Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents
Исследовано влияние пенообразующих добавок гидрида титана TiH₂ и карбоната кальция CaCО₃ на энергопоглощение в пористых структурах с закрытыми ячейками на основе алюминиевого сплава А356. Образцы с двумя различными пористыми структурами были получены путем добавки TiH₂ и CaCО₃ в расплав алюминиевого...
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
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irk-123456789-1734822020-12-06T01:26:27Z Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents Movahedi, N. Mirbagheri, S.M.H. Научно-технический раздел Исследовано влияние пенообразующих добавок гидрида титана TiH₂ и карбоната кальция CaCО₃ на энергопоглощение в пористых структурах с закрытыми ячейками на основе алюминиевого сплава А356. Образцы с двумя различными пористыми структурами были получены путем добавки TiH₂ и CaCО₃ в расплав алюминиевого сплава А356 при температуре 700°С. Электронно-микроскопический анализ образцов показывает, что ячейки структур, полученных путем добавки CaCО₃, являются более мелкими и однородными, чем в случае добавки TiH₂. Механические характеристики пористых образцов определяли по данным испытания на одноосное сжатие. Установлено, что при 50%-ном уровне деформации энергопоглощение образцов, полученных путем добавки CaCО₃, на 100% выше такового образцов, полученных при добавке TiH₂. Досліджено вплив пінотвірних додатків гідриду титана TiH₂ і карбонату кальцію СаСО₃ на енергопоглинання у пористих структурах із закритими комірками на основі алюмінієвого сплаву. Зразки з двома різними пористими структурами отримано шляхом додатка TiH₂ і СаСО₃ у розплав алюмінієвого сплаву А356 за температури 700°С. Електронно-мікроскопічний аналіз зразків показав, що комірки структур, отриманих шляхом додатка СаСО₃, є більш мілкими й однорідними, ніж у випадку додатка TiH₂. Механічні характеристики пористих зразків визначали за даними випробувань на одновісний стиск. Установлено, що за 50%-ного рівня деформації енергопоглинання зразків, що отримані шляхом додатка СаСО₃, на 100% більше, ніж зразків, отриманих при додатку TiH₂. 2016 Article Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents / N. Movahedi, S.M.H. Mirbagheri // Проблемы прочности. — 2016. — № 3. — С. 128-134. — Бібліогр.: 9 назв. — англ. 0556-171X http://dspace.nbuv.gov.ua/handle/123456789/173482 539.4 en Проблемы прочности Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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Научно-технический раздел Научно-технический раздел |
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Научно-технический раздел Научно-технический раздел Movahedi, N. Mirbagheri, S.M.H. Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents Проблемы прочности |
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Исследовано влияние пенообразующих добавок гидрида титана TiH₂ и карбоната кальция CaCО₃ на энергопоглощение в пористых структурах с закрытыми ячейками на основе алюминиевого сплава А356. Образцы с двумя различными пористыми структурами были получены путем добавки TiH₂ и CaCО₃ в расплав алюминиевого сплава А356 при температуре 700°С. Электронно-микроскопический анализ образцов показывает, что ячейки структур, полученных путем добавки CaCО₃, являются более мелкими и однородными, чем в случае добавки TiH₂. Механические характеристики пористых образцов определяли по данным испытания на одноосное сжатие. Установлено, что при 50%-ном уровне деформации энергопоглощение образцов, полученных путем добавки CaCО₃, на 100% выше такового образцов, полученных при добавке TiH₂. |
| format |
Article |
| author |
Movahedi, N. Mirbagheri, S.M.H. |
| author_facet |
Movahedi, N. Mirbagheri, S.M.H. |
| author_sort |
Movahedi, N. |
| title |
Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents |
| title_short |
Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents |
| title_full |
Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents |
| title_fullStr |
Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents |
| title_full_unstemmed |
Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents |
| title_sort |
comparison of the energy absorption of closed cell aluminum foam produced by various foaming agents |
| publisher |
Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| publishDate |
2016 |
| topic_facet |
Научно-технический раздел |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/173482 |
| citation_txt |
Comparison of the Energy Absorption of Closed Cell Aluminum Foam Produced by Various Foaming Agents / N. Movahedi, S.M.H. Mirbagheri // Проблемы прочности. — 2016. — № 3. — С. 128-134. — Бібліогр.: 9 назв. — англ. |
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Проблемы прочности |
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AT movahedin comparisonoftheenergyabsorptionofclosedcellaluminumfoamproducedbyvariousfoamingagents AT mirbagherismh comparisonoftheenergyabsorptionofclosedcellaluminumfoamproducedbyvariousfoamingagents |
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2025-07-15T10:08:48Z |
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2025-07-15T10:08:48Z |
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1837707170365308928 |
| fulltext |
UDC 539.4
Comparison of the Energy Absorption of Closed Cell Aluminum Foam
Produced by Various Foaming Agents
N. Movahedi
a,1
and S. M. H. Mirbagheri
b
a Department of Materials and Industrial Engineering, Semnan University, Semnan, Iran
b Department of Mining and Metallurgical Engineering, Amirkabir University of Technology,
Tehran, Iran
1 Nima.movahedi@gmail.com
ÓÄÊ 539.4
Ñðàâíèòåëüíûé àíàëèç ýíåðãîïîãëîùåíèÿ ïîðèñòûõ ñòðóêòóð ñ
çàêðûòûìè ÿ÷åéêàìè íà îñíîâå àëþìèíèåâîãî ñïëàâà ñ ðàçëè÷íûìè
ïåíîîáðàçóþùèìè äîáàâêàìè
Í. Ìîâàõåäè
à
, Ñ. Ì. Õ. Ìèðáàãõåðè
á
à Óíèâåðñèòåò ã. Ñåìíàí, Èðàí
á Òåõíîëîãè÷åñêèé óíèâåðñèòåò èì. Àìèðà Êàáèðà, Òåãåðàí, Èðàí
Èññëåäîâàíî âëèÿíèå ïåíîîáðàçóþùèõ äîáàâîê ãèäðèäà òèòàíà TiH2 è êàðáîíàòà êàëüöèÿ
CaCÎ3 íà ýíåðãîïîãëîùåíèå â ïîðèñòûõ ñòðóêòóðàõ ñ çàêðûòûìè ÿ÷åéêàìè íà îñíîâå
àëþìèíèåâîãî ñïëàâà À356. Îáðàçöû ñ äâóìÿ ðàçëè÷íûìè ïîðèñòûìè ñòðóêòóðàìè áûëè
ïîëó÷åíû ïóòåì äîáàâêè TiH2 è CaCÎ3 â ðàñïëàâ àëþìèíèåâîãî ñïëàâà À356 ïðè òåìïåðàòóðå
700�Ñ. Ýëåêòðîííî-ìèêðîñêîïè÷åñêèé àíàëèç îáðàçöîâ ïîêàçûâàåò, ÷òî ÿ÷åéêè ñòðóêòóð,
ïîëó÷åííûõ ïóòåì äîáàâêè CaCÎ3, ÿâëÿþòñÿ áîëåå ìåëêèìè è îäíîðîäíûìè, ÷åì â ñëó÷àå
äîáàâêè TiH2. Ìåõàíè÷åñêèå õàðàêòåðèñòèêè ïîðèñòûõ îáðàçöîâ îïðåäåëÿëè ïî äàííûì
èñïûòàíèÿ íà îäíîîñíîå ñæàòèå. Óñòàíîâëåíî, ÷òî ïðè 50%-íîì óðîâíå äåôîðìàöèè ýíåðãî-
ïîãëîùåíèå îáðàçöîâ, ïîëó÷åííûõ ïóòåì äîáàâêè CaCO3, íà 100% âûøå òàêîâîãî îáðàçöîâ,
ïîëó÷åííûõ ïðè äîáàâêå TiH2.
Êëþ÷åâûå ñëîâà: ïîðèñòàÿ ñòðóêòóðà ñ çàêðûòûìè ÿ÷åéêàìè íà îñíîâå àëþìè-
íèåâîãî ñïëàâà, ïåíîîáðàçóþùàÿ äîáàâêà, ÿ÷åèñòàÿ ñòðóêòóðà, ýíåðãîïîãëîùåíèå.
Introduction. Aluminum foam (AF) is one of the most important types of cellular
metals that can be produced with an open or closed cell structure. This material has a broad
range of applications in a variety of industries such as transportation, building, aerospace,
and automotive. Aluminum foams can be produced with powder metallurgy or melting
techniques. On an industrial scale, the most promising method for the production of
aluminum foam is melting. According to the bubble formation mechanism, there are two
methods for the production of closed-cell aluminum foams through melting: air injection
[1] or incorporation of foaming agent [2] in powder form to the aluminum melt. In both
methods, the aluminum melt would first be thickened by appropriate additives such as SiCp
[3], Al2O3 [4] particles, or calcium granules [5]. Then, the foaming process would be
completed by the injection of air or the addition of an appropriate foaming agent. Titanium
hydride (TiH2) is the material most frequently used as a foaming agent in the aluminum
foam production industry. But there are some important considerations that should be taken
into account during the fabrication of aluminum foam with TiH2 in order to avoid
deterioration of the mechanical properties of the resultant foam. For example, Matijasevic
© N. MOVAHEDI, S. M. H. MIRBAGHERI, 2016
128 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2016, ¹ 3
and Banhart showed that heat pre-treatment of the TiH2 powder is necessary to improve cell
size distribution [6]. The price of this material is also a controversial topic which exists
among producers of aluminum foam on an industrial scale. And, one of the important
factors that influence the final price of closed-cell aluminum foam in the market is related
to TiH2 cost. Other foaming agents, such as CaCO3, have also been applied successfully to
produce closed cell aluminum foams [7]. In this research, two distinct closed cell aluminum
foams produced with TiH2 and CaCO3 as foaming agents at the same foaming temperature
with a casting method. In spite of studies done separately producing closed cell aluminum
foams with these foaming materials, a comparative study to analyze the cellular structures
and mechanical properties of relevant foams has not been done carefully. The main
objective of this study is to evaluate and compare the mechanical properties and cellular
structure of these foams. This study will help to determine which of these two foaming
agents is more suitable for the synthesis of closed cell aluminum foam for applications such
as energy absorption. In fact, in this study no foaming agent has been rejected, but which
one is more appropriate for particular applications was shown.
1. Materials and Experimental Methods. The aluminum foams in this study were
synthesized by melting. For this purpose, two distinct closed-cell A356 alloy structures
were prepared by adding TiH2 and CaCO3 as foaming agents at the same foaming
temperature. The foaming process is comprised of four stages when TiH2 is used as the gas
releasing agent: (i) melting aluminum alloy at 700�C; (ii) the addition of 2 wt.% calcium
metal (1–3 mm) and stirring the molten aluminum at 500–700 rpm for 10 min to make the
molten metal viscous enough; (iii) the addition of 1 wt.% heat treated TiH2 to the Al–Ca
composite at 1200–1500 rpm for 1 min; (iv) pouring the precursor to the mold and holding
it for 3 min at 700�C to produce closed aluminum foam. For the aluminum foam structure
that was made with calcium carbonate, the foaming procedure involved three stages: (i)
melting A356 aluminum alloy at 700�C; (ii) incorporation of 5 wt.% CaCO3 into the melt
and stirring for 1 min at 1200–1500 rpm; (iii) holding the precursor at 700�C for 5 min. In
the latter sample, it was shown that the calcium oxide produced as a result of CaCO3
decomposition will thicken the molten aluminum, therefore no other ingredient was added
before the foaming stage. The calcium oxide makes the molten aluminum viscous enough
to entrap the produced CO2 bubbles inside the liquid phase. Uniaxial compressive tests
according to ASTM E9 were performed on aluminum foam rectangular specimens with a
dimension of 25 25 20� � mm to evaluate the mechanical properties and energy absorption
of the cellular structures. A scanning electron microscope was also utilized to observe the
pore structure and morphology of the aluminum foams.
2. Results and Discussions. Figure 1 reveals the compressive stress–strain curves of
the foam samples under a uniaxial compression test. In both cases, the curves exhibit three
distinct regions. The first stage is the initial deformation zone where stress increases linear
to the peak. After that, the curve continues into the stress plateau region � pl , which
represents cell collapse. In this stage, cells will collapse and strain is not recoverable. This
behavior is important for cellular materials when their main application is energy absorption.
In the third stage, densification of the foam will occur. In Fig. 2, the relative density (�r )
and porosity (�) of the synthesized cellular structures in this study is shown. The relative
density and porosity of the aluminum foams are calculated in Eqs. (1) and (2), respectively,
[8]. The density of the foam samples was determined according to the ASTM D6683
standard for each sample
�
�
�r
f
s
� , (1)
�
�
�
� �1
f
s
. (2)
Comparison of the Energy Absorption of Closed Cell Aluminum Foam ...
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2016, ¹ 3 129
The relative density of AFCaCO3
is about 18% higher than that of AFTiH2
. It can be
seen that the relative density of the foam affects the compressive stress–strain curves. The
plateau region in the aluminum foam sample with CO2 applied to produce the pores is
shorter in comparison with the AFTiH2
sample, or, in other words, under compressive loads,
N. Movahedi and S. M. H. Mirbagheri
130 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2016, ¹ 3
Fig. 1. Compressive stress–strain curves of AFCaCO3
(1) and AFTiH 2
(2) samples.
a
b
Fig. 2. Relative density (a) and porosity of aluminum foam samples (b).
the use of TiH2 as a foaming agent produces a cellular structure with a higher porosity level
that density the cellular structure at higher strains, meaning that this structure allows the
bubbles to collapse and deform. This behavior is also reported for aluminum foams that are
produced using a powder metallurgy method [4]. Also, the relative density of the aluminum
foam has an important effect on the mechanical properties of the cellular structure. From
the compressive stress–strain curves, it can be deduced that the closed cell structures in
AFCaCO3
show greater compressive strength in comparison to the AFTiH2
sample (Fig. 3).
Under compressive loads, according to the Gibson–Ashby model, a linear relationship
exists between relative yield stress and relative density [8]. Unlike open cell foams, the
stretching of the cell faces also occurs, as well as cell edge bending. Therefore, the
structure of the foam in this case would be important. The microstructure of the aluminum
foams is illustrated in Fig. 4.
It is obvious that the pore size of the closed cell aluminum foams produced with
CaCO3 is considerably smaller than those synthesized with TiH2. The polygonal shape of
the pores in the cellular structure reveals that the interaction of the bubbles within the
molten aluminum that has been foamed with TiH2 is greater than with CO2 gases.
In Fig. 5, the interaction of two adjacent growing bubbles and the development of the
transient cell wall is shown. As a result of rapid bubble expansion, transient cell walls
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2016, ¹ 3 131
Comparison of the Energy Absorption of Closed Cell Aluminum Foam ...
Fig. 3. Compressive strength of aluminum foam samples.
a b
Fig. 4. Microstructure of aluminum foam samples produced with different foaming agent TiH2 (a)
and CaCO3 (b).
develop between the two pores and will produce a cellular structure with non-rounded
bubbles and move the system away from equilibrium. The magnitude of the interaction
between two neighboring cells depends on surface tension, viscosity, growth velocity, and
the size of the bubbles [9]. As the foaming agent is added to the molten aluminum at a
specific temperature, decomposition will occur, and the gas released will interact with the
molten aluminum. According to the macroscopic images of the cellular structures in Fig. 6,
it is obvious that in the aluminum foam sample with TiH2 there are some signs of cell wall
curvature.
Under compressive deformation, these polygonal shaped cells will behave as stress
concentration centers and deteriorate the mechanical properties of the cellular structures.
While in the aluminum foam sample with CaCO3, the microscopic structure reveals a more
uniform cell shape. So, under compressive loads, the cellular structure resists plastic hinges
and more stress is required to collapse the structure. The compressive stress–strain curve of
AFCaCO3
shows the sample hardening in the first stage of deformation. This phenomenon
contributes to the thicker cell walls of this sample, while the thinning, rupture, and
curvature of the cell walls and cell faces in the aluminum foam sample with TiH2 foaming
agent deteriorates the yield strength of the cellular structure considerably. (Cell wall and
cell edge ruptures and curvatures are indicated in Fig. 4a and Fig. 6a.) Another parameter
that may increase the strength of the aluminum foam sample produced with CaCO3 is the
intrinsic property of CaO in improving cell wall stability and strength in comparison to
calcium. Energy absorption is an important factor in evaluating the properties of metal
foams, and the energy absorption of the aluminum foams was calculated according to Eq. (3)
[8]:
W d
D
� �
,
0
(3)
132 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2016, ¹ 3
N. Movahedi and S. M. H. Mirbagheri
Fig. 5. Interaction of growing adjacent bubbles and development of transient cell wall [9].
a b
Fig. 6. Pore morphology and cell wall of produced aluminum foam sample with TiH2 (a) and
CaCO3 (b).
where W is the absorbed energy, � is the compressive stress, and
D is the densification
strain.
In Fig. 7, the energy absorption of the aluminum foam samples is shown. The strain at
which densification takes place is known as the densification strain (
D ) and is calculated
by Eq. (4):
�
�
�
�
�D
f
s
f
s
� �
�
��
�
�
���
�
��
�
�
��
�
�
�
�
�
�
�
�
1 14 04
3
. . , (4)
where � is a constant, approx. 1 for cellular structure, and � f and �s are the foam and
cell wall material density [9].
As seen in Fig. 1, the densification strain of AFCaCO3
is about 0.48, and for AFTiH2
is
about 0.77. This means that in AFTiH2
, densification will occur at higher strain levels, and
consequently the surface area under the compressive stress–strain curve will increase.
However, up to 50% strain, the energy absorption of AFCaCO3
is considerably higher.
Conclusions. In this work, two distinct closed cell aluminum foams were fabricated
via melting at identical foaming temperature. Mechanical investigations revealed that due
to the thicker cell walls and finer pores within AFCaCO3
, the energy absorption was
considerably higher than that of AFTiH2
. This characteristic makes AFCaCO3
more suitable
for certain applications, particularly in the automotive industry. It is also important to take
into account that the processing and fabrication of closed cell aluminum foam with calcium
carbonate is cheaper and easier to handle in comparison to the TiH2 foaming agent.
Ð å ç þ ì å
Äîñë³äæåíî âïëèâ ï³íîòâ³ðíèõ äîäàòê³â ã³äðèäó òèòàíà TiH2 ³ êàðáîíàòó êàëüö³þ
ÑàÑÎ3 íà åíåðãîïîãëèíàííÿ ó ïîðèñòèõ ñòðóêòóðàõ ³ç çàêðèòèìè êîì³ðêàìè íà îñíîâ³
àëþì³í³ºâîãî ñïëàâó. Çðàçêè ç äâîìà ð³çíèìè ïîðèñòèìè ñòðóêòóðàìè îòðèìàíî
øëÿõîì äîäàòêà TiH2 ³ ÑàÑÎ3 ó ðîçïëàâ àëþì³í³ºâîãî ñïëàâó À356 çà òåìïåðàòóðè
700�Ñ. Åëåêòðîííî-ì³êðîñêîï³÷íèé àíàë³ç çðàçê³â ïîêàçàâ, ùî êîì³ðêè ñòðóêòóð, îòðè-
ìàíèõ øëÿõîì äîäàòêà ÑàÑÎ3, º á³ëüø ì³ëêèìè é îäíîð³äíèìè, í³æ ó âèïàäêó
äîäàòêà TiH2. Ìåõàí³÷í³ õàðàêòåðèñòèêè ïîðèñòèõ çðàçê³â âèçíà÷àëè çà äàíèìè
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2016, ¹ 3 133
Comparison of the Energy Absorption of Closed Cell Aluminum Foam ...
Fig. 7. Energy absorption of aluminum foams.
âèïðîáóâàíü íà îäíîâ³ñíèé ñòèñê. Óñòàíîâëåíî, ùî çà 50%-íîãî ð³âíÿ äåôîðìàö³¿
åíåðãîïîãëèíàííÿ çðàçê³â, ùî îòðèìàí³ øëÿõîì äîäàòêà ÑàÑÎ3, íà 100% á³ëüøå, í³æ
çðàçê³â, îòðèìàíèõ ïðè äîäàòêó TiH2.
1. D. Wang, W. Xue, and Z. Shi, “Cell size prediction of a closed aluminum foam,”
Mater. Sci. Eng. A, 431, No. 1-2, 298–305 (2006).
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Received 27. 04. 2015
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