Browsing by Author "Sirikham, Adisorn"

Now showing 1 - 8 of 8
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    A confidence map based damage assessment approach using pulsed thermographic inspection
    (Elsevier, 2017-10-07) Zhao, Yifan; Addepalli, Sri; Sirikham, Adisorn; Roy, Rajkumar
    In the context of non-destructive testing, quantification of uncertainty caused by various factors such as inspection technique, testing environment and the operator is important and challenge. This paper introduces a concept of contour-based confidence map and an application framework for pulsed thermography that offers enhanced flexibility and reliability of inspection. This approach has been successfully applied to detect three flat-bottom holes of diameter 32, 16 and 8 mm drilled onto a 5 mm thick aluminium plate with a high accuracy of damage detection (R > 0.97). Its suitability and effectiveness in assessing impact damage occurring in composites have also been demonstrated.
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    Determination of thermal wave reflection coefficient to better estimate defect depth using pulsed thermography
    (Elsevier, 2017-08-22) Sirikham, Adisorn; Zhao, Yifan; Mehnen, Jorn
    Thermography is a promising method for detecting subsurface defects, but accurate measurement of defect depth is still a big challenge because thermographic signals are typically corrupted by imaging noise and affected by 3D heat conduction. Existing methods based on numerical models are susceptible to signal noise and methods based on analytical models require rigorous assumptions that usually cannot be satisfied in practical applications. This paper presents a new method to improve the measurement accuracy of subsurface defect depth through determining the thermal wave reflection coefficient directly from observed data that is usually assumed to be pre-known. This target is achieved through introducing a new heat transfer model that includes multiple physical parameters to better describe the observed thermal behaviour in pulsed thermographic inspection. Numerical simulations are used to evaluate the performance of the proposed method against four selected state-of-the-art methods. Results show that the accuracy of depth measurement has been improved up to 10% when noise level is high and thermal wave reflection coefficients is low. The feasibility of the proposed method in real data is also validated through a case study on characterising flat-bottom holes in carbon fibre reinforced polymer (CFRP) laminates which has a wide application in various sectors of industry.
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    Estimation of damage thickness in fibre-reinforced composites using pulsed thermography
    (2018-10-31) Sirikham, Adisorn; Zhao, Yifan; Nezhad, Hamed Yazdani; Du, Weixiang; Roy, Rajkumar
    Non-destructive-testing (NDT), including active thermography, has become an inevitable part of composite process and product verification, post-manufacturing. However, there is no reliable NDT technique available to ensure the interlaminar bond integrity during composite laminates integration, bonding or repair where the presence of thin airgaps in the interface of dissimilar polymer composite materials would be detrimental to structural integrity. This paper introduces a novel approach attempting to quantify the damage thickness of composites through a single-side inspection of pulsed thermography. The potential of this method is demonstrated by testing on three specimens with different types of defect, where the Pearson Correlation Coefficients of the thickness estimation for block defects and flat-bottom holes are 0.75 and 0.85, respectively. This approach will considerably enhance the degradation assessment performance of active thermography by extending damage measurement from currently two dimensions to three dimensions, and become an enabling technology on quality assurance of structural integrity.
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    A miniaturised active thermography system for in-situ inspections
    (Elsevier, 2020-12-18) Du, Weixiang; Liu, Haochen; Sirikham, Adisorn; Addepalli, Sri; Zhao, Yifan
    With the increase of the functionalisation, integration and complexity of industrial components and systems, deploying Non-Destructive Testing (NDT) devices for ‘in-situ’ inspection has become a major challenge for high-value assets. Due to the mismatching of size and volume between the existing inspection unit and the targeted complex object, inaccessibility and inapplicability have limited the applicability of NDT techniques. To address this challenge, this paper introduces a novel miniaturised active thermography system based on a commercial thermal imaging sensor featured with small size and low cost. Combining with different excitation sources, its detection performance on different types of defect of carbon fibre reinforced polymer (CFRP) is investigated and compared with an existing system. The results show that the proposed system can work with laser and flash effectively for degradation assessment although the detectability is compromised. Such a technique will play a unique role in the in-situ inspection where the space to deploy the device is limited.
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    A miniaturised active thermography system to inspect composite laminates
    (IEEE, 2020-10-13) Du, Weixiang; Liu, Haochen; Zhao, Yitian; Sirikham, Adisorn; Addepalli, Sri; Zhao, Yifan
    With the rapid increase of the integration and complexity of industrial components, the inaccessibility and inapplicability of existing Non-destructive testing devices have become a bottleneck for in-situ inspection of these objects. This paper introduces a miniaturised active thermography system featured with a small size, low resolution and low-cost thermal sensor, where two optional excitation sources including flash and laser are integrated. Dedicated data analysis approaches to evaluate defects are proposed considering the degraded signal quality. Three carbon fibre reinforced polymer laminates with a variety of defects are evaluated quantitatively and qualitatively using the proposed system by comparing with two existing non-miniaturised inspection systems. The results show that the proposed system can work effectively for the degradation assessment of composite laminates. Even with the technical limitations that affect the detectability, for instance, the low pixel resolution, this technique will play an important role to inspect components featured with geometrically intricate space
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    A novel defect depth measurement method based on nonlinear system identification for pulsed thermographic inspection
    (Elsevier, 2016-08-30) Zhao, Yifan; Mehnen, Jorn; Sirikham, Adisorn; Roy, Rajkumar
    This paper introduces a new method to improve the reliability and confidence level of defect depth measurement based on pulsed thermographic inspection by addressing the over-fitting problem. Different with existing methods using a fixed model structure for all pixels, the proposed method adaptively detects the optimal model structure for each pixel thus targeting to achieve better model fitting while using less model terms. Results from numerical simulations and real experiments suggest that (a) the new method is able to measure defect depth more accurately without a pre-set model structure (error is usually within 1% when SNR>32 dB) in comparison with existing methods, (b) the number of model terms should be 8 for signals with SNR∈View the MathML source 8–10 for SNR>40 dB and 5–8 for SNR<30 dB, and (c) a data length with at least 100 data points and 2–3 times of the characteristic time usually produces the best results.
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    Three-dimensional subsurface defect reconstruction for industrial components using pulsed thermography
    (Cranfield University, 2020-05) Sirikham, Adisorn; Zhao, Yifan; Mehnen, Yorn
    Pulsed thermography is a promising method for detecting subsurface defects, but most pulsed thermographic inspection results are represented in the form of 2D images. Such a representation can limit the understanding of where the defects initiate and how they grow by time, which is a key to predict the remaining use of life of component and feedback to the design to avoid such defects. Threedimensional subsurface defect visualisation is a solution that can unlock this limitation. A straightforward approach to reconstruct 3D subsurface defect is conducting two inspections on both front and rear sides. However, the deployment of this approach can be limited because 1) one side of the inspected component could be inaccessible; 2) the accuracy of measurement could be compromised if the defect thickness is very thin due to extreme closed values of defect depths from two inspections; and 3) if the defect is too deep for one side, the defect could be missed. Addressing the challenge of 3D subsurface defect reconstruction and visualisation, this thesis proposes a novel technique to measure defect depth and estimate defect thickness simultaneously through estimating the thermal wave reflection coefficient value achieved by introducing a modified heat transfer model based on a single-side inspection method. The proposed method is validated through model simulations, experimental studies, and a use case. Four composite samples with different defect types, sizes, depths and thicknesses, are used for experimental studies; a steel sample with a ‘s’ shape triangular air-gap inside is used for a use case. The simulation results show that under the noise level of 25 dB, the percentage error of the developed depth measurement method is 0.25% whilst the minimum error of the best existing method is 2.25%. From the experimental study results, the averaged percentage error of the defect thickness estimation is less than 10% if the defect thickness is no more than 3 mm. For the use case, the reconstructed defect shape is similar to the X-ray image.
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    Three-dimensional subsurface defect shape reconstruction and visualisation by pulsed thermography
    (Elsevier, 2019-12-04) Sirikham, Adisorn; Zhao, Yifan; Liu, Haochen; Xu, Yigeng; Williams, Stewart; Mehnen, Jorn
    Defects detected by most thermographic inspection are represented in the form of 2D image, which might limit the understanding of where the defects initiate and how they grow over time. This paper introduces a novel technique to rapidly estimate the defect depth and thickness simultaneously based on one single-side inspection. For the first time, defects are reconstructed and visualised in the form of a 3D image using cost-effective and rapid pulsed thermography technology. The feasibility and effectiveness of the proposed solution is demonstrated through inspecting a composite specimen and a steel specimen with semi-closed airgaps. For the composite specimen, this technique can deliver comparatively low averaged percentage error of the estimated total 3D defect volume of less than 10%.