Mathematical Modelling to Evaluate the Superplastic Material Constants by Bulge Test

2014 ◽  
Vol 607 ◽  
pp. 29-32
Author(s):  
Giuliano Gillo
Keyword(s):  
Mathematical Modelling ◽  
Experimental Tests ◽  
Limited Range ◽  
Equivalent Strain ◽  
Bulge Test ◽  
Strain Rates ◽  
Superplastic Material ◽  
Material Constants ◽  
Die Geometry ◽  
Equivalent Strain Rate

The mechanical behaviour of a superplastic material is often modelled by the power law relationship between the equivalent flow stress, the equivalent strain and the equivalent strain-rate at least over a limited range of strain rates. This paper introduces an original mathematical modelling to determine the superplastic material constants m, n and K by means of experimental tests carried out using a standard forming die geometry.

Numerical-Experimental Comparison to Validate a Mathematical Model for the Determination of the Superplastic Material Constants

2014 ◽  
Vol 607 ◽  
pp. 25-28
Author(s):  
Giuliano Gillo
Keyword(s):  
Mathematical Model ◽  
Experimental Tests ◽  
Experimental Comparison ◽  
Superplastic Material ◽  
Material Constants ◽  
Die Geometry ◽  
Alloy Az31

This paper shows a numerical-experimental comparison to validate a mathematical model which is able to determine the superplastic material constants by means of experimental tests carried out using a standard forming die geometry. In particular, the constants m, n and K for the lead-tin alloy PbSn60, for the alloy AZ31 at different forming temperatures and for the alloy AA5083 are evaluated.

AZ31 Magnesium Alloy Parameters Identification through Inverse Analysis at 713 K

2012 ◽  
Vol 504-506 ◽  
pp. 643-646 ◽  
Author(s):  
Gillo Giuliano
Keyword(s):  
Strain Rate ◽  
Power Law ◽  
Inverse Analysis ◽  
Constant Pressure ◽  
Az31 Alloy ◽  
Equivalent Strain ◽  
Strain Rate Range ◽  
Displacement Curve ◽  
Material Constants ◽  
Equivalent Strain Rate

This paper introduces a fast and accurate procedure for determining the constants of magnesium AZ31 alloy at 713 K. The material behaviour is modelled by means of the power law relationship between the equivalent flow stress, the equivalent strain and the equivalent strain-rate within a narrow equivalent strain-rate range. Bulging tests were carried out in isothermal conditions (713 K) and at constant pressure in order to determine the material constants. It is necessary to evaluate the displacement and the thickness evolutions at the dome apex of the metal sheet. The time-displacement curve was obtained by laser measurements whereas a large number of bulging tests, interrupted at preset time intervals, were carried out to evaluate the thickness. The thickness was measured directly using a two-digit micrometer. The material constants, m, n and K were obtained in the power law relationship by means of constant pressure bulging tests coupled with the use of an inverse analysis technique. The results of comparison between experimental and numerical tests are shown and they indicate that the material constants can be accurately evaluated.

scholarly journals Static Mechanical Properties of Expanded Polypropylene Crushable Foam

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 249
Author(s):  
Przemysław Rumianek ◽  
Tomasz Dobosz ◽  
Radosław Nowak ◽  
Piotr Dziewit ◽  
Andrzej Aromiński
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Energy Absorption ◽  
Experimental Tests ◽  
Absorption Capacity ◽  
Strain Rates ◽  
Foam Density ◽  
Energy Absorption Capacity ◽  
Closed Cell

Closed-cell expanded polypropylene (EPP) foam is commonly used in car bumpers for the purpose of absorbing energy impacts. Characterization of the foam’s mechanical properties at varying strain rates is essential for selecting the proper material used as a protective structure in dynamic loading application. The aim of the study was to investigate the influence of loading strain rate, material density, and microstructure on compressive strength and energy absorption capacity for closed-cell polymeric foams. We performed quasi-static compressive strength tests with strain rates in the range of 0.2 to 25 mm/s, using a hydraulically controlled material testing system (MTS) for different foam densities in the range 20 g/dm3 to 220 g/dm3. The above tests were carried out as numerical simulation using ABAQUS software. The verification of the properties was carried out on the basis of experimental tests and simulations performed using the finite element method. The method of modelling the structure of the tested sample has an impact on the stress values. Experimental tests were performed for various loads and at various initial temperatures of the tested sample. We found that increasing both the strain rate of loading and foam density raised the compressive strength and energy absorption capacity. Increasing the ambient and tested sample temperature caused a decrease in compressive strength and energy absorption capacity. For the same foam density, differences in foam microstructures were causing differences in strength and energy absorption capacity when testing at the same loading strain rate. To sum up, tuning the microstructure of foams could be used to acquire desired global materials properties. Precise material description extends the possibility of using EPP foams in various applications.

Design and Analysis of Automotive Bumper Covers in Transient Loading Conditions

2016 ◽  
Vol 715 ◽  
pp. 174-179 ◽  
Author(s):  
Chih Hsing Liu ◽  
Ying Chia Huang ◽  
Chen Hua Chiu ◽  
Yu Cheng Lai ◽  
Tzu Yang Pai
Keyword(s):  
Optimal Design ◽  
Numerical Model ◽  
Design Method ◽  
Experimental Tests ◽  
Cost Effective ◽  
Limited Range ◽  
Optimization Approach ◽  
Loading Conditions ◽  
Element Analysis ◽  
Design Guideline

This paper presents the analysis methods for design of automotive bumper covers. The bumper covers are plastic structures attached to the front and rear ends of an automobile and are expected to absorb energy in a minor collision. One requirement in design of the bumper covers is to minimize the bumper deflection within a limited range under specific loadings at specific locations based on the design guideline. To investigate the stiffness performance under various loading conditions, a numerical model based on the explicit dynamic finite element analysis (FEA) using the commercial FEA solver, LS-DYNA, is developed to analyze the design. The experimental tests are also carried out to verify the numerical model. The thickness of the bumper cover is a design variable which usually varies from 3 to 4 mm depending on locations. To improve the stiffness of the bumper, an optimal design for the bumper under a pre-defined loading condition is identified by using the topology optimization approach, which is an optimal design method to obtain the optimal layout of an initial design domain under specific boundary conditions. The outcome of this study provides an efficient and cost-effective method to predict and improve the design of automotive bumper covers.

Strain Rate Effect on Progressive Failure and Tensile Behaviour of Kevlar Epoxy Composites

2020 ◽  
Vol 12 (4) ◽  
Author(s):  
C. Ganesan ◽  
P.S. Joanna ◽  
Dalbir Singh
Keyword(s):  
Mechanical Properties ◽  
Progressive Failure ◽  
Axial Loading ◽  
Experimental Tests ◽  
Strain Rate Effect ◽  
Matrix Cracking ◽  
Epoxy Composites ◽  
Tensile Behaviour ◽  
Strain Rates ◽  
The Difference

This study investigates about the effect of different strain rates on the tensile behaviour of kevlar epoxy composites and progressive failure of kevlar epoxy composites under displacement controlled axial loading. A series of experimental tests were conducted under different strain rates to find out the tensile behaviour of kevlar epoxy composites. Two different strain rates 0.5mm/ min and 1.5mm/ min were applied to the kevlar epoxy specimen in order to understand the difference in mechanical properties and progressive failures of composites. Tensile strength increases with an increase in strain rates. Failure in kevlar epoxy composites is analysed under different stages for both 0.5mm/min and 1.5 mm/min. For all the tests, failure starts with matrix cracking followed by delamination and ends with fracture.

scholarly journals Strain-controlled bulge test

2008 ◽  
Vol 23 (12) ◽  
pp. 3295-3302 ◽  
Author(s):  
B. Erdem Alaca ◽  
K. Bugra Toga ◽  
Orhan Akar ◽  
Tayfun Akin
Keyword(s):  
Strain Rate ◽  
Rate Control ◽  
Closed Loop ◽  
Temporal Evolution ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Bulge Test ◽  
Strain Rates ◽  
Strain Formulation ◽  
Control Criterion

A closed-loop approach is adopted to implement strain rate control during the bulge test. Due to the difficulty of measuring strains directly, the technique is based on the conversion of displacement measurements to the corresponding strains using the plane-strain formulation. The necessary temporal evolution of the midpoint displacement of a rectangular diaphragm is derived under the condition of constant strain rate and is imposed as a control criterion. The technique is demonstrated on 500-nm-thick Au diaphragms by applying strain rates ranging from 2 × 10−6 to 2 × 10−4 s–1. By measuring the corresponding yield strength values, a strain rate sensitivity of 0.11 is obtained, which is close to what was previously reported on similar specimens using the microbending test.

scholarly journals Theoretical and Experimental Analysis of Formability of Explosive Welded Mg/Al Bimetallic Bars

2017 ◽  
Vol 62 (2) ◽  
pp. 501-507 ◽  
Author(s):  
S. Mróz ◽  
P. Szota ◽  
T. Bajor ◽  
A. Stefanik
Keyword(s):  
Plastic Deformation ◽  
Experimental Analysis ◽  
Physical Modeling ◽  
Explosive Welding ◽  
Experimental Tests ◽  
The Other ◽  
Outer Diameter ◽  
Theoretical Studies ◽  
Strain Rates ◽  
Cladding Layer

AbstractThe paper has presented the results of theoretical studies and experimental tests of the plastic deformation of Mg/Al bimetallic specimens. Theoretical studies were carried out using the Forge2011® computer program. Physical modeling, on the other hand, was performed using the Gleeble3800 simulator. Bimetallic bars of an outer diameter of 22.5 mm and a cladding layer thickness of 1.7 mm were obtained by the explosive welding method. Samples for formability tests, characterized by a diameter-to-length ratio of 1, were taken from the bars. The theoretical studies and experimental tests were carried out for the temperature range from 300 to 400°C and for different strain rates. Based on the obtained investigation results it has been found that the main parameters influencing the formability of Mg/Al bimetallic bars are strain rate than the process temperature.

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 An An Analysis of Strain Rate Distribution Using Streamline Model and A Quick Stop Device in Metal Cutting

2019 ◽  
Vol 22 (2) ◽  
pp. 136-142
Author(s):  
Osama Ali Kadhim ◽  
Fathi A. Alshamma
Keyword(s):  
Strain Rate ◽  
Chip Formation ◽  
Metal Cutting ◽  
Equivalent Strain ◽  
Element Analysis ◽  
Rate Distribution ◽  
Equivalent Strain Rate ◽  
Cumulative Plastic Strain ◽  
Cutting Speeds ◽  
Strain Rate Distribution

In this paper, a quick stop device technique and the streamline model were employed to study the chip formation in metal cutting. The behavior of chip deformation at the primary shear zone was described by this model. Orthogonal test of turning process over a workpiece of the 6061-T6 aluminum alloy at different cutting speeds was carried out. The results of the equivalent strain rate and cumulative plastic strain were used to describe the complexity of chip formation. Finite element analysis by ABAQUS/explicit package was also employed to verify the streamline model. Some behavior of formation and strain rate distribution differs from the experimental results, but the overall trend and maximum results are approximately close. In addition, the quick stop device technique is described in detail. Which could be used in other kinds of studies, such as the metallurgical observation.

Development of a Material Constitutive for High-Rate Using a Combined Experiment/Computation Method

2004 ◽  
Vol 261-263 ◽  
pp. 269-276
Author(s):  
J.F. Lu ◽  
Zhuo Zhuang ◽  
K. Shimamura
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Equivalent Strain ◽  
High Rate ◽  
Computation Method ◽  
Failure Behavior ◽  
Hopkinson Pressure Bar ◽  
Material Constants ◽  
Split Hopkinson ◽  
Pressure Bar

To describe the high-rate behaviour of metals, a revised form of the classic Johnson-Cook strength model with unknown material constants has been used. The 1D stress-strain relations as well as the effects of strain, strain rate and temperature are examined by Split Hopkinson Pressure Bar (SHPB) test. The undetermined material constants are solved using a variable-dissociation method. The element failure criterion based on maximum equivalent strain is also introduced to estimate the material failure behavior under high strain rate. A corresponding user-defined material subroutine (UMAT) has been developed for revised Johnson-Cook model, which is implemented into ABAQUS. Using this implicit scheme, several groups of finite element simulations under different strain rates are completed in ABAQUS/Standard. The results agree well with the test data and other results by explicit code.

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