Academia.eduAcademia.edu

Figure 12 – uploaded by Jin-Keun Choi

See full PDFdownloadDownload figure
Fig. 11. Mean depth of erosion (based on mass loss) versus time curves obtained from G32 tests for various materials. Solid lines are fits of the data with the mathematical model of Eq. (6). Modified ASTM G32 method was used in these tests; (reg) represents the direct method, (alt) represents the alternative method.

Figure 11 Mean depth of erosion (based on mass loss) versus time curves obtained from G32 tests for various materials. Solid lines are fits of the data with the mathematical model of Eq. (6). Modified ASTM G32 method was used in these tests; (reg) represents the direct method, (alt) represents the alternative method.

Related Figures (18)

Fig. 2. Typical G32 test erosion curves: weight loss S-curve and erosion rate versus time curve. Cavitation erosion, no matter where and how it is generated, results from the repeated impulsive loading of the material by high intensity short duration pressures loads, due to shock waves and bubble reentrant jet impacts [23,24,34-37]. These are diffi- cult to measure but can be inferred from acoustic signals and pit measurements [7,27,29,33]. Statistical correlations can be obtained between these measurements and can be associated with the facil- ity producing the erosion and with empirically accepted cavitation intensity indicators, such as flow speed, ambient pressure, ampli- tude and frequency of ultrasonic horn. While “weak” materials may fail rapidly under the repeated shock waves and jet impacts, a more “resistant” material will accumulate stain and experience over a long period the symptoms of fatigue. Initially the material sur- face gets deformed and is modified microscopically without any loss of material (incubation period). This is accompanied by work It is known that the weight loss curve has an S shape, as illus- trated in Fig. 2, which shows an erosion acceleration phase during which the erosion rate increases until attaining a maximum. This is called the Accumulation or Acceleration Period. In this phase, the material experiences increased fracture and weight loss following the end of hardening in the incubation period. The extent of this zone depends upon the strain-hardening properties of the mate- rial and involves microscopic chunks of material being removed following propagation of large cracks in between the grains of the material. The accumulation period ends once the surface proper- ties of the material have changed so much that an interaction begins
Fig. 2. Typical G32 test erosion curves: weight loss S-curve and erosion rate versus time curve. Cavitation erosion, no matter where and how it is generated, results from the repeated impulsive loading of the material by high intensity short duration pressures loads, due to shock waves and bubble reentrant jet impacts [23,24,34-37]. These are diffi- cult to measure but can be inferred from acoustic signals and pit measurements [7,27,29,33]. Statistical correlations can be obtained between these measurements and can be associated with the facil- ity producing the erosion and with empirically accepted cavitation intensity indicators, such as flow speed, ambient pressure, ampli- tude and frequency of ultrasonic horn. While “weak” materials may fail rapidly under the repeated shock waves and jet impacts, a more “resistant” material will accumulate stain and experience over a long period the symptoms of fatigue. Initially the material sur- face gets deformed and is modified microscopically without any loss of material (incubation period). This is accompanied by work It is known that the weight loss curve has an S shape, as illus- trated in Fig. 2, which shows an erosion acceleration phase during which the erosion rate increases until attaining a maximum. This is called the Accumulation or Acceleration Period. In this phase, the material experiences increased fracture and weight loss following the end of hardening in the incubation period. The extent of this zone depends upon the strain-hardening properties of the mate- rial and involves microscopic chunks of material being removed following propagation of large cracks in between the grains of the material. The accumulation period ends once the surface proper- ties of the material have changed so much that an interaction begins
Fig. 1. Erosion progression curve for aluminum 1100-0 obtained in a cavitation jet erosion test. Inserts show a picture during the incubation period and another picture during the acceleration period.
Fig. 1. Erosion progression curve for aluminum 1100-0 obtained in a cavitation jet erosion test. Inserts show a picture during the incubation period and another picture during the acceleration period.
Fig. 3. Ultrasonic technique eroded samples pictures. Left: tested G32 metallic button sample; right: eroded composite material sample from the alternative G32 method.
Fig. 3. Ultrasonic technique eroded samples pictures. Left: tested G32 metallic button sample; right: eroded composite material sample from the alternative G32 method.
Materials tested in this study. Table 1 water tank so that the sample was subjected to only cavitation bubbles but not to water droplet impacts. A photograph showing a typical setup of the jet nozzle and the sample in its holder is shown in Fig. 4. The overall test procedure is similar to that of the G32 tests other than using a cavitating jet. The time intervals are appropri- ately selected to capture a cumulative weight loss curve displaying as much as possible the characteristic S-curve.
Materials tested in this study. Table 1 water tank so that the sample was subjected to only cavitation bubbles but not to water droplet impacts. A photograph showing a typical setup of the jet nozzle and the sample in its holder is shown in Fig. 4. The overall test procedure is similar to that of the G32 tests other than using a cavitating jet. The time intervals are appropri- ately selected to capture a cumulative weight loss curve displaying as much as possible the characteristic S-curve.
Fig. 4. Nozzle and sample holder in the DyNAFLow’s “7 ksi - 5 gpm” cavitation jet erosion test loop. where m(t) and A(t) are the mass loss and eroded area at time t, and p is the material density.
Fig. 4. Nozzle and sample holder in the DyNAFLow’s “7 ksi - 5 gpm” cavitation jet erosion test loop. where m(t) and A(t) are the mass loss and eroded area at time t, and p is the material density.
Fig. 5. Cavitation erosion average depth versus time on AL7075 resulting from a DynaJets® nozzle cavitation at different nozzle pressures (jet velocities). The solid lines are analytical curves obtained from the mathematical erosion evolution model shown in Eq. (6).
Fig. 5. Cavitation erosion average depth versus time on AL7075 resulting from a DynaJets® nozzle cavitation at different nozzle pressures (jet velocities). The solid lines are analytical curves obtained from the mathematical erosion evolution model shown in Eq. (6).
Fig. 7. Normalized cavitation erosion average depth versus normalized time on AL7075 resulting from DynaJets cavitation at different nozzle pressures (jet veloci- ties) and G32. The solid line is obtained from the mathematical erosion progression model shown in Eq. (6). These two functions are shown in Fig. 6, which illustrates that the mean erosion depth rate achieves its maximum when t=0.75t*. This provides a good interpretation for t*, as being 4/3 the time at which the rate of the mean depth of erosion attains its maximum. It would have been more eloquent to change variables to have the maximum at t*, but this would affect the simplicity of Eq. (6), which is very easy to remember in the present form.
Fig. 7. Normalized cavitation erosion average depth versus normalized time on AL7075 resulting from DynaJets cavitation at different nozzle pressures (jet veloci- ties) and G32. The solid line is obtained from the mathematical erosion progression model shown in Eq. (6). These two functions are shown in Fig. 6, which illustrates that the mean erosion depth rate achieves its maximum when t=0.75t*. This provides a good interpretation for t*, as being 4/3 the time at which the rate of the mean depth of erosion attains its maximum. It would have been more eloquent to change variables to have the maximum at t*, but this would affect the simplicity of Eq. (6), which is very easy to remember in the present form.
Fig. 6. Cavitation erosion mean depth of erosion rate, dh /dt (left) and its time derivative, dh /dt? (right) versus nondimensional time, f, as described by the mathematical erosion evolution model shown in Eqs. (6)-(8). Maximum erosion depth rate, (dh/dt) occurs when t=0.75t*. max?
Fig. 6. Cavitation erosion mean depth of erosion rate, dh /dt (left) and its time derivative, dh /dt? (right) versus nondimensional time, f, as described by the mathematical erosion evolution model shown in Eqs. (6)-(8). Maximum erosion depth rate, (dh/dt) occurs when t=0.75t*. max?
Fig. 8. Comparison of normalized erosion rate curves of AL7075 erosion daté obtained by various test methods.
Fig. 8. Comparison of normalized erosion rate curves of AL7075 erosion daté obtained by various test methods.
Table 2
Table 2
Fig. 9. Cavitation erosion average depth versus time on AL7075 resulting from a DyNaJETS nozzle cavitation at different nozzle pressures (jet velocities) shown in log-log scales. The solid lines are analytical curves from the mathematical erosion model shown in Eq. (6). The almost horizontal initial 2 ksi dots correspond to the incubation period. Normalized standard deviation or error in expressing the erosion data with Eq. (6).
Fig. 9. Cavitation erosion average depth versus time on AL7075 resulting from a DyNaJETS nozzle cavitation at different nozzle pressures (jet velocities) shown in log-log scales. The solid lines are analytical curves from the mathematical erosion model shown in Eq. (6). The almost horizontal initial 2 ksi dots correspond to the incubation period. Normalized standard deviation or error in expressing the erosion data with Eq. (6).
Fig. 10. Scaling of the characteristic erosion depth, h* (left) and the characteristic time, t* (right) with the cavitating jet nozzle pressure. Similarly, DyNaJETs® cavitating jets erosion tests were con- ducted with a 5000 psi jet for the same materials presented in Fig. 11 for G32. The cavitating jet results are shown in Fig. 13. Here again, all of the data are also relatively very well fitted with the mathematical expression (6). Fig. 14 shows the normalized
Fig. 10. Scaling of the characteristic erosion depth, h* (left) and the characteristic time, t* (right) with the cavitating jet nozzle pressure. Similarly, DyNaJETs® cavitating jets erosion tests were con- ducted with a 5000 psi jet for the same materials presented in Fig. 11 for G32. The cavitating jet results are shown in Fig. 13. Here again, all of the data are also relatively very well fitted with the mathematical expression (6). Fig. 14 shows the normalized
Parameters of the erosion mathematical model and characteristic erosion rates fo! the different materials tested with G32 ultrasonic tests. The materials are orderec by increasing value of the characteristic erosion depth rate.
Parameters of the erosion mathematical model and characteristic erosion rates fo! the different materials tested with G32 ultrasonic tests. The materials are orderec by increasing value of the characteristic erosion depth rate.
Fig. 12. Curves of the normalized mass loss versus normalized time. m* is the char- acteristic mass loss. All curves start from the origin, but for the same physical time, the tested materials reached different erosion stages. Tables 3 and 4 show the numerical coefficients used to fit the erosion data of the different materials tested by the G32 method
Fig. 12. Curves of the normalized mass loss versus normalized time. m* is the char- acteristic mass loss. All curves start from the origin, but for the same physical time, the tested materials reached different erosion stages. Tables 3 and 4 show the numerical coefficients used to fit the erosion data of the different materials tested by the G32 method
Fig. 13. Mean depth of erosion (based on mass loss) versus time curves obtained from a 5000 psi jet cavitation and curve fits of the data to the mathematical model shown in Eq. (6).
Fig. 13. Mean depth of erosion (based on mass loss) versus time curves obtained from a 5000 psi jet cavitation and curve fits of the data to the mathematical model shown in Eq. (6).
Parameters of the erosion mathematical model and characteristic erosion rates for the different materials tested with 5000 psi DynaJets® cavitating jet tests. The materials are ordered by increasing value of the characteristic erosion depth rate.
Parameters of the erosion mathematical model and characteristic erosion rates for the different materials tested with 5000 psi DynaJets® cavitating jet tests. The materials are ordered by increasing value of the characteristic erosion depth rate.
Comparison of erosion rates between G32 tests and 5000 psi cavitating jet erosion tests. Materials are presented ranked by the jet erosion results. Table 5 and the 5000 psi jet cavitation. In these tables, the materials are listed in the order of increasing characteristic erosion rate. The rankings by the two test methods in Tables 3 and 4 agree in general, but a couple of materials did not rank the same way. For example, HY80 was more resistant than SS 316 in G32 tests, but the order reversed in the 5000 psi cavitating jet tests. From the observed ero- sion rates of the two test methods, it is obvious that the cavitation field of a 5000 psi jet is much more intense and erosive than the cavitation field generated in G32 ultrasonic tests. This tells that, rel- ative to SS 316, HY80 has greater resistance in a weaker cavitation field but is less resistant in an intense cavitation field. Comparing NAB and LTCSS is also interesting. The LTCSS shows higher ero- sion resistance than NAB in the weaker cavitation field of the G32 test, but not in the intense cavitation field of 5000 psi jet cavitation test. These tell that the material erosion response of some materials depends on the intensity of the cavitation field.
Comparison of erosion rates between G32 tests and 5000 psi cavitating jet erosion tests. Materials are presented ranked by the jet erosion results. Table 5 and the 5000 psi jet cavitation. In these tables, the materials are listed in the order of increasing characteristic erosion rate. The rankings by the two test methods in Tables 3 and 4 agree in general, but a couple of materials did not rank the same way. For example, HY80 was more resistant than SS 316 in G32 tests, but the order reversed in the 5000 psi cavitating jet tests. From the observed ero- sion rates of the two test methods, it is obvious that the cavitation field of a 5000 psi jet is much more intense and erosive than the cavitation field generated in G32 ultrasonic tests. This tells that, rel- ative to SS 316, HY80 has greater resistance in a weaker cavitation field but is less resistant in an intense cavitation field. Comparing NAB and LTCSS is also interesting. The LTCSS shows higher ero- sion resistance than NAB in the weaker cavitation field of the G32 test, but not in the intense cavitation field of 5000 psi jet cavitation test. These tell that the material erosion response of some materials depends on the intensity of the cavitation field.
Fig. 14. Curves of the normalized erosion depth versus normalized time for alu- minum, NAB, and stainless steel tested with cavitating jets at various pressures. Curves are the mathematical expressions (6) and the symbols are the measured data points.
Fig. 14. Curves of the normalized erosion depth versus normalized time for alu- minum, NAB, and stainless steel tested with cavitating jets at various pressures. Curves are the mathematical expressions (6) and the symbols are the measured data points.
Related topics:
Materials EngineeringMechanical Engineering
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved