# Assessment of Coating Properties in Car Body by Ultrasonic Method
###### Abstract  
Adhesive bonds, including car putty coatings, are used in the construction of modern motor vehicles. Therefore, it is important to improve methods that allow nondestructive evaluation of the properties of these joints. The main objective of this study was to evaluate selected properties of putty coatings such as the width of the applied coating and adhesion to the substrate based on changes in ultrasonic wave parameters. The research was carried out in two stages. In the first, the values of the surface wave amplitude were determined as a function of the width of the coating to the substrate. It was found that as the width of the coating increases, the amplitude of the surface wave pulse decreases. The second stage involved correlation studies to relate the reflection coefficient |r| to the adhesion of the coating to the substrate. Based on the results, it was found that as the value of the reflection coefficient decreases, the value of the coating's adhesion to the substrate increases. The determined values of this parameter range from 0.30 to 0.86, which correspond to the adhesion of the range 1.51 to 18.97 MPa. The obtained test results have practical significance and can be used in evaluating the condition of coatings in vehicle body repair shops. adhesion; coatings; ultrasound; nondestructive testing; structural health monitoring; reflection coefficient; automotive +
Footnote †: journal: Accepted: 8 September 2024  
the quality and durability of these joints. The ultrasonic method, which uses a transducer to generate surface waves, meets these requirements. Ultrasonic testing of adhesive joints has been implemented to verify defects such as kissing bond [13; 14], the lack of adhesive where it should be applied [15], or to evaluate the adhesion of the coating to the substrate during the service life and observe changes based on ultrasonic surface wave parameters [16]. In addition, time-amplitude analysis of ultrasonic signals allows for assessing the thickness of layers and the uniformity of adhesion over the entire surface of the coating application, which is crucial for ensuring the durability and reliability of joints in not only the automotive industry but also other industries [17]. Other studies in the amplitude-frequency scope [18; 19] leads to the conclusion that the ultrasonic wave can be a diagnostic parameter indicating the state of the adhesive joint. The use of ultrasound in the testing of adhesive joints not only improves the safety of structures but also allows for the optimization of manufacturing processes through early detection of defects and minimization of the risk of their occurrence, especially within the car body repair process. Ultrasonic testing of adhesive coatings used in machinery and vehicles is a crucial method for assessing the technical condition and durability of these coatings [20]. This technique utilizes ultrasonic waves for nondestructive testing of materials, allowing for the detection of defects such as cracks, delaminations [21], or blisters [22] that may arise from usage. Due to its high precision and accuracy, ultrasonic testing enables the monitoring of adhesive coating quality without the need for the disassembly of components, significantly reducing downtime for machines and vehicles [23]. The application of this technology is particularly important in the automotive and aerospace industries, where reliability and safety are paramount. Moreover, regular ultrasonic inspections can prevent costly failures and extend the lifespan of machines, translating to greater operational efficiency and financial savings for enterprises. The main objective of this study was to evaluate selected properties of putty coatings such as the width of the applied coating and adhesion to the substrate based on changes in ultrasonic wave parameters. The research was divided into two main stages. In the first stage, a surface wave was used to assess the width of the car putty coating applied to the body sheet.