Hot Forming Optimization of ZK30 Magnesium Alloy

2018 ◽  
Vol 941 ◽  
pp. 2325-2330 ◽  
Author(s):  
Manuel Carsí ◽  
Fernando Carreño ◽  
Oscar A. Ruano
Keyword(s):  
Magnesium Alloy ◽  
Lyapunov Stability ◽  
Stability Criterion ◽  
Strain Rates ◽  
Optimum Temperature ◽  
Compression Tests ◽  
Deformation Bands ◽  
Lyapunov Stability Criterion ◽  
Reduced Costs ◽  
Using Data

The modeling of the forming of materials at high homologous temperatures allows obtaining optimum forming parameters, reduced costs and improving final properties of the finished product. In this work, the behavior of the ZK30 Magnesium alloy was characterized by means of compression tests at temperatures 300 to 450oC and strain rates between 0.1 and 8.7 s-1. Using data from these tests, the parameters of the Garofalo equation are calculated. In addition, by means of the second Lyapunov stability criterion, the optimum temperature at a given temperature is determined which should minimize the appearance of deformation bands and cracks during hot working. This temperature was found to be 641 K (368oC) at 8.7 s-1.

scholarly journals Hot Deformation Behavior of a Ni-Based Superalloy with Suppressed Precipitation

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 605
Author(s):  
Franco Lizzi ◽  
Kashyap Pradeep ◽  
Aleksandar Stanojevic ◽  
Silvana Sommadossi ◽  
Maria Cecilia Poletti
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Strain Rates ◽  
Compression Tests ◽  
Deformation Bands ◽  
Stress Softening ◽  
Relative Stress ◽  
The Matrix ◽  
Thermomechanical Processes

Inconel®718 is a well-known nickel-based super-alloy used for high-temperature applications after thermomechanical processes followed by heat treatments. This work describes the evolution of the microstructure and the stresses during hot deformation of a prototype alloy named IN718WP produced by powder metallurgy with similar chemical composition to the matrix of Inconel®718. Compression tests were performed by the thermomechanical simulator Gleeble®3800 in a temperature range from 900 to 1025 °C, and strain rates scaled from 0.001 to 10 s−1. Flow curves of IN718WP showed similar features to those of Inconel®718. The relative stress softening of the IN718WP was comparable to standard alloy Inconel®718 for the highest strain rates. Large stress softening at low strain rates may be related to two phenomena: the fast recrystallization rate, and the coarsening of micropores driven by diffusion. Dynamic recrystallization grade and grain size were quantified using metallography. The recrystallization grade increased as the strain rate decreased, although showed less dependency on the temperature. Dynamic recrystallization occurred after the formation of deformation bands at strain rates above 0.1 s−1 and after the formation of subgrains when deforming at low strain rates. Recrystallized grains had a large number of sigma 3 boundaries, and their percentage increased with strain rate and temperature. The calculated apparent activation energy and strain rate exponent value were similar to those found for Inconel®718 when deforming above the solvus temperature.

Research on Control Algorithm for Mobile Welding Robot Using Kinematics Oscillator

2013 ◽  
Vol 303-306 ◽  
pp. 1678-1684
Author(s):  
Xian Chun Meng ◽  
Kai Li ◽  
Dong Mei Zhang ◽  
Jian Hu Zuo ◽  
Yan Jun Li
Keyword(s):  
Lyapunov Stability ◽  
Stability Criterion ◽  
Control Algorithm ◽  
Controller Design ◽  
Dynamic Parameters ◽  
Welding Robot ◽  
Holonomic Constraint ◽  
Lyapunov Stability Criterion ◽  
Mobile Welding Robot ◽  
Instantaneous Center

The dynamics equation of mobile welding robot is established. In controller design of the mobile welding robot, the non-holonomic constraint is introduced that limits the size of the transverse sliding and avoid the coordinates of the instantaneous center of rotation is larger than the wheelbase, to ensure the robot’s stability. Based on kinematics oscillator, the effect of uncertain dynamic parameters is considered. According to the Lyapunov stability criterion, the control algorithm is deduced. Simulating results by MATLAB software shows that the design of the control algorithm is stable, convergent and effective.

Bio-Inspired Nonholonomic Tracking Control

2013 ◽  
Author(s):  
Adam Shoemaker ◽  
Alexander Leonessa
Keyword(s):  
Obstacle Avoidance ◽  
Lyapunov Stability ◽  
Stability Criterion ◽  
Tracking Control ◽  
High Speed ◽  
Speed Tracking ◽  
Tracking Controller ◽  
Lyapunov Stability Criterion ◽  
Saturation Constraints ◽  
Nonholonomic Vehicles

The behavior of nature’s predators is considered for designing a high speed tracking controller for nonholonomic vehicles, whose dynamics are represented using a unicycle model. To ensure that the vehicle behavior closely resembles that of a predator, saturation constraints are added and accounted for using Lyapunov stability criterion. Following verification and comparison of the saturation constraints, the proposed algorithm is implemented on a testing platform. Based on the results presented, we believe the algorithm shows significant promise in high speed control and obstacle avoidance.

Stochasticity of Galactic Orbits of Star Clusters

2015 ◽  
Vol 24 (2) ◽  
Author(s):  
L. V. Smirnova
Keyword(s):  
Lyapunov Exponents ◽  
Lyapunov Stability ◽  
Stability Criterion ◽  
Star Clusters ◽  
Open Clusters ◽  
Stability Criteria ◽  
Poincaré Sections ◽  
Lyapunov Stability Criterion ◽  
Poincare Sections

AbstractThe Lyapunov, Lagrange and Poincaré criteria are tested for orbits of 461 open clusters in an axisymmetric potential. Lyapunov exponents and Poincaré sections are computed, and all of the trajectories are found to be stable according to the Lagrange and Poincaré stability criteria. At the same time, some trajectories appear to exhibit minor instability according to the Lyapunov stability criterion.

Workability of ZK60A Alloy Depending on Microstructure

2012 ◽  
Vol 217-219 ◽  
pp. 373-376 ◽  
Author(s):  
K.H. Jung ◽  
Yong Bae Kim ◽  
Byung Min Ahn ◽  
Sang Mok Lee ◽  
Jong Sup Lee ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Uniaxial Compression ◽  
Microstructural Evolution ◽  
Elevated Temperatures ◽  
Electron Backscatter Diffraction ◽  
Strain Rates ◽  
Compression Tests ◽  
Electron Backscatter ◽  
Before And After ◽  
Backscatter Diffraction

In this study, the variation of workability of semi-continuously casted and extruded ZK60A magnesium alloy was investigated. To determine the deformation capability of two different billets, uniaxial compression tests were conducted at elevated temperatures and two different strain rates. In addition, the microstructural evolution was investigated using electron backscatter diffraction (EBSD) to compare the microstructure before and after the extrusion. The formability of ZK60A depending on the microstructure is discussed based on the experimental results obtained in this study, and is compared with earlier research in the literature.

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