Creep Damage Evaluation Using Steel Strip Mediator
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Solution Overview
Problem
Small diameter metal pipes, such as boiler pipes, experience rapid creep void development and rupture, making it difficult to apply existing service life evaluation methods without surface scraping, which shortens the pipe's service life.
Innovation Solution
A method involving a steel strip wrapped around the pipe under tension, with a master curve correlation to evaluate service life based on the strip's deterioration, using internal pressure creep tests and heat treatment to accelerate damage, allowing non-invasive assessment of remaining service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surface scraping is performed to measure wall thickness and bulging, then measurement precision is improved, but the pipe wall thickness decreases and service life is shortened
Solution Approach 1:
A steel strip is introduced as an intermediary element wrapped around the metal pipe. The steel strip serves as a mediator that transfers the deformation state of the pipe to a measurable form through its own deformation, allowing non-contact assessment of pipe condition without removing material from the pipe itself.
Solution Approach 2:
The steel strip creates a copy or replica of the pipe's circumferential deformation state. By measuring the deformation of the steel strip (which mirrors the pipe's deformation), the actual pipe condition can be assessed without directly measuring or damaging the pipe surface.
2Duration of action of stationary object
If a steel strip is wrapped around the pipe to monitor deformation, then service life is preserved, but measurement of creep damage becomes indirect and potentially less accurate
Solution Approach 1:
The method transforms the measurement parameter from direct wall thickness measurement to steel strip deformation measurement. The steel strip's dimensional changes (length, circumference) serve as proxy parameters that correlate with the pipe's creep damage state, enabling indirect measurement that preserves the pipe while maintaining measurement capability.
Solution Approach 2:
The steel strip is positioned to wrap around specific critical sections of the pipe where creep damage is most likely to occur. This localized monitoring approach focuses measurement quality on the most vulnerable areas, ensuring accurate detection of creep damage where it matters most while preserving the overall pipe structure.
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 precise evaluation of remaining service life without surface scraping, using a steel strip with similar material properties to the pipe, allowing for accurate durability correlation and extended pipe life prediction.
Implementation Method 1
a steel strip, made of a metal material having a thermal expansion coefficient and strength of the metal pipe or greater, is wrapped under tension around an outer peripheral face of a test piece made of the same material
Implementation Method 2
the steel strip is subjected to heat treatment in advance. In this method, deterioration of the steel strip is accelerated by the heat treatment
Implementation Method 3
a steel strip, made of a metal material having a thermal expansion coefficient and strength of the metal pipe or greater
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3
AI summary
[Problem] Remaining service life of a metal pipe suffering from creep damage is measured without scraping the surface of the metal pipe. [Solution] In a remaining service life evaluation method according to the present invention, the remaining service life of a metal pipe (1) suffering from creep damage is evaluated on the basis of a master curve that is prepared in advance. The master curve is prepared by performing an internal pressure creep test in a state in which a steel strip (2), made of a metal material having a thermal expansion coefficient and strength of the metal pipe or greater, is wrapped under tension around an outer peripheral face of a test piece (11) made of the same material and having the same inner and outer diameters as the metal pipe. The master curve indicates a relationship between a degree of deterioration of the steel strip and remaining service life of the metal pipe. To evaluate the remaining service life, a steel strip is wrapped around an outer peripheral face of the metal pipe under the same conditions as those during the internal pressure creep test. The degree of deterioration of the steel strip with the use of the metal pipe is then measured, and applied to the master curve.