a b s t r a c tThe development of the self-piercing riveting (SPR) technology in recent years has broadened the application of the technology in the automobile industry. However, the SPR process currently utilises high-strength steel rivets; and the combination between steel rivets with an aluminium car body makes recycling a challenge. The possibility of replacing a steel self-piercing rivet with an aluminium one has thus been raised as an interesting topic. Within this framework, the objective of the present paper is to provide an experimental database on the riveting process using an aluminium self-piercing rivet. An experimental programme has been carried out, where two similar sheets in aluminium alloy 6060 in three different tempers (temper W, temper T4, and temper T6) have been joined by using a self-piercing rivet in three different alloys, i.e. 6082-T6, 7108-T5, and 7278-T6. The influence of the die shape on the SPR of aluminium sheets using aluminium rivets was also considered. Conventional rivets and dies according to the Boellhoff standards were employed. The test results were exploited in terms of the riveting force-displacement curves and cross-sectional geometries of the riveted joints. The test data were also used to validate a 2D-axisymmetric model, which was originally developed at SIMLab for modelling the riveting process using a steel rivet. Finally, the mechanical behaviour of a riveted connection using an aluminium rivet under quasi-static loading conditions (i.e. combined pure shear and pure opening loads) was experimentally studied and compared with corresponding tests using a steel rivet in terms of forcedisplacement curves.
The
understanding of the formation of silicate oligomers in the
initial stage of zeolite synthesis is important. The use of organic
structure-directing agents (OSDAs) is known to be a key factor in
the formation of different silicate species and the final zeolite
structure. For example, tetraethylammonium ion (TEA
+
) is
a commonly used organic template for zeolite synthesis. In this study,
ab initio
molecular dynamics (AIMD) simulation is used to
provide an understanding of the role of TEA
+
in the formation
of various silicate oligomers, ranging from dimer to 4-ring. Calculated
free-energy profiles of the reaction pathways show that the formation
of a 4-ring structure has the highest energy barrier (97 kJ/mol).
The formation of smaller oligomers such as dimer, trimer, and 3-ring
has lower activation barriers. The TEA
+
ion plays an important
role in regulating the predominant species in solution via its coordination
with silicate structures during the condensation process. The kinetics
and thermodynamics of the oligomerization reaction indicate a more
favorable formation of the 3-ring over the 4-ring structure. The results
from AIMD simulations are in line with the experimental observation
that TEA
+
favors the 3-ring and double 3-ring in solution.
The results of this study imply that the role of OSDAs is not only
important for the host–guest interaction but also crucial for
controlling the reactivity of different silicate oligomers during
the initial stage of zeolite formation.
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