Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Improved high velocity cold copaction processing: polymer powder to high performance parts
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
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.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 45 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:25
Keyword [en]
high-velocity compaction, powder polymers, polyamide-11, relaxation assist, compactibility, relative green density, morphology, pull-out, springback
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-407OAI: oai:DiVA.org:kth-407DiVA: diva2:10623
Presentation
2005-09-21, Sal B1, Brinellvägen 23, Stockholm, 10:05 (English)
Opponent
Supervisors
Note
QC 20100506Available from: 2005-09-07 Created: 2005-09-07 Last updated: 2010-11-23Bibliographically approved
List of papers
1. Development of a High-Velocity Compaction process for polymer powders
Open this publication in new window or tab >>Development of a High-Velocity Compaction process for polymer powders
2005 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 24, no 7, 909-919 p.Article in journal (Refereed) 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.

Keyword
high-velocity compaction, polyamide-11, powder polymers, compactibility, green density, morphology, relaxation assist, pull-out
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-6226 (URN)10.1016/j.polymertesting.2005.06.008 (DOI)000232677300015 ()2-s2.0-25844462783 (Scopus ID)
Note

QC 20100506

Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2017-12-14Bibliographically approved
2. Determination of springback gradient in the die on compacted polymer powders during high-velocity compaction
Open this publication in new window or tab >>Determination of springback gradient in the die on compacted polymer powders during high-velocity compaction
2006 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 25, no 1, 114-123 p.Article in journal (Refereed) 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.

Keyword
high-velocity compaction; powder polymers; polyamide-11; relaxation assist; strain rates; relative green density; morphology; springback gradient
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-6227 (URN)10.1016/j.polymertesting.2005.09.002 (DOI)000235262700017 ()2-s2.0-31444445807 (Scopus ID)
Note

QC 20100506

Available from: 2006-10-06 Created: 2006-10-06 Last updated: 2017-12-14Bibliographically approved

Open Access in DiVA

fulltext(1227 kB)1886 downloads
File information
File name FULLTEXT01.pdfFile size 1227 kBChecksum MD5
be9a629fe628fe49833e084cdb4c1ee494dcb4451cfeac33c1ce8a14fe6ff7e55f316826
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Azhdar, Bruska
By organisation
Polymer Technology
Polymer Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 1886 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 874 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf