Flow Curve Determination at Large Plastic Strain Levels: Limitations of the Membrane Theory in the Analysis of the Hydraulic Bulge Test

2011 ◽  
Author(s):  
X. Lemoine ◽  
A. Iancu ◽  
G. Ferron
Keyword(s):  
Plastic Strain ◽  
Flow Curve ◽  
Bulge Test ◽  
Membrane Theory ◽  
Large Plastic Strain ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge ◽  
Curve Determination

Comparison of the Identifiability of Flow Curves from the Hydraulic Bulge Test by Membrane Theory and Inverse Analysis

2011 ◽  
Vol 473 ◽  
pp. 360-367 ◽  
Author(s):  
Markus Bambach
Keyword(s):  
Flow Curve ◽  
Inverse Analysis ◽  
Elastic Behavior ◽  
Bulge Test ◽  
Membrane Theory ◽  
Direct Identification ◽  
Flow Curves ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge ◽  
Bulge Height

In the hydraulic bulge test, flow curves are determined by applying a hydrostatic pressure to one side of a clamped sheet metal specimen, which bulges freely into a circular cavity under the pressure. The pressure and various data such as bulge height, curvature and equivalent strain at the pole are recorded and used to calculate the flow curve of the specimen material using analytical equations based on membrane theory. In the determination of the flow curve, the elastic behavior of the specimen, the elastic-plastic transition and bending effects are neglected, and the flow curves calculated this way are affected by these simplifications. An alternative to this procedure is an inverse analysis, which proceeds by searching for a flow curve that minimizes the difference between computed and measured data, e.g. bulge height vs. pressure. An inverse analysis based on a finite element model takes into account elastic and bending effects but since it involves the solution of an optimization problem, it is not clear whether it yields more accurate results than membrane theory. The objective of this paper is to compare the ‘identifiability’ of a given flow curve from the bulge test by direct identification based on membrane theory and by inverse analysis with different objective functions to be minimized. Using a re-identification procedure, it is shown that an inverse analysis can improve the results of the direct identification if a suitable objective function is chosen.

Analysis of the Hydraulic Bulge Test with FEA Concerning the Accuracy of the Determined Flow Curves

2009 ◽  
Vol 410-411 ◽  
pp. 439-447 ◽  
Author(s):  
Alper Güner ◽  
Alexander Brosius ◽  
A. Erman Tekkaya
Keyword(s):  
Flow Curve ◽  
Material Flow ◽  
High Strength ◽  
Bulge Test ◽  
Flow Curves ◽  
Element Analysis ◽  
Hydraulic Bulge ◽  
The Finite Element Analysis ◽  
Curve Determination ◽  
Set Up

This work covers the finite element analysis of geometric and process parameters in hydraulic bulge tests in terms of the accuracy of the evaluated flow curve. The important parameters are identified and varied to cover the whole range of possible uses. The effects of these parameters are analyzed for three representative materials: aluminium, mid-strength steel, and high-strength steel. The flow curves of the materials for each set of parameters are calculated by using the results of the simulations and the membrane theory. It is seen that even with simulation results, it is not always possible to obtain the input flow curve, especially towards the end of the test. The dimensions of the sheet and the tooling affect the plastic strain development and geometry of the bulge, leading to errors in computed flow curves. In order to observe the effect of the material flow from the flange on the determined yield stresses, the function and position of the drawbeads are also examined. These parameters, together with the method used to calculate the radius of the bulge, determine the accuracy of the calculated flow curve. Guidelines for an accurate flow curve determination regarding the test set-up and calculation methods are given.

Determination of Mechanical Properties for the Hydroforming of Magnesium Sheets at Elevated Temperature

2005 ◽  
Vol 6-8 ◽  
pp. 779-786 ◽  
Author(s):  
J. Hecht ◽  
S. Pinto ◽  
Manfred Geiger
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Tensile Test ◽  
Flow Curve ◽  
Elevated Temperatures ◽  
Biaxial Stress ◽  
Bulge Test ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge

Thanks to the low weight, magnesium alloys feature high specific strength and stiffness properties. Thus they prove to be promising materials for todays ambitious automotive light weight construction efforts. Due to their comparative low formability at room temperature the process of magnesium sheet hydroforming can be improved at temperatures higher than 200 °C by the activation of additional sliding planes. This paper illustrates the determination of mechanical properties for the hydroforming of magnesium sheets at elevated temperature. In particular the mechanical behavior at elevated temperature was investigated by means of the tensile test and of the hydraulic bulge test. For the determination of the strains an optical measurement system was introduced into the experimental set-up. The exact knowledge of the strain condition in the area of diffuse necking enabled the determination of the flow curve in the tensile test also beyond the uniform elongation. The influence of temperature and strain rate was analyzed as well as the influence of uni- and biaxial stress state on the flow curve. Using circular and elliptic dies with different aspect ratio the hydraulic bulge test served to determinate the forming limit curves at three different elevated temperatures.

Estimation of Fracture Toughness JIC by Miniature Specimen Hydraulic Bulge Test

2017 ◽  
Vol 898 ◽  
pp. 753-757
Author(s):  
Le Le Gui ◽  
Tong Xu ◽  
Bin An Shou ◽  
Han Kui Wang ◽  
Jing Xiang
Keyword(s):  
Fracture Toughness ◽  
Fracture Energy ◽  
Fracture Strain ◽  
Bulge Test ◽  
Miniature Specimen ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge ◽  
Resistance Curves ◽  
Miniature Specimens ◽  
Load Deflection Curve

The fracture toughness tests and a new miniature specimen technology named hydraulic bulge test (HBT) of 3Cr1Mo1/4V at four service time were carried out. Four J-R resistance curves by single-specimen method with one inch CT specimens were obtained to compute the JIC. Different definitions of equivalent fracture strain according to the section morphologies of HBT testing specimens were compared, and fracture energy of miniature specimens with three different thicknesses (0.4mm, 0.5mm and 0.6mm) were also calculated. Results showed that the typical HBT load-deflection curve can be divided into four sections like SPT curve. Equivalent fracture strain and fracture energy EHB can be chosen as two fracture parameters for the HBT specimen. Ductile fracture toughness JIC can be related approximately linearly to both the equivalent fracture strain and fracture energy EHB.

Hydraulic Bulge Test of Electrodeposited Copper Foil

1999 ◽  
Vol 77 (2) ◽  
pp. 55-59 ◽  
Author(s):  
H. D. Merchant ◽  
M. G. Rozboril
Keyword(s):  
Copper Foil ◽  
Bulge Test ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge

scholarly journals Study of the Hydraulic Bulge Test in T-shape Hydroforming Die

2015 ◽  
Vol 19 ◽  
pp. 70-76 ◽  
Author(s):  
Amir Ashrafi ◽  
Khalil Khalili
Keyword(s):  
Bulge Test ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge
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