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© WZL/Fraunhofer IPT
Forming technology basics
Simulation Techniques in Manufacturing Technology
Lecture 2
Laboratory for Machine Tools and Production Engineering
Chair of Manufacturing Technology
Prof. Dr.-Ing. Dr.-Ing. E.h. Dr. h.c. Dr. h.c. F. Klocke
Seite 2 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 3 © WZL/Fraunhofer IPT
Introduction
Historical perspective
Source: Industrieverband Massivumformung e. V.
Metal forming is one of the oldest human work techniques.
Already 4.000 BC metals were processed by forging. Around
2.500 BC first copper alloys were found which lead to the name
Bronze Age
Between 700 and 500 BC iron replaced the use of bronze. The
process of melting the iron ore and the following forging process
cohered till the 13. and 14. century
About 1900 the forges produced widespread product lines for the
railway, the automotive industry and agricultural engines with
hammers driven by transmissions
Even today metal forming is an integral part of production industry.
There are hardly possible any technical products without formed
components
Seite 4 © WZL/Fraunhofer IPT
Metals account for about two thirds of all
the elements and about 24 % of the mass
of the planet and are still widely available
Wide industrial application of metals
throughout centuries can be explained by
their properties:
– Strength
– Toughness
– High melting point
– Thermal and electrical conductivity
– Ductility
Ductility of metals enables their shaping
by means of forming operations
Introduction
Metals
Seite 5 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 6 © WZL/Fraunhofer IPT
All materials and in particular metals
consist of atoms
The bond between metal atoms is
called metallic bond
At metallic bond the valence electrons
(outer most electrons of an atom) are
free to move in a metal structure
consisting of positively charged ions
Atoms in metals are not free but stay
in an equilibrium state:
– Attraction forces between ions and
electrons
– Repulsive forces between ions
Attraction force
distance
between
atoms X
Resulting Force
Fc - cohesion force
X0 - smallest equilibrium distance between atoms
Repulsive force
X0
Fc
Fo
rce
F
F < Fc F > Fc
+ + + + + + + + +
+ + + + + + + + +
+ + + + + + + + +
Positively charged ions
Negatively charged
electron gas
Basics of material Science
Molecular structure of metals
Seite 7 © WZL/Fraunhofer IPT
Yo
un
g‘s
mo
du
lus
[MP
a]
Temperature T
[°C] 0
200
100
50
150
0 200 400 600 800 1000
Basics of material Science
Spring model by Gottstein
Interatomic forces keep the atoms in a
stable arrangement at a minimum of
potential energy
Elastic deformation of the system due
to an external force leads to the
displacement of atoms and storing of
the potential energy in the system
Load relieve leads to a return of the
atoms to their original position at the
potential energy minimum
Distance between atoms and the
magnitude of forces acting between
them is a material property
Temperature dependency of Young‘s modulus
γ-Fe Cu
Mg
Al
α-Fe
Source: Gottstein, G: Materialwissenschaft und Werkstofftechnik, 4. Auflage, 2014, ISBN: 978-3-642-36602-4
Atomic shell
Interatomic forces
Atomic core
Spring model by Gottstein
x0
Seite 8 © WZL/Fraunhofer IPT
Basics of material Science
Crystal lattice
Atoms of a metal have determined
spatial distribution i.e. crystal lattice
For a description of the crystal lattice
simple geometrical forms unit cells are
used
There are three unit cells of metals:
– fcc – face centered cubic
– bcc – body centered cubic
– hex – hexagonal
The crystal lattice is characterized
through the distance between atoms
(for most of the metals 0.25 – 0.5 nm)
Unit cells usually have anisotropic
material properties along different
directions
Crystal lattice
Unit cell
Seite 9 © WZL/Fraunhofer IPT
Basics of material Science
Lattice types of an unit cell
Face-centred
cubic
(fcc)
Body-centred
cubic
(bcc)
Hexagonal
(hex)
Examples:
Sliding planes:
Sliding directions:
Sliding systems:
Formability:
g-Fe, Al, Cu
4
3
12
Very good
a-Fe, Cr, Mo
6
2
12
Good
Mg, Zn, Be
1
3
3
Poor
Seite 10 © WZL/Fraunhofer IPT
fcc
bcc
Basics of material Science
Iron-Carbon Phase Diagram
Carbon content in weight percent
Cementite content in weight percent
d-Fe
d- + g-Fe
Te
mp
era
ture
in °
C
Liquid + d-Fe
Liquid
Fe3C
(Cementite)
Liquid +
Fe3C
Liquid + g-Fe
g-Fe + Fe3C
g-Fe
(Austenite)
a-Fe (Ferrite)
g- + a-Fe
a-Fe + Fe3C
mixed a -Fe + Fe3C
Seite 11 © WZL/Fraunhofer IPT
Basics of material Science
Atomic and macroscopic view of metal structures
Ideal
crystal
structure
Special agglomeration of crystals
Section plane
a
Crystal lattice Unit cell
2D–Cut
of the microstructure
Microstructure
Scheme Photograph
Real
crystal
structure
Seite 12 © WZL/Fraunhofer IPT
Basics of material Science
Macroscopic understanding of metals
Real metals are polycrystals i.e.
consist of many single crystals
The reason for a formation of the
multiple crystalites or grains is that the
crystalization starts at many points of
the molten material simultaneously
Every single grain of a metal has a
different crystallographic orientation
If two grains with different orientations
meet a grain boundary is formed
Different orientation of grains
compensate for the anisotropy of their
mechanical properties so that metals
behave quasiisotropic on the macro
scale (if not textured, i.e. rolled sheet
metal)
Seite 13 © WZL/Fraunhofer IPT
Basics of material Science
Equilibrium state of a crystal lattice
Crystal structure of real metals has a
lot of deviations from the ideal regular
lattice
Each deviation leads to a distortion of
the lattice and results in a misbalance
of the electrostatic forces between
atoms
Additional electrostatic forces increase
the potential energy of the atomic
lattice
Due to lattice defects there is
potentially another equilibrium state of
the crystal which it can take if
provided some external energy (e.g.
mechanical work A)
A
x1 x0
Fre
e e
nerg
y
Seite 14 © WZL/Fraunhofer IPT
Basics of material Science
1D lattice defects
Vacancy Intermediate-lattice atom FRENKEL-matching
Substituting atom Emplacement atom
The foreign atoms induce
stress to the crystal lattice.
This stress affects crystal
strengthening of the
material.
Seite 15 © WZL/Fraunhofer IPT
Basics of material Science
2D lattice defects
Screw dislocation Edge dislocation
Dislocations are linear defects in the lattice
Seite 16 © WZL/Fraunhofer IPT
Basics of material Science
3D lattice defects
Low angle grain boundary High angle grain boundary
Seite 17 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Creep 3.3
Plasticity 3.2
Elasticity 3.1
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 18 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Creep 3.3
Plasticity 3.2
Elasticity 3.1
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 19 © WZL/Fraunhofer IPT
Unloaded Tensile-loaded
s - Nominal stress
e - Natural strain
E - Young‘s Modulus
l0 l1
s
s
Mechanical material behavior
Atomic representation of pure elastic-tensile deformation
00
01
l
Δl
l
ll ε
E
ele
s
Seite 20 © WZL/Fraunhofer IPT
g
g - Shear angle
- Shear stress
G - Shear modulus
n - Poisson‘s ratio
E - Young‘s modulus
Mechanical material behavior
Atomic representation of pure elastic-shear deformation
Gelg
1-
2G
E n
Unloaded Shear-loaded
Seite 21 © WZL/Fraunhofer IPT
For elastic behavior:
Mechanical material behavior
Stress-strain curve for elastic behavior
00
01
l
l 00 l
Δl
l
ll
l
dl ε
l
dl d
1
0
e
A
F
0
s
tanel
el
e
sa E
ele
s
Str
ess
Strain
Re
sel
eel
Natural strain:
Natural stress:
α
for σ ≤ Re
with: tan α = E
F
F
A
A0 l 0
l
∆l
Seite 22 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Creep 3.3
Plasticity 3.2
Elasticity 3.1
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 23 © WZL/Fraunhofer IPT
Mechanical material behavior
Types of plastic deformation
Dislocation movement
Low force requirements
Sliding
High force requirements
Before
After
Seite 24 © WZL/Fraunhofer IPT
Mechanical material behavior
Sliding and dislocation movement
Dislocation movement Sliding
Seite 25 © WZL/Fraunhofer IPT
Mechanical material behavior
Constraints on dislocation movement
Constraints on dislocation
movement are induced by:
Edge dislocation
Substituting atom
Emplacement atom
Unit cell of
ferrite
0,286 nm Screw dislocation
Grain boundary scarf dispersion Grain diameter
Incoherent dispersions
Coherent, lattice oriented dispersions
High melting point
phase
Slip line
Grain boundary
dispersions
Further dislocations within
the crystal
Grain boundaries and grain
boundary dispersions
Knots (networks of locked
dislocations)
Foreign atoms in the lattice
Dispersions (Orowan
mechanism)
Other phases
Seite 26 © WZL/Fraunhofer IPT
Grain boundary hardening – Hall-Petch-Relation
With increasing change in shape close adjacent dislocations impede each other because of surrounding stress fields, which results in a strain hardening of the material
Mechanical material behavior
Strain hardening
D
kσRes 0
Dislocation movement
(scheme)
Sliding plane
Dislocation source
Movement direction
Grain boundary
S
D
k, σ0
Res
= average grain size
= Hall-Petch-Constant
= Yield stress
S1 S2
Grain 1 Grain 2
Grain boundary
2
D
Piled up dislocations
at a grain boundary
Seite 27 © WZL/Fraunhofer IPT
Mechanical material behavior
Recording of dislocation movement by an infrared camera
F
Tensile specimen of tempered aluminum
with a reflective surface
F
Seite 28 © WZL/Fraunhofer IPT
Mechanical material behavior
Stress-strain curve up to the uniform elongation
A
)l(F
0
s
Str
ess
Strain
Nominal stress: (related to starting cross section)
Rm
Re ,se
eel epl
Load
relieving Reload
)l(A
)l(F s
True stress: (related to real cross section)
σ‘
σ
Ag – Uniform elongation
F
F
A
A0 l 0
l
∆l
Seite 29 © WZL/Fraunhofer IPT
Mechanical material behavior
Flow stress determination using the example of a tensile test
)l(A
)l(F´s
Strain
True stress:
Rm
Re ,se
eel j or epl Ag
Fracture
s0
s‘
kf
l0
l
l
A0
A
elf εA
F(l)
l
l
A
F(l)
A(l)
F(l)k 1
000
Flow stress:
Usable region to
determinate the flow stress
Str
ess
F
F
A
A0 l 0
l
∆l
lΔ
Seite 30 © WZL/Fraunhofer IPT
Mechanical material behavior
Flow curve
Flo
w s
tress k
f
True strain j
Required stress to overcome
strain hardening
Minimal required stress for
initial plastic deformation
Seite 31 © WZL/Fraunhofer IPT
Mechanical material behavior
Movie: Methods for determination of the yield stress
Tension test Compression test Torsion test
Low deformation
Uniaxial stress state to the uniform elongation Au , then multiaxial elongation
To true strain φ = 1
Multiaxial stress state in case of insufficient lubrication
Use of Teflon foil for uniform friction
High deformation
Multiaxial stress state
Especially suitable for determining of flow curves at high temperatures
The stress state during determination of the flow curve and the forming should be equal.
Seite 32 © WZL/Fraunhofer IPT
Mechanical material behavior
Limits for cold forming without annealing
Overload machine
Overload tool
Critical deformation /
fracture
jVB – Fracture strain
Flo
w s
tress k
f
True strain j
With increasing strain hardening the flow stress increases.
Seite 33 © WZL/Fraunhofer IPT
Mechanical material behavior
Static Recrystallisation
requirements:
- jv > 0
- T > T Recrystallisation
- impact time
Schematic course of recrystallisation of cold formed structure
du
cti
le y
ield
A10,
ten
sil
e s
tre
ng
th R
m
cry
sta
l
reg
en
era
tio
n
temperature, °C
small decrease of Rm
large increase of A10
Seite 34 © WZL/Fraunhofer IPT
Mechanical material behavior
Effective Strain and Temperature Influence the Grain Size g
rain
siz
e
effective strain
range of
recrystallisation
Seite 35 © WZL/Fraunhofer IPT
Mechanical material behavior
Static and dynamic recrystallization
Static recrystallization
– Static recrystallization occurs at a
tempering above TR ≈ 0,4TS after a cold
forming process and before reaching the
fracture strain φVB
– Annealing processes for recrystallization
purpose reset the grain structure leading
to a reduction of strain hardening and thus
increase the formability
Dynamic recrystallization
– Dynamic recrystallization only occurs at
hot forming processes (T >> TR) and is a
continuously neutralization of the
dislocation density during the process
φVB1 φVB2 Effective strain j
Annealing process
for recrystallization
(Static recrystallization)
Cold forming T << T Rekri
Hot forming
T >> T Rekri Dynamic recrystallization
Flo
w s
tress k
f
Seite 36 © WZL/Fraunhofer IPT
Mechanical material behavior
Forming Temperature and Velocity Influence the Flow Stress
forming temperature below
recrystallisation temperature
high forming velocity
low forming velocity
forming temperature above
recrystallisation temperature
effective strain
flo
w s
tre
ss
Seite 37 © WZL/Fraunhofer IPT
Mechanical material behavior
Influence of temperature on dynamic recrystallization
Hot-compression tests at different temperatures
– Compression on the same compression level = same deformation
– Recrystallization was immediately stopped by quenching after testing
Different grain structure depending on process-temperature
– 700°C: Hardly any recrystallization, heavily deformed structure
– 800°C: Nucleation = beginning recrystallization
– 1000°C: Nearly complete recrystallization, uniform structure
Source: IBF, Exzellenzcluster „Integrative Produktionstechnik für Hochlohnländer“, Teilprojekt B21; WZL
Werkstoff Stauchprobe: 25MoCrS4
T = 700°C
50 µm
T = 800°C
50 µm
T = 1000°C
50 µm
Seite 38 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Creep 3.3
Plasticity 3.2
Elasticity 3.1
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 39 © WZL/Fraunhofer IPT
Mechanical material behavior
Creep definition
Creep material behavior should be
taken into account for the
constructions operating at
temperature 𝑇 above 0.3𝑇𝑚 (𝑇𝑚 is the
melting temperature)
The applied stress is usually less than
the yield stress of the material 𝑅eS
Uniaxial creep curve is obtained from
tensile creep test at constant load and
constant temperature
Three creep stages are distinguished
at creep strain vs. time diagram: I –
primary creep, II – secondary creep
and III – tertiary creep
Creep is the progressive time-dependent inelastic deformation under constant load and
temperature.
Relaxation is related to creep phenomena, which can be defined as time-dependent
decrease of stress under the condition of constant deformation and temperature.
Time
I II III
creep fracture
minimum creep
rate
Seite 40 © WZL/Fraunhofer IPT
Mechanical material behavior
Creep modelling
Secondary creep
Models assuming existence of creep
potential:
𝒔 is stress deviator, the function for
equivalent creep rate could be defined as:
Power law 𝜀 𝑒𝑞𝑐𝑟 =
3
2𝑎 𝜎𝑒𝑞
𝑛−1𝒔
Exponential law 𝜀 𝑒𝑞𝑐𝑟 = 𝑏 𝑒𝑥𝑝
𝜎𝑒𝑞
𝜎0− 1
Hyperbolic sine law:𝜀 𝑒𝑞𝑐𝑟 = 𝑎𝑠𝑖𝑛ℎ
𝜎𝑒𝑞
𝜎0
For many materials secondary creep lasts the most life-time of the construction. To predict
long term behavior of the structure only the secondary creep can be described.
a, n, b, 𝜎0, m, k, l are material parameters, which should be determined by fitting the family of creep
curves, obtained from creep tests at a given temperature. Given secondary and primary creep models
are available as standard material behavior in Abaqus Software.
Primary creep
Time hardening 𝜺 𝑐𝑟 =3
2𝑎 𝜎 𝑒𝑞
𝑛−1𝑡𝑚𝒔
Strain hardening 𝜺 𝑐𝑟 =3
2𝑏 𝜎 𝑒𝑞
𝑘−1 𝜀 𝑒𝑞𝑐𝑟 𝑙
𝒔
Tertiary creep and Damage
Continuum damage mechanics approach
𝜺 𝑐𝑟 =3
2𝑎
𝜎𝑒𝑞
1 − 𝜔
𝑛 𝑺
𝜎𝑒𝑞
𝜔 is Rabotnov parameter related to the reduction of
the cross-section area due to accumulated voids,
cavities, etc.
𝜺 𝑐𝑟 =3
2𝜀 𝑒𝑞
𝒔
𝜎𝑣𝑀
Seite 41 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 42 © WZL/Fraunhofer IPT
Workpiece
Lubricant
Tool Substrate
Boundary zone
Interface
Coating
Interaction
Tribological interactions
Tribological system
Friction and wear emerge as a
consequence of relative motion
between tool and workpiece
Interaction between tool and
workpiece is described by
means of the tribological
system
Scientific description of friction
and wear is denoted as
tribology
Friction and wear are minimized
by means of:
– Lubricants and/or
– Coatings
Process forces
Temperature
Relative velocity
…
System input
Friction
Wear
System output
Tribological system
Ambient medium
Seite 43 © WZL/Fraunhofer IPT
v
Tribological interactions
Friction laws and friction models
Model representation Friction laws
Coulomb‘s law
Friction factor law
Reality
Coulomb’s law:
- Sheet metal forming
Friction factor law (shear friction):
- Bulk forming
S
he
ar
str
ess
Normal stress 𝜎𝑁
Body A with mass 𝑀𝐴
Body B with mass 𝑀𝐵
𝐹𝐴 = 𝑀𝐴 ∙ 𝑔
𝑚 –proportionality factor
𝑘 – shear flow stress of the
softer material
𝜏𝑅 = 𝜇 ∙ 𝜎𝑁
𝜏𝑅 = 𝑚 ∙ 𝑘 = 𝑚 ∙𝑘𝑓
3
0 ≤ 𝑚 ≤ 1
𝑚 = 0 – frictionless state
𝑚 = 1 – condition of adhesion
𝜎𝑁
𝜏𝑅
Seite 44 © WZL/Fraunhofer IPT
Tribological interactions
Wear mechanisms (1/2)
Adhesion Adhesion Surface fatigue Surface fatigue
Cleaving or micro cutting by means of an
interlocking contact of abrasive particles or
roughness peaks of an opposite body
Surface material change due to chemical
reaction with the components of
intermediate medium
Wear is a progressive material loss from the surface of a solid body (base body), caused due to
mechanical reasons, i.e. contact- and relative motion of a solid, liquid or gaseous counter body
[GfT Arbeitsblatt 7].
Adhesive interactions (secondary forces or
primary valence forces) on the surface can
exceed bonding forces within the material
Cyclic loads lead to the crack initialization,
crack growth and, eventually, to the particle
erosion
Abrasion Abrasion Tribochemical reaction Tribochemical reaction
Seite 45 © WZL/Fraunhofer IPT
Tribological interactions
Wear mechanisms (2/2)
200 μm 200 μm 10 μm
100 μm 100 μm
Smearing on an HSS extrusion punch Fatigued lateral surface of a HSS fine blanking
punch
Abrasion on a ceramic deep drawing ring Tribochemical wear on a borated steel
Tool wear consists of different wear types: adhesion, surface fatigue, abrasion and tribochemical wear
Adhesion Adhesion Surface fatigue Surface fatigue
Abrasion Abrasion Tribochemical wear Tribochemical wear
Seite 46 © WZL/Fraunhofer IPT
Summary 6
Sheet metal separation 5.3
Sheet metal forming 5.2
Bulk metal forming 5.1
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 47 © WZL/Fraunhofer IPT
Overview of forming processes
Classification of manufacturing processes (selection)
Forming
Bulk metal
forming
Manufacturing Processes
Casting Cutting
Cold
forging
Semi-hot
forging
Sheet metal
forming
Sheet
cutting
Rolling
Extruding
Compressive
forming
Extruding
Compressive
forming
Semi-hot rolling
Forging
Deep drawing
Stretch forming
Hydroforming
Shearing
Fine Blanking
Tearing
Forging
Seite 48 © WZL/Fraunhofer IPT
Overview of forming processes
What is the meaning of forming?
Manufacturing by plastic deformation
Constant workpiece volume
Constant workpiece mass
Cohesion of workpiece is retained
Source: GCFG, Feintool
Manufacturing by cutting
Material cohesion is released locally
No generation of formless substance
(no chips)
Cutting
Forming Bulks and wires
Sheets
Sheet metal forming
Cutting:
Fineblanking, Shearing
Bulk metal forming
Seite 49 © WZL/Fraunhofer IPT
Overview of forming processes
Bulk forming – Sheet metal forming – Blanking
Source: Saarstahl AG, Benteler AG, Feintool AG
Geometry
Process temperature
Strain hardening
Tool loads
Cross section changing
Forces
Plane (h << b, t)
Low up to medium
Low
Low
Low
Low up to medium
Sheet metal forming
Plane (h << b, t)
Low
Low
Low
Low
Low up to medium
Blanking
Spatial
Low up to high
Low up to high
Medium up to high
High
High
Bulk forming
Seite 50 © WZL/Fraunhofer IPT
Summary 6
Sheet metal separation 5.3
Sheet metal forming 5.2
Bulk metal forming 5.1
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 51 © WZL/Fraunhofer IPT
Bulk metal forming
Component spectrum of bulk forming
Hinge bearing
Cardan shaft
Crank shaft
Gear shaft
Gear wheels
Drive shaft
Axle journal
Wheel carrier
Turbine blade
Source: Infostelle Industrieverband Massivumformung e.V.
Seite 52 © WZL/Fraunhofer IPT
1,3 kg
0,4 kg
Bulk metal forming
Advantages of bulk forming
Cutting Forming
Semi-finished part Component Semi-finished part Component
Seite 53 © WZL/Fraunhofer IPT
Bulk formed component
Bulk metal forming
Advantages of bulk forming
Source: Infostelle Industrieverband Massivumformung e.V., ThyssenKrupp Presta
Fiber orientation
Seite 54 © WZL/Fraunhofer IPT
Bulk metal forming
Process variants of bulk forming
Temperature
Cold forming T ≈ 25 °C Warm forming T ∈ [500, 900] °C Forging T ∈ [900, 1250] °C
Advantages:
Less force and work
requirements
High fracture strain
Disadvantages:
High energy input for heating
High thermal impact on tools
High material costs for tools
Dimension faults by shrinkage
Material loss and increased
finishing caused by scale
formation
Advantages:
Lower tool material costs as for
hot forging
Low influence of forming velocity
No energy costs for heating
No dimensional faults caused by
shrinkage
High surface quality
Increasing strength of the
workpiece due to strain
hardening
Disadvantages:
High force and work
requirements
Limited plastic strain
Often complex and polluting
lubrication necessary
Advantages:
Strengthening of the workpiece
Small range of tolerance caused
by shrinkage
Good surface quality
Disadvantages:
Energy input for heating
High flow stresses
Seite 55 © WZL/Fraunhofer IPT
Initial condition
Cold forming
Warm forming
Forging
0,001 – 30 kg
0,001 – 50 kg
0,05 – 1500 kg
< 1,6
< 4
< 6
Less
Low
High
Workpiece
weight
Fracture strain,
φVB
Finishing effort
Bulk metal forming
Efficiency of bulk metal forming
Seite 56 © WZL/Fraunhofer IPT
Forming process IT-statement according DIN ISO quality
5 6 7 8 9 10 11 12 13 14 15 16
Cold extrusion
Warm extrusion
Hot extrusion
Mean roughness index Ra / µm
0,5 1 2 3 4 6 8 10 12 15 20 25 30
Achievable with special efforts Achievable without special efforts
Bulk metal forming
Efficiency of bulk metal forming
Seite 57 © WZL/Fraunhofer IPT
Summary 6
Sheet metal separation 5.3
Sheet metal forming 5.2
Bulk metal forming 5.1
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 58 © WZL/Fraunhofer IPT
Sheet metal forming
Techniques of metal forming; Bulk forming – sheet metal forming
Bulk half-finished products
High changes in cross sections and dimensions
High plastic deformation
High strain hardening (in cold forming)
High forces
High tool loads
Plane half-finished product: Sheet metal (t << b, l)
No or low unwanted changes of the original wall thickness
Lower plastic deformation
Lower strain hardening
Lower forces
Lower tool loads
Source: G. Siempelkamp GmbH & Co. KG, Saarstahl AG, BMW Group AG
Bulk forming Sheet metal forming
Seite 59 © WZL/Fraunhofer IPT
Sheet metal forming
Typical sheet metal products
Half-finished product: Sheet metal
Products: Hollow parts with constant wall thickness
Low deformation compared to bulk forming
Low forces compared to bulk forming
Process example:
– Deep drawing
– Hydroforming
– Spinning
– Stretch forming etc.
Source: Benteler AG
Passenger car structure elements
Roof
reinforcement
Underbody
Door Impact
protection
Base plate
Tunnel
Dashboard
support
Front bumper
Rear
bumper
B-Pillar
reinforcement
Door sill
reinforcement
A-Pillar
reinforcement
Side frame
reinforcement
Window frame
reinforcement
Seite 60 © WZL/Fraunhofer IPT
Sheet metal forming
Typical sheet metal processes
Sheet metal forming
Bending Stretch forming process
Quelle: Total Materia
Hydroforming
Deep drawing Ironing
Seite 61 © WZL/Fraunhofer IPT
Summary 6
Sheet metal separation 5.3
Sheet metal forming 5.2
Bulk metal forming 5.1
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 62 © WZL/Fraunhofer IPT
Sheet metal separation
Overview
Half-finished product:
Sheet metal
Mechanical cutting of work
pieces
No appearance of formless
material (no chipping)
Process example:
– Blanking
– Fine blanking
Source: Dr. Karl Bausch GmbH Co. KG, Otto Bauckhage
Seite 63 © WZL/Fraunhofer IPT
Sheet metal separation
Comparison of blanking and fine blanking (1/2)
Assembly of high-precision work pieces with
smooth cutting surfaces free from cracks
Cutting surfaces often serve as functional
surface without finishing processes
Triple action press required (Punch force, Vee
ring and blank holder force, Counter punch
force)
Sheet metal thickness up to 16 mm
Main field of application: automotive
engineering, medical technology, household
equipment
Shearing is the most used blanking process
Manufacturing of sheet metal components with
very high output
Simple and cheap tool geometry
Manufacturing of sheet thickness up to 20 mm
Main field of application: automotive
engineering, medical technology, household
equipment
Fine blanking Blanking
Seite 64 © WZL/Fraunhofer IPT
1 Cutting die
2 Guiding plate
3 Punch
1 Cutting die
2 Vee ring and
blank holder
3 Punch
4 Counter punch
FS – Punch force
FR – Vee ring and blank
holder force
FG – Counter punch
force
Blanking Fine blanking
Fs = Punch force
Fs Fs
FR FR
FG
Die clearance ca. 5,0% of sheet
metal thickness
ca. 0,5% of sheet
metal thickness
Sheet metal separation
Comparison of blanking and fine blanking (2/2)
1
2 3
1
2 3
4
Source: Feintool
Seite 65 © WZL/Fraunhofer IPT
In fineblanking, the smooth sheared zone can take a share of 100%
Sheet metal separation
Comparison of sheared edges in blanking and fine blanking
Shearing
Fineblanking
Zone of die roll
Smooth sheared zone
Rupture zone
burr
Smooth sheared zone
burr
Zone of die roll
Seite 66 © WZL/Fraunhofer IPT
Sheet metal separation
Comparison of sheared edges in blanking and fine blanking
Method IT - classification Costs Output
high
rough (IT 11) low high
low fine (IT 7)
Sheared
surface
Fineblanking
Shearing
Source: Feintool
Seite 67 © WZL/Fraunhofer IPT
Summary 6
Overview of forming processes 5
Tribological interactions 4
Mechanical material behavior 3
Basics of material science 2
Introduciton 1
Table of contents
Seite 68 © WZL/Fraunhofer IPT
Summary
Recap of the material science basics concerning
metals structure
Discussion of the elastic and plastic material
behavior
Introduction to the basic tribological aspects
Presentation of the basic information on the creep
behavior of metals
Brief Introduction of the basic forming processes:
– Bulk forming
– Sheet metal forming
– Sheet metal separation
Deep understanding of the boundary conditions of a forming process including material and tribological
behavior are obligatory prerequisites for a set-up of a realistic simulation model