Quest Reliability possesses extensive expertise and a variety of tools for performing life assessment of components subject to cyclic loading. The available methodologies and tools include:
Fatigue Crack Propagation Analysis
Fracture mechanics-based models are typically used to determine the number of cycles required to grow a crack from an initial size to a final size. The fracture mechanics module in the Signal Fitness-for-ServiceTM software performs both constant-amplitude and variable-amplitude fatigue analyses. The materials database in Signal Fitness-For-Service™ contains fatigue crack propagation constants for several hundred alloys, as well as an extensive library of stress intensity factor (K) solutions, including weight functions for complex stress distributions.
Finite Element Analysis of Fatigue Crack Propagation
Quest Reliability possesses a truly unique capability for performing fatigue crack propagation analyses for complex cases that are beyond standard fracture mechanics models. Our FEACrack software can perform finite element-based fatigue crack propagation analysis. Starting with an initial crack, the stress intensity factor is computed along the crack front. The crack is then advanced at each node point based on the local growth rate. Unlike standard fracture mechanics models that idealize the crack profile as elliptical or some other simple shape, the growing crack can take on any shape in response to the applied loading.
The Structural Stress Method for Welded Joints
This method is described in both API 579-1/ASME FFS-1 and an upcoming release of Section VIII, Division 2 of the ASME Boiler and pressure vessel code. The method requires a finite element analysis of the component of interest. Stresses are linearized over the cross section and substituted into a fatigue master curve for welded joints. This method is far less mesh sensitive than other finite element-based fatigue analyses, and it has been validated with numerous fatigue tests of welded joints.
Strain Life Curves
This method is suitable for predicting crack initiation, particularly in the low-cycle fatigue regime. It can be used in conjunction with a fatigue crack propagation analysis.
For further information about Fatigue Analysis, please contact us.