Fundamental of “Cavitation Peening” is now on YouTube. 3 min. https://youtu.be/BurRGrmOGQY

Invited review paper about “cavitation peening” is available on following URL as OPEN ACESS Journal. http://www.oldcitypublishing.com/wp-content/uploads/2017/11/IJPSTv1n1p3-60Soyama.pdf

H. Soyama,

“Key Factors and Applications of Cavitation Peening” International Journal of Peening Science and Technology Vol. 1 (2017), pp. 3-60.

Cavitation S Peening® S：Shotless, Shockwave, Smooth, Soyama

is a peening method

using cavitation impacts in the same way as shot peening

to improve fatigue strength and/or to introduce compressive

residual stress. The peening method using cavitation

impact is called “cavitation shotless peening (CSP)”, as

shots are not required (see Fig. 1). In the case of cavitation

shotless peening, cavitation is generated by cavitating jet.

is phase change phenomena from

liquid-phase to gas-phase. It is similar to boiling,

but, in the case of cavitation, liquid-phase becomes

gas-phase by decrease of static pressure until

saturated vapor pressure due to increase of flow

velocity (see Fig. 2). When the static pressure is

increased by decrease of the flow velocity, the

cavitation bubble is collapsed. At the cavitation

bubble collapse, a part of the bubble is deformed

and a micro-jet is produced (see Fig. 3). As the

speed of the micro-jet is about 1,500 m/s, the

micro-jet produces plastic deformation pit on the

solid surface. After the cavitation bubble shrink, the

cavitation bubble rebounds. At the rebound, shock

wave is produced. The shock wave also produces

plastic deformation (see Fig. 3).

is a jet with cavitation bubbles produced by injecting a high-speed water jet into water

(see Fig. 4). The cavitation bubbles take place in the low pressure region of vortex core in the shear layer

around the jet. The vortex cavitations combine and big cavitation cloud is produced. When the cavitation

cloud hit the surface, cavitation impacts are produced at bubble collapses. Soyama successfully produced

cavitating jet in air by injecting a high-speed water jet into a low-speed water jet.

*1 H.Soyama, Trans. ASME, Journal of Fluids Engineering, Vol. 127, No. 4, 2005, pp. 1095-1101. [2015.5.15]

Cavitation S Peening®

Nozzle

Flow

Fig. 1 Shotless peening and shot peening

Cavitation

.2

2

constzgpv

Head Static pressure

Flow velocity

Bernoulli’s equation

Fig. 2 Phase diagram of water and Bernoulli’s equation

Solid surface

Micro-jetShock waveCavitation bubble

Rebound

In Water

Plastic deformation[High speed/Low pressure region] [Low speed/High pressure region]

Fig. 3 Schematic diagram of cavitation bubble

Cavitating jet

Fig. 4 Schematic diagram and photo of cavitating jet

Schematic diagram Cavitating jet in water Cavitating jet in air*1

Shotless Shot

Cavitating Jet

CavitationImpact

― Improvement of Fatigue Strength ― Cavitation S Peening® improves the fatigue strength of gear made of carburized chromium molybdenum steel SCM420H*1. It also enhances the fatigue strength of carburized chromium molybdenum SCM420*2 and SCM415*3, aluminum alloy AC4CH-T6*4, Duralumin, magnesium alloy, stainless steel, silicon manganese steel and other materials.

*1 H.Soyama and Y.Sekine, “Sustainable Surface Modification Using Cavitation Impact for Enhancing Fatigue Strength

Demonstrated by a Power Circulating-Type Gear Tester,” International Journal of Sustainable Engineering, Vol. 3, No. 1, 2010, pp. 25 - 32.

*2 H.Soyama, “Improvement of Fatigue Strength of Metallic Materials by Cavitation Shotless Peening,” Metal Finishing News, Vol. 7, March issue, 2006, pp. 48 - 50.

*3 D.Odhiambo and H.Soyama, “Cavitation Shotless Peening for Improvement of Fatigue Strength of Carbonized Steel,” International Journal of Fatigue, Vol. 25, Nos. 9-11, 2006, pp. 1217 - 1222.

*4 H.Soyama, K.Sasaki, K.Saito and M.Saka, “Cavitation Shotless Peening for Improvement of Fatigue Strength of Metallic Materials,” Transaction of Society of Automotive Engineers of Japan, Vol. 34, No. 1, 2003, pp. 101 - 106.

Intelligent Sensing of Materials Lab., Department of Nanomechanics, Tohoku University

300

350

400

450

500

Fig. 5 Improvement of fatigue strength of gear demonstrated using a power circulating type gear tester (Carburized SCM420H)*1

105 106 107

Number of cycles to failure N

Torq

ue

Dn

Nm

Not peened

Shot Peening

Cavitation Peening

700

800

900

1000

104

Not peened

SP1

SP2 CSP

Am

plitu

de o

f be

ndin

g st

ress

a

M

Pa

105 106 107 108

Number of cycles to failure N

Fig. 6 S-N curve of rotating bending fatigue test (Carburized SCM420)*2

700

800

900

1000

CSP

SP

Not peened

106 104 107 108 105

Am

plitu

de o

f be

ndin

g st

ress

a

M

Pa

Number of cycles to failure N

Fig. 7 S-N curve of rotating bending fatigue test (Carburized SCM415)*3

80

120

160

200

CSP

SP

Not peened

Am

plitu

de o

f be

ndin

g st

ress

a

M

Pa

Number of cycles to failure N

106 107 108 105

Fig. 8 S-N curve of rotating bending fatigue test (AC4CH-T6)*4

― Peened Surface ― Cavitation S Peening® introduces compressive residual stress with a considerable less surface roughness compared to that from shot peening (see Figs. 9 and 10). Individual pit induced by Cavitation S Peening® does not have sharp tip up around the pit, compared to a pit induced by ball indentation at nearly constant volume and depth (see Fig. 11). It is very shallow compared to the pit at constant depth of plastic deformation area (see Fig. 12).

*5 H.Soyama, D.O.Macodiyo and S.Mall, “Compressive Residual Stress into Titanium Alloy Using Cavitation Shotless Peening Method,” Tribology Letters, Vol. 17, No. 3, 2004, pp. 501 - 504.

*6 H.Soyama, “Introduction of Compressive Residual Stress Using a Cavitating Jet in Air,” Trans. ASME, Journal of Engineering Materials and Technology, Vol. 126, No. 1, 2004, pp. 123 - 128.

*7 H.Soyama, “Distribution of Residual Stress around Plastic Deformation Pit Induced by Cavitation Shotless Peening,” Proceedings of 2005 Annual Meeting of JSME/MMD, 2005, pp. 361 - 362.

*8 A. Kai and H.Soyama, “Visualization of the Plastic Deformation Area beneath the Surface of Carbon Steel Induced by Cavitation Impact,” Scripta Materialia, Vol. 59, No. 3, 2008, pp. 272 - 275.

Intelligent Sensing of Materials Lab., Department of Nanomechanics, Tohoku University

CSP (Ra = 0.53 m) SP (Ra = 2.44 m) -1200

-800

-400

0

400

0 50 100 150 200

SP

Distance from the surface z m

Res

idua

l str

ess

MP

a

Not peened

CSP

Fig. 9 Peened surface and residual stress (Ti-6Al-4V)*5

-1000

-800

-600

-400

-200

0

200

0 20 40 60 80CSP (Ra = 0.10 m) SP (Ra = 1.01 m) Distance from the surface z m

Res

idua

l str

ess

MP

a

SP

Not peened

CSP

Fig. 10 Peened surface and residual stress (SKD61)*6

400 m

40 m

400 m

400 m

40 m

400 m

(a) CSP (b) Ball indentation

Fig. 11 Aspect of pit*7

35 m 90 %

450 m

Volume 2.3 mm3 32 m

480 m

2.2 mm3 90 %

Fig. 12 Depth and plastic deformation area*8

h' h

― Singularity of CSP ― Full width at half maximum of diffracted X-ray profile from alloy tool steel peened by Cavitation S Peening® becomes narrower than that of not peened specimen (see Fig. 13). The ratio of arc height between N-gage and A-gage of Almen strip peened by Cavitation S Peening® is different from that of shot peening (see Fig. 14).

― Peening Effect ― Cavitation S Peening® can be applied for suppression of cracks induced by heat cycle (see Fig. 15), relief of micro strain (see Fig. 16), peen forming (see Fig. 17), and enhancement of CVT element (see Fig. 18).

*9 H.Soyama, “Macro and Micro Strain in Polycrystalline Metal Controlled by Cavitation Shotless Peening,” Metal Finishing News, Vol. 7, November issue, 2006, pp. 48 - 50.

*10 H.Soyama, H. Kumano, K. Saito and M. Saka, “Evaluation of Peening Intensity of Cavitation Shotless Peening by Using Almen Strip,” Proceedings of APCFS & ATEM '01, 2001, pp. 1047 - 1050.

*11 H.Soyama, “Surface Modification of Metallic Materials by Using String Cavitation,” Journal of Japan Society for Heat Treatment, Vol. 48, No. 2, 2008, pp. 74 - 78.

*12 H.Soyama and N.Yamada, “Relieving Micro-Strain by Introducing Macro-Strain in a Polycrystalline Metal Surface by Cavitation Shotless Peening,” Materials Letters, Vol. 62, No. 20, 2008, pp. 3564 - 3566.

*13 H.Soyama and K. Saito, “Peen Forming Using a Cavitating Jet in Air,” Proceedings of Pacific Rim International Conference on Water Jetting Technology, 2003, pp. 429 - 436.

*14 H.Soyama, M.Shimizu, Y.Hattori and Y.Nagasawa, “Improving the Fatigue Strength of the Elements of a Steel Belt for CVT by Cavitation Shotless Peening,” Journal of Materials Science, Vol. 43, No. 14, 2008, pp. 5028 - 5030.

Intell igent  Sensing  of  Materials  Lab. Intell igent  Sensing  of  Materials  Lab. Intelligent  Sensing  of  Materials  Lab. Intell igent  Sensing  of  Materials  Lab. Intell igent  Sensing  of  Materials  Lab.

Prof. Hitoshi Soyama, Department of Nanomechanics, Tohoku University 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai, 980-8579, JAPAN

0

20

40

102 104 106 108Rel

ativ

e in

tens

ity o

f X

-ray

Diffraction angle 2��

SP

CSP

NP NNNPPP

PPPiii tttsss

CCCSSSPPP

SSSPPP

Fig. 13 Diffracted X-ray profile and peened surface of alloy tool steel SKD61*9

0.00

0.04

0.08

0.12

0 2 4 6 8 10Processing time t s/mm

Mic

ro-s

trai

n

(1 1 0)

(2 0 0)

(2 1 1)

Fig. 16 Relief of micro strain by CSP*12

0.8

1.0

1.2

1.4

1.6

1.8

Not peened

106 104 105 103 Number of cycle to failure N

Nor

mal

ized

ben

ding

fo

rce

F CSP

Fig. 18 S-N curve of CVT elements*14

0

0.2

0.4

0.6

0.8

0 5 10 15Processing time t s/mm

Cur

vatu

re m

-1

Fig. 17 Curvature induced by CSP*13

p1 = 30 MPa

20 MPa

0 200 400 600 800

SB-nitriding + FPB Gas nitridung + SP SB-nitriding + HSP Gas nitriding + HSP SB-nitriding + CSP Gas nitriding + CSP

Fig. 15 Number of cracks after heat cycle test*11 Number of cracks

Fig. 14 Relation on arc height between N-and A-gauge, and surface of Almen strip*10

42.0N

A

dH

dH

33.0N

A

dH

dH

CSP

SP

(c) SP HN =0.15 mm

(b) CSP HN =0.32 mm

(a) Not peened

0.00

0.05

0.10

0.15

0.20

0.00 0.10 0.20 0.30 0.40Arc height H N mm

Arc

hei

ght H

A m

m

Intelligent Sensing of Materials Lab., Department of Nanomechanics, Tohoku University

Cavitation S Peening® ― Several Types of Cavitating Jets and Water Jet ―

*1 H.Soyama, Trans. ASME, Journal of Engineering Materials and Technology, Vol. 126, No. 1, 2004, pp. 123 - 128. *2 H.Soyama, Trans. ASME, Journal of Fluids Engineering, Vol. 127, No. 4, 2005, pp. 1095- 1101. *3 H.Soyama, Journal of Materials Science, Vol. 42, No. 16, 2007, pp. 6638-6641. *4 H.Soyama et al., ISIJ International, Vol. 48, No. 11, 2008, pp. 1577-1581. *5 H.Soyama et al., Surface & Coatings Technology, Vol. 205, 2011, pp. 3167-3174. *6 H.Soyama and O.Takakuwa, Journal of Fluid Science and Technology, Vol. 6, No. 4, 2011, pp. 510-521.

Cavitating jet in water

Water jet in water

Cavitating jet in air

Water jet with associated water jet in air

Cavitating jet in water with associated water jet

Water jet with associated water jet in water

Cavitating jet in water with pressurized chamber

Water jet with associated water jet in water

Normal water jet

Water jet in air

Fig. 1 Erosion pattern of several types of cavitating jets and a normal water jet *1, *2, *3, *4, *5, *6

At cavitation peening, there is no erosion, as process is finished before erosion takes place.

t = 0 ms

0

20 mm

0.600 msFig. 2 Changing appearance of a cavitating jet in air with time*2

250

300

350

400

Number of cycles to failure N

Am

plitu

de

of b

endi

ng s

tres

s

a M

Pa

Cavitating jet in air

104 105 106 107 108

Not peened

Cavitating jet in water at s = 65mm

Cavitating jet in water at s = 25mm

Fig. 3 S-N curve of SUS316L*3

300

350

400

450

500

104 105 106 107

Am

plitu

de

of b

endi

ng s

tres

s

a M

Pa

Number of cycles to failure N

Not peened

Cavitating jet in water with associated water jet

Fig. 4 S-N curve of grinded SUS316L*4

Intelligent Sensing of Materials Lab., Department of Nanomechanics, Tohoku University 1

Severe erosive vortex cavitationRing vortex cavitation

Cloud cavitation

Vortex cavitation in shear layer

Impinging surface

Nozzle

High-speedwater jet

Schematic diagram of cavitating jet

High speed photographof cavitating jettaken by Soyama

WATER

How to Produce Cavitation; Cavitating JetH.Soyama，J. Soc. Mater. Sci., Japan,，47 (1998), pp. 381-387.

Intelligent Sensing of Materials Lab., Department of Nanomechanics, Tohoku University0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 4002

Developing regionOf vortex cavitation

Collapsing region ofvortex cavitation

Surface

Cloud cavitation

Ring erosion

Vortex cavitation

In Water

Pressurizedwater

DropletsCollapsing region ofvortex cavitationCavitation

impacts

Inve

rse

of c

urva

ture

1/

m-1

Normalized standoff distance s/d

p1 = 300 MPa, d = 0.4 mm

p1 = 30 MPa, d = 2 mm

Dropletsimpacts

Cavitation impacts

Dropletsimpacts Cavitation impacts

(Arc

hei

gh

t)

H.Soyama,Mechanical Engineering Review,Vol. 2, No. 1 Jan. 2015,Paper No. 14-00192, pp. 1-20.

“Cavitation Peening” and “Water Jet Peening”

d

Standoff distance sStandoff distance s

Potential core

p1 = 300 MPa

Ag

gre

ssiv

ity

of

jet

Jet power （= injection pressure x flow rate）is nearly equal.

Droplet and/or shot impacts are used.Cavitation impacts are used

Intelligent Sensing of Materials Lab., Department of Nanomechanics, Tohoku University 3

≧ 1.8 .

＜1.8 .

Cavitation Peening

Water Jet Peening

H.Soyama,

Mechanical Engineering Review,Vol. 2, No. 1 Jan. 2015,Paper No. 14-00192, pp. 1-20.

1

2

21

2

p

p

pp

pp v

Cavitation number :

Injection pressure of the jet : p1

Down stream pressure of nozzle : p2

Vapor pressure : pv

“Cavitation Peening” and “Water Jet Peening”

Ag

gre

ssiv

ity

of

jet

Droplet and/or shot impacts are used.Cavitation impacts are used

Intelligent Sensing of Materials Lab., Department of Nanomechanics, Tohoku University 4

Injection Pressure and Nozzle Size

In order to avoid the damage, the low injection pressure and large nozzle size is better than the high injection pressure for cavitation peening.

Jet power = (Injection pressure) X (Flow rate)

Standoff distance

ppvvpp11

pp22

Peenedsurface

dd

Standoff distance

ppvvpp11

pp22

Peenedsurface

dd

H. Soyama and O. Takakuwa, Journal of Fluid Science and Technology, Vol. 6 (2011), pp. 510-521.

Damage

-300

-200

-100

0

100

0 200 400 600Depth from the surface z m

Res

idu

al s

tres

s

RM

Pa

Not-peened

Compression

Tension

p1 = 300 MPa, d = 0.35 mm

p1 = 30 MPa, d = 2 mm

Jet power is nearly equal.