Uncertainty of Elastoplastic Material Parameters Calculated from the Spherical Indentation in the Macro Range

2021 ◽  
Vol 49 (6) ◽  
pp. 20200683
Author(s):  
Christian Ullner ◽  
Andreas Subaric-Leitis ◽  
Matthias Bartholmai
Keyword(s):  
Spherical Indentation ◽  
Elastoplastic Material ◽  
Material Parameters

A study on determination of tensile properties of metals at elevated temperatures from spherical indentation tests

2019 ◽  
Vol 54 (5-6) ◽  
pp. 331-347
Author(s):  
Tairui Zhang ◽  
Shang Wang ◽  
Weiqiang Wang
Keyword(s):  
Tensile Properties ◽  
Analytical Model ◽  
Elevated Temperatures ◽  
Regression Function ◽  
Maximum Error ◽  
Analytical Models ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Material Parameters ◽  
Indentation Tests

In this study, spherical indentation tests were used to determine the uniaxial tensile properties of metals at elevated temperatures (200 °C, 400 °C, and 600 °C). Taking the difference between spherical indentation tests at room and elevated temperatures into consideration, the incremental and analytical models were used to determine material parameters ( σ0, Ep, and n) and thermal softening parameters ( Eeff and m) in the Johnson–Cook constitutive equation, respectively. A discussion on the stability of the analytical model proved that despite in relative complicated forms and with three intercoupling material parameters, the analytical model is still effective for tensile property calculation. From the investigation on the relationship between pm and pi, it was found that correlating coefficient ξ is actually a function of both indentation depth and material parameters, and thus, a regression function was proposed for a more accurate description of ξ. Effectiveness of the spherical indentation tests was verified through experiments on three steels, SA508, 15CrMoR, S30408, and one titanium alloy, TC21, which proved that the spherical indentation tests can provide both proof and tensile strength calculations with a maximum error around 15% at room temperature and within 20% at elevated temperatures, and thus satisfy the demands for engineering applications.

scholarly journals Application of Evolutionary Algorithm in Elasticity

2015 ◽  
Vol 816 ◽  
pp. 363-368
Author(s):  
Jozef Bocko ◽  
Michael Dorn ◽  
Viera Nohajová
Keyword(s):  
Evolutionary Algorithms ◽  
Evolutionary Algorithm ◽  
Mechanical Engineering ◽  
Material Behavior ◽  
Elastoplastic Material ◽  
Main Body ◽  
Selection Methods ◽  
Material Parameters ◽  
Tension Load

This article introduces evolutionary algorithms and their utilization in mechanical engineering. First part of this work describes evolutionary algorithms and their characteristica. The main body of evolutionary algorithms, the selection methods for parents and the types of reproduction are explained in the next part of this article. Termination conditions are also discussed. Finally, the application of evolutionary algorithms to a problem in mechanical engineering is described. Thereby, the material parameters for a Bodner-Partom model describing visco-elastoplastic material behavior are determined by fitting data from experiments on Aluminum test samples under tension load.

Identification of viscoplastic material parameters from spherical indentation data: Part II. Experimental validation of the method

2006 ◽  
Vol 21 (3) ◽  
pp. 677-684 ◽  
Author(s):  
D. Klötzer ◽  
Ch. Ullner ◽  
E. Tyulyukovskiy ◽  
N. Huber
Keyword(s):  
Yield Stress ◽  
Young’S Modulus ◽  
Experimental Validation ◽  
Young's Modulus ◽  
Surface Preparation ◽  
Small Variation ◽  
Application Rate ◽  
Spherical Indentation ◽  
Viscoplastic Material ◽  
Material Parameters

A neural network-based analysis method for the identification of a viscoplasticity model from spherical indentation data, developed in the first part of this work [J. Mater. Res.21, 664 (2006)], was applied for different metallic materials. Besides the comparison of typical parameters like Young’s modulus and yield stress with values from tensile experiments, the uncertainties in the identified material parameters representing modulus, hardening behavior, and viscosity were investigated in relation to different sources. Variations in the indentation position, tip radius, force application rate, and surface preparation were considered. The extensive experimental validation showed that the applied neural networks are very robust and show small variation coefficients, especially regarding the important parameters of Young’s modulus and yield stress. On the other hand, important requirements were quantified, which included a very good spherical indenter geometry and good surface preparation to obtain reliable results.

Inverse Finite Element Analysis of the Indentation Response of Human Cervical Tissue

2013 ◽  
Author(s):  
Kristin Myers ◽  
Wang Yao ◽  
Kyoko Yoshida ◽  
Joy Vink ◽  
Noelia Zork ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Viscoelastic Material ◽  
Material Model ◽  
Spherical Indentation ◽  
Cervical Tissue ◽  
Tissue Slices ◽  
Element Analysis ◽  
Material Parameters ◽  
Inverse Finite Element Analysis

The mechanical function of the cervix is crucial during pregnancy when it is required to resist the compressive and tensile forces generated from the growing fetus. Pathologies of the cervical extracellular matrix (ECM), premature cervical remodeling, and alterations of cervical material properties have been implicated in placing women at high-risk for preterm birth (PTB). To understand the mechanical role of the cervix during pregnancy and to potentially identify etiologies for PTB, the overall goal of our group is to quantify ECM-material property relationships in normal and diseased human cervical tissue. In this study we present an inverse finite element analysis (IFEA) that optimizes material parameters of a viscoelastic material model to fit the stress-relaxation response of excised tissue slices to spherical indentation. Here we detail our IFEA methodology, report viscoelastic material parameters for cervical tissue slices from nonpregnant (NP) and pregnant (PG) hysterectomy patients, and report slice-by-slice data for whole cervical tissue specimens.

A new loading history for identification of viscoplastic properties by spherical indentation

2004 ◽  
Vol 19 (1) ◽  
pp. 101-113 ◽  
Author(s):  
N. Huber ◽  
E. Tyulyukovskiy
Keyword(s):  
Strain Curve ◽  
Material Behavior ◽  
Creep Process ◽  
Spherical Indentation ◽  
Loading History ◽  
Viscoplastic Material ◽  
Stress Strain Curve ◽  
Material Parameters ◽  
Depth Data ◽  
Variable Combination

In this paper a new loading history for extracting the stress–strain curve as well as the viscosity and creep behavior from indentation experiments is developed. It is based on a simple model describing the viscoplastic spherical indentation with a power-law hardening rule and a velocity-dependent overstress. Using this model, patterns were generated consisting of load-depth data and corresponding material parameters. The loading history for the simulation of the patterns was considered as a variable combination of loading and creep processes. To compare the identification potential of different loading histories, the inverse problem of determining the viscoplastic material parameters was solved by using neural networks. The emerging loading history uses a multiple-creep process with equidistant load steps and allows an identification of material parameters with much higher accuracy than with single creep. It will be used for further work, where the identification method is generalized using more realistic finite element simulations for a finite deformation elastic–viscoplastic material behavior.

scholarly journals Influence of the elastic and elastic-plastic material parameters on the mechanical properties of slewing bearings

2021 ◽  
Vol 13 (1) ◽  
pp. 168781402199215
Author(s):  
Peiyu He ◽  
Yun Wang ◽  
Hong Liu ◽  
Erkuo Guo ◽  
Hua Wang
Keyword(s):  
Finite Element ◽  
Carrying Capacity ◽  
Plastic Material ◽  
Elastoplastic Material ◽  
Finite Element Models ◽  
Material Parameters ◽  
Load Carrying ◽  
Elastic Plastic Material ◽  
Critical Components ◽  
Slewing Bearings

Slewing bearings are critical components of rotating equipment. Large structure sizes and heavy working load conditions require an extremely high load-bearing capacity and reliability. Overall and local contact finite element models of slewing bearings are verified by the empirical formula and Hertz contact theory. Validated finite element models are used to analyse the influence of the elastic material (E 1) and elastoplastic material parameters (EP 1, EP 2 and EP 3) on the load carrying capacity. The following conclusions are obtained by comparing the maximum contact load, the contact stress, the load distribution and the full-circle deformation. The influence of the material parameters on the slewing bearing is investigated to improve the analysis accuracy of the carrying capacity of the slewing bearings.

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