Micro-shot Peening Research Articles

Effect of Microshot Peening on Fatigue Strength of Austenite Stainless Steel

The effects of the peening conditions on the surface characteristics and fatigue strength of stainless steel were investigated by microshot peening (MSP). In recent years, MSP technology has attracted attention. The use of MSP technology with minute media has become more widespread in consideration of the reduction of the notch effect in the material surface. However, the effect of MSP technology on stainless steel has not been much studied. In the present study, an air-type machine was used. The media used was high-carbon cast steel (490 HV) and Fe-Cr-B alloy (1130 HV), with an average diameter of 0.1 mm. The peening time was in the range of 0 - 100 s. Four types of stainless steels, SUS304, SUS304L, SUS316, and SUS316L, were tested. The workpieces were annealed at 1100 K for 1.2 ks in air. In the measurement of fatigue strength, the workpieces were machined in hour-glass shape. As the results, surface roughness of the workpieces treated by MSP was small. Work hardening was evident to the depth of approximately 0.2 mm from the surface. This depth was about twice the diameter of shot media. However, the effect of the peening time on the hardness distribution was not large. The compressive residual stress was added in the surface vicinity. It is assumed that the fatigue limit had increased because the work hardened layer was formed near the workpiece surface.

Effect of Microshot Peening on Fatigue Strength of Low Temperature Heat Treated Stainless Seel

Effect of Microshot Peening on Fatigue Strength of Low Temperature Heat Treated Stainless Seel

Analysis on the Fatigue Properties of Shot-Peened Al-Si-Mg Alloy and Its Fatigue Life Prediction

Ceramic micro-shot peening (CMSP) and steel micro-shot peening (SMSP) were utilized to investigate the effect of micro-shot peening (MSP) on the high-cycle fatigue properties of Al-7Si-0.3Mg casting aluminum alloy in a previous study. However, the improvement effects of CMSP and SMSP on the fatigue strength (at 5 × 107 cycles) were only 33% because the depth of harden layers was only 20 and 55 μm while the depth of compressive residual stress affected layers was only 37 and 68 μm. In this study, conventional shot peening (CSP) was utilized, and the results were compared with those of MSP, with the expectation that CSP would provide a greater improvement in the fatigue strength. The affected surface layers of the shot-peened specimens were characterized using surface morphology, microhardness, and residual stress analyses. In addition, the effect of CSP on the fatigue strength at 5 × 107 cycles was investigated using a rotating bending fatigue test (R = − 1). An investigation of the extensive surface compressive residual stress relaxation process for the three different shot-peened specimens during cyclic loading was conducted using x-ray diffraction. In addition, the initiation sites for fatigue cracks on the fracture surface were observed using scanning electron microscopy. Furthermore, the fatigue life of the samples with the internal casting defect failure mode was predicted using linear elastic fracture mechanics, while that for samples with the surface crack initiation failure mode was predicted using the modified Morrow model considering the residual stress.

Very High Cycle Fatigue Properties of Ferritic-Pearlitic Steel after Micro-Shot Peening

An alloyed ferritic-pearlitic steel is studied after micro-shot peening with balls from a high-speed steel. The morphology and the roughness of the surface of the specimens are determined. Specimens with smooth and notched surfaces are subjected to multi-cycle fatigue tests. The fatigue resistance of the specimens with a smooth surface and with a notched surface increases by 22 and 27%, respectively, after the shot-peening. Observation of crack growth in specimens with small holes shows that micro-shot peening hinders crack propagation.

Fatigue properties and fatigue strength evaluation of railway axle steel: Effect of micro-shot peening and artificial defect

In this study, the effects of micro-shot peening and artificial defect on the fatigue properties of EA4T railway axle steel were evaluated. Un-peened (UP) and micro-shot peened (MSP) EA4T axle steel specimens were drilled to introduce artificial defects on the surface. Then the fatigue tests were conducted on a rotary bending fatigue machine (R = −1). The test results showed that the fatigue limit of the UP specimens was improved by 25% after MSP; when the equivalent defect sizes were less than 60 and 70 μm respectively, they had no negative effect on the fatigue strength of the UP and MSP drilled specimens, otherwise the fatigue strength of both specimens decreased with the increase of the defect size. The fracture surfaces were analyzed by scanning electron microscopy (SEM) observations, which indicated that crack initiation sites for the as-prepared UP and MSP specimens were on the surface, while for the drilled specimens, they were on the vicinity of hole defects. The effect of artificial defect size on the fatigue strength of the UP and MSP specimens and the critical defect size were analyzed with fracture mechanics approach, the results of which showed that the relationship between defect size and fatigue strength of the UP and MSP specimens can be well evaluated by the modified Haddad model, and the critical defect size of the UP specimens was 65 μm while that of the MSP specimens was increased to 76 μm due to the introduction of compressive residual stress.

Effect of micro-shot peening, conventional shot peening and their combination on fatigue property of EA4T axle steel

In this study, EA4T axle steel specimens were subjected to three shot peening treatments: conventional shot peening (CSP), micro-shot peening (MSP) and their combination, i.e. dual shot peening (DSP). The residual stress, surface roughness, morphology, microhardness, were used to characterize the affected surface layer. The results indicated that MSP achieved maximum surface compressive residual stress (SCRS), minimum surface roughness, high surface microhardness. Moreover, compared to CSP, DSP improved the SCRS and microhardness while reducing surface roughness. However, scanning electron microscopy (SEM) observations indicated the presence of intensive defects of the DSP-treated specimens, which hindered the fatigue strength of the specimens. Fatigue tests were conducted to evaluate the effect of different treatments on fatigue life, the median S-N curve demonstrated that the fatigue limit at 107 cycles was improved by 24, 32, and 27% for the CSP, MSP, and DSP specimens, respectively. Furthermore, SEM observation was conducted to analyze the fracture mechanisms, the results indicated that the failure of all specimens originated at the surface and the fracture mechanisms were not changed by the shot peening treatments. The SCRS during the cyclic loading have also been analyzed. Moreover, the factors influencing fatigue limit improvement were discussed.

Effect of Different Shot Peening Treatments on Fatigue Life in Ti Alloy

The effects of peening conditions on the surface characteristics and fatigue life of titanium alloy was investigated using microshot peening, ultrasonic shot peening, and multiple shot peening. The use of microshot peening technology with minute media has become more widespread in consideration of the reduction of the notch effect in the material surface. The ultrasonic shot peening that uses media of several millimeters in size with ultrasonic vibration has attracted attention as a means to reduce the surface roughness. In the present study, an air-type and an ultrasonic type machine were used. In the microshot peening process, the media used was high-carbon cast steel and the hard powder, with an average diameter of 0.1 mm. The workpiece was commercial titanium alloy Ti-6Al-4V. In the microshot peening (MSP), work hardening was evident to the depth of approximately 0.3 mm from the surface. This depth was approximately three times the diameter of the media. However, the influence of the peening time on the hardness distribution was not great. In the ultrasonic shot peening (USP), work hardening was deeper in the material. This is because the diameter of the media used for ultrasonic machining was large. On the other hand, in the combined shot peening (CSP), a degree of hardness was higher at the top surface. However, the hardness patterns and values were pretty much identical to ultrasonic shot peening. The fatigue limit was thought to be greater in the microshot peening experiment because the work-hardened layer was formed near the workpiece surface.

Effect of micro-shot peening on fatigue properties of precipitate strengthened Cu-Ni-Si alloy in air and in salt atmosphere

In this study, the precipitate strengthened Cu-Ni-Si alloy was micro-shot peened by ceramic balls with a diameter of 40 μm. The fatigue tests using the peened specimens were conducted in air and in salt atmosphere respectively. The results show that a fine and hardening layer is formed on the surface of peened specimen and the compressive residual stress is introduced. There is no fatigue limit for specimens in both test conditions. The S-N curve of specimens in salt atmosphere shows a continuous decrease with the increasing number of loading cycles, while that in air shows a step-wise shape. Compared with the un-peened specimens, the fatigue strengths of specimens at 107 cycles are increased by 47% and 67% in air and in salt atmosphere respectively. The peened specimens in air condition failed from subsurface zone in high cycle fatigue region, while all the other specimens failed from surface. The micro-shot peening can improve the surface property and delay the crack initiation and propagation, so as to enhance the fatigue strength greatly.

Simultaneous Shot-Peening of hard and soft particles for friction reduction in reciprocal sliding

Friction between mechanical components experiencing relative motion is responsible for about 20% of the total world energy consumption. In this work, an experimental study is presented to evaluate the effect of Simultaneous Shot-Peening (SSP) of hard and soft particles on friction reduction between mechanical components experiencing reciprocal motion, such as in piston ring and cylinder liner in internal combustion engines (ICE). A novel micro-shot peening device for simultaneous treatment with hard and soft particles is described, along with a reciprocal test rig. Total of 25 combinations of normal load and sliding speed were tested. Comparison between a Treated SSP and Reference specimens shows an average friction reduction of up to 33% with local maximum friction reduction of up to 65%.

Influence of Wet Micro-Shot Peening on Surface Properties and Corrosion Resistance of AISI 304 Stainless Steel

Influence of Wet Micro-Shot Peening on Surface Properties and Corrosion Resistance of AISI 304 Stainless Steel

Surface layer modifications of micro-shot-peened Al-7075-T651: Experiments and stochastic numerical simulations

Shot peening is widely used to improve the fatigue resistance of metallic components, but the optimal tuning of the treatment parameters is not an easy task. Finite element (FE) dynamic simulations proved to be a reliable tool to estimate the effect of the main treatment parameters on surface roughness and residual stresses. This paper presents one of the first attempts to numerically simulate a micro-shot peening treatment; indeed, this is a tremendous numerical challenge given the large number of impacts to be simulated and the fine mesh needed to discretize the small impact dimples. The target material is the aeronautical aluminium grade Al-7075-T651. To best represent the hardening rule of the target material, the Lemaitre-Chaboche model is tuned on the basis of fully reverse axial strain tests. The statistical nature of the peening treatment is taken into account by randomly generating sets of bead individuals characterized by stochastic variability in dimension, velocity and impact location. Surface roughness and residual stresses resulting from the numerical analyses are compared with experimental measurements. A specific novel procedure is proposed to take into account the effect of surface roughness and radiation penetration on the in-depth residual stress profile measured by XRD. In addition, a static finite element model is devised to estimate the concentration effect exerted by the surface roughness on the external stress field.

Effect of microshot peened treatment on the fatigue behavior of laser-melted W6Mo5Cr4V2 steel gear

In this paper, W6Mo5Cr4V2 steel gear tooth flank was firstly melted by laser irradiation, and then treated by microshot peening (MSP) with shot particles of different materials and peening time. The materials of shot particles were high-carbon cast steels and ceramics. The peening time was from 20s to 100s. The fatigue behavior of gear was tested using Forschungsstelle für Zahnräder und Getriebebau (FZG) back-to-back spur gear test machine. The experimental results have showed that the microhardness of gears increased, and the surface roughness of gears decreased after microshot peening treatment. In addition, the residual stress state in the near-surface layer of microshot peened gears was changed from tensile stress to compressive stress. The microshot peening treatment has improved the fatigue strength of gears in comparison with gears undergoing the laser surface melted (LSM). The material of microshot particle influenced the fatigue behavior of gears going through laser surface melting and microshot peening (LSMMSP). The fatigue properties of LSMMSP gears did not enhance with an increase in shot peening time. The effects of the relaxation mechanism of the compressive residual stress on the fatigue performance of LSMMSP gears have also been discussed. Retained austenite has played a positive role in improving the fatigue limit of LSMMSP gears.

マイクロショットと超音波の複合ピーニングによるチタン合金の疲労改善

The fatigue improvement of titanium alloy by microshot peening and ultrasonic peening was investigated. In the peening process, the equipment were used an air-type machine and ultrasonic peening machine. The microshot used were high-carbon cast steel with an average diameter of 0.1mm. The surface hardness data showed that, in the case of microshot peening, work hardening extended deeper than the mean diameter of the media. In addition, in the case of ultrasonic peening, the surface hardness increased slowly with the projection time. The rotary bending fatigue tests were carried at a frequency of 3150 cycles/min. Improvement of the fatigue strength was observed by both treatments.

Effect of microshot peening on fatigue strength of spring steel

Effect of microshot peening on fatigue strength of spring steel

Improvement of Fatigue Life by Microshot Peening for Inconel Alloy

Improvement of Fatigue Life by Microshot Peening for Inconel Alloy

A comparison of the effects of traditional shot peening and micro-shot peening on the scuffing resistance of carburized and quenched gear steel

Carburized and quenched specimens of 17CrNiMo6 gear steel were given two different shot peening treatments. Post-treatment Vickers hardness, residual stress, roughness and topography were determined. Traditional shot peening can increase surface hardness, residual stress and roughness. By contrast, micro-shot peening can decrease of surface roughness and increase both the surface hardness and residual stress even more. Scuffing tests were carried out using a ring-in-V-notch test configuration. It was found that shot peening can improve the scuffing resistance properties of gear steel, and that a combination of traditional shot peening and micro-shot peening can improve the scuffing resistance of carburized and quenched gear steel to the largest degree. The hardness and residual compress stress, roughness and topography produced during shot peening have an effect on the scuffing resistance of the carburized and quenched gear steel.

Improvement in fatigue life of Al 7475-T7351 alloy specimens by applying ultrasonic and microshot peening

Shot peening and ultrasonic peening are widely used mechanical surface treatment in the automotive and aerospace industries to improve the fatigue life of metallic components. This work aims to further improve the mechanical properties of the AA7475-T7351 alloy by applying three different peening processes: Ultrasonic Peening (USP) and Microshot Peening with two different beads size (MSP).A systematic study was carried out on the roughness, surface hardening, residual stress profiles and fatigue life. Uniaxial fatigue tests were conducted. Residual stresses were evaluated by X-ray diffraction, and the fracture surface was observed and analysed with a Scanning Electron Microscope. The microstructures of the specimens were observed by optic microscope. Microhardness and roughness were also measured.All of the surface treatments enhanced the specimens fatigue lives, despite having created different superficial conditions. In addition, the experimental results and analytic predictions based on the Molski-Glinka approach were compared, and in general, agree well.

Effect of thermal exposure on the residual stress relaxation in a hardened cylindrical sample under creep conditions

This paper describes the effect of thermal exposure (high-temperature exposure) (T = 675◦C) on the residual creep stress relaxation in a surface hardened solid cylindrical sample made of ZhS6UVI alloy. The analysis is carried out with the use of experimental data for residual stresses after micro-shot peening and exposures to temperatures equal to T = 675◦C during 50, 150, and 300 h. The paper presents the technique for solving the boundary-value creep problem for the hardened cylindrical sample with the initial stress–strain state under the condition of thermal exposure. The uniaxial experimental creep curves obtained under constant stresses of 500, 530, 570, and 600 MPa are used to construct the models describing the primary and secondary stages of creep. The calculated and experimental data for the longitudinal (axial) tensor components of residual stresses are compared, and their satisfactory agreement is determined.

Fabrication of a micro-nano structure on steel surface and surface wetting

Micro-shot peening (MSP) was combined with subsequent anodization to produce a micro-nano structure on a carbon steel surface.

超音波ショットピーニングとマイクロショットピーニングによるステンレス鋼の疲労特性

The effects of projection conditions on the surface hardness and fatigue strength of stainless steel was investigated. In the peening process, the equipment were used an air-type machine and ultrasonic peening machine. The microshot media used were high-carbon cast with an average diameter of 0.1mm. The surface hardness data showed that, in the case of microshot peening, work hardening extended deeper than the mean diameter of the media. In addition, in the case of ultrasonic peening, the surface hardness increased slowly with the projection time. The rotary bending fatigue tests were carried at a frequency of 3150 cycles/min. Improvement of the fatigue strength was observed by both treatments. The higher effect was found in the ultrasonic peening treatment, because a work-hardened layer was formed deeper in the material.