scholarly journals FepiM: A Novel Inverse Piecewise Method to Determine Isothermal Flow Curves for Hot Working

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 602
Author(s):  
Aditya Vuppala ◽  
Alexander Krämer ◽  
Johannes Lohmar ◽  
Gerhard Hirt
Keyword(s):  
Flow Curve ◽  
Elevated Temperatures ◽  
Isothermal Flow ◽  
Inverse Methods ◽  
Material Behavior ◽  
Maximum Deviation ◽  
Compression Tests ◽  
Complex Flow ◽  
Flow Curves ◽  
Curve Determination

In forming simulations, flow curves are cardinal inputs to predict features, such as forming forces and material flow. The laboratory-scale experiments to determine them, like compression or tensile tests, are affected by deformation heating, restricting direct flow curve determination. In principle, the current analytical and inverse methods determine flow curves from these tests, but while the analytical methods assume a simplified temperature profile, the inverse methods require a closed-form flow curve equation, which mostly cannot capture complex material behavior like multiple recrystallization cycles. Therefore, the inverse piecewise flow curve determination method “FepiM” previously developed and published by the current authors is extended by introducing a two-step procedure to obtain isothermal flow curves at elevated temperatures and different strain rates. Thereby, the flow curve is represented as tabular data instead of an equation to reproduce complex flow curve shapes while also compensating the effect of inhomogeneous temperature profiles on the flow stress. First, a flow curve at the highest temperature is determined. In the second step, using this first flow curve as a reference, the flow curves at lower temperatures are obtained via interpolation. Flow curves from conventional compression tests for aluminum and copper in the temperature range of 20–500 °C are predicted, and it is shown that these flow curves can reproduce the experimental forces with a maximum deviation of less than 1%. Therefore, the proposed new piecewise method accurately predicts isothermal flow curves for compression tests, and the method could be further extended to highly inhomogeneous methods in the future.

Analysis of the Hydraulic Bulge Test with FEA Concerning the Accuracy of the Determined Flow Curves

2009 ◽  
Vol 410-411 ◽  
pp. 439-447 ◽  
Author(s):  
Alper Güner ◽  
Alexander Brosius ◽  
A. Erman Tekkaya
Keyword(s):  
Flow Curve ◽  
Material Flow ◽  
High Strength ◽  
Bulge Test ◽  
Flow Curves ◽  
Element Analysis ◽  
Hydraulic Bulge ◽  
The Finite Element Analysis ◽  
Curve Determination ◽  
Set Up

This work covers the finite element analysis of geometric and process parameters in hydraulic bulge tests in terms of the accuracy of the evaluated flow curve. The important parameters are identified and varied to cover the whole range of possible uses. The effects of these parameters are analyzed for three representative materials: aluminium, mid-strength steel, and high-strength steel. The flow curves of the materials for each set of parameters are calculated by using the results of the simulations and the membrane theory. It is seen that even with simulation results, it is not always possible to obtain the input flow curve, especially towards the end of the test. The dimensions of the sheet and the tooling affect the plastic strain development and geometry of the bulge, leading to errors in computed flow curves. In order to observe the effect of the material flow from the flange on the determined yield stresses, the function and position of the drawbeads are also examined. These parameters, together with the method used to calculate the radius of the bulge, determine the accuracy of the calculated flow curve. Guidelines for an accurate flow curve determination regarding the test set-up and calculation methods are given.

Compressive Flow Behavior of AZ61 Mg Alloy at Elevated Temperatures

2011 ◽  
Vol 311-313 ◽  
pp. 587-590
Author(s):  
Horng Yu Wu ◽  
Pin Hou Sun ◽  
Jie Chen Yan ◽  
Jing Hao Liao ◽  
Feng Jun Zhu ◽  
...  
Keyword(s):  
Structural Changes ◽  
Elevated Temperatures ◽  
Flow Behavior ◽  
Mg Alloy ◽  
Strain Rates ◽  
Compression Tests ◽  
Flow Curves ◽  
Hollomon Parameter ◽  
Compressive Flow ◽  
Az61 Mg Alloy

The flow behavior and associated structural changes of an AZ61 Mg alloy were analyzed by using hot compression tests in the temperature and strain rate ranges of 250–400 °C and 0.001 to 1 s–1, respectively. The stress–strain curves exhibited the trend typical of materials in which deformation is recovery-controlled in the high Z regime (Z is the Zener–Hollomon parameter), while at low strain rates and high T, the flow curves exhibited a softening typical of recrystallization phenomena. Microstructure analysis has been performed to correlate the microstructure changes to the flow behaviors.

scholarly journals Mathematical modeling of AZ30 magnesium alloys at high temperature using the ring compression test and genetic algorithm method

2021 ◽  
Vol 30 (1) ◽  
pp. 103-109
Author(s):  
Farzan Barati ◽  
Mona Esfandiari ◽  
Sajjad Babaei ◽  
Zahra Hoseini-Tabar ◽  
Aida Atarod
Keyword(s):  
Genetic Algorithm ◽  
Strain Rate ◽  
Flow Curve ◽  
Elevated Temperatures ◽  
Optical Microscope ◽  
Test Method ◽  
Ring Test ◽  
Strain Rates ◽  
Compression Tests ◽  
Ring Compression

Abstract In the present investigation, a new method is proposed to study the AZ30 flow curve at elevated temperatures and various strain rate. Experiments were carried out with the goal of obtaining flow curve of AZ30 at three different temperature and strain rates by using the ring test method. The presented work aims to develop a model using genetic algorithm for AZ30 flow stress prediction during different test conditions. The Santam machine was implicated that was able to perform experiments by controlling both the position and load modes. At each temperature and strain rate the isothermal test was performed respectively. In the present investigation for three varios temperatures and strain rates, 54 ring compression tests were carried out with different levels of reduction in height. Then each specimen was water cooled quickly to investigate the microstructure of AZ30 magnesium alloy by using optical microscope. The model used in the present study was able to predict the flow curve with an 2.3% accuracy. This model has excellent potential to be employed in various industry applications.

scholarly journals A Modified Constitutive Model for the Description of the Flow Behavior of the Ti-10V-2Fe-3Al Alloy during Hot Plastic Deformation

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 844 ◽  
Author(s):  
Wang ◽  
Shen ◽  
Zhang ◽  
Ning
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
Flow Behavior ◽  
Strain Rates ◽  
Compression Tests ◽  
Flow Curves ◽  
Deformation Parameters ◽  
Predicted Values

The hot deformation behavior of the aerospace Ti-10-2-3 alloy was investigated by isothermal compression tests at temperatures of 740 to 820 °C and strain rates of 0.0005 to 10 s−1. The results show that the studied alloy is extremely sensitive to deformation parameters, like the temperature and strain rate. The temperature mainly affects the magnitude of flow stress at larger strains, while the strain rate not only affects the value of flow stress but also the shape of the flow curves. At low strain rates, the flow stress increases with strain, followed by a broad peak and then remains almost constant. At high strain rates, the flow curves exhibit a hardening to a sharp peak at small strains, followed by a rapid dropping to a plateau caused by dynamic softening. In order to describe such flow behavior, a constitutive model considering the effect of deformation parameters was developed as an extension of an existing constitutive model. The modified constitutive model (MC) was obtained based on the original constitutive model (OC) by introducing a new parameter to compensate for the error between the experimental data and predicted values. Compared to the original model, the developed model provides a better description of the flow behavior of Ti-10-2-3 alloy at elevated temperatures over the specified deformation domain.

scholarly journals A New Inverse Explicit Flow Curve Determination Method for Compression Tests

2020 ◽  
Vol 47 ◽  
pp. 824-830
Author(s):  
Aditya Vuppala ◽  
Alexander Krämer ◽  
Alexander Braun ◽  
Johannes Lohmar ◽  
Gerhard Hirt
Keyword(s):  
Flow Curve ◽  
Determination Method ◽  
Compression Tests ◽  
Curve Determination

Polymer Flow Behavior from Multispeed Viscometry

1965 ◽  
Vol 38 (4) ◽  
pp. 769-781 ◽  
Author(s):  
W. E. Wolstenholme
Keyword(s):  
Activation Energy ◽  
Flow Curve ◽  
Flow Behavior ◽  
Standard Procedure ◽  
Isothermal Flow ◽  
Thermal Dependence ◽  
Flow Curves ◽  
Polymer Flow ◽  
Constant Rate ◽  
Constant Viscosity

Abstract A practical viscometric technique has been developed for measuring flow of commercial elastomeric and thermoplastic materials at processing temperatures. A standard procedure for testing bulk polymer samples in a modified shearing disk Mooney viscometer with rotor speeds from .05 to 77 rpm is described in detail. Research, development or process control personnel can rapidly convert viscometer torque dial readings at the various rotor speeds to an isothermal flow curve in absolute units of shear stress and rate of shear by either of two methods shown by examples. Total time to test a polymer sample and plot the flow curve is less than one hour. Representative flow curves illustrate how polymers with essentially equivalent ML-4 @ 212° F can have large differences in flow at processing conditions. A set of isothermal flow curves covering a desired temperature range provides an excellent estimate of processing behavior over a range of temperatures. Numerical determination of the thermal dependence of flow is easily evaluated in terms of activation energy at constant shearing stress, constant rate of shear, or constant viscosity. Activation energy is a useful constant for characterization of non-Newtonian polymer flow.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Measurement of the Material State Including the Effects of Recovery and Recrystallization

2000 ◽  
Author(s):  
M. E. Bange ◽  
A. J. Beaudoin ◽  
M. G. Stout ◽  
S. R. MacEwen
Keyword(s):  
Elevated Temperatures ◽  
High Strain ◽  
Quantitative Measure ◽  
Experimental Program ◽  
Strain Rates ◽  
Compression Tests ◽  
State Variable ◽  
Mechanical Threshold ◽  
Material State

Abstract Deformation at elevated temperatures in combination with high strain rates leads to recovery and recrystallization in aluminum alloys. Previous work in recrystallization has emphasized the detailing of microstructural trend in progression from the deformed to the annealed state. In the following, we examine the effect of rate dependence on deformation on AA 5182 and AA 6061. It is demonstrated that identification of underlying microstructural mechanisms is critical. An experimental program is then outlined for characterization of recovery and recrystallization of AA 5182. Instantaneous hardening rate and flow stress are developed from interrupted compression tests. These data are used to establish a quantitative measure of recovery through evaluation of a state variable for work hardening, the mechanical threshold. It is intended that the results serve as a foundation for development of relations for evolution of a mechanical state variable in the presence of recrystallization. Such a framework is necessary for the practical prediction of interstand recrystallization in hot rolling operations.

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