A Comparative Study on Hydraulic Bulge Testing and Analysis Methods

2008 ◽  
Author(s):  
Eren Billur ◽  
Muammer Koc¸
Keyword(s):  
Flow Stress ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Material Behavior ◽  
Biaxial Stress ◽  
Dome Height ◽  
Bulge Test ◽  
Analysis Methods ◽  
Bulge Testing ◽  
Hydraulic Bulge

Hydraulic bulge testing is a material characterization method used as an alternative to tensile testing with the premise of accurately representing the material behavior to higher strain levels (∼70% as appeared to ∼30% in tensile test) in a biaxial stress mode. However, there are some major assumptions (such as continuous hemispherical bulge shape, thinnest point at apex) in hydraulic bulge analyses that lead to uncertainties in the resulting flow stress curves. In this paper, the effect of these assumptions on the accuracy and reliability of flow stress curves is investigated. The goal of this study is to determine the most accurate method for analyzing the data obtained from the bulge testing when continuous and in-line thickness measurement techniques are not available. Specifically, in this study the stress-strain relationships of two different materials (SS201 and Al5754) are obtained based on hydraulic bulge test data using various analysis methods for bulge radius and thickness predictions (e.g., Hill’s, Chakrabarty’s, Panknin’s theories, etc.). The flow stress curves are calculated using pressure and dome height measurements and compared to the actual 3-D strain measurement from a stereo optical and non-contact measurement system ARAMIS. In addition, the flow stress curves obtained from stepwise experiments are compared with the ones from above methods. Our findings indicate that Enikeev’s approach for thickness prediction and Panknin’s approach for bulge radius calculation result in the best agreement with both stepwise experiment results and 3D optical measurement results.

Evaluation of Flow Stresses of Tubular Materials Considering Anisotropic Effects by Hydraulic Bulge Tests

2006 ◽  
Vol 129 (3) ◽  
pp. 414-421 ◽  
Author(s):  
Yeong-Maw Hwang ◽  
Yi-Kai Lin
Keyword(s):  
Flow Stress ◽  
Analytical Model ◽  
Effective Strain ◽  
Tensile Tests ◽  
Biaxial Stress ◽  
Bulge Test ◽  
The Finite Element Method ◽  
Biaxial Stress State ◽  
Hydraulic Bulge ◽  
Bulge Height

This paper aims to evaluate the stress-strain characteristics of tubular materials considering their anisotropic effects by hydraulic bulge tests and a proposed analytical model. In this analytical model, Hill’s orthogonal anisotropic theory was adopted for deriving the effective stresses and effective strains under a biaxial stress state. Annealed AA6011 aluminum tubes and SUS409 stainless-steel tubes were used for the bulge test. The tube thickness at the pole, bulge height, and the internal forming pressure were measured simultaneously during the bulge test. The effective stress-effective strain relations could be determined by those measured values and this proposed analytical model. The flow stress curves of the tubular materials obtained by this approach were compared with those obtained by the tensile test with consideration of the anisotropic effect. The finite element method was also adopted to conduct the simulations of hydraulic bulge forming with the flow stress curves obtained by the bulge tests and tensile tests. The analytical forming pressures versus bulge heights were compared with the experimental results to validate the approach proposed in this paper.

HYDRAULIC BULGE TESTING TO COMPARE FORMABILITY OF CONTINUOUS AND STRETCH BROKEN CARBON FIBER PREPREG LAMINATES

2021 ◽  
Author(s):  
YONI SHCHEMELININ ◽  
JARED W. NELSON ◽  
ROBERTA AMENDOLA
Keyword(s):  
Carbon Fiber ◽  
High Strength ◽  
Biaxial Stress ◽  
Fiber Reinforced Polymer ◽  
Aviation Industry ◽  
Strain Behavior ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites ◽  
Bulge Testing ◽  
Hydraulic Bulge

The use of carbon fiber reinforced polymer composites has increased with the increased need for high-strength, low-density materials, particularly in the aviation industry. Stretch broken carbon fiber (SBCF) is a form of carbon fiber created by the randomized breaking of aligned fibers in a tow at inherent flaw points, resulting in a material constituted of collimated fiber fragments longer than chopped fibers. While continuous carbon fibers possess desirable material properties, the limited formability prevents their wider adoption. SBCF composites exhibit pseudo-plastic deformation that can potentially enable the use of traditional metal forming techniques like stamping and press forming well established in mass production applications. To investigate the formability of SBCF composites prepared with either continuous or stretch broken Hexcel IM-7 12K fiber, impregnated with Huntsman RDM 2019-053 resin, hydraulic bulge testing was performed to explore the strain behavior under biaxial stress conditions at elevated temperature under atmospheric pressure. Initial results show better formability of SBCF compared to continuous fiber, characterized by the axisymmetric response to the applied stress.

Determination of Flow Curves under Equibiaxial Stress Conditions

2012 ◽  
Vol 504-506 ◽  
pp. 53-58 ◽  
Author(s):  
J. Mulder ◽  
Henk Vegter ◽  
Jin Jin Ha ◽  
A.H. van den Boogaard
Keyword(s):  
Low Carbon Steel ◽  
Temperature Correction ◽  
Stress Conditions ◽  
Biaxial Stress ◽  
Bulge Test ◽  
Low Carbon ◽  
Flow Curves ◽  
Hydraulic Bulge ◽  
The Individual

Three experimental methods have been used to establish flow curves for a low carbon steel under biaxial stress conditions: the hydraulic bulge test, the stack compression test and the biaxial tensile test. The individual tests are discussed and the results for a DC06 IF steel grade compared. Initially the results appear to be different but after compensation, including strain rate and temperature correction, the true hardening curves are coinciding.

Understanding the Differences in Hemispherical Dome and Biaxial Test During Equi-Biaxial Tension on Cruciform

2016 ◽  
Author(s):  
Chetan P. Nikhare ◽  
Emmett Vorisek ◽  
John Nolan ◽  
John T. Roth
Keyword(s):  
Sheet Metal ◽  
Test Data ◽  
Biaxial Tension ◽  
Testing Machine ◽  
Biaxial Stress ◽  
Dome Height ◽  
Bulge Test ◽  
Biaxial Test ◽  
Hemispherical Dome ◽  
Biaxial Tests

One metal manufacturing process which uses thousands of processes to trim, stretch, draw, bend etc. under a big umbrella is sheet metal forming. Using heavy equipment, the sheet metal parts are deformed into complex geometries. The complexity in these parts produces multi-axial stress and strain, a state for which it is critical to analyze using conventional tools. Traditionally, the mechanical properties of materials have been characterized using the uniaxial tension test. This test is considered adequate for simple forming operations where single axis loading is dominant. Previous studies, however, have noted that the data acquired from this type of testing is not enough and additional details in other axes under simultaneous deformation conditions are important. To analyze the biaxial strain, some studies have suggested using the limiting dome height test and bulge test. However, these tests limit the extent of using multi-axial loading and the resulting stress pattern due to contact surfaces. Therefore, researchers devised the biaxial machine which is designed specifically to provide biaxial stress components using multiple and varying loading conditions. The idea of this work is to evaluate the relationship between the dome test data and the biaxial test data. For this comparison, cruciform specimens with a diamond shaped thinner gage in the center were deformed with biaxial stretching on the biaxial testing machine. In addition, the cruciform specimens were bi-axially stretched with a hemispherical punch in a conventional die-punch setting. Furthermore, in each case, the process was simulated using a 3D model generated on ABAQUS. These models were then compared with the experimental results. The forces on each arm, strain path, forming and formability was analyzed. The differences between the processes were detailed. It was found that biaxial tests eliminated the pressurization effect which could be found in hemispherical dome tests.

Evaluation of Mechanical Properties of Tubular Materials With Hydraulic Bulge Test for Superconducting Radio Frequency (SRF) Cavities

2013 ◽  
Vol 23 (3) ◽  
pp. 3500604-3500604 ◽  
Author(s):  
H Kim ◽  
M Sumption ◽  
H Lim ◽  
E Collings
Keyword(s):  
Mechanical Properties ◽  
Flow Stress ◽  
Constitutive Equation ◽  
Bulge Test ◽  
Hydraulic Pressure ◽  
Hydraulic Bulge ◽  
Superconducting Radio Frequency ◽  
Constitutive Properties ◽  
Srf Cavities ◽  
Bulge Height

The plastic constitutive equation of tubular materials under hydraulic pressure needs to be determined for the successful application of hydroforming technique to the seamless fabrication of multicell superconducting radiofrequency cavities. This paper provides the empirical constitutive properties of tubular material determined by tensile and hydraulic bulge tests. During an experimental bulge test, the internal pressure, bulge height and wall thickness were continuously measured. Based on this data, the flow stress curves were calculated using an analytical model. From the obtained flow stress curves, numerical simulations were performed, and the resulting bulge heights and wall thicknesses obtained were compared with the experimental results to verify the procedure.

Optimized Yield Curve Determination Using Bulge Test Combined with Optical Measurement and Material Thickness Compensation

2013 ◽  
Vol 549 ◽  
pp. 389-396 ◽  
Author(s):  
Harald Friebe ◽  
Markus Klein ◽  
Ingo Heinle ◽  
Arnulf Lipp
Keyword(s):  
Stress State ◽  
Flow Curve ◽  
Test Specimen ◽  
Yield Curve ◽  
Optical Measurement ◽  
Biaxial Stress ◽  
Bulge Test ◽  
Forming Process ◽  
Biaxial Stress State ◽  
Curve Determination

Axisymmetric die and binder are typically used in the bulge test, where the test specimen is formed by increasing the level of oil pressure (Fig. 1). With this experimental setup a biaxial stress state is induced at the specimen dome, assuming that it is not influenced by friction. The increasing oil pressure in the region of the top of the dome is recorded and the deformation field measured during the forming process. The optical measurement system determines the coordinates, the deformations and the curvature on the outer surface. Based on the forthcoming ISO 16808 these results are directly used for the calculation of the flow curve. In order to determine the flow curve based on the bulge test, an analytical approach is needed for the computation of the stress state at the top of the dome.

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