Applied Mechanics

Permanent magnet thrust bearings offer advantages such as non-contact operation, high-speed capability, and low noise, but their load-carrying performance is highly sensitive to magnet arrangement and geometric configuration. This study proposes a novel four-layer nested three-pole cross-type permanent magnet thrust bearing assembled from modular permanent magnet units. The bearing structure and magnetic circuit are first developed, followed by an axial force model based on the equivalent magnetic circuit method and a three-dimensional finite element model established in ANSYS Maxwell. The numerical model is further validated through experiments. Results show good agreement among theoretical, numerical, and experimental trends, confirming the reliability of the proposed modeling approach. Parametric analyses reveal that radial magnetization provides the highest load-carrying capacity, reaching approximately 16.8 kN. Among the investigated magnet geometries, trapezoidal magnets achieve the highest simulated load-carrying capacity, followed by fan-shaped and rectangular magnets. Under a fixed permanent magnet volume, the 6-layer × 15 mm axial stacking configuration and the 9-layer × 12 mm radial stacking configuration achieve the highest load-carrying capacities in their respective arrangements. These findings provide guidance for the structural optimization of multilayer permanent magnet thrust bearings.

To meet the requirements for a long buffering stroke and a stable load response within a limited installation space, this study investigates a guide-wheel-constrained plate-flow energy absorber (GPEA) that dissipates impact energy through repeated bending–straightening deformation of a steel plate. Quasi-static compression and drop-hammer impact tests were conducted. Under the investigated loading conditions, the experimental results showed that the No. 20 carbon-steel plate underwent stable and continuous bending–straightening deformation under the constraint of the guide wheels without fracture. After entering the stable deformation stage, the quasi-static load remained at approximately 9.3 kN, while the plateau force under impact loading was about 10 kN, with an effective crushing stroke of 145.5 mm. On this basis, a finite element model was established, and the predicted deformation mode and stable load response showed good agreement with the experimental results. Furthermore, an elastic–plastic bending model incorporating linear material hardening was developed to quantitatively describe the through-thickness stress–strain evolution, energy absorption, and mean force of the steel plate. For idealized frictionless single-cycle cases with plate thicknesses of 2 mm and 5 mm, the differences between the theoretical predictions and numerical results were 3.6% and 4.3%, respectively. The proposed theoretical model, derived from the elastic–plastic bending and straightening process, reveals the underlying mechanism of plastic deformation accumulation and continuous energy dissipation during repeated changes in plate curvature.

In plateau constant-pressure barracks, indoor pressure is maintained above outdoor pressure, placing window seals under a sustained pressure differential after installation pre-compression. This study develops a two-dimensional nonlinear contact model of a hollow D-shaped silicone rubber sealing strip, a pressure bead, and a mounting groove using the fluid pressure penetration method. A sequential pre-compression and pressure-differential loading procedure was applied to investigate the effects of fluid pressures of 5, 15 and 25 kPa and compression ratios (CRs) of 10%, 15%, 20% and 25% on contact behavior, while additional stress analyses were conducted at compression ratios of 10%, 20%, and 30%. Most investigated cases exhibit an asymmetric double-peak contact-pressure distribution, with a lower-pressure region between the two peaks, with lower pressure in the central region and higher peaks on both sides. Increasing fluid pressure redistributes the contact load toward the low-pressure side, whereas increasing compression strengthens interfacial constraint and reduces the sensitivity of the contact state to pressure variations. At a compression ratio of 25%, the contact-pressure curves under different fluid pressures show high consistency and stable peak positions. Within the investigated conditions, CR = 25% is recommended as a numerical reference for the representative straight section because of its favorable contact length and reduced peak-pressure sensitivity to a pressure differential. This recommendation concerns numerical contact characteristics and does not establish optimum airtightness or a minimum leakage rate.