Volume 9, Issue 6 (November 1981)
Residual Stress Profile in Machined Parts
The processes of machining precision parts have to be planned to result in low residual stresses, and a fast and reliable method is required to determine such stresses. A system was developed to meet this need. This system is based on continuous etching of a cylindrical specimen. Changes in specimen length are monitored as a function of etching time. The residual stress is then calculated with the Bauer and Heyn equation. Residual stress profiles caused by single point turning of 4340 steel (Unified Numbering System [UNS] G 43400) and maraging 300 steel specimens were evaluated by this procedure. This profile provides stress distribution in depth below the machined surface at various turning feeds, and it is used to define a residual tensile force. It is shown that an increase of feed increases the depth of the residual stressed layer and also increases the residual tensile forces. The ratio of residual tensile force to tool force as a function of the turning feed has a minimum.