Fracture and Failure Analysis
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.
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
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.
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.
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.
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.