Investigation of the Shape of a Cruciform Biaxial Tensile Specimen Intended for a Combination of Plane Strain Tensile States

2014 ◽  
Vol 622-623 ◽  
pp. 308-313 ◽  
Author(s):  
Hayato Usui ◽  
Takashi Iizuka
Keyword(s):  
Plane Strain ◽  
Forming Limit Diagram ◽  
Strain Ratio ◽  
Tensile Tests ◽  
Tensile Specimen ◽  
Forming Limit ◽  
Cruciform Specimen ◽  
Minimum Cross Section ◽  
Flat Type ◽  
Width Direction

This study investigates the shape of a cruciform specimen that is stretched in the normal direction of the minimum cross section using FEM. In addition, plane strain tensile states exist in the measurement region in order to determine the forming limit diagram not by an arbitrary stress ratio but by the strain ratio. We propose two types of cruciform specimens. One is a flat-type cruciform specimen, which has deep slits in the middle of the arm region in the width direction. The other specimen is a reduced measurement region type, which also has deep slits as well as a shape that is a biaxial combination of two plane strain tensile specimens. We analyze equibiaxial tensile tests of these two proposed cruciform specimen types using FEM.

Influence of Different Pre-Stretching Modes on the Forming Limit Diagram of AA6014

2012 ◽  
Vol 504-506 ◽  
pp. 71-76 ◽  
Author(s):  
Alexandra Werber ◽  
Mathias Liewald ◽  
Winfried Nester ◽  
Martin Grünbaum ◽  
Klaus Wiegand ◽  
...  
Keyword(s):  
Plane Strain ◽  
Biaxial Loading ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Linear Strain ◽  
Forming Limits ◽  
Systematic Analysis ◽  
Measurement Systems ◽  
Non Linear ◽  
Strain Paths

In order to evaluate the formability of sheet materials forming limit diagrams (FLD) are recorded which represent the values of major and minor strain when necking occurs. FLDs are recorded based on the assumption that exclusively linear strain paths occur. In real forming parts, however, particularly in those with complex shapes, predominantly non-linear strain paths occur which reduce the accuracy of the failure prediction according to a conventional FLD. For this reason forming limits after loading with non-linear strain paths have to be investigated. In this contribution a systematic analysis of the forming limits of a conventional AA6014 alloy after loading with non-linear strain paths is presented. This material is pre-stretched in uniaxial, plane strain and biaxial direction up to several levels before performing Nakajima experiments in order to determine FLDs. During the pre-stretching process as well as during the Nakajima experiment the strain distribution can be measured online very precisely with the optical deformation measurement systems GOM Aramis or VIALUX. The gained curves are compared to the FLD of the as-received material. The results prove a significant influence of the pre-stretching condition on the forming limits of the used aluminum alloy. For a low pre-stretching in uniaxial as well as in biaxial direction the FLDs show a slightly reduced formability while after higher pre-stretching levels the forming limit can be improved such as for biaxial loading after uniaxial pre-stretching. The formability after pre-stretching in plane strain direction was changed. Also, a shift of the FLD depending on the direction of pre-stretching can be observed.

Theoretical and Experimental Evaluation of the Formability of Anisotropic Zinc Sheets

2011 ◽  
Vol 473 ◽  
pp. 390-395 ◽  
Author(s):  
Yann Jansen ◽  
Roland E. Logé ◽  
Marc Milesi ◽  
S. Manov ◽  
Elisabeth Massoni
Keyword(s):  
Metal Forming ◽  
Mechanical Response ◽  
Damage Model ◽  
Rolling Direction ◽  
Forming Limit Diagram ◽  
Tensile Tests ◽  
Forming Limit ◽  
The Past ◽  
Force Criterion ◽  
Critical Strains

. Formability of metal sheet has been widely studied for the past 40 years. This study leads to the well known Forming Limit Diagram (FLD) proposed by Keeler and Backhofen [1]. Such a diagram needs typical drawing and stretching experiments to be achieved. Lots of different metals have been considered as steel, aluminium, titanium or magnesium alloys [2]. Despite of the large amount of papers about sheet metal forming, few deal with Zinc sheets. The material has an anisotropic mechanical response due to its hexagonal crystallographic lattice and its microstructural texture. In the presented work, Nakazima and tensile tests have been performed for different mechanical orientations (0°, 45° and 90° angle to the rolling direction) in order to characterise this typical response. A high anisotropic behaviour has been noticed for the hardening and for the critical strains. The FLD is therefore a function of the orientation. Moreover thickness sensitivity is observed and leads to some criticisms about the plane stress assumption usually used in the FLD predictive models [3, 4]. The Modified Maximum Force Criterion (MMFC) is evaluated, and discussed. Then, this model is compared to a damage model used in [5] within an FEM formulation.

Investigation of forming limit diagram and mechanical properties of the bimetallic Al/Cu composite sheet at different temperatures which fabricated by explosive welding

2020 ◽  
Vol 235 (1-2) ◽  
pp. 73-84
Author(s):  
Ali Alaie ◽  
Ramin Hashemi ◽  
Farshad Kazemi
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Explosive Welding ◽  
Welding Process ◽  
Forming Limit Diagram ◽  
Tensile Tests ◽  
Considerable Effect ◽  
Effect Of Temperature ◽  
Forming Limit ◽  
Composite Sheet

This research aims to investigate the mechanical properties, fractography and formability of Al/Cu two-layer composite sheets at three temperatures (23 °C, 120 °C and 220 °C). The bimetal sheet was fabricated by the explosive welding method. The anisotropy of the Al/Cu bimetallic composite sheet was investigated. The result showed significant anisotropy in the Al/Cu composite sheet due to the explosive welding process. The Vickers hardness measurements demonstrated that the hardness in both aluminum and copper sides increased because of the work hardening phenomenon. The fractography of the surfaces was investigated by the scanning electron microscope after tensile tests to study the effect of temperature and the direction, which the samples prepared for the tensile test with respect to the explosion direction, on the mechanism of the fracture. For the tensile test, the samples were prepared parallel to the detonation direction [Formula: see text] and two other directions with respect to the explosion direction [Formula: see text] from the AA1100/Cu10100 bimetallic sheet. Finally, the forming limit diagram of the Al/Cu composite sheet was determined at the three mentioned temperatures. The results demonstrated that temperature and the direction had a considerable effect on the mechanism of the rupture and formability. As the temperature of the specimen rises, the regions that brittle fracture happened became less and the formability improved significantly. The formability of the Al/Cu composite sheet enhanced about 34.8% when the temperature increased from 23 °C to 120 °C and 67.5% when it increased from 120 °C to 220 °C.

Forming Limit Diagram of Magnesium Alloy ZK60 at Elevated Temperature

2011 ◽  
Vol 308-310 ◽  
pp. 2442-2445 ◽  
Author(s):  
Hong Wei Liu ◽  
Sheng Jie Yao ◽  
Wen Liang Liu ◽  
Zhao Duo Zhang
Keyword(s):  
Elevated Temperature ◽  
Magnesium Alloy ◽  
Grain Boundaries ◽  
Forming Limit Diagram ◽  
Strain Ratio ◽  
Instability Criterion ◽  
Forming Limit ◽  
Relationship Of ◽  
Zk60 Magnesium Alloy ◽  
The Relationship

The forming limit diagram of magnesium alloy ZK60 was developed with Hill’s instability criterion and M-K analysis. The relationship of forming limit with stain path, temperature and the thickness irregular coefficient were analyzed. The results show that the forming limit of ZK60 magnesium alloy increased little with the rising of strain ratio, but influenced greatly by the failure definition , and forming limit of is increased with the rising of temperature and thickness irregular coefficient, the most suitable value of f0 is 0.99, the fracture occur on the grain boundaries with significant cavities formation.

scholarly journals The Sheet Metal Formability of AA-5083-O Sheets Processed by Friction Stir Processing

2015 ◽  
Vol 2015 ◽  
pp. 1-21
Author(s):  
G. F. Miori ◽  
E. C. Bordinassi ◽  
S. Delijaicov ◽  
G. F. Batalha
Keyword(s):  
Sheet Metal ◽  
Friction Stir Processing ◽  
Forming Limit Diagram ◽  
Tensile Tests ◽  
Forming Limit ◽  
Sheet Metals ◽  
Close Approximation ◽  
Nonlinear Fem ◽  
Friction Stir ◽  
Software Products

The aim of this study is to determine the sheet metal formability of AA-5083-O sheets processed by the Friction Stir Processing (FSP). The FSP process was studied and a FSP tool was built. Processing quality was verified by the metallography in the processing region, which established the voids presence. Tensile tests were carried out on FSP and non-FSP specimens, and the results showed that FSP specimens have 30% greater resistance than non-FSP ones. The formability of FSP sheets was produced in MSC-MARC and Abaqus and these software products were compared by using the nonlinear FEM code. The Forming Limit Diagram was built with the results from both software products. A device to process FSP sheet metals was developed and the sheets were processed to validate the results from the software. The tools made for the bulge tests were circular and ellipse-shaped. After the bulge tests, the commercial sheets showed close approximation to those obtained from the software. The FSP sheets broke when inferior pressure was applied because of the defects in the FSP process. The results of the FSP presented the same formability of commercial sheets, however, with 30% greater strength.

Developing Uniaxial Tensile Test as an Alternate Method for Thermo Mechanical Process Evaluation

2011 ◽  
Vol 383-390 ◽  
pp. 5404-5408
Author(s):  
Dedi Priadi ◽  
Richard A. M. Napitupulu ◽  
Eddy S. Siradj
Keyword(s):  
Tensile Test ◽  
Plane Strain ◽  
Testing Machine ◽  
Forming Limit Diagram ◽  
Grain Structure ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Mechanical Process ◽  
Uniaxial Test

The alternate method for evaluating the thermo mechanical process has been developed. Small attention has been paid to the mechanism of plastic deformation especially plane strain analysis. Modified the specimen geometry and using uniaxial tensile test was done to view the process. Experimental results show that the forming limit diagram as one of the formability characteristic can be view the plane strain condition that present on the thermo mechanical process. The microstructure result shows that there is a similar grain structure between hot tensile test and hot rolling results as one of thermo mechanical process method. It was concluded that the uniaxial test using universal testing machine could be done to evaluate the thermo mechanical process.

Optimizing Material Parameters for Better Formability of DQ Steel Pipe

2019 ◽  
Author(s):  
Shabbir Memon ◽  
Obaidur Rahman Mohammed ◽  
D. V. Suresh Koppisetty ◽  
Hamid M. Lankarani
Keyword(s):  
Additive Model ◽  
Forming Limit Diagram ◽  
Strain Ratio ◽  
Forming Limit ◽  
Bulge Test ◽  
Optimum Process ◽  
Strain Hardening Exponent ◽  
Hydraulic Pressure ◽  
Plastic Strain Ratio ◽  
Material Parameters

Abstract As Pipelines are subjected to bursting failure, the prediction of the burst capacities of corroded pipelines is of significant relevance to the pipeline industry. The Single mode deformation processes, most commonly used in laboratory evaluations like tensile test, may not realistically predict formability performance. Therefore, limit strains tests that use multiple deformation stages would better simulate actual material performance hence bulge test is widely used in pipeline industry for analyzing formability. The tube bulge test is an advanced testing material in which the tube is placed in a die cavity and is sealed from both the ends, the water is injected from the hole inside the sealing punch and hydraulic pressure is increased and the tube gets deformed at the center. The objective of this work is to utilize Taguchi coupled finite element computational methodology to determine the optimum material parameters to attain better formability without necking-splitting failure. To evaluate the dependence of the slope of the forming limit diagram on the material parameters, the simulation under various combinations of strain-hardening exponent (n), plastic strain ratio (r) and thickness of tube (t) is carried out and using thickness gradient criterion, the occurrence of necking i. e. forming limit strains during tube bulging is examined. By observing the optimum condition obtained for maximum plain strain it is concluded that higher the n, r and t more the limit strains will be. It is also observed that among n, r and t, n is the most prominent factor contributing on limit strains followed by r and t. The verification of optimum process parameters obtained through Taguchi technique is carried out using additive model and it is found that the observed value is well in agreement with the predicted value, the extra validation simulation is carried out to validate the Taguchi results.

Forming Limit Diagram of Stainless Steel-Aluminum Alloy Clad

2010 ◽  
Vol 152-153 ◽  
pp. 541-544
Author(s):  
Hong Wei Liu ◽  
Peng Zhang
Keyword(s):  
Stainless Steel ◽  
Aluminum Alloy ◽  
Forming Limit Diagram ◽  
Strain Ratio ◽  
Thickness Ratio ◽  
Instability Criterion ◽  
Forming Limit ◽  
Interfacial Cracks ◽  
Positive Strain

The forming limit diagram of clad was developed with Hill’s instability criterion and M–K analysis at the positive strain ratio. The relationships of forming limit with stain path, thickness ratio and thickness irregular coefficient were analyzed. The results show that the forming limit of clad material is between those of its component materials, and increase with the rising of stainless steel thickness ratio and the thickness irregular coefficient. The most suitable value of f0 is 0.094 and the stainless steel aluminum clad break with local interfacial cracks.

Orientation and formability of orthotropic sheet metals

1997 ◽  
Vol 32 (1) ◽  
pp. 61-81 ◽  
Author(s):  
D W A Ress ◽  
R K Power
Keyword(s):  
Plane Strain ◽  
Principal Stress ◽  
Stress Ratio ◽  
Rolling Direction ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Sheet Metals ◽  
Principal Stresses ◽  
Thickness Strain ◽  
Automotive Sheet

This paper examines the formability of automotive sheet metals: CR steels and 6000 series aluminium-magnesium alloys. Necking strains are used to determine the forming limits; i.e. a diffuse instability condition is reached under in-plane biaxial stressing. The theory admits material anisotropy, work-hardening and sheet orientation under any ratio of applied principal stresses. It has been programmed to accept orientations between the principal stress axes and the sheets' rolling direction in 15° increments between 0° and 90°. The ratio between the principal stresses may vary between 0 and ± 1. The input data required are the width-thickness strain ratios ( r values) in directions 0°, 45° and 90° to the roll and the Hollomon hardening exponent ( n value). The output is presented in four diagrams: the critical subtangent-stress ratio and plots between three combinations of the limiting principal engineering strains: (a) two in-plane strains, (b) major in-plane strain versus thickness strain and (c) minor in-plane strain versus thickness strain. Each diagram shows the influence of rotating the principal stress axes in increments of 15° to the roll. The forming limit diagram of type (a) gives the traditional presentation of a forming limit diagram (FLD). This FLD may be established experimentally from the strain in a surface grid lying around splits. In practice, a few production panels may be gridded for die-tryout and to examine a change in material. The alternative FLDs, types (b) and (c), are proposed to provide quality control with the increasing use of ultrasonics to monitor thickness of pressed panels. An example of type (b) is determined experimentally for CR1 steel.

Prediction of plane-strain specimen geometry to efficiently obtain a forming limit diagram by Marciniak test

2018 ◽  
Vol 25 (5) ◽  
pp. 539-545 ◽  
Author(s):  
Qing-bao Yang ◽  
Jun-ying Min ◽  
John E. Carsley ◽  
Yuan-yuan Wen ◽  
Bernd Kuhlenkötter ◽  
...  
Keyword(s):  
Plane Strain ◽  
Forming Limit Diagram ◽  
Specimen Geometry ◽  
Forming Limit ◽  
Marciniak Test
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