Material Flow Curve Influence on Macroscopic Residual Stresses in the Workpiece Bottom in High-Pressure Sheet Metal Forming

2006 ◽  
Vol 524-525 ◽  
pp. 173-178
Author(s):  
Rainer Krux ◽  
Werner Homberg ◽  
Matthias Kleiner
Keyword(s):  
High Pressure ◽  
Residual Stresses ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Flow Curve ◽  
Material Flow ◽  
Sheet Material ◽  
Detailed Knowledge ◽  
Process Strategy

The further development of innovative forming processes like sheet metal hydroforming is only possible with the help of detailed knowledge about the workpiece properties and their formation depending on the process strategy. Up to now, the knowledge about the formation of macroscopic residual stresses in high-pressure sheet metal forming (HBU), regarding the influence of the sheet material properties, is still insufficient. The characteristics of the specific forming procedure HBU lead to specific stress and strain gradients in the sheet cross-section, and therefore lead to a characteristic distribution of the induced macroscopic residual stresses, particularly in the workpiece bottom zone. This paper decribes the investigations on the influence of the sheet material flow curve on the macroscopic residual stress distribution in the workpiece bottom.

Analysis of Residual Stresses in High-Pressure Sheet Metal Forming

CIRP Annals ◽  
2004 ◽  
Vol 53 (1) ◽  
pp. 211-214 ◽  
Author(s):  
M. Kleiner ◽  
R. Krux ◽  
W. Homberg
Keyword(s):  
High Pressure ◽  
Residual Stresses ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming

Material Flow Control in High Pressure Sheet Metal Forming of Large Area Parts with Complex Geometry Details

2005 ◽  
Vol 76 (12) ◽  
pp. 905-910 ◽  
Author(s):  
Michael Trompeter ◽  
Erkan Önder ◽  
Werner Homberg ◽  
Erman Tekkaya ◽  
Matthias Kleiner
Keyword(s):  
High Pressure ◽  
Flow Control ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Material Flow ◽  
Complex Geometry ◽  
Large Area ◽  
Material Flow Control

Die Surface Structures and Hydrostatic Pressure System for the Material Flow Control in High-Pressure Sheet Metal Forming

2005 ◽  
Vol 6-8 ◽  
pp. 385-392 ◽  
Author(s):  
Rainer Krux ◽  
Werner Homberg ◽  
M. Kalveram ◽  
Michael Trompeter ◽  
Matthias Kleiner ◽  
...  
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Material Flow ◽  
Surface Structures ◽  
Pressure System ◽  
Tool Surface ◽  
Material Flow Control

A promising approach to control the material flow within deep drawing and workingmedia based forming processes is the structuring of the tool surfaces in the contact zones between workpiece and die. In order to obtain a sufficient and an optimised material flow respectively – especially for non-symmetric or non-uniform workpiece geometries – a locally adapted distribution of surface structures is a practicable solution. The macroscopic, and also the microscopic surface structures can be manufactured sufficiently by means of a high-speed cutting process. The shape of the tool surface structure has a significant influence on the tribological conditions between workpiece and die. To adjust the surface structure distribution to the required material flow distribution, detailed knowledge about the correlation of the material flow from the tribological conditions between sheet and the forming tool is required. A further innovative approach, particularly for decreasing the friction coefficient, is the use of an innovative hydrostatic pressure system using fluid ducts. Its functional principle is based on the reduction of the contact shear stress at the sheet surface in the contact zone with the forming tool by means of locally applying a hydrostatic fluid pressure. To obtain information about the correlation of the material flow from the tool surface structures and from the parameters of the hydrostatic pressure system respectively, fundamental investigations have been carried out. In order to optimise the material flow, these toolbased approaches can be used as stand-alone solution, or in addition to other systems. If the surface structures and a hydrostatic pressure system are used in combination with the multi-point blank holder, which has already been qualified for the high-pressure sheet metal forming (HBU), a powerful system for the material flow control is available.

Influence of Hole Shape and Pattern on the Prediction of Limiting Strain for Perforated Commercial Pure Aluminium Sheets

2012 ◽  
Vol 232 ◽  
pp. 961-965 ◽  
Author(s):  
G. Venkatachalam ◽  
S. Narayanan ◽  
S. Patel Nilay ◽  
Prabhakar Nishant ◽  
C. Sathiya Narayanan
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Sheet Material ◽  
Pure Aluminium ◽  
Numerical Techniques ◽  
Local Necking ◽  
Hole Shape ◽  
Reliable Knowledge ◽  
Aluminium Sheets

One of the needs of modern sheet metal forming is reliable knowledge about the formability of a given material. In sheet metal forming formability is usually related to the ability to have high values of the strain until failure, where this failure can be local necking and/or fracture. This high values of strain is called limiting strain which is not only influenced by material but also by the geometric features of sheet material. In this work, influence of hole shape and the patterns in which holes are arranged on limiting strain, are studied using experimental and numerical techniques. Both experimental and numerical analysis reveals the same.

Multi-Input Multi-Output (MIMO) Modeling and Control for Stamping

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yongseob Lim ◽  
Ravinder Venugopal ◽  
A. Galip Ulsoy
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Material Flow ◽  
Process Model ◽  
Complex Geometry ◽  
Flow Characteristics ◽  
Forming Process ◽  
Punch Force ◽  
Force System

The binder force in sheet metal forming controls the material flow into the die cavity. Maintaining precise material flow characteristics is crucial for producing a high-quality stamped part. Process control can be used to adjust the binder force based on tracking of a reference punch force trajectory to improve part quality and consistency. The purpose of this paper is to present a systematic approach to the design and implementation of a suitable multi-input multi-output (MIMO) process controller. An appropriate process model structure for the purpose of controller design for the sheet metal forming process is presented and the parameter estimation for this model is accomplished using system identification methods. This paper is based on original experiments performed with a new variable blank holder force (or variable binder force) system that includes 12 hydraulic actuators to control the binder force. Experimental results from a complex-geometry part show that the MIMO process controller designed through simulation is effective.

Numerical Investigation of Dry and Lubricated Sheet Metal Forming Processes

2015 ◽  
Vol 651-653 ◽  
pp. 1029-1035 ◽  
Author(s):  
Marion Merklein ◽  
Emanuela Affronti ◽  
Jennifer Steiner
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Material Flow ◽  
Test Procedure ◽  
Discrete Control ◽  
Experimental Investigations ◽  
Finite Element Software ◽  
Dry Forming ◽  
Sustainable Usage

The current global development towards efficient and sustainable usage of resources as well as a stronger environmental awareness motivates lubrication abandonment in metal forming. Dry forming processes accomplish besides a green production technology also a shortage in production steps and time. However, the change of the tribological conditions influences the material flow during the forming operations and has therefore to be taken into account for the design of complex sheet metal forming operations. The aim of this study is a comparison of dry and lubricated processes by numerical as well as experimental investigations. To ensure reliable results a test setup is necessary which provides a discrete control of the process parameters. Furthermore, an analysis of the local material flow by an optical strain measurement system during the whole test procedure should be possible. These requirements are well fulfilled by the so called Nakajima test, which is typically used for the characterisation of the formability of sheet metals. The influence of varying friction coefficients on the material behaviour is discussed based on the numerical model built up in the Finite Element Software LS-Dyna. The numerical results show a good conformity with the experimental outcomes by identifying the strain localisation. Based on the gained knowledge of the investigations an increase of process understanding for dry forming operations will be derived.

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