Fatigue analysis - TRaC can solve your product failure issues

Fatigue Failure Analysis

Metal fatigue is a significant problem because it can occur due to repeated loads below the static yield strength. This can result in an unexpected and catastrophic failure in use. Because most engineering materials contain discontinuities most metal fatigue cracks initiate from discontinuities in highly stressed regions of the component. The failure may be due the discontinuity, design, improper maintenance or other causes. TRaC are experts in both FEA analysis and physical testing and it is this wealth of experience and knowledge which places us at the forefront in this complex and critical area. A failure analysis can determine the cause of the failure and enable an informed redesign to be created to address the problem.

Metal fatigue is caused by repeated cycling of the load. It is a progressive localised damage due to fluctuating stresses and strains on the material. Metal fatigue cracks initiate and propagate in regions where the strain is most severe. TRaC is proud to be the first UKAS accredited facility for Highly Accelerated Life Testing. Accreditation is specifically for our QRS - 410T HALT chamber from Screening Systems Incorporated.

The process of fatigue consists of three stages:

Initial crack initiation - Crack initiation is related to the stress-strain hysteresis loop. The area within this loop dissipates energy which promotes crack initiation and propagation. While each cycle represents an infinitesimally small amount of energy, when this process is repeated over and over again, the total energy can be quite significant. TRaC are experts in fatigue testing and analysis and regularly carry out research for a number of aerospace and defence companies.

Progressive crack growth across the part - The material properties, the stress range, and the crack size all impact the crack propagation rate for a part. Environmental chemistry at the crack tip can have a key effect on crack growth rate. The combined action of corrosion and fatigue does substantially increase the crack growth rate. Other factors effecting growth rate include the temperature and structural resonance and material purity. The technology of fracture mechanics, crack infiltration, and growth is well understood at TRaC.

Final sudden fracture of the remaining cross section - This is when the component reached a critical point and failure results.

Recent Fatigue projects include:

Weld Analyses - Reduce weld size, Reduce costs and environmental impact, and improve length of product life
Brazing Analysis
Hydrogen Fuel Cell Ceramics

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