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The hydraulic leveling system plays an important role in the crane load-bearing platform (Referred to as CBP). In recent years, a lot of work has been done to improve the performance of the leveling system. However, all these efforts are focused on control techniques and methods, while ignoring other comprehensive improvement options. This article takes the hydraulic legs subjected to the synchronous drive system of CBP (Referred to as CBP) as the research object, a set of hydraulic synchronous leveling system used for the valve-controlled cylinder was designed, and the mathematical model of transfer function for the valve-controlled cylinder and the theoretical solutions of main parameters in hydraulic oil circuit are obtained, then establish a mechanical model suitable for the attitude position of CBP. After that, a composite leveling strategy applied to the fuzzy PID (Proportional Integral Differential) synchronous leveling system with hydraulic legs driven synchronously was proposed, and a fuzzy PID controller was mapped out independently. Meanwhile, the above-designed sync-drive system coupling synchronous leveling process suitable for the CBP legs was carried out by AMESim and MATLAB/Simulink software. In addition, the correctness and robustness of the simulation model were verified by the leveling experiment, and the validity and reliability of the previously designed oil circuit scheme was proved. The results proposed in this paper improve the hydraulic leveling accuracy and response speed to optimize the performance of the hydraulic leveling system. [ABSTRACT FROM AUTHOR]

The decrease of stress amplitude is generally believed as the mechanism of fatigue life enhancement in interference fit joints under cyclic loading for each load cycle. In order to exactly estimate it, a new analytical model was presented. In this model, influences of mass, geometry, and plastic deformation are considered to modify and improve the spring model, and, moreover, the stress amplitude at the smallest crossing section is investigated. Taking these factors into account, stress amplitude decrease of various interference values can be calculated more accurately; therefore, the analytical solutions have good agreement with the finite element numerical and experimental results under different interference values and load levels. The analytical model indicates that the decrease ratio of stress amplitude is of a certain value for a specific interference value with the external load under the critical value. Furthermore, the decrease ratio of stress amplitude mainly depends on the stiffness of the pin and plate, which is mostly affected by the geometric shapes and plastic deformation ranges of the pin and plate. In addition, raising the interference value leads to larger stress amplitude reduction since the plastic deformation areas expand with the increment of interference values. [ABSTRACT FROM AUTHOR]

Highlights The electromagnetic force dynamic installation (DI) method of interference fit fasteners has significant advantages in improving the quality of the assembly interface of composite structure. This study aims to investigate how improving assembly interface quality may help in achieving high‐precision interference‐fit joints in composites. Single‐lap joint specimens were prepared using electromagnetic installation technique, the fatigue life and failure behaviors of the joints under different bolt‐hole clearances were measured and analyzed experimentally. In addition, a three‐dimensional finite element model was developed to predict the radial pre‐compression stresses around the hole and the progressive failure behavior of various typical damage modes in carbon fiber‐reinforced polymer induced by the interference. The results show that the critical interference range for the DI‐composite bolted structure is 1.0%–1.2%. The fatigue life of the best interference (1.0%) and the worst interference (0%, neat fit) have a difference of 36 times in amplitude. The residual stress with uniform distribution and high amplitude reduces the stress concentration of the hole wall and improves the failure evolution of the loaded hole. The contribution of this study provides vital guidance for improving the fatigue performance of CFRP bolted structures using a novel DI method. I = 1.0% is the critical damage‐enhancing interference size for dynamically installation interference fit bolts with electromagnetic forces. The residual stress amplitude introduced by the interference does not increase uniformly as the interference size increases. Excessive interference significantly reduces the uniformity and magnitude of residual stresses. Under subsequent cyclic loading, the fifth layer near the inlet and outlet of the extruded lower laminate appears to be the critical ply of extrusion deformation, and severe damage is concentrated in the critical ply of deformation. The decrease of stress amplitude and the variation of mean stress are the mechanisms of fatigue life enhancement in interference fit joints under external cyclic loading. [ABSTRACT FROM AUTHOR]