A Study of Die Failure Mechanisms in Aluminum Extrusion

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A Study of Die Failure Mechanisms in Aluminum
Extrusion
Authors A.F.M Arif, A.K. Sheikh, S.Z. Quamar
Received November 27, 2001 Published By
Journal of Materials Processing Technology,

• Presented By Brian B. Cherry
• Date September 15, 2004
• Class Me 582, Professor Ed Red

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OUTLINE

• Introduction
• Profile terminology / Die Profiles
• Overall and class-wise break-up of failure
  modes
• Type failure analysis per shape
• Shape-wise breakdown of each failure mode
• Conclusion / References

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What is Extrusion?

• A compression forming process in which the work
  metal is forced through a die opening to produce
  a desired cross-sectional shape.

Relatively simple shapes
The bulk of aluminum profiles in the construction
industry is produced through hot extrusion.
Above is An extrusion press container.
..Or more complex shapes
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Purpose of Technical Paper

• Productivity, cost and quality are the overriding
  commercial factors. All three are related to the
  performance of the die.
• Due to the high cost of a die based on material
  processing and fine tolerances, the most critical
  extrusion component is the die.
• It is of considerable interest to focus on the
  relationship between die profiles and modes of
  die failure.
• Testing 616 dies, 17 various profiles, H-13
  steel.
• All billets are made of Al-6063.

Bling..Bling!!
Getting Rejected is Expensive And Embarrassing!!
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OUTLINE

• Introduction
• Profile terminology / Die Profiles
• Overall and class-wise break-up of failure
  modes
• Various complexity failure analysis
• Shape-wise breakdown of each failure mode
• Conclusion / References

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Die and Tooling Configuration
Liner Provides protection against thermal and
mechanical stresses to the large and
expensive container.
Dummy Pad Floating or fitted in front of the
stem. It protects the life of the costly
stem.
Pressure Pad Transfers the extrusion load from
the bolster to the pressure plate and also
guards against bolster deflection.
Die and Tooling Configuration for hot extrusion
of A1-6063.
Die Produces the extrusion shape.
Die Ring Holds the die, the feeder plate and
the die backer together.
Die Bolster Provides support to the die against
collapse or fracture. Transfers the
extrusion load from the die to the pressure ring.
Stem It is fitted with the main ram to force
the billet through the container.
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Configuration of a Typical Die
Configuration of a solid flat-face die.
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Die Profiles
Three types of die profiles
Hollow Dies
Solid Dies
Semi-Hollow Dies
Common features of die profiles
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Die Profiles
Sketches and die profiles used in the study.
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OUTLINE

• Introduction
• Profile terminology / Die Profiles
• Overall and class-wise break-up of failure
  modes
• Various complexity failure analysis
• Shape-wise breakdown of each failure mode
• Conclusion / References

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More Terminology

• Crack A visible, generally uneven fissure on
  the surface.
• Break Component is broken in two.
• Chip off A small piece is chipped off the
  surface.
• Wash Out Tiny but sig. craters or depressions
  cause by pitting or erosion.
• Fracture All fatigue failures. Cracking,
  chipping, breaking, surface fatigue, ect.
• Wear Gradual surface deterioration.
• Deflection Going out of shape, or sub-component
  owing to excessive plastic deformation.
• Mixed A combination of the above failures.
• Mandrel When the die has to be scrapped due to
  any failure in the mandrel.
• Miscellaneous Not specifically any of the above
  failures. Softening of the die or bearing

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Class-Wise Breakup of Failure Modes
1. It should be pointed out that the replacement
of the die takes place after cleaning and repair
have occurred many times. The part produced
simply is too far out of dimension.
1. With uneven and unsymmetrical sections, and
existing maximum pressure and friction, the die
(bearing) is most likely to plastically deform.
1. Nitriding oven failures cause sub-optimal
hardening or heat treatment of the die. This
makes the die and bearing softer than is needed.
BPBbrush path broken CCcorner crack DBdie
broken BCObearing chipping
1. In retrospect, brush paths are the most
frequently repeated critical section and thus
play a predominant role in fatigue failure.

• Observations
• This supports intuitive reasoning. With large
  number sharp corners, projections and
  protrusions, slots and grooves, combination of
  thick and thin sections and general lack of
  symmetry, thermal and mechanical fatigue should
  be the primary failure mode.
• Friction between hard aluminum-oxide layer on
  billet and iron-oxide layer on bearing causes
  hard wear problems.
• Due to high temperatures and high extrusion
  speeds, plastice deformation should be expected.

DimCdimension change BWObearing
wash-out Dfdie deflected TBttongue
bent/deflected BDbearing damage DSdie softening
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OUTLINE

• Introduction
• Profile terminology / Die Profiles
• Overall and class-wise break-up of failure
  modes
• Various complexity failure analysis
• Shape-wise breakdown of each failure mode
• Conclusion / References

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Types of Failure per Die Type
1. Since semi-hollow dies are a cross between a
hollow and a solid die, the even contribution of
failure should be expected.

1. Due to lack of mandrel, forces at the die are far
   less wear critical.
2. This would indicate lower heat of friction
   deformation.

1. Since a large majority of the hollow dies
were simple in geometry, there was far less of a
contribution due to fracture.
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OUTLINE

• Introduction
• Profile terminology / Die Profiles
• Overall and class-wise break-up of failure
  modes
• Various complexity failure analysis
• Shape-wise breakdown of each failure mode
• Conclusion / References

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Shape-Wise Breakdown
1. Additional friction, temperatures and forces
at the bearing inlet due to the presence of the
mandrel would indicate the large proportion of
deflection failures in hollow dies.
1. Since contributions of the hollow and
semi-hollow dies are almost equally smalll, it
shows that the predominant failure for solid dies
is fatigue fracture.

1. This confirms the previous conclusion that hollow
   dies fail primarily through wear.
2. Why are the solid and semi-hollow dies about the
   same even though one has a mandral and the other
   does not?

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OUTLINE

• Introduction
• Profile terminology / Die Profiles
• Overall and class-wise break-up of failure
  modes
• Various complexity failure analysis
• Shape-wise breakdown of each failure mode
• Conclusion / References

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Conclusions

• Testing supported the fact that the predominant
  failure for solid dies is fatigue fracture.
• Hollow dies fail primarily by wear.
• Additional friction, temperatures and forces at
  the bearing inlet due to the presence of the
  mandrel and re-weld chambers in hollow dies are
  the reason for the large proportion of deflection
  failures associated with hollow dies.
• Mixed mode failure is prevalent with hollow dies.
• Miscellaneous failure is predominant with solid
  dies.
• Mandrel failure was obviously dominant in hollow
  dies.

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Flaws in Technical Paper

• Very few shape complexities were incorporated in
  the study.
• Only one material type die, and one material type
  billet was tested.
• Time line failure wasnt included to incorporate
  the data with useful economics.
• There variety of hollow dies used in the test
  didnt have many details, and could bias the test
  data.

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Refrences
8 M Gupta, R. Sikand, A.K. Gupta, Scr.
Metallurgy Material, (1994), 30, 1343-1348. 9
M. C. Shaw and J. P. Avery, Forming limits
reliablilty, stress analysis and failure
prevention methods in mechanical design, ASME
Centennial Bound Volume, 297-303, (1980), Century
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Questions?