In order to explore the relationship between lapping process parameters and surface machining quality, to solve the problem of active calculation of micro-topography of the gear lapping surface, a method for predicting the micro-topography of hypoid gear lapping surfaces is proposed. Firstly, the meshing motion model of hypoid gears is established and tooth contact analysis is carried out. On the basis of comprehensive consideration of the characteristics of the gear lapping process and surface generation laws by lapping fluid, the formula for the cutting depth of the lapping abrasive particles is derived. Then, material removal calculations are performed on the initial profile to predict the height parameters of the tooth surface after lapping. The predicted results are then subjected to surface reconstruction using the Fast Fourier Transform method, and a micro-topography prediction model for the lapping surface considering initial workpiece topography and random wear mechanisms is established. By comparing with the lapping test results of the main reducer gear of a certain automobile drive axle, it is proven that this model can effectively predict the micro-topography of the hypoid gear lapping surface. Finally, different combinations of lapping process parameters are designed to discuss their influence on surface roughness variations.

A functional beamforming(FB) method is proposed for identifying the natural frequencies of rotating blades from under-sampled blade tip timing(BTT) signals. Compared with the conventional subspace method, the proposed FB method eliminates the need for pre-estimating the number of frequencies, which makes it more valuable for application in practical scenarios. From the perspective of conventional beamforming(CB), the point spread function(PSF) of frequency in the spectrum is derived, and the contribution of the frequency components in the spectrum to the CB output is obtained. Further, combining the properties of the PSF of frequency, the concept of exponent is introduced into the cross-correlation matrix and output of the CB, the aliasing components in the spectrum are suppressed, and the output of the FB is constructed. The effectiveness and superiority of the proposed FB method are verified by numerical simulation and rotating blade disc experiments. The results show that the proposed FB method can effectively suppress spectral aliasing and identify the target frequency. At a signal-to-noise ratio of 5 dB, the proposed method can achieve a 100% identification success rate in the given numerical examples; in the rotating blade disc experiment, the absolute errors for identifying two-order natural frequencies of the blade do not exceed 1 Hz.

Monitoring composite fatigue damage is of great significance to ensure the safety of composite structures, for this reason, a composite fatigue damage monitoring method based on the combination of ultrasonic guided wave and machine learning model is proposed, aiming to improve the accuracy of damage identification. The method firstly screens out the ultrasonic guided wave signal features that are greatly affected by fatigue damage, then carries out covariance analysis to reduce the redundancy of the feature matrix, and preprocesses it to form a sample library. Subsequently, the signal feature matrix is used as the input, and the damage features are used as the output to construct a convolutional neural network(CNN) damage prediction model. This model is then combined with the bayesian optimization(BO) to adjust the hyperparameters of the model. Ultimately, the sample library is randomly divided into training set, validation set and test set according to the ratio of 8∶1∶1, using the validation set for hyper-parameter selection and the test set for model evaluation. The experimental results show that the constructed BO-CNN damage prediction model has better damage diagnosis capability relative to the CNN damage prediction model, the quantization accuracy is improved from 0.94 to 0.98, and the damage regression prediction task shows higher reliability.

Low carbon martensitic stainless steel is widely used in water conservancy and hydropower, petrochemical and other fields due to its excellent corrosion resistance and comprehensive mechanical properties. As a common joining method, welding is indispensable in the application of martensitic stainless steel. However, the problem of insufficient toughness of weld metal restricts the further application of martensitic stainless steel. Therefore, improving the toughness of weld metal is of great significance for the application of martensitic stainless steel. Based on the relevant research results in recent years, the influencing factors and toughening mechanisms of martensitic stainless steel were systematically summarized, including retained austenite, reversed austenite, δ ferrite, grain refinement and inclusions. The controlling methods of toughness of martensitic stainless steel weld metal are reviewed, such as alloy element controlling, welding process optimization, weld deoxidation and post-weld heat treatment. At the same time, the abnormal phenomena of impact fracture of martensitic stainless steel weld metal are summarized. Suggestions and prospects for follow-up research are put forward.

Investigated the effect of submerged abrasive water jet peening (SAWJP) on the low-cycle fatigue properties of Inconel 690 material. The Inconel 690 specimens were surface strengthened by abrasive water jet peening, and low-cycle fatigue tests under strain control were carried out before and after strengthening. Internal stress partitioning was performed using Matlab programs to analyze the influence of water jet strengthening on the evolution of internal stress. Additionally, the fatigue crack propagation patterns of the alloy during the fatigue tests were examined using a scanning electron microscope (SEM). The results indicate that the surface and subsurface hardness of the Inconel 690 specimens significantly increased after strengthening, introducing a certain depth of residual compressive stress. The material's surface underwent considerable plastic deformation, with the depth of the plastic deformation layer reaching up to 35.63 μm. The cyclic deformation response of the specimens before and after strengthening both exhibited rapid cyclic hardening followed by continuous cyclic softening until final fracture. After water jet strengthening, the maximum stress value of the material increased, and the plastic strain decreased. Additionally, the contribution of back stress in the strengthened specimens increased, reflecting that water jet strengthening introduced a certain thickness of plastic layer and a high-density dislocation layer. An increase in heterogeneously distributed structures at different scales was observed, and this effect persisted into the mid to late stages of cyclic loading. The source of fatigue cracks in the strengthened specimens shifted from the edges or surface to the subsurface and internal areas of the specimen edges. Compared to the original specimens, the fatigue striations of the strengthened specimens had relatively larger intervals.

Gradient composite plate structures have excellent synergistic advantages owing to their strength and toughness and have important application prospects in the fields of aerospace and national defense. The bonding interface performance is key to ensuring the mechanical properties of functional-gradient composite plates. In response to the demand for new functional structural materials, a technical approach for preparing functional-gradient composite plates with a sphere-array interlayer using explosive welding is explored. The static and dynamic parameters used in explosive welding process are within the welding window. The mechanism of wavy interface formation for a typical TA1/Q235 steel balls/Q235B functional-gradient composite plate is studied by combining experiment and numerical simulation methods. The fracture surfaces of the specimens, including the spheres, in the two types of mechanical tests exhibit ductile and quasi-cleavage fracturing. In impact toughness tests, the crack propagation direction extends directly towards the bonding interface in specimens with spheres protruding above the base plate; however, it extends perpendicularly through the interface and then into the flyer plate in specimens with non-protruding spheres. The experimental results and numerical simulation are in good agreement. A metallurgical bonding is formed on the top of the embedded spherical structure, and the middle and bottom of it are bonded by direct extrusion. The spherical structure protruding from the base plane hinders the bonding of the composite plate. In numerical simulation, the physical characteristics values of structure with spheres protruding at the interface after the spheres, such as collision velocity and pressure, are weaker than those of a structure with non-protruding spheres. The uneven plane aggravates the disturbance of the wavy interface, causing an increase in wavy amplitude and elongation of wavelength, and then a stable wavy interface will be re-formed.

Delving into the application of power spinning technology in the shaping of cylindrical components, examining the disparities in forming characteristics between ring rollers and conventional rollers, as well as their respective influences on the deformation behavior of the workpiece. An interference test was conducted to assess the geometrical differences in the deformation zones generated by the two types of roller during the forming process. Finite element analysis was employed to simulate the push power spinning processes for both types of rollers, providing a methodology for calculating the spinning force and analyzing the patterns of deformation zone states, loads on the rollers and mandrel. Additionally, the geometric features of the workpiece after push power spinning with both types of rollers were examined. The findings indicate that under the same forming conditions, the application of push power spinning with ring rollers produced greater loads, and the forming process exhibited a more significant compressive stress state and a smaller gradient of equivalent plastic strain. The specific experimental outcomes are detailed as follows: under equivalent reduction conditions, the ring roller increased the interference wrap angle by approximately 1.5 times; the roller and mandrel experienced higher loads during the push power spinning, approximately 1.5 times greater than those observed in the traditional rollers; the stress triaxiality induced by the ring roller in push power spinning was found to be lower and more uniform, with the maximum differences in stress triaxiality at positions R16, R17, and R18 being 0.55, 0.39, and 0.74, respectively; the springback after forming with the ring roller was approximately 0.15 mm, which is about 43% of that observed with traditional roller (0.35 mm), and the uniformity of wall thickness was superior; the circumferential wall thickness error of the workpiece obtained through ring roller spinning was less than 0.001 mm; the ring roller facilitated the torsional deformation of the workpiece and improved the uniformity of the torsion.

Cohesive model is widely used to simulate delamination in composite materials. The most crucial parameters for the cohesive model are the interfacial strength, fracture toughness and the shape of the traction-separation law. Although the effect of the interfacial strength and fracture toughness were extensively reported, the extraction method for the shape of the traction-separation curve is not fully explored, which has significant effect on the simulation results when non-linear damage mechanisms are involved. The measurement of the traction-separation law requires special-purpose equipment such as digital image correlation (DIC), and there is a lack of testing standard. In this work, a reconstruction method for the mode-I traction-separation curve is proposed. Firstly, a finite element model is built to iteratively update the crack opening displacement (COD), which is then used to calculate the strain energy release rate (SERR) of the cohesive zone using J-integral. Secondly, the analytical solution for the double cantilever beam is used, and a SERR equilibrium is established based on Dugdale’s condition. Finally, a reconstruction algorithm based on gradient descent is proposed to calculate the traction-separation curve. The proposed method only requires the load-displacement data of the DCB test configuration as input without the need to physically measure the COD using DIC. Validations are conducted using virtual experiments to test the effectiveness of the proposed method with exponential, trapezoidal and multi-linear shaped traction-separation laws as target. Parametric studies regarding the load-displacement data size, mesh size of the finite element model and measurement noise are also conducted.

In recent years, in the face of the urgent need to improve the surface accuracy of complex components in additive manufacturing, a hybrid manufacturing technology combining additive manufacturing and subtractive manufacturing in the same equipment is proposed. In this paper, the thin-walled sample of 5356 aluminum alloy is prepared by the hybrid manufacturing method of wire arc additive manufacturing and subtractive manufacturing. The microstructure and static and dynamic mechanical properties are tested and analyzed, and compared with the wire arc additive manufacturing method. The results show that the microstructures of the two are α phase (Al) matrix and β phase (Al₃Mg₂) precipitated at the grain boundary, which are composed of fine columnar grains and equiaxed grains. The grain sizes are 71.81 μm and 62.05 μm, respectively. The quasi-static mechanical properties of the two are equivalent, and the direction perpendicular to the deposition direction (horizontal) is better than the direction parallel to the deposition direction (vertical). With the increase of strain rate, the yield stress and flow stress increase continuously, showing obvious strain rate strengthening effect, and the horizontal direction also exhibits better dynamic mechanical properties than the vertical. When the strain rate is 3 800 s^-1, the yield stress and flow stress in the horizontal direction under the additive subtractive hybrid manufacturing method are 185 MPa and 615 MPa, respectively, which are 1.5 times and 2.3 times under quasi-static strain. Finally, a complex tube structure made of 5356 aluminum alloy is successfully prepared by the additive subtractive hybrid manufacturing method, maintaining a surface roughness at the sub-micron level. The feasibility of the method in manufacturing complex components made of 5356 aluminum alloy, and relevant experimental data are accumulated, providing valuable experience and guidance for the future fabrication of other complex components.

The cold expansion process of holes has been widely used in aviation, railways, automobiles and other fields to im-prove the fatigue life of fastening holes. The strengthening mechanism of cold expansion is to introduce circumferential residual compressive stress to reduce the average alternating stress around the hole. In order to overcome the short-comings of present method in determining the optimal interference level, such as high cost, time consuming, poor operability, and large errors, the present work proposed a new method based on the mandrel extrusion force to determine the optimal interference level. To achieve the above objectives, the present work employed a thick walled cylindrical mechanical model to build the relationship between the extrusion force of the mandrel and the residual stress around the hole. By using a conical mandrel combined with a slotted bush with a slope, a continuous extrusion force-interference level curve was obtained, and the reduction amount of slope of the extrusion force-interference level curve was proposed as a parameter to determine the optimal interference level. In order to verify the effectiveness of the above method, three cold expansion finite element models of AL-7050 holes with different specifications were established. The predicted optimal interference level of cold expansion of holes with different specifications agreed well with relevant experimental data. The present work provided a simple, fast and effective method of determing the optimal interference level of cold expansion holes with different specifications.

The radial cracks generated by the friction of the turbine blade crown endanger the safe operation of the engine, and its evolution mechanism has not been verified. To clarify the evolution mechanism of radial cracks, the thermal cycle tests were conducted on the fins, and numerical analysis were conducted using the XFEM method based on Abaqus software. Under cyclic high-temperature loading at 700 ℃, the fins did not initiate cracks and the prefabricated cracks did not propagate. Under cyclic high-temperature loading at 900 ℃, no cracks appeared on the fins, and the prefabricated cracks opened but propagated along the circumference and eventually peeled off. The radial cracks were formed under cyclic high-temperature loading at 1 050 ℃, and the crack length increased with the increase of the number of cycles. The parallel test under the load of 1 050 ℃ also formed radial cracks, which propagated to the blade crown，and the fitting formula of crack length with the number of cycles was obtained. The results show that the radial crack is caused by the circumferential tensile stress in the cooling process. When the circumferential tensile stress is greater than the yield strength, the crack initiates at the junction of the top and side of the fin. The crack first propagates the top surface of the fin and then propagates along the radial direction. The increase of temperature will promote the crack initiation and propagation. Therefore, the experimental and numerical studies under thermal cyclic loading verify the evolution mechanism of radial cracks, and thermal load is the driving force for the initiation and propagation of radial cracks.

To accurately assess the structural integrity of multiple cracks, effectively addressing the interactions between cracks is crucial. This requires evaluating adjacent cracks based on the coalescence criterion：if adjacent cracks satisfy the criterion, they are merged into a single crack for assessment; otherwise, they are assessed separately as individual cracks. However, the coalescence criteria established by different countries vary, leading to divergent results when different criteria are applied. To develop a more precise coalescence criterion for double cracks, this study investigates the coalescence behavior of non-collinear parallel double cracks in homogeneous plates using a combined experimental and finite element numerical simulation approach. The experimental and numerical simulation results are compared with those derived from various international coalescence criteria, highlighting the limitations of existing standards. Based on the ratio of the horizontal distance between the double cracks to the average length of the cracks, and the ratio of the vertical distance to the length of the shorter crack, a new coalescence criterion for double cracks is proposed.

The study of crack initiation and propagation in polymethyl methacrylate (PMMA) is of great significance to the structural integrity analysis and life prediction of its engineering components. The semi-elliptical surface crack propagation of PMMA is investigated by using the cohesive zone model. Firstly, the cohesive zone model parameters of PMMA are determined by using the standard fracture toughness test and the finite element inversion method. Then the tensile test and finite element simulation of wide plate with a semi-elliptical surface crack are carried out, and the experimental and simulated results are compared. Finally, the crack propagation behavior of the semi-elliptical surface crack with various shapes is studied by using the cohesive zone model. The results show that the peak load and quasi-static crack growth morphology of the simulation and experiment are in good agreement, which proves the validity of the cohesive zone model and parameters. When the initial crack depth is the same, the peak load decreases with the increase of the initial crack length. At the initial stage of crack propagation, long cracks expand more in the depth direction and less in the length direction, while short cracks are the opposite. However, their shape ratios in the depth and length direction tend to a constant with the crack propagation.

The stability and reliability of the transmission system is critical to the safe operation of trains. However, existing fault diagnosis methods have limitations in handling non-stationary signals and capturing complex features. To overcome these limitations, a train traction driveline fault diagnosis method based on Gram angular field(GAF) and parallel convolutional Transformer is proposed. The GAF is used to generate time-frequency images to capture the global information and nonlinear features of the time series. Further, the Gram sum field and Gram difference field maps are sampled by means of parallel convolutional processing, respectively, to enrich the fault information from different dimensions and effectively improve the feature extraction capability and computational efficiency of the model. In addition, the Transformer Encoder structure is introduced at the back-end of the model, which is used in conjunction with the convolutional neural network to enhance the expression and analysis capability of complex time-frequency features. Experimental validation shows that the proposed method has high accuracy and efficiency in train transmission system fault diagnosis.

LMA wheel profile has good dynamic performance when matching with 60 rail, but its equivalent conicity is lower when matching with 60N rail, which easily leads to vehicle shaking at low frequency, and insufficient curve passing ability when vehicle passes through small radius curve. Therefore, it is necessary to optimize the LMA profile so that it can have the same dynamic performance as the LMA-60 when it matches the 60N rail. In order to solve the above problems, based on wheel-rail contact relationship and vehicle system dynamics theory, and based on the wheel profile inverse design method, an improved method of linear recurrence inverse design is put forward on the basis of wheel profile inverse design method, the contradiction between wheel diameter difference and contact point distribution during profile design is solved, and an improved method of linear recursive inverse design of wheel profile is put forward. This method is applied to optimize the LMA wheel profile, obtaining the LMA04N wheel profile, the wheel-rail relationship and dynamic performance of LMA and LMA04N profiles are compared and analyzed. The results show that the wheel-rail relationship of LMA-60 is achieved by matching LMA04N wheel profile with 60N rail profile, with nominal equivalent conicity of 0.04, more uniform distribution of wheel-rail contact points, optimizing wheel-rail stress and improving wheel concave wear. When LMA04N wheel profile is used to match the 60N rail, the critical speed is 20% higher than that of LMA profile. The shaking of the vehicle with low conicity is effectively suppressed and the safety of small radius curve is improved. At the same time, LMA04N wheel profile and 60 rail profile also achieve a good match. In conclusion, the fast recursive algorithm for wheel profile reversal design can effectively realize the wheel profile optimization design, and the optimized profile LMA04N achieves a good match with the 60N rail, which can better guarantee the dynamic performance of the vehicle.

To improve the carrying capacity and stability of transmission system, the transmission system of the newly developed 400 km/h high-speed train in China adopts double-helical transmission gear for the first time. The installation errors and unique symmetry errors of double-helical gear will lead to deviation load on the gear surfaces at both ends, reducing the service life of gears. This paper established a train-track coupling dynamic model considering the gear transmission system to obtain the dynamic contact loads of double-helical gear in wheel-rail excitation environment, and analyzed the gear deviation load behavior under different forms of machining and installation errors. The results show that, under the axial constraint of small gear, when symmetry errors of 10 μm and 50 μm exist in the double-helical gear, the average errors of gear surfaces contact load reach 17.2% and 145.3%, respectively. Under the axial floating of small gear, when symmetry error of 100 μm exists in the double-helical gear, the average error of gear surfaces contact load is 1.0%, which can effectively improve the deviation load behavior of double-helical gear. Slight parallelism installation errors can cause significant deviation load on individual gear surfaces, however, the contact load distribution of left and right gear surfaces remains generally consistent. The partial deviation load behavior of the double-helical transmission gear of high-speed train can be suppressed by modifying the gear surface. The research results provide guidance for determining the reference value of machining error and installation forms of double-helical transmission gear in China’s new generation of high-speed train.

Aiming at the problems of incomplete consideration of product design stage and structure optimization level in the optimization process of subway car body, unclear correspondence between the two, and the challenges of traditional finite element model optimization method such as large calculation amount, long time and difficult to meet the actual programming requirements, a full-stage multi-objective optimization design method of product design based on section performance parameterization was proposed. Firstly, the theoretical calculation formula of the section performance parameters which affect the quality and stiffness of the frame is derived. Then, the multi-objective optimization of the whole stage of product design was carried out for the aluminum alloy subway body underframe. In this optimization process, the minimum weighted flexibility (i.e. maximum stiffness) is taken as the optimization objective, and the variable density method is used to optimize the topology in the conceptual design stage of the frame section. In both the basic design stage and detailed design stage, combined with the deduced theoretical calculation formula of the frame section performance parameters,Non-dominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ) is used to carry out shape-free dimension collaborative optimization. Finally, the topology optimization results and the whole stage optimization results are reconstructed respectively, and the detailed analysis and check are carried out. The results show that：This method can significantly improve the static rigidity of the bottom frame section and achieve the purpose of lightweight. The section area A (mass) of the three profiles is reduced by 4.06%, 1.31% and 5.17% respectively, and the bending moment of inertia I_x is increased by 9.50%, 5.21% and 9.00% respectively. The section performance of the designed profiles is excellent. It has guiding significance for systematic optimization design of products.

Problems with out-of-round wheels are widespread in subway trains. They can result in impact loads between wheels and rails, increase vehicle vibrations and noise, and cause fatigue fractures of vehicle/track components, which has a significant effect on ride comfort, operational safety, and wheel maintenance. The out-of-roundness test data of more than 9,000 wheels from 21 subway lines in China are statistically analyzed, covering four types of subway trains with maximum speeds of 80, 90, 100, and 120 km/h. The characteristics of wheel out-of-roundness such as radial run-out, orders, and wavelengths are determined. Welch’s method is used to estimate the spectra of all measured out-of-roundness data of the wheels. Then, the two-segment power function is used to obtain the roughness spectra, which are compared with the roughness spectra of high-speed wheels. The results show that the subway wheels have out-of-round problems to varying degrees, with about 10% of the wheels having radial run-out greater than 0.5 mm. The order of wheel polygonal wear is mainly 1st order (eccentric), 5th to 9th, and 12th to 16th order. The dominant wavelength of high-order polygonal wear (more than 10th order) is in the range of 160-200 mm in the 1/3 octave band. Compared with the roughness spectra of high-speed wheels, the roughness spectra of subway wheels are higher. The results of this paper can be helpful in the evaluation, maintenance, and repair of subway wheels in out-of-round conditions, as well as provide important information for dynamic wheel-rail interaction and wheel-rail noise simulation.

Accurate and efficient battery health estimation is very important for vehicle battery management. The data-driven method, which does not depend on the complex reaction mechanism and underlying mechanism inside the battery, is widely used in the field of SOC and state of health estimation. Due to the high computational complexity caused by training and testing a large amount of data in the previous methods, a new data mining technology of fuzzy information granulation is proposed. Firstly, the asymmetric Gaussian membership function is proposed to further improve the performance of data mining at three granular levels: upper boundary, mean and lower boundary. Then, a lithium-ion battery cycle test is conducted in combination with the Gaussian process regression method to verify the performance of the state of charge estimation. Finally, a battery capacity estimation model is established and the performance of the health state prediction is verified using a public dataset. The results show that by combining the fuzzy information granulation technology, the state of charge estimation accuracy of the Gaussian process regression method is improved by 15.38% and 31.25%, respectively, under the two current conditions, and the computation time can be reduced from 26.9 s to 3.3 s. The state of charge estimation by fuzzy information granulation can achieve high accuracy among the five machine learning methods and require only the lowest computational cost, thus providing ideas and guidance for highly efficient state of charge estimation of lithium-ion batteries based on data-driven methods.

Lithium-ion batteries are widely used in new energy vehicles and electrochemical energy storage systems, and are an important support for achieving the goal of carbon neutrality. Accurately obtaining the state of health(SOH) is the basis for the safe and efficient application of lithium-ion batteries. However, the SOH is an implicit state inside the battery and is difficult to measure directly. Aiming at the problem that the external characterization parameters of the battery are difficult to accurately map the internal aging state, an online capacity estimation method of lithium iron phosphate batteries based on incremental capacity(IC) analysis is proposed. Firstly, the changes of IC curve characteristics under different aging states and operating temperatures are analysed. Secondly, the curve features strongly related to the health state of the battery are extracted as health indicators. Then, the mapping relationship between the health indicators and the aging state of the battery is constructed. Finally, a compensation mechanism is introduced for the impact of charging temperature on the estimation results, ultimately achieving accurate estimation of the maximum available capacity of the battery under different charging conditions. The verification results show that the maximum error in capacity estimation is 0.36 A·h, the corresponding estimation result is 47.747 A·h, and the maximum relative error of 0.75%.

Based on the random plane wave theory of turbulent flow fields, the heat-fluid coupling governing equation of the simply-supported plate under turbulent boundary layer excitation is first deduced by incorporating the coupling effects of turbulent flow and thermal environment on the structure. Subsequently, the vibration response model of the heat-fluid coupled plate is established, with the synergistic interactions between the turbulent field and thermal field systematically integrated into the analytical framework to comprehensively characterize the dynamic behavior of the plate under multifield coupling conditions. The vibration response characteristic of the plate under the coupling of turbulence load and thermal load is investigated. The traditional turbulent field transfer function method is used to calculate the vibration response characteristic of the plate, and the calculation result is also compared with the random field plane wave model to verify the heat-fluid coupling model excited by random plane waves; finally, using the verified plane wave model and considering the influence of the transfer function of the heat-fluid coupling model, the distribution characteristics of the wall fluctuating pressure in the wavenumber-frequency space is analyzed, and the wavenumber truncation criterion for the coupling of strong turbulence load and heat load is proposed. The research results show that the heat-flow coupling effect has a great influence on the vibration characteristics of the plate. After considering the heat-flow coupling load, the natural frequency of the plate is lower, the vibration response curve moves to lower frequencies as a whole, and the response amplitude of the fundamental frequency decreases.

The CR450 and other high-speed trains are anticipated to reach a speed of 450 km/h. To assess the safety of trackside signal equipment under current installation conditions, this study develops an aerodynamic model for tunnel-train-signal lights, investigating the formation and variation of pressure waves on signal light equipment during single-vehicle operation and constant-speed interactions of high-speed trains in tunnels. Results indicate that as vehicle speed increases, the peak values of both positive and negative waves of signal lights within the tunnel, along with the amplitude of pressure changes, also increase. Notably, the amplitude of the signal light pressure wave is directly proportional to the square of the train's speed. In a 1 000 m tunnel operating at a speed of 450 km/h, the signal light pressure wave amplitude is 9 157 Pa, representing an increase of approximately 97.4% compared to a speed of 350 km/h. The pressure wave amplitude experienced by the signal lights under the most challenging tunnel intersection conditions exceeds that of single-vehicle operation in the most adverse tunnel scenarios. The pressure and pressure wave amplitude experienced by the signal lights under the most adverse tunnel conditions exceed those in a 1 000 m tunnel at comparable vehicle speeds. At a speed of 450 km/h in a 217 m tunnel, the most adverse condition results in a signal light pressure wave amplitude of 22 085 Pa, which is approximately 26.1% higher than the 17 511 Pa amplitude in a 1 000 m tunnel at the same speed. For facilities situated midway along the tunnel, when the lead and tail vehicles enter the tunnel at a time difference equivalent to the tunnel length divided by the vehicle speed, they are subjected to two compression waves, leading to secondary pressure fluctuations. The signal light's pressure fluctuation is minimal at the tunnel entrance, suggesting placement there to minimize the effects of tunnel pressure waves and enhance safety.

With the rapid development of generative artificial intelligence, the field of mechanical design has ushered in new changes. The design concept is gradually developed from the traditional “computer-aided + artificial experience” to “historical design data and knowledge + generative modeling” with advanced intelligence, and specific design behavior is developed from “manual modeling” to “generative modeling”, and the mechanical product design driver is developed from manual experience to data knowledge. In response to this development trend, a new mechanical design concept is proposed: Intelligent generative design (IGD). The content composition, core operation mechanism, design features, and key technologies of IGD are described in this article. On this basis, this study explores the application value of IGD in mechanical product design, and points out the new trend and development direction for the design of mechanical products.

High speed on/off valve(HSV) is the core control component of digital hydraulic systems, offering advantages such as fast response, strong contamination resistance, and simple design. Dynamic characteristic is the key performance indicator of HSVs, directly determining the response speed and control accuracy of the systems. Therefore, in applications where multiple HSVs are used synchronously or cooperatively, ensuring consistency in dynamic characteristic of each HSV is particularly crucial. However, even with the improvement in machining precision, the use of high-performance materials, and the optimization of assembly process, discrepancies in dynamic characteristic within the same batch of HSVs still cannot be completely eliminated. To address this issue, the traditional approach of improving consistency through enhanced manufacturing precision is bypassed. Instead, it proposes an innovative method to compensate for differences in dynamic characteristic via optimizing control algorithm. Firstly, a dynamic characteristic mathematical model of HSV is developed. Based on this model, the effects of initial coil current and electromagnetic force on the dynamic characteristic are analyzed. Then, a multi-voltage compound driving algorithm is proposed to compensate for differences in dynamic characteristic of HSVs. The algorithm adjusts the driving voltage at each stage of the HSV's movement in a targeted manner, thereby modifying the switching delay time and moving time. By doing so, the differences in the dynamic characteristic among the HSVs are effectively eliminated. Finally, a dynamic characteristic difference compensation experiment is conducted on three HSVs of the same batch. The effectiveness of the compensation algorithm is validated by testing the variation of dynamic characteristic and pressure-flow characteristic. The results show that, after compensation, the maximum difference in switching delay time and moving time among the three HSVs is reduced from 1.94 ms to 0.01 ms. Additionally, the maximum difference rate in switching delay time and moving time is decreased from 29.79% to 1.67%. The maximum difference rate in pressure-flow characteristic is dropped from 9.73% to 3.03%.

The rotary drilling rig, as the most widely used equipment in foundation construction, relies on its drilling efficiency as the core competitive strength. However, after long-term service, the pressurization system inevitably experiences performance degradation, which seriously affects pressure control and even lead to a loss of pressure, thereby impacting both construction efficiency and quality. First, a parameter identification model is established using the recursive least squares method with a forgetting factor, which is used to identify the degraded parameters and determine the health status of the pressurization system. Then, based on model reference adaptive control theory, an adaptive compensation controller for pressurization is designed to compensate for the degraded pressurization system. A performance degradation compensation method, coupling health monitoring and compensation control for the pressurization system, is proposed. Simulation and experimental results show that the controller can effectively improve the pressure output of the faulty rig, thus enhancing construction efficiency. Under the same experimental conditions, compared to the original rig, the pressure output of the measured rig increased by 17.8%, and drilling efficiency improved by 8.8%, verifying the effectiveness and feasibility of the controller.

Aiming at the problems of the characteristics of the digital directional valve drive system that is too sensitive to the change of the drive motor parameters, not strong in load disturbance resistance, and the insufficiency of the traditional P-control in high-precision position control, which seriously affects the control accuracy and stability of the digital directional valve drive system, the sliding-mode variable-structure composite control strategy with an improved convergence rate is proposed. In order to meet the demand of high-precision position control, in this strategy, the anti-interference and parameter time-variation of sliding mode control are utilized, and the combination of sliding mode control, predictive adaptive control and optimal control is used to design a position-loop controller for the digital directional valve, which realizes the high precision and fast response of the system. Simulation and experimental results show that the proposed position loop control strategy effectively improves the stability and accuracy of the system, as well as its effectiveness in improving the system's anti-interference capability, when analyzed in comparison with the traditional P control. This study is of great significance for improving the performance of digital directional valves and provides theoretical guidance for the control strategies of similar systems.

Hydroforming equipment is widely used in large tonnage, large size stamping, forging and other forming processes. Hence, high performance leveling system is needed to ensure the forming accuracy of the equipment. However, the traditional diagonal couple leveling system and its identity control strategy cannot accurately eliminate the inclination torque, which affects the forming quality of the workpiece. To solve the above problems, a four-corner leveling electro-hydraulic system based on independent metering for high-speed hydraulic presses is designed. In terms of leveling control, a diagonal cross and mean coupled synchronous control strategy based on pump-valve coordinate control is proposed. For the meter-out displacement controller design, the tracking error of each leveling cylinder is taken as negative feedback input, and the mean of tracking error and diagonal error are taken as compensation input into the sliding mode controller, so as to achieve accurate tracking and synchronous control of each cylinder. For the meter-in pressure controller design, the pressure servo valve is adjusted according to the working mode at the left and right maximum opening, so that the flow into the leveling cylinder is maximum and the pressure is minimum. For the pump flow controller design, the motor speed is determined according to the working mode of the leveling cylinder. Finally, an experimental platform for four-corner leveling of hydraulic press was built. The experimental results show that compared with the traditional identity control strategy, the proposed leveling control strategy improves the synchronization accuracy by 9.26%. At the same time, due to the energy-saving characteristics of the independent metering system, the power consumption of the system is reduced by 54% under the action of the control strategy. This study shows practical significance for the research and development of leveling system of high-speed forming equipment.

To study the relationship between wheel wear and equivalent conicity of high-speed trains, the UIC519 integration method is applied in combination with partial least square, backpropagation neural network, and Ridge Regression models. The wear of LMA-type wheel profile and its relationship with equivalent conicity are analyzed both qualitatively and quantitatively, resulting in the establishment and validation of mathematical models based on these three methods. The study results indicate that the Ridge Regression model is more suitable for analyzing the correlation between wheel wear and equivalent conicity in high-speed trains, effectively capturing the impact of wear on equivalent conicity. Further analysis shows that when the wheel wear reaches 0.42～0.84 mm, corresponding to a mileage of approximately 57 000 km to 122 000 km for high-speed trains, concave wear is observed near the nominal rolling circle of the wheel profile. This phenomenon significantly influences the variation in equivalent conicity, leading to larger modeling errors in this range. It is further demonstrated that the primary factor affecting the relationship between wheel wear and equivalent conicity is the concave wear of the wheel profile.

Offshore single-point hoisting, luffing, and positioning processes for slender-beam payload(SBP) frequently encounter low operational efficiency due to payload sway. To mitigate this problem, a novel multi-tagline anti-sway and positioning system (MTAPS) is proposed. The offshore lifting procedure for the SBP is divided into two stages: single-point hoisting, and luffing and positioning. Dynamic models for these stages are established based on classical Newtonian mechanics and multi-body dynamics. Subsequently, dynamic simulations are performed in Matlab/Simulink for detailed analysis. Both simulations and experiments confirm that the MTAPS effectively eliminates the initial sway angle generated during the single-point hoisting stage of the SBP. Under luffing conditions, relative motion between the payload’s center of gravity and the crane boom head is significantly reduced. During the positioning stage, an average sway reduction ratio exceeding 88% is achieved for the SBP double-pendulum system. Rapid transfer and precise positioning of the offshore SBP become possible through the utilization of this system. Moreover, the proposed dynamic modeling method offers valuable insights for solving engineering challenges in multi-tagline lifting and related applications.

Aiming at the application scenario of underwater object transportation in a multi-obstacle environment, the formation reconfiguration and trajectory planning issues during the cooperative transportation and point-to-point delivery of underwater object by multiple unmanned underwater vehicles(UUVs) are explored. A formation control and motion planner for the multi-UUV cooperative transportation system is designed. Firstly, to meet the formation control requirements of multi-UUV cooperative transportation, a formation controller for the multi-UUV system is designed based on rigid graph theory, affine transformation, and backstepping control theory. The core function of this controller is to control the multi-UUV system to form a specific formation configuration, thereby steadily lifting and transporting underwater object. During transportation, the system can reconfigure the shape of the formation using affine transformation according to different obstacle environment information or specific task requirements. The stability of the closed-loop formation control system is analyzed using Lyapunov function, which verifies the reliability of the control scheme. Secondly, to address the trajectory planning challenges of multi-UUV cooperative transportation in complex multi-obstacle environments, a collision-free trajectory planning algorithm suitable for multi-UUV formations is designed based on the fluid disturbance strategy, ensuring that the formation can safely avoid obstacles in complex environments. Finally, the effectiveness of the proposed algorithm is verified using Matlab simulations. The simulation results show that the UUVs in the formation can quickly form and stably maintain the desired transportation formation, and can flexibly maneuver along the planned trajectory to avoid obstacles. Ultimately, the goal of collaborative transportation of large underwater object by multiple UUVs is achieved.