Multi-objective Optimization Of The Space Path Of Pipe Based On ISIGHT Platform

With the rapid development of our country’s aerospace industry, the pipe as "cardiovascular" of aero engine plays a very important role, and related research also gets more and more attentions. Pipe is widely used in aviation, aerospace, automobile and other core components, mainly used for transporting fuel, lubricating oil and other medium such as air. If the pipe is broken, experiment or flight safety of the aero engine will be effected to cause immeasurable loss. In the failure mode of pipe, the damage caused by random vibration fatigue has the largest proportion. This paper is based on the horizontal topic-random vibration characteristic analysis of a engine pipe. In the paper, for increasing the fatigue life of small pipes in aero engine, space path is redesigned through structural optimization.In the paper, based on ISIGHT platform to realize the multi-objective optimization, the specific studies are done as follows:(1) Beam-solid hybrid model is introduced to establish the pipe parametric finite element model in ANSYS, describing a simplified model of pipe. Three interval method based on Gaussian distribution and Miner rule are applied in the analysis of random vibration fatigue life of both simplified model and fine finite element model.(2) Mechanics model considering the effect of the mass and stiffness factors of the model is established. By using the theory of cantilever beam and structure optimization function of ANSYS, a conclusion is proposed that height of vertical beam in the pipe is fixed in a range which is important in the pipe design. Based on the dynamic analysis in ANSYS, a dynamics analysis software is created by packaging ANSYS batch orders.(3) In ANSYS, the pipe parametric finite element model is created with the method of using one or more control points to control the B-spline describing the space path of pipe. Coordinate values of control points are set as design variables, and each random fatigue life in different directions under the action of power spectral density function is set as objective function on ISIGHT platform. NSGA-II algorithm is used to design the space path of the pipe of four types (mechanics model, acute angle head out of plane, acute angle head in plane, obtuse angel head out of plane) for solving multi-objective optimization problem. Random vibration fatigue life of some pipe in single direction is increased by dozens of times, and the lowest life of all directions is also increased by2-10times. The optimum results are compared between ISIGHT and ANSYS.(4) For the requirements of actual application, new model which improves its random fatigue life is available on ISIGHT platform. And there is a certain damping point in the new model. Random vibration fatigue life of the minimum direction is greatly increased nearly55times, and minimum life of all directions is increased almost four times.This paper will provide reasonable technical support and help engineers in designing the geometric model of pipe, which needed to improve random vibration fatigue life.