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Enhancement of Contact Acoustic Nonlinearity Effect in a Concrete Beam using Ambient Vibrations 利用环境振动增强混凝土梁中的接触声非线性效应
IF 1.1 Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-12-28 DOI: 10.1115/1.4064374
Yikuan Wang, Abhijit Mukherjee
Contact acoustic nonlinearity (CAN) is generated when oscillating crack faces open and close while a wave passes through it. However, reliably assessing the nonlinear effect due to micro-scale defects is challenging, especially in concrete structures, due to their large size, high attenuation and low signal-to-noise ratio. However, concrete facilities vibrate due to ambient excitations such as vehicle movement, wind, and water flow. These ambient vibrations can be utilised in amplifying CAN. For example, a vehicle can be moved at a particular velocity over a bridge to amplify a particular natural mode of vibration. This paper illustrates a method of enhancing contact acoustic nonlinearity with the help of ambient vibrations of the structure. A finite element (FE) model of a concrete beam with a thin crack is developed. The base of the beam was oscillated at 100 Hz. Simultaneously, a 200 kHz ultrasonic excitation was applied on the beam to monitor its propagation through the crack. The closing and opening of the crack generate the nonlinear behavior of the ultrasonic pulse. A considerable increment of nonlinearity was observed demonstrating the efficacy of the proposed method. The time windows for the nonlinear zone have been identified. A laboratory experiment has been performed to demonstrate the proposed method in reinforced concrete beams. This investigation demonstrates that CAN can be utilised in monitoring concrete structures when ambient vibrations are taken into account.
接触声非线性(CAN)是在波通过振荡裂纹面时,裂纹面开合产生的。然而,由于微尺度缺陷尺寸大、衰减高、信噪比低,可靠地评估微尺度缺陷引起的非线性效应具有挑战性,尤其是在混凝土结构中。然而,混凝土设施会因车辆行驶、风和水流等环境激励而振动。这些环境振动可用于放大 CAN。例如,车辆可以特定的速度在桥上行驶,以放大特定的自然振动模式。本文阐述了一种借助结构的环境振动来增强接触声非线性的方法。本文建立了一个带有细裂缝的混凝土梁的有限元 (FE) 模型。梁的底部以 100 Hz 的频率振动。同时,在梁上施加 200 kHz 超声波激励,以监测其在裂缝中的传播。裂缝的闭合和打开产生了超声波脉冲的非线性行为。观察到了非线性的显著增加,证明了所建议方法的有效性。非线性区的时间窗口已经确定。在钢筋混凝土梁中进行的实验室实验证明了所提出的方法。这项研究表明,在考虑到环境振动的情况下,CAN 可用于监测混凝土结构。
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引用次数: 0
Identification of spalling fault size of ball bearing based on modified energy value 基于修正能量值的球轴承剥落故障尺寸识别
IF 1.1 Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-12-04 DOI: 10.1115/1.4064186
Ke Zhang, Ru Zhang, Zinan Wang, X. Bai, H. Shi
The size of bearing outer ring spalling failures has a significant impact on the vibration and service life of rotating machinery. It is necessary to judge the size of the outer ring fault size. Most of the vibration analyses identify the bearing fault size only in terms of the shock interval. The decreasing impact of the shock on the vibration signal will be related to the identification accuracy of the shock interval. This study aims to identify some feasible vibration signal processing methods for the identification of outer ring spalling sizes of ball bearings based on a modified energy value. The method involves the influence of impact forces on the measured vibration characteristics. According to the simulation analysis, the mapping relationship between the vibration signals with different fault sizes and the modified energy value is obtained. Then, the size of the spalling failure size of the ball bearing outer ring is determined. Compared to existing methods, the proposed method is less affected by impact forces. Simulation and experiment results have verified the accuracy of this fault size identification.
轴承外圈剥落故障的大小对旋转机械的振动和使用寿命有重大影响。有必要判断外圈故障大小的大小。大多数振动分析仅根据冲击间隔来识别轴承故障大小。冲击对振动信号影响的减小将与冲击区间的识别精度有关。本研究旨在基于修正能量值识别球轴承外圈剥落尺寸,找出可行的振动信号处理方法。该方法涉及到冲击力对被测振动特性的影响。通过仿真分析,得到了不同故障大小的振动信号与修正能量值之间的映射关系。然后,确定了球轴承外圈剥落破坏尺寸的大小。与现有方法相比,该方法受冲击力的影响较小。仿真和实验结果验证了该方法识别故障大小的准确性。
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引用次数: 0
Deep Learning based Time-Series Classification for Robotic Inspection of Pipe Condition using Non-Contact Ultrasonic Testing 基于深度学习的非接触式超声管道状态机器人检测时序分类
Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-11-08 DOI: 10.1115/1.4063694
Steven Hespeler, Hamidreza Nemati, Nihar Masurkar, Fernando Alvidrez, Hamidreza Marvi, Ehsan Dehghan Niri
Abstract This journal paper explores the application of Deep Learning (DL)-based Time-Series Classification (TSC) algorithms in ultrasonic testing for pipeline inspection. The utility of Electromagnetic Acoustic Transducers (EMAT) as a non-contact ultrasonic testing technique for compact robotic platforms is emphasized, prioritizing computational efficiency in defect detection over pinpoint accuracy. To address limited sample availability, the study conducts benchmarking of four methods to enable comparative evaluation of classification times. The core of the DL-based TSC approach involves training DL models using varied proportions (60%, 80%, and 100%) of the available training dataset. This investigation demonstrates the adaptability of DL-enabled anomaly detection with shifting data sizes, showcasing the AI-driven process's robustness in identifying pipeline irregularities. The outcomes underscore the pivotal role of artificial intelligence (AI) in facilitating semi-accurate but swift anomaly detection, thereby streamlining subsequent focused inspections on pipeline areas of concern. By synergistically integrating EMAT technology and DL-driven TSC, this research contributes to enhancing the precision and near real-time inspection capabilities of pipeline assessment. This investigation collectively highlights the potential of DL networks to revolutionize pipeline inspection by rapidly and accurately analyzing ultrasound waveform data.
摘要:本文探讨了基于深度学习(DL)的时间序列分类(TSC)算法在管道超声检测中的应用。强调了电磁声换能器(EMAT)作为紧凑型机器人平台的非接触式超声波检测技术的实用性,优先考虑缺陷检测的计算效率而不是精确的精度。为了解决有限的样本可用性,本研究对四种方法进行基准测试,以便对分类时间进行比较评估。基于DL的TSC方法的核心是使用可用训练数据集的不同比例(60%、80%和100%)来训练DL模型。该研究展示了基于dl的异常检测随数据大小变化的适应性,展示了人工智能驱动过程在识别管道不规则性方面的鲁棒性。研究结果强调了人工智能(AI)在促进半准确但快速的异常检测方面的关键作用,从而简化了后续对管道关注区域的集中检查。本研究将EMAT技术与dl驱动的TSC技术协同集成,有助于提高管道评估的精度和近实时检测能力。这项研究共同强调了DL网络通过快速准确地分析超声波形数据来彻底改变管道检查的潜力。
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引用次数: 0
Longitudinal wave propagation in an elastic cylinder embedded in a viscoelastic fluid 纵波在嵌入粘弹性流体中的弹性圆柱体中的传播
Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-11-07 DOI: 10.1115/1.4064012
Mohamed Aninou, Adil El Baroudi, Jean Yves Le Pommellec
Abstract A novel analytical investigation of longitudinal wave propagation in an elastic cylinder embedded in a viscoelastic fluid is proposed. The Maxwell model is used to describe the viscoelastic fluid behavior. With appropriate boundary conditions, a complex dispersion equation of longitudinal wave has been established. The aim of this paper is to study the effect of the fluid rheological properties on the longitudinal wave characteristics (attenuation and velocity). It is shown that the attenuation is the sum of a viscous and non viscous component. The viscosity induced attenuation is predominant at low frequencies. On the other hand, the effect of the liquid amount and elastic cylinder radius on the attenuation and velocity are studied. A critical normalized liquid thickness is highlighted. Beyond this critical value, the influence of the outer boundary condition can be neglected. At last, among other interesting phenomena, it is highlighted that if the Deborah number increases, the attenuation decreases. This variation characterize a stiffening of the viscoelastic medium. In addition, the obtained results show that the viscosity measurement should be performed at low frequencies using small elastic cylinder radius. Accordingly, these investigations are novel and can be applied in geophysics, food industry, medicine, non-destructive testing of materials, design and development of fluid sensors.
摘要提出了一种新的纵波在嵌入粘弹性流体中的弹性圆柱体中的传播解析方法。麦克斯韦模型用于描述粘弹性流体的行为。在适当的边界条件下,建立了纵波的复色散方程。本文的目的是研究流体流变特性对纵波特性(衰减和速度)的影响。结果表明,衰减是粘性分量和非粘性分量之和。粘滞性衰减在低频下占优势。另一方面,研究了液量和弹性圆柱半径对衰减和速度的影响。一个临界归一化液体厚度被突出显示。超过这个临界值,外边界条件的影响可以忽略不计。最后,在其他有趣的现象中,强调了当波底拉数增加时,衰减减小。这种变化表现为粘弹性介质的硬化。此外,得到的结果表明,粘度测量应在低频率下进行,使用小弹性圆柱半径。因此,这些研究是新颖的,可以应用于地球物理、食品工业、医学、材料无损检测、流体传感器的设计和开发。
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引用次数: 0
AI-enabled crack-length estimation from acoustic emission signal signatures 基于声发射信号特征的人工智能裂纹长度估计
Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-11-07 DOI: 10.1115/1.4064011
Shane Ennis, Victor Giurgiutiu
Abstract This article addresses the classification of fatigue crack length using artificial intelligence (AI) applied to acoustic emission (AE) signals. The AE signals were collected during fatigue of two specimen types. One specimen type had a 1-mm hole for crack initiation. The other specimen type had a 150-micron wide slit of various lengths. Fatigue testing was performed under stress-intensity-factor control to moderate crack advancement. The slit specimen produced AE signals only from crack advancement at the slit tips whereas the 1-mm hole specimens produced AE signals both from crack tip advancement and crack rubbing or clapping. The AE signals were captured with a piezoelectric wafer active sensor (PWAS) array connected to MISTRAS instrumentation and AEwin software. The collected AE signals were preprocessed using time-of-flight filtering and denoising. Choi Williams transform converted time-domain AE-signals into spectrograms. To apply machine learning, the spectrogram images were used as input data for the training, validation, and testing of a GoogLeNet convolutional neural network (CNN). The CNN was trained to sort the AE signals into crack-length classes. CNN performance enhancements, including synthetic data generation and class balancing were developed. A three-class example with crack lengths of (i) 10-12 mm; (ii) 12-14 mm; and (iii) 14-16 mm is provided. Our AI approach was able to classify the AE signals into these three classes with 91% accuracy thus proving that the AE signals contain sufficient information for crack estimation using an AI-enabled approach.
摘要本文研究了利用人工智能(AI)对声发射信号进行疲劳裂纹长度分类。采集了两种试样疲劳过程中的声发射信号。一种样品类型有一个1毫米的孔,用于裂纹萌生。另一种类型的标本具有150微米宽的不同长度的狭缝。在应力强度因子控制下进行疲劳试验,以调节裂纹的扩展。狭缝试样只产生裂纹尖端推进的声发射信号,而1 mm孔试样同时产生裂纹尖端推进和裂纹摩擦或拍击声发射信号。声发射信号由连接到MISTRAS仪器和AEwin软件的压电片有源传感器阵列捕获。对采集到的声发射信号进行飞行时间滤波和去噪预处理。Choi Williams将转换后的时域ae信号转换成频谱图。为了应用机器学习,频谱图图像被用作GoogLeNet卷积神经网络(CNN)的训练、验证和测试的输入数据。训练CNN将声发射信号分类为裂缝长度类。CNN的性能增强,包括合成数据生成和类平衡。裂隙长度为(i) 10 ~ 12mm的三级实例;(ii) 12-14毫米;(iii)提供14- 16mm。我们的人工智能方法能够以91%的准确率将AE信号分为这三类,从而证明AE信号包含足够的信息,可以使用启用人工智能的方法进行裂缝估计。
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引用次数: 0
CT Artifact Reduction Employing A Convolutional Neural Network Within the Context of Dimensional Metrology 基于卷积神经网络的CT伪影降阶方法
Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-10-31 DOI: 10.1115/1.4063805
Mahdi Ghafarzadeh, Mohammad Tavakoli Kejani, Mehdi Karimi, Amirreza Asadi
Abstract Utilizing accurate, nondestructive testing methods to improve quality control and reduce manufacturing errors has gained prominence in light of industry development in various fields. Industrial computed tomography (CT) scanning carries considerable weight among all conventional methods because of their unique features, such as providing a three-dimensional specimen model. Due to the prevalence of metals with high linear attenuation coefficients in industrial applications, beam hardening and scatter artifacts are two of the most prevalent artifacts in any reconstructed volume. Other notable artifacts include those with a nonideal focal spot and conical beam radiation. These artifacts may manifest as a distortion of gray value peaks, systematic discrepancies, blurring-like cupping, and streaking in reconstructed images, degrading volume reconstruction quality. In this paper, the effect of these artifacts is illustrated and mitigated by adopting our proposed method, a combination of conventional and contemporary techniques, including the use of a pretrained convolutional neural network (CNN). Five tests are replicated in different geometric parameters to perform a geometric configuration analysis, indicating how effective the proposed approach is at encountering different geometric situations. The results demonstrate that the proposed method has substantially achieved its goal of improving the accuracy of dimensional metrology performed on our phantom.
摘要随着工业的发展,利用精确的无损检测方法来提高质量控制和减少制造误差已成为各个领域的突出问题。工业计算机断层扫描(CT)由于其独特的特点,如提供三维标本模型,在所有传统方法中占有相当大的份量。由于具有高线性衰减系数的金属在工业应用中的普遍存在,光束硬化和散射伪影是任何重建体积中最常见的两种伪影。其他值得注意的人工制品包括那些具有非理想焦斑和锥形光束辐射。这些伪影可能表现为灰度值峰值失真、系统差异、模糊样拔罐和重建图像中的条纹,降低体积重建质量。在本文中,通过采用我们提出的方法来说明和减轻这些伪影的影响,该方法结合了传统和现代技术,包括使用预训练的卷积神经网络(CNN)。在不同的几何参数下重复进行了五次测试,以进行几何构型分析,表明所提出的方法在遇到不同几何情况时的有效性。结果表明,所提出的方法基本上达到了提高我们的模型尺寸测量精度的目标。
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引用次数: 0
The Efficacy of EMI Monitoring of Embedded PZT Sensors in Different Orientations for Hybrid Fibre Reinforced Concrete Structures Hydration 不同方向嵌入式PZT传感器对混杂纤维混凝土水化的电磁干扰监测效果
Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-10-27 DOI: 10.1115/1.4063845
None Shivangi, Priyanka Singh, Bashar S Mohammed
Abstract In this study, the influence of the orientation of embedded piezoelectric ceramic lead zirconium titanate (PZT) on the mechanical performance of hybrid fiber-reinforced (polypropylene and glass fiber) concrete beams was evaluated. The performance of concrete was evaluated under self-weight, followed by assessing the mechanical property using the electromechanical impedance (EMI) technique after optimization of M30 grade concrete with polypropylene fiber and glass fiber. PZT patches are embedded at different orientations, i.e., 0 deg, 45 deg, and 90 deg, with the axis of the structure for monitoring the hydration of the RC beam. The change in stiffness due to heat hydration in the concrete structure after 5, 7, 14, 21, and 28 days was observed by curing hybrid concrete beams and examining them after 5, 7, 14, 21, and 28 days. On the fifth day, beams were simply supported and allowed to deflect under their weight, and measurements of heat hydration in terms of conductance at frequencies ranging between 1 and 1000 kHz were done. Similarly, days 7, 14, 21, and 28 were done. Day 5 was considered the baseline. It is noted that the PZT sensor placed at an angle of 45 deg is the least effective in recording the incremental changes in hydration that occurred in the concrete beam. The highest quality results were obtained at 90 deg, which is further demonstrated by statistically quantifying the changes using the root-mean-square deviation (RMSD) percentage method and proves to be the most optimized orientation to obtain the stiffness of the hybrid reinforced beam in terms of conductance.
摘要本文研究了压电陶瓷钛酸铅锆(PZT)埋置取向对混杂纤维增强(聚丙烯和玻璃纤维)混凝土梁力学性能的影响。在自重条件下对混凝土性能进行了评价,然后用聚丙烯纤维和玻璃纤维对M30级混凝土进行优化后,采用机电阻抗(EMI)技术对其力学性能进行了评价。PZT贴片与结构轴线分别以0°、45°和90°的不同方向嵌入,用于监测RC梁的水化作用。通过养护混合混凝土梁,观察混凝土结构在5、7、14、21和28天后由于热水化引起的刚度变化,并在5、7、14、21和28天后对其进行检查。第五天,梁被简单地支撑并允许在其重量下偏转,并在1到1000 kHz的频率范围内进行热水化测量。类似地,第7、14、21和28天完成。第5天为基线。值得注意的是,放置在45度角的PZT传感器在记录混凝土梁中发生的水化增量变化方面效果最差。采用均方根偏差(RMSD)百分比法对90°方向的变化进行了统计量化,结果表明,90°方向是获得混合配筋梁电导刚度的最优方向。
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引用次数: 0
Diagnostics of Concrete Box Beam Bridges using Wireless Sensors and Finite Element Analysis 基于无线传感器和有限元分析的混凝土箱梁桥诊断
Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-10-17 DOI: 10.1115/1.4063804
Piervincenzo Rizzo, Alireza Enshaeian, Behzad Ghahremani
Abstract Three pretensioned adjacent concrete box beam bridges were studied with a structural health monitoring (SHM) paradigm based on strain measurements and finite element static analysis. An accurate model for one bridge and an approximate model for the other two were created using ANSYS software. The analysis was used to calculate the strains generated by six concentrated loads that mimic the presence of a truck. Pristine and damage scenarios were implemented, and the associated numerical strains were compared to the experimental strains measured with proprietary wireless sensors during a truck test. As the results from the approximate models revealed that the approximations did not capture the field response of the bridge, the accurate model applied to one bridge was extended to the other two. The comparison between numerical and experimental results revealed the presence of non-critical anomalies related to strain distribution across adjacent beams. Such issues were confirmed with the examination of the historical strains streamed for several months to a repository, using simple data processing strategies. The intellectual contribution of the work resides in the combination of finite element analysis and SHM paradigm on three existing bridges with very similar structural characteristics. This combination showed the limitations of approximated modeling and the possibilities to unfold critical and non-critical issues with SHM.
摘要采用基于应变测量和有限元静力分析的结构健康监测(SHM)范式对3座相邻预应力混凝土箱梁桥进行了研究。利用ANSYS软件建立了一座桥梁的精确模型和另外两座桥梁的近似模型。该分析用于计算模拟卡车存在的六个集中载荷产生的应变。在原始和损坏情况下,将相关的数值应变与在卡车测试中使用专有无线传感器测量的实验应变进行比较。由于近似模型的结果表明,近似不能反映桥梁的场响应,因此将适用于一座桥梁的精确模型推广到其他两座桥梁。数值结果与实验结果的比较表明,相邻梁之间的应变分布存在非临界异常。使用简单的数据处理策略,对几个月来流入储存库的历史菌株进行了检查,证实了这些问题。这项工作的智力贡献在于将有限元分析和SHM范式结合在三座结构特征非常相似的现有桥梁上。这种组合显示了近似建模的局限性,以及用SHM展开关键和非关键问题的可能性。
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引用次数: 0
A Note on Performance Assessment of Signal Energy-Based Acoustic Source Localization in a Carbon Fiber-Reinforced Polymer Plate 基于信号能量的碳纤维增强聚合物板声源定位性能评价研究
Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-10-06 DOI: 10.1115/1.4063698
Hamad Alnuaimi, Umar Amjad, Novonil Sen, Tribikram Kundu
Abstract The effectiveness of the signal energy-based acoustic source localization approach in practical applications has yet to be established. This is addressed herein by conducting an experimental study on a 500 mm × 500 mm carbon fiber-reinforced polymer plate and generating artificial acoustic events in the plate. Upon acquiring the propagating wave signals at several well-scattered sensors, the signal energy-based approach is applied, and the accuracy of the source localization results is noted. Seven experiments are performed with varying source locations, sensor-plate bonding, and excitation types. This approach has performed well for five experiments with source localization error below 15 mm. The remaining two experiments where the acoustic sources are relatively close to the plate edges compared to the other experiments have, however, produced large localization errors, indicating a scope of improvement in the approach to encompass all situations.
基于信号能量的声源定位方法在实际应用中的有效性尚未得到证实。本文通过在500 mm × 500 mm碳纤维增强聚合物板上进行实验研究,并在板中产生人工声事件来解决这一问题。通过对几个散射良好的传感器上的传播波信号进行采集,采用基于信号能量的方法,对源定位结果的精度进行了验证。七个实验进行了不同的源位置,传感器板键合,和激励类型。该方法在5次源定位误差小于15 mm的实验中取得了良好的效果。然而,与其他实验相比,声源相对靠近板边缘的其余两个实验产生了较大的定位误差,这表明该方法在涵盖所有情况方面还有很大的改进余地。
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引用次数: 0
Evaluation of flaw detection algorithm using simulated X-ray computed tomography of ground truth data 基于地面真值数据的模拟x射线计算机断层扫描探伤算法的评价
IF 1.1 Q2 ENGINEERING, MULTIDISCIPLINARY Pub Date : 2023-08-14 DOI: 10.1115/1.4063170
F. Kim, A. Pintar, J. H. Scott, E. Garboczi
A framework to generate simulated X-ray computed tomography (XCT) data of ground truth (denoted here as ‘GT’) flaws was developed for evaluation of flaw detection algorithms using image comparison metrics. The flaws are mimicking some of those found in additively manufactured parts. The simulated flaw structure gives a GT data set with which to quantitatively evaluate, by calculating exact errors, the results of flaw detection algorithms applied to simulated XCT images. The simulated data avoid time-consuming manual voxel labeling steps needed for many physical data sets to generate GT images. The voxelated pore meshes that exactly match GT images avoid approximations due to converting continuum pore meshes to voxelated GT images. Spherical pores of varying sizes were randomly distributed near the surface and interior of a cylindrical part. XCT simulation was carried out on the structure at three different signal-to-noise levels by changing the number of frames integrated for each projection. Two different local thresholding algorithms (a commercial code and the Bernsen method) and a global thresholding algorithm (Otsu) were used to segment images using varying sets of algorithm parameters. The segmentation results were evaluated with various image evaluation metrics, which showed different behaviors for the three algorithms regarding “closeness” to the GT data. An approach to optimize the thresholding parameters is demonstrated for the commercial flaw detection algorithm based on the semantic evaluation metrics. A framework to evaluate pore sizing error and binary probability of detection was further demonstrated to compare the optimization results.
开发了一个框架,用于生成地面真值(这里表示为“GT”)缺陷的模拟x射线计算机断层扫描(XCT)数据,用于使用图像比较度量来评估缺陷检测算法。这些缺陷与在增材制造零件中发现的一些缺陷相似。模拟的缺陷结构提供了一个GT数据集,通过计算精确误差,可以定量评估应用于模拟XCT图像的缺陷检测算法的结果。模拟数据避免了许多物理数据集生成GT图像所需的耗时的手动体素标记步骤。体素孔网格完全匹配GT图像,避免了近似,因为将连续体孔网格转换为体素GT图像。圆柱形零件的表面和内部随机分布着不同大小的球形孔。通过改变每个投影的帧数,在三种不同的信噪比下对结构进行XCT模拟。使用两种不同的局部阈值算法(商业代码和Bernsen方法)和全局阈值算法(Otsu)使用不同的算法参数集来分割图像。使用不同的图像评价指标对分割结果进行评价,结果表明三种算法在与GT数据的“接近度”方面表现出不同的行为。针对商用缺陷检测算法,提出了一种基于语义评价指标的阈值参数优化方法。在此基础上,提出了一个评估孔径误差和二值检测概率的框架,并对优化结果进行了比较。
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引用次数: 0
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Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems
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