Technology and
Equipment for Ultrasonic Impact Treatment (UIT/UP)
Origins and Contribution of Our Team
The ultrasonic impact treatment (UIT) is one of the
new and promising processes for fatigue life improvement of welded elements and
structures [1-7]. In most industrial applications this process is also known as
ultrasonic peening (UP) [8-12]. The beneficial effect of UIT/UP is achieved
mainly by relieving of harmful tensile residual stresses and introducing of
compressive residual stresses into surface layers of materials, decreasing of
stress concentration in weld toe zones and enhancement of mechanical properties
of the surface layers of the material. The fatigue testing of welded specimens
showed that the UP is the most efficient improvement treatment when compared
with such traditional techniques as grinding, TIG-dressing, heat treatment,
hammer peening, shot peening and application of LTT electrodes [4, 6].
The UP technique is based on the combined effect of
high frequency impacts of special strikers and ultrasonic oscillations in
treated material. The developed system for UP treatment (total weight - 11 kg)
includes an ultrasonic transducer, a generator and a laptop (optional item)
with software for optimum application of UP - maximum possible increase in
fatigue life of parts and welded elements with minimum cost, labor and power
consumption. In general, the basic UP system shown in Figure 1 could be used
for treatment of weld toe or welds and larger surface areas if necessary.
Figure 1. Basic ultrasonic peening system for fatigue
life improvement of welded elements and structures [6]
The most recent
design of the UP equipment is based on "Power on Demand" (PoD)
concept. Using the PoD concept, the power and other operating parameters of the
UP equipment are adjusted to produce the necessary changes in residual
stresses, stress concentration and mechanical properties of the surface layers
of materials to attain the maximum possible increase in fatigue life of welded
elements and structures.
The effects of different improvement treatments,
including the UP treatment, on the fatigue life of welded elements depend on
the mechanical properties of used material, the type of welded joints,
parameters of cyclic loading and other factors. For effective application of
the UP, depending on the above-mentioned factors, a software package for
Optimum Application of UP was developed that is based on original predictive
model. In the optimum application, a maximum possible increase in fatigue life
of welded elements with minimum time/labor/cost is thought.
The developed technology and computerized complex for
UP were successfully applied for increasing of the fatigue life of welded
elements, elimination of distortions caused by welding and other technological
processes, relieving of residual stress, increasing of the hardness of the
surface of materials and surface nanocrystallization. The areas/industries where the UP was applied successfully
include: Railway and
Highway
Bridges, Construction
equipment, Shipbuilding, Mining, Automotive and Aerospace to name a few.
The UIT/UP equipment is based on known from the 40’s
of last century technical solutions of using working heads with freely movable
strikers for hammer peening. At that time and later, a number of different tools
based on using freely movable strikers were developed for impact treatment of materials
and welded elements by using pneumatic [13, 14] and ultrasonic [15-21]
equipment. The more effective impact treatment is provided when the strikers
are not connected to the tip of actuator but could move freely between the
actuator and the treated material. The tools for impact treatment of materials
and welded elements with the freely movable strikers (12 on Figure 1a and 21 on
Figure 1b) that are mounted in a holder are shown in Figure 2. In the case of
so-called intermediate element-striker(s) a force of only 30 - 50 N is required
for treatment of materials.
Figure 3 shows a standard set of easy replaceable
working heads with freely movable strikers for different applications of UP.
The UP technique is based on
the combined effect of the high frequency impacts of the special strikers and
ultrasonic oscillations in treated material. Some specific features of the
ultrasonic impact treatment of metals are described in [16], where it is shown that the operational frequency of the
transducer and the frequency of the intermediate element-striker are not the same.
Figure 2. Sectional view through tools with freely
movable strikers (12 on Figure 1a and 21 on Figure 1b)
for surface impact treatment: a –
described in [13], b – described in [14]
Figure 3. A set of interchangeable working heads for UIT/UP [6]
During the ultrasonic treatment, the striker
oscillates in the small gap between the end of the ultrasonic transducer and
the treated specimen, impacting the treated area [15-18]. This kind of high
frequency movements/impacts in combination with high frequency oscillations
induced in the treated material is typically called the ultrasonic impact.
There are a number of effects of ultrasound on metals
that are typically considered: acoustic softening, acoustic hardening, acoustic
heating, etc. In the first of these (acoustic softening that is
also known as acoustic-plasticity effect), the acoustic irradiation reduces the
level of stress necessary for plastic deformation. In general, the effect of
ultrasound on the mechanical behavior could be compared with the effect of
heating on a material. The difference is that acoustic softening takes place
immediately when a metal is subjected to ultrasonic irradiation. Also,
relatively low-amplitude ultrasonic waves leave no residual effects on the
physical properties of metals after acoustic irradiation is stopped [22].
The ultrasonic transducer oscillates at a high
frequency, with 20-30 kHz being typical. The ultrasonic transducer may be based
on either piezoelectric or magnetostrictive technology. Whichever technology is
used, the output end of the transducer will oscillate, typically with amplitude
of 20 – 40 mm. During the oscillations, the transducer tip will
impact the striker(s) at different stages in the oscillation cycle. The
striker(s) will, in turn, impact the treated surface. The impact results in
plastic deformation of the surface layers of the material. These impacts,
repeated hundreds to thousands of times per second, in combination with high
frequency oscillation induced in the treated material result in a number of
beneficial effects of UP.
The UP is an effective way for relieving of harmful
tensile residual stresses and introducing of beneficial compressive residual
stresses in surface layers of parts and welded elements. The mechanism of
residual stress redistribution is connected mainly with two factors. At a
high-frequency impact loading, oscillations with a complex frequency mode
spectrum propagate in a treated element. The nature of this spectrum depends on
the frequency of ultrasonic transducer, mass, quantity and form of strikers and
also on the geometry of the treated element. These oscillations lead to
lowering of residual welding stresses. The second and the more important
factor, at least for fatigue improvement, is surface plastic deformation that
leads to introduction of the beneficial compressive residual stresses.
In the fatigue improvement, the beneficial effect is achieved mainly by
introducing of the compressive residual stresses into surface layers of metals
and alloys, decrease in stress concentration in weld toe zones and the
enhancement of the mechanical properties of the surface layer of the material.
The schematic view of the cross section of material/part improved by UP is
shown on Figure 4 with the attained distribution of the stresses after the UP.
The description of the UP benefits is presented in Table 1.
Figure 4. Schematic view of the cross section of
material/part improved by Ultrasonic Peening [11]
Table 1. Zones of Material/Part Improved by Ultrasonic
Peening [11]
(see Figure 3 for illustration of the zones)
Figure 5 illustrates the concept of the fatigue life improvement of welded elements by UP. In case of welded elements, it is enough to treat only the weld
toe zone – the zone of transition from base metal to the weld, for a
significant increase of fatigue life of welded elements. The produced by UP so-called
“groove”, characterized by certain geometrical parameters is shown in Figures 5
and 6 [8, 11].
Figure 5. Profile of weld toe improved by Ultrasonic
Peening [11]
Figure 6. The view of the butt welds in as-welded condition (left side sample) and after application of UP (right side sample) [8]
It should be noted that the so-called “groove”
produced by UIT/UP and its efficiency for fatigue improvement of welded elements
was for the first time described in literature in 1989 [1]. Figure 6 shows the photo
published in [1] of the “groove” that was produced by ultrasonic impact
treatment of the end of welded stiffener that is critical from the fatigue
point of view of the considered welded element. SINTEC’s leading scientist Dr.
Kudryavtsev was actively involved in the development of UIT/UP technology for
fatigue improvement of welded elements and structures and in studies of the “groove”
and its influence on the fatigue life of welded joints in 80s and 90s of the
last century [1-5].
Figure 7. Photo of the “groove” produced by ultrasonic
impact treatment of the end of welded stiffener published in 1989 [1]:
1 – welded stiffener, 2 - base plate, 3 – strikers, 4
– “groove” produced by UIT/UP
There are two general types of ultrasonic transducers
which can be used for UP: magnetostrictive and piezoelectric. Both accomplish
the same task of converting alternating electrical energy to oscillating
mechanical energy but do it in a different way. In magnetostrictive transducer
the alternating electrical energy from the ultrasonic generator is first
converted into an alternating magnetic field through the use of a wire coil.
The alternating magnetic field is then used to induce mechanical vibrations at
ultrasonic frequency in resonant strips of magnetostrictive material. Magnetostrictive transducers are generally less
efficient than the piezoelectric ones.
This is due primarily to the fact that
the magnetostrictive transducer requires a dual energy conversion from
electrical to magnetic and then from magnetic to mechanical. Some efficiency is
lost in each conversion. Magnetic hysteresis effects also detract from the
efficiency of the magnetostrictive transducer. In addition, the
magnetostrictive transducer for UP needs forced water-cooling.
Piezoelectric transducers convert the alternating electrical energy directly to mechanical energy through the piezoelectric effect. Today's piezoelectric transducers incorporate stronger, more efficient and highly stable ceramic piezoelectric materials, which can operate under the temperature and stress conditions, making them reliable and allowing to reduce the energy costs for operation by as much as 60%. Due to the high energy efficiency of piezoelectric transducers, the effect in fatigue life improvement by UP is practically the same by using of the magnetostrictive transducer with power consumption of 1000 Watts and piezoceramic transducers with power consumption of only 300-600 Watts [11]. A basic UP system that is based on piezoceramic transducer is shown in Figure 1.
Industrial Applications of UP
The UP could be effectively applied for fatigue life
improvement during manufacturing, rehabilitation and repair of welded elements
and structures. The UP technology and equipment were successfully applied in
different industrial projects for rehabilitation and weld repair of parts and
welded elements. The areas/industries where the UP
was applied successfully include: Railway and
Highway
Bridges,
Construction Equipment, Shipbuilding, Mining, Automotive and Aerospace.
An example of application of UP for repair and
rehabilitation of welded elements subjected to fatigue loading in mining
industry is shown in Figure 7. Around
300 meters of welds, critical from fatigue point of view, were UP treated to
provide improved fatigue performance of large grinding mills.
Figure 8. Application of UP for rehabilitation of welded elements of a large grinding mill
Based on the fatigue data and the solution described in [10], the UP was also applied during the rehabilitation of welded elements of a highway bridge over the Ohio River in the USA.
The bridge was
constructed about 30 years ago. The welded details of the bridge did not have
macroscopic fatigue cracks. The motivation for application of the UP for
fatigue life improvement of this bridge was the fatigue cracking in welded
elements and failure of one of the spans of another bridge of approximately the
same age and design. The stages of preparation for UP treatment of the bridge
and the process of UP treatment of one of the welded vertical stiffeners are
shown in Figures 8 and 9. More than two thousand and five hundred welded details
of the bridge structure that were considered to be fatigue critical were UP
treated.
Figure 9. Ultrasonic Peening of a welded bridge: preparation for UP
treatment (2 UP systems/lifts)
Figure 10. Ultrasonic Peening of a welded bridge: UP of the end of one of welded vertical stiffeners
Our Historical
1. Y. Kudryavtsev, V. Korshun and A. Kuzmenko.
Improvement of Fatigue Life of Welded Joints by Ultrasonic Impact Treatment. Paton
Welding Journal. 1989. No. 7. p. 24-28.
2. V. Trufyakov, P. Mikheev, Y. Kudryavtsev and D. Reznik. Ultrasonic
Impact Peening Treatment of Welds and Its Effect on Fatigue Resistance in Air
and Seawater. Proceedings of the
Offshore Technology Conference. OTC 7280. 1993. p. 183-193.
3. Y. Kudryavtsev, P. Mikheev and V. Korshun.
Influence of Plastic Deformation and Residual Stresses Created by Ultrasonic
Impact Treatment on Fatigue Strength of Welded Joints. Paton Welding
Journal. 1995. No. 12. p. 3-7
4. V. Trufyakov, P. Mikheev and Y. Kudryavtsev.
Fatigue Strength of Welded Structures. Residual Stresses and Improvement
Treatments. Harwood Academic Publishers GmbH.
London.
1995. 100 p.
5. V. Trufiakov, P. Mikheev, Y. Kudryavtsev and E.
Statnikov. Ultrasonic Impact Treatment of Welded Joints. International
Institute of Welding. IIW Document XIII-1609-95. 1995.
Our recent
6. Y. Kudryavtsev and J. Kleiman. Increasing Fatigue Strength
of Welded Elements and Structures by Ultrasonic Impact Treatment. International
Institute of Welding. IIW Document XIII-2318-10.
2010.
7. Y. Kudryavtsev and J. Kleiman. Fatigue Improvement
of Welded Elements and Structures by Ultrasonic Impact Treatment (UIT/UP). International
Institute of Welding. IIW Document
XIII-2276-09. 2009.
8. Y. Kudryavtsev, J. Kleiman and Y. Iwamura. Fatigue
Improvement of HSS Welded Elements by Ultrasonic Peening. Proceedings of the International Conference on High Strength Steels for
Hydropower Plants, July 20-22, 2009.
Takasaki,
Japan.
9. Y. Kudryavtsev, J. Kleiman, A. Lugovskoy et al. Fatigue Life
Improvement of Tubular Welded Joints by Ultrasonic Peening. International
Institute of Welding. IIW Document XIII-2117-06. 2006. 24 p.
10. Y. Kudryavtsev, J. Kleiman, A. Lugovskoy et
al. Rehabilitation and Repair
of Welded Elements and Structures by Ultrasonic Peening. International
Institute of Welding. IIW Document XIII-2076-05. 2005. 13 p.
11. Y. Kudryavtsev, J. Kleiman, L. Lobanov et al. Fatigue
Life Improvement of Welded Elements by Ultrasonic Peening. International
Institute of Welding. IIW Document XIII-2010-04. 2004. 20 p.
12. Patent of USA # 6467321. 2002. Device for Ultrasonic Peening of Metals. George I.
Prokopenko, Jacob I. Kleiman, Oleksandr I. Kozlov, Pavel P. Micheev, Vitaly V.
Knysh and Yuriy F. Kudryavtsev.
Origins of UIT/UP Technology
13. Patent of
USA No. 2,356,314. 1944. Scaling
Tool. Reo D. Grey and James R. Denison.
14. Patent of
USA No. 3,349,461. 1967. Descaling
Tool. Joseph F. Niedzwiecki.
15. Krilov N. A., Polishchuk A. M. Using
of ultrasonic apparatus for metal structure stabilization. Physical
background of industrial using of ultrasound. Part 1. LDNTP.
Leningrad..- P. 70-79. 1970.
16.
Patent of
USA
No. 3,609,851. 1971. Metal Working Apparatus and Process. Robert C. McMaster
and Charles C. Libby.
17. Patent of
USA No. 3,595,325. 1971. Intermediary
Impact Device. Charles C. Libby and William J. White.
18. C. Feng and K. Graff. Impact of a
Spherical Tool against a Sonic Transmission Line. The Journal of the
Acoustical Society of
America.
Volume 52, Number 1 (Part 2), 1972. pp. 254-259.
19. I. Polozky, A. Nedoseka, G. Prokopenko et al. Relieving of
welding residual stresses by ultrasonic treatment. The Paton Welding Journal.
1974. pp. 74-75.
20. Author’s Certificate (USSR) # 472782. 1975. Ultrasonic head for
strain hardening and relaxation treatment. E. Statnikov, L. Zhuravlev, A.
Alexeyev, Yu. Bobylev, E. Shevtsov, V. Sokolenko and V. Kulikov.
21. Author’s Certificate (USSR) # 601143. 1978. Ultrasonic multiple-strikers device. G. Prokopenko and
V. Krivko.
22. B. Langenecker. Effects of Ultrasound on
Deformation Characteristics of Metals. IEEE
Transactions on Sonics and Ultrasonics. Vol. SU-13, No. 1, March 1966, pp. 1-8.
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