Abstract: Experimental investigation on the formability limits of aluminum and magnesium alloys
are conducted through hydraulic bulging and deep drawing. New tube hydroforming tooling was
designed and the submerged tool concept is introduced. Tube hydroforming experiments were
conducted with and without axial feed by using AA6061 tubes. The formability of Mg AZ31-O
sheets are determined by hydraulic bulging using similar submerged tool. Finally the effect of
temperature and initial blank size on the attainable highest punch velocity is investigated and round
cups from Mg AZ31-O were successfully formed in a heated tool with punch speeds up to 300
Abstract: In this paper a neural network approach is used to model the diode laser assisted forming
process. In particular thin sheets of Aluminum alloy AA 6082 were bended in the elastic range and
then treated with a diode laser with the aim to reduce the spring back phenomenon. Experimental
tests were performed to study the influence of the process parameters such as laser power, laser
speed and starting elastic deformation on the evolution of forming process. In particular the heating
effects on the elastic properties of the material was studied. A statistical approach is used to define
the experimental plan and discuss the experimental results. Interesting trend of the effects of the
diode laser on the forming process were found. Subsequently in order to predict the residual
inflexion, during the laser forming, a multilayer feedforward artificial neural network has been
implemented. A sensitivity analysis on the artificial neural network model is used to show the
significance of all the input data employed. As a result of sensitivity analysis, a check between
experimental and calculated trends for each investigated variables was performed, which revealed
an appreciable fit between data displayed.
Abstract: Using the optimum blank in sheet metal forming process not only can decrease the
material wasting but also avoid possible defects such as local severe thinning, wrinkling and
fracture. Since it is practical technology for industrial production, many blank optimization methods
have been proposed and their validity was verified by some forming tests of typical or complicated
components. However, all the forming tests were carried out at room temperature or under
isothermal condition. In present work, a blank optimization method was employed to evaluate its
efficiency in deep drawing of rectangular magnesium alloy cups under non-isothermal condition. It
is proved by experiment that the employed blank optimization method can predict successfully the
optimum initial blank shape for the component with specified shape and dimension.
Abstract: Deep-drawing operations are performed widely in industrial applications. It is very
important for efficiency to achieve parts with no defects. In this work, a finite element method is
developed to simulate deep-drawing operation including wrinkling. A four nodded five degree of
freedom shell element is formulated. Isotropic elasto-plastic material model with Von Mises yield
criterion is used. By using this shell element, the developed code can predict the bending behavior
of workpiece besides membrane behavior. Simulations are carried out with four different element
sizes. The thickness strain and nodal displacement values obtained are compared with results of a
commercial finite element program and results of previously conducted experiments.
Abstract: Demand for an increase in the useable properties of a drawn-part made of stainless steel
has been the inspiration for the work. The use of 4H13 steel instead of 3H13 has resulted in the
higher strength of the drawn-part but also a decrease in drawability. Therefore, some modifications
to the original design of the sheet-metal forming process were necessary. A numerical simulation
was applied to optimise of the stamping process. The ADINA System based on the finite element
method (MES) was used. Frictional conditions on the contact surfaces, blank diameter and the
course of the blank holding force versus time were analysed. In this paper, the test results of the
mechanical properties of the analysed sheets (3H13 and 4H13 stainless steel) are given, some
differences in the way of stamping drawn-parts made of these materials are discussed and the results
of the numerical simulation are presented. A 3D model and perfectly rigid tool were assumed in the
numerical model. The sheet was modelled using shell elements. The elastic and plastic properties of
the sheet material were assumed and the frictional conditions on the contact surfaces were taken into
consideration during the numerical simulation. Based on the numerical simulation the stamping
process was optimised. A comparison between the numerical calculation and test results shows
good convergence. Thanks to the MES analysis and the application of the new technological
parameters, the desired drawn-part with the better useable properties was obtained.
Abstract: The present paper is the continuation of a research conducted on hemming operations by
using rolling tools. Sheet hemming is a joining operation widely used in automotive industry when
it is necessary to join two sheet parts (such as the engine hood or the door panels with their internal
frame) by plastic deformation of the edge of the outer part. The whole process is characterised by a
90° sheet flanging, a pre-hemming (up to approximately 135°) and the final hemming where the
outer sheet edge is bended up to 180° clamping the inner sheet. Hemming processes are normally
performed using rigid dies in series production and manually in pre-series and small batch
production, due to the high cost of the dies. Nowadays, rollers moved by robots are becoming an
interesting alternative to the manual operations especially when flexible productions are required.
Even if the process time is higher, this solution can help in minimizing set-up times and costs. The
required equipments are a support and a blocking system for the sheets together with the rollers
mounted on a CNC machine or on a robot. The production flexibility is guaranteed by changing the
3D tool path using a CAD/CAM system. Authors are dealing with this technique having conducted
many experiments studying the influence of the hemming process parameters such as flange
geometry (edge height, fillet radius), distance of the inner panel from the flange, tool path sequence,
along straight paths on steel sheets. The goal of the present research is to study the material
behaviour and the produced parts quality when working on aluminium sheets. In particular, both
experimental tests and simulations will be carried out in order to optimize the process.
Abstract: Hemming is the last or one of the latest stage operations for the stamped parts. For this
reason it has a critical importance on the performance and perceived quality of assembled vehicles.
It is used to attach two sheet metal parts together or to improve appearance creating a smooth edge
rather than a razor edge with burrs.
However, designing the hemmed union is not always easy and is deeply influenced by the
mechanical properties of the material of the bended part. Main problems for the automotive industry
arise when bending aluminum alloys.
Aluminum sheet is more difficult to hem due to its susceptibility to strain localization during the
hemming process. This phenomenon produces cracking on the hemmed edge .
In order to avoid this problem and due to the limitations of conventional flanging and hemming
technologies, the flange radii must be increased and a rope hem used (instead of the flat hem used
with steels) when working with aluminum alloys. These changes on the design of the hem union
give as a result a lower quality final product .
Dies and tools used for the hemming process are designed based on experience and on lengthy and
costly die tryouts.
Continuing with the development of new applications for the Electromagnetic Forming (EMF)
technology, LABEIN-Tecnalia and Professor Glenn Daehn’s group from The Ohio State University
carried out some first straight flat hemming experiments using the AA 6016 T4 aluminum alloy.
The results obtained from these first trials are presented in this paper giving a first sight of the
possibilities, advantages and disadvantages of using the Electromagnetic Forming technology for
the hemming of aluminum sheet panels.
Using a non-clouped FEM simulation method, the experimental results are compared to the ones
obtained with the simulations.
The future working line in developing this new application for the Electromagnetic Forming
technology will be based on the results obtained by this study.
Abstract: Taking advantage of high-tech welding methods, a concept is formed in sheet metal
forming community. The so-called tailor-welded blanks (TWBs) are sheet metals that are welded
together prior to forming. This technology dates back to the 80’s, and numerous studies are
conducted in order to explore different aspects of it. This review paper concerns with mechanics of
TWBs. The paper is divided into three major chapters. The first chapter is devoted to mechanical
properties of TWBs. Tensile testing, tensile properties, and hardness of TWBs are covered in this
chapter. The second chapter deals with the formability of TWBs. The formability testing methods,
effect of different parameters on the formability of TWBs, material flow phenomena, control of
material flow, stress and strain distributions, and springback behavior are covered in the second
chapter. The third chapter is focused on failure and fracture of TWBs. Failure modes and failure
criteria are the principal topics of this chapter.
Abstract: Tailored Heat Treated Blanks (THTB) are blanks that exhibit locally different strength
specifically optimized for the succeeding forming process. The strength distribution is set by a local,
short-term heat treatment modifying the mechanical properties of the material. Hence, THTB allow
enhancing forming limits significantly leading to shorter and more robust manufacture process
chains. In order to qualify the use of THTB under quasi series conditions, the interdependencies of
the blank’s local heat treatment and the entire process chain of the car body manufacture have to be
analyzed. In this respect, the impact of a short-term heat treatment on the mechanical properties of
AA6181PX, a commonly used aluminum alloy in today’s car bodies, was studied. Also the
influence of a short-term heat treatment on the coil lubricant, usually already applied by the material
supplier, was given a closer look. Based on these experiments process restrictions for the
application of THTB in an industrial automotive environment were derived and a process window
for the THTB design was set up. In conclusion, strategies were defined how to enhance the found
process boundaries leading to a more robust process window.
Abstract: A test rig was developed to investigate springback in stretch draw forming processes,
which are considered to be nominally uniaxial. An interchangeable tool allows the examination
of both single and double curvature surfaces. Two double curvature tools with the following
radii were used in the experiments, (A) 200mm by 450mm and (B) 450mm by 200mm. The
first radius in each case corresponds to the direction of stretch. Obviously the smaller radius
results in a larger moment, which creates a negative springback in the orthogonal direction.
This effect is more pronounced in tool (A) due to the higher tensile strain levels in the direction
of stretch directly affecting the strains in the orthogonal direction. By considering the resultant
moment in each axis of the sheet independently, an analytical method was devised to give an
approximation of the springback profile. Overall the analytical data correlates well with both
experimental and Finite Element (FE) results.