Centrifugal Compressor Wheel Treatment for Low-Cycle Fatigue
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Centrifugal compressor wheels face life-limiting low-cycle fatigue (LCF) failures, particularly due to cracks initiating at the bore surface or in the back disk, which existing technologies have not adequately addressed.
Innovation Solution
A treatment process involving cold working of the bore to induce compressive residual hoop stresses and surface peening to create compressive residual stresses on the compressor wheel surfaces, using a mechanical tool for bore expansion and shot peening to enhance the LCF life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compressor wheel operates under cyclic loading conditions, then it performs its compression function, but low-cycle fatigue cracks initiate at the bore surface or back disk reducing component life
Solution Approach 1:
Compressive residual stresses are induced in the bore surface and back disk regions through cold working and surface peening operations performed before the compressor wheel enters service. This preliminary action creates a protective stress state that counteracts the tensile stresses developed during cyclic operation, preventing crack initiation and extending the component's fatigue life.
Solution Approach 2:
The invention applies compressive residual stresses as a preliminary counter-action to the tensile stresses that cause fatigue failure. By pre-establishing this opposing stress state in critical regions (bore surface and back disk), the component is protected against the harmful effects of cyclic loading before service begins.
2Reliability
If cold working is applied to the bore to induce compressive residual stresses, then fatigue resistance improves, but the manufacturing process complexity increases
Solution Approach 1:
The fatigue protection is applied segmentally to specific critical regions rather than uniformly across the entire component. Cold working is targeted at the bore surface where cracks commonly initiate, and surface peening is applied to the back disk and blade root fillet areas. This segmented approach provides effective fatigue protection while minimizing unnecessary manufacturing complexity in non-critical regions.
3Reliability
If surface peening is performed to induce compressive residual stresses, then crack propagation is inhibited, but the manufacturing time and process complexity increase
Solution Approach 1:
Surface peening is applied with local quality by targeting specific regions where cracks are most likely to propagate, such as the back disk and blade root fillet areas. The peening intensity and coverage are optimized for these critical zones rather than uniformly treating the entire component surface, thereby improving crack propagation resistance while minimizing unnecessary manufacturing time spent on non-critical areas.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly extends the low-cycle fatigue life of centrifugal compressor wheels by inducing compressive residual stresses, reducing the likelihood of crack initiation and propagation.
Implementation Method 1
cold working the metal at an inner surface of the bore beyond the tensile yield strength in a hoop-wise direction about the bore, so as to induce compressive residual hoop stresses in the metal adjacent the inner surface of the bore
Implementation Method 2
surface peening is performed on at least a portion of the compressor wheel to induce compressive residual stresses in surfaces of the wheel
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
A process for treating a centrifugal compressor wheel includes a combination of cold expansion of at least part of the bore of the wheel to induce residual compressive stresses in a region around the bore, and surface peening at least parts of the compressor wheel such as the back disk and portions of the blades.