scholarly journals Forming Limit Differences in Hemispherical Dome and Biaxial Test During Equibiaxial Tension on Cruciform

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Chetan P. Nikhare ◽  
Emmett Vorisek ◽  
John R. Nolan ◽  
John T. Roth
Keyword(s):  
Test Data ◽  
Testing Machine ◽  
Biaxial Stress ◽  
Dome Height ◽  
Forming Limit ◽  
Bulge Test ◽  
Biaxial Test ◽  
Biaxial Testing ◽  
Hemispherical Dome ◽  
Biaxial Tests

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 are 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 biaxially stretched with a hemispherical punch in a conventional die-punch setting. Furthermore, in each case, the process was simulated using a three-dimensional (3D) model generated on abaqus. These models were then compared with the experimental results. The forces on each arm, strain path, forming, and formability were 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.

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.

scholarly journals Experimental and Numerical Investigation of Forming Limit Differences in Biaxial and Dome Test

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Chetan P. Nikhare
Keyword(s):  
Contact Pressure ◽  
Material Behavior ◽  
Dome Height ◽  
Forming Limit ◽  
Bulge Test ◽  
Biaxial Test ◽  
Multiaxial Stress ◽  
Sample Geometry ◽  
Biaxial Tests ◽  
Stress States

For centuries, metals and materials have been characterized using a traditional method called a uniaxial tension test. The data acquired from this test found to be adequate for operations of simple forming where one axis stretching is dominant. Currently, due to the demand of lightweight component production, multiple individual parts eliminated by stamping a single complex shape, which also further reduces many secondary operations. This change is driving by the new fuel-efficiency requirement by corporate average fuel economy of 55.8 miles per gallon by 2025.1 Due to complex part geometry, this forming method induces multiaxial stress states, which are difficult to predict using conventional tools. Thus, to analyze these multiaxial stress states limiting dome height tests and bulge tests were recommended in many research publications. However, these tests limit the possibilities of applying multiaxial loading and rather a sample geometry changes are required to imply multiaxial stresses. Even this capability is not an option in bulge test due to leakage issue. Thus, a test machine called a biaxial test was devised that would provide the capability to test the specimen in multiaxial stress states by varying the independent load or displacement on two independent axis. In this paper, two processes, limiting dome tests and biaxial tests were experimented, modeled, and compared. For the biaxial tests, a cruciform test specimen was utilized, and conventional forming limit specimens were used for the dome tests. Variation of sample geometry in limiting dome test and variation of loading in biaxial test were utilized to imply multiaxial stress states in order to capture the limit strain from uniaxial to equibiaxial strain mode. In addition, the strain path, forming, and formability investigated and the differences between the tests provided. From the results, it was noted that higher limit strains were acquired in dome tests than in biaxial tests due to contact pressure from the rigid punch. The literature shows that the contact pressure (which occurs when the rigid tool contacts the deformed body), increases the deformation and thus increases the limit strains to failure. This contact pressure parameter is unavailable in biaxial test, and thus, a pure material behavior can be obtained. However, limit strains from biaxial test cannot be considered for a process where rigid tool is processing the metal, and thus, calibration is necessary.

Analysis of Forming Limits in Biaxial and Dome Test

2017 ◽  
Author(s):  
Chetan P. Nikhare
Keyword(s):  
Axial Stress ◽  
Axial Loading ◽  
Dome Height ◽  
Forming Limit ◽  
Bulge Test ◽  
Test Machine ◽  
Biaxial Test ◽  
Complex Part ◽  
Single Complex ◽  
Stress States

From centuries the metals and materials has been characterized using a traditional method called uniaxial tension test. The data acquired from this test found adequate for operations of simple forming where one axis stretching is dominant. Currently due to the demand of lightweight component production, multiple individual parts are eliminated by stamping in a single complex shape which further reduces many secondary operation. This need is driven by the requirement of 54 miles per gallon by 2025. Due to the complex part geometry, the forming method induces multi-axial stress states, which found difficult to predict using conventional tools. Thus to analyze these multi-axial stress states limiting dome height test and bulge test were recommended in many research. However, these tests limit the possibilities of applying multi-axial loading and resulting stress patterns due to contact surfaces. Thus a test machine called biaxial test is devised which would provide the capability to test the specimen in multi-axial stress states with varying load. In this paper, two processes, limiting dome test and biaxial test were modeled and compared. For this, the cruciform test specimens were used in biaxial test and conventional forming limit specimens for dome test. Variation of loadings were provided multi-axially in both test to capture the limit strain from uniaxial to equi-biaxial strain mode. In addition, the strain path, forming and formability was investigated and difference between the tests were provided.

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.

scholarly journals Evaluation of Different in Vitro Testing Methods for Mechanical Properties of Veneer Ceramics/ Евалуација На Тестовите In Vitro За Одредување На Механичките Особини На Порцеланските Маси За Фасетирање

PRILOZI ◽  
2015 ◽  
Vol 36 (1) ◽  
pp. 225-230 ◽  
Author(s):  
Aneta Mijoska ◽  
Mirjana Popovska
Keyword(s):  
Flexural Strength ◽  
Mechanical Characteristics ◽  
Testing Machine ◽  
In Vitro Testing ◽  
Biaxial Test ◽  
Testing Methods ◽  
Dental Ceramic ◽  
Universal Testing ◽  
Biaxial Tests

Abstract Metal-ceramic and all-ceramic prosthetic restorations in the patient mouth are often damaged by esthetic and functional problems that reduce their success and longevity. Аim: To evaluate methods for testing mechanical characteristics of dental ceramics through analysis of different testing methods. Material and methods: Dental ceramic materials are tested with in vivo and in vitro methods for their most important mechanical characteristics: hardness, toughness, flexural strength and abrasion. In vitro testing methods are faster and more efficient, without subjective factors from the patient according to ISO standards. Testing is done with universal testing machines, like Zwick 1445, Universal Testing Machine (Zwick DmbH & Co.KG, Ulm, Germany), Instron 4302 (Instron Corporation, England), MTS Sintech ReNew 1123 or in oral chewing simulators. Results: According to the testing results, flexure strength is one of the most important characteristic of the dental ceramic to be tested, by the uniaxial and biaxial tests. Uniaxial tests three-point and four-point flexure are not most appropriate because the main stress on the lower side of the tested specimens is tension that causes beginning fractures at the places with superficial flow. Uniaxial results for flexural strength are lower than actual force, while with biaxial test defects and flows on the edges of tested specimens are not directly loaded. Conclusion: Biaxial flexural method has advantages over uniaxial because of real strength results, but also for simple shape and preparing of the testing specimens.

scholarly journals Biaxial testing of textile material - methodology and instrument assembly procedure

2021 ◽  
Vol 1209 (1) ◽  
pp. 012030
Author(s):  
N Freiherrova ◽  
M Hornakova ◽  
D Juracka ◽  
L Stulerova ◽  
L Kapolka
Keyword(s):  
Material Model ◽  
Full Potential ◽  
Biaxial Test ◽  
Nonlinear Behaviour ◽  
Membrane Structures ◽  
Biaxial Testing ◽  
Textile Materials ◽  
Biaxial Tests ◽  
Specific Material ◽  
Assembly Procedure

Abstract Membrane structures are becoming popular because of the potential usage in structures with higher aesthetic claims. For the roofing of these structures, different textile materials are used. These special materials offer an alternative to conventional roofing materials and allow, besides its lightweightness, also a possibility to roof a difficult floor plan and big span. When designing such a construction, there are some challenges related to the properties of the specific material. In order to exploit the full potential of textile membrane materials, it is necessary to choose an appropriate material model for numerical modelling, which takes into account its nonlinear behaviour. The two most important material characteristics needed for characterizing the behaviour are Young’s modulus of elasticity and Poisson’s ratio. Since the material is orthotropic in most cases, it is necessary to test the material in two directions; therefore, these characteristics need to be obtained from the biaxial test. This contribution is focused on the research of the methodology of biaxial tests and test instrument assembly procedure, which will be used for the following testing of textile materials.

Fundamental Investigation for Tensile Test Using Conical Cupping Die

2014 ◽  
Vol 622-623 ◽  
pp. 292-299 ◽  
Author(s):  
Tomoyuki Ota ◽  
Takashi Iizuka
Keyword(s):  
Tensile Test ◽  
Testing Machine ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Bulge Test ◽  
Uniaxial Tensile Test ◽  
Biaxial Tensile ◽  
Specimen Shape ◽  
Specimen Edge

A number of researches have conducted in order to evaluate the ductile fracture occurrence by using forming limit diagram. However, specimen shape and testing machine for obtaining forming limit diagram of sheet metal have some problems. The problem about specimen shape is occurring at the specimen edge. In uniaxial tensile test, the specimen edge may cause a defused neck in width direction and may have influence on fracture occurrence. In biaxial tensile test by using a cruciform specimen, a uniform biaxial deformation is not obtained because uniaxial tensile stress occurs at the specimen edge. Tensile test by using a specimen which does not have such edges should carry out, for example, in bulge test and multi-axial tube expansion test, specimens without edge are used. However, these methods need special machines. Therefore, new biaxial tensile testing method is required. By this method, materials deform depending on biaxial strain state by using popular pressing machines.

Investigation of Anisotropy Effect on the Material Properties Obtained from Biaxial Tests

2020 ◽  
Vol 856 ◽  
pp. 128-134
Author(s):  
Chalida Udomraksasakul ◽  
Thanasan Intarakumthornchai ◽  
Yingyot Aue-u-Lan
Keyword(s):  
Flow Stress ◽  
Tensile Test ◽  
Mechanical Test ◽  
Rolling Direction ◽  
Uniaxial Tensile ◽  
Bulge Test ◽  
Uniaxial Tensile Test ◽  
Biaxial Test ◽  
Anisotropy Effect ◽  
Biaxial Tests

Hydraulic bulge test or biaxial test is a well-known mechanical test used to determine a flow stress of material because of the large level of effective strains and not interfered by the necking unlike in uniaxial tensile test. However, the flow stress obtained is influenced by the anisotropy effect. That flow stress needs to be corrected by the anisotropic values (r-values) obtained from the uniaxial tensile test which limited by the necking. Therefore, to obtain the accurate flow stress the r-values should be determined directly from the biaxial test. The elliptical tests with ratio of 2 (the ratio between major and minor axis) at different sheet orientations (0๐ and 90๐ from the rolling direction) and the equibiaxial test were proposed. In this research, the effect of the sheet orientations upon the flow stress (K and n values) under biaxial tests was investigated by experiment and equation of material grade SPCD with the thickness of 0.8mm. The results showed that the flow stress without correcting r-values gave more variations than those with correcting one with the r-values obtained from the uniaxial test. Therefore, the r-values used to correct the flow stress under biaxial test should be directly determined from the biaxial test.

Development of a Mini-LDH Test for Sheet Metal

2000 ◽  
Author(s):  
James C. Gerdeen
Keyword(s):  
Sheet Metal ◽  
Thin Sheet ◽  
Testing Machine ◽  
Experimental Results ◽  
Dome Height ◽  
Forming Limit ◽  
Universal Testing ◽  
Thin Sheet Metal ◽  
Force Range ◽  
Forming Limit Curves

Abstract The literature on formability and LDH (Limited Dome Height) testing is reviewed. The LDH tooling uses a 4.0 inch (100 mm) diameter punch, and various widths of specimens are used to give various strain ratios. The strains are then plotted on forming limit curves (FLD’s). In this paper, the development of a new mini-LDH test for thin sheet metal is described. The test involves a new geometry of specimens and a fixture which can be mounted in any universal testing machine with a low enough force range. The size effect is studied by conducting LDH tests with smaller diameter punches: 2.0 inch (50.8 mm), 0.50 inch (12.7 mm), and 0.25 inch (6.35 mm) diameters. Experimental results are presented for 0.010 inch (0.254 mm) thick 1100-H19 aluminum, and 5182-H19 aluminum. An analysis is also presented for the fully biaxial case and the plane strain case in order to model the experimental results.

Assessment of Work-Hardening Characteristics and Limit Strains of Anisotropic Aluminum Sheets in Biaxial Stretching

1986 ◽  
Vol 108 (3) ◽  
pp. 250-257 ◽  
Author(s):  
A. R. Ragab ◽  
A. T. Abbas
Keyword(s):  
Work Hardening ◽  
Pure Aluminum ◽  
Material Behavior ◽  
Biaxial Stress ◽  
Forming Limit ◽  
Flow Rule ◽  
Biaxial Test ◽  
Biaxial Stretching ◽  
Aluminum Sheets ◽  
New Material

In this work, commercially pure aluminum sheets in both the as-received and annealed conditions are tested in uniaxial and biaxial tension. Biaxial stretching is performed in dies giving different degrees of stress biaxiality. Resulting effective stresses and plastic strains are estimated according to the original Hill’s theory in the two situations where planar anisotropy is either neglected or taken into consideration. In both situations discrepancies between biaxial and uniaxial flow curves are observed. By analyzing the above uniaxial and biaxial test results according to the flow rule associated with a yield function recently proposed by Hill, a new material index describing the anisotropic behavior has been evaluated. This new material behavior description realized a satisfactory agreement between work-hardening characteristics of the tested aluminum sheets under various biaxial stress systems. The same tested aluminum sheet materials have been then tested in order to determine their forming limit curves. Correlation between these curves and the theoretical predictions of limit strains according to various instability analyses, is sought through the use of the above description of material work-hardening.

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