Influence Of Shot Peening On The Bending Fatigue Behaviour Of Notched Specimens Of Ck 45

Author:  Hoffmann, Lohe, Macherauch
Source:  Conf Proc: ICSP-3, (p.631-638)
Doc ID:  1987051
Year of Publication:  1987
Abstract:  
As a consequence of shot peening of steel parts, the surface topography will be changed and at and below the surface characteristic residual stress states the workhardening states will be produced. It is well established that these quantities influence the bending fatigue behaviour of smooth specimens. In most cases, considerable improvements of the bending fatigue strengths are observed. In two recent investigations it was shown that shot peened notched specimens reveal stronger increase in bending fatigue strength compared with smooth specimens peened under the same conditions. However, the material states near the notch root were unknown and different surface states existed at smooth and notched specimens, respectively. Of course, to assess the increase of fatigue strength due to shot peening the precise knowledge of the material state at and below the notch root surface should be known. In particular, quantitative data of the residual stresses at and near the very surface of the notches are necessary. In this respect only X-ray diffraction procedures promise definite results. In the following, shot peened material states at and below the notch root surface of quenched and quenched and tempered bending specimens of a medium carbon steel (German grade Ck 45, SAE 1045) are analyzed. The results of bending fatigue tests with several stress amplitudes on smooth and notched specimens are shown. Finally, the results obtained from shot peened and ground specimens are compared and discussed applying the local fatigue strength concept.