Abstract
Residual stress has a significant effect for improving engineering properties for metals .Most of the surface treatments produce compressive residual stress at the metal surfaces, which reduce crack initiation and increasing the metal resistance to fatigue, which is shot peening process. Shot peening is usually used for this purpose for producing plastic deformations of surface of the metal which can lead to creation high residual compressive stresses at metal surface .This research include study the influence of shot peening process on fatigue resistance, surface hardness and surface roughness for low carbon steel (AISI 1008). This process accomplished with different times which were (10, 20 and 30(minutes. The result of the fatigue test showed that the fatigue limit increase when shot peening time increased and the best fatigue limit obtained when shot peening process was carried out at 30 minutes. Results of hardness test showed that surface hardness increased with increase of shot peening time. It can be seen that highest value of surface hardness is obtained from shot peening process at time (30 minutes) which is (235.1 HVN). Results of surface roughness test showed that the surface roughness of metal increased when time of shot peening increased.
Highlights
Shot peening is a cold working in which surfaces of partsare bombarded with a small spherical media called shot
Three-point the bending fatigue testing was achieved in the highfrequency fatigue-test machine and apparent fatigue limits were determined by up-and-down methods
Figures [(8), (9), (10) and (11)] explained the fatigue curves for each condition, it can be seen that the highest value of fatigue limit was (119.36MPa) for samples that treated with (30) minutes time of shot peening process, this is due to creation high residual compressive stress at surface of specimens and reduce the crack initiation and increase dislocations density during this process
Summary
Shot peening is a cold working in which surfaces of partsare bombarded with a small spherical media called shot. Hornbogen et al(1981)[9], point out that shot peening has improved the fatigue life due to surface cold-working than the un peened or bulk-formed (steel) specimen. The shot velocity (function of air pressure or wheel speed), diameter, hardness and the peening time (coverage) increase magnitude of maximum compressive residual stress value as well as push its location further inside away from the surface. Wang S et al [11] investigated that shot peening pushes cracks initiation points beneath residual compressive stresses zones in all cases studied except for 0.45% carbon steel. It is usually that relaxation of the CRSF during fatigue process was not considered.W. Shengping, et al, [12] (1998) studied fatigue limits for shot peened 20Cr, 30CrMo, 40Cr, GC4, 45 steel and Alalloy 7075. Depth at which the maximum compressive residual stresses happens with respect of material grain size is most important factor in determining fatigue threshold
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
