Abstract

Nowadays X70 steel has been used as a core material for the construction of high-pressure, large-diameter and high-strength steel pipelines. The wall of piplines of an operating pipline system will deform in various degrees. Severe deformation will lead to microcracks or even a fracture. The ultrasonic flaw detection method is designed for the detection and evaluation of microcracks and defects caused by the deformation of X70 steel. However, an effective method to measure the stress level of X70 steel accurately is still lacking since the deformation of X70 steel often occurs within the elastic stage or plastic stage. Through conducting an experiment to study the tensile test of X70 steel specimens under a constant temperature, and measuring the propagation time and amplitude of ultrasonic L_CR wave simultaneously to conclude the law of the propagation of ultrasonic L_CR wave in elastic-plastic deformation of X70 steel, and determine the relationship between the propagation time and the amplitude of ultrasonic L_CR wave and the deformation degree of X70 steel. According to the study, the deformation degree of X70 steel could be determined by the propagation time of ultrasonic L_CR wave and the amplitude of the first wave: the level of stress could be calculated within the elastic stage and the deformation degree could be calculated within the plastic stage. The study results provide an effective support for the stress measurement of X70 steel by ultrasonic L_CR wave.

中文翻译：

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X70钢弹塑性变形中超声波LCR波传播时间和幅值的响应规律

摘要

目前X70钢已被用作建造高压、大口径、高强度钢管的芯材。运行中的管道系统的管道壁会发生不同程度的变形。严重的变形会导致微裂纹甚至断裂。超声波探伤方法是为检测和评价X70钢变形引起的微裂纹和缺陷而设计的。然而，由于X70钢的变形往往发生在弹性阶段或塑性阶段，因此仍缺乏准确测量X70钢应力水平的有效方法。通过实验研究X70钢试样在恒温下的拉伸试验，并测量超声波L _CR的传播时间和振幅同时波结束超声波L的传播定律_CR波在X70钢的弹塑性变形，并确定传播时间和超声波L的振幅之间的关系_CR波和X70钢的变形程度。根据研究，X70钢的变形程度可以由超声波L _CR波的传播时间和第一波的振幅来确定：应力水平可以在弹性阶段计算，变形程度可以在塑料舞台。研究结果为X70钢超声L _CR波应力测量提供了有效支持。