Improvement of Fatigue Strength by Using Cavitating Jet in Air

2004 ◽  
Author(s):  
Hitoshi Soyama ◽  
Dan Macodiyo
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
High Speed ◽  
Diffraction Method ◽  
Water Jet ◽  
Bubble Collapse ◽  
Surface Residual Stress ◽  
Hydraulic Machinery ◽  
Rotating Bending Fatigue ◽  
Cavitating Jet

Cavitation normally causes severe damage in hydraulic machinery such as pumps and valves. However, the cavitation impacts at the bubble collapse can be used to enhance the surface of metallic materials just as the same way as shot peening. In case of peening using cavitation impact, the cavitation is produced by injecting a high-speed water jet in a water-filled chamber. The authors have already demonstrated the fatigue strength improvement of materials using a high-speed water jet in water. Recently the authors succeeded in producing a cavitating jet in air by injecting a high-speed water jet into a low-speed water jet using a concentric nozzle. Cavitating jet in air can be used to peen parts of plant which cannot peened by the water-filled chamber, thereby impeding the initiation and/or the development of cracks. In this study, in order to demonstrate the improvement of fatigue strength of materials using cavitating jet in air, stainless steel (JIS SUS316L) was peened and the residual stress measured using the X-ray diffraction method. The surface residual stress of non-peened and peened specimen was −68 MPa and −350 MPa, respectively. The fatigue strength of the specimen were then investigated using the rotating bending fatigue test, with a stress ratio of R = −1. The fatigue strength of peened specimen by cavitating jet in air improved by 20% compared with nonpeened specimen.

Use of Cavitating Jet for Introducing Compressive Residual Stress

1999 ◽  
Vol 122 (1) ◽  
pp. 83-89 ◽  
Author(s):  
H. Soyama ◽  
J. D. Park ◽  
M. Saka
Keyword(s):  
Residual Stress ◽  
Exposure Time ◽  
High Speed ◽  
Compressive Residual Stress ◽  
Diffraction Method ◽  
Water Jet ◽  
Material Surface ◽  
Principal Stresses ◽  
Plane Normal ◽  
Cavitating Jet

In an attempt to strengthen the surface of materials, the potential of using a cavitating jet to form compressive residual stress has been investigated. Introducing compressive residual stress to a material surface provides improvement of the fatigue strength and resistance to stress corrosion cracking. In general, cavitation causes damage to hydraulic machinery. However, cavitation impact can be used to form compressive residual stress in the same way as shot peening. In the initial stage, when cavitation erosion progresses, only plastic deformation, without mass loss, takes place on the material surface. Thus, it is possible to form compressive residual stress without any damage by considering the intensity and exposure time of the cavitation attack. Cavitation is also induced by ultrasonic, high-speed water tunnel and high-speed submerged water jet, i.e., a cavitating jet. The great advantage of a cavitating jet is that the jet causes the cavitation wherever the cavitation impact is required. To obtain the optimum condition for the formation of compressive residual stress by using a cavitating jet, the residual stresses on stainless steel (JIS SUS304 and SUS316) and also copper (JIS C1100) have been examined by changing the exposure time of the cavitating jet. The in-plane normal stresses were measured in three different directions on the surface plane using the X-ray diffraction method, allowing for the principal stresses to be calculated. Both of the principal stresses are found changing from tension to compression within a 10 s exposure to the cavitating jet. The compressive residual stress as a result of the cavitating jet was found to be saturated after a certain time, but it starts decreasing, and finally, it approaches zero asymptotically. It could be verified in the present study that it was possible to form compressive residual stress by using a cavitating jet, and the optimum processing time could also be realized. The great difference between the water jet in water and air has also been shown in this regard. [S1087-1357(00)00501-3]

Prediction of Residual Stress Improvement by Water Jet Peening Using Cavitating Jet Simulation With Bubble Flow Model

2010 ◽  
Author(s):  
Masashi Fukaya ◽  
Ren Morinaka ◽  
Noboru Saitou ◽  
Hisamitsu Hatou ◽  
Yoshiaki Tamura ◽  
...  
Keyword(s):  
Residual Stress ◽  
Flat Plate ◽  
Power Plants ◽  
Compressive Residual Stress ◽  
Flow Model ◽  
Water Jet ◽  
Bubble Collapse ◽  
Bubble Flow ◽  
Bubble Pressure ◽  
Cavitating Jet

We developed the new method for predicting a region of compressive residual stress on the weld surface after water jet peeing (WJP), which is a preventive maintenance technology for nuclear power plants. A cavitating jet is impinged on the weld surfaces of structures in a nuclear reactor. Bubble collapse impact causes plastic deformation of the weld surface, and changes the residual stress from tensile to compressive. Compressive residual stress prevents the occurrence of stress corrosion cracking (SCC) on the weld surface. A cavitating jet vertically injected into a submerged flat plate was investigated. Tensile stress was introduced onto the surface of the stainless steel plate by grinding before WJP in the experiment. We numerically simulated impulsive bubble pressure that varied by microseconds in the cavitating jet with the “bubble flow model”. The bubble flow model simulates the abrupt time-variations in the radius and inner pressure of bubbles based on the Rayleigh-Plesset equation in a cavitating flow. The cavitation collapse energy was estimated based on the bubble pressure. The cavitation collapse energy was compared with the measured compressive residual stress on the flat plate after WJP. The radial range of the compressive residual stress from the jet center axis is one of the most important measures of performance of WJP. The radial range of the cavitation collapse energy corresponded to that of compressive residual stress with a prediction error of +/− 20% under different conditions of jet velocity and the distance between the jet nozzle and plate surface. The results confirmed that the method we developed for predicting the region of compressive residual stress after WJP was valid.

Improvement of Fatigue Strength of Aluminum Alloy by Cavitation Shotless Peening

2002 ◽  
Vol 124 (2) ◽  
pp. 135-139 ◽  
Author(s):  
Hitoshi Soyama ◽  
Kenichi Saito ◽  
Masumi Saka
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Strength ◽  
Shot Peening ◽  
High Speed ◽  
Bending Fatigue ◽  
Hydraulic Machinery ◽  
Bending Fatigue Test ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Cavitation Shotless Peening

Cavitation impact, which normally produces severe damage in hydraulic machinery, can be used to modify surfaces in the same way as shot peening. Cavitation impact enables the surface of a material to be peened without the use of shot, thus it is called cavitation shotless peening. As there are no solid body collisions occurring in this peening process, the roughness of the peened surface should be less than that produced by shot peening. This characteristic makes it suitable for peening soft metals. In order to demonstrate the improvement of the fatigue strength of aluminum alloy by this process, specimens were subjected to the process, and then tested in a rotating bending fatigue test. Cavitation impacts were produced and controlled by using a submerged high speed water jet with cavitation, i.e., a cavitating jet. It was revealed that the fatigue strength of an aluminum alloy specimen treated by this peening process was 50% stronger than that of a specimen without peening.

Mitigation of Stress Corrosion Cracking Based on Residual Stress Improvement by Water Jet Peening (WJP)

2011 ◽  
Author(s):  
Masashi Fukaya ◽  
Fujio Yoshikubo ◽  
Hisamitsu Hatoh ◽  
Yuji Matsui ◽  
Yoshiaki Tamura ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Water Jet ◽  
Corrosion Cracking ◽  
Bubble Collapse ◽  
Bubble Pressure ◽  
Stress Simulation ◽  
Cavitating Jet

We have developed a practical peening technology using cavitating water jet. Water jet peening (WJP) is a preventive maintenance technology for nuclear power plants. WJP changes the residual stress on weld surfaces of reactor internals from tensile to compressive to mitigate the stress corrosion cracking (SCC). The operating conditions of WJP are controlled on the basis of ‘JSME Codes for Nuclear Power Generation Facilities.’ WJP has several advantages of operation, especially no foreign material is left in the reactor vessel since only water is injected, and wide range of the residual stress improvement is obtained since the cavitating flow spreads along the weld surface. We have also developed a prediction method of the residual stress improvement by WJP using a combination of a cavitating jet simulation and a residual stress simulation. We numerically simulated impulsive bubble pressure that varied in microseconds in the cavitating jet with ‘bubble flow model’. The bubble collapse energy was estimated by the bubble pressure. The residual stress simulation was conducted under the input conditions obtained from the bubble collapse energy. The residual stress distributions on and under the weld surface were predicted. The distributions were compared with measured data, and the result confirmed that the developed method for predicting the compressive residual stress after WJP was valid.

A Review High-Speed Milling of Meshing Cylindrical Surface

2012 ◽  
Vol 723 ◽  
pp. 82-86
Author(s):  
Pu Zhang ◽  
Pei Quan Guo ◽  
Yan Ke Cao ◽  
Xiao Wei Wang
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Surface Quality ◽  
Cylindrical Surface ◽  
High Speed ◽  
Metal Cutting ◽  
Surface Residual Stress ◽  
Surface Strength ◽  
Workpiece Surface ◽  
High Speed Milling

Meshing cylindrical surface always bears the alternating stress in the practical application. It will bring fatigue failure and fracture phenomena if the alternating stress is uncontroled, seriously affect the service life of the mechanical devices. The fatigue strength of the workpiece will be improved to boost the surface quality and surface strength and use the way of controling the workpiece surface residual stress brought by metal cutting to compressive stress. High-speed milling technology can greatly enhance the surface strength and surface quality of the workpiece surface, it can also change the cutting parameters to control the residual stress of the workpiece surface, so that it can greatly improve the fatigue strength of the workpiece.

A Method for Improving Compressive Residual Stress of Small Holes Surface by Water-Jet Cavitation Peening

2009 ◽  
Vol 614 ◽  
pp. 137-142 ◽  
Author(s):  
B. Han ◽  
Dong Ying Ju
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Compressive Residual Stress ◽  
Diffraction Method ◽  
Water Jet ◽  
Surface Residual Stress ◽  
Near Surface ◽  
Stress Zone ◽  
Strengthening Technique ◽  
Small Holes

As a novel surface strengthening technique, Water-jet cavitation peening has been applied to improve the fatigue life by inducing the compressive residual stress in the near surface layer of mechanical components. Compared with conventional shot peening, one advantage of WCP is that the complicated and tiny surface can be peened more easily. In this study, the small holes with various diameters and depths in the SUS304 stainless steel specimens were treated by WCP. In order to estimate its strengthening capability to the small holes, the surface residual stress and the depth distributions in the near surface layer of the small holes were measured by X-ray diffraction method. The experimental results show that WCP can successfully improve the near surface compressive residual stress of small holes. The maximum of surface compressive residual stress of WCP state is up to around –450 MPa. The dept of compressive residual stress zone is up to around 125 μm.

Effect of Cavitation Number on the Improvement of Fatigue Strength of Carburized Steel Using Cavitation Shotless Peening

2004 ◽  
Vol 261-263 ◽  
pp. 1245-1250 ◽  
Author(s):  
D.O. Macodiyo ◽  
H. Soyama ◽  
Masumi Saka
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
High Speed ◽  
Compressive Residual Stress ◽  
Cavitation Number ◽  
Material Surface ◽  
Carburized Steel ◽  
Upstream Pressure ◽  
Cavitating Jet ◽  
Cavitation Shotless Peening

Peening can be used to produce a layer of compressive residual stress at the surface of components which are subject to fatigue or stress corrosion, thereby retarding crack initiation and/or impeding the development of new cracks and hence improving their fatigue life. We have developed a new peening method, Cavitation Shotless Peening (CSP), which makes use of cavitation impacts induced by the collapse of the cavitation bubbles to produce compressive residual stress and work hardening on the material surface. CSP is a surface enhancement technique which differs with shot peening in that shots are not used. CSP uses a submerged high-speed water jet with cavitation, herein referred to as a cavitating jet, whose intensity and occurring region can be controlled by parameters such as upstream pressure and nozzle size. Cavitation number , which is defined by the ratio of upstream pressure to downstream pressure, is the main parameter of the cavitating jet. In this paper, the pit distribution on the specimen was observed with cavitating numbers  = 0.0057 and  = 0.0142. The improvement of fatigue strength and introduction of residual stress were investigated for both conditions using carburized alloy steel (JIS SCM415). It was evident from a comparison between non-peened and cavitation shotless peened specimens that the cavitation number has influence on the fatigue strength of metallic materials. Comparison of shot peened and CSP specimens has also been discussed.

Introduction of Compressive Residual Stress Using a Cavitating Jet in Air

2004 ◽  
Vol 126 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Hitoshi Soyama
Keyword(s):  
Residual Stress ◽  
Mass Loss ◽  
Shot Peening ◽  
High Speed ◽  
Compressive Residual Stress ◽  
Injection Pressure ◽  
Water Jet ◽  
Low Speed ◽  
Aluminum Specimen ◽  
Cavitating Jet

Cavitation impact from a cavitation jet, which is formed from bubbles induced by a high-speed water jet in water, can be used for surface modification in a similar manner to shot peening. A cavitating jet is normally produced by injecting a high-speed water jet into a water-filled chamber. It is possible to make a cavitating jet in air by injecting a high-speed water jet into a concentric low-speed water jet that surrounds the high-speed jet. In order to demonstrate this, a high-speed water jet with a concentric low-speed water jet was impacted onto an aluminum specimen to observe the pattern of erosion. The mass loss of the specimen was weighed to measure the capability of the jet, since a more powerful jet produces a larger mass loss. It was shown that the combination of high- and concentric low-speed water jets produced a typical erosion pattern such as that obtained using a cavitating jet in a water-filled chamber. When the injection pressure of the concentric low-speed water jet was optimized, the capability of the cavitating jet in air was much greater than that of a cavitating jet in a water-filled chamber. It was demonstrated that an optimized cavitating jet in air introduced more compressive residual stress in the surface of tool steel alloy than that from a cavitating jet in a water-filled chamber. In addition, this stress was larger than that induced by shot peening. The peened surface was also less rough compared with shot peening.

scholarly journals Cavitating Jet: A Review

2020 ◽  
Vol 10 (20) ◽  
pp. 7280 ◽  
Author(s):  
Hitoshi Soyama
Keyword(s):  
High Speed ◽  
Injection Pressure ◽  
Water Jet ◽  
Cavitation Number ◽  
Estimation Methods ◽  
Metallic Materials ◽  
Hydraulic Machinery ◽  
Cavitating Jets ◽  
Mechanical Surface ◽  
Cavitating Jet

When a high-speed water jet is injected into water through a nozzle, cavitation is generated in the nozzle and/or shear layer around the jet. A jet with cavitation is called a “cavitating jet”. When the cavitating jet is injected into a surface, cavitation is collapsed, producing impacts. Although cavitation impacts are harmful to hydraulic machinery, impacts produced by cavitating jets are utilized for cleaning, drilling and cavitation peening, which is a mechanical surface treatment to improve the fatigue strength of metallic materials in the same way as shot peening. When a cavitating jet is optimized, the peening intensity of the cavitating jet is larger than that of water jet peening, in which water column impacts are used. In order to optimize the cavitating jet, an understanding of the instabilities of the cavitating jet is required. In the present review, the unsteady behavior of vortex cavitation is visualized, and key parameters such as injection pressure, cavitation number and sound velocity in cavitating flow field are discussed, then the estimation methods of the aggressive intensity of the jet are summarized.

A Method for Evaluating Intensity of Water Cavitation Peening Processing

2011 ◽  
Vol 675-677 ◽  
pp. 747-750
Author(s):  
B. Han ◽  
Dong Ying Ju ◽  
Xiao Guang Yu
Keyword(s):  
Residual Stress ◽  
Process Capability ◽  
Diffraction Method ◽  
Spring Steel ◽  
Bubble Collapse ◽  
Plastic Layer ◽  
Process Conditions ◽  
X Ray Diffraction ◽  
Near Surface ◽  
The Impact

Water cavitation peening (WCP) with aeration, namely, a new ventilation nozzle with aeration is adopted to improve the process capability of WCP by increasing the impact pressure induced by the bubble collapse on the surface of components. In this study, in order to investigate the process capability of the WCP with aeration a standard N-type almen strips of spring steel SAE 1070 was treated byWCP with various process conditions, and the arc height value and the residual stress in the superficial layers were measured by means of the Almen-scale and X-ray diffraction method, respectively. The optimal fluxes of aeration and the optimal standoff distances were achieved. The maximum of arc height value reach around 150μm. The depth of plastic layer observed from the results of residual stresses is up to 150μm. The results verify the existence of macro-plastic strain in WCP processing. The distributions of residual stress in near-surface under different peening intensity can provide a reference for engineers to decide the optimal process conditions of WCP processing.

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