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.

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 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.

Flow Stress Determination of Steel Tube for Hydroformability Evaluation

2012 ◽  
Vol 622-623 ◽  
pp. 656-660
Author(s):  
P. Boonpuek ◽  
S. Jirathearanat ◽  
N. Depaiwa
Keyword(s):  
Flow Stress ◽  
Analytical Model ◽  
Effective Stress ◽  
Steel Tube ◽  
Bulge Test ◽  
Stress Strain ◽  
Contact Points ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge ◽  
Internal Pressures

This study aims to determine flow stress of a steel tube by using hydraulic bulge test. A new proposed analytical model for analyzing bulge shapes of hydroformed tubes is postulated. Bulge test apparatus designed using FEA simulation of hydroforming and STKM 11A steel tubes are used in the hydraulic bulge test. Bulge heights and internal pressures are measured during bulge testing. Tube thicknesses at vertex of a bulge shape are measured by a dial caliper gauge. Bulge curvatures and contact points are measured by taking digital photos of bulge shapes combined with measurement methods in CAD software. Effective stress - strain relationships are obtained from the newly developed analytical model using those measured values. Flow stress curves obtained from the effective stress – strain relationships are compared with those by other researchers and tensile test. Finite element analysis methods are used to conduct simulation of tube hydroforming using the flow stress curves. Predicted internal pressures versus bulge heights and tube thicknesses are compared with experimental results. Verification of the developed analytical model is presented. The flow stress at neck point of formed tube is determined.

scholarly journals Design and Analysis of a Bulge Test Device

2021 ◽  
Vol 41 (3) ◽  
pp. e85756
Author(s):  
Luis Humberto Martínez Palmeth ◽  
María Angelica Gonzalez Carmona ◽  
José Miranda Castro
Keyword(s):  
Mechanical Design ◽  
Plate Theory ◽  
Biaxial Stress ◽  
Analytical Models ◽  
Bulge Test ◽  
Plastic Behavior ◽  
Test Device ◽  
Biaxial Stress State ◽  
The One ◽  
Main Components

The aim of this work is to present the methodological process to design a device capable of performing Bulge tests. This kind of device allows obtaining more information about the plastic behavior of a material than the one provided by a traditional tensile test. The engineering specifications of the device were evaluated through the QFD methodology. Then, a basic design of the device was performed based on available analytical models such as thick-walled pressure vessel theory, annular plate theory, and a basic plasticity model for the biaxial stress state. Later, a detailed design of the device was proposed, which was evaluated by means of a 3D model of finite elements and a linearstatic analysis for the main components. Finally, a 2D axisymmetric model and a dynamic non-linear analysis were performed to validate the proposed design. The main novelty of the work consists of articulating the methodology of the mechanical design process and the conception, design, and validation of a Bulge device while solving the deficiencies found in the literature regarding the design and validation processes of this type of devices.

Hydraulic Bulge Tests of Magnesium Tubes at Elevated Temperatures

2009 ◽  
Vol 83-86 ◽  
pp. 1135-1142 ◽  
Author(s):  
Yeong-Maw Hwang ◽  
H.C. Chuang ◽  
B.J. Chen
Keyword(s):  
Magnesium Alloy ◽  
Elevated Temperatures ◽  
Testing Machine ◽  
Tube Hydroforming ◽  
Tensile Tests ◽  
Biaxial Stress ◽  
Tube Length ◽  
Uniaxial Tensile ◽  
Hydraulic Bulge ◽  
Different Temperatures

Evaluation of the formability of tubes is an important issue in tube hydroforming processes. Since tubular materials during tube hydroforming are under a biaxial even triaxial stress state, other biaxial-stress-based testing methods are needed. In this paper, uniaxial tensile tests at different temperatures are firstly employed to evaluate the material properties of magnesium alloy AZ61 tubes. A hydraulic bulge warm forming machine, which is used for hydraulic bulge tests with a fixed tube length, is also designed and manufactured. Using this self-designed testing machine, experiments of bulge tests of magnesium alloy AZ61 tubes at elevated temperatures are carried out. From the experimental results, the bulge formability of the magnesium alloy tubes at different temperatures is discussed.

scholarly journals Influence of elongation factor on distributions of effective strain and flow stress for pushing through a conical die process of round bars made from S355 steel

2019 ◽  
Vol 252 ◽  
pp. 05004
Author(s):  
Tomasz Miłek
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Flow Stress ◽  
Computer Modelling ◽  
Effective Strain ◽  
Elongation Factor ◽  
The Finite Element Method ◽  
Elongation Factors ◽  
Conical Die ◽  
Commercial Code

The paper presents computer modelling results of researches on pushing through a conical die process of round bars. Calculations were carried out using the commercial code QFORM-2D, based on the Finite Element Method (FEM). Investigations involved the use of circular sectioned S355 (1.0577) steel segments of rods with diameter of 9 mm and conical dies with different diameter of sizing portion of a die (d = 7.1 mm; 7.6 mm and 8.0 mm). The aim of the paper is to compare distributions of effective strain and flow stress in longitudinal sections of round bars at different elongation factors (λ1 = 1.24, λ2 = 1.37 and λ3 = 1.57).

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.

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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