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Improved high velocity cold copaction processing: polymer powder to high performance parts
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
2005 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

A uniaxial High-Velocity Compaction (HVC) process for polymer powder using a cylindrical, hardened steel die and a new technique with relaxation assist was tested with a focus on the compactibility characteristics and surface morphology of the compacted materials using various heights of relaxation assist device with different compacting profiles.

Relaxation assist device was presented as a new technique to reduce springback, pull-out phenomenon and to improve the compaction process.

The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomenon during the decompacting stage. In this study, polyamide-11 powders with different particle size distributions have been compacted with the application of different compaction profiles, e.g. different energies and velocities. It was found that the relative green density is influenced more by the pre-compacting (primary compaction step) than by the post-compacting (secondary compaction step).

Experimental results for different compaction profiles were presented showing the effect of varying the opposite velocity during the decompacting stage and how to improve the homogeneous densification between the upper and lower surface and the evenness of the upper surface of the compacted powder bed by using relaxation assists, and the influences of the relaxation assist device on the process characteristics. It was found that the relaxation assist improves the compaction of the polymer powder by locking the powder bed in the compacted form. In addition, the relative times of the compacting stage, decompacting stage and the reorganisation of the particles can be controlled by altering the height of the relaxation assist. It was found that the high-velocity compaction process is an interruption process and that the delay times between the pressure waves can be reduced by increasing the height of the relaxation assist device. Furthermore, the first gross instantaneous springback and the total elastic springback are reduced.

Two bonding strain gauges and a high-speed video camera system were used to investigate the springback phenomenon during the compaction process. Scanning electron microscopy (SEM) and image computer board Camera (IC-PCI Imaging Technology) were used to the study the morphological characteristics, the limit of plastic deformation and particle bonding by plastic flow at contact points, and pull-out phenomena.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH , 2005. , s. 45
Serie
Trita-FPT-Report, ISSN 1652-2443 ; 2005:25
Nyckelord [en]
high-velocity compaction, powder polymers, polyamide-11, relaxation assist, compactibility, relative green density, morphology, pull-out, springback
Nationell ämneskategori
Polymerkemi
Identifikatorer
URN: urn:nbn:se:kth:diva-407OAI: oai:DiVA.org:kth-407DiVA, id: diva2:10623
Presentation
2005-09-21, Sal B1, Brinellvägen 23, Stockholm, 10:05 (Engelska)
Opponent
Handledare
Anmärkning
QC 20100506Tillgänglig från: 2005-09-07 Skapad: 2005-09-07 Senast uppdaterad: 2010-11-23Bibliografiskt granskad
Delarbeten
1. Development of a High-Velocity Compaction process for polymer powders
Öppna denna publikation i ny flik eller fönster >>Development of a High-Velocity Compaction process for polymer powders
2005 (Engelska)Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 24, nr 7, s. 909-919Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The High-Velocity Compaction (HVC) process for powder polymers has been studied, with a focus on the compactibility characteristics and surface morphology of the compacted materials, with and without relaxation assists, by increasing compacting quantity and direction. The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomena during the decompacting stage. Polyamide-11 powders with different particle size distributions have been compacted with the application of different compaction profiles, e.g. different energies and velocities. Scanning electron microscopy (SEM) and image computer board camera, (IC-PCI Imaging Technology) have been used to the study the morphological characteristics, the limit of plastic deformation and particle bonding by plastic flow at contact points, and pull-out phenomena. The relative green density is influenced more by the pre-compacting (primary compaction step) than by the post-compacting (secondary compaction step). The pressure and density distribution differences between the upper and lower surface are not uniform. Projectile supports or 'relaxation assists' are presented as a new technique to reduce pull-out phenomenon. Experimental results for different compaction profiles are presented showing the effect of varying the opposite velocity during the decompacting stage, and how to improve the homogeneous densification between the upper and lower surface and the evenness of the upper surface of the compacted powder bed by using relaxation assists.

Nyckelord
high-velocity compaction, polyamide-11, powder polymers, compactibility, green density, morphology, relaxation assist, pull-out
Nationell ämneskategori
Polymerkemi
Identifikatorer
urn:nbn:se:kth:diva-6226 (URN)10.1016/j.polymertesting.2005.06.008 (DOI)000232677300015 ()2-s2.0-25844462783 (Scopus ID)
Anmärkning

QC 20100506

Tillgänglig från: 2006-10-06 Skapad: 2006-10-06 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
2. Determination of springback gradient in the die on compacted polymer powders during high-velocity compaction
Öppna denna publikation i ny flik eller fönster >>Determination of springback gradient in the die on compacted polymer powders during high-velocity compaction
2006 (Engelska)Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 25, nr 1, s. 114-123Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A uniaxial high-velocity compaction process for polymer powder using a cylindrical, hardened steel die and a new technique with relaxation assist was tested with various heights. The influences of the relaxation assist device on the process characteristics are discussed. Two bonded strain gauges and a high-speed video camera system were used to investigate the springback phenomenon during the compaction process. It was found that the relaxation assist improves the compaction of the polymer powder by locking the powder bed in the compacted form. It is shown that the high-velocity compaction process is an interruption process and that the delay times between the pressure waves can be reduced by increasing the height of the relaxation assist device. The delay times between the pressure waves are also strongly dependent on the strain rate. If the height of the relaxation assist device is increased, the first gross instantaneous springback, and the total elastic springback, are reduced. In addition, the density of the powder bed is increased. The relative times of the compacting stage, decompacting stage and the reorganisation of the particles can be also controlled by altering the height of the relaxation assist.

Nyckelord
high-velocity compaction; powder polymers; polyamide-11; relaxation assist; strain rates; relative green density; morphology; springback gradient
Nationell ämneskategori
Polymerkemi
Identifikatorer
urn:nbn:se:kth:diva-6227 (URN)10.1016/j.polymertesting.2005.09.002 (DOI)000235262700017 ()2-s2.0-31444445807 (Scopus ID)
Anmärkning

QC 20100506

Tillgänglig från: 2006-10-06 Skapad: 2006-10-06 Senast uppdaterad: 2017-12-14Bibliografiskt granskad

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