This work presents a nonlinear dynamic model considering the multi-tooth meshing behaviour and mass eccentricity of an involute spline coupling to tackle the serious problem of involute spline failure, in aviation power transmission systems. The dynamic meshing force is calculated for the same. Based on this, the influence of different mass eccentricities on the nonlinear dynamic response of the spline coupling was investigated in aero-engines. The results show that when the mass eccentricity is small, its impact on the system is insignificant. When the eccentricity reaches a certain value, the quasi-periodic and chaotic state appears alternately. Meanwhile, it can be concluded that the acceleration-frequency spectrum during the multi-periodic phase is an approximation of the working frequency with the accuracy affected by multiple teeth engagements. This was validated by the vibration experiments of the involute spline coupling. The proposed model, which considers the multi-tooth meshing behaviour and the mass eccentricity provides a reference model for the dynamic analysis of similar structures. The nonlinear dynamic response results attained lay a good theoretical foundation for fretting damage analysis and precise designs for involute spline couplings.
Most of the time, mass eccentricity, and misalignment exist at the same time with aviation spline coupling working. Therefore, in this paper, the function of dynamic meshing force between multi-teeth and a non-linear dynamic model of involute spline coupling system in aero-engine with mass eccentricity and misalignment were presented. And then, the non-linear dynamic meshing force of spline coupling in aero-engine on different misalignment and mass eccentricity was investigated. The result shows that when the mass eccentricity and the misalignment are both small, the aviation involute spline coupling can run steady. And with the increase of mass eccentricity or misalignment, the dynamic load coefficient of the aviation involute spline coupling gradually increase. At the same time, as the mass eccentricity or misalignment increases, some teeth suffer more load, some teeth suffer less load, and some teeth are out of engagement so that they do not suffer any load. The running state of spline coupling becomes more and more unstable.
This work studies the tooth surface wear of floating involute spline couplings. Based on the energy dissipation method, this study takes the floating involute spline couplings as the research object, divides the whole wear cycle into three wear stages and analyzes its wear mechanism, and proposes a wear prediction model suitable for floating involute spline couplings. By using Abaqus, the simulation of the involute spline couplings before and after carburizing was carried out when the floating distance was 0 mm, 0.3 mm and 0.6 mm, respectively. The wear depth of each tooth was compared and analyzed, and the axial and radial distributions of the wear on the tooth surface of the involute spline couplings were explored. Finally, the floating involute spline couplings test bench was used to verify the spline wear before and after carburizing. The results show that with the increase in floating distance, the wear of the tooth surface also increases, and the upper edge of the tooth surface is seriously worn. Through the comparative analysis of the spline tooth surface wear before and after carburizing treatment, it can be seen that carburizing treatment can effectively reduce the wear degree of the spline couplings tooth surface and improve the service life of the spline couplings, but at a high floating distance, carburizing treatment has no significant effect on improving the performance of the tooth surface.
To investigate the fretting wear of involute spline couplings in aerospace, rack-plane spline couplings rather than the conventional involute spline couplings in aerospace were used to conduct tribological experiments, and it was assumed that the rack-plane spline couplings exhibit consistent contact stress with the real involute spline couplings in aerospace. The relationships among the static friction coefficient, dynamic friction coefficient, and fretting friction coefficient were established via tribological experiments, as well as the fretting-wear mechanism of the rack-plane spline couplings was examined. A fretting-wear estimation model based on the fretting-wear mechanism was developed. By applying the modified Archard equation and Arbitrary Lagrangian–Eulerian adaptive, mesh smoothing algorithm of Abacus was used. According to our experimental results, the fretting wear of the rack-plane spline couplings consisted primarily of abrasive wear, oxidative wear, and adhesive wear. For both, lubrication and non-lubrication settings, the fretting friction coefficient of 18CrNi4A steel (0.27) fluctuated between 0.12 (dynamic friction coefficient) and 0.35 (static friction coefficient). The fretting-wear results estimated via numerical prediction were consistent with the experimental results. When sm (vibration amplitude) was 20, 35, and 50 µm, the most difference in the fretting wear between the experimental results and numerical estimation was 0.001, 0.0007, and 0.001 mm, respectively. Therefore, the proposed model provides a method for accurate estimation of the fretting-wear. Additionally, the model contributes to the precise design of involute spline couplings in aerospace.
Based on the research on the wear mechanism of floating involute spline coupling, combined with the traditional Archard wear equation, a wear prediction model of aviation floating involute spline coupling was established. The transient simulation of spline coupling with floating distances of 0 mm, 0.3 mm, and 0.6 mm was carried out using Abaqus, and the accuracy of the theoretical model was verified by analyzing the wear and failure parts of the spline coupling. The analysis results show that there is oxidation wear, adhesive wear, abrasive wear, and other wear forms on the tooth surface of the aviation floating involute spline coupling. Under the influence of the floating distance of the spline coupling, the calculation results are closer to the actual working situations. In addition, with increasing floating distance, the wear depth of the tooth surface increases significantly, and the wear depth becomes larger and larger along the floating end. The above study provides a theoretical basis for designing and maintaining aerospace involute spline couplings.
For injection mold with core, during the injection molding process, the pressure on the core
is usually uneven and will cause the core to deform. In this paper, on the basis of some predigestions
and assumptions of the model, formulas for forecasting the deformation of the circular cross-section
and the rectangular cross-section cores under three different injection ways are analyzed. The
theoretical analysis results of a core with special section are validated through finite element software.
At the end, some suggestions are given to minish the core deformation when the calculation value is
too large.
A controlled foam injection (CFI) method has been developed, tested and demonstrated to have capabilities to fracture and strip reinforced concrete structures such as pavements and bridge decks. The method uses a high-pressure foam to initiate and propagate fractures in concrete structures. In contrast to methods using explosives to fracture and break concrete or rock, the CFI method does not generate ground vibrations or airblast. The foam components are biodegradable and environmentally benign. The CFI method can be used for demolition work or the repair and rehabilitation of degraded concrete structures.
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