In view of the shortcomings of the existing accident causation models, such as simple listing and superposition of causative factors, not considering the coupling effect between factors, unable to make quantitative analysis and so on,a new nonlinear multi⁃factor coupling accident causation model was proposed and applied to the prevention of oil depot accidents. In the new model, the calculation formulas of the main influencing factors, the influence coefficient and the multi factor coupling rheological nonlinear damage were proposed. The most prominent feature of the model is that it can distinguish the dynamic influence of the rheology of the main influencing factors on the damage of the complex system under the coupling action of multiple factors. MATLAB software was used to simulate the changing state of the oil depot system after single factor rheology, main influencing factor rheology and non⁃main influencing factor rheology. The results show that the main factor affecting the safety of oil depot is the lack of safety consciousness,and the lack of safety consciousness of oil depot personnel has the greatest influence on other factors. For oil depot accident prevention, according to the nonlinear multi⁃factor coupling accident cause model proposed in this paper, it is necessary to take effective measures to control the main influencing factors and seize the main time nodes.

In engineering design, special area of pressure vessels always needs opening nozzles in order to satisfy complexity of technologies. Only considering the single load condition of the pressure vessels, the calculation of opening⁃nozzles in GB 150—2011 does not involve additional external load on opening⁃nozzles in practical projects. The SolidWorks software was used to locally model the tangentially opened pressure vessel of the cylinder, and the finite element analysis method was used to apply two internal conditions of the internal pressure and the external load of the internal pressure to the three⁃dimensional solid model to obtain the structural stress. Distribution and strength evaluation were carried out, and the influence of the additional external load on the structure of the pressure vessel was studied.The results show that the stress value in nozzle⁃vessel junction area increases sharply and it changes symmetrical distribution of stress in the connection between the nozzle and the vessel because of the external load of the nozzles. The analyzing results can provide some reference in stress analysis of the opening⁃nozzles with the united static load.

Based on the traditional prediction model of triangular fuzzy accident tree, which had the defect of large error caused by linear approximation, the source of error was analyzed according to the truncated set theorem, and the improved algorithm for drawing membership curve of triangular fuzzy number of accident treetop events was given according to the representation theorem. Matlab software was used to program, the modified and traditional triangle fuzzy accident prediction algorithms were used to predict the electrostatic accumulation accidents in oil depots, and calculated the fuzzy importance of 8 causes. According to the calculation results, compared with the traditional algorithm, the average error value of the fuzzy importance calculation of the eight basic events is reduced by 11.91%，which shows that the modified algorithm greatly optimizes the shortcomings of the traditional algorithm.

The problems of deformation failure of vertical storage tank under wind load were studied. The floating roof tank was established by using the Workbench software. The eigenvalues were used for buckling analysis and the buckling deformation diagrams of the tank were plotted. The modal maps of different orders were read by software to analyze the locations and causes of deformation of the tank. And by changing the wind speeds, the changes of the stress on the windward and leeward sides of the tank were studied. The results show that the displacement of the shell is mainly radial displacement. As the height increases, the stress caused by wind load is mainly changed from axial stress to circumferential stress. The equivalent stress is generally rising at the circumferential angle of 0°. The equivalent stress of the tank wall at the circumferential angle of 180° decreases first and then increases. The research results can provide reference for the wind resistant design of storage tanks.

The effect of temperature on corrosion behavior of 316L stainless steel (316L SS) in 3.5% NaCl solution was studied by potentiodynamic polarization and electrochemical impedance，the semiconductor properties of the passivated film were analyzed by Mott⁃Schottky curve. The surface morphology of 316L SS after corrosion was observed by metallographic microscope.The results show that in the NaCl solution with a mass fraction of 3.5%, the open circuit potential and corrosion potential of 316L SS gradually decrease with the gradual increase of temperature, and the self⁃corrosion current density increases gradually.And the pitting potential is also gradually reduced. The results of surface corrosion morphology observation showed that the number and diameter of corrosion pits on the surface of 316L SS increased as the temperature increased.This is mainly because the temperature decreased the density of the passivation film and increased the dissolution rate of the passivation film, and decreases the corrosion resistance.

The theoretical analysis of the stress concentration factor K of three types of tubes with three different types of unfused defects is very complicated. In this paper, the finite element numerical analysis software is used to be established the finite element model of the three⁃way pipe with defects under the action of internal pressure. After calculation, the stress concentration factor K and its variation law under the four influencing factors are obtained. The results show that the stress concentration factor K of the three⁃way tube with three different unfused defects is relatively large in the shoulder and collar region, and the stress concentration is serious. The stress concentration factor K increased slowly with the increase of the axial length and depth of the defect, and decreased rapidly with the increase of the circumferential length of the defect.

In order to solve the problem of complex system in the security field by theory and computer， the objectives, conditions, and characteristics of incompatible problems in the field of security were defined from the perspective of acceptable security state value and the four elements of security on the basis of studying the theory and method of inconsistent problems, and the corresponding mathematical model was given. The key conjugate elements for the extension of the incompatible problem were defined: The hard part was the safe person and the safe thing, and the soft part was the safe society and the security system. The mathematics strategy to solve the incompatible problems in a gas station, the result showed that the application of this method could solve the problem of the safety of the gas station and provide the new ideas and the basis for safety performance management.

Once hydrogen sulfide is leaked and diffused, the consequences are unimaginable. In order to master the law of hydrogen sulfide diffusion, the diffusion law of hydrogen sulfide under the influence of source strength, wind speed and source height was numerical simulated by MATLAB and VC++ software. The simulation results show that at night, when the source strength increases, the downwind direction diffusion range increases under the leakage source, the hydrogen sulfide mass concentration gradient increases in the diffusion area, and when the source height increases, the maximum width of the downwind direction diffusion area under the leakage source becomes narrower and the area becomes smaller. During the daytime, when the sunlight intensity is low and the wind speed is greater than or equal to 4 m/s, the downwind direction diffusion range of the leakage source decreases as the wind speed increases, and the hydrogen sulfide mass concentration gradient decreases in the diffusion area. Increasing the source height and wind speed is beneficial to reducing the mass concentration of hydrogen sulfide and the hazard. The research results can provide a basis for accident prevention and emergency rescue.

The DEMATEL algorithm is an algorithm for analyzing the relationship between the influencing factors of complex systems. The algorithm has important application value for identifying the key factors of complex security system. First, on the basis of the DEMATEL algorithm, according to the knowledge of cognitive psychology and the status quo of the safety management of a gas station, the complex gas station safety system is divided into 4 subsystems, and further refined into 31 specific factors. Secondly, according to the DEMATEL algorithm, the MATLAB program is compiled to divide the cause factors and the result factors, and the influence degree, cause degree and center degree of each factor are calculated. Finally, the location of the key factors are displayed intuitively by drawing the cause results diagram. The results show that the information channel interruption, lack of recognition and information uncertainty, contingency plans and response defects are the key factors affecting the safety of gas stations. The longterm solution for gas station safety management is to control these 4 factors.

The probability of a number of basic events itself was uncertain and fuzzy when the traditional FTA method was used in the practical quantitative analysis quite. It was difficult to obtain the exact probability from failures, which violated the premise of exact probability selected. In order to solve the traditional fault tree analysis (FTA) of the probability the basic event fuzzy and uncertain problems, the concept of fuzzy theory were introduced, and the fuzzy probability was used to deal with the basic events lack of statistical data. The basic events of fuzzy probability were described by using a clear triangular fuzzy number, the fuzzy probability distribution of top event layer by layer was obtained, and the fuzzy importance of each basic event was determined by using fuzzy numbers value method. And the sort of top event of failure factors was obtained, the main factors influencing the accident were identified and effective measures from fundamentally preventive and the key points to control the top event were proposed.

The Drilling machine is a modern coal mining technology and equipment of minecoaling.When Drilling machine work properly, the power feed part is under the complicated forces, and the working environment is harsh. In order to ensure product quality and reliability, using finite element analysis software ANSYS dedicated feed module the stress and vibration modes of calculation. By calculating the results obtained ZDY2000L rig feed module in a state of extreme working stress distribution and rail stiffness and deformation values and found that the design of the product in the case of reducing the amount of steel, while ensuring the strength of the structure of local requirements and overall stiffness deformation requirements. Structure necessary vibration modal analysis of the natural frequencies has been submitted so as to provide a theoretical basis for improving the mechanical properties of the system.