the problem of the complexity and inefficiency of lip seal performance evaluation for lip seal, the rapid simulation process customization technology of static sealing performance of lip seal based on physical model of lip seal which was referred to the physical model and combined with Femap & NX Nastran platform was proposed. First of all, based on Mooney-Rivilin constitutive relationship of rubber material, an axisymmetric numerical model of lip seal was established by using FEA (finite element analysis) software, the convergence control techniques was applied to the nonlinear problem of the model, and the good convergence was obtained. At the same time, the relevant sealing performance parameters during the assembly of the lip seal was verified by finite element simulation, and the effectiveness of the sealing performance evaluation was verified by the rotational torque experiment. Then, the simulation process customization technology based on the physical model of the lip seal and considering the design engineers' requirements for product performance evaluation was developed by using Visual Basic language and Femap API. Next, an example was performed to verify the effectiveness and universality of the performance simulation, and the structure optimization was carried on by using the CAD (computer aided design) parameterization technology to improve the static sealing performance of lip seal on the basis of sensitivity analysis. The sealing performance of lip seal and evaluation efficiency of the product are improved finally.

In order to meet different requirements of backlash in gear transmission performance and trapped-oil performance of external gear pumps, an H-shaped backlash structure with large-small-large gap on the non-working surface of driven gear is put forward. Firstly, after analyzing the trapped-oil process of gear pumps, two kinds of area formulas necessary for connection and relief backlash were derived under the connection condition of two different trapped-oil volumes in double teeth meshed range and the relief condition of trapped-oil performance in single tooth meshed range. Secondly, through the derived minimum backlash area, the geometric size of the H-shaped backlash structure was calculated. Finally, a feed-through relief groove with asymmetric micro circular profile was invented for trapped-oil relief in double teeth meshed range. It was showed that whatever the backlash size was, the absolute connection and the absolute trapped-oil relief were not existed, but only the relative connection and relative relief under a certain permission pressure difference. Even if the connection was really satisfied in the backlash connection range, the trapped-oil phenomenon in this range was still not solved, and it must be unloaded by supplemented relief groove. On the premise of keeping transmission performance of gear pairs, the trapped-oil performance of pumps was greatly improved by the H-shaped backlash structure, combined with the circular material removal near the root circle on double gear end faces, larger relief area was built by the feed-through relief groove with double micro circular profiles symmetrical about pitch circle node. It is concluded that the combination of the H-shaped backlash structure and the circular material removal structure and the feed-through relief groove structure can fully meet the requirements of gear transmission performance and trapped-oil performance, and it has the characteristics of simple structure and easy processing. It provides a new relief structure for eliminating the hazards of trapped-oil in external meshing gear pump.

There are some uncertainties in the parameters of the new escape pipeline and the single-objective optimization has its limitations. To realize the multi-objective robust design of the new escape pipeline, a multi-objective robust design method based on satisfaction function was proposed combining with Taguchi robust design approach. This method converted the signal-to-noise ratio of the product quality characteristics to the degree of satisfaction which had the larger-better characteristics of Taguchi robust design, and the multi-objective robust design of the structure was realized by weighted geometric mean. The finite element model of the new escape pipeline was established and verified by using Hypermesh and LS-DYNA, and then the proposed method was applied to the multi-objective robust design of the new escape pipe. The results showed that the signal-to-noise ratio of the new escape pipe after the robust design was increased by 5.3%, the ability of pipeline to resist noise factor interference was enhanced, and the structure was more robust. The weight of the new escape pipeline was reduced by 9.6%, and the purpose of pipeline lightweight was achieved. The research results have certain theoretical and engineering significance for improving the robustness of the new escape pipeline.

To systematically study mechanism and factors affecting the thermal error of feed system of precision machine tools, a modeling method for the thermal error of the feed system considering the structural thermal deformation is proposed. Besides analyzing the temperature changing and thermal deformation of screw caused by inner heat resources in feed system and cooling system, the influence of inner heat source in feed system on the thermal characteristics of large structural components(bed, pillar, slide) of precision machine tool was also considered. The relative position changing between motor-box and bear-box of the feed system caused by the structural thermal deformation was analyzed, and a thermal error model of feed system considering the thermal deformation of large parts and screw was established. Thermal errors of the feed system of JIG630 precision horizontal machining center were simulated and modeled with and without considering the structural thermal deformation, and the corresponding verification experiments were carried out. The results illustrated that the thermal error model of the feed system considering the structural thermal deformation was more consistent with the experimental results. This modeling method is of great importance for thermal balance design, thermal error control and compensation of feed system of precision machine tools.

The load distribution ratio of the bolted joint structure is closely related to the axial relative stiffness between the bolt and the connected parts. In order to more accurately calculate the axial relative stiffness of the bolt and the connected parts of bolted joint structure, according to the analytical formula of axial compression deformation based on uniform and non-uniform distribution of compressive stress in each compressed layer of connected parts perpendicular to bolt axis,and combined with the finite element simulation results, the initial diameter modified formula and the axial compression deformation modified analytical formula for the compression deformation body of connected parts were proposed. By extracting simulated stress values, the integral calculation for theoretical modified equation and the simulated fitting equation of compressive stress was carried out. By comparing the computation results, it was found that the errors of the axial compressive deformation of the compression deformation body of connected parts calculated by the simulated fitting equation and the theoretical modified equation were less than 2.5%. It was shown that the accuracy of solving the axial compressive deformation of the compression deformation body of connected parts by simulated fitting equation was high. The results showed that the modified initial diameter was linear with the clamping length and the diameter of bearing surface between bolt head and nut. Under the non-uniform distribution of compressive stress, the errors of calculating the axial relative stiffness between the bolt and connected parts by using the modified analytical formulas of the axial compressive deformation of compression deformation body of connected parts were less than 2%, which indicated that the modified analytical formulas could calculate the axial relative stiffness between the bolt and connected parts more accurately. On the basis of the modified initial diameter, the calculation results of the axial relative stiffness based on the non-uniform distribution of compressive stress were more accurate than that based on the uniform distribution. The research results provide reference for accurately analyzing the force of bolts in the theoretical research and actual engineering.

When subjected to cyclic frictional thermal load during the emergency braking process, the brake disc of ultra deep mine hoist generates large internal thermal stress. In the meantime, the high temperature can decrease the friction braking performance of brake disc and brake pad and even cause brake disc failure. Aiming at the thermal performance problem of brake disc, based on the heat conduction theory and the finite element analytic method, the three-dimentional finite element model of the brake disc component was built. The thermal stress field during the braking process was simulated by direct coupling method, and the validity of the simulation parameter setting was verified by experiments. The influences of number and arrangement of brake pads on temperature and stress distribution of brake disc under braking condition were studied. The results indicated that the temperature and stress on the friction surface rose sharply firstly, and then dropped slowly during the braking stage, and the temperature had serrated fluctuations. In the braking process, the variation of stress was the same as that of temperature. The maximal temperature of the original brake disc during the braking process was 134.8℃, while the maximal stress was 230.2 MPa. Also, the high temperature and large stress areas were concentrated near the friction surface. The maximal temperature of the brake disc with increased number of brake pads during the braking process was 142.4℃, the maximal stress was 251.1 MPa, and the high temperature and large stress areas were also concentrated near the friction surface. Through optimization of the arrangement of brake pads, the maximal temperature of brake disc was 86.45℃, the maximal stress was 119.1 MPa, and the high temperature and large stress areas concentrated in a smaller range. It could be seen that change of the arrangement of brake pads could significantly reduce the temperature and stress of the brake disc, and the distribution of temperature field and stress field become more even. The research results can provide a theoretical reference for thermal performance optimization design of brake disc.

Crossbeam is the main moving part of bridge gantry milling machine, and its structure design directly affects the working performance of machine tool. Therefore, a structure design and optimization method for crossbeam based on orthogonal experimental design, improved fuzzy comprehensive evaluation and size sensitivity analysis was proposed. According to the multi-factor and multi-level characteristics of crossbeam structure design, eight kinds of representative parameter combinations were selected as the structure design scheme of crossbeam by orthogonal experimental design. The improved fuzzy comprehensive evaluation method was used to process the finite element simulation data, so that the optimum selection scheme of crossbeam with parameters combination "box in box-well-20 mm-linear guideway" was determined. And the sensitivity analysis and optimization of its key design sizes were carried out to obtain the specific of crossbeam structure design size. After optimization, the static performance and anti-vibration performance of crossbeam were improved obviously while the lightweight design of crossbeam was also realized, which played a guiding role in the actual manufacture of machine tool crossbeam. The research result shows that the proposed structure design and optimization method for crossbeam has high engineering practicability, and it also provides a new idea for the design of other key parts of CNC machine tools.

Aiming at the motion deviation in the use of lower limb rehabilitation exoskeleton, the structure design and kinematics analysis of a lower limb rehabilitation exoskeleton was completed based on the human-exoskeleton movement model and adjustment model. Firstly, using the theory of human-machine deviation variable and the theory of human-machine compatibility, the human-exoskeleton adjustment model was established by adding the passive degree of freedom to the human-exoskeleton movement model. Based on the human-exoskeleton movement model and the human-exoskeleton adjustment model, the lower limb rehabilitation exoskeleton was designed. The lower limb rehabilitation exoskeleton provided movement mode and adjustment mode, which could be switched by the sliding deviation detection device of the human-machine. The kinematics model of single lateral exoskeleton mechanical leg was established, and the motion equation and the linkage transformation matrix were solved. The MATLAB and ADAMS software were used to simulate the exoskeleton model and the human-exoskeleton model, the simulation results were compared and analyzed. The results showed that the moving space in the sagittal plane of the exoskeleton could cover the end trajectory of the human body. The movement trend and theoretical movement trend of the exoskeleton joints were basically consistent, and the adjustment mode compensated the motion deviation of the movement mode,which proved the rationality of the lower limb rehabilitation exoskeleton. The lower limb rehabilitation exoskeleton mechanism based on human-machine closed chain can compensate the motion deviation and avoid the secondary damage. It can be used for reference in the practical design of exoskeleton, and provides a theoretical basis for exoskeleton mechanism research.

Aiming to penetrate approximately two meters below the lunar surface, a rotary-percussive sampling drill is used for the lunar exploration project in China. The cutting heat generated by drilling is completely conducted by the drilling tool during the drilling process. Due to the ultra-high vacuum and harsh temperature environment of the Moon, the efficiency of the conduction is much lower than that of regular drilling operation on the Earth. As the drilling condition is unknown, the high temperature area in certain part of the drilling tool may be formed, which will reduce the overall performance of the drilling tool, particularly the coring performance of the drilling tool. Through the EDEM software, the lunar soil particle microelement model with different shapes and sizes were established to form the lunar soil simulation model. The thermal characteristics of the lunar soil in the drilling process were simulated based on the high temperature small particle cluster method in order to reveal the distribution rule of different temperature rise particle. Based on the distribution rule, a mathematical expression between the temperature rise particle number and temperature rise was built. In addition, in the simulated lunar drilling experiment, several temperature measurement points were supplemented on the original drilling tool by the fiber grating sensor technology. The thermal characteristic experiments of drilling tool were completed to obtain the temperature rise rule in different locations of drill bit and the influence of rotary speed or penetrating velocity on the temperature of drilling tool. Both the temperature rise particle number model and the traditional thermal characteristic experiment can predict the temperature rise of the drilling tool, which provides a basis for the thermal safety on the lunar simulation environment or extreme drilling condition.

Abrasive water jet technique is a special process popularized and applied in many fields due to its advantages like no tool contact, no heat-affected zone and high machining versatility, etc. In order to investigate the erosion effect on brittle materials, the erosion simulation model of abrasive water jet at outer flow field and abrasive water jet erosion experiment were designed. The abrasive water jet erosion simulation model was set up based on the 30 mm×50 mm outer flow field of the nozzle. The distribution of pressure, velocity of water and abrasive and their attenuation law on the center line of jet in the erosion process were fully analyzed. Through the erosion test of alumina ceramic material, the influence of process parameters on the erosion hole diameter was analyzed as well. Combining with the simulation results, the relationship between jet beam width and erosion hole diameter was compared and analyzed. The results indicated that the water velocity decreased with the increase of nozzle distance and the distribution range became wider, and the width of jet increased linearly. The abrasive velocity decreased with the increase of nozzle distance while the distribution width was almost unchanged. The velocity of water and abrasive on the center-line of jet showed three-stage attenuation. During the first stage, the length of the velocity attenuation section of water was longer than that of abrasive, but during the second one, the length of the velocity attenuation section of water was shorter than that of abrasive. In addition, the effective utilization of jet energy decreased gradually. However, in the target range of 15~25 mm, the effective utilization part was more stable at around 40%, and the erosion hole diameter increased linearly with the nozzle distance increasing. The research results can provide experimental basis for the parameter selection of abrasive water jet cutting, milling and polishing, and provide reference for the simulation of abrasive water jet machining.

Aiming at the problem that the hydraulic impactor cannot be industrialized because of serious erosion during mud drilling, a neo-type hydraulic impactor for anti-erosion was designed from the point of structural innovation. Based on the liquid-solid two-phase flow dynamics and erosion theory, the hydraulic impactor erosion model was established. The Lagrange tracing algorithm was applied to calculate the movement trajectory of solid particles, and the distribution of erosion area, the influence of particle impact velocity on erosion of the main working elements (impact hammer, upper sleeve and shell) and their working life were predicted based on the inner velocity distribution analysis of neo-type hydraulic impactor. According to numerical simulation results, the erosion area was concentrated on the bottom of upper chamber of hammer,impact hammer corner,inlet wall of the orifice,inlet of the flow channel hole in piston upper chamber and upper wall in upper sleeve. Power function relationship was identified with tool average erosion rate and impact velocity with velocity factor of 1-4. Theoretical anti-erosion life of key working elements of neo-type impactor had an obvious improvement under comparative analysis of existing impactor. The research work has important reference value for promoting the industrial application of the neo-type hydraulic impactor.

Marine riser is an important part of offshore oil and gas gathering and transportation system, which is used to connect submarine oil and gas wellheads and offshore oil and gas gathering and transportation stations. In oil and gas storage and transportation projects, marine oil and gas gathering and transportation media are mostly oil-gas-water three-phase fluids. In order to investigate the coupled vibration problem of the oil-gas-water three-phase flow marine riser system under severe slug flow, numerical calculation and empirical research were carried out. Based on the multiphase fluid mechanics theory and kinetic theory, a three-phase severe slug flow model of oil-gas-water and structural dynamics model were constructed. Combining these two models, the coupled vibration response process of the riser was simulated, and the L-type oil-gas-water three-phase flow riser system with the inclined pipe tilt angle of 3° was designed and tested. Comparing the calculated and tested values, the results showed that the proposed coupled vibration response model was more suitable for studying the coupled vibration response of marine riser caused by the oil-gas-water three-phase of flug flow than the severe slug flow transient mathematical model, and the simulation of results were in good agreement with the experimental results. The pressure and displacement of the riser bottom changed periodically, and the period of change was basically the same; the pressure of fluid was the key factor that caused the coupled vibration response of the riser system. These research results provide a reference for the analysis of the coupled vibration response characteristics and structural design of the oil-gas-water three-phase flow marine riser system under severe slug flow.

The surface topography of ground has great influence on the contact properties between the vibrator baseplate and ground. In order to investigate the effects of the ground surface parameters on the contact properties and vibration character of the vibrator baseplate-ground contact system, the three dimensional surface topography of rough ground was generated by the fractal function theory and then the vibrator baseplate-ground contact model was established. The contact curves between vibrator baseplate and ground under different ground surface topography and material parameters were obtained. The dynamics equation of the vibrator baseplate-ground contact model was further established, and the displacement response and energy transfer of the vibrator baseplate were calculated. The results showed that the nonlinearity of the contact force between the vibrator baseplate and the ground increased with the increase of the ground surface roughness. The natural frequency of the vibrator baseplate-ground contact system decreased with the increase of the ground surface roughness, as well as the energy transfer of the baseplate per cycle. Meanwhile, the nonlinearity of the ground material parameters also influenced the vibration response and energy transfer of the vibrator baseplate-ground contact system. Consequently, the ground surface roughness and material nonlinearity were important reasons which restricted the output of the vibroseis in high frequency phase. The study has a positive effect for optimization and high frequency expansion of the vibroseis.

Traditional FDM(fused deposition molding)3D printer needs to set up auxiliary foothold structure when it prints inverted parts, and the foothold structure needs to be removed from the prints after printing, which will reduce the precision of prints. In order to solve the problem, a FDM 3D printer based on hybrid coordinate system was designed. The principle of motion in new FDM 3D printer was based on quasi-spherical coordinate system instead of Cartesian coordinate system. The rotational motion in X-Z plane and X-Y plane combined with the linear motion in Z-axis direction made up the motion in quasi-spherical coordinate system, to realize the unsupported 3D printing. The hardware and software design for control system of the FDM 3D printer based on hybrid coordinate system was introduced. Printing experiments were performed by using traditional FDM 3D printer and FDM 3D printer based on hybrid coordinate system. The comparison result showed that the FDM 3D printer based on hybrid coordinate system had higher printing accuracy under the same level of precision hardware configuration. The FDM 3D printer based on hybrid coordinate system has high innovation and low cost with independent intellectual property rights, and it has vast market prospect.

The construction quality and efficiency of waterproofing process directly affect the project progress in tunnel construction. However, there are many problems in the waterproof laying trolley, such as high labor intensity, low laying efficiency, poor safety, and so on. Therefore, a multi-functional waterproof laying trolley equipment and its hydraulic control system were designed to solve the problems mentioned above. First of all, the overall mechanical structure of the equipment was introduced, which contained gantry support mechanism, moving mechanism, hoisting mechanism, crawler and synchronous mechanism, scaling platform and support mechanism, and so on. Then, parameters of hydraulic system and hydraulic components were analyzed and selected on the basis of analyzing the working requirement and working principle of the hydraulic system, and the optimal scheme was confirmed. Meanwhile, according to the characteristics of the parallel loop of the hydraulic system, the hydraulic simulation model of lifting loop was established based on AMESim for dynamic simulation analysis and the response characteristic curves such as work pressure, flow and displacement of hydraulic cylinder were obtained. The experimental results showed that the hydraulic system had the advantages of reasonable design, fast response speed, stable performance, high reliability and could meet the work requirements. The research result provides guidance for the optimization design of the hydraulic system of laying trolley.