Fatigue Usage Factor Calculation Using Characteristic Curves
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Solution Overview
Problem
Conventional methods for calculating fatigue in mechanical devices overestimate fatigue usage, leading to a shortened expected lifespan due to the use of design-transient state fatigue values, which are not reflective of actual operational changes in temperature, pressure, and flow rate.
Innovation Solution
An apparatus and method that calculate a fatigue usage factor based on an operation-transient state by generating a characteristic fatigue usage factor curve, which accurately reflects changes in the operation environment, allowing for a more accurate calculation by multiplying the design-transient state fatigue usage factor by a predetermined rate specific to the operation-transient state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the design-transient state fatigue usage factor is used for calculation, then the safety margin is increased, but the accuracy of fatigue usage factor calculation deteriorates and the expected lifespan is shortened
Solution Approach 1:
The patent transitions from using a static design-transient state to dynamically tracking the actual operation-transient state. The system continuously monitors real-time operation parameters (temperature, pressure, flow rate) and calculates fatigue usage factors based on the actual transient state the device is experiencing, rather than applying a fixed conservative design assumption throughout operation.
Solution Approach 2:
The patent changes the parameters used for fatigue calculation from fixed design-transient state parameters to variable operation-transient state parameters. By monitoring actual operation parameters and adjusting the fatigue usage factor calculation based on real-time conditions, the system adapts the calculation parameters to match actual operating conditions, resolving the contradiction between safety and accuracy.
2Ease of manufacture
If the design-transient state fatigue usage factor is used, then the calculation method is simple, but the expected lifespan prediction becomes conservative and inaccurate
Solution Approach 1:
The patent replaces the manual or static calculation method with an automated system that continuously monitors operation parameters and dynamically calculates fatigue usage factors. This substitution of the calculation approach maintains relative simplicity through automation while dramatically improving lifespan prediction accuracy by using real-time data.
Solution Approach 2:
The system implements feedback by continuously monitoring actual operation parameters and using this information to adjust the fatigue usage factor calculation. The real-time feedback loop allows the system to maintain simple automated calculation while accurately reflecting actual operating conditions, thereby improving lifespan predictions without sacrificing methodological simplicity.
3Reliability
If the design-transient state is assumed for all operation conditions, then the design stage requirements are met, but the actual operational fatigue is overestimated
Solution Approach 1:
The patent segments the operation into distinct states: design-transient state for compliance verification and actual operation-transient state for accurate fatigue calculation. By separating these functions, the system maintains design stage compliance while using actual operational data for precise fatigue assessment, eliminating the overestimation caused by applying design assumptions to all conditions.
Solution Approach 2:
The patent applies different quality standards to different operational contexts. The design-transient state criteria are applied specifically for design compliance verification, while the actual operation-transient state parameters are used for operational fatigue calculation. This localized application of different standards ensures both design compliance and operational accuracy without mutual interference.
Data Source
AI summary
The present invention relates to an apparatus and a method for calculating a fatigue usage factor with respect to fatigue generated in the material of a mechanical device depending upon changes of an operation environment during operation of the mechanical device. A fatigue usage factor UOP.cyc,transient n, which is based on the operation-transient state n, is calculated by multiplying a fatigue usage factor based on a design-transient state UDSGN.cyc,transient n by the value of a characteristic fatigue usage factor F (k) as shown in the following equation:UOP.cyc,transient n=F(k)×UDSGN.cyc,transient n Since a characteristic fatigue usage factor curve devised in accordance the present invention uses the characteristic fatigue usage factor curve obtained on the basis of the operation-transient state when calculating a transient-based fatigue usage factor, it is possible to much more accurately calculate the fatigue usage factor with respect to any operation-transient state of the mechanical device compared with the prior art.