Fatigue crack growth analysis in non-standard geometries
Broad Application for Multi-Point Fatigue (BAMpF®) enables fatigue crack growth analysis of parts with non-standard geometry, loading, and residual stress conditions through the implementation of multi-point fracture mechanics (MPFM). This user-friendly software environment provides structural analysts and engineers a tool to accurately and efficiently complete challenging fatigue crack growth problems.
Starting from an assumed initial flaw, BAMpF® implements a multi-point fracture mechanics approach that allows crack shapes to evolve naturally as a function of the underlying, spatially varying stress fields and stress intensity factors. As illustrated in the figure below, the user specifies the number of points along the crack front to be used in the analysis. For each individual point, BAMpF® queries the stress intensity factor specific to the part geometry and loading through an interface with StressCheck® (a leading finite element software tool), provides the necessary inputs to AFGROW (a leading fatigue life assessment tool), and stores the expected fatigue crack growth for a given number of cycles. BAMpF® then combines the growth of each individual point into a new crack shape that serves as the starting point for the next increment of the analysis. This process is repeated until the fatigue crack reaches a critical size.
The use of MPFM is especially important when non-standard conditions like complex loading, complex geometry, and/or residual stresses are present as these factors tend to drive the evolution of the fatigue crack shape away from the circular/elliptical constraints imposed by the traditional analysis methods.
Accurate
The utilization of MPFM in BAMpF® improves the accuracy of fatigue crack growth calculations relative to traditional analysis methods by eliminating assumptions and constraints related to the shape of the crack (e.g. elliptical crack shapes are not required by MPFM).
Fast
BAMpF® shortens the analysis time relative to other multi-point fracture mechanic codes by utilizing StressCheck p-element FEA, producing results significantly faster than the competition.
Adaptable
BAMpF® provides for a variety of loads and boundary conditions. Fatigue crack growth analyses can reflect a wide range of scenarios that accurately capture service history and advanced solution strategies like contact or local breakout models.
Features
- Natural fatigue crack shape progression
- Fully 3D analysis
- Complex loading
- Multi-crack interactions and link-up
- Residual stress
Image from a BAMpF analysis showing the stress in a specimen with a small crack near a hole
Illustration of multi-point fracture mechanics approach to defining individual control points around the crack front
Fatigue crack growth analysis (BAMpF) and experimental results for a cold expanded hole test specimen