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With the increase in running speed, the aerodynamic characteristics of high-speed trains have a significant impact on running stability, energy consumption and passenger comfort. Since the shape of the high-speed train head can directly influence the surrounding airflow, optimizing the head shape is the primary way to improve the aerodynamic performance of the train. This paper reviews current research studies on the surrogate-based aerodynamic shape optimization of high-speed train heads, aiming to provide a comprehensive reference for designers to enhance design efficiency and optimization performance. The entire optimization process is divided into four essential steps, and the key optimization technologies in each step are discussed, including parametric modeling, computational fluid dynamics (CFD) simulation, surrogate model and optimization algorithm. By introducing the practical applications of these technologies, we summarize their advantages and disadvantages and suggest four potential research directions for the future. [ABSTRACT FROM AUTHOR]

R-test is widely used to measure the rotary axis errors of five-axis machine tools due to its accuracy and convenience. There are some deficiencies in the research on the customized design of contact R-test under certain requirements of measuring range and accuracy. A novel hardware configuration method of contact R-test is proposed in this paper to realize customized configuration of hardware parameters of R-test. Firstly, a theoretical measurement model is established according to the structural characteristics of the contact R-test and is used as the evaluation model for measuring accuracy. Secondly, the influence of hardware parameters on the performance indexes is analyzed and the corresponding performance-constrained model is established. Thirdly, the configuration method of hardware parameters based on constraint models is proposed using the exhaustive search method and variable parameter method respectively. Finally, a prototype based on the configuration method is developed and calibrated on the Coordinate Measuring Machine (CMM), then the measuring performance evaluation and on-machine error measuring experiment are performed. The results show that the configuration method satisfies certain measuring requirements without range and precision waste. The proposed methods can guide the customized design of contact R-test. [ABSTRACT FROM AUTHOR]

In finishing machining, the quality of workpiece is significantly influenced by the performance of solid cutting tool. Solid cutting tool flank is ground by CNC tool grinder in accordance with the tool path of grinding wheel. In actual grinding process, the grinding area of wheel will be gradually worn down, resulting in the decrease of geometric accuracy of flank and even wrong profile. In order to compensate the error, a compensation algorithm of tool path for solid cutting tool flank based on grinding wheel wear is proposed. Firstly, the coordinate systems are defined for the grinding process of flank, and the orientation and location calculation model of ideal wheel with the grinding process parameters is derived. Secondly, based on the profile description of wheel wear, flank errors are analyzed. Then, the compensation algorithm for anastomosis of cutting edge and relief angle is proposed. Finally, series of experiments of simulation and actual grinding are carried out. The comparison of the results shows that the algorithm can reduce the influence of wheel wear effectively, which can also improve the grinding quality stability and prolong the service life of grinding wheel. [ABSTRACT FROM AUTHOR]

The determination of AGV vehicle requirements in a manufacturing system has a great impact on the system performance. This paper first defines the AGV vehicle requirement determination as a general optimization problem, and secondly develops a new AGV vehicle requirement determination method capable of effective solving the problem. This method features with the combination of discrete event simulation (DES), sensitivity analysis, fractional factorial design (FFD) and response surface methodology (RSM). Tests and comparisons with other simulation based methods have shown that the proposed method combining the simulation method with analytical method, can make full use of their respective advantages and overcome the defects of existing methods. It is more practical. [ABSTRACT FROM AUTHOR]

In five-axis multi-layer flank milling process, the geometric error of tool rotation profile caused by radial dimension error and setup error has great influence on the machining accuracy. In this work, a new comprehensive error prediction model considering the inter-layer interference caused by tool rotation profile error is established, which incorporates a pre-existing prediction model dealing with a variety of errors such as geometric errors of machine tool, workpiece locating errors, and spindle thermal deflection errors. First, a series of tool contact points on the tool swept surface in each single layer without overlapping with others are calculated. Second, the position of the tool contact points on the overlapped layers is updated based on the detection and calculation of inter-layer interferences. Third, all evaluated tool contact points on the final machined surface are available for completing the accuracy prediction of the machined surface. A machining experiment has been carried out to validate this prediction model and the results show the model is effective. [ABSTRACT FROM AUTHOR]

The workpiece contour errors from previous process affect current process. In order to improve workpiece allowance distribution, this article presents a workpiece registration and localization adjustment method with contact inspection. According to the analysis of machining deviation, the rotational and translational registration matrixes from multi-tolerance surfaces to workpiece are obtained by surface characteristic and translational vectors. The workpiece localization (position and orientation) adjustment can be realized by transforming coordinate systems of 5-axis machine tool. Through adaptive and iterative registration and adjustment, the optimized workpiece localization for current process is obtained. The experimental results show that the method can improve allowance uniformity effectively. [ABSTRACT FROM AUTHOR]

For a toroid-shaped end-milling cutter to have multi-structure features of tooth offset center and introversion of bottom edge, this article proposes a generalized parametric modeling method of the bottom edge, including a straight edge segment and a circular arc edge segment. And based on the parametric model, this article also deduces the corresponding tool path for grinding of the bottom edge's rake and flank faces. The parametric modeling method is based on the geometric analytic equations while the grinding method is driven by the proposed parametric model and the parameters of rake and flank faces. The two methods can be applied to a bottom edge of a cutter with multi-structure features to guarantee G1 continuity at the two joints for connecting a circular arc edge with a straight edge and a conical helix edge, respectively. In order to verify the accuracy of proposed methods, experiments were carried out. The modeling and grinding experimental results verified the accuracy and utility of the methods. [ABSTRACT FROM AUTHOR]

A railway vehicle is a complicated mechatronic system. Its mechanical structure and connections are key influences on its performance. When a railway vehicle runs at very high speeds its dynamic performance becomes of considerable interest. Therefore, the identification of the design factors that significantly impact on the vehicle’s running behavior, such as safety, stability, comfort and reliability, is a key step towards vehicle design optimization. The optimal design of a railway vehicle is difficult to perform using existing methods due to the complexity inherent in rail/track interactions. Thus, performing a sensitivity analysis of a railway vehicle can be seen as a bridge between performance analysis and an optimal design. This paper presents a sensitivity model that can be used to analyze the performance parameters of a railway vehicle in terms of variation of its design parameters. First, the railway vehicle is described as a multi-body system that can be broken down into its component parts and then, the dynamic behavior of the system is investigated. To simplify the model, a spring/damper connection is used in the classic Hertz nonlinear elastic contact model to represent the force in the normal direction at the wheel/rail contact point. Finally, based on the adjoint variable method, the equations that constitute the sensitivity model of the railway vehicle are derived and analysis software is developed. A case study shows the reliability of the proposed approach. [ABSTRACT FROM PUBLISHER]

Machining accuracy is the most critical indicator to evaluate the machining quality of parts in metal cutting industry. However, it is difficult to be identified before real cutting, because of a variety of error sources presented in a machining process system, such as assembly inaccuracy of machine tool, deformation caused by temperature variation and dynamic cutting force, tool wear, servo lag and so on. Consequently, it is difficult to determine whether a new machining process can satisfy accuracy requirements beforehand. Traditionally, a machining process is validated through the “trial and error” approach, which is time consuming and costly. If machining accuracy can be predicted to a large extent, a rational process can be planned to ensure the precision of parts and even to maximize resource utilization without trial cuts. For this purpose, this work focuses on machining accuracy prediction for five-axis peripheral milling based on the geometric errors. An error synthesis modeling method is proposed to integrate the geometric errors of the process system, including machine tool geometric error, workpiece locating error, cutting tool dimension error and setup error. From a multi-body system point of view, all these errors are synthesized to generate position error of the cutting contact point in the workpiece coordinate system. Then the machining error is obtained by projecting the position error to the workpiece normal vector, which can be measured by a coordinate measuring machine. The prediction model has been evaluated by a cutting test with our in-house-developed prototype software. The result shows that the proposed method is feasible and effective. [ABSTRACT FROM PUBLISHER]

Ball-end milling cutter with tooth offset center is widely used in machining industry, because it has higher machining efficiency and better stability compared with the ball-end milling cutter without tooth offset center. In addition, the tooth offset center has lower wear rate of the tool tip so the life of the milling cutter is improved. However, up to present, there is no mature and effective theory for the design and manufacture of this kind of milling cutters. This article presents a new mathematical model for S-shaped edge curve of the ball end taking the tooth offset center into account, which can construct accurate S-shaped edge curve for the ball-end cutting tools with tooth offset center as well as without tooth offset center. This model overcomes the complex computation and bad adaptability of the traditional modeling method. At the same time, a five-axis grinding algorithm for rake face of the ball end is also presented in this article. Finally, based on the application programming interface of CATIA™, a three-dimensional computer-aided design and computer-aided manufacturing system is developed. The accuracy and effectiveness of the grinding algorithm are verified by simulation in VERICUT™ and machining experiment in tool grinding machine. [ABSTRACT FROM PUBLISHER]

This article presents a new integrated geometric model that takes worktable as reference for five-axis machine tools. It could simplify the description of different machine kinetic structures and uniform the measurement coordinate system and machining coordinate system. Based on this model, a new method of measuring geometric errors with conventional instruments is proposed. It could break through some existing limitations, such as special instrument, specific machine kinetic structures, or errors incompletion. In addition, some deviation errors in measuring process could be eliminated to improve accuracy further. Finally, a series of experiments are conducted on a five-axis machine tool with rotary worktable and tilting head. The results show that the error model and measuring method are effective and applicable. [ABSTRACT FROM AUTHOR]

For complex mechanical systems, to overcome design inconsistencies, it is becoming more and more necessary that product design system is effectively integrated with various analysis models and tools from multiple engineering domains at different design stages. In this article, a Holistic Product Design and Analysis Model, which is well supported by Top–Down design method, is conceptualized to define design and analysis integration at different levels, which will help enhance engineering design and analysis interoperability and integrate the design methods and analysis tools across multiple engineering domains. It is based on four design levels: system, subsystem, machine and component designs; at each level, design and analysis models are integrated under a Generalized Multirepresentation Architecture supporting design, analysis and optimization appropriately. For cross-level integration from top to bottom, the design models are transferred and mapped with more structural and geometric details, while analysis models obtain more detailed design constraints from the top levels. This new architecture has been developed and demonstrated with an application in a railway vehicle system design, although its optimization components have not been fully implemented. This model can be used for general mechanical product system design. [ABSTRACT FROM AUTHOR]