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Comparison between the isotropic hardening law and the kinematic hardening law for cyclic loading with different colors indicating different cycles: a history profile of the load,
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In this paper, we investigate the effect of the initial surface finish of the target on shot peening effectiveness using realistic 3D finite element simulations. Specifically, a large number of random shot impingements were simulated using an enhanced periodic cell model. The target material which is made from TI-6Al-4V is assumed to be strain-rate...
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... of r 0 can be determined using the data of Premack and Douglas [38], which was also used for the rate sensitivity of the isotropic hardening model described by Meguid et al. (2007). To compare the kinematic hardening law and the isotropic hardening law, a uniaxial cyclic loading case was investigated. The loading history profile is shown in Fig. 2a. The stress-strain curves are plotted in Fig. 2b, c for the isotropic hardening and the kinematic hardening models, respectively. The mismatch in the loading and the unloading curves for cycles other than the first in Fig. 2b is caused by the strain rate sensitivity of the material model. Without strain rate sensitivity, the isotropic ...
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... Premack and Douglas [38], which was also used for the rate sensitivity of the isotropic hardening model described by Meguid et al. (2007). To compare the kinematic hardening law and the isotropic hardening law, a uniaxial cyclic loading case was investigated. The loading history profile is shown in Fig. 2a. The stress-strain curves are plotted in Fig. 2b, c for the isotropic hardening and the kinematic hardening models, respectively. The mismatch in the loading and the unloading curves for cycles other than the first in Fig. 2b is caused by the strain rate sensitivity of the material model. Without strain rate sensitivity, the isotropic hardening model can only lead to coincident ...
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... and the isotropic hardening law, a uniaxial cyclic loading case was investigated. The loading history profile is shown in Fig. 2a. The stress-strain curves are plotted in Fig. 2b, c for the isotropic hardening and the kinematic hardening models, respectively. The mismatch in the loading and the unloading curves for cycles other than the first in Fig. 2b is caused by the strain rate sensitivity of the material model. Without strain rate sensitivity, the isotropic hardening model can only lead to coincident loading and unloading curves following the first cycle. On the other hand, the kinematic hardening model can well depict the hysteresis ...
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... " e pl increases with the accumulative number of impingements. Unlike the residual stress field, the " e pl profile does not converge with the increase in the current number of shots. This is because the target material experiences substantial reverse plasticity in each loading-unloading-reloading cycle due to repeated shot peening as shown in Fig. 2c. Comparing Fig. 10a with Fig. 8a, one observes that the size of plastic zone is a little smaller than the size of the compressed layers. Figure 10b shows the profile of relative RMS deviation of " e pl from its average value for different number of impinging shots. It shows that the deviation of " e pl decreases as the number of shots ...
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... is interesting to find that for the targets with initial roughness less than 14 lm, R a converges to a similar value around 5.5 lm after considerable exposure to shot impingements. Figure 20 depicts the final surface morphology with displacement coutours for the five investigated targets It clearly shows that a rougher initial surface results in larger displacement fields at the surface. Figure 21 shows evolution of the surface profile during the peening treatment for the rough target with initial R a of 55 lm. ...
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... the same shot size, the smooth target has larger compressed layer than the rough target. Figure 24 plots the history curves of surface roughness for the investigated cases. It is interesting to note that after considerable exposure of peening in our simulations, the surface roughness R a will converge to an asymptotic value. ...
Citations
... Some researchers have attempted to investigate the effect of initial topography on peened surface topography and CRS distribution using numerical methods. The initial surface morphology, which follows a bi-sinusoidal function, was introduced into the finite element analysis by Yang et al. [56]. They found the initial surface topography has a significant effect on the CRS distribution induced by shot peening. ...
... Zhao et al. [45] found that the equivalent plastic strain distribution changes slightly as the initial S a rises from 0 to 1 μm through finite element analysis. It should be noted that the residual stress distribution may vary considerably if the initial surface is further roughened [56]. ...
Despite the broad study of surface integrity in shot peening, the evolution mechanism of surface morphology considering the initial processing feature is still unclear, which hinders the optimization of peened surface quality. In this study, two typical surfaces (grinding and polishing) were selected to be the initial surface morphology for shot peening. Then the effects of initial surface morphology on peened surface integrity were investigated, including 3D surface morphology, surface roughness, residual stress distribution, and microhardness. It could be found that the processing features of the initial surface still exist but are flattened, even at a relatively high coverage. The shot peening simulation also revealed this flattening effect. Besides, the effect of coverage on surface integrity was investigated. The 12Cr2Ni4A sample with 200% coverage has smaller surface roughness and similar residual stress distribution than 100% coverage, which is different from previous studies on medium-strength steels and lightweight alloys. These results provide a reference for understanding the surface integrity evolution in shot peening.
... The process parameters affecting the shot peening effect include various factors such as projectile diameter, shot peening speed, and projectile coverage. In order to study the influence of these parameters on the shot-peening effect, scholars have established a variety of shot-peening models [5][6][7][8][9]. Al-Hassani [10,11] used the analytical method to study the distribution of compressive stress field and studied the static and dynamic impact models under the action of a single shot. ...
Shot peening technology is used to improve the fatigue strength of materials and parts, and is one of the most effective surface engineering techniques to prolong fatigue life. In this paper, according to the finite element simulation analysis of shot peening, a randomly distributed multiple-shot finite element model was established. The superimposed effects of multiple projectile impact craters in shot peening are fully considered. The effects of shot velocity, shot peening angle and shot coverage on the residual stress field and surface roughness were studied. The alloy steel 20MnTiB, widely used in the automotive industry, was used as the raw material to process the specimens. The shot peening tests of different process parameters were carried out. The test results verified the correctness and accuracy of the random distribution model of multiple-shot. The shot-peening simulation model proposed in this paper allows a more accurate analysis of the effect of shot-peening parameters on the surface residual stress field and helps to quickly set the correct shot-peening process parameters. This paper further investigates the effect of shot peening parameters on fatigue life, providing a basis for the rational development of shot peening solutions.
... Therefore, it is crucial to predict the surface residual stress of the part after shot peening accurately, which can optimize the peening parameters without tedious experiments. Studies have shown that [21,22] characterization of the mechanical properties of the target material has a great influence on the accuracy of residual stress prediction in shot peening numerical models. Both strain rate [23] and temperature influence the properties of materials greatly. ...
Shot peening is widely used in gear surface strengthening. Due to the complex 3D geometry of the gear target, the collision of shots occurs in the tooth space, resulting in the different shot dynamic and nonuniform features of surface integrity along the tooth profile. The existing models cannot accurately predict the surface integrity of gear shot peening, which hinders the process improvement. In this paper, a sequential coupled DEM-FEM method is proposed. The DEM model is used to represent the collision between shots and the final velocity distribution. Besides, with the determined shot kinematics, the FEM simulation for the gear shot peening process and its time optimization strategy are presented. The proposed method is validated by the gear shot peening tests. Based on the proposed method, the influence of gear geometry on shot impacts and uniformity of tooth surface integrity (surface roughness, surface topography, and compressive residual stress field) is investigated. This study provides an effective tool for optimizing gear shot peening technology and could be extended to other industrial parts with complex shapes.
... This increase is not so pronounced as the increase in the CRS induced by SP (Fig. 6). In this sense, some authors reported a non-linear relationship between these two variables after SP treatments (Ref [58][59][60]. Particularly, Maleki et al. (Ref 58) studied the effects of different SP Almen intensities on the residual stress distribution and the roughness. Results show that as the Almen intensities increase, the CRS are higher. ...
In this work, as received (AR) and shot peened (SP) SAF 2507 duplex stainless steel (DSS) is plasma nitrided (PN) at 400°C for 6 hours. Two different atmospheres are used: 75%N2 - 25%H2 and 25%N2 - 75%H2. Microstructural characterizations by optical and scanning electron microscopy (SEM) and X-Ray diffraction (XRD) are carried out. Also, residual stress, microhardness and roughness are measured. Finally, corrosion tests are conducted. XRD of PN samples indicates the presence of expanded austenite γN, expanded ferrite αN, iron nitride -Fe3N and chromium nitride CrN. Though all PN samples present a γN decomposition into CrN, α and γ, this reaction is more pronounced in samples treated with lower N2 atmosphere. Microhardness is significantly increased along the nitrided layers. Roughness is slightly increased after PN treatments due to the sputtering effect of the active species in the plasma. Though PN was carried out at 400°C, that it is reportedly safe to sustain corrosion resistance, it causes CrN precipitation in the studied DSS, which deteriorates corrosion properties.
... Therefore, it is crucial to predict the surface residual stress of the part after shot peening accurately, which can optimize the peening parameters without tedious experiments. Studies have shown that [21,22] characterization of the mechanical properties of the target material has a great influence on the accuracy of residual stress prediction in shot peening numerical models. Both strain rate [23] and temperature influence the properties of materials greatly. ...
AISI 9310 high strength steel is widely used in aviation products. Very few studies were available concerning the mechanical properties of the steel based on measured data, while the accuracy of the equations is crucial in the digital design and manufacturing of related products. In this study, we carried out quasi-static tensile/compressive experiments and split Hopkinson tension/pressure bar tests to investigate the mechanical response of 9310 alloy steel. Samples with three levels of hardness were made for comparison. The Johnson-Cook constitutive model is applied to describe the tensile/compressive deformation behavior of samples with different hardness. An improved equation considering hardness is proposed based on the Johnson-Cook model. A numerical model of calculating residual stress after shot peening is established to apply and verify the constructed equations. The calculated results agree well with the measured results, with differences less than 17%. The compressive constitutive equation is more reasonable than the tensile constitutive equation for the calculation of the residual stress after shot peening.
... The shot material parameters are summarized as follows: density is 7800 kg/m 3 , Young's modulus is 210 GPa and Poisson's ratio is 0.3. When the hardness of the target is low, the shot is usually defined as a rigid [29,42] or elastic body [32,43]. The plastic deformation of the shot during impact must be considered because the hardness of the shot is slightly higher than that of the sample in this study. ...
... However, the residual stress distribution of shot peening may change significantly if the initial surface roughness increases further. Yang et al. [42] found that both the size and depth of the compressible layer decreased as the initial surface roughness increased. High-performance components, such as gears, have smaller surface roughness after grinding. ...
Shot peening is a widely used surface strengthening technique which can improve the fatigue life of metal components by introducing reasonably distributed compressive residual stress. The accurate prediction of residual stress distribution of parts is a tough challenge in the simulation of shot peening. In this paper, the numerical calculation of the residual stress of shot peening is investigated with 12Cr2Ni4A steel as the target. A two-dimensional Gaussian distribution model is proposed to calculate the number of impact shots. A method is proposed to calculate shot peening coverage using displacement and displacement gradient, which increases the identification accuracy of peened surface topography and provides a scientific method for coverage calculation. A random multi-shot finite element model for high strength steel is established considering the elastoplastic of shot. The effects of the process parameters, initial surface morphology and initial residual stress on the residual stress distribution after shot peening are investigated. The accuracy of the proposed method is verified by comparing the measured and simulated results.
... The initial surface morphology has a strong influence on the characteristics of the peened surface since the dimple depth after shot peening is comparable to the depth of the ground groove before shot peening. Yang et al. [32] investigated the effect of the initial surface finish on surface roughness after shot peening. However, the initial rough surface established by this method is idealized and needs to be improved. ...
... The parameters of cast steel shot S110 are: density ρ = 7800 kg/m 3 , Young's modulus E = 210GPa, and Poisson's ratio μ = 0.3. When the hardness of the shots is much higher than that of the target material, the balls were usually defined as rigid [27,32] or elastic [26,41]. In this study, the balls were defined as elasticplastic bodies because the hardness of shots and target material are similar. ...
Shot peening is widely used as a surface strengthening technology as it can enhance fatigue life of mechanical components by introducing reasonably distributed compressive residual stress. However, improper selection of processing parameters would inevitably lead to deterioration of the surface quality, and negatively affect on the fatigue performance. In this paper, a random multiple-shot model was proposed to accurately calculate the evolution of 3D surface topography 12Cr2Ni4A steels during shot peening. The simulated results are in good agreement with the experimental results, with an error of less than 10%. It is found that surface roughness parameter Sa first increases significantly and then decreases slowly with the increase of peening time. Moreover, the surface height after shot peening obeys a normal distribution and the 3D surface roughness is positively correlated with the initial roughness.
... High surfaces stress concentrations due to severe SP with a coverage exceeding 1000% or insufficient SP will result in different SRs. The stress concentration induced by higher SRs can initiate cracks under fatigue loading [11,13,[27][28][29]. Additionally, the SP process can cause refined grains near the treated surface, which improves the mechanical and physical properties of the material. ...
Shot peening (SP) parameters are optimized and their effects on fatigue life are investigated using a response surface methodology (RSM) for AA7B50-T7751. Three parameters (SP velocity, nozzle distance (hereafter called distance), and coverage) are optimized using the finite element method (FEM) to obtain the appropriate residual stress, average surface roughness (SR), grain-refinement, and micro-strain. The grain-refinement and induced micro-strain are calculated based on the full width at half maximum (FWHM). Moreover, the FEM results are consistent with the experiments. Optimized parameters are obtained by employing the Box-Behnken design (BBD) response surface methodology (RSM) based on the FEM results. Finally, fatigue experiments show improved fatigue lives for the treated specimens using the optimal scheme. It noted that the optimized parameters of SP velocity, distance, and coverage were 100 m/s, 14.2 cm, and 300%, respectively. Further, the fatigue lives of the AA7B50 samples peened using optimized parameters improve to 314.1%, 173.1%, and 23.9%, respectively, compared to three control groups.
... In the last 20 years, many scholars have done fruitful researches on SP simulation via FEM, discrete element method (DEM) or other numerical method. The representative works are from research groups of Schulze [15][16][17][18], Meguid [12,[19][20][21], Guagliano [22][23][24][25], Lévesque [26][27][28][29] and etc. The work of Schulze group focused on the establishment of material constitutive models for describing the materials response in highly irregular cyclic loading with high strain rates in SP process. ...
As an important mean of shot peening (SP) research, finite element simulation has been widely and successfully employed in estimating the surface characteristic and residual stress distribution after SP treatment. In this study, the effects of shot overlap and rigid body assumptions on dimple geometry and residual stress distribution in depth were discussed via the validated ordered dimple pattern and stochastic dimple pattern SP models for quenched and tempered 42CrMo steel. The results show that shot overlap assumption has a great influence on the surface plastic deformation of peened material. The simulated value of plastic deformation is much larger than the experimental value, which results in the residual stress of the overlapping shot SP model deviating from the actual result seriously. For the prediction of the residual stress distribution, the shot must be set as an elasto-plastic body when the number of shot is large. The shot can be set as a rigid body for the aim of reducing the calculation time when the number of shots is small. In addition, the influence of material hardness on residual stress and equivalent plastic strain (PEEQ) was investigated via simulating the residual stress and PEEQ of different hardness materials treated by SP process.
... Generell werden seit etwa 2010 zunehmend gekoppelte DEM (Diskrete Elemente Methode) -FEM Modelle (Jebahi et al., 2016;Tu et al., 2017) oder periodische berandete Modelle (Yang et al., 2015(Yang et al., , 2014 zur Simulation von konventionellen oder Ultraschallkugelstrahlen mit einer steigenden Anzahl von Partikeln eingesetzt (Chen et al., 2019). Die generelle Modellierung von Mehrfachaufschlägen mit Mikromodellen hat sich seither nur unwesentlich weiterentwickelt (Chen et al., 2019). ...
Die Ermüdungsfestigkeitsteigerung von Schweißverbindungen durch das High Frequency Mechanical Impact (HFMI)-Verfahren ist hinreichend statistisch belegt. Die Wirkweise des Verfahrens beruht auf der Änderung der Kerbgeometrie am Nahtübergang, sowie auf der Verfestigung der Randschicht und die Entstehung oberflächennaher Druckeigenspannung. Der Einfluss dieser Effekte wird im Rahmen dieser Arbeit sowohl experimentell als auch numerisch an gekerbten und geschweißten Proben aus niederfestem Stahl (S355J2+N) und hochfesten Stahl (S960QL) untersucht. Durch gezielte Seperationsexperiemente an gekerbten Grundwerkstoffproben erfolgte experimentell eine teilweise Trennung der Effekte der Randschichtverfestigung sowie der Induzierung von Druckeigenspannung im Schwingfestigkeitsversuch. Durch Prozesssimulation des Schweißprozesses, der HFMI-Nachbehandlung sowie der Schwingbelastung mit der Finiten Elemente Methode (FEM) wurde der Eigenspannungszustand nach der Behandlung errechnet und mit Röntgen- und Neutronenbeugungsmessungen abgeglichen. Bei der numerischen Analyse des
Ermüdungsverhaltens lag der Fokus auf der Phase der Rissbildung, die durch dehnungsbasierte Schädigungsparameter abgebildet wurde. Dabei wurde die zyklisch-stabile Eigenspannung als zusätzliche Mittelspannungskomponente berücksichtigt. Als Kriterium der Unterscheidung zwischen der Phase des Anrisses und des stabilen Rissfortschritts wurde der Spannungsabstandsansatz (engl. critical distance method) verwendet. Die Untersuchungen zeigten, dass die Schwingfestigkeitssteigerung bei den gekerbten Proben aus S355J2+N in erster Linie auf die Randschichtverfestigung zurückzuführen sind, während bei den gekerbten Proben aus S960QL fast ausschließlich die induzierte Druckeigenspannung für den Schwingfestigkeitsgewinn verantwortlich
ist.
