High-precision terahertz frequency modulated continuous wave imaging method using continuous wavelet transform

Zhou, Yu; Wang, Tianyi; Dai, Bing; Li, Wenjun; Wang, Wei; You, Chengwu; Wang, Kejia; Liu, Jinsong; Wang, Shenglie; Yang, Zhengang

doi:10.1117/1.oe.57.2.023108

Cited by 3 publications

(1 citation statement)

References 21 publications

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“…The graphs of the RMS values of the current for the L1, L2, and L3 current loop for two configurations: N-new friction elements simulating correct operation of the extruder and W-worn-out friction elements simulating incorrect condition of the extruder friction elements, are shown in Figure 7. Scalograms are a useful tool widely deployed in many fields of science and technology, such as aerospace [31], seismic analysis [32], vibroacoustics [33], or image analysis [34,35]. By comparing the frequency components of the variation in the current values of the two extruder working element configurations and presenting the scalograms, final conclusions can be formulated regarding the effect of wear on the current at different frequencies.…”

Section: Resultsmentioning

confidence: 99%

Wear Detection of Extruder Elements Based on Current Signature by Means of a Continuous Wavelet Transform

Danielak,

Witaszek,

Ekielski

et al. 2023

Processes

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Assessing the wear of components in a single-screw extruder and its condition during the process is difficult. In this context, wavelet analysis was used to investigate the wear condition of extruder elements, which yielded data on current waveforms obtained from 1 kHz frequency converters. To date, no tests of this type have been conducted on single-screw food extruders, which further emphasizes the relevance of the research undertaken by the authors. Experimental tests have been conducted to verify the hypothesis that it is possible to assess the level of wear of the working elements of an extruder by monitoring the variations in the frequencies on the current spectrum using wavelet analysis tools. The root mean square (RMS) values of the current were compared for two configurations of the working elements of the device, i.e., new and used. Observation of the frequency variations of the current spectrum values using wavelet analysis tools can provide valuable information on the technical condition of the working elements of an industrial extruder. Therefore, they can indicate the need for prompt replacement of friction elements in order to improve the efficiency and performance of the machine.

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Section: Resultsmentioning

confidence: 99%

Wear Detection of Extruder Elements Based on Current Signature by Means of a Continuous Wavelet Transform

Danielak,

Witaszek,

Ekielski

et al. 2023

Processes

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Defect Detection in Bidirectional Glass Fabric Reinforced Thermoplastics Based on 3-D-THz Imaging

Souliman

Kahl

Stock

et al. 2023

IEEE Trans. THz Sci. Technol.

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Non-homogeneous, bi-directional glass fabric reinforced thermoplastic (GFRT) composites are used in the automobile industry to produce economic and environmentally friendly vehicles. Despite the fact that GFRT materials have superior mechanical characteristics and lower manufacturing cost compared with traditional materials, they are prone to significant deformation and defect emergence during the forming/manufacturing of parts from prefabricated laminates. Some defects, especially hidden ones like delamination and consolidation defects, can significantly reduce the mechanical properties of the final parts. It is essential to use 3D non-destructive testing (NDT) technology to detect and identify such hidden defects. This research investigates the ability of 3D THz imaging to detect hidden defects (i.e., delamination and consolidation) in GFRT composite materials. Frequency modulated continuous wave (FMCW) technique is used to generate 3D-THz cross-sectional images. Non-defective and defective samples with a thickness of 1.5 mm have been measured with two 3D THz imaging systems operating in the frequency range from 238 to 316 GHz and from 499 to 733 GHz. In addition, a simulation of the reflected FMCW spectrum is presented to analyze the measurements and intercompare the performance of the two imaging systems. A systematic analysis in a large sample set demonstrates that a delamination defect with a thickness of 125 µm as well as a consolidation defect with a difference in thickness less than 0.4 mm can be successfully detected by the 700-GHz imaging system.

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Three-dimensional reconstruction method for layered structures based on a frequency modulated continuous wave terahertz radar

Xue,

Zhang,

Song

et al. 2024

Opt. Express

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The feasibility of employing a continuous-wave terahertz detection system for non-contact and non-destructive testing (NDT) in multi-layered bonding structures is assessed in this study. The paper introduces the detection principle of terahertz frequency modulated continuous wave (FMCW) radar and outlines the two-dimensional (2D) scanning platform, which integrates optical lenses, three linear actuators, a control platform, and data acquisition units. Experimental results on two types of insulation with prefabricated defects demonstrate the capability of terahertz waves for transparent inspection imaging. These results confirm the viability of terahertz FMCW detection technology as an advanced NDT tool for multi-layered bonding structures. However, the inherent limitations of terahertz wavelength and hardware systems pose challenges in discriminating reflection peaks on upper and lower surfaces. To address this issue, a local adaptive empirical wavelet coefficient modal decomposition (LAEWCMD) method is proposed to enhance the longitudinal discrimination ability of terahertz detection. The proposed method involves segmenting the 2D terahertz detection image into regions to differentiate between defective and non-defective areas. Continuous wavelet transforms (CWT) are then applied to the range signals of each region to derive continuous wavelet coefficients (CWCs). Subsequently, empirical mode decomposition (EMD) is performed on the CWCs to decompose them into intrinsic mode functions (IMFs) and residual signals. The 1st IMF is utilized for three-dimensional (3D) reconstruction, and the regions are fused to generate the final output. The effectiveness of the proposed method is validated on aircraft thermal protection structures (TPS), achieving high-precision 3D reconstruction. This offers a novel approach for the application of terahertz computed tomography imaging and NDT.

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High-precision terahertz frequency modulated continuous wave imaging method using continuous wavelet transform

Cited by 3 publications

References 21 publications

Wear Detection of Extruder Elements Based on Current Signature by Means of a Continuous Wavelet Transform

Wear Detection of Extruder Elements Based on Current Signature by Means of a Continuous Wavelet Transform

Defect Detection in Bidirectional Glass Fabric Reinforced Thermoplastics Based on 3-D-THz Imaging

Three-dimensional reconstruction method for layered structures based on a frequency modulated continuous wave terahertz radar

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