A novel temperature-strain synchronous measurement method

https://doi.org/10.1016/j.optlaseng.2021.106723Get rights and content

Highlights

  • A measurement method for temperature field and strain field coupling measurement.

  • A new calibration panel is designed for infrard camera and visible camera.

  • A new method of temperature field and strain field coupling is presented.

  • The proposed method has been evaluated using simulation experiments and actual experiments.

Abstract

Thermal-mechanical coupling deformation is inevitable in the operation of materials and structures. Traditional deformation researches have mainly focused on temperature or deformation measurement at a specific temperature, but few studies have investigated the coupling relationship between temperature and deformation in a non-uniform thermal environment. This study presents a novel method of measuring the temperature and strain distribution of an object synchronously. A calibration object and its calibration method were designed to be utilized in the synchronous calibration of both the infrared and visible cameras, and a matching method of the infrared image and the visible image was proposed. The data in the non-uniform temperature field and the non-uniform strain field corresponded accurately using the proposed method. A simulation experiment and actual thermal coupling deformation experiments were utilized to verify the effectiveness and accuracy of the proposed method. The proposed method can realize the accurate correspondence of the temperature and strain fields in the measurement area and provide technical support for studying the actual thermal-mechanical coupling deformation of materials and structures.

Introduction

During the operation of aerospace vehicles and industrial components, thermal-mechanical coupling deformation is inevitable. Traditional researches mainly focus on the deformation of materials in a uniform thermal environment, and the non-uniformity of thermal distribution is often ignored. However, the requirements for operational safety and stability have increased, and new requirements have been put forward to correspond between the temperature field and the strain field in the thermal-mechanical coupling deformation process [1]. The traditional full-field measurement method can obtain accurate strain-field information through digital image correlation and has already been used in many successful applications [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. The infrared camera can also obtain precise temperature-field information [12], [13], [14]. However, the infrared image and the visible image cannot be matched due to the non-overlapping spectra, leading to the inaccuracy of structural deformation analysis.

Digital image correlation is a method of deformation measurement based on image-feature matching. The infrared camera obtains the temperature field information of the material or structure surface through infrared radiation. The acquired images of the visible-light camera and the infrared camera do not correspond because of the different spectra. When the temperature field is uniform, the average temperature-field information is often used to correspond with the strain information. However, in the actual deformation measurement, the temperature field is not uniform, causing the deformation analysis to encounter significant problems.

Due to the uneven distributions of temperature and deformation during component operation, both strain and temperature full-field information need to correspond. Traditional measurement methods cannot solve temperature and strain, so it is necessary to measure temperature and strain synchronously. Therefore, when the temperature and strain fields are not uniform, the question of how to measure the temperature-mechanical deformation arises. This is caused by two major problems: how to calibrate the visible and infrared cameras in a unified coordinate system, and how to match the temperature and strain data.

For this paper, a calibration object and its calibration method were designed to be utilized in the synchronous calibration of the infrared and visible cameras, and a matching method of the infrared and visible images was proposed. The data in the non-uniform temperature field and the non-uniform strain field corresponded accurately through the proposed method. A simulation experiment and actual thermal-coupling deformation experiments were utilized to verify the effectiveness and accuracy of the proposed method.

Section snippets

Calibration panel for infrared and visible light

The specimen's surface temperature information can be obtained using the infrared camera, but the infrared image cannot illustrate the texture information of objects. Due to this, it is impossible to use the infrared image to directly calculate the strain or match the visible camera image. In addition, the gap between the visible and infrared wavelengths makes it impossible for the infrared and visible cameras to obtain intervisibility images. A calibration method was presented and implemented

Simulation experiment

This paper's main innovation was to design a new infrared-visible synchronous-calibration panel and a calibration reconstruction method to go with it. A simulation experiment was carried out to verify the calibration and reconstruction methods’ effectiveness. A visible-light camera with a similar resolution to the infrared camera was utilized to replace the infrared camera, and the calibration panel was used for 3D calibration. The calibration method was similar to the infrared-visible cameras’

Conclusion

This paper proposed an effective measurement method for temperature and strain during non-uniform deformation. A new synchronous infrared and visible calibration panel was designed in this paper, and a new calibration and reconstruction method were presented. The internal and external parameters of infrared and visible cameras were calibrated by the proposed calibration method. The non-uniform deformation of temperature and strain was measured and reconstructed, and the effectiveness and

Author statement

A novel temperature-strain synchronous measurement method:

All persons who have made substantial contributions to the work reported in the manuscript, including those who provided editing and writing assistance but who are not authors, are named in the Acknowledgments section of the manuscript and have given their written permission to be named. If the manuscript does not include Acknowledgments, it is because the authors have not received substantial contributions from nonauthors.

Declaration of Competing Interest

The authors declared that they have no conflicts of interest to this work.

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

Acknowledgments

This work was supported by grants from the National Natural Science Foundation of China (Nos. 12072279, 11372256, 11527803, 11602201, 11502216, and 11602202) and Natural Science Basic Research Plan in Shaanxi Province of China (No. 2018JQ1060).

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