Modification of ultrasonic transducers to study crack propagation in vinyl polymers, supported by SEM technique

Abstract

Detecting defects in various industrial products remains a challenging task in the industry. Researchers are constantly working to improve detection techniques and tools for various defects, particularly cracks. Many industrial structures suffer from cracks. The selection of a suitable technique and/or tool is based upon the tested structures and the accuracy of the technique and/or tool. The work's novelty is the development of a fully accurate, simple, and safe ultrasonic tool for precisely scanning cracks. A pen-shaped cone was added to the ultrasonic transducers to improve their performance. Different crosshead speeds and annealing techniques were used to cause cracks on medium density polyethylene (MDPE) and poly-methyl-methacrylate (PMMA) polymer plates with specific dimensions. Cone reduced the front diameter of the transducers from 12 to 2 mm (cone tip diameter). It improved the transducers by giving them new properties such as a small near field, a collimated beam, high sensitivity, and high wave reflection. The modified transducers tracked the cracks at discrete sequential sites, where the ultrasonic velocity was measured to determine the crack speed, critical crack speed, dynamic stress intensity factor, and crack branching phenomenon. Additionally, ultrasonic attenuation was measured in order to accurately determine crack growth behavior, the crack's neck zone, and the crack growth dependency on both plate thickness and annealing. Scanning electron microscope (SEM) images revealed crack propagation in polymer plates. The results of ultrasonic testing and SEM evaluations were consistent. This guaranteed that the modified transducers could scan cracks accurately.

Solar photovoltaic module defect evaluation with higher order modes of Lamb waves

“…Hence no sudden transition exists. This issue can be mitigated by using transducers with pointy faces like the one proposed in reference [8]. In the Mode 11 ESD plot of section C, it is also noticeable that the percentage level exhibits a particular manner.…”

Fabrication of metal–polymer matching layers to improve some ultrasonic transducers for NDT and calibration

“…The beam diameter (BD) of the transducer is a function of focal length (F), effective diameter of the transducer, the transducer operating frequency (f 0 ), and the load specimen thickness (t) [17].…”

“…Generally, the noisy echoes emerge from many factors, like surface miniature cracks in the specimen, rough specimen surface, non-straight surface, transducer bandwidth, etc. [17]. The noisy echoes can be determined by measuring the signal-to-noise ratio (S/N), which could influence the test measurements of any designed transducer.…”

Rheometeric, ultrasonic and acoustical shielding properties of Cu-alloy/silicone rubber composites for electronic applications

“…Researches demonstrated the efficiency of ultrasonic to detect defects in silicon rubber. 15 In addition, ultrasonic can be used to analyze a material’s qualities, such as its porosity, microstructure, grain size, etc. For such purposes, ultrasonic velocity and ultrasonic attenuation coefficient are employed.…”