In order to improve the high temperature wear resistance and extend its service life of 304 stainless steel, the high temperature wear-resistant NiCrAlY/Co coating was prepared on the surface of 304 stainless steel by the laser cladding.The morphology, phase composition and microhardness of the coating were analyzed.The tribological properties of 304 stainless steel and NiCrAlY/Co coating at different temperatures（the room temperature to 800 ℃) were studied, and the wear mechanism was analyzed. The results show that the coating is metallurgically bonded to the 304 stainless steel substrate; the coating is mainly composed of γ-Co,(Cr, Ni) and AlNi₃ phases; the average microhardness of the coating（303 HV) is about 1.6 times that of the substrate（194 HV); Compared with the substrate, the coating has a smaller friction coefficient at 200-600 ℃,the friction coefficient is comparable at 800 ℃, and the lowest friction coefficient of the coating is 0.5 at 600 ℃.The wear rate of the coating from the room temperature to 800 ℃ is lower than that of the substrate，and the lowest wear rate is 1.91×10^-5 mm³/(N·m) at 400 ℃, which is about 1/3 of the substrate, indicating that the NiCrAlY/Co coating improves the high temperature wear resistance of 304 stainless steel. At medium and low temperatures，the wear mechanism of the substrate is mainly abrasive wear and adhesive wear, and the wear mechanism of the NiCrAlY/Co coating is mainly abrasive wear and gradually slight adhesive wear.At 800 ℃, the wear mechanism of the substrate is plastic deformation, and the wear mechanism of the coating is oxidation wear.

Aiming at the problem that loop-end braided stents are prone to loop-end fracture during crimping, the key design parameters affecting the structural stability of loop-end braided stents were explored, and an improvement scheme was proposed.Numerical simulation of crimping for magnesium alloy loop-end braided stents was conducted using Abaqus analysis software. The results showed that increasing the braiding angle can effectively reduce the risk of loop-end fracture.Based on this finding, a variable pitch stent was designed, which features increasing the braiding angle at both ends to form sparse segments while maintaining the braiding angle in the middle of the stent. The influence of adjusting the length and braiding angle of the sparse segments on the mechanical response of the stent was evaluated.The research results showed that increasing the braiding angle and length of the sparse segments can effectively reduce the axial elongation and loop-end stress of the stent, but it will shorten the length of the middle dense segment, thereby reducing the radial force of the stent. Different from the flared expansion of the constant pitch open-end stent, the variable pitch stent presents a shape with large middle expansion and small end expansion after expansion.This study reveals the potential of variable pitch design in controlling loop-end fracture and provides a reference for the structural optimization of magnesium alloy braided stents.

Aiming at the issues of fracture and weight reduction in the wheel hub motor housing of an off-road vehicle, a structural strength finite element simulation analysis and structural topology optimization design were conducted. Firstly, a multi-body dynamics model of the entire vehicle was established, and a simulation analysis was performed to determine the load boundary conditions of the hub motor housing. Secondly, based on the spatial position relation between the housing and interconnected structures, a finite element model of the motor housing and suspension system was constructed for dynamic simulation analysis. Subsequently,using the OptiStruct software platform,with the objective of minimizing structural compliance and constraints on volume ratio before and after optimization as well as the maximum stress, a mathematical topology optimization model for the motor housing under various typical operating conditions was established and solved to obtain the optimal material distribution scheme. Finally, the optimization results were verified by simulation. The results indicate that compared to the existing design,the optimized hub motor housing structure experiences a stress reduction of over 40% and a weight reduction of 2.6%. It addresses the original fracture issue and eliminates the phenomenon stress concentration, thus providing the valuable reference for the design of similar hub motor housing structures.

In order to study the strain softening phenomenon of ultra-fine grain (UFG) metal materials under uniaxial tensile loading, a modified model considering the effect of residual internal stress was proposed based on the classical crystal plasticity constitutive model, and the specific form of residual internal stress and its evolution were programmed into the user subroutine. The uniaxial tensile test data were fitted to verify the validity of the model, and the finite element simulation results of crystal plasticity were compared with and without the residual internal stress. The results show that the simulation results obtained by using the modified crystal plasticity constitutive model are in good agreement with the experimental results, indicating that the modified crystal plasticity constitutive model can effectively capture the strain-softening phenomenon of UFG metal materials, and the simulation results show different properties under the two conditions whether the residual internal stress is taken into account. It is reasonable to explain the strain softening phenomenon of UFG metal materials from the perspective of the formation and action of residual internal stress.

Minimal surfaces are characterized by spatially continuous smoothness, which can effectively avoid the problem of the stress concentration, and have become a significant focus in the research of mechanical metamaterials. A Scherk single-periodic minimal surface (SPMS) was studied, and the spatially continuous smooth geometrical model was generated using a voxel reconstruction technique with multi-software association method. The mechanical behavior and energy absorption characteristics of the single-period Scherk surface structure were investigated using finite element simulation. The impact of the mathematical parameters of the minimal surface on the geometric configuration was examined.Five minimal surfaces with different parameters were established, and the deformation patterns and stress distributions of the five structures were explored under positive and lateral compression conditions. The Scherk surface structures were fabricated by metal printing technology, and quasi-static compression tests were conducted. The results show that the Scherk single-period surface has an obvious negative Poisson ratio effect, and the SPMS structure exhibits X-and V-shaped deformation modes, which can well withstand the external loading effects. The compression tests show the hump phenomenon of the reaction force and displacement curves of the SPMS structure, indicating that the structure has a negative Poisson ratio and negative stiffness property. This property provides a wide space for its application research in large deformation damage and structural energy absorption.

In practical operation, the loads borne by electric excavators often exhibit significant non-stationary random characteristics, leading to complex vibration phenomena of the battery pack, which directly affects the safe and reliable operation of the battery pack. To address this issue, the characteristics of road excitation, plunger pump pressure pulsation excitation, and impact excitation on electric excavators under complex working conditions were investigated. The vibration transmission paths under various excitations were analyzed, a dynamic model of the battery pack was established, the vibration characteristics of the battery pack under non-stationary random excitation were revealed, and case studies were conducted for analysis and verification. The research shows that reconstructing road excitation signals based on wavelet transform and Grey Wolf Optimization-Variational Mode Decomposition (GWO-VMD) signal analysis algorithm can effectively reflect the characteristics of road excitation. The road excitation borne by electric excavators under driving conditions exhibits significant non-stationary characteristics. Under non-stationary random excitations such as road excitation, the battery pack of electric excavators produces complex and changeable vibrations, whose power spectral density of dynamic response changes significantly with time, showing obvious non-stationary random characteristics.This study provides a reference for the safe and reliable operation of battery packs in electric excavators.

This article took the folding section cam linkage mechanism of a carton folding machine as an example.Firstly, a preliminary design of the cam was carried out based on actual working conditions. Then, combined with the analytical method designing the cam mechanism based on the allowable pressure angle of the cam, a mathematical model was established with the swing rod angle and the center distance between the cam and the swing rod as design variables. Using the NSGA-Ⅱ optimization algorithm, perform multi-objective optimization design on the cam linkage mechanism and select the optimal solution from the generated Pareto solution set. Based on the optimization results, the preliminary design of the cam linkage combination mechanism was adjusted, and the contour of the cam was obtained through Matlab programming,verifying that the optimized cam pressure angle met the allowable pressure angle. Finally, simulation analysis was conducted on the optimized cam linkage mechanism using Adams software. It is found that the displacement, velocity, and acceleration of the blade movement meet the design requirements, verifying the correctness and feasibility of the optimization results. At the same time, it also provides a reference method for the optimization design of other cam linkage mechanisms.

The main types of carbides in M50 bearing steel are MC, M₂C and M₂₃C₆. Under the scanning electron microscopy (SEM), they exhibit significant differences in the shape, size, and distribution. Some carbides have larger sizes and uneven distribution. They become areas of stress concentration under loading，which has a negative impact on the bearing fatigue performance. So an improved mask region-based convolutional neural network (Mask R-CNN) model was proposed which can batch identify the types of three kinds of carbides in SEM pictures, the diameters of carbides were measured, and the distribution of carbides was showed. The output images and histogram results show that the size of M₂C carbide in M50 bearing steel is large and unevenly distributed, but the distribution of MC carbide with the largest size and M₂₃C₆ with the smallest size is reasonably uniform.

The telescopic arm, a pivotal component in the pipeline grabbing vehicle, links the lifting platform and the mechanical claw, shouldering the majority of the load. Conducting a reliability analysis is imperative. Traditional methods for reliability face challenges like high computational costs and low accuracy dealing with multidimensional uncertainties. To overcome these, our study proposed an engineering mechanical reliability analysis method, leveraging Adams dynamic simulation, semi-supervised learning, deep neural networks, and Monte Carlo method. In this study, a virtual prototype model of the pipeline grabbing vehicle was established, identifying hazardous operating conditions. Combining the telescopic arm model’s geometric parameters and overall structure, uncertain factors influencing the maximum von Mises stress were determined, conducting a sensitivity analysis was conducted. Utilizing optimal Latin hypercube sampling based on uncertain parameter distributions, Ansys Workbench was employed to build a finite element model, obtain output results for the sample size. Semi-supervised learning processed the finite element simulation data, enhanced deep neural network training accuracy.Finally, based on the fourth strength theory, a failure criteria for the telescopic arm component was determined. Combining deep neural networks and Monte Carlo method, the reliability and failure probability were predicted. Results show that this method surpasses actual engineering precision requirements，provides a certain guiding significance.

Due to the needs of transportation, installation, grid connection, and maintenance, the construction of offshore wind farms in inshore areas often cannot be far from busy surrounding waterways, which significantly increases the probability of offshore wind turbines being impacted by ships. To analyze the performance and damage of different hollow ratios of protective devices when offshore wind turbines are hit by ships，the collision process of a 5000-ton bow-downward ship with an offshore wind turbine at a speed of 2.0 m/s was simulated using Ansys/Ls-Dyna. The influence of the hollow ratio on the anti-collision performance of Ogden rubber，Mooney-Rivlin rubber and Aluminum foam aluminum constitutive protective devices was studied and compared. The results show that with the increase of hollow ratio, the impact duration of aluminum foam protective devices increases, and the contact force decreases accordingly, while rubber materials show the opposite trend. As the hollow ratio decreases, the protective device is more similar to a solid tube, with a relatively smaller maximum indentation depth. Under the influence of hyperelastic properties, the indentation depth of rubber materials is smaller than that of aluminum foam after the collision is completed, and the material damage of the protective device is smaller. However, the proportion of internal energy in the support area gradually increases, so the influence of hollow ratio on the leg support needs to be considered in the design and research of protective devices.