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In this paper, 3D braided composites are considered for high-performance piezoelectric energy harvester designing, and a 3D braided composite piezoelectric energy harvester (3D BCPEH) is proposed. The advantage of 3D BCPEH is that the natural frequency of the device can be adjusted by adjusting the stiffness of the spring, making the natural frequency of the device close to the vibration frequency of the environment, thereby achieving the best harvesting effect of the energy harvester. During the vibration process, spring support can cushion the impact and stress on the piezoelectric energy harvester, thereby protecting the device from damage and helping to improve the stability and performance of the system. Finite element analysis is used to obtain the elastic modulus, shear modulus, and Poisson’s ratio of 3D braided composites with varying braiding angles. Based on Hamilton’s variational principle, the vibration control equation of the spring supported 3D BCPEH is derived. The effects of spring rate, braiding angle, external excitation acceleration, external load resistance, and structure size on the output response of 3D BCPEH are simulated and analyzed. The validity of the proposed 3D BCPEH with spring support is confirmed by the simulation results.

When the helicopter tail transmission shafting is over-critical, the shafting vibration intensifies, which restricts the overall performance of the helicopter. The smart spring support is an active damping device, which can effectively suppress the vibration of multi-span shafting. In this paper, the configuration and structural design of the smart spring support for multi-span shafting are studied, and its vibration damping performance is verified by experiments. Firstly, based on the vibration reduction principle of the smart spring support, the vibration characteristics of the smart spring are analyzed. The motion equation of the smart spring support was established, the influence of the configuration parameters on its vibration characteristics was analyzed, and the configuration parameters of the smart spring support were determined. On this basis, the configuration schemes of the smart spring support are proposed, the structural design of the smart spring support is carried out, and the structural parameters are determined. The shafting vibration reduction test system with the smart spring support was built, and the smart spring vibration damping tests were conducted under different control voltages. The results show that the smart spring support has a good suppression effect on the accelerated over-critical vibration response of the shaft system.

Vortex-induced vibration (VIV) in flexible cylinders typically exhibits the coexistence of several natural modes. In this work, we conduct a fundamental investigation of coupled VIV responses in a simplified scenario where rigid-body and flexible modes coexist. The experimental setup comprises a flexible cylinder of 0.7 m in length, with external diameter, aspect ratio, and mass ratio of D = 25 mm, L / D = 28 , and m ∗ ≈ 4.5 , respectively, which is vertically cantilevered from a one-degree-of-freedom leaf spring support, with natural frequency controlled by changing its spring stiffness. Through this assembly, it is possible to investigate the modal coexistence due to VIV when the natural frequency of the rigid body is properly calibrated to values close to the first two natural frequencies of the flexible cylinder. These conditions were investigated for a wide range of 20 reduced velocities. For measurement purposes, a motion capture system recorded rigid-body dynamics, while four inertial measurement units (IMUs) placed inside the flexible cylinder were used to record acceleration and rotational rate data during testing. A signal processing procedure has been developed and applied to transform accelerations into displacements along the flexible cylinder, which is a complete reference framework for the analysis of simultaneously excited VIV responses. In this sense, frequencies and nondimensional amplitudes are evaluated during the tests, obtained based on the application of Fourier and Hilbert–Huang transforms. These findings enrich VIV research by providing information that can improve the theoretical models currently used to predict coupled VIV responses, particularly regarding the interdependence between natural modes in relation to the reduced velocity that has excited them. The contribution is intentionally fundamental, offering clean benchmarks that stimulate an informed discussion of the topic.

The purpose of this study is to explore the influence of different spring support structures and hydrostatic recess areas on the characteristics of hybrid tilting pad bearings lubricated by high-pressure CO2 to promote the development of high-pressure CO2-lubricated bearings. A high-pressure CO2 hybrid tilting pad bearing experiment system was designed and built, and performance comparison experiments were carried out under various speed and load conditions. The performance differences of bearings with different spring support structures and hydrostatic recess areas under high-pressure CO2 lubrication were obtained. The results show that compared with the bearing structure, the bearing stiffness has a more significant effect on the bearing performance. The design of the bearing should consider the matching of stiffness and rotor dynamics.

Background Due to the large span of Mach, supersonic vehicles experience complex nonlinear factors. Considering the nonlinear aeroelastic problems in practical operation is vital for the safety design of new aircraft. Purpose This paper deals with the nonlinear flutter characteristics of a nonlinear spring supported variable-stiffness laminate panel in the supersonic airflow. Methods The nonlinear equations are obtained by applying Hamilton’s principles in the framework of the von-Karman’s nonlinear theory and the third-order piston aerodynamic theory. The time-domain dynamic response of the variable-stiffness composite panel is obtained through the fourth-order Runge–Kutta method. Results In the numerical illustration, the effects of several parameters such as the nonlinear aerodynamic force, nonlinear spring coefficients and support position, curved fiber angle orientation of the composite panel are studied. Conclusions From numerical results, it was concluded that the curved fiber composite panel incorporating spring-support could obviously change the limit cycle oscillation (LCO) response.

Conventional design method of the downhole tractor is based on cementing casing, which is only suitable for the smooth wellbore. For the open hole well, the conventional downhole tractor has poor adaptability and even cannot work normally. In order to improve the obstacle surmounting performance of the wheeled downhole tractor (WDR) and expand the application range of the WDR, a double push rod-double spring support adjustment mechanism (DPRDSSAM) is proposed in this paper. Meanwhile, the proposed DPRDSSAM also needs to increase the traction force and the stability of the WDR in the open hole well. Kinematic simulation numerical models of both conventional support adjustment mechanism and the DPRDSSAM are established. The two models comprehensively considere the influence of different obstacle forms and sizes on the obstacle surmounting performance of the tractor. The influence of different obstacle forms on the obstacle surmounting performance of DPRDSSAM and single push rod support adjustment mechanism (SPRSAM) is analyzed. Results show that the DPRDSSAM has better obstacle surmounting performance than the SPRSAM. The DPRDSSAM can effectively promote further research and application of the tractor in the open hole well.

In this study,a new approach of optimization algorithm is developed. The optimum distribution of elastic springs on which a cantilever Timoshenko beam is seated and minimization of the shear force on the support of the beam is investigated.The Fourier transform is applied to the beam vibration equation in the time domain and transfer function, independent from the external influence, is used to define the structural response. For all translational modes of the beam, the optimum locations and amounts of the springs are investigated so that the transfer function amplitude of the support shear force is minimized. The stiffness coefficients of the springs placed on the nodes of the beam divided into finite elements are considered as design variables. There is an active constraint on the sum of the spring coefficients taken as design variables and passive constraints on each of them as the upper and lower bounds. Optimality criteria are derived using the Lagrange Multipliers method. The gradient information required for solving the optimization problem is analytically derived. Verification of the new approach optimization algorithm was carried out by comparing the results presented in this paper with those ones from analysis of the model of the beam without springs, with springs with uniform stiffness and with optimal distribution of springs which support a cantilever beam to minimize the tip deflection of the beam found in the literature. The numerical results show that the presented method is effective in finding the optimum spring stiffness coefficients and location of springs for all translational modes.The proposed method can give designers an idea of how to support the cantilever beams under different harmonic vibrations.

A thorough examination of the use of the differential quadrature method has been presented, including an analysis of the weighting coefficient, several methods for implementing the boundary conditions, and the ultimate advantages it offers compared to other numerical techniques. The authors have detailed the technical techniques involved in this study, including the discretization of the computational domain, the generation of mass, damping, and stiffness matrices, and the subsequent partitioning of these matrices into submatrices. Exemplifications have been given for the differential quadrature (DQ) approaches that meet the clamped-spring support boundary requirement. This study on the principles of the differential quadrature technique will provide valuable insights for a research scholar, novice researcher, and academician in the field of computation.

The space nuclear reactor control rod mechanism plays a decisive role in the start-up and power regulation of the reactor, and it is related to the success or failure of the nuclear-powered aircraft. This paper designs and analyzes the control rod mechanism of the space nuclear reactor. The mechanism design includes the top compression release mechanism, the locking mechanism that ensures the critical safety of the reactor, the spring support mechanism and the driving mechanism. At the same time, the design effectiveness of the mechanism is analyzed, including modal and harmonic response analysis, thermal performance analysis, etc. The analysis results show that the natural frequency of the first 4th order of the safety rod mechanism is 67~138.45Hz; the harmonic response analysis frequency range is 5~100Hz. The harmonic response analysis is performed on the spring support mechanism, and the frequency-acceleration, frequency-displacement response curves of the rod body node were obtained. The results show that the amplitude dropped from 13.009mm to 1.46mm after adding the spring support mechanism, and the acceleration response dropped from 265.73m/s 2 to 349.59m/s 2 . The mechanism thermal analysis calculation results show that the temperature rise speed of the motor and rotary transformer are slower than that of the multi-layer, and the temperatures are the same at 11.1h, which meets the design indicators of the control rod working in place for 6~8h and temperature below 200 °C.

The paper focuses on developing a simple symmetric planar truss structure that could be effectively used to understand and study nonlinearities in large structures. A simple two-member truss model was defined and used for the study. A simple analytical model was derived using the theories of first and second order, which were then solved using the numerical formulations. To validate the model, an experimental setup was created and mounted on a tensile testing machine to apply required loads on the system. The results obtained from the test are used to validate the numerical model. Different parametric studies were conducted using the validated model to further understand the effects of the different variables on the model’s behaviour.