Temperature-Controlled Forming of 7075-T6 Aluminum Using Linearly Decaying Direct Electric Current

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Brandt J. Ruszkiewicz ◽  
Laine Mears
Keyword(s):  
Flow Stress ◽  
Stress Model ◽  
Temperature Prediction ◽  
Direct Electric Current ◽  
Stress Effects ◽  
Electrically Assisted ◽  
Continuous Current ◽  
Tension Testing ◽  
Temperature Controlled ◽  
Flow Stress Model

7075-T6 aluminum suffers from limited elongation during tensile forming; electrically assisted forming (EAF), which uses direct current to improve formability, is a viable candidate process to improve this effect. In past electrical tension testing by various authors, two types of waveforms have been examined: continuous current and square waveforms. For tension, it was shown that the applying current using square waveforms was able to extend formability beyond what continuous current could do, due to reducing the overheating in the necking region. The goal of this paper is to model the temperature and flow stress effects of saw tooth waves by modifying an existing square wave temperature prediction model and combining it with a theoretical flow stress model. Nondecaying and linearly globally decaying saw tooth waveforms are used in an attempt to control the temperature of the necking zone to allow for increased strain at fracture. Comparisons between saw tooth waveforms and square waveforms are exhibited, and it is found that the saw tooth waveforms are inferior to square waves for increasing strain at fracture for 7075-T6.

Temperature Controlled Forming of 7075-T6 Aluminum Using Linearly Decaying Direct Electric Current

2016 ◽  
Author(s):  
Brandt J. Ruszkiewicz ◽  
Laine Mears
Keyword(s):  
Flow Stress ◽  
Fuel Efficiency ◽  
High Strength ◽  
Cold Forming ◽  
Direct Electric Current ◽  
Wave Forms ◽  
Continuous Current ◽  
Tension Testing ◽  
Material Forming ◽  
Sawtooth Waveform

The push in the automotive industry towards lightweighting to meet new stricter fuel efficiency standards has driven the need to research lightweight material forming. This requires research into forming high strength materials, as well as lower strength lightweight materials that may typically have poor formability characteristics. 7075-T6 aluminum suffers from limited elongation during tensile forming; electrically-assisted forming, which uses direct current to improve formability, is a viable candidate process to improve formability. In past electrical tension testing by various authors, two types of wave forms have been examined: continuous current and square waveforms. For tension it was shown that applying current using square waveforms was able to extend formability beyond what continuous current could produce, due to reducing the overheating in the necking region. This paper examines the effect of a non-decaying and linearly globally decaying saw tooth wave on the formability and flow stress of 7075-T6 aluminum in tension. It is shown that EAM using a sawtooth waveform can result in further elongation than cold forming, with similar elongation to previously-investigated square waves. An existing temperature model is adapted to the saw tooth waveform and used to calculate the change in material properties to find the flow stress using a theoretical strength equation.

Hot Forming Flow Stress Model of Steel 50A1300

2012 ◽  
Vol 446-449 ◽  
pp. 3591-3595
Author(s):  
Xu Dong Zhou ◽  
Xiang Ru Liu ◽  
Xu Yi Shan
Keyword(s):  
Flow Stress ◽  
Hot Forming ◽  
Stress Model ◽  
Flow Stress Model

Study on High Temperature Flow Stress Model of As-cast SA508-3 Low Alloy Steel

2020 ◽  
Vol 831 ◽  
pp. 25-31
Author(s):  
Pan Fei Fan ◽  
Jian Sheng Liu ◽  
Hong Ping An ◽  
Li Li Liu
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Alloy Steel ◽  
Flow Behavior ◽  
Peak Stress ◽  
Stress Model ◽  
Low Alloy Steel ◽  
Two Stage ◽  
Flow Stress Model

In order to obtain the high temperature flow behavior of as-cast SA508-3 low alloy steel, the stress-strain curves of steel are obtained by Gleeble thermal simulation compression test at deformation temperature 800°C-1200°C and strain rate 0.001s-1-1s-1. Based on Laasraoui two-stage flow stress model, a high temperature flow stress model is established by multiple linear regression method. The results show that the peak stress characteristics are not obvious at low temperature and high strain rate, which is a typical dynamic recovery characteristic. Meanwhile, the peak stress characteristics are obvious at high temperature and low strain rate, which is a typical dynamic recrystallization characteristic. By means of the comparisons between experiments and calculations, the Laasraoui two-stage flow stress model can truly reflect flow behavior of steel at high temperature, which provides theoretical guidance for the hot deformation of the steel.

scholarly journals Johnson Cook Material and Failure Model Parameters Estimation of AISI-1045 Medium Carbon Steel for Metal Forming Applications

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 609 ◽  
Author(s):  
Mohanraj Murugesan ◽  
Dong Jung
Keyword(s):  
Flow Stress ◽  
Metal Forming ◽  
Flow Behavior ◽  
Medium Carbon Steel ◽  
Material Behavior ◽  
Model Parameters ◽  
Stress Model ◽  
Medium Carbon ◽  
Aisi 1045 ◽  
Flow Stress Model

Consistent and reasonable characterization of the material behavior under the coupled effects of strain, strain rate and temperature on the material flow stress is remarkably crucial in order to design as well as optimize the process parameters in the metal forming industrial practice. The objective of this work was to formulate an appropriate flow stress model to characterize the flow behavior of AISI-1045 medium carbon steel over a practical range of deformation temperatures (650–950 ∘ C) and strain rates (0.05–1.0 s − 1 ). Subsequently, the Johnson-Cook flow stress model was adopted for modeling and predicting the material flow behavior at elevated temperatures. Furthermore, surrogate models were developed based on the constitutive relations, and the model constants were estimated using the experimental results. As a result, the constitutive flow stress model was formed and the constructed model was examined systematically against experimental data by both numerical and graphical validations. In addition, to predict the material damage behavior, the failure model proposed by Johnson and Cook was used, and to determine the model parameters, seven different specimens, including flat, smooth round bars and pre-notched specimens, were tested at room temperature under quasi strain rate conditions. From the results, it can be seen that the developed model over predicts the material behavior at a low temperature for all strain rates. However, overall, the developed model can produce a fairly accurate and precise estimation of flow behavior with good correlation to the experimental data under high temperature conditions. Furthermore, the damage model parameters estimated in this research can be used to model the metal forming simulations, and valuable prediction results for the work material can be achieved.

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