scholarly journals Local One-Sided Rubber Bulging Test to Measure Various Strain Paths of Metal Tube

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 751
Author(s):  
Hidenori Yoshimura ◽  
Kana Nakahara ◽  
Masaaki Otsu
Keyword(s):  
Strain Path ◽  
Biaxial Tension ◽  
Forming Limit ◽  
Hydraulic Pressure ◽  
Test Machine ◽  
Biaxial Deformation ◽  
Universal Compression ◽  
Simple Tension ◽  
Strain Paths ◽  
Bulging Test

We proposed a local one-sided rubber bulging method of metal tubes to evaluate various strain paths at an aimed portion and measured the forming limit strains of metal tubes at the place of the occurrence of necking under biaxial deformation. Using this method, since rubber is used to give pressure from the inner side of the tube, no sealing mechanisms were necessary unlike during hydraulic pressure bulging. An opening was prepared in front of the die to locally bulge a tube at only the evaluation portion. To change the restriction conditions of the bulged region for biaxial deformation at the opening, a round or square cutout, or a slit was introduced. The test was conducted using a universal compression test machine and simple dies rather than a dedicated machine. Considering the experimental results, it was confirmed that the strain path was varied by changing the position and size of slits and cutouts. Using either a cutout or a slit, the strain path in the side of the metal tubes can be either equi-biaxial tension or simple tension, respectively. Additionally, by changing the size of the cuts or slits, the strain path can be varied.

Orientation and Path Dependence of Formability in the Stress- and the Extended Stress-Based Forming Limit Curves

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
C. Hari Manoj Simha ◽  
Kaan Inal ◽  
Michael J. Worswick
Keyword(s):  
Strain Path ◽  
Path Dependence ◽  
Forming Limit ◽  
Stress Space ◽  
Forming Limit Diagrams ◽  
Metall Trans ◽  
Strain Paths ◽  
Strain Path Changes ◽  
Path Dependent ◽  
Forming Limit Curves

This article analyzes the formability data sets for aluminum killed steel (Laukonis, J. V., and Ghosh, A. K., 1978, “Effects of Strain Path Changes on the Formability of Sheet Metals,” Metall. Trans. A., 9, pp. 1849–1856), for Al 2008-T4 (Graf, A., and Hosford, W., 1993, “Effect of Changing Strain Paths on Forming Limit Diagrams of Al 2008-T4,” Metall. Trans. A, 24A, pp. 2503–2512) and for Al 6111-T4 (Graf, A., and Hosford, W., 1994, “The Influence of Strain-Path Changes on Forming Limit Diagrams of Al 6111 T4,” Int. J. Mech. Sci., 36, pp. 897–910). These articles present strain-based forming limit curves (ϵFLCs) for both as-received and prestrained sheets. Using phenomenological yield functions, and assuming isotropic hardening, the ϵFLCs are transformed into principal stress space to obtain stress-based forming limit curves (σFLCs) and the principal stresses are transformed into effective stress and mean stress space to obtain the extended stress-based forming limit curves (XSFLCs). A definition of path dependence for the σFLC and XSFLC is proposed and used to classify the obtained limit curves as path dependent or independent. The path dependence of forming limit stresses is observed for some of the prestrain paths. Based on the results, a novel criterion that, with a knowledge of the forming limit stresses of the as-received material, can be used to predict whether the limit stresses are path dependent or independent for a given prestrain path is proposed. The results also suggest that kinematic hardening and transient hardening effects may explain the path dependence observed in some of the prestrain paths.

Effect of Strain Paths on Formability Evaluation of TRIP Steels

2010 ◽  
Vol 89-91 ◽  
pp. 214-219 ◽  
Author(s):  
David Gutiérrez ◽  
A. Lara ◽  
Daniel Casellas ◽  
Jose Manuel Prado
Keyword(s):  
Strain Path ◽  
High Strength Steels ◽  
High Strength ◽  
Test Method ◽  
Forming Limit ◽  
Trip Steels ◽  
Advanced High Strength Steels ◽  
Strain Paths ◽  
Analysis System

The Forming Limit Diagrams (FLD) are widely used in the formability analysis of sheet metal to determine the maximum strain, which gives the Forming Limit Curve (FLC). It is well known that these curves depend on the strain path during forming and hence on the test method used to calculate them. In this paper, different stretching tests such as the Nakajima and the Marciniak tests were performed, with different sample geometries to obtain points in different areas of the FLD. An optical analysis system was used, which allows following the strain path during the test. The increasing use of advanced high-strength steels (AHSS) has created an interest in determining the mechanical properties of these materials. In this work, FLCs for a TRIP steel were determined using Nakajima and Marciniak tests, which revealed different strain paths depending on the type of test. Determination of the FLCs was carried out following the mathematical calculations indicated in the ISO 12004 standard and was also compared with an alternative mathematical method, which showed different FLCs. Finally, the tests were verified by comparing the strain paths of the Nakajima and Marciniak tests with a well-known mild steel.

A Novel Experimental Design to Obtain Forming Limit Diagram of Aluminium Alloys for Solution Heat Treatment, Forming and In-Die Quenching Process

2014 ◽  
Vol 622-623 ◽  
pp. 241-248 ◽  
Author(s):  
Zhu Tao Shao ◽  
Qian Bai ◽  
Jian Guo Lin
Keyword(s):  
Heat Treatment ◽  
Solution Heat Treatment ◽  
High Efficiency ◽  
Biaxial Tension ◽  
Forming Limit ◽  
Air Cooling ◽  
Connecting Rod ◽  
Form Complex ◽  
Die Quenching ◽  
Strain Paths

Solution heat treatment, forming and in-die quenching (HFQ) is a patented process to form complex shape metal components at a high efficiency and a low cost. Conventional experiment approaches to determine forming limit curves (FLCs) at different strain paths are not applicable for the HFQ forming process. A novel biaxial tensile test rig is designed to overcome the difficulties and determine the FLCs at high temperatures based on the commercial Gleeble machine. This test device employs the circle plate and connecting rod mechanism in order to achieve different strain states, such as uniaxial tension, plane strain and biaxial tension. Resistance heating and air cooling are adopted to obtain an isothermal environment and to control cooling rates in Gleeble respectively. The designs of the cruciform specimen for this test are also introduced in this paper.

A comparative study on determination of forming limit diagrams for industrial aluminium sheet alloys considering combined effect of strain path, anisotropy and yield locus

2012 ◽  
Vol 47 (6) ◽  
pp. 350-361 ◽  
Author(s):  
Milad Janbakhsh ◽  
Faramarz Djavanroodi ◽  
Mohammad Riahi
Keyword(s):  
Finite Element ◽  
Strain Path ◽  
Small Deviation ◽  
Axial Strain ◽  
Simulation Software ◽  
Forming Limit ◽  
Plastic Strain Ratio ◽  
Forming Limit Diagrams ◽  
Aluminium Sheet ◽  
Strain Paths

Suitability of AA2024-T3 and AA5083-H111 aluminium sheet alloys for forming operations in room temperature were examined by using forming limit diagrams with different strain paths. In the experimental part, circular bulge, non-grooved tensile as well as grooved tensile specimens were used. This was done to simulate the following: (a) biaxial stretching region (positive range of minor strain), (b) uni-axial strain path and (c) strain path from uni-axial tension to plane strain region of the forming limit diagram, respectively. The effects of combined strain paths coupled with material anisotropy were taken into account in each stage. Tensile properties as well as formability parameters were correlated in accordance with the attained forming limit diagrams. Average plastic strain ratio and planar anisotropy, in addition to work hardening exponents of the samples, were calculated from the test data and the effects on the forming limit diagrams were discussed. Moreover, comparisons were made between experimental and theoretical forming limit diagrams. It is shown that experimental forming limit diagrams are in very good agreement with the theoretical predictions, particularly when BBC2000 yield criteria are used for the M–K model. In addition, theoretical prediction by using the Hill93–Swift model showed small deviation with the experimental forming limit diagrams. Finally, finite element simulations were carried out to investigate the numerical forming limit diagrams through an industrial sheet metal forming simulation software. It was consequently shown that, due to frictional effects resulting from hemispherical-shaped punch, the finite element results depicted small deviation compared to the experimental data.

Influence Analysis of Multifactor on LCF Damage of Single Crystal Nickel-Based Superalloy under Multiaxial Non-Proportional Loading

2010 ◽  
Vol 139-141 ◽  
pp. 198-204
Author(s):  
Zhi Ping Ding ◽  
Ji Ping Chen ◽  
Teng Fei Wang ◽  
Ming Li
Keyword(s):  
Single Crystal ◽  
Fatigue Damage ◽  
Phase Angle ◽  
Strain Path ◽  
Biaxial Tension ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Cycle Fatigue ◽  
Nickel Based Superalloy ◽  
Strain Paths

A formula of equivalent strain for FCC single crystal superalloy was derived based on Hill’s yield criterion and was used for design of biaxial tension-torsion strain paths and loading levels of specimens. biaxial tension-torsion non-proportional cyclic loading process for single crystal nickel-based superalloy at the temperature of 680°C and 850°C was simulated by FEM analyzes; and influence degree of factors, such as strain range, strain path angle, tension-torsion loading phase angle, cycle characteristics and temperature etc., to low cycle fatigue damage of single crystal nickel-based superalloy were analyzed by using analysis of variance based on orthogonal experiments. The results show that if Hill’s equivalent stress range is used as a fatigue damage parameter, the factors produce effects on low cycle fatigue damage of single crystal nickel-based superalloy. The factors are listed in the order of significance as followed: temperature, strain range, tension-torsion loading phase angle, strain path angle and axial loading strain ratio.

Evaluation of the Work-Hardening of Brass Sheets Following Strain Path Changes

2010 ◽  
Vol 89-91 ◽  
pp. 353-358
Author(s):  
Wellington Lopes ◽  
Elaine Carballo Siqueira Corrêa ◽  
Haroldo Béria Campos ◽  
Maria Teresa Paulino Aguilar ◽  
Paulo Roberto Cetlin
Keyword(s):  
Simple Shear ◽  
Work Hardening ◽  
Tensile Testing ◽  
Strain Path ◽  
Adequate Description ◽  
Simple Tension ◽  
Strain Paths ◽  
Strain Path Changes ◽  
Machining Operations

The strain paths followed by metals during sheet forming can be quite complex, especially when successive forming steps are involved. The work hardening of metals associated with these strain paths differs from that caused only by monotonic straining, such as simple tension or compression. It is important to have an adequate description of the work hardening of the material under processing, especially when numerical simulations of the forming are used. The experimental evaluation of the effect of strain path changes on the material work hardening is usually performed through tensile testing following the strain path changes. This technique, however, demands complex machining operations of the formed sheets and the imposed strain is severely limited by impending necking. The present paper utilizes simple shear as a tool for the determination of the work hardening of CuZn34 brass sheets following various strain path changes associated with combinations of different modes of deformation such as rolling, tension, cyclic and forward shears. The results indicate that the cyclic shearing delays the occurrence of plastic instabilities for brass previously tensioned, occurring the opposite for final monotonic shearing. These phenomena were correlated with the probable microstructural evolution of the CuZn34 brass.

Intrinsic diagram of sheet metal forming limits for arbitrary strain paths

2008 ◽  
Vol 222 (4) ◽  
pp. 223-229 ◽  
Author(s):  
H. Fatmaoui ◽  
R. Mesrar ◽  
J. Chaoufi
Keyword(s):  
Biaxial Tension ◽  
Effective Strain ◽  
Forming Limit ◽  
Forming Limits ◽  
Stress Criterion ◽  
Localized Necking ◽  
Strain Paths ◽  
Mk Analysis ◽  
Localization Approach ◽  
Intrinsic Character

Localized necking in sheets under biaxial tension is analysed by an Marciniak—Kuczynski localization approach (MK-analysis) along with a new plane-stress criterion. Analysis is developed for a rigid viscoplastic behaviour based on flow-theory of plasticity. The model is introduced in numerical calculations to determine forming limits to ductility under linear and non-linear strain paths. However, the results are presented in a new diagram that represent the effective strain as a function of the current strain-rate ratio. A comparison with classical forming limit diagrams shows the intrinsic character of the new diagram.

Research on the Forming Limit Diagram Based on Laser Shock Forming

2010 ◽  
Vol 44-47 ◽  
pp. 148-152
Author(s):  
Yin Fang Jiang ◽  
Zhen Zhou Tang ◽  
Zhi Fei Li ◽  
Lei Fang
Keyword(s):  
Sheet Metal ◽  
Strain Path ◽  
Reduction Rate ◽  
Forming Limit Diagram ◽  
Thickness Reduction ◽  
Forming Limit ◽  
Laser Shock ◽  
Maximum Thickness ◽  
Laser Shock Forming ◽  
Strain Paths

Laser shock forming (LSF) of sheet metal is a novel technology in plastic deformation. It is necessary to correctly predict the Forming Limit Diagram (FLD) based on LSF. New failure maximum thickness reduction rate criterion is used to determine the forming limit based on the numerical system during LSF. The relationship model between maximum thickness reduction rate and the strain path is built. In addition, the effects of strain path and strain-hardening exponent on forming limit are considered. The maximum thickness reduction rate under equi-biaxial tensile strain path can be determined easily during LSF and the expression of the criterion is determined finally. Then the limit strains under other strain paths between uniaxial tension to equi-biaxial tension can be determined by the criterion combined with numerical simulation of forming process. The criterion can predict forming limits for sheet metal exactly and makes it possible to determine forming limit strains under different strain paths only through equi-biaxial tensile test during LSF.

Forming Limit Curves for Complex Strain Paths

2013 ◽  
Vol 58 (2) ◽  
pp. 587-593 ◽  
Author(s):  
J. Rojek ◽  
D. Lumelskyy ◽  
R. Pęcherski ◽  
F. Grosman ◽  
M. Tkocz ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Strain Path ◽  
Experimental Studies ◽  
Polar Coordinates ◽  
Forming Limit ◽  
Effective Plastic Strain ◽  
Steel Blank ◽  
Strain Paths ◽  
Complex Strain ◽  
Forming Limit Curves

This paper presents results of experimental studies of forming limit curves (FLC) for sheet forming under complex strain paths. The Nakazima-type formability tests have been performed for the as-received steel blank and for the blank pre-strained by13%. Prestraining leads to abrupt change of strain path in the blank deformation influencing the forming limit curve. The experimental FLC of the pre-strained blank has been compared with the FLC constructed by transformation of the as-received FLC. Quite a good agreement has been found out. The concept of strain-path independent FLCs in polar coordinates has been verified. Two types of the polar diagrams have been considered, the first one with the strain-path angle and effective plastic strain as the polar coordinates, and the second one originally proposed in this work in which the thickness strain has been used instead of the effective plastic strain as one of the polar coordinates. The second transformation based on our own concept has given a better agreement between the transformed FLCs, which allows us to propose this type of polar diagrams as a new strain-path in dependent criterion to predict sheet failure in forming processes.

scholarly journals Influence of the Laser Heat Treatment on the AA5754-H32 strain path during hydraulic bulge tests

2021 ◽  
Author(s):  
Angela Cusanno ◽  
Shanmukha Moturu ◽  
David Carty ◽  
Gianfranco Palumbo
Keyword(s):  
Strain Path ◽  
Forming Limit Diagram ◽  
Local Heat ◽  
Forming Limit ◽  
Bulge Test ◽  
Forming Limit Curve ◽  
Hydraulic Bulge ◽  
Strain Paths ◽  
The Right

The hydraulic bulge test represents an effective experimental method to characterise sheet metals since the equivalent strains before failure are much larger than those measured during tensile testing and there is nearly no frictional effect on the results. Recently this test has been proposed not only for extracting data concerning the equi-biaxial strain condition, but to determine the forming limit diagram (FLD) in the range of positive minor strains. In the proposed methodology, different strain paths can be obtained by merely using a test blank having two holes with a suitable geometry and position to be tested, without the need of dies with elliptical apertures. However, a carrier sheet is necessary, thus implying results may be affected by friction effects. This paper proposes a new methodology for the determination of the right side of the Forming Limit Curve (FLC), based on the adoption of local heat treatments aimed at determining different strain paths on the blank to be tested while using the classical circular die for bulge tests. In particular, the formability of the alloy AA5754-H32 was investigated; 3D Finite Element simulations were conducted setting different laser strategies and monitoring the resulting strain path. Results revealed that the proposed methodology supports obtaining many additional points in the right side of the FLC, thus being effective and friction free.

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