Deformation processing of porous metals.

Format:

Book

Thesis/Dissertation

Author/Creator:

Govindarajan, Rajasekaran Mayuram.

Contributor:

Aravas, Nikolaos, advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Mechanical engineering.

0548.

Penn dissertations--Mechanical engineering and applied mechanics.

Mechanical engineering and applied mechanics--Penn dissertations.

Local Subjects:

Penn dissertations--Mechanical engineering and applied mechanics.

Mechanical engineering and applied mechanics--Penn dissertations.

0548.

Physical Description:

179 pages

Contained In:

Dissertation Abstracts International 53-11B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

Deformation processing of porous metals and metal powders is analyzed using analytical and numerical techniques. Porous metals are assumed to have dilute concentration of voids (10%) and the initial density of the metal powder compact is about 62%.

In the first phase of this thesis, plane strain extrusion of porous metals is analyzed using asymptotic techniques. The asymptotic expansions are based on a small parameter $\epsilon$ which is defined as the ratio of the reduction to the length of the die in the reduction region. The constitutive behavior of the power-law hardening 10% porous metal is described using Gurson's plasticity model. The frictional forces that develop at the die-metal interface are taken into account by the Coulomb's law of friction. Asymptotic analysis of porous metal shows that the leading order solution is the same as that of the fully dense metal and the effects of porosity enter as an O($\epsilon$) correction. It is also shown that the flow within the die is radial up to this order. A Finite Element program is developed implementing Gurson's plasticity model. The results of asymptotic analysis agree well with those of finite element calculations.

In the second part of the thesis, emphasis is laid on developing Finite Element programs to model Cold and Hot Isostatic Pressing of metal powder compact. In addition, a simple analytical model is developed to analyze CIPing of a long cylindrical specimen; the results of this analysis and finite element simulation agree well with the experimental observations. The finite element code is designed to take into account the compressible nature of plastic and creep strains predicted by the HIP constitutive models. Analytical solutions are obtained for one element tests and closed die compaction of metal powders under different heat/pressure cycles to test the validity of the developed finite element method. Finally a computer simulation of HIPing of a specimen is carried out for different heat/pressure cycles and the results are compared with the experimental observations. These simulations give some pointers to the origin of "shape change" that is seen in HIPed products.

Notes:

Thesis (Ph.D. in Mechanical Engineering and Applied Mechanics) -- Graduate School of Arts and Sciences, University of Pennsylvania, 1992.

Source: Dissertation Abstracts International, Volume: 53-11, Section: B, page: 5935.

Supervisor: Nikolaos Aravas.

Local Notes:

School code: 0175.

Access Restriction:

Restricted for use by site license.