Automated Parameter Determination of Advanced Constitutive Models

2005 ◽  
Author(s):  
Syed M. Rahman ◽  
Tasnim Hassan ◽  
S. Ranji Ranjithan
Keyword(s):  
Heuristic Search ◽  
Constitutive Models ◽  
Cyclic Stress ◽  
Cyclic Plasticity ◽  
Parameter Determination ◽  
Model Parameters ◽  
Optimization Approach ◽  
Analysis And Design ◽  
Chaboche Model

Parameter determination of advanced cyclic plasticity models which are developed for simulation of cyclic stress-strain and ratcheting responses is complex. This is mainly because of the large number of model parameters which are interdependent and three or more experimental responses are used in parameter determination. Hence the manual trial and error approach becomes quite tedious and time consuming for determining a reasonable set of parameters. Moreover, manual parameter determination for an advanced plasticity model requires in-depth knowledge of the model and experience with its parameter determination. These are few of the primary reasons for advanced cyclic plasticity models not being widely used for analysis and design of fatigue critical structures. These problems could be overcome through developing an automated parameter optimization system using heuristic search technique (e.g. genetic algorithm). This paper discusses the development of such an automatic parameter determination scheme for improved Chaboche model developed by Bari and Hassan [4]. A new stepped GA optimization approach which is found to be more efficient over the conventional GA approach in terms of fitness quality and optimization time is presented.

Object Oriented Dexterity Analysis and Design Application for Spatial Robot Hands

1989 ◽  
Author(s):  
L. Lu ◽  
C. Cai ◽  
A. H. Soni
Keyword(s):  
Performance Evaluation ◽  
Object Oriented ◽  
Kinematic Parameter ◽  
Least Square ◽  
Parameter Determination ◽  
Robot Hand ◽  
Kinematic Parameters ◽  
Analysis And Design ◽  
Robot Hands

Abstract For an arbitrarily shaped object manipulated by a robot hand, this paper presents a procedure for analyzing the position and rotation ranges of the object, and a procedure for designing the kinematic parameters of a hand to meet given requirements on the motion ranges. Rotation dexterity index, dexterity charts, and a dexterity scalar characterizing both position range and rotation range are introduced for the performance evaluation of a robot hand. Least-square-error iteration and steps are detailed for the kinematic parameter determination of a robot hand.

A Simple Analogous Model for the Determination of Cyclic Plasticity Parameters of Thin Wires to Model Wire Drawing

2007 ◽  
Vol 129 (3) ◽  
pp. 488-495
Author(s):  
T. Schenk ◽  
T. Seifert ◽  
H. Brehm
Keyword(s):  
Tensile Tests ◽  
Wire Drawing ◽  
Cyclic Stress ◽  
Cyclic Plasticity ◽  
Integration Time ◽  
Model Parameters ◽  
Compression Tests ◽  
Thin Wires ◽  
Fe Simulations ◽  
Analogous Model

Cyclic stress-strain measurements have to be performed in order to determine the cyclic plasticity parameters of material models describing the Bauschinger effect. For thin wires, the performance of tensile tests is often not possible due to necking of the specimen on exceeding the yield stress, whereas compression tests are uncritical. This paper presents an approach to determine the cyclic plasticity parameters by performance of compression tests for wires before and after drawing. Here, a simple analogous model is used instead of finite-element (FE) simulations. This approach has been applied for two different integration time steps in order to evaluate their influence on the fit and the accuracy of the integration. It is shown that good accuracy can be obtained for the cyclic plasticity parameters. For FE simulations using larger integration time steps, large deviations have been noted. However, there the analogous model could also be adopted in order to find appropriate model parameters. In general, it is the intention of this paper to show that searching an analogous model can be a very time- and cost-saving task.

A Two Surface Model for Transient Nonproportional Cyclic Plasticity, Part 2: Comparison of Theory With Experiments

1985 ◽  
Vol 52 (2) ◽  
pp. 303-308 ◽  
Author(s):  
D. L. McDowell
Keyword(s):  
Temperature Cycling ◽  
Cyclic Plasticity ◽  
304 Stainless Steel ◽  
Surface Model ◽  
Model Parameters ◽  
Tubular Specimen ◽  
Cyclic Plasticity Model ◽  
Type 304 ◽  
Type 304 Stainless Steel

For the two surface cyclic plasticity model introduced in Part 1, methods for determination of model parameters are described. The model is specialized to axial-torsional loading of a thin-walled tubular specimen, and applied to non-proportional, room-temperature cycling of type 304 stainless steel. Computer simulations for two complex histories show good general agreement with experimental data obtained by the author.

Automated procedures for the determination of high temperature viscoplastic damage constitutive equations

1992 ◽  
Vol 437 (1901) ◽  
pp. 527-544 ◽  
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Strain Rate ◽  
Cyclic Plasticity ◽  
Parameter Determination ◽  
Nominal Composition ◽  
Strain Rates ◽  
Material Parameters ◽  
The Matrix

Methods have been developed for the determination of the material parameters in the Chaboche viscoplasticity model, and in the evolution equation for cyclic plasticity damage. The matrix of cyclic plasticity tests required for parameter determination consists of nine tests to be carried out for three strain ranges, and for each strain range, three strain rates. A programme of uni-axial cyclic plasticity tests has been carried out on cast copper (nominal composition: 99.99% Cu, 0.005% O 2 , B. S. 1035-1037) at strain ranges ± 0.3%, ± 0.6%, and ± 1.0%, each at strain rates 0.6% s -1 , 0.06% s -1 , and 0.006% s -1 . The matrix of tests has been carried out at each of the following temperatures: 20, 50, 150, 250 and 500 °C. At elevated temperature, strain rate has been found to have a significant effect on specimen lifetime. Low strain rates lead to increased creep damage evolution at high temperature, and hence lead to reduced cycles to failure. Cast copper has been found to be a rate sensitive material at temperatures above 150 °C. No strain rate effect was observed at temperatures below 150 °C. Ratchetting tests have been carried out at 20, 150, 250 and 500 °C. The effect of mean stress and stress rate on ratchet rates and lifetimes has been examined. Mean stresses of the order of 1 % of the applied stress range have been found to lead to significant ratchet rates for this material, resulting in failure by plastic collapse at elevated temperature. The methods presented for the determination of the material parameters and the results of the cyclic plasticity testing programme have enabled the viscoplastic damage model to be developed.

scholarly journals An analytical approach to the HEMT noise wave model parameter determination

2017 ◽  
Vol 14 (1) ◽  
pp. 35-49
Author(s):  
Vladica Djordjevic ◽  
Zlatica Marinkovic ◽  
Olivera Pronic-Rancic ◽  
Vera Markovic
Keyword(s):  
Analytical Approach ◽  
Wave Model ◽  
High Electron Mobility Transistor ◽  
Intrinsic Noise ◽  
Parameter Determination ◽  
Second Step ◽  
Model Parameters ◽  
High Electron ◽  
Noise Parameters

This paper presents an analytical approach to determination of the noise wave model parameters for a high electron-mobility transistor working under different temperature and frequency conditions. The presented approach is composed of two steps and provides more efficient determination of these parameters than in the case of optimization procedures commonly applied for that purpose in circuit simulators. The first step is extraction of the noise parameters of transistor intrinsic circuit from the measured noise parameters of whole transistor using an analytical noise de-embedding procedure. The second step is calculation of the noise wave model parameters from the de-embedded intrinsic noise parameters using existing formulas. The accuracy of the presented approach is validated in a wide frequency and temperature range by comparison of the transistor noise parameters simulated for the determined noise wave model parameters with the measured noise parameters.

scholarly journals On the Application of the Particle Swarm Optimization to the Inverse Determination of Material Model Parameters for Cutting Simulations

Modelling ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 129-148
Author(s):  
Marvin Hardt ◽  
Deepak Jayaramaiah ◽  
Thomas Bergs
Keyword(s):  
Particle Swarm Optimization ◽  
Particle Swarm ◽  
Material Model ◽  
Cutting Process ◽  
Parameter Determination ◽  
Model Parameters ◽  
Swarm Optimization ◽  
Cutting Simulations ◽  
Number Of Iterations

The manufacturing industry is confronted with increasing demands for digitalization. To realize a digital twin of the cutting process, an increase of the model reliability of the virtual representation becomes necessary. Thereby, different models are required to represent the experimental behavior of the workpiece material or frictional interactions. One of the most utilized material models is the Johnson–Cook material model. The material model parameters are determined either by conventional or by non-conventional material tests, or inversely from the cutting process. However, the inverse parameter determination, where the model parameters are iteratively modified until a sufficient agreement between experimental and numerical results is reached, is not robust and requires a high number of iterations. In this paper, an approach for the inverse determination of material model parameters based on the Particle Swarm Optimization (PSO) is presented. The approach was investigated by the inverse re-identification of an initial parameter set. The conducted investigations showed that a material model parameter set can be determined within a small number of iterations. Thereby, the determined material model parameters resulted in deviations of approximately 1% in comparison to their target values. It was shown that the PSO is suitable for the inverse material parameter determination from cutting simulations.

scholarly journals CORRELATION RELATIONSHIPS FOR THE HYPOPLASTIC MODEL FOR FINE GRAINED SOILS

2017 ◽  
Vol 10 ◽  
pp. 7-11
Author(s):  
Tomáš Kadlíček ◽  
Tomáš Janda ◽  
Michal Šejnoha
Keyword(s):  
Research Effort ◽  
Constitutive Models ◽  
Model Parameters ◽  
Computational Tools ◽  
Ongoing Research ◽  
Individual Model ◽  
Hypoplastic Model ◽  
Preliminary Results ◽  
Fine Grained

The paper is concerned with our ongoing research effort devoted to the development of reliable computational tools for the calibration of advanced constitutive models of soils. At present, such software is available for the hypoplastic model of clays applicable to soft soils. This software provides a stepping stone for the determination of potential links between individual model parameters and fundamental characteristics of soils. Identifying such links would allow for tuning the model without performing time consuming experiments, particularly in the case of an initial design. Some preliminary results are presented in the paper.

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