Accurately predicting the fatigue life of products plays an important role in the structural strength design and reliability design of key components of electric vehicles.Starting from the measured road load spectrum of the reinforced road,a method for data processing and analysis of measured load spectrum was proposed, based on the Miner criterion, the load data of the vehicle under no-load, half-load and full load were obtained, and the key data for vibration simulation analysis and indoor bench test were obtained through time-domain frequency domain processing and damage equivalent treatment.A parallel-shaft electric drive axle was designed and developed, the statics analysis and modal analysis were carried out for key components such as the bridge shell, and the results concluded that the bridge shell would not have torsion and bending caused by road surface excitation.Based on nCode DesignLife simulation analysis software, the fatigue life and damage value distribution of the bridge shell were obtained, and the accuracy of the simulation analysis was verified by the bridge shell durability test.Based on the measured road load spectrum of the reinforced road, a 15 000 km vehicle vibration test was carried out on the vehicle vibration test bench for the electric drive axle.The test shows that the overall life and reliability of the electric drive axle meet the design requirements, and the reliability of the analysis method is verified.

Octet-truss lattice structure is one of the preferred materials in engineering field with light, high strength and high toughness properties.Three-point bending experiments were carried out on Ti6Al4V Octet-truss lattice structure with shallow pre-crack, and the fracture process was observed by digital image correlation (DIC) technique.To further study the fracture toughness of Octet-truss lattice structure, the fracture behavior of the structure under three-point bending load was analyzed by finite element method.The mechanical response of the truss member for the structure was characterized by the isotropic elastoplastic mechanical model.The validity of the finite element model was verified by experiments.Based on the elastic-plastic fracture behavior of the structure, the J-integral method was used to calculate the fracture toughness of the Octet-truss lattice structures.The results show that the fracture toughness of the Octet-truss lattice structure increases linearly with the relative density and the square root of the truss length.For the truss member at the crack tip, truss in different planes have different stress states and deformation modes with the same cross-sectional size.According to the failure mode of the structure,the stress state of truss from different planes is balanced by optimizing the proportion of the cross-section size, which can optimize toughness of the lattice structure with same relative density.

Accidental mechanical impacts such as forklifts may lead to serious degradation of the stability of industrial rack uprights.The finite element simulation model of the upright bending damage was established based on the physical test mechanism with five types of common upright in the industry as examples, and the analysis found that even a small impact deformation (1 mm) may lead to a decrease in the ultimate bearing capacity of the upright (maximum about 37%).Compared with other impacted positions, the bending damage at the prism made the upright stability decrease more significantly.Based on this, an intelligent prediction model of the bending damage state of the upright was established by physical simulation and convolutional neural network method.The results show that the residual load capacity values of the damaged upright obtained from the prediction model agree well with the finite element simulation data (the mean absolute percentage error is 5.99%) and can be used for rapid assessment of the bending damage performance of the rack upright.

In order to study the influence of residual stress and hardness on bending fatigue performance of gear, the 20MnCrS5 steel gear with carburizing heat treatment was taken as the research object, and composite small diameter shot peening strengthening treatment was carried out to realize the gear with different hardness and residual stress states of the same material.Based on the maximum principal strain criterion, incorporating separate factors for residual stress influence and residual stress-hardness coupling influence were introduced respectively to establish the fatigue life prediction model.Through shot-peened gear bending fatigue tests, optimal values for both the residual stress influence coefficient and correction coefficient were determined.The two models’ accuracy for life prediction was contrasted, and the accuracy of these models was further verified through unshot peened gear bending fatigue test.The results show that considering only residual stress influence yielded an optimal value of 0.09 for the residual stress influence coefficient, the model achieving high life predictive accuracy.Whereas considering the effects of residual stresses and hardness, it requires a correction coefficient with an optimal value of 0.04, the model achieve even higher predictive accuracy.

The traditional Markov chain Monte Carlo (MCMC) simulation method is inefficient and difficult to converge in high dimensional problems and complicated posterior probability density.In order to overcome these shortcomings, a Bayesian finite element model updating algorithm based on Markov chain population competition was proposed. First, the differential evolution algorithm was introduced in the traditional method of Metropolis-Hastings (MH) random walk algorithm.Based on the interaction of different information carried by Markov chains in the population, optimization suggestions were obtained to approach the objective function quickly. It solves the defect of sampling retention in the updating process of high-dimensional parameter model. Then, the competition algorithm was introduced, which has constant competitive incentives and a built-in mechanism for losers to learn from winners. Higher precision was obtained by using fewer Markov chains, which improves the efficiency and precision of model updating. Finally, a numerical example of finite element model updating of a truss structure was used to verify the proposed algorithm.Compared with the results of standard MH algorithm, the proposed algorithm can quickly update the high-dimensional parameter model with high accuracy and good robustness to random noise. It provides a stable and effective method for finite element model updating of large-scale structure considering uncertainty.

To address the issue of gearboxes’ vibration and noise, multi-objective topology optimization was adopted to optimize the box structure.First, a combination weighting method known as game theory comprehensive analytic hierarchy process and grey correlation was proposed to allocate optimal weight values to sub-objectives. At the same time, the iterative curves of the optimization results of the three weighting methods were compared to verify the advantages of the combination weighting method.Then, the compromise programming method was used to normalize the sub objectives to obtain the comprehensive objective function.Finally, based on the topology optimization results, stress displacement nephogram, and modal shapes, the box structure was improved.Compared with the original box, the improved box reduces the mass by 11.2%,the maximum stress of the box decreases by 39.6%, the displacement decreases by 5.1%, the node displacement amplitude response decreases by 82.8%, and the all first four-order frequencies increase.The proposed weight allocation method improves the disadvantages of low reliability of sub objective weight value allocation and ignoring subjective judgment,realizes the lightweight of the box. After the improvement of the box structure, the static and dynamic performances are significantly improved.

Based on two basic configurations of hexagonal and inner concave shapes, by utilizing experimental test and finite element simulation method, the crack expansion law of laminated porous structures under three-point bending was studied, the influence of cellular element angle of laying direction on failure mode, load capacity, and deformation of the laminated porous structures was discussed. The results indicate that the crack expansion path in the bilayer model deviates towards the weaker layer with less crack expansion inhibition capability. The weaker side experiences greater deformation,leading to a deviation of the model towards the stronger side. Under certain angle combinations, the bilayer model shows significantly improved load-bearing capacity and toughness compared to the corresponding single-layer model.

The structure of the manipulator has the characteristics of high nonlinearity and strong coupling, and high-precision motion control is a hot topic of concern for scholars.The AR4 manipulator was used as the research object to systematically analyze the forward and inverse kinematics that greatly impact the control of the manipulator, determining the manipulator’s corresponding structural parameters.And the D-H method was used to solve the numerical calculation model of the manipulator forward and inverse kinematics.The cubic spline interpolation algorithm was used to optimize the manipulator's jitter phenomenon in the joint space.In Cartesian space planning, the linear interpolation method was used to reduce the end effector’s motion distance.The specific planning points were obtained by Matlab simulation, meeting the design requirements.Finally, the SolidWorks was used to establish a three-dimensional model of the manipulator and generate an unified robot description formatc (URDF) model.The actual trajectory of the manipulator in joint and Cartesian space was planned according to MoveIt, and through RViz, the movement process was displayed.The results show that after adding the cubic spline interpolation algorithm, the joint motors of the manipulator can maintain stable operation, and the joint trajectory curvature is respectively reduced by 15.4%, 35.6%, 21.3%, 26.8%, 18.98% and 45.7%, which effectively solves the jitter vibration problem during joint movement and achieves smooth motion of the manipulator.

Aiming at the issues of under-maintenance or over-maintenance in preventive maintenance of DSA200 type pantograph, a method was proposed to optimize inspection and maintenance parameters by using pantograph failure data.Firstly, the failure datas of the pantograph components were analyzed by using graph parameter method, which failure time distribution models were fitted.The failure datas were preliminarily determined to obey the exponential distribution, and the Bartlett value method was further used to verify the validity of the failure data obey exponential distribution.Secondly, based on the structure and working characteristics of pantographs, a reliability block diagram model with pantograph components in series was constructed.According to the characteristics of constant failure rate of pantograph components, the failure rate of pantographs was obtained.Thirdly, the minimum cost model of preventive maintenance and replacement of pantographs was established, and the optimal preventive maintenance interval and the optimal number of spare parts were obtained.Finally, the structure importance, probability importance and critical importance of pantograph components were analyzed by using fault tree analysis method, and the failure probability of pantograph and the key components in inspection and maintenance were obtained.The optimized pantograph inspection and maintenance parameters can provide scientific reference for maintenance personnel to improve their maintenance level and reduce maintenance costs.

In order to investigate the nature and causes of the cracked passage hole of the low-pressure turbine shaft of aero-engine during the high and low circumference compound fatigue test, the low-pressure turbine shaft crack location was examined in appearance, fracture analysis, surface inspection, metallographic organization, finite element analysis and crack expansion simulation.The results show that the low-pressure turbine shaft passage hole crack failure is a fatigue crack, which is caused by the incomplete removal of the remelting layer after the passage hole is cut by electrical discharge machining,resulting in the existence of part of the unremoved remelting layer and visible microcracks on the internal surface, and the fatigue crack sprouted and crack expansion occurred under the action of large high and low circumferential composite load,thus leading to the passage hole crack failure. The initial crack length is estimated to be between 0.2-0.3 mm by the crack expansion simulation analysis. In order to ensure the processing quality of the through oil hole, considering the poor processing accessibility of this location, it is suggested that special tooling can be designed and the machining technology can be used for processing, on the basis of ensuring the processing, fundamental eliminate the influence of the remelting layer.