Develop a method for the determination of crack tip radius or the differentiation between sharp crack tips and volumetric defects such as slag.
Determine a methodology that can be applied in a practical engineering environment.
TWI is undertaking an exploratory project using ultrasonic inspection to explore the possibility of crack tip sharpness determination. The results to date of this project are encouraging. This project will build on this early work.
Stage 1: Test blocks will be manufactured with a variety of artificial and real flaws. These flaws will be modelled to determine the energy envelope associated with each type of flaw edge. There are long established validated theories predicting energy patterns from sharp crack tips. These basic theories will be modelled and extended to determine the type and direction of ultrasonic illumination best suited to detect the energy distribution patterns generated by different crack shapes.
Stage 2: Once the data has been collected it will be carefully analysed for each type of crack tip. The flaws to be analysed will include the following.
Lack of fusion
Lack of weld penetration
Volumetric flaws such as slag and lack of fusion with associated slag
In particular the amplitude of the ultrasonic signals with respect to insonification angle and radiation angle
Stage 3: Based on this data an algorithm will be generated to predict crack tip acuity from the ultrasonic data. This will then be tested on a selection of real flaws which then be sectioned.
Relevant Industry Sectors
Power, Petrochemical and Construction.
Technical and Economic Benefits
Increased service life for structures via correct flaw sentencing.
Cost savings due to extended service life.
Increased safety by minimisation of unnecessary weld repairs.