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    Method and apparatus for quantitative nondestructive evaluation of metal airfoils using high resolution transient thermography
    2.
    发明授权
    Method and apparatus for quantitative nondestructive evaluation of metal airfoils using high resolution transient thermography 失效
    使用高分辨率瞬态热成像技术对金属翼型进行定量非破坏性评估的方法和装置

    公开(公告)号：US06394646B1

    公开(公告)日：2002-05-28

    申请号：US09292886

    申请日：1999-04-16

    Applicant: Harry Israel Ringermacher ,  Donald Robert Howard ,  Ravindra Kumar Pandey

    Inventor： Harry Israel Ringermacher ,  Donald Robert Howard ,  Ravindra Kumar Pandey

    IPC: G01N2572

    CPC classification number: G01B21/085 ,  G01B11/06 ,  G01J5/0088 ,  G01J5/0896 ,  G01J2005/0081 ,  G01N25/72

    Abstract: An IR transient thermography imaging system includes high-power flash lamps fitted with spectrally tuned optical filters and a focal-plane array camera for IR image data acquisition. The image data processing control computer analyzes acquired IR image data frames and provides a color-keyed display of an imaged object that correlates to object thickness over the imaged surface area. Acquisition of IR data is initiated at a firing of flash lamps used to heat a surface of the object along with a reference standard. A predetermined number of IR image frames are acquired and recorded over a predetermined period of time after firing of the lamps to develop a temperature-time (T-t) history of the object surface and the reference standard. A contrast curve is calculated for each pixel in the image frame, each pixel corresponding to an elemental region on the object surface. Gaussian temporal smoothing of contrast curve data is performed to improve signal-to-noise characteristics and a derivative of the contrast curve is determined using data points mathematically related to image frame number. All local peaks in the derivative of the contrast curve are identified and given significance according to a predetermined weighting function. The frame number of the most significant peak is used to determine time of occurrence of an “inflection point” in the contrast curve which is then used in determining object thickness. Gain correction of pixel intensity data is employed to offset IR emissivity variations caused by surface curvatures and varying surface conditions on an object.

    Abstract translation: IR瞬态热成像系统包括配有光谱调谐光滤波器的大功率闪光灯和用于IR图像数据采集的焦平面阵列相机。 图像数据处理控制计算机分析获取的IR图像数据帧，并提供与成像表面区域上的物体厚度相关的成像对象的彩色键控显示。 红外线数据的获取是在用于加热物体表面的闪光灯与参考标准一起发射的。 在点火之后的预定时间段内获取并记录预定数量的IR图像帧，以形成对象表面和参考标准的温度 - 时间（T-t）历史。 对图像帧中的每个像素计算对比度曲线，每个像素对应于物体表面上的元素区域。 执行对比度曲线数据的高斯时间平滑以改善信噪比特性，并且使用与图像帧号数学相关的数据点来确定对比度曲线的导数。 对比度曲线的导数中的所有局部峰值根据预定的加权函数被识别并给出重要性。 最高有效峰的帧数用于确定对比度曲线中出现“拐点”的时间，然后将其用于确定物体厚度。 采用像素强度数据的增益校正来抵消由物体表面曲率和表面条件变化引起的红外辐射率变化。

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