Reverse bending fatigue of shot peened 7075-T651 aluminium alloy: The role of residual stress relaxation

Benedetti, M.; Fontanari, V.; Scardi, Paolo; Ricardo, Cristy Leonor Azanza; Bandini, Michele

doi:10.1016/j.ijfatigue.2008.11.017

Cited by 144 publications

(112 citation statements)

References 24 publications

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“…At the 1 mm depth, the residual stress profiles changed to low tensile values. The thicknesses of the surface compression layers from the dengeling treatments studied here appear to be large, about two to four times of that commonly found for shot peened high strength aluminum alloys, see for example [3][4][5]. The large penetration depth of the dengeling treatment could partly be explained by a more efficient transfer of kinetic energy from the indenter to the part surface, in comparison with shot peening in which free bouncing of the shots are allowed.…”

Section: Figure 3 Backscatter Electron Images Of Same Magnification Smentioning

confidence: 52%

“…Similar to the widely used shot peening process in which the surface is bombarded by hard shots, the dengeling treatment induces compressive residual stresses in a surface layer. As a considerable number of publications on shot peening have demonstrated [1][2][3], compressive stresses in near surface regions can greatly improve the fatigue resistance of a part. Dengeling has certain benefits over shot peening.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Residual Stresses in Dengeling-Treated Aluminum Alloy AA 7050

Ess¹,

Selegård²,

Jonsson³

et al. 2016

Residual Stresses 2016

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Abstract. Dengeling is a new method for mechanical surface treatment of metallic parts to enhance fatigue properties. The treatment produces consecutive lines of indents by a spherical indenter, resulting in compressive residual stresses in a surface layer. This paper investigated residual stresses, surface roughness and near surface deformation, in specimens of AA 7050 T7451 after different dengeling treatments. The effect of indent overlap (0%, 25% and 50%) and indenter size (∅3 and ∅8 mm) were studied. X-Ray diffraction measurements revealed that plastic deformation and compressive residual stresses were generated in a surface layer of about 1 mm by treatments using the ∅3 mm indenter and about 1.2 mm by treatment using the ∅8 mm indenter. Anisotropic residual stress fields were observed with higher compressive residual stresses (-360 MPa for 50% indent overlap, independent of indenter size) perpendicular to indent lines and lower (max -270 MPa for all the treatments) parallel to indent lines. Increasing the overlap between indents gave higher subsurface compressive residual stresses only in the transverse direction of indent lines. It also reduced the surface roughness. Best surface finish (Ra below 1 μm) was obtained when using the ∅8 mm indenter and 50% indent overlap. IntroductionDengeling is a new method for mechanical surface treatment of metallic parts to enhance fatigue properties. The treatment is carried out on a numerically controlled machine using a special indenter which moves and strikes the surface of the metal part in a given pattern and at a high frequency, up to 600 Hz. The transfer of kinetic energy from the indenter upon impact causes in-plane plastic deformation, producing consecutive lines of indents in the treated surface. Similar to the widely used shot peening process in which the surface is bombarded by hard shots, the dengeling treatment induces compressive residual stresses in a surface layer. As a considerable number of publications on shot peening have demonstrated [1][2][3], compressive stresses in near surface regions can greatly improve the fatigue resistance of a part. Dengeling has certain benefits over shot peening. The process is NC controlled, thus the operator can control exactly the location and magnitude of the generated residual stresses. Furthermore, the dengeling treatment is performed on the same machine that is used for machining the part; it can therefore be integrated into the machining process of metallic parts. That machining and surface mechanical treatment are carried out on the same machine means a great reduction of production cycle time and cost.

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Section: Figure 3 Backscatter Electron Images Of Same Magnification Smentioning

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Residual Stresses in Dengeling-Treated Aluminum Alloy AA 7050

Ess¹,

Selegård²,

Jonsson³

et al. 2016

Residual Stresses 2016

View full text Add to dashboard Cite

show abstract

“…Studies carried out by [11][12][13][14][15] indicate that the SP process generates compressive stresses. Research carried out by Benedetti M., Fontanari V. using alloy AA7050-T7451 has shown that the diameter of shot used does not significantly affect the amount of residual stresses.…”

Section: Introductionmentioning

confidence: 99%

“…Research carried out by Benedetti M., Fontanari V. using alloy AA7050-T7451 has shown that the diameter of shot used does not significantly affect the amount of residual stresses. It does however significantly influence the range of generated stress [11]. Aside from the abovementioned factors, the range of stresses generated during the process depends on the working pressure, distance between the nozzle and the angle of attack of the processing medium.…”

Section: Introductionmentioning

confidence: 99%

Synergy of the Plastic Treatment HPT and Shot Peening in Aluminium Alloy Al-Mg-Mn-Sc-Zr

Stegliński

Byczkowska

Sawicki

et al. 2016

Archives of Metallurgy and Materials

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An improvement in fatigue strength is one of the main factors enabling the use of high-durability Al-Mg-Mn-Sc-Zr alloys in functional components of mobile robots. As part of this study, a computer simulation was carried out using ANSYS LS-DYNA software that involved the hybridization of high pressure torsion (HPT) and shot peening (SP) forming processes. The numerical analysis was aimed at determining residual stresses and strains that affect the durability and stress characteristics of the analyzed Al alloy. Results of the study indicate that tensile stresses of σ = 300 MPa generated as a result of HPT are transformed into a beneficial stress of σ = 25 MPa resulting from plastic strains caused by SP surface treatment.

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“…In contrary, it has been demonstrated that the compressive residual stress, generated by controlled machining processes and surface treatments, improves the fatigue strength by delaying the crack nucleation and by reducing the crack propagation rate [2, 7,8]. However, most of published data related to fatigue crack nucleation and growth involving residual stress were discussed on the basis of their initial distribution [9][10][11]. Moreover, the majority of fatigue predictive methods take into account the initial measured residual stress values and neglect their evolution under cyclic loading.…”

Section: Introductionmentioning

confidence: 99%

Effect of Surface Properties on the Fatigue Life of Manufactured Parts: Experimental Analysis and Multi-Axial Criteria

Sidhom¹,

Moussa²,

Fathallah³

et al. 2014

AMR

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The effects of machined and treated surface characteristics on the fatigue strength were analyzed on the basis of experimental results related to AISI D2 ground surface and AA 5083-H111 hammered surface. The fatigue strength improvement resulting from controlled grinding and mechanical surface treatment was discussed on the basis of the beneficial effect of the work hardening and the stabilized residual stress. A numerical procedure using F.E.M for calculating residual stress and work hardening evolution under cyclic loading has been developed. The validation of the numerical procedure was carried out by comparing the calculated residual stress profiles to those resulted from XRD measurements. The multi-axial criterion accounting for the work hardening and the residual stress was used to predict the fatigue life of notched samples. IntroductionIt is well established that residual stress and work hardening, generated by machining and surface treatment processes, influence the fatigue life of mechanical parts [1][2][3]. That is why they are often considered in fatigue strength predictive models using multi-axial fatigue criteria [3] and fatigue life assessment by local strain-life approaches [4,5]. Experimental and modeling results confirm the detrimental effect of tensile residual stress which is considered to promote fatigue crack nucleation and to accelerate their propagation [6]. In contrary, it has been demonstrated that the compressive residual stress, generated by controlled machining processes and surface treatments, improves the fatigue strength by delaying the crack nucleation and by reducing the crack propagation rate [2,7,8]. However, most of published data related to fatigue crack nucleation and growth involving residual stress were discussed on the basis of their initial distribution [9][10][11]. Moreover, the majority of fatigue predictive methods take into account the initial measured residual stress values and neglect their evolution under cyclic loading. This assumption is controversial by published data related to stabilized residual stress profiles showing relaxation and redistribution phenomena [2,8,12,13]. Moreover, it has been reported that the most fraction of residual stress relaxation is monotonic, since it occurs at first cycles. Relaxation could progress under cyclic loading if the plastic misfit itself continues to change until stability [13][14][15]. Since the stabilized residual stress state is an important parameter for fatigue life prediction, it is of paramount importance to determine, in this study, the parameters that govern their evolution during cyclic loading. These parameters will be taken into account by the developed numerical procedure to calculate stabilized residual stresses and therefore fatigue life time. Analysis of the residual stress cyclic stability is based on the experimental results of surface characterization and fatigue tests conducted on AISI D2 ground surface and AA 5083-H111 machined and wire brush hammered surfaces.

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Reverse bending fatigue of shot peened 7075-T651 aluminium alloy: The role of residual stress relaxation

Cited by 144 publications

References 24 publications

Residual Stresses in Dengeling-Treated Aluminum Alloy AA 7050

Residual Stresses in Dengeling-Treated Aluminum Alloy AA 7050

Synergy of the Plastic Treatment HPT and Shot Peening in Aluminium Alloy Al-Mg-Mn-Sc-Zr

Effect of Surface Properties on the Fatigue Life of Manufactured Parts: Experimental Analysis and Multi-Axial Criteria

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