Search Results (14)

In the search for lightweight and sustainable engineering approaches, enhancing the surface wear resistance of structural materials, such as 6061-T6 aluminum alloy, has become increasingly important. This study investigates the effect of coverage rates on the tribological properties of shot-peened 6061-T6 alloy, aiming to improve its usage in industries where weight reduction and durability are important, such as aerospace, automotive, railway, and renewable energy systems. A shot peening process was applied at four different coverage rates of 100%, 200%, 500%, and 1500% for comprehensive evaluation. A series of experimental analyses were conducted, including microhardness tests, ball-on-plate wear tests, residual stress measurements, and surface roughness evaluations. Furthermore, microstructural analysis was performed to investigate subsurface deformation, and scanning electron microscopy (SEM) was carried out to identify the wear mechanisms of the worn surfaces in detail. The results demonstrated a clear trend of gradual improvement in wear resistance with increasing shot peen coverage. The sample treated at a 1500% coverage rate exhibited 1.34 times higher hardness and 19 times higher wear resistance compared to the untreated sample. This study highlights that shot peening is an effective and feasible surface engineering method for enhancing the wear performance of 6061-T6 alloy. The findings offer valuable contributions for the development of lightweight and wear-resistant components considering sustainable material design. Full article

The rising demand for aluminium and environmental concerns highlight the need for a circular economy using recycled alloys. This study examines the effect of shot peening on the high-cycle fatigue life of secondary AlZn10Si8Mg alloys with different iron contents: Alloy A (0.14 wt.% Fe) and Alloy B (0.56 wt.% Fe). Although both alloys showed similar tensile properties, Alloy B had higher porosity and finer β-Al₅FeSi intermetallics. Shot peening was applied at 100% and 1000% coverage to evaluate changes in surface roughness, porosity, residual stresses, and fatigue performance. The treatment significantly reduced surface-connected porosity via plastic deformation, enhancing fatigue life despite increased roughness. Fatigue tests showed a 21% increase in fatigue limit for Alloy A and a 6% gain for Alloy B at higher coverage. Fractographic analysis revealed that 95% of fatigue cracks initiated at surface pores. Residual stress measurements confirmed compressive stresses were limited to the near-surface layer, with minimal influence on subsurface crack propagation. Overall, shot peening proves to be an effective method for improving fatigue resistance in recycled aluminium alloys, even in alloys with elevated iron content, reinforcing their potential for structural applications under cyclic loading. Full article

As a surface peening technique, shot peening introduces residual compressive stresses to the surface of the part, which effectively increases the fatigue life of the structure and material. However, when structures are subjected to alternating loads, this can lead to stress relaxation on the material surface, weakening the effectiveness of the shot peening process. In addition, reasonable shot peening parameters are essential. In this paper, the effects of shot peening pressure and shot coverage on the fatigue life of materials during shot peening were investigated, followed by fatigue tests on 20CrMnTi specimens using a high-frequency fatigue testing machine to study the effects of shot peening and re-shot peening on the fatigue life of shot-peened materials after different load cycles. The results show that a reasonable shot peening pressure and coverage rate can significantly improve the fatigue life of the material, while a shot peening pressure higher than 0.4 MPa will reduce the fatigue life of the material 20CrMnTi. Coverage rates of 100% and 200% can both improve the fatigue life of the material, while a 200% coverage rate has a better strengthening effect. Re-shot peening removes the residual compressive stress relaxation on the surface of the material caused by cyclic loading and improves the fatigue life of the material. The maximum value of the residual compressive stress on the surface of the test material after shot peening is 443 MPa, and after a certain number of fatigue loads, the residual compressive stress on the surface is reduced to 203 MPa, which is subjected to secondary shot peening, and the residual compressive stress is restored to 415 MPa, and the fatigue life is significantly increased. When the second shot peening time is taken as 25% of the fatigue life of the initial shot blasting of the material, the shot peening effect is better. Full article

In the present study, the experimental data of a shot-peened (TiB + TiC)/Ti–6Al–4V composite with two volume fractions of 5 and 8% for TiB + TiC reinforcements were used to develop a neural network based on the deep learning technique. In this regard, the distributions of hardness and residual stresses through the depth of the materials as the properties affected by shot peening (SP) treatment were modeled via the deep neural network. The values of the TiB + TiC content, Almen intensity, and depth from the surface were considered as the inputs, and the corresponding measured values of the residual stresses and hardness were regarded as the outputs. In addition, the surface coverage parameter was assumed to be constant in all samples, and only changes in the Almen intensity were considered as the SP process parameter. Using the presented deep neural network (DNN) model, the distributions of hardness and residual stress from the top surface to the core material were continuously evaluated for different combinations of input parameters, including the Almen intensity of the SP process and the volume fractions of the composite reinforcements. Full article

Shot peening is a surface-strengthening process that is widely used in various industries, such as aerospace, automotive, and biomedical engineering. The process involves the impact of small, spherical media, called shots, onto the surface of a material, resulting in residual compressive stress and improved surface properties. This review aims to provide an overview of the state of the art and perspectives on surface strengthening by shot peening. The review covers various aspects of shot peening, including process parameters, shot materials, and quality control techniques. The advantages and limitations of shot peening in comparison to other surface-strengthening techniques are also discussed. The findings of this review indicate that shot peening is a versatile and effective surface-strengthening technique with numerous applications, and further research is needed to fully realize its potential. In conclusion, this review provides insights into the current status and future perspectives on surface strengthening by shot peening, and it is expected to be useful for researchers, engineers, and practitioners in the field of material science and engineering. Full article

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. Full article

AA1050 Al alloy samples were shot-peened using stainless-steel shots at shot peening (SP) pressures of 0.1 and 0.5 MPa and surface cover rates of 100% and 1000% using a custom-designed SP system. The hardness of shot-peened samples was around twice that of unpeened samples. Hardness increased with peening pressure, whereas the higher cover rate did not lead to hardness improvement. Micro-crack formation and embedment of shots occurred by SP, while average surface roughness increased up to 9 µm at the higher peening pressure and cover rate, indicating surface deterioration. The areal coverage of the embedded shots ranged from 1% to 5% depending on the peening parameters, and the number and the mean size of the embedded shots increased at the higher SP pressure and cover rate. As evidenced and discussed through the surface and cross-sectional SEM images, the main deformation mechanisms during SP were schematically described as crater formation, folding, micro-crack formation, and material removal. Overall, shot-peened samples demonstrated improved mechanical properties, whereas sample surface integrity only deteriorated notably during SP at the higher pressure, suggesting that selecting optimal peening parameters is key to the safe use of SP. The implemented methodology can be used to modify similar soft alloys within confined compromises in surface features. Full article

Impact surface treatments are well-known for their efficiency in enhancing the mechanical properties of metallic materials, especially under cyclic loadings. These processes, which encompass a wide range of surface treatments based on repetitive impacts of tools of various types, induce surface plastic deformation, compressive residual stresses, and grain refinement alter the surface roughness as a side effect. Thus, it is essential to have suitable indexes to quantify the surface features caused by the typically random nature of these treatments. Herein, we evaluated the rationality of using standard roughness parameters for describing the morphological characteristics of surfaces treated by shot peening as a representative and widely used treatment of the category. A detailed numerical model of the peening process was developed. The output data were elaborated to extract the surface roughness parameters following the standard procedures. The results revealed the validity of the surface roughness parameters to describe the topography of material treated with adequate surface coverage, also highlighting the necessity to use a set of parameters rather than the common practice of relying on single parameters. Not considering a comprehensive set of amplitude and spacing parameters can result in significant, inconsistent, and misleading results while comparing the performance of surfaces. Full article

The effectiveness of shot peening is mainly determined by the peening coverage. The peening coverage is required to be 100% for current technical standards of shot peening. With the increase of material strength, higher peening coverage is required in shot peening process. However, the influence of high peening coverage on Almen intensity and residual compressive stress is unclear, the difficulty mainly lies in the lack of quantitative description of peening coverage in finite element analysis. To analyze the influence of high peening coverage on Almen intensity and residual compressive stress, firstly an approximate quantitative description of peening coverage based on dent size, the distance of shots and shot numbers is proposed in this study. Based on this quantitative description of peening coverage, the arc height and residual stress of the Almen test are simulated with the finite element method. The simulation results of arc height and saturation curve agree well with that of the Almen test, by which the effectiveness of the quantitative description and FE simulation are proved. The further study indicates that in shot peening processes, the excessive peening coverage doesn’t improve Almen intensity and residual compressive stress. Full article

Shot peening is one of the most famous mechanical surface treatments to improve fatigue performance of metallic components, which is attributed to high amplitude compressive residual stresses. A numerical approach is developed to analyze the residual stresses in 301LN metastable austenitic stainless steel by shot peening. The material behavior is described by a proposed constitutive model in which strain-induced martensitic transformation, isotropic hardening and kinematic hardening effects are taken into account properly. Both single shot and random multiple shots peening were simulated and analyzed. A numerical method is presented with the Python programming language to make the multiple shots follow a random probability distribution. Results demonstrate that the simulated equivalent plastic strains and martensitic volume fractions agree well with the experimental ones, which verify the validity of the constitutive model. Besides, the numerical method is effective at achieving a realistic surface coverage. The maximum compressive residual stress by the Johnson–Cook model is 12% higher than that of the proposed model. Additionally, each hardening effect has an effect on the simulated residual stress. The developed numerical approach can provide a feasible simulation of the shot-peening process and makes an accurate prediction of the residual stress field in 301LN steel. Full article

Shot peening is a mechanical surface treatment to improve the fatigue strength of metallic components. Similarities exist between regular shot peening and conventional industrial clean blasting. However, the main difference between these two processes is the peening media used and the lack of control and documentation of peening parameters. The clean blasting process is not yet qualified to optimize fatigue enhancement, although it holds a similar potential to regular shot peening. Clean blasting is frequently applied to welded components, with the purpose of surface preparation for application of corrosion protection. This article presents the results of regular shot peened double V-groove (DV) butt welds made from construction steels S355N and S960QL, as well as the high strength aluminum alloy Al-6082. The peening parameters are varied widely. Furthermore, the effect of coverage and intensity is investigated to test the robustness of the peening processes. The data is completed with industrially clean blasted welds, representing typical workshop conditions. The overall objective of this work is to derive minimum peening parameters that still allow significant fatigue strength benefits. The presented data show a high robustness of the fatigue results to peening parameters. Full article

Almen intensity and surface coverage are well-known to be the defining parameters of shot peening-based surface treatments. These parameters are directly affected by material properties, the extension of the contact zone, the geometry of the impact pair, as well as the impact rate and velocity. Such intricate relationships have resulted in often dissimilar predictions of shot peening effects even while using an identical combination of Almen intensity and surface coverage. With the fast pace introduction of new generation impact-based surface treatments, there is a need to find a more widespread parameter that would facilitate the direct comparison of all different treatments and relate the main process parameters to the resultant mechanical characteristics. Herein, we propose to use an energy-based parameter to describe the peening process in a more widespread approach, which collectively incorporates the effects of the Almen intensity and surface coverage, as well as the diameter, material, and velocity of the impact media. A set of finite element analyses was developed to demonstrate the correlation of the peening process effects with this energetic approach. Comparisons with the experimental data served as proof of concept, confirming that the proposed method could provide a quite good estimation of the effect of peening parameters on the treated material. Full article

Recent studies have shown that severe shot peening can be categorized as a severe plastic deformation surface treatment that is able to strongly modify the microstructure of the surface layer of materials, by both increasing the dislocation density and introducing a large number of defects that define new grain boundaries and form ultrafine structure. In this work, conventional shot peening and severe shot peening treatments were applied to 39NiCrMo3 steel samples. The samples were characterized in terms of microstructure, surface roughness, microhardness, residual stresses, and surface work-hardening as a function of surface coverage. Particular attention was focused on the analysis of the microstructure to assess the evolution of grain size from the surface to the inner material to capture the gradient microstructure. Severe shot peening proved to cause a more remarkable improvement of the general mechanical characteristics compared to conventional shot peening; more significant improvement was associated with the microstructural alteration induced by the treatment. Our datas provide a detailed verification of the relationship between shot peening treatment parameters and the microstructure evolution from the treated surface to the core material. Full article

Shot peening is a well-known surface treatment method used for fatigue life improvement of cyclically loaded structural components. Since three main variables are considered in the peening process (peening intensity, coverage and peening media type), there is no direct way to choose the best combination of treatment parameters for the best performance, thus it has to be based on experience and laboratory tests. When shot peening is performed with inadequate parameters, or the peening process is not stable in time (decrease of the peening pressure, deterioration of the peening media and so on), it can result in significant degradation of the treated component fatigue properties, what is commonly called as the “overpeening” effect. When a premature fatigue fracture occurs in operation, the fracture surface analysis is usually the most important method of revealing the damage mechanism. This work is aimed at the study of the relation between the shot peening parameters and the fatigue fracture surface character on an AW 7075 aluminium alloy with an objective of identifying marks of overpeening and investigating the fatigue crack initiation mechanism. After performing the tests, it was observed that shot peening with optimized parameters creates a surface layer that is able to change the mechanism of the fatigue crack propagation and improve fatigue strength. On the other hand, using extensive peening parameters decrease the fatigue strength due to the creation of surface cracks and surface layer delamination. Full article