Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests
Основным критерием прочности заклепочных соединений при их разработке является сопротивление материала заклепок сдвиговому нагружению. При испытании на сдвиг обычных заклепочных соединений определяющими являются механические характеристики материала заклепки. Поэтому необходимо описание механизма ра...
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
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irk-123456789-1733862020-12-03T01:27:15Z Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests Mucha, J. Witkowski, W. Научно-технический раздел Основным критерием прочности заклепочных соединений при их разработке является сопротивление материала заклепок сдвиговому нагружению. При испытании на сдвиг обычных заклепочных соединений определяющими являются механические характеристики материала заклепки. Поэтому необходимо описание механизма разрушения различных соединений при испытаниях на растяжение. Оценивается прочность разных листовых материалов (сталь DC01, алюминиевый сплав AW-5754 и их комбинация) в заклепочном соединении. Анализируется механизм разрушения заклепочных соединений при одноосном растяжении Т-образных образцов из различных листовых материалов. Выполнено сравнение экспериментальных результатов, полученных при растяжении и сдвиге заклепочных соединений внахлестку для одного и того же типа. Основним критерієм міцності заклепочних з’єднань при їх розробці є опір матеріалу заклепок зсувному навантаженню. При випробуваннях на зсув звичайних заклепочних з’єднань визначальними є механічні характеристики матеріалу заклепки. У зв’язку з цим необхідно описання механізму руйнування різних з’єднань при випробуваннях на розтяг. Оцінюється міцність різних листових матеріалів (сталь DC01, алюмінієвий сплав AW-5754 та їх комбінація) у заклепочних з’єднаннях. Аналізується механізм руйнування заклепочних з’єднань при одновісному розтязі Т-подібних зразків із різних листових матеріалів. Виконано порівняння експериментальних результатів, отриманих при розтязі і стиску заклепочних з’єднать внапуск для одного і того ж типу. 2015 Article Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests / J. Mucha, W. Witkowski // Проблемы прочности. — 2015. — № 5. — С. 126-142. — Бібліогр.: 36 назв. — англ. 0556-171X http://dspace.nbuv.gov.ua/handle/123456789/173386 539.4 en Проблемы прочности Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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Научно-технический раздел Научно-технический раздел |
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Научно-технический раздел Научно-технический раздел Mucha, J. Witkowski, W. Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests Проблемы прочности |
| description |
Основным критерием прочности заклепочных соединений при их разработке является сопротивление материала заклепок сдвиговому нагружению. При испытании на сдвиг обычных заклепочных соединений определяющими являются механические характеристики материала заклепки. Поэтому необходимо описание механизма разрушения различных соединений при испытаниях на растяжение. Оценивается прочность разных листовых материалов (сталь DC01, алюминиевый сплав AW-5754 и их комбинация) в заклепочном соединении. Анализируется механизм разрушения заклепочных соединений при одноосном растяжении Т-образных образцов из различных листовых материалов. Выполнено сравнение экспериментальных результатов, полученных при растяжении и сдвиге заклепочных соединений внахлестку для одного и того же типа. |
| format |
Article |
| author |
Mucha, J. Witkowski, W. |
| author_facet |
Mucha, J. Witkowski, W. |
| author_sort |
Mucha, J. |
| title |
Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests |
| title_short |
Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests |
| title_full |
Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests |
| title_fullStr |
Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests |
| title_full_unstemmed |
Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests |
| title_sort |
mechanical behavior and failure of riveting joints in tensile and shear tests |
| publisher |
Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| publishDate |
2015 |
| topic_facet |
Научно-технический раздел |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/173386 |
| citation_txt |
Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests / J. Mucha, W. Witkowski // Проблемы прочности. — 2015. — № 5. — С. 126-142. — Бібліогр.: 36 назв. — англ. |
| series |
Проблемы прочности |
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AT muchaj mechanicalbehaviorandfailureofrivetingjointsintensileandsheartests AT witkowskiw mechanicalbehaviorandfailureofrivetingjointsintensileandsheartests |
| first_indexed |
2025-07-15T10:02:59Z |
| last_indexed |
2025-07-15T10:02:59Z |
| _version_ |
1837706804354613248 |
| fulltext |
UDC 539.4
Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear
Tests
J. Mucha
1
and W. Witkowski
Faculty of Mechanical Engineering and Aeronautics, Rzeszow University of Technology, Rzeszow,
Poland
1 j_mucha@prz.edu.pl
ÓÄÊ 539.4
Ìåõàíè÷åñêèå õàðàêòåðèñòèêè è ðàçðóøåíèå çàêëåïî÷íûõ ñîåäèíåíèé
ïðè ñòàòè÷åñêèõ èñïûòàíèÿõ íà ðàñòÿæåíèå è ñäâèã
ß. Ìóõà, Â. Âèòêîâñêèé
Ôàêóëüòåò ìàøèíîñòðîåíèÿ è àýðîíàâòèêè, Òåõíîëîãè÷åñêèé óíèâåðñèòåò ã. Ðæåøîâ, Ïîëüøà
Îñíîâíûì êðèòåðèåì ïðî÷íîñòè çàêëåïî÷íûõ ñîåäèíåíèé ïðè èõ ðàçðàáîòêå ÿâëÿåòñÿ ñîïðî-
òèâëåíèå ìàòåðèàëà çàêëåïîê ñäâèãîâîìó íàãðóæåíèþ. Ïðè èñïûòàíèè íà ñäâèã îáû÷íûõ
çàêëåïî÷íûõ ñîåäèíåíèé îïðåäåëÿþùèìè ÿâëÿþòñÿ ìåõàíè÷åñêèå õàðàêòåðèñòèêè ìàòåðèàëà
çàêëåïêè. Ïîýòîìó íåîáõîäèìî îïèñàíèå ìåõàíèçìà ðàçðóøåíèÿ ðàçëè÷íûõ ñîåäèíåíèé ïðè
èñïûòàíèÿõ íà ðàñòÿæåíèå. Îöåíèâàåòñÿ ïðî÷íîñòü ðàçíûõ ëèñòîâûõ ìàòåðèàëîâ (ñòàëü
DC01, àëþìèíèåâûé ñïëàâ AW-5754 è èõ êîìáèíàöèÿ) â çàêëåïî÷íîì ñîåäèíåíèè. Àíàëèçè-
ðóåòñÿ ìåõàíèçì ðàçðóøåíèÿ çàêëåïî÷íûõ ñîåäèíåíèé ïðè îäíîîñíîì ðàñòÿæåíèè Ò-îáðàçíûõ
îáðàçöîâ èç ðàçëè÷íûõ ëèñòîâûõ ìàòåðèàëîâ. Âûïîëíåíî ñðàâíåíèå ýêñïåðèìåíòàëüíûõ ðå-
çóëüòàòîâ, ïîëó÷åííûõ ïðè ðàñòÿæåíèè è ñäâèãå çàêëåïî÷íûõ ñîåäèíåíèé âíàõëåñòêó äëÿ
îäíîãî è òîãî æå òèïà.
Êëþ÷åâûå ñëîâà: èñïûòàíèÿ íà ðàñòÿæåíèå, ïðî÷íîñòü ïðè ñäâèãå, ðàçðóøåíèå
çàêëåïî÷íûõ ñîåäèíåíèé, çàêëåïêè ñàìîïðîáèâíîãî òèïà.
Introduction. Selection of the optimal materials for construction of thin-walled
structures is currently in a transient phase. The elements, which previously have been
manufactured from steel, are now increasingly made of fiber-reinforced plastic and alloy of
light metals, such as aluminum and magnesium. The new materials generate the need for
the development of appropriate joining technologies. The use of the new material types
forced the use of alternative joining technologies, in comparison to traditional connecting
techniques. This implies the need for experimental studies related to the evaluation of the
formation and strength of new joints. New solutions are not always good enough to provide
an adequate strength. In some cases, formation for new materials’ joints is quite problematic.
Hence, the classic riveting technologies with the blind rivet or with the blind hermetic rivet
are still widely applied and will probably continue to be used in the future. In the industry
of public utility buildings and residential houses, these joints are the most widely used
because of their high degree of certainty. Thin profiles are joined by means of various
fasteners, usually by blind rivets [1–4] or, in case of composite structures, either by screws
[5–7] or by special tubular rivets [8–11]. The self-piercing riveting technology is also
commonly used [12–18]. There are few variations in the technology of their formation. One
of them is a solid self-piercing riveting (SSPR) technology proposed by Kerb-Konus-
Vertriebs-GmbH company [19]. During the formation of clinching, self-piercing riveting or
© J. MUCHA, W. WITKOWSKI, 2015
126 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 5
clinching riveting joints the material can fracture, especially the bottom sheet from the die
side. These joint types are characterized by embossments, which depend on the forming
process. The SSPR joining technology provides a flat surface on the rivet punching side
[20–22]. This also allows one to effectively join materials of various mechanical properties,
e.g., soft materials with hard ones [23].
Notwithstanding the fact that many scientists have published their results of the
research, most of them are related to static shear tests or the fatigue tests of the riveting lap
joints [1–16]. A number of international standards define dimensions, testing conditions
and the fracture mechanism of lap joints [24–26]. The main types of lap joint separation
during shear tests (Fig. 1) were included in the aforementioned standards and their
descriptions can be found in various scientific papers. However, there are only few papers
related to comparing the joint strength during a unilateral tensile test. One of the relevant
publications is the study [27] of SPR joints. The results of the multiaxial joint strength and
discussion of these results were presented in work [28]. One of the first papers, which
contain a comprehensive analysis of the joint shear and tensile test results, was related to
the solid self-piercing riveting joints [20]. Bartczak et al. have also studied the joint
strength of H-shaped specimens during tensile tests. In paper [29], they analyzed the effect
of welded joint strengthened by adhesive on the absorption of fracture energy. Mucha and
Witkowski [30] presented a comprehensive analysis of the strength of clinching joints in
multiaxial loading conditions.
In case of shear of the riveting joints, the rivet material determines the strength of
joints. These joints are designed with consideration of the strength of fasteners. Hence, it is
expedient to identify the fracture mechanism for various joints in tensile tests. The strength
analysis of various riveting joints extends the knowledge needed for their designing. The
presented results of the analysis can be helpful in designing the joints used for assembling
thin-walled sheet structures.
The paper discusses the influence of sheet material type on the strength of joints in
unilateral tensile tesst of standard riveting joints and new joints with SSPR. The obtained
results are compared with those obtained from the shear tests of lap joints. In both cases,
the same types of rivets are used.
1. Methodology and Materials. The impact of the arrangement of sheet material on
the force–displacement curves constructed during shear and tensile tests for various
riveting technologies was experimentally studied. The mechanism of fracture during the
tests on the maximum load-bearing capacity of joints was also analyzed. For this analysis,
four types of riveting joint were selected. The fasteners were: blind rivet (BR), blind
Fig. 1. Failure types of riveting joints according to the standard ISO/FDIS 12996: (a) failure of the
specimen material; (b) impermissible specimen deformation; (c) fastener failure; (d) fastener pull- out
from bottom sheet; (e) pull-out of fastener head.
a b
c
d e
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Mechanical Behavior and Failure of Riveting Joints ...
hermetic rivet (BHR), closing-up rivet (COUR), and SSPR (see Fig. 2). Rivet length, rivet
diameter, hole diameter, and squeeze force are major parameters that affect the quality of
formed rivets [31]. All rivets had the same diameter of cylindrical parts dr � 4 mm, and the
remaining geometry was selected for the total thickness of joined sheets t tot � 4 mm. For
the proper insertion of rivets for closing up, there were chamfers prepared in the holes on
one side of the sheets during the joining process. The specimens were prepared according
to the joining industrial conditions.
For the experiments, the sheet materials were made of DC01 steel (material number
1.0330) and aluminum alloy in O/H111 state (material number 3.3535). The yield strength
values of these materials were 160 and 85 MPa, respectively, while the respective tensile
strength values were 290 and 220 MPa. The thickness of each sheet was the same (2 mm).
The specimens (Fig. 3) were prepared in accordance with the recommendations included in
ISO/FDIS 12996 standard [24]. The selected sheet arrangements for the tensile and shear
tests are tabulated in Table 1. All joints were prepared carefully in identical conditions of
their formation. In the hybrid arrangements of sheet materials, the primary rivet head was
positioned in the steel sheet (Fig. 3), while the secondary rivet head was formed on the
aluminum alloy sheet side. For all joints, the static shear tests (lap joints) and tensile tests
(T-shaped specimens) were performed with the force–displacement curves recorded via an
Instron 3382 testing machine. The traversing speed of the machine traverse was 10 mm/min.
The displacements in shear and tensile tests were recorded using the extensometer system
with the measuring distance of 60 mm, as shown in Fig. 3b. There were seven specimens
prepared for each arrangement of sheets and types of rivets.
T a b l e 1
Fasteners and Sheet Material Combinations Used in Riveting Joints
Sheet material Fastener
BHR1 BR2 COUR3 SSPR4
Steel DC01/DC01 1-1 1-2 1-3 1-4
Hybrid
(steel-aluminum)
DC01/AW-5754 2-1 2-2 2-3 2-4
Aluminum AW-5754/AW-5754 3-1 3-2 3-3 3-4
1 ISO 15974:2003; 2 ISO 15978:2003; 3 ISO 1051:1999; 4 Catalog No. 492 000 007.900 [19].
a b c d
Fig. 2. Fasteners used in riveting joints: (a) aluminum-steel BR; (b) aluminum-steel BHR; (c) aluminum
alloy COUR; (d) steel SSPR.
128 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 5
J. Mucha and W. Witkowski
2. Results and Discussion.
2.1. Riveting Joint Failure in the Tensile Test. The standards for tensile tests envision
a specific procedure of joint preparation and test conditions. Joints should be located in
sheet structures to transmit the shear load. However, in many cases, this is not possible.
Hence, tensile tests of joints are an equally important issue. At present, there are no
guidelines, such as standards, for the preparation and geometry of riveting joint specimens
used in tensile tests. In case of a unilateral tensile test of T-shaped specimens, a rivet is
uniformly loaded at the initial loading phase (Fig. 4a). For a certain force value the
load-bearing capacity of bended sheets is less than that of the riveting joint. After reaching
this force value, sheets start to bend (Fig. 4b). Further tensile loading is continued with
strongly bended sheets.
Blind rivet joints are formed in the similar conditions. However, in this case, it is
difficult to maintain high repeatability of formation (the upsetting of the tubular part). Often
the process of head formation is accidental [32]. Aluminum alloy sheets joined by a blind
hermetic rivet in a tensile test behave in a similar way (Fig. 5a). In most cases (five out of
seven specimens) the mechanism of fracture implies a pull-out of the rivet head from
bottom sheets (Fig. 6a). In two other cases, the tubular part of a rivet exhibited a failure.
This implies that the maximum strength of a joint was at the same level as the tubular part,
in respect to the rivet maximum durability. In case of steel sheets (Fig. 5b), five out of
seven specimens underwent a failure of the tubular part of a rivet in unilateral tensile tests
(Fig. 6b). The yield strength Re of DC01 steel is higher than that of AW-5754 alloy by
75 MPa (88%). Therefore, fracture of the joint of steel sheets was caused by the rivet
failure (five out of seven specimens). However, during the tensile test of a hybrid joint
a
b
Fig. 3. The specimen geometry and the rivet position in the hybrid connection: (a) T-shaped
specimen joint; (b) lap joint.
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Mechanical Behavior and Failure of Riveting Joints ...
a b
Fig. 4. The tensile test of T-specimens and the loading conditions: (a) T-specimen in the holder; (b)
joint after tensile test.
a
b
Fig. 5. The BHR joint after a unilateral tensile test. The sheet material: (a) AW-5754; (b) DC01.
130 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 5
J. Mucha and W. Witkowski
(combination of two materials: DC01 and AW-5754) two damage mechanisms were
observed. The most common case was the rivet tubular part failure, while the second one,
which occurred sporadically, was a fastener being pulled out from the bottom sheet (Fig. 7).
Hence, the conclusion is that the load-bearing capacity of the joint is at the same level as
the rivet tubular part and aluminum alloy (AW-5754) strength values.
The BR joint capacity conditions (Fig. 8) are as follows:
� � �p r1 � , (1)
� � �p p1 2 , (2)
� � � � �p t t1 2 1� � , (3)
and for the COUR:
� r p� 1 , (4)
p p2 1� , (5)
� �t t2 1� . (6)
a b
Fig. 6. The BHR surface of the upturned part (a) and crack surface (b).
Fig. 7. The joint of sheet material DC01/AW-5754 with the BHR after the tensile test.
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 5 131
Mechanical Behavior and Failure of Riveting Joints ...
During unilateral tensile tests of the AW-5754 sheet being joined by the closing-up
rivet, the specimens exhibited a high stiffness, so that the rivet head failed (Fig. 9). The
maximum strength of a joint was the same for the seven specimens. A similar mechanism of
fracture was observed in the closing-up rivet for other sheet material arrangements. As the
rivet under study had a conical part for its insertion into the hole, some hole chamfers were
prepared, while the BR and SSPR rivets required no such hole preparations. The formed
rivet head, despite its small height, was not sheared due to significant strengthening of the
material. The flat rivet head in the hole of a conical part was upturned, and there were
tensile stresses at the surface near the head. After the joint formation large residual stresses
were concentrated in the rivet head, where the conical part changes into the cylindrical one
[33]. Finally, the rivet failure occurred by separation of the head and the tubular part
(Fig. 10). The residual stress concentration has a high impact on the joint fracture
mechanism. During the tensile test, the residual stresses and the load-induced stresses are
superimposed.
For the SSPR joint, the same mechanism of fracture was exhibited in the unilateral
tensile tests (Fig. 11). Irrelevant of the sheet material arrangement, the force–displacement
curves of high repeatability were obtained (Fig. 12). In the unilateral tensile tests, the rivet
is loaded at one-side, hence the rivet head failure is likely to occur [20]. For properly
selected parameters of formation (forming force) of the SSPR joint, a high repeatability of
Fig. 8. The COUR and BR loading conditions.
Fig. 9. The COUR joint after a unilateral tensile test (the sheet material: AW-5754).
132 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 5
J. Mucha and W. Witkowski
Fig. 10. The primary head failure of the COUR.
Fig. 11. The SSPR joint after a unilateral tensile test. The sheet material: DC01.
a b
c
Fig. 12. The SSPR tensile curves for different combinations of sheet materials: (a) DC 01/AW-5754;
(b) AW-5754/AW-5754; (c) DC01/DC01.
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 5 133
Mechanical Behavior and Failure of Riveting Joints ...
joint load-bearing capacity by the same joint fracture mechanism can be obtained. During
the tensile test of T-shaped specimens the fastener was pulled out from the bottom sheet by
shear of the sheet material within the grooves (Fig. 13). Thus, the sheet material type
(especially bottom sheet) determined (in addition to the forming force of a joint) the
capacity of the joint maximum load.
2.2. Joint Load-Bearing Capacity in Shear and Tensile Tests. Force–displacement
curves obtained have a similar form in the tensile tests of different sheet arrangements for
all three joint types (with blind rivet, blind hermetic rivet, and closing-up rivet), as is shown
in Fig. 14a–c. The maximum forces of joint separation were nearly identical. The
differences in the maximum force of a joint load and the total dissipation energy were
obtained for the SSPR joint of steel, aluminum alloy and hybrid arrangements (Fig. 14d).
Fig. 13. The SSPR shank surface with the truncated bottom sheet material visible fragments.
a b
Fig. 14. The tensile test joint curves for the different arrangements of sheet materials and joining
systems (I – steel/steel, II – aluminum/steel, and III – aluminum/aluminum): (a) BHR; (b) BR; (c)
COUR; (d) SSPR.
c d
134 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 5
J. Mucha and W. Witkowski
The sheet material in joint grooves was subjected to shear during the joint loading. After
pulling-out from the bottom sheet, the remaining sheet material can be observed at the rivet
surface.
The maximum forces of the joint loadings reached close values for the particular rivet
type and three different sheet arrangements (Fig. 15a, b). However, the force–displacement
curves had different shapes (Fig. 15a–d). The highest values of the total dissipation energy
were obtained for the EN AW-5754 sheet material, and the lowest value for the DC01 sheet
material – for joints with BR (Fig. 15a, b). For the joints with COUR the force–
displacement curves of the shear test had similar forms (Fig. 15c), so the total dissipation
energy values were nearly identical. The fasteners exhibited such a low strength, in relation
to the sheet material, that the mechanisms of fracture of joints were the same during the
tests. The highest stress concentration was observed at the joint shear surface (Fig. 16a, b).
c d
a b
Fig. 15. The shear test joint curves for the different arrangements of sheet materials and joining
systems: (a) BHR; (b) BR; (c) COUR; (d) SSPR.
Fig. 16. The rivet impact on the sheet metal hole surface: (a) without clearance; (b) with clearance;
(c) the deformed hole in the aluminum alloy sheet after the joint shear test.
a
b
c
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Mechanical Behavior and Failure of Riveting Joints ...
The stress concentration factor depends on several parameters, including clearance/gap
between the rivet and the hole. In a riveting joint, the hole diameter is larger than that of the
rivet. The clearance between them makes the rivet rotate during the joint loading (Fig. 16a).
When the load increases, the contact area increases as well, whereas the stress level
decreases. The sheet material is being upset at the hole surface. At the same time, the
cylindrical shape of a hole changes into the oval one (Fig. 16c). If the sheets are bended,
the stress concentration factor will be reduced. The mechanism of the stress concentration
is depicted in Fig. 16b. The second factor causing the stress concentration of the hole
surface is a secondary bending, as a result of the lack of a uniform head shape of a primary
and secondary rivet. The unequal levels of stress at the contact between the rivet and the
sheets result in sheet bending. The hole surface areas are deformed during the shear tests of
the sheet material EN AW-5754 joined by a blind rivet and a closing-up rivet. When the
rivet in the transverse cross section of the load capacity was reached, the rivet failed. The
greatest hole deformations were observed for the aluminum alloy sheet material (Fig. 16c).
Hole ovalization in the lap joints with a larger number of fasteners can occur in different
varieties, depending on the number of rivet rows [34–36]. There is no clearance between a
rivet and a hole in the SSPR joints, and the head is present only at one side of the rivet.
Therefore, there is a significant rivet rotation and bending of the sheet so that pulling out
the rivet from the bottom sheet is possible. Thus, after separation of the lap joint, the rivet
rotation and significant hole deformation are observed (Fig. 17a). One of the most vexing
problems confronting a structural designer is the design of joints. To first order, the
objective in joint design is to maximize the joint efficiency �:
��
Failure load of the
Failure load of the surrounding
joint
sheet
. (7)
The joint true efficiency is the minimum of all the possible joint efficiencies one can
calculate for all possible failure modes of the joint (Fig. 1). For the riveting joints, the
Fig. 17. The contact surface view after the shear test of the steel sheet material: (a) with SSPR joint;
(b) with COUR joint; (c) with BHR joint; (d) with BR joint.
a
b
c
d
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J. Mucha and W. Witkowski
maximum capacity of the surface load of the sheet material should be higher than that
controlled by the shear stress of a rivet material. This relation allows one to predict the
joint strength based on the rivet shear condition using a certain ratio of the sheet thickness
and the hole diameter:
�d
mnk ntdkt
2
0
4
, (8)
where m is the number of the rivet transverse cross sections subject to shear, n is the
number of rivets in the joint, t is the thickness of the thinner sheet, d is the rivet/hole
diameter, k0 is the allowable surface pressure of the sheet material, and kt is the
allowable rivet material shear stress.
Assuming that k kt0 2 5� . we obtained the following condition:
d
t m
3 2.
. (9)
For unilateral rivets under shear loading – the lap joint (the number of rivet transverse
cross sections sheared) m� 1, hence the condition is d t0 3 2
. , while for the strapped joint
m� 2 – thus, d t0 1 6
. . If this relation is satisfied, then the maximum load-bearing capacity
can be calculated from the shear condition. When the rivet fills the hole, a uniform
load-bearing pressure distribution exists in the thickness direction of the sheet. The
increased clamping is beneficial with respect to improving the load transfer by friction
between the contacting surfaces of sheets.
Designers of thin-walled structures often have a dilemma as to which types of rivet
should be used, in order to provide the specified load-bearing capacity. Sometimes, they
make use of fasteners, which are already used in the company, without paying attention to
the rivet diameter and the sheet thickness. The mechanism of fracture of a joint presented
above does not include the fourth joint type with the SSPR. Since a self-piercing rivet is
punching a hole, it must have an appropriate hardness, e.g., 58 HRC [20]. In this type of
joints, the rivet rotates and is pulled out from the bottom sheet (Fig. 17a). In case of
aluminum alloy sheets, the lowest values of the maximum tensile shear force are obtained
(Fig. 15d). The joint load capacity depends on the mechanical properties of the sheet
material, rather than those of the rivet material. To present the capabilities of shear and
tensile load-bearing capacity of the four selected joining techniques, the steel sheet
specimens were chosen (Fig. 18). The highest value of the shear force was obtained for the
SSPR joints, and the lowest one for the joint with the closing-up rivet. The capacities of a
a b
Fig. 18. The joint force characteristic of DC01/DC01 steel sheet: (a) shear test; (b) tensile test.
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Mechanical Behavior and Failure of Riveting Joints ...
tensile load transfer are lower than those of a shear transfer. In tensile tests, the maximum
values of the joint fracture force were observed for the steel sheets joined by the blind
hermetic rivet (Fig. 18b). For this joint type, the dissipated energy is the highest. The rivet
failure occurred in the tubular part near the rivet head. In shear tests, the SSPR joints were
more durable than others. For the SSPR joints the differences in the maximum shear and
tensile forces were observed for variable sheet arrangements (Fig. 19). The average value
of shear force for the DC01 material was 5.26 kN and for the EN AW-5754 – 3.42 kN. In
this case, the value variation was 35%. For the sheet thickness of 2 mm and equal forming
force 30 kN, the largest difference between shear and tensile forces was obtained for DC01
material (3.73 kN). For the combination of EN AW-5754 and DC01 sheet materials (hybrid
joint) the difference was 2.64 kN, and for EN AW-5754 aluminum alloy this difference was
2.52 kN. For other joints with blind and closing-up rivets there was no significant influence
of the sheet material arrangements on the maximum loading force of the joint. Out of seven
tests, the largest difference in the average values of shear and tensile forces was obtained
for the SSPR joints (Fig. 19). Hence, for these joints the selected indicators from the lap
shear test were presented according to the ISO/FDIS 12996 standard [22]. The highest
value of dissipated energy was obtained for the steel sheet material, and the lowest value
for the hybrid sheet arrangement (Fig. 20). When the bottom sheet material was replaced
from steel by aluminum alloy, the total dissipated energy decreased by 58%. For the SSPR
joint, the normal distribution curve and frequency of the maximum joint strength are
depicted in Fig. 21.
a b
Fig. 19. The arithmetic average of the maximum tensile force.
Fig. 20. The SSPR joint shear strength for different sheet materialss. (FSmax
is the maximum tensile
shear load, Et is the dissipated energy, EFmax
is the dissipated energy up to maximum tensile shear
load, st is the total displacement, sFmax
is the displacement at the maximum tensile shear load.)
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J. Mucha and W. Witkowski
Conclusions. This paper presents the experimental analysis of the capacity of a joint
load for four different rivets and the statistical analysis of the results. The most important
conclusions are:
1. For joints with conventional rivets, the same level connection strength is reached,
regardless of the joint sheet materials. The fastener strength corresponds to the maximum
load-bearing capacity of the joints.
2. For the joints with tubular BR, the maximum load-bearing capacity is reached at the
sheet material limit (from the rivet secondary head) and the tensile strength limit of the rivet
tubular part.
3. For the SSPR joints, the joint strength depends on the mechanical properties of the
joined sheets. It is highest for steel sheets and lowest for the aluminum alloy sheets.
4. For the SSPR joints, rivets are is pulled out in tensile tests of T-shaped specimens.
In shear tests, rivets are turned and pulled out from the sheet material. There was no SSPR
failure. In case of other rivets, fastener failed was always observed.
Acknowledgments. This work was prepared in cooperation with the Department of
Mechanical Engineering, Rzeszow University of Technology with AGRMAR S.A. company
headquartered in Mielec. The authors thank the company employees for the assistance in
a b
Fig. 21. The maximum shear (a) and tensile (b) strength normal probability density distributions for
SSPR joints.
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Mechanical Behavior and Failure of Riveting Joints ...
the laboratory researches. They also thank Prof. Sieniawski (Head of the Research and
Development Laboratory for Aerospace Materials-LabMatPL) for making the test machine
available to our tests.
Ð å ç þ ì å
Îñíîâíèì êðèòåð³ºì ì³öíîñò³ çàêëåïî÷íèõ ç’ºäíàíü ïðè ¿õ ðîçðîáö³ º îï³ð ìàòåð³àëó
çàêëåïîê çñóâíîìó íàâàíòàæåííþ. Ïðè âèïðîáóâàííÿõ íà çñóâ çâè÷àéíèõ çàêëåïî÷-
íèõ ç’ºäíàíü âèçíà÷àëüíèìè º ìåõàí³÷í³ õàðàêòåðèñòèêè ìàòåð³àëó çàêëåïêè. Ó
çâ’ÿçêó ç öèì íåîáõ³äíî îïèñàííÿ ìåõàí³çìó ðóéíóâàííÿ ð³çíèõ ç’ºäíàíü ïðè âèïðî-
áóâàííÿõ íà ðîçòÿã. Îö³íþºòüñÿ ì³öí³ñòü ð³çíèõ ëèñòîâèõ ìàòåð³àë³â (ñòàëü DC01,
àëþì³í³ºâèé ñïëàâ AW-5754 òà ¿õ êîìá³íàö³ÿ) ó çàêëåïî÷íèõ ç’ºäíàííÿõ. Àíàë³çó-
ºòüñÿ ìåõàí³çì ðóéíóâàííÿ çàêëåïî÷íèõ ç’ºäíàíü ïðè îäíîâ³ñíîìó ðîçòÿç³ Ò-ïîä³á-
íèõ çðàçê³â ³ç ð³çíèõ ëèñòîâèõ ìàòåð³àë³â. Âèêîíàíî ïîð³âíÿííÿ åêñïåðèìåíòàëüíèõ
ðåçóëüòàò³â, îòðèìàíèõ ïðè ðîçòÿç³ ³ ñòèñêó çàêëåïî÷íèõ ç’ºäíàòü âíàïóñê äëÿ îäíîãî
³ òîãî æ òèïó.
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Received 05. 07. 2015
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