Mechanical Life Evaluation of Distribution Network Cable Sheath Based on Indenter Modulus Test

ABSTRACT To address the challenge of nondestructively assessing the mechanical degradation state of poly(vinyl chloride) (PVC) outer sheaths in distribution cables, accelerated thermal‐aging and hygrothermal‐aging tests are conducted to investigate the evolution of elongation at break and indenter modulus with temperature, humidity, and aging time, and a mechanical lifetime assessment model is established. The results show that the elongation at break of the PVC outer sheath decreases continuously with aging, whereas the indenter modulus generally increases, with a significant negative correlation between the two parameters ( R 2 > 0.93). At 120°C, increasing the relative humidity markedly accelerates the increase in indenter modulus. Based on the mechanical degradation behavior, Arrhenius and Peck lifetime assessment models are established. The Arrhenius model achieves a coefficient of determination of 0.9986, while the Peck model yields R 2 > 0.95 for all specimen datasets. Multipoint sampling and Savitzky–Golay (S–G) filtering are further employed to reduce the effects of spatial measurement‐point variability and environmental disturbances during on‐site indentation testing. These results provide a basis for the nondestructive assessment of aging and mechanical lifetime prediction of PVC cable outer sheaths.