scholarly journals Determination of Forming Limits Based on Finite Element Simulations

2021 ◽  
Author(s):  
Fuhui Shen ◽  
Kai Chen ◽  
Junhe Lian ◽  
Sebastian Münstermann
Keyword(s):  
Finite Element ◽  
Damage Mechanics ◽  
Tensile Tests ◽  
Finite Element Simulations ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
Anisotropic Plasticity ◽  
Forming Limits ◽  
Dog Bone ◽  
Spatio Temporal

Two categories of experiments have been performed to obtain the experimental forming limits of a ferritic stainless steel from uniaxial to equibiaxial tension, including Nakajima tests and tensile tests of flat specimens with different geometries of the central hole as well as the notched dog bone. The plasticity behavior of the investigated material is described using an evolving non-associated anisotropic plasticity model, which is calibrated based on experimental results of uniaxial tensile tests along different loading directions. A damage mechanics model is calibrated and validated based on the global force and displacement response of tensile tests. Finite element simulations of the Nakajima tests and the tensile tests of various geometries have been performed using the anisotropic material model. A novel spatio-temporal method is developed to evaluate the forming limits under different stress states by quantitatively characterizing the plastic strain distribution on the specimen surface. The forming limits have been independently determined from finite element simulation results of tensile specimens and Nakajima specimens using the spatio-temporal evaluation method. The forming limits obtained from numerical simulations of these two types of experiments are in good agreement with experimental results.

scholarly journals Effect of the thickness reduction of specimens on the limit strains in thermomechanical tensile tests for hot-stamping studies

2018 ◽  
Vol 5 ◽  
pp. 11
Author(s):  
Connor Lane ◽  
Zhutao Shao ◽  
Kailun Zheng ◽  
Jianguo Lin
Keyword(s):  
Axial Strain ◽  
Hot Stamping ◽  
Tensile Tests ◽  
Thickness Reduction ◽  
Uniaxial Tensile ◽  
Testing System ◽  
Biaxial Testing ◽  
Forming Limits ◽  
Dog Bone ◽  
Selection Of

Sheet metal formability under hot stamping conditions has been evaluated using a novel planar testing system developed previously, being used within a Gleeble machine. Nevertheless, the specimen design with the central recess was not standardised, and the thickness reduction was not applied to the dog-bone type of specimen for testing at the uniaxial straining state. In this paper, effect of thickness reduction of dog-bone specimens on limit strain measurement under hot stamping conditions is investigated, and two types of dog-bone specimens without and with central recess are presented. Thermomechanical uniaxial tensile tests were performed at various deformation temperatures and strain rates, ranging from 370–510 °C and 0.01–1/s, respectively, by using the developed biaxial testing system in the Gleeble. The distributions of temperature and axial strain along gauge region of the two types of specimen were measured and compared. The specimen with consistent thickness had a better uniformity of temperature and strain distributions, compared to that with thickenss reduction. Forming limits for both types of specimen were also determined using the section-based international standard method. It is found that the accuracy of the calculation of forming limits based on the use of specimen with thickness reduction was highly dependent on the selection of the stage of the deformation of the specimen.

Anisotropic Behavior in Plasticity and Ductile Fracture of an Aluminum Alloy

2015 ◽  
Vol 651-653 ◽  
pp. 163-168 ◽  
Author(s):  
Yan Shan Lou ◽  
Jeong Whan Yoon
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloy ◽  
Ductile Fracture ◽  
Stress Triaxiality ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Anisotropic Plasticity ◽  
Dog Bone ◽  
Associate Flow Rule ◽  
Anisotropic Plastic

Anisotropic mechanical behavior is investigated for an aluminum alloy of 6K21-IH T4 both in plastic deformation and ductile fracture. Anisotropic plastic deformation is characterized by uniaxial tensile tests of dog-bone specimens, while anisotropy in ductile fracture is illustrated with specimens with a central hole, notched specimens and shear specimens. All these specimens are cut off at every 15º from the rolling direction. The r-values and uniaxial tensile yield stresses are measured from the tensile tests of dog-bone specimens. Then the anisotropic plasticity is modeled by a newly proposed J2-J3 criterion under non-associate flow rule (non-AFR). The testing processes of specimens for ductile fracture analysis are simulated to extract the maximum plastic strain at fracture strokes as well as the evolution of the stress triaxiality and the Lode parameter in different testing directions. The measured fracture behavior is described by a shear-controlled ductile fracture criterion proposed by Lou et al. (2014. Modeling of shear ductile fracture considering a changeable cut-off value for stress triaxiality. Int. J. Plasticity 54, 56-80) for different loading directions. It is demonstrated that the anisotropic plastic deformation is described by the J2-J3 criterion with high accuracy in various loading conditions including shear, uniaxial tension and plane strain tension. Moreover, the anisotropy in ductile fracture is not negligible and cannot be modeled by isotropic ductile fracture criteria. Thus, an anisotropic model must be proposed to accurately illustrate the directionality in ductile fracture.

Effect of specimen crack lengths on stress intensity factor for Al6061-TiC composites using experimental and 3D numerical methods

2017 ◽  
Vol 8 (5) ◽  
pp. 506-515 ◽  
Author(s):  
Raviraj M.S. ◽  
Sharanaprabhu C.M. ◽  
Mohankumar G.C.
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Length ◽  
Finite Element Simulations ◽  
Experimental Results ◽  
Crack Mouth Opening Displacement ◽  
3D Finite Element ◽  
Content Type

Purpose The purpose of this paper is to present the determination of critical stress intensity factor (KC) both by experimental method and three-dimensional (3D) finite element simulations. Design/methodology/approach CT specimens of different compositions of Al6061-TiC composites (3wt%, 5wt% and 7wt% TiC) with variable crack length to width (a/W=0.3-0.6) ratios are machined from as-cast composite block. After fatigue pre-cracking the specimens to a required crack length, experimental load vs crack mouth opening displacement data are plotted to calculate the KC value. Elastic 3D finite element simulations have been conducted for CT specimens of various compositions and a/W ratios to compute KC. The experimental results indicate that the magnitude of KC depends on a/W ratios, and significantly decreases with increase in a/W ratios of the specimen. Findings From 3D finite element simulation, the KC results at the centre of CT specimens for various Al6061-TiC composites and a/W ratios show satisfactory agreement with experimental results compared to the surface. Originality/value The research work contained in this manuscript was conducted during 2015-2016. It is original work except where due reference is made. The authors confirm that the research in their work is original, and that all the data given in the article are real and authentic. If necessary, the paper can be recalled, and errors corrected.

Methods for the Experimental Evaluation of True Stress-Strain Curves After Necking of Conventional Tensile Specimens: Exploratory Investigation and Proposals

2012 ◽  
Author(s):  
Grace Kelly Q. Ganharul ◽  
Nick de Brangança Azevedo ◽  
Gustavo Henrique B. Donato
Keyword(s):  
Real Time ◽  
Weighted Average ◽  
Tensile Tests ◽  
Plastic Instability ◽  
True Stress ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
High Definition ◽  
Stress Strain

Numerical elastic-plastic simulations have undergone significant expansion during the last decades (e.g. refined fracture mechanics finite element models including ductile tearing). However, one limitation to increase the accuracy of such models is the reliable experimental characterization of true stress-strain curves from conventional uniaxial tensile tests after necking (plastic instability), which complicates the direct assessment of the true stress-strain curves until failure. As a step in this direction, this work presents four key activities: i) first, existing correction methods are presented, including Bridgman, power law, weighted average and others; ii) second, selected metals are tested to experimentally characterize loads and the geometric evolution of necking. High-definition images are used to obtain real-time measurements following a proposed methodology; iii) third, refined non-linear FEM models are developed to reproduce necking and assess stresses as a function of normalized neck geometry; iv) finally, existing correction methods are critically compared to experimental results and FEM predictions in terms of potential and accuracy. The experimental results evaluated using high-definition images presented an excellent geometrical characterization of instability. FEM models were able to describe stress-strain-displacement fields after necking, supporting the exploratory validations and proposals of this work. Classical methodologies could be adapted based on experiments to provide accurate stress-strain curves up to failure with less need for real-time measurements, thus giving further support to the determination of true material properties considering severe plasticity.

Validation of the Hardening Behaviors for Metallic Materials at High Strain Rate and Temperature by Using the Taylor Impact Test

2016 ◽  
Vol 715 ◽  
pp. 153-158
Author(s):  
Ming Jun Piao ◽  
Hoon Huh ◽  
Ik Jin Lee ◽  
Hyung Won Kim ◽  
Lee Ju Park
Keyword(s):  
Tensile Tests ◽  
Thermal Softening ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Metallic Materials ◽  
Softening Effect ◽  
Impact Tests ◽  
Wide Range ◽  
Taylor Impact

This paper is concerned with the validation of the dynamic hardening behaviors of metallic materials by comparing numerical and experimental results of the Taylor impact tests. Several uniaxial tensile tests are performed at different strain rates and temperatures by using three kinds of materials: 4130 steel (BCC); OFHC copper (FCC); and Ti6Al4V alloy (HCP). Uniaxial material tests are performed at a wide range of strain rates from 10−3 s−1 to 103 s−1. Moreover, tensile tests are performed at temperature of 25 °C and 200 °C at strain rates of 10−3 s−1, 10−1 s−1, and 102 s−1, respectively. A modified Johnson–Cook type thermal softening model is utilized for the accurate application of the thermal softening effect at different strain rates. The hardening behaviors of the three materials are characterized by comparing the seven sequentially deformed shapes of the projectile from numerical and experimental results of Taylor impact tests.

Finite Element Simulations for Investigating the Effects of Specimen Geometry in Superplastic Tensile Tests

2010 ◽  
Vol 20 (6) ◽  
pp. 865-876 ◽  
Author(s):  
Mohammad Nazzal ◽  
Fadi Abu-Farha ◽  
Richard Curtis
Keyword(s):  
Finite Element ◽  
Tensile Tests ◽  
Finite Element Simulations ◽  
Specimen Geometry

Determining Representative Stress and Representative Strain in Deriving Indentation Flow Curves Based on Finite Element Analysis

2005 ◽  
Vol 297-300 ◽  
pp. 2152-2157 ◽  
Author(s):  
Eun Chae Jeon ◽  
Min Kyung Baik ◽  
Sung Hoon Kim ◽  
Baik Woo Lee ◽  
Dong Il Kwon
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Indentation Test ◽  
Plastic Property ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Flow Curves ◽  
Element Analysis ◽  
Representative Strain ◽  
Instrumented Indentation Test

A new method [1] to evaluate indentation flow curves using an instrumented indentation test has been applied to many materials for several years. Though the method produces relatively good results compared to uniaxial tensile tests, a few parameters had not been verified by theoretical or numerical methods. In this study, proportional constants of representative strain and representative stress were verified using finite element analysis and proven to be unaffected by the elastic property and strain level. The constants were generally dependent on the plastic property; however, one combination of the constants is independent of all properties. The values of this combination are consistent with early research and produced overlapping indentation flow curves with uniaxial curves.

Development of a Pneumatic Bulge Test for High Temperatures and Controlled Strain Rates

2014 ◽  
Vol 1018 ◽  
pp. 245-252 ◽  
Author(s):  
Alexander Braun ◽  
Johannes Storz ◽  
Markus Bambach ◽  
Gerhard Hirt
Keyword(s):  
Finite Element ◽  
Hot Stamping ◽  
High Strength ◽  
Tensile Tests ◽  
Finite Element Simulations ◽  
Bulge Test ◽  
Strain Rates ◽  
Hot Gas ◽  
Pneumatic Bulge Test ◽  
Simulation Input

Due to new material concepts (e.g. boron-manganese steels), hot stamping of sheet metal parts has emerged in order to produce high strength components. Thereby, the design of hot stamping processes by means of finite element simulations requires information about the thermo-mechanical material behaviour up to high strain levels at various temperatures as simulation input. It is known that hot tensile tests are only evaluable until low strain levels. Therefore, a hot gas bulge test for temperatures in the range of 600 °C to 900 °C and strain rates up to 1/s is being developed. In order to design such a hot gas bulge test, the requirements (e.g. forming pressure) are estimated by finite element simulations. The result is a test bench, which already enables a pneumatic forming of specimens at room temperature and pressures up to 200 bar without any unexpected side effects.

scholarly journals EVALUATION OF IMPACT OF ELEVATED TEMPERATURES ON YOUNG’S MODULUS OF GLT BEAMS

2021 ◽  
Vol 30 ◽  
pp. 41-47
Author(s):  
Lucie Kucíková ◽  
Michal Šejnoha ◽  
Tomáš Janda ◽  
Pavel Padevět ◽  
Guido Marseglia
Keyword(s):  
Mechanical Behavior ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Experimental Results ◽  
Fire Tests ◽  
Dog Bone ◽  
Glued Laminated Timber ◽  
Crack Type ◽  
Variable Duration ◽  
Timber Beams

The influence of elevated temperatures on mechanical behavior of glued laminated timber beams is examined on the basis of tensile tests. Dog bone samples prepared from beams exposed to fire of variable duration were categorized with respect to the type and position of the failure crack, type and number of discontinuities such as knots, and the level of browning. The acquired experimental results suggest that the wood variability and the effect of growth discontinuities are probably more significant than the effect of elevated temperatures. To support this conclusion, further study is currently under way, exploring samples from the second series of the fire tests.

scholarly journals The influence of sample geometry and size on porcine aortic material properties from uniaxial tensile tests using custom-designed tissue cutters, clamps and molds

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0244390
Author(s):  
Ming Pei ◽  
Donghua Zou ◽  
Yong Gao ◽  
Jianhua Zhang ◽  
Ping Huang ◽  
...  
Keyword(s):  
Material Properties ◽  
Tensile Testing ◽  
Tensile Tests ◽  
Optimal Choice ◽  
The Other ◽  
Uniaxial Tensile ◽  
Test Results ◽  
Uniaxial Tensile Testing ◽  
Dog Bone ◽  
Weibull Theory

The aim of this study was to identify the influence of specimen geometry and size on the results of aortic uniaxial tensile tests using custom-designed tissue cutters, clamps and molds. Six descending thoracic aortas from pigs were used for rectangular sample tests, in which the circumferential and axial specimens had widths of 6 mm, 8 mm and 10 mm. The other six aortas were used for the dog-bone-shaped sample tests and were punched into circumferential, axial and oblique specimens with widths of 2 mm, 4 mm and 6 mm. We performed uniaxial tensile tests on the specimens and compared the test results. The results showed that mid-sample failure occurred in 85.2% of the dog-bone-shaped specimens and in 11.1% of the rectangular samples, which could be caused by Saint-Venant’s principle. Therefore, rectangular specimens were not suitable for aortic uniaxial tensile testing performed until rupture. The results also showed that the size effect of the aorta conformed to Weibull theory, and dog-bone-shaped specimens with a width of 4 mm were the optimal choice for aortic uniaxial tensile testing performed until rupture.

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