3 Fundamentals of press design

30 Basic principles of metal forming
specific deformation work w id
1000
Nmm
mm 3
800
700
600
500
400
300
200
100
0
flow stress k f
1000
N
mm 2
800
700
600
500
400
300
200
100
If there is no flow curve available for a particular material, it can be
determined by experimentation. A tensile, compressive or hydraulic
indentation test would be a conceivable method for this. If the specific
deformation work w id and the entire volume V or the displaced volume
V d are known quantities, the total deformation work W is calculated on
the following basis:
2.2.4 Formability
0
St 14
St 37
C35(normally annealed)
0,2 0,4 0,6 0,8 1,0 1,2
log. principle deformation g ϕ
W V w k
V V k
id
fm
= ⋅ ≅ ⋅ϕg⋅ = d ⋅
η
η η
F
Fig. 2.2.2
Flow curves
and curves
showing the
specific deformation
work
for different
materials
The identification of formability should only be based on those cases of
material failure caused as a result of displacement or cleavage fractures
where no further deformation is possible without failure. If, therefore, a
material breaks before reaching maximum force as a result of a cleavage
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
F
fm
F