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With the operation of China’s large aircraft, operational safety has become an important issue. The manufacturer uses operation data and design data to carry out safety assessments in the operation phase. Operation safety assessment evaluates whether the conclusion of the safety assessment is still valid and analyzes the safety margin of the aircraft in the operating environment. Model-based civil aircraft operation safety assessment method uses the model-based ideology to propose a technical method of operating safety assessment based on the failure propagation model. The relevant practice also shows that this method is effective and can improve efficiency and accuracy.

The rationality design of the sluice gate directly influences the flood control capacity of hydropower stations. To demonstrate the rationality of the creation of the spillway gate of a hydropower station in the Yellow River Basin, this paper adopts the method of combining model test with a mathematical model to study the pressure, flow velocity, and water level changes of the spillway gate of the hydropower station under the working conditions of check flood and design flood. The research results show that there is no negative pressure in the whole flood discharge sluice dam section under check flood and desert flood conditions. The pressure characteristics of each area of the sluice floor are good, and the velocity distribution is uniform. However, the outflow velocity of the reinforced cage section is greater than the anti-scour velocity of the river under the two working conditions, which impacts the downstream river, so it is necessary to increase the length of the reinforced cage section appropriately. The water flow falls twice in the spillway dam section. The initial position of the first fall is the same under two working conditions. However, the falling depth decreases with the decrease of reservoir water level. The second fall position moves backward with the reduction of the water level. This paper provides a theoretical reference for the demonstration of flood discharge capacity of other hydropower stations through the analysis and research of the flood discharge sluice state of this hydropower station.

Accurate monitoring of electrical equipment temperature can effectively ensure the safety of electrical equipment operation. It is worth further study to use limited temperature monitoring equipment to obtain a comprehensive temperature distribution of electrical equipment. Based on the study of nearest neighbor interpolation bilinear interpolation and bicubic interpolation these three methods are applied to image processing of temperature distribution in 10kV switchgear cabinets. Compared with the three methods, bilinear interpolation and bicubic interpolation can accurately reflect the non-measured temperature, and can be used in image processing of temperature distribution in high-voltage switchgear temperature measurement system.

The multi-disc wet clutch is widely used in high-power vehicles and large construction machinery due to its capacity for high torque transfer and compact efficiency. However, the early-stage failure such as the buckling of the friction disk is hard to detect since its external performance is not obvious, which can impair the reliability of the system largely. This paper presents an online fault diagnosis method for wet clutch based on vibration signal analysis to detect the deformation of the friction components. A bench test is designed to acquire the vibration signal of the clutch pack with four different fault levels. Then an online monitoring method for clutch early fault based on wavelet analysis and EMD algorithm is proposed. The analysis shows that the method can extract the abnormal vibration characteristics and shock signals caused by the local deformation of the clutch pair, which can be feasible in the engineering practice of online fault diagnosis for multi-disc clutch early failure.

A theoretical model of friction plate is established by using Resal theorem, and the inertia resistance of the friction plate is obtained from this theoretical model. Focusing on the bias phenomenon in friction pairs, a new model is investigated for analyzing the bias state under low speed difference considering about the gyro effect. As for the gap shrinkage under high speed difference, the negative pressure contraction model for the friction pairs is built by analyzing the oil film and the pressure between plates. Based on that, the influences of the inertia resistance of the friction plates for these two models are also discussed. Afterwards the gap dynamic change between friction pairs is investigated in the whole variation range of the relative speed. Finally, an improved model, considering the influence of the gap dynamic change between friction pairs, is proposed to simulate the drag torque. The results obtained from the simulation and test data indicate that, under the same lubrication condition, the drag torque in the wet multi-disk clutch increases at first and then decreases and finally increases with the rise of the rotational speed difference. Furthermore, the main factors influencing the drag torque are the bias of plates in the low speed difference (0∼1000r/min) and the gap shrinkage in the medium and high speed difference (>1000r/min) respectively. From the comparison between test data and the simulation results obtained from the improved model, the average relative error is only 6.34% at medium and high speed difference (>1000r/min), which can greatly improve the accuracy for the estimation of the drag torque in wet multi-disk clutch.