Effect Of Shot Peening Treatment Research Articles

Effect of different underhead shot-peening and lubrication conditions on high-strength screws undergoing multiple tightenings

This study investigates the effect of shot-peening on the bearing friction coefficient of 42CrMoV grade 14.9 screws. An experimental campaign was conducted on a tribological testing rig, investigating the combined effects of shot peening treatments, lubrication conditions, and number of tightenings on the frictional coefficient. A first set of tests was performed, considering the same shot-peening conditions as in a previous study to highlight the role of different material. A second campaign was carried out, adjusting the process parameters to enhance the tribological response. Small shots and high-impact energy are suitable for tightening with lubricant, whereas, in dry conditions, larger shots and lower-impact energy lead to particularly low friction coefficients that are well aligned to those achievable when using lubricants.

Influence of Conventional Shot Peening Treatment on the Service Life Improvement of Bridge Steel Piles Subjected to Sea Wave Impact

The first goal of the current study is to estimate the fatigue life of the middle steel piles of an integrated bridge installed in water and subject to the impact of sea waves. In the following, the authors have tried to improve the service life of this critical part of the bridge, which is also the main purpose of the study. To this end, conventional shot peening, as one of the most well-known surface treatments, was used. Axial fatigue tests were performed on samples fabricated from IPE-220 steel piles in two states without and with shot peening surface treatment. Next, the modified S-N curve was entered into the finite element software to define the effect of shot peening treatment. Different analysis, including thermal, thermal-structural coupled, and transient dynamic, were performed and various outputs were extracted for the entire structure. In all these analyses, changes in air temperature have been neglected. The most important achievement of this research is the discovery that motionless water cannot cause serious damage to steel piles. Moreover, application of conventional shot peening can increase the fatigue life of steel piles, or in other words the service life of the bridge, subjected to the impact of sea waves by about 22%.

Tribological Behavior of a Shot-Peened Nickel-Based Single Crystal Superalloy at High Temperature

The tribological behavior of a nickel-based single crystal superalloy treated by shot-peening has been investigated. Friction tests under three normal loads and three temperatures were carried out based on the ball-on-disk configuration. The results showed that coefficient of friction (COF) and wear rate of the shot-peened nickel-based single crystal superalloy (SP-NBSC) at room temperature were nearly 2 times and 4 times that at 600 ℃, respectively. However, there were no significant differences in COF and wear rate between the SP-NBSC superalloy and the as-received NBSC superalloy, which was ascribed to the competing effects between the increased hardness and roughness of the SP-NBSC superalloy. High-temperature friction promoted the formation of a glaze-layer on the substrate, which was derived from the sintering and compacting of the wear debris. The formed glaze-layer prevented the direct contact of the friction pair and contributed to the reduced COF and wear rate. The wear mechanism of the SP-NBSC superalloy at high temperature including oxidation, adhesion, and abrasion. With the decreasing normal load and increasing temperature, the adhesive wear weakened. This work provided insights into the effects of shot-peening treatment on the tribological properties of the NBSC superalloy.Graphical Abstract

Effect of Shot Peening Treatment on Residual Stress and Magnetic Barkhausen Noise of AISI 201LN and AISI 304L Stainless Steels

This work evaluates microstructural changes and residual stresses on surface samples of AISI 201LN and 304L subjected to shot peening. The residual stresses were measured by X‑ray diffraction and magnetic Barkhausen noise (MBN) in different shot-peened conditions. The results showed that the 201LN steel presented more martensite than the 304L steel in the initial condition, but with lower δ‑ferrite contents. These ferromagnetic phases were present in a low amount with high tensile residual stresses due to brush cleaning and light cold‑rolling in the final stage of the fabrication process. The shot peening process promoted compressive residual stresses mainly in the δ‑ferrite. However, some “fresh” martensite exhibited tensile residual stress represented by higher and thinner peaks, which together with the low-intensity amplitude in the neighborhood, represented all formed martensite. Thus, small microstructural changes provoked high residual stresses behavior, which can be detected in ferromagnetic phases by MBN.

Improvement the Mechanical Characteristics of Alloy Steel DIN 41Cr4 by Shot Peening

The effects of shot peening treatment (SPT) were studied at (10,20, and 30) minutes on the rotating bending fatigue behavior and the behavior of the alloy steel DIN 41Cr4 vibrations. The hardness test, tensile test, constant amplitude fatigue tests, and the vibration measurements were performed on samples with and without cracks at room temperature (RT), also, the fracture surface was examined and analyzed by a Scanning Electron Microscope (SEM). The results of the investigations, for example, Stress to Number of cycles to failure (S-N) curves, fatigue strength improvement factor of 5% to 10%, the decreasing percentage of maximum Fast Fourier Transform (FFT) acceleration of the shot-peened condition were compared to untreated conditions ranging between 25% and 40%. All these improvements occurred for up to 20 minutes of shot peening time (20 SPT), exceeding that time the fatigue behavior tended to decrease due to high roughness and the generation of tensile residual stress.

Analytical and Experimental Approaches to Shot Peening


 
 
 This paper is a first attempt on analytical approach to shot peening. Shot peening improves the surface engineering quality by eliminating the tool marks, such as machining, grinding, stamping and other surface defects. Most importantly, the improvements of shot peening are produced by combination of compressive stress and cold work. Compressive stresses are beneficial in increasing resistances to fatigue failures, while the cold work effects of shot peening treatments can increase the surface hardness. Although shot peening is extensively used in the industry, its academic understanding is very low. Shot peening has been considered as a black art and black engineering in the industry. The focus of this research is to layout foundation of the shot peening research in academic world. Only then, will the research propel more systematically rather than via the conventional industrial trial and error approach. In this research, analytical approach with experimental verification is presented.
 
 

An analysis of fatigue failure mechanisms in an additively manufactured and shot peened IN 718 nickel superalloy

The family of additive manufacturing techniques has been attracting significant attention of manufacturers and researchers, due to its unrivalled flexibility to fabricate and repair geometrically complex objects. However, material shaping is not sufficient: wide adoption of additive manufacturing can only occur upon the achievement of satisfactory mechanical performance in terms of structural integrity. The present study exploits a wide range of micro-scale experimental techniques to shed light on fatigue failure mechanisms of Laser Metal Deposition IN718 Ni-base superalloy, and to study the effect of shot peening treatment. Thorough microstructural and fractographic analyses revealed the main deformation mechanism associated with twinning during crack propagation, while crack initiation was found to be promoted by both slip system deformation and twinning around microstructural defects, rather than at sample free-surfaces. It was found that precipitates played a major role in determining the deformation mode. It was discovered that in this case-study, shot-peening residual stresses may have a detrimental effect, in view of the presence of the largest defects within a region where tensile residual stress was present. The results presented here improve understanding of failure mechanisms and thus define future directions of development for manufacture optimisation.

Effect of shot-peening treatment on the bio-tribological properties of a Ni+ implantation layer formed on the surface of Ti6Al4V

To improve the bio-tribological properties of the Ti6Al4V surface, the Ti6Al4V alloy was subjected to a shot-peening treatment and a subsequent Ni+ implantation process. The phase composition, phase content and grain size of the resulting Ni+ implantation layer formed on the surface were evaluated via x-ray diffraction. The nano-hardness of the modified layer was measured with a nano-micro mechanical probe. Moreover, after bio-tribological testing, the scratch morphology of the layer was observed with a scanning electron microscope. The results revealed that this layer was composed mainly of Ti2Ni. The shot-peening pretreatment yielded a significant increase in the Ti2Ni content and the nano-hardness of the layer, resulting in grain size refinement of the formation phase. When a Ni+ implantation energy of 45 keV was employed, the Ti2Ni phase content and the grain size of the shot-peened layer increased by 33.6% and decreased by 65.9%, respectively. The corresponding friction coefficients under artificial saliva and a sodium hyaluronate pure water solution decreased by 20.9% and 29.3%, respectively. In the case of samples implanted at an energy of 40 keV, the nano-hardness of the shot-peened layer was 50.8% higher than that of the non-peened layer. Therefore, a shot-peening pretreatment can yield a significant improvement in the properties of the single Ni+ implantation layer on the Ti6Al4V surface.

The Effect of Controlled Shot Peening on the Microstructure and Fatigue Behavior of Wet Copper-Based Powder Metallurgy Friction Plates

The effects of shot peening treatments on the microstructure and fatigue behavior of the teeth root in wet copper-based powder metallurgy friction plates were investigated and an efficient method for selecting optimal shot peening parameters for friction plates was proposed. Different experimental processes including microscopy observation, microhardness, roughness and X-ray diffraction measurements have been performed to characterize the treated surface of specimens. It is found that fatigue life of friction plates firstly increases and then decreases with the increase of Almen intensity, and the optimal fatigue life has improved over 55%. It is considered that both surface grain refinement and high residual compressive stress are the main ingredients responsible for the improved fatigue life. With further increase of Almen intensity, surface roughness of the teeth root gradually increases to a critical point, where rough peened surface may induce crack initiation due to stress concentration, and finally lead fatigue deteriorate.

Effect of Shot Peening on the High-Cycle Fatigue Behavior of High-Strength Cast Iron with Nodular Graphite

The effect of shot peening treatment on high-cycle fatigue of high-strength cast iron with globular graphite is studied. The fatigue curves are plotted, the microhardness and the surface roughness are measured. An analysis of fracture surfaces is performed, and the thickness of the hardened layer is determined. The shot peening is shown to affect favorably the fatigue resistance of the iron but to worsen the condition of the surface.

The Effect of Shot-Peening Treatment on Microstructure and Corrosion Behavior of Closed-Cell Aluminum Foam

Closed-cell aluminum foam was shot peened at different processing time (0 s, 5 s, 10 s, and 20 s), the intensity was the 0.12 mmA. The X-ray diffraction results showed that the reflections became weakened obviously with the shot peened time increased. Combined with Popa model and lognormal distribute model, the surface microstructure of closed-cell aluminum foam was inves-tigated by using the Rietveld whole pattern fitting analysis method. The results revealed that domain size and microstrain fluctuated along different reflection directions after shot peened, which attributed to the random and anisotropic deformation direction. With the shot peened processing time prolonged, a decrease in domain size and an increase in microstrain were also observed. Moreover, the corrosion behavior of closed-cell aluminum foam was studied by weight-loss test. The results indicated that corrosion properties of specimen subjected to shot peened processing was better than the unpeened specimens.

Effect of coverage and double peening treatments on the fatigue life of a quenched and tempered structural steel

The effects of shot peening treatments comprising different degrees of coverage and also the influence of double treatments applied to a quenched and tempered medium-carbon alloyed steel were analyzed. The latter consisted, in one case, of high intensity peening followed by a lower intensity peening treatment and, in the other, of the removal of the damaged surface layer. Surface roughness, subsurface hardening and the residual stress profiles were determined and compared. Furthermore, the fatigue life corresponding to the different shot peening treatments was assessed on a rotating beam machine under alternative stresses of 50% of the tensile strength of the steel. The full coverage peening treatment gave rise to the best fatigue behavior, as under-coverage produces a heterogeneous surface stress field, while overlong shot peening treatments probably lead to surface damage. On the other hand, double surface treatments are at least partially able to mitigate the surface damage produced by a first high intensity peening treatment. Nevertheless, none of the applied double treatments was able to exceed the fatigue life of the optimal single shot peening.

Influence of Precorrosion on Fatigue Properties of Shot-Peened Aluminium 7075-T651

Abstract Pitting corrosion has a major influence on aging of structural elements made of high-strength aluminium alloys as corrosion pits lead to much earlier fatigue crack initiation under tensile dynamic loading. In order to improve material resistance to corrosion fatigue, it is necessary to reduce pit-tip stresses in the corroded pits areas. Shot peening (SP) is an important and well-known cold working process, having been used in industrial applications for a long time. Shot peening as intense plastic deformation in the thin surface layer affects cold surface hardening by primary inducing favorable residual compressive stresses. It is used in order to increase fatigue strength in operation and to improve fatigue resistance of precorroded material. The paper deals with the surface integrity of shot-peened high-strength 7075-T651 aluminium alloy. The paper describes the effects of SP treatment by presenting analyses of surface roughness measurement, residual stresses, material bending fatigue resistance, fractographic analysis of fatigued specimens, and electrochemical potentiodynamic testing.

Evaluation of the residual stresses induced by shot peening on some sintered steels

The effect of shot peening treatment on sintered steels plates were analyzed in terms of micro-structural and mechanical properties and residual stress profiles. Two high performances powder metallurgy steels were considered: the former was obtained starting from diffusion bonded powders, whereas the latter starting from pre-alloyed powders. Two different nominal densities were considered, 6.9g/cm3 and 7.1g/cm3. After a preliminary optimization, two shoot peening cycles were selected and carried out on the investigated materials. Residual stresses after the treatment were measured by means of the hole drilling technique and related to the mechanical properties and the surface densification of both steels, varying the nominal density.

各種機械構造用炭素鋼ばり付摩擦圧接継手の疲労強度に及ぼすショットピーニングの影響

Effects of base metal hardness on improvement of fatigue strength by shot peening treatment are investigated using various carbon steels for machine construction. Furthermore, an effect of shot peening treatment on improvement of fatigue strength of friction welding is investigated.The results are summarized as follows.1) The improvement of fatigue strength by shot peening treatment is effective in the case of harder material on using the high carbon steel.2) Fatigue strength of a friction welded joint becomes higher than the base metal although the flash does not be removed if shot peening treatment is applied.3) The fatigue strength increases in proportion to the raise in hardness near the surface in the both cases of base material and the one with shot peening treatment.

Improvement of tribological performance of steel by solid lubricant shot-peening in dry rolling/sliding contact wear tests

The effect of shot-peening treatment with the particulate MoS 2 solid lubricant on the wear resistance of steel in the dry rolling/sliding contact wear tests was investigated. The duplex shot-peening treatment with ceramic balls and the particulate MoS 2 solid lubricant provided excellent wear resistance under a severe loading and sliding condition because the uniform and minute surface roughness given by shot-peening treatment with ceramic balls could keep shot-peened MoS 2 particles with a low friction coefficient on the sample surface. Furthermore, the sample surface was covered with shot-peened MoS 2 particles by a MoS 2 layer formed during the rolling/sliding contact wear test.

Effect of Shot Peening Treatment on High Cycle Fatigue Property in Long Life Regime of Austempered Ductile Cast Iron

Rotating bending fatigue tests were carried out on austempered ductile cast iron (ADI) with shot peening (SP) treatment, and influences of the SP treatment on fatigue properties and fracture morphologies were investigated in the long life regime. As a result, improvement of fatigue strength for shot peened ADI specimen was identified before the region of the 107 cycles. Moreover the S-N diagram of shot peened ADI and fatigue limit of non-shot peened ADI cross at over 108 cycles. Then fatigue strength at 109 cycles of non-shot peened ADI was about 360 MPa and that of shot peened ADI was about 280 MPa. To invistigate the reason for fatigue strength reduction of shot peened ADI, residual stress distribution and hardness distribution were measured and fracture origin was observed by SEM. As a result, the reason why the fatigue strength of shot peened ADI decreases more than non-shot peened ADI was that the tensile residual stress had acted inside the specimen. The fatigue limits of shot peened ADI were estimated by casting defects size and actual stress distribution in the specimen.

Effect of shot-peening treatment on high cycle fatigue property of ductile cast iron

Rotating bending fatigue tests were carried out on shot-peening (SP) treated specimens of two types of ductile cast iron (ferrite–pearlitic ductile cast iron, FPDI, and pearlitic ductile cast iron, PDI). The SP treatment gives high-level work hardening and high-level compressive residual stress near the surface layer thereby improving the fatigue strength. In addition, it can reduce the number of casting defects that initiate the fatigue cracks near the surface. In this report, the fracture morphology and the fatigue properties were investigated from the viewpoints of crack behavior and residual stress change. Therefore, the initial residual stress distribution and its change during the high cycle fatigue test of the SP-treated specimen were investigated. Furthermore, from detailed observations of crack initiation sites using a scanning electron microscope (SEM), the difference in the fatigue fracture morphology between the shorter and longer fatigue life regions was investigated and the shape of the S–N diagram was discussed.

Effects of the distribution of multiple surface cracks on fatigue life of a shot-peened specimen.

Rotary bending fatigue tests were performed on annealed and shot-peened specimens in laboratory air and in salt water. During the fatigue process of a shot-peened specimen in air, many cracks are initiated but each crack growth is suppressed by work-hardening and compressive residual stresses produced by shot-peening treatment ; hence, under this condition, crack coalescence is the only possible way for crack growth to occur, and is thus one of the most important factors to decide fatigue life. On the other hand, during the fatigue process of a shot-peened specimen in salt water, especially at low stress amplitude, suppressive effects of shot-peening treatment on crack growth are lost under a strong corrosive environment. In this case, many cracks can grow to a considerable long crack size, and they distribute not only in a circumferential direction but also in a longitudinal direction of the specimen. Consequently, stress relaxation will occur in the cracked part of the specimen and crack growth rate will be reduced. This stress relaxation effect on crack growth exceeds the crack coalescence effects in a corrosion fatigue process at low stress amplitude.