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- Arén, Björn, et al.
(författare)
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Die tool dimensioning by finite element method
- 1987
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Ingår i: Powder Metallurgy. - : Informa UK Limited. - 0032-5899 .- 1743-2901. ; 30:2, s. 87-96
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Tidskriftsartikel (refereegranskat)abstract
- Stress and strain are studied using the finite element method in the dimensioning of prestrained die tools for powder compaction. The die geometry has been varied and the die has also been subjected to different types of load. The study shows that the mean pressure transverse to the pressing direction is a dimensioning factor, but that the distribution itself is not very important. For a linear pressure distribution, the stress and strain within the die will differ little from results produced under the assumption of an exponential pressure distribution. Attention is also paid to the possibilities of treating the three-dimensional situation in a real die by different methods of two-dimensional FEM analysis
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- Arén, Björn
(författare)
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Hot working of powders : procedure and products
- 1982
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation can be divided into two main parts. The first deals with the hot working conditions of mild steels in powder forging, the second with the deformation behaviour of powder forged products; both monolithic and compound parts are studied. Hot forging of low alloy steel powders makes it possible to produce complicated parts with properties comparable with homogeneous forged parts, whilst reducing the machining operations necessary to a minimum. This powder forging technique is a high production rate method, and can only be applied to mass produced components. It also gives the possibility of complete reconstruction of the shape of the part. Forging of porous preforms however require certain precautions to be made to prevent working faults and to optimize the densification process. These things are therefore studied with some interest. In order to compete with other high production rate methods such as hot forging, the powder forged parts must be economically advantageous. Therefore the most attractive parts to be produced are those in which substantial material is saved, where most machining operations can be excluded and in which material of substantial structure is required. A method to produce compound structural parts of high strength hardened steel and ductile mild steel from alloyed powders is presented. It involves the manufacture of compound preforms by forging and their heat treatment to produce an optimal structure. On examining the deformation behaviour of compound parts produced, a substantial rise in the fracture toughness is seen, which is associated with the interface between hard and ductile material zones.
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- Arén, Björn, et al.
(författare)
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Investigation of hot iostatic pressing of metal powder to near net shape
- 1988
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Ingår i: HIP. - Luleå : CENTEK. - 918699834X ; , s. 117-124
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Konferensbidrag (refereegranskat)abstract
- Shape control during HIP is influenced by many variables such as container properties, powder filling method, initial density, temperature and pressure cycle, etc. Experiments have been performed using ASP30 aimed at the study of how to produce parts near net shape through the optimization of these variables. Special care was given to the powder filling and laser welded sheet metal containers of special geometry was used. The results indicate that the temperature and pressure cycles during the first stages of the HIP-process have a pronounced effect on the final shape. A HIP-cycle which will result in a close shape is also presented. Graphs
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- Arén, Björn, et al.
(författare)
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Modelling shape change of parts produced by hot isostatic pressing of powders
- 1988
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Ingår i: Powder Metallurgy. - : Informa UK Limited. - 0032-5899 .- 1743-2901. ; 31:2, s. 101-105
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Tidskriftsartikel (refereegranskat)abstract
- Models for analysing shape changes during the HIPping of powder compacts enclosed in preshaped containers are presented. Two limiting mechanisms are considered: homogeneous densification and the motion of a sharply defined densification front through the compact as HIPping proceeds. The shape changes and shrinkages occurring in a number of simple one, two, and three dimensional shapes are analysed and illustrated. Although some of the assumptions implicit in the model are at variance with the conditions found in practice, it is concluded that useful insights are provided into the shape changes occurring during HIPping
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- Arén, Björn, et al.
(författare)
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Modelling the shape change of parts produced by hot iostatic pressing of powders
- 1988
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Ingår i: HIP. - Luleå : CENTEK. - 918699834X ; , s. 107-115
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Konferensbidrag (refereegranskat)abstract
- Densification in a HIP cycle is non-uniform because of the temperature gradient in the powder body. This gradient gives rise to a densification front, which moves from the surface inward. The densification front will, in reality, be more or less diffuse, but may be considered as extremely sharp for the purpose of modelling the shape and dimensional changes of idealized powder bodies. The geometrical considerations presented show that extreme shape change can occur in a practical HIP cycle. As an example, a square cross-section powder body acquires a star-like shape, in which the angle at the edges depends solely on the densification ratio. The results may serve as a base for an improved powder capsule design, taking into account the effects of non-uniform densification
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