1、A Study of Die Failure Mechanisms in Aluminum Extrusion,Presented By: Brian B. Cherry Date: September 15, 2004 Class: Me 582, Professor Ed Red,Authors: A.F.M Arif, A.K. Sheikh, S.Z. Quamar,Received: November 27, 2001 Published By: Journal of Materials Processing Technology,OUTLINE,Introduction Profi
2、le 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,What is Extrusion?,A compression forming process in which the work metal is forced through a die opening to produce a desir
3、ed cross-sectional shape.,Relatively simple shapes,Or more complex shapes,The bulk of aluminum profiles in the construction industry is produced through hot extrusion. Above is An extrusion press container.,Purpose of Technical Paper,Productivity, cost and quality are the overriding commercial facto
4、rs. 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. Testin
5、g: 616 dies, 17 various profiles, H-13 steel. All billets are made of Al-6063.,BlingBling!,Getting Rejected is Expensive And Embarrassing!,OUTLINE,Introduction Profile terminology / Die Profiles Overall and class-wise break-up of failure modes Various complexity failure analysis Shape-wise breakdown
6、 of each failure mode Conclusion / References,Die and Tooling Configuration,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
7、or fracture. Transfers the extrusion load from the die to the pressure ring.,Liner: Provides protection against thermal and mechanical stresses to the large and expensive container.,Stem: It is fitted with the main ram to force the billet through the container.,Dummy Pad: Floating or fitted in front
8、 of the stem. It protects thelife of the costly stem.,Pressure Pad: Transfers the extrusion load from the bolster to the pressure plate and also guards against bolster deflection.,Configuration of a Typical Die,Configuration of a solid flat-face die.,Die Profiles,Common features of die profiles,Thre
9、e types of die profiles,Hollow Dies,Semi-Hollow Dies,Solid Dies,Die Profiles,Sketches and die profiles used in the study.,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
10、mode Conclusion / References,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. C
11、racking, 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. Mis
12、cellaneous: Not specifically any of the above failures. Softening of the die or bearing,Class-Wise Breakup of Failure Modes,BPB=brush path broken CC=corner crack DB=die broken BCO=bearing chipping,DimC=dimension change BWO=bearing wash-outDf=die deflected TBt=tongue bent/deflectedBD=bearing damage D
13、S=die softening,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 h
14、ard 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.,1. In retrospect, brush paths are the most frequently repeated critical section and thus play a predominant role
15、in fatigue failure.,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 (bearin
16、g) 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.,OUTLINE,Introduction Profile terminology / Die Profiles Overall and class-wise break-up of failure modes Various complex
17、ity failure analysis Shape-wise breakdown of each failure mode Conclusion / References,Types of Failure per Die Type,Due to lack of mandrel, forces at the die are far less wear critical. This would indicate lower heat of friction deformation.,1. Since a large majority of the hollow dies were simple
18、in geometry, there was far less of a contribution due to fracture.,1. Since semi-hollow dies are a cross between a hollow and a solid die, the even contribution of failure should be expected.,OUTLINE,Introduction Profile terminology / Die Profiles Overall and class-wise break-up of failure modes Var
19、ious complexity failure analysis Shape-wise breakdown of each failure mode Conclusion / References,Shape-Wise Breakdown,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.,This confirms the pre
20、vious conclusion that hollow dies fail primarily through wear. Why are the solid and semi-hollow dies about the same even though one has a mandral and the other does not?,1. Additional friction, temperatures and forces at the bearing inlet due to the presence of the mandrel would indicate the large
21、proportion of deflection failures in hollow dies.,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,Conclusions,Testing supported the fact that
22、 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 ass
23、ociated 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.,Flaws in Technical Paper,Very few shape complexities were incorporated in the study. Only one material type die, an
24、d 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.,Refrences,1 I. Flitta, T. Sheppard, Nature of friction in extrusion process and
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26、hakkingal, P. Venugopal, Analysis of forming loads, microstructure development and mechanical property evolution during equal channel angular extrusion of a commercial grade aluminum alloy, Journal of Materials Processing Technology, 135 (2003) 59-67. 4 S. Malayappan, R. Narayanasamy, Barrelling of
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28、ce and Technology, August (2002) 803-808. 6 Bruce Chalmers, Physical Metallurgy, 321-327, 332,1959, John Wiley and Sons. 7 F. J. Humphreys, W. S. Miller, M. R. Djazeb, Materials Science and Technology, (1990), 6, 1157-1166.,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 Publications.,Questions?,
