Ultrasonic Evaluation Method for Damaged Materials Using Inverse Problem Technique

1.聚焦式超声探头的研制为提高背散射法疲劳蠕变损伤评估性能，研制了一种聚焦式超声探头。将探针应用于受损材料，但与正常探针类型相比，没有观察到明显的改善。实验结果表明，测量系统的改进对测量精度的提高至关重要。2.超声波测量系统的研制开发了一套由工作站、脉冲接收机和数字示波器组成的超声波测量系统。借助工作站的高性能，利用直流电磁铁实现了探头压力载荷的在线实时处理。3.蠕变-疲劳损伤准损伤试件的研制实验制备了寿命比为25%~ 100%的准损伤材料。材料为Cr-Mo-V钢，该材料是电厂中常用的转子材料。4.基于反问题技术的损伤材料评价方法的研究在常规超声衰减法的基础上，提出了两种新的损伤材料评价方法。一种是对后向散射波功率谱进行积分并归一化的噪声能量法，另一种是对功率谱进行积分的加权噪声能量法，但在加权函数下进行计算。5.结果加权噪声能量法具有不受频率积分范围影响的优点。此外，建议的噪声能量法被发现有上级性能的损伤材料的评估相比，正常的超声衰减方法。

1.Development of Ultrasonic probe with focusing sensorAn ultrasonic probe with focusing sensor was newly developed to improve the evaluation performance by back-scattering method for fatigue-creep damage. The probes were applied to damaged materials but no distinct improvement was observed compared with the normal probe type. It was shown that the improvement of measuring system is more important for the measuring accuracy.2.Development of Ultrasonic measuring systemAn Ultrasonic measuring system, which is composed of Work Station, pulser-receiver and digital oscilloscope, was developed. Aided by high performance of Work Station, the on-line real-time processing of the pressure load of the probe was developed using the DC solenoid. This greatly improves the measuring accuracy of ultrasonic properties.3.Development of quasi-damaged specimen for creep-fatigue damageQuasi-damaged materials with life ratio from 25% to 100% were made experimentally. The material is Cr-Mo-V Steel, which is often used as Rotor material in the electric power plant.4.Development of evaluation method for damaged matcrials using inverse problem techniqueTwo evaluation methods for damaged materials were newly developed in addition to the normal ultrasonic attenuation method. One is a noise energy method which evaluates the damage by integrating the power spectrum of back-scattering wave and normalizing it. The other is a weighted noise energy method which also utilize integral of the spectrum but calculated under the weighted function.5.ResultIt was shown that the proposed weighted noise energy method has great advantage that the damage evaluation is not affected by the integral range of frequency. Moreover, the proposed noise energy method was found to have superior properties for the evaluation of damaged material compared with the normal ultrasonic attenuation method.