Transcript 04-4 Case study outer race

COLT Design Manual for Cold Forging Dies
Case study: CV joint outer races (1)
Case study: Cold forging of outer race
Axisymmetric model of the die prestressed by STRECON E+:
Load distribution:
1500 – 2500 MPa
Carbide winding
core, E=540GPa
n=0.23, elastic
• Die geometry:
Cold forging die for a
CV joint outer race
• Die material:
Hot-working steel
Stripwinding and
casing, E=205 GPa
n=0.3, elastic
Die:
Hot-working steel
50 / 54 / 56 HRc
E=220GPa, n=0.3
elastic-plastic
• Prestressing system:
ID 150 mm, OD 350 mm
Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools
with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community.
COLT Design Manual for Cold Forging Dies
Case study: CV joint outer races (2)
How to determine the optimum combination of
material hardness and prestressing conditions
Circumferential stress distribution
at max. process load:
450
Circumferential stress distribution
at max. process load:
450
MPa
300
300
150
150
0
-150
-300
-450
300
MPa
risk of
axial
cracks
0
MPa
-70
MPa
-150
-300
-450
-600
-600
-750
-750
-900
-900
-1050
-1050
Prestressed by conventional stress ring
at 0.6% interference, die steel 50 HRc
Prestressed by STRECON E+
at 0.6% interference, die steel 56 HRc
Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools
with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community.
COLT Design Manual for Cold Forging Dies
Case study: CV joint outer races (3)
Design A: Prestressing by conventional stress ring
at 0.6% interference, hardness of the die 50 / 54 / 56 HRc
Tangential stress-strain responses in critical area (for two load cycles)
500
500
500
0
0
0
0
Depl=
0.53
0,5
1-1
-500
Ds=
1500
%
-0.5
0
Depl=
0.30
Ds=
-500
1730
%
MPa
-1000
MPa
-1000
0.5
1
Depl=
0.30
Ds=
1735
%
MPa
-1000
56 HRc
-2000
-2000
Total strain in %
0
54 HRc
50 HRc
-2000
-0.5
-1500
-1500
-1500
1-1
0.5
Stress in MPa
-500
-0,5
Stress in MPa
Stress in MPa
-1
Total strain in %
Total strain in %
 risk of early crack initiation due to high tensile stresses and cyclic plastic strains
Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools
with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community.
COLT Design Manual for Cold Forging Dies
Case study: CV joint outer races (4)
Design B: Prestressing by a STRECON® E+ container
at 0.6% interference, hardness of the die 50 / 54 / 56 HRc
Tangential stress-strain responses in critical area (for two load cycles)
500
500
500
50 HRc
0
-0,5
0
Depl=
0.16
0,5
1-1
Stress in MPa
Stress in MPa
-1
%
-1000
-500
Ds=
1515
-0.5
0
Depl=
0.05
%
-1000
MPa
0.5
-500
Ds=
1640
-1000
-0.5
0
Depl<
0.01
0.5
1
Ds=
1675
%
MPa
MPa
-1500
-1500
-1500
56 HRc
0
1-1
Stress in MPa
0
-500
54 HRc
50 HRc
-2000
-2000
-2000
Total strain in %
Total strain in %
Total strain in %
 no tensile stresses, minimized cyclic plastic strains for 56 HRc
Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools
with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community.
COLT Design Manual for Cold Forging Dies
Case study: CV joint outer races (5)
Recommendations for the design
of dies for the warm forging of outer races
Recommended die material:
• High-performance hot-working steel at high hardness
provides an excellent fatigue strength
• In case of prestressing by a stiff STRECON® E+ container,
the hardness can be increased from 50 to 54-56 HRc
Recommended prestressing system:
• STRECON® E+
reduces the stresses and cyclic plastic strains in
circumferential direction, leads to improved fatigue life
 important: right combination of
die material and prestressing system!
Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools
with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community.