Steel Pipe Deformability Evaluation Using Wavy Shape Power Spectrum
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Solution Overview
Problem
Existing methods for evaluating the deformability of steel pipes manufactured through pipe expansion using a die are inadequate, as they assume uniform amplitude and frequency of waves, failing to account for variations in pitch and resulting random wavy shapes, which affect buckling resistance.
Innovation Solution
A method involving spectral analysis to evaluate deformability by measuring the power spectrum of the steel pipe's outer shape, integrating it over specific wavelength ranges, and adjusting the pipe expansion pitch based on the integral value to ensure sufficient deformability, regardless of pitch coarseness or fineness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pipe expansion is performed with a coarse pitch, then a long-period large-amplitude wave is obtained, but the steel pipe has poor deformability and high buckling risk
Solution Approach 1:
The patent applies parameter changes by systematically varying the pipe expansion pitch and analyzing the resulting power spectrum characteristics. By changing the pitch parameter and evaluating the integral of the power spectrum, the method identifies optimal pitch values that balance manufacturing efficiency with deformability requirements, resolving the contradiction between coarse pitch (high productivity) and fine pitch (high reliability).
Solution Approach 2:
The patent implements feedback by using the power spectrum integral value as an evaluation criterion to guide pipe expansion pitch selection. The measured outer shape is transformed into a power spectrum, integrated over specific wavelength ranges, and used to feedback into the pitch determination process, enabling iterative optimization of both productivity and deformability.
2Reliability
If pipe expansion is performed with a fine pitch, then a short-period small-amplitude wave is obtained, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent uses parameter changes to systematically explore the relationship between pipe expansion pitch and deformability. By varying the pitch parameter and evaluating the corresponding power spectrum integral, the method identifies an optimal pitch range that achieves sufficient deformability without unnecessarily fine pitch, thus maintaining manufacturing efficiency.
Solution Approach 2:
The power spectrum integral serves as a feedback mechanism that provides quantitative evaluation of deformability for different pitch values. This feedback enables the selection of the coarsest pitch that still meets deformability requirements, avoiding the inefficiency of overly fine pitch while ensuring reliability.
3Device complexity
If the amplitude of wavy shape is assumed to be constant, then evaluation is simplified, but the evaluation does not accurately reflect actual buckling resistance
Solution Approach 1:
The patent replaces the simplified mechanical assumption of constant amplitude with a spectral analysis approach. By transforming the outer shape measurement into a power spectrum and integrating over wavelength ranges, the method captures the actual distribution of shape variations without requiring complex mechanical measurement systems, thus improving accuracy while maintaining evaluation feasibility.
Solution Approach 2:
The patent changes the evaluation parameter from simple amplitude to the integral of the power spectrum over specific wavelength ranges. This parameter transformation allows accurate reflection of buckling resistance by capturing the energy distribution across different wavelengths, while the integration process keeps the evaluation methodology manageable.
Data Source
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AI summary
An object is to provide a method of evaluating deformability of steel pipe with which deformability of a steel pipe can be evaluated regardless of whether the pitch of pipe expansion is coarse or fine, and also to provide a method of manufacturing steel pipe using the method of evaluating deformability of steel pipe. A method of evaluating deformability of steel pipe according to the present invention is a method for evaluating deformability of a steel pipe manufactured through a pipe expanding step performed using a die. The method of evaluating deformability of steel pipe includes a outer shape acquiring step of measuring a shape of the steel pipe to acquire a outer shape, a power spectrum acquiring step of acquiring a power spectrum from a wavy shape of the acquired outer shape, and a determining step of integrating the acquired power spectrum for a predetermined wavelength range and determining deformability on the basis of the resulting integral.