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A review on hot stamping
The production of high strength steel
components with desired properties by
hot stamping (also called press
hardening) requires a profound knowledge and
control of the forming procedures. In
this way, the final part properties become
predictable and adjustable on the basis
of the different process parameters
and
their interaction. In addition to parameters of
conventional cold forming,
thermal and
microstructural parameters complicate the
description of
mechanical phenomena
during hot stamping, which are essential for the
explanation of all physical phenomena
of this forming method.
In
this article, the state of the art in the thermal,
mechanical, microstructural,
and
technological fields of hot stamping are reviewed.
The investigations of all
process
sequences, from heating of the blank to hot
stamping and subsequent
further
processes, are described. The survey of existing
works has revealed
several gaps in the
fields of forming-dependent phase transformation,
continuous flow behavior during the
whole process, correlation between
mechanical and geometrical part
properties, and industrial application of some
advanced processes. The review aims at
providing an insight into the forming
procedure backgrounds and shows the
great potential for further investigations
and innovation in the field of hot
sheet metal forming.
Development of tribo-simulator for hot
stamping
冲压工艺过程仿真开发
Coefficients
of
friction
were
measured
at
elevated
temperatures
using
a
hot
flat
strip
drawing test machine newly developed by
the authors for the purpose of confirming the
coefficients
of
friction
used
for
the
FEM
simulation
of
hot
stamping.
To
examine
the
functions of the tribo-simulator, the
coefficients of friction are measured using hot
rolling oil
with
an
emulsion,
which
is
supplied
continuously,
while
varying
the
drawing
speed,
drawing pressure and temperature. From
the experimental results, it was shown that the
coefficient
of
friction
in
hot
stamping
can
be
measured
using
this
tribo-simulator.
The
measured
coefficients
of
friction
can
be
used
as
values
in
the
FEM
simulation
of
hot
stamping. Moreover, the tribological
behavior at the interface between the die and
strip in
hot
stamping
can
be
evaluated
from
the
coefficient
of
friction,
because
it
is one
of
the
quantitative values used
to represent the tribological behavior between the
die and blank.
Die design
for stamping a notebook case with magnesium alloy
sheets
In the present
study, the stamping process for manufacturing a
notebook top cover case
with LZ91
magnesium
–
lithium alloy
sheet at room temperature was examined using both
the
experimental
approach
and
the
finite
element
analysis.
A
four-
operation
stamping
process
was developed to eliminate both the fracture and
wrinkle defects occurred in the
stamping process of the top cover case.
In order to validate the finite element analysis,
an
actual four-operation stamping
process was conducted with the use of 0.6 mm thick
LZ91
sheet as the blank. A good
agreement in the
thickness distribution
at various
locations
between
the experimental data and the finite element
results confirmed the accuracy and
efficiency of the finite element
analysis. The superior formability of LZ91 sheet
at room
temperature was also
demonstrated in the present study by successful
manufacturing of
the
notebook
top
cover
case.
The
proposed
four-operation
process
lends
itself
to
an
efficient
approach
to
form
the
hinge
in
the
notebook
with
less
number
of
operational
procedures than
that required in the current practice. It also
confirms that the notebook
cover cases
can be produced with LZ91 magnesium alloy sheet by
the stamping process.
It
provides
an
alternative
to
the
electronics
industry
in
the
application
of
magnesium
alloys.
Improving
the
accuracy
of
contact-type
drawbead
elements
in
panel
stamping
analysis
面板冲压的材料与接触类型
A
finite element modeling technique is proposed to
improve the accuracy of contact-type
drawbead elements in panel forming
analyses, and a performance assessment in terms of
part
border
and
thickness
predictions
is
presented
in
conjunction
with
panel
stamping
experiments of two automotive sheets.
Inherent model limitations causing incorrect part
geometry and thickness predictions are,
firstly, evaluated considering blank deformations
on a plain
–
strain
section of a stamping die. The influence of
omitted drawbead geometry
and
overestimated drawbead exit thickness are
described analytically, and a closed form
expression is obtained to correct draw-
in model error. Then a sectional deformation model
is used to calculate restraint force
and drawbead exit thickness for a particular blank
and
drawbead
design.
The
proposed
technique
is
applied
in
process
modeling
of
polygon
shaped
panels
made
of
draw-quality
and
bake-hardenable
steels.
Three
bead
penetrations were investigated in
process simulations as well as in stamping
experiments.
The same blankholder force
was applied in all process conditions. Computed
draw-in and
thickness distributions
were compared with on-part measurements using an
experimental
panel-draw die. It was
determined that drawbead models based on force
parameters only
resulted in remarkably
high thickness values at the die entry and mostly
overestimated
draw-in along panel
border lines. An evaluation of thickness
distributions computed with
proposed
technique showed an improved correlation with
experiment results of both blank
materials and confirmed the use of the
drawbead exit thickness as a drawbead modeling
parameter.
Effects
of
bead
penetration
on
panel
border
lines
were
also
simulated
in
accord with stamping experiments.
热冲压机床与设备及其冷却系统设计
Design of Hot Stamping Tools with
Cooling System
Hot
stamping with high strength steel is becoming more
popular in automotive industry. In
hot
stamping, blanks are hot formed and press hardened
in a water-cooled tool to achieve
high
strength. Hence, design of the tool with necessary
cooling significantly influences the
final properties of the blank and the
process time. In this paper a new method based on
systematic
optimization
to
design
cooling
ducts
in
tool
is
introduced.
The
optimization
procedure was coupled with FE analysis
and a specific evolutionary algorithm. Through
this
procedure
each
tool
component
was
separately
optimized.
Subsequently,
the
hot
stamping
process
was
simulated
both
thermally
and
thermo-mechanically
with
the
combination of optimized
solutions.
热冲压的材料机械性能
Investigation of the thermo-mechanical
properties of hot stamping steels
Within
the
innovative
hot
forming
process
for
sheet
metals,
called
hot
stamping,
it
is
possible
to
combine
forming
and
quenching
in
one
process
step.
This
affords
the
opportunity
to
manufacture
components
with
complex
geometric
shapes,
high
strength
and
a
minimum
of
springback
which
currently
find
applications
as
crash
relevant
components
in
the
automotive
industry.
As
standard
material
for
hot
stamping
the
quenchenable
high
strength
steel
22MnB5
is
commonly
used.
With
regard
to
the
numerical
modeling
of
the
process,
the
knowledge
of
thermal
and
thermo-mechanical
properties
of
the
material
is
required.
To
determine
the
thermo-mechanical
material
characteristics,
the
flow
behavior
of
the
steel
22MnB5
in
the
austenitic
state
has
been
investigated by conductive, hot tensile
tests with a Gleeble 1500 system dependent on the
time
–
temperature
characteristic of the hot stamping process.
金属钣金快速冲压先进系统
Fast FE analysis system for sheet metal
stamping
—
FASTAMP
FASTAMP is a fast FE analysis system
for sheet metal stamping, which is based on an
improved
inverse
approach
and
dynamic
explicit
method.
The
improved
algorithm
successfully avoids the strain
localization problem existing in plastic
deformation theory to
lay foundation
for the inverse approach. Quadrilateral membrane
elements together with
DKQ bend element
are used in the algorithm to considering bending
effect. More accurate
model is built in
the system so that the process parameters, such as
blank-holding force,
friction and
drawbead restriction, can be taken into account.
Press types, eject plate and
other
influence factors on sheet metal forming are also
considered. As a result, the system
can
be applied to potential defects detection,
formability analysis, material selection and
process verification. Product design,
process planning and die design can be integrated
by
FASTAMP
,
so
that
product
formability
can
be
ensured,
optimization
of
stamping
process and die
structure achieved.
钣金冲压的电子电磁辅助自控设施
Electromagnetically assisted sheet
metal stamping
A new
approach, electromagnetically assisted sheet metal
stamping, has been developed
to alter
strain distribution and improve formability in
sheet metal stamping. In this study,