Computer modelling and tooling design for near net shaped components using hot isostatic pressing

doi:10.1016/j.jmatprotec.2006.07.006

Journal of Materials Processing Technology

Volume 182, Issues 1–3, 2 February 2007, Pages 39-49

https://doi.org/10.1016/j.jmatprotec.2006.07.006 Get rights and content

Abstract

The fundamental principles and assumptions underlying an FEM model are described and this model has been used to predict the final dimensions of shaped components produced by hot isostatically pressing (HIPping) Ti–6Al–4V powder. A CAD module (solidworks) has been used for dimensional calibration, tooling design and engineering drawings. A relatively simple small casing component has been produced and the dimensions compared with those predicted from the modelling. It has been shown that there is agreement within about 2% between the achieved geometries and the predictions for this axial-symmetric cylinder body. The physical bases for some of the local discrepancies are discussed and future developments required for improved modelling are outlined.

Introduction

Hot isostatic pressing (HIPping) has been applied to consolidate powder and to close porosity in castings in a wide range of industries, including aerospace, marine, automotive and metal working. Recently, the potential economic advantages of net shape HIPping of powder to produce complex shape and fully dense components from titanium and nickel based alloys [1], [2] or other expensive metal powders has been investigated. In this process, a containing-capsule, together with internal cavities, defined by appropriately shaped tooling, is filled with powder. The capsule is then HIPped under defined conditions, after evacuating air and sealing the capsule and after HIPping the tooling and capsule (commonly of mild steel) are removed by etching or machining. Clearly the accuracy of the final shape is defined by the initial dimensions of the tooling and capsule which in turn are defined by appropriate modelling. This paper is concerned with attempts to model a simple shape and uses an established FEM HIPping model [3] interfaced to an in-house CAD design module.

The precise shaping design requirement for net shape HIPping process has stimulated intensive research activities in the development of computer calculation methods for the prediction of the shape change between the initial and final configurations. A variety of mathematical models have been developed either based on the microscopic approach [2], [4] in which the powder densification behaviour is computed as a sum of contributions from various microscopic densification mechanisms or based on the continuum approach [5], [6], [7], [8] in which the macroscopic deformation of the constituent (powder) is estimated based on conventional theory of material yield flow. These models must be evaluated and validated by comparison of predicted and actual dimensions of components [9]. Understanding and modelling of HIPping [10] and modelling using finite element methods (FEM) [6] have recently been reviewed.

In this paper, the model theory for the analysis of powder densification behaviour is first described in Section 2 and the whole design process is outlined in Section 3. The modelling and manufacture capabilities are demonstrated in Section 4 through the study of a simple small casing component. The achieved casing sample was measured using a coordinate measurement machine (CMM) and the measurements were compared with the predicted results. Some local discrepancies between the realized physical component and the predictions are discussed.

Section snippets

General remarks

Although powder consolidation during HIPping involves several densification mechanisms [2], e.g. mechanical compacts, plastic yield, creep, and diffusion, the model used here is based on a pure continuum plasticity theory [11], with the theory embracing both the powder matrix and the canning/tooling materials. Seliverstov et al. [3] justified the use of plasticity theory by the fact that more than 90% of powder density is gained within this instantaneous plastic yield mechanism, and the model

Computer aided 3D CAD design

The above model has been developed into a commercial software [3] using Visual C++ computer languages and used as an analytical tool for predicting the powder response and shape changes that occur during HIPping. This FEM computing model is integrated with a FEM meshing tool (ABAQUS/CAE) and a computer-assisted design module (3D CAD, solidworks) for the analysis and tooling design purposes. The FEM meshing tool automatically generates and adjusts the meshes that are needed for the FEM

General remarks

A simplified small casing demonstrator, has been modelled, designed and manufactured by HIPping commercial Ti–6Al–4V (Ti6/4) powder into ‘near net’ shape. The proposed demonstrator, as shown in Fig. 2, consists of an axial-symmetric cylindrical body with two small bosses, two edge flanges, two body rings and two reinforced ribs. The whole design and manufacturing process involves initial prediction of the powder response and shape changes (FEM model), subsequent tooling design (CAD drawing) and

Conclusions

A FEM model [3] for predicting the final dimensions of shaped components produced by HIPping has been developed and incorporated into a CAD module for tooling and capsule design and site HIPping control. A simple small casing component has been modelled, designed and produced. The application shows general agreement (better than 2%) between the achieved geometries and the predictions at axial-symmetric cylinder body. Over predictions on ribs and boss features are observed due to the

Acknowledgements

This research is jointly funded by DTI, Rolls-Royce and QinetiQ. Thanks are also due to Prof M.H. Loretto for useful technical discussion and Dr. W. Voice for his constant support in this project.

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Computer modelling and tooling design for near net shaped components using hot isostatic pressing

Abstract

Introduction

Section snippets

General remarks

Computer aided 3D CAD design

General remarks

Conclusions

Acknowledgements

Mater. Design

Int. J. Mech. Sci.

Comput. Meth. Appl. Mech. Eng.

Comput. Meth. Appl. Mech. Eng.

Int. J. Mech. Sci.

Int. J. Mech. Sci.

Int. J. Solids Struct.

Eur. J. Mech. A/Solid

Int. J. Mech. Sci.