scholarly journals Evaluation Study on Iterative Inverse Modeling Procedure for Determining Post-Necking Hardening Behavior of Sheet Metal at Elevated Temperature

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1044 ◽  
Author(s):  
Han Mei ◽  
Lihui Lang ◽  
Kangning Liu ◽  
Xiaoguang Yang
Keyword(s):  
Tensile Test ◽  
Sheet Metal ◽  
Inverse Modeling ◽  
Inverse Method ◽  
Modeling Method ◽  
Biaxial Stress ◽  
Uniaxial Tensile ◽  
Cruciform Specimen ◽  
Hardening Behavior ◽  
Modeling Procedure

The identification of the post-necking strain hardening behavior of metal sheet is important for finite element analysis procedures of sheet metal forming process. The inverse modeling method is a practical way to determine the hardening curve to large strains. This study is thus focused on the evaluation of the inverse modeling method using a novel material performance test. In this article, hot uniaxial tensile test of a commercially pure titanium sheet with rectangular section was first conducted. Utilizing the raw data from the tensile test, the post-necking hardening behavior of the material is determined by a FE-based inverse modeling procedure. Then the inverse method is compared with some classical hardening models. In order to further evaluate the applicability of the inverse method, biaxial tensile test at elevated temperatures was performed using a special designed cruciform specimen. The cruciform specimen could guarantee that the maximum equi-biaxial deformation occurs in the center section. By using the inverse modeling procedure, the hardening curves under biaxial stress state are able to be extracted. Finally the stress-strain curves obtained from the two experiments are compared and analysis studies are provided.

Inverse determination of the flow curve in large range of strains for cylindrical tensile specimen

2020 ◽  
Vol 234 (11) ◽  
pp. 2256-2265
Author(s):  
Junfu Chen ◽  
Zhiping Guan ◽  
Changhai Yang
Keyword(s):  
Tensile Test ◽  
Flow Curve ◽  
Inverse Method ◽  
Large Range ◽  
Cylindrical Specimen ◽  
Uniaxial Tensile ◽  
Model Parameters ◽  
Displacement Curve ◽  
Simulation And Optimization ◽  
Load Displacement

In this study, an inverse method with the integration of finite element simulation and optimization algorithms is proposed to determine the flow curve of cylindrical specimen characterized by the modified Voce hardening model. The tensile test is repetitiously simulated with different combinations of model parameters designed through Latin hypercube design method, where the baseline values and variation ranges of model parameters are identified through Leroy–Bridgman method, obtaining different simulated load–displacement curves. The corresponding response is defined as the sum of the absolute area difference between the simulated load–displacement curves and the experimental one. The relationship between the model parameters and the response is established through response surface methodology and the optimal parameters combination in the modified Voce model is then determined through nonlinear programming by quadratic Lagrangian. In the case of uniaxial tensile test of mild steel Q345, the inversely identified flow curve is validated by numerically reproducing the experimental load–displacement curve and necking profile. The results indicate that the proposed inverse method is capable of evaluating the flow curve in large range of strains for cylindrical specimen accurately.

Fundamental aspect of stretch-flangeability of sheet metals

2018 ◽  
Vol 233 (10) ◽  
pp. 2115-2119 ◽  
Author(s):  
Surajit Kumar Paul
Keyword(s):  
Tensile Test ◽  
Sheet Metal ◽  
Expansion Ratio ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Hole Expansion ◽  
Expansion Test ◽  
Localized Necking ◽  
Hole Expansion Test ◽  
Hole Expansion Ratio

Stretch-flangeability of sheet metal is normally represented by hole expansion ratio. Hole expansion ratio cannot be determined from uniaxial tensile test though uniaxial tensile deformation occurs at the hole’s edge, because of fundamental difference in deformation and damage processes present between hole expansion test and uniaxial tensile test. It is proposed that only localized necking is observed in hole expansion test; however, diffuse necking followed by localized necking is observed in uniaxial tensile test of sheet metal. It is noticed that the hole expansion ratio is marginally higher than maximum diffuse neck strain determined from uniaxial tensile test with local strain measurement by digital image correlation technique. The absence of diffuse neck in hole expansion test with defect-free central hole (i.e. electrical discharge machined hole) results far higher hole expansion ratio than uniform elongation of the material.

Formability Evaluation Using Modified Cockcroft Criterion with Strain Paths for Sheet Metal Forming

2014 ◽  
Vol 626 ◽  
pp. 495-501 ◽  
Author(s):  
Rong Shean Lee ◽  
Ta Wei Chien
Keyword(s):  
Tensile Test ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Strain Path ◽  
Dome Height ◽  
Bulge Test ◽  
Cruciform Specimen ◽  
Strain Paths ◽  
Good Agreement

In most situations, original Cockcroft criterion underestimates material formability in the first quadrant of FLD. So far, some modified Cockcroft criteria have been reported for different applications. This presentation will focus on the modified Cockcroft criterion which takes strain-path effect into consideration. This paper demonstrates the accuracy of this criterion through limiting dome height test, free bulge test, and the biaxial tensile test using cruciform specimen respectively. The results showed that the modified Cockcroft criterion with strain path effect has good agreement with experimental results.

Determination of Yield Locus of Sheet Metal at Elevated Temperatures: A Novel Concept for Experimental Set-Up

2007 ◽  
Vol 344 ◽  
pp. 97-104 ◽  
Author(s):  
Andrea Ghiotti ◽  
Stefania Bruschi ◽  
Paolo F. Bariani
Keyword(s):  
Sheet Metal ◽  
Structural Control ◽  
Elevated Temperatures ◽  
Heating System ◽  
Vertical Movement ◽  
Yield Locus ◽  
Biaxial Stress ◽  
Test Machine ◽  
Cruciform Specimen ◽  
Set Up

The constant demand of increasing performances and safety in vehicle industry has led significant innovations in the materials used in sheet metal forming processes. In particular, multiphase steels and lightweight alloys have known higher and higher importance, thanks to the development of new stamping processes at elevated temperatures, which guarantee, at the same time, better formability, lower springback and more accurate micro-structural control in the formed sheets. With respect to these aspects, the correct design and optimization of the new processes cannot prescind of the mechanical characterization of materials in biaxial stress conditions, especially when it strongly varies according to the stress and temperature. In this paper, a novel experimental set-up is presented for determining the in-plane yield locus of sheet metals at elevated temperatures. A cruciform specimen, whose geometry was optimized by numerical simulation, is used for the study of the yield locus in the range of biaxial tensile stresses. The test machine concept is based on punch-wedge mechanism, which uses the vertical movement of the press for the deformation of the specimen along two perpendicular axes. In the first part of the paper, the optimization of the cruciform specimen by thermo-mechanical FE analyses is outlined. Details on the experimental set-up are then given with the description of the apparatus, the measurement of plastic strains and the heating system for tests at elevated temperatures.

Tensile Testing for Determining Sheet Formability

2004 ◽  
pp. 101-114
Keyword(s):  
Tensile Test ◽  
Plane Strain ◽  
Sheet Metal ◽  
Tensile Testing ◽  
Large Family ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Accurate Indication ◽  
Complex Shapes ◽  
Sheet Formability

Abstract Sheet metal forming operations consist of a large family of processes, ranging from simple bending to stamping and deep drawing of complex shapes. Because sheet forming operations are so diverse in type, extent, and rate, no single test provides an accurate indication of the formability of a material in all situations. However, as discussed in this chapter, the uniaxial tensile test is one of the most widely used tests for determining sheet metal formability. This chapter describes the effect of material properties and temperature on sheet metal formability. Information on the types of formability tests is also provided. The chapter discusses the processes involved in uniaxial and plane-strain tensile testing. Examples include the uniaxial tensile test and the plane-strain tensile test which are subsequently described.

scholarly journals Calibration of Advanced Yield Criteria Using Uniaxial and Heterogeneous Tensile Test Data

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 542
Author(s):  
Andraž Maček ◽  
Bojan Starman ◽  
Nikolaj Mole ◽  
Miroslav Halilovič
Keyword(s):  
Tensile Test ◽  
Strain Field ◽  
Plastic Anisotropy ◽  
Testing Machine ◽  
Biaxial Stress ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Biaxial Test ◽  
Test Results ◽  
Full Field

Conventionally, plastic anisotropy is calibrated by using standard uniaxial tensile and biaxial test results. Alternatively, heterogeneous strain field specimens in combination with full-field measurements can be used for this purpose. As reported by the literature, such an approach reduces the number of required tests enormously, but it is challenging to obtain reliable results. This paper presents an alternative methodology, which represents a compromise between the conventional and heterogeneous strain field calibration technique. The idea of the method is to use simple tests, which can be conducted on the uniaxial testing machine, and to avoid the use of advanced measuring equipment. The procedure is accomplished by conducting standard tensile tests, which are simple and reliable, and by a novel heterogeneous strain field tensile test, to calibrate the biaxial stress state. Moreover, only two of the parameters required for full characterisation need to be inversely identified from the test response; the other parameters are directly determined from the uniaxial tensile test results. This way, a dimension of optimization space is reduced substantially, which increases the robustness and effectiveness of the optimization algorithm.

Optimizing the Shape and Size of Cruciform Specimens Used for Biaxial Tensile Test

2014 ◽  
Vol 658 ◽  
pp. 167-172 ◽  
Author(s):  
Liviu Andrusca ◽  
Viorel Goanta ◽  
Paul Doru Barsanescu
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Continuous Monitoring ◽  
Biaxial Tension ◽  
Cruciform Specimen ◽  
Testing Method ◽  
Biaxial Tests ◽  
Properties Of Materials ◽  
Failure Theories ◽  
Shape And Size

Testing cruciform specimens subjected to biaxial tension is one of the most widely used experimental techniques and more accurate at this time to determine the mechanical properties of materials and to verify the failure theories. This type of experiment allows the continuous monitoring of behavior of materials from the beginning of deformation until fracture under different ratios of forces and directions of the deformation, which transforms it into a very versatile testing method. We have varied the number of parameters and their values in order to achieve a uniform distribution of biaxial state of stresses and strains in the area tested. In theory, any material can be tested by stretching a biaxial cruciform specimen, but must be investigated in what way the shape of the specimen influence the data obtained. In this paper are presented the requirements that must be fulfilled by the samples used for tensile / compression biaxial tests and the design of cruciform specimens through FEA that meet these demands.

A Newly Developed Clamping Device for the Tension/Compression Test at Various Strain Rates

2014 ◽  
Vol 626 ◽  
pp. 353-358
Author(s):  
Geun Su Joo ◽  
Min Kuk Choi ◽  
Hoon Huh
Keyword(s):  
Strain Rate ◽  
Sheet Metal ◽  
Metal Forming ◽  
Loading Condition ◽  
Strain Rates ◽  
Compression Tests ◽  
Compression Behavior ◽  
Compression Loading ◽  
Hardening Behavior ◽  
Clamping Device

The tension/compression hardening behavior is important in sheet metal forming processes because of complicated loading paths. Experimental methods to measure the tension/ compression behavior have not considered the effect of the strain rate although the strain rate is related to the hardening behavior of sheet metal. The tension/compression tests need to be conducted considering the strain rate to acquire accurate hardening behavior.This paper deals with an experimental technique to measure the tension/compression behavior of sheet metal at various strain rates. A new clamping device was developed to prevent a sheet specimen from buckling under compression loading condition. Compared to previous clamping devices, the clamping device was devised to uniformly impose a clamping force and easily measure the strain from side of a specimen. Tension/compression tests have been conducted at various strain rates for SPCC and DP590 with displacement of 10%. Hardening curves under the tension or compression loading condition were obtained and analyzed with respect to the strain rate.

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