The concept of technology symmetry was proposed, and a multi-level classification system including technological method symmetry, technological process symmetry and technological equipment symmetry was presented to support systemically researching the existences, functions and application rules of symmetry in mechanical technology. Subdivisions of combination/decomposition symmetry and space-time symmetry inside technology symmetry were made and the differences between them were illustrated with examples. Mechanical manufacturing technology symmetry can be used to enhance not only the level of manufacturing technology, but also the level of mechanical construction design. The relationship, difference and interaction between them were also illustrated. Analysis of instances showed that the concept system could completely contain all kinds of existence of symmetry in mechanical technology, and it offered theoretic foundation for further research on mechanical technology symmetry design principles and the development of mechanical technology symmetry design methods．

Mould-repair is an important task in the mould production and depends especially upon the experience of the engineer. How to find and conclude the knowledge of mould repair is an important problem for all the mould manufacturers in the industry. Using the fuzzy rules induction to help the technician establishing the mould-repair project was put forward. The main design idea and the realization process of this algorithm have been analyzed. At last the rules about the defect of “flashing” were concluded by the knowledgeminer software. Results show that the rules are consistent with the facts. The correct rate is about 84%．

Starting from the essence of design and analysis and combing the characteristics of complex systems, and meantime by analyzing the difficulties and defects of traditional design optimization methods in solving complex system problems, the multidisciplinary design optimization (MDO) was proposed as an effective method to solving optimization design of complex systems. On this basis, the basic ideal of MDO was presented,and the coupling modes of subsystems and common methods of processing coupling were summarized, and the knowledge frame and main research contents of MDO was concluded. Based on the existing research results, several reference opinions were pointed out for future research．

To improve the safety and reliability of mechanical components, the theory of Reliability-based Robust Optimization Design (RROD) and multi-objective decision-making approach were employed. The multi-objective optimal modes established are suitable for RROD of structural system. In order to solve multi-objective optimal mode with constrained conditions rapidly and accurately, a fuzzy theory was presented to solve the constrained conditions. Then, the grey particle swarm algorithm was employed for this mode. Experimental results of torsion bar with normal distribution parameters and arbitrary distribution parameter show that the aforementioned methods are effective．

 Based on the finite element analysis and modal analysis theory, the FEM model of the inner supporting structure of laser emission turntable was built by adopting the Patran & Nastran software package. And its dynamic characteristics were analyzed. The results show that the structure design meets the requirements but optimization is necessary. By adopting the structure optimization theory, the mathematical optimization model of the inner supporting structure was established, and the dimension optimization for the structure was done. Through optimization the total weight of the structure reduced by 41.13 % and the first nature frequency only varied by 17.10%. Finally, the static and dynamic analysis for the optimized structure was validated, and the results are desirable．

The theoretical calculation and experimental analysis have been done to solve the deformation problem of flexible fixture in the process of high-precision machining. First of all, the deformation of the existing flexible fixture had been analyzed using the CAE software. And then, the structure of fixture had been optimized by changing the parameters of the structure and dimension of fixture using the CAD software to reduce the deformation of the fixture in the process of positioning. To verify the effect of optimization, the deformation of the optimized fixture had been analyzed using the CAE software once again. The calculation results showed that, in order to ensure the maximum deformation to satisfy the machining accuracy requirements, many measures could be taken, such as increasing the stiffness of the principal plane, increasing the stiffness of the ribbed slab and changing the locating points of the fixture, and so on. Finally, the deformations of the locating points of the fixture were analyzed by experiments. The deformation of four points in the clamping process are less than 001 mm, which meets the accuracy requirement in the high-precision machining. The experimental results are basically in line with theoretical results. The optimized scheme has a good effect in producing process.

Design parameters of water lubricated bearings are always get by reverse from overseas products. Design rules and manufacture process parameters will be obtained from experiments in the research. Design parameters such as bearing structure and long-diameter ratio (L/D) were analyzed, which were the main influence factors for lubrication property of water lubricated bearings. The empirical formula of the multi-curved and circle contacting face of bearings and the relation between the thickness of plastic alloys and the inner diameter of bearings were obtained. And then, the impact of manufacture process parameters including vulcanization time, temperature and pressure on the performance of bearing materials was analyzed through experiments. The main performance included peel strength, tensile strength and wearing capacity. Optimization of manufacture process parameters and the orthogonal experiments on them were carried out by integrating the results of experiments and finally the optimal manufacture process was achieved. The performance of water lubricated bearings with L/D=2 that made on vulcanization temperature 180 ℃, time 20 min and pressure 2 MPa can reach or exceed the standard of MIL-B-17901 (marine) published by USA Ministry of National Defense．

To solve the problem that it is hard to model heatsinks with complex structure, the heat transfer coefficient method, which uses its base to replace the whole heatsink, was proposed to simplify the analytical model. First of all, the approximate solution of fins' heat conduction and the heat flow of the convective heat transfer were derived by using Fourier's law and Newton's heat transfer formula. The convective heat transfer coefficient's expressions for the fins were derived under natural convective condition and forced convective condition, respectively. And according to the principle of energy conservation, the heat exchange coefficient of the base was calculated. Then the thermal analysis software Flotherm was used to simulate the pre-equivalent model and post-equivalent model respectively and it is indicated that the heat transfer coefficient method is an effective way to simplify the hearsink model and this method is also applicable to other thermal simulation software.

Based on the bond graph theory, a bond graph model of speed-sensor-mechanism was  established. This paper had  established the mixture simulation model in the 20-sim simulation software. After dynamic simulation, the authors got the sliding curve of the core displacement and the rotation angular velocity of the wheel curve. The simulation result indicated that the sliding core of speed-sensor-mechanism could reach enough distance to trigger the embracing-track-type device at the critical speed. It is obvious that the design of speed-sensor-mechanism is reasonable.It can be a meaningful method to refer to for the dynamic design and analysis of mechanisms．

To develop a new composite material excavator dipper teeth, which matches the holder of excavators in service on worksites, all design data of old tooth should be available. The excavator dipper tooth is a functional component with irregular shape, fitting constraints in inner cavity, and complex figure. It is extremely time-consuming to measure the size of teeth through general instruments, meanwhile the measuring accuracy can not be guaranteed, and especially its inner cavity and pinhole position was even harder to measure. So the material object reverse engineering technique was used to obtain the sizes and 3D model of the tooth exactly. The methods for extracting feature curves needed in the following tooth modeling from measured 3D coordinate points of the tooth were proposed, including the tooth 3D modeling based on extracted curves. The procedures and key links during feature extracting using Imageware and solid modeling based on those curves in Pro/E were also presented. First-trial-production dipper teeth according to the drawing generated from reconstructed CAD model can match with its holder and work well on the worksite, it indicates that the model reconstruction method mentioned above is effective and practical.

On the basis of finite element analysis, the maximum principal stress finite element method was presented to solve the theoretical stress concentration factor K_t, the result of which was consistent with the value of theoretical calculations and experimental measurements. Moreover, further analysis on the impact of refining the grid was done. The results showed that when the grid was refined to a certain extent, the accuracy was improved and the stress concentration factor tended to a stable value. The maximum principal stress orientation agreed with stress orientation of the fatigue life estimation, which further ensures the accuracy of the calculation of life. This approach provides an important basis for the parameters for the fatigue analysis．

The basic principle of predicting vapor cloud explosion overpressure by BP neural network was discussed. The influencing factors of overpressure were analyzed emphatically. Based on this, a network model between overpressure and its influencing factors was established after a training process with 80 experimental data groups. Using this model, prediction was conducted for other 20 data groups. The results show the model is basically capable of formulating the relationship between overpressure and its influencing factors. It is an effective means for the predicting vapor cloud explosion overpressure. It is of certain practical significance and applicative value in engineering．

According to the theory of gear meshing, gear contact analysis and tribology theory, a general methodology was proposed for predicting the friction power losses of involute gears, which considered the gears whose transmission efficiency changed with gear surface contact load. This methodology integrated a relative sliding speed model, gear contact pressure model and a sliding friction coefficient model with a heat generation formulation to predict the friction power losses of involute gears. And the calculation software was developed. The influence of basic gear geometric parameters, operating conditions and lubricant temperature on friction power losses of involute gears were investigated. This methodology and conclusions may be helpful for the design of gearing and lubricating system．

The abnormal noise which occurres in the course of work process of shock absorber is the outer reflection of its interior quality, and is also one of important factors to affect vehicle acoustics comfort. By imitating the installation of shock absorber in the real car, the rig test of shock absorber was performed on the electro-hydraulic servo shock absorber road analogous system for better analysis of the abnormal noise, and then its creation mechanism was researched separately by making use of time domain analysis and frequency domain analysis. When the direction of the shock absorber was switching, the acceleration peak value of normal workpiece piston rod was less than the abnormal noise workpiece's. There is a big difference between the normal shock absorber and abnormal noise shock absorber in the acceleration power spectrum RMS value of piston rod from 500 Hz to 1 000 Hz, and the difference was more obvious along with the increasing of the test frequency, moreover in this bandwidth the piston rod vibration energy of normal shock absorber is less than the abnormal noise shock absorber's. By carrying out abnormal noise test and analysis on the twin-tube shock absorber, it can provide references for the analysis and evaluation as well as study of shock absorber in the engineering applications．

In existing service robot market, time cost on development can not meet market requirement because of the redundant design work. Designing and building a service robot using commercial off-the-shelf components was proposed. By considering the requirements in development cycle and production cost for the industrialization of service robots, the feasibility of using commercial off-the-shelf components was presented. By taking a service robot as an example, called Panpan as an example, the analysis and design of the structure of chassis and manipulators were carried out. Experiments indicate that this method has the advantages of less both time and material cost while ensuring high robustness, reliability and performance. The low and mid-range service robot market can be filled by this product.