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.

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.

Mechanical properties testing of sheet metal by hydraulic bulge test

2014 ◽  
Author(s):  
Autthasit Dimarn ◽  
Charn Thanadngarn ◽  
Vichit Buakaew ◽  
Yongyuth Neamsup
Keyword(s):  
Mechanical Properties ◽  
Sheet Metal ◽  
Bulge Test ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge ◽  
Mechanical Properties Testing

An Engineering Approach to Strain Rate and Temperature Compensation of the Flow Stress Established by the Hydraulic Bulge Test

2015 ◽  
Vol 651-653 ◽  
pp. 138-143 ◽  
Author(s):  
J. Mulder ◽  
Henk Vegter ◽  
A.H. van den Boogaard
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Thickness Distribution ◽  
Accurate Determination ◽  
Plastic Work ◽  
Bulge Test ◽  
Hydraulic Bulge Test ◽  
Hydraulic Bulge ◽  
Steel Grades ◽  
Optical Strain

Optical measuring systems enable a very accurate determination of the flow stress for the hydraulic bulge test. The flow stress is strain rate and temperature dependent and for the description of work hardening an approximation of the temperature during the test is required. Measuring the temperature during the test usually interferes with the optical strain measurement. A model for the temperature distribution on the bulged surface is developed based on heat generated by plastic work, convection to air on the outer surface, conduction to the tools at the die diameter and conduction to oil on the inside. The plastic work is derived from an approximation of the shape of the bulged surface and an approximation for the thickness distribution, starting from the initial thickness at the die ring to the established thickness at the pole, making use of volume conservation for the bulged sheet. The parameters of the model are tuned to bulge test temperature measurements of four different steel grades using a thermo couple at the pole. The results of the analytical temperature model are in good agreement with the measurements.

A Procedure for the Evaluation of Flow Stress of Sheet Metal by Hydraulic Bulge Test Using Elliptical Dies

2012 ◽  
Vol 504-506 ◽  
pp. 107-112 ◽  
Author(s):  
Lucian Lazarescu ◽  
Ioan Pavel Nicodim ◽  
Dan Sorin Comsa ◽  
Dorel Banabic
Keyword(s):  
Flow Stress ◽  
Sheet Metal ◽  
Equivalent Stress ◽  
Equivalent Strain ◽  
Bulge Test ◽  
Sheet Metals ◽  
Experimental Procedure ◽  
Hydraulic Bulge ◽  
Two Parameters

The paper describes a new experimental procedure for the determination of the curves relating the equivalent stress and equivalent strain of sheet metals by means of the hydraulic bulge tests through elliptical dies. The procedure is based on an analytical model of the bulging process and involves the measurement of only two parameters (pressure acting on the surface of the specimen and polar deflection).

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.

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.

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