Objective Advanced equipment is the cornerstone of industrial modernization. New-energy vehicle manufacturing requires large servo presses to improve the quality and efficiency of automotive body stamping. However, the power fluctuation in such presses significantly increases grid capacity requirements. This study investigates the characteristics of power fluctuation in large servo presses with six-link mechanisms. Methods Based on the principle of the six-link transmission mechanism, the kinematic model of the transmission system of the press was established, and the motion relationships between the bars, slider, and crank were obtained. Specifically, the expressions for the load torque, inertia torque, load power, and inertia power transmitted to the main motor shaft were derived, considering the stamping load and system inertia. Finally, an analytical model for the output power of the main motor was obtained. Taking the 2 500 t servo press produced by Jinan No. 2 Machine Tool Factory as an example, the fluctuation law of the output power of the main motor of the press during the stamping cycle and the cause of the peak power were analyzed by combining the analytical model and experimental data. Results The established power analytical model can effectively capture the power fluctuation characteristics of a large servo press with a six-bar linkage. The main factors affecting the inertia power are the inertia and acceleration of the main transmission system of the press. Conversely, the main factors affecting the load power are the load applied to the slider and its speed. During the slider movement from the upper dead point to the starting point of the workpiece drawing, the inertia power initially increased and then decreased; the load power increased rapidly when the drawing pad started to operate. In the deep drawing stage of the workpiece, the inertia power fluctuated around zero, but the load power increased. During the upward movement of the slider from the bottom dead point, the inertia power initially decreased and then increased; the load power gradually decreased. The largest power peak was observed when the drawing pad started to operate, and the slider just crossed the bottom dead point; this is attributed to the speed fluctuations at both phases. When the drawing pad started to operate, speed fluctuation was caused by the rapid load increase, leading to a large positive power peak; when the slider just crossed the bottom dead point, speed fluctuation was caused by the change in the load direction, resulting in a large negative power peak. Conclusions To reduce the impact of power fluctuations in servo presses on the grid side, it is necessary to reduce the load impact when the drawing pad starts to operate, and the slider just crosses the bottom dead point. When the hydraulic drawing pad starts to operate, the speed difference when it contacts the slider can be reduced by optimizing the motion control algorithm of the drawing pad. The load impact when the slider crosses the lower dead point can be suppressed by reducing the link clearance of the transmission system.

This paper aims to quantify the nonlinear characteristics of quasi-zero stiffness (QZS) cruciform maglev isolators (CMI), including maglev forces, stiffness and vibration transmission. A multi-degree-of-freedom analytical model of CMI was built based on equivalent charge theory. The changes of maglev force and stiffness with vibration displacements, magnet geometry parameters and air gap were analyzed by using the model. The vibration transmission characteristics of CMI were quantitatively evaluated by applying an experiment-based method based on Volterra series and conditioned spectral analyses (CSA). It was revealed that vibration displacements have distinct nonlinear effects on the maglev forces and stiffness of CMI in both vertical and horizontal directions, and the effects are intercoupled with each other. For instance, the magnitude of vertical maglev force changes up to 12.17 x when y=4 mm, but only 1.16 y=2 mm. The sizes of magnets and air gap also have nonlinear influences on vertical maglev forces. However, the QZS property of CMI is robust to the geometric variations at the equilibrium point. The different order nonlinear vibration frequency responses of CMI were successfully identified under the conditions of random excitations in both vertical and horizontal directions. The maglev forces and stiffness of CMI are distinctly influenced by vibration displacements, magnet geometry parameters and air gap. Most of the influences are nonlinear and intercoupled, leading to the CMI having nonlinear vibration transmission characteristics, which can be identified by using the method of Volterra series combined with CSA.

Laser additive manufacturing offers significant advantages for fabricating and repairing complex components. However, the complex solidification and remelting processes in nickel-based superalloys for additive manufacturing can introduce defects such as voids and cracks. Therefore, process parameters are crucial, as they significantly impact solidification and remelting, thereby affecting defect formation. In this study, laser-directed energy deposition was employed to evaluate the effects of our key process parameters on the formation of voids and cracks in a novel superalloy. The findings reveal that laser power and linear energy density significantly influence the void content and crack density. However, the influence of other process parameters on defect formation is relatively minimal. The optimal parameter space is characterized by a laser power range of 600~700 W, a linear energy density range of 60~90 J/mm and a powder feeding rate of 0.7~0.8 rpm. Moreover, the precipitation of fine MC-type carbides near the dendrites and grain-boundary misorientations within the range of 31~42° are associated with a higher propensity for crack formation. These insights provide a valuable reference for controlling the process parameters and understanding the cracking mechanisms in laser additive manufacturing of superalloys.

This article takes the active isolation platform voice coil motor actuator as the research object, designs a dual permanent magnet opposed excitation voice coil motor, designs the structural dimensions of the motor stator and mover, calculates the output thrust, simulates and optimizes the distribution of eddy currents generated during the motion of the voice coil motor mover, and finally compares the isolation performance of the isolation table before and after the mover optimization to determine the feasibility of the scheme.

This paper focuses on the issue of quantifying nonlinear output frequency response components of different orders of nonlinear dynamical systems for a general excitation. An alternative approach is presented based on Volterra series and conditioned spectral analysis (CSA) theories. Firstly, a multiple-input/single-output (MISO) linear system with a series of power characterized inputs is obtained by decomposing the nonlinear system under analyzed based on Volterra series. Secondly, the correlations among the inputs of different orders are removed by utilizing CSA approach, obtaining an algorithm of identifying the nonlinear output frequency response functions (NOFRFs) and evaluating the contributions of different order nonlinearities to the output of the system. Two kinds of nonlinear systems were simulated numerically to verify the accuracy of the method. The results reached by the proposed method are very close to the numerical results obtained by the fourth order Runge–Kutta method. Finally, an experiment analysis was carried out, in which the vibration transmission properties of a bolt connection were tested when the bolt was fastened and loose respectively. The results of experiments reflected further the effectiveness of the method on distinguishing quantitatively the contributions of each order nonlinearities to the output of a nonlinear system.

This paper focuses on the issue of nonlinear vibration responses identification of nonlinear systems. An efficient algorithm is presented, in which the nonlinear vibration system under studied is decomposed into a multiple-input/single-output (MISO) linear system with a series of power characterized inputs based on Volterra series, and the nonlinear output responses of different orders are identified by taking power spectra operation to the input and output data, revealing the contributions of each order nonlinearity to the output of the system. Compared to the existing method, the input signal of the system required in the presented approach need not remain unchanged in waveform and adjustable in magnitude. To verify the approach, a classic Duffing-Van der Pol oscillator was simulated, obtaining results very close to the fourth order Runge-Kutta method. Finally, an experiment analysis was carried out, in which the vibration transmission properties of a bolt connection were tested when the bolt was tight and loose, respectively. The results proved that the approach is effective in identifying nonlinear vibration frequency responses.

This paper aims to study the maglev force and vibration attenuation characteristics of quasi-zero stiffness cruciform maglev isolators (CMIs). The maglev force and stiffness of CMIs were analytically computed based on equivalent charge theory, and the transfer function of the system was conducted. The effects of magnet geometry parameters and air gap on the maglev force, stiffness, and vibration transmission characteristics of the CMI system were revealed through parametric analyses. With the increase in magnet length and width, the maximum value of maglev force increases, but the displacement range of near-zero stiffness, amplitude, and phase of the system gradually decrease. With the increase in magnet height, the displacement range of near-zero stiffness increases, while the variation in the amplitude and phase of the system has minimal impact. Meanwhile, in the Halbach array, the height variation of the magnet at different positions has different impacts on the magnetic force. As the air gap increases, the maximum value of maglev force decreases, but the amplitude and phase gradually increase, and the displacement range of near-zero stiffness first rises and then decreases. Finally, an experimental study was carried out to test the vibration attenuation characteristics of CMIs, in which sinusoidal excitation, hammer strike excitation, and random excitation were applied.

Passive vibration isolation systems are widely employed in high-precision instruments to ensure the stability of their operational environment. First, a theoretical model of the six-degree-of-freedom passive vibration isolation system is established based on the principles of rigid body dynamics. The modal decoupling of the free vibrations in the six-degree-offreedom system is analyzed, and MATLAB simulations are conducted to obtain the six mode shapes and the time-domain response of the displacement for each of the six degrees of freedom. Secondly, the dynamic characteristics of the passive vibration isolation system are analyzed under various key parameters, providing a theoretical basis for the design and optimization of active vibration control.

Coated particle-dispersed fuel pellets have the characteristics of high thermal conductivity and multilayer protection against fission products, which are an important component of ATF fuel. In this paper, by carrying out research on the dressing process of TRISO particles, it is realized that SiC powder completely encapsulates TRISO particles. The hot-pressing sintering method was used to study the influence of different sintering aids, different hot-pressing sintering holding time, different hot-pressing sintering temperature, different hot-pressing sintering pressure and different powder particle size on the density of pellets. The power with a particle size of 10nm is sintered at 3

This paper focuses on the issue of evaluating nonlinear frequency response functions (NOFRFs) of the nonlinear systems with a general input. A new digital approach of evaluating NOFRFs is proposed based on the method of conditioned spectral analysis (CSA). Firstly, a multiple-input/single-output (MISO) linear system with a series of power characterized inputs is obtained by decomposing a nonlinear system according to the NOFRFs theory. Secondly, the correlations among the inputs of various orders are removed by applying CSA method, obtaining an algorithm of identifying the NOFRFs and evaluating the contributions of different order nonlinearities to the output of the system. In the CSA procedure, the different order inputs are conditioned in the sequence from the first order to the highest order. Lastly, two kinds of nonlinear systems with a general input are simulated to verify the effectiveness of the proposed approach on evaluating the frequency response properties of nonlinear systems. It is shown that the results reached by the proposed method are very close to the numerical results obtained by the fourth order Runge-Kutta method, verifying that the proposed method is very effective on the evaluation of NOFRFs.

This paper presents a new method of postweld treatment. The 5154 aluminum alloy was cleaned by Nd:YAG laser after welding. The surface morphology, energy spectrum, friction and wear properties, hardness, and residual stress of the welded joint at different cleaning speeds were studied. The results show that an Nd:YAG laser can effectively remove the welding slag and eliminate the pores in the weld under a certain cleaning speed. When the cleaning speed is in the range of 5.2-20.7 mm/s, laser cleaning can improve the heat-affected zone's tribological characteristics. Laser cleaning can eliminate the residual stress of the welded joint and improve the welding joint's strength, which provides a reference for laser cleaning instead of traditional heat treatment.

Improving the property of coating is the focus of current marine protection research. In this paper, the Zn-Al-Mg-TiO2 and ZnAl coatings were prepared by cold spraying. The wear, electrochemical experiment and methyl blue degradation tests were carried out to study the tribological, anticorrosive and antifouling properties of coatings. The microstructure, composition, and wear scar of coatings were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and white-light interferometer. The results showed that the wear mechanism of the Zn-Al-Mg-TiO2 coating was mainly abrasive wear, and the wear property of the Zn-Al-Mg-TiO2 coating was better than ZnAl coating. Compared with the ZnAl coating, Zn-Al-Mg-TiO2 coating had lower corrosion current density. In addition, the Zn-Al-Mg-TiO2 coating can rapidly degrade methyl blue in a UV-rich environment, but ZnAl coating did not.

According to research, we have learned that Mg and TiO2 are new types material of 12 marine protective coatings. We found that the addition of Mg can improve the performance of 13 Zn-Al coating passivation film, and TiO2 has excellent photocatalytic self-cleaning performance. In 14 this paper Zn-Al pseudo alloy coating was prepared by cold spray technique, and Zn-Al-Mg-TiO2 15 pseudo alloy composite coating was prepared by adding Mg and nano-TiO2. The effects of Mg and 16 TiO2 to the marine protective properties of Zn-Al coatings were studied by friction and wear test, 17 dynamic salt water corrosion test, electrochemical test, scanning electron microscope(SEM), energy 18 dispersive spectrometer(EDS) and super deep scene 3D microscope. The results show that the 19 addition of Mg and nano-TiO2 not only fills the gap of the coating and improves the density of the 20 coating, but also generates grid-like flocculent corrosion products on the surface of the coating 21 which can gather other corrosion products to improve the density of corrosion products, reduce the 22 friction coefficient and corrosion rate of the coating surface, effectively prevent the invasion of Clin 23 solution, and improve the wear and corrosion resistance of the coating. 24

TiO2 nanotube coatings with different structures were prepared on bone plate surface by anodic oxidation at different voltages or time and in an ethylene glycol solution containing 0.3 wt% ammonium fluoride (NH4F) and 2 vol% deionized water. Subsequently, the morphology, elemental composition, crystalline structure, surface roughness, microhardness, contact angle, adhesion force, corrosion resistance and wear resistance of the as prepared coatings were characterized. At the optimized oxidation voltage of 60 V in microstructural, biocompatibility and properties of coatings considerations, the prolonged oxidation within a certain range led to increasing nanotube thickness and inner diameter, which further improved the properties of TiO2 nanotube coating samples. Specifically, surface roughness and adhesion force of the coatings increased progressively, the maximum adhesion force was (12.10 +/- 0.50) N, while their contact angle and microhardness decreased gradually. Moreover, the coatings also exhibited the enhanced corrosion resistance in simulated body fluid (SBF), with the corrosion potential or the corrosion current increased by 56.91% or decreased by 79.45% to the largest extent. During dry friction, both friction coefficient and wear groove depth declined, corresponding reduction rates up to 22.52% and 49.01% evidenced the improved wear resistance. Besides, the major wear mechanism of the coating was a combination of abrasive and adhesive wear. Accordingly, the voltage of oxidation at 60 V and the oxidation time of 6 h were determined as the optimum processing parameters for preparing TiO2 nanotube coating on the bone plate surface, and the nanotube inner diameter and coating thickness were (118 +/- 3.5) nm and (34 +/- 2.8) mu m, respectively. The novelties of the present study are: 1. A uniform and neat TiO2 nanotube coatings were fabricated using the anodic oxidation method. The effects of oxidation voltage and oxidation time on the microstructure of TiO2 nanotube array were further examined, and the relationship between oxidation parameters and coating morphology was concluded. On that basis, the changes in the structural parameters of TiO2 nanotube coatings under other oxidation parameters can be inferred. 2. The morphology, elemental composition, crystalline structure, surface roughness, microhardness, contact angle, adhesion force, corrosion resistance and wear resistance of TiO2 nanotube coatings were systematically studied, and the relationship between roughness and hydrophilicity of the coatings was discussed. 3. The wear process of anodized TiO2 nanotube coatings under dry friction conditions was explained according to the friction coefficient curves, and the wear mechanism of the coating was clarified based on the wear morphology and the energy spectrum analysis of the coatings. 4. The optimum oxidation voltage and oxidation time for preparing of TiO2 nanotube coating on the bone plate surface by anodization were determined as 60 V and 6 h, respectively, when the electrolyte was an ethylene glycol solution containing 0.3 wt% NH4F and 2 vol% deionized water.

According to research, we have learned that Mg and TiO2 are new types material of marine protective coatings. We found that the addition of Mg can improve the performance of Zn-Al coating passivation film, and TiO2 has excellent photocatalytic self-cleaning performance. In this paper Zn-Al pseudo alloy coating was prepared by cold spray technique, and Zn-Al-Mg-TiO2 pseudo alloy composite coating was prepared by adding Mg and nano-TiO2. The effects of Mg and TiO2 to the marine protective properties of Zn-Al coatings were studied by friction and wear test, dynamic salt water corrosion test, electrochemical test, scanning electron microscope(SEM), energy dispersive spectrometer(EDS) and super deep scene 3D microscope. The results show that the addition of Mg and nano-TiO2 not only fills the gap of the coating and improves the density of the coating, but also generates grid-like flocculent corrosion products on the surface of the coating which can gather other corrosion products to improve the density of corrosion products, reduce the friction coefficient and corrosion rate of the coating surface, effectively prevent the invasion of Cl- in solution, and improve the wear and corrosion resistance of the coating.

The influences of different laser power density in LSP (laser shock peening) on the corrosion performance of biocompatible magnesium alloy ZK60 were researched via SBF (Simulated Body Fliud) immersion testing and electrochemical testing. Corrosion morphology and corrosion products were observed and analyzed using SEM (Scanning Electron Microscope) outfitted with EDS (Energy Dispersive Spectrometer) and XRD (X-ray Diffraction). Simultaneously, 3D morphology, surface roughness, residual stress, and microstructure were also characterized. Results reveal that the modified samples can obtain higher residual compressive stress, which can lead to lower degradation rates in SBF solution. In terms of the weight loss of the samples, corrosion resistance increased by 52.1% maximally. The corrosion potential of modified samples in the SBF solution positively shifted from −1.3884 V to −1.1094 V and the corrosion current density decreased by 13.2% at most. The anti-corrosion ability of ZK60 is significantly enhanced by the LSP process.

To enhance the mechanical properties and corrosion resistance of magnesium alloys, high-energy shot peening (HESP) was used. According to the results, the in-situ surface nanocrystallization (ISNC) microstructure was fabricated on the magnesium alloy surface, and its formation mechanism was the coordination among twins, dislocations, subgrain boundary formation and dynamic recrystallization. Under the released surface stress of sample, the residual compressive stress and microhardness rose, thus enhancing compactness of the surface passivation film Mg(OH)2. Besides, the corrosion rate dropped by 29.2% in maximum. In the polarization curve, the maximum positive shift of the corrosion potential of sample was 203 mV, and the corrosion current density decreased by 31.25% in maximum. Moreover, the compression resistance and bending resistance of the bone plate were enhanced, and the maximum improvement rates were 18.2% and 23.1%, respectively. Accordingly, HESP significantly enhanced mechanical properties and corrosion resistance of magnesium alloys.

According to research, we have learned that zinc has excellent cathodic protection performance, that the corrosion products of aluminum and magnesium can form dense and stable passivation films to protect internal materials of coatings, and that TiO2 has excellent photocatalytic self-cleaning performance which will form a physical adsorption film on the surface to isolate the external corrosion solution. In this paper, a Zn-Al-Mg-TiO2 pseudo alloy coating was prepared by cold spray technique on a Q235 substrate. The protective performance of Zn-Al-Mg-TiO2 for marine metal equipment was studied using dynamic salt water corrosion testing, electrochemical testing, and friction and wear testing. The microstructure, composition, and wear marks of coatings were observed using a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and white-light interferometer. The results show that the Zn-Al-Mg-TiO2 coating has excellent corrosion and wear resistance, which can provide long-term and stable protection for the substrate.

The surface of the aluminum alloy is prone to oxidation, which in turn affects the quality of the weld. The 5A12 aluminum alloy was cleaned by acousto-optic Q-switched diode-pumped Nd:YAG laser and the effects of different laser powers and different cleaning speeds on the surface roughness, microstructure, element content, microhardness, residual stress and corrosion resistance of aluminum alloy were investigated. The results show that when the power is 98W and the cleaning speed is 4.1 mm/s, the effect of Nd: YAG laser on the removal of oxide film on 5A12 aluminum alloy surface is the most effective. After laser cleaning, the smoothness and strength of aluminum alloy surface can be effectively improved. However, as a major element in 5A12 aluminum alloy, the content of magnesium decreased. At the same time, the residual tensile stress was generated on the surface of the aluminum alloy after cleaning, and the corrosion resistance slightly decreased.

The influence of laser shock peening (LSP) on tribological properties of magnesium alloy ZK60 was investigated adopting different laser power density. Surface wear morphology, elemental composition and content in wear debris were observed and analyzed using SEM and EDS. Meanwhile, surface roughness, profiles, microhardness, and microstructure were also characterized. It was proven that the roughness increased from 0.32 mu m to 9.3 mu m, microhardness improved by 39%, the number of grains augmented from 1045 to 1461, and wear rate decreased by 17.6% in maximum. Adhesive wear and oxidation wear were the main mechanisms of the original sample, and the wear mechanism of modified specimens was dominated by abrasive wear. In conclusion, LSP can improve wear resistance under the higher normal force.