Failure Prediction in Hydroforming of Pre-Bent HSLA Tube Using an Extended Stress-Based Forming Limit Curve

2006 ◽  
Author(s):  
M. Sorine ◽  
C. H. M. Simha ◽  
I. van Riemsdijk ◽  
M. J. Worswick
Keyword(s):  
Tube Hydroforming ◽  
Forming Limit ◽  
Limit Curve ◽  
Expansion Tube ◽  
Forming Limit Curve ◽  
Free Expansion ◽  
Explicit Finite Element ◽  
User Subroutine ◽  
Failure Location ◽  
Good Agreement

This paper examines the prediction of failure during the hydroforming of pre-bent HSLA350 tubes using the Extended Stress-Based Forming Limit Curve (XSFLC) [1]. The process of obtaining a strain-based forming limit curve (ε-FLC) for the tube and its application to the prediction of failure in tube hydroforming, utilizing the XSFLC, is presented in detail. The XSFLC was obtained from ε-FLC that was calibrated using the results of free expansion tube burst tests. Tube bending and hydroforming experiments were carried out and modeled using the dynamic explicit finite element code, LS-DYNA. An LS-DYNA user subroutine that utilizes the XSFLC to predict the onset of necking was used to model the tube material. The predicted failure location and pressure at the onset of necking were found to be in a good agreement with the experimental results.

Application of an Extended Stress-Based Forming Limit Curve to Predict Necking in Stretch Flange Forming

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
C. Hari Manoj Simha ◽  
Rassin Grantab ◽  
Michael J. Worswick
Keyword(s):  
Aluminum Alloy ◽  
Metal Forming ◽  
Shell Element ◽  
Forming Limit ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Circumferential Crack ◽  
Flange Forming ◽  
Failure Location ◽  
Forming Limit Curves

An extension of the stress-based forming limit curve (FLC) advanced by Stoughton (2000, “A General Forming Limit Criterion for Sheet Metal Forming,” Int. J. Mech. Sci., 42, pp. 1–27) is presented in this work. With the as-received strain-based FLCs and stress-strain curves for 1.6-mm-thick AA5754 and 1-mm-thick AA5182 aluminum alloy, stress-based FLCs are obtained. These curves are then transformed into extended stress-based forming limit curves (XSFLCs), which consist of the invariants, effective stress, and mean stress. By way of application, stretch flange forming of these aluminum alloy sheets is considered. The AA5754 stretch flange displays a circumferential crack during failure, whereas the AA5182 stretch flange fails through a radial crack at the edge of the cutout. It is shown that the necking predictions obtained using the strain- and stress-based FLCs in conjunction with shell element computations are inconsistent when compared with the experimental results. By comparing the results of the shell element computations with those in which the mesh comprises eight-noded solid elements, it is demonstrated that the plane stress approximation is not valid. The XSFLC is then used with results from the solid-element computations to predict the punch depths at the onset of necking. Furthermore, it is shown that the predictions of failure location and failure mode obtained using the XSFLC are in accord with the differences observed between the two alloys/gauges.

Study on the Formability and its Geometric Factors of Seamed Tube Hydroforming

2011 ◽  
Vol 314-316 ◽  
pp. 733-737
Author(s):  
Xian Feng Chen ◽  
Zhong Qi Yu ◽  
Shu Hui Li
Keyword(s):  
Tube Hydroforming ◽  
Fem Simulation ◽  
Numerical Approach ◽  
Strain Increment ◽  
Forming Limit ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Geometric Factors ◽  
Geometrical Features ◽  
Sensitivity Studies

Forming limit curve (FLC) is an important tool for assessing formability of steel metal. It is commonly obtained from experiment, theoretical calculation and finite element method (FEM) simulation. In this study, the FLC of a seamed tube hydroforming is established by combining the failure criterion of strain increment ratio and FEM simulation. The numerical method is verified by tube bulge tests. Then the sensitivity studies are carried out to evaluate the effect of the geometrical features of seamed tube on its formability by numerical approach. Results show that the changes of the formability with the geometrical features of a seamed tube.

Prediction of Necking in Tubular Hydroforming Using an Extended Stress-Based Forming Limit Curve

2006 ◽  
Vol 129 (1) ◽  
pp. 36-47 ◽  
Author(s):  
C. Hari Manoj Simha ◽  
Javad Gholipour ◽  
Alexander Bardelcik ◽  
Michael J. Worswick
Keyword(s):  
Finite Element ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
Forming Limit ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Load Paths ◽  
Final Failure ◽  
Stress States ◽  
Failure Location

This paper presents an extended stress-based forming limit curve (XSFLC) that can be used to predict the onset of necking in sheet metal loaded under non-proportional load paths, as well as under three-dimensional stress states. The conventional strain-based ϵFLC is transformed into the stress-based FLC advanced by Stoughton (1999, Int. J. Mech. Sci., 42, pp. 1–27). This, in turn, is converted into the XSFLC, which is characterized by the two invariants, mean stress and equivalent stress. Assuming that the stress states at the onset of necking under plane stress loading are equivalent to those under three-dimensional loading, the XSFLC is used in conjunction with finite element computations to predict the onset of necking during tubular hydroforming. Hydroforming of straight and pre-bent tubes of EN-AW 5018 aluminum alloy and DP 600 steel are considered. Experiments carried out with these geometries and alloys are described and modeled using finite element computations. These computations, in conjunction with the XSFLC, allow quantitative predictions of necking pressures; and these predictions are found to agree to within 10% of the experimentally obtained necking pressures. The computations also provide a prediction of final failure location with remarkable accuracy. In some cases, the predictions using the XSFLC show some discrepancies when compared with the experimental results, and this paper addresses potential causes for these discrepancies. Potential improvements to the framework of the XSFLC are also discussed.

A New Calibration Method for FLCs in the M-K Frame-Work

2011 ◽  
Vol 341-342 ◽  
pp. 426-431
Author(s):  
Amir Ghazanfari ◽  
Ahmad Assempour
Keyword(s):  
Metal Forming ◽  
Calibration Method ◽  
Forming Limit ◽  
Experimental Point ◽  
Trial And Error ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Frame Work ◽  
Inhomogeneity Factor ◽  
Good Agreement

The main drawback of the method proposed by Marciniak and Kuczynski for prediction of the limit strains in sheet metal forming processes is requirement of an experimental point of the forming limit curve (FLC) in order to calibrate the curve. The purpose of this work is to introduce a new method to calibrate the FLC using the M-K model in which no experimental data is needed. To achieve this goal, many experimental FLCs were collected from the literature and the values of the initial inhomogeneity factors were determined for them with trial and error aproach. Using these data, an empirical law was developed to predict the value of inhomogeneity factor. The resultant curves show good agreement with the experiments.

Formability Analysis of AA6061 Sheet in T6 Condition

2015 ◽  
Vol 766-767 ◽  
pp. 416-421
Author(s):  
S. Vijayananth ◽  
V. Jayaseelan ◽  
G. Shivasubbramanian
Keyword(s):  
Experimental Method ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Ansys Software ◽  
Limit Curve ◽  
High Corrosion Resistance ◽  
Forming Limit Curve ◽  
Drawing Test ◽  
Deep Drawing Test ◽  
Alloy 6061

Formability of a material is defined as its ability to deform into desired shape without being fracture. There will always be a need for formability tests, a larger number of tests have been used in an effort to measure the formability of sheet materials. Aluminium Alloy 6061 is a magnesium and silicon alloy of aluminium. It is also called as marine material as it has high corrosion resistance to seawater. In this paper Formability test of AA6061 sheet is done by Forming Limit Diagram (FLD) Analysis. FLD or Forming Limit Curve (FLC) for the forming processes of AA6061 sheets is obtained by Experimental method and FEM. Experimental method involves Deep drawing test of the sheet and ANSYS software is used for FEM.

Experimental and Numerical Analysis of Forming Limits in CNC Incremental Sheet Forming

2007 ◽  
Vol 344 ◽  
pp. 511-518 ◽  
Author(s):  
Markus Bambach ◽  
M. Todorova ◽  
Gerhard Hirt
Keyword(s):  
Sheet Metal ◽  
Sheet Forming ◽  
Incremental Sheet Forming ◽  
Negative Slope ◽  
Evaluation Procedure ◽  
Forming Limit ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Forming Limits ◽  
Straight Line

Asymmetric incremental sheet forming (AISF) is a relatively new manufacturing process for the production of low volumes of sheet metal parts. Forming is accomplished by the CNC controlled movements of a simple ball-headed tool that follows a 3D trajectory to gradually shape the sheet metal blank. Due to the local plastic deformation under the tool, there is almost no draw-in from the flange region to avoid thinning in the forming zone. As a consequence, sheet thinning limits the amount of bearable deformation, and thus the range of possible applications. Much attention has been given to the maximum strains that can be attained in AISF. Several authors have found that the forming limits are considerably higher than those obtained using a Nakazima test and that the forming limit curve is approximately a straight line (mostly having a slope of -1) in the stretching region of the FLD. Based on these findings they conclude that the “conventional” forming limit curves cannot be used for AISF and propose dedicated tests to record forming limit diagrams for AISF. Up to now, there is no standardised test and no evaluation procedure for the determination of FLCs for AISF. In the present paper, we start with an analysis of the range of strain states and strain paths that are covered by the various tests that can be found in the literature. This is accomplished by means of on-line deformation measurements using a stereovision system. From these measurements, necking and fracture limits are derived. It is found that the fracture limits can be described consistently by a straight line with negative slope. The necking limits seem to be highly dependent on the test shapes and forming parameters. It is concluded that standardisation in both testing conditions and the evaluation procedures is necessary, and that a forming limit curve does not seem to be an appropriate tool to predict the feasibility of a given part design.

Visual method for measuring forming limit curve of pliable composite film

2021 ◽  
Vol 0 (0) ◽  
pp. 1-12
Author(s):  
CHEN Ren-hong ◽  
◽  
◽  
LIANG Jin ◽  
YE Mei-tu ◽  
...  
Keyword(s):  
Composite Film ◽  
Forming Limit ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Visual Method

Experimental Investigation on Forming Limit Curve at Elevated Temperature Through Dome and Biaxial Test

2020 ◽  
Author(s):  
Chetan P. Nikhare ◽  
Evan Teculver ◽  
Faisal Aqlan
Keyword(s):  
Air Pollution ◽  
Fuel Consumption ◽  
Axial Stress ◽  
High Strength ◽  
Tension Test ◽  
Forming Limit ◽  
Biaxial Test ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Stress States

Abstract The characteristics of metal and materials are very important to design any component so that it should not fail in the life of the service. The properties of the materials are also an important consideration while setting the manufacturing parameters which deforms the raw material to give the design shape without providing any defect or fracture. For centuries the commonly used method to characterize the material is the traditional uniaxial tension test. The standard has been created for this test by American Standard for Testing Materials (ASTM) – E8. This specimen is traditionally been used to test the materials and extract the properties needed for designing and manufacturing. It should be noted that the uniaxial tension test uses one axis to test the material i.e., the material is pulled in one direction to extract the properties. The data acquired from this test found enough for manufacturing operations of simple forming where one axis stretching is dominant. Recently a sudden increase in the usage of automotive vehicles results in sudden increases in fuel consumption which results in an increase in air pollution. To cope up with this challenge federal government is implying the stricter environmental regulation to decrease air pollution. To save from the environmental regulation penalty vehicle industry is researching innovation which would reduce vehicle weight and decrease fuel consumption. Thus, the innovation related to light-weighting is not only an option anymore but became a mandatory necessity to decrease fuel consumption. To achieve this target, the industry has been looking at fabricating components from high strength to ultra-high strength steels or lightweight materials. This need is driven by the requirement of 54 miles per gallon by 2025. In addition, the complexity in design increased where multiple individual parts are eliminated. This integrated complex part needs the complex manufacturing forming operation as well as the process like warm or hot forming for maximum formability. The complex forming process will induce the multi-axial stress states in the part, which is found difficult to predict using conventional tools like tension test material characterization. In many pieces of literature limiting dome height and bulge tests were suggested analyzing these multi-axial stress states. However, these tests limit the possibilities of applying multi-axial loading and resulting stress patterns due to contact surfaces. Thus, a test machine called biaxial test is devised which would provide the capability to test the specimen in multi-axial stress states with varying load. In this paper, two processes, limiting dome test and biaxial test were experimented to plot the forming limit curve. The forming limit curve serves the tool for the design of die for manufacturing operation. For experiments, the cruciform test specimens were used in both limiting dome test and biaxial test and tested at elevated temperatures. The forming limit curve from both tests was plotted and compared. In addition, the strain path, forming, and formability was investigated and the difference between the tests was provided.

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