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Recognition method for weld defect signal in ultrasonic testing of austenitic stainless steel

A technology for austenitic stainless steel and ultrasonic testing, applied in the direction of processing detection response signals, etc., can solve problems such as difficult identification of defect signals, influence of noise suppression effect, identification of noise suppression defect signals, etc., to overcome the difficulty of identifying weld defects and Quantitative measurement, good noise suppression effect, and defect signal enhancement effect

Inactive Publication Date: 2011-10-05
HARBIN INST OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In the actual noise suppression process, the threshold value is obtained by the empirical formula, and the reliability of the noise suppression method in this way is relatively high, but for the ultrasonic detection signal of the coarse-grained austenitic stainless steel weld, the existing traditional wavelet packet Technology fails to achieve effective noise suppression and defect signal identification
Especially for thick-walled welds, due to the increased travel distance of sound waves, the noise interference is serious, which will eventually have a great impact on the noise suppression effect, making it difficult to identify defect signals

Method used

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  • Recognition method for weld defect signal in ultrasonic testing of austenitic stainless steel
  • Recognition method for weld defect signal in ultrasonic testing of austenitic stainless steel
  • Recognition method for weld defect signal in ultrasonic testing of austenitic stainless steel

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specific Embodiment approach 1

[0014] Specific implementation mode one: combine figure 1 To illustrate this embodiment, the method for identifying defect signals of ultrasonic detection of austenitic stainless steel welds described in this embodiment, the specific steps are:

[0015] Step 1: Use the ultrasonic transducer to detect the point to be measured of the austenitic stainless steel weld by the pulse reflected wave method, obtain a series of A-scan signals a, and perform detection at the detection point adjacent to the point to be measured , to obtain another column of A-scan signal b, wherein A-scan signal a is a signal to be processed;

[0016] Step 2: Select the mother wavelet and determine the decomposition level, perform wavelet packet decomposition on the A-scan signal a, and obtain the wavelet packet tree and details at all levels of the signal a;

[0017] Step 3: Select the same mother wavelet and decomposition level as in Step 2, and perform wavelet packet decomposition on the A-scan signal ...

specific Embodiment approach 2

[0022] Specific Embodiment 2: This embodiment is an illustration of a method for identifying defect signals in ultrasonic detection of austenitic stainless steel welds. The following combination figure 2 Description of this method: the detection object of this embodiment is a flat-bottomed hole in an austenitic stainless steel weld with a thickness of 23.5mm, the diameter of the flat-bottomed hole is 2.0mm, the depth is 8mm, the depth of the water layer is 25mm, the system gain is 50dB, and the excitation voltage is 200V ; figure 2 Among them, 1 is the water tank, 2 is the position X, 3 is the position X', 4 is the ultrasonic probe, 5 is the water, 6 is the flat bottom hole, and 7 is the weld test piece;

[0023] Step 1: If figure 2 As shown, the ultrasonic probe 4 is used to detect the position X2 directly above the flat-bottomed hole 6 in the austenitic stainless steel weld to obtain a series of A-scan signals a, as shown in image 3 As shown, where A is the surface wa...

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Abstract

The invention discloses a recognition method for weld defect signals generated in ultrasonic testing of austenitic stainless steel, and relates to a recognition method for weld defect signals in ultrasonic testing. The objective of the invention is to solve the existing problem that weld defect signals generated in ultrasonic testing of austenitic stainless steel are hard to recognize. The recognition method comprises the following steps: detecting a weld joint to be measured on the austenitic stainless steel and obtaining a column of A scanning signals a, and detecting an adjacent weld joint and obtaining another column of A scanning signals b; respectively carrying out wavelet packet decomposition on a and b so as to obtain corresponding wavelet packet trees and details of all branches of a and b; carrying out multiplicative operation on the details of all branches of a and b so as to obtain multiplicative details and corresponding multiplicative wavelet packet trees; carrying out noise reduction on the multiplicative wavelet packet trees so as to obtain A scanning signals with abated noise, and recognizing defect signals through the A scanning signals. The method provided in the invention has a good noise suppression effect, can effectively overcome the difficulty in recognition and quantificational measurement of austenitic stainless steel weld defects, and is applicable to the field of ultrasonic testing.

Description

technical field [0001] The invention relates to a method for identifying defect signals in ultrasonic detection. Background technique [0002] Austenitic stainless steel has the characteristics of corrosion resistance, high toughness, weldability and good comprehensive mechanical properties, and it has been widely used in the fields of petroleum, chemical and nuclear industries. In order to ensure the production quality and in-service safe operation of austenitic stainless steel welded components, non-destructive testing of internal defects is required. Ultrasonic pulse echo method is a non-destructive testing method that is widely used at present, but when using this method to detect defects in austenitic stainless steel welds, it is difficult to identify defect information in time-domain signals. First, coarse dendritic grains are formed when austenitic steel is cooled; second, the face-centered cubic lattice increases the concentration of grain boundary inclusions, which...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N29/44
Inventor 迟大钊刚铁姚英学麦成乐赵立彬袁媛
Owner HARBIN INST OF TECH
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