Abstract: Self-pierce riveting (SPR) is nowadays widely used in the car manufacturing industry
where aluminium alloys are used for body construction. For the design of mechanical structures,
formed by the joining of component parts, a knowledge of the vibration characteristics of different
joint types (adhesive bonding, spot welding, SPR etc) is essential. The free transverse vibration
characteristics of single lap-jointed encastre SPR beams are investigated theoretically in this paper
using the three dimensional finite element method (FEM). Numerical examples are provided to
show the influence on the natural frequencies, natural frequency ratios and mode shapes of these
beams caused by variations in the material properties (E and υ) of the sheet material. It is shown
that the transverse natural frequencies of single lap jointed encastre SPR beams increases
significantly as the Young’s Modulus of the sheets increases, but only slight changes are
encountered for variations of Poisson’s Ratio. It is found that an exponential curve gives an
acceptable fit to the relationship between natural frequency and Young’s Modulus. As expected,
odd modes shapes were found to be symmetrical about the mid-length position and even modes
Abstract: The present paper aims at defining a numerical tool for the efficient design of the selfpiercing
riveting process by means of FE simulations. Abaqus Explicit v.6.4 software has been used
to establish a model for 3D simulation of the joining process and of the shearing test on the riveted
joint, in order to understand the joint formation and failure mechanisms. The obtained indications
have been validated experimentally through joint sectioning and comparison between real geometry
and numerical results. Furthermore, shear tests have been performed to compare the experimental
and numerical results in terms of joint resistance.
Abstract: Self-pierce riveting (SPR) is a sheet material joining technique which is suitable for
joining dissimilar materials, as well as coated and pre-painted materials. Published work relating to
finite element analysis of SPR joints is reviewed in this paper, in terms of process, static strength,
fatigue strength, vibration characteristics and assembly dimensional prediction of the SPR joints. A
few important numerical issues are discussed, including material modelling, meshing procedure,
failure criteria and friction between substrates and between rivet and substrate. It is concluded that
the finite element analysis of SPR joints will help future applications of SPR by allowing system
parameters to be selected to give as large a process window as possible for successful joint
manufacture. This will allow many tests to be simulated that would currently take too long to
perform or be prohibitively expensive in practice, such as modifications to rivet geometry, die
geometry or material properties. The main goal of the paper is to review recent progress in finite
element analysis of SPR joints and to provide a basis for further research.
Abstract: The efforts of new automotive industry are mainly directed towards the substitution of
aluminum for steel in the body structure because the aluminum structures are lighter than traditional
steel ones and meet the requirements, in terms of both vehicle design and manufacture. However,
this substitution is not so automatic, but it is important to study the material properties and the
structure design, focusing the attention on the methods of joining.
Welding, typical technique to joint steel parts, is particularly difficult when applied on aluminum
ones and then, in many cases, the adhesive bonding is preferred.
To optimise the joint performances it is necessary to pre-treat the metal surface, not only to remove
contaminants, but also to provide the intimate contact needed for the adhesive to successfully bond
with the adherent surface.
The mere cleaning of aluminum surfaces is not suitable for their bonding due to the oxide layer that
naturally occurs on exposure to air so we need to apply a more effective treatment (mechanical or
chemical etching) to increase the adhesion capability of the substrates.
In this work different adhesive joint configurations (single lap) between aluminum substrates are
studied. Two different resins are employed to evaluate the influence of the adhesive on the joint
performances. Moreover the aluminum sheets are treated with a chemical etching with two different
Abstract: The increasing individualization of products assigns manufacturing companies to new
tasks like manufacturing various products in a more efficient way. This progression in the market
leads on the one hand to a new product design and on the other hand to an improved production
process. Both are necessary to reduce assembly, service and recycling costs. Hence the joining
technology is and will become more and more important. The conventional joining technologies
like welding, bonding, bolting or clamping have their own disadvantages especially in the field of
flexibility. In order to reduce the effort for assembling and disassembling by retaining the
requirements of the connection a new innovative joining technology is needed. In this study a new
joining technology is introduced to become faster and more flexible in assembling and
disassembling. The basic idea of this manufacturing technology comes from a “metal hook and loop
fastener”. A hook and loop fastener consisting of metal has a lot of advantages for the fields of
industrial assembly, service and recycling. Similar to the synthetic hook and loop fastener a metal
one is characterized by easy closing and opening without special tools. And in comparison to the
synthetic hook and loop fastener the transmissible forces are very high. An additional benefit can be
gained for instance in shock absorbing or resistance against chemical and thermal influence. Two
solutions are followed up to invent the “metal hook and loop fastener”. A one-to-one copy of the
conventional hook and loop fastener is constructed in metal and specific solutions for the use of
metal are tested. A conventional finite element program was used in order to optimize the
construction of a metal cocklebur and the results show a good agreement with the experiment.
Abstract: In this paper a development of clinching, called flat clinching, is presented. After a press
clinching process, the joined sheets have been deformed by a punch with a lower diameter against a
flat die. In this way a new configuration is created with a geometry that has no discontinuity on the
external surface (bottom). A new procedure has also been tested: the second step is perfomed by
pressing the joint between two flat dies. This second case has revealed itself to be very
effective.Tensile tests have been done to compare the joints strength among the various joining
techniques. Moreover some joints have been cut to analyse the changing of the contact line shape
and how its characteristics parameters can influence the bonding performances.
To optimise the process a finite element analysis has been performed.
Abstract: Joining by forming of magnesium alloys is restricted by the limited forming capability of
magnesium at room temperature. For this reason heating of the parts to temperatures of 220 °C or
more is required to form connections without cracks. State-of-the-art joining by forming methods
(such as clinching or self-pierce riveting) are usually working with a contoured die as a counter tool.
Researches on these joining methods have shown that a minimum heating time of 3 to 6 seconds is
needed to achieve connections of acceptable quality. New joining by forming methods working with
a flat anvil as counter tool make it possible to decrease the heating time considerably. In this paper
two methods – the dieless clinching and the dieless rivet-clinching – and their potential for the
joining of magnesium parts shall be introduced in detail. The results of extensive research on the
influence between heating parameters and the formation of the connections as well as the results of
tensile test done to characterize the strength of dieless joined connections are discussed.
Abstract: A numerical model of the electric arc is coupled to a model for the convective flow in the
molten pool of a stainless steel sheet during a stationary TIG welding process. This approach allows
us to predict the shape of the bead, which is determined by the balance between the Marangoni
forces on the free surface and the radial drag from the arc jet impingement.
The surface tension of the molten steel is greatly influenced by its temperature and sulphur
content, as experiments showed very different bead shapes associated to the same welding
parameters. We simulate three sulphur contents, namely 10 ppm, 40 ppm and 100 ppm, showing
their effects on the velocity and temperature distributions in the molten pool. A transition between
drag-dominated and surface tension-dominated pools is found at a sulphur content of few dozens, in
agreement with previous experimental observations.
Abstract: In the present study the use of diode laser for stainless steel aesthetic welding is
considered. In fact the surface smoothness of the weld bead, attributed to the mode stability of the
laser system, suggests its application for aesthetic weld joint. The aims of this work were to: define
a process map, based on an aesthetic criterion; mechanically characterize the weld joints (by Vickers
micro-hardness and tensile test); analyse the surface of the specimens in terms of roughness.
Moreover, gas tungsten-arc (TIG) weld joints were carried out and analogously tested to make a
comparison with the diode laser results.
Good aesthetic butt joints were obtained with diode laser welding. The same results were found
working with constant power speed ratio (i.e. constant fluence).
Comparison between TIG and Laser Beam Welding (LBW), showed no significant difference in
roughness, while ultimate tensile load was higher for TIG welding. The differences in joint strength
depend on the different cross-sectional area and on the extension and microstructure of the base
metal, heat-affected zone and melted zone. However, diode laser technology allows to obtain
smaller bead size.
Abstract: The residual stress in steel welding can highly influences the performance of the joint
during its working life. Both boundary conditions and metal phase transformations have influence
on the levels of the residual stress in the weld.
In this paper the residual stress for AISI 4047 bead-on-plate samples were measured by strain gage
method after laser welding with different values for the laser speed and power, and focus height.
The laser used for this project was the ROFIN DC 015 Industrial CO2 Slab Laser. This laser,
registered as class 4 laser product in accordance with the European Norm EN 60825 is an high
frequency excited, diffusion cooled C02 gas laser, designed to be used for processing materials in a
The measurement procedure was performed on all the welded specimens taking notes of 3 strains
(ε1 ε2 ε3) relative to as many gages at different depths, following the American Society for Testing
Materials (ASTM) standard.
Thereafter the residual stresses were calculated by means of a non-linear finite element analysis.
The analysis took in account the thermo-mechanical phenomena with temperature dependent steel
properties. The other considered also the phase transformation and phase-dependent thermal and