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Studies of density variations in iron powder caused by the filling operation
Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
2001 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Detailed information about the density within a part produced by compression of a granular material is perhaps the most important piece of information you need if you are to predict its properties. Nearly all mechanical properties are strongly dependent on the density and the density of a very small region within the part can potentially be disastrous if it has a density level considerably lower then the rest of the part. Filling induced density variations is a problem that long has been overlooked by powder metallurgy scientists. One of the factors that are making investigations difficult is the lack of methods to make experimental data available. In this work four different methods for this purpose have been evaluated.

Metallographic examinations

Has proven to be a reliable method to provide information about the density variations in cut, 2 dimensional cross sections of PM samples. To produce the amount of data necessary to study the filling operation is however considered too labour intensive.

Bulk densitv measurements of compressed samples

A simple and reliable method, perfect for thorough investigations of densityvariations in industrially produced PM components.

Density measurements of filled powder

Although not as accurate as bulk density measurements the increased flexibility of this method can be an advantage when investigating filling behaviour. A novel test rig was constructed that was able to identify and link several different factors to the resulting density variations.

Computerised Tomography

This method has the potential to deliver the same information as metallographic examinations in a much faster and more reliable way. It has however not yet been established if the accuracy ofthe method is sufficient to provide information about the density variation in PM samples caused by the filling operation.

With the bulk density and the filled powder methods deeper studies were also performed to increase the knowledge of powder filling behaviour. It has been established that the filling operation causes density variations within PM parts and that these variations are highly systematic. With the construction of the test rig it was possible to determine several aspects of the feed shoe cycle as responsible for these variations.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2001. , 18 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 905
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-30050Local ID: 15510ISBN: 91-7373-122-6 (print)OAI: oai:DiVA.org:liu-30050DiVA: diva2:250871
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-11-28
List of papers
1. Density Variations in Iron Powder Caused by Die Filling
Open this publication in new window or tab >>Density Variations in Iron Powder Caused by Die Filling
2000 (English)In: PM2000, 2000Conference paper, Published paper (Other academic)
Abstract [en]

In this work the influence of the filling shoe movement on the powder density in a lilled. ring shaped cavity has been investigated. The outer diameter of the cavity was 29 cm and the approximate weight of powder in a filled cavity was 650g. The density variations between different parts of the ring and different types of filling operations have been measured. It has been determined that the movement of the filling shoe causes density variations in the filled powder and that these density variations are identical for rings filled under the same conditions. Conventional filling. where the filling shoe only performs one filling cycle resulted in density variations from 0.354 to 0.363 in relative density. By measuring the particle size distribution in different sections of the rings by laser interferometry it was also possible to detem1ine that the filling shoe movement has a segregating effect on the filled powder. By comparing the amount of segregation with other investigations it was possible to determine that this segregation only has a limited influence (less then 10 %) on the powder density and that the major part of the densification originated from the physical rearrangement of the powder particles.

Keyword
Powder Metallurgy, Powder Filling, Density Variations, Segregation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-30163 (URN)15649 (Local ID)15649 (Archive number)15649 (OAI)
Conference
PM2000, November 12-16 2000, Kyoto, Japan.
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-11-28
2. Filling induced density variations in metal powder
Open this publication in new window or tab >>Filling induced density variations in metal powder
2002 (English)In: Powder Metallurgy, ISSN 0032-5899, Vol. 45, no 2, 146-153 p.Article in journal (Refereed) Published
Abstract [en]

Filling induced density variations is a problem that has long been overlooked by powder metallurgy scientists. In this paper,densityvariations are addressed, both why they occur and what problems they may cause. A test method, including a test rig, is presented that is able to link several different factors to resulting powder densities. The relations are analysed and several density affecting mechanisms are suggested. These mechanisms could be used either to minimise density differences within parts or to control density by directing powder to critical areas.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-30012 (URN)10.1179/003258902225002578 (DOI)000176949500025 ()15456 (Local ID)15456 (Archive number)15456 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-11-28
3. Attempts to use computerised tomography and image analysis to investigate the influence of the filling operation on the density of compressed rings
Open this publication in new window or tab >>Attempts to use computerised tomography and image analysis to investigate the influence of the filling operation on the density of compressed rings
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Computerised tomography has the potential to become an invaluable tool for R&D activities within the field of powder metallurgy. At the present the method is however not sufficiently adapted for this application. Here a novel experimental routine combining computerised tomography with image analysis have been used to investigate the influence of the filling operation on the density distributions within compressed rings. Sufficient time was however not available to fully interpret the produced result and to validate the reliability of this technique. Analysis of less complex samples with known density distributions is suggested as a way to continue this investigation and to test the reliability of the method. The outline for a project where such a study could be perfom1ed is included in this report.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-102052 (URN)
Available from: 2013-11-28 Created: 2013-11-28 Last updated: 2013-11-28

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