Key Engineering Materials Vols. 579-580

Abstract: The assembly of ship blocks is achieved through welding. To get a high level of closure accuracy, finite element analysis (FEA) is always needed to predict the welding deformation. However, the fast automatic mesh generation technique during the finite element method (FEM) for the ship assembly is not mature enough yet. Due to the complex ship architecture, during FEA, the model must be built up manually in most cases. This process is complicated and the errors are easy to occur. Consequently, the efficiency of FEA during the ship assembly is highly affected. Automatic mesh generation is a key factor restricting the development of FEM, since the quality and speed of the mesh generation directly influence the accuracy of calculation and the efficiency of analysis. In the field of marine engineering and aerospace engineering, the mesh elements are required to be quadrilateral. However, the technique of the quadrilateral mesh generation is still more difficult and less mature than that of the triangular mesh generation. This work proposed a hybrid mesh generation algorithm, borrowing the advantages from both the quad-morphing algorithm and the paving algorithm as well as considering the factor of multi-constraints. An example case is also given to illustrate the result of this proposed algorithm.

Abstract: Resilient modulus (M_R) of cohesive subgrade soil is a critical parameter for pavement design and evaluation with mechanistic-empirical method. The objective of this paper was to establish a constitutive model of M_R of cohesive subgrade soil on the basis of triaxial repeated loading tests considering moisture condition coupled with stress. Major findings can be seen from this study. Firstly, M_R increases with the increase of confining pressure under the condition of the same deviator stress. The increase rate of M_R of cohesive subgrade soil with higher water content is more obvious than that of cohesive subgrade soil with lower water content. Secondly, M_R decreases with the increase of deviator stress under the condition of the same confining pressure. The decrease rate of M_R of cohesive subgrade soil with different water contents keeps the same range, which keeps between 30 percent and 35 percent. Thirdly, the effect of deviator stress on M_R is more than that of confining pressure. Cohesive subgrade soil exhibits the feature of the stress softening. Finally, the predicted value of M_R based on the established constitutive model has a good relevancy to its measure value. There is litter doubt that these findings provide practical supports for attaining M_R in the design of pavement structure.

Abstract: To improve the smoothness of SFS reconstructed surface, a new approach based on genetic algorithm is proposed. First, by analyzing the principle of SFS, the reason for surface error and distortion zone are found. By adding data according to the symmetric and asymmetric principle and B spline, data in the distortion zone are added and the reconstruction of SFS is realized. The evaluation criteria for smoothness of curves and surfaces are given according to the mathematical sense and concurrent level of CAGD/CAD/CAM. The surface smoothing process is turn into two curve smoothing process in two directions. The evaluation criteria is taken as the constraint condition and then the smoothing of SFS reconstructed surface based on the genetic algorithm is realized. The experimental results show that this new approach is an effective way to eliminate the bad points of SFS surface, improve the surface quality so it is a practical method for surface smoothing.

Abstract: Lane changing is the common behavior when cars are running. It will produce traffic conflict, reduce the efficiency of road system, and lead to malignant traffic accidents. Based on the analysis and evaluation of circular, cosine type, constant lane migration type and ladder lane transformation type, considering the driver behavior, vehicles control and dynamic constraints and thinking the obstacles as an infinite number of circles to idealize them, this paper establishes polynomial in horizontal and vertical directions respectively to indicate the position of vehicle, obtains the lane changing trajectory by testing whether the distance between circles meet some conditions, builds polynomial for the safe lane changing trajectory and real-time dynamic optimal distances between vehicles, and then utilize the MATLAB as the simulation tool to make experiments in various cases. Simulations and experimental results show that the method given in this paper to calculate the vehicle safety lane changing trajectory in the case of high-speed vehicle is feasible, effective and can give quickly safety lane changing distance.

Abstract: Orderly organization of traffic engineering in the urban CBD (Center Business District) is a difficult problem, with crowding people flow, heavy traffic flow and complex surrounding situation. This paper set CBD along Xinhua Street in Jinhua city center as an example, focused on the organization optimization process of traffic engineering in CBD. Through the survey on traffic engineering status of sections and intersections, it analyzed road congestion characteristics and intersection signal timing with Vissim software emulation, proposed traffic optimization methods as road channelization, intersection signal timing adjustment of Xinhua-Liberation Road. In Xinhua Street section, it can effectively canalized traffic flow by broadening 2 two-way lanes, adding four pedestrian crossing refuges, and separating Motor vehicle and non-motor vehicle separation barrier. It took queue length, number of stops, delay time three indicators as the objective function with the application of Synchro software adjusting the intersection signal timing. As a result, the total queue length could be reduced from 708.5m to 586.6m and total capacity from 2041 pcu/ h to 2838 pcu/ h.

Abstract: Due to the change of car-body design, the location of exhaust systems hanger is uncertain and always fluctuates around the initial design position. So the Taguchi method is introduced to conduct exhaust systems optimal design. Firstly, the parameterization of hanger location under the grid environment was realized by combining NastranHypermesh and Isight. Then, the Taguchi robust design of the exhaust system is performed taking the hanger location as noise factors and the stiffness of hanger shock absorber as control factors. As a result, modal property and robustness of the exhaust system are improved. At last, the results of Taguchi robust design and traditional sensitivity optimization design based on the finite element method are compared, which reveals the advantage of Taguchi robust design in improving product quality.

Abstract: The safety and reliability of railway vehicle braking system is put forward higher requirement for railway speed increasing. Compared with domestic product, foreign disc brake unit has obvious advantage on compactness of structure, stability of braking pad friction coefficient, braking power, safety and reliability etc. Thus, the research has theoretical significance and engineering value. Firstly, the working principle of disc brake unit is obtained by performing spatial mechanisms analysis of some imported disc brake unit and adjuster structure, then using MBD (Multi-body Dynamics) simulation software, by importing the geometric model of brake unit into RecurDyn, to make preprocess of simplifying and merging and add constraints and contact relation, driving control functions, etc, finally to establish a simulation experiment model. The working characteristic of the brake unit and adjuster's displacement curve of clearance compensation is obtained through the braking and releasing simulation results of braking pad before and after wear out. The research results provide a method based on virtual prototype for analyzing and validating working mechanism of disc brake unit.

Abstract: To accurately calibrate the working range of equilibrium moisture of clay subgrade, according to unsaturated soil mechanics basic theories, the filter paper method was used to measure matrix suction and to establish soil-water characteristic curve (SWCC) model with reflecting function between moisture and metrics suction. The prediction method about the working range of equilibrium moisture of unsaturated clay subgrade was proposed and the model was tested. The results show that equilibrium moisture of clay subgrade out the affected range of the precipitation and evaporation is mainly controlled by the impact of groundwater. The Fredlund & Xing model can better characterize the unsaturated cohesive subgrade soil humidity and the correlation matrix suction and the model parameters possessed highly reliability. The prediction result of clay subgrade's equilibrium moisture on groundwater control area has high uniformity with experimental result. The prediction method is reasonable and reliable. The results provide new perspectives and standpoints to objectively characterize the equilibrium moisture status of unsaturated clay subgrade.

Abstract: t is a big challenge faced by the enterprises that how to trace and manage the quality information of complex products effectively in the overall life circle. In this paper, two-dimensional code is regarded as a carrier of quality information,and statistical process control (SPC) is used to evaluate the production process and control the on-line quality.Quality tracing and management model is established which consists of three parts:the identification of parts by two-dimensional code,the real-time acquisition of process information and the quality management.The proposed model is validated and successfully implemented in a typical complex products manufacturer for quality tracing and management.

Abstract: Parabolic trough solar thermal power generation system is always restricted by high drive torque, low thermal efficiency and high investment cost. In this paper, the parabolic trough solar collector in a solar energy application base is taken as the research object and FEM was used to realizing its structural light-weighting design. The structural overall performance is improved to lay a foundation for innovating drive mode and expanding the rotation scope. Beginning of the paper, the wind load characteristic was analyzed and its computational formula was provided the magnitude of wind load was computed; then, the static performance of the solar collector was analyzed by using ANSYS Workbench and the worst working condition of each static characteristic was confirmed to service for the later structural optimization; last, the overall optimization scheme of the solar collector was put forward, the position of the reflectors supporting point and the structure of the solar collectors cantilever was optimized.