Experimental Study of Residual Stress Distributions in Quenched Parts by the Incremental Large Hole Drilling Method and by the Neutron Diffraction Method
Résumé
The incremental hole-drilling method has been used to measure the residual stress field in a quenched part. In quenched parts, there is great compressive residual stress at the surface and tensile residual stress in the middle of the part, so in this case we used an unusually large hole diameter. The classical rosette system cannot be used. The rosette we studied is made up of six strain gages that are placed in a circle with a diameter two times the hole diameter. This system can be adapted to any chosen hole diameter. An error estimation about the positions of the gages has been developed. This procedure is based on a statistical study of measured strains by the six gages. To learn the validity of the incremental large hole drilling and to obtain the complete residual stress field through the thickness of the part, the neutron diffraction method has been used as well. This second method, however, is time consuming and expensive. The aim of this study is to integrate the residual stress field due to quenching into a fatigue life calculation. As is known, only the compressive residual stress field influences the fatigue life, so in the case of quenched parts only the part depth with compressive residual stress need be studied. The quenching of the studied part has been modeled by the finite element method. All the experimental results have been compared to numerical results.