For revolving components like compressor stages in aero-engine, it is critical to ensure that the overall concentric performance of the assembly is extremely excellent to satisfy the requirements of vibration-free and noise-free. However, in practical production, it is hard to meet the target requirement by manual adjustments; in virtual assembly, it is difficult to build an effective deviation propagation model with traditional methods. This article focuses on two points: one is the assembly technique of multistage rotational optimization and the other is the deviation propagation model for revolving components assembly. The revolution joint was introduced in the unified Jacobian–Torsor model to provide the rotary regulating effects. This modified model has advantages of being able to consider rotating optimization, geometric tolerance, and percentage contribution compared with other mathematical methods. General formulas for the n-stage components assembly were derived including the deviation propagation function and optimization destination expression. Comparisons between three assembly techniques and experiments were made to prove the suggested method was feasible and of high practicability. It can be integrated with computer-aided design systems to propose assistance for operators in assembling stage or redesign parts tolerances where FEs’ percentage contributions can be obtained in design preliminary stage.
21 November 2014 in Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science
The small displacement torsor model is a classic three-dimensional tolerance analysis method. It uses three translational vectors and three rotational vectors to represent tolerance information in three-dimensional Euclidean space. However, the target features of this model mainly focused on planes and cylinders in previous studies. Little attention is invested to conical features and their joints which are used widely and more complex than the planar and cylindrical features. The objective of this article is to present a three-dimensional mathematical method of tolerance representation about conical surfaces and their joints based on the small displacement torsor model, and propose a mathematical model of variations and constraint relations of components of the small displacement torsor for conical surfaces caused by geometric tolerances limited by its tolerance zone. In addition, a simple example involving conical structures is used to demonstrate three-dimensional conical tolerance propagation. Both deterministic and statistical results are obtained by this model.
1 January 2016 in Journal of Mechanical Engineering