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Abstract of

" Development of a technological processor for 3D-FEA of rotary swaging processes "

by P. Groche, T. Rathmann

Institute for Production Engineering and Forming Machines,

Darmstadt University of Technology, Petersenstr. 30, D-64287 Darmstadt, Germany rathmann@ptu.tu-darmstadt.de

Title: " Development of a technological processor for 3D-FEA of rotary swaging proc-esses" Authors: Prof. Dr.-Ing. Dipl.-Wirtsch.-Ing. P. Groche, Dipl.-Ing. T. Rathmann Topic: Incremental Forming and Process Simulation Process: Rotary Swaging Address of correspondence: Dipl.-Ing. Thomas Rathmann

PtU, TU Darmstadt Petersenstraße 30 D-64287 Darmstadt

Tel: 06151-165356 Fax: 06151-163021 Email: rathmann@ptu.tu-darmstadt.de

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" Development of a technological processor for 3D-FEA

of rotary swaging processes "

P. Groche, T. Rathmann Institute for Production Engineering and Forming Machines,

Darmstadt University of Technology, Petersenstr. 30, D-64287 Darmstadt, Germany rathmann@ptu.tu-darmstadt.de

Abstract:

Rotary Swaging is an incremental cold-forging technology used to produce axisymmetrical work-

pieces. Most applications involve a reduction of diameter and tapering of the tubular or solid work-

piece. High attainable strains allow a manifold spectrum of possible shapes. The process is repro-

duceable and enables the production of parts with tight tolerances and a surfaces similar to metal-

cutting manufacturing. The use of tubular instead of solid parts as semi-finished products allows

components for lightweight construction. Thus, this process is applied especially in automotive

engineering, where the economisation of resources and weight reduction are considered to be

global objectives.

At present the correlation between the process-dominating parameters remains unknown. This

leads to difficulties in the design of rotary swaging machines as well as to longer try-out times if

component geometries are changed. Sensitivity analyses of process parameters in rotary swaging

are possible by experimental trials or numerical methods. However, experiments have the disad-

vantage of not being able to provide information about important parameters, such as tensions and

strains. Furthermore the experiments themselves are highly cost intensive. In contrast, numerical

calculations like Finite-Element-Analyses provide the opportunity to determine all relevant parame-

ters at moderate cost.

One purpose of this project is to gain basic insights into the influence of single process parameters

on the material flow, tensions, strains and power requirements for rotary swaging. Therefore, the

process variants - infeed and recess swaging - each with or without mandrel should be analysed.

In order to describe the process parameters correctly, it is necessary to built up 3D-models of

workpieces and tools. It is only in this manner that the performing forces and the occurring effects

can be rendered in the tangential direction and realistically reproduced.

Particularities concerning the 3D-simulation of rotary swaging processes are:

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Incremental forming operation with 100 to 300 cycles

Tool-Separation in every cycle

Calculation of large displacements (geometric non-linearity)

Plasticity (non-linear material behaviour)

Contact and friction (non-linear boundary conditions)

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Representation of complex tool kinematics

Calculation of spring-back behaviour

A 3D-model was developed with these particularities in mind. Initial process designs revealed that

the computational time will be a limiting factor despite high-end computer technologies. Addition-

ally, the high amounts of data output represent another problem. Thus, possibilities for simplifica-

tion were elaborated. The computing time could be reduced by using symmetries as well as an

optimized spatial and temporal discretization. The reduction of data was reached by fixing the out-

put at a specific time.

Experimental verifications were carried out after the 3D-simulation-model of the rotary swaging

process was succesfully assemled. In order to obtain online process data of axial and radial forces,

the die segments and infeed chuck were equipped with load cells.

The verification of simulation and experiments was conducted by the comparison of the following

variables:

geometric part properties

process forces

material grain structure of experimental samples and material flow in the FEA

hardness distribution and equivalent plastic strain

After the verification of the simulation-model the influence of potential parameters was elaborated

systematically.

The objective of the next step considered the development of a technological processor. Its main

purpose is to make 3D-FEA for the rotary swaging processes available to "non-FE-users". All re-

quirements for the use have to be restricted to the field of work of the user. Thus, an interface that

allows the 3D-simulation to start by entering user known parameters (machine and process data)

using predefined input masks was programmed.

Routines then compile all necessary input data and subroutines required for the successful simula-

tion. After the computation and simulation is finished an automated evaluation of the FE-results

can be carried out. The analysis of the results is simplified by the graphical display of all relevant

output variables.

Recent investigations on selected geometries confirmed the capability of the 3D-FEA for the rotary

swaging process. With a suitable modeling the rotary swaging process can be sufficiently and ac-

curately simulated and evaluated. Using the technology processor, it is possible to drastically re-

duce the temporal effort of the pre- and post-processing. By the use of the developed interfaces

the 3D-FEA of the rotary swaging process is even available for users without any knowledge or

experience about Finite Element Analysis.