The imaging of failure in structural materials by synchrotron radiation X-ray microtomography

• Published in: Engineering fracture mechanics 2017-09, Vol.182, p.127-156
• Main Authors: Wu, S.C., Xiao, T.Q., Withers, P.J.
• Format: Article
• Language: English
• Subjects: Alloy steels; Aluminum; Cast iron; Composite materials; Crack closure; Crack initiation; Crack opening displacement (COD); Crack propagation; Cracks; Damage accumulation; Damage tolerance approach; Failure mechanisms; Fatigue crack growth; Fracture mechanics; Grain structure; Linear elastic fracture mechanics (LEFM); Nickel base alloys; Polymer matrix composites; Porosity; Precipitates; Propagation (polymerization); Radiation damage; Safety critical; Short cracks; Spatial resolution; Stress intensity factor; Structural damage; Superalloys; Synchrotron radiation; Titanium base alloys; X ray microtomography
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2017.07.027

•We present the unique characteristics of SR-μCT to study of fatigue behaviors in engineering structural materials.•There is a wealth of information about fracture and fatigue in both 3D and 4D non-destructively.•It permits 3D imaging of damage accumulation and the time lapse imaging of damage evolution for environmental and mechanical loading.•It provides quantitative information about key fracture mechanics parameters.•We predict X-ray free-electron lasers (XFELs) will allow at the nanometer spatial scale or over femtosecond time scales. The initiation and propagation of short cracks are critical to the detailed understanding of the failure mechanisms of engineering materials and structures. Therefore, for a safety critical component, it is beneficial to be able to follow the progress of cracks in loaded structures and real environments ideally at sub-micron spatial resolution and/or sub-second time resolution. Here we review the great progress that has been made in the application of synchrotron radiation X-ray computed microtomography (SR-μCT) to the study of internal damage accumulation and evolution in structural materials including cast irons and steel, nickel superalloys, lightweight titanium and aluminum alloys as well as metallic, ceramic and polymer composite materials together with additatively manufactured or three-dimensional (3D) printed metallic materials. SR-μCT is shedding light on the complex interactions of cracks with intrinsic porosity, precipitates and intermetallic inclusions and grain structure, as well as macroscopic features such as holes and joints. Furthermore it is enabling qualitative and quantitative relations between the microstructural features and engineering performance to be established and validated under realistic service loading and environmental conditions. Here we introduce the basic 3D and time-lapse (4D) tomographic methods and discuss their strengths and limitations across a range of the applications, as well as identify opportunities for the future.