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.

Porous metals are widely used in filtration, catalysis, adsorption and heat transfer because of their excellent mechanical properties. However, creep failure is a primary failure mode for porous metal parts experiencing the high temperature and constant stress. The research progress of the creep resistance of porous metal materials was summarized from four aspects, pore structure，edge structure, micro-defect and creep life prediction. The effects of pore structure, such as porosity, pore shape and pore diameter, on the stress index, creep resistance and deformation mechanism of porous metals were expounded. The creep resistance of the hollow and solid edge under different stress conditions was analyzed, and the effect law of edge size on the creep rate of porous metals was revealed. The effect of micro-defects on the creep mechanism of porous metals was clarified, and the constitutive model for predicting the creep life of porous metals was introduced. These studies provide scientific guidance for the long-life service and reliable operation of porous metal structures.

Aiming at the vibration fatigue problem of the battery box of electric vehicles, based on the test loads in the real vehicle test field, the fatigue performance of the battery box was compared and analyzed based on single-axis and multi-axis (sequential loading, coupled loading) vibration loads. Firstly, the three-directional acceleration loads were collected at the sensitive points on the battery box in the test field. The power spectral densities were fitted and compared in the same direction of the loads at different measurement points respectively, and the power spectral densities were accelerated through the frequency-domain damage equivalence method to obtain the distribution characteristics of the random vibration three-directional acceleration power spectral densities under the test field specification. Secondly, based on the theory of random vibration fatigue analysis, the multi-axis sequential excitation and multi-axis coupled excitation of the battery box were constructed. Based on fatigue damage equivalence, a uniaxial strengthening spectrum excitation was constructed. Finally, the fatigue damage of the battery box under three kinds of excitation was compared and analyzed by the numerical simulation.The results show that the damage locations of the battery box are consistent under the three excitations. The damage under multi-axis coupled excitation is greater than that under multi-axis sequential excitation, and the single-axis enhancement spectrum has a better reproduction effect on the multi-axis coupled damage. This can provide guidance for conducting rapid vibration fatigue tests of battery boxes based on uniaxial enhanced load spectra.

To investigate the mechanical properties of woven composite hybrid bonded/bolted joints, a mechanical failure model for hybrid bonded/bolted joints based on 3D progressive damage model and cohesive force model was developed to simulate the mechanical behavior and damage evolution of the joints. Based on the Abaqus finite element software, a finite element simulation model for hybrid bonded/bolted joints woven composites was established. The damage initiation and propagation of the composite material were judged using the three-dimensional Linde criterion. The cohesive force model was used to simulate the damage failure process of the adhesive layer. On the basis of test verification of the model accuracy, the strength and damage failure process of the joints were analyzed under different tightening torques. The test and simulation results indicate that as the tightening torque increases, the extension of adhesive layer damage can be effectively suppressed.However, the shear strength of the adhesive layer in the hybrid bonded/bolted joints firstly increases and then decreases,because increasing the tightening torque can reduce the peeling stress of the adhesive layer in the joints. However, the excessive tightening torque will strengthen the stress around the adhesive layer hole, leading to a decrease in the shear srength of the adhesive layer and a decrease in the strength of the connection structure. The load-displacement curve of the numerical simulation is consistent with the test results, and the predicted adhesive layer fracture load is equivalent to the test results. At the same time, the fiber damage, matrix damage, and delamination damage on the laminated plate can also be well reflected in the numerical model, which is similar to the damage form after the connection test, verifying the effectiveness of the damage prediction model.

The eccentric installation of high-lock titanium alloy bolts (an assembly angle between the bolt head and the fastening plate) leads to premature failure, which seriously affects the safe operation of aerospace aircraft. Currently, the test research is difficult to obtain the bolt fracture process, which in turn limits the revealing of fracture mechanism. Meanwhile,test research cannot obtain the fracture strength variation value of bolts with different assembly angles. Therefore, in response to the problem of premature fracture of high-lock bolts in the eccentric installation, finite element analysis method was employed and the model was verified by test. The verified finite element model was used to visualize the fracture process of eccentric installation bolts and predict the tensile strength of eccentric installation bolts with different angles. The research results indicate that the tensile strength and fracture position of bolts with installation angles of 0° and 3° obtained from finite element analysis are consistent with the test results, which show that the finite element model has good accuracy. As the installation angle increases, both the bolt head and thread are subjected to eccentric loads, and the bending moment generated aggravates the stress concentration in these two areas. When the assembly angle is less than 3°, the stress at the thread is larger,and when the angle is over 3°, the stress on the head is greater. The finite element model successfully predicts the tensile strength of bolts with an assembly angle of 1°, 2°, and 4°. The research results effectively reveal the fracture mechanism of high-lock titanium alloy bolts under the eccentric load. Meanwhile, the simulation model can predict the tensile strength of bolts under different installation angles, and provide technical specifications for the service of eccentric bolts.

The subsurface damage depth of grinding WC-10Co-4Cr coating with a cup wheel was investigated in an effort to address the issue that the subsurface damage will cause the coating's performance to deteriorate. The theoretical formula of single particle grinding force was obtained based on the principles of indentation fracture mechanics and grinding material removal theory. A theoretical subsurface damage depth prediction model was developed based on the cup wheel's surface grinding properties. The design of the single factor surface grinding test and the single point polishing test was to confirm the model's accuracy. Analysis was done on how various grinding parameters affected the workpiece's surface roughness and depth of subsurface damage. The maximum relative error is 15. 8%, and the predicted subsurface damage depth agrees with the measured value, according to the results. Surface roughness and subsurface damage depth rise with feed speed and grinding depth, but fall with spindle speed. The study has some theoretical significance for directing the process parameter optimization of cup wheel grinding of WC-10Co-4Cr coatings.

The disc spring will bear the cyclic displacement load during using, resulting in the fatigue damage and the stiffness degradation of the disc spring, which causes irreversible influence on the compensation function when accumulated sufficiently to cause fracture. Therefore, the disc spring material which occurred internal fatigue and structural stiffness degradation was studied under the cyclic load. By considering characteristics of the geometric nonlinearity and the action of the cyclic load, based on the traditional stiffness degradation model, a stiffness degradation model fitting for disc springs was established. The force change of the structural system, the law of stiffness degradation of the disc spring, and the stiffness degradation model were analyzed and verified with the finite element software. The model was modified based on the test data to obtain the model that can be used to calculate the degradation of the disc spring stiffness. This model can predict the deformation of disc springs’ structure in service, and determine the fatigue damage and performance degradation degree,which can provide some basis and reference for the application of disc springs.

Metro gearbox is a key component for torque transmission in vehicles, and its failure will directly affect the safety of train operation. The vibration characteristics of tooth breakage faults in metro gearbox were studied by combining dynamic simulation and vibration test. Firstly, based on the dynamic relationships and constraint characteristics between various components of metro gearbox, a rigid-flexible coupling dynamic model of metro gearbox with tooth breakage faults was established through the impact function method, Coulomb friction model, bearing modeling, flexible body of the housing and gear system dynamics theory. The dynamic response of the gearbox under different types of tooth breakage faults was studied, and the influence of operating parameters on the vibration characteristics of tooth breakage was analyzed. Then,through vibration test, the dynamic response of metro gearbox under normal state and broken tooth fault was obtained,verifying the accuracy of the dynamic simulation model. The results indicate that the rigid-flexible coupling dynamic model can effectively calculate the acceleration response of gearbox in different operating states, provide diagnostic basis for the prediction and identification of tooth breakage faults in the gearbox.

As a common material for flow components, 17-4PH(0Cr17Ni4Cu4Nb) martensitic stainless steel is vulnerable to serious cavitation damage. Based on the corrosion inhibition effect of array texture structure，this study focused on the cavitation characteristics and inhibition mechanism of 17-4PH material under the surface structure of hundred-micron groove array. Based on the ultrasonic cavitation test platform, the experimental data were obtained by the weight loss method, and the data points were fitted by Logistic equation to obtain the nominal incubation period and other parameters. The results show that the surface groove target with groove spacing W and groove width L in the range of hundred-micron has a good inhibitory effect on cavitation damage. The geometric parameters of the groove array structure with the appropriate ratio can further reduce the cavitation damage of the material. The groove array target with groove width L=700 μm and groove spacing W=400 μm has the longest incubation period (22. 79 h) and the smallest cumulative mass loss (10.92 mg) after continuous cavitation for 50 h, thereby exhibiting the best cavitation resistance. This study can provide reference for practical engineering applications in preventing cavitation erosion.

The rapid assessment method for metal fatigue performance based on the infrared thermography presents advantages such as short testing cycles, low costs, and high efficiency. However, accurately quantifying factors influencing the dissipation of energy, such as convective heat transfer and thermal radiation, proves challenging. The difficulty leads to complications in achieving the precision necessary to meet test standards in the final assessment results. A mixed-hardening constitutive model for 304 stainless steel was established and coupled with the low-cycle fatigue thermomechanical mechanism, to analyze the evolution pattern of dissipated energy caused by convective heat transfer and thermal radiation during the loading process. Furthermore, the impact of low-cycle fatigue loading frequency on the rapid assessment results of fatigue performance was explored based on the critical threshold of dissipated energy. The research indicates that during the low-cycle fatigue process of 304 stainless steel, the dissipated energy from convective heat transfer and thermal radiation constitutes over 54% of the total dissipated energy. Moreover, this proportion continuously increases with the augmentation of the convective heat transfer coefficient. Therefore, it is crucial not to neglect these factors in dissipated energy assessment calculations. With an increase in loading frequency, the peak load narrows within the region of action time. Consequently, the dissipated energy of each load cycle decreases, leading to a rapid assessment result of fatigue performance that tends to be larger than the test value.