In order to improve the detection sensitivity of ultrasonic inspection for creep in P91 weldments, a relative inspecting signal processing method is proposed. To apply this method, firstly a non-creep feature space should be generated from all the ultrasonic inspecting signals acquired from no creep specimens; then a residual vector can be calculated by projecting inspecting signal to the non-creep feature space; lastly the deviation ratio can be calculated by dividing the residual vector energy by signal energy. The deviation ratio reflects the distance between inspecting signal and non-creep feature space, higher deviation ratio means worse creep damage in the inspecting target. A general mathematic expression of the non-creep feature space projection method is deduced. For the convenience of signal processing, a simplified linearization algorithm based on blind source separation theory is suggested. To verify this new method, a testing experiment is conducted with P91 steel weldment specimens of different creep status. The results showed that, the new method provides higher sensitivity than usual ultrasonic method. As this method is a relative one, the accuracy of creep evaluation by the method depends on the completeness of non-creep feature space. In addition, as this method is based on evaluating the distance between inspecting target and no-defect feature space, it also can be used for detecting other types of defects.
YUAN Keyi
,
HAN Zandong
,
CHEN Yifang
,
ZHONG Yuexian
. Ultrasonic Inspection for Creep in P91 Steel Weldments Based on Non-creep Feature Space Projection[J]. Journal of Mechanical Engineering, 2016
, 52(8)
: 51
-57
.
DOI: 10.3901/JME.2016.08.051
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