热氧老化造成的PE管材料力学性能退化必然会使管道的服役寿命下降，是社会经济发展和人民生命财产安全的严重隐患。提出热氧老化管材的非线性超声评价方法，通过搭建水浸非线性超声检测系统提取PE管的非线性超声检测信号，建立了非线性超声检测特征参数与断裂伸长率、断裂应力的相关性模型，通过观察PE管老化后微观组织变化揭示非线性超声检测机理。试验结果表明：PE管材料的断裂伸长率、断裂应力随非线性系数的增大而降低，管材老化后形成的表面微裂纹、孔洞、褶皱是导致管材力学退化和非线性超声检测系数增大的主要原因，非线性系数可用于评价由热氧老化导致的管道力学性能退化。

The degradation of mechanical properties of PE pipe materials caused by hot oxygen aging will inevitably reduce the service life of the pipe, which is a serious hidden danger to social and economic development and people's life and property safety. A nonlinear ultrasonic evaluation method for thermo-oxygen aging pipes was proposed. The nonlinear ultrasonic detection signals of PE pipes were extracted by building a nonlinear ultrasonic detection system for water immersion, and a correlation model between the characteristic parameters of nonlinear ultrasonic detection and elongation at break and fracture stress was established. The nonlinear ultrasonic detection mechanism was revealed by observing the micro-structure changes of PE pipes after aging. The experimental results show that the elongation at break and profit at break of PE pipe materials decrease with the increase of the nonlinear coefficient. The surface micro-cracks, holes and folds formed after the aging of the pipe are the main reasons for the mechanical degradation of the pipe and the increase of the nonlinear ultrasonic detection coefficient. The nonlinear coefficient can be used to evaluate the mechanical degradation of the pipe caused by thermal oxygen aging.