Residual Stress Evaluation from Cavitation Impact Pressure Mapping
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Solution Overview
Problem
Existing methods for evaluating residual stress after water jet peening (WJP) rely on analyzing cavitation energy and bubble collapse pressure, which do not accurately predict the distribution of impact pressure on the surface, limiting the effectiveness of stress corrosion cracking prevention.
Innovation Solution
A method that analyzes the generation and disappearance state of cavitation bubbles during WJP to predict the actual impact pressure distribution, allowing for the evaluation of residual stress and adjustment of processing conditions to achieve target stress values, using a computer program that models jet flow and calculates impact pressure correlation values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cavitation energy analysis is used to evaluate residual stress, then the evaluation method is simple, but the prediction accuracy of impact pressure distribution is insufficient
Solution Approach 1:
The patent introduces an impact pressure correlation value as an intermediary parameter that connects the cavitation bubble dynamics (void fraction and collapse fraction) to the actual impact pressure distribution. This correlation value, obtained through CFD analysis, serves as a bridge that translates bubble generation and disappearance states into meaningful impact pressure predictions, thereby improving accuracy without requiring direct complex measurement of impact pressure
Solution Approach 2:
The patent creates a virtual model (CFD simulation) that copies and replicates the physical WJP process, allowing the impact pressure distribution to be predicted through simulation rather than direct measurement. The simulation model reproduces the cavitation bubble behavior and calculates the resulting impact pressure field, providing accurate predictions without the complexity of experimental measurement systems
2Productivity
If WJP is performed under unproven processing conditions, then productivity is improved by avoiding extensive experimentation, but reliability of residual stress evaluation is reduced
Solution Approach 1:
The patent performs preliminary CFD analysis and calculations of impact pressure correlation values before actual WJP processing. By pre-evaluating the impact pressure distribution and predicted residual stress for different processing conditions through simulation, the optimal parameters can be determined in advance, allowing direct application to actual processing without extensive trial-and-error experimentation
Solution Approach 2:
The patent establishes a feedback loop where the predicted residual stress results are compared against target values, and the processing conditions are adjusted accordingly. The system provides feedback on whether the predicted outcomes meet the desired specifications, enabling iterative optimization of processing parameters while maintaining reliability even when working with unproven conditions
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
Enables accurate evaluation and adjustment of residual stress after WJP, ensuring effective prevention of stress corrosion cracking and reliable operation under specific plant specifications, even with unproven processing conditions.
Implementation Method 1
highpressure water is injected from a nozzle to the surface of a target to produce bubbles (cavitation bubbles), and the impact pressure generated at the collapse of the cavitation bubbles is made use of to create plastic deformation on the surface of the target
Implementation Method 2
in WJP, highpressure water is injected from a nozzle to the surface of a target to produce bubbles (cavitation bubbles)
Implementation Method 3
the void fraction f and the collapse fraction η of bubbles in the jet flow are calculated, and an impact pressure correlation value Pc which is a correlation value of an impact pressure P is calculated on the basis of the void fraction f and the collapse fraction η
Data Source
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AI summary
A method of evaluating a residual stress, comprising includes: a condition setting step of setting a processing condition of water jet peening for a processing target; an analysis step of analyzing a jet flow when a fluid is injected from a nozzle model to a processing target model in accordance with the processing condition, and obtaining a void fraction which is a volume fraction of bubbles contained in a unit volume of the fluid, and a collapse fraction, which is a volume fraction of the bubbles which collapse in a unit time in the unit volume of the fluid, at each position on a surface of the processing target model; an impact pressure correlation value calculating step of obtaining an impact pressure correlation value, which is a product of the void fraction and the collapse fraction at each position; an experimental value acquisition step of obtaining an impact pressure experimental value, which is an experimental value of an impact pressure applied to a surface of the processing target due to the water jet peening under the processing condition; a prediction step of obtaining an impact pressure predicted value, which is a predicted value of the impact pressure applied to each position on the surface of the processing target due to the water jet peening under the processing condition, by associating the impact pressure correlation value at each position on the surface of the processing target model with the impact pressure experimental value applied to the surface of the processing target by the water jet peening under the processing condition; and a residual-stress evaluation step of calculating a residual stress of the processing target after the water jet peening under the processing condition by using the impact pressure predicted value obtained in the prediction step as an input condition.