# Research on Defect Detection of Bare Film in Landfills Based on a Temperature Spectrum Model
## 6 Conclusions  
In this paper, the distribution model of temperature difference characteristics is established, the defects of HDPE film surface defect are studied, and the temperature difference characteristics between the complete area and the defect area are analyzed; the shape of the defects in the weld area was also recognized and the size of the defects was determined by improving the test set-up.  
1. Using temperature difference model can detect defects of the HDPE film in the state of bare film. Under the action of a continuous natural heat source, when the HDPE film is fully covered and tested, the continuous heating time is controlled at 10-20 min. The temperature difference between the defect area and complete area is obvious at the same time, which can be used as the best detection time domain for the whole film defect. For the detection of defects in the welding seam area, under the action of an active heating source, at 3-5 min, the temperature difference between defects in the welding seam area of the HDPE film and complete area is obvious. This period can be considered the optimal time for detecting defects in the weld area.
2. Based on the research object of HDPE film infrared images, the recognition effect and characteristics of traditional classic edge detection algorithms are analyzed, and an HDPE defect edge detection algorithm combining improved guide image filtering and Canny is proposed. By performing denoising and edge retention on the collected image, the edge of the defect of the final image can be improved. Based on edge extraction, the defect size is estimated. The recognition error between defect size and actual size is not greater than 10%.
3. Under the action of a heat source, HDPE film will have a temperature difference characteristic in the defect and complete area in the same time period. Based on this characteristic, the temperature difference model can detect HDPE film defect placement. It avoids contact damage to the film and realizes nondestructive testing of HDPE film.  
For HDPE film defect detection, although this paper achieves the identification of defects on the surface of HDPE film and the contour recognition of defects in the weld area based on infrared detection technology, there are still inconvenient detection conditions in specific environments. So, in the follow-up research, the development of an infrared detection system of the piggybacking mechanism should be carried out to facilitate the detection system in order to adapt to the different environments and situations so as to make it more practical and effective.  
F.J.: Methodology, Formal analysis, Software, Validation, and Writing--original draft. Y.C.: Funding acquisition, Methodology, Project administration, and Writing--review and editing. W.H.: Software and Validation. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Defect Number** & **1** & **2** & **3** & **4** \\ \hline True size/cm & 1.50 & 2.00 & 3.00 & 2.50 \\ Calculate size/cm & 1.56 & 2.20 & 3.19 & 2.33 \\ Recognition error/\% & 4.6 & 10.0 & 6.3 & 6.8 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Defect length dimension.  
**Funding:** This research was founded by Science Research Project of Hebei Education Department (CXY2024016).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author (The data are not publicly available due to the restrictions on the company's data information security).  
**Conflicts of Interest:** The authors declare no conflicts of interests.