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.

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.

Characteristics of Residual Stress by Water-Jet Peening

2013 ◽  
Vol 768-769 ◽  
pp. 564-571 ◽  
Author(s):  
Kenji Suzuki ◽  
Takahisa Shobu ◽  
Ayumi Shiro
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Water Jet ◽  
Biaxial Stress ◽  
X Rays ◽  
Lattice Plane ◽  
Scanning Method ◽  
Depth Direction ◽  
Biaxial Stress State ◽  
Specimen Material

The specimen material was austenitic stainless steel, SUS316L. The residual stress was induced by water-jet peening. The residual stress was measured using the 311 diffraction with conventional X-rays. The measured residual stress showed the equi-biaxial stress state. To investigate thermal stability of the residual stress, the specimen was aged thermally at 773 K in air to 1000 h. The residual stress kept the equi-biaxial stress state against the thermal aging. Lattice plane dependency of the residual stress induced by water-jet peening was evaluated using hard synchrotron X-rays. The residual stress measured by the soft lattice plane showed the equi-biaxial stress state, but the residual stress measured by the hard lattice plane did not. In addition, the distributions of the residual stress in the depth direction were measured using a strain scanning method with hard synchrotron X-rays and neutrons.

Plastic behaviour of perforated sheets under biaxial stress state

1997 ◽  
Vol 39 (7) ◽  
pp. 781-793 ◽  
Author(s):  
Seung Chul Baik ◽  
Heung Nam Han ◽  
Sang Heon Lee ◽  
Kyu Hwan Oh ◽  
Dong Nyung Lee
Keyword(s):  
Stress State ◽  
Biaxial Stress ◽  
Plastic Behaviour ◽  
Biaxial Stress State ◽  
Perforated Sheets

Mastering the biaxial stress state in nanometric thin films on flexible substrates

2014 ◽  
Vol 306 ◽  
pp. 70-74 ◽  
Author(s):  
D. Faurie ◽  
P.-O. Renault ◽  
E. Le Bourhis ◽  
G. Geandier ◽  
P. Goudeau ◽  
...  
Keyword(s):  
Thin Films ◽  
Stress State ◽  
Biaxial Stress ◽  
Flexible Substrates ◽  
Biaxial Stress State

Application of a Multiaxial Fatigue Criterion for the Evaluation of Life of Gears of Complex Geometry

2003 ◽  
Author(s):  
Leonardo Borgianni ◽  
Paola Forte ◽  
Luigi Marchi
Keyword(s):  
Fatigue Life ◽  
Stress State ◽  
Life Prediction ◽  
Complex Geometry ◽  
Biaxial Stress ◽  
Fatigue Life Prediction ◽  
Random Loading ◽  
Complex Load ◽  
Biaxial Stress State ◽  
Principal Axes

Gears can show significant biaxial stress state at tooth root fillet, due to the way they are loaded and their particular geometry. This biaxial stress state can show a significant variability in principal axes during meshing. Moreover loads may have non predictable components that can be evaluated with the aid of recorded data from complex spectra. In these conditions, commonly adopted approaches for fatigue evaluation may be unsuitable for a reliable fatigue life prediction. This work is aimed at discussing a computer implementation of a fatigue life prediction method suitable for multiaxial stress states and constant amplitude or random loading. For random loading a counting procedure to extract cycles from complex load histories is discussed. This method, proposed by Vidal et al., is based on the r.m.s. value of a damage indicator over all the planes through the point where the fatigue life calculation is made. Miner’s rule is used for the evaluation of the overall damage. The whole fatigue life of the component is evaluated in terms of the numbers of repetitions of the loading block. FEM data are used to evaluate stresses under load. The implementation was validated using test data found in the technical literature. Examples of applications to gears are finally discussed.

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