A Robot Trajectory Optimization Approach for Thermal Barrier Coatings Used for Free-Form Components
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A Robot Trajectory Optimization Approach for Thermal Barrier Coatings Used for Free-Form Components Zhenhua Cai1 • Beichun Qi2 • Chongyuan Tao1 • Jie Luo1 • Yuepeng Chen1 Changjun Xie1
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Submitted: 30 September 2016 / in revised form: 9 July 2017 Ó ASM International 2017
Abstract This paper is concerned with a robot trajectory optimization approach for thermal barrier coatings. As the requirements of high reproducibility of complex workpieces increase, an optimal thermal spraying trajectory should not only guarantee an accurate control of spray parameters defined by users (e.g., scanning speed, spray distance, scanning step, etc.) to achieve coating thickness homogeneity but also help to homogenize the heat transfer distribution on the coating surface. A mesh-based trajectory generation approach is introduced in this work to generate path curves on a freeform component. Then, two types of meander trajectories are generated by performing a different connection method. Additionally, this paper presents a research approach for introducing the heat transfer analysis into the trajectory planning process. Combining heat transfer analysis with trajectory planning overcomes the defects of traditional trajectory planning methods (e.g., local over-heating), which helps form the uniform temperature field by optimizing the time sequence of path curves. The influence of two different robot trajectories on the process of heat transfer is estimated by coupled FEM models which demonstrates the effectiveness of the presented optimization approach. Keywords heat transfer analysis off-line programming thermal barrier coatings & Beichun Qi [email protected] Zhenhua Cai [email protected] 1
Automation School, Wuhan University of Technology, Wuhan 430000, China
2
School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430000, China
Introduction The thermal spray process can be applied to deposit a broad range of materials (metals, carbides, ceramics, plastics, etc.) in molten, semi-molten or solid states on components to create a functional film with optimum properties (Ref 1-3). This technology is extremely effective at prolonging the service life of the products, decreasing machinery downtime, and increasing performance in a great variety of industrial applications. For high reproducibility and optimum deposition quality of complex components (e.g., a gas turbine blade), thermal spray processes are usually guided by programmed industrial robots. Therefore, a well-designed robot trajectory should first ensure an accurate control of some process parameters in thermal spraying (e.g., scanning speed, spray distance, scanning step, etc.) to fulfill the coating quality requirements (e.g., coating thickness uniformity, etc.). During the thermal spray process, heat and mass transfer plays a crucial role in the development of residual stresses, which in turn has a vital influence on a large number of coating properties such as adhesion stress, hardness, formation of microcracks, and t
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