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Durability and Fatigue

Light weight of vehicles is receiving great attention as automobile industry started to set targets for reduction of CO2 emission. With the trend of light weight, chassis parts are increasingly attempting to apply high strength steel as a means to increase strength and stiffness and reduce weight of existing hot rolled PO products. Durability of parts is the most important point to be considered when trying to reduce weight of chassis parts.

POSCO provides physical properties on fatigue test for durability analysis to its clients. We manufacture a variety of test specimens under different steel types, specimen shapes, test conditions, basic materials and welding conditions wanted by customers, providing S/N (stress amplitude-number of cycles) curve and Ɛ-N (total strain amplitude-number of reversals) curve as results of fatigue test. We also support stiffness / durability test on parts when requested by clients.

POSCO also conducts EVI activities on suggestion of optimized steel and parts design to be satisfied to customer’s durability performance specifications. Among chassis parts, parts that require durability such as CTBA (Coupled Torsion Beam Axle), wheel, engine cradle, lower control arm and stabilizer bar are interlinked with fatigue data of POSCO steel to provide the results of durability analysis and suggest the most appropriate steel type. Furthermore, we support joint research with clients, parts design, manufacture, and durability / stiffness evaluation. We also analyze causes of fatigue failure through SEM imaging of fatigue fracture surface, measurement of surface roughness, and measurement of strain rate and residual stress.

Sequence of durability test, Stiffness / durability / buckling analysis results