Determination of Crack Tip Acuity

In this section

Back to Core Research Programme AMorph – 4D Printing for Field Morphing Structures Automation of Composite and Hybrid Joining Process Coaxial Wire Additive Manufacturing Processes and In-Line Monitoring Tools Development of Coded Excitation Technique for Non-Metallic Pipes Inspection Development of Digital Twin technology as a demonstrator for real-time integrity assessment of crack growth in tensile specimens Development of Friction Stir Welding (FSW) for Hydrogen Fuel Storage Tanks Development of Leak-Before-Break Hydrogen Storage Composite Pressure Vessels With Polymeric Liner Establishing Assessment Methods for Determining Safe Service Limits of High-Temperature Materials in Extreme Environments Fracture toughness in aggressive environments: effect of crack monitoring techniques on test results In-process detection and non-destructive testing of electron beam weld imperfections Internal Bore Coatings for Applications in Corrosion and Hydrogen Environment Joining of Additively Manufactured Materials Long term behaviour of polymeric liner materials/coatings in hydrogen service Techniques for High Temperature Ultrasonic Inspection of Arc Welding Ultimate Leverage Fund

Project Code: 0901-08

Objectives

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.

Project Outline

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.

Fatigue

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.