A Modified Johnson-Cook Model for Sheet Metal Forming at Elevated Temperatures and Its Application for Cooled Stress-Strain Curve and Spring-Back Prediction

2011 ◽  
Author(s):  
Nguyen Duc-Toan ◽  
Banh Tien-Long ◽  
Kim Young-Suk ◽  
Jung Dong-Won
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Spring Back ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cook Model

scholarly journals Springback Analysis in Sheet Metal Forming Using Modified Ludwik Stress-Strain Relation

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Sanjay Kumar Patel ◽  
Radha Krishna Lal ◽  
J. P. Dwivedi ◽  
V. P. Singh
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Spring Back ◽  
Stress Strain ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Strain Relationship ◽  
Von Mises ◽  
Strain Hardening Index

This paper deals with the springback analysis in sheet metal forming using modified Ludwik stress-strain relation. Using the deformation theory of plasticity, formulation of the problem and spring back ratio is derived using modified Ludwik stress strain relationship with Tresca and von Mises yielding criteraia. The results have been representing the effect of different value of or ratio, different values of Strain hardening index (), Poisson’s ratio (), and thickness on spring back ratio (). The main aim of this paper is to study the effects of the thickness, ratio, and Poisson’s ratio in spring back ratio.

Stress-Based Forming Limits in Sheet-Metal Forming

2000 ◽  
Vol 123 (4) ◽  
pp. 417-422 ◽  
Author(s):  
Thomas B. Stoughton
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Strain Path ◽  
Forming Limit ◽  
Stress Strain ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
The Stability ◽  
Definition Of

A strain-based forming limit criterion is widely used throughout the sheet-metal forming industry to gauge the stability of the deformed material with respect to the development of a localized neck prior to fracture. This criterion is strictly valid only when the strain path is linear throughout the deformation process. There is significant data that shows a strong and complex dependence of the limit criterion on the strain path. Unfortunately, the strain path is never linear in secondary forming and hydro-forming processes. Furthermore, the path is often found to be nonlinear in localized critical areas in the first draw die. Therefore, the conventional practice of using a path-independent strain-based forming limit criterion often leads to erroneous assessments of forming severity. Recently it has been reported that a stress-based forming limit criterion appears to exhibit no strain-path dependencies. Subsequently, it has been suggested that this effect is not real, but is due to the saturation of the stress-strain relation. This paper will review and compare the strain-based and stress-based forming limit criteria, looking at a number of factors that are involved in the definition of the stress-based forming limit, including the role of the stress-strain relation.

The Effect of Anisotropy on Spring-Back of CK67 Steel Sheet in L-Dies Bending Processes

2011 ◽  
Vol 291-294 ◽  
pp. 672-675
Author(s):  
Jafar Bazrafshan ◽  
A. Gorji ◽  
A. Taghizadeh Armaky
Keyword(s):  
Numerical Simulations ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Steel Sheet ◽  
Elastic Recovery ◽  
Sheet Thickness ◽  
Bend Angle ◽  
Spring Back ◽  
Geometric Changes

One of the most sensitive features of sheet metal forming processes is the elastic recovery during unloading, called spring-back, which leads to some geometric changes in the product. This phenomenon will affect bend angle and bend curvature, and can be influenced by various factors. In this research, the effects of sheet thickness and die radiuses an sheet anisotropy on spring-back in L-die bending of CK67 steel sheet were studied by experiments and numerical simulations.

Sheet Metal Forming - A New Kind of Forge for the Future

2007 ◽  
Vol 344 ◽  
pp. 9-20 ◽  
Author(s):  
Manfred Geiger ◽  
Marion Merklein
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Elevated Temperatures ◽  
High Strength ◽  
Light Weight ◽  
Influencing Parameters ◽  
General Possibility ◽  
Industrial Relevance ◽  
Weight Structures

Within the last years in sheet metal forming a trend towards forming at elevated temperatures as well as temperature assisted forming technologies can be observed. This development is caused by the increasing need on light and high strength materials in order to fulfill the demands of light weight structures. The decision which kind of temperature assistance is the most useful in order to improve the formability of the material depends on a hugh number of process influencing parameters, like e.g. the material itself, the geometry of the component, the number of forming operations etc.. In this paper the general possibility to separate different temperature assisted forming processes with regard to the used materials will be introduced. The different forming procedures will be explained and discussed. Examples with an industrial relevance are shown.

Deformational characteristics of thermally treated sandstone from an underground coalmine fire region, India

2021 ◽  
Author(s):  
Adarsh Tripathi ◽  
Noopur Gupta ◽  
Ashok Kumar Singh ◽  
Nachiketa Rai ◽  
Anindya Pain
Keyword(s):  
Large Scale ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Small Scale ◽  
Carbonaceous Shale ◽  
Deformation Pattern ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Thermomechanical Behaviour ◽  
Thermally Treated

<p>The Jharia region of lower Gondwana in India is one of the largest Underground Coalmine Fires (UCF) affected coalfield in the world. The UCF induced small scale as well as large-scale surface fracturing often creates the life-threatening conditions to coal miners and local surroundings. So, there is a need to understand the thermomechanical behaviour of coal measures rocks to predict the land disturbances in thermo-environmental conditions. It will provide an insight into the UCF induced subsidence mechanism and its preventive measures. The Jharia coal field predominantly consists of sandstone (75-80% by volume) and rest is composed of coal, shale and carbonaceous shale. The present study focuses on thermo-mechanical behaviour of Barakar sandstone (BS) under elevated temperatures. The cores of BS sample were prepared according to the ISRM standards. Further, samples were grouped and thermally treated in temperature range of 25°C, 100°C, 150°C, 300°C, 400°C, 500°C, 600 °C, 700°C and 800°C at a heating rate of 5°C/min for 24 hours in furnace.  Then, these thermally treated BS samples were subjected to laboratory test for stress-strain characteristics. In the process of deformational characteristics evaluation, effect of mineralogical changes and mode of fracture pattern were also studied at the mentioned elevated temperature. Based on the obtained results, the deformational behaviour of thermally treated BS specimens can be grouped into three zones, viz., zone 1 (25-300°C), zone 2 (300-500°C) and zone 3 (500-800°C). In zone 1, the characteristics of the stress-strain curve is similar to those under air dried sandstone specimen. However, small increment in stiffness were observed upto 300°C. The stress-strain curves in this zone shows dominantly brittle fracturing. The increment in stiffness may be related to evaporation of pore water that increases the cohesion between the mineral grains resulting higher stiffness value. In zone 2, the deformation pattern again shows brittle fracturing with continuous decrement in stiffness. The reduction in stiffness may be related to thermally induced porosity and increased microcrack density. In zone 3, the stress strain curve is observed to be concave upward. It indicates the pseudo-ductile behaviour of the thermally treated BS specimens. The observed results suggest a typical behaviour of deformation pattern under UCF induced rock fracturing which may be useful in predicting the land subsidence in UCF affected areas. Present research outcome may be used to design the support measures to reduce the associated hazards.</p>

Sheet metal forming at elevated temperatures

CIRP Annals ◽  
2006 ◽  
Vol 55 (2) ◽  
pp. 793-816 ◽  
Author(s):  
R. Neugebauer ◽  
T. Altan ◽  
M. Geiger ◽  
M. Kleiner ◽  
A. Sterzing
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Elevated Temperatures
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