{'fraction_non_alphanumeric': 0.02169811320754717, 'fraction_numerical': 0.0, 'mean_word_length': 5.50920245398773, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Investigation of PVC physical ageing in field test specimens using ultrasonic and dielectric measurements

Physical ageing in PVC is studied using two techniques: a) non-linear ultrasonic measurements based on the non-collinear wave interaction theory and b) dielectric measurements. The ultrasonic measurement results are compared with dielectric measurement results. The comparison shows that the used non-linear ultrasonic measurement technique is more sensitive to the effects of physical ageing than the dielectric measurements. The influence of temperature on the ultrasonic measurements is studied experimentally. Finally, the ultrasonic measurements, linear and initial non-linear, are used for C-scanning of a natural crack in an old PVC water supply pipe. The linear ultrasonic measurements are performed in a pulse-echo mode. The experimental results show that the natural crack, which consists of a through-thickness crack and microcrack zones, is detected using both measurement methods. All measurements are performed in field PVC test specimens.