Axial force measurement device, axial force measurement method, and axial force measurement system

The axial force measuring device corrects for eccentricity in fastening elements by using image analysis and a database to accurately determine axial force, addressing the precision issues in existing methods.

WO2026140559A1PCT designated stage Publication Date: 2026-07-02HITACHI LTD
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Patent Information

Authority / Receiving Office
WO · WO
Patent Type
Applications
Current Assignee / Owner
HITACHI LTD
Filing Date
2025-11-11
Publication Date
2026-07-02

AI Technical Summary

Technical Problem

Existing methods for measuring axial force in fastening elements like bolts fail to account for eccentricity, leading to low measurement accuracy due to misalignment and uneven compliance, which affects the precision of axial force estimation.

Method used

An axial force measuring device that utilizes an image acquisition unit, strain calculation unit, strain distribution extraction unit, eccentricity calculation unit, and axial force search unit to measure radial strain and correct for eccentricity by referencing an axial force database, enabling accurate axial force determination.

Benefits of technology

Enables high-accuracy measurement of axial force in fastening elements even when eccentricity occurs, improving measurement precision by accounting for eccentricity direction and magnitude.

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Abstract

The present invention measures axial force with high precision in a fastening element even if eccentricity occurs.　This axial force measuring device comprises: an image acquisition unit that acquires at least two images of a fastening element in a state in which a change in axial force has occurred; a strain calculation unit that calculates, on the basis of the images of the fastening element, radial strain generated in the fastening element; a strain distribution extraction unit that extracts a radial strain distribution of a predetermined cross-section of the fastening element from the radial strain and identifies a direction of eccentricity of the fastening element; an eccentricity calculation unit that calculates the magnitude of the eccentricity of the fastening element on the basis of the radial strain distribution; an axial force database in which, for each axial force generated in the fastening element, radial strain distributions are associated with a combination of eccentricity direction and magnitude and registered; and an axial force retrieval unit that refers to the axial force database and retrieves the axial force corresponding to the calculated eccentricity direction and magnitude, as well as the extracted radial strain distribution.
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