A quantitative super-sensitivity photogrammetry method for full-field dynamic strain measurements

IF 8.9 1区 工程技术 Q1 ENGINEERING, MECHANICAL
Guojian Cui , Shanwu Li , Yongchao Yang
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引用次数: 0

Abstract

Full-field, high-precision strain measurements are critical for accurately characterizing structural dynamic behavior and local damage states. While traditional strain measurement techniques (e.g., strain gauges) typically provide only discrete point measurements, incoherent optical methods especially photogrammetry with digital image correlation and optical flows, provide a practical alternative to enable full-field strain estimation; however, their sensitivity remains insufficient for precise strain measurement applications. In this work, we quantitatively study the key influencing factors on the sensitivity limit of strain measurements and develop a super-sensitivity photogrammetry method for precise full-field dynamic strain measurement. Specifically, first, the developed method builds upon the recent advances in super-sensitivity optical flows that statistically exceeds the sensitivity limit for full-field displacement measurements. Then, it incorporates a Locally Estimated Scatterplot Smoothing (LOESS) algorithm to further suppress minor residual errors remaining in the obtained localized displacement field, coupled with higher pixel spatial resolution, to eventually achieve high-precision full-field strain measurements. Furthermore, a quantitative mathematical model of the achievable strain measurement sensitivity is theoretically derived based on uncertainty propagation theory, as δɛ=2/Naσ/Ns1/(2B1)+b. This model elucidates the parametric dependence of strain measurement sensitivity on five key factors: imaging noise level (σ), number of effective spatial pixels (Ns), camera bit depth (B), pixel gauge length (N), and effect of displacement smoothing algorithm (a,b). The effectiveness of the proposed method for full-field, high-precision strain measurement, and the derived quantitative theoretical model are validated through both numerical simulations and laboratory experiments on fundamental beam-type structures; notably, the developed method is found to be able to achieve a level of precision at microstrain, comparable to contact discrete strain gauge measurements. Moreover, observations on the parametric analysis of number of effective spatial pixels (Ns) and pixel gauge length (N) are consistent, quantitatively, with the derived mathematical model of the achievable strain measurement sensitivity. Thus, this work provides a novel quantitative super-sensitivity photogrammetry method for high-precision full-field dynamic strain estimation. Finally, remaining challenge associated with the fundamental mechanism of the strain measurement sensitivity is also discussed.
一种用于全场动态应变测量的定量超灵敏度摄影测量方法
全场、高精度应变测量是准确表征结构动态行为和局部损伤状态的关键。虽然传统的应变测量技术(如应变片)通常只提供离散点测量,但非相干光学方法,特别是具有数字图像相关和光流的摄影测量,提供了一种实用的替代方案,可以实现全场应变估计;然而,它们的灵敏度仍然不足以用于精确的应变测量应用。本文定量研究了影响应变测量灵敏度极限的关键因素,提出了一种高精度全场动态应变测量的超灵敏度摄影测量方法。具体来说,首先,开发的方法建立在超灵敏度光流的最新进展之上,统计上超过了全场位移测量的灵敏度限制。然后,结合局部估计散点图平滑(local Estimated Scatterplot Smoothing,黄土)算法,进一步抑制得到的局部位移场残留的微小误差,再加上更高的像素空间分辨率,最终实现高精度的全场应变测量。在此基础上,基于不确定性传播理论推导了可实现应变测量灵敏度的定量数学模型:δ δ =2/N⋅a⋅σ/Ns⋅1/(2B−1)+b。该模型阐明了应变测量灵敏度对成像噪声级(σ)、有效空间像元数(Ns)、相机位深(B)、像元计长(N)和位移平滑算法效果(a, B)五个关键因素的参数依赖性。通过数值模拟和室内试验,验证了该方法对基梁型结构进行全场高精度应变测量的有效性,并建立了定量理论模型;值得注意的是,发现开发的方法能够在微应变下达到一定程度的精度,可与接触离散应变计测量相媲美。此外,有效空间像元数(Ns)和像元计长度(N)的参数分析结果与推导的可实现应变测量灵敏度数学模型在定量上是一致的。因此,本工作为高精度全场动态应变估计提供了一种新的定量超灵敏度摄影测量方法。最后,讨论了与应变测量灵敏度的基本机制相关的遗留问题。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Mechanical Systems and Signal Processing
Mechanical Systems and Signal Processing 工程技术-工程:机械
CiteScore
14.80
自引率
13.10%
发文量
1183
审稿时长
5.4 months
期刊介绍: Journal Name: Mechanical Systems and Signal Processing (MSSP) Interdisciplinary Focus: Mechanical, Aerospace, and Civil Engineering Purpose:Reporting scientific advancements of the highest quality Arising from new techniques in sensing, instrumentation, signal processing, modelling, and control of dynamic systems
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