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Case study: tripods and cross-joints (1)
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: Cold forging of tripods and cross-jointsCase study: Cold forging of tripods and cross-joints
• Die material: ASP 23, 60 HRc
• Prestressing system: ID 85 mm, OD 280 mm
Cold forged tripods and cross-joints
Case study: tripods and cross-joints (2)
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
Typical failure modeTypical failure mode
Fatigue cracks in a tripod die Fatigue cracks in a cross-joint die
Case study: tripods and cross-joints (3)
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
FE analysis of the tooling systemFE analysis of the tooling system
winding core
windingsand casing
die
A) conventional container with a double ring0.6% interference
B) STRECON® Basic, 0.8% interference
C) STRECON® E+, 0.6% interference
Case study: tripods and cross-joints (4)
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
A) Prestressing by a double stress ring at 0.6% interferenceA) Prestressing by a double stress ring at 0.6% interference
Circumferential stress distributionat max. process load
risk of early crack initiation due to tensile stresses and large plastic strains
400
200
0
-200
-400
-600
-800
-1000
-1200
-1400
-1600
MPa
Tangential stress-strain responsein the critical area (5 load cycles)
330 MPa
-2500
-2000
-1500
-1000
-500
0
500
-1.5 -1 -0.5 0 0.5 1
Tangential total strain in %
Tang
entia
l str
ess
in M
Pa
Case study: tripods and cross-joints (5)
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
B) Prestressing by STRECONB) Prestressing by STRECON®® Basic at 0.8% interference Basic at 0.8% interference
Circumferential stress distributionat max. process load
Reduced max. tensile stress, but still considerable plastic strains
400
200
0
-200
-400
-600
-800
-1000
-1200
-1400
-1600
MPa
Tangential stress-strain responsein the critical area (5 load cycles)
60 MPa
-2500
-2000
-1500
-1000
-500
0
500
-1.5 -1 -0.5 0 0.5 1
Tangential total strain in %
Tan
gent
ial s
tres
s in
MP
a
Case study: tripods and cross-joints (6)
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
C) Prestressing by a STRECONC) Prestressing by a STRECON®® E E+ + at 0.6% interferenceat 0.6% interference
-2500
-2000
-1500
-1000
-500
0
500
-1.5 -1 -0.5 0 0.5 1
Tangential total strain in %
Circumferential stress distributionat max. process load
Improved fatigue life: no tensile stresses, reduced stress range and cyclic plastic strains
400
200
0
-200
-400
-600
-800
-1000
-1200
-1400
-1600
MPa
Tangential stress-strain responsein the critical area (5 load cycles)
-320 MPa
Tan
gent
ial s
tres
s in
MP
a
Case study: tripods and cross-joints (7)
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
Recommendations for the designRecommendations for the designof dies for the cold forging of tripods and cross-jointsof dies for the cold forging of tripods and cross-joints
Recommended die material:
• Power-metallurgical tool steel (instead of carbide),provides an excellent fatigue strength
Recommended prestressing system:
• STRECON® E+
reduces the stresses and cyclic plastic strains,leads to improved fatigue life- the outer diameter of the die insert should be close to the inner contour (better effectivity of the carbide winding core)
• STRECON® Basicin case of long-legged parts (especially cross-joints), where a carbide winding core would not be that effective
