Fatigue & DurabilityAnalysis Services

Fatigue analysis estimates how repeated loading can accumulate damage and limit the useful life of a component or welded detail. Depending on the problem, it can report predicted cycles to a defined criterion, cumulative damage, critical locations and sensitivity to duty or design changes. The result is an engineering estimate based on the load history, structural response, fatigue data and assumptions rather than an unconditional guarantee of service life.

Static analysis checks the response to a defined load event, while fatigue analysis evaluates damage accumulated through repeated loading. A component can remain below yield under each individual cycle and still develop a fatigue crack after enough repetitions. Fatigue assessment therefore requires cycle information, fatigue data and a defined life or damage criterion in addition to the structural stress result.

Useful inputs include a 3D model or drawings, material and manufacturing condition, weld details where relevant, operating loads, duty cycle or measured time history, number of cycles or required design life, support conditions, surface and environmental information and any known failure locations. Fabrixon identifies missing inputs and proposes sensitivity cases where the duty cannot be defined exactly.

Stress life methods use S N data and are generally suited to predominantly elastic response over a comparatively high number of cycles. Strain life methods use E N data and are considered where local cyclic plasticity or lower cycle counts affect the response. The method is selected from the expected behaviour, available data and decision that must be supported.

Welded joints are assessed using a method appropriate to the geometry, model detail and governing reference. This can include nominal stress, structural hot spot stress or effective notch stress methods. The selected fatigue class, stress extraction route, mesh requirements, weld toe or root location and thickness or mean stress treatment are documented in the report.

A variable load history can be reduced into cycles using a recognised counting method such as rainflow counting, then combined through a cumulative damage model where appropriate. When the stress direction changes materially within the cycle, a multiaxial method such as a critical plane or suitable equivalent stress approach may be required. The chosen method and its limitations are defined before life results are interpreted.

Cost and duration depend on model quality, structural analysis complexity, availability of a representative duty cycle, number of load histories, weld or material data, fatigue method, sensitivity studies, redesign iterations and reporting depth. A component with a clear load spectrum can be scoped quickly, while a large welded assembly or uncertain duty requires staged definition. The programme and commercial basis are confirmed after the initial engineering review.