The understanding of the relationship between fatigue life, process effects and residual stresses needs to be evaluated carefully before the manufacturing process can be optimised for enhanced quality and product characteristics. Residual stresses in manufactured components are those stresses that exist without prior application of service or external loads. Virtually all manufacturing and surface treatments will introduce residual stresses into a component which may either be beneficial or detrimental to the ftigue properties. This paper investigates the mechanism that exists between fatigue properties and residual stresses and its relation to process effects by withdrawing samples from different stages of the manufacturing process. In order to measure the residual stresses present, the locked-in stresses must be relieved by removing material to enable a sensor to register the change in strain. These measurements were done by means of Centre Hole Drilling using an Air Abrasive Powder System and residual strain rosettes as sensors. The results revealed the nature and magnitude of the stresses induced into each component by every manufacturing process and the relation these induced stresses have on the fatigue properties of the components. In thefinal analysis this research should reveal the relation and impact of the manufacturing processes on residual stresses and fatigue properties of 55Cr3 spring steel.
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