<p>Transverse breathing cracks are common failures of rotor systems that seriously affect the safety of machines. Under multi-crack fault conditions, the relative orientation angle between cracks may cause the cracks’ breathing state to be out of sync, so as to change the systems’ dynamic characteristics. Currently, relevant research mainly focuses on models with fixed cracks, whereas the effect of relative orientation angle is supposed to be studied deeply. To address this issue, a non-equally spaced gas turbine rotor system with multiple breathing cracks has been constructed. Further, the dynamic equations of this system are established through the Finite Element Method (FEM), and the crack influence on rotor stiffness is calculated by the Fracture Mechanics Theory (FMT). Comparisons with previously published research are made to prove the validity of this model. Results notably indicate the reduction of natural frequency due to the breathing crack, which is much more significant in multi-crack cases and can be disturbed by the relative orientation angle. In addition, the relative orientation angle has a significant impact on the vibrations at the <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40430_2025_5484_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">$2\omega$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>2</mn> <mi>ω</mi> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40430_2025_5484_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">$3\omega$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>3</mn> <mi>ω</mi> </mrow> </math></EquationSource> </InlineEquation> characteristic frequencies. This paper highlights the significant reduction of systems’ natural frequency due to the multi-crack fault and the influence of crack relative orientation angle on vibration characteristics. These insights provide a theoretical basis for multi-crack fault detection and rotor system diagnostics.</p>

Dynamic characteristics of a multiple-crack rotor system versus crack relative orientation angle

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发表日期：

2025年3月21日

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Cheng Hu,
Shun Jiang,
Jian Duan,
Tielin Shi

摘要

Transverse breathing cracks are common failures of rotor systems that seriously affect the safety of machines. Under multi-crack fault conditions, the relative orientation angle between cracks may cause the cracks’ breathing state to be out of sync, so as to change the systems’ dynamic characteristics. Currently, relevant research mainly focuses on models with fixed cracks, whereas the effect of relative orientation angle is supposed to be studied deeply. To address this issue, a non-equally spaced gas turbine rotor system with multiple breathing cracks has been constructed. Further, the dynamic equations of this system are established through the Finite Element Method (FEM), and the crack influence on rotor stiffness is calculated by the Fracture Mechanics Theory (FMT). Comparisons with previously published research are made to prove the validity of this model. Results notably indicate the reduction of natural frequency due to the breathing crack, which is much more significant in multi-crack cases and can be disturbed by the relative orientation angle. In addition, the relative orientation angle has a significant impact on the vibrations at the $2\omega$ $2 ω$ and $3\omega$ $3 ω$ characteristic frequencies. This paper highlights the significant reduction of systems’ natural frequency due to the multi-crack fault and the influence of crack relative orientation angle on vibration characteristics. These insights provide a theoretical basis for multi-crack fault detection and rotor system diagnostics.