New design of closed loop servo hydraulic device for thermal fatigue testing
The paper presents the proposal of new design of closed loop servo hydraulic device for fatigue testing, induced by mechanical loading spectrum and variation of temperature. In addition to easier testing performance and more accurate results, the use of this solution offers significant saving in tes...
Saved in:
| Published in: | Надійність і довговічність машин і споруд |
|---|---|
| Date: | 2009 |
| Main Authors: | , , , |
| Format: | Article |
| Language: | English |
| Published: |
Інститут проблем міцності ім. Г.С. Писаренка НАН України
2009
|
| Online Access: | https://nasplib.isofts.kiev.ua/handle/123456789/36909 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Cite this: | New design of closed loop servo hydraulic device for thermal fatigue testing / M. Zrilic, T. Vuherer, Lj. Milovic, S. Sedmak // Надійність і довговічність машин і споруд. — 2009. — Вип. 32. — С. 35-40. — Бібліогр.: 5 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860232911830122496 |
|---|---|
| author | Zrilic, M. Vuherer, T. Milovic, Lj. Sedmak, S. |
| author_facet | Zrilic, M. Vuherer, T. Milovic, Lj. Sedmak, S. |
| citation_txt | New design of closed loop servo hydraulic device for thermal fatigue testing / M. Zrilic, T. Vuherer, Lj. Milovic, S. Sedmak // Надійність і довговічність машин і споруд. — 2009. — Вип. 32. — С. 35-40. — Бібліогр.: 5 назв. — англ. |
| collection | DSpace DC |
| container_title | Надійність і довговічність машин і споруд |
| description | The paper presents the proposal of new design of closed loop servo hydraulic device for fatigue testing, induced by mechanical loading spectrum and variation of temperature. In addition to easier testing performance and more accurate results, the use of this solution offers significant saving in test duration and energy consummation.
Представлено новое серво-гидравлического устройство с замкнутым контуром для усталостных испытаний в широком спектре механических нагрузок и при высоких и низких температурах. Наряду с более доступными испытаниями, большей производительностью и более точными результатами предлагается значительная экономия продолжительности испытания и потребляемой энергии.
Представлено новий серво-гідравлічний пристрій з замкнутим контуром для втомних випробувань в широкому спектрі механічних навантажень і при високих і низьких температурах. Поряд з більш доступними випробуваннями, більшою продуктивністю і більш точними результатами пропонується значна економія тривалості випробування і споживаної енергії.
|
| first_indexed | 2025-12-07T18:22:04Z |
| format | Article |
| fulltext |
ISSN 0206-3131. Надійність і довговічність машин і споруд, 2009. Вип. 32 35
УДК 539.4
2009 M. Zrilicа, T. Vuhererb, Lj. Milovica, S. Sedmaka
а Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia
b Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia
NEW DESIGN OF CLOSED LOOP SERVO HYDRAULIC DEVICE
FOR THERMAL FATIGUE TESTING
The paper presents the proposal of new design of closed loop servo hydraulic device for
fatigue testing, induced by mechanical loading spectrum and variation of temperature. In
addition to easier testing performance and more accurate results, the use of this solution
offers significant saving in test duration and energy consummation.
Keywords: fatigue testing, thermal fatigue, closed loop servo hydraulic testing
device, load spectrum simulation.
Introduction. It is of utmost importance to have the data of material
response to load and environment in heavy duty equipment like nuclear and
thermal power plants, or aircraft structures, which are exposed to variable
mechanical loading of high intensity, combined with the thermal loading caused by
variation in temperature. In these structures material is exposed to a very complex
operating condition due to simultaneous effects high cycle loading and of different
thermal loading due to different operating temperatures. Safe service and
economical operation of thermally loaded structures require continuous monitoring
of loaded material, but initial data about materials properties are precondition for
successful design and use. For that, basic mechanical properties of material
together with material response to complex operating conditions, consisting of high
variable mechanical loading and thermal effects at different temperatures, varying
in random broad limits, which can be experienced in service, present continuous
problem for safe service and extended life of equipment.
Load spectrum. It is not an easy task to define and simulate fatigue loading
spectrum combined with thermal fatigue. In fact, two interactive effects have to be
recognized, monitored and analyzed, what is very complicated due to simultaneous
changes of material properties by variable mechanical loading and in the same time
by temperature variation. When these effects are individually and separately
considered in experiments, the only way to get sufficiently accurate data is to
model temperature effect on mechanical cycle fatigue. But only valid and fully
acceptable material response is to simulate real operating conditions in unique
spectrum as close as possible, and in this way to obtained valid results of loading
and of temperature effects in the shortest time period. However, it is difficult to
simulate even separately high cycle fatigue and temperature variation.
The simulation of loading spectrum in cycle fatigue has been solved
successfully by introduction of closed loop testing equipment in 1950 [1]. Much
more difficult is the simulation of thermal fatigue due to very sharp gradient of
temperature change rate because this gradient is also affected with the thermal
capacity of tested structure [2]. Next complication is connected with material
ISSN 0206-3131. Надійність і довговічність машин і споруд, 2009. Вип. 32 36
properties change caused by variation of temperature. This problem is partly
considered and solved by small sized specimens heated by induction and fast
cooled by liquid gases [3], or simulating real structures and application of fluids
heated to the proper temperatures using one or several heat sources [4, 5]. This
approach exhibited excellent results of solution for streaming in the pipelines of
nuclear thermal equipment.
Studying the problems of fatigue at variable temperatures authors have
notice the possibility to apply some very interesting sophisticated solution. The
solution can be applied to mechanical engineering equipment, but also it can be
used to model testing of civil engineering products. In general, mechanical
equipment is typically very compact, but with possible sharp change of temperature
gradient, whereas civil engineering structures are of higher thermal capacity, with
slower change of temperature gradient.
In the case of equipment and structures in mechanical and civil engineering
the problems connected with fatigue at temperature variation requires somewhat
different approach, but following the same approach and general solution.
Proposed design of closed loop servo hydraulic device for fatigue testing.
In Figure 1 servo hydraulic device for fatigue testing by variable loading at high
and low temperature is schematically presented.
Fig. 1. Servo hydraulic device designed for fatigue testing at two different temperatures: 1 –
upper servo hydraulic cylinder (actuator); 2 – servo valve; 3 – piston; 4 – load cell; 5 –
extending rod, upper; 6 – upper chamber; 7 – structural specimen (sample); 8 – Insulation
wall; 9 – lower chamber; 10 – extending rod, lower; 11 – linear variable displacement
transducer LVDT); 12 – lower servo hydraulic cylinder (actuator).
ISSN 0206-3131. Надійність і довговічність машин і споруд, 2009. Вип. 32 37
Basically, the device consists from two chambers, upper (6), and lower (9),
and two actuators - servo hydraulic cylinders, upper (1), and lower (12), acting in
opposite directions, which form hydraulic closed loop. Upper chambers (6) is
designed for high temperatures, and the lower one (9) for low temperatures (in this
example). The chambers are separated by insulation wall (8), which can be
performed in the form of two movable screens, or, in the case of specimens (7) of
round cross section in the form of photographic lens diaphragm, depending on
tested specimen shape and size. In operating condition this separation wall serves
as a fine sealant of piston (3) hole, passing, in this case, through lower chamber.
Upper actuator (1) operates in load control regime, and it is connected to load cell
(4), involved to measure load. Because of dimension of load cell it is necessary to
involve upper extending rod (5) between it and tested sample (7), which should
assure the sealing at the entrance to the upper chambers. This rod must have
sufficient length to enable an easy specimen displacement from one chamber to the
other, and also to have diameter of cross section with tolerance limits assuring
acceptable sealing level. However, this is the requirement only for upper rod (5)
because lower rod (10) always operates in stroke control and is connected with
linear variable displacement transducer – LVDT (11). Anyhow, LVDT is of
inductive type, built-in into actuator, and for that does not induce any trouble and
special requirements. Lower actuator (12) serves to bring the specimen in requested
position (in upper or lower chamber). In presented stage the control of upper
cylinder is positioned to zero loading (0 kN). This enabled to move freely the
specimen from one chamber in another one, the duration of this operation is only
few seconds. This very short time period of specimen transfer from low
temperature chamber to high temperature chamber, and vice verse, is a valuable
advantage of proposed solution.
It is to underline that this device can be constructed very easy at reasonable
low expanses, since no heavy frame with the cross head is necessary, as this is the
case with standard closed loop servo hydraulic machines in which hydraulic lift
together with hydraulic lock are required for positioning. In fact, for new designed
device it is sufficient to construct stiff structure on which the actuators and twofold
chamber should be fixed following here presented instructions. Laboratories having
multi channel close loop systems for testing of real structures or their models have
to assure (to buy or to construct) only twofold chamber requested by testing
procedure, that means to fulfill the dimensional specification and temperature
testing interval. In addition, proposed solution offers significant saving in testing
time and energy consummation.
Anyhow, for larger specimens the chambers of high volume are required,
and it is clear that in this case that very fast change in chamber temperature is not
possible. The second problem is quantum of energy which should be consumed in
each temperature spectrum change.
Function of closed loop servo hydraulic device for fatigue testing at
different temperatures. Based on the laboratory experience in performing load
spectra experiments, including those at different temperatures, the authors
envisaged the idea how to improve load spectra testing at different temperatures.
The principle of device function is explained on fatigue testing with load spectra
applying to structural specimen (sample), at high and low temperatures. This is
presented in Fig. 2.
ISSN 0206-3131. Надійність і довговічність машин і споруд, 2009. Вип. 32 38
a) b) c)
Fig. 2. Function of the closed loop servo hydraulic testing device with load control spectra
of the main actuator and positioning of specimen: a) application of load spectrums in cold
chamber (at low temperature); b) the procedure of changing chamber for the testing at high
temperature; c) performance of testing under load spectrums at high temperature.
From the upper side in the upper chamber (6) a main cylinder is introduced,
which operates in load control, except the phase of specimen positioning, fixing
and removing. This means that test load spectrum is induced only through this
actuator. From the lower side, in lower chamber (9) is introduced positioning
cylinder, operating in stroke control. Lower, positioning cylinder has a function to
select proper position for the specimen (in upper or lower chamber), that enable
specimen to be exposed to high or low temperature.
Testing procedure from the positioning of specimen till its removal from the
device can be described as follows. The door of lower chamber (9) are opened,
both cylinders, upper (1), and lower (12) are set to stroke control to position
convenient for specimen introducing. The specimen is fixed in corresponding
clamps. Fine positioning is possible by switching-on upper cylinder (1) to be in
load controlled, setting to nil loading (0 N). By this step in testing procedure lower
cylinder can bring the specimen in required position, with no danger to load it.
Now, the temperatures in both chambers can be set to test level. Only when the
specimen is heated to the test temperature through the cross section, the
corresponding load spectrum may be introduced by activating the main actuator
(1). During this operation the positioning cylinder held the specimen in a constant
position (Fig. 2,a). After this phase of testing it is necessary to bring the specimen
in the chamber for high temperature. Insulation wall (8) is opened as necessary to
put through loosely the specimens and appliances, Fig. 2,b. The form of big
opening should correspond to specimen transverse profile. For the zero load settled
ISSN 0206-3131. Надійність і довговічність машин і споруд, 2009. Вип. 32 39
(0 N) positioning cylinder (12) pushes the specimen in the upper chamber (6) to
required position. In the instance when specimen passed insulation wall zone, the
wall closes assuring fine sealing between the chambers. Depending on specimen
size, the phase of temperature spectrum change lasts few seconds. Positioning
cylinder bring the specimen in required position and held it in this position,
Fig. 2,c. The main cylinder starts to convey corresponding load spectrum when the
specified temperature is reached, i.e. when test program requirements are satisfied.
The described cycle will be repeated with the new specimen.
It is to underline the capacity of the device in recording and loading. Two
types of records are presented in Fig. 2, the change of load F (in kN) vs. time t (in
s), which corresponds to upper actuator, and stroke displacement s (in mm) vs. time
t (in s), corresponding to lower actuator. Upper actuator convey load spectrum,
previously defined experimentally in real service condition of a structure for
corresponding operating temperature. For that this actuator is active only in
variable load testing performance by load spectrum (Fig. 2,a, at low temperature,
Fig. 2,c, at high temperature). In these testing conditions lower actuator is inactive,
that is its function is just to hold the specimen in selected position indicated at
corresponding level. In Fig. 2,b lower actuator operates in stroke control,
performing movement from lower to upper level, whereas upper actuator is silent,
held at zero load.
Conclusions. The basic advantage which can be gained applying proposed
design of device is to shift the specimen form one temperature to another in simple
way and in very short time. This will allow to shorten the time for testing, on one
hand, but also to reduce the expanses for testing, saving required energy.
However, proposed solution is limited by the size of specimen, and there is
probably an optimum for specimen size in this application.
Acknowledgements. The authors acknowledge the financial support
obtained for this development from the Ministry of Science and Technological
Development of Republic of Serbia by funding the project number TR 14014.
Резюме
Представлено новое серво-гидравлического устройство с замкнутым
контуром для усталостных испытаний в широком спектре механических
нагрузок и при высоких и низких температурах. Наряду с более доступными
испытаниями, большей производительностью и более точными результатами
предлагается значительная экономия продолжительности испытания и
потребляемой энергии.
Ключевые слова: испытания на усталость, термическая усталость, серво-
гидравлическое устройство с замкнутым контуром, моделирование спектра
нагрузок.
Резюме
Представлено новий серво-гідравлічний пристрій з замкнутим контуром для
втомних випробувань в широкому спектрі механічних навантажень і при
ISSN 0206-3131. Надійність і довговічність машин і споруд, 2009. Вип. 32 40
високих і низьких температурах. Поряд з більш доступними випробуваннями,
більшою продуктивністю і більш точними результатами пропонується значна
економія тривалості випробування і споживаної енергії.
Ключові слова: втомні випробування, термічна втома, серво-гідравлічний
пристрій з замкнутим контуром, моделювання спектру навантажень.
1. Course in Machine Design, Fatigue I, Machine Design, Computational
Mechanics – AAU, Esbjerg.
2. Blackford J. Engineering of Superalloys,
http://www.cmse.ed.ac.uk/MSE3/Topics/MSE-nonferrous-2.pdf.
3. Equipment for high rate thermal fatigue testing, original construction, G. S.
Pisarenko Institute for Problems of Strength.
4. Ravindranath V. at all. Thermal Fatigue of High-Heat-Load Synchrotron
Components – MEDSI, 2008.
5. Prasser H-M. Laboratory of Thermal Hydraulics. General Overview – Paul
Scherrer Institut, 2008.
Поступила 21.05.2009
|
| id | nasplib_isofts_kiev_ua-123456789-36909 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0206-3131 |
| language | English |
| last_indexed | 2025-12-07T18:22:04Z |
| publishDate | 2009 |
| publisher | Інститут проблем міцності ім. Г.С. Писаренка НАН України |
| record_format | dspace |
| spelling | Zrilic, M. Vuherer, T. Milovic, Lj. Sedmak, S. 2012-08-05T07:02:12Z 2012-08-05T07:02:12Z 2009 New design of closed loop servo hydraulic device for thermal fatigue testing / M. Zrilic, T. Vuherer, Lj. Milovic, S. Sedmak // Надійність і довговічність машин і споруд. — 2009. — Вип. 32. — С. 35-40. — Бібліогр.: 5 назв. — англ. 0206-3131 https://nasplib.isofts.kiev.ua/handle/123456789/36909 539.4 The paper presents the proposal of new design of closed loop servo hydraulic device for fatigue testing, induced by mechanical loading spectrum and variation of temperature. In addition to easier testing performance and more accurate results, the use of this solution offers significant saving in test duration and energy consummation. Представлено новое серво-гидравлического устройство с замкнутым контуром для усталостных испытаний в широком спектре механических нагрузок и при высоких и низких температурах. Наряду с более доступными испытаниями, большей производительностью и более точными результатами предлагается значительная экономия продолжительности испытания и потребляемой энергии. Представлено новий серво-гідравлічний пристрій з замкнутим контуром для втомних випробувань в широкому спектрі механічних навантажень і при високих і низьких температурах. Поряд з більш доступними випробуваннями, більшою продуктивністю і більш точними результатами пропонується значна економія тривалості випробування і споживаної енергії. The authors acknowledge the financial support obtained for this development from the Ministry of Science and Technological Development of Republic of Serbia by funding the project number TR 14014. en Інститут проблем міцності ім. Г.С. Писаренка НАН України Надійність і довговічність машин і споруд New design of closed loop servo hydraulic device for thermal fatigue testing Новое серво-гидравлическое устройство с замкнутым контуром для термических усталостных испытаний Article published earlier |
| spellingShingle | New design of closed loop servo hydraulic device for thermal fatigue testing Zrilic, M. Vuherer, T. Milovic, Lj. Sedmak, S. |
| title | New design of closed loop servo hydraulic device for thermal fatigue testing |
| title_alt | Новое серво-гидравлическое устройство с замкнутым контуром для термических усталостных испытаний |
| title_full | New design of closed loop servo hydraulic device for thermal fatigue testing |
| title_fullStr | New design of closed loop servo hydraulic device for thermal fatigue testing |
| title_full_unstemmed | New design of closed loop servo hydraulic device for thermal fatigue testing |
| title_short | New design of closed loop servo hydraulic device for thermal fatigue testing |
| title_sort | new design of closed loop servo hydraulic device for thermal fatigue testing |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/36909 |
| work_keys_str_mv | AT zrilicm newdesignofclosedloopservohydraulicdeviceforthermalfatiguetesting AT vuherert newdesignofclosedloopservohydraulicdeviceforthermalfatiguetesting AT miloviclj newdesignofclosedloopservohydraulicdeviceforthermalfatiguetesting AT sedmaks newdesignofclosedloopservohydraulicdeviceforthermalfatiguetesting AT zrilicm novoeservogidravličeskoeustroistvoszamknutymkonturomdlâtermičeskihustalostnyhispytanii AT vuherert novoeservogidravličeskoeustroistvoszamknutymkonturomdlâtermičeskihustalostnyhispytanii AT miloviclj novoeservogidravličeskoeustroistvoszamknutymkonturomdlâtermičeskihustalostnyhispytanii AT sedmaks novoeservogidravličeskoeustroistvoszamknutymkonturomdlâtermičeskihustalostnyhispytanii |