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

2020 ◽  
Author(s):  
Boris Vasilyev ◽  
Nikita Zhukov ◽  
Igor Kiselev ◽  
Alexander Selivanov
Keyword(s):  
Residual Stresses ◽  
Turbine Blade ◽  
Shot Peening ◽  
Strain State ◽  
Multiple Impacts ◽  
Tree Roots ◽  
Turbine Wheel ◽  
Suggested Approach ◽  
Cyclic Durability ◽  
Compressive Residual Stresses

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.

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

2013 ◽  
Vol 768-769 ◽  
pp. 519-525 ◽  
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.

scholarly journals Modelling of multiple impacts for the prediction of distortions and residual stresses induced by ultrasonic shot peening (USP)

2012 ◽  
Vol 212 (10) ◽  
pp. 2080-2090 ◽  
Author(s):  
Thibaut Chaise ◽  
Jun Li ◽  
Daniel Nélias ◽  
Régis Kubler ◽  
Said Taheri ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Shot Peening ◽  
Multiple Impacts ◽  
Ultrasonic Shot Peening

Numerical Simulation of Residual Stresses Induced from Shot Peening with Finite Element Method

2013 ◽  
Vol 433-435 ◽  
pp. 1898-1901
Author(s):  
Li Juan Cao ◽  
Shou Ju Li ◽  
Zi Chang Shangguan
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Residual Stress ◽  
Surface Layer ◽  
Residual Stresses ◽  
Shot Peening ◽  
Target Material ◽  
Residual Stress Field ◽  
State Of Stress ◽  
Compressive Residual Stresses

Shot peening is a manufacturing process intended to give components the final shape and to introduce a compressive residual state of stress inside the material in order to increase fatigue life. The modeling and simulation of the residual stress field resulting from the shot peening process are proposed. The behaviour of the peened target material is supposed to be elastic plastic with bilinear characteristics. The results demonstrated the surface layer affected by compressive residual stresses is very thin and the peak is located on the surface.

Polycrystal Plasticity Modeling of Cyclic Residual Stress Relaxation in Shot Peened Martensitic Gear Steel

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Rajesh Prasannavenkatesan ◽  
David L. McDowell
Keyword(s):  
Residual Stress ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Shot Peening ◽  
Cyclic Plasticity ◽  
Residual Stress Field ◽  
Residual Stress Relaxation ◽  
Gear Steel ◽  
Polycrystal Plasticity ◽  
Compressive Residual Stresses

Using a three-dimensional crystal plasticity model for cyclic deformation of lath martensitic steel, a simplified scheme is adopted to simulate the effects of shot peening on inducing initial compressive residual stresses. The model is utilized to investigate the subsequent cyclic relaxation of compressive residual stresses in shot peened lath martensitic gear steel in the high cycle fatigue (HCF) regime. A strategy is identified to model both shot peening and cyclic loading processes for polycrystalline ensembles. The relaxation of residual stress field during cyclic bending is analyzed for strain ratios Rε=0 and −1 for multiple realizations of polycrystalline microstructure. Cyclic microplasticity in favorably oriented martensite grains is the primary driver for the relaxation of residual stresses in HCF. For the case of Rε=−1, the cyclic plasticity occurs throughout the microstructure (macroplasticity) during the first loading cycle, resulting in substantial relaxation of compressive residual stresses at the surface and certain subsurface depths. The initial magnitude of residual stress is observed to influence the degree (percentage) of relaxation. Describing the differential intergranular yielding is necessary to capture the experimentally observed residual stress relaxation trends.

Microscale Modeling to Study Shot Peening Effects on Aluminum Alloy

2016 ◽  
Author(s):  
H. Bae ◽  
M. Ramulu ◽  
A. Hossain
Keyword(s):  
Residual Stress ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Single Shot ◽  
Impact Model ◽  
Multiple Impacts ◽  
Residual Stress Field ◽  
Multiple Impact ◽  
Microscale Modeling ◽  
Compressive Residual Stresses

Shot peening is a cold working process used to produce a compressive residual stress to modify mechanical properties of metals. It causes impacting a surface with shots with significant force to create plastic deformation. The compressive residual stresses developed by shot peening process helps to avoid the propagation of micro-cracks exist in surface. Shot peening process is often used in aircraft industries to relieve tensile stresses built up in the grinding process, and replace them with beneficial compressive residual stresses. Shot peening has been developed to increase the fatigue strength of metallic parts. Compressive residual stress and surface hardening induced by shot peening process are found beneficial to increase the fatigue life and the resistance to stress corrosion cracking within the metallic component. Even though shot peening has been used for more than 50 years, a review of published papers indicates a lack of studies in numerical modeling. In particular, the effect of complex shot peening process to predict the target material responds to the multiple impacts of shots is not fully revealed. Most studies have investigated the fundamental mechanism and characteristics of fatigue improvement by single shot peening, and have studied the compressive residual stress induced by single normal impact on the surface of the specimen. However, single impact model is appropriate and efficient for sensitivity studies, local plastic effect, and indentation estimation. It is well known that the residual stress by single shot model is not suitable for practical use. The residual stress field from multi impacts is the resultant sum of all the fields by repeated and progressive impacts. It is not feasible to extrapolate results from the single impact model to a practical shot peening process with multiple impacts. Therefore, this research attempts to conduct a microscale modeling to study the shot peening effects of aluminum alloy responds to single and multiple impacts. First, a single shot impact model, representing single shot peening process, has been developed for the estimation of indentations at different velocities. The numerical simulations has been performed with the finite element software code LS-DYNA. The validations of the numerical simulations has been made from experimentally measured surface roughness data. Once the finite element code of single shot peening model is validated, additional numerical models are developed to simulate multiple shot peening process, using multiple impact shots. The multiple impact model are developed for the estimation of the residual stress field.

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