Internal leakage caused by seal wear is one of the most common faults in hydraulic cylinders, and the timely diagnosis of seal wear and internal leakage is crucial for ensuring the reliable operation of hydraulic systems. Therefore, a diagnostic method based on multi-sensor, multi-level information fusion is proposed in this paper. First, an improved wavelet threshold denoising method based on ensemble empirical mode decomposition (IWTD-EEMD) is used to denoise and preprocess multi-sensor signals, which makes fault features more obvious. Secondly, statistical features are extracted from the preprocessed signals to form the original feature set. Then, the coupled feature selection method combining the distance evaluation technique (DET) and max-correlation min-redundancy (mRMR) is used to optimize the original feature set, forming the optimal feature subset to achieve feature-level information fusion. Finally, decision-level fusion diagnosis is performed based on a convolutional neural network (CNN) and Dempster–Shafer (D-S) evidence theory. The experiments are conducted under five load conditions, and the proposed method achieves a diagnostic accuracy of 99.26%. Compared with SVM, BPNN, and DBN models, the proposed method demonstrates superior performance in identifying seal wear states, indicating that it can effectively determine the severity of seal wear. However, this study relies on a limited experimental dataset and does not directly measure actual leakage flow rates. Further validation on independent seals and unseen operating conditions is required before practical application.
Reliable identification of drill-string–wellbore friction is important for evaluating mechanical load transfer and contact behavior during drilling. However, friction estimation from surface hook-load measurements can be affected by non-frictional contributions from the hoisting system and drilling-fluid-induced forces. This study develops a multi-physics hook-load correction framework incorporating sheave efficiency, traveling-block and hook weight, mud-hose catenary force, drilling-line weight, annular and internal viscous forces, swab/surge effects, and pump-on hydraulic lift. Field data from a 3500 m directional well were analyzed using a yield-power-law (YPL)/Herschel–Bulkley fluid model. For representative slide- and rotary-drilling intervals, measured average hook loads of 442.21 and 481.01 kN were corrected to 294.92 and 332.89 kN, corresponding to correction ratios of 33.31% and 30.79%. Corrected off-bottom hook loads were then used to identify state-dependent effective drill-string–wellbore friction factors of 0.180, 0.154, and 0.104 at three calibration states. These factors were transferred to subsequent drilling intervals for surface-torque reconstruction. After one-point baseline alignment, the remaining torque samples yielded mean relative reconstruction errors of 2.28%, 4.22%, and 3.21%, respectively. Removing these non-frictional contributions allows the effective drill-string–wellbore friction factor to be identified from a corrected surface load and subsequently compared with the measured torque response.
High-elastic seals with a D-shaped cross-section are extensively used in engineering assemblies, yet the quantitative relationship between their sealing capability and the governing material and dimensional factors remains insufficiently understood. Clarifying these factors is of considerable practical significance, as it supports reliable design and broadens the applicability of such components. In this work, a planar finite element model discretized with a highly refined mesh is established, in which the D-section seal is idealized as a Mooney–Rivlin hyperelastic material. The evolution of the von Mises stress field throughout the seal body during the downward travel of the indenter is adopted as the evaluation metric, permitting a quantitative assessment of sealing performance with respect to both material formulation and cross-sectional dimensions. Relative to the unfilled matrix, the mean peak stresses of the filled NR, VMQ, NBR and EPDM compounds are amplified by factors of 2.09, 2.22, 1.33 and 1.71, respectively; their carbon-fiber-reinforced counterparts exhibit a further increase to 5.46, 2.42, 3.13 and 9.59 times. A sensitivity hierarchy of the geometric variables is subsequently established, ranked in descending order of influence as the crest arc radius R1, the rigid indenter radius R0, the seal thickness a, the transition fillet radius R2, the bond length L and the clearance to the side wall S. The trends identified here elucidate the underlying deformation and contact mechanisms, thereby providing a quantitative foundation for the further application-specific design of D-section rubber seals.
Squeeze-Film Dampers (SFDs), with their fixed structural parameters, can easily induce detrimental nonlinear dynamic behaviors, resulting in rotor instability and fatigue damage. This paper proposes a novel partitioned oil film control method to adjust oil film stiffness and damping, thereby reducing the nonlinear vibration level of the rotor. The SFD is designed with an outer ring comprising three independently adjustable bearing pads (referred to as SSFD). The radial position of each pad is controlled by a piezoelectric actuator (PZT), enabling localized regulation of oil film clearance in different circumferential regions. This study involved developing a dynamic model of the SSFD-rotor system, which was experimentally validated. Through analysis of oil film pressure and force, we revealed the controllable mechanical properties of the SSFD. The nonlinear dynamics were thoroughly investigated. The proposed partitioned control method proved superior to the SFD, demonstrating a significant reduction in system nonlinear vibrations.
Wheel polygonization and rail corrugation are typical forms of periodic wheel-rail surface damage occurring on metro vehicles. Their interaction produces coupled dynamic excitation that modifies wheel–rail contact behavior under wet, low-adhesion conditions. This paper develops a wheel–rail dynamic adhesion model integrating vehicle–track dynamics, mixed elastohydrodynamic lubrication, and extended creep force theory. Using measured wheel polygonization and sinusoidal rail corrugation as inputs, the model solves the 3D contact geometry via coordinate transformation and analyzes how their coupling affects normal force, tangential force, and the dynamic adhesion coefficient. Results show that low-amplitude polygonization and corrugation mainly excite dynamic load oscillations, with a limited effect on peak contact stress. Yaw angle changes contact point migration and contact patch morphology, causing non-monotonic variations in tangential stress and flash temperature; at zero yaw angle, the adhesion coefficient approaches typical wet-condition levels. Under coupled excitation from measured multi-order polygonization and short-wavelength corrugation, the normal dynamic force fluctuates sharply, frequently causing local transient separation and low-adhesion events, with an average adhesion coefficient of about 0.06. Dynamic adhesion is jointly governed by the load-carrying effect of the water film, the proportion of asperity contact, flash temperature, and the elastoplastic behavior of third-body materials.
