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Aiming at the problem of fatigue life prediction of aluminum alloy wheel hub, a fatigue life prediction model considering damage accumulation is proposed and tested. The Finite Element Models of a wheel hub under bending fatigue test and radial fatigue test are established, and the main failure positions are studied by simulation analysis. The S-N curves of material and part are established by using the nominal stress method, and the average stress of the asymmetric cyclic load borne by the wheel hub is corrected by using the Morrow line. Considering the rotation process of the wheel hub, a theoretical model for predicting the fatigue life is constructed by using the linear cumulative damage theory. Taking an aluminum alloy wheel hub as an example, the life calculated by the theoretical model is 448.2 thousands revolutions. Compared with the fatigue life of 473.3 thousands revolutions given by the bending fatigue test, the error is about 5.6%, which verifies the effectiveness of the fatigue life prediction theoretical model.

Accurate automobile-demand forecasting can provide effective guidance for automobile-manufacturing enterprises in terms of production planning and supply planning. However, automobile sales volume is affected by historical sales volume and other external factors, and it shows strong non-stationarity, nonlinearity, autocorrelation and other complex characteristics. It is difficult to accurately forecast sales volume using traditional models. To solve this problem, a forecasting model combining trend extrapolation and causality analysis is proposed and derived from the historical predictors of sales volume and the influence of external factors. In the trend-extrapolation model, the historical predictors of sales series was captured based on the Seasonal Autoregressive Integrated Moving Average (SARIMA) and Polynomial Regression (PR); then, Empirical Mode Decomposition (EMD), a stationarity-test algorithm, and an autocorrelation-test algorithm were introduced to reconstruct the sales sequence into stationary components with strong seasonality and trend components, which reduced the influences of non-stationarity and nonlinearity on the modeling. In the causality-analysis submodel, 31-dimensional feature data were extracted from influencing factors, such as date, macroeconomy, and promotion activities, and a Gradient-Boosting Decision Tree (GBDT) was used to establish the mapping between influencing factors and future sales because of its excellent ability to fit nonlinear relationships. Finally, the forecasting performance of three combination strategies, namely the boosting series, stacking parallel and weighted-average parallel strategies, were tested. Comparative experiments on three groups of sales data showed that the weighted-average parallel combination strategy had the best performance, with loss reductions of 16.81% and 4.68% for data from the number-one brand, 25.60% and 2.79% for data from the number-two brand, and 46.26% and 14.37% for data from the number-three brand compared with the other combination strategies. Other ablation studies and comparative experiments with six basic models proved the effectiveness and superiority of the proposed model. [ABSTRACT FROM AUTHOR]

Triangular track wheels of emergency rescue vehicles need high mobility and reliability under various terrain conditions. Aiming at overlong time of multi-working fatigue optimization calculation,ensemble of surrogate model is used to accelerate the optimization solution. In order to ensure convergence accuracy,a new evaluation index of surrogate model is proposed. First of all,fatigue life of support frame of replaceable triangular track wheel under four working conditions is analyzed.Then,based on Kriging model and response surface model,ensemble of surrogate model is constructed for mass and fatigue life.In order to approach global optimal point more easily,ensure same concavity and convexity between predicted value and observed value,local trend deviation is proposed as evaluation criterion of constructing ensemble model. Finally,size optimization of support frame is constructed. Results show ensemble of surrogate model not only ensures calculation accuracy,but also has robustness. Fatigue life of triangular track wheel after lightweight design is increased by 43. 59%.

The topology optimization of dynamic stress constraints is highly nonlinear and singular and has been little studied. Dynamic stress based on progressive structural optimization is only available by applying the modal iteration method, but due to the nonlinear limitations of the modal superposition method, there is an urgent need to develop a progressive structural optimization method based on dynamic stress sensitivity under direct integration. This method is for the dynamic stresses under non-periodic loading with iterative cycle updating variations. This article proposes a topological optimization method of continuum structures with stress constraints under an aperiodic load based on the Bi-directional Evolutionary Structural Optimization Method (BESO). First, the P-norm condensation function was used to obtain the global stress to approximate maximum stress. By introducing the Lagrange multiplier, the design goal was to increase the P-norm stress on the basis of the smallest volume. After that, based on the dynamic finite element theory, the sensitivity of each cell formula of the objective function and the constraint conditions of the design variables were strictly derived. Then, the performance evaluation index was put forward based on volume and stress, and the convergence criterion based on the performance evaluation index was defined. This method solves the topology optimization problem of stress constraints under a non-periodic load and the topology optimization problem of stress constraints under a periodic load, such as a simple harmonic load. [ABSTRACT FROM AUTHOR]

The wheel rim is an annular and thin-walled structure with complex structural features and working conditions. Guaranteeing its safety and lightweight are two major concerns in wheel rim design. In this study, a shape optimization method based on load path analysis is proposed to evaluate and optimize the structure of the wheel rim. The load-transfer law of the wheel rim is identified based on the load path visualization. Two design criteria are put forward to evaluate the load-bearing performance and give the improvement suggestions. Then, the shape optimization problem is simplified to a parameter optimization problem, and the optimal size combination performance-oriented is obtained using the non-dominated sorting genetic algorithm II (NSGA-II). As a case study, a wheel rim is redesigned and the optimization result shows that the stiffness and strength are improved under bending and radial fatigue simulation, while the weight is reduced by 3.78%. Two stages of experimental studies are carried out to verify the optimization method. The static pressure test shows that the bending resistance performance of the wheel rim is improved by 4.57%, and the load transfer is more uniform. The radial impact test shows that the impact deformation at a high energy level is reduced by 13.77%, indicating that the impact resistance performance is significantly improved. [ABSTRACT FROM AUTHOR]

Dissipative particle dynamics simulations were adopted to study the mechanism of lyotropic liquid crystal (LLC) formation and the synthesis process of silica nanowires by LLC template method. Simulation results show that the one-dimensional (1D) LLC channel can be formed at the Pluronic F127 concentration range of 61 ∼ 67%. With the increase of Pluronic F127 concentration, the diameter of LLC channel decreases and the deformation degree increases. The effect of PEO: PPO ratio on the diameter of LLC channel is slight. The appropriate PEO: PPO ratio of Pluronic is 40:70 for the formation of 1D LLC channel, as the deformation degree of channel is the smallest in this case. The effect of polymerisation degree on the diameter and deformation degree of LLC channel is both little. With the increase of TEOS concentration, the nanowire diameter increases rapidly at first, and then increases quite slowly. This work can provide guidance for silica nanowires synthesis by LLC template method. [ABSTRACT FROM AUTHOR]