Effects of strain rates and biaxial stress conditions on plastic yielding and flow stress of solder alloys

2006 ◽  
Vol 35 (2) ◽  
pp. 372-379 ◽  
Author(s):  
J. Liang ◽  
N. Dariavach ◽  
G. Barr ◽  
Z. Fang
Keyword(s):  
Flow Stress ◽  
Stress Conditions ◽  
Biaxial Stress ◽  
Strain Rates ◽  
Plastic Yielding ◽  
Solder Alloys

A Numerical and Experimental Study of Cavitation in a Hot Tensile Axisymmetric Testpiece

2005 ◽  
Vol 40 (6) ◽  
pp. 571-586 ◽  
Author(s):  
Y Liu ◽  
J Lin ◽  
T. A Dean ◽  
D. C. J Farrugia
Keyword(s):  
Experimental Study ◽  
Flow Stress ◽  
Grain Boundary ◽  
Thermal Gradient ◽  
Tensile Testing ◽  
Tensile Deformation ◽  
Strain Rates ◽  
Test Results ◽  
Integrated Technique ◽  
Hot Tensile Deformation

During axisymmetric hot tensile testing, necking normally takes place due to the thermal gradient and the accumulation of microdamage. This paper introduces an integrated technique to predict the damage and necking evolution behaviour. Firstly, a set of multiaxial mechanism-based unified viscoplastic-damage constitutive equations is presented. This equation set, which models the evolution of grain boundary (intragranular) and plasticity-induced (intergranular) damage, is determined for a free-cutting steel tested over a range of temperatures and strain rates on a Gleeble thermomechanical simulator. This model has been implemented using the CREEP subroutine of the commercial finite element (FE) solver ABAQUS. Numerical procedures to simulate axisymmetric hot tensile deformation are developed with consideration of the thermal gradient along the axis of the tensile testpiece. FE simulations are carried out to reproduce the necking phenomenon and the evolution of plasticity-induced and grain boundary damage. The simulated results have been validated with experimental tensile test results. The effects of necking and its associated stress state on flow stress and ductility are investigated. The flow stress and ductility data obtained from a Gleeble material simulator under various hot deformation conditions have also been numerically studied.

A Comparative Study on Hydraulic Bulge Testing and Analysis Methods

2008 ◽  
Author(s):  
Eren Billur ◽  
Muammer Koc¸
Keyword(s):  
Flow Stress ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Material Behavior ◽  
Biaxial Stress ◽  
Dome Height ◽  
Bulge Test ◽  
Analysis Methods ◽  
Bulge Testing ◽  
Hydraulic Bulge

Hydraulic bulge testing is a material characterization method used as an alternative to tensile testing with the premise of accurately representing the material behavior to higher strain levels (∼70% as appeared to ∼30% in tensile test) in a biaxial stress mode. However, there are some major assumptions (such as continuous hemispherical bulge shape, thinnest point at apex) in hydraulic bulge analyses that lead to uncertainties in the resulting flow stress curves. In this paper, the effect of these assumptions on the accuracy and reliability of flow stress curves is investigated. The goal of this study is to determine the most accurate method for analyzing the data obtained from the bulge testing when continuous and in-line thickness measurement techniques are not available. Specifically, in this study the stress-strain relationships of two different materials (SS201 and Al5754) are obtained based on hydraulic bulge test data using various analysis methods for bulge radius and thickness predictions (e.g., Hill’s, Chakrabarty’s, Panknin’s theories, etc.). The flow stress curves are calculated using pressure and dome height measurements and compared to the actual 3-D strain measurement from a stereo optical and non-contact measurement system ARAMIS. In addition, the flow stress curves obtained from stepwise experiments are compared with the ones from above methods. Our findings indicate that Enikeev’s approach for thickness prediction and Panknin’s approach for bulge radius calculation result in the best agreement with both stepwise experiment results and 3D optical measurement results.

A modified Arrhenius model for as-quenched Al-Mg-Si alloy considering the effect of cooling rate

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ruichao Guo ◽  
Jianjun Wu ◽  
Yinxiang Ren
Keyword(s):  
Residual Stress ◽  
Flow Stress ◽  
Cooling Rate ◽  
Flow Behavior ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
Arrhenius Model ◽  
Content Type ◽  
Stress Behavior ◽  
Flow Stress Behavior

Purpose Accurate prediction of residual stress requires precise knowledge of the constitutive behavior of as-quenched material. This study aims to model the flow stress behavior for as-quenched Al-Mg-Si alloy. Design Methodology Approach In the present work, the flow behavior of as-quenched Al-Mg-Si alloy is studied by the hot compression tests at various temperatures (573–723 K), strain rates (0.1–1 s−1) and cooling rates (1–10 K/s). Flow stress behavior is then experimentally observed, and an Arrhenius model is used to predict the flow behavior. However, due to the fact that materials parameters and activation energy do not remain constant, the Arrhenius model has an unsatisfied prediction for the flow behavior. Considering the effects of temperatures, strain rates and cooling rates on constitutive behavior, a revised Arrhenius model is developed to describe the flow stress behavior. Findings The experimental results show that the flow stress increases by the increasing cooling rate, increasing strain state and decreasing temperature. In comparison to the experimental data, the revised Arrhenius model has an excellent prediction for as-quenched Al-Mg-Si alloy. Originality Value With the revised Arrhenius model, the flow behaviors at different quenching conditions can be obtained, which is an essential step to the residual stress prediction when the model is implemented in a finite element code, e.g. ABAQUS, in the future.

scholarly journals Hot Deformation Behavior of a New Al–Mn–Sc Alloy

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 22
Author(s):  
Weiqi Kang ◽  
Yi Yang ◽  
Sheng Cao ◽  
Lei Li ◽  
Shewei Xin ◽  
...  
Keyword(s):  
Flow Stress ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Material Model ◽  
Strain Rates ◽  
Hot Workability ◽  
Hot Deformation Behavior ◽  
Hollomon Parameter ◽  
Dynamic Material Model ◽  
Optimal Processing

The hot deformation behavior of a new Al–Mn–Sc alloy was investigated by hot compression conducted at temperatures from 330 to 490 °C and strain rates from 0.01 to 10 s−1. The hot deformation behavior and microstructure of the alloy were significantly affected by the deformation temperatures and strain rates. The peak flow stress decreased with increasing deformation temperatures and decreasing strain rates. According to the hot deformation behavior, the constitutive equation was established to describe the steady flow stress, and a hot processing map at 0.4 strain was obtained based on the dynamic material model and the Prasad instability standard, which can be used to evaluate the hot workability of the alloy. The developed hot processing diagram showed that the instability was more likely to occur in the higher Zener–Hollomon parameter region, and the optimal processing range was determined as 420–475 °C and 0.01–0.022 s−1, in which a stable flow and a higher power dissipation were achieved.

Plastic Flow Stress and Constitutive Model for H96 Brass Alloy

2015 ◽  
Vol 782 ◽  
pp. 130-136 ◽  
Author(s):  
Ping Zhou ◽  
Wei Guo Guo ◽  
Hai Hui Wu
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Plastic Flow ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Experimental Results ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Brass Alloy ◽  
Plastic Flow Stress

To explore the thermo-mechanical response of H96 brass alloy, the quasi-static (universal-testing machine) and dynamic (the split Hopkinson pressure bar apparatus) uniaxial compression experiments have been performed under the temperatures from 293 K to 873 K and the strain rates from 0.001 s-1 to 6000 s-1, and the strains over 60% are obtained. Results show that, H96 brass alloy has strong strain hardening behavior, and it becomes weaker with the increasing temperature. In addition, this alloy is sensitive to strain rates; and, it has temperature sensitivity, the dynamic strain aging occurs at the temperature of 473 K and a quasi-static strain rate of 0.001 s-1. Based on the thermal activation dislocation mechanism, paralleled with the experimental results, a plastic flow constitutive model with the physical conception is developed. The model is suitable to predict the plastic flow stress at different temperatures and strain rates. According to comparing results, the model predictions are in good agreement with the experimental results.

Ball Burnishing Under High Velocities Using a New Rolling Tool Concept

2017 ◽  
Author(s):  
Lars Hiegemann ◽  
A. Erman Tekkaya
Keyword(s):  
Flow Stress ◽  
Local Strain ◽  
Strain Rates ◽  
Ball Burnishing ◽  
Rolling Velocity ◽  
Milling Machines ◽  
Surface Irregularities ◽  
Burnishing Process ◽  
Stress Drops ◽  
Incremental Process

Ball burnishing is a process used to smooth rough surfaces. For not rotational symmetric parts, the process is typically conducted on milling machines. Since it is an incremental process, it is relatively time consuming. Therefore, a rolling tool is developed, which superposes the rotation of the milling spindle with the feed of the machine to increase the rolling velocity. In order to achieve constant rolling forces, hydrostatic ball burnishing tools are used. Within this work, the influence of this tool concept on the processing time as well as on the leveling of surface irregularities is investigated. This is achieved by a comparison with a conventional ball burnishing process. Finally, the rotating tool is used to investigate the influence of high rolling speeds on the leveling of the surface. All experiments were carried out with thermally coated specimens. A model for calculating the strain rates at the roughness peaks during ball burnishing is derived. For the experiments carried out with the rotating rolling tool, rolling velocities of 50,000 mm/min were realized. Calculations with the developed model showed that this results in local strain rates at the roughness peaks of up to 1,384 s−1. In addition, the flow stresses at the roughness peaks were calculated. Compared with quasi static experiments, the flow stress drops to less than the half under high velocities. This results in a better leveling of the surface for rolling velocities between 10,000 mm/min and 25,000 mm/min. A further rise of the rolling speed increases the flow stress again and thereby reduces the possible leveling.

Flow Stress Behavior of Nanometric Al2O3 Particulate Reinforced Al Alloy Composites Manufactured by Casting

2012 ◽  
Vol 430-432 ◽  
pp. 1294-1297
Author(s):  
Zhi Min Zhang ◽  
Yong Biao Yang ◽  
Xing Zhang
Keyword(s):  
Grain Size ◽  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Al Alloy ◽  
Strain Rates ◽  
Stress Behavior ◽  
Flow Stress Behavior ◽  
Increasing Temperature ◽  
Particulate Reinforced ◽  
Temperature Dynamic

The flow stress behavior of nanometric Al2O3 particulate reinforced Al alloy composites were investigated using thermal simulation machine Gleeble-1500. Microsturctural analysis were carried out on optical microscopy. The results showed that the flow stress increased with increasing strain rate and decreased with decreasing temperature. Dynamic recovery and dynamic recrystallization occurred during hot compression of the Al composites. The grain size increased with increasing temperature (590k-710k) and decreased at 750k due to dynamic recrystallization. The grain size decreased with increasing strain rates at 750k.

Thermal Deformation Behavior and Processing Map of Al-Mg-Er Alloy

2018 ◽  
Vol 913 ◽  
pp. 30-36
Author(s):  
Ran Liu ◽  
Hui Huang ◽  
Ya Liu ◽  
Li Rong
Keyword(s):  
Flow Stress ◽  
Deformation Behavior ◽  
Deformation Temperature ◽  
Material Model ◽  
Instability Criterion ◽  
Strain Rates ◽  
Processing Maps ◽  
Hot Workability ◽  
Compression Tests ◽  
Dynamic Material Model

To study the hot deformation behavior of Al-Mg-Er alloy, hot compression tests were conducted on a Gleeble-1500D thermal simulator at the temperature range of 200-500°C with the strain rates from 0.001 to 10s-1. With the increase in the deformation temperature and the decrease in strain rates, the flow stress of the Al-Mg-Er alloy decreased. Processing maps were constructed to study on hot workability characteristics. The results showed that the flow stress curves exhibited the typical dynamic recrystallization characteristics and the stress decreased with the increase of deformation temperature and the decrease of strain rate. Moreover, the processing maps were established on the basis of dynamic material model and Prasad’s instability criterion.

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