Reliable analysis on TOFD technique

2015 1.21-22,The shanghai organized a technology research experiment about phase array ,the experimental location is shanghai nuclear power group and shanghai boiler factory,experimental purpose was aimed at verify some technology parameter of phased array, and providing technique support for domestic standard(GB)

Currently ,TOFD technique has been widely used in China.

This test blocks adopted in this experiment had many defects (up to sixteen),and the kind、position、dimension of flaw were different,testing difficulty was harder,but TOFD technique detected 87% flaws, (there were two air hole that didn’t detected,the true condition was displayed on hapmap,but testing staff didn’t point) ,this indicated TOFD technique has higher reliability on detecting embedded flaws.

In this experiment,TOFD technique can detect incomplete fusion and strip slag inclusion,this indicated TOFD technique has high reliability on detecting dangerous area type defect and big flaw.

In the aspect of quantitative ,TOFD technique has high precision on height detection of incomplete fusion flaw ; the precision on detecting strip flaw can satisfy engineering application;there is big error on round flaw and small strip flaw,the error is positive deviation,namely measuring length is longer physical length.

In the aspect of qualitative ,TOFO technique has certain ability of judgement on flaw property，but the accuracy is not high，and has high factor that affected by human .

In this experiment ,high relevance ratio on incomplete fusion verified diffracted wave is sensitive to this flaw,so using TOFD technique with diffracted wave principle to make sure detect incomplete fusion in vertical direction，no longer need to do incomplete fusion series scanning detection on detecting vertical direction.

Although the experiment adopted sample pre-buried flaw had no nature flaw,and didn’t get TOFD technique to detect data of nature flaw,but in this experiment ,relevance ratio of incomplete fusion and quantitate precision are high verify diffracted wave is sensitive to area type flaw ,and incomplete fusion and flaw are belong to area type flaw,so we can infer from this,the TOFD technique that takes advantage of diffracted wave principle is sensitive to detect embedded flaw.In big thickness welding joint,TOFD technique is superior to ray photo technique on embedded flaw.

TOFD testing equipment can record ultrasonic information in the process of flaw detection,the whole system is more light and convenient，automatically scanning reliability of equipment,the operating properties and suitability are great.

In conclusion,we think that TOFD technique has better prospect in big thickness welding joint (such as more than 100mm),by further study and improvement,TOFD technique has chance to replace ray photo detection in application of big thickness welding joint.

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