Modeling of Residual Stresses After Shot Peening and the Effect of Accounting Their Influence on the Stress State of Turbine Blade Fir Tree Roots

Abstract Numerical modeling approaches have been developed for simulating shot peening processes and consideration of compressive residual stresses when performing strength calculations of turbine wheel joints. A three-stage method is presented to combine strength analyses of turbine blade with the output of LS-DYNA simulations (RS diagrams) of multiple impacts. Predictions of RS distributions obtained using the suggested approach are compared with experimental data and good correlation was achieved. The effect of the RS diagrams obtained using various SP parameters on the stress-strain state of the turbine blade root and the values of its cyclic durability are estimated.

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Influence of process parameters on the residual stress state and properties in disc springs made by incremental sheet forming (ISF)

Forschung im Ingenieurwesen ◽

10.1007/s10010-021-00491-w ◽

2021 ◽

Author(s):

Muhammad Junaid Afzal ◽

Ramin Hajavifard ◽

Johannes Buhl ◽

Frank Walther ◽

Markus Bambach

Keyword(s):

Residual Stress ◽

Stress State ◽

Residual Stresses ◽

Process Parameters ◽

Shot Peening ◽

Sheet Forming ◽

Incremental Sheet Forming ◽

Installation Space ◽

Residual Stress State ◽

Compressive Residual Stresses

AbstractDisc springs are machine elements that are used when high forces need to be supplied and in limited installation space. They need to fulfil high demands on the stability of the spring characteristics, reliability and lifetime. In corrosive environments, metastable austenitic stainless steels (MASS) disc springs are often used. Tensile stresses that occur during service limit the lifetime of disc springs. Usually, their durability is enhanced by generating favorable compressive residual stresses using shot peening operations. Such operations lead to extra efforts and additional production costs. In this study, the adaptive and targeted generation of residual stresses via incremental sheet forming (ISF) is investigated as alternative to shot peening focusing on EN 1.4310 and EN 1.4401 stainless steel. Previous work has shown that ISF is capable of controlling the radial and tangential stresses in the springs. However, no analysis of the influence of the residual stress state in the rolled sheet strips and the ISF process parameters was performed. The goal of the current work is to analyze the evolution of residual stress during rolling and subsequent incremental forming of disc springs. In order to examine the role of dissipation and temperature increases in the rolling process, sheet blanks rolled at room and elevated temperature are analyzed. The characteristics of the compressive residual stresses induced by ISF are studied for different process parameters. X‑ray diffraction is used to investigate the buildup of these stresses. Using ISF, the generation of compressive residual stresses can be integrated into the forming process of disc springs, and further post-treatment may be skipped. The results show that the residual stress state in the rolled material is crucial, which requires tight control of the rolling temperature. Another result is that ISF is able to yield high compressive residual stresses and improved spring characteristics when small tool diameters and step-down values are used.

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Influence of Shot Peening on the Isothermal Fatigue Behavior of the Gamma Titanium Aluminide Ti-48Al-2Cr-2Nb at 750 °C

Metals ◽

10.3390/met11071083 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1083

Author(s):

Christoph Breuner ◽

Stefan Guth ◽

Elias Gall ◽

Radosław Swadźba ◽

Jens Gibmeier ◽

...

Keyword(s):

Residual Stresses ◽

Shot Peening ◽

Elevated Temperatures ◽

Stress Amplitude ◽

Negative Impact ◽

Fatigue Behavior ◽

Surface Hardness ◽

Fatigue Tests ◽

Positive Effects ◽

Isothermal Fatigue

One possibility to improve the fatigue life and strength of metallic materials is shot peening. However, at elevated temperatures, the induced residual stresses may relax. To investigate the influence of shot peening on high-temperature fatigue behavior, isothermal fatigue tests were conducted on shot-peened and untreated samples of gamma TiAl 48-2-2 at 750 °C in air. The shot-peened material was characterized using EBSD, microhardness, and residual stress analyses. Shot peening leads to a significant increase in surface hardness and high compressive residual stresses near the surface. Both effects may have a positive influence on lifetime. However, it also leads to surface notches and tensile residual stresses in the bulk material with a negative impact on cyclic lifetime. During fully reversed uniaxial tension-compression fatigue tests (R = −1) at a stress amplitude of 260 MPa, the positive effects dominate, and the fatigue lifetime increases. At a lower stress amplitude of 230 MPa, the negative effect of internal tensile residual stresses dominates, and the lifetime decreases. Shot peening leads to a transition from surface to volume crack initiation if the surface is not damaged by the shots.

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Surface Modification Analysis after Shot Peening of AA 7075 in Different States

Materials Science Forum ◽

10.4028/www.scientific.net/msf.768-769.519 ◽

2013 ◽

Vol 768-769 ◽

pp. 519-525 ◽

Cited By ~ 1

Author(s):

Sebastjan Žagar ◽

Janez Grum

Keyword(s):

Residual Stress ◽

Surface Layer ◽

Residual Stresses ◽

Aluminium Alloy ◽

Shot Peening ◽

Fatigue Testing ◽

Stress Profile ◽

Treatment Conditions ◽

Stress Profiles ◽

Compressive Residual Stresses

The paper deals with the effect of different shot peening (SP) treatment conditions on the ENAW 7075-T651 aluminium alloy. Suitable residual stress profile increases the applicability and life cycle of mechanical parts, treated by shot peening. The objective of the research was to establish the optimal parameters of the shot peening treatment of the aluminium alloy in different precipitation hardened states with regard to residual stress profiles in dynamic loading. Main deformations and main residual stresses were calculated on the basis of electrical resistance. The resulting residual stress profiles reveal that stresses throughout the thin surface layer of all shot peened specimens are of compressive nature. The differences can be observed in the depth of shot peening and the profile of compressive residual stresses. Under all treatment conditions, the obtained maximum value of compressive residual stress ranges between -200 MPa and -300 MPa at a depth between 250 μm and 300 μm. Comparison of different temperature-hardened aluminium alloys shows that changes in the Almen intensity values have greater effect than coverage in the depth and profile of compressive residual stresses. Positive stress ratio of R=0.1 was selected. Wöhler curves were determined in the areas of maximum bending loads between 30 - 65 % of material's tensile strength, measured at thinner cross-sections of individual specimens. The results of material fatigue testing differ from the level of shot peening on the surface layer.

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About Residual Stress State of Castings: The Case of HPDC Parts and Possible Advantages through Semi-Solid Processes

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.327.272 ◽

2022 ◽

Vol 327 ◽

pp. 272-278

Author(s):

Elisa Fracchia ◽

Federico Simone Gobber ◽

Claudio Mus ◽

Yuji Kobayashi ◽

Mario Rosso

Keyword(s):

Residual Stress ◽

Stress State ◽

Residual Stresses ◽

Casting Process ◽

Ray Method ◽

Premature Failure ◽

Thin Walls ◽

Residual Stress State ◽

Semi Solid ◽

Pressure Die Casting

Nowadays, one of the most crucial focus in the aluminium-foundry sector is the production of high-quality castings. Mainly, High-Pressure Die Casting (HPDC) is broadly adopted, since by this process is possible to realize aluminium castings with thin walls and high specific mechanical properties. On the other hand, this casting process may cause tensile states into the castings, namely residual stresses. Residual stresses may strongly affect the life of the product causing premature failure of the casting. Various methods can assess these tensile states, but the non-destructive X-Ray method is the most commonly adopted. Namely, in this work, the residual stress analysis has been performed through Sinto-Pulstec μ-X360s. Detailed measurements have been done on powertrain components realized in aluminium alloy EN AC 46000 through HPDC processes to understand and prevent dangerous residual stress state into the aluminium castings. Furthermore, a comparison with stresses induced by Rheocasting processes is underway. In fact, it is well known that Semi-Solid metal forming combines the advantages of casting and forging, solving safety and environmental problems and possibly even the residual stress state can be positively affected.

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Limitation of Distortion in Friction Stir Welded (FSW) Panels Using Needle Peening

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.1203 ◽

2010 ◽

Vol 638-642 ◽

pp. 1203-1208 ◽

Cited By ~ 2

Author(s):

Simon Larose ◽

Laurent Dubourg ◽

C. Perron ◽

Mohammad Jahazi ◽

Priti Wanjara

Keyword(s):

Residual Stresses ◽

Shot Peening ◽

Sheet Material ◽

Travel Speed ◽

Needle Size ◽

Friction Stir ◽

Average Value ◽

Aa 2024 ◽

Induced Stresses ◽

Needle Diameter

Friction stir welding (FSWing) induces residual stresses and distortions in welded structures. Such residual stresses reduce the fatigue life of welded components, while the induced distortions prevent the welding of large or thin components. In the present study, needle peening was used to induce additional residual stresses in 2.3-mm thick (FSWed) aluminum alloy (AA) 2024-T3 sheets. This was done with the objective to counterbalance the welding-induced stresses and thus reduce the overall stresses and distortions. The needle peening process, which stems from shot peening, consists of hammering a surface using cylindrical spherical ended shots sliding back and forth in a treatment head. An instrumented needle peening machine was used to carry out peening on as-received (or bare) and bead-on-plate FSWed AA2024-T3 material. In both cases, the width of the peening area corresponded to that of a typical weld. The influence of the peening process parameters such as needle size, applied power and travel speed on the surface quality and magnitude of the induced distortions were evaluated. The results indicate that, by increasing the needle diameter from 1.2 mm to 2.0 mm, the peening-induced deflection on bare sheet material increased by an average value of 27% while the roughness average, Ra, decreased by an average value of 47%. It was also found that a surface finish qualitatively similar to that of conventional shot peening could be obtained by using appropriate needle peening trajectories. Finally, needle peening with an applied power of 10% was sufficient for eliminating 37% of the welding-induced transverse curvature and 82% of the welding-induced longitudinal curvature.

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Stress state investigation and evaluation of residual stresses in thermoformed polycarbonate sheet

Plasticheskie massy ◽

10.35164/0554-2901-2019-3-4-21-24 ◽

2019 ◽

pp. 21-24 ◽

Cited By ~ 1

Author(s):

A. V. Markov ◽

D. I. Derivolkov ◽

D. S. Duvanov

Keyword(s):

Stress State ◽

Residual Stresses

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A Kinematic Hardening Finite Elements Model to Evaluate Residual Stresses in Shot-Peened Parts, Local Measurements by X-Ray Diffraction

Materials Science Forum ◽

10.4028/www.scientific.net/msf.524-525.161 ◽

2006 ◽

Vol 524-525 ◽

pp. 161-166 ◽

Cited By ~ 2

Author(s):

Choumad Ould ◽

Emmanuelle Rouhaud ◽

Manuel François ◽

Jean Louis Chaboche

Keyword(s):

Finite Elements ◽

Residual Stresses ◽

Shot Peening ◽

Kinematic Hardening ◽

Constitutive Law ◽

Loading Path ◽

Isotropic Hardening ◽

X Ray Diffraction ◽

X Ray ◽

Local Measurements

Experimental analysis can be very costly and time consuming when searching for the optimal process parameters of a new shot-peening configuration (new material, new geometry of the part…). The prediction of compressive residual stresses in shot-peened parts has been an active field of research for the past fifteen years and several finite elements models have been proposed. These models, although they give interesting qualitative results, over-estimate, most of the time, the level of the maximal compressive stresses. A better comprehension of the phenomena and of the influence of the parameters used in the model can only carry a notable improvement to the prediction of the stresses. The fact that the loading path is cyclic and is not radial led us to think that a model including kinematic hardening would be better adapted for the modelling of shot peening. In this article we present the results of a simulation of a double impact for several constitutive laws. We study the effect of the chosen constitutive law on the level of residual stresses and, in particular, we show that kinematic hardening, even identified on the same tensile curve than isotropic hardening, leads to lower stress levels as compared with isotropic hardening. Furthermore, the overall shape of the stress distribution within the depth is significantly different for the two types of hardening behaviour. Further, in order to check the modelisations, local measurements were carried on with X-ray diffraction on a large size impact and correlated with the topography of the impact.

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