The document discusses cavitation erosion resistance testing of marine propeller materials. It describes cavitation as the formation of vapor bubbles in liquids under low pressure that can cause damage. The study aims to test different materials' resistance to cavitation erosion using water jet cavitation testing techniques. Aluminum and various copper alloy samples were tested at different cavitation numbers, standoff distances, and durations. The test results showed that cavitation erosion increased with lower cavitation number, shorter standoff distance, and longer test duration. Harder copper alloy materials exhibited greater resistance to cavitation erosion.

1. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
CAVITATION EROSION RESISTANCE
OF MARINE PROPELLER MATERIALS

2. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
CONTENTS:
Cavitation
Need to study cavitation
Testing techniques
Test Procedure and Experimental setup
Cavitation number and Standoff distance
Cavitation erosion investigation on aluminium sample
Cavitation erosion test on propeller materials
Conclusion
References

3. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
WHAT IS CAVITATION?
• Cavitation is formation of vapor
bubbles within a liquid at low-pressure
regions that occur in places where the
liquid has been accelerated to high
velocities, as in the operation of
centrifugal pumps, water turbines, and
marine propellers.
• Cavitation results in increase in noise
and vibration, loss in performance as
well as high maintenance cost.

4. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
NEED TO STUDY CAVITATION
• Prediction of cavitation erosion will help designer of the ship in selecting
proper material for the ship and propeller and to develop newer material
which is stronger for resisting to cavitation erosion.
• Types Of Cavitation
Sheet
Bubble
Cloud
Tip vortex
• There are two popular techniques for testing of cavitation erosion
characteristic of materials: ultrasonic and water jet technique.

5. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
ULTRASONIC CAVITATION
TESTING TECHNIQUE
In ultrasonic cavitation test, the cavitation
is generated by a vibratory device
employing a magneto strictive ultrasonic
horn. The high frequency oscillations of
the horn, typically tens of kilohertz, induce
cyclic formation of very high and very low
pressures, which generate high negative
tension in the liquid. The ultrasonic horn
tip vibrates at 20 kHz and generates
cavitation bubbles around the tip

6. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
WATER JET CAVITATION
TESTING TECHINQUE
• In water jet cavitation testing
technique specimen is placed
under water below the cavitating
jet.

7. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Test procedure:
• Sample was prepared suitably for the sample holder geometry
and sample surface was polished up to mirror like surface.
• Weight of the sample was measured by an electronic balance
and recorded before and after the tests.
• Sample surface was scanned using an optical profilometer
before and after the tests.
• Sample was exposed to the cavitating jet for a predetermined
period of time.
• The sample was taken out from its holder and carefully dried in
a dry environment.

8. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Experimental setup
Water jet cavitation test rig and cavitation chamber Photograph of cavitation
erosion test

9. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Cavitation Number Definition
• The cavitation number (σ) is a dimensionless number used in
flow calculations. It expresses the relationship between the
difference of a local absolute pressure from the vapor
pressure and the kinetic energy per volume, and is used to
characterize the potential of the flow to cavitate.it can be
expressed as: σ
σ

10. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
The Stand-off distance
• The stand-off distance (Soff), is
defined as the measured distance
from the exit of the nozzle to the
target surface of the test sample. It
is a major parameter in the
cavitation erosion tests. Because it
determines the extent of
cavitation damage on the test
material depending on the given
parameters (ASTM, 2010)

11. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
CAVITATION EROSION INVESTIGATION ON
ALUMINIUM SAMPLES
Aluminum metal was chosen
to shorten the experiment
time.
Validation was established by
comparing the results with
Momma
(Momma, 1991)
Material Al-6063
T(min) 30 min
P2(bar) 3.6
P1(bar) 120
Cavitation number,σ 0.03
Soff distance(mm) 5, 8, 10, 12, 18, 15, 20, 25
Dnozzle (mm) 1.4
• P2 is chamber pressure
• P1 is waterjet pressuer

12. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Soff
(mm)
∆m(gr) ER x 10-
4
(gr/min)
Hmax(µ
m)
EI(µm/
min)
5 0.0113 3.766 130 4.333
8 0.0091 3.033 106 3.533
10 0.0062 2.066 99 3.300
12 0.0020 0.666 92 3.066
15 0.0014 0.466 86 2.866
18 0.0004 0.133 29 0.966
20 0.0001 0.033 23 0.766
25 0 0.000 17 0.566

13. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
EROSION RATE GRAPH
HEIGHT OF EROSION DEPTH ON
TESTEDSAMPLE SURFACE

14. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Effect of Soff distance to the cavitation erosion
Optical profilometer analysis of the Al-6063 surfaces showing the highest pitting
depth on the surfaces. (a) untested surface, (b) Soff=20 mm and (c) Soff=10 mm (3-D)
(a) (b) (c)

15. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
CAVITATION EROSION TESTS OF
PROPELLER MATERIALS
Materials Cu1, cu3, cu4
T(min) 30, 60, 90
P2 (bar) 2.5, 5, 7.5
P1 (bar) 250
Cavitation number 0.01, 0.02, 0.03
Soff distance(mm) 5
Dnozzel (mm) 1.4
CONDITION FOR HIGH PRESSURE WATERJET
CAVITATION TEST
A 1.4 mm diameter steel nozzle sprayed high pressure
water to the Cu1, Cu3 and Cu4 propeller materials at 250
bar inlet pressure during 30, 60 and 90 minutes. The
chamber pressure were 2.5, 5 and 7.5 bar ( σ = 0.01, 0.02
and 0.03). Thus, 27 cavitation erosion tests were carried
out (3 different propeller materials, 3 different test periods
and 3 different cavitation numbers; 33=27).
Tested samples of the Cu1, Cu3 and Cu4 materials

16. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Materials Used in the Tests
Alloy type Yield strength
[n/mm2]
Tensile
strength
[n/mm2]
Brinell
hardness[3000
kg force]
Rockwell B
hardness
Cu1 175 440 130 65-70
Cu3 245 590 159 84-89
Cu4 275 630 180 85-90
Tested samples of the Cu1, Cu3 and Cu4 materials
Mechanical properties
of the samples used in
tests

17. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Test Results of the Propeller Materials
Test results of erosion rate change with time σ (a) 0.01 (b) 0.02 (c) 0.03
(a) (b) (c)

18. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
Cavitation erosion test for 30min, 60min & 90min duration

19. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
CONCLUSION
• Performing cavitating jet test is a simpler and cheaper way to investigate the resistance
of different materials to cavitation erosion comparing the cavitation tunnel tests.
• Cavitation erosion occurrence for tested materials depends on the cavitation number.
• The stand-off distance is a crucial parameter for bubble collapse effect on the sample
surfaces. As the stand-off distance decreases, cavitation erosion on the sample surface
increases
• As the cavitation number decreases, the mass loss, the erosion rate, and the eroded area
increase.
• As the erosion test time increases, erosion formation on the surface also increases.

20. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
REFRENCES:
• Cheng, F., Ji, W., Qian, C., & Xu, J. (2018). Cavitation bubbles dynamics and cavitation
erosion in water jet. Results in Physics, 9, 1585-1593.
• ASTM Standard, Standard No: G134-95. (2010). Standard Test Method for Erosion of
Solid Materials by a Cavitating Liquid Jet, Annual Book of ASTM Standards, Vol. 03.02,
West Conshohocken, pp 558– 571.
• Laguna-Camachoa, J. R., Lewis, R.,Vite-Torres, M. and Mendez-Mendez, J. V. (2013). A
study of cavitation erosion on engineering materials, Wear, Vol. 301, pp. 467–476.
• March, P. A. (1987). Evaluating the Relative Resistance of Materials to Cavitation Erosion:
a Comparison of Cavitating Jet Results and Vibratory Results, Proc. Cavitation and
Multiphase Flow Forum, ASME, Cincinnati.

21. INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
DEPARTMENT OF OCEAN ENGINEERING AND NAVAL
ARCHITECTURE
THANK YOU