Gas Turbine Engine Flange Bolt Hole Strengthening
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Solution Overview
Problem
Fixed engine flanges in gas turbine engines are vulnerable to stress and cracking due to heat and pressure loads, particularly around bolt holes, which can lead to premature failure and safety risks.
Innovation Solution
The method involves expanding the diameter of bolt holes in engine flanges through plastic deformation using shot peening, burnishing, or explosive treatment to strengthen the material around the bolt holes, making them more resistant to stress and increasing the flange's operational life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine flange is exposed to heat and pressure loads, then the engine operates normally, but the area around bolt holes becomes vulnerable to stress and cracking
Solution Approach 1:
The patent applies shot peening treatment to the bolt hole areas before the flange is put into service. This preliminary action creates compressive residual stresses in the critical regions around bolt holes, which counteract the tensile stresses that develop during normal operation under heat and pressure loads, thereby preventing cracking and extending flange life
Solution Approach 2:
The patent changes the physical and mechanical parameters of the flange material in the bolt hole areas through shot peening. This process alters the material's surface properties by introducing compressive residual stresses and work hardening the surface layer, transforming the stress state from vulnerable to strengthened without changing the overall flange design
2Duration of action of stationary object
If shot peening is applied to strengthen the bolt hole area, then the flange life is extended, but the bolt hole diameter increases
Solution Approach 1:
The patent carefully controls the shot peening parameters (shot size, shot velocity, treatment duration, and coverage) to achieve the desired compressive residual stress depth and magnitude while limiting the plastic deformation that causes hole expansion. By optimizing these parameters, the process extends flange life through stress modification without excessive dimensional change
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
The treatment methods significantly extend the life of the engine flanges by increasing their strength, making them less prone to cracking and breakage, with improvements ranging from two to ten times the original cycle life depending on the method used.
Implementation Method 1
plastic deformation of the material proximate the bolt hole circumference in response to applying the plurality of shot to the bolt hole circumference
Implementation Method 2
The plurality of shot is applied to the bolt hole circumference. The material proximate the bolt hole circumference is plastically deformed, thereby strengthening the material, in response to applying the plurality of shot to the bolt hole circumference.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A method may comprise providing an M-flange (200; 400; 450) of a gas turbine engine (100), wherein the M-flange (200; 400; 450) may comprise a bolt hole (240; 440; 460) therethrough defined by a bolt hole circumference (245; 445; 465) between an inner diameter (204) and an outer diameter (202) of the M-flange (200; 400; 450); heating a mandrel (422; 432; 473); inserting the heated mandrel (422; 432; 473) into the bolt hole (240; 440; 460) such that an outer edge (423; 433) of the heated mandrel (422; 432; 473) contacts the bolt hole circumference (245; 445; 465); and plastically deforming the bolt hole circumference (245; 445; 465) to strengthen the bolt hole circumference (245; 445; 465) in response to the applying the heated mandrel (422; 432; 473), producing a plastically deformed bolt hole (240; 440; 460).