Shot Peening Research Articles

Optical heterodyne detection system for a high-speed camera based on the HSA phase compensation method.

This study proposes an innovative active optical heterodyne detection system to address the limitations of existing swarm intelligence algorithms in resolving phase compensation issues within coherent detection systems. The design incorporates a high-speed camera array detector, offering improved practicality and a simplified structure. Employing a heuristic search algorithm (HSA) transforms the high-dimensional problem into multiple one-dimensional optimization problems, significantly enhancing algorithmic running speed. The HSA maintains excellent performance even with increased array elements, allowing for real-time phase correction in large arrays. Experimental results using shot peening comparison samples reveal a substantial amplification of the heterodyne signal spectrum amplitude peak, approximately 60 times greater than the original signal. This innovative approach holds great potential for active optical heterodyne detection of dim targets, paving the way for further research in the field.

Shot peening simulation oriented to residual stress interaction with gear grinding

The current study proposes a shot peening model which enables the residual stress interaction with grinding, a typical combination for gear finishing. The effect of the interaction on the stress state development was addressed by comparing the residual stress state from a standalone shot peening procedure, against the residual stress state arising from a manufacturing route where the interaction of shot peening and grinding takes place. In the interaction model, the grinding procedure generates a pre-loaded condition on the material, modifying the internal strain system of the gear tooth. This pre-loaded system, when disturbed by shot peening, reaches a new internal strain equilibrium. In the interaction model, a 24% less compressive stress state was attained when compared with the standalone shot peening process. A significant shift in the depth and magnitude of the peak compressive stress was also observed. On account of the numerical study of the processes’ interaction, the developed model substantially contributed to understanding the residual stress formation during manufacturing chains.

Fatigue crack propagation behavior in Ti−6Al−4V alloy with surface gradient structure fabricated by high-energy shot peening

A gradient structure was successfully fabricated on the surface of Ti−6Al−4V alloy by high-energy shot peening (HESP), and its effect on fatigue crack propagation was investigated. Optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffractometer were used to characterize the microstructure and residual stress evolution during HESP. The results show that a gradient nanostructure with residual compressive stress layer of 220 μm in depth is formed. The generation of gradient nanostructures improves the strength−ductility combination of the alloy. Maximum residual compressive stress is generated on the subsurface, which gradually increases with the increase of shot peening time. HESP treatment effectively reduces the crack propagation rate and increases the fatigue crack propagation life. The residual compressive stress reduces the effective stress intensity factor range at crack tip, thereby generating the crack closure effect and delaying the crack propagation. At the same time, the synergy effects of increase in grain boundaries, decrease in effective slip length and the plastic zone at the crack tip caused by the refinement of the surface grains can increase the crack propagation resistance as well.

On the severe shot peening effect to generate nanocrystalline surface towards enhancing fatigue life of injection-moulded Ti-6Al-4V alloy

On the severe shot peening effect to generate nanocrystalline surface towards enhancing fatigue life of injection-moulded Ti-6Al-4V alloy

Microstructure and Fatigue Life of Surface Modified PBF-LB Manufactured Maraging Steel

The present work was aimed at increasing the fatigue life of laser powder bed fusion manufactured maraging steel (MS) using surface modification. Samples were manufactured to investigatethe mechanical properties of the material with two types of heat treatment routes that were both subjected to severe shot peening (SSP). In addition, bending fatigue testing was utilized to reveal theeffect of shot peening (SP) and SSP on fatigue resistance of the MS. Microhardness profiles weremeasured near the surface and electron backscatter diffraction analysis was used for microstructuralanalysis. A thin layer of austenite was noted on the surface making it a softer section, which SP orSSP was able to transform. The fatigue life of the MS was notably icreased by the SP processing andeven greater improvement was achieved with the SSP, which raised the fatigue limit of the materialfrom 200 MPa to nearly 500 MPa.

The Effect of Laser Heat Treatment and Severe Shot Peening on Laser Powder Bed Fusion Manufactured AISI 316L Stainless Steel

In this study the effect of laser heat treatment (LHT) and severe shot peening (SSP) on laser powder bed fusion manufactured AISI 316L stainless steel is investigated. The effect of LHT and SSP on the hardness of the surface of the PBF-LB 316L is studied performing microhardness measurements. Microstructure is evaluated in the EBSD investigation. The residual stresses will be measured to determine the influence of LHT and SSP. The effects of LHT and SSP on tensile and bending fatigue strength will be evaluated. LHT altered the microstructure 200 µm from the surface. The grain structure on the surface was more ordered and no substructure or local strains were present. Finer grain features adjacent to the sample surface were found, which are most likely caused by effective recrystallization and fast cooling. The grain morphology was left relatively unchanged when SSP was applied on LHT surface. However, local deformation has occurred on the surface, and clear orientation gradient within grains is seen. LHT had no effect on the hardness. SSP increased the surface hardness by 205%. LHT decreased the yield or tensile strength of the PBF-LB 316L. Residual stress measurements showed that SSP induced a high compressive stress in the PBF-LB 316L. LHT and SSP significantly improved the fatigue strength of the PBF-LB manufactured 316L.

Microstructural and mechanical characterization of pearlitic steel after high intensity laser peening and shot peening

This study investigated the microstructural/mechanical properties of annealed 4340 pearlitic steel after shot peening (SP) and high intensity laser peening (LP). SP at 0.012–0.016 A resulted in fragmentation of the pearlite colonies ∼1–2 µm from the treated surface and sub-surface cracking as well as significant distortion of pearlite colonies ∼30 µm from the treated surface. LP at a pulse energy of 19 J with a pulse full-width half height of 27 ns and a square spot size of 3x3 mm2 resulted in an intense irradiance on the metal surface of 8 GW/cm2. During this process a thin, micrometer-range layer of surface material is ablated which generates and heats a plasma plume in less than 1 ns to a temperature in the range of 15,000 K. A recast layer ∼5–10 µm in thickness from the treated surface with significant porosity was observed in the LPed specimen. The highest average microhardness (266 ± 9 HV) was observed in the SPed specimen ∼63 µm from the treated surface, however the hardness quickly returned to the baseline hardness (218 HV) ∼250–500 µm from the treated surface. In the LPed specimen, the averaged microhardness values exceeded the baseline hardness up to a depth of ∼1500–2000 µm with an average microhardness of 237 ± 4 HV from ∼60–2500 µm from the treated surface. It is shown that LP not only improves the sub-surface microhardness of the 4340 pearlitic steel up to greater depths than SP, but that it also preserves the pearlitic microstructure near the treated surface.

Исследование усталостной долговечности пружин боковых скользунов тележки модели 18-9891

Purpose: To conduct comprehensive experimental studies on the fatigue strength of side bearing springs for freight bogies, evaluating the effectiveness of thermal and shot peening treatments during their manufacturing process. Methods: The method of stand endurance (fatigue) testing of constant contact side bearing springs has been applied, allowing for obtaining endurance characteristics of actual components. Metallographic studies of spring steel have been conducted to investigate the influence of strengthening operations during spring manufacturing on their fatigue strength, with the assessment of mechanical characteristics of surface layers in various zones of the helical spatial beam. Results: Experimental force characteristics of spring sets for side bearings of an innovative freight bogie with a load of 25 tons (245 kN) on the axle have been obtained. Fatigue curves of the springs have been presented in a probabilistic aspect, enabling the determination of load factor for fatigue strength of the springs considering operational loading, as well as justifying the compliance of the spring sets with the regulatory requirements. Practical significance: Based on the research results, the considered constructive-technological variant of the constant contact side bearing spring for the freight bogie has been put into serial production. The test results allow us to reasonably determine the warranty mileage of the responsible assembly of the bogie and to conduct further work on the design modernization with the aim of increasing operational life.

A computational model of wear evolution for shot peened surfaces of gear steel

In mechanical engineering, shot peening is frequently used to reinforce the surfaces of some crucial components. Currently, there are no models available which can accurately predict the long-term wear behavior of surfaces treated with shot peening. This research proposes a computational model and technique for simulating the evolution of wear on gear steels with shot-peened surfaces in a ball-on-flat contact. Based on the fundamental Archard’ s equation, a wear equation is derived from the perspective of a contacting point on the static flat to represent the wear loss. The model takes into account the effects of abrasive particles and variations in hardness along the vertical direction by introducing a scaling factor in the wear equation and stratification of the flat material, respectively. The proposed model and developed method are validated through experiments and can be utilized to predict the wear evolution of shot peened surfaces on gear steels under the application of various loads and friction duration. Furthermore, the model and method can be easily extended to other materials as well.

Smart vibratory peening: An approach towards digitalisation and integration of vibratory special process into smart factories

Shot peening is a widely used technique in aerospace to enhance the fatigue life of a part. However, it leads to an increased surface roughness, which necessitates an additional Vibropolishing technique to improve the fatigue life and aerodynamic efficiency. Alternatively vibratory peening, a relatively new technology, can replace both Shot peening and Vibropolishing and achieve similar fatigue life and aerodynamic efficiency. This paper reports the development of a novel smart vibratory peening system, using which several experimental investigations are conducted to characterize the part and validate them using the conventional Almen strips. Data from the experimental investigations are used to train a machine learning model and predict the characteristics of the given part and hence eliminating the use of Almen strips. With the help of the feature redundancy removal technique, 79% of the redundant features were removed to retain 94% of the process information. The results show that out of various established machine learning models, the Kernel Ridge model demonstrated the best performance with an RMSE of 0.0443. With the introduction of the smart vibratory peening system, the overall process time has been significantly reduced by 76%.

Study on the Influence of Surface Integrity on Hydrogen Permeation Resistance of Hydrogen Production Reactor Materials

Hydrogen permeation reduces a material’s properties and increases the risk of brittle fracture, which causes a potential safety hazard. A workpiece’s hydrogen permeation resistance could be improved by improving its surface integrity through surface processing. This paper studies low-alloy steel’s surface integrity and its hydrogen permeation resistance in a hydrogen production reactor, using the electrochemical cathodic hydrogen-charging method to carry out electrochemical hydrogen-charging experiments. After the specimens were pretreated using different surface-grinding methods and shot peening pressure strengthening, they were hydrogen-charged on a self-designed and built electrolytic hydrogen charging platform. Before and after hydrogen charging, the specimens’ section hardness and tensile strength were tested, and the fracture morphology of the specimens was observed. The influence laws of surface roughness and surface residual compressive stress on the distribution of material hardness along the depth, the variation in material hardness, the fracture morphology, and the decline in the tensile properties of the low-alloy steel specimens after 5 h of hydrogen charging were analyzed. The reasons for the influence of surface integrity indexes on the hydrogen permeation resistance of the specimens were also analyzed. Based on the experimental results, a series of mechanical processing parameters were proposed to improve the material’s permeation resistance, which provides a theoretical and practical basis for the processing of materials with high surface integrity and hydrogen permeation resistance. Through the experiments, it was found that the hydrogen permeation resistance of the Ra 0.17 μm surface roughness specimen was the best of all specimens with different surface roughness values, and its hydrogen embrittlement sensitivity index was 20.96%. The specimen had the best hydrogen permeation resistance under 336 MPa surface residual compress stress, and its hydrogen embrittlement sensitivity index was 16.45%.

Effects of Shot Peening Pressure on Friction and Wear of High Pressure Cold Sprayed Ti-6Al-4V Coatings Under Dry and Lubrication Conditions

Effects of Shot Peening Pressure on Friction and Wear of High Pressure Cold Sprayed Ti-6Al-4V Coatings Under Dry and Lubrication Conditions

Study on Residual Stresses of 2219 Aluminum Alloy with TIG Welding and Its Reduction by Shot Peening

Large residual stress of 2219 aluminum alloy induced by Tungsten Inert Gas (TIG) welding decreases its service performances. Shot peening was adopted to decrease the residual stress of TIG welding. Numerical models of TIG welding and shot peening were established using the combined discrete and finite element methods (DEM–FEM). The results show that TIG welding induces tensile residual stress due to the heat exchange effect and the longitudinal stress is larger than that in the transverse direction. The maximum tensile stress occurs at a depth of 0.1 mm. The surface tensile stress changes to compressive stress after shot peening as the severe deformation induced by the shots changes the stress state of the plate. The maximum value of compressive stress (σm) and the peened depth with compressive stress (Z0) are adopted to describe the peening effect. The absolute value of σm increases with the increased peening speed and nozzle height. Mixed shots with a diameter of 0.8 mm and 1.2 mm induce larger value of σm than those with only a diameter of 1.2 mm. The value of Z0 increases with the ascending shots diameter and nozzle height, while it varies nonmonotonically with the peening speed. The effect of shot peening on the residual stress in TIG welding is discussed.

Fatigue crack growth prediction for shot-peened steel considering residual stress relaxation

The compressive residual stress field (CRSF) relaxes during the fatigue crack growth (FCG) process, and the pattern of this relaxation remains unclear. Residual stress (RS) relaxation leads to a change in residual stress intensity factor (RSIF), which significantly affects the fatigue crack growth rate (FCGR) and thus affects the assessment of fatigue crack growth rate. To this end, this work designed a series of experiments to explore the FCG behaviour in compressive residual stress fields (CRSFs) by considering RS relaxation. Firstly, shot peening(SP) treatments were conducted on the specimens. Then, residual stress fields (RSFs) at different crack propagation stages were measured to analyse the relationship between surface RS and inner RSF distribution. The derived weight function and the real-time RSF are combined to calculate the RSIF with/without considering RS relaxation. Finally, the effect of RS relaxation on the accuracy of FCGR assessment was investigated. The results show that the positive effect of CRS on the fatigue performance of the peened specimens is primarily embodied in the early stage of the FCG process. With the continuous relaxation of the CRSF, the difference in FCGR between the peened and unpeened specimens gradually decreases and tends to disappear. When the applied SIFs are large enough, the CRS would completely relax, and the inhibiting effect of CRSF on FCGR would fail. The proposed method in this work can effectively predict the FCGR of the peened specimen when considering the RS relaxation. This work could provide some meaningful insights for the assessment method of FCGR prediction in CRSF induced by surface strengthening treatment.

Laser Peening: A Review of the Factors, Effects, Applications, Comparison with Shot Peening and State-of-the-Art

Laser Peening: A Review of the Factors, Effects, Applications, Comparison with Shot Peening and State-of-the-Art

An experimental and numerical coupled method to predict grain refinement and mechanical properties of gradient microstructure material by shot peening

An experimental and numerical coupled method to predict grain refinement and mechanical properties of gradient microstructure material by shot peening

Enhancing the fatigue strength of stir-casted Al7075-SiC composites through heat treatment and shot peening

An attempt has been made in the present study to analyze the impact of shot peening on the fatigue strength of Al-SiC (8 wt%) composites. Composite samples prepared using stir casting method is machined to meet ASTM E466 standards, and a portion of them are subjected to T6 heat treatments. Shot peening is performed on various combinations of specimens, and fatigue tests are conducted and compared. The fatigue strength of Al7075 is 156.5 MPa and it increases to 165.8 MPa for heat-treated shot-peened Al-SiC composites. Design expert software is used for designing experiments in order to optimize process parameters and enhance the fatigue strength of the specimens. The fatigue strength of the specimens increased to 174 MPa when the test was repeated using optimized experimental parameters. The fatigue test results revealed that the heat-treated, cum shot-peened Al-SiC composite exhibited the highest performance compared to the other samples. Surface residual stress of the specimens is measured, and it is found that shot peening increases the compressive residual stress on the surface of the specimen. The surface roughness of the specimen increases with shot peening. Microstructural analysis is conducted on the specimens to determine the effect of shot peening on the surface of the composite specimens. The strengthening mechanisms of the composite samples are discussed using microstructural images.

Effect of Severe Shot Peening on Mechanical Properties and Fatigue Resistance of Wire Arc Additive Manufactured AISI 316L

The wire arc additive manufacturing (WAAM) technology has become very popular recently. However, the properties of printed pieces are not yet examined properly. In this paper the effect of severe shot peening (SSP) on mechanical properties of wire arc additive manufactured AISI 316L is investigated. The effect of SSP on the surface hardness of the WAAM 316L is investigated by performing microhardness measurements. Changes to the surface microstructure caused by SSP are evaluated in the EBSD investigation. The effects of SSP on tensile and fatigue strength are investigated experimentally. The EBSD analysis showed that there has been remelting of each printed layer due to the heat input from the next printed layer, and heavy epitaxial grain growth was present in the microstructure. This led to coarse columnar grain structure. Investigation of deformed SSP surface layer indicated that the main deformation type was either conventional dislocation glide or twinning. This meant that no martensite formation was present on the surface. The SSP increased the surface hardness of WAAM printed 316L by 225% and the hardened layer was 0.4 mm thick. The SSP improved the yield strength of WAAM 316L by 34%. The SSP significantly improved WAAM 316L fatigue resistance in both low-cycle and high-cycle regime.

Antipathogenic copper coatings: electrodeposition process and microstructure analysis

Copper coatings are an important group of decorative-protective materials characterised by high corrosion resistance, excellent thermal and electrical conductivity, which lately gained more significance due to their antimicrobial activity. The main aim of the presented research was to electrodeposit homogenous copper coatings from the non-cyanide electrolyte solution in galvanostatic conditions on steel (1.4024) and nickel (Ni201) substrates, commercially used for surgical instruments. The effect of substrate finishes used in the production line, by shot peening with glass balls, corundum treatment and brushing on the coatings surface formation, was investigated. The substrates’ and coatings’ microstructural properties were analyzed by scanning and transmission electron microscopy, atomic force microscopy, and X-ray diffraction analysis. The current efficiency of the copper reduction on nickel and steel substrates was found to be above 95%. The copper layers adhere to both substrates, except those deposited on a brushed surface. Regardless of the substrate used, they have a nanocrystalline structure with an average crystallite size of 30 nm. Moreover, the coating surface morphology, which affects the nature of interaction with microorganisms, was effectively modified by the appropriate substrate finishing without changing the electrodeposition conditions.

Hot salt corrosion behavior of Ti–6Al–4V alloy treated with different surface deformation strengthening processes

In this study, the effects of shot peening (SP) and ultrasonic surface rolling process (USRP) on the high-temperature oxidation and hot salt corrosion (HSC) behavior of the Ti–6Al–4V alloy were systematically investigated. The results showed that the high-temperature oxidation resistance of this titanium alloy can be significantly improved by the above two treatments. However, the hot salt corrosion resistance of Ti–6Al–4V alloy cannot be improved by SP due to surface roughness increasement, the surface defects and the complete relaxation of compressive residual stress (CRS) at high temperature. On the contrary, the hot salt corrosion resistance of USRP treated specimen was remarkably improved because USRP treatment significantly reduced the surface roughness and introduced deep CRS field with good thermal stability. In addition, the refined surface microstructure promoted the formation of a protective oxide film, which was also beneficial for inhibiting hot salt corrosion.