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Fracture and Failure Analysis

  • Complex Fitness-for-Service (FFS) under BS 7910 / API 579 (Creep, Fatigue, etc)
  • Fracture comprises a significant portion of unforeseen failures in the industrial world around us, and the art of controlling fractures is being continuously advanced through the development of computational models that can provide a case-specific understanding of material behavior over the course of service. My team delivers a cutting-edge solution to your fracture analysis including case-specific algorithms that predict the evolution of damage in a weld in particular in the interface of weld and base metal i.e. fusion line. We offer a full spectrum of skills, capability, and experience in precisely computing fracture evolution using coupled damage algorithms on a case-by-case assessment in order to make a dependable structural integrity decision. Our previous projects and experience include hundreds of all-purpose Fitness for Service (FFS) assessments under API 579 and BS 7910 Level I, II, III, and full 3D structural damage assessment on service life.

     

     

     




  • Non-Planar 3D Transient Irregular Crack Growth Analysis in Weld & HAZ
  • As a representative of Zencrack software (http://www.zentech.co.uk), we deliver software as well as analysis using the state-of-the-art software tool for 3D fracture mechanics simulation, including non-planar crack growth predictions for fatigue and time-dependent loading conditions. Our work with the R&D team from Zencrack in the UK has led to the development of an exclusive capability for growth prediction including the metallurgical notch effect in material such as the weld fusion line.

     




  • Forensic Fracture Loading of a Failed Structure from Fracture Surface
  • A failure occurs under a mixed mechanism of tearing and fracture failure. The tearing failure caused by local stresses concentration exceeding the ultimate tensile strength of the remaining ligament of the cracked region, and, the fracture failure associated with the stress intensity at the crack tip exceeding the material toughness. BS7910 standard provides an assessment option under the Failure Assessment Diagram (FAD) where both mechanisms are active. A typical procedure uses the loading condition and the crack shape to determine if the structure is safe (i.e. the structure will not fail under the mixed effect). We used a reverse procedure in accordance with BS7910 to define the loading condition for the observed crack shape forms the fracture surface at the start of bolt instability to fail. The objective is to determine loading level that the structure was exposed at the final failure point.

     

     




  • Computational Fracture Analysis
  • My team of computational engineers are skilled in the use of general modeling software but are also expert in time-effective programming and scripting subroutines for custom-made numerical recipes in the Abaqus platform. We are also working directly with SIMULIA South to help develop the Abaqus Welding Interface (AWI). We use these computer and math algorithms to solve physics-based equations which enable us to make predictions and simulate scenarios for a variety of industries. The result is a practical solution to your fracture problem


    A case-specific creep damage model was constructed for welded P91 materials based on DMM
    Gray color shows creep damage evolution over time of service


    A case-specific model to predict CGHAZ, FGHAZ, ICHAZ, and the tempered region around the weld.




  • Constructing 3D Map of Multiple Flaws from 2D Radiography Films for ECA
  • Flaw acceptance criteria in welding standards are typically based on normally achievable workmanship criteria and are conservative, however, a weld may be able to tolerate defects in excess of those allowed for by the governing standard. Going beyond the standard relies on the science of fracture mechanics that allows for case-specific Engineering Critical Assessments (ECA) on our structures based on readily available tools for advanced analysis rather than strict adherence to general workmanship criteria in codes. However, a critical task to start ECA is to exactly define the location, shape, orientation, and size of each flaw in the structure. This has been the bottleneck of many ECAs because an engineer needs to map flaws from 2D film back into 3D a challenging task in particular when dealing with multiple flaws. We have automated this process such that we can map multiple flaws from the standard 3-shots RT images. This information, then, is used to justify waive or repair decisions for unexpected flaws found in welded joints. Other uses include failure analysis, setting inspection acceptance criteria, extending the life of structures and justifying deviations from a design code.