Abstract
Joints are commonly used in many large-scale engineering systems to ease assembly, and ensure structural integrity and effective load transmission. Most joints are designed around friction interfaces, which can transmit large static forces, but tend to introduce stick-slip transition during vibrations, leading to a nonlinear dynamic system. Tools for the complex numerical prediction of such nonlinear systems are available today, but their use for large-scale applications is regularly prevented by high computational cost. To address this issue, a novel adaptive reduced-order model (ROM) has recently been developed, significantly decreasing the computational time for such high fidelity simulations. Although highly effective, significant improvements to the proposed approach is presented and demonstrated in this paper, further increasing the efficiency of the ROM. An energy-based error estimator was developed and integrated into the nonlinear spectral analysis, leading to a significantly higher computational speed by removing insignificant static modes from the stuck contact nodes in the original reduced basis, and improving the computational accuracy by eliminating numerical noise. The effectiveness of the new approach was shown on an industrial-scale fan blades system with a dovetail joints, showing that the improved adaptive method can be 2–3 times more computationally efficient than the original adaptive method especially at high excitation levels but also effectively improve the accuracy of the original method.
Highlights
The assembly of single components into a more complex structure always leads to the presence of mechanical joints
Where φ are the modes of the linearized system from eigenanalysis of Eq (2); ψ are the constrain modes obtained by imposing unit displacement on the DOFs associated with internal variable Δp; η is the modal participation factors of the selected dynamic modes; ΔpR is the nonzero part of Δp; B is the Boolean matrix that to capture the nonzero part of Δp; is the overall transformation matrix for the adaptive reduced-order model
The maximum difference occurs in the frequency close to resonance at high excitation level of 8 N, which is around 2.2% lower than that from Rubin method
Summary
The assembly of single components into a more complex structure always leads to the presence of mechanical joints. The essence of this method consists in a re-written equation of motion describing the assembled structure with an underling linearized system and an adaptive internal variable that accounts the nonlinear effects from contact interface Such a formulation would allow the subsequent ROM to remove a number of redundant static modes associated with sticking nodes adaptively. The paper is organized as follows: firstly, the formulation of the adaptive ROM and the proposed error estimator is presented; it is followed by the detailed description of automatic size update algorithm with error estimator; after that, the fan blade FE model as well as its modal characteristics and the general contact mechanics in its joint will be described; the comparison of forced responses and associated computational cost between the proposed and benchmark methods is presented and discussed followed by the conclusion
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